# Spure Dike

## Experiment Setup

The laboratory flume experiment of Rajaratnam and Nwachukwu (1983) consists of a rectangular 37 x 0.92 m flume with open-channel flow and a thin plate of length 0.1524 m used to simulate a groin-like structure. Here the numerical model is compared to experiment A1 of Rajaratnam and Nwachukwu (1983). For this case, the flow depth and discharge were 0.189 m and 0.0453 m^{3}/sec, respectively.

## Model Setup

The computational grid size is 152 x 36 and has a variable grid resolution of 0.01 to 0.05 m (Figure 1). The mesh was refined manually near the structure, near the walls within the recirculation zone behind the structure. A constant flux was specified at the inflow boundary and a zero water level at the outflow boundary.

## Results

Flow velocities were measured down stream of the flow structure along 4 transects in the transverse direction and at two arbitrary levels or heights y/y0=0.03 and y/y0=0.85. The velocities from y/y0=0.85 are compared to the calculated depth-averaged velocities and are shown in Figure 2.

**Table 1. Goodness of fit statistics for U-velocity, m/s**

Transect 1 |
Transect 2 |
Transect 3 |
Transect 4
| |

RMSE | 0.0504 | 0.0690 | 0.0557 | 0.0627 |

RMAE | 0.0239 | 0.0725 | 0.0884 | 0.1038 |

R^{2} |
0.978 | 0.951 | 0.975 | 0.993 |

- For a definition of the goodness of fit statistics see Goodness of fit statistics.

## References

- Rajaratnam, N. and Nwachukwu, B.A. (1983). "Flow near groin-like structures."
*Journal of Hydraulic Engineering*, 109(3), 463-480.