Hydro- and thermo-dynamic characteristics of a circular cylinder placed in mixed convection flow

Abstract

The fluid–thermal–structure interaction of a heated circular cylinder is numerically investigated at Pr = 0.71, Re = 60–160, and Ri = 0–2.0 in this article using the stabilized finite element method. The heat convection characteristics along the cylinder's surface in both forced and mixed convection subject to cross buoyancy are discussed and linked to the fluid instabilities. Additionally, the hydrodynamic characteristics are investigated in both time and frequency domains according to the strength of thermal cross buoyancy. Multiple harmonics of hydrodynamic coefficients and heat convection are identified from their frequency domains. Reynolds stresses are utilized to study the energy cascade of fluid kinetic energy and thermal energy via the fine-scale fluid fluctuation in the wake. Furthermore, the dynamic mode decomposition (DMD) technique is employed to extract the dominant spatial-temporal modes from the original field data. It is found that more linear DMD modes are required to accurately reconstruct the vorticity and temperature contours. It implies that strong nonlinear features exist in the wake and are influenced by the thermal buoyancy.