Starting flow and heat transfer downstream of a backward-facing step

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Journal of Heat Transfer (Transactions of the ASME (American Society of Mechanical Engineers), Series C); (United States)

DOI:https://doi.org/10.1115/1.2910605· OSTI ID:5629471

Tsou, F K ^[1]; Chen, Shihjiun ^[2]; Aung, W ^[3]

---

1. Drexel Univ., Philadelphia, PA (United States)
2. Temple Univ., Philadelphia, PA (United States)
3. National Science Foundation, Washington, DC (United States)

Experiments are performed to study the starting process of heat transfer downstream of a backward-facing step. A Ludweig tube wind tunnel is employed to produce the incompressible flow, which accelerates from a zero velocity to a steady state value with an accelerating period of 7 ms and a steady-state period of 12 ms. Hot-wire anemometry and heat flux gages are used to measure the flow and heat transfer history, respectively. The onset of transition in the free shear layer shows that the disturbance originates from the top corner of the step, then propagating to the free stream. The velocity and turbulence profiles in the free shear layer reach steady-state values after the leading edge disturbance etraverses to the measurement locations. In regions upstream and far downstream of the step, heat flux history data suggest the transformation of the flow from laminar to transitional and finally to turbulent flow. Hot-wire anemometry measurements indicate high-frequency turbulence with a short characteristic time. In the recirculating region, however, a longer characteristic time is observed because of the existence of large-scale eddies. The dimensionless reattachement length (x{sub r}/H) is shown to increase with time from the bottom corner (x{sub r}/H = 0) in the laminar regime to a maximum value of 13.6 in the transitional regime, and decreases to a constant value of 7.6 in the turbulent regime. The steady-state flow field and heat transfer compare favorably with existing data obtained using steady-state techniques.

• OSTI ID: 5629471
• Journal Information: Journal of Heat Transfer (Transactions of the ASME (American Society of Mechanical Engineers), Series C); (United States), Journal Name: Journal of Heat Transfer (Transactions of the ASME (American Society of Mechanical Engineers), Series C); (United States) Vol. 113:3; ISSN 0022-1481; ISSN JHTRA
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420400* -- Engineering-- Heat Transfer & Fluid Flow
ANEMOMETERS
BENCH-SCALE EXPERIMENTS
DUCTS
ENERGY TRANSFER
FLOW RATE
FLUID FLOW
HEAT FLUX
HEAT TRANSFER
HOT WIRE ANEMOMETERS
LAMINAR FLOW
MEASURING INSTRUMENTS
TUNNELS
TURBULENT FLOW
UNDERGROUND FACILITIES
WIND TUNNELS