Fluid flow and mixed convective heat transfer around a semi-circular cylinder at incidence with a tandem downstream square cylinder in cross flow

•Thermal buoyancy effects on semicircular and square cylinders in tandem is studied.•Steady separated flow becomes unsteady periodic under superimposed thermal buoyancy.•Critical Richardson number for onset of vortex shedding depends on incidence angle.•Vortex shedding frequency increases with increasing Reynolds and Richardson numbers.

The present paper presents fluid flow and mixed convective heat transfer characteristics past a semi-circular cylinder at incidence with a tandem square cylinder in cross flow. Using air (Pr=0.71) as an operating medium, numerical simulations are performed for the range of Reynolds numbers, 10≤Re≤45 and incidence angles, 00≤α≤1800. The effect of thermal buoyancy is brought about by varying the Richardson number in the range 0≤Ri≤2. The mathematical model is firstly validated with the experimental and numerical results from the literature and found to be in good agreement. The steady separated flow is observed to become unsteady periodic under the superimposed thermal buoyancy. Furthermore, apart from thermal buoyancy effect, angle of incidence is found to play a pivotal role in bringing hydrodynamic instabilities and thereby vortex shedding for such steady mixed convective flows. Functional dependence of drag (CD), lift (CL), and moment (CM) coefficients on the combined influence of α and Ri, is explored and analysed in detail. Additionally, other global quantities, such as local and average Nusselt number distribution, Strouhal number (St) are determined with respect to the various ranges of parameters considered in the present investigation.