Vortex-Enhanced Heat Transfer in Turbulent Flow over a Plate with Transverse, V- and Λ-Shaped Single Grooves of Equal Length

Numerical simulations of turbulent separated air flow and heat transfer over a thermally insulated plate containing single V-shaped grooves with hemispherical ends and opening angles of 95°, 180°, and 275° on an isothermal rectangular insert were performed by solving the Reynolds-averaged Navier–Stokes and energy equations using multiblock computational techniques. The closure of the momentum equations employed the differential equations of the SST shear stress transport model. The results revealed a fundamental difference in the mechanisms that enhance separated flow and heat transfer in the grooves, associated with the formation of a U-shaped vortex at the bend of the V-groove and two tornado-like vortices at the upstream-facing ends of the Λ-shaped groove. A localized static pressure drop of about 0.3 between the external flow stagnation regions and low-pressure zones accelerated both the recirculating and secondary swirling flows. The total relative heat transfer from the rectangular section bounding the contour of the V-groove increased by nearly 30% compared to a flat plate, whereas for a transverse groove, the corresponding value reached 1.12.