Laminar natural convection flow over a vertical backward-facing step

Measurements and predictions of laminar boundary-layer air flow in natural convection over a vertical two-dimensional backward-facing step are reported. The upstream and downstream walls and the step itself were heated to a uniform and constant temperature. The experiment was carried out for the ranges of step heights 3.5 mm less than or equal to s less than or equal to 9 mm, temperature differences of 5.8 degrees C less than or equal to Delta T less than or equal to 23 degrees C between the heated wall and the free stream (corresponding to 2.238 X 10(7) < Gr(xi) < 8.877 X 10(7)), and reference velocities of 0.24 m/s less than or equal to u* less than or equal to 0.47 m/s. Laser-Doppler velocimeter and cole-wire anemometer were utilized to measure, respectively, the velocity and the temperature distributions simultaneously. Flow visualization was also performed to determine the reattachment length. Measurements compare favorably with predictions. These results reveal that the step height significantly affects the velocity and temperature distributions, the friction coefficient, and the rate of heat transfer down-stream of the backward-facing step.