ASSESSMENT FLOW 3D PROGRAM EFFICIENCY COMPARING WITH LABORATORY MODELS.

scour a major risks which Threaten Hydraulic Structures that intersect runoff in rivers or in canals and scour increases in times of flood or when the high slope of the river or irrigation canals, which leads to increased flow velocity will be greater than the force of the bottom cohesion of the river bed components or channel, scour treatment neglecting may be lead of hydraulic structures failuer. There are many ways to reduce scour behind hydraulic structures, which rely on the principle of dissipating energy among these methods and the most important is the weirs, the weir is structure placed on a river width or the channel to change the flow characteristics, weirs are smaller than conventional dams, the most important benefits of weirs is to prevent flooding and measure the amount of discharge and raise the water level in the upstream as well as provide assistance to the river navigable and the study migration of fish. The best simulation software to represent the flow and what happens from scour behind the weirs is Flow 3D program, which represents the flow corresponds to the reality of the true representation and to study the efficiency of the program and its ability in represent of flow and study its properties has been applied to some laboratory models for weir made by the researcher (Abdelnasser, 2015) and which has been used different models of weir, were taken one model for three different discharges to examine the program and measure the flow velocity and its depth, and pressure in the upstream and the downstream in addition to measuring the depth and length of the scour. Results of the Flow 3D program is identical for laboratory results as tables (2, 4). Clear that the Flow 3D software program can be relied upon in modeling of flow and find appropriate designs for weirs to its ability in fact represent a real form where provide time and reduces the cost of the work of laboratory models.