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Parameter meaning is not clear

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Old   May 4, 2022, 10:09
Default Parameter meaning is not clear
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shuqichang
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Hi,
I encountered some parameters with unclear meanings during data post-processing. I hope you can help me explain them.
In the REEF3D_CFD_6DOF file:
REEF3D_6DOF_forces_0.dat: Fx_p、Fy_p、Fz_p、Fx_v、Fy_v、Fz_v
REEF3D_6DOF_position_0.dat: Phi、Theta、Psi
Looking forward to your reply.
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Old   May 5, 2022, 09:13
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Arun Kamath
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Hi,
Here is a short explanation of the notation in the outputs you mention
forces:

_p = pressure forces

_v = viscous forces


motions:

Phi- rotational motion around x-axis (roll)

Theta - rotational motion around y-axis (pitch)

Psi- rotational motion around z-axis (yaw)
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Old   May 5, 2022, 10:08
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Quote:
Originally Posted by kamath View Post
Hi,
Here is a short explanation of the notation in the outputs you mention
forces:

_p = pressure forces

_v = viscous forces


motions:

Phi- rotational motion around x-axis (roll)

Theta - rotational motion around y-axis (pitch)

Psi- rotational motion around z-axis (yaw)

Hi,I am very glad to receive your reply.
I understand what these parameters mean, but there are still some problems.
What is the difference between Phi in Reef3D_6DOF_POSItion_0.dat and phi selected by Contour filter when the free surface was obtained in Paraview? There is another parameter phi that I cannot express, so I will show it to you in the figure. Do these three mean different things?
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Old   May 6, 2022, 03:21
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Arun Kamath
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As you might be aware different fields have coincidentally (and unfortunately, but understandably) picked the same alphabets for representing different parameters in that field.

Welcome to computational modelling where you work with all of them together.

When you are looking at the free surface, the function phi is the level set function.

when you are looking at the Laplace equations, Phi is the velocity potential.

when you are looking at floating bodies, phi is the rotation around the x-axis.

You might find several variables which have multiple meanings, but if you look closer and relate them to the equations that are used/ specific field, you will find the answer

Hope that helped
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Old   May 6, 2022, 08:56
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Quote:
Originally Posted by kamath View Post
As you might be aware different fields have coincidentally (and unfortunately, but understandably) picked the same alphabets for representing different parameters in that field.

Welcome to computational modelling where you work with all of them together.

When you are looking at the free surface, the function phi is the level set function.

when you are looking at the Laplace equations, Phi is the velocity potential.

when you are looking at floating bodies, phi is the rotation around the x-axis.

You might find several variables which have multiple meanings, but if you look closer and relate them to the equations that are used/ specific field, you will find the answer

Hope that helped
Thank you very much for your reply. Now I understand the meaning of these parameters.
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