Hydrodynamic and thermal oscillations in a non-isothermal laminar jet

Oscillations in two-dimensional laminar jets have been studied numerically over a wide range of Reynolds and Grashof numbers. A finite volume approach based on primitive variables has been adopted. The numerical scheme is first validated using available experimental data for both the mean flow and the oscillatory behavior of isothermal jets, and then it is used to simulate results of the present study. The results indicate a strong spatial dependence of amplitude and existence of a broad band of frequencies, particularly in non-isothermal jets. High frequency oscillations are observed for forced convection dominated situations, while low frequency oscillations occur when buoyancy effects are predominant. With increasing buoyancy effect, the amplitudes are significantly modified and the oscillations become non-periodic even at low Reynolds number. The jet orientation is also found to influence the spectral distribution of oscillations. The predicted results can be significant in practical applications to devices in which mixing of non-isothermal jets occurs.