Comments on ''Structure of the plasma sheath in collisional to weakly collisional plasmas'' [Phys. Fluids B 2, 647 (1990)]

Recently, Zawaideh et al. published a paper [Phys. Fluids B 2, 647 (1990)] asserting that they had obtained, from a more accurate set of fluid equations, physically reasonable plasma sheath solutions of an oscillating nature violating Bohm's criterion. In contrast to this statement, it is shown here that the violation of Bohm's criterion is based on an incorrect interpretation of the plasma sheath concept and that the oscillations are due to an incorrect initial condition in the calculations