Buoyancy effects on unsteady laminar and rotationally symmetrical boundarylayer

Initial development of the laminar boundary-layer flow over an impulsively started translating and spinning isothermal body of revolution ire the case of mixed convection is investigated. Velocity components and temperature a re expanded in series in powers of time. Leading and first order functions are obtained analytically and second order functions are determined numeric ally. The general results are applied to a sphere to investigate the effect s of density variations on velocity field and on the onset of separation. T he buoyancy force is more effective for small rotational speeds and facilit ates the onset of separation for opposing flow and retards it for aiding fl ow.