EFFECTS OF FIRST ORDER CHEMICAL REACTION ON FLOW PAST AN OSCILLATING SEMI-INFINITE VERTICAL PLATE A.R. VIJAYALAKSHMI , R. MUTHUCUMARASWAMY Department of Applied Mathematics, Sri Venkateswara College of Engineering Sriperumbudur 602 105, INDIA. ABSTRACT Effects of homogeneous chemical reaction of first order on unsteady flow past an oscillating semi-infinite vertical plate have been studied. The dimensionless governing equations are solved by an unconditionally stable and fast converging implicit finite difference scheme. The effect of velocity and temperature for different parameters like chemical reaction parameter, thermal Grashof number, mass Grashof number and time are studied. It is observed that due to the presence of first order chemical reaction, the velocity increases during generative reaction and decreases in destructive reaction. Keywords: Chemical reaction, oscillating vertical plate, isothermal, heat transfer, mass diffusion. 1. INTRODUCTION Chemical reactions can be codified as either heterogeneous or homogeneous processes. In well- mixed systems, the reaction is heterogeneous, if it takes place at an interface and homogeneous, if it takes place in solution. In most cases of chemical reactions, the reaction rate depends on the concentration of the species itself. In many chemical engineering processes, there does occur the chemical reaction between a foreign mass and the fluid in which the plate is moving. These processes take place in numerous industrial applications, e.g., polymer production, manufacturing of ceramics or glassware and food processing. Oscillating plate is used in cooling systems as heat exchangers. Chambre and Young [1] have analyzed a first order chemical reaction in the neighbourhood of a horizontal plate. Das et al [3] have studied the effect of homogeneous first order chemical reaction on the flow past an impulsively started infinite vertical plate with uniform heat flux and mass transfer. Again, mass transfer effects on moving isothermal vertical plate in the presence of chemical reaction studied by Das et al [4]. The flow of a viscous, incompressible fluid past an infinite isothermal vertical plate, oscillating in its own plane, was solved by Soundalgekar [5]. Soundalgekar et al[6] derived an exact solution for the effect of mass transfer on the flow past an infinite vertical oscillating plate in the presence of constant heat flux. Mass transfer effects on isothermal vertical oscillating plate in the presence of chemical reaction was solved analytically by Muthucumarasamy et al[7]. In all the above cases the dimensionless governing equations were solved by the Laplace-transform technique and the solutions are valid only at lower time level. Analytical or numerical work on transient flow past an oscillating semi-infinite vertical plate under the combined buoyancy effects of heat and mass diffusion in the presence of chemical reaction has not received attention of any researcher. Hence, the present study is to investigate the flow past an oscillating semi-infinite vertical plate with homogeneous first order chemical reaction by an implicit finite-difference scheme of Crank-Nicolson type. 2. FORMULATION OF THE PROBLEM Consider a laminar, unsteady natural convection flow of a viscous incompressible fluid past an oscillating semi-infinite vertical plate which is at rest and surrounds the plate with temperature T' and concentration C' It is assumed that there is a first order chemical reaction between the diffusing species and the fluid. Here, the x-axis is taken along the plate in the vertically upward direction and the y-axis is taken normal to the plate. Initially, it is assumed that the plate and the fluid are of the same temperature and concentration. At time t'>0, the plate starts oscillating in its own plane with frequency and the temperature of the plate and the concentration level are also raised linearly with time. Then by usual Boussinesq's approximation, the unsteady flow is governed by the following equations : ∞ ∞ ' ω 173 Tome VIII (year 2010), Fascicule 3, (ISSN 1584 – 2673)