Fluid impact quantitative evaluation method and device suitable for local sunken structure

Abstract

The invention discloses a fluid impact quantitative evaluation method and device suitable for a local sunken structure, and the method comprises the following steps: dividing a local sunken structure test model into three test regions, including a sunken region, an edge region and a raised region; acquiring the unit area, the total area and the impact load peak value of the three test areas; calculating a weighted quantized impact load based on the cell area and the impact load peak; and carrying out dimensionless processing on the weighted quantitative impact load to obtain an evaluation coefficient, and carrying out impact quantitative evaluation based on the evaluation coefficient. According to the method, the fluid impact action on the whole test model of the structure with the local recess on the surface is quantitatively evaluated, and the dimensionless coefficient is used for analysis, so that a basis is provided for verifying the similarity between the test and engineering practice, and a new angle is provided for evaluation of a test result.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering test and experiment, and in particular relates to a fluid impact quantitative evaluation method and device suitable for a local concave structure. Background Art

[0002] In actual engineering, fluid impact is often accompanied by strong nonlinearity and randomness. It is difficult to standardize the fluid impact load used to evaluate the strength of the structure, so the fluid impact load is usually simplified and equivalent. Hammer test is widely used to study the response of structures under impact. This type of test is easy to operate, can accurately control the test parameters and can achieve accurate measurement of the structural response. However, the test principle of simulating fluid impact by solid impact ignores the original fluid-solid coupling phenomenon. Especially for structures with local depressions on the surface, such as the Mark III membrane LNG containment system, the load generated by this type of test cannot cover the entire structural surface, nor can it reflect the gas entrainment and air cushion effects that occur when the fluid impacts the structure. Using artificial focused waves to impact structures in a wave pool can more accurately reflect the physical phenomena when the fluid impacts the structure, but the difficulty and cost of the test are relatively large, especially the limitations of the test site and equipment. Moreover, it is difficult to accurately control the fluid impact position and it is difficult to achieve accurate measurement of the response. In addition, in the actual test process, the load conditions of a single fixed measuring point and the impact force on the test model are often used to evaluate the impact of the fluid. For test models with complex surface features, the influence of geometric features on pressure measurement results and local flow characteristics before impact cannot be ignored. The air cushion generated in the depression will also greatly reduce the impact of the fluid on the structure. Therefore, it is unreasonable to evaluate the fluid impact effect based on the total impact force and the load conditions of a single fixed measuring point. At present, there is still no suitable solution for structures with local depressions on the surface to quickly and accurately evaluate the fluid impact effect on the model under different working conditions and make quantitative comparisons between different working conditions. Summary of the invention

[0003] The present invention aims to solve the deficiencies of the prior art and provides the following solutions:

[0004] A method for quantitatively evaluating fluid impact applicable to a local concave structure comprises the following steps:

[0005] The local concave structure test model is divided into three test areas, and the three test areas include: a concave area, an edge area and a convex area;

[0006] Obtaining the unit area, total area and impact load peak value of the three test areas;

[0007] Calculate a weighted quantized impact load based on the unit area and the impact load peak value;

[0008] The weighted quantized impact load is dimensionally processed to obtain an evaluation coefficient, and an impact quantization evaluation is performed based on the evaluation coefficient.

[0009] Preferably, the method for obtaining the impact load peak value comprises: setting pressure sensors in the three test areas of the test model, lowering the test model from a high place using an evaluation device, and obtaining the impact load peak values ​​of the three test areas; the impact load peak values ​​include: the impact load peak value P of the concave area mmi , Peak impact load P in edge area emi and the peak impact load P of the raised area cmi .

[0010] Preferably, the method for obtaining the unit area includes: taking the measuring range of the pressure sensor as the unit area; the unit area includes: the unit area S of the concave region mi , edge area unit area S ei and the raised area unit area S ci .

[0011] Preferably, the method for calculating the weighted quantized impact load includes:

[0012] Based on the impact load peak value, the average value of the top 10% maximum values ​​of the impact load peak values ​​of the three test areas is calculated:

[0013]

[0014] Among them, Q m It represents the average value of the first 10% of the maximum value of the impact load peak in the concave area, Q e It represents the average value of the first 10% of the maximum value of the impact load peak in the edge area, Q c It represents the average value of the first 10% maximum value of the impact load peak in the convex area, and k, n, and r represent natural numbers;

[0015] Calculate the water fall inclination factor based on the average value:

[0016]

[0017] Among them, k a represents the water fall inclination factor;

[0018] The weighting coefficients of the three test areas are calculated based on the average value, the water falling inclination factor and the total area:

[0019]

[0020] ξ m +ξ e +ξc =1

[0021] Among them, ξ m represents the weighting coefficient of the concave area, ξ e represents the weighting coefficient of the edge area, ξ c represents the weighting coefficient of the convex area, γ e represents the structural coefficient of the edge region, γ c represents the structural coefficient of the raised area, S e represents the total area of ​​the edge region, S m represents the total area of ​​the concave region;

[0022] The weighted quantized impact load is calculated based on the impact load peak value, the unit area, the total area and the weighting coefficient:

[0023]

[0024] Among them, P ma represents the weighted quantized impact load, S c Represents the total area of ​​the raised region.

[0025] Preferably, the method for calculating the evaluation coefficient includes:

[0026]

[0027] Among them, λ v represents the velocity coefficient, ρ w represents the density of water, v0 represents the speed of entry into water, H0 represents the height of entry into water, λ m represents the mass coefficient, m0 represents the mass of the test model, and S0 represents the projection area of ​​the test model in the thickness direction.

[0028] The present invention also provides a fluid impact quantitative evaluation device applicable to a local concave structure, the evaluation device is used to perform any of the above-mentioned evaluation methods, comprising: a ground drop frame, an underground guide rail frame, a sliding bearing platform and a flip platform;

[0029] The ground drop frame is fixed to the ground outside the pool by anchor bolts;

[0030] The underground guide rail frame is arranged in the pool, the bottom is fixed to the bottom of the pool, and the top is connected to the ground throwing frame;

[0031] Pulleys are arranged on both sides of the sliding platform and are in contact with the underground guide rail frame;

[0032] The overturning platform is connected with the sliding platform and the test model.

[0033] Preferably, an electric fall chain is provided on the top crossbeam of the ground throwing frame;

[0034] The four corners of the sliding platform are provided with lifting rings, and the sliding platform is connected to the unhooking device below the electric fall chain through the lifting rings using a lifting rope;

[0035] The overturning platform is divided into a connecting frame and a rotating frame, the rotating frame is connected to the test model, and the connecting frame is connected to the sliding platform;

[0036] The cross section of the connecting frame is T-shaped, and the lower end is connected to the rotating frame through a rotating shaft. The rotating frame is fixed with a flip angle through 10 groups of support rods.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The present invention quantitatively evaluates the fluid impact effect on the entire test model of a structure with local depressions on the surface and uses dimensionless coefficients for analysis, thereby providing a basis for verifying the similarity between the test and engineering practice and providing a new perspective for evaluating the test results.

[0039] (2) The present invention measures the model surface in different regions and performs weighted averaging of the test results to comprehensively consider the influence of the geometric characteristics of the structure surface on the fluid impact. The weighted quantified fluid impact load represents the fluid impact effect on the model as a whole. From this perspective, comparing the test results under different working conditions can more comprehensively reflect the anti-slamming capability of the structure.

[0040] (3) In the quantitative evaluation method of the present invention, the weighted coefficient obtained by processing the load peak values ​​of different measuring points in different measuring areas can reflect the conditions of fluid impact in different test areas. In particular, for the working conditions of inclined impact and vertical impact, the weighted coefficient can directly reflect the weakening effect of the air cushion generated in the recessed area of ​​the model on the fluid impact in the vertical impact condition. In addition, the influence of the fluid impact on the structure is also considered in the calculation process of the weighted coefficient. For areas that are more susceptible to damage under the action of fluid impact, the weight ratio of the area is increased to reflect the effect of the fluid impact on the model.

[0041] (4) The present invention uses the total mass and the water entry velocity (initial height) to make the weighted quantized fluid impact load dimensionless. On the one hand, it is convenient to compare the fluid impact of the model under different working conditions. On the other hand, it is convenient to analyze the influence of the working condition change on the fluid impact so as to realize the rapid estimation of the fluid impact in the subsequent test design process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 A schematic diagram of a method flow chart of an embodiment of the present invention;

[0044] Figure 2 is a schematic diagram of a test model with a local depression according to an embodiment of the present invention;

[0045] Figure 3 A schematic diagram of the division of the test area according to an embodiment of the present invention;

[0046] Figure 4 The detection range area division of the pressure monitoring point in the embodiment of the present invention;

[0047] Figure 5 A schematic diagram of a test device according to an embodiment of the present invention;

[0048] Figure 6 Schematic diagram of a flip platform according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Embodiment 1

[0052] In this embodiment, if Figure 1 As shown, a method for quantitatively evaluating fluid impact applicable to a local concave structure comprises the following steps:

[0053] S1. The local concave structure test model is divided into three test areas, including a concave area, an edge area and a convex area.

[0054] In this embodiment, the test model with local depression is as follows Figure 2As shown in the figure, the relevant test model of the structure with local depression on the surface must contain at least 2×2 depression areas in the center, and the areas are divided as follows Figure 3 shown.

[0055] S2. Obtain the unit area, total area and impact load peak value of the three test areas.

[0056] The method for obtaining the impact load peak value includes: setting pressure sensors in three test areas of the test model, lowering the test model from a high place using an evaluation device, and obtaining the impact load peak values ​​of the three test areas; the impact load peak value includes: the impact load peak value P of the concave area mmi , Peak impact load P in edge area emi and the peak impact load P of the raised area cmi .

[0057] The method for obtaining the unit area includes: taking the measuring range of the pressure sensor as the unit area. In this embodiment, the detection range area of ​​the pressure monitoring point is divided as follows: Figure 4 As shown; the unit area includes: the unit area of ​​the concave area S mi , edge area unit area S ei and the raised area unit area S ci .

[0058] S3. Calculate the weighted quantified impact load based on the unit area and the peak impact load.

[0059] The method for calculating the weighted quantitative impact load includes: calculating the average of the top 10% maximum impact load peak values ​​of the three test areas based on the impact load peak value:

[0060]

[0061] Among them, Q m It represents the average value of the first 10% of the maximum value of the impact load peak in the concave area, Q e It represents the average value of the first 10% of the maximum value of the impact load peak in the edge area, Q c It represents the average value of the first 10% of the maximum value of the impact load peak in the raised area. k, n, and r represent natural numbers. The water inclination factor is calculated based on the average value:

[0062]

[0063] Among them, k a Indicates the falling water inclination factor; the weighting coefficients of the three test areas are calculated based on the average value, the falling water inclination factor and the total area:

[0064]

[0065] ξ m+ξ e +ξ c =1

[0066] Among them, ξ m represents the weighting coefficient of the concave area, ξ e represents the weighting coefficient of the edge area, ξ c represents the weighting coefficient of the convex area, γ e represents the structural coefficient of the edge region, γ c represents the structural coefficient of the raised area, S e represents the total area of ​​the edge region, S m Indicates the total area of ​​the concave area; in the process of quantitatively evaluating the fluid impact, three weighting coefficients are used to reflect the contribution of the load peaks in different areas to the fluid impact on the entire model. Considering that the convex part of the structure is more prone to plastic deformation in actual engineering, it is used by γc to increase the proportion of the fluid impact on the convex area in the fluid impact on the entire model. Q c / Q m It is used to evaluate the loading patterns of the structure and possible failure modes. c / Q m The increase indicates that the protrusions of the structure bear more fluid impact, and the protrusions are more susceptible to plastic deformation or cracking. Therefore, its weight should be increased. ξ m With ξ c They correspond to the concave area and the edge area respectively. These two areas often have similar geometric features, and the weight reflects the ratio of the areas of the two areas. Because the edge area is located at the edge of the model, its structural strength is lower and it is more prone to damage. However, there is generally no edge area in actual structures. The edge area is a special form that exists in the test model. Therefore, γe is used to reduce the weight of the edge area, and the fluid impact on the edge area is taken into account more. The formula also uses the falling water inclination factor k a To determine m With ξ c In the case of vertical impact, due to the influence of the air cushion, the peak impact load in the concave area is smaller than the peak impact load in the edge area. In the case of inclined impact, there is no obvious air cushion, so the peak impact load in the concave area will not be smaller than the peak impact load in the edge area. Therefore, Q m / Q e It is used to evaluate the effect of air cushion at different water drop angles. m / Q e <1 indicates that there is an air cushion in the concave area, which will weaken the fluid impact on the structure. Therefore, the weight of the concave area should be increased to reflect the influence of the air cushion on the fluid impact on the entire model. m / Q e>1 indicates that no obvious air cushion is generated during the falling process, k a =1 means that the nature of the fluid load on the concave area and the edge area is the same; the weighted quantitative impact load is calculated based on the impact load peak, unit area, total area and weighting coefficient:

[0067]

[0068] Among them, P ma represents the weighted quantized impact load, S c Represents the total area of ​​the raised region.

[0069] S4. Perform dimensionless processing on the weighted quantified impact load to obtain an evaluation coefficient, and perform impact quantification evaluation based on the evaluation coefficient.

[0070] In order to quantitatively evaluate the fluid impact on the model as a whole under different working conditions, the methods for calculating the evaluation coefficient are as follows based on the total mass of the model, the water entry speed and the initial height of the model:

[0071]

[0072] Among them, λ v represents the velocity coefficient, ρ w represents the density of water, v0 represents the speed of entry into water, H0 represents the height of entry into water, λ m represents the mass coefficient, m0 represents the mass of the test model, and S0 represents the projection area of ​​the test model in the thickness direction.

[0073] Embodiment 2

[0074] In this embodiment, if Figure 5 As shown, a fluid impact quantitative evaluation device suitable for local depressed structures includes: a ground drop frame, an underground guide rail frame, a sliding support platform and a flip platform.

[0075] The ground throwing frame is fixed to the ground outside the pool by anchor bolts; an electric fall chain is arranged on the top crossbeam of the ground throwing frame to realize the lifting and movement of the model; the underground guide frame is arranged in the pool, the bottom is fixed to the bottom of the pool, and the top is connected to the ground throwing frame; pulleys are arranged on both sides of the sliding platform, which are in contact with the underground guide frame. Under the constraint of the underground guide frame, the sliding platform can only move vertically; lifting rings are arranged at the four corners of the sliding platform, and the sliding platform is connected to the unhooking device under the electric fall chain through the lifting rings by using a lifting rope. After the unhooking device is released, the platform falls freely to realize the falling and slamming of the model; the flipping platform is connected to the sliding platform and the test model. The flipping platform is divided into a connecting frame and a rotating frame, such as Figure 6As shown, the rotating frame is connected to the test model, and the connecting frame is connected to the sliding platform; the cross-section of the connecting frame is T-shaped, and the lower end is connected to the rotating frame through a rotating shaft, and the rotating frame fixes the flip angle through 10 groups of support rods.

[0076] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for quantitatively evaluating fluid impact of a local concave structure, characterized in that: The following steps are involved: The local concave structure test model is divided into three test areas, and the three test areas include: a concave area, an edge area and a convex area; Obtaining the unit area, total area and impact load peak value of the three test areas; Calculate a weighted quantized impact load based on the unit area and the impact load peak value; The weighted quantized impact load is dimensionally processed to obtain an evaluation coefficient, and an impact quantization evaluation is performed based on the evaluation coefficient.

2. According to claim 1, a method for quantitatively evaluating fluid impact applicable to a local concave structure is characterized in that: The method for obtaining the impact load peak value comprises: setting pressure sensors in the three test areas of the test model, lowering the test model from a high place by using an evaluation device, and obtaining the impact load peak values ​​of the three test areas; the impact load peak values ​​include: the impact load peak value P of the concave area mmi , Peak impact load P in edge area emi and the peak impact load P of the raised area cmi .

3. According to claim 2, a method for quantitatively evaluating fluid impact applicable to a local concave structure is characterized in that: The method for obtaining the unit area includes: taking the measuring range of the pressure sensor as the unit area; the unit area includes: the unit area S of the concave region mi , edge area unit area S ei and the raised area unit area S ci .

4. According to claim 3, a method for quantitatively evaluating fluid impact applicable to a local concave structure is characterized in that: The method for calculating the weighted quantized impact load includes: Based on the impact load peak value, the average value of the top 10% maximum values ​​of the impact load peak values ​​of the three test areas is calculated: Among them, Q m It represents the average value of the first 10% of the maximum value of the impact load peak in the concave area, Q e It represents the average value of the first 10% of the maximum value of the impact load peak in the edge area, Q c It represents the average value of the first 10% maximum value of the impact load peak in the convex area, and k, n, and r represent natural numbers; Calculate the water fall inclination factor based on the average value: Among them, k a represents the water fall inclination factor; The weighting coefficients of the three test areas are calculated based on the average value, the water falling inclination factor and the total area: Among them, ξ m represents the weighting coefficient of the concave area, ξ e represents the weighting coefficient of the edge area, ξ c represents the weighting coefficient of the convex area, γ e represents the structural coefficient of the edge region, γ c represents the structural coefficient of the raised area, S e represents the total area of ​​the edge region, S m represents the total area of ​​the concave region; The weighted quantized impact load is calculated based on the impact load peak value, the unit area, the total area and the weighting coefficient: Among them, P ma represents the weighted quantized impact load, S c Represents the total area of ​​the raised region.

5. A method for quantitatively evaluating fluid impact applicable to a local concave structure according to claim 4, characterized in that: The method for calculating the evaluation coefficient includes: Among them, λ v represents the velocity coefficient, ρ w represents the density of water, v0 represents the speed of entry into water, H0 represents the height of entry into water, λ m represents the mass coefficient, m0 represents the mass of the test model, and S0 represents the projection area of ​​the test model in the thickness direction.

6. A fluid impact quantitative evaluation device suitable for a local concave structure, the evaluation device is used to perform the evaluation method according to any one of claims 1 to 5, characterized in that: include: Ground drop rack, underground guide rail rack, sliding platform and turning platform; The ground drop frame is fixed to the ground outside the pool by anchor bolts; The underground guide rail frame is arranged in the pool, the bottom is fixed to the bottom of the pool, and the top is connected to the ground throwing frame; Pulleys are arranged on both sides of the sliding platform and are in contact with the underground guide rail frame; The overturning platform is connected with the sliding platform and the test model.

7. A fluid impact quantitative evaluation device suitable for a local concave structure according to claim 6, characterized in that: An electric fall chain is arranged on the top crossbeam of the ground throwing frame; The four corners of the sliding platform are provided with lifting rings, and the sliding platform is connected to the unhooking device below the electric fall chain through the lifting rings using a lifting rope; The overturning platform is divided into a connecting frame and a rotating frame, the rotating frame is connected to the test model, and the connecting frame is connected to the sliding platform; The cross section of the connecting frame is T-shaped, and the lower end is connected to the rotating frame through a rotating shaft. The rotating frame is fixed with a flip angle through 10 groups of support rods.

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