2017 No. 6

Fundamental Research and Application
Experimental studies of Curved Cone Waverider forebody Inlet(CCWI) at low Mach number range
Wei Feng, Zhou Zheng, Li Li, He Xuzhao
2017, 31(6): 1-7. doi: 10.11729/syltlx20170049
Abstract:
The self-start ability, anti-backpressure performance and side slip influences to the performance of the Curved Cone Waverider forebody Inlet(CCWI) were experimentally studied in the present paper. Based on the geometrically constrained and bluntly modified practical CCWI wind tunnel experimental model, using the inlet throttling systems, the static pressure distributions and high resolution sherilen maps of the CCWI's flow field were obtained at free steam Mach numbers(Ma) 3.0, 3.5 and 4.0 at different throttling cone positions. The experimental results show that the integrated CCWI model can self-start at Ma 3.5 and 4.0. At the angle of attack 0°, its maximum anti-back pressure abilities is about 24 and 33 times of the free stream static pressure(p) at Ma 3.5 and 4.0, respectively. Side slip has little influence on mass flow capture and flow compression abilities for CCWI. The study on CCWI can be used for practical integration studies with scramjet engine and air-breathing vehicles.
Investigation of turbulence modification by PIV tracer particles in a supersonic mixing layer
Chen Xiaohu, Chen Fang, Liu Hong, Sha Sha, Lu Xueling, Zhang Qingbing
2017, 31(6): 8-14, 21. doi: 10.11729/syltlx20160144
Abstract:
The turbulence modification by Particle Image Velocimetry (PIV) tracer particles was investigated with the two-way coupling of 2D spatial development supersonic gas-solid two-phase mixing layer. The gas phase coupled with the dispersion phase were simulated by the large eddy simulation and the Lagrangian trajectory model, respectively. It is found that the streamwise turbulence of the mixing layer is weakened, the transverse turbulence of the mixing layer strengthened and the Reynolds stress peak value increased by 9.68% than that of the unladen mixing layer due to the small Stokes particles. However, the root mean square velocity of the mixing layer is weakened by the large Stokes particles, and the Reynolds stress peak value is only 41.74% of that of the unladen mixing layer. The root mean square transverse velocity with the large mass loading is 38.63% of that of unladen mixing layer, and it is partly counteracted by the motion of particles. The root mean square transverse velocity and the Reynolds stress with the middle mass loading are almost equal to those of the unladen mixing layer. The largest root mean square streamwise velocity is reduced by 19.29% whereas the root mean square transverse velocity near the centerline of the mixing layer is increased by the small mass loading. The modification to the turbulence of the supersonic mixing layer under the small Stokes number and middle mass loading condition is smaller than other cases. The study provides important reference for improving PIV experiment in high speed flows.
PIV measurement on streamwise vortex generated by undulating fins
Zhang Jun, Bai Yaqiang, Zhai Shucheng, Zhang Guoping, Xu Lianghao
2017, 31(6): 15-21. doi: 10.11729/syltlx20170017
Abstract:
The Gymnarchus Niloticus Fish (GNF) with long undulating fins generally cruises with high efficiency and extra-ordinal maneuverability while keeping its body for straight line. The flow field around andulating fins are measured by phase-locked PIV in the stationary water. Four cross sections including front part, middle part, after-body and wake flow are measured, respectively. Eight equal spaced phases are measured at each cross section, and one hundred instantaneous velocity fields are phase-averaged analyzed to extract the characteristics of vortex structure at each phase. The results indicate in cross sections the streamline vortexes are periodically generated near the fin tip as the fin swings to nearby maximum angle, and shed from the tip of the fin surface, There are two streamwise vortexes generated during each period at the two side maximum angle. On the other hand, as fin swings to the near mid-sagittal plane in the cross section, the fully developed streamwise vortexes begin to decay, and finally disappear. Meanwhile a high speed jet is generated in the direction from the root to the tip of the fin. Comparing the flow structure in the forepart, middle part and posterior cross sections, it is obvious that the streamwise vortex structure and its evolution with phases are similar in these three sections. From the forepart to the posterior along the shaft axis, the flow structure becomes more and more complicated as waves spread downstream, the jet ejected outward from the fin tip becomes stronger, and its sphene of influence seems enlarged. But the flow structure in the wake is different from the above three cross sections, which is less changed with the wave phases. The two large streamwise vortexes are formed under the fin surface, and stably and symmetrically locate on two sides of the mid-sagittal plane with opposite rotation directions.
Experimental investigation on the effects of vortex generator on corner separation in a high-load compressor cascade
Li Renkang, Wang Rugen, He Cheng, Hu Jiaguo, Ma Caidong, Huang Danqing
2017, 31(6): 22-28, 36. doi: 10.11729/syltlx20160195
Abstract:
The vortex generator could effectively reduce corner separation in the compressor cascade. To assess the flow control effects, schemes with different vortex generator's circumference positions were proposed and experimental investigations were performed. The results show that the vortex generator changes the vortices' structure by generating a trailing vortex, which enhances the mixing of the end-wall low momentum flow with the main flow and suppresses the corner separation. After application of VG scheme A, the averaged pressure loss coefficient is reduced by 5%~14% and the averaged flow turning angle increases 2.49°~3.15° with the incidence angle from -3° to 3°. Compared with VG scheme A, if the vortex generator gets 0.15 pitch length farther away from the suction surface then the corner vortex is enhanced and the aerodynamic performance is unsatisfactory; while additional corner loss can emerge and the control effect gets weakened if the vortex generator gets 0.15 pitch length closer to the suction surface.
Experimental study of coherent structures in a solid-liquid turbulent boundary layer
Zhao Huiling, Sun Jiao, Xuan Ruixiang, Chen Wenyi
2017, 31(6): 29-36. doi: 10.11729/syltlx20160199
Abstract:
Solid-liquid turbulent flows are common in industrial and engineering processes.Study of the interactions between particles as well as turbulence and turbulence modulation is extremely significant, which can play an guidance role in practical engineering application for heat and/or mass transfer in chemical processes.Coherent structure in the turbulent boundary layer of particle-laden flows is experimentally investigated using Particle Image Velocimetry (PIV). Study of the change of the mean velocity profile and the turbulent intensity in the horizontal turbulent boundary layer of water and with polythene is conducted, which is used as the dispersed phase.Based on the concept of multi-scale spatial locally averaged structure function, conditional sampling and phase average methods are employed to extract and analyze the spatial topologies of the streamwise and normal fluctuating velocities, spanwise vorticity, Reynolds shear stress of the ejection and sweep events.The results show that the buffer layer of the turbulent boundary layer has thinning tendency and logarithmic layer down-shift, the turbulence intensity and the Reynolds stress are also enhanced due to the existence of particles.The amplitude of longitudinal and vertical fluctuating velocity components, as well as that of the spanwise vorticity and Reynolds shear stress can be manipulated obviously both in ejection and sweeping events, all parameters were increased. It imply that the turbulence intensity in the near-wall region in the two burst events increase, and the momentum and energy transport strengthen for the exist of particle in the experiment.
Hypersonic wind tunnel flutter test research on rudder models by continuously varying dynamic pressure
Ji Chen, Zhao Ling, Zhu Jian, Liu Ziqiang, Li Feng
2017, 31(6): 37-44. doi: 10.11729/syltlx20170088
Abstract:
In order to study the hypersonic flutter behavior of rudder models, a hypersonic wind tunnel flutter test technique by continuously varying dynamic pressure was developed and experimentally studied in China Academy of Aerospace Aerodynamics. The models with the same structural and aerodynamic design were tested at Mach number 4.95 and 5.95. The flutter critical parameters were obtained by slowly increasing the dynamic pressure until flutter onset. The short-time-fourier-transform time-frequency domain analysis method was used to study the frequency coupling characteristics. The analysis shows that it is the classic flutter that the bending and torsion mode couples as the dynamic pressure increases. Based on the structural dynamic parameter identification method, the damping ratio extrapolation method and the flutter margin method were used to predict the flutter critical parameters with the subcritical data. Both methods show a good prediction accuracy. The results also indicate that the rate of increase of dynamic pressure has small effect on the prediction of the flutter boundary. The temperature field measurements show that the maximum temperature of the model appears at the leading edge of the wing root. The temperatures of the leading edge and the rear part of the slope of the rudder are also relatively high. The temperature of the leading edge of the rudder shaft exposed to the flow field is not high, which might be due to the influence of the reflector surface boundary layer.
Wind tunnel drop model test of nose cap separation of supersonic vehicle
Song Wei, Lu Wei, Jiang Zenghui
2017, 31(6): 45-50, 70. doi: 10.11729/syltlx20170026
Abstract:
This paper studies the motion characteristic of the nose cap revolving separation of the supersonic vehicle in the stiff atmosphere by the wind tunnel drop model test and acquiares the law of the centroid distance and pitch angle variance for the two part nose cap when the nose cap separate. The experiment Mach number is Ma=1.5. The study shows that when the nose cap splays out by the intrinsic constringent spring, the high dynamic pressure afflux into the antrum of the two nose cap and makes the nose cap go round and round by caudal gemel. Then the mantle break away from the forebody when the rotate angle arrive at the preconcerted angle, the aerodynamic force is several orders of magnitude greater than the inertial force, the nose cap trajectory is absolutely controlled by the aerodynamic force and the mantle statement changes violently. The two nose cap have a symmetrical motion distance and pitch angle in the angle of attack α=0°, however, the separate characteristic is unsymmetrical in the angle of attack α=-5°. The angle of attack for the supersonic vehicle has a prominent effect on the motion characteristic for the two nose cap. The study can provide an according and reference for the nose cap separation precept and flighting control system.
Measuring Technique
Research on application of Rayleigh scattering velocity measurement in hypersonic low density wind tunnel
Chen Aiguo, Chen Li, Li Zhihui, Li Zhonghua, Yang Furong, Li Sixin, Yan Bo
2017, 31(6): 51-55. doi: 10.11729/syltlx20170020
Abstract:
The velocity and turbulence level of Mach 5, 6 and 12 flow fields have been measured in the Φ0.3m hypersonic low density wind tunnel by the Rayleigh scattering principle using a Fabry-Perot interferometer. The application of the Rayleigh scattering measuring system in the velocity measurement of the hypersonic flow field is understood and realized. The turbulence level of the wind tunnel is below 1%, and the maximum deviation between the velocity measurement result and the flow-field calibration is 1.3%. The velocity in the flow field around the re-entry module after the shock wave has also been measured. The experimental result of the Mach 6 incoming flow is in agreement with numerical simulation results, but in the case of the Mach 12 incoming flow the deviation is 69%, and the reason is analyzed. It is found that through the experiment a certain condensation exists in the Φ0.3m hypersonic low density wind tunnel. Further research scheme is suggested.
Research of the measurement method for the pressure distribution along the micro/mini-channel
Wang Haoli, Wang Bing
2017, 31(6): 56-61. doi: 10.11729/syltlx20170050
Abstract:
In this study, a system was designed and built up for the pressure measurement along micro/mini-channel, which mainly includes micro/mini-channel and square pressure cavities on PMMA chip, micro-strain sensors and multi-channel strain instruments. The static pressure in micro/mini-channel was provided by the syringe pump, and the high precision pressure values measured by the micromanometer of FCO510 was employed as the standard pressure. The strain values from the strain sensors installed on the square pressure cavities were obtained by multi-channels strain gauge, and the calibration functions between the standard pressure and the strain were established. The pressure distributions of three kinds of micro pressure chips were measured under flow rates of 80, 70, 60 and 50mL/min, respectively. The pressures have good linear distribution.The uncertainty analysis indicates that the relative uncertainty of the pressure error is between 0.15% and 6.82%. The validity and reliability of pressure measurement are high.
Experimental Equipment and Method
Application of additive manufacturing to 30CrMnSiA high speed wind tunnel test model design and fluid-structure interaction analysis
Hong Xingfu, Ye Cheng, Wang Linzhi
2017, 31(6): 62-70. doi: 10.11729/syltlx20170074
Abstract:
Additive manufacturing technology can be processed in any complex shape parts. The short manufacturing cycle and low cost are its unique advantages compared to the traditional machining, and thus it has wide application prospects in the wind tunnel test model manufacture. In view of the material 30CrMnSiA commonly used in the high speed wind tunnel model processing, the metal powder preparation, detection and material specimen manufacture are studied. On this basis, with test piece data as a yardstick for material performance, an AgardB model with hollow airfoil is designed based on the additive manufacturing process. Moreover, fluid-structure interaction analysis is conducted for the model using Ansys and the optimal design is carried out. The results indicate that the model structure can meet the requirement of high-speed wind tunnel testing.
Research on metric thrust jet-effects testing methodology in high-speed wind tunnel
Ji Jun, Song Xiaoyu, Deng Xiangdong, Guo Dapeng, Li Peng
2017, 31(6): 71-77. doi: 10.11729/syltlx20160176
Abstract:
The metric thrust jet-effects testing methodology is introduced in FL-3 wind tunnel. Different from the sleeve type jet-effects testing methodology, the airframe is integrated with the nozzle by using the bellows system, and the balance can measure simultaneously the aerodynamic characteristics and the nozzle thrust. The problems such as nozzle geometric incomplete similarity, touching possibility between the model and the nozzle, imprecise modification of the pressure in the model cavity, etc, which exist in the sleeve type jet-effects testing methodology can be avoided by using the metric thrust methodology. The similarity theory, testing methodology and bellows technology of the metric thrust jet-effects testing are discussed in detail in this paper. The experimental results show that jet-effects under different test conditions including different nozzle pressure ratios and vectoring jets can be gained by the metric thrust jet-effects testing methodology. After further improvements of some details, the test capability can be enhanced, and the nozzle performance wind tunnel testing methodology and the thrust vector wind tunnel testing methodology can also be developed based on this methodology.
Development and application of the measurement system for thrust vectoring tests at 2.4m×2.4m transonic wind tunnel
Miao Lei, Xie Bin, Li Jianqiang, Li Yaohua, Huang Cundong, Jia Wei, Ma Tao
2017, 31(6): 78-85. doi: 10.11729/syltlx20160105
Abstract:
The thrust vectoring control (TVC) technology enables aircraft to fly in post-stall maneuver, which is very important for breaking through obstacle stall, enhancing mobility and improving take-off/landing and cruise performance. For TVC test at 2.4m×2.4m transonic wind tunnel, three six-component strain-gauge balances and two separate air systems are applied to respectively measure the performance of the whole model and nozzles at the same time. The thrust vector test model is flat, so that the layout and structure design of the measurement system is constrained. In the small internal model, it is very difficult to set up three six-component balances, two separate air bridge systems and pipeline, a supporting system, a pressure measurement system and so on. The complex system design cannot be realized by traditional methods and neither can the matching design of the air bridge system and the force balance under the condition of high pressure be accomplished. In the development of the measurement system, the integrated design concept and the stiffness matching design method are adopted. Combined with ANSYS finite element software, the layout and structure optimization of each component of the system have been solved. The results of balance calibration and wind tunnel test prove that the measurement system meets the requirement of thrust vector test.
Investigation on test technique for hypersonic flow-through model nozzle outlet airflow parameters measurement
Shu Haifeng, He Chao, Guo Leitao, Xu Xiaobin, Fan Xiaohua
2017, 31(6): 86-92, 99. doi: 10.11729/syltlx20160018
Abstract:
The accurate measurement of hypersonic flow-through model nozzle outlet airflow parameters is significant for the estimation of the inner flow path aerodynamic characteristics. The presently available test methods are not satisfactory. A new test technique for measuring the outlet parameters is investigated, using a lifting body with air-breathing inlet, but without rudders, elevators and all stabilizers. The interference of two static tubes at different distances and the possible measurement error caused by the angle of airflow and static tube were studied by CFD. And a three degrees of freedom pressure measurement device was developed. The tests at Mach 6 were conducted to measure the nozzle wall pressure, static pressure and pitot pressure of nozzle outlet in Φ1m hypersonic wind tunnel of CARDC. Results indicate that the temperature of the nozzle outlet wall has significant impact on the repeatability of the measurement. When the distance between the nozzle outlet wall and the pressure harrow is less than six times of the static pressure tube diameter, the accuracy of the static pressure measurement would decrease.
Research on control method of spraying system in the icing wind tunnel
Li Shucheng, Luo Qiang, Chen Dan, Huang Weikai
2017, 31(6): 93-99. doi: 10.11729/syltlx20160036
Abstract:
Spraying system is the core supporting equipment of the Icing wind tunnel, which is mainly used for simulating aerial environment. The investigation for the precision control method of pressure and temperature was developed, according to the complicated structure and high control accuracy of spraying system. The problem of spray rake pressure inconsistent and mutual coupling were solved, by giving pumps rotating speed, presetting inlet and outlet regulating values opening ratio, and feedback controlling outlet regulating values. Base on which, the high accuracy and wide range control of water pressure were achieved at last. Accurate water temperature control was gained through circular calefaction in seedtime and accurate temperature adjustment using variable parameter PID in test time. The problems of air pressure and temperature mutual coupling and the temperature change time delay were solved, through the method of fuzzy adaptive PID for temperature control and variable proportion coefficient PID for pressure control, and then realized the accurate air supply pressure and temperature control. Experimental results proved that the control algorithm is feasibility, and the performance of the spraying system can satisfy the technical requirements.
Design and application of wind tunnel strain gauge balance protective device based on 3D printing
Xiang Guangwei, Wang Chao, Wan Liqiang, Mi Peng, Wang Shumin
2017, 31(6): 100-104. doi: 10.11729/syltlx20160114
Abstract:
The strain gauge balance is the main equipment used in wind tunnel test, which has an important influence on the quality of test data and operational efficiency. To improve the balance self-protection performance and lower balance failure rate in test operations, a quick development method based on three-dimensional (3D) printing for the wind tunnel strain gauge balance (SGB) protective device is proposed. By decomposing the design factors, the key factors pertaining to the design of balance protective device are studied. A design flow and method based on 3D printing is put forward. The 3D printing technology can be applied to the optimization of balance guards in two aspects:(1) to optimize and visualize design schemes; (2) to protect strain gauges and circuit on balances for wind tunnel tests. Both water-cooled balance protective device and assembly type mechanical protective device are designed. For the water-cooled device with complex internal structure, 3D printing technology makes design to be visualized, which is helpful for design verification before manufacturing. The assembly type product, manufactured by means of 3D printing technology, is applied in corresponding balance protection for wind tunnel force measurement test. The perfect combination of strain gauge balances with their highly customized, lightweight balance protective devices by 3D printing, serves not only to protect the strain gauges and wires from damages in the process of calibration, transportation, model assembly and testing, but also to make impressive visual artworks of the balances, rendering them functional, practical, economical and artistic. Compared with machining of a balance protective device in the traditional way, 3D printing can greatly reduce the processing cycle and the cost. Meanwhile design visualization can validate technical solutions in the design stage. Both applications promote the overall performance of the balance.