Pulse Burst PIV Measurements of Transient Phenomena in a Shock Tube
Time resolved particle image velocimetry (TR PIV) measurements were made in a shock tube using a pulse burst laser. Two transient flowfields were investigated including the baseline flow in the empty shock tube and the wake growth downstream of a cylinder spanning the width of the test section. Boundary layer growth was observed following the passage of the incident shock in the baseline flow, while the core flow velocity increased with time. The measured core flow acceleration was compared to that predicted using a classical unsteady boundary layer growth model. The model typically provided good estimates of core flow acceleration at early times, but then typically underestimated the acceleration. As a result of wall boundary layers, a significant amount of spatial non uniformity remained in the flow following the passage of the end wall reflected shock, which could be an important factor in combustion chemistry experiments. In the transient wake growth measurements, the wake downstream of the cylinder was symmetric immediately following the passage of the incident shock. At later times 0.5 ms) the wake transitioned to a von Karman vortex street. The TR PIV data were bandpass filtered about the vortex shedding frequency to reveal additional details on the transient wake growth.