Session: 11-52-01: Computational Thermal/Fluids

Paper Number: 94742

94742 - The Analysis of Interaction Between Reflected Shock Wave and Boundary Layers in a Shock Tube 

This study involves a computational investigation to determine the interference between a reflective shock wave and the wall boundary layer formed by gas flow in a shock tube. Two gases, namely, Argon and Helium, are examined as the working fluid in each case at different pressure ratios. Shock tubes generate a shock wave that travels and reflects at the closed end of the tube. The reflected wave imposes an adverse pressure gradient on the velocity boundary layer formed adjacent to the walls. The present computations consider the viscous effects and implement turbulence through the Spalart-Allmaras model. This investigation observes and analyzes the non-ideal transient behavior in the shock tube, thermal effects, and the shock bifurcation for two gases at different pressure ratios of 10 and 100, respectively. The shock tube consists of two straight sections with different pressures in this study. A diaphragm initially separates the sections. The tube's total length is 1.5 m. The initial gas temperature is 288 K. The pressure ranges from 30 to 300  kPa in one case and 30 to 3000 kPa in the other. A grid study determined an optimum setting for this case. The present simulations allow understanding the temperature distribution behind the bifurcated shock waves. The preliminary results indicate that the range of disturbance formation for each gas differs with different pressure ratios. The outcomes of this study agree well with theoretical methods, which assumed uniformity behind the reflected shock wave under ideal conditions. However, consistent with the past studies, this investigation confirms that reflected shock waves interact with the wall boundary layers. These velocity boundary layers first appear when the generated shock waves travel through the tube. Bifurcated shock waves emerge after the wave reflects. The bifurcation travels against the gas flow because the stagnation pressure behind the reflected shock wave exceeds the boundary layer's stagnation pressure. The uniformity behind the reflected shock wave collapses over time, and the non-uniformity is more evident. We noticed the gas pressure ratio plays a significant contribution to the tendency and strength of the bifurcation. The higher the pressure ratio, the faster the incidence shock wave traveled, and the quicker the relative bifurcated foot velocities increased with the Mach number at that region. This research contributes and sheds some light on the role of gas type and other parameters on the nature of the interaction between a traveling shock wave and a weak boundary layer. This investigation's findings will benefit the supersonic compressible flow applications and experiments.

Presenting Author: Abdulmumin Olaoke Southern Illinois University, Edwardsville.

Presenting Author Biography: Abdulmumin Olamilekan Olaoke<br/>Mechanical and Mechatronics Engineering<br/>Southern Illinois University Edwardsville<br/>Edwardsville, IL 62025<br/> Email: aolaoke@siue.edu

Authors:

Abdulmumin Olaoke Southern Illinois University, Edwardsville.
Majid Moliki Southern Illinois University, Edwardsville.