On the stability of an axisymmetric plume in a uniform stream

The linear stability equations for a round laminar thermal plume in a coflowing vertical stream have been solved numerically. Both symmetric and asymmetric disturbances have been considered for strengths of the forced flow varying between very weak and very strong. The parallel flow analysis confirms that the forced flow has a stabilizing effect. The upper branch of the neutral curve for sinuous disturbances is qualitatively like that of a round momentum jet. However, neither a critical Reynolds number nor a lower branch of the neutral curve was found. Non-parallel effects are discussed.