Shock Tube Experiment Report

An Experimental and Theoretical Study of Compressible Flows in Shock Tubes

Samuel Kim, Dan Carollo, Mahmoud Elkayal, Brad Strzelewicz, Alice Tchoudov, Niraj Thakkar
Department of Mechanical and Aerospace Engineering Rutgers University, Piscataway, NJ 08854

Abstract

The theory of compressible flows is experimentally verified using a shock tube featuring four pressure transducers and a Kistler 5126A Piezotron® Coupler. The average calibration constants for pressure transducers 2 and 3 are found to be 23.9 and 43.4 psia/V, respectively. The pressure transducer data for driver pressures of 6, 10 and 14 psig are plotted and analyzed. The experimental shock strength ratios and shock wave Mach numbers for driver/driven pressure ratios ranging

Shock tubes are also widely used to study the aerodynamics of flow under a wide range of high temperature and pressure conditions. In this study, our goal is to verify shock tube theory with experimental results. Fundamentally, a shock tube is simply a long, hollow tube that consists of two regions separated by a diagram or membrane. Figure 1a shows these two sections for a completely sealed shock tube.

Figure 1. Dynamic pressure profile inside a closed shock tube. When the diaphragm is broken in (b), rarefaction and shock waves propagate in opposite directions. In (c), the rarefaction wave reflects off the left wall, and in (d), the shock wave reflects off the right wall, resulting in a greater pressure difference.

The first region (4), known as the driver section, is sealed via the diaphragm and pressurized to a controlled experimental pressure, P4. The second region (1), known as the driven section, is open to the atmosphere at P1. Although the driven and driver gases are typically air, other gases, such as helium, can also be used. In addition, the driver and driven gases may be different from each other. To fire the shock tube, a sharp tool is used to pierce the

The transducers were situated at specific known locations to measure the dynamic pressure profile within the tube. Using plastic film as the diaphragm, the driver region was pressurized with air from 6 to 14 psig in 2 psig increments to study the effects of driver pressure on the resulting shock wave. The right end of the shock tube was left open for all trials except one, in which it was closed at 8 psig to study the effects of shock wave reflection. In addition, helium was used in one trial at 8 psig to study the effects of driver gas on the resulting shock wave. After pressurization, the diaphragm was penetrated using a sharp metal plunger that slid into a small hole in the shock tube near the driver region. We used LabVIEW to store the voltage data measured by the pressure transducers 2 and 3, which collected data at a sample rate of 106 Hz, resulting in a total of 175,000 data points. Lastly, to convert the measured transducer voltages into pressures, the calibration constant of each transducer was determined using equation