Experimental Investigation on 3D Turbulent Flow around Straight and T-Shaped Groynes in a Flat Bed Channel

Abstract

Laboratory measurements were conducted to investigate the three-dimensional turbulent flow field around a single straight (SD) and two different T-shape groynes (TH and TF) under smooth flat-bed conditions. An acoustic Doppler velocimeter (ADV) was used in the measurements. Experimental results showed profound effects of the groyne shape on both the mean and turbulent flow characteristics, especially for the near bed region. The near bed velocity amplifications due to both of the local effects of groyne structure and constriction of the channel cross section in the SD is higher than T-shape groynes. The horseshoe vortex at the base of the SD has more compact and strong rotational momentum and lasts a longer distance downstream compared with T-shape groynes. By increasing the wing length of the T-shape groyne the flow structure at the upstream mini embayment changes from the vertical to the dominantly horizontal circulation, the horseshoe vortex disappears, and the wing segment acts as a scour countermeasure.