EFFECT OF ROUGHNESS ON HEATING AT THE FORWARD SURFACE OF A SPHERE AT MACH 5
Abstract
Heat transfer rates to the forward surface of a 4-in. diameter sphere were measured at a flow of Mach 5 at Re from 1,300,000 to 2,900,000. The sphere surface varied in roughness in terms of stagnation-point boundary-layer thicknesses from smooth to 12.5 boundary layer thicknesses with the roughness dimension characterized by Nikuradse's equivalent sand roughness dimension. For the smooth wall, the boundary layer remained laminar over the Re range. Transition was obtained by the addition of roughness equal to the boundary layer thicknesses; however, the resulting turbulent heating was lower than that predicted by an exact solution of the smooth-wall boundary-layer equations. When the roughness was changed to 2 to 3 boundary layer thicknesses, the peak heating reflected the predictions more closely. In comparison with essentially steady wind-tunnel measurements at equivalent flow conditions, the work yielded generally lower heat-transfer rates for similar roughness dimensions. It is proposed that the different character of the roughness as well as its magnitude could influence the measured heat-transfer rates.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 15, 1970
- Accession Number
- AD0708471
Entities
People
- Robert L. Varwig
Organizations
- The Aerospace Corporation