LES of an asymmetrically heated high aspect ratio duct at high reynolds number at different wall temperatures

We present the results of well-resolved large-eddy simulations (LES) of an asymmetrically heated high aspect ratio cooling duct (HARCD) with an aspect ratio of AR = 4.3 for two different wall temperatures. The temperature difference with respect to the bulk flow is ∆T = 40 K, respectively ∆T = 60 K. The HARCD is operated with liquid water at a Reynolds number of Reb = 110 ⋅ 103 based on bulk velocity and hydraulic diameter. The generic HARCD setup follows a reference experiment. The main goal of the present study is the numerical investigation of the interaction of turbulent heat transfer and the turbulent duct flow, specifically the heating induced changes in mean flow and turbulent statistics with a spatially developing temperature boundary layer. Furthermore, we investigate the influence of asymmetric wall heating on streamwise vorticity and its dynamics as well as the turbulent Prandtl number and the effect of the secondary flow on its distribution.Aerodynamic

Turbulent flow through a high aspect ratio cooling duct with asymmetric wall heating

We present well-resolved large-eddy simulations of turbulent flow through a straight, high aspect ratio cooling duct operated with water at a bulk Reynolds number of Reb = 110 × 103 and an average Nusselt number of Nuxz = 371. The geometry and boundary conditions follow an experimental reference case and good agreement with the experimental results is achieved. The current investigation focuses on the influence of asymmetric wall heating on the duct flow field, specifically on the interaction of turbulence-induced secondary flow and turbulent heat transfer, and the associated spatial development of the thermal boundary layer and the inferred viscosity variation. The viscosity reduction towards the heated wall causes a decrease in turbulent mixing, turbulent length scales and turbulence anisotropy as well as a weakening of turbulent ejections. Overall, the secondary flow strength becomes increasingly less intense along the length of the spatially resolved heated duct as compared to an adiabatic duct. Furthermore, we show that the assumption of a constant turbulent Prandtl number is invalid for turbulent heat transfer in an asymmetrically heated duct.Aerodynamic

Large-eddy simulation of the high-Reynolds-number flow through a high-aspect-ratio cooling duct

We present well-resolved large-eddy-simulations (LES) of a straight, high-aspect-ratio cooling duct (HARCD) at a bulk Reynolds number of Re = 110 • 103 and an average Nusselt number of Nu = 371. The geometry and boundary conditions have been defined together with Rochlitz et al. (2015), who conducted the experimental measurements for this case. Water was chosen as coolant. The current investigation focuses on the influence of asymmetrical wall heating on the flow field and specifically on the influence of the turbulence-induced secondary flow on turbulent heat transfer, the spatial development of the temperature boundary layer and the accompanying viscosity modulation. Due to the viscosity drop in the vicinity of the heated wall we observe a decrease in turbulent length scales and in turbulence anisotropy, resulting in a decrease of turbulent mixing and the secondary flow strength along the duct.Aerodynamic