Ship hull hydrodynamic model test method suitable for ship transverse free running

Abstract

This invention relates to a hydrodynamic model testing method for ships undergoing transverse free-propulsion. A blower is placed symmetrically fore and aft of the hull. Each blower, along with a corresponding blower speed measurement module and a unidirectional thrust sensor, constitutes a propulsion blower system. During transverse free-propulsion in cross waves, the blower thrust is adjusted by adaptively regulating the blower speed, thus balancing the ship and preventing bow rolling. The measured thrust of the propulsion blower system is processed and converted into the magnitude of the wave force experienced by the ship during transverse free-propulsion. The ship's motion is not constrained by the towing vehicle, and this method solves the problem of transverse free-propulsion dynamics, while avoiding the impact of transverse navigation instability on hydrodynamic testing and analysis. Furthermore, it allows for relatively accurate measurement of transverse wave drift force. The method proposed in this invention is scientifically sound, easy to implement, and has good prospects for widespread application.

Description

Technical Field

[0001] This invention relates to a ship performance testing technology, and more particularly to a hydrodynamic model test method for ships that are capable of lateral free propulsion. Background Technology

[0002] When a ship maneuvers in waves, wave drift forces significantly influence its maneuvering characteristics. Currently, the mainstream method for predicting ship maneuvering in waves is to directly derive wave forces using traditional ship seakeeping theory. However, this method does not consider the impact of slant motion on wave loads, leading to significant prediction errors and failing to meet the accuracy requirements for engineering applications. Some Chinese scholars have considered the impact of slant motion based on potential flow theory; however, potential flow theory is only applicable to small drift angles (ψ<5°), slender bodies, and streamlined shapes, making it difficult to apply to actual ship types. Considering decomposing slant motion into longitudinal motion along the ship's length and transverse motion perpendicular to the ship's length, assuming that the wave forces during longitudinal and transverse motions are uncoupled (i.e., the wave force of slant motion is the sum of the longitudinal and transverse wave forces), the measurement method for longitudinal wave force is relatively mature. Regarding the measurement of transverse wave force, if the ship's motion is constrained by trailers or springs, it is difficult to obtain accurate hydrodynamic measurements in waves because the ship's degrees of freedom are restricted by external mechanisms. Summary of the Invention

[0003] To address the existing problem of measuring the lateral free-propulsion dynamics of ships, a hull hydrodynamic model test method suitable for lateral free-propulsion of ships is proposed, which can accurately measure the lateral free-propulsion wave drift force of ships.

[0004] The technical solution of this invention is as follows: a hydrodynamic model test method for a ship hull that is suitable for transverse free-propulsion. A fan is placed symmetrically fore and aft of the ship. Each fan, together with a corresponding fan speed measurement module and a fan thrust unidirectional force sensor, constitutes a propulsion fan system. When the ship model is transversely free-propulsion in transverse waves, the fan speed is adaptively adjusted to regulate the fan thrust, thereby balancing the ship and preventing bow rolling. The thrust of the propulsion fan system measured during the process is processed and converted into the magnitude of the wave force experienced by the ship during transverse free-propulsion in transverse waves.

[0005] Furthermore, the method specifically includes the following steps:

[0006] 1) Determine the location of the wind turbine based on the symmetry of the ship's midships, and fix the propulsion wind turbine system on the base at the determined wind turbine location;

[0007] 2) Assemble the data acquisition system and propulsion fan system on the bare ship model;

[0008] 3) Set the initial speed of the wind turbine so that the ship can freely navigate laterally at the set speed. Due to the wave force, the ship speed changes. Adjust the wind turbine speed according to the ship speed feedback from the six-degree-of-freedom motion non-contact optical measuring instrument of the ship model; measure the lateral thrust generated by the wind turbine using the force sensor on the base.

[0009] 4) Based on the bow angle fed back by the heading gyroscope, the wind turbine speed adaptive adjustment system is used to adjust the speed to ensure that the ship does not experience bow rolling.

[0010] Furthermore, before step 1) is executed, before the propulsion fan system is assembled onto the ship model, the thrust generated by the two fans at different speeds is measured, and the speed-thrust correlation curves of the two fans are simulated.

[0011] Furthermore, in step 3), the initial speed of the wind turbine and the ship speed are obtained through a free-roaming test in still water to ensure that the ship does not experience bow roll.

[0012] Furthermore, in step 3), the corresponding wind turbine speed in still water is first used as the initial speed. The ship will slow down due to the wave force. Based on the ship speed fed back by the ship speed of the six-degree-of-freedom motion non-contact optical measuring instrument of the ship model, the wind turbine speed is adjusted to be the same as the corresponding speed in still water. Then the ship's course is adjusted, the speed of one wind turbine is increased, and the speed of the other wind turbine is decreased. The ship speed, wind turbine thrust, and wind turbine speed are recorded in the experiment.

[0013] Furthermore, the wind turbine speed adjustment is as follows: the point of application of the forces of the two wind turbines is determined according to the midship position, and then the ratio of the thrust generated by the two wind turbines at the speed is calculated according to the torque formula, thereby determining the wind turbine speed.

[0014] Furthermore, the method for obtaining the magnitude of the wave force experienced by the ship during transverse free navigation in cross waves is as follows: at the corresponding speed, the difference between the wind turbine thrust in the waves and the wind turbine thrust in still water is used to obtain the magnitude of the wave force experienced by the ship during transverse free navigation in cross waves.

[0015] A test system for a test method of a ship hull hydrodynamic model suitable for lateral free propulsion includes a bare hull model, a data acquisition system, a data processing module, two sets of propulsion fan systems, and a non-contact optical measuring instrument for six degrees of freedom motion of the ship model;

[0016] The data acquisition system includes a gyroscope and an accelerometer, which are used to measure the ship's heading angle and acceleration in three directions, respectively.

[0017] The data processing module is a host computer that receives the hydrodynamic data collected by the data acquisition system via a wireless bridge.

[0018] The two sets of propulsion fan systems each include: a fan, a fan speed measurement module, and a fan thrust unidirectional force sensor, which are used to provide continuous power to the hull, measure the fan speed, and measure the thrust generated by the fan, respectively.

[0019] The six-degree-of-freedom motion non-contact optical measuring instrument for the ship model is used to capture the ship's motion and speed.

[0020] Preferably, the system also includes a trailer placed above the hull model for mounting a six-DOF non-contact optical measuring instrument for the hull model.

[0021] Preferably, the system also includes a wave height meter for measuring wave height.

[0022] The beneficial effects of this invention are as follows: This invention is applicable to the hydrodynamic model test method of ships undergoing lateral free-propulsion. The ship's motion is not constrained by the tow truck, and it solves the problem of lateral free-propulsion dynamics. It also avoids the influence of the ship's lateral navigation instability on the hydrodynamic testing and analysis, and can accurately measure the lateral wave drift force. The method proposed in this invention is scientifically sound, easy to implement, and has good prospects for widespread application. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the installation of the hydrodynamic model test device for lateral free propulsion of ships according to the present invention;

[0024] Figure 2 This is a schematic diagram of a ship equipped with a propulsion wind turbine system, which is freely navigating in transverse waves. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0026] Since the main reason for free lateral propulsion is the lack of lateral power, wind turbines were used as the ship's lateral power source in the experiment. The main factor affecting the placement of the wind turbines was the ship's bow roll motion. One wind turbine was placed fore and aft of the ship's midship (midship refers to the midpoint of the load waterline length). Together with the corresponding wind turbine speed measurement module and wind turbine thrust unidirectional force sensor, they formed a propulsion wind turbine system. The two wind turbines were placed symmetrically fore and aft. In the experiment, the wind turbine speed was adjusted in real time by monitoring the ship's bow roll angle data, thereby preventing the ship from experiencing bow roll motion.

[0027] To better determine the thrust generated by the wind turbines at different speeds, before assembling the propulsion wind turbine system onto the ship model, the thrust generated by the two wind turbines at different speeds was first measured, and the speed-thrust correlation curves of the two wind turbines were simulated.

[0028] At the designated installation location of the wind turbine, two wooden planks are installed and fixed on the ship's side. The wind turbine is then secured to the planks. Since the direction of the wind turbine's thrust changes due to the ship's movement, a force sensor is installed on the wooden plank where the wind turbine is mounted to monitor the lateral thrust.

[0029] like Figure 1 The diagram shows the installation of a hydrodynamic model test setup for ships that are capable of lateral free propulsion. The test setup includes:

[0030] The trailer, placed on top of the ship model, is mainly used to carry the six-degree-of-freedom motion non-contact optical measuring instrument for the ship model.

[0031] Bare hull model;

[0032] A wave height meter is used to measure wave height.

[0033] The data acquisition system includes: a heading gyroscope and an accelerometer, which are used to measure the ship's heading angle and acceleration in three directions, respectively.

[0034] Data processing module Figure 1 The host computer receives the hydrodynamic data collected by the data acquisition system via a wireless bridge;

[0035] Two sets of propulsion fan systems are used, each including a fan, a fan speed measurement module, and a unidirectional thrust sensor. These are used to provide continuous power to the hull, measure the fan speed, and measure the thrust generated by the fan. The point of application of the forces between the two fans is determined based on the ship's position amidships. Then, using the torque formula, the proportion of thrust required by the two fans at each speed is calculated, thereby determining the fan speed.

[0036] A six-DOF non-contact optical measuring instrument for ship models, used to capture ship motion and speed.

[0037] Based on the above hydrodynamic testing equipment and calibration method, the method for testing the lateral free-propulsion wave force of a ship is as follows:

[0038] Step S1: Determine the location of the wind turbine based on the symmetry between the ship and the midships;

[0039] Step S2: Assemble the data acquisition system and propulsion fan system onto the bare ship model;

[0040] Step S3: As Figure 2The diagram shows a ship freely navigating laterally in transverse waves. The initial speed of the wind turbine is set so that the ship can freely navigate laterally at the set speed. Due to the wave force, the ship's speed changes. The wind turbine speed can be adjusted according to the ship's speed feedback from the ship model's six-degree-of-freedom motion non-contact optical measuring instrument. To measure the lateral thrust generated by the wind turbine, a force sensor is installed on the wind turbine mounting base.

[0041] Step S4: Based on the bow angle fed back by the heading gyroscope, adjust the speed using the wind turbine speed adaptive adjustment system to ensure that the ship does not experience bow roll.

[0042] To measure the lateral wave force of the ship, a free self-propelled lateral test in still water was first conducted. During the test, based on the ship's heading angle fed back by the heading gyroscope, the speed of the two wind turbines was adjusted using an adaptive wind turbine speed control system to ensure that the ship did not roll (the ship's length direction always formed a 90° angle with the wave direction), and the ship model speed, wind turbine thrust, and wind turbine speed were recorded.

[0043] Based on the test results (fan speed and ship model speed) in still water, a free-roaming test of the ship model in waves was conducted. To ensure stable navigation of the ship at the corresponding speed and course in still water, the corresponding fan speed in still water was initially used as the initial speed. However, due to the wave force, the ship's speed would decrease. The fan speed was adjusted to match the corresponding speed in still water based on the ship's speed feedback from the ship model's six-degree-of-freedom motion non-contact optical measuring instrument. Then, the ship's course was adjusted, with one fan speed increased and the other fan speed decreased. The ship's speed, fan thrust, and fan speed were recorded during the test.

[0044] Finally, by subtracting the wind turbine thrust in the waves from the wind turbine thrust in still water at the corresponding speed, the magnitude of the wave force experienced by the ship during transverse free navigation in cross waves can be obtained.

[0045] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A test method for a ship's hydrodynamic model suitable for lateral free propulsion, characterized in that, Two fans are placed symmetrically, one fore and one aft, amidships. Each fan, together with its corresponding fan speed measurement module and fan thrust unidirectional force sensor, constitutes a propulsion fan system. The specific steps include the following: 1) Determine the location of the wind turbine based on the symmetry of the ship's midships, and fix the propulsion wind turbine system on the base at the determined wind turbine location; 2) Assemble the data acquisition system and propulsion fan system on the bare ship model; 3) First, conduct a free self-propulsion test in still water. Based on the ship's heading angle fed back by the heading gyroscope, use the wind turbine speed adaptive adjustment system to adjust the speed of the two wind turbines to ensure that the ship does not roll forward. Record the ship model speed, wind turbine thrust, and wind turbine speed. 4) Based on the results of the ship's free self-propulsion test in still water, a free self-propulsion test of the ship model in waves was conducted. First, the corresponding wind turbine speed in still water was used as the initial speed. The ship's speed would decrease due to the wave force. According to the ship's speed fed back by the ship model's six-degree-of-freedom motion non-contact optical measuring instrument, the wind turbine speed was adjusted to be the same as the corresponding speed in still water. Then, the ship's course was adjusted, with the speed of one wind turbine increasing and the speed of the other wind turbine decreasing. The ship's speed, wind turbine thrust, and wind turbine speed were recorded during the test. 5) The difference between the wind turbine thrust in the waves and the wind turbine thrust in still water at the corresponding speed is used to obtain the magnitude of the wave force experienced by the ship during transverse free navigation in cross waves.

2. The test method for a ship's hydrodynamic model suitable for lateral free propulsion as described in claim 1, characterized in that, Before step 1) is executed, before the propulsion fan system is assembled onto the ship model, the thrust generated by the two fans at different speeds is measured, and the speed-thrust correlation curves of the two fans are simulated.

3. The test method for a ship's hydrodynamic model suitable for lateral free propulsion as described in claim 1, characterized in that, The wind turbine speed adjustment is as follows: the point of application of the forces of the two wind turbines is determined according to the midship position, and then the ratio of the thrust generated by the two wind turbines at the speed is calculated according to the torque formula, thereby determining the wind turbine speed.

4. A test system for a test method of a ship's hull hydrodynamic model suitable for transverse free propulsion, characterized in that, It includes a bare hull model, a data acquisition system, a data processing module, two sets of propulsion fan systems, and a six-degree-of-freedom motion non-contact optical measuring instrument for the ship model; The data acquisition system includes a gyroscope and an accelerometer, which are used to measure the ship's heading angle and acceleration in three directions, respectively. The data processing module is a host computer that receives the hydrodynamic data collected by the data acquisition system via a wireless bridge. The two sets of propulsion fan systems each include: a fan, a fan speed measurement module, and a fan thrust unidirectional force sensor, which are used to provide continuous power to the hull, measure the fan speed, and measure the thrust generated by the fan, respectively. The six-degree-of-freedom motion non-contact optical measuring instrument for the ship model is used to capture the ship's motion and speed.

5. The test system used in the test method for hydrodynamic models of ships under transverse free propulsion as described in claim 4, characterized in that, It also includes a trailer, placed on top of the ship model, for mounting the ship model's six-degree-of-freedom motion non-contact optical measuring instrument.

6. The test system used in the test method for hydrodynamic models of ships under transverse free propulsion as described in claim 4, characterized in that, It also includes a wave height meter, used to measure wave height.

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