FLOW AROUND RECTANGULAR CYLINDERS - PRESSURE FORCES AND WAKE FREQUENCIES

This paper concerns an experimental investigation of the flow around and pressure forces on fixed (non-vibrating) rectangular cylinders at angles of attack 0 degrees -90 degrees. Pressure forces and moments for cylinders with side ratios B/A = 1, 1.62, 2.5 and 3 (shortest side A = 20 mm) were estimated from measurements of static pressure distributions at midspan. Wake frequencies and associated Strouhal numbers were determined from hot mire measurements in the near-wake regions (A = 4 and 20 mm). With the smaller cylinders 12 side ratios within B/A = 1-5 were investigated. The free stream turbulence intensity was less than 0.06%, blockages less than 5% and aspect ratios L/A greater than 50. Reynolds numbers, based on A, ranged from about Re = 400 to Re = 3 x 10(4) (pressure measurements from about Re = 3 x 10(3)). For the square cylinder, the measured pressure forces were used for calculations of quasi-steady galloping response in the plunging mode.