Overall scheme stage ship stern mechanical noise evaluation method and system and storage medium

Abstract

The invention discloses an overall scheme stage ship stern mechanical noise evaluation method and system and a storage medium. Comprising the following steps: determining geometric parameters, material attributes and damping laying conditions of a stern structure according to an overall design scheme of a ship; the length l of an underwater ship stern truncation model is determined, and a statistical energy model is established; combing a stern noise excitation source, and determining an excitation load; and calculating a sound pressure level LPi of the stern radiation noise, and converting the sound pressure level LPi into a total sound source level LPoa and a frequency band sound source level LPo, thereby realizing evaluation of the stern mechanical noise in the ship overall scheme design stage. The method has the advantages of being high in forecasting efficiency, few in resources needed by calculation and wide in calculation frequency band.

Description

Technical Field

[0001] The present invention belongs to the technical field of ship vibration and noise reduction demonstration and evaluation, and particularly relates to a method, a system and a storage medium for evaluating the mechanical noise of the stern part of a ship in the overall scheme stage. Background Art

[0002] The index of underwater radiated noise of a ship is one of the core indexes of the ship, which directly determines the concealment and survivability of the ship. Moreover, the underwater radiated noise of the ship will also interfere with the normal operation of underwater equipment, such as hydrophones and sonars. And the mechanical noise of the stern part accounts for the main part of the underwater radiated noise of the ship. Therefore, it is necessary to strengthen the evaluation of the mechanical noise of the stern part of the ship, which is of great significance for promoting the acoustic design of the overall scheme and ensuring the realization of the mechanical noise index.

[0003] At present, there is no method for quantitative calculation and evaluation based on the statistical energy method for the mechanical noise of the stern part of the ship's overall scheme at home and abroad. Therefore, according to the drawing data in the ship's overall scheme design stage, the present invention clarifies the structural dimension parameters, determines the excitation load, and establishes a method for evaluating the mechanical noise of the stern part of the ship based on these parameters, which is of great significance for realizing the quantitative evaluation of the mechanical noise of the stern part of the ship's overall scheme. Summary of the Invention

[0004] The purpose of the present invention is to provide a method, a system and a storage medium for evaluating the mechanical noise of the stern part of a ship in the overall scheme stage.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A method for evaluating the mechanical noise of the stern part of a ship in the overall scheme stage, the specific steps are as follows:

[0007] Step 1: Analyze the design results of the ship's overall scheme to obtain the characteristic parameters of the stern structure;

[0008] Step 2: According to the structural characteristic parameters obtained in Step 1, establish a truncated model of the ship's stern structure by using the three-dimensional modeling method;

[0009] Step 3: According to Step 2, establish a SEA model of the mechanical noise of the stern based on the statistical energy method;;

[0010] Step 4: Determine and apply the excitation load;

[0011] Step 5: Solve by using the statistical energy method to obtain the calculation result of the sound pressure at the radiation noise assessment point; calculate the source level according to the sound source level calculation formula, and then obtain the total source level and the frequency band source level of the stern radiation noise;

[0012] Step 6: Evaluation of the mechanical noise at the stern of the ship. Obtain the mechanical noise index at the stern of the ship according to the actual application requirements and relevant indicators of the ship, and compare it with the calculation results of the total sound source level and the frequency band sound source level of the mechanical noise at the stern of the ship obtained in Step 5 to determine the magnitude of the risk of the mechanical noise index at the stern of the ship, and judge whether the ship continues to be designed or optimize the stern and evaluate again.

[0013] Further, the characteristic parameters of the stern structure obtained in Step 1 include: inner and outer hulls, brackets, shafting, pedestals, bulkheads and deck platforms; for the structures with unclear parameters, refer to the values of the parent ship type.

[0014] Further, the truncated model length l in Step 2 satisfies:

[0015]

[0016] In the formula, ζ is the damping ratio; N is the ratio of the maximum response value of the original structure vibration to the negligible response limit value; t is the thickness of the plate and shell; E is the elastic modulus; ρ is the density of the plate and shell material; μ is the Poisson's ratio of the material; ω is the excitation frequency.

[0017] Further, the number of modes n within the calculation bandwidth Δf of the SEA model subsystem in Step 3 satisfies n≥4; the internal loss factor η and the coupling loss factor η of the structure 12 Adopt the test values; establish a seawater medium acoustic cavity between the hulls, apply seawater loading to the side where the hull structure contacts the seawater or the water between the hulls to simulate the influence of the attached water, and connect the outer hull plate to the semi-infinite domain; set a sound pressure assessment point 1000 m to the left of the center of the hull.

[0018] Further, the mechanical noise excitation loads in Step 4 include the propeller bearing force load, the load at the front bearing of the stern shaft, and the load at the thrust bearing; the propeller bearing force includes the axial force F x , the lateral force F y , and the vertical force F z ;

[0019] The axial force F x , the lateral force F y , and the vertical force F z The blade frequency loads F x1 , F y1 , F z1 , and the formula is as follows:

[0020]

[0021] In the formula, SHP - the shaft power of the propeller, kW; n - the shaft speed, r / min; D - the diameter of the propeller, m;

[0022] The blade frequency load F1 of the propeller bearing force and the n-fold blade frequency load F of the propellern , the formula is as follows:

[0023] F n = F1 × 0.15 n

[0024] The bearing force is processed into a 1 / 3 octave form and loaded on the plate subsystem at the hub. Among them, the axial force F x points to the bow, the lateral force F y points to the port side, and the vertical force F z is vertically upward; the loads at the front bearing of the stern shaft and the thrust bearing are based on the test data of the parent ship and are loaded on the plate subsystem at the die head and the plate subsystem at the thrust bearing pedestal in the form of 1 / 3 octave vibration acceleration level.

[0025] Furthermore, for the total sound source level and the band sound source level of the stern radiation noise in step 5, the formula is as follows:

[0026]

[0027] In the formula, P i is the sound pressure at the i-th frequency point; P ref is the reference sound pressure, and the reference sound pressure is taken as 1 × 10 -9 Pa; L Poi is the sound source level at the i-th frequency point; L Po is the band sound source level, and when taking the full frequency band, it is the total sound source level.

[0028] Furthermore, if the risk of the mechanical noise index of the ship's stern in step 6 meets the index requirements, enter the next stage of work; if not, optimization measures need to be taken for the stern vibration and noise reduction design, and the mechanical noise of the stern is calculated again and evaluated according to the index until the index requirements are met.

[0029] A computer device / equipment / system includes a memory, a processor, and a computer program stored on the memory. The processor executes the computer program to implement the steps of evaluating the mechanical noise of the ship's stern in a general scheme stage.

[0030] A computer-readable storage medium stores a computer program / instructions. When the computer program / instructions are executed by a processor, the steps of a method for evaluating the mechanical noise of the ship's stern in a general scheme stage are implemented.

[0031] A computer program product includes a computer program / instructions. When the computer program / instructions are executed by a processor, the steps of a method for evaluating the mechanical noise of the ship's stern in a general scheme stage are implemented.

[0032] The beneficial effects of the present invention are as follows:

[0033] Compared with the prior art, the present invention has the advantages of high prediction efficiency, less resources required for calculation, and a wide calculation frequency band. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of a ship stern mechanical noise evaluation model;

[0035] Figure 2 It is a schematic diagram of the 1 / 3 octave band curve of the vertical, lateral or axial bearing force;

[0036] Figure 3 It is a schematic diagram of the 1 / 3 octave band curve of the load of the front bearing or thrust bearing of the stern shaft;

[0037] Figure 4 It is a schematic diagram of the excitation load application;

[0038] Figure 5 It is a schematic diagram of the calculation result of the stern mechanical noise;

[0039] Figure 6 It is a schematic diagram of the comparison between the calculation result of the stern mechanical noise and the index;

[0040] Figure 7 It is a flow chart of the method for evaluating the stern mechanical noise in the overall ship design stage. Detailed Embodiment

[0041] The technical solutions in the embodiments of the present invention will be clearly and detailedly described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] According to Figure 7 shown, a method for evaluating the stern mechanical noise of a ship in the overall design stage of the present invention is as follows:

[0043] Step 1: Analyze the results of the overall ship design and sort out the structural parameters;

[0044] According to the results of the overall ship design, sort out the structural modeling parameters of the ship, and analyze the results of the overall ship design, including the overall design specification, basic structural design specification, hull form drawing, basic structure drawing and general arrangement drawing, to clarify the structural forms, dimensions and shell plate thickness parameters of the inner and outer hull structures, pedestal structures, bulkhead structures and deck platform structures, as well as the damping laying conditions; for structures with unclear structural parameters, refer to the parent ship for values.

[0045] Step 2: Establish a truncated geometric model of the ship stern;

[0046] Based on the ship structure parameters obtained in Step 1, a truncated model of the ship's stern structure is established using three-dimensional modeling method. The length l of the truncated model satisfies where ζ is the damping ratio; N is the ratio of the maximum response value of the original structure vibration to the negligible response limit value; t is the thickness of the plate and shell; E is the elastic modulus; ρ is the density of the plate and shell material; μ is the Poisson's ratio of the material; ω is the excitation frequency. Taking N = 10, ζ = 0.2, f = 10 Hz, it is obtained that l ≥ 10.8 m, that is, the length of the truncated model should be greater than 10.8 m. The established model structure includes inner and outer shells, pallet, shafting, pedestal, bulkhead and deck platform structures, and mechanical equipment is not established.

[0047] Step 3: Establish the SEA model of the stern mechanical noise;

[0048] Based on the geometric model of the ship's stern structure established in Step 2, a SEA model of the stern mechanical noise is established based on the statistical energy method. The number of modes n within the calculation bandwidth Δf of the SEA model subsystem satisfies n ≥ 4. The internal loss factor η and the coupling loss factor η 12 of the structure adopt the test values. A seawater medium acoustic cavity is established between the hulls. The hull structure is loaded with seawater on the side in contact with seawater or the water between the hulls to simulate the influence of the attached water. The outer hull plate is connected to the semi-infinite domain. A sound pressure assessment point is set at 1000 m to the left of the center of the hull. The schematic diagram of the SEA model of the ship's stern mechanical noise is as Figure 1 shown.

[0049] Step 4: Determination and loading of excitation loads;

[0050] Determination and loading of excitation loads; The excitation loads of the stern mechanical noise include the propeller bearing force load, the load at the front bearing of the stern shaft, and the load at the thrust bearing. The propeller bearing force includes the axial force F x , the lateral force F y , and the vertical force F z .

[0051] The axial force F x , the lateral force F y , and the vertical force F z of the blade frequency load F x1 , F y1 , F z1 are calculated according to the following formula:

[0052]

[0053] In the formula, SHP - propeller shaft power, kW; n - shaft speed, r / min; D - propeller diameter, m;

[0054] The blade frequency load F1 of the propeller bearing force and the n-fold blade frequency load F n are calculated according to the following formula:

[0055] F n = F1 × 0.15 n

[0056] The bearing force is processed into a 1 / 3 octave form and loaded on the board subsystem at the hub. Among them, the axial force F x points to the bow, the lateral force F y points to the port side, and the vertical force F z is vertically upward. The loads at the front bearing of the tail shaft and the thrust bearing are adopted from the test data of the parent ship and loaded on the board subsystem at the die head and the board subsystem at the thrust bearing pedestal in the form of 1 / 3 octave vibration acceleration level.

[0057] A vertical, lateral or axial bearing force load is as Figure 2 shown, and a schematic diagram of the load spectrum curve of the front bearing of the tail shaft or the thrust bearing is as Figure 3 shown. The schematic diagram of the load loading is as Figure 4 shown.

[0058] Step 5: Calculate the mechanical noise at the stern of the ship;

[0059] Calculate the mechanical noise at the stern of the ship. The statistical energy method is used to solve it, and the calculation result of the sound pressure at the radiation noise assessment point is obtained; the source level is calculated according to the source level calculation formula, and then the total source level and the frequency band source level of the stern radiation noise are obtained.

[0060]

[0061]

[0062] In the formula, P i is the sound pressure at the i-th frequency point; P ref is the reference sound pressure, and the reference sound pressure is taken as 1 × 10 -9 Pa; L Poi is the source level at the i-th frequency point; L Po is the frequency band source level, and when taking the full frequency band, it is the total source level.

[0063] Step 6: Evaluate the mechanical noise at the stern of the ship;

[0064] Sort out the mechanical radiation noise indicators at the stern of the ship according to relevant indicators, including the total source level and the frequency band source level. Compare the calculation results of the total source level and the frequency band source level of the mechanical noise at the stern of the ship obtained in Step 5 with the requirements of the mechanical noise indicators at the stern of the ship obtained in this step to determine the magnitude of the risk of the mechanical noise indicators at the stern of the ship. If the calculation result meets the indicator requirements, the work of the next stage can be entered; if not, optimization measures need to be taken for the stern structure design, and the mechanical noise at the stern is calculated again and evaluated according to the indicators until the indicator requirements are met.

[0065] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for evaluating mechanical noise at the stern of a ship at the overall scheme stage, characterized by: The specific steps are as follows: Step 1: Analyze the overall design results of the ship and obtain the characteristic parameters of the stern structure; Step 2: Based on the structural characteristic parameters obtained in step 1, a 3D modeling method is used to establish a truncation model of the ship stern structure; Step 3: According to step 2, the SEA model of stern mechanical noise is established based on the statistical energy method; Step 4: Determination and loading of excitation load; Step 5: Use the statistical energy method to solve and obtain the calculation result of the sound pressure at the radiation noise assessment point; calculate the sound source level according to the sound source level calculation formula, and then calculate the total sound source level and frequency band sound source level of the stern radiation noise; Step 6: Ship stern machinery noise assessment. The ship's stern mechanical noise index is obtained according to the actual application needs and related indicators of the ship, and compared with the calculation results of the total sound source level and frequency band sound source level of the ship's stern mechanical noise obtained in step 5 to determine the risk of the ship's stern mechanical noise index, and to determine whether to continue designing the ship or take optimization measures for the stern to re-evaluate.

2. According to the overall scheme stage of claim 1, the method for evaluating the mechanical noise of the stern of a ship is characterized by: Step 1: Obtain the characteristic parameters of the stern structure, including the inner and outer shells, support plates, shafting, foundation, bulkheads and deck platform structures; for structures with unclear parameters, refer to the parent ship for values.

3. According to the overall scheme stage of claim 1, the method for evaluating the mechanical noise of the stern of a ship is characterized by: The step 2 cuts the model length l to meet the following requirement: Where ζ is the damping ratio; N is the ratio of the maximum response value of the original structure vibration to the negligible response limit; t is the thickness of the plate and shell; E is the elastic modulus; ρ is the density of the plate and shell material; μ is the Poisson's ratio of the material; ω is the excitation frequency.

4. The method for evaluating mechanical noise at the stern of a ship at the overall scheme stage according to claim 1 is characterized by: In step 3, the SEA model subsystem calculates the mode number n within the bandwidth Δf to satisfy n≥4; the loss factor η and the coupling loss factor η within the structure 12 The test value is adopted; a seawater medium sound cavity is established between the sides; the side of the hull structure in contact with seawater or between-side water is loaded with seawater to simulate the influence of attached water; the hull outer plate is connected to a semi-infinite domain; a sound pressure assessment point is set at 1000m on the port side of the hull center.

5. According to the overall scheme stage of claim 1, the method for evaluating the mechanical noise of the stern of a ship is characterized by: The stern mechanical noise excitation load in step 4 includes propeller bearing force load, load at the stern shaft front bearing, and load at the thrust bearing; the propeller bearing force includes the axial force F x , lateral force F y , vertical force F z ; The axial force F x , lateral force F y , vertical force F z The blade frequency load F x1 、F y1 、F z1 , the formula is as follows: Where, SHP is propeller shaft power, kW; n is shaft speed, r / min; D is propeller diameter, m; The propeller bearing force blade frequency load F1 and n times the blade frequency load F n , the formula is as follows: F n =F1×0.15 n The bearing force is treated as a 1 / 3 octave band and loaded on the hub plate system, where the axial force F x Pointing to the bow, the lateral force F y Pointing to port, the vertical force F z Vertically upward; the loads at the front bearing of the stern shaft and the thrust bearing adopt the test data of the parent ship, and are loaded on the plate system at the mold head and the plate system at the thrust bearing base in the form of 1 / 3 octave vibration acceleration level.

6. The method for evaluating the mechanical noise of the stern of a ship at the overall scheme stage according to claim 1 is characterized by: The total sound source level and frequency band sound source level of the stern radiated noise in step 5 are as follows: Where P i is the sound pressure at the ith frequency; P ref is the reference sound pressure, which is 1×10 -9 Pa;L Poi is the sound source level at the ith frequency point; L Po It is the frequency band sound source level, and when the full frequency band is taken, it is the total sound source level.

7. The method for evaluating the mechanical noise of the stern of a ship at the overall scheme stage according to claim 1 is characterized by: If the risk index of the mechanical noise index of the stern of the ship meets the index requirements in step 6, proceed to the next stage of work; If it is not satisfied, it is necessary to take optimization measures for the stern structure design, calculate the stern mechanical noise again and evaluate it according to the indicators until the index requirements are met.

8. A computer device / equipment / system comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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