Method for Applying Pulsating Pressure in Prediction of Overall Vibration of Ship

Abstract

The present invention discloses a method for applying pulsating pressure in the prediction of total ship vibration, which is characterized by the following steps: obtaining the values of the total pulsating pressure P at different measuring points, the pulsating pressure P1 of the non-cavitating propeller, the phase angle θ when the total pulsating pressure P occurs, and the phase angle θ1 when the pulsating pressure P1 of the non-cavitating propeller occurs from the ship cavitation test report; calculating the pulsating pressure P2 of the cavitating propeller and the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs at different measuring points; calculating the pulsating pressure P1r of the non-cavitating propeller and the pulsating pressure P2r of the cavitating propeller when the propeller speed is r; applying the values of P1r and P2r obtained in step 3 to the hull surface to complete the application of pulsating pressure in the prediction of total ship vibration. The present invention applies separately according to different components of the pulsating pressure, providing a reliable and reasonable application method for the accuracy of the prediction result of total ship vibration.

Description

Technical Field

[0001] The present invention relates to the technical field of ships, and in particular to a method for applying pulsating pressure in ship total vibration prediction. Background Art

[0002] In the current conventional ship total vibration prediction, the pulsating pressure is usually applied on the outer surface of the hull using the concentrated force or surface load method, and the total pulsating pressure from the cavitation test report is used as the input load.

[0003] The current prediction of total ship vibration does not distinguish between the different components of pulsating pressure, that is, it does not distinguish between the pulsating pressure caused by cavitation and the pulsating pressure caused by non-cavitation, nor does it distinguish the attenuation laws of the two, nor does it distinguish the different phase angles of the two. Its calculation results lack rationality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art and provide a method for applying pulsating pressure in ship total vibration prediction.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] A method for applying pulsating pressure in ship total vibration prediction comprises the following steps:

[0007] Step 1: Obtain the total pulsating pressure P at different measuring points, the pulsating pressure P1 of the non-cavitating propeller, the phase angle θ when the total pulsating pressure P occurs, and the phase angle θ1 when the pulsating pressure P1 of the non-cavitating propeller occurs from the ship cavitation test report;

[0008] Step 2: Calculate the pulsating pressure P2 of the cavitating propeller at different measuring points and the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs;

[0009] Step 3: Calculate the pulsating pressure P of the non-cavitating propeller when the propeller speed is r 1r and the pulsating pressure P of the cavitating propeller when the propeller speed is r 2r ;

[0010] Step 4: P obtained in step 3 1r and P 2r The value is applied to the hull surface to complete the application of pulsating pressure in the total vibration prediction of the ship.

[0011] In step 2, the calculation formula for the pulsating pressure P2 of the cavitating propeller at different measuring points is:

[0012]

[0013] where, ε1 = θ - θ1.

[0014] According to the values of P, θ, P1, and θ1 in Step 1, the value of P2 is obtained.

[0015] In Step 2, the calculation formula for the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs is:

[0016]

[0017] According to the values of P, θ, P1, and θ1 in Step 1, the value of θ2 is obtained.

[0018] In Step 3, for the non-cavitating propeller, the pulsating pressure P 1r when the propeller rotation speed is r, the calculation formula is:

[0019]

[0020] where, N m is the rotation speed of the propeller in the cavitation test report in Step 1.

[0021] Take the maximum value of the pulsating pressure P1 of the non-cavitating propeller measured in the ship cavitation test report in Step 1 and input it into the calculation formula of P 1r to obtain the value of P 1r of.

[0022] In Step 3, for the cavitating propeller, the pulsating pressure P 2r when the propeller rotation speed is r, the calculation formula is:

[0023]

[0024] where, N m is the rotation speed of the propeller in the ship cavitation test report in Step 1.

[0025] Take the maximum value of the pulsating pressure P2 of the cavitating propeller at all measurement points obtained in Step 2 and input it into the calculation formula of P 2r to obtain the value of P 2r of.

[0026] In Step 4, after the pulsating pressure is applied in the ship total vibration prediction, the total hull vibration calculation is carried out.

[0027] The beneficial effects of the present invention are as follows: The present invention solves the problem that the total vibration calculation cannot accurately predict due to the inconsistency of the cavitation pressure and non-cavitation pressure in magnitude and phase angle.The pulsating pressure application method in the ship total vibration prediction of the present invention distinguishes the cavitation pressure and non-cavitation pressure, and applies them separately according to different components of the pulsating pressure, providing a reliable and reasonable application method for the accuracy of the ship total vibration prediction result. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the steps of a preferred embodiment of the present invention.

[0029] Figure 2 It is a vector relationship diagram of various parameters in a preferred embodiment of the present invention.

[0030] Figure 3 It is a finite element analysis diagram after applying the pulsating pressure of a non-cavitating propeller to the hull surface in a preferred embodiment of the present invention.

[0031] Figure 4 It is a finite element analysis diagram after applying the pulsating pressure of a cavitating propeller to the hull surface in a preferred embodiment of the present invention. Detailed Description of the Preferred Embodiment

[0032] The following is a preferred embodiment, and the present invention will be more clearly and completely described in conjunction with the accompanying drawings.

[0033] As Figure 1 shown, a method for applying pulsating pressure in the prediction of total ship vibration includes the following steps:

[0034] Step 1: Obtain the values of the total pulsating pressure P, the pulsating pressure P1 of the non-cavitating propeller, the phase angle θ when the total pulsating pressure P occurs, and the phase angle θ1 when the pulsating pressure P1 of the non-cavitating propeller occurs at different measurement points from the ship cavitation test report.

[0035] The vector relationships of the total pulsating pressure P, the pulsating pressure P1 of the non-cavitating propeller, the phase angle θ when the total pulsating pressure P occurs, the phase angle θ1 when the pulsating pressure P1 of the non-cavitating propeller occurs, the pulsating pressure P2 of the cavitating propeller, and the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs are as Figure 2 shown.

[0036] Step 2: Calculate the pulsating pressure P2 of the cavitating propeller and the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs at different measurement points.

[0037] In Step 2, the calculation formulas for the pulsating pressure P2 of the cavitating propeller and the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs at different measurement points are respectively:

[0038]

[0039]

[0040] where ε1 = θ - θ1.

[0041] According to the values of P, θ, P1, and θ1 in Step 1, the values of P2 and θ2 are obtained.

[0042] Step 3: Calculate the pulsating pressure P of the non-cavitating propeller at a propeller rotation speed of r 1r and the pulsating pressure P of the cavitating propeller at a propeller rotation speed of r 2r .

[0043] In Step 3, the formula for calculating the pulsating pressure P of the non-cavitating propeller at a propeller rotation speed of r 1r is as follows:

[0044]

[0045] where N m is the rotation speed of the propeller in the ship cavitation test report in Step 1.

[0046] Take the maximum value of the pulsating pressure P1 of the non-cavitating propeller measured in the cavitation test report in Step 1 and input it into the calculation formula of P 1r to obtain the value of P 1r .

[0047] In Step 3, the formula for calculating the pulsating pressure P of the cavitating propeller at a propeller rotation speed of r 2r is as follows:

[0048]

[0049] where N m is the rotation speed of the propeller in the ship cavitation test report in Step 1.

[0050] Take the maximum value of the pulsating pressure P2 of the cavitating propeller at all measurement points obtained in Step 2 and input it into the calculation formula of P 2r to obtain the value of P 2r .

[0051] Step 4: Apply the values of P 1r and P 2r obtained in Step 3 to the hull surface to complete the application of the pulsating pressure in the ship total vibration prediction.

[0052] After the application of the pulsating pressure in the ship total vibration prediction is completed, the total hull vibration calculation is performed.

[0053] In this embodiment, the finite element analysis diagrams of a certain type of ship after actually applying the pulsating pressure of the non-cavitating propeller and the pulsating pressure of the cavitating propeller to the hull 10 surface are as shown in Figure 3 and Figure 4 .

[0054] Figure 3 is the pulsating pressure distribution state diagram of the non-cavitating propeller on the hull surface, Figure 4 is the pulsating pressure distribution state diagram of the cavitating propeller on the hull surface.

[0055] From Figure 3 and Figure 4 it can be seen that there are significant differences in both the acting area and the numerical value of the pulsating pressure of the non-cavitating propeller and that of the cavitating propeller on the hull surface.

[0056] The present invention solves the problem that the total vibration calculation cannot be accurately predicted due to the inconsistency in the magnitude and phase angle of the cavitation pressure and the non-cavitation pressure.

[0057] The method for applying pulsating pressure in the prediction of the total vibration of a ship according to the present invention differentiates between the cavitation pressure and the non-cavitation pressure and applies them separately according to different components of the pulsating pressure, providing a reliable and reasonable application method for the accuracy of the prediction result of the total vibration of the ship.

[0058] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only an example, and the protection scope of the present invention is defined by the appended claims. Without departing from the principle and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A method for applying pulsating pressure in ship total vibration prediction, characterized in that: It includes the following steps: Step 1: Obtain the total pulsating pressure P at different measuring points, the pulsating pressure P1 of the non-cavitating propeller, the phase angle θ when the total pulsating pressure P occurs, and the phase angle θ1 when the pulsating pressure P1 of the non-cavitating propeller occurs from the ship cavitation test report; Step 2: Calculate the pulsating pressure P2 of the cavitating propeller at different measuring points and the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs; Step 3: Calculate the pulsating pressure P of the non-cavitating propeller when the propeller speed is r 1r and the pulsating pressure P of the cavitating propeller when the propeller speed is r 2r ; Step 4: P obtained in step 3 1r and P 2r The value is applied to the hull surface to complete the application of pulsating pressure in the total vibration prediction of the ship.

2. The method for applying pulsating pressure in ship total vibration prediction according to claim 1, characterized in that: In step 2, the calculation formula for the pulsating pressure P2 of the cavitating propeller at different measuring points is: Among them, ε1=θ-θ1.

3. The method for applying pulsating pressure in ship total vibration prediction according to claim 2, characterized in that: Based on the values of P, θ, P1, and θ1 in step 1, the value of P2 is obtained.

4. The method for applying pulsating pressure in ship total vibration prediction according to claim 2, characterized in that: In step 2, the calculation formula for the phase angle θ2 when the pulsating pressure P2 of the cavitating propeller occurs is:

5. The method for applying pulsating pressure in ship total vibration prediction according to claim 4, characterized in that: Based on the values of P, θ, P1, and θ1 in step 1, the value of θ2 is obtained.

6. The method for applying pulsating pressure in ship total vibration prediction according to claim 1, characterized in that: In step 3, the pulsating pressure P of the non-cavitating propeller when the propeller speed is r 1r The calculation formula is: Among them, N m is the propeller speed from the cavitation test report in step 1.

7. The method for applying pulsating pressure in ship total vibration prediction according to claim 6, characterized in that: Take the maximum value of the pulsating pressure P1 of the non-cavitating propeller measured in the ship cavitation test report in step 1 and input it into P 1r The calculation formula for P 1r The numerical value of .

8. The method for applying pulsating pressure in ship total vibration prediction according to claim 1, characterized in that: In step 3, the pulsating pressure P of the cavitating propeller when the propeller speed is r 2r The calculation formula is: Among them, N m is the propeller speed in the ship cavitation test report in step 1.

9. The method for applying pulsating pressure in ship total vibration prediction according to claim 8, characterized in that: Take the maximum value of the pulsating pressure P2 of the cavitating propeller at all measuring points obtained in step 2 and input it into P 2r The calculation formula for P 2r The numerical value of .

10. The method for applying pulsating pressure in ship total vibration prediction according to claim 1, characterized in that: In step 4, after the pulsating pressure in the ship's total vibration prediction is applied, the total vibration of the hull is calculated.

Images