This is a test case for algorithms to model the free surface with gravity on an unstructured grid. The new algorithm implemented in SSIIM 2 is much more stable than the old algorithm in SSIIM 1. The spillway is located at 0.8 m above the bed. The channel width is 1 meter, and the spillway width (length of the flat area) is also 1 meter. The discharge is kept konstant at 1 qubic meter/s.

Longitudinal view of the case. The flow is from left to right. The colours shows the pressure, with red as high pressure and blue as low pressure.

The computational time for the case is under 1 minute on a 2 GHz PC.

Some animations have been made using ParaView and Tecplot.

A side-view animation made by ParaView can be downloaded here (7 MB).

A 3D view animation made by ParaView can be downloaded here (12 MB).

A 2D animation made by Tecplot can be downloaded here (8 MB).

A 3D animation made by Tecplot can be downloaded here (9 MB).

The Tecplot animations were made by Nils Rüther. The scales on the Tecplot axis are in meters, and the pressure in Pascal.

Input files for the case:

To test the accuracy of the computation, case ARB1 of Sargison and Percy (2009) was computed. The results are shown below. The difference between upstream water elevation and the crest of the spillway was found to be 0.147 m in the lab experiments and 0.144 m from the numerical model. The difference is 2 %.

A similar case was used for testing OpenFOAM. A web page with more information is given here

References:

Sargison, J. E. and Percy, A. (2009) "Hydraulics of Broad-Crested Weirs with Varying Side Slopes", Journal of Irrigation and Drainage Engineering, ASCE, February, pp. 115-118.

Haun, S., Olsen, N. R. B. and Feurich, R. (2011), Numerical modelling of flow over a trapezoidal broad-crested weir, Engineering Applications of Computational Fluid Mechanics, Vol. 5, No. 3, pp 397-405.

*This page was last updated: 6. February 2012*