Hydrodynamic test and analysis method for ship inclined towing motion in waves

Abstract

A hydrodynamic test and analysis method for ship inclined towing motion in waves comprises the steps that S1, a coordinate system is given, a ship inclined towing motion hydrodynamic model in waves is provided, an inclined towing motion hydrodynamic coefficient expression form is given, and a test scheme is determined; s2, selecting a proper force sensor according to an input test object, and completing sensor calibration and installation of a ship model; s3, according to the input wave parameters, debugging of actual wave making parameters is completed, and a wave file is generated; s4, installing and connecting the ship model-sensor and a hydrodynamic test device, carrying out a hydrodynamic test of inclined towing motion in waves, and completing the collection of test parameters; and S5, performing signal processing and analysis on the test signals acquired in the test process to obtain inclined towing motion hydrodynamic test results under different working conditions, and obtaining the ship inclined towing motion hydrodynamic coefficient in the wave according to the processing results, thereby providing important support for researching the hydrodynamic change rule and manipulation motion prediction in the ship manipulation process in the wave.

Description

Technical Field

[0001] The invention relates to the technical field of ship hydrodynamic testing, in particular to a test and analysis method for hydrodynamic testing of oblique towing motion of a ship in waves. Background Art

[0002] At present, the evaluation of ship maneuverability is mostly based on a calm water environment. However, when a ship is maneuvering in an actual marine environment, it is affected by waves, resulting in significant sway coupling motion, which affects the ship's maneuverability safety. Therefore, predicting and evaluating the maneuverability of a ship in waves is of great significance for ship navigation safety, effective control, and improvement of ship combat capabilities, and has always been a research hotspot.

[0003] When a ship is maneuvering in waves, the response of the ship's heading change caused by steering has a lag, which often causes the ship's forward direction to be inconsistent with the direction of the ship's length during the ship's maneuvering process. The ship has a lateral oncoming flow in the body coordinate system, and there are vortices on the inside of the oncoming flow, which causes the hull force, especially the lateral force and bow rolling moment and other maneuvering hydrodynamics to change significantly, making it difficult to obtain data sources and verify the accuracy of the maneuvering motion prediction method based on the ship's maneuvering motion equation.

[0004] The main methods for studying the hydrodynamics of oblique towing motion in waves are based on CFD (Computational Fluid Dynamics, CFD) and model test methods. The CFD method uses overlapping grid technology to realize the multi-degree-of-freedom motion of the hull, and combines numerical wave generation and wave elimination technology to construct a numerical model of ship maneuvering motion in waves. Since the CFD method needs to simulate multi-degree-of-freedom coupled motion and relative motion, the prediction is difficult, and the relevant methods need to be verified and confirmed by the results of tank model tests. Similar model test research has not been carried out at home and abroad.

[0005] Therefore, it is urgent to establish a test method for the hydrodynamics of oblique towing motion of a ship in waves. By using a specific test device in a water tank, the multi-degree-of-freedom motion of a ship in waves is simulated, and the hydrodynamic forces acting on the hull during the oblique towing motion of the ship are tested, so as to separate the hull hydrodynamic coefficients related to the ship's motion drift angle β and forward speed U, provide important verification data for the CFD method, and lay a technical foundation for the accurate prediction of the ship's maneuvering motion in waves. Summary of the invention

[0006] In view of the shortcomings in the above-mentioned existing production technology, the applicant provides a method for testing and analyzing the hydrodynamics of the oblique towing motion of a ship in waves, which can be used to solve the problems of hydrodynamic testing and analysis of the maneuverability of ship models in waves, and solving and expressing the hydrodynamic coefficients of the oblique towing of ships in waves, and provides important support for studying the laws of hydrodynamic changes in the process of ship maneuvering in waves and the prediction of maneuvering motions.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for testing and analyzing hydrodynamic force of oblique towing motion of a ship in waves, comprising the following operation procedures:

[0009] S1: Provide a coordinate system, propose a hydrodynamic model for oblique towing motion of a ship in waves, provide an expression for the hydrodynamic coefficients of oblique towing motion, and determine the test plan;

[0010] S2: Select a suitable force sensor according to the input test object, and complete the sensor calibration and installation on the ship model;

[0011] S3: According to the input wave parameters, the actual wave making parameters are debugged and the wave file is generated;

[0012] S4: Install and connect the ship model-sensor with the hydrodynamic test device, carry out the hydrodynamic test of oblique towing motion in waves, and complete the test parameter collection;

[0013] S5: Perform signal processing and analysis on the test signals collected during the test to obtain the hydrodynamic test results of the oblique towing motion under different working conditions, and obtain the hydrodynamic coefficient of the oblique towing motion of the ship in the waves based on the processing results.

[0014] Its further technical solution is:

[0015] The selection process of the force sensor in S2 is as follows:

[0016] The selection criteria of force sensors are related to the estimation of the actual force on the ship model. Suitable force sensors are selected according to the test parameters such as ship model parameters, speed, drift angle and other test parameters required by the test. The types of force sensors include three types: ship model longitudinal force, lateral force sensor and bow moment sensor. The installation method is determined according to the independent measurement and combined measurement of the three types of sensors. In order to make the electrical signal output by the sensor meet the electrical signal size range required by the test acquisition program, the force sensor is calibrated before the test to obtain the "multiplier" between the output signal of the ship model longitudinal force, lateral force sensor and bow moment sensor and the electrical signal received by the acquisition program, so as to convert the hydrodynamic test signal of the oblique towing motion in the waves into the actual size of the force and moment.

[0017] Ship model parameters include length, displacement and draft.

[0018] The process of calibrating the force sensor and installing the model in S2 is as follows:

[0019] Before the test, it is necessary to calibrate the hull hydrodynamic force balance, propeller thrust-torque autopropellant and rudder force balance respectively to obtain the calibration coefficient between the electrical signal and the hydrodynamic force, and further complete the installation between the ship model and the force sensor. The force sensor and the ship model are installed through a connecting mechanism, and the rotation center of the connecting mechanism coincides with the center of gravity of the ship model.

[0020] In S3, the wave parameters of the hydrodynamic test of the oblique towing motion of a ship in waves mainly include the wave period, wave height and wave propagation direction. Since the water depth environment of the test pool is inevitably slightly different from the ideal state, it is necessary to complete the wave debugging before the test, keep the actual generated wave parameters consistent with the input wave parameters, and generate a wave file. In this way, the required waves can be directly generated during the hydrodynamic test of the oblique towing motion of a ship in actual waves.

[0021] In S4, in the hydrodynamic test of oblique towing motion in waves, the ship model-sensor is installed and connected to the hydrodynamic test device, and the hydrodynamic test device is connected to a trailer that can provide a forward speed, wherein the action center of each force sensor is at the center of gravity of the ship, and the drift angle of the ship model is adjusted by the hydrodynamic test device, and the speed of the ship model is adjusted by changing the forward speed of the trailer.

[0022] In S4, the contents of the hydrodynamic test of oblique towing motion in waves are as follows: according to the hydrodynamic model of oblique towing motion of a ship in waves, by carrying out oblique towing motion test in waves, the longitudinal force X, lateral force Y and bow rolling moment N under different drift angles β and forward speeds U are obtained, and then the relevant hull hydrodynamic coefficients are separated. The drift angle is usually selected from -15° to 15°, with an interval of 5°; the speed selection is to determine 3 speeds near the design speed of the test object; when carrying out the test, first read the pre-generated wave file to generate waves in the test pool, start the trailer to tow the ship model forward at a fixed drift angle, measure the hull motion of the ship model, the longitudinal force X, lateral force Y and bow rolling moment N of the hull during oblique towing in waves, and the measured wave signals during the test, and the above signals are output in the form of electrical signals.

[0023] In S5, the hydrodynamic test of oblique towing in waves mainly collects the hull motion of the ship model, the longitudinal force X, lateral force Y, bow rolling moment N exerted on the hull during oblique towing in waves, and the measured wave signals during the test, and processes the signals through spectral analysis methods.

[0024] The beneficial effects of the present invention are as follows:

[0025] The present invention mainly proposes a hydrodynamic model of the oblique towing motion of a ship in waves under a given coordinate system, gives an expression form of the hydrodynamic coefficient of the oblique towing motion, determines an experimental test plan, selects a suitable force sensor according to the input test object, completes the sensor calibration and installation with the ship model, and at the same time, according to the input wave parameters, completes the debugging of the actual wave-making parameters and generates a wave file, then installs and connects the ship model-sensor with the hydrodynamic test device, carries out the hydrodynamic test of the oblique towing motion in waves, and completes the hull movement (rolling, pitching) of the ship model, the longitudinal force, lateral force and bow moment of the hull in the oblique towing process in waves, and the actual wave signal test parameter collection during the test process. Finally, the test signal collected during the test process is processed and analyzed, and the hydrodynamic test results of the oblique towing motion under different working conditions are obtained, and the hydrodynamic coefficient of the oblique towing motion of the ship in waves is obtained according to the processing results. The method can be used to solve the hydrodynamic test and analysis of the maneuverability of the ship model in waves, and the problem of solving and expressing the hydrodynamic coefficient of the oblique towing of the ship in waves, and has the advantages of high precision and high reliability.

[0026] The present invention decomposes the whole process of water tank testing from the key points of pre-test preparation, test conduction, test data processing, etc., mainly including the hydrodynamic model of the oblique towing motion of a ship in waves and the expression of the hydrodynamic coefficients, sensor calibration and installation, the connection method of the ship model-sensor and the hydrodynamic test device, and the separation method of the hydrodynamic coefficients of the oblique towing motion of a ship in waves. It can be applied to the prediction of the hydrodynamic test of the oblique towing motion of a ship in waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a specific scheme diagram of the hydrodynamic test and analysis method for the oblique towing motion of a ship in waves of the present invention.

[0028] Figure 2 It is a schematic diagram of the spatial fixed coordinate system and the ship translational coordinate system of the present invention.

[0029] Figure 3 It is the definition of the wave angle in the present invention.

[0030] Figure 4 The following are examples of the drift angle and lateral force curves at various speeds for the oblique towing motion of the present invention. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0032] like Figure 1-Figure 4 As shown, the specific process of the hydrodynamic test and analysis method of the oblique towing motion of a ship in waves described in the present invention is as follows:

[0033] Step 1: Give the coordinate system, propose the hydrodynamic model of the oblique towing motion of the ship in the waves, give the expression of the hydrodynamic coefficient of the oblique towing motion, and determine the test plan.

[0034] Step 2: Select the appropriate force sensor according to the input test object, and complete the sensor calibration and installation on the ship model.

[0035] Step 3: According to the input wave parameters, complete the debugging of the actual wave making parameters and generate the wave file.

[0036] Step 4: Install and connect the ship model-sensor to the hydrodynamic test device, carry out the hydrodynamic test of oblique towing motion in waves, and complete the test parameter collection.

[0037] Step 5: Process and analyze the test signals collected during the test to obtain the hydrodynamic test results of the oblique towing motion under different working conditions, and obtain the hydrodynamic coefficient of the oblique towing motion of the ship in waves based on the processing results.

[0038] Embodiment 1:

[0039] Step 1: Give the coordinate system, propose the hydrodynamic model of the oblique towing motion of the ship in the waves, give the expression of the hydrodynamic coefficient of the oblique towing motion, and determine the test plan.

[0040] Define the geodetic coordinate system O0-x0y0z0 and the ship coordinate system o-xyz to describe the ship maneuvering motion. Figure 2 As shown in , they all satisfy the right-hand rule; the wave direction is defined as Figure 3 As shown. In the attached coordinate system o-xyz, the origin o is located at the center of gravity of the ship, the ox axis points to the bow along the centerline of the ship, and oy points to the starboard. The angle ψ between the O0x0 axis and the ox axis is defined as the heading angle, and it is stipulated that the positive direction of ψ is the direction from the O0x0 axis to the ox axis according to the right-hand rule with the O0x0 axis as the starting position; the angle β between the speed U direction and the ox axis is defined as the drift angle, and it is stipulated that the positive direction of β is the direction from the O0z0 axis to the ox axis according to the right-hand rule with the velocity vector direction as the starting position; the angle between the wave propagation direction and the O0x0 axis is defined as the wave direction angle θ, and it is stipulated that the positive direction of θ is the direction from the O0x0 axis to the wave propagation direction according to the right-hand rule with the O0z0 axis as the starting position, and the wave propagates along the O0x0 axis direction θ=0°.

[0041] The hydrodynamic coefficient of the oblique towing motion of a ship in waves is obtained by towing the hull obliquely at different fixed drift angles β. The longitudinal, lateral force and bow moment values ​​under different working conditions can be obtained. According to the known conditions, the ship moves at a uniform speed U in the longitudinal direction. According to the ship coordinate system, the following is decomposed:

[0042] u=Ucosβ

[0043] v=-Usinβ

[0044] Substitute the control motion equation into it and simplify it to get:

[0045] X=X * +X u|u| u|u|

[0046] Y=Y v uv+Y v|v| v|v|

[0047] N=N v uv+N v|v| v|v|

[0048] Where X * is the straight-line resistance, X, Y, and N are the longitudinal force, lateral force, and bow moment of the ship in the ship coordinate system o-xyz during the oblique towing process. u|u| , Y v , Y v|v| 、N v and N v|v| The hull hydrodynamic coefficients related to the ship's drift angle β and forward speed U extracted from the oblique towing motion test.

[0049] Step 2: Select the appropriate force sensor according to the input test object, and complete the sensor calibration and installation on the ship model.

[0050] (1) Force sensor selection:

[0051] The selection criteria of the force sensor are related to the estimation of the actual force on the ship model. According to the ship model parameters (length, displacement, draft, etc.), speed, drift angle and other test parameters required by the test, the appropriate force sensor is selected; the types of force sensors mainly include three types of ship model longitudinal force, lateral force sensor and bow moment sensor. The installation method is determined according to the three types of sensors, which are measured separately (single-component force sensor) and combined measurement (three-component force sensor). In order to make the electrical signal output by the sensor meet the electrical signal size range required by the test acquisition program, the force sensor is calibrated before the test to obtain the "multiplier" between the output signal of the ship model longitudinal force, lateral force sensor and bow moment sensor and the electrical signal received by the acquisition program, so as to convert the hydrodynamic test signal of the oblique towing motion in the wave into the actual size of the force and moment.

[0052] (2) Force sensor calibration and model installation:

[0053] Before the test, the hull hydrodynamic force balance, propeller thrust torque autopropellant and rudder force balance need to be calibrated to obtain the calibration coefficient between the electrical signal and the hydrodynamic force. The installation between the ship model and the force sensor is further completed. The force sensor and the ship model are installed through a connecting mechanism, and the rotation center of the connecting mechanism coincides with the center of gravity of the ship model.

[0054] Step 3: According to the input wave parameters, complete the debugging of the actual wave making parameters and generate the wave file.

[0055] The wave parameters of the hydrodynamic test of oblique towing motion of a ship in waves mainly include wave period, wave height and wave propagation direction. Since the water depth environment of the test pool is inevitably slightly different from the ideal state, it is necessary to complete the wave debugging before the test, keep the actual generated wave parameters consistent with the input wave parameters, and generate a wave file. In this way, the required waves can be directly generated during the hydrodynamic test of oblique towing motion of a ship in actual waves.

[0056] Step 4: Install and connect the ship model-sensor to the hydrodynamic test device, carry out the hydrodynamic test of oblique towing motion in waves, and complete the test parameter collection.

[0057] (1) Connection method between ship model-sensor and hydrodynamic test device:

[0058] In the hydrodynamic test of oblique towing in waves, the ship model-sensor is installed and connected to the hydrodynamic test device, and the hydrodynamic test device is connected to a trailer that can provide forward speed, wherein the action center of each force sensor is at the center of gravity of the ship. The drift angle of the ship model is adjusted by the hydrodynamic test device, and the speed of the ship model is adjusted by changing the forward speed of the trailer.

[0059] (2) Main contents of the hydrodynamic test of oblique towing motion in waves:

[0060] According to the hydrodynamic model of oblique towing motion of ships in waves, by conducting oblique towing motion tests in waves, the longitudinal force X, lateral force Y, and bow moment N under different drift angles β and forward speeds U are obtained, and then the relevant hull hydrodynamic coefficients are separated. The drift angle is usually selected from -15° to 15°, with an interval of 5°; the speed selection is determined by determining 3 speeds near the design speed of the test object.

[0061] When conducting the test, first read the pre-generated wave file to generate waves in the test pool, start the trailer to tow the ship model forward at a fixed drift angle, and measure the hull motion (roll and pitch) of the ship model, the longitudinal force X, lateral force Y, bow roll moment N exerted on the hull during oblique towing in the waves, and the measured wave signals during the test. The above signals are output in the form of electrical signals.

[0062] Step 5: Process and analyze the test signals collected during the test to obtain the hydrodynamic test results of the oblique towing motion under different working conditions, and obtain the hydrodynamic coefficient of the oblique towing motion of the ship in waves based on the processing results.

[0063] The hydrodynamic test of oblique towing in waves mainly collects the hull motion (roll and pitch) of the ship model, the longitudinal force X, lateral force Y, bow moment N exerted on the hull during oblique towing in waves, and the measured wave signals during the test, and processes the signals through spectral analysis methods.

[0064] Taking the signals collected under regular wave conditions as an example, the hull motion of the ship model, the longitudinal force, lateral force and bow moment of the hull during the oblique towing process in the waves, and the measured wave signals during the test process all show sine or cosine transformation over time. The spectrum analysis method is used to transform the N point data x of the random signal x(n) into N (n) is regarded as a finite signal and x is directly taken N The Fourier transform of (n) gives X N (e jω ), then take the square of its amplitude and divide it by the number of data samples N as an estimate of the mean of x(n), expressed as follows:

[0065]

[0066] After the above processing, the longitudinal force X, lateral force Y, and yaw moment N obtained from the test of different drift angles β and forward speeds U are taken as an example, and the simplified control motion equation is obtained:

[0067] Y=Y v uv+Y v|v| v|v|=-Y v sinβcosβU+Y v|v| sin 2 βU

[0068] According to trigonometric function transformation, sinβcosβ=sin2β / 2, sin 2 β=(1-cos2β) / 2Substituting in, we have:

[0069]

[0070] Let A1 = -0.5Y v V,B1=-0.5Y v|v| V,A2=-0.5N v V,B2=-0.5N v|v| V has:

[0071] Y=A1sin2β+B1cos2β+C1

[0072] Then the longitudinal force X, lateral force Y and bow moment N in the process of oblique towing motion with different drift angles β and forward speed U in the wave are fitted by Fourier series, and the coefficients A1, B2 and C3 in the above formula can be obtained. The hull hydrodynamic coefficient X related to the ship motion drift angle β and forward speed U can be further solved. u|u| , Y v , Y v|v| 、N v and N v|v| , refer to Figure Figure 4 .

[0073] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A method for testing and analyzing the hydrodynamic force of a ship's oblique towing motion in waves, characterized by: The following operation procedures are included: S1: Provide a coordinate system, propose a hydrodynamic model for oblique towing motion of a ship in waves, provide an expression for the hydrodynamic coefficients of oblique towing motion, and determine the test plan; S2: Select a suitable force sensor according to the input test object, and complete the sensor calibration and installation on the ship model; S3: According to the input wave parameters, the actual wave making parameters are debugged and the wave file is generated; S4: Install and connect the ship model-sensor with the hydrodynamic test device, carry out the hydrodynamic test of oblique towing motion in waves, and complete the test parameter collection; S5: Perform signal processing and analysis on the test signals collected during the test to obtain the hydrodynamic test results of the oblique towing motion under different working conditions, and obtain the hydrodynamic coefficient of the oblique towing motion of the ship in the waves based on the processing results.

2. A method for testing and analyzing hydrodynamic forces of oblique towing motion of a ship in waves as claimed in claim 1, characterized in that: The selection process of the force sensor in S2 is as follows: The selection criteria of force sensors are related to the estimation of the actual force on the ship model. Suitable force sensors are selected according to the test parameters such as ship model parameters, speed, drift angle and other test parameters required by the test. The types of force sensors include three types: ship model longitudinal force, lateral force sensor and bow moment sensor. The installation method is determined according to the independent measurement and combined measurement of the three types of sensors. In order to make the electrical signal output by the sensor meet the electrical signal size range required by the test acquisition program, the force sensor is calibrated before the test to obtain the "multiplier" between the output signal of the ship model longitudinal force, lateral force sensor and bow moment sensor and the electrical signal received by the acquisition program, so as to convert the hydrodynamic test signal of the oblique towing motion in the wave into the actual size of the force and moment.

3. A method for testing and analyzing hydrodynamic forces of oblique towing motion of a ship in waves as claimed in claim 2, characterized in that: Ship model parameters include length, displacement and draft.

4. A method for testing and analyzing hydrodynamic forces of oblique towing motion of a ship in waves as claimed in claim 1, characterized in that: The process of calibrating the force sensor and installing the model in S2 is as follows: Before the test, it is necessary to calibrate the hull hydrodynamic force balance, propeller thrust-torque autopropellant and rudder force balance respectively to obtain the calibration coefficient between the electrical signal and the hydrodynamic force, and further complete the installation between the ship model and the force sensor. The force sensor and the ship model are installed through a connecting mechanism, and the rotation center of the connecting mechanism coincides with the center of gravity of the ship model.

5. A method for testing and analyzing hydrodynamic forces of oblique towing motion of a ship in waves as claimed in claim 1, characterized in that: In S3, the wave parameters of the hydrodynamic test of the oblique towing motion of a ship in waves mainly include the wave period, wave height and wave propagation direction. Since the water depth environment of the test pool is inevitably slightly different from the ideal state, it is necessary to complete the wave debugging before the test, keep the actual generated wave parameters consistent with the input wave parameters, and generate a wave file. In this way, the required waves can be directly generated during the hydrodynamic test of the oblique towing motion of a ship in actual waves.

6. A method for testing and analyzing hydrodynamic forces of oblique towing motion of a ship in waves as claimed in claim 1, characterized in that: In S4, in the hydrodynamic test of oblique towing motion in waves, the ship model-sensor is installed and connected to the hydrodynamic test device, and the hydrodynamic test device is connected to a trailer that can provide a forward speed, wherein the action center of each force sensor is at the center of gravity of the ship, and the drift angle of the ship model is adjusted by the hydrodynamic test device, and the speed of the ship model is adjusted by changing the forward speed of the trailer.

7. A method for testing and analyzing hydrodynamic forces of oblique towing motion of a ship in waves as claimed in claim 1, characterized in that: In S4, the contents of the hydrodynamic test of oblique towing motion in waves are as follows: according to the hydrodynamic model of oblique towing motion of a ship in waves, by carrying out oblique towing motion test in waves, the longitudinal force X, lateral force Y and bow rolling moment N under different drift angles β and forward speeds U are obtained, and then the relevant hull hydrodynamic coefficients are separated. The drift angle is usually selected from -15° to 15°, with an interval of 5°; the speed selection is to determine 3 speeds near the design speed of the test object; when carrying out the test, first read the pre-generated wave file to generate waves in the test pool, start the trailer to tow the ship model forward at a fixed drift angle, measure the hull motion of the ship model, the longitudinal force X, lateral force Y and bow rolling moment N of the hull during oblique towing in waves, and the measured wave signals during the test, and the above signals are output in the form of electrical signals.

8. A method for testing and analyzing hydrodynamic forces of oblique towing motion of a ship in waves as claimed in claim 1, characterized in that: In S5, the hydrodynamic test of oblique towing in waves mainly collects the hull motion of the ship model, the longitudinal force X, lateral force Y, bow rolling moment N exerted on the hull during oblique towing in waves, and the measured wave signals during the test, and processes the signals through spectral analysis methods.

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