抄録
The stability of a horizontal layer of a viscoelastic fluid (Oldroyd fluid) heated from below is considered. Linear stability theory is used to derive an eigenvalue equation system of sixth order. Consideration is given to the two cases (a) both bounding surfaces free and (b) both bounding surfaces rigid, the former being solved exactly and the latter approximately by the Galerkin method. Tables of the various critical values for the onset of instability are provided for various assigned values of parameters. It is shown that the principle of exchange of stabilities does not hold for moderately elastic fluids; and that the critical Rayleigh number is lowered by the presence of a stress relaxation time and raised by the presence of a strain retardation time.
