2009 Vol. 23, No. 4

Display Method:
Numerical simulation and experimental investigation of excited oscillation in a H-S tube
GU Sheng-long, CHEN Li-hong, ZHANG Xin-yu
2009, 23(4): 1-6. doi: 10.3969/j.issn.1672-9897.2009.04.001
Abstract(177) PDF(4)
Abstract:
Under some certain conditions in Hartmann-Sprenger (H-S) tube there can be resulted in intense jet oscillation at a specified frequency.The oscillation flow in the H-S tube was investigated numerically and experimentally.The numerical simulation results indicate the periodical changes of the flow field while the transient schlieren images of the corresponding case show the taking-in jet and the taking-out shock wave.Those results reveal the mechanism of the excited oscillation in the H-S tube.Based on the experimental data,the expression for estimating the oscillation frequency in the small-diameter case was modified which can help to design the jet nozzle at a given excitation frequency.
Experimental investigation of the pulse detonation rocket engines with variable cross-section
YAN Yu, FAN Wei, YAN Chuan-jun, LI Jian-ling, QIN Hong-qiang
2009, 23(4): 7-10,27. doi: 10.3969/j.issn.1672-9897.2009.04.002
Abstract(105) PDF(4)
Abstract:
The pulse detonation rocket engine(PDRE) with variable cross-section was investigated using kerosene as fuel and oxygen as oxidizer at the equivalence ratio 1.0 and the working frequency of 8Hz, including constant cross-section engine, divergent engine, convergent engine, divergent-convergent engine and convergent-divergent engine. The effect of cross-section change on the propagation process of detonation in the pulse detonation rocket engine was studied. We could also obtain the effect of cross-section change on the average thrust of engines.
Effect of incidence on the flow field in turbine static cascade
ZHOU Xun, WANG Zhen-feng, WANG Xiang-feng, HAN Wan-jin
2009, 23(4): 11-14. doi: 10.3969/j.issn.1672-9897.2009.04.003
Abstract(225) PDF(3)
Abstract:
To investigate the aerodynamic characteristics under the different incidences of original and modified designed high pressure static cascades used in the 9th stage of 600MW subcritical steam turbine,the two types of annular turbine cascades were studied in the low speed wind tunnel of HIT under the 0°and ±10°incidences.The test results show that the different incidences only effected on the transverse pressure gradient near the front half part of the flow passage of two cascades,the flow near the rear half part of passage was almost not changed.And compared with the original designed cascade,the modified designed cascade not only reduced the flow loss,but also had the better incidence adaptability.
Analysis of vortex-induced vibration of large-scale section model of girder in wind tunnel
XIAN Rong, LIAO Hai-li, LI Ming-shui
2009, 23(4): 15-20. doi: 10.3969/j.issn.1672-9897.2009.04.004
Abstract(116) PDF(4)
Abstract:
Section model wind tunnel test is one kind of effective method to estimate vortex-induced vibration (VIV) response of long span bridge girder.The large-scale (usually from 1:15 to 1:20) section model has larger geometry scale.And the Reynolds number of large-scale section model wind tunnel test is close to that of prototype.Moreover,the geometry detail could be simulated more accurately by the large-scale section model.A large scale(1:20) section model of one flat steel box bridge girder was tested to get accurate VIV response and the optimized position of check vehicle rail.And several characteristics of VIV were discussed in detail such as VIV amplitude vs.damping ratio or Scruton number,VIV wind speed range vs.damping ratio or Sc,wind attack angle vs.Strouhal number,double vertical VIV phenomenon and so on.Theoretic and experimental foundation is provided here to expand the section model test result to prototype.
Correlation analysis of wind characteristic and wind-induced response of CITIC Plaza
LI Zheng-nong, SONG Ke, LI Qiu-sheng, ZHI Lun-hai, WU Jiu-rong
2009, 23(4): 21-27. doi: 10.3969/j.issn.1672-9897.2009.04.005
Abstract(154) PDF(3)
Abstract:
This paper presented the analysis results based on the field measurement data of wind velocity and acceleration of main tower in CITIC Plaza during Typhoon Damrey.The results revealed that turbulence intensity of Typhoon Damrey was larger than the normal,and the across-wind dynamic response of CITIC Plaza approached the along-wind dynamic response under Typhoon Damrey.Meanwhile,the correlation of wind characteristic and wind-induced structure vibrations was investigated in selected different time intervals.The research indicated that 3-minute mean wind speed was reasonable in calculating the wind load and the wind-induced response.
PIV technology and its application in the investigation of asymmetric vortices structure over forebody
DONG Chao, DENG Xue-ying, WU Bin, WANG Yan-kui
2009, 23(4): 28-33. doi: 10.3969/j.issn.1672-9897.2009.04.006
Abstract(126) PDF(7)
Abstract:
In this paper,the arrangement of PIV system and the experiment scheme in D4 wind tunnel in BUAA were presented.The application of PIV technology in the investigation of asymmetric vortices structure over forebody was also presented.The flow structures of sections X/D=2 and 3.35 were investigated at 50° angle of attack and Re=0.14×10~6~0.55×10~6.Experiment results showed that with the increase of Reynolds number the flow structures on the sections had the trend of developing from two vortices to three vortices.In the sub-critical regime,the vortices had the main effect on the asymmetry of pressure distribution.In the initial critical and critical regime,the flow condition and the separation shape of the boundary layer had the main effect on the asymmetry of pressure distribution.In the initial critical regime,the trend of developing from two vortices to three vortices along the model axis happened more upriver than the trend in the sub-critical regime.
Experimental research on vertical coherence function of wind velocities in atmospheric boundary layer wind field
HUANG Dong-mei, ZHU Le-dong, DING Quan-shun
2009, 23(4): 34-40. doi: 10.3969/j.issn.1672-9897.2009.04.007
Abstract(116) PDF(5)
Abstract:
Atmospheric boundary layer flow field was simulated in TJ-2 wind tunnel by using the passive turbulence devices composed of spires,grid and roughness components.The wind filed parameters,including mean wind velocities profile,turbulence intensity profiles,turbulence integral scale,wind spectrum and so on,were measured.The vertical spatial correlation curves of wind velocities were analyzed on focus.Aiming at the phenomenon of low frequency "turns around"in the vertical spatial correlation curves of wind velocities ,the revised exponential decay functions were put forward to fit it,which improves the shortage of traditional simplified decay exponential function in low frequency.The result shows the revised vertical spatial correlation functions of wind velocities proposed by the author are more precise.
Sublimation investigation of artificial abduction crossflow stationary wave in swept wing
LI Yue-li, LI Dong, YANG Yong, ZUO Sui-han
2009, 23(4): 41-45. doi: 10.3969/j.issn.1672-9897.2009.04.008
Abstract(217) PDF(4)
Abstract:
The author improved the method of appending roughness,and by silk-screen method appended the specific space roughness to the leading-edge of swept wing.This technique has been successful in introducing specific wavelength disturbance into the boundary layer,and improves the artificial abduction wavelength precision.The single disturbance evolution was investigated by using sublimation technique in the low-turbulence wind tumel of NWPU,and its evolution trend is consistent with the calculation results.
Practices on simulation of Reynolds number effects for the hyperbolic circular section structures
CAO Jin-xin, ZHAO Lin, GE Yao-jun, HE Gui-tang, GAO Ling
2009, 23(4): 46-50,55. doi: 10.3969/j.issn.1672-9897.2009.04.009
Abstract(148) PDF(3)
Abstract:
In wind tunnel tests,the Reynolds number plays a crucial role in the evolution of the flows around streamlined structures which determines the evaluation of its wind loading and aerodynamic performances.Previous works suggests the effects of high Reynolds number can be simulated by increasing the surface roughness,but the effects of the simulations are usually influenced by artificial factors.Little is known about the relationship between surface roughness and the change of flow features which makes the practical simulations difficult.Two comparative wind tunnel tests of Hyperbolic circular section structures in difficult Reynolds number range were designed.By changing the thickness of the strips on the model surfaces,the effects of high Reynolds numbers were simulated,including the investigation of both transverse pressure distribution and drag coefficient.A serial of results provide a detailed understanding of the regularity of surface roughness parameters with different model scales,which helps the practices of similar future projects.
Investigation on spray characteristics of bi-centrifugal swirl injector
GUO Zhi-hui, XU Hao, MAO Xiao-fang
2009, 23(4): 51-55. doi: 10.3969/j.issn.1672-9897.2009.04.010
Abstract(186) PDF(6)
Abstract:
The stable and pulse spray characteristics of a type of bi-centrifugal swirl injector were studied experimentally with particle dynamic analyzer.Properties of droplets such as velocities,size distribution,and volume flux were measured.The results show that the two sprays produced separately by the inner and outer nozzle converged to form one spray,which was as same as that of a simplex injector.The distributions of velocities, mean diameters and volume flux showed hollow cone spray characteristics.The velocities distributions of pulse spray were identical to that of stable spray,but the distinct difference was the RMS velocities were bigger than the mean velocities at the center zone of pulse spray.The Sauter mean diameters of pulse spray are bigger than that of stable spray.The poor atomization is due to the unstable and discontinuous liquid film formed in each nozzle at pulse conditions.The experimental results can provide important references to injectors design.
An investigation of background noise measurement technology in aeroacoustic wind tunnel
ZHU Bo, TANG Geng-Sheng, GU Guang-Wu, LI Peng
2009, 23(4): 56-59,64. doi: 10.3969/j.issn.1672-9897.2009.04.011
Abstract(133) PDF(8)
Abstract:
This paper presented the background noise measurement technology scheme of 0.55m×0.4m aeroacoustic pilot wind tunnel newly designed in China.It made some comparative tests and data analysis of condenser microphone,piezoresistive transducer,prepolarized microphone,externally polarized microphone,free-field microphone,pressure-field microphone,sensor installing methods and acoustic frequency spectrum algorithm.According to the obtained data,some measures were taken to optimize the noise reduction performance of the wind tunnel.It showed that condenser microphone is more accurate than piezoresistive transducer used for background noise measurement.After correction,pressure-field microphone and free-field microphone could be replaced by each other.Spectrum linear average algorithm should be used to calculate the muffler noise transmission loss for the sake of repetitive precision.The conclusion is helpful for background noise measurement of low speed aeroacoustic wind tunnel.
PIV experiment of steady flow within the human upper respiratory tract
ZHAO Xiu-Guo, XU Xin-Xi, TAN Shu-Lin, GAO Zhen-Hai, LIU Ya-Jun
2009, 23(4): 60-64. doi: 10.3969/j.issn.1672-9897.2009.04.012
Abstract(126) PDF(3)
Abstract:
The study on the air patterns in the human upper respiratory tract plays a very important role in investigating the aerosol deposition in the human upper respiratory tract.PIV (Particle Image Velocity) technology was used to study the steady flow in the human upper respiratory tract.The results show that the airflow velocity is high in the middle and lower part of the oral and low in the other part.The airflow velocity increases at the outer wall of the pharynx.The airflow with the high velocity flow downstream anear the inner wall of the larynx and the trachea with the high velocity zone appearing near the inner wall of the larynx and the trachea.The shearing strength acting on the outer wall of the pharynx,the inner wall of the larynx as well as the trachea are high,which endure the high load,finally may lead to the wall strain and tissue injury at these zones.
Micrography technique of particle velocity measurement in the high temperature jet flow
YANG Hong, XIE Ai-min, TANG Jing-wei
2009, 23(4): 65-68. doi: 10.3969/j.issn.1672-9897.2009.04.013
Abstract(99) PDF(5)
Abstract:
In order to gain the particle velocity of high temperature jet flow,a set of micrography system was built.The system includes double pulse YAG laser,particle magnifying and imaging system,image incepting system.After using the technique of micrography,compensating filter,sequence imaging,which helped with overcome the difficulties of small size of particle and flow field with violent irradiance and high temperature,the sequence photos of the same particle have been gotten.According to the photos,the particle velocity has also been obtained.In this paper,the principle,structures of the system and the experiment results were presented.
The development of low range and high accuracy strain gauge pressure transducer
YU Wei, YANG Mei, ZHAN Hua-hai
2009, 23(4): 69-72. doi: 10.3969/j.issn.1672-9897.2009.04.014
Abstract(119) PDF(5)
Abstract:
In order to improve the precision of low range and high precision strain gauge pressure sensors, a new beam-film structure was designed. The structure as an elastic element is made up of a wheel hub beam and a film with a center rigid core. We found the most appropriate structure parameters of the elastic element through finite element analysis and tested these parameters by an experiment on a real object. As a result, we achieved the conclusion that the parameters were appropriate and the performance of the sensor was greatly improved. The precision met the request of high precision measuring in low range. Also, the sensor has simple structure and low cost. These characters matched the trend of sensor technology development.
Study of the performance of contractive curve for the wind tunnel
LI Guo-wen, XU Rang-shu
2009, 23(4): 73-76,81. doi: 10.3969/j.issn.1672-9897.2009.04.015
Abstract(183) PDF(12)
Abstract:
Design method of a new contractive curve for the wind tunnel contractive segment is introduced in this paper, namely the design of contractive curve of the parameter based on UG. The performance of contractive curve was simulated by Fluent. Favorable flow field quality is attained. A new design idea for design of the wind tunnel and flow optimize is offered. A low-speed wind tunnel with this contractive curve was made,and the flow field of this wind tunnel was measured. Contrast of the simulation result and experiment result, and the analysis of the performance of the flow field were made. The design idea can be used to other wind tunnel design.
Flow field calibration of NUAA Φ0.5m hypersonic wind tunnel
XU Xiang, CHENG Ke-ming, WANG Zhi-jian, XU Yun
2009, 23(4): 77-81. doi: 10.3969/j.issn.1672-9897.2009.04.016
Abstract(178) PDF(25)
Abstract:
Here presented in this paper are the calibration of flow field and force experiments of standard model AGARD-HB-2 carried out in NUAA Φ0.5m hypersonic wind tunnel at Mach number of 5,6,7 and 8.Calibration tests and standard model tests for nozzles at M5 and M8 are given in this paper.Diameters of the uniform field reach 336mm; maximum deviation of Mach number |Δma_j|_(max) is 0.006 at M5 and 0.007 at M8 respectively; standard deviation of Mach number σ_(Maj) is 0.378 at M5 and 0.484 at M8.All the parameters mentioned above meet the requirements of GJB4399-2002.Comparison of AGARD-HB-2 model force measurement data with domestic wind tunnels validated the accuracy of test data obtained by this facility.The flow field calibration and standard model tests indicate that this wind tunnel has met the design requirements.
The development of wind velocity adaptive control system based on neural networks for NF-3 wind tunnel
L(U) Peng-tao, HUI Zeng-hong
2009, 23(4): 82-86. doi: 10.3969/j.issn.1672-9897.2009.04.017
Abstract(190) PDF(9)
Abstract:
This paper describes the structure and the characters of wind velocity control system for NF-3 low speed wind tunnel which is located at Northwestern Polytechnical University.Due to the difficulties of establishing precise mathematical model,the complicated nonlinear characteristics of the system and the change of parameters of the wind tunnel itself,the velocity system is not easy to control in the traditional control theory.In this new system we applied the multithreading digital data acquiring method,PSD neural networks with dead line control algorithm to solve these problems.Compared with the former fuzzy control systems,this system is not only easier to operate,less time to stable,but also have higher control performance from 0.3% to 0.1% when the velocity is greater than 10m/s.
Research of data process methods and model excitation for transonic flutter experiments in wind tunnel
RAN Jing-hong, JI Chen, LIU Zi-qiang, ZHAO Ling
2009, 23(4): 87-91,97. doi: 10.3969/j.issn.1672-9897.2009.04.018
Abstract(115) PDF(6)
Abstract:
The advantages and disadvantages of some main excitation methods for the flutter experiments are briefly described in the paper.Then the ground-model experiments were conducted by using impulse excitation,finite-bandwidth white noise excitation and harmonic excitation,and the structural response was measured at the same time.On the base of STD,ARMA and LSCE,the frequency and damping ratio were identified.Through comparing and analyzing them and the results from NASTRAN,the influence of model exciting techniques and parameters identification methods were discussed.Finally,the optimal scheme of model excitation and parameter identification was evaluated for flutter test techniques.
Hot jet initiation of detonation in serial detonation chambers
LI Mu, YAN Chuan-jun
2009, 23(4): 92-97. doi: 10.3969/j.issn.1672-9897.2009.04.019
Abstract(166) PDF(7)
Abstract:
To avoid the dependence of external pulse ignition source and increase operating frequency of a pulse detonation engine, a novel serial detonation chambers scheme PDE was offered. Detonation was initiated through hot jet from conjoint detonation chamber, from one to the next. Experimental results show that the hot jet can spread through chambers and each chamber can be initiated fast in a short distance. The initiation time is about 1.0~1.2ms, and the distance is about 500mm. Weak hot jet also can be enhanced after a few tubes and initiate mixtures in a certain chamber downstream. The time between jet-in and jet-out in one chamber is 1.2~1.5ms, considering other time in a whole cycle, maybe 8 chambers are needed for running at the mode of close spread jet.
Forcing balance development of a certain airplane components in high speed wind tunnel
PENG Chao, SHI Yu-jie, CHEN Zhu
2009, 23(4): 98-101. doi: 10.3969/j.issn.1672-9897.2009.04.020
Abstract(164) PDF(8)
Abstract:
The component forcing balances were developed for measuring aerodynamic loads on the different components of airplane.The design loads of these component forcing balances did not match in all components,and the sizes were rigorously confined by models' space.In balance design,the support behind the airplane's abdomen was used for the airplane balance,and the balance was fixed under the airframe's horizontal line,which provide the feasibility for the component balance installation.The different structures in different component balances were adopted to meet the need of balance measurement and ensured the balances installing position in the model and to meet the need for interval in test.The structure of equilateral octagon was used for the wing balance,the three sheet girder was used for the vertical wing balance,the rectangle girder was used for the horizontal wing balance,nacelle balance,nacelle and it's bracket balance,the "Z"structure was used for the little wing at the tip of the wing balance.The successful development of these component balances provides the reliable testing data for the models' development.