DEVELOPMENT OF TURBULENT TRANSPORT IN A VERTICAL NATURAL-CONVECTION BOUNDARY-LAYER

Three calibrated hot-wire sensors and a thermocouple were used to measure the longitudinal and normal components of velocity, u and v, and the temperature, t, in the transition flow regime of the buoyancy induced boundary layer adjacent to a constant heat flux vertical surface. Analog signals of the sensor were digitized and recorded on magnetic tape in real time. The digital data were processed using a fast-Fourier transform algorithm to calculate variances, u'2 t'2, covariances, u'v', v't', correlation coefficients, Rv't', Ru't'; and variance spectra of u'2 and t'2. In transition, velocity and temperature fluctuation levels, u'2 and t'2, increased with increasing distance downstream and the disturbance spectrum broadened to a larger range of frequencies. At the end of transition, the growth of velocity fluctuations, u'2, was sharply reduced. However, another flow regime beyond transition was identified in which the spectra of velocity fluctuations continued to broaden and temperature fluctuation levels t'2, as well as turbulent heat fluxes continued to increase. © 1979.