Investigation of Local Laminar Heat Transfer on a Hemisphere for Supersonic Mach Numbers at Low Rates of Heat Flux

Abstract

SUMMARY Pressure and local heat-transfer measurements were made on the hemispherical nose of a 2-in. -diameter hemisphere-cylinder with laminar boundary-layer flow. The tests were conducted in the NOL 40- by 40-cm. Aeroballistics Tunnel No. 1 with atmos­ pheric supply conditions. Pressure distributions were measured for the Mach Number range of 0.26 to 4.87, and heat-transfer measurements were made for the Mach Number range of 1.90 to 4.87. The heat-transfer measurements were made with iso­ thermal temperature distributions over the hemisphere and indicate that local heat-transfer coefficients are independent of surface temperature in the range of db50°C. However, the heat-transfer coefficients must be defined in terms of effective temperatures rather than adiabatic wall temperatures. These effective temperatures, though lower, probably do not differ by more than 5 per cent from adiabatic wall temperatures. From local velocities outside the boundary layer as determined from static pressure measurements, it was found that the velocity could be made nondimensional so that a single curve represented the velocity distribution along the hemisphere for the entire Mach Number range. Using this velocity distribution, a single theoretical curve has been derived and used to correlate the local supersonic heat-transfer data in the Mach Number range 1.90 a = sonic velocity (m. /sec.) c = specific heat of model material (k-cal./kg., °C.) cp = specific heat of air at constant pressure (k-cal./kg., °C.) D = body diameter (m.) d = thickness of thin-walled model (m.) g = gravitational constant (9.81 m./sec.2) h = local convective heat-transfer coefficient (k-cal./hour, m.2, °C.) k = thermal conductivity of air (k-cal./hour, m., °C.) / = length (m.) m = model segment weight (kg.) a = time rate of heat transfer per unit area (k-cal./hour, m.2)