Showing papers on "Groyne published in 1990"

2‐D Depth‐Averaged Flow Computation near Groyne

Abstract: The depth-averaged velocity and bottom shear stress distributions in a rectangular channel near a groyne are computed by using a 2-D depth averaged model. The model uses a hybrid finite difference scheme and an iterative method to solve the governing equations of flow and turbulence transport. Due to streamline curvature effects in the region near the groyne tip, a correction factor is incorporated into the \Ik\N=ϵ\N turbulence model that significantly improves the agreement between the computed and experimental data of the velocities and of the streamline pattern compared to previous numerical methods. In this region the bottom shear stress is found to be largely influenced by the 3-D effects. A 3-D correction factor is introduced which considerably improves the computed bottom shear stresses. Sensitivity analysis is made on the \Ik\N=ϵ\N model coefficients and on the correction factors of the streamline curvature and the 3-D effects. The experimental errors in the velocity and bottom shear stress measurements are analyzed. The average errors between the computed and previous experimental results are presented with confidence intervals.

Beach and dune nourishment in the netherlands

Abstract: In the Netherlands up to the fifties of this century, dike and groyne building were the most important coastal defence measures Because of the increased awareness of the importance of the sandy coast the demand for a more environmentally friendly coastal protection measure increased However, artificial beach nourishment was very expensive In the past two decades the costs of nourishment have decreased as a result of technical developments in the dredging industry, and erosion control by means of sandfills has become in general cheaper than the construction of groynes and dikes In that period also large volumes of sand have become available from harbour extension and maintenance dredging These have been the conditions that led to a new coastal defence method Up till now nearly 50 beach nourishment projects have been carried out, with a total amount of 60 million m This paper provides a review of the projects carried out in the last 4 decades, with a description of the most important aspects

Three-Dimensional Modelling of Recirculation Behind a Groyne

Abstract: Extensive investigation on the three-dimensional flow patterns behind a groyne have been carried out in a small-scale experiment. A three-dimensional hydrodynamic numerical model is verified on the basis of these data. The main point of interest is the correct reproduction of the eddy formation its size, and the reattachment point. The representation of the turbulance and of the wall boundary turns out to be most important to reproduce the essential features of the measured data. Two improvements are carried out. First a mixing length formulation for the vertical domains is used. The second improvement concerns the boundary representation at the wall. A Neumann boundary condition to simulate the turbulent boundary layer is implemented. The results of the numerical studies demonstrate the applicability and the validity of the three-dimensional numerical model for simulation of complex flow patterns behind a groyne.