Measurements of Laminar Mixed Convection Flow Over a Horizontal Forward-Facing Step


Measurements and prediction of buoyancy-assisting laminar mixed convection flow over a horizontal, two-dimensional forward-facing step are reported. Laser-Doppler velocimeter (LDV) and cold wire anemometer were used to simultaneously measure the velocity and the temperature distributions, respectively. Flow visualizations were conducted to determine the reattachment lengths for different inlet velocities (0.2555 m/s ≤ μ0 ≤ 0.50 m/s), wall freestream temperature differences (0°C ≤ ΔT ≤ 37°C) and step heights (0.79 cm ≤ s ≤ 1.75 cm). The results reveal that the buoyancy force due to wall heating has a negligible effect on the velocity and temperature distributions and the reattachment lengths, as long as the flow remains stable and two-dimensional (i.e. prior to the onset of vortex instability on the heated wall). The inlet velocity and the step height, on the other hand, significantly affect the flow and thermal fields. The local heat transfer coefficient is found to increase as the inlet velocity increases and the step height decreases. On the other hand, the length of the recirculation regions upstream and downstream of the step are found to increase as the inlet velocity and the step height increase. Correlation equations are developed to predict the reattachment lengths that appear upstream and downstream of the step. The measured results agree well with numerical predictions.


Mechanical and Aerospace Engineering

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Article - Journal

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© 1993 American Institute of Aeronautics and Astronautics (AIAA), All rights reserved.

Publication Date

01 Jan 1993