CN110341883B - Method for correcting ship stability by using free liquid level of liquid tank - Google Patents

Method for correcting ship stability by using free liquid level of liquid tank Download PDF

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CN110341883B
CN110341883B CN201910676597.4A CN201910676597A CN110341883B CN 110341883 B CN110341883 B CN 110341883B CN 201910676597 A CN201910676597 A CN 201910676597A CN 110341883 B CN110341883 B CN 110341883B
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inertia
width
area
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CN110341883A (en
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薛孝行
胡甚平
席永涛
轩少永
吴建军
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Shanghai Maritime University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B79/00—Monitoring properties or operating parameters of vessels in operation
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Abstract

The invention discloses a method for correcting ship stability by using a free liquid level of a liquid tank, in particular to a method for correcting ship stability by using the free liquid level of the liquid tank when the liquid level width of the liquid tank can change in a jumping manner along with the height change of the liquid level. When the area moment of inertia method is used for calculating the free liquid surface of the liquid tank with the special shape, when the liquid surface is higher than the critical liquid surface, the alternative liquid tank method is adopted for calculating the area moment of inertia of the liquid surface. The liquid level width of the substitute liquid tank is changed continuously, so that the risk of calculating the free liquid level of the liquid tank with the special shape according to the actual liquid level by adopting an area inertia moment method can be avoided when the liquid level width of the liquid tank with the special shape is changed in a jumping manner along with the increase of the liquid level height. Based on the improved correction method of the free liquid level of the liquid tank to the ship stability, the ship stability calculation result corrects the risk of the ship stability calculation when the free liquid level of the liquid tank with the special shape is calculated according to the actual liquid level by adopting an area inertia moment method, and the calculation result is safe and reasonable for the actual work.

Description

Method for correcting ship stability by using free liquid level of liquid tank
Technical Field
The invention relates to the field of a calculation method for correcting ship stability by using free liquid surface of a liquid tank or a liquid cargo tank of a ship (including an offshore mobile facility), in particular to a method for correcting the ship stability by using free liquid surface of the liquid tank.
Background
The ship stability is an important performance for ensuring safe sailing or floating of the ship on water, and the basic and special alignment requirements of the ship stability specified in relevant legal rules must be met during the operation of the ship. The requirement of ship stability alignment is the lowest requirement of ship stability. Whether the ship stability meets the stability alignment requirement is determined based on or through the initial stability height of the ship and the size of the ship restoring moment arm.
The ship is provided with liquid tank cabinets such as a fresh water tank, a fuel oil tank, a ballast water tank and the like, if the tank is not full of liquid in the tank, the liquid in the tank flows to an inclined side when the ship transversely inclines, the liquid level can be set to be parallel to the outboard water level, and the liquid level capable of freely flowing is called as free liquid level.
The effect of free liquid level on stability must be taken into account when loading a vessel with liquid or liquid cargo. The influence of the free liquid level on the ship stability can be realized by correcting the initial stability height of the ship and the ship restoring force arm through the free liquid level. At present, in practice, the ship stability is corrected by free liquid surface mostly by adopting an area moment of inertia method, and the ship stability is corrected by the free liquid surface of a liquid tank according to the area moment of inertia of an actual liquid surface.
When the area moment of inertia method is used for calculating the special-shaped liquid tank, when the liquid level is higher than the critical liquid level, the correction of the ship stability by the free liquid surface cannot be directly calculated according to the area moment of inertia of the actual liquid level, the main reason is that the liquid level width of the special-shaped liquid tank is likely to generate jumping sudden change near the critical liquid level, the area moment of inertia calculated according to the actual liquid level by adopting the area moment of inertia method is also likely to generate jumping sudden change, and the corrected value of the ship stability by the free liquid surface is also likely to generate jumping sudden change, so that the ship stability calculation result corrected by the free liquid surface under certain conditions meets the requirements of relevant legal rules, but the ship actual stability may not meet the requirements of the relevant legal rules, and therefore, a correction method which is also suitable for the special-shaped liquid tank and is applied to the ship.
Disclosure of Invention
The invention aims to provide a method for correcting ship stability by using a free liquid level of a liquid tank, in particular to a method for correcting ship stability by using the free liquid level of the liquid tank when the liquid level width of the liquid tank can change in a jumping manner along with the height change of the liquid level. When the area moment of inertia method is used for calculating the free liquid surface of the liquid tank with the special shape, when the liquid surface is higher than the critical liquid surface, the liquid tank replacing method is adopted when the liquid surface area moment of inertia is calculated or a relation table or a graph of the liquid surface height and the liquid surface area moment of inertia is manufactured. Because the liquid level width of the substitute liquid tank is changed continuously, when the liquid level width of the liquid tank with the special shape changes in a jumping manner along with the increase of the liquid level height, the risk that the free liquid level of the liquid tank with the special shape is calculated by adopting an area moment of inertia method according to the actual liquid level can be avoided.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a method for correcting ship stability by using free liquid level of a liquid tank comprises the following steps:
s1, determining the liquid level attribute of a preset liquid level, wherein the preset liquid level comprises liquid levels at different liquid level heights and/or liquid levels at different liquid volumes;
s2, calculating the liquid level area moment of inertia of the preset liquid level according to the liquid level attribute;
s3, according to the liquid level area moment of inertia of the preset liquid level calculated in the step S2, making a parameter table or graph of the relation between different liquid level heights and/or different liquid volumes of the liquid cabin and the liquid level area moment of inertia;
s4, according to the liquid level height and/or the liquid volume of the actual liquid level, consulting the parameter table or the map made in the step S3, and determining the liquid level area moment of inertia of the actual liquid level;
s5, calculating the correction of the actual liquid level to the ship stability calibration index according to the liquid level area inertia moment of the actual liquid level obtained in the step S4;
wherein the step S2 specifically includes:
s21, judging whether the width of the preset liquid level can be in a jumping change trend through the critical liquid level:
s21.1, if yes, determining in which region the preset liquid level is located, which specifically includes: s21.11, the preset liquid level is located in the liquid level width continuous area before jumping, and the liquid level area inertia moment of the preset liquid level is calculated according to the liquid level attribute; or S21.12, the preset liquid level is located in the liquid level width continuous area after jumping, the liquid level area inertia moment corresponding to the preset liquid level is calculated by adopting a substitute liquid tank method, and the step S3 is switched to;
if the width of the liquid level of the liquid tank can be changed in a jumping manner, the tank body is divided into a liquid level width continuous region before jumping and a liquid level width continuous region after jumping; the liquid level width continuous area before jumping is as follows: with the increase of the height of the preset liquid level, the width of the preset liquid level is a liquid level height range or a liquid volume range which is continuously changed; the liquid level width continuous area after jumping is as follows: the method comprises the following steps that (1) as the height of a preset liquid level increases, the preset liquid level passes through a certain critical liquid level, the width of the preset liquid level has a jumping change, after the jumping change, as the height of the preset liquid level increases, the width of the preset liquid level is a liquid level height range or a liquid volume range which changes continuously; the critical liquid level is: along with the increase of the height of the liquid level, presetting the corresponding liquid level when the liquid level width is subjected to jumping change;
s21.2, if not, calculating the area moment of inertia of the liquid surface corresponding to the preset liquid surface according to the liquid surface attribute of the preset liquid surface, and turning to the step S3.
Preferably, the liquid level attributes of the preset liquid level specifically include: the shape, width and length of the liquid surface.
Preferably, the alternative tank method in step S21.12 comprises the following:
the preset liquid level is located in the liquid level width continuous region after jumping, and the range of the substitute liquid tank is a region determined by the top surface of the liquid level width continuous region after jumping and the critical liquid level during jumping change; the substitute liquid level of the preset liquid level is the liquid level corresponding to the liquid level height or the liquid volume of the preset liquid level in the substitute liquid tank.
Preferably, the alternative liquid tank method adopts a first alternative liquid level method, and the first alternative liquid level method is as follows: and replacing the preset liquid level with the first substitution liquid level, replacing the width of the preset liquid level with the width of the first substitution liquid level, and directly calculating the liquid level area moment of inertia of the first substitution liquid level.
Preferably, the first alternative liquid level method specifically comprises the following:
the first alternative liquid surface width bxIs composed of
Figure BDA0002143480700000031
Or
Figure BDA0002143480700000032
Wherein b1 is the maximum liquid level width of the critical liquid level at the time of the jump change; b2 is the maximum liquid level width of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the maximum in the continuous liquid level width area after jumping; h isxIs the level of the first replacement level; h is1The liquid level height of the critical liquid level is the liquid level height when the liquid level width is changed in a jumping way; h is2The height of the liquid level corresponding to the highest liquid level height in the continuous area of the liquid level width after jumping, v1The volume of liquid corresponding to the critical liquid level when the liquid level width changes in a jumping way, v2Is the volume of liquid after jumping corresponding to the maximum volume of liquid in the continuous region of the liquid level widthxThe volume of liquid corresponding to the first substitution level;
a surface area moment of inertia i of the first alternate liquid surfacex1Is composed of
Figure BDA0002143480700000033
Wherein ix1Is the area moment of inertia of the first surrogate liquid level; l is the maximum length of the liquid tank; bxIs the width of the first surrogate liquid level; k is a dimensionless coefficient that is related to the level property of the first surrogate level.
Preferably, the alternative tank process employs a second alternative level process,
the second alternative liquid level method is as follows: and (3) replacing the preset liquid level with the second substitute liquid level, calculating the maximum area moment of inertia of the critical liquid level during the jumping change and the area moment of inertia of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the maximum in the liquid level width continuous region after jumping, and calculating the area moment of inertia of the second substitute liquid level according to an interpolation method.
Preferably, the second alternative liquid level method specifically comprises the following:
the calculation method of the liquid level area moment of inertia i of the liquid level comprises the following steps:
Figure BDA0002143480700000041
wherein i is the area moment of inertia of the liquid level; l is the maximum length of the liquid tank; b is the maximum width of the liquid level; k is a dimensionless coefficient and is related to the liquid level property of the liquid level;
calculating the maximum area moment of inertia i1 of the critical liquid level when the liquid level is changed in a jumping way according to the formula (4);
calculating the area moment of inertia i2 of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the largest in the liquid level width continuous region after jumping according to the formula (4);
calculating the liquid level area moment of inertia i of the second substitute liquid level by interpolationx2Comprises the following steps:
Figure BDA0002143480700000042
or
Figure BDA0002143480700000043
Preferably, in step S3, a parameter table or map is created according to the liquid level height value or the liquid volume value of the arithmetic progression.
Preferably, in step S4, when there is no corresponding liquid level height or liquid volume value of the actual liquid level in the parameter table, an interpolation method is used to calculate the liquid level area moment of inertia of the actual liquid level;
the specific method for calculating the liquid level area inertia moment of the actual liquid level by adopting an interpolation method comprises the following steps:
selecting the liquid level corresponding to the first liquid level height or liquid level volume larger than the actual liquid level in the parameter table as the upper limit liquid level, selecting the liquid level corresponding to the first liquid level height or liquid level volume smaller than the actual liquid level in the parameter table as the lower limit liquid level, and looking up the parameter table to obtain the liquid level area inertia moment i corresponding to the upper limit liquid levelbLiquid level area moment of inertia i corresponding to lower limit liquid levelsCalculating the inertia of the liquid surface area of the actual liquid surface by linear interpolationMoment ixComprises the following steps:
Figure BDA0002143480700000044
wherein ixThe liquid level area moment of inertia of the actual liquid level; h is the liquid level height of the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; h isbThe liquid level height value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; h issThe liquid level height value corresponding to the lower limit liquid level;
or, calculating the liquid level area inertia moment i of the actual liquid level by adopting a linear interpolation methodxComprises the following steps:
Figure BDA0002143480700000051
wherein ixThe liquid level area moment of inertia of the actual liquid level; v is the liquid volume at the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; v. ofbThe liquid volume value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; v. ofsThe liquid volume value corresponding to the lower limit liquid level is shown.
Compared with the prior art, the invention has the following advantages:
(1) the method for correcting the ship stability by the free liquid level of the liquid tank improves a calculation method for correcting the ship stability by calculating the free liquid level according to the actual liquid level by adopting an area inertia moment method; when the free liquid level of a special-shaped liquid tank (comprising a liquid tank with a convex section and a liquid tank with an L-shaped section or other tank-shaped liquid tanks) is calculated by adopting an area moment of inertia method to correct ship stability, when the liquid level is higher than a critical liquid level, the area moment of inertia of the liquid level is calculated or a relation table or a graph between the height (or volume) of the liquid level and the area moment of inertia of the liquid level is manufactured, a substitute liquid tank method is adopted, and when the width of the liquid level of the special-shaped liquid tank is changed in a jumping manner along with the increase of the height of the liquid level, the risk that the free liquid level of the special-shaped liquid tank is calculated by adopting the area moment; based on the improved correction method of the free liquid level of the liquid tank to the ship stability, the ship stability calculation result corrects the risk of the ship stability calculation when the free liquid level of the liquid tank with a special shape is calculated according to the actual liquid level by adopting an area inertia moment method, and the calculation result is safe and reasonable for the actual work;
(2) when the area moment of inertia method is used for calculating the special-shaped liquid tank, the correction of the ship stability by the free liquid surface can not be directly calculated according to the area moment of inertia of the actual liquid surface when the liquid surface is higher than the critical liquid surface, the main reason is that the liquid surface width of the special-shaped liquid tank generates jumping sudden change near the critical liquid surface, the area moment of inertia calculated according to the actual liquid surface by adopting the area moment of inertia method also generates jumping sudden change, and the corrected value of the ship stability by the free liquid surface also generates jumping change, so that the ship stability calculation result corrected by the free liquid surface under certain conditions meets the related legal rule requirements, but the ship actual stability can not meet the related legal rule requirements, and the correction method of the ship stability by the liquid tank free liquid surface has continuous change because the liquid surface width of the substitute liquid surface, and the calculation result is consistent with the actual condition, the risk of calculating the free liquid level of the liquid tank with a special shape by a traditional method can be avoided;
(3) the method for correcting the ship stability by the free liquid level of the liquid tank can be used for calculating the ship stability and can also be used for calculating the stability of an offshore mobile facility.
Drawings
FIG. 1 is a flow chart of a method for correcting ship stability by the free liquid level of a liquid tank with a special shape according to a first method of the invention;
FIG. 2 is a flow chart of a method for correcting ship stability by the free liquid level of a liquid tank with a special shape according to a second method of the invention;
FIG. 3 is a schematic view of a section of a special tank-shaped liquid tank with a convex cross section and an alternative liquid level thereof according to one embodiment;
FIG. 4 is a schematic view of a section of a special tank-shaped liquid tank with a reverse L-shaped cross section and an alternative liquid level in the second embodiment;
fig. 5 is a schematic view of the section of a special tank-shaped liquid tank with a positive L-shaped section and an alternative liquid level in the third embodiment.
Detailed Description
The present invention will now be further described by way of the following detailed description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings.
When the ship is designed and built, a parameter table or graph (called a liquid tank parameter relation table or graph) of the liquid level height or the liquid volume of the liquid tank and the liquid level area moment of inertia can be manufactured, wherein the liquid level height or the liquid volume is a table look-up exponent of the liquid tank parameter table, and the liquid level area moment of inertia is a checked value. The liquid level of the tank is the distance between the liquid level in the tank and the tank bottom. The liquid level heights or liquid volumes in the tank parameter table or map are usually set at equal intervals by a discrete method (for example, different liquid level heights are different by 0.1m), but the individual liquid level heights or liquid volumes may not meet the equal interval requirement.
Due to the tank shape, the width of the free liquid level of some tanks is changed in a jumping way as the liquid level height is increased, which is characterized in that the liquid level width is suddenly and obviously increased or decreased in a jumping way when the liquid level height is increased to a certain value, and the increased or decreased liquid level width is kept constant or continuously changed in a certain liquid level height range as the liquid level height is continuously increased. The liquid level at which the width of the free liquid level of the tank exhibits a sudden change is called the critical level.
At the critical liquid level, the liquid level area moment of inertia calculated according to the actual liquid level also shows jumping change, and based on the area moment of inertia, the correction of the initial stability height and the recovery moment arm of the ship by the free liquid level calculated by adopting an area moment of inertia method also shows jumping change.
If the liquid level width changes in a jumping manner along with the increase of the liquid level height, when the free liquid level is above the critical liquid level and is close to the critical liquid level, the corrected values of the free liquid level to the initial stability height and the restoring force arm of the ship calculated by the conventional method possibly have larger difference compared with the actual values, so that the corrected ship stability calibration index value is larger, and the ship has safety risk.
As shown in fig. 1 and fig. 2, the present invention is a flow chart of a method for correcting ship stability by using a free liquid level of a tank, and the method is not only suitable for a tank with a common shape, but also suitable for a tank with a special shape. The specially shaped tanks may be cargo tanks with large hatch enclosures for carrying liquid cargo or similar liquid cargo, ballast tanks and cargo tanks in ships or offshore moving installations featuring such shapes. It should be noted that the cross section of the special-shaped tank of the present invention may be convex or L-shaped, but is not limited to this shape. In addition, the correction method can be used for calculating ship stability and can also be used for calculating the stability of the offshore mobile facility.
Specifically, the method for correcting the ship stability by the free liquid level of the liquid tank comprises the following steps:
step 1, determining liquid level attributes of a preset liquid level, wherein the preset liquid level comprises liquid levels at different liquid level heights and/or liquid levels at different liquid volumes (the liquid level attributes comprise the shape or approximate shape of the liquid level, the width of the liquid level along the ship width direction, the length of the liquid level along the ship length direction and the like);
step 2, calculating the liquid level area moment of inertia of the preset liquid level according to the liquid level attribute;
step 3, according to the liquid level area moment of inertia of the preset liquid level calculated in the step 2, making a parameter table or graph of the relation between different liquid level heights or liquid volumes of the liquid tank and the liquid level area moment of inertia;
step 4, according to the liquid level height and/or the liquid volume of the actual liquid level, looking up the parameter table or the map manufactured in the step 3, and determining the liquid level area moment of inertia of the actual liquid level;
and 5, calculating the correction of the actual liquid level of the liquid tank, namely the free liquid level of the liquid tank to the stability calibration index of the tank body according to the liquid level area inertia moment of the actual liquid level obtained in the step 4.
Wherein, the step 2 specifically comprises:
step 21, judging whether the width of the preset liquid level can be in a jumping change trend through the critical liquid level:
step 21.1, if yes, determining in which region the preset liquid level is located, specifically including: 21.11, the preset liquid level is positioned in the liquid level width continuous area before jumping, and the liquid level area inertia moment of the preset liquid level is calculated according to the liquid level attribute; or 21.12, calculating the area moment of inertia of the liquid level corresponding to the preset liquid level by adopting a substitute liquid tank method when the preset liquid level is positioned in the liquid level width continuous area after jumping, and turning to the step 3; (ii) a
If the width of the liquid level of the liquid tank can be changed in a jumping manner, the tank body is divided into a liquid level width continuous region before jumping and a liquid level width continuous region after jumping; the liquid level width continuous area before jumping is as follows: with the increase of the height of the preset liquid level, the width of the preset liquid level is a liquid level height range or a liquid volume range which is continuously changed; the liquid level width continuous area after jumping is as follows: the liquid level width is changed in a jumping manner along with the increase of the height of the preset liquid level and the increase of the height of the preset liquid level, and the preset liquid level width is a liquid level height range or a liquid volume range which is changed continuously along with the increase of the height of the preset liquid level after the jumping change. The critical liquid level is: along with the increase of the height of the liquid level, presetting the corresponding liquid level when the liquid level width is subjected to jumping change;
and 21.2, if not, calculating the area moment of inertia of the liquid level corresponding to the preset liquid level according to the liquid level attribute of the preset liquid level, and turning to the step 3.
Example one
Fig. 3 is a schematic diagram showing a section of a special tank with a convex structure section and a section of an alternative tank, and fig. 3 shows that the actual width of the liquid level decreases and changes in a jumping manner through the critical liquid level as the height of the liquid level increases gradually. In the figure b1The maximum liquid level width of the critical liquid level when the liquid level is changed in a jumping way; b2The maximum liquid level width of the corresponding liquid level when the liquid level height is highest or the liquid volume is maximum in the continuous liquid level width area after jumping is shown as a dotted line MN, h is the critical liquid level position1The liquid level height of the critical liquid level is the liquid level height when the liquid level width is changed in a jumping way; h is2The height of the liquid level corresponding to the highest liquid level height in the continuous liquid level width area after jumping.
hkB is the liquid level height of the kth liquid level in the liquid level width continuous region after the jump when the liquid level width is changed in a stepwise decreasing mannerkFor replacement of a liquid level of the tank at the kth levelThe width, dot-dash line EA is the line connecting point E and point A, dot-dash line FD is the line connecting point F and point D, and dot-dash lines EA and FD are auxiliary lines for determining the substitute liquid level.
The flow of the method for correcting the ship stability of the free liquid surface of the special cabin-shaped liquid cabin can be specifically calculated according to the following method:
method 1
As shown in fig. 1, the calculation flow of the first method is that the special tank-shaped liquid level can be divided into a continuous liquid level width area before the jump (referred to as a large liquid level area, for example, the tank area with the section of ABCD in fig. 3) in the lower part and a continuous liquid level width area after the jump (referred to as a small liquid level area, for example, the tank area with the section of EFNM in fig. 3) in the upper part.
Wherein the liquid level width continuous region before jumping is: along with the increase of the height of the preset liquid level, the liquid level width of the liquid cabin is a liquid level height range or a liquid volume range which is continuously changed; the liquid level width continuous area after jumping is as follows: along with the increase of the height of the liquid level of the liquid tank, the liquid level of the liquid tank passes through the critical liquid level where MN is located, the width of the liquid level of the liquid tank has jumping change, and after the jumping change, along with the increase of the height of the liquid level of the liquid tank, the width of the liquid level of the liquid tank is the liquid level height range or the liquid volume range which changes continuously.
The specific method comprises the following steps: and S1, determining the liquid level and the liquid level properties (such as liquid level shape, length of the liquid level along the length direction of the ship, width of the liquid level along the width direction of the ship, and the like) of the liquid tank at different liquid level heights according to the selected different liquid level heights.
And S2, calculating the area moment of inertia of the liquid level at different liquid level heights or liquid volumes according to the liquid level attributes (liquid level shape, width and length) of different liquid levels.
The step S2 specifically includes:
s21, judging whether the selected different liquid level widths can be in a jumping change trend along with the change of the liquid level heights: s21.1, if yes, judging which area the liquid level is in; s21.11, if the liquid level is located in the large liquid level area, calculating the area moment of inertia corresponding to the liquid level directly according to the liquid level attribute; s21.12, if the liquid level is located in the small liquid level area, calculating the area moment of inertia corresponding to the liquid level by adopting a substitute liquid tank method, and then turning to the step S3; s21.2, if not, calculating the area moment of inertia corresponding to the liquid level according to the liquid level attribute, and then turning to the step S3.
The selected liquid level is positioned in the liquid level width continuous region after jumping, and the range of the substitute liquid tank is the region coated by the top surface of the liquid level width continuous region after jumping and the liquid level width continuous region before jumping plus the liquid level width continuous region before jumping; and the substitute liquid level of the selected liquid level is the liquid level corresponding to the liquid level height or the liquid volume of the selected liquid level in the substitute liquid tank.
The alternative liquid tank method of this embodiment adopts a first alternative liquid level method, which is: replacing the selected liquid level with the first substitute liquid level, replacing the width of the selected liquid level with the width of the first substitute liquid level, and directly calculating the area moment of inertia of the first substitute liquid level as the area moment of inertia of the actual liquid level;
area moment of inertia i of the first alternate liquid levelxThe calculation method is as follows:
as shown in fig. 3, the calculated width of the selected liquid level, i.e. the first alternative liquid level width bxIs composed of
Figure BDA0002143480700000091
Or
Figure BDA0002143480700000092
Wherein, b1The maximum liquid level width of the critical liquid level when the liquid level is changed in a jumping way; b2The maximum liquid level width of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the maximum in the liquid level width continuous area after jumping; h isxIs the level of the first replacement level; h is1The liquid level height of the critical liquid level is the liquid level height when the liquid level width is changed in a jumping way; h is2The height of the liquid level corresponding to the highest liquid level height in the continuous area of the liquid level width after jumping, v1The volume of liquid corresponding to the critical liquid level when the liquid level width changes in a jumping way, v2Is the volume of liquid after jumping corresponding to the maximum volume of liquid in the continuous region of the liquid level widthxThe volume of liquid corresponding to the first substitution level;
replacing the width of the selected liquid level with the width of the first alternative liquid level, and calculating the area moment of inertia of the liquid level at different liquid level heights or liquid volumes, namely the area moment of inertia of the first alternative liquid level, wherein the area moment of inertia i of the first alternative liquid levelxIs composed of
Figure BDA0002143480700000101
Wherein ixIs the area moment of inertia of the free liquid level; l is the maximum length of the liquid tank; bxIs a first alternative liquid level width; k is a dimensionless coefficient that is related to the meniscus shape of the first surrogate meniscus.
And S3, according to the area moment of inertia of different liquid level heights or liquid volumes calculated in the step S2, making a parameter table or graph of the relation between the liquid level heights or the liquid volumes of the liquid tank and the area moment of inertia of the liquid level.
And S4, according to the liquid level height or the liquid volume of the actual liquid level, searching the area moment of inertia corresponding to the actual liquid level from the parameter table or the map manufactured in the step S3, wherein the liquid level height or the liquid volume is a table searching argument, and the area moment of inertia of the liquid level is a searched parameter. If the parameter table or the map has no corresponding liquid level height or liquid volume value of the actual liquid level, the area moment of inertia of the actual liquid level is calculated by using a linear interpolation method to look up the table.
In step S4, the area moment of inertia of the actual liquid level calculated by the interpolation method is specifically:
selecting the liquid level height or the liquid level volume corresponding to the first liquid level larger than the actual liquid level in the parameter table or map in the step S3 as the upper limit liquid level, selecting the liquid level height or the liquid level volume corresponding to the first liquid level smaller than the actual liquid level in the parameter table as the lower limit liquid level, and looking up the parameter table to obtain the liquid level area moment of inertia i corresponding to the upper limit liquid levelbLiquid level area moment of inertia i corresponding to lower limit liquid levelsCalculating the liquid level area of the actual liquid level by linear interpolationMoment of inertia ixComprises the following steps:
Figure BDA0002143480700000102
wherein ixThe liquid level area moment of inertia of the actual liquid level; h is the liquid level height of the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; h isbThe liquid level height value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; h issThe liquid level height value corresponding to the lower limit liquid level is obtained.
Or, calculating the liquid level area inertia moment i of the actual liquid level by adopting a linear interpolation methodxComprises the following steps:
Figure BDA0002143480700000111
wherein ixThe liquid level area moment of inertia of the actual liquid level; v is the liquid volume at the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; v. ofbThe liquid volume value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; v. ofsThe liquid volume value corresponding to the lower limit liquid level is shown.
And S5, calculating the ship stability correction of the free liquid surface of the liquid tank according to the area moment of inertia obtained in the step S4.
Method two
As shown in fig. 2, which is a calculation flow of the second method, the special cabin-shaped liquid level may be divided into a continuous liquid level width area before the jump (referred to as a large liquid area, for example, the cabin area with the section of ABCD in fig. 3) in the lower portion and a continuous liquid level width area after the jump (referred to as a small liquid area, for example, the cabin area with the section of EFNM in fig. 3) in the upper portion.
The specific method comprises the following steps: t1, determining the liquid level and the liquid level property (such as liquid level shape, length of the liquid level along the length direction of the ship, width of the liquid level along the width direction of the ship, etc.) of the liquid tank at different liquid level heights according to the selected different liquid level heights;
and T2, calculating the area moment of inertia of the liquid level at different liquid level heights or liquid volumes according to the liquid level attributes (liquid level shape, width and length) of the different selected liquid levels.
The step T2 specifically includes:
t21, judging whether the widths of the different liquid levels are in a jumping change trend along with the height change of the liquid levels, and T21.1, judging which area the liquid level is in if the widths of the different liquid levels are in; t21.11, if the liquid level is located in the large liquid level area, directly calculating the area moment of inertia corresponding to the liquid level according to the liquid level attribute; t21.12, if the liquid level is located in the small liquid level area, calculating the area moment of inertia corresponding to the liquid level by adopting a substitute liquid tank method, and turning to the step T3; t21.2, if not, calculating the area moment of inertia corresponding to the liquid level according to the liquid level attribute, and turning to the step T3.
The selected liquid level is positioned in the liquid level width continuous region after jumping, and the range of the substitute liquid tank is the region coated by the top surface of the liquid level width continuous region after jumping and the liquid level width continuous region before jumping plus the liquid level width continuous region before jumping; and the substitute liquid level of the selected liquid level is the liquid level corresponding to the liquid level height or the liquid volume of the selected liquid level in the substitute liquid tank.
The substitute liquid tank method of the embodiment adopts a second substitute liquid level method, which specifically comprises the following steps: and replacing the selected liquid level with a second substitute liquid level, calculating the maximum area moment of inertia of the critical liquid level during the jumping change and the area moment of inertia of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the maximum in the liquid level width continuous region after jumping, and calculating the area moment of inertia of the second substitute liquid level according to an interpolation method.
In general, the area moment of inertia i of the liquid level is calculated by:
Figure BDA0002143480700000121
wherein i is the area moment of inertia of the liquid level; l is the maximum length of the liquid tank; b is the maximum width of the liquid level; k is a dimensionless coefficient and is related to the liquid level property of the liquid level;
calculating the maximum critical liquid level in the case of a sudden change according to the formula (4)Area moment of inertia i1；
Calculating the area moment of inertia i of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the largest in the liquid level width continuous region after jumping according to the formula (4)2；
A surface area moment of inertia i of the second substitute liquid surfacex2Comprises the following steps:
Figure BDA0002143480700000122
or
Figure BDA0002143480700000123
T3, according to the area moment of inertia of different liquid level height or liquid volume calculated in the step T2, making a parameter table or graph of the relation between the area moment of inertia and the different liquid level height or liquid volume of the liquid cabin.
And T4, according to the liquid level height or the liquid volume of the actual liquid level, searching the area moment of inertia corresponding to the actual liquid level from the parameter table or the map manufactured in the step T3, wherein the liquid level height or the liquid volume is a table searching argument, and the area moment of inertia of the liquid level is a searched parameter. If the parameter table does not have the corresponding liquid level height or liquid volume value of the actual liquid level, the area moment of inertia of the actual liquid level is calculated by using a linear interpolation method to look up the table.
The calculation of the area moment of inertia of the actual liquid level by the interpolation method in the step T4 is specifically as follows:
selecting the liquid level height or the liquid level volume corresponding to the first liquid level larger than the actual liquid level in the parameter table or the map in the step T3 as an upper limit liquid level, selecting the liquid level height or the liquid level volume corresponding to the first liquid level smaller than the actual liquid level in the parameter table as a lower limit liquid level, and obtaining the liquid level area moment of inertia i corresponding to the upper limit liquid level by looking up the parameter tablebLiquid level area moment of inertia i corresponding to lower limit liquid levelsCalculating the liquid level area moment of inertia i of the actual liquid level by linear interpolationxComprises the following steps:
Figure BDA0002143480700000131
wherein ixThe liquid level area moment of inertia of the actual liquid level; h is the liquid level height of the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; h isbThe liquid level height value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; h issThe liquid level height value corresponding to the lower limit liquid level is obtained.
Or, calculating the liquid level area inertia moment i of the actual liquid level by adopting a linear interpolation methodxComprises the following steps:
Figure BDA0002143480700000132
wherein ixThe liquid level area moment of inertia of the actual liquid level; v is the liquid volume at the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; v. ofbThe liquid volume value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; v. ofsThe liquid volume value corresponding to the lower limit liquid level is shown.
And T5, calculating the correction of the actual liquid level of the liquid tank to the stability of the cabin according to the area moment of inertia obtained in the step T4.
The actual liquid level is corrected for cabin stability as follows: if the liquid in the tank is not full, the liquid in the tank flows to the inclined side when the ship inclines, so that the gravity center of the liquid moves along with the liquid, and the moment generated by the movement of the gravity center of the liquid before and after the inclination is called free liquid level tilting moment, also called free liquid level tilting moment.
The free liquid level roll moment can reduce the ship stability, so the influence of the roll moment on the ship stability needs to be considered when the ship stability is calculated, and the specific expression is that the free liquid of the liquid corrects the ship stability calibration index. There are many ways to correct this, and the common method is the area moment of inertia method. The specific modifications are as follows:
1) correction of ship initial stability height by free liquid level
Figure BDA0002143480700000133
In the formula:
δGMf.s.-correction of the height of the initial stability by the free liquid level, m;
ixthe area moment of inertia of the free liquid surface, m4；
Rho-liquid density, t/m3.
Initial stability height corrected by free liquid level
GM＝GM0-δGMf.s.(10)
In the formula:
δ gmf.s. -correction of the height of the initial stability by the free liquid level, m;
GM0-initial stability height, m, without free level correction;
GM is the initial stability height, m, corrected by the free liquid level.
2) Correction of free liquid level to ship restoring force arm
For the base point method
GZ＝KN-(KG0+δGMf.s.)·sinθ (11)
In the formula:
GZ-restoring force arm corrected by free liquid level, m;
KH-shape stable moment arm, m,;
KG0-the height of the centre of gravity of the vessel, m, without free level correction;
δ gmf.s. -correction of the height of the initial stability by the free liquid level, m;
theta-ship bank angle, °.
For the assumed center of gravity point method
GZ＝GAZA-(KG0+δGMf.s.-KGA)·sinθ (12)
In the formula:
GZ-restoring force arm corrected by free liquid level, m;
GZZA-restoration arm of force, m, assuming height of center of gravity;
KG0-the height of the centre of gravity of the vessel, m, without free level correction;
KGA-assuming the height of the center of gravity of the vessel, m;
δ gmf.s. -correction of the height of the initial stability by the free liquid level, m;
theta-ship bank angle, °.
For the method of heart-stabilizing point
GZ＝MS+(GM0-δGMf.s.)·sinθ (13)
In the formula:
GZ-restoring force arm corrected by free liquid level, m;
MS-arm of residual stability, m;
GM0-the initial stability height, m, of the vessel not corrected by the free level;
δGMf.s.-correction of the height of the initial stability by the free liquid level, m;
theta-ship bank angle, °.
Example two
Fig. 4 is a schematic cross section of a special tank-shaped liquid tank with a reversed L-shaped cross section and an alternative tank cross section, and fig. 4 shows that the actual liquid level width changes in a jumping decreasing manner as the liquid level height increases. In the figure b1The maximum liquid level width of the critical liquid level when the liquid level is changed in a jumping way; b2The maximum liquid level width of the corresponding liquid level when the liquid level height is highest or the liquid volume is maximum in the continuous liquid level width area after jumping is shown as a dotted line MN, h is the critical liquid level position1The liquid level height of the critical liquid level is the liquid level height when the liquid level width is changed in a jumping way; h is2The height of the liquid level corresponding to the highest liquid level height in the continuous liquid level width area after jumping.
hkB is the liquid level height of the kth liquid level in the liquid level width continuous region after the jump when the liquid level width is changed in a stepwise decreasing mannerkThe width of the substitute liquid level of the substitute liquid tank at the kth liquid level is indicated by a dot-dash line EA, which is a line connecting point E and point a, and is an auxiliary line for determining the substitute liquid level. Then according to the method one or the method twoThe calculation method calculates the area moment of inertia of the liquid level or makes a parameter table or graph of the liquid level height (or liquid volume) and the liquid level area moment of inertia, and calculates the correction of the free liquid surface of the liquid tank on the stability of the cabin.
EXAMPLE III
Fig. 5 is a schematic cross section of a special tank-shaped liquid tank with a positive L-shaped cross section and a cross section of an alternative liquid tank, and fig. 5 shows that the actual width of the liquid level decreases and changes in a jumping manner as the height of the liquid level increases. In the figure b1The maximum liquid level width of the critical liquid level when the liquid level changes in a jumping way; b2The maximum liquid level width of the corresponding liquid level when the liquid level height is highest or the liquid volume is maximum in the continuous liquid level width area after jumping is shown as a dotted line MN, h is the critical liquid level position1The liquid level height of the critical liquid level is the liquid level height when the liquid level width is changed in a jumping way; h is2The height of the liquid level corresponding to the highest liquid level height in the continuous liquid level width area after jumping.
hkB is the liquid level height of the kth liquid level in the liquid level width continuous region after the jump when the liquid level width is changed in a stepwise decreasing mannerkThe width of the substitute liquid level of the substitute liquid tank at the kth liquid level is indicated by a dot-dash line EA, which is a line connecting point E and point a, and is an auxiliary line for determining the substitute liquid level. And then calculating the area moment of inertia of the liquid level or making a parameter table or graph of the liquid level height (or liquid volume) and the area moment of inertia of the liquid level according to the calculation method of the method I or the method II, and calculating the correction of the free liquid surface of the liquid tank on the stability of the ship tank.
According to the three embodiments, the method for correcting the ship stability by the free liquid level of the liquid tank is not only suitable for the liquid tank with the liquid level width continuously changing along with the height change of the liquid level, but also suitable for various liquid tanks with the liquid level width gradually changing along with the height change of the liquid level, and has strong applicability.
In summary, the method for correcting ship stability by using the free liquid level of the liquid tank, particularly the method for correcting ship stability by using the free liquid level with the liquid level width in jumping change along with the height change of the liquid level, is to use a substitute liquid tank method when the liquid level is higher than the critical liquid level. Because the width of the liquid level of the substitute liquid tank is continuously changed, the risk of calculating the free liquid level of the liquid tank with the special shape according to the actual liquid level by adopting an area inertia moment method can be avoided, and based on the improved method for correcting the ship stability of the free liquid level of the liquid tank, the ship stability calculation result corrects the risk of the ship stability when the free liquid level of the liquid tank with the special shape is calculated according to the actual liquid level by adopting the area inertia moment method, and the calculation result is safe and reasonable for actual work.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.

Claims (5)

1. A method for correcting ship stability by using free liquid level of a liquid tank is characterized by comprising the following steps:
s1, determining the liquid level attribute of a preset liquid level, wherein the preset liquid level comprises liquid levels at different liquid level heights and/or liquid levels at different liquid volumes;
s2, calculating the liquid level area moment of inertia of the preset liquid level according to the liquid level attribute;
s3, according to the liquid level area moment of inertia of the preset liquid level calculated in the step S2, making a parameter table or graph of the relation between different liquid level heights and/or different liquid volumes of the liquid cabin and the liquid level area moment of inertia;
s4, according to the liquid level height and/or the liquid volume of the actual liquid level, consulting the parameter table or the map made in the step S3, and determining the liquid level area moment of inertia of the actual liquid level;
s5, calculating the correction of the actual liquid level to the ship stability calibration index according to the liquid level area inertia moment of the actual liquid level obtained in the step S4;
wherein the step S2 specifically includes:
s21, judging whether the width of the preset liquid level can be in a jumping change trend through the critical liquid level:
s21.1, if yes, determining in which region the preset liquid level is located, which specifically includes: s21.11, the preset liquid level is located in the liquid level width continuous area before jumping, and the liquid level area inertia moment of the preset liquid level is calculated according to the liquid level attribute; or S21.12, the preset liquid level is located in the liquid level width continuous area after jumping, the liquid level area inertia moment corresponding to the preset liquid level is calculated by adopting a substitute liquid tank method, and the step S3 is switched to;
if the width of the liquid level of the liquid tank can be changed in a jumping manner, the tank body is divided into a liquid level width continuous region before jumping and a liquid level width continuous region after jumping; the liquid level width continuous area before jumping is as follows: with the increase of the height of the preset liquid level, the width of the preset liquid level is a liquid level height range or a liquid volume range which is continuously changed; the liquid level width continuous area after jumping is as follows: the method comprises the following steps that (1) as the height of a preset liquid level increases, the preset liquid level passes through a certain critical liquid level, the width of the preset liquid level has a jumping change, after the jumping change, as the height of the preset liquid level increases, the width of the preset liquid level is a liquid level height range or a liquid volume range which changes continuously; the critical liquid level is: along with the increase of the height of the liquid level, presetting the corresponding liquid level when the liquid level width is subjected to jumping change;
s21.2, if not, calculating the area moment of inertia of the liquid level corresponding to the preset liquid level according to the liquid level attribute of the preset liquid level, and turning to the step S3;
the alternative liquid tank method adopts a first alternative liquid level method or a second alternative liquid level method;
the substitute liquid tank method adopts a first substitute liquid level method, and the first substitute liquid level method is as follows: replacing the preset liquid level with the first substitution liquid level, replacing the width of the preset liquid level with the width of the first substitution liquid level, and directly calculating the liquid level area inertia moment of the first substitution liquid level;
the first alternative liquid level method specifically comprises the following:
the first alternative liquid surface width bxIs composed of
Figure FDA0002433724250000021
Or
Figure FDA0002433724250000022
Wherein, b1The maximum liquid level width of the critical liquid level when the liquid level changes in a jumping way; b2The maximum liquid level width of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the maximum in the liquid level width continuous area after jumping; h isxIs the level of the first replacement level; h is1The liquid level height of the critical liquid level is the liquid level height when the liquid level width is changed in a jumping way; h is2The height of the liquid level corresponding to the highest liquid level height in the continuous area of the liquid level width after jumping, v1The volume of liquid corresponding to the critical liquid level when the liquid level width changes in a jumping way, v2Is the volume of liquid after jumping corresponding to the maximum volume of liquid in the continuous region of the liquid level widthxThe volume of liquid corresponding to the first substitution level;
a surface area moment of inertia i of the first alternate liquid surfacex1Is composed of
Figure FDA0002433724250000023
Wherein ix1Is the area moment of inertia of the first surrogate liquid level; l is the maximum length of the liquid tank; bxIs the width of the first surrogate liquid level; k is a dimensionless coefficient related to the level property of the first substitute level;
the alternative liquid tank method adopts a second alternative liquid level method,
the second alternative liquid level method is as follows: replacing the preset liquid level with a second substitute liquid level, calculating the maximum area moment of inertia of the critical liquid level during the jumping change and the area moment of inertia of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the maximum in the liquid level width continuous region after jumping, and calculating the area moment of inertia of the second substitute liquid level according to an interpolation method;
the second alternative liquid level method specifically comprises the following:
the calculation method of the liquid level area moment of inertia i of the liquid level comprises the following steps:
Figure FDA0002433724250000024
wherein i is the area moment of inertia of the liquid level; l is the maximum length of the liquid tank; b is the maximum width of the liquid level; k is a dimensionless coefficient and is related to the liquid level property of the liquid level;
calculating the maximum area moment of inertia i of the critical liquid level in the case of a jumping change according to the formula (4)1；
Calculating the area moment of inertia i of the corresponding liquid level when the liquid level height is the highest or the liquid volume is the largest in the liquid level width continuous region after jumping according to the formula (4)2；
Calculating the liquid level area moment of inertia i of the second substitute liquid level by interpolationx2Comprises the following steps:
Figure FDA0002433724250000031
or
Figure FDA0002433724250000032
2. The method for correcting vessel stability with tank free level according to claim 1,
the liquid level attributes of the preset liquid level specifically include: the shape, width and length of the liquid surface.
3. The method for modifying vessel stability with tank free level according to claim 1, wherein the alternative tank method in step S21.12 comprises the following:
the preset liquid level is located in the liquid level width continuous region after jumping, and the range of the substitute liquid tank is a region determined by the top surface of the liquid level width continuous region after jumping and the critical liquid level during jumping change; the substitute liquid level of the preset liquid level is the liquid level corresponding to the liquid level height or the liquid volume of the preset liquid level in the substitute liquid tank.
4. The method for correcting vessel stability with tank free level according to claim 1,
in step S3, a parameter table or map is created based on the liquid level height value or the liquid volume value of the arithmetic progression.
5. The method for correcting ship stability according to claim 1, wherein in step S4, when there is no corresponding liquid level height or liquid volume value of the actual liquid level in the parameter table, the liquid level area moment of inertia of the actual liquid level is calculated by interpolation;
the specific method for calculating the liquid level area inertia moment of the actual liquid level by adopting an interpolation method comprises the following steps:
selecting the liquid level corresponding to the first liquid level height or liquid level volume larger than the actual liquid level in the parameter table as the upper limit liquid level, selecting the liquid level corresponding to the first liquid level height or liquid level volume smaller than the actual liquid level in the parameter table as the lower limit liquid level, and looking up the parameter table to obtain the liquid level area inertia moment i corresponding to the upper limit liquid levelbLiquid level area moment of inertia i corresponding to lower limit liquid levelsCalculating the liquid level area moment of inertia i of the actual liquid level by linear interpolationxComprises the following steps:
Figure FDA0002433724250000041
wherein ixThe liquid level area moment of inertia of the actual liquid level; h is the liquid level height of the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; h isbThe liquid level height value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; h issThe liquid level height value corresponding to the lower limit liquid level;
or, calculating the liquid level area inertia moment i of the actual liquid level by adopting a linear interpolation methodxComprises the following steps:
Figure FDA0002433724250000042
wherein ixThe liquid level area moment of inertia of the actual liquid level; v is the liquid volume at the actual liquid level; i.e. ibThe area moment of inertia of the liquid level corresponding to the upper limit liquid level; v. ofbThe liquid volume value corresponding to the upper limit liquid level is set; i.e. isThe liquid level area inertia moment corresponding to the lower limit liquid level; v. ofsThe liquid volume value corresponding to the lower limit liquid level is shown.
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