Numerical flow simulation in gated hydraulic structures using smoothed fixed grid finite element method

Successful design and operation of hydraulic structures require more effective and reliable tools to be used in a variety of practical problems, including bottom outlets, intakes and/or spillways. Until recently, physical modeling has been the principal approach in studying the flow pattern and behavior of such structures. The main concerns might generally be related to estimating of discharge coefficients, frictional losses, details of local flow patterns, position of the free surface, and air entrainment. The application of a new developed numerical modeling for free surface flow simulation in gated tunnels is presented here. Among various parameters, the free surface profile, pressure distribution and discharge of the flow passing through gated hydraulic structures are considered in the present study. The solution of free surface flow problems is usually carried out through an iterative process due to unknown geometry and nonlinear boundary conditions. Therefore, the solution of these problems using traditional numerical methods presents some difficulties since the computational mesh needs to be modified for each iteration. The application of the smoothed fixed grid finite element method in the solution of free surface flow problems is investigated in this paper. The main advantage of the proposed method is that it is based on non-boundary-fitted meshes which simplify the solution procedure. In this method, the gradient smoothing technique is used to facilitate formulation of boundary intersecting elements. To evaluate the applicability of the proposed method, three representative examples are solved and the results are compared with experimental and numerical results available in the literature. The results of the present study indicated the power of smoothed fixed grid finite element method in solving the free surface potential flows through gated hydraulic structures.