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How to get the real height?

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Hi there,

I have a problem to locate the actual height in a certain location. When I have a look at predefined point of my OC, the value of the elevation is above the WSEs height. Additionally, the height of the GRID - while using the plot wizzard - is differnt to the height of the elevation of the generated mesh! Now I´m not sure about the reliability of my model. Could anyone explain the reason for these circumstances?

kind regards

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Could you please identify the model that you are using?

Rusty

Hi there,

I have a problem to locate the actual height in a certain location. When I have a look at predefined point of my OC, the value of the elevation is above the WSEs height. Additionally, the height of the GRID - while using the plot wizzard - is differnt to the height of the elevation of the generated mesh! Now I´m not sure about the reliability of my model. Could anyone explain the reason for these circumstances?

kind regards

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TUFLOW is a little bit different than our other models with the input going in on a grid and the output comes out on a 2D mesh. It works well since this gives it the opportunity to mix 1D and 2D domain data in the output mesh. The elevation values going in come from 9 locations on each cell the corners, each of the cell faces, and the center point. The solution is computed at the cells. The default is to show the solution on the 4 corner nodes of each element so the data is interpolated to these locations. Since the elevations at each node come directly from the input grid and the solution values are interpolated from the 4 neighboring cells, it is possible to incorrectly show a negative depth. One thing you might try is to change the output option to have TUFLOW display the solution on all 9 cell locations. This is done by changing the format in the Output Options tab to "SMS High Res." In this format the values at the cell centers will be the computed values and the corners will be interpolated. So the actual elevations and depths can be seen at the center nodes.

TUFLOW can also sometimes generate negative depths when doing its calculations. You can see these in the screen output as TUFLOW runs, in the tlf file, or by loading the _messages.mif file. Negative depths are a sign of an unhappy model. When this happens you should read in the _messages.mif file to see where the instabilities are happening. It sometimes helps to smooth the bathymetry in this area. You can do this manually or by right clicking on the grid and choosing smooth. You can also try lowering the timestep and in rare cases even increase the number of iterations.

I hope this helps.

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