Large-eddy simulation of turbulent duct flow: heating and curvature effects

Large eddy simulations of the turbulent gas flow within ducts of square cross-section are performed. The spatial development of turbulent flow inside a heated straight duct is first considered with a higher temperature suddenly imposed at one of the duct walls. The downstream development of the thermal boundary layer is then studied and compared with the fully developed turbulent case. The gradual increase with temperature of the viscosity near the heated wall yields a progressive enhancement of the turbulent structures and to a single ejection localized near the middle plane of the heated wall. e of curvilinear coordinates allows to consider ducts of more complex geometries and to investigate the combined effects of heating and curvature. The case of an S-shape duct is then considered exhibiting both convex and concave curvatures. The pressure gradient between the inner and outer wall of the curved sections leads to the apparition of intense counter-rotating Dean vortices associated with an intense transverse flow with a maximum intensity of 22% of the bulk velocity. Downstream of the second curved section of the duct, the flow exhibits a complex distribution of various vortices. In the heated case, the mutual interaction between the heating and the Dean vortices is investigated. The heating is seen to enhance both the size and intensity of the Dean vortices when situated close to the heated wall.