Abstract
Stability properties of an unstably stratified parallel flow with vertical and horizontal shears are investigated by solving numerically a system of perturbation equations. Horizontal shear as well as vertical shear tends to suppress thermal instability. Stabilizing influence of the shear on perturbations is more efficient as the wavelength in the longitudinal direction is shorter, while the longitudinal roll perturbation is free from the stabilizing effect of the shear. A longitudinal roll convection may thus be most favorable for development.
Conversion between the kinetic energy of the basic flow and that of the perturbation is found besides conversion of potential to kinetic energy. A longitudinal perturbation which is of the preferred mode is associated with horizontal and vertical transports of momentum to decrease the shear which result in transforming the kinetic energy of the flow into that of the perturbation.
