TURBULENT-FLOW FRICTION AND HEAT-TRANSFER CHARACTERISTICS FOR SPHERICAL CAVITIES ON A FLAT-PLATE

Experimental investigations were made of friction and heat transfer on surfaces shaped by systems of spherical cavities streamlined by a tur bulent flow. The experiments were run on a special aerodynamic test be d using a traditional procedure for diagnosing a boundary layer in con ditions of outer flow. Ten plates were used as prototypes. nine of whi ch had surfaces shaped by staggered ordered systems of spherical cavit ies at various densities and geometries, and one smooth surface for te st experiments. All measurements were made with a DISA-55M thermoanemo metric set and direct-acting standard transducers with 2.5 mum diamete r filaments. For direct measurement of heat flux on a smooth surface, DTP-05 transducers were used. which did not produce any significant ch anges in the temperature field of the specimen. From the results obtai ned we conclude that such a shaping of a heating surface has no apprec iable effect on the hydrodynamics of a flow with considerable (up to 3 0-40%) heat transfer enhancement. Experimental data on heat transfer a re generalized, and a relationship suitable for engineering estimation of heat transfer on surfaces shaped by a regular relief of spherical cavities and valid for the investigated geometric parameters of shapin g and flow regimes has been obtained.