实验流体力学

Bevelopment of PIV-based instantaneous pressure determination

Wang Yong, Chen Peng, Geng Zihai, Wang Wanbo, Li Shiwei

2014, (4): 1-8,24. doi: 10.11729/syltlx20140012

Abstract(303) PDF(48)

Abstract:
Instantaneous planar pressure field calculation based on the velocity fields obtained from partical image velocimetry (PIV)measurement data is a new technique for the measurement of pressure field.Recent research results acquired in computation fluid dynamics and wind tunnel tests abroad have demonstrated the feasibility and significance of PIV-based instantaneous pres-sure determination.This paper presents a description of the fundamental operation principles of the methods addressing the different procedures for obtaining the local pressure gradient by local-ly applying the incompressible momentum equation (Lagrangian form and Eulerian form)and for the subsequent spatial integration to evaluate the planar pressure field from these pressure gradi-ents (an in-plane Poisson formulation and direct spatial integration).The influence of the viscous term in the incompressible momentum equation is discussed,with the conclusion that its effect on the local pressure gradient determination can generally be neglected and will therefore be omitted safely.In the second part of the present paper,some key technologies and current developments of the PIV-based instantaneous pressure determination are reported.It is revealed that the overall uncertainty in determining the error in pressure is dominated by errors in velocity measurement and thus the first key point to the success of determining the instantaneous planar pressure field is to obtain faithful velocity field from PIV as soon as possible.A comparative assessment of the Lagrangian approach and the Euleiran approach to determine the local pressure gradient is consid-ered,which would promote the use of the Lagrangian approach though they are found to have dif-ferent merits and demerits.For the two different methods to evaluate the pressure in a plane from the estimated pressure gradient,it is illustrated that the Poisson approach is clearly better than the direct spatial integration approach since the latter introduces a dependence on the inte-gration path and shows a ‘memory’effect in the marching direction.Finally,several potential research directions for the practial application of the PIV-based instantaneous pressure determina-ton are discussed,including the improvement of the velocity filed measurement from PIV,the i-dentification of the key parameters that need to be taken into account and the optimization of them,the innovation of the methods to obtain the pressure gradient and the pressure field itself, and the reconstrution of the pressure field in 3D flow and compressible flow,etc.

An exploration on the unusual self-starting behaviors of a hypersonic inlet under low Reynolds number condition

Ling Gang, Li Zhufei, Xiao Fengshou, Jiang Hongliang, Liu Kunwei, Gao Wenzhi, Yang Jiming

2014, (4): 9-15. doi: 10.11729/syltlx20140045

Abstract(250) PDF(5)

Abstract:
With the help of combined experimental observation and numerical analysis,an in-vestigation is carried out on the unusual self-starting behaviors of a 2-D hypersonic inlet under low Reynolds number condition.Based on a series of repeated shock tunnel experiments,it is found that with a continuous decrease of the unit Reynolds number,an unexpected inlet self-starting configuration reappears after the unstarting process.The observation of the flow field a-grees fairly well with the results of the laminar simulation,but differs remarkably from the com-putational results obtained with turbulent model.The numerical simulations demonstrate that for laminar flow,a separation zone spreads out extensively to nearly entire forebody compression surface,which releases the high adverse pressure gradient and results in forming a supersonic path at the inlet throat.However,for turbulent flow,the separation can hardly reach far up-stream and consequently generates a strong concentrated separation bubble near the throat, which appears as an obviously choked and unstarting configuration.It needs to be emphasized that although the laminar inlet flow behaves with starting-like characteristics,the captured flow ratio is evidently lower than that of the choked turbulent flow under the same incoming flow con-dition.Therefore the so-called “unusual self-starting”inlet flow observed in the present study is not a true self-starting flow in reality.

TR-PIV measurement of the turbulent submerged jet and POB analysis of the dynamic structure

Wen Qian, Sha Jiang, Liu Yingzheng

2014, (4): 16-24. doi: 10.11729/syltlx20130056

Abstract(198) PDF(10)

Abstract:
The flow field of a submerged turbulent jet interacting with a free surface was measured using laser-induced fluorescence and time-resolved PIV techniques,and the dynamics of the flow structures were examined further using the proper orthogonal decomposition (POD)a-nalysis technique.The jet axis was located at the depth of H/D =4 below the free surface and the Reynolds number was 5600.The LIF results show that the jet flow exhibits an upwelling motion due to the existence of the free surface.The time-averaged flow field shows that the upper half portion of the jet flow spreads faster and the maximum velocity is located towards the free sur-face.The typical off-axis double peaks distribution of stream-wise turbulent intensity disappears as the downstream distance increases.The POD results show that the upstream well-organized coherent structures rise up rapidly when the jet is about to approach the free surface and the sub-sequent strong interaction occurrs.The dominant large-scale structures begin to develop down-ward in the further downstream due to the confinement in the vertical direction.

Wind tunnel test on the influence of col features on wind speed distribution

Zhang Hongjie, Zhao Jinfei, Cai Dazhang, Niu Huawei

2014, (4): 25-30. doi: 10.11729/syltlx20130044

Abstract(140) PDF(8)

Abstract:
The investigation on meteorological and micro-topography disasters of transmission lines shows that,due to the influence of col,windage yaw flashover and tower failure occurr fre-quently in the mountain region.However,studies on the topography formed by double three di-mension hills are relatively rare,and thus the distribution law of wind profile at different loca-tions is still indefinite.Under this situation,some wind tunnel tests about four types of col mod-el with different hill slopes and different valley widths are carried out.Then,on the analysis of wind tunnel test results,the influence law of some geomorphic features such as hill slope and val-ley width on wind profile is researched in this paper.Finally,some conclusions are derived as fol-lows.Compared with flat land,the degrees of wind speed-up at valley axis and hill peak reach 33% and 53% respectively,which are higher than the 10% stipulated in regulation,tending to cause more windage yaw flashover or tower failures.The wind speed at the valley axis will in-crease with the increasing of hill slope,and decrease with the increasing of valley width.Further-more,an equation matching this regularity is offered.At the valley axis of the col model,the wind speed-up effect of the downwind is a little stronger than the upwind,that may be caused by flow separation and more intensive fluid huddled at the downwind.At the hill peak,col features basically have no influence on the wind speed,so that the wind speed correction coefficients ob-tained by wind tunnel test display a good agreement with those obtained by fitted equation for so-lo hill.Since the wind speed correction coefficients at the hill peak are higher than those at the valley axis,in design the wind speed correction coefficients at the hill peak can be conservatively utilized for the whole col.

Experimental research on multiphase flow of ventilated cavity around a hemisphere cylinder

Duan Lei, Wang Guoyu, Fu Xineng

2014, (4): 31-36,64. doi: 10.11729/syltlx20130040

Abstract(166) PDF(5)

Abstract:
To understand the characteristics of ventilated cavity,ventilated cavity flow around a hemisphere cylinder is experimentally studied by applying the high speed visualization technolo-gy.The results show that the gravity effect and air entrainment play a major role in forming mul-tiphase flows of ventilated cavity.Froude number and air entrainment coefficient are defined. Five multiphase flows of ventilated cavity around a hemisphere are denoted,which are transpar-ent bubble flow,transparent slug flow,transparent layering flow,air-water mixture flow and semitransparent air-water mixture flow.The influence of flow parameters on fluid structure is analyzed,and there are two stages.One is the stage where the gravity plays a critical role,and the other is the stage where the gravity effect is limited.In the stage where the gravity plays a critical role,when air entrainment coefficient is fixed,fractured cavity changes into steady cavity attaching to the surface of the cylinder as Froude number increases;when Froude number is fixed,the scale of fractured bubble increases as air entrainment coefficient increases.In the stage where gravity effect is limited,when air entrainment coefficient is fixed,Reynolds number and turbulence intensity increase and bubbly wakes created by ventilated cavity become turbulent as Froude number increases;when Froude number is fixed,cavity number based on cavity pressure decreases and cloud cavity around a cylinder changes into transparent cavity as air entrainment co-efficient increases.Finally unsteady bubble shedding is described when fluid structure is domina-ted by gravity and by re-entrant jet.

Numerical methods exploration and experimental validation of Ahmed model with consideration of fluid-solid-interaction effect

Shen Chen, Yang Zhigang

2014, (4): 37-42. doi: 10.11729/syltlx20130017

Abstract(136) PDF(5)

Abstract:
Fluid-solid interaction (FSI)between the crosswind and the moving vehicle exerts an impact on driving safety.The reliability of the FSI numerical simulation method needs to be verified.Numerical simulation method and wind-tunnel test method are used with an Ahmed model in the research.Arbitrary Lagrange-Euler (ALE)method is applied to the Ahmed model FSI numerical simulation under crosswinds at velocities of 20m/s,25m/s,30m/s,35m/s,and 40m/s.Through comparison between numerical solution of the Ahmed model and experimental results,it can be claimed that the displacement difference is less than 20%.The experimental methods contain pressure and deformation measurements and flow visualization technique (plume-tracer technique and thread-tracer technique).The flow visualization results are com-pared with the numerical results to verify the reliability.After the comparison of the coupled and uncoupled numerical results,it is found that variation in aerodynamic forces is mainly caused by ever-changing topologic structure of vortices.In this paper,it is found that:(1)FSI effect main-ly intensifies the aerodynamic lift force on the vehicle under crosswind condition(especially at a velocity higher than 25m/s).(2)Aerodynamic lift force increase is mainly caused by the topolog-ical change of the separation bubble above the Ahmed body.FSI effect significantly expands the scale of the separation bubble.(3)Under crosswind condition,FSI effect will increase the rolling trend,so the actual vehicle security is lower than the yield of numerical results with FSI effect unconsidered.Therefore,the use of non-coupling calculation results as a design basis is some-what risky.The present study has laid a theoretical foundation for the upcoming research on the two-way FSI effect on vehicle under time-dependent crosswind condition.In short,the work aims to quantify crosswind acceleration effect and fluid-structure interaction effect of aerodynamic force,to provide a method to research the real vehicle crosswind stability in a finer and more precise way, and to provide a reference to simulate the vehicle travelling status more thoroughly.

PIV measurement of inner flow field in exhaust manifold junction

Wang Wenhui, Lu Zhenhua, Liu Sheng, Deng Kangyao, Cui Yi

2014, (4): 43-48. doi: 10.11729/syltlx20130049

Abstract(166) PDF(11)

Abstract:
The inner flow field in the 45°sharp-edged T type junction of the axial section was measured on the pressure loss of the exhaust system by Particle Image Velocimetry (PIV).Char-acteristics of flow type 6 were obtained at different mass flow rate ratios and Mach numbera.The pipe area in each branch of the tested 45°junction remained constant,D =50mm.The axes in all branches were coplanar and the corners at the point of intersections between lateral branch and main branch were sharp edged.The experimental data were measured for the junction with vari-ous mass flow rate ratios (q =0,0.25,0.5,0.75 and 1)and Mach number in common branch (Ma=0.13,0.31 and 0.59).Comparatively analysed the data of the velocity field and streamline pattern.Conclusion were drawn out that flow contraction occurred in downstream of the junc-tion.The feature of the flow field was related to the Mach number in common branch and the mass flow rate ratio between branch and duct in type 6.As the mass flow rate ratio of branch and duct increased,the turbulent region was enhanced and pressure loss enlarged.Mach number would also change the flow characteristics and pressure loss.The variation in the total pressure loss coefficient with Ma was fairly small in the range of 0.13 up to 0.31.However,along with the Mach number increased to 0.59,the coefficient increased more rapidly.

Technique investigation on force test with multi-balance in hypersonic wind tunnel

Shu Haifeng, Xu Xiaobin, Sun Peng

2014, (4): 49-53. doi: 10.11729/syltlx20130018

Abstract(283) PDF(11)

Abstract:
The aerodynamic characteristics of aerocrafts can be acquainted with multi-balance which also helps to reduce the cost of experiments and raise efficiency.The force test technique with multi-balance was quite mature in transonic and supersonic wind tunnel.However,it was not widely used in hypersonic wind tunnel because of the small model scale and the high tempera-ture.In order to meet the need for project development,the force test technique with multi-bal-ance investigation was carried out in Ф1m hypersonic wind tunnel of CARDC.Three controlling rudders of the same aerocraft were chosen as research objects.The axes of hinge-moment bal-ances and the rotation axes of the measured rudders were vertical.The rational miniaturized six component balance configuration style was adopted.For example,the sizes of the elevator bal-ance’s measuring elements were 20mm×20mm×25mm.The calibration method of the balances was investigated.The calibration results had shown that the static calibration accuracy of the main components of balances was less than 0.7%;the zero excursion clearly reduced after the temperature compensation methods were used;the integral design of balance and angle transfor-mation device improved the accuracy of orientation and installation in effect.The wind tunnel ex-periment with Ma=5 was performed and the results of typical conditions had been given.The ex-perimental results indicated that force test technique with multi-balance could be used in hyper-sonic wind tunnel aerodynamic test.

Investigation of the performance of flow field in supersonic/hypersonic wind tunnel with different test section geometry configurations

Yang Bo, Liu Sen

2014, (4): 59-64. doi: 10.11729/syltlx20130023

Abstract(121) PDF(18)

Abstract:
The steady flow fields of the Ф1 m hypersonic wind tunnel are simulated under Mach number 3 and 6 by solving axisymmetric N-S equations.The comparison between the nu-merical simulation and experimental data validates that this numerical method is feasible.And then the flowfields of wind tunnels with closed straight round and unclosed free-jet test sections under these Mach numbers are simulated respectively.The results of uniformity test core of closed straight round and unclosed free-jet test sections meet the requirement of relevant stand-ards.The results show that the minimum diameter of the uniformity test core in Mach 3 nozzle with closed test section reaches Φ882mm at the axial coordinate from-300mm to 900mm.The test core increases by about 31.57% compared with free-jet test section,which significantly im-proves the test capacity of wind tunnel.For Mach 6 nozzle with closed test section,the uniformi-ty test core only increases by about 8.24% compared with unclosed test section,which makes lit-tle improvement on the flowfield performance.The uniformity test core of supersonic wind tun-nel with closed test section enlarges observably,but it is little larger in hypersonic wind tunnel with closed test section than that with unclosed free-jet test section.

Floating suspension system for full model flutter tests at low speed

Tang Jianping, Yang Yuanzhi, Liang Jian

2014, (4): 65-69. doi: 10.11729/syltlx20130014

Abstract(234) PDF(8)

Abstract:
To meet the increasing requirement for full model flutter tests in low speed wind tunnel,a sort of floating suspension system(FSS)is built in WT 3.2m of LSAI of CARDC. The FSS is divided into two parts:vertical part and horizontal part.The horizontal part of FSS consists of horizontal cable device and tensioning mechanism.For general function,the FSS can provide a model 5 degrees of freedom:in the vertical and lateral directions,pitch,yaw and roll. Each degree of freedom of the model can be changed individually with other degrees of freedom unaffected.The FSS can ensure a model supported in the middle of the test section in the verti-cal,lateral and fore-and-aft directions.It is convenient to adjust the attack angle and roll angle of a model in FSS.For a flutter model in FSS,technical requirement and method of choosing pa-rameters are presented in this paper.The same flutter model has been used in contrast tests in WT 3.2m of LSAI of CARDC and WT T-103 of TsAGI.The critical flutter speed and frequency of the model in the contrast tests are almost the same.It is testified that the FSS is reasonably designed and can be well put in use in low speed full model flutter tests.

Research on structural health monitoring method for locating space debris impact on spacecraft seal structures

Wang Xiaoyu, Zhang Chao, Sun Wei, Qiu Jinhao, Zang Xiaoyun

2014, (4): 70-77. doi: 10.11729/syltlx2014pz20

Abstract(158) PDF(13)

Abstract:
During long-term work,the spacecraft seal structure suffers impacts from the space debris.If the damage can not be detected immediately,disastrous consequences will happen. Therefore the detection of the impacts caused by space debris is essential and meaningful.This work focuses on an ultrasonic guided wave structural health monitoring (SHM)system developed for the spacecraft seal structure inspection.In part one of the study,the Finite Element Modeling of the reinforced panel is created using the finite element software ABAQUS.Then the simula-tion of the impact made by a small iron ball is presented,and the velocity of the ball increases from 500m/s to 10000m/s.Besides,the elastic wave propagation in the panel is also discussed, and the elastic wave propagation characteristics in the stiffened panel are analyzed.The wavelet transform method is used to find out the appropriate analysis frequency of the elastic waves.The conclusion is that the signal components in 50kHz is the optimal selection to detect and locate the iron ball impact.In part two,permanently mounted ultrasonic piezoelectric (PZT)disc sensors arranged as a spatially distributed array is considered for in situ impact monitoring.The impact location and imaging algorithm is based upon the cross correlation between waveforms received by two different transducers.The cross correlation waveforms,which capture the arrival time difference between two pairs,are similarly distributed and summed to form the final image via a hyperbolic relationship.In order to find out the optimal solution among the sensor number,the accuracy of the impact location and the time-consuming,several different arrangements of the sensors are presented.A comparison based on location accuracy in central region,border area and computing time-consuming is made to find out the optimal sensor arrangement in the reinforced panel.In part three,the effects of the algorithm and the sensor arrangement are tested in a labo-ratory environment.Hammer percussion is used as a substitute for the iron ball impact in these tests.As many as 20 repeated hammer shocks are made for each selected point in the stiffened panel.The results verify the accuracy and stability of the algorithm for impact detection and lo-calization in the complex spacecraft structure.

Numerical simulation of fragment generation from satellite breakup

Zhang Xiaotian, Jia Guanghui

2014, (4): 78-83. doi: 10.11729/syltlx2014pz32

Abstract(133) PDF(8)

Abstract:
A numerical method for simulating fragment generation from satellite breakup is proposed and the impact case relevant with the test is simulated.Currently HVI numerical simu-lation technique is mainly used in spacecraft protective structure analysis.And the most widely used method is SPH.In this paper,the complete disintegration of spacecraft will not occur be-cause of the small size of the impactor.Protective structure HVI simulation focuses on the pene-tration limit of the shield while the individual fragment characteristics in the secondary debris cloud are not concerned much about,such as:amount of fragments,size and mass of each frag-ment,etc.In contrast,the purpose of spacecraft breakup model is to provide the characteristics of individual fragment,which are also supposed to be the output of breakup dynamics simulation. Finite element reconstruction method is a hybrid of finite element method and the smoothed par-ticle hydrodynamics method.The characteristics of the individual fragments can be obtained from the simulation.The confidence individual fragment can be identified by reconstructing finite ele-ments from the smoothed particles.The size,velocity vector,and mass can be computed with the fragment statistics method based on graph theory.The fragment distribution can be obtained from the individual fragment data.The good agreement of simulated output and the test shows the feasibility of this method.The main difference between NASA model output and test data lies in the smaller size range.The possible reason might be the test for building NASA model is dif-ferent from the test of CARDC.The main data source for small fragment part in NASA model is SOCITE4 breakup test.The target used in the test is OSCAR satellite which has a more compact internal structure.It indicates that the material and internal structure do affect the distribution of breakup fragments,and it is necessary to analyze the fragment based on the impact dynamics.Finite el-ement reconstruction approach can model the spacecraft and the impactor in details including the shape,internal structure,material feature,impact velocity magnitude and direction,and also im-pact location.The simulation can provide the total number of fragments and the mass,size,ve-locity vectors of each fragment.With high resolution simulation model,the approach can output characteristics of small fragments.Further work aims at two aspects.First,the effect of the im-pact location to the breakup fragments distribution will be analyzed with the simulation approach,especially for large impactors.Different impact locations in the target will result in various debris characteristics,for example:the velocity direction,and then the orbit,of fragments.Second, the simulation approach will be applied to historical on-orbit breakup events.SSN data of frag-ments larger than 10cm could be used as a reference to verify the approach and to calibrate the true impact location which can not be observed.The disintegration process reproduced with the simulation and fragments smaller than 10cm can also be analyzed.The fragment output of FER can be directly imported into an orbit propagator to analyze the orbit distribution and lifetime of each fragment and so on.

Research and application of multi sequences laser shadowgraph technique

Xie Aimin, Huang Jie, Song Qiang, Zheng Lei, Ke Fawei, Liu Sen

2014, (4): 84-88. doi: 10.11729/syltlxpz04

Abstract(356) PDF(27)

Abstract:
Multi sequences laser shadowgraph technique has been developed for getting the pill pose and the debris cloud in the hypervelocity impact experiment.Double,four,and eight se-quences laser shadowgraph systems have been set up successively on the hypervelocity impact range at the base of the technique of multi-light source divided in space,polarization decomposi-tion,light angle magnification and compensated filter,etc.The noise of diffraction and interfer-ence with homochromy light has been resolved by using the techniques.The systems can get many images at different time in the hypervelocity variety process.When the least interval is 1μs,the time of exposure is 10ns and the image pixel is ten million.The systems were also used in the impact experiments.The multi sequences laser shadow images have been gotten at differ-ent conditions with the impact velocity from 2km/s to 7km/s,which describe the outline chan-ging process of the debris cloud.This technique meets the need of showing the flight attitude of projectile and debris cloud at low cost,and can be used to measure in the field of other hyperve-locity process as well as show the flow structure.

Research on photoelectric detection of submillimeter projectile

Ren Leisheng, Luo Jinyang, Luo Qing, Long Yao, Huang Jie

2014, (4): 89-93. doi: 10.11729/syltlx2014pz09

Abstract(130) PDF(6)

Abstract:
The single flake light projectile detecting technology is used for measuring the pro-jectile velocity exactly in hypervelocity impact test that are usually carried out for space debris re-search.For detecting projectiles with diameter less than 1mm,we develope the photoelectric ar-ray projectile detecting technology based on the single flake light projectile detecting technology. The key problem of detecting projectile with diameter less than 1mm is to increase the intensity of detected signal.It could be resolved by increasing the ratio of the projectile diameter to the flake light width.A test device for the photoelectric array detection system is developed and in-stalled at the hypervelocity ballistic range.A series of tests were carried out at the hypervelocity range,which show that the SNR is enhanced and projectile with diameter of 0.6mm was able to be reliably detected with the photoelectric array detection technology.Data analysis shows that the technology can be used for reliably detecting projectile with diameter of 0.1mm.

Impact test on soap target with steel projectile

Chen Ping, Liu Sen, Li Yi, Huang Jie, Wen Xuezhong

2014, (4): 94-98. doi: 10.11729/syltlx2014pz37

Abstract(178) PDF(3)

Abstract:
In order to study the damage of a biological organism impacted by incident objects, experiments have been carried out using soap to simulate an organism at hypervelocity impact range of Hypervelocity Aerodynamics Institute,CARDC.In the tests,the soap targets are im-pacted by 3.0mm steel sphere projectile at high velocity conditions of 0.96km/s and 1.88km/s, and hypervelocity conditions of 3.52km/s and 4.98km/s.The characteristics and damage pat-terns of the soap target under test conditions are obtained.It is found that,at high impact veloci-ty,the soap target is perforated by the steel projectile.A long pole perforation is formed at the impact velocity of 0.96km/s and an evase perforation shows up at the impact velocity of 1.88km/s. At hypervelocity impacts (3.52km/s and 4.98km/s),big hemisphere craters are produced.The damage of the target could be considered in two aspects.On the one hand,the sizable craters produced at hypervelocity impacts lead to direct volume remove.This would bring severe wound to an organism.On the other hand,as a result of the extensive shockwave load,the damage area is larger than the carter zone.Analysis shows that the extensive shockwave load will not only cause serious damage to an organism by direct volume remove,but also cause a damage to putres-cence of tissues,organs,and fractures near the ballistic trajectory of the projectile.

A brief introduction on NASA’s two stage light gas guns

Wang Dongfang, Xiao Weike, Pang Baojun

2014, (4): 99-104. doi: 10.11729/syltlx2014pz02

Abstract(533) PDF(52)

Abstract:
With the increasing frequency of human spaceflight activities,space debris popula-tion is increasing year after year.Nowadays space debris impacts are more and more dangerous to astronauts doing extravehicular maneuvers and to high-pressure vessels and toxic aerospace mate-rials carried aboard spacecraft.The protection strategy against the impact of millimeter space debris is mainly by shielding.In order to design effective shielding for spacecraft and to evaluate the risk posed by debris and meteoroids,we must be able to perform tests in the laboratory. Hypervelocity impact testing has some extreme requirements.The core of the problem is to find a way to launch projectiles at speeds more than seven times faster than the fastest bullet,to measure how fast the projectile is traveling before impact,and to take pictures of impact event that lasts only a few microseconds.Launching projectiles at velocities high enough to simulate or-bital debris impacts requires some remarkable equipment called “two stage light gas gun”.The technology is one of the most important factors in the improvement of experimental ability,and therefore it is considered as a significant indicator to evaluate the experimental level of a laboratory, or even a country.National Aeronautics and Space Administration (NASA),the leading agency in the aerospace area in America as well as in the world,is supported by several laboratories with the ability of performing hypervelocity impact tests,where the two stage light gas guns play a critical role.The White Sands Test Facility (WSTF),located at remote desert foothills of New Mexico,works in close partnership with NASA Johnson Space Center Hypervelocity Impact Technology Facility (HITF).HITF determines the risk of spacecraft posed by space debris,and then designs spacecraft shields based on probability of impact and spacecraft geometry.HITF also builds and sends target shields to WSTF for ballistic-limit,verification testing and accordingly analyzes the results.Other spacecraft materials and components are targeted too,as well as toxic and explosive cargo,including fuel.The WSTF Hypervelocity Impact Testing Program assesses candidate shield materials with the help of two stage light gas guns.These guns shoot projectiles at hypervelocities up to roughly six times faster than the fastest rifle bullet,and mimic the impact of real space debris traveling at even higher speeds.Some other laboratories in America also present a remarkable performance in improving the ability of two stage light gas guns,such as NASA A-mes Research Center,McDonnell-Douglas Corporation,General Motor Corporation,Naval Ord-nance Laboratory,and United States Naval Research Laboratory.

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旋转流场下的振荡动导数试验技术研究

Wu Jinhua, Sun Haisheng, Shen Zhihong, Jiang Yubiao

2014, (4): 54-58. doi: 10.11729/syltlx20130057

Abstract(160) PDF(9)

Abstract:

为研究飞机在旋转流场下的非定常气动特性,中国空气动力研究与发展中心低速所在Φ5m 立式风洞开展了旋转流场下的振荡动导数试验技术研究。本文推导了在旋转流场下识别组合动导数的方法,介绍了试验设备,获得了在旋转的同时,由振荡产生的3个组合动导数,并对试验结果进行了分析与讨论。将单自由度动导数结果与Φ3.2m 风洞试验结果进行了对比,旋转/振荡耦合试验结果表明:旋转运动使得俯仰组合动导数变得不稳定,而对于横向组合动导数,大转速则会显著增大非线性。该试验技术能够为研究旋转流场下的非定常气动特性提供一个有效的试验平台。

2014 Vol. 28, No. 4