A hydrodynamic model test method for direct measurement of splash resistance

Abstract

The present invention belongs to the field of measuring splash resistance during a hydrodynamic model test of a planing body in a fixed state, and specifically relates to a hydrodynamic model test method for directly measuring splash resistance. The method comprises: using an integrated model to conduct a fixed state test to determine a splash station line and a resistance F, specifically: using a trailer (5) to drive the integrated model to move, and after reaching a test speed V, obtaining the splash station line of the integrated model by taking a photo with a camera mounted on the trailer (5); using a split model to conduct a fixed state test, the split model including a front model and a rear model, specifically: using a trailer (5) to drive the integrated model to move, and after reaching a test speed V, obtaining the front model resistance F1 and the rear model resistance F2, wherein the dividing line between the front planing body hydrodynamic model (1-1) and the rear planing body hydrodynamic model (1-2) is the splash station line; and when the error between the sum of the front model resistance F1 and the rear model resistance F2 and the resistance F is less than a predetermined value, determining the front model resistance F1 as the splash resistance.

Description

Technical Field

[0001] The invention belongs to the field of splash resistance measurement during hydrodynamic model tests of planing bodies in fixed navigation states, and particularly relates to a hydrodynamic model test method for directly measuring splash resistance. Background Art

[0002] High-speed planing fluid dynamics is a complex problem with strong nonlinear characteristics. The splashing phenomenon that accompanies navigation, including the description of the splash zone geometry, the analysis of flow field characteristics and flow regime transitions, and the calculation of splash resistance, further complicates the calculation of fluid dynamic loads and the analysis of splash mechanisms. During planing, significant splashing occurs at the bottom, creating splash resistance. The resulting water separation, vortexing, and eddying create a vigorous mixing of the water-air two-phase fluid at the free surface, exhibiting strong nonlinear characteristics. Therefore, accurately measuring splash resistance is crucial for calculating the fluid dynamic loads on surface vehicles and planing craft. By placing pressure sensors on the bottom of the craft to measure the hydrodynamic pressure during navigation and simultaneously capturing the splash zone and planing surface with high-speed video, the planing surface pressure sensor data can be processed and analyzed to determine the drag characteristics of the planing surface. This is an indirect method for analyzing and calculating the splash resistance of a planing craft. In this method, the pressure within the contour of the splash area of ​​the sliding surface changes with the arrangement position of the pressure sensor. There is undoubtedly a large error in obtaining the splash resistance by integrating the points instead of the surface. Summary of the Invention

[0003] Purpose of the invention: To provide a hydrodynamic model test method for direct measurement of splash resistance, so as to improve the measurement accuracy of splash resistance.

[0004] Technical solution:

[0005] A hydrodynamic model test method for direct measurement of splash resistance, comprising:

[0006] A fixed-state test was conducted using an integrated model to determine the splash station line and the drag force F. Specifically, the integrated model was driven by a trailer 5 to reach a test speed V. The splash station line of the integrated model was then photographed using a camera mounted on the trailer 5. The integrated model included a planing body hydrodynamic model 1, a connector 2, and a force balance 3. The connector 2 fixedly connected the planing body hydrodynamic model 1 to the force balance 3. The integrated model was connected to the trailer 5 via a pipe 4. The model drag force F was measured using the force balance 3.

[0007] A split model is used to conduct a fixed navigation test. The split model includes a front model and a rear model. Specifically, the trailer 5 is used to drive the integrated model to move. After reaching the test speed V, the front model resistance F1 and the rear model resistance F2 are obtained. The front model includes a front gliding body hydrodynamic model 1-1, a front connector 2-1, and a front force balance 3-1. The front connector 2-1 fixedly connects the front gliding body hydrodynamic model 1-1 with the front force balance 3-1; the rear model includes a rear gliding body hydrodynamic model 1-2, a rear connector 2-1, and a rear force balance 3-1. Connector 2-2, rear force balance 3-2, rear connector 2-2 fixedly connects rear gliding body hydrodynamic model 1-2 to rear force balance 3-2; the dividing line between front gliding body hydrodynamic model 1-1 and rear gliding body hydrodynamic model 1-2 is the splash station line, and the gap is sealed with transparent tape. The front model and rear model are connected to trailer 5 via front pipe 4-1 and rear pipe 4-2 respectively. The resistance F1 of the front model is measured via front force balance 3-1, and the resistance F2 of the rear model is measured via rear force balance 3-2;

[0008] When the error between the sum of the front model resistance F1 and the rear model resistance F2 and the resistance F is smaller than a predetermined value, the front model resistance F1 is determined as the splash resistance.

[0009] Furthermore, the sliding body hydrodynamic model 1 in the integrated model is a sliding surface made of 20 mm thick acrylic material, and grid lines with a side length of 2 cm are engraved on the non-sliding surface of the sliding body hydrodynamic model 1 .

[0010] Furthermore, the cross section of the sliding surface of the hydrodynamic model 1 in the integrated model is a V-shaped extension surface or an arc-shaped extension surface.

[0011] Furthermore, the force balance 3 , the front force balance 3 - 1 and the rear force balance 3 - 2 should at least measure the resistance along the speed direction.

[0012] Furthermore, the gap between the front gliding body hydrodynamic model 1-1 and the rear gliding body hydrodynamic model 1-2 is 2 to 3 mm.

[0013] Furthermore, the test speed V is greater than a predetermined speed, and the predetermined speed is a speed at which the splashing area does not change with the speed.

[0014] Furthermore, the front connecting member 2-1 includes four angle aluminums 2-1-1 connected to the front gliding body hydrodynamic model 1-1, a docking plate 2-1-3 connected to the front force measuring balance 3-1, and a supporting aluminum plate 2-1-2 connecting the four angle aluminums 2-1-1 and the docking plate 2-1-3; the rear connecting member 2-2 includes four angle aluminums 2-2-1 connected to the rear gliding body hydrodynamic model 2-1, a docking plate 2-2-3 connected to the rear force measuring balance 3-2, and four supporting aluminum plates 2-2-2 connecting the angle aluminums 2-2-1 and the docking plate 2-2-3.

[0015] Furthermore, the sliding body hydrodynamic model 1 is a prismatic sliding body.

[0016] Beneficial effects:

[0017] The present invention solves the problem of directly measuring the splash resistance of the hydrodynamic model and overcomes the difficulty in separating the splash resistance from the total resistance. Through a structure composed of pipes, a force balance, connectors, and a sliding body hydrodynamic model, the present invention realizes direct measurement of the splash resistance of the hydrodynamic model in two tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Attachment Figure 1 This is a schematic plan view of the prismatic planing body and the splash zone under deep draft conditions;

[0019] Attachment Figure 2 This is a schematic plan view of the prismatic planing body and the splash zone in shallow draft conditions;

[0020] Attachment Figure 3 It is a schematic diagram of the integrated model structure;

[0021] Attachment Figure 4 This is a side view of the integrated model installed on a trailer;

[0022] Attachment Figure 5 It is a schematic diagram of the split model structure;

[0023] Attachment Figure 6 This is a side view of the split model installed on a trailer;

[0024] Attachment Figure 7 It is a schematic diagram of the hydrodynamic model of the front planing body in the split model;

[0025] Attachment Figure 8 It is a schematic diagram of the front connecting part in the split model;

[0026] Attachment Figure 9 It is a schematic diagram of the hydrodynamic model of the rear gliding body in the split model;

[0027] Attachment Figure 10 It is a schematic diagram of the rear connector in the split model;

[0028] Attachment Figure 11 It is the percentage of splash resistance to total resistance in the embodiment. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] like Figure 1 、 Figure 2As shown, the wetted area can be divided into two regions. One is the area from the stagnation line to the stern, which is considered to be the planing surface. It is bounded by the wetted keel length, the two wetted kink line lengths, the stern plate and the stagnation line. The stagnation line is usually regarded as the splash root line. The direction of the flow velocity in this area is mainly towards the stern and attached to the bottom of the planing surface. The flow velocity along the splash root line is mainly in the direction of the stagnation line. The total viscous drag of the planing body is calculated using the area behind the splash root line as the total wetted area. The other wetted area is the area in front of the stagnation line. It is usually regarded as the whisker splash zone. This area can be clearly observed using a transparent model.

[0031] like Figure 3 、 Figure 4 As shown, the integrated model comprises a hydrodynamic model 1 for the planing body, a connector 2, and a force balance 3. The integrated model is connected to a trailer 5 via a pipe 4. In this embodiment, the hydrodynamic model 1 uses a 20 mm thick acrylic material as its planing surface. The model is 1.4 m long, 0.5 m wide, with a pitch angle β of 20° and a pitch angle τ of 3°. The planing surface of the hydrodynamic model 1 is flat in this embodiment, but is not limited to this. The cross-section can also be a curved surface. A grid line with a side length of 2 cm is engraved on the non-planing surface of the hydrodynamic model 1, which is made of transparent acrylic. Fixed-state tests of the integrated model were conducted, and the splash line of the integrated model was obtained by photographing with a camera mounted on the trailer. The splash line is the boundary between the planing zone and the splash zone. The planing zone is primarily water flowing and appears black when observed; the splash zone is primarily a water-air mixture, i.e., splashing, and appears white when observed. The force balance 3 should be capable of measuring forces and moments in at least three directions: drag along the velocity direction, lift in the vertical direction, and pitching moment in the pitch direction. The drag measured by the force balance 3 is the sum of water drag and splash resistance. The splash area gradually increases at low speeds (test speed V less than 5 m / s). At medium and high speeds (test speed V greater than 5 m / s), the splash area remains essentially unchanged, i.e., it does not vary with speed.

[0032] According to the positions of the splash stationary lines on the grid lines of the planing body hydrodynamic model 1, the planing body hydrodynamic model 1 is divided into a front planing body hydrodynamic model 1-1 and a rear planing body hydrodynamic model 1-2.

[0033] like Figure 5 、 Figure 6As shown, the split model consists of a front gliding body hydrodynamic model 1-1, a rear gliding body hydrodynamic model 1-2, a front connector 2-1, a rear connector 2-2, a front force balance 3-1, and a rear force balance 3-2. The split model is connected to a trailer 5 via a front pipe 4-1 and a rear pipe 4-2. During a fixed-state test of the split model, the resistance measured by the front force balance 3-1 is the splash resistance, while the resistance measured by the rear force balance 3-2 is the water resistance (including friction resistance and form resistance).

[0034] The gap between the front gliding body hydrodynamic model 1-1 and the rear gliding body hydrodynamic model 1-2 is 2 to 3 mm. The gap between the front gliding body hydrodynamic model 1-1 and the rear gliding body hydrodynamic model 1-2 is sealed with transparent tape to prevent water from flowing into the gap from the gliding surface.

[0035] like Figure 7 As shown, the front sliding body hydrodynamic model 1-1 is a hydrodynamic model of the vehicle, which is made of transparent acrylic material.

[0036] like Figure 8 As shown, the rear sliding body hydrodynamic model 1-2 is a hydrodynamic model of the vehicle, which is made of transparent acrylic material.

[0037] like Figure 9 As shown, the front connecting member 2-1 includes four angle aluminums 2-1-1 connected to the front gliding body hydrodynamic model 1-1, a docking plate 2-1-3 connected to the front force measuring balance 3-1, and four supporting aluminum plates 2-1-2 connecting the angle aluminums 2-1-1 and the docking plates 2-1-3.

[0038] like Figure 10 As shown, the rear connecting member 2-2 includes four aluminum angles 2-2-1 connected to the rear gliding body hydrodynamic model 2-1, a docking plate 2-2-3 connected to the rear force measuring balance 3-2, and four supporting aluminum plates 2-2-2 connecting the aluminum angles 2-2-1 and the docking plate 2-2-3.

[0039] The test steps are as follows:

[0040] a) Installation of integrated model

[0041] Refer to the attached Figure 4 , install the hydrodynamic model of the sliding body 1, the connector 2, and the force balance 3 in sequence from bottom to top. The integrated model is connected to the trailer 5 through the pipe 4.

[0042] b) Integrated model fixed flight test

[0043] The trailer 5 is started and reaches the test speed. A camera mounted on the trailer is used to capture the splash line of the integrated model. The splash line is the boundary between the sliding zone and the splash zone. The resistance measured by the force balance 3 is the sum of the water resistance and the splash resistance.

[0044] c) Split the integrated model and process the split model

[0045] According to the positions of the splash stationary lines on the grid lines of the planing body hydrodynamic model 1, the planing body hydrodynamic model 1 is divided into a front planing body hydrodynamic model 1-1 and a rear planing body hydrodynamic model 1-2.

[0046] d) Installation of split model

[0047] Reference Figure 6 From bottom to top, install the front hydrodynamic model 1-1, front connector 2-1, and front force balance 3-1, connecting them to the trailer 5 via the front pipe 4-1. Install the rear hydrodynamic model 1-2, rear connector 2-2, and rear force balance 3-2, connecting them to the trailer 5 via the rear pipe 4-2. The gap between the front and rear hydrodynamic models 1-1 and 1-2 is 2-3 mm. Use transparent tape to seal the gap between the front and rear hydrodynamic models to prevent water from flowing into the gap from the gliding surface.

[0048] e) Split model fixed flight test

[0049] When the trailer 5 is started and reaches the test speed, the resistance measured by the front force balance 3-1 is the splash resistance, and the resistance measured by the rear force balance 3-2 is the water resistance (including friction resistance and shape resistance).

[0050] The present invention provides the test results of one embodiment for reference to the implementation effect of the present invention.

[0051] Table 1 Main scales of the hydrodynamic model 1 of the planing body

[0052]

[0053] The test was carried out when the draft of the lower edge of the keel at the rear end of the planing body hydrodynamic model 1 was 58 mm, and the test speed range was 5 m / s to 15 m / s.

[0054] like Figure 11 As shown, in this embodiment, the average percentage of the splash resistance to the total resistance is 21.18%.

Claims

1. A hydrodynamic model test method for direct measurement of splash resistance, characterized in that: include: A fixed-state test using an integrated model was conducted to determine the splash station line and drag force F. Specifically, the integrated model was driven by a trailer to reach a test speed V. The splash station line of the integrated model was then photographed using a camera mounted on the trailer. The integrated model included a hydrodynamic model of the planing body, a connector, and a force balance. The connector fixedly connected the hydrodynamic model to the force balance. The integrated model was connected to the trailer via a pipe fitting, and the model drag force F was measured using the force balance. A fixed navigation state test is carried out using a split model, which includes a front model and a rear model. Specifically, the trailer is used to drive the integrated model to move, and after reaching the test speed V, the front model resistance F1 and the rear model resistance F2 are obtained, wherein the front model includes a front planing body hydrodynamic model, a front connector, and a front force balance, and the front connector fixedly connects the front planing body hydrodynamic model to the front force balance; the rear model includes a rear planing body hydrodynamic model, a rear connector, and a rear force balance, and the rear connector fixedly connects the rear planing body hydrodynamic model to the rear force balance; the dividing line between the front planing body hydrodynamic model and the rear planing body hydrodynamic model is the splash station line, and the gap is pasted with transparent tape, the front model and the rear model are connected to the trailer through the front pipe and the rear pipe respectively, the front model resistance F1 is measured by the front force balance, and the rear model resistance F2 is measured by the rear force balance; When the error between the sum of the front model resistance F1 and the rear model resistance F2 and the resistance F is smaller than a predetermined value, the front model resistance F1 is determined as the splash resistance.

2. The hydrodynamic model test method for direct measurement of splash resistance according to claim 1 is characterized in that: The hydrodynamic model of the sliding body in the integrated model is a sliding surface made of 20 mm thick acrylic material, and grid lines with a side length of 2 cm are engraved on the non-sliding surface of the hydrodynamic model of the sliding body.

3. The hydrodynamic model test method for direct measurement of splash resistance according to claim 1 is characterized in that: The cross section of the sliding surface of the hydrodynamic model in the integrated model is a V-shaped extension surface or an arc-shaped extension surface.

4. The hydrodynamic model test method for direct measurement of splash resistance according to claim 1 is characterized in that: The force balance, front force balance and rear force balance should at least measure the resistance in the direction of velocity.

5. The hydrodynamic model test method for direct measurement of splash resistance according to claim 1 is characterized in that: The gap between the front and rear hydrodynamic models is 2-3 mm.

6. The hydrodynamic model test method for direct measurement of splash resistance according to claim 1 is characterized in that: The test speed V is greater than a predetermined speed, and the predetermined speed is a speed at which the splashing area does not change with the speed.

7. The hydrodynamic model test method for direct measurement of splash resistance according to claim 1 is characterized in that: The front connecting part includes four first angle aluminums connected to the front sliding body hydrodynamic model, a first docking plate connected to the front force measuring balance, and a first supporting aluminum plate connected to the four first angle aluminums and the first docking plate; the rear connecting part includes four second angle aluminums connected to the rear sliding body hydrodynamic model, a second docking plate connected to the rear force measuring balance, and four second supporting aluminum plates connecting the second angle aluminums and the second docking plates.

8. The hydrodynamic model test method for direct measurement of splash resistance according to claim 1 is characterized in that: The hydrodynamic model of the sliding body is a prismatic sliding body.

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