Heat and Mass Transfer Australasia

ISBN Print: 978-1-56700-099-3

On the thermal stability of a flow beneath a rigid insulating wall with a longitudinal temperature gradient

DOI: 10.1615/978-1-56700-099-3.110
pages 81-88

Résumé

Horizontal flows between an upper rigid, insulating and a lower free, constant heat-flux boundary are studied. The flows exhibit a horizontal temperature gradient (TG) which, in the stationary case, is in balance with the heat loss at the lower boundary. If the gradient is larger than its stationary value the flow is quasi-stationary with constantly moving isotherms and a potentially unstable vertical temperature profile. The stability of these flows with respect to longitudinal thermal convection rolls is analyzed. Threshold and critical wave numbers are found to be about 35 percent lower than those for the same vertical temperature profiles in the absence of the horizontal TG. Conclusions are drawn for the gravity intrusion flow at the top of a side-heated cavity. The instability occurring there is argued to be thermally driven. A mechanical explanation for the undulating shape of the intrusion front is given.