A method for analyzing the drag components of a waterjet propulsion ship model

Abstract

This invention relates to a method for analyzing the resistance components of a waterjet-propelled ship model. First, a resistance test is conducted on the bare hull. Next, a self-propelled test is performed to determine the rotational speed of the waterjet propulsion device at a given self-propelled point. Then, an L-shaped nozzle is installed, and the waterjet propulsion device operates at the self-propelled point rotational speed at a specific speed, measuring the total hull resistance. Simultaneously, the flow field in the flow region is measured using PIV technology, and the inlet longitudinal momentum is calculated. Finally, the total resistance is subtracted from the bare hull resistance and the inlet longitudinal momentum to obtain the impact of the propeller operation on the hull resistance at the corresponding self-propelled point. This invention employs conventional resistance tests, L-shaped nozzle resistance tests, self-propelled tests, and flow field measurements in the flow region to decompose the resistance into the hull's own resistance components and the hull resistance increment caused by the suction effect of the waterjet propulsion device. This allows for the identification of the propeller's impact on the hull, reducing hull shape optimization to a single objective function optimization problem and improving hull shape optimization efficiency.

Description

Technical Field

[0001] This invention relates to a method and experimental apparatus for analyzing the drag components of a waterjet-propelled ship model. Background Technology

[0002] Waterjet propulsion is a type of propeller suitable for high-speed ships, characterized by high propulsion efficiency and maneuverability, and is widely used in high-speed surface vessels. For waterjet-propelled ships, speed model testing is an effective means of verifying their speed performance during the design phase, generally including scaled-down resistance, open-water, and self-propulsion tests. Ship model resistance tests and propeller open-water tests respectively verify the performance of the hull and propeller themselves, and then self-propulsion tests characterize the relationship and interaction between the two in the form of self-propulsion factors, thereby predicting the actual ship's performance. A hull shape that is optimal in resistance tests may not be optimal in self-propulsion tests, and the same applies to propeller performance. Therefore, from an optimization design perspective, hull form optimization and propeller design should not only focus on resistance and open-water conditions, but also on resistance and propulsion performance under self-propulsion conditions. If resistance and propulsion performance under self-propulsion conditions can be separated, then hull form optimization and propeller design will be simplified to a single objective function optimization and design problem. However, current conventional resistance and self-propulsion test methods cannot analyze the various resistance components under self-propulsion conditions. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes a resistance component analysis method for waterjet-propelled ships, using waterjet-propelled vessels as the application target. Through conventional resistance tests, L-shaped nozzle resistance tests, self-propulsion tests, and flow field tests in the flow acquisition zone, the resistance is decomposed into the hull's own resistance component and the hull resistance increment caused by the suction effect of the waterjet propulsion device during operation. This allows for the identification of the propeller's impact on the hull, reducing hull shape optimization to a single objective function optimization problem, thus improving hull shape optimization efficiency. This method has significant practical value for ship hull shape optimization and propeller design.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a method for analyzing the resistance components of a waterjet-propelled ship model. First, a resistance test is conducted on the bare hull. Next, a self-propulsion test is conducted to determine the rotational speed of the waterjet propulsion device at a given self-propulsion point. Then, an L-shaped nozzle is installed, and the waterjet propulsion device operates at the self-propulsion point rotational speed at a specific speed. The total resistance of the hull is measured, and the flow field in the flow region is measured using PIV technology to calculate the inlet longitudinal momentum. Finally, the total resistance is subtracted from the bare hull resistance and the inlet longitudinal momentum to obtain the resistance increase caused by the suction effect of the waterjet propulsion device during operation. This distinguishes the various resistance components of the waterjet-propelled ship model under self-propulsion conditions, thus obtaining the influence of the propeller on the hull resistance at the corresponding self-propulsion point.

[0005] Furthermore, when a waterjet-propelled ship is sailing, the hull resistance is divided into two parts: the hull's own resistance and the impact of the waterjet propulsion system on the hull.

[0006] Furthermore, the hull's own resistance is obtained through resistance tests on the bare hull.

[0007] Furthermore, the effect of the waterjet propulsion device on the hull is obtained indirectly using an L-shaped nozzle device.

[0008] Furthermore, the L-shaped nozzle device is used for resistance testing of water-jet propulsion ship models. It is connected to the rear end of the water-jet propulsion device, changing the direction of water jetting from longitudinal to transverse.

[0009] Furthermore, in the drag test with L-shaped nozzles, the waterjet propulsion device was operated at the self-propulsion point speed at a specific speed, and the total hull drag was measured.

[0010] Furthermore, the total resistance includes three parts: the resistance of the bare hull, the resistance increased by the hull due to the operation of the propeller, and the resistance of the waterjet propulsion device.

[0011] Furthermore, the resistance of the water jet propulsion device is obtained through the longitudinal momentum difference between the inlet and outlet.

[0012] A method for analyzing the drag components of a waterjet-propelled ship model, using a high-speed surface vessel equipped with four identical waterjet propulsion devices as the analysis object, includes the following specific steps:

[0013] Step 1: Conduct a conventional resistance model test, which is to complete the resistance test with both the inlet and nozzle of the waterjet propulsion device closed. The ship model is 5.5m long, and the resistance of the ship model at a given speed V1 = 4.1m / s is measured to be R1 = 260N.

[0014] Step 2: Keep the inlet and nozzle open, and at a given speed V1, adjust the rotational speed of the water jet propulsion device. Based on the forced force Fd, find the rotational speed N1 corresponding to the self-propulsion point at that speed.

[0015] Step 3: Install an L-shaped nozzle after the conventional nozzle. The speed is V1 and the rotation speed is fixed at N1. At this time, the water flow is changed from longitudinal to transverse by the L-shaped nozzle. The hull resistance R1' = 440N is measured at this time. At the same time, the flow field in the flow area is measured by the PIV method, and the longitudinal momentum Min at the propeller inlet is calculated.

[0016] In step three, since the longitudinal momentum of the L-shaped nozzle is zero and the longitudinal momentum Min at the inlet is 172N, the thruster resistance is -Min. Therefore, R1'-Min = 268N is the hull resistance considering the effect of the thruster on the hull surface flow during operation. Compared with the bare hull resistance R1, R1'-Min-R1 = 8N is the part of the hull resistance increase caused by the thruster operation.

[0017] Furthermore, the inner diameter of the L-shaped nozzle is 1.5 times that of a conventional nozzle, and a guide vane is provided at the bend. It is connected and fixed to the stern sealing plate of the hull and the conventional nozzle through a flange.

[0018] The beneficial effects of this invention are:

[0019] This invention employs conventional resistance tests, L-shaped nozzle resistance tests, self-propelled tests, and flow field tests in the flow acquisition zone to decompose resistance into the hull's own resistance components and the hull resistance increment caused by the suction effect of the waterjet propulsion device. This allows for the differentiation of the propeller's impact on the hull, reducing hull shape optimization to a single objective function optimization problem and improving hull shape optimization efficiency. This invention has significant practical value for ship hull shape optimization and propeller design. Attached Figure Description

[0020] Figure 1 A schematic diagram of a waterjet-propelled vessel;

[0021] Figure 2 A schematic diagram of a waterjet propulsion vessel with an L-shaped nozzle device;

[0022] Figure 3 This is a schematic diagram of an L-shaped nozzle device. Detailed Implementation

[0023] The following specific examples illustrate the implementation methods, but are not intended to limit the scope of the invention.

[0024] I. Basic Principles of Resistance Component Analysis Method for Waterjet Propulsion Ship Models

[0025] When a waterjet-propelled ship is sailing, the hull resistance can be divided into two parts: the hull's own resistance and the effect of the propeller's operation on the hull. The former can be obtained through resistance tests on the bare hull, while the latter is obtained indirectly using the L-shaped nozzle device 2, see [reference needed]. Figure 1 The L-shaped nozzle is a device used for resistance testing of waterjet propulsion ship models. Connected to the rear end of the waterjet propulsion system, its function is to change the direction of the water jet from longitudinal to transverse. It is installed on hull 1, see [reference 1]. Figure 2 .

[0026] In the drag test with an L-shaped nozzle, the waterjet propulsion device is operated at its self-propulsion speed at a specific speed, and the total hull drag is measured. The total drag includes three parts: the bare hull drag, the drag added to the hull by the propeller operation, and the drag from the waterjet propulsion device. The bare hull drag is measured using conventional drag tests. The drag from the waterjet propulsion device is obtained by the difference in longitudinal momentum between the inlet and outlet. Due to the L-shaped nozzle, the longitudinal momentum at the outlet is zero, while the longitudinal momentum at the inlet can be measured using particle imaging velocimetry (PIV) technology. Therefore, subtracting the bare hull drag and the drag from the waterjet propulsion device from the total drag yields the drag added to the hull by the propeller's suction effect. This allows for the differentiation of the various drag components in the self-propulsion state of the waterjet propulsion model, more fully considering the impact of the propeller on the hull drag.

[0027] II. Main Steps

[0028] First, a resistance test is conducted on the bare hull. Next, a self-propulsion test is conducted to determine the rotational speed of the waterjet propulsion device at a given speed. Then, an L-shaped nozzle is installed, and the waterjet propulsion device is operated at the self-propulsion point speed at a specific speed. The total resistance of the hull is measured, and the flow field in the flow region is measured using PIV technology to calculate the longitudinal momentum at the inlet. Finally, by subtracting the bare hull resistance and the longitudinal momentum at the inlet from the total resistance, the impact of the propeller on the hull resistance at the corresponding self-propulsion point can be obtained.

[0029] This embodiment describes a high-speed surface vessel equipped with four identical waterjet propulsion devices. Step one: Conduct a conventional resistance model test, i.e., complete the resistance test with both the inlet and nozzle of the waterjet propulsion device closed. The model length is 5.5m, and the resistance R1 = 260N is measured at a given speed V1 = 4.1m / s. Step two: Keeping the inlet and nozzle open, at the given speed V1, adjust the rotational speed of the waterjet propulsion device, and find the rotational speed N1 corresponding to the self-propulsion point at that speed based on the forced force Fd. Step three: Add an L-shaped nozzle 2-1 after the conventional nozzle, see... Figure 3Its inner diameter is 1.5 times that of a conventional nozzle. A guide vane 2-2 is installed at the bend, and it is connected and fixed to the stern sealing plate 2-3 and the conventional nozzle via a flange. The speed is V1, and the rotational speed is fixed at N1. At this time, the water flow is changed from longitudinal to transverse by the L-shaped nozzle 2-1. The hull resistance R1' = 440N is measured at this time. Simultaneously, the flow field in the flow acquisition zone (the area at a characteristic diameter at the inlet front) is measured using the PIV method, and the longitudinal momentum Min at the propeller inlet is calculated. In the state of step three, since the longitudinal momentum of the L-shaped nozzle 2-1 is zero, the longitudinal momentum Min at the inlet is 172N. Therefore, the propeller resistance is -Min. R1' - Min = 268N is the hull resistance considering the influence of the propeller on the hull surface flow during operation. Compared with the bare hull resistance R1, R1' - Min - R1 = 8N is the increase in hull resistance caused by the propeller operation.

[0030] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of analyzing the resistance components of a waterjet-propelled model, characterized by: First, a resistance test was conducted on the bare hull. Next, a self-propulsion test was performed to determine the rotational speed of the waterjet propulsion device at a given self-propulsion point. Then, an L-shaped nozzle was installed, and the waterjet propulsion device was operated at the self-propulsion point rotational speed at a specific speed. The total resistance of the hull was measured, and the flow field in the flow region was measured using PIV technology to calculate the inlet longitudinal momentum. Finally, the resistance of the bare hull and the inlet longitudinal momentum were subtracted from the total resistance to obtain the resistance increase caused by the suction effect of the waterjet propulsion device during operation. This allowed for the differentiation of the various resistance components in the self-propulsion state of the waterjet propulsion model, revealing the impact of the propeller operation on the hull resistance at the corresponding self-propulsion point. The impact of the waterjet propulsion device on the hull was determined using an L-shaped nozzle. The nozzle device is obtained indirectly; the L-shaped nozzle device is used for the resistance test of the waterjet propulsion ship model, and is connected to the rear end of the waterjet propulsion device to change the direction of water jet from longitudinal to transverse; in the resistance test with the L-shaped nozzle, for a specific speed, the waterjet propulsion device is made to operate at the self-propulsion point speed at that speed, and the total hull resistance is measured; the total resistance includes three parts: the bare hull resistance, the resistance added to the hull by the operation of the propeller, and the resistance of the waterjet propulsion device; the resistance of the waterjet propulsion device is obtained by the longitudinal momentum difference between the inlet and outlet. Due to the addition of the L-shaped nozzle, the longitudinal momentum at the outlet is zero, and the longitudinal momentum at the inlet is measured by particle imaging velocimetry technology in the flow field of the flow acquisition area.

2. The method for analyzing the resistance components of a waterjet propulsion ship model according to claim 1, characterized in that: When a waterjet-propelled ship is sailing, the ship's resistance is divided into two parts: the resistance of the ship itself and the effect of the waterjet propulsion device on the ship.

3. The method for analyzing the resistance components of a waterjet propulsion ship model according to claim 2, characterized in that: The hull's own resistance was obtained through resistance tests on the bare hull.

4. A method for analyzing the resistance components of a waterjet-propelled ship model as described in claim 1, using a high-speed surface vessel equipped with four identical waterjet propulsion devices as the analysis object, characterized in that... The specific steps are as follows: Step 1: Conduct a conventional resistance model test, which is to complete the resistance test with the inlet and nozzle of the waterjet propulsion device closed. The ship model is 5.5m long, and the resistance of the ship model at a given speed V1=4.1m / s is measured to be R1=260N. Step 2: Keep the inlet and nozzle open, and at a given speed V1, adjust the rotational speed of the water jet propulsion device. Based on the forced force Fd, find the rotational speed N1 corresponding to the self-propulsion point at that speed. Step 3: Install an L-shaped nozzle after the conventional nozzle. The inner diameter of the L-shaped nozzle is 1.5 times that of the conventional nozzle. A guide vane is installed at the bend. The nozzle is connected and fixed to the stern plate of the hull and the conventional nozzle through a flange. The speed is V1 and the rotational speed is fixed at N1. At this time, the water flow is changed from longitudinal to transverse by the L-shaped nozzle. The hull resistance R1' is measured to be 440N. At the same time, the flow field in the flow area is measured by the PIV method, and the longitudinal momentum Min at the propeller inlet is calculated. In step three, since the longitudinal momentum of the L-shaped nozzle is zero and the longitudinal momentum Min at the inlet is 172N, the thruster resistance is -Min. Therefore, R1'-Min=268N is the hull resistance considering the effect of the thruster on the hull surface flow during operation. Compared with the bare hull resistance R1, R1'-Min-R1=8N is the part of the hull resistance increase caused by the thruster operation.

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