Experimental and numerical study of three-dimensional laminar separated flow adjacent to backward-facing step

Measurements and numerical predictions of three-dimensional laminar and mixed convection flow and heat transfer adjacent to backward-facing step are reported. Predictions of laminar forced convection flow and laminar, buoyancy assisting, mixed convection flow are presented for the case where the duct's aspect ratio is eight (AR = 8), its expansion ratio is two (ER = 2), and the step height (S) is 1.00cm. The flow, upstream of the step, is treated as fully developed and isothermal. The stepped wall downstream from the step is treated as being heated with a uniform heat flux, and the other duct walls are treated as adiabatic surfaces. The results illustrate the complex three-dimensional flow and heat transfer characteristics in the separated and developing flow region downstream from the step. A vortex flow develops near the sidewall downstream from the step, and this three dimensional feature increases with increasing Reynolds number as well as with increasing Grashof number. The effects of the Reynolds number and Grashof number on the distributions of the three-velocity components, temperature, reattachment region, friction coefficient, and Nusselt number are presented.; Laser-Doppler measurements of velocity distributions and reattachment lengths are reported for three-dimensional forced and mixed convection airflow downstream of a backward-facing step with geometry similar to the one described above. Temperature distributions at the uniform heat flux wall are measured for buoyancy assisting mixed convection flow using Thermochromic Liquid Crystal (TLC). The effects of Reynolds number and buoyancy force on the flow and heat transfer characteristics are reported and analyzed.