Thermal and kinetic energy dissipation rates in vertical convection over rough sidewalls

Adding roughness elements to walls is an effective method for enhancing heat transfer. However, the mechanism governing heat transfer variations, specifically the distribution and variation of energy dissipation remain unclear, particularly in vertical convection (VC). This study investigates how rough elements on the sidewalls affect both thermal and kinetic energy dissipations in vertical convection. Two-dimensional direct numerical simulations are conducted over a range of roughness heights and Rayleigh numbers. The results identify distinct critical roughness heights for thermal and kinetic energy dissipations, and illustrate the probability density function of them across the entire domain, demonstrating markedly different responses of thermal and kinetic energy dissipations to roughness modulation. By examining the spatial distribution of temperature and velocity fields, as well as the thermal and kinetic energy dissipations in the boundary layer and bulk, we identify the underlying mechanisms responsible for these differences. These findings provide new insights into how wall roughness modulates heat transfer and flow structures in vertical convection.