Compression waves in front of and behind a piston launched in a shock tube

Approximate formulas to simulate interior ballistic flow in a shock tube are proposed. Simulation by shock tubes with reflection of the shock on a free piston offers interesting advantages. In order to define the experimental conditions it is required to calculate the piston trajectory, the compression waves in front of and behind the piston, and the trajectories of reflected compression waves. Approximate formulas for these calculations with a pocket calculator are presented. Tables and diagrams give information about the relations describing the operation of the shock tube with pure monoatomic and biatomic gases. These relations are used to determine optimal ratios between the length of the high pressure tube, launching tubes and measuring tube in front of and behind the piston initial position.