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A theoretical study of the effect of variable viscosity and variable thermal conductivity on the classical plane Couette-Poiseuille flow is presented in this brief communication. The investigation concerns engine oil, air, and water taking into account the variation of these quantities with temperature. The results are obtained with the numerical simulation of the governing equations and cover large temperature differences. Velocity and temperature profiles are presented as well as the volume flow rate and the heat flux between the plates. It is found that temperature profiles are close to the straight line for oil and water and depart significantly from the straight line for air due to nonlinear thermal conductivity. Dynamic viscosity plays an important role on the results which depart significantly from those of a fluid with constant properties. [DOI: 10.1115/1.2238878] Keywords: Couette-Poiseuille flow, variable properties, forced convection

A study was conducted to understand how the steady laminar fully developed flow between two isothermal parallel plates and the investigation concerns air, engine oil, and water taking into account the variation of all physical properties with temperature. The results are obtained with the direct numerical solution of the governing equations and cover large temperature differences, which were not treated until then.

Previously, it was shown that, in Turner's formula which predicts the penetration depth of negatively buoyant jets, the classical initial densimetric Froude number should be replaced by an initial effective Froude number if the formula is applied to a heated water jet discharged downward. In the present paper, this conclusion is extended to double-diffusive plumes with two buoyancy components (heat and salt) which both oppose the downward flow. A new effective Froude number is introduced for double-diffusive plumes. For the calculation of the penetration depth a modified version of the integral Fan-Brooks model has been used. The same model is used to calculate the vertical penetration in the strongly nonlinear regions around the density maxima that appear in water at some special values of temperature and salinity. It is found that the penetration depth becomes very large if the existing ambient temperature and salinity are close to density extremum values and becomes infinite if the existing ambient temperature and salinity coincide with the maximum density values. DOI: 10.1061/(ASCE)0733-9429(2003)129:7(541) CE Database subject headings: Plumes; Penetration; Froude number; Buoyant jets.