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Old   December 23, 2021, 03:54
Default Force and Pressure
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Ismael Incoencio
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Hi all, it's been a while. I just wanted to ask if there is a paper/reference on how the force computation if I use the force box or how the pressure is computed? I am trying to validate the hydrodynamic forces on a stepped outfall with some baffles that our structural team has to consider. I have attached a snippet of the results; on the left is a slice just above the first step showing the Pressure, while the image on the right just shows the velocities.
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Old   December 23, 2021, 07:19
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Felix S.
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Hey,

This here helps me all the time: https://doi.org/10.1016/j.compfluid.2016.09.012
Maybe the official team has something even better.

It is stated the force F is calculated by:

F = \int_\Omega \left(-\textbf{n}p + \textbf{n} \cdot  \tau \right)d\Omega

with:
\Omega: surface
\textbf{n}: unit normal vector
p: pressure
\tau: viscous stress tensor

The exact paragraph reads:

"The pressure p and the normal component of viscous stress tensor \tau are integrated over the surface \Omega of the structure. The integration is performed in a discrete manner, by using p and \tau for each cell surface of the structure:"; then the forumla
"here \textbf{n} is the unit normal vector to the surface, pointing into the fluid. The Navier-Stokes equations in Eq. (2) are solved including the gravity term. Then the pressure obtained from the projection method includes the hydrostatic part in addition to the dynamic part. Consequently, it is the total force acting on a structure that is determined by Eq. (28)."

Happy holidays!
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Old   January 20, 2022, 02:07
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Ismael Incoencio
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Thanks Felix, apologies for the late reply. I will look into this paper; it looks like they have also published it on the Reef3D main website. https://reef3d.files.wordpress.com/2...wt_cf-2016.pdf
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Old   January 20, 2022, 03:31
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Arun Kamath
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The postscript versions of all our publications are/will/should be available on the REEF3D homepage.
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