SHOCK ANGLE RELATION IN TWO-DIMENSIONAL SOAP FILM

The two-dimensional soap film flow is similar to the compressible gas flow because their governing equations are alike. An archetypal example of this gasdynamic analogy is the formation of oblique shock when a needle is inserted to the soap film flow. We further investigate the shock formation in soap film by inserting wedges of various angles and measuring the resultant shock angle. By controlling the flow speed and relating two angles, we measure the shock angle relation for the soap film flows. Our result shows that the shock angle changes only gradually with respect to the wedge angle, indicating that the soap film flow resembles the gas flow with the heat capacity ratio close to 1.