Examples of Couette flows are used to demonstrate that the critical pressure gradient during the injection of an identical gas is greater in the case of convex solid walls and smaller in the case of concave walls than that for plane solid surfaces. The injection of a gas whose viscosity is lower than that of the main flow reduces the pressure gradient as compared to the injection of an identical gas. The injection of a gas with greater viscosity than that of the main flow increases the critical pressure gradient.
Edited trans. of Tsentralnyi Aerogidrodinamicheskii Institut. Uchenye Zapiski (USSR) v1 p60-68 1970, by Victor Mesenzeff.