JP2010018242A - Low vibration marine vessel structure and its design method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low vibration marine vessel structure reducing effective excitation force of propeller excitation force effectively utilizing a joint and a body of a vibration mode. <P>SOLUTION: In the low vibration marine vessel structure, a hull main structure has an inherent main hull upper and lower joint vibration mode. An acting position L1 of the propeller excitation force F and a joint position N1' of the main hull upper and lower joint vibration mode are made coincident with each other by an excitation frequency fp of the propeller excitation force F, and an excitation component of the propeller excitation force, i.e., an effective excitation force component can be reduced or eliminated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a low vibration ship structure applied to a ship having a stern cant, such as a gas tanker or a container ship, and a design method thereof.

Conventionally, in the anti-vibration design of a ship, eigenvalue analysis is performed on the main structure of the ship's hull, and a structure and a design that avoid resonance with the main vibration component are assumed. Therefore, in order to avoid resonance with a main vibration component such as a propeller vibration force, a large structural reinforcement may be required for the main hull structure of the ship. Such structural reinforcement is not preferable because it requires a great deal of cost.
As a conventional technique related to vibration isolation of a ship, a stern overhanging part structure has been proposed in which hull vibration generated by the vibration force of a propeller is reduced. (For example, see Patent Document 1)
JP 59-77997 A

As described above, in the anti-vibration design and anti-vibration structure of a ship, in order to avoid the resonance with the effective excitation force caused by the propeller excitation force, a large amount of cost is required by performing large-scale structural reinforcement. There is a case. For this reason, it is desired to effectively utilize the nodes and antinodes of the vibration mode and eliminate the structural reinforcement to avoid resonance.
The present invention has been made in view of the above circumstances, and the object of the present invention is to reduce the effective vibration force of the propeller vibration force by effectively utilizing the nodes and bellies of the vibration mode. It is to provide a ship structure and a design method thereof.

In order to solve the above problems, the present invention employs the following means.
The low-vibration ship structure according to the present invention is a low-vibration ship structure in which the hull main structure has a unique main hull upper and lower vibration mode. The node position is the same as the vibration frequency of the propeller vibration force.

  According to such a low-vibration ship structure, the position of the propeller vibration force and the node position of the main hull upper and lower vibration mode match (intersect) at the vibration frequency of the propeller vibration force. The vibration component of the propeller vibration force, which is an effective vibration force component, can be reduced or eliminated.

In the above invention, the node position of the main hull vertical joint vibration mode is preferably adjusted by changing the rigidity of the main structure of the hull. It can be matched to the working position.
In this case, the rigidity of the hull main structure can be changed by adjusting any one of the height of the sunken deck, the vertical wall in the stern structure, the stern length, and the stern cross-sectional shape, or a combination thereof.

In the above-mentioned invention, it is preferable that the action position of the propeller vibration force is adjusted by movement of the propeller position, so that the action position of the propeller vibration force coincides with the node position of the main hull upper and lower vibration mode. be able to.
In this case, the movement of the propeller position means changing the shape and / or length around the boshing.

  The design method of a low vibration ship structure according to the present invention is a design method of a low vibration ship structure in which the main hull structure has a unique main hull upper and lower vibration mode. The node position of the vibration mode is matched with the vibration frequency of the propeller vibration force.

  According to such a low-vibration ship structure design method, the effective position of the propeller vibration force and the node position of the main hull upper / lower vibration mode are matched with the vibration frequency of the propeller vibration force. The vibration component of the propeller vibration force that is the vibration force component can be reduced or eliminated.

  According to the present invention described above, since the vibration component of the propeller vibration force, which is an effective vibration force component, is reduced or eliminated, the effective vibration generation of the propeller vibration force can be achieved by effectively utilizing the nodes and the belly of the vibration mode. It is possible to provide a low vibration ship structure with reduced vibration force and a design method thereof.

Hereinafter, an embodiment of a low vibration ship structure and a design method thereof according to the present invention will be described with reference to the drawings.
FIG. 1 shows a main hull upper / lower vibration mode for a ship provided with a bulging part (stern space) called a stern cant at the stern part such as a gas tanker (LNG ship, LPG ship) or a container ship. It is explanatory drawing which showed the node position. This main hull upper / lower vibration mode is an inherent vibration mode of the main hull structure of the ship.

In the ship 1 shown in FIG. 1, a sunken deck 3 lower than the upper deck is provided at the stern part of the ship 1 having the stern cant 2. In addition, the code | symbol 4 in a figure is a propeller which gives the propulsive force to the ship 1. FIG.
Moreover, in FIG. 1, the node position N is shown with the continuous line N1-N4 about the intrinsic | native main hull upper and lower node vibration mode which the hull main structure of the ship 1 has. The horizontal axis in this case is the longitudinal position of the ship 1, and the vertical axis is the frequency. The longitudinal position in FIG. 1 indicates the direction of the ship 1, and the left side of the page is the stern side of the ship 1.

On the stern side of the ship 1, due to the rotation of the propeller 4, a propeller vibration force is generated as indicated by an arrow F in the figure. In the example shown in the figure, the frequency (propeller vibration frequency) of the propeller vibration force F is fp, and the node position N that coincides with the frequency fp at the action point (propeller vibration point) L1 of the propeller vibration force F is Absent. That is, at the action point L1, which is the action position of the propeller vibration force F, the solid line N1 to N4 indicating the node position N has a ship structure that does not intersect the frequency fp.
Therefore, in the low vibration ship structure of the present invention, the position L1 of the propeller vibration force F and the node position N in the main hull upper / lower hull vibration mode inherent to the hull main structure are vibrated with the propeller vibration force F. They are matched at the frequency fp. That is, in the low vibration ship structure of the present invention, the node position N in the main hull upper / lower knot mode is adjusted so as to intersect the excitation frequency fp at the point of action L1 by changing the rigidity of the hull main structure in the ship 1. Has been.

Hereinafter, a specific example of adjusting the node position N in the main hull upper / lower knot mode by changing the rigidity of the hull main structure will be described as a first embodiment with reference to FIGS.
In the ship 1A of the first embodiment, the height H of the sunken deck 3 is adjusted to H 'so that the stern rigidity of the hull main structure is increased. As a result, the node position N1 indicated by the solid line in FIG. 1 has an increased inclination due to the improved rigidity, as indicated by the broken line N1 ′ in the figure.

Accordingly, in the ship 1A described above, the point a on the node position N1 that was at the frequency position lower than the excitation frequency fp at the operating point L1 moves to the upper point b and coincides with the excitation frequency fp of the propeller 4. To do.
That is, since the ship 1A changes the rigidity of the hull main structure by adjusting the height of the sunken deck 3, if the inclination change of the node position N1 is adjusted by this rigidity change, at the point of action L1 of the propeller vibration force F, The node position N1 in the main hull upper / lower node mode can be crossed with the excitation frequency fp at the point b. In other words, in the ship 1A in which the rigidity of the hull main structure is changed by adjusting the height of the sunken deck 3, the frequency at which the node position N1 exists increases from the point a to the point b. At the action point L1, the node position N1 in the main hull upper / lower node mode can be crossed with the excitation frequency fp at the point b.

According to such a low-vibration ship structure, the action position (action point) L1 of the propeller vibration force F and the node position N1 ′ in the main hull vertical joint vibration mode have the vibration frequency fp of the propeller vibration force F. Therefore, the excitation component of the propeller excitation force F, which is an effective excitation force component for the ship 1A, can be reduced or eliminated.
Further, the adjustment of the rigidity by changing the height of the sunken deck 3 includes raising the sunken deck 3 to the same height as the upper deck and changing the structure to make it lower than the current sunken deck 3. That is, as in the modified example shown in FIG. 3, the point a on the node position N1 may be raised to the point b by changing the rigidity, or the point c at the node position N2 is lowered to the point b. Changes may be made.

Subsequently, the first embodiment for adjusting the node position N in the main hull upper and lower node mode by changing the rigidity of the main structure of the hull will be described with reference to FIGS. To do.
In the ship 1 of the first modified example shown in FIG. 4, the rigidity of the hull main structure is adjusted by the vertical wall 10 in the stern structure shown hatched in the figure. The vertical wall 10 is a vertical wall member installed so as to partition the width direction of the stern space formed in the stern cant 2 and extends in the length direction of the stern space.

  In the illustrated ship 1, a lower vertical wall 10a and an upper vertical wall 10b exist. One lower vertical wall 10 a is provided over the entire length with respect to the lower space of the stern cant 2. The other upper vertical wall 10 b is provided up to a substantially intermediate position on the bow side with respect to the upper space of the stern cant 2. That is, in the illustrated stern cant 2, the vertical wall 10 is provided up to the height of the sunken deck 3 in a range that is a substantially middle position on the bow side, and the vertical wall 10 is provided in the sunken deck 3 in a substantially half range on the stern side. It is provided up to a substantially middle position.

As for the vertical wall 10 in such a stern structure, for example, as shown in the ship 1B in the illustrated example, the vertical wall 11 is additionally provided so as to extend the upper vertical wall 10b to the stern, thereby changing the shape of the hull main structure. The rigidity is improved. On the contrary, the rigidity of the main structure of the hull is lowered by changing the shape in which the upper vertical wall 10b is abolished or by changing the shape in which the opening 12 is provided in the lower vertical wall 10a, as in the illustrated ship 1B ′. .
In addition, adjustment of the rigidity by the shape change of the vertical wall 10 described above is not limited to that shown in FIG. 4, and the number of divisions in the vertical direction, the presence or absence of the ship direction, the presence or absence of the opening 12, etc. Combinations and changes can be made as necessary.

The second modification shown in FIG. 5 adjusts the rigidity of the hull main structure by changing the number of vertical walls 10 installed in the ship width direction. That is, when the number of vertical walls is increased by adding auxiliary vertical walls 13 to the vertical walls 10 that define the space of the stern cant 2 as in the illustrated ship 1C, the rigidity of the hull main structure is improved.
In addition, such a change in the number of vertical walls is combined with the change in the vertical wall shape described above, whereby the adjustable range of rigidity is expanded and the adjustment is facilitated.

The third modification shown in FIG. 6 adjusts the rigidity of the hull main structure by changing the stern length in the ship 1 having the stern cant 2. That is, the rigidity of the hull main structure is adjusted by increasing or decreasing the length of the stern cant 2 forming the stern space.
In the ship 1D of the illustrated example, the length L of the stern space where the sunken deck 3 is formed is extended by Sa to the stern side to decrease the rigidity, or is shortened by Sb to the bow side to increase the rigidity. The rigidity of the main structure of the hull is adjusted by improving it.
Such a change in the stern length is combined with the change in the vertical wall shape and the number of vertical walls described above, so that the adjustable range of rigidity is expanded and the adjustment is facilitated.

The fourth modification shown in FIG. 7 adjusts the rigidity of the hull main structure by changing the cross-sectional shape of the stern in the ship 1 having the stern cant 2. That is, as shown in FIG. 7 showing the AA cross-sectional shape of FIG. 6, if the cross-sectional shape (2 ′ indicated by a one-dot chain line) slimmed from the standard shape of the stern cant 2 indicated by the solid line is improved, the rigidity is increased and the size is enlarged If the cross-sectional shape is changed (2 ″ indicated by a two-dot chain line), the rigidity is lowered.
Such a change in the stern cross-sectional shape is combined with the change in the vertical wall shape, the number of vertical walls, and the stern length described above, thereby expanding the adjustable range of rigidity and facilitating the adjustment.

Hereinafter, a specific example of adjusting the node position N in the main hull upper and lower node mode by moving the propeller vibration generating position will be described as a second embodiment with reference to FIG. In addition, the same code | symbol is attached | subjected to the part similar to the Example mentioned above, and the detailed description is abbreviate | omitted.
In the ship 1E of this embodiment, for example, the position of the propeller 4 is moved backward toward the stern side by ΔL. That is, the installation position of the propeller 4 is structured to match the node position N in the main hull vertical joint vibration mode, and the propeller 4 is moved to the position of the propeller 4 '.
As a result, the vibration force acting position of the propeller 4 'also moves to the stern side from L1 to L2, and intersects the node position N1 at the point d at the propeller vibration frequency fp. In this case, the position movement of the propeller 4 may be dealt with by changing the shape and length around the boshing 4.

According to such a low-vibration ship structure, the action position (action point) L2 of the propeller vibration force F and the node position N1 in the main hull vertical joint vibration mode are at the vibration frequency fp of the propeller vibration force F. Since they coincide, it is possible to reduce or eliminate the vibration component of the propeller vibration force F, which is an effective vibration force component for the ship 1E.
It should be noted that such a change in the operation position of the propeller vibration force F can be combined with the change in the rigidity of the main structure of the hull in the first embodiment described above, and the adjustment can be facilitated by expanding the adjustable range of the rigidity. , Design flexibility is improved.

  The low-vibration ship structure described above is a design method in which the operating position of the propeller vibration force F and the node position N in the main hull upper and lower vibration mode are matched with the vibration frequency fp of the propeller vibration force F. The vibration generating component of the propeller vibration generating force F, which is an effective vibration generating force component, can be reduced or eliminated.

As described above, the effective positions N1 and N2 of the propeller vibration force F and the node positions N1 and N1 ′ in the main hull vertical vibration mode are made to coincide with each other by the vibration frequency fp of the propeller vibration force F. It is possible to reduce or eliminate the vibration component of the propeller vibration force F, which is a strong vibration component. That is, since the effective vibration force that the propeller vibration force F acts on the hull structure can be reduced by using the vibration mode antinode / node position, resonance avoidance itself becomes unnecessary and the hull structure needs to be reinforced. Also disappear.
In other words, the effective vibration force is reduced by adjusting the position of the propeller vibration force F to the node position N in the main hull upper and lower vibration mode, so that hull vibration is induced regardless of the magnitude of the propeller vibration force F. The effective force to do this is reduced, and the hull vibration itself is also reduced.

Further, since the restriction on the propeller vibration force F is reduced, the propulsion efficiency of the propeller 4 can be improved.
In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably.

It is explanatory drawing which shows 1st Example about the low vibration ship structure and its design method which concern on this invention. It is explanatory drawing which shows the example which adjusts the rigidity of the hull main structure by adjustment of sunken deck height. It is explanatory drawing which shows a modification about the node position of the main hull upper and lower node vibration mode. It is explanatory drawing which shows the 1st modification of 1st Example. It is explanatory drawing which shows the 2nd modification of 1st Example. It is explanatory drawing which shows the 3rd modification of 1st Example. It is explanatory drawing which shows the 4th modification of 1st Example. It is explanatory drawing which shows 2nd Example about the low-vibration ship structure which concerns on this invention, and its design method.

Explanation of symbols

1,1A-1E Ship 2 Stern Kant 3 Sunken Deck 4 Propeller

Claims (5)

In the low vibration ship structure where the hull main structure has its own main hull upper and lower section vibration mode,
A low-vibration ship structure characterized in that an action position of a propeller vibration force and a node position in the main hull vertical vibration mode coincide with each other at a vibration frequency of the propeller vibration force.   The low vibration ship structure according to claim 1, wherein a node position in the main hull vertical joint vibration mode is adjusted by changing a rigidity of the main hull structure.   The low vibration ship structure according to claim 2, wherein the rigidity of the hull main structure is adjusted by at least one of a sunken deck height, a vertical wall in the stern structure, a stern length, and a stern cross-sectional shape. .   The low-vibration ship structure according to claim 1, wherein an operation position of the propeller vibration generating force is adjusted by movement of the propeller position. In the design method of a low vibration ship structure in which the main structure of the hull has an inherent main hull upper and lower vibration mode,
A design method for a low-vibration ship structure, wherein an action position of a propeller vibration force and a node position of the main hull upper / lower vibration mode are made to coincide with each other at a vibration frequency of the propeller vibration force.

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