Temperature field of a fully pulsed heated air jet

Measurements have been performed in a fully pulsed, heated air jet discharging into still air. Such a jet is found to have considerably enhanced entrainment compared with steady jets of identical mass flow. The increased jet momentum due to pulsation leads to a corresponding increase in Reynolds stress which in turn results in increased entrainment which is consistent with Taylor's entrainment hypothesis. Extension of measurements to the heated case at sufficiently low overheats, so that heat acts as a passive scalar, show significantly enhanced thermal mixing. Hot-wire anemometer measurements also indicate that, for the fully pulsed jet, unlike the unpulsed case, a considerable portion of the total axial heat flux is carried by the pulsating component. Both the velocity and the temperature fields are pulse dominated up to 50 diameter from the jet exit. (orig.)