Similarity criterion establishment method suitable for simultaneous ejection of multiple navigation bodies

Abstract

The invention discloses a similarity criterion establishment method suitable for multi-vehicle all-shot water discharge, which comprises the following steps of: analyzing physical parameters of an underwater all-shot process of multiple vehicles to obtain two most important physical quantities, namely a dimensionless time interval parameter and a dimensionless transverse spacing parameter, which influence the all-shot water discharge process of the multiple vehicles; similarity parameters, namely Froude number and cavitation number, which need to be emphatically guaranteed and are obtained on the basis of a similarity criterion of a single-shot navigation body water outlet test are combined, a dimensionless time interval parameter and a dimensionless transverse spacing parameter are set, the Froude number is similar to the cavitation number, and therefore the similarity criterion suitable for multi-navigation-body jet water outlet is established. According to the method, the problem of converting the multi-navigation-body jet water scaling test data into the multi-navigation-body jet water actual data is solved, the method has great reference value for modeling of a prototype test, and the related engineering development cost is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of water emergence of a navigation body across a medium, and more specifically, to a method for establishing similarity criteria applicable to the simultaneous water emergence of multiple navigation bodies. Background Art

[0002] When studying cross-medium high-speed hydrodynamics and cavitation characteristics, the most reliable method is to test on prototype size. However, in most cases, it is too expensive to test with real objects, and it is extremely difficult to implement. For the development of multi-vessel salvo water exit projects, although prototypes can be used for testing, the physical test project is extremely expensive and difficult to meet the design requirements of the engineering model scheme. Therefore, in the early stages of underwater launch-related engineering development, the cavitation flow field characteristics of the salvo water exit process are generally studied through scaled model tests.

[0003] At present, the cavitation test of single-engine vehicle out of water adopts the scaled model, and the obtained test flow field data is transformed and analyzed by similarity criteria, so as to obtain the evolution law of the cavitation flow field around the actual scale single-engine vehicle. However, in the process of multiple vehicles out of water, the surrounding flow field of the previous vehicle will affect the next vehicle, which is a typical unsteady multiphase flow interference problem. The traditional similarity criteria applicable to the single-body out of water process are difficult to transform the scaled test data of multi-body out of water to the actual scale, which greatly reduces the research value of the test data of multiple vehicles out of water, and greatly increases the cost of engineering development.

[0004] Therefore, the present invention provides a similarity criterion establishment method applicable to the simultaneous launch of multiple navigation bodies out of water. Summary of the invention

[0005] In view of this, the present invention provides a similarity criterion establishment method applicable to the simultaneous launch of multiple navigation bodies out of water, comprising:

[0006] Acquire physical parameters involved in the underwater salvo process of multiple navigation bodies, and construct a first expression by taking the cavitation length as a dependent variable and combining the physical parameters;

[0007] Converting the first expression into a dimensionless form to obtain a second expression, wherein the second expression includes a dimensionless time interval parameter and a dimensionless lateral spacing parameter;

[0008] Establishing a similarity criterion, wherein the similarity criterion includes similarity of the dimensionless time interval parameter, the dimensionless lateral spacing parameter, the Froude number, and the cavitation number;

[0009] According to the similarity criterion, the scaled-down test data of multiple-vehicle salvo out of water is converted into actual data of multiple-vehicle salvo out of water.

[0010] Optionally, the first expression is calculated in the following manner:

[0011] L=f(t,Δt,ρ w ,ρ v ,ρ a ,v,μ,H,p ∞ ,p v ,g,D0,ΔD,T s ,N)

[0012] Where L is the bubble length, t is the time, Δt is the emission time interval, ρ w is the density of liquid water, ρ v is the water vapor density, ρ a is the air density, v is the velocity, μ is the dynamic viscosity coefficient, H is the launch depth, p ∞ is the far-field pressure, p v is the saturated water vapor pressure, g is the gravitational acceleration, D0 is the model diameter, ΔD is the lateral emission spacing, T s is the surface tension coefficient, and N is the volume density of the gas core.

[0013] Optionally, the second expression is calculated as follows:

[0014]

[0015] in, is the dimensionless cavitation length, is the Strouhal number, is the dimensionless time interval parameter, is the Reynolds number, is the dimensionless depth parameter, is the cavitation number, is the Froude number, is the dimensionless lateral spacing parameter, is the Weber number, N 1 / 3 D0 is the number of gas nuclei.

[0016] Optionally, the similarity criteria further include:

[0017] The geometric scaling relationship satisfies the following relationship:

[0018]

[0019] The speed scaling relationship satisfies the following relationship:

[0020]

[0021] The time reduction ratio satisfies the following relationship:

[0022] The far-field pressure reduction ratio satisfies the following relationship:

[0023] (p p,∞ -p p,v ) / (p m,∞ -p m,v )=λ

[0024] Among them, λ is the scaled size, D p is the diameter of the navigation body, D m is the diameter of the model corresponding to the navigation body in the scaled-down test, v p is the launch speed of the vehicle, v m is the launch speed of the model corresponding to the navigation body in the scaled-down test, t p is the motion time of the vehicle, t m is the movement time of the model corresponding to the navigation body in the scaled-down test, p p,∞ is the actual far-field pressure, p p,v is the actual saturated vapor pressure, p m,∞ is the far-field pressure in the scaled-down test, p m,v is the saturated vapor pressure in the scale-down test.

[0025] Compared with the prior art, the present invention provides a similarity criterion establishment method applicable to the simultaneous launch of multiple navigation bodies out of water, which achieves at least the following beneficial effects:

[0026] The present invention provides a method for establishing a similarity criterion applicable to the salvo discharge of multiple navigation bodies. The method analyzes the physical parameters of the underwater salvo discharge process of multiple navigation bodies, and obtains the two most important physical quantities affecting the salvo discharge process of multiple navigation bodies, namely, the dimensionless time interval parameter and the dimensionless lateral spacing parameter. The similarity parameters that need to be guaranteed, namely, the Froude number and the cavitation number, are obtained based on the similarity criterion of the single-engine navigation body water-break test. The dimensionless time interval parameter, the dimensionless lateral spacing parameter, the Froude number and the cavitation number are set to be similar, thereby establishing a similarity criterion applicable to the salvo discharge of multiple navigation bodies. The method solves the problem of converting the scaled-down test data of the salvo discharge of multiple navigation bodies into the actual data of the salvo discharge of multiple navigation bodies. The method has a great reference value for the modeling of prototype tests and greatly reduces the development cost of related projects.

[0027] Of course, any product implementing the present invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0028] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0030] Figure 1 It is a flow chart of a method for establishing similarity criteria applicable to the simultaneous launch of multiple navigation bodies out of water provided by the present invention.

[0031] Figure 2 It is a structural schematic diagram of a multifunctional reduced compression ratio model salvo water discharge experimental device.

[0032] Figure 3 This is a schematic diagram of the test results of a water cavitation test on a single-engine scaled model.

[0033] Figure 4 This is a schematic diagram of the test results of a water cavitation test on a double-engine reduction model. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0035] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0036] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0037] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0038] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0039] Reference Figure 1 , Figure 1 1 is a flow chart of a method for establishing similarity criteria applicable to multiple navigation bodies being launched out of water at the same time provided by the present invention, to illustrate a specific embodiment of a method for establishing similarity criteria applicable to multiple navigation bodies being launched out of water at the same time provided by this embodiment, including:

[0040] S101: obtaining physical parameters involved in the underwater salvo process of multiple navigation bodies, and constructing a first expression by taking the cavitation length as a dependent variable and combining the physical parameters;

[0041] S102: converting the first expression into a dimensionless form to obtain a second expression, where the second expression includes a dimensionless time interval parameter and a dimensionless lateral spacing parameter;

[0042] S103: establishing similarity criteria, the similarity criteria including similarity of dimensionless time interval parameters, similarity of dimensionless lateral spacing parameters, similarity of Froude numbers and similarity of cavitation numbers;

[0043] S104: According to a similarity criterion, the scaled-down test data of the multi-vehicle salvo out of water is converted into actual data of the multi-vehicle salvo out of water.

[0044] It should be noted that the scaled-down test is usually to study the process characteristics of the process of launching a salvo of navigation bodies out of the water, and cavitation is a relatively important research object, so in step S101, the cavitation length is used as the dependent variable to establish the first expression. In step S102, the first expression is converted into a dimensionless form to obtain a second expression. At this time, the second expression contains multiple parameters, but only the dimensionless time interval parameter and the dimensionless lateral spacing parameter can reflect the connection between multiple navigation bodies. Therefore, when establishing the similarity criterion for the salvo of multiple navigation bodies out of the water, the dimensionless time interval parameter and the dimensionless lateral spacing parameter should be considered.

[0045] The similarity criterion of a single-vehicle launch may provide inspiration for the similarity criterion of multiple-vehicle launches, so it is necessary to analyze the parameters in the similarity criterion of a single-vehicle launch.

[0046] The parameters related to the similarity criterion of a single-vessel exiting the water include the Strouhal number, cavitation number, Froude number, Weber number, gas nucleation number and Reynolds number. t =(tv0) / D0, t is time, v0 is the initial launch velocity, D0 is the model diameter, which is used to describe the unsteady characteristics of the water flow; cavitation number σ = (p ∞ -p v ) / (0.5ρ w v0 2 ), p ∞ is the far-field pressure, p v is the saturated water vapor pressure, ρ w is the density of liquid water, v0 is the initial launch velocity, which is used to describe the difficulty of cavitation in the flow field; Froude number F r =(gH) / (v0 2 ), g is the gravitational acceleration, H is the launch depth, v0 is the initial launch velocity, which is used to describe the effect of gravity; Weber number W e =(ρ w v0 2 D0) / T s , ρw is the density of liquid water, v0 is the initial launch velocity, D0 is the model diameter, T s is the surface tension coefficient, which is used to describe the effect of surface tension; the number of gas nuclei N is the volume density of the gas core, D0 is the model diameter, which is used to describe the number of gas cores in the flow field and is related to factors such as water quality; Reynolds number R e =(ρ w v0D0) / μ,ρ w is the density of liquid water, v0 is the initial launch velocity, D0 is the model diameter, and μ is the dynamic viscosity coefficient, which is used to describe the ratio of inertial force to viscous force.

[0047] In the actual engineering research of underwater launch of navigation bodies, since water is used as the flow field medium in different scaled experiments, the physical parameters of the medium such as temperature, density and salinity are difficult to adjust. Even after the scale and speed parameters are adjusted, the complete equality of all similarity criteria cannot be satisfied. When the physical properties of liquid water are the same, the Reynolds number and the Froude number cannot be the same at the same time. Since the gravity effect cannot be ignored during underwater vertical launch, the Froude number is guaranteed to be the same. The number of gas nuclei is also difficult to be similar due to the uncontrollable content of gas nuclei, so the number of gas nuclei can be ignored. Since the surface tension coefficient of water is relatively small, it is 10 at room temperature. -2 The convection effect is much greater than the surface tension effect, so the influence of the Weber number can be ignored.

[0048] In summary, the Froude number and the cavitation number are two relatively important parameters. Therefore, when establishing the similarity criterion for the salvo discharge of multiple vehicles, the similarity of the Froude number and the cavitation number is considered, and then the similarity of the dimensionless time interval parameter and the dimensionless lateral spacing parameter is combined to obtain the similarity criterion for the salvo discharge of multiple vehicles. Based on this similarity criterion, the scaled-down test data of the salvo discharge of multiple vehicles can be converted into the actual data of the salvo discharge of multiple vehicles.

[0049] Compared with the prior art, the present embodiment provides a method for establishing a similarity criterion applicable to the salvo launch of multiple navigation bodies out of water, analyzes the physical parameters of the underwater salvo launch process of multiple navigation bodies, and obtains the two most important physical quantities affecting the salvo launch process of multiple navigation bodies, namely, the dimensionless time interval parameter and the dimensionless lateral spacing parameter, combined with the similarity parameters that need to be guaranteed based on the similarity criterion of the single-engine navigation body water breakthrough test, namely, the Froude number and the cavitation number, and sets the dimensionless time interval parameter, the dimensionless lateral spacing parameter, the Froude number and the cavitation number to be similar, thereby establishing a similarity criterion applicable to the salvo launch of multiple navigation bodies out of water, solving the problem of converting the scaled-down test data of the salvo launch of multiple navigation bodies into the actual data of the salvo launch of multiple navigation bodies out of water, having great reference value for the modeling of prototype tests, and greatly reducing the cost of related engineering development.

[0050] In some optional embodiments, the first expression is calculated as follows:

[0051] L=f(t,Δt,ρ w ,ρ v ,ρ a ,v,μ,H,p ∞ ,p v ,g,D0,ΔD,T s ,N)

[0052] Where L is the bubble length, t is the time, Δt is the emission time interval, ρ w is the density of liquid water, ρ v is the water vapor density, ρ a is the air density, v is the velocity, μ is the dynamic viscosity coefficient, H is the launch depth, p ∞ is the far-field pressure, p v is the saturated water vapor pressure, g is the gravitational acceleration, D0 is the model diameter, ΔD is the lateral emission spacing, T s is the surface tension coefficient, and N is the volume density of the gas core.

[0053] In some optional embodiments, the second expression is calculated as follows:

[0054]

[0055] in, is the dimensionless cavitation length, is the Strouhal number, is the dimensionless time interval parameter, is the Reynolds number, is the dimensionless depth parameter, is the cavitation number, is the Froude number, is the dimensionless lateral spacing parameter, is the Weber number, N 1 / 3 D0 is the number of gas nuclei

[0056] In some optional embodiments, the similarity criteria further include:

[0057] The geometric scaling relationship satisfies the following relationship:

[0058]

[0059] The speed scaling relationship satisfies the following relationship:

[0060]

[0061] The time reduction ratio satisfies the following relationship:

[0062]

[0063] The far-field pressure reduction ratio satisfies the following relationship:

[0064] (p p,∞ -p p,v ) / (p m,∞ -p m,v )=λ

[0065] Among them, λ is the scaled size, D p is the diameter of the original scale vehicle, D m is the diameter of the model corresponding to the navigation body in the scaled-down test, v p is the launch speed of the vehicle, v m is the launch speed of the model corresponding to the vehicle in the scaled-down test, t p is the motion time of the vehicle, t m is the motion time of the model corresponding to the navigation body in the scaled-down test, p p,∞ is the actual far-field pressure, p p,v is the actual saturated vapor pressure, p m,∞ is the far-field pressure in the scaled-down test, p m,v is the saturated vapor pressure in the scaled-down test.

[0066] It is understandable that in order to ensure the authenticity and effectiveness of the same laws obtained by the scaled model test, it is necessary to change the atmospheric pressure in the high-speed cavitation hydrodynamics related problems in the field of underwater vertical launch engineering. Therefore, in the similarity criteria of multiple navigation bodies, in addition to the basic geometric scaling relationship, speed scaling relationship and time scaling relationship, the far-field pressure scaling relationship must also be considered.

[0067] In some optional embodiments, referring to Figure 2 , Figure 3 and Figure 4 , Figure 2 This is a structural diagram of a multifunctional reduced compression ratio model volley water discharge experimental device. Figure 3 This is a test result diagram of a water cavitation test on a single-engine scale model. Figure 4 This is a test result diagram of a double-engine reduction ratio model cavitation test. Based on the above-established multi-vehicle salvo water exit similarity criterion, a set of multifunctional reduced-compression ratio model salvo water exit experimental equipment with a continuously adjustable decompression range of 10Kpa to 101Kpa, a time interval of 1ms, a launch speed range of 0 to 40m / s, and a platform speed range of 0 to 2m / s was developed. Figure 2 As shown, the diameter of the experimental device is 55 mm.

[0068] The experimental model was used to carry out single-engine scaled-down model and double-engine scaled-down model tests. The test results are as follows: Figure 3 and Figure 4 shown.

[0069] The above derivation results are explained with specific examples as follows:

[0070] In the actual water launch process, it is assumed that the research object is three navigation bodies launched simultaneously, the diameter of the original scale model of the navigation body is 2m, the lateral spacing between the original scale models of the navigation body is 1.3 times the diameter, the launch time interval is 10s, the exit speed is 45m / s, and the Reynolds number ranges from 6×10 7 Up to 8×10 7 , then when the actual water outlet cavitation effect occurs, the cavitation number at the water outlet time ranges from 0.213 to 0.479.

[0071] When the scaled model has a diameter of 50 mm and an aspect ratio of 6, the scale ratio is 40 according to the geometric scaling relationship, and the lateral launch spacing is 1.3 times; according to the speed scaling relationship, the launch speed is 7.11 m / s; according to the time scaling relationship, the launch time interval is 1.58 s; in order to ensure that the cavitation number is equal at the time of water exit, the far-field pressure in the scaled test is determined to be 4812 Pa according to the far-field pressure scaling relationship. On this basis, the dimensionless time interval parameter, dimensionless lateral spacing parameter, Froude number and cavitation number are kept similar, and the scaled test data of multiple vehicles launching out of water are converted into the actual data of multiple vehicles launching out of water.

[0072] Based on the similarity criterion of single-engine vehicle out of water, the present invention analyzes in detail the similarity parameters that need to be guaranteed in engineering research and development, and introduces the two most important physical quantities that affect the process of multiple vehicles being launched out of water, namely, the launch time interval and the lateral launch spacing, thereby establishing a similarity criterion suitable for the study of cavitation characteristics of multiple vehicles being launched out of water at once, solving the problem of converting the traditional scaled-down test data of multiple vehicles being launched out of water at once to the actual scale, having great reference value for the modeling of prototype tests, and greatly reducing the cost of related engineering research and development.

[0073] It can be seen from the above embodiments that the method for establishing a similarity criterion applicable to the simultaneous launch of multiple navigation bodies out of water provided by the present invention achieves at least the following beneficial effects:

[0074] The present invention provides a method for establishing a similarity criterion applicable to the salvo discharge of multiple navigation bodies. The method analyzes the physical parameters of the underwater salvo discharge process of multiple navigation bodies, and obtains the two most important physical quantities affecting the salvo discharge process of multiple navigation bodies, namely, the dimensionless time interval parameter and the dimensionless lateral spacing parameter. The similarity parameters that need to be guaranteed, namely, the Froude number and the cavitation number, are obtained based on the similarity criterion of the single-engine navigation body water-break test. The dimensionless time interval parameter, the dimensionless lateral spacing parameter, the Froude number and the cavitation number are set to be similar, thereby establishing a similarity criterion applicable to the salvo discharge of multiple navigation bodies. The method solves the problem of converting the scaled-down test data of the salvo discharge of multiple navigation bodies into the actual data of the salvo discharge of multiple navigation bodies. The method has a great reference value for the modeling of prototype tests and greatly reduces the development cost of related projects.

[0075] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A similarity criterion establishment method applicable to the simultaneous launch of multiple vehicles out of water, characterized in that: include: Acquire physical parameters involved in the underwater salvo process of multiple navigation bodies, and construct a first expression by taking the cavitation length as a dependent variable and combining the physical parameters; Converting the first expression into a dimensionless form to obtain a second expression, wherein the second expression includes a dimensionless time interval parameter and a dimensionless lateral spacing parameter; Establishing a similarity criterion, wherein the similarity criterion includes similarity of the dimensionless time interval parameter, the dimensionless lateral spacing parameter, the Froude number, and the cavitation number; According to the similarity criterion, the scaled-down test data of multiple-vehicle salvo out of water is converted into actual data of multiple-vehicle salvo out of water.

2. A similarity criterion establishment method applicable to multiple vehicles launching out of water at the same time according to claim 1, characterized in that: The first expression is calculated as follows: L=f(t,Δt,ρ w ,r v ,r a ,v,μ,H,p ∞ ,p v ,g,D0,ΔD,T s ,N) Where L is the bubble length, t is the time, Δt is the emission time interval, ρ w is the density of liquid water, ρ v is the water vapor density, ρ a is the air density, v is the velocity, μ is the dynamic viscosity coefficient, H is the launch depth, p ∞ is the far-field pressure, p v is the saturated water vapor pressure, g is the gravitational acceleration, D0 is the model diameter, ΔD is the lateral emission spacing, T s is the surface tension coefficient, and N is the volume density of the gas core.

3. A similarity criterion establishment method applicable to multiple vehicles launching out of water at the same time according to claim 1, characterized in that: The second expression is calculated as follows: in, is the dimensionless cavitation length, is the Strouhal number, is the dimensionless time interval parameter, is the Reynolds number, is the dimensionless depth parameter, is the cavitation number, is the Froude number, is the dimensionless lateral spacing parameter, is the Weber number, N 1 / 3 D0 is the number of gas nuclei.

4. A similarity criterion establishment method applicable to multiple vehicles launching out of water at the same time according to claim 1, characterized in that: The similarity criteria also include: The geometric scaling relationship satisfies the following relationship: The speed scaling relationship satisfies the following relationship: The time reduction ratio satisfies the following relationship: The far-field pressure reduction ratio satisfies the following relationship: (p p,∞ -p p,v ) / (p m,∞ -p m,v )=λ Among them, λ is the scaled size, D p is the diameter of the original scale vehicle, D m is the diameter of the model corresponding to the navigation body in the scaled-down test, v p is the launch speed of the vehicle, v m is the launch speed of the model corresponding to the navigation body in the scaled-down test, t p is the motion time of the vehicle, t m is the movement time of the model corresponding to the navigation body in the scaled-down test, p p,∞ is the actual far-field pressure, p p,v is the actual saturated vapor pressure, p m,∞ is the far-field pressure in the scaled-down test, p m,v is the saturated vapor pressure in the scale-down test.

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