Experimental study on surface pressure and flow structure around a triangular prism located behind a porous fence

Flow structure around porous wind fences and the rear coal stockpile model embedded in an atmospheric boundary layer was investigated experimentally by measuring the surface pressure and flow velocity. The experiments were carried out in a closed-return type subsonic wind tunnel with various oncoming atmospheric boundary layers. Various front fences with different porosity and a back fence of porosity epsilon = 40% were tested. The fence and prism models were both 40 mm high; the Reynolds number based on the model height (h) and free stream velocity was about Re = 3.9 x 10(4). The velocity field around the prism model and surface pressures were measured using the single-frame double-exposure particle image velocimetry system and an electronic pressure scanner, respectively. As a result, the mean pressure and pressure fluctuations on the model surface were strongly affected by the porosity of front fence. The wind fence with porosity epsilon = 40-50% seems to be effective for attenuating the pressure fluctuations on the prism surface. A back fence behind the prism model reduces pressure fluctuations largely on the leeward surface of the prism, compared with the single front fence case. When a wind fence of porosity epsilon = 40% is installed in front of the prism, the speed of bleed-flow behind the fence is largely reduced down to 1/3 compared with no fence case. (C) 2002 Elsevier Science Ltd. All rights reserved.