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ISSN オンライン: 2642-0554

STRUCTURE OF A TWO-DIMENSIONAL TURBULENT BOUNDARY LAYER OVER A SUBMERGED CYLINDRICAL PROTURBERANCE

Jacob George
Department of Aerospace and Ocean Engineering Virginia Tech, Blacksburg, VA 24061-0203

Roger L . Simpson
Department of Aerospace and Ocean Engineering Virginia Polytechnic Institute and State University Blacksburg, VA 24061-0203 USA

要約

Detailed individual measurements are made in the downstream flow-fields of three cylindrical protuberances of heights, h+, non-dimensionalized by friction velocity (Uτ) of the approach turbulent boundary layer (BL), of 23, 46 and 92 using a special fine-measurement-volume (30 microns diameter) three-orthogonal-velocity-component fiber-optic Laser Doppler Velocimeter (LDV) system. The trailing legs of the horseshoe vortex formed in front of the single element causes an increased downwash, bringing greater momentum fluid closer to the wall. For all cases, this "sweep" type motions causes higher Reynolds stresses (v2,w2 and −uv) downstream of the element. Further, this greater momentum fluid close to the wall leads to greater skin-friction drag. However, for the lowest element, the skin-friction drag is lower than that for the undisturbed approach boundary layer at locations further downstream from the element.