LEADING-EDGE EFFECT DURING TRANSIENT BUOYANCY INDUCED FLOW ADJACENT TO A VERTICAL CYLINDER

The rate of propagation of the leading edge effect (LEE) during transi ent natural convection adjacent to a vertical solid cylinder is estima ted from five different criteria. The cylinder has an appreciable ther mal capacity and is subjected to a sudden heat generation. Numerical r esults are presented for a wide range of cylinder radii and heat flux values for two fluids, air and water. It is found that unlike the case of a flat plate, there is no unique criterion which would always esti mate the fastest rate of propagation of LEE in water. However in air, the criterion due to Brown and Riley (J. Fluid Mech. 59, 225-237 (1973 )) always predicts the fastest rate of propagation. Also, the effect o f cylinder radius on the rate at which the LEE propagates through diff erent fluids is different. For identical conditions, the LEE propagate s faster in air than in water, as expected. Present results obtained b y dropping the curvature terms in the governing equations match very w ell with previous analytical results for a flat plate.