الفهرس 
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Abstract
The existence of human kind is mainly related to rivers which are considered tha main source of fresh water, but unfortunately the river systems as a part of our nature needs to be measured and trained to verify the basic requirements of human being. River training is a process involving construction of structures across or along the river and that can`t be done by force but only by understanding. One of the most common used river training structures are groins which are mainly used for bank protection against erosion and for channerl rehabilitation.
The present study aims at using a physically verified 2-D mathematical model based on finite theory to simulate and predict the flow pattern around non-submerged groins. The simulation is focused on the study of velocity in the longitudinal and transverse directions. in addition, the length of separating point and reattachment length are also investigated. Two effective parameters were examined; the first is the contraction ratio which is defined as the groin length to channel width. Four constraction ratio`s of 0.1. 0.15, 0.2 and 0.30 were used. The second is the groin orientation angle; seven orientation angles were tested to define three types of groins. Angles 30.45 and 60 degree define repelling groin type which is looking to the upstream direction or opposite to flow direction. Angle 90 degree is defining the straight groin or the groin pointed perpendicular to flow direction. Angle of 120.135 and 150 degrees define the attracting type groin which defined as the groin looking to the downstream of the same direction of flow. Each orientation angle is simulated with the four contraction ratios.
The study cases represent several concluding remarks. The reattachment length indicate similar trend for all tested contraction ratios. However, the angles represents repelling groins indicate longer reattachment lengths than similar angles represents attracting groins, despite that the straight droins shows the longest reaattachment lengths. The constraction ratio of 0.1 dosen`t show a noticeable effect on the reattachment length. The separation point length shows that all contraction ratios have similar trend which is inversely proportional to the orientation angle. All the angles of attracting groins don`t from any separation point length. similar bahaviour indicated by the contraction ratio of 0.1 as the spur length too short to formualte any separation point length. The tested orientation angles of repelling groins expect for angle 30 which introduces the longest separation point lenght for all tested contraction ratios. Therefore it`s preferred to use the repelling groin of 30 orientation angle with any contraction ratio as general for the longest upstream protection and the repelling groin of 60 orietation angle with 0.2 contraction ratio for the best upstream and downstream bank protection.