Numerical investigation of two-dimensional unsteady flow and heat transfer from rounded equilateral isothermal triangular cylinders in cross flow

In this study, two-dimensional numerical investigation of unsteady heat and fluid flow over a triangular cylinder with rounded corners is carried out. An equilateral triangular cylinder of side length D is subjected to fluid flow (50 ≤ Re ≤ 250). The study explores the effects of fluids (air, water), corner rounding, and cylinder orientation on the heat and flow characteristics. Three corner rounding cases are investigated; r = d/D = 0.05, 0.1 and 0.15. Cylinder orientations include; cylinder sitting on its flat surface (Case 1), a flat face of cylinder facing the cross flow (Case 2), and a corner facing the flow (Case 3). Mean drag/lift coefficients, Strouhal and mean Nusselt number are obtained and discussed. Case 3 yields 10%–18% higher Nusselt values than other cases. Case 2 and 3 generates no significant lift force regardless of the rounding ratio. Case 1 generates significant lift force which is reduced by about 40% as corner rounding is increased. The effects of d/D, Pr and Re numbers on the flow and heat transfer patterns are comparatively presented. It is observed that the cylinder orientation and corner rounding do have effect on the flow and heat transfer characteristics. Correlations for the flow and heat transfer characteristics have r2 > 0.999. •Two-dimensional forced convection from rounded triangular cylinders in Pr = 0.7 and Pr = 7 fluids is investigated.•Cylinders with rounding radius of d/D = 0.05, d/D = 0.10 and d/D = 0.15 is considered.•Three different cylinder positions (rotation angles of 0, 30 and 90°) are considered.•Strouhal number, Drag and lift coefficients and local and mean Nusselt numbers are computed for flows in the range 0 ≤ Re ≤ 250.•Flow and heat transfer characteristics are correlated using nonlinear regression.