Calculation of surface heat transfer coefficient based on Reynolds-averaged Navier-Stokes equations

Reynolds-averaged Navier-Stokes (RANS) equations governing two-dimensional external flow were numerically solved using finite volume method. Local surface heat transfer coefficients on surface of smooth and rough NACA0012 airfoil and cylinder were calculated. The effects of near wall mesh spacing, turbulent and surface roughness model on the numerical calculation results were discussed. The features of convective heat transfer in laminar and turbulent boundary layers can be distinguished by shear stress transport(SST)turbulent model, moreover, the transition can be predicted using SST turbulent model. The reasonable heat transfer coefficients on rough walls are calculated using Spalart-Allmaras (S-A) extended model, but the convection heat transfer coefficients in laminar boundary layer can not be calculated effectively by S-A turbulent model neglecting transition function. The near wall mesh spacing should approach order of 10^-5 in viscous sub-layer for obtaining accurate heat transfer coefficients on both smooth and rough walls. The curves of surface heat transfer coefficients are close to experimental results if appropriate near wall mesh spacing, turbulent and surface roughness models are used. The effect of compressibility and viscous dissipation is neglected by incompressible RANS equations, but can be incorporated into overall thermal analysis in the form of adiabatic heating term.