Test Time and Particle Paths in Low-Pressure Shock Tubes

Measurements are reported on shocked-gas-flow duration in small-diameter shock tubes at low initial pressures. They are correlated with expressions derived from Mirels' theory for such flows, and substantial agreement is obtained, with closer correlation in the smaller-diameter shock tube. An expression is developed from Mirels' theory to relate particle and laboratory time coordinates, and a direct experimental measurement of particle paths in the flow is described. The time transformation introduces a significant correction to the ρ2/ρ1 linear transformation more generally used, and this is seen to be important in investigations of relaxation processes and rate kinetic measurements carried out in shock tubes. Some of the values of rate coefficients previously reported in the literature may well require revision in the light of this correction.