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-   -   Spillway symulation (https://www.cfd-online.com/Forums/flow-3d/64512-spillway-symulation.html)

 Ghirghidov May 13, 2009 10:46

Spillway symulation

I solve a problem - a sloping spillway. The grid consists cubes and therefore spillway looks as a stairway. Is it possible to exclude this effect from simulations

Thanks a lot.

 otd May 13, 2009 20:34

Make your mesh slope by rotating the gravity vector.

The bed of your channel should be 0 < x < L. The bed is tilted at an angle Q from horizontal and lies along the y = 0 line (x axis). The gravity vector G = abs(G)cosQ + abs(G)sinQ. Make sure your signs are all OK - this is written pretty sloppy.

Good luck.

 Ghirghidov May 15, 2009 03:22

I am not sure I understand the F3D possibility right. Does this mean I have to rotate spillway, topography and water also?

 otd May 15, 2009 09:33

The equations you're solving can be expressed in a variety of coordinate systems. It seems to me that system you need is for the x axis to coincide with the bottom of your spillway and the y axis to be perpendicular to the bottom of the spillway. In this system, your solid boundary coincides with the x axis (y = 0) and your boundary has no staggered blocks in it.

You pick the system - that is, you "tilt" the spillway by changing the orientation of the gravity vector relative to the coordinate system.

The gravity vector has two components. The x component in your new coordinate system points along the main flow direction - it drives the flow. The y component is no longer "straight down" but is perpendicular to the bottom of your spillway.

The solution flow-3d calculates, u, v, p, is in the tilted system. The symbols don't change, they just need to be interpreted in the tilted system.