Three-dimensional laminar and turbulent convection in separated flow

Three-dimensional laminar and turbulent separated flow and heat transfer in plane symmetric sudden expansion and plane backward facing step is examined in this dissertation. In Papers I, II, and III, simulations of 3-D laminar forced convection in plane symmetric expansion is studied. Flow bifurcation could develop in this geometry under specific flow and thermal conditions causing asymmetric temperature and heat transfer distributions in a symmetric geometry with symmetric inlet flow conditions. In Paper I, the forced convection case is examined to establish the critical Reynolds number range; and in Paper II, the mixed convection case is examined to establish the critical wall heat flux range for which bifurcation exists in this geometry. In Paper III, the mixed convection is examined in the symmetric flow regime that also develops in this geometry at higher heating or flow conditions. The results in Papers I and II demonstrate that the maximum Nusselt number on one stepped wall is larger than the one on the other stepped wall. The results in Paper III demonstrate that the recirculation flow regions downstream from the sudden expansion can disappear from the flow when the wall heat flux is increased. In Paper IV, 3-D turbulent flow measurements using Laser Doppler Velocimeter are made in a backward facing step flow and the three velocity components and the Reynolds stresses are measured in the separated and redeveloping flow region. These measurements can be used as benchmark in developing improvements to existing 3-D turbulence models. In Paper V, the 2-D behavior of a thin film that is shear driven by turbulent air flow is simulated. Film thickness decreases but its surface velocity increases with increasing air flow rate, but film thickness increases and surface velocity increases for increasing liquid flow rates. Results compare favorably with measurements.