Speaker
Description
Coaxial pipe flow is encountered in many engineering applications, such as in heat exchangers, chemical reactors or cooling systems in nuclear engineering. These applications require an accurate modelling of the momentum transport, as it is a prerequisite for the transport of additional scalar quantities. The presence of an inner curved wall in coaxial pipe flows poses a challenge for modelling, especially when the viscous length scale is of the same order of magnitude as the inner wall span-wise curvature radius. Previously, various experimental and numerical experiments have been conducted for different radius ratios to investigate the effects of the inner wall span-wise curvature radius on the flow. In particular, for small radius ratios (wide annular gaps), recent work has shown that traditional wall models fail in predicting bulk quantities due to insufficient representation of the inner wall. In this contribution, we evaluate the suitability of high Reynolds number (HRN) Reynolds-Averaged Navier-Stokes (RANS) models to predict mean flow profiles considering the usual assumptions from boundary layer theory. Specifically, we check whether it is possible for data-informed HRN-RANS model coefficients to reliably predict mean flow statistics. Model coefficients are obtained by regression of simulation results to match available reference data. As an additional insight, we test Clauser's assumptions on the outer layer dynamics of wall-bounded flows, related to the constancy of the turbulent viscosity at very large Reynolds numbers.
