Assessment of BSL kω Turbulence Model for Predicting Flow Characteristics in a Solitary Wave Motion

A deep understanding of boundary layer characteristics under wave motion, especially bottom shear stress on the seabed, is critical in sediment transport calculation and modeling. In this present study, boundary layer characteristics under solitary wave motion over the smooth bed are investigated through the Baseline (BSL) kω model. It will also consider the result of a laboratory experiment performed in a closed conduit generation system. The conclusion said that the BSL kω model can replicate well on horizontal and vertical velocity distribution at Reynolds number (Re) = 2.25 x 105. In addition, a turbulent spike which was occurred during decelerating phases of oscillatory motion can be predicted well also by the BSL kω model at Reynolds number (Re) = 6.06 x 105.

Evaluation of Incipient Motion of Sand Particles by Different Indirect Methods in Erosion Function Apparatus

An experiment was carried out in an acrylic glass-sided re-circulating closed conduit with a rectangular cross section, which is similar in construction to an erosion function apparatus. An adjustable sand box, made of acrylic glass, was attached to the bottom of the conduit as the sand zone or the test section. The hydraulics of the flow in the erosion function apparatus is complicated due to the limited part of the non-smooth and erodible soil surface attached to the closed conduit. As the bed shear stress changes with the bed roughness, even though the flow velocity does not change, establishing a method to estimate the incipient motion is an important challenge for an erosion function apparatus. The present study was conducted to explore the incipient motion of sands from bed shear stress estimated by four different indirect methods on both the sand bed and the smooth bed installed in the erosion function apparatus. In the experiment, particle image velocimetry (PIV) was used to investigate flow dynamics and incipient motion in terms of dimensionless critical bed shear stress. The experimental results show that the bed shear stress estimated from the log-law profiles in the sand zone and the smooth zones are relatively higher than those of the other indirect methods. The dimensionless critical bed shear stress of threshold condition evaluated by all indirect methods was found in good agreement with those of previous results in both zones. The Manning roughness and Darcy–Weisbach friction coefficients were evaluated based on the critical shear velocity at the incipient motion. Although these coefficients were found slightly greater in the smooth zone than in the sand zone, in both zones, they showed good agreement with previous studies.

Decision of The Hydraulic State of Rivers within Growth Cities using GIS: Al-Hneidiyah River as Example

Generally, the rivers in both the natural and lined form use the open-section system to carry water, either for distribution or conveyance purposes. With time and depreciation effect, this system needs to be changed or modified to become more indirectly suitable with cities' growth, especially with the transformation of land use from agricultural to residential. The present paper aims to reach a proper decision to select the best hydraulic section for a part of Al-Hneidiyah river in Karbala city by determining the remain agricultural lands within the study area, for the distance between stations (0+000) and (4+000), to choose between keeping up the currently open section or change, (modify), it to a closed conduit. For this study, the cadastral maps were used as a reference to determine the agricultural areas served by the river during its route within the study area, and geographic information system to monitor the change like these areas represented by a gradual transformation from agricultural to residential purpose, by using of satellite images for four different years, 2002, 2007, 2013, and 2016. The results of this study showed a significant recession in the agricultural areas on both sides of the chosen length of river route by a percentage of 13.45%, which leads to an urgent need to change or modify the flow system from opened to closed and use it only for conveyance purposes to protect the water quality and water shares. The geographic information system is a good and helpful technique for evaluation and makes water-related subjects decisions by giving a clear vision of the studied problem.