Model Study of Morphological Changes in the Base Morphology of Soil Channels Due to Groyne Structure
Abstract
The impact of flow velocity is effectively regulated and mitigated by permeable groynes, which also induce changes in riverbed morphology due to abrupt fluctuations in flow velocity. Therefore, this research investigated the effects of permeable groynes on flow characteristics, channel bottom morphology, and derived empirical equations to quantify their influence. A channel with width (b), height (h), and length (L) of 35 cm, 45 cm, and 900 cm, respectively, was utilized in the experimental setup. Several research variations were implemented, which involved three variations each of flow rate (Q) and channel bottom slope (So). Moreover, two variations of groyne density (ak1=0.09 cm, ak1=0.12 cm), distance (Lk1= 60 cm, Lk1= 90 cm), and diameter (dk1 = 0.09 cm, dk1 = 0.17 cm) were considered. To measure flow velocity, a current meter was employed at three segments, with five points each, to determine the flow depth in the vertical dir. Before and after the introduction of the permeable groyne, flow velocity measurements and sampling of sediment transport volume and scour patterns were conducted. The data analysis was carried out using an empirical equation approach. The result showed that the flow characteristics were turbulent and reduced the flow velocity by 8.55% due to the presence of permeable groyne. Furthermore, changes in channel bottom morphology, which occurred around the permeable groyne point, are attributed to scour when τo > τc, whereas sedimentation occurred at a distance from the groyne due to lower flow shear stress (τo < τc). The extent of channel bed scour was directly proportional to the distance of the permeable groyne (Lk), with increased sediment transport leading to more tenuous contours. Conversely, a smaller groyne distance resulted in reduced sediment transport, leading to denser contours. Empirical equations were derived to desgroynee the sediment transport (qb) induced by the permeable groyne. The relatively high resistance to flow velocity causes resistance to flow turbulence and scour and has an impact on new phenomena around the permeable groyne area.
