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 m³/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.

Outlet, given Pressure BC

Grid A a. Outlet, given WSE BC Inlet, Flux BC File:Spure Dike 14.png

Grid B b. Outlet, given WSE BC Inlet, Flux BC File:Spure Dike 15.png

Figure 1. Computational grids used in experiment A1.

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

File:Spure Dike 16.png

=0.03 and

File:Spure Dike 17.png

=0.85. The velocities from

File:Spure Dike 18.png

=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
R2	0.978	0.951	0.975	0.993

Results and Discussion

References

Rajaratnam,N. and Nwachukwu, B.A. (1983). "Flow near groin-like structures." J. Hydraulic Eng., 109(3), 463-480.