EFFECT OF CORNER MODIFICATION ON TWO-DIMENSIONAL TURBULENT FLOW AROUND A SQUARE CYLINDER WITH INCIDENCE

Abstract

RNG k- model is used to analyze the aerodynamic performance of an isolated square cylinder with different wind angles, turbulence intensities and corners shapes (sharp, chamfered and rounded). The analysis is made for unsteady two-dimensional turbulent flow. The results are presented in the form of drag coefficient, lift coefficient, RMS lift coefficient and Strouhal number. The present work is compared with previous experiments from published literature and the data gave a qualitative agreement. It is found that drag coefficient, lift coefficient, RMS lift coefficient and Strouhal number are sensitive to angle of incidence, turbulence intensity and corner modification. The average reduction in drag coefficient of square cylinder with modified corners is about 44.5 % for 6.5% turbulence intensity and 41.5 % for 14 % turbulence intensity compared with that of square cylinder with sharp corners. Results indicated that the best fit equation of drag coefficient of sharp corners square cylinder at 45 angle of incidence and 14% turbulence intensity in terms of Reynolds number; ranging from 3.0×10 4 to 2.825×10 5 , is the second order polynomial equation; C d = 0.0536×(Re/10 5) 2-0.3518×(Re/10 5) + 2.0128. Nomenclature B Breadth, (m)  Dynamic viscosity, (kg/m.s) C d Time-averaged drag coefficient, (-)  Kinematic viscosity, (m 2 /s) C L Time-averaged lift coefficient, (-)  Angle of incidence, (degree) C l,rms RMS lift coefficient, (-) k Turbulent kinetic energy (J/kg) D Rectangular cylinder side, (m) and Drag, (N)  Dissipation rate of turbulent kinetic energy, (J/kg.s) I Turbulence intensity = u 1rms /U, (-) H Square cylinder height , (m) Abbreviations L Lift, (N) C Chamfered corners p Pressure, (Pa) LES Large Eddy Simulation r Corner radius, (m) R Rounded corners 92