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apeech

31/05/2016 22:05:51

Please look at the following images:

http://imgur.com/a/FEXim

 

As noted above each image, the grid size was changed each time the simulation was run. Absolutely nothing else changed, the flow rate coming in is the same in each flood scenario, time step is set at 1 second.

Why is there a drastically different amount of water flowing across the property when higher grid size is selected? If I lower the grid size even more, there is even less water coming across the property. I'm not sure which I'm supposed to clam is an accurate depiction of water in the flood scenario....

There is a green polyline (exit boundary) at the edge of the property. With the smaller grid size, is more water draining outside of the active area?

davehughes87

31/05/2016 22:37:20

Hi there,

My initial guess from looking at the mapping is that there are some features in your underlying elevation data (e.g. the roads) that are being picked up differently in the 8m grid model to the larger grid sizes. Perhaps use a z-line to ensure that the elevations along the road are being set at the correct elevations in the larger grid simulations? Or stick with the 8m grid if you trust the elevations in the model.

Perhaps take a look at section 3.3.1 of the TUFLOW manual to see how grid size can affect simulation results - depths, velocities, everything! (I know this is Flood Modeller - but the same basic principles apply.)

Hope that's clear!

Dave

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