Study of Transition in Unsteady Boundary Layr induced by Propagating Compression Wave Using Laser Differential Interferometry

点击翻译按钮获取中文摘要

1. The first project was carried out to develop an open-ended shock tube with a fast opening gate valve instead of a diaphragm. The results show that the opening time of a gate valve decreases with an increasing the initial pressure of the actuating chamber.2. The strength, maximum rate of pressure rise and length of wavefront are strongly dependent on the initial pressure of the actuating chamber and the opening speed of a gate valve.3. The second project was carried out to develop a laser differential interferometry method using Wollaston prisms. The sensitivity was sufficiently high to record the density variations by compression waves.4. The measurements of the time-dependent profiles gave detailed information on the process of formation of the unsteady boundary layr induced by propagating compression wave in a constant-area duct.5. The third project was carried out to investigate experimentally and numerically the attenuation of a compression wave. The experimental data were compared with the numerical results by TVD scheme, which takes into account a fluid friction for a transient duct flow.6. It was shown that the attenuation and distortion rates are strongly dependent on a fluid friction term for unsteady laminar or turbulent flow.7. The final project was carried out to investigate experimentally the transition of unsteady boundary layr. The experimental data were compared with the theoretical results for a weak shock wave.8. It was found that the laminar-to-turbulent transition in unsteady boundary layr flow, which describes the density profiles at strength of the initial compression wave from 9kPa, exists.