Ricerc@Sapienza

We propose to carry out a synergistic computational study of conjugate heat transfer in rectangular cooling channels typical of liquid propellant rocket engines, with the goal of establishing the predictive capability of Reynolds averaged Navier-Stokes (RANS) solvers. A classical Spalart-Allmaras RANS solver will be used as a first attempt, which will be iteratively coupled with a Fourier solver to account for thermal conduction within the duct walls. Comparison will made with reference solutions of the same problem obtained with direct numerical simulation (DNS) , which allows to describe the full features of flow and heat evolution in the channel. Numerical simulations will be carried out for different values of the fluid-solid thermal conductivity ratio to bring out conjugate heat transfer effects. Finite conductivity of the solid implies reduced thermal efficiency of the overall system as a result of both increased thermal resistance, and asymmetric heat loading on the fluid. Preliminary simulations carried out with the Spalart-Allmaras model have shown that despite the absence of the secondary motions, the RANS/Fourier solver can accurately estimate the pressure drop. Differences in the prediction of thermal effects are generally larger, amounting to underestimation of the overall heat transfer coefficient by about 10%. Additional turbulence models based on nonlinear constitutive relationships will be considered in the present project which are capable of correctly accounting for secondary motions, and modifications will be pursued to achieve accurate prediction of heat exchanges. Improvement of RANS model predictive capabilities would provide large competitive advantage to the national and European launch vehicle industry.