Analysis of the anomalous intensification of a separate flow and heat transfer in a stabilized section of a narrow channel with single-row, inclined, oval-trench dimples with the use of various grids and turbulence models

In this paper, we analyze the intensification of the separated flow and heat transfer in single-row, oval-trench dimples with a $45^{\circ}$ incline on the heated wall of a narrow channel in the stabilization section of a turbulent flow at $\rm Re = 10^4$. Anomalously high velocities of the return and secondary flows (on the order of the average mass velocity in the channel), as well as in the entrance part of the dimples, and a multiple excess of the absolute values of negative friction $(4.5$ times$)$ and heat fluxes (five times) over the friction and Nusselt number on the heated wall of a plane-parallel smooth channel were found. The connection of this phenomenon with the total pressure difference between the close zones of flow deceleration on the windward slope of the dimple and rarefaction at the place of generation of a tornado-like vortex structure was established. The uncertainties in numerical predictions with the use of various grids and semi-empirical turbulence models in the $\rm StarCCM+$ and $\rm VP2/3$ packages are discussed.