Acta Mechanica 136, 133 141 (1999) ACTA MECHANICA 9 Springer-Verlag 1999 Combined heat and mass transfer in natural convection flow from a vertical wavy surface M. A. Hossain, Dhaka, Bangladesh, and D. A. S. Rees, Bath, United Kingdom (Received June 7, 1998) Summary. In the present paper, effects of combined buoyancy forces from mass and thermal diffusion by natural convection flow from a vertical wavy surface have been investigated using the implicit finite differ- ence method. Here we have focused our attention on the evolution of the surface shear stress, f"(0), rate of heat transfer, 9'(0), and surface concentration gradient, h'(0) with effect of different values of the governing parameters, such as the Schmidt number Sc ranging from 7 to 1500 which are appropriate for different species concentration in water (Pr = 7.0), the amplitude of the waviness of the surface ranging from 0.0 to 0.4 and the buoyancy parameter, w, ranging from 0.0 to 1. Notation C c~ c~ D f g Grx N P T ~/,~V x~y species concentration in the boundary layer species concentration of the ambient fluid species concentration at the surface chemical molecular diffusivity dimensionless stream function acceleration due to gravity local modified Grashof number ratio of the buoyancy forces due to the temperature difference and the concentration difference pressure of the fluid temperature of the fluid in the boundary layer temperature of the ambient fluid temperature at the surface the x- and y-components of the velocity field axis in the direction along and normal to the plate Greek symbols ~c r] L)o~ // T # thermal diffusivity volumetric coefficient of thermal expansion volumetric coefficient of expansion with concentration stream function nondimensionalsimilarity variable x/L density of the ambient fluid kinematic coefficient of viscosity stream function dimensionless skin friction fluid viscosity