There are many different types of scour protection structures. The groyne is an obstacle located at the outer bank of a channel, reducing the water velocity and scour potential.
The flow in a channel with one or more groynes mounted perpendicular to the flow direction was in 1993-1995 used by Hydraulic Research Wallingford, UK, to test CFD models. A number of groyne and geometry configuratios were tested. Physical model tests were done, enabeling verification of the CFD model.
In the present study, a single groyne in a straight channel was tested. The case was run with the following parameter variations:
- The number of grid cells was varied
- Two discretization schemes were tested
- A stress term in Navier-Stokes equation, that had previously
been neglected, was introduced
- The upstream boundary condition was varied
- The roughness was varied
3D view of the bed, shown as a blue grid, and several longitudinal velocity profiles, with colours showing the horizontal velocity. The groyne is shown in black. The flow direction is from left to right.
Longitudinal profile close to the right bank. The colours show the horizontal velocity.
Longitudinal profile at the middle of the groyne. The colours show the horizontal velocity.
Longitudinal profile at the tip of the groyne. The colours show the horizontal velocity
Plan view close to the bed. The colours show the horizontal velocity.
Plan view at 15% distance from the bed. The colours show the horizontal velocity.
Plan view close to the water surface. The colours show the horizontal velocity.
Plan view close to the water surface. The colours show the vertical velocity.
The results above show the best case. Tests with a finer grid showed the results to be grid-independent.
Changing the roughness and including a previously neglected term in the Boussinesq approximation did not give significant changes in the results. Using the second-order upwind scheme, the recirculation zones and secondary currents were slightly larger than using the first-order upwind scheme.
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