CN117963104A - Method for judging ship bottom pollution state - Google Patents
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Abstract
A method for judging the dirty bottom state of a ship establishes a ship navigation and environmental data acquisition, storage and processing system and screens abnormal data. And selecting the navigational speed loss value of the ship in the actual operation state under the same host power compared with the navigational speed loss value in the clean ship body state as a quantitative evaluation object of the pollution bottom degree, and completing the navigational speed loss value calculation in the whole period to be evaluated. And carrying out regression statistics and trend analysis on the calculated navigational speed loss values in the whole period to be evaluated, and taking the ratio of the navigational speed loss values corresponding to all moments in the trend line to the preset navigational speed loss values to be docked for cleaning as a judging condition of the ship pollution bottom degree. The ship pollution bottom state judging method established by the invention can realize quantitative characterization of the pollution bottom degree of the ship without additional software and hardware investment, and effectively saves manpower and material resources. The influence of irrelevant environmental conditions on the evaluation result is effectively eliminated, and the operation convenience is considered while the calculation efficiency is ensured.
Description
Technical Field
The invention belongs to the field of ship construction and design, and particularly relates to a method for judging a ship bottom state.
Background
The attached accumulation of aquatic organisms in the portion below the waterline of the ship is called a ship's sump. The ship bottom reduces the surface finish of the ship body, increases the sailing resistance, reduces the sailing speed, and further can cause the improvement of the fuel consumption of the ship and the corresponding pollutant emission. Meanwhile, the corrosion of the steel plate at the bottom of the ship can be accelerated by the local slightly acidic environment caused by biological metabolism, so that the normal work of a seawater cooling system, a depth finder, a log, sonar and the like of the ship is influenced, and the safety of the ship is endangered in severe cases.
At present, ships can inhibit the adhesion of aquatic organisms by adopting various measures, but the formation of ship pollution bottom cannot be completely avoided, and the ships need to be regularly docked for outer plate cleaning. The precondition of dock cleaning is to accurately grasp the pollution bottom degree of the ship. The existing ship dirty bottom state judging method is mainly divided into static observation and dynamic monitoring. The static observation needs to shoot and record the outer plate state of the ship through a diver or a robot carrying shooting equipment in the ship stopping state, and huge manpower and material resource investment is often needed. Dynamic monitoring requires additional sensors and software systems, with poor reliability and high initial investment costs.
Disclosure of Invention
In order to solve the problems, the invention provides a method for judging the ship bottom state, which adopts the following technical scheme:
a judging method for the ship dirty bottom state comprises the following steps:
S1: the method comprises the steps of monitoring ship navigation and environmental data, wherein the data to be monitored are a ship ground speed Vs, a host power Pe, a displacement delta, a bow draft Tf, a stern draft Ta, a relative wind speed AWS, a relative wind direction AWA, a water depth Dp, a wave height HWAVE, a surge height HSWELL, a flow velocity Vc, a flow direction Dc, a sea water temperature Tem_w, a sea water density ρS, an air temperature Tem_a, an air pressure P_a and an air density ρA;
Sequentially calculating the average difference value of each data point and the nearest 10 data points of the data points, comparing the average difference value with a threshold value, if the average difference value is larger than the threshold value, judging the data points as abnormal points, and eliminating the abnormal points to obtain the screened collected data values;
S2: obtaining a 'speed-power' corresponding value of a ground speed Vs of a target ship under design draft, structural draft and ballasted draft with respect to a host power Pe through a static water ship model test, wherein the corresponding value is the speed power characteristic of the target ship under the condition without any pollution bottom;
(1) Converting the environmental wind, wave, surge, sea water temperature, density and displacement parameters screened in the step S1 into an increase or decrease value delta P of host power, wherein the specific conversion is as follows:
Resistance R AA caused by ambient wind:
wherein A XV is the transverse projection area of the superstructure above the waterline of the target ship;
C AA (AWA) and C AA (0) are resistance coefficients at 0 degrees and AWA, respectively, relative to wind direction, and are obtained by the STA-JIP database;
resistance R WL caused by waves and surges:
Wherein g is gravity acceleration, B is target ship type width,
L BWL is the distance from the bow of the target vessel to 95% of the maximum width of the waterline,
H 1/3 is sense wave height:
resistance R AS caused by seawater temperature and density:
Wherein ρ S0 is the sea water density in standard state, the water temperature is 15 ℃, the density is 1026kg/m 3,
R T0 is the total resistance in the reference state,
R F is the friction resistance of the target ship in the current state,
S is the wet surface area of the target vessel,
C T0 is the total drag coefficient in standard condition,
C F0 is the coefficient of friction resistance in the standard state,
C F is the friction resistance coefficient of the ship with the bubble drag reduction system in the current state,
C T0,CF0,CF can be obtained by a still water ship model test;
resistance R ADIS caused by displacement:
wherein delta 0 is the displacement closest to the current displacement delta of the target ship among the displacement corresponding to the design draft, the structural draft and the ballast draft in the ship model test,
R T0 is the total resistance of the target ship under the condition of eating, and can be obtained through a ship model test;
The total resistance increase ΔR is the sum of the resistance values increased by the above factors, namely:
ΔR＝RAA+RWL+RAS+RADIS
The increase in total drag translates into an increase or decrease in host power deltap,
Wherein eta Did is the propulsion efficiency coefficient of the target ship under the current draft and navigational speed Vs in the windless, wave-less and flueless state, can be obtained through a ship model test,
Xi P is the load coefficient, which can be obtained by ship model test;
(2) Converting the parameters of the flow speed, the flow direction and the water depth after the screening in the step S1 into an increase or decrease value DeltaV of the speed of the ground, wherein the increase or decrease value DeltaV c of the speed of the ground is caused by the flow speed and the flow direction:
Vector decomposition is carried out on the flow velocity Vc and the flow direction Dc along the ship navigation direction to obtain a component Vcx of the flow velocity Vc along the ship navigation direction and a component Vcy vertical to the ship navigation direction,
Wherein Vcx is the increase or decrease value of the speed to ground caused by the flow velocity and the flow direction, Δv c =vcx;
the increase or decrease in speed to ground caused by water depth is a value of DeltaV d:
the water depth correction threshold h is calculated according to the following formula:
if the water depth Dp is greater than the correction threshold h, the water depth has no effect on the speed of the ground, i.e. Δv d =0,
If the water depth Dp is smaller than the correction threshold h, the increase or decrease value of the speed to the ground caused by the water depth is calculated according to the following formula:
wherein A M is the area of the part below the water line of the section in the target ship;
the increase value or decrease value DeltaV of the speed to ground is the sum of the change values caused by the factors, namely:
ΔV＝ΔVc+ΔVd；
(3) Combining the ground speed Vs and the host power Pe screened in the step S1 with the ground speed increase or decrease value Δv and the host power increase or decrease value Δp, respectively, to obtain a corrected ground speed Vs corr and a corrected host power Pe corr:
VScorri＝VS+ΔV
Pecorri＝Pe+ΔP
thus, the navigational speed power characteristic correction aiming at the group of recorded data is completed; the data is recorded at regular intervals. The data recorded each time is referred to as a set of data.
Performing navigational speed power characteristics on all recorded data according to the correction methods (1) (2) (3) to form corrected navigational speed Vs corri (i=1, 2, …) and host power Pe corri (i=1, 2, …) so as to finish navigational speed power characteristic correction of the target ship in the whole data acquisition period range;
s3: establishing a two-dimensional rectangular coordinate system by taking the ground speed Vs as a horizontal axis and the host power Pe as a vertical axis, and drawing a Pe-Vs curve of the host power Pe relative to the ground speed Vs, which is obtained in the specific underwater static water ship model test in the step S2, in the two-dimensional rectangular coordinate system;
taking the ground speed Vs corri (i=1, 2, …) and the host power Pe corri (i=1, 2, …) obtained by correction in the step S2 as characteristic points, and determining the translation quantity delta Vs of the Pe-Vs curve, which is required to translate along a Vs axis, relative to the characteristic points by using a least square method, wherein the delta Vs is a speed loss value of the ship during actual sailing compared with a clean hull condition;
S4: repeating steps S2-S3 until the translation amount Δvs i (i=1, 2, …) within the whole data acquisition period range is completed;
s5: taking time as an independent variable and delta Vs as an independent variable, and establishing a two-dimensional rectangular coordinate system;
Performing unitary linear regression on each navigational speed loss value DeltaVs i obtained in the step S4 to obtain a trend function f (DeltaVs) of DeltaVs with respect to time, wherein DeltaVs_c i (i=1, 2, …) corresponding to each moment in the trend function f (DeltaVs) is the equivalent navigational speed loss value of the ship at the moment;
A speed loss threshold deltavs_set for dock cleaning is preset, the ratio CV S of the equivalent ship speed loss value deltavs_c i (i=1, 2, …) at each moment and the speed loss threshold deltavs_set is defined as a pollution bottom coefficient for quantitatively representing the pollution bottom degree of the ship,
When CVS is more than or equal to 0 and less than 0.25, the dirty bottom state is slight;
when CVS is more than or equal to 0.25 and less than or equal to 0.5, the dirty bottom state is mild;
when CVS is more than or equal to 0.5 and less than or equal to 0.75, the state of the sewage bottom is medium;
when CVS is more than or equal to 0.75 and less than or equal to 1.0, the dirty bottom state is 'severe';
When the CVS is more than or equal to 1.0, the dirty bottom state is 'dirty to be cleaned'.
In the above method for determining the ship bottom state, in step S5, a two-dimensional rectangular coordinate system is established by taking time as a horizontal axis and Δvs as a vertical axis, and each navigational speed loss value Δvsi calculated in step S4 is drawn in the two-dimensional rectangular coordinate system to form a navigational speed loss value scatter diagram at each moment;
And adding trend lines of all scattered points into the scattered points of the navigational speed loss value, representing the trend of the ship bilge by using the trend lines, and taking delta Vs_ci (i=1, 2, …) corresponding to all moments in the trend lines as equivalent navigational speed loss values of the ship at the moment.
In the above method for determining a ship bottom state, in step S1, data is collected and stored at intervals of "10 seconds".
In the method for judging the ship bottom state, the ship ground speed Vs, the bow draft T f, the stern draft T a, the sea water temperature tem_w, the sea water density ρ S, the air temperature tem_a, the air pressure p_a, the air density ρ A and the threshold value are 1;
The wave height H WAVE, the surge height H SWELL, the relative wind speed AWS, the relative wind direction AWA, the water depth Dp, the flow velocity Vc, the flow direction Dc and the threshold value are taken as 10; the threshold is set to 50 for the displacement Δ, the main power Pe.
In the above-mentioned method for determining a ship bottom state, in step S5, the speed loss threshold Δvs_set=1 knots.
In the above method for determining a ship bottom state, in step S2, C T0、CF、CF0、RT0、ηDid、ξP may be obtained through a ship model test.
The ship pollution bottom state judging method established by the invention can realize quantitative characterization of the pollution bottom degree of the ship without additional software and hardware investment, and effectively saves manpower and material resources. The quantitative evaluation algorithm effectively eliminates the influence of irrelevant environmental conditions on the evaluation result, ensures the calculation efficiency and simultaneously gives consideration to the operation convenience. Through actual ship application verification, the method for judging the dirty bottom state established by the invention has higher accuracy and can be reliably applied to ship dirty bottom state monitoring and dirty bottom degree judgment.
Drawings
FIG. 1 is a diagram of the steps of the method;
FIG. 2 is a graph of Pe-Vs;
FIG. 3 is a schematic diagram of the Pe-Vs curve translated by a translation amount ΔVs along the Vs axis relative to the feature points;
Fig. 4 is a schematic diagram in which each scatter trend line is added to a scatter plot having the horizontal axis and the vertical axis of the shift amount Δvs.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
As shown in fig. 1, the present embodiment provides a method for determining a ship bottom state, including:
Step S1: monitoring ship navigation and environmental data, comprising: the ship has a ground speed Vs, a main power Pe, a displacement delta, a bow draft Tf, a stern draft Ta, a relative wind speed AWS, a relative wind direction AWA, a water depth Dp, a wave height H WAVE, a surge height H SWELL, a flow velocity Vc, a flow direction Dc, a sea water temperature Tem_w, a sea water density ρ S, an air temperature Tem_a, an air pressure P_a and an air density ρ A. The data is preferably collected and stored at "10 second" intervals.
And then screening the acquired data, and eliminating abnormal data values. Specifically, the average difference between each data point and the 10 data points nearest thereto is calculated for each data point in turn, and the calculated difference is compared with a threshold value, and if the calculated difference is larger than the threshold value, the data point is regarded as an abnormal point. For the ship ground speed Vs, the bow draft T f, the stern draft T a, the sea water temperature Tem_w, the sea water density rho S, the air temperature Tem_a, the air pressure P_a and the air density rho A, the threshold value is 1; for the wave height H WAVE, the surge height H SWELL, the relative wind speed AWS, the relative wind direction AWA, the water depth Dp, the flow velocity Vc and the flow direction Dc, and the threshold value is 10; for displacement delta, the host power Pe, the threshold is taken to be 50. And taking the screened collected data value as input for quantitative calculation of the ship pollution bottom degree.
Step S2: and converting the environmental parameters into an increased value or a decreased value of the ship ground speed and the host power by using a certain correction method so as to realize the result of correcting the monitored ship ground speed and host power to a specific no-wind, no-wave and no-flow under the condition of no-water. The method comprises the following steps:
And obtaining the 'speed-power' corresponding value of the ground speed Vs of the target ship under the design draft, structural draft and ballasted draft with respect to the host power Pe through a static water ship model test, wherein the corresponding value is the speed power characteristic of the target ship under the condition without any pollution bottom.
And then converting the parameters of the environmental wind, wave, surge, sea water temperature, density and water displacement after the screening in the step S1 into the increase or decrease value of the power of the host, specifically:
The calculation formula of the resistance R AA caused by the ambient wind is as follows:
Wherein A XV is the transverse projection area of the superstructure above the waterline of the target ship; c AA (AWA) and C AA (0) are drag coefficients at 0 degrees and AWA, respectively, relative to wind direction, and are obtained from the STA-JIP database.
The calculation formula of the resistance R WL caused by waves and surges is as follows:
Wherein g is gravity acceleration, and B is the target ship type width; l BWL is the distance from the bow of the target ship to 95% of the maximum width of the waterline; h 1/3 is sense wave height:
The calculation formula of the resistance R AS caused by the temperature and the density of the seawater is as follows:
Wherein ρ S0 is the sea water density in the standard state, the water temperature in the standard state is 15 ℃, and the density is 1026kg/m 3;RT0, which is the total resistance in the reference state; r F is the friction resistance of the target ship in the current state; s is the wet surface area of the target ship; c T0 is the total resistance coefficient in the standard state, C F0 is the friction resistance coefficient in the standard state, C F is the friction resistance coefficient in the current state of the ship with the added bubble drag reduction system, and C T0,CF0,CF can be obtained through a still water ship model test.
The calculation formula of the resistance R ADIS caused by the water displacement is as follows:
wherein delta 0 is the displacement closest to the current displacement delta of the target ship among the displacement corresponding to the design draft, the structural draft and the ballast draft in the ship model test; r T0 is the total resistance of the target ship under the condition of eating, and can be obtained through a ship model test.
The total resistance increase ΔR is the sum of the resistance values increased by the above factors, namely:
ΔR＝RAA+RWL+RAS+RADIS
The calculation formula for the conversion of the total resistance increment into the increase or decrease in the host power Δp is as follows:
Where η Did is the coefficient of propulsion efficiency of the target vessel in the windless, wave-less, no-current state at the current draft and voyage speed Vs, and can be obtained by model test. And xi P is a load coefficient, and can be obtained through a ship model test. And (3) converting the parameters of the environmental wind, wave, surge, sea water temperature, density and displacement after the screening in the step (S1) into the increase or decrease value of the power of the host machine.
Further, the flow speed, flow direction and water depth parameters screened in the step S1 are converted into increasing or decreasing values of the speed of the ground navigation, specifically:
The increase or decrease in speed to ground caused by the flow rate, direction, deltaV c is calculated as follows:
Vector decomposition is carried out on the flow velocity Vc and the flow direction Dc along the ship navigation direction, and a component Vcx of the flow velocity Vc along the ship navigation direction and a component Vcy perpendicular to the ship navigation direction are obtained. Vcx is the increase or decrease in the speed to ground caused by the flow rate and direction, Δv c =vcx.
The increase or decrease in speed to ground caused by water depth, deltaV d, is calculated as follows:
the water depth correction threshold h is calculated according to the following formula:
If the water depth Dp is greater than the correction threshold h, the water depth has no effect on the speed to ground, i.e., Δv d =0; if the water depth Dp is smaller than the correction threshold h, the increase or decrease value of the speed to the ground caused by the water depth is calculated according to the following formula:
where A M is the area of the section below the waterline in the target vessel.
The total increase or decrease DeltaV of the speed to ground is the sum of the change values caused by the factors, namely:
ΔV＝ΔVc+ΔVd
So far, the parameters of the flow speed, the flow direction and the water depth after the screening in the step S1 are converted into the increase or decrease value of the speed of the ground navigation.
Further, the ground speed Vs and the host power Pe screened in the step S1 are combined with the ground speed correction value Δv and the host power Δp to obtain a corrected ground speed Vs corr and a corrected host power Pe corr, which have the following specific formulas:
VScorri＝VS+ΔV
Pecorri＝Pe+ΔP
thus, the navigational speed power characteristic correction for the set of recorded data is completed, and navigational speed power characteristics are performed on all the recorded data according to the correction method, so that corrected navigational speed Vs corri (i=1, 2, …) and host power Pe corri (i=1, 2, …) are formed. Thus, the calculation of the navigational speed power characteristics of the target ship in the whole data acquisition period range is completed.
Step S3: and establishing a two-dimensional rectangular coordinate system by taking the ground navigation speed Vs as a horizontal axis and the host power Pe as a vertical axis. Further, a Pe-Vs curve of the host power Pe obtained by the static water ship model test under specific draught described in step S2 with respect to the speed Vs of navigation to the ground is plotted therein, as shown in fig. 2. Further, using the corrected ground speed Vs corri (i=1, 2, …) and the host power Pe corri (i=1, 2, …) in the step S2 as the feature points, a least square method is applied to determine the translation Δvs of the Pe-Vs curve relative to the feature points, which is required to be translated along the Vs axis, as shown in fig. 3. Delta Vs is the loss of speed during the actual sailing of the ship compared to the clean hull condition.
Step S4: steps S2 to S3 are repeated until the calculation of the translation amount Δvs i (i=1, 2, …) over the entire data acquisition period is completed. The Δvs i (i=1, 2, …) will be used as the basis for determining the degree of fouling of the ship.
Step 105: taking time as an independent variable and delta Vs as a dependent variable, performing unitary linear regression on each navigational speed loss value delta Vs i calculated in the step S4 to obtain a trend function f (delta Vs) of the delta Vs with respect to time, wherein delta Vs_c i (i=1, 2, …) corresponding to each moment in the trend function f (delta Vs) is the equivalent navigational speed loss value of the ship at the moment. Taking an image as an example, the step is demonstrated and described as follows: and establishing a two-dimensional rectangular coordinate system by taking time as a horizontal axis and DeltaVs as a vertical axis. Further, each of the speed loss values Δvs i calculated in step S4 is plotted in the two-dimensional rectangular coordinate system, and a speed loss value scatter diagram at each time is formed. Further, a trend line of each scattered point is added in the scattered point diagram, and the trend line is used for representing the trend of the ship pollution bottom, as shown in fig. 4. And taking DeltaVs_c i (i=1, 2, …) corresponding to each moment in the trend line as an equivalent ship navigational speed loss value at the moment.
Subsequently, a speed loss threshold Δvs_set for the dirt to be removed by the docking station is preset, and a preferable speed loss threshold Δvs_set=1 knots. The ratio CV S of the equivalent ship speed loss value Δvs_c i (i=1, 2, …) at each time to the speed loss threshold Δvs_set is defined as a fouling coefficient for quantitatively characterizing the fouling degree of the ship.
When CV S is more than or equal to 0 and less than 0.25, the state of the soil bottom is 'slight'; when CV S is more than or equal to 0.25 and less than 0.5, the state of the soil bottom is mild; when CV S is less than or equal to 0.5 and less than 0.75, the state of the soil bottom is medium; when CV S is more than or equal to 0.75 and less than 1.0, the state of the soil bottom is 'severe'; when CV S is more than or equal to 1.0, the state of the dirt bottom is 'to be cleaned' urgently. And judging the dirty bottom state of the target ship, and completing the demonstration of the specific example.
Claims (6)
1. A method for judging the state of a ship at the bottom is characterized by comprising the following steps:
S1: the method comprises the steps of monitoring ship navigation and environmental data, wherein the data to be monitored are a ship ground speed Vs, a host power Pe, a displacement delta, a bow draft Tf, a stern draft Ta, a relative wind speed AWS, a relative wind direction AWA, a water depth Dp, a wave height H WAVE, a surge height H SWELL, a flow speed Vc, a flow direction Dc, a sea water temperature Tem_w, a sea water density ρ S, an air temperature Tem_a, an air pressure P_a and an air density ρ A;
Sequentially calculating the average difference value of each data point and the nearest 10 data points of the data points, comparing the average difference value with a threshold value, if the average difference value is larger than the threshold value, judging the data points as abnormal points, and eliminating the abnormal points to obtain the screened collected data values;
S2: obtaining a 'speed-power' corresponding value of a ground speed Vs of a target ship under design draft, structural draft and ballasted draft with respect to a host power Pe through a static water ship model test, wherein the corresponding value is the speed power characteristic of the target ship under the condition without any pollution bottom;
(1) Converting the environmental wind, wave, surge, sea water temperature, density and displacement parameters screened in the step S1 into an increase or decrease value delta P of host power, wherein the specific conversion is as follows:
Resistance R AA caused by ambient wind:
wherein A XV is the transverse projection area of the superstructure above the waterline of the target ship;
C AA (AWA) and C AA (0) are resistance coefficients at 0 degrees and AWA, respectively, relative to wind direction, and are obtained by the STA-JIP database;
resistance R WL caused by waves and surges:
Wherein g is gravity acceleration, B is target ship type width,
L BWL is the distance from the bow of the target vessel to 95% of the maximum width of the waterline,
H 1/3 is sense wave height:
resistance R AS caused by seawater temperature and density:
Wherein ρ S0 is the sea water density in standard state, the water temperature is 15 ℃, the density is 1026kg/m 3,
R T0 is the total resistance in the reference state,
R F is the friction resistance of the target ship in the current state,
S is the wet surface area of the target vessel,
C T0 is the total drag coefficient in standard condition,
C F0 is the coefficient of friction resistance in the standard state,
C F is the friction resistance coefficient of the ship with the bubble drag reduction system in the current state,
C T0,CF0,CF can be obtained by a still water ship model test;
resistance R ADIS caused by displacement:
wherein delta 0 is the displacement closest to the current displacement delta of the target ship among the displacement corresponding to the design draft, the structural draft and the ballast draft in the ship model test,
R T0 is the total resistance of the target ship under the condition of eating, and can be obtained through a ship model test;
The total resistance increase ΔR is the sum of the resistance values increased by the above factors, namely:
ΔR＝RAA+RWL+RAS+RADIS
The increase in total drag translates into an increase or decrease in host power deltap,
Wherein eta Did is the propulsion efficiency coefficient of the target ship under the current draft and navigational speed Vs in the windless, wave-less and flueless state, can be obtained through a ship model test,
Xi P is the load coefficient, which can be obtained by ship model test;
(2) Converting the parameters of the flow speed, the flow direction and the water depth after the screening in the step S1 into an increase or decrease value DeltaV of the speed of the ground, wherein the increase or decrease value DeltaV c of the speed of the ground is caused by the flow speed and the flow direction:
Vector decomposition is carried out on the flow velocity Vc and the flow direction Dc along the ship navigation direction to obtain a component Vcx of the flow velocity Vc along the ship navigation direction and a component Vcy vertical to the ship navigation direction,
Wherein Vcx is the increase or decrease value of the speed to ground caused by the flow velocity and the flow direction, Δv c =vcx;
the increase or decrease in speed to ground caused by water depth is a value of DeltaV d:
the water depth correction threshold h is calculated according to the following formula:
if the water depth Dp is greater than the correction threshold h, the water depth has no effect on the speed of the ground, i.e. Δv d =0,
If the water depth Dp is smaller than the correction threshold h, the increase or decrease value of the speed to the ground caused by the water depth is calculated according to the following formula:
wherein A M is the area of the part below the water line of the section in the target ship;
the increase value or decrease value DeltaV of the speed to ground is the sum of the change values caused by the factors, namely:
ΔV＝ΔVc+ΔVd；
(3) Combining the ground speed Vs and the host power Pe screened in the step S1 with the ground speed increase or decrease value Δv and the host power increase or decrease value Δp, respectively, to obtain a corrected ground speed V scorr and a corrected host power Pe corr:
VScorri＝VS+ΔV
Pecorri＝Pe+ΔP
Thus, the navigational speed power characteristic correction aiming at the group of recorded data is completed;
Performing navigational speed power characteristics on all recorded data according to the correction methods (1) (2) (3) to form corrected navigational speed Vs corri (i=1, 2.) and host power Pe corri (i=1, 2.), and finishing navigational speed power characteristic correction of the target ship within the whole data acquisition period range;
s3: establishing a two-dimensional rectangular coordinate system by taking the ground speed Vs as a horizontal axis and the host power Pe as a vertical axis, and drawing a Pe-Vs curve of the host power Pe relative to the ground speed Vs, which is obtained in the specific underwater static water ship model test in the step S2, in the two-dimensional rectangular coordinate system;
Taking the ground speed Vs corri (i=1, 2) and the host power Pe corri (i=1, 2) obtained by correction in the step S2 as characteristic points, and determining the translation quantity delta Vs of the Pe-Vs curve, which is required to be translated along a Vs axis, relative to the characteristic points by a least square method, wherein the delta Vs is a speed loss value of the ship during actual sailing compared with a clean hull condition;
S4: repeating steps S2-S3 until the translation amount Δvs i (i=1, 2,) over the entire data acquisition period is completed;
s5: taking time as an independent variable and delta Vs as an independent variable, and establishing a two-dimensional rectangular coordinate system;
Performing unitary linear regression on each navigational speed loss value DeltaVs i obtained in the step S4 to obtain a trend function f (DeltaVs) of DeltaVs with respect to time, wherein DeltaVs_c i (i=1, 2.) corresponding to each moment in the trend function f (DeltaVs) is the equivalent navigational speed loss value of the ship at the moment;
A speed loss threshold deltavs_set for dock cleaning is preset, the ratio CV s of the equivalent ship speed loss value deltavs_c i (i=1, 2,) at each moment and the speed loss threshold deltavs_set is defined as a pollution bottom coefficient for quantitatively representing the pollution bottom degree of the ship,
When CV S is more than or equal to 0 and less than 0.25, the state of the dirt bottom is slight;
When CV S is more than or equal to 0.25 and less than 0.5, the state of the soil bottom is mild;
when CV S is more than or equal to 0.5 and less than 0.75, the state of the soil bottom is medium;
when CV S is more than or equal to 0.75 and less than 1.0, the state of the soil bottom is 'severe';
When CV S is more than or equal to 1.0, the state of the dirt bottom is 'to be cleaned' urgently.
2. The method according to claim 1, wherein in step S5, a two-dimensional rectangular coordinate system is established with time as a horizontal axis and Δvs as a vertical axis, and each of the navigational speed loss values Δvs i calculated in step S4 is plotted in the two-dimensional rectangular coordinate system to form a navigational speed loss value scatter diagram at each time;
And adding trend lines of all scattered points into the scattered points of the navigational speed loss value, representing the trend of the ship bilge by using the trend lines, and taking delta Vs_c i (i=1, 2) corresponding to all moments in the trend lines as equivalent navigational speed loss values of the ship at the moment.
3. The method according to claim 1, wherein in step S1, data is collected and stored at intervals of "10 seconds".
4. The method according to claim 1, wherein the ship ground speed Vs, the fore draft T f, the aft draft T a, the sea water temperature tem_w, the sea water density ρ S, the air temperature tem_a, the air pressure p_a, the air density ρ A, and the threshold value are 1;
The wave height H WAVE, the surge height H SWELL, the relative wind speed AWS, the relative wind direction AWA, the water depth Dp, the flow velocity Vc, the flow direction Dc and the threshold value are taken as 10; the threshold is set to 50 for the displacement Δ, the main power Pe.
5. The method according to claim 1, wherein in step S5, the speed loss threshold Δvs_set=1 knots.
6. The method according to claim 1, wherein in step S2, C T0、CF、CF0、RT0、ηDid、ξP is obtained by a ship model test.
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