Mixed convection in a variable size cavity: Effect of flexible wall characteristics

Abstract

Boosting the mixed convection in vented cavities using a moving wall results in a disturbed strong circulation. This study investigates the mitigation of the disturbed circulation to promote the transfer of heat by providing additional size to the circulation. The use of deformable walls with different thicknesses, lengths and modulus of elasticity is suggested for this problem. The top wall of the cavity is adiabatic and moves in the positive direction, and four speeds were studied; 0.5, 1, 2 and 4 times the fluid velocity at the inlet vent. The ratio of the natural to forced convection is controlled by ranging Richardson number by 0.01 ≤ Ri ≤ 100. Three aspect ratios are studied; AR = 0.5 (horizontal cavity), 1 and 2 (tall cavity). The problem is treated numerically using the finite element method. Results indicate that the fluid flow inside the vented square cavity changes from major single vortices into multi vortices at high (Ri = 100). Results affirm that a flexible wall yields a higher Nusselt number than the rigid wall, it's about 12 %, and 20 % for Ri = 0.01 and 10, respectively. A thicker flexible wall augments the Nusselt number for Ri ≤ 10. For specified conditions, the Nusselt number of the horizontal cavity is 17.7 % greater than the tall cavity. The lid speed of uLid = 4 uin exhibits a competent role in raising the Nusselt number for low Richardson number.