ON THE INSTABILITY OF AN AIR-WATER INTERFACE

Air entrainment is one of the most important characteristics of self-aerated open channel flows like spillway and steep chute flows in hydraulic engineering. In the present analysis, a mathematical model is formulated on the lines of the treatment adopted by Chandrashekhar, for the inception of instability of the interface between air and water media and the breaking of waves at which local inception of air entrainment occurs. Equations for inception of instability of free surface leading to air entrainment between air and water interface have been worked out theoretically for the most general case, including the effect of slope, for viscousnd nonviscous flow conditions. The critical relative velocities for horizontal flow, computed from these equations for both viscous and inviscid cases, are in fairly good agreement with experimental values reported in literature.