Numerical Investigation of Evolution of Plume Structure in Rayleigh-Benard Convection

Author : SYAM JOY

Abstract :Numerical Investigations were carried out to study the Evolution of plume structure in Rayleigh-Benard convection at a constant Pr = 5.2 (water) and over a range of Rayleigh number 4.43 ×105 < RaH < 7.95 × 108. Three domains of cross-section 15 cm × 15 cm and height of 5 cm, 10 cm and 20 cm were used to study the plume structure rising from the thermal boundary layer over the high-temperature bottom plate. Transient simulations were carried out in ANSYS Fluent to study the evolution of plume structures. Four different regimes where observed viz, initiation phase; characterised by stable boundary layer across the planform, impingement phase; characterised by the destabilisation of the boundary layer and impingement of bulk flow, plume formation phase; characterised by the formation of line plume from the boundary layer, and plume dynamics phase; characterised by the lateral movement of plume, formation of new plumes and merging of plumes. Total length of plume (Lp ) and plume thickness (tp ) were measured from the planforms, and mean plume spacing (λ) and plume area ratio (Ap /A) were calculated using λ =A/ Lp and Ap /A = tp ×Lp / A. Total length of plume was found to increase with RaH, whereas mean plume thickness was found to decrease with RaH ; these opposing trends result in plume area ratio nearly independent of RaH .

Keywords :Convection, plume structure, boundary layer, plume spacing, length of plumes, plume thickness, and plume area ratio.

Conference Name :International Conference on Engineering & Technology (ICET - 25)

Conference Place Bangalore,India

Conference Date 29th Nov 2025