Subcritical Flow Around Bluff Bodies

Abstract

Results of experimental investigations of vortex-shedding frequencies and surface pressures of circular and square cylinders with the same hydraulic diameter are described. Pressure measurements on circular and square cylindersandhot-e lm measurementsinthewakeswereconducted. TherangeofReynoldsnumberswas1 :3 £ 10 4‐ 2 £ 10 5 , which is characterized as subcritical e ow regimes. Also, to reveal the combined ine uence of Reynolds number and angle of incidence on the pressure and spectral density distributions of velocities, experiments were carried out on square and rectangular cylinders for the angle of incidence in the range 0 < ®< 45 deg. At zero incidence,pressurecoefe cientsonthefrontandsidefacesofthesquarecylinderchangeconsiderablywithReynolds number, whereas as the angle of incidenceincreasesto 30 deg, theeffectoftheReynolds numberseemsto diminish. Spectral density distributions in the wake and surface pressures depend on Reynolds number and the angle of incidence.Thevariationsofthestrengthofthespectraldensitieswith Reynoldsnumberinthewakesofcircularand square cylinders show different characteristics. Variations of spectral density distributions and vortex shedding with Reynolds number, geometric dimensions of models, and angle of incidence are presented.