Advancing drag crisis of a sphere via the manipulation of integral length scale

作者：Moradian Niloofar; Ting David S K; Cheng Shaohong^*

来源：Wind and Structures, 2011, 14(1): 35-53.

• sphere
• orifice perforated plate
• turbulence
• drag coefficient
• integral length scale

Spherical object in wind is a common scenario in daily life and engineering practice. The main challenge in understanding the aerodynamics in turbulent wind lies in the multi-aspect of turbulence. This paper presents a wind tunnel study, which focuses on the role of turbulence integral length scale A on the drag of a sphere. Particular turbulent flow conditions were achieved via the proper combination of wind speed, orifice perforated plate, sphere diameter (D) and distance downstream from the plate. The drag was measured in turbulent flow with 2.2 x 10(4) <= Re <= 8 x 10(4), 0.043 <= A/D <= 3.24, and turbulence intensity Tu up to 6.3%. Our results confirmed the general trends of decreasing drag coefficient and critical Reynolds number with increasing turbulence intensity. More interestingly, the unique role of the relative integral length scale has been revealed. Over the range of conditions studied, an integral length of approximately 65% the sphere diameter is most effective in reducing the drag.

• 出版日期2011-1