实验流体力学

AExperimental investigation of heat transfer distributions in a deep gap

TANG Gui-ming

2000, 14(4): 1-6. doi: 10.3969/j.issn.1672-9897.2000.04.001

Abstract(125) PDF(5)

Abstract:
Detailed heat transfer distributions within a deep gap were measured with both a sharp leading edge flat plate and a flat cylinder at free-stream Mach numbers of 9.85,12.0,15.5 and corresponding unit Reynolds numbers of (1.0 × 107, 6.4 × 105, 3.2 × 105 )/m in CAS impulse tunnels. The gap was 2mm wide, 25mm deep and 100mm long. Attack angles α ranged from 0° to 90° and deflectionsβ from 0° to 90°. In this paper, typical heating distributions on the gap wall were presented; effects of Mach number, attack angle and deflection on heat transfer to the gap wall were discussed;and comparisons between measured and predicted gap heating were made.

diagnosis technique of boundary layer

BIAN Yu-Zhong, XU Tie-jun, FAN Jie-chuan, MA Jun-ping, TU Xing, BAI Cun-ru, HE Ke-min, YIN Di-yi, ZHAO Zong-fu

2000, 14(4): 7-13. doi: 10.3969/j.issn.1672-9897.2000.04.002

Abstract(174) PDF(4)

Abstract:
This paper gives visualising and measuring results of the surface boundary layer transitions for two dimensional airfoil and three dimensional delta wing models using the surface hot film (HF) technique, the infrared image technique (IIT) and the liquid crystal technique (LCT) in same wind tunnel. The results detected the surface boundary layer transition positions by three techniques were excellent identical for two dimensional NACA-0012 airfoil model. The results detected for three dimensional 60°delta wing model showed that the surface hot film technique can give quantitative information of the surface boundary layer transition positions, both the infrared image and the liquid crystal techniques as using were affected by environmental conditions.At appropriate conditions they can also give quantitative information of the surface boundary layer transition position.

AExperimental studies of ablation-controlled arc discharges in plasma generator

LI Bao-ming, Li Hong-zhi, YUAN Wei-qun

2000, 14(4): 14-19. doi: 10.3969/j.issn.1672-9897.2000.04.003

Abstract(132) PDF(3)

Abstract:
Ablation-controlled arcs (ACA' s) compensated by materials being ablated from the capillary wall are of great interest. The pulsed power supply used to perform the experiments consisted of three modules storing 800kJ as a driver for an ablation-controlled arc plasma generator. A sequence of tests in which the capillary radius, length and ablated material are varied and in which the capillary power dissipation levels are varied in a certain range are discussed in order to determine the impedance matching between the discharge and the power source. By the analytical model, dependence of the plasma temperature and pressure on above variations could be known.

The investigation of flow field and heat transfer in cavity of labyrinth seal

HUANG Xiao-guang, WU Ding-yi

2000, 14(4): 20-25. doi: 10.3969/j.issn.1672-9897.2000.04.004

Abstract(183) PDF(4)

Abstract:
We built a labyrinth heat transfer wind tunnel. Detailed experimental results on the flow field reveal the velocities and vortices distribution in the cavity of labyrinth seal and lo-cal heat transfer coefficient distribution on the roof of labyrinth. Analyzing the results obtained at different Reynolds number and T/C, We found the influence on the velocity and pressure distribution in cavity of labyrinth and the influence of different Reynolds number and T/C on the heat transfer coefficient on the roof of labyrinth seal.

An experimental investigation on unsteady aerodynamics and modeling for a fighter configuration

JIANG Yu-biao, SHEN Li-min

2000, 14(4): 26-31. doi: 10.3969/j.issn.1672-9897.2000.04.005

Abstract(130) PDF(4)

Abstract:
The experimental investigation conducted in CARDC-Dia. 3.2m subsonic wind tunnel for a fighter model with 57° delta wing are presented and the typical results are also discu.ssed in this paper. During the test forces and moments are measured under pitching, yawing and rolling oscillation with the amplitude of 20° ,35° and reduced frequency from 0 to 0.2 at various side slip and angles of attack for longitudinal and lateral motion respectively. On the basis of Fourier functional analysis and the linear aerodynamic theories, two aerodynamic models were built up. The calculated results with the models, the Fourier analysis model and the nonlinear model, show good agreement between different methods and test results.

Investigation on wing rock in low speed wind tunnel for a fighter configuration

SUN Hai-sheng, JIANG Yu-biao

2000, 14(4): 32-35. doi: 10.3969/j.issn.1672-9897.2000.04.006

Abstract(101) PDF(6)

Abstract:
The wing rock test technique in low speed wind tunnel is presented in this paper, including test apparatus and test methods as well as data acquisition. The typical test results about wing rock for a fighter configuration conducted in CARDC 4m × 3m low speed wind tunnel are also discussed briefly. Finally, the mechanism of wing rock is explored.

Reservoir gas temperature measurement in detonation driven shock tunnel by chemical temperature scale

HE Yu-Zhong, WANG Su, ZHAO Wei, FAN Bing-cheng, GU Jia-hua, WANG Jing, CUI Ji-Ping

2000, 14(4): 36-40. doi: 10.3969/j.issn.1672-9897.2000.04.007

Abstract(112) PDF(3)

Abstract:
For measuring the temperature of reservoir gas in the detonation driven shock tunnel (DDST) directly, argon is used as the driven gas with small amount of CF4 added as reagent to produce the temperature indicator C2 F4 based on a kinetic analysis of the thermal decomposition during the shock process. By using a high speed one-way valve connected directly to the shock tunneljust ahead of the entrance of the nozzle, a sarnpling system is constructed to sample the reservoir gas to a gas chromatography. The experimental results show that the sampling technique suggested here is available and the chemical temperature scale determined is convenient. The effects of condensation water on the wall of the driven section, as we use the oxyhydrogen detonation as the driven gas, are also discussed.

An investigation on characteristics of base drag reduction with base bleed in subsonic and transonic speeds

CHEN Shaosong, DING Ze-sheng, LUO Rong, CAO Ding-gui

2000, 14(4): 41-45. doi: 10.3969/j.issn.1672-9897.2000.04.008

Abstract(127) PDF(6)

Abstract:
An investigation of wind tunnel tests of base bleed is conducted, in order to research the characteristics of base drag reduction with base bleed burning H2 + air and base bleed cold air in subsonic and transonic speeds. The Mach numbers are 0.71 ~ 1.55. From results of it, the base drag reduction rate with base bleed cold air is low, but it with base bleed burning H2 + air is much higher than base bleed cold air, that its maximum of base drag reduction rate is 40% ~120%. It is shown that reducing the base drag of projectile and increasing the range of it are possible by means of base bleed burning in subsonic and transonic speeds.

Investigation of mechanical behaviors of droplets in the discrete phase of oil-water emulsion Effect of a shear flow on agglomeration of droplets in emulsion

HU Meng-ming, DONG Shou-ping

2000, 14(4): 46-50. doi: 10.3969/j.issn.1672-9897.2000.04.009

Abstract(131) PDF(6)

Abstract:
Oil-water separation is the main subject in many oil fields in the world. The mechanical behaviors and features of discrete phase droplet in oil-water emulsion are close related to separator efficiency. In this paper through the shear flow induced by rotation of two concentric barrels, the effect of shear stress on separation of oil-water emulsions was investigated experimentally. Some regulations of discrete droplet movement and agglomeration were discovered. Meanwhile, a criterion to estimate the effect of a shear flow on separation efficiency of emulsions by the distortions of droplet applied by the shear stress was proposed.This project provides not only a guide to the subsequent research on the mechanical behaviors and features of separated phase droplet in oil-water emulsion,but also a new way to develop oil-water separation facilities of high-efficiency.

The investigation of perturbation phenomena in hypersonic boundary layer with electronic beam fluorescence technique

LIN Zhen-bin, GUO Da-hua, ZHU Jin-sheng, YU Xi-long

2000, 14(4): 51-57. doi: 10.3969/j.issn.1672-9897.2000.04.010

Abstract(113) PDF(4)

Abstract:
The perturbation phenomena in hypersonic flat plate boundary layer are investigated with electronic beam fluorescence technique in a gun wind tunnel. Mach number of free stream is about 7.8 and Reynolds number per unit length is 3.5 × 107/m. Average density distribution and fluctuation desity distribution are measured. The correlation distribution of turbulent density fluctuation and frequency spectrum distribution is obtained. Our experi mental results show that the phenomena are coexisted in order and at random in transition area.

Hydrodynamical problems of water flow field measurement with a probe

QIU Bao-yun, LIU Chao, HUANG Hai-tian, TANG Fang-ping, YUAN Jia-bo, ZHOU Ji-ren, YAN Bi-peng, CHEN Yu-ming, CHENG Li, YANG Hua

2000, 14(4): 58-63. doi: 10.3969/j.issn.1672-9897.2000.04.011

Abstract(137) PDF(2)

Abstract:
The factors were studied that affect reacting time of hole pressure of a probe measuring water flow field. The reasonable parameters of combined probe measuring system was presented. The influence was analysized of probe hydraulic resonance and bending under circufluent drag on the measurement. The countermeasures were advanced to improve the measuring precicion.

Research on the sensing technology for pressure measurement in the transient temperature flow field

ZHANG Cong-he

2000, 14(4): 64-68. doi: 10.3969/j.issn.1672-9897.2000.04.012

Abstract(102) PDF(3)

Abstract:
Proceeding from analyzing unstable phenomenon of the planar diaphragm structure of the pressure sensor in the rapid temperature-changing field, the author broke free from conventional designing methods and adopted novel spherical-shell-shaped diaphragm structure to overcome the unstable phenomenon. The author also combined this technique with a series of corresponding technical measures to realize real-time precision measurement of rapid changing pressure in the transient temperature flow field.

The analysis of errors with the real-time holometry performed in tunnel test

DONG Xiao-gang, PU Hong-tu, ZHOU Xian-wei

2000, 14(4): 69-74. doi: 10.3969/j.issn.1672-9897.2000.04.013

Abstract(134) PDF(4)

Abstract:
Based on experiments author performed and theories concerned, this paper analyses emphatically the errors probably resulted from the real-time holometry(RTH) for the tunnel flow visualization and shows the way how to determine and to correct them. It has been shown practically that RTH, fitted with suitable light source and visualizing/recording system, enables hologram to be reconstructed directly and to be visualized even adjustable/controllable in the testing ground and, excuses experiments from blindness and lots of follow-up processes. In addition, RTH selects flexibly the interference terms and so is of particular advantage to other optical methods which are very hard to be used either in real-time inspecting/visulizing or in diagnosis researching of the twinkling and progressing states of hightemperature dense plasma with strong raeiation.After all,provided the test device elements have not considerably shifted over-dampingly and plastically,RTH is an effective and reliable technique for tunnel test.

The determination of projection center and perspective plane of perspective image in 3-D PIV

DENG Guo-qiang 、, SUN J1ng-ao, DONG Shou-ping

2000, 14(4): 75-80. doi: 10.3969/j.issn.1672-9897.2000.04.014

Abstract(136) PDF(5)

Abstract:
The techniques of projection center finding and perspective plane determination in 3-D PIV have been investigated profoundly. A basic approach,which is to find out the projection center and perspective plane with some known particle positions and their spot images, has been proposed. Some related mathematical models have been given. Finally, the techniques have been proofed with experimental methods.

Control strategy and software design of the 2.4m wind tunnel unpressurized running

ZHOU Ping, HAN Jie, LI Shang-chun, TANG Geng-sheng, ZHANG Jun-sheng

2000, 14(4): 81-89. doi: 10.3969/j.issn.1672-9897.2000.04.015

Abstract(127) PDF(3)

Abstract:
2.4m wind tunnel is one of the biggest injecter powered transonic wind tunnels in the world. Considering the problem of the specific characteristc of the control systems of nonlinear, time-varying, large time delay, intensive interaction between the inputs and the requirements of the control systems that must be of quick response and high stable state accuracy, the advanced DCS hardware system and intelligent control strategies for the wind tunnel control system are used. Actual test results are provided to illustrate the control precision of P0 and Mach number excels 0. 3% and 0. 002 respectively,and the feasibility of the control strategies.

Application of neural network to aerodynamic interaction effects of rotor wake on fuselage

Xu Jin-fa, GAO Zheng, MEI Wei-sheng

2000, 14(4): 90-95. doi: 10.3969/j.issn.1672-9897.2000.04.016

Abstract(97) PDF(2)

Abstract:
Due to the characters of helicopter itself, the interaction effects of rotor wake on fuselage show obviously nonlinearity, and are correlate with several factors. Adopting a neural network is a better way to resolve a nonlinear problem. A neural network model can be built with experimental data which are constructed as a pattern set for training of net parameters.The neural network model may be used to research aerodlynamie characters of the interaction effects of rotor wake on fuselage, and the trained model can be directly used in the design of aerodynamics and real-time simulation for helicopter. In addition to analyze the neural net work modeling, the experiment about aerodynamic interaction effects of rotor wake on fuselage were simply introduced.

2000 No. 4