Calibration method for wind tunnel simulation refueling machine wake flow field

Abstract

The invention discloses a calibration method for a wind tunnel simulation refueling machine wake flow field, and relates to the field of low-speed wind tunnel test methods. The problem of flow field calibration when a refueling machine wake flow field active simulation generation device is used for testing in a wind tunnel at present is solved. According to the scheme, the method comprises the steps that 1, the average trailing vortex circular rector parameter of a target refueling machine is calculated and serves as a true value of calibration; 2, measuring a wind tunnel wake flow field by using a PIV method to obtain a particle image; 3, processing the particle image to obtain the tangential velocity of the wind tunnel flow field; and step 4, performing wind tunnel simulation wake flow field parameter calculation according to the wind tunnel flow field tangential velocity, obtaining an average trailing vortex circular rector parameter of a simulated refueling machine wake flow field in a wind tunnel test section, and comparing the average trailing vortex circular rector parameter with an average trailing vortex circular rector parameter of a target refueling machine. And obtaining a difference value between the average trailing vortex circular rector parameter of the simulated refueling machine wake flow field and the average trailing vortex circular rector parameter of the target refueling machine. The method has a wide application prospect in the aspects of aircraft aerodynamic performance evaluation and the like.

Description

Technical Field

[0001] The invention relates to the field of low-speed wind tunnel test methods, and in particular to a calibration method for a wind tunnel simulating a fuel tanker wake field. Background Art

[0002] In the field of aircraft aerial refueling research, the wake of the tanker has an important impact on the safety of the receiving aircraft during the refueling process, as well as the efficiency and accuracy of docking. The wake field of the tanker is extremely complex, and studying the wake field of the tanker and analyzing its influence on the aerodynamic characteristics of the receiving aircraft has an important role in promoting aerial refueling research.

[0003] At present, experimental research and numerical simulation calculation are two important research methods for aircraft aerial refueling, and wind tunnel test can be used as an effective research method. At present, the wind tunnel test for simulating the wake of the tanker mainly adopts the direct simulation method, that is, the scaled model of the tanker is directly arranged at the front end of the wind tunnel test section, and the wind tunnel air flows through the surface of the scaled model to generate the tanker wake field at its rear. Although this method is simple, it has many problems, including being easily limited by the size of the test wind tunnel, making the scaled tanker model too small, resulting in distortion of the simulated wake field, and at the same time, when evaluating the aerodynamic characteristics of the receiving aircraft, the scaled model of the receiving aircraft is too small to arrange sensors, etc., which seriously restricts the application of wind tunnel tests in scenarios such as evaluating the aerodynamic characteristics of the tanker and the receiving aircraft, and also causes uneconomical phenomena such as occupying large low-speed wind tunnels for research. Using a blade rotating mechanism instead of a scaled-down model of a tanker can generate an approximate tanker wake field for wind tunnel test research on aerial refueling. This is a simple and effective solution. However, the quality of the simulated wake field generated by the blade rotating mechanism and its similarity to the tanker wake field need further evaluation. Currently, there is a lack of calibration methods for related flow fields. Summary of the invention

[0004] In order to solve the insufficiency of direct simulation test capability of the wake field of a refueling machine in the existing wind tunnel test, the present invention provides a calibration method for simulating the wake field of a refueling machine in a wind tunnel, the method comprising the following steps:

[0005] Step 1, calculate the average tail vortex circulation parameter of the target tanker as the true value of the calibration;

[0006] Step 2: Use the PIV method to measure the wind tunnel wake field and obtain a particle image;

[0007] Step 3, processing the particle image to obtain the tangential velocity of the wind tunnel flow field;

[0008] Step 4: Calculate the wind tunnel simulated wake field parameters according to the tangential velocity of the wind tunnel flow field, obtain the average wake vortex circulation parameters of the simulated tanker wake flow field in the wind tunnel test section, compare them with the average wake vortex circulation parameters of the target tanker, and obtain the difference between the average wake vortex circulation parameters of the simulated tanker wake flow field and the average wake vortex circulation parameters of the target tanker.

[0009] Further, step 1 is specifically as follows:

[0010] Step 11, determining characteristic parameters of the tail vortex model of the target tanker according to the Kutta-Joukowski theorem;

[0011] Step 12, obtaining the tangential velocity of any point on the wake field cross section according to the Burnham-Hallock wake model combined with the characteristic parameters of the wake vortex model of the target tanker;

[0012] Step 13, calculating the average value of the tail vortex circulation according to the tangential velocity at any point on the tail flow field cross section;

[0013] Step 14: Scale down the average value of the tail vortex circulation according to the size of the wind tunnel test section and the scaling criterion, and take the average value of the tail vortex circulation after scaling as the true value of the calibration.

[0014] Further, step 2 is specifically as follows:

[0015] Step 21, installing a PIV measurement system, wherein the PIV measurement system includes: a camera, a laser, and tracer particles;

[0016] Step 22: In the wind tunnel experiment, first adjust the wind speed and start the wake simulation device, then spread the tracer particles, and capture the particle image with the camera after the flow stabilizes.

[0017] Further, step 3 is specifically as follows:

[0018] Step 31, dividing the two frames of particle images to be processed into a plurality of regions of equal area;

[0019] Step 32: perform cross-correlation calculation on the above regions on the two frames of images to obtain the tangential velocity of the wind tunnel flow field.

[0020] Further, in step 4, the wind tunnel simulated wake field parameters are calculated according to the tangential velocity of the wind tunnel flow field to obtain the average wake vortex circulation parameters of the wake flow field of the tanker simulated in the wind tunnel test section. Specifically, by processing the point velocity data on the measurement section, a circle is taken and sampled within a specified range in a plane coordinate system with the center point of the section as the origin, and the average wake vortex circulation parameters of the wake flow field of the tanker simulated in the wind tunnel are calculated.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The test method of the present invention can perform flow field calibration on the wake field of a refueling machine simulated by a blade rotating mechanism in a wind tunnel environment, thereby solving the problems caused by directly using a scaled-down model of a refueling machine to simulate the wake field of a refueling machine, solving the insufficiency of the direct simulation test capability of the wake field of a refueling machine in existing wind tunnels, and broadening the application prospects of wind tunnel tests in evaluating the influence of the wake of a refueling machine on the aerodynamic characteristics of a receiving aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart in an embodiment of the present invention;

[0024] Figure 2 It is a simplified model schematic diagram of the tail flow field of the tanker in an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the PIV measurement section position in an embodiment of the present invention;

[0026] Figure 4 Schematic diagram of the cross-correlation calculation range of the PIV particle image in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0029] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0030] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0031] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0032] Embodiment 1, combination Figure 1-Figure 4 This embodiment is described as a method for calibrating a wind tunnel to simulate the wake flow field of a refueling machine. The method comprises the following steps:

[0033] Step 1, calculate the average tail vortex circulation parameter of the target tanker as the true value of the calibration;

[0034] Step 2: Use the PIV method to measure the wind tunnel wake field and obtain a particle image;

[0035] Step 3, processing the particle image to obtain the tangential velocity of the wind tunnel flow field;

[0036] Step 4: Calculate the wind tunnel simulated wake field parameters according to the tangential velocity of the wind tunnel flow field, obtain the average wake vortex circulation parameters of the simulated tanker wake flow field in the wind tunnel test section, compare them with the average wake vortex circulation parameters of the target tanker, and obtain the difference between the average wake vortex circulation parameters of the simulated tanker wake flow field and the average wake vortex circulation parameters of the target tanker.

[0037] Step 1 is as follows:

[0038] Step 11, determining characteristic parameters of the tail vortex model of the target tanker according to the Kutta-Joukowski theorem;

[0039] Step 12, obtaining the tangential velocity of any point on the wake field cross section according to the Burnham-Hallock wake model combined with the characteristic parameters of the wake vortex model of the target tanker;

[0040] Step 13, calculating the average value of the tail vortex circulation according to the tangential velocity at any point on the tail flow field cross section;

[0041] Step 14: Scale down the average value of the tail vortex circulation according to the size of the wind tunnel test section and the scaling criterion, and take the average value of the tail vortex circulation after scaling as the true value of the calibration.

[0042] Specifically, the near-field wake field of the target tanker is simplified into a pair of wake vortices of equal size, height and opposite rotation direction, as shown in the figure below. Figure 2 As shown, the characteristic parameters of the tail vortex model of the target tanker are determined according to the Kutta-Jukovsky theorem, including the initial tail vortex circulation, the initial vortex core spacing and the vortex core radius. The Kutta-Jukovsky theorem is as follows:

[0043]

[0044] r c =0.05b0

[0045] Where b0 is the initial vortex core spacing, b is the wingspan of the target tanker, Γ0 is the initial tail vortex circulation, M is the weight of the tanker, g is the gravity acceleration, ρ is the air density at the target tanker flight altitude, V is the tanker flight speed, and r is the initial tail vortex circulation. c is the initial vortex core radius.

[0046] Furthermore, the tangential velocity at any point on the wake field cross section can be obtained according to the Burnham-Hallock wake model. The tangential velocity is obtained by:

[0047]

[0048] Obtain, where r is the distance from this point to the vortex core.

[0049] Take the average value of the tail vortex circulation in the range of r = 5-15m

[0050]

[0051] Where i is an integer from 5 to 15, r i is the radius of the corresponding circle, from 5m to 15m, is the average value of the tangential velocity on circles of different radii.

[0052] According to the wind tunnel test section size and the reduction ratio criterion, the vortex core spacing b0 and vortex core radius r of the target tanker are cThe reduction ratio is d times, the flight speed is V, the reduction ratio is m times, and the average value of the tail vortex circulation after the reduction ratio is taken. as the true value for calibration.

[0053] Step 2 is as follows:

[0054] Step 21, installing a PIV measurement system, wherein the PIV measurement system includes: a camera, a laser, and tracer particles;

[0055] Step 22: In the wind tunnel experiment, first adjust the wind speed and start the wake simulation device, then spread the tracer particles, and capture the particle image with the camera after the flow stabilizes.

[0056] Specifically, as attached Figure 3 As shown, the PIV measurement section is located in the l / 2 position plane perpendicular to the incoming flow direction in the wind tunnel test section, where l is the length of the test section. The PIV measurement section is a rectangular area (camera field of view) with an area of ​​(2b0 / d)×(b0 / d). The center point of the measurement section is at the same horizontal height as the hub and blade center of the active simulation generator of the tanker wake field, and the measurement section is symmetrical about the vertical center line of the wind tunnel. The PIV tracer particles are generated by a dedicated particle generation and spreading system and spread in the upstream stable section of the wind tunnel test section. The particle size is mainly concentrated in the range of 0.5 to 1.5 μm.

[0057] After the wind tunnel is started to reach the specified wind speed V / m and stabilize, the motor is started to drive the active simulation generating device of the fuel dispenser wake field, and tracer particles are spread upstream of the wind tunnel test section. After the tracer particles stabilize with the flow, the camera is used to capture the particles illuminated by the extremely short-duration pulse laser, and two or more frames of particle images containing Q pixels with a time interval of Δt are obtained.

[0058] Step 3 is as follows:

[0059] Step 31, dividing the two frames of particle images to be processed into a plurality of regions of equal area;

[0060] Step 32: perform cross-correlation calculation on the above regions on the two frames of images to obtain the tangential velocity of the wind tunnel flow field.

[0061] Specifically, the particle image is cross-correlated and processed to obtain the velocity distribution of the flow field on the measurement section. First, the two frames of particle images to be processed are divided into several regions of equal area, where the size of each region is represented by the number of pixels it contains. The number of pixels should be selected according to the actual particle image size and the flow field conditions. Under the premise of ensuring good calculation results, the region can be selected as small as possible. At the same time, it is better to have more than 10 tracer particles in the region. In this embodiment, the region size is 8×8 pixels, that is, each frame of the image is divided into Q / 64 regions. Figure 4 As shown, taking a certain area D on the first frame image as an example, when performing cross-correlation calculation with the second frame image, the corresponding calculation area range on the second frame image is:

[0062]

[0063] s max =v max ·Δt

[0064] where v max It represents the estimated maximum tangential velocity in the simulated wake field, s max It represents the maximum distance that the tracer particle can move on the PIV measurement surface within the shooting time interval Δt. That is to say, the area D′ where the cross-correlation calculation is performed on the second frame particle image is expanded from area D to the surrounding area s max Distance area.

[0065] Furthermore, the above regions on the two frames of images are cross-correlated. When the calculation results show an obvious peak, it is considered that the particle groups in the two regions are sufficiently similar and contain several pairs of particles. The distance that the cross-correlation peak deviates from the center of the region is the average displacement of the particles in the region within the Δt time interval. Dividing it by Δt, the velocity of the particles in the region can be obtained:

[0066]

[0067] in is the particle speed, is the average displacement of the particles in the time interval Δt. The time interval Δt needs to be estimated based on the test wind speed and the size of the image taken, and adjusted based on the measurement results.

[0068] In step 4, the wind tunnel simulated wake field parameters are calculated according to the tangential velocity of the wind tunnel flow field to obtain the average wake vortex circulation parameters of the wake field of the tanker simulated in the wind tunnel test section. Specifically, the point velocity data on the measurement section is processed, and a circle is taken and sampled within a specified range in a plane coordinate system with the center point of the section as the origin, so as to calculate the average wake vortex circulation parameters of the wake field of the tanker simulated in the wind tunnel.

[0069] Specifically, the point velocity data on the measurement section obtained above is processed, and a plane coordinate system is established with the center point of the section as the origin, the horizontal as the x-axis, and the vertical as the y-axis. The projections of the two sets of fan devices of the active simulation generation device of the wake field of the tanker on the plane coordinate system are located at the coordinate points L (-b0 / 2d, 0) and R (b0 / 2d, 0). Taking the left vortex of the wake field as an example, with point L as the origin, 11 circles are taken with a radius interval of 1 / d within the radius range of 5 / d to 15 / d, and j points are evenly taken on each circle to obtain the average wake vortex circulation of the left vortex:

[0070]

[0071] Where j is the subscript of the point on the circle, v L,ij is the tangential velocity of the area where the jth point on the i-th circle with point L as the center, v L,i is the average tangential velocity on the circle i with point L as the center, Γ L,i is the tail vortex circulation of the left tail vortex i circle, is the average tail vortex circulation of the simulated wake field. The difference K between the simulated average tail vortex circulation and the target tail vortex circulation is obtained as:

[0072]

[0073] The above is only one of the preferred embodiments of the present invention and an explanation of the device and technical principles used. Those skilled in the art should understand that the scope of disclosure involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features. This embodiment cannot be considered to limit the scope of implementation of the present invention. All changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A wind tunnel simulation method for calibrating the wake field of a refueling machine, characterized in that: The method comprises the following steps: Step 1: Calculate the average tail vortex circulation parameter of the target tanker as the true value of the calibration; Step 2: Use the PIV method to measure the wind tunnel wake field and obtain a particle image; Step 3, processing the particle image to obtain the tangential velocity of the wind tunnel flow field; Step 4: Calculate the wind tunnel simulated wake field parameters according to the tangential velocity of the wind tunnel flow field, obtain the average wake vortex circulation parameters of the simulated tanker wake flow field in the wind tunnel test section, compare them with the average wake vortex circulation parameters of the target tanker, and obtain the difference between the average wake vortex circulation parameters of the simulated tanker wake flow field and the average wake vortex circulation parameters of the target tanker.

2. The method for calibrating the wake field of a wind tunnel simulating a refueling machine according to claim 1, characterized in that: Step 1 is as follows: Step 11, determining characteristic parameters of the tail vortex model of the target tanker according to the Kutta-Joukowski theorem; Step 12, obtaining the tangential velocity of any point on the wake field cross section according to the Burnham-Hallock wake model combined with the characteristic parameters of the wake vortex model of the target tanker; Step 13, calculating the average value of the tail vortex circulation according to the tangential velocity at any point on the tail flow field cross section; Step 14: Scale down the average value of the tail vortex circulation according to the size of the wind tunnel test section and the scaling criterion, and take the average value of the tail vortex circulation after scaling as the true value of the calibration.

3. The method for calibrating the wake field of a wind tunnel simulating a refueling machine according to claim 1, characterized in that: Step 2 is as follows: Step 21, installing a PIV measurement system, wherein the PIV measurement system includes: a camera, a laser, and tracer particles; Step 22: In the wind tunnel experiment, first adjust the wind speed and start the wake simulation device, then spread the tracer particles, and capture the particle image with the camera after the flow stabilizes.

4. The method for calibrating the wake field of a wind tunnel simulating a refueling machine according to claim 1, characterized in that: Step 3 is as follows: Step 31, dividing the two frames of particle images to be processed into a plurality of regions of equal area; Step 32: perform cross-correlation calculation on the above regions on the two frames of images to obtain the tangential velocity of the wind tunnel flow field.

5. The method for calibrating the wake field of a wind tunnel simulating a refueling machine according to claim 1, characterized in that: In step 4, the wind tunnel simulated wake field parameters are calculated according to the tangential velocity of the wind tunnel flow field to obtain the average wake vortex circulation parameters of the wake field of the tanker simulated in the wind tunnel test section. Specifically, the point velocity data on the measurement section is processed, and a circle is taken and sampled within a specified range in a plane coordinate system with the center point of the section as the origin, so as to calculate the average wake vortex circulation parameters of the wake field of the tanker simulated in the wind tunnel.

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