# Parameter meaning is not clear

 Register Blogs Members List Search Today's Posts Mark Forums Read

 May 4, 2022, 10:09 Parameter meaning is not clear #1 New Member   shuqichang Join Date: Feb 2022 Posts: 22 Rep Power: 4 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.

 May 5, 2022, 09:13 #2 Super Moderator   Arun Kamath Join Date: Nov 2014 Location: Trondheim, Norway Posts: 250 Rep Power: 12 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) __________________ Arun X years with REEF3D

May 5, 2022, 10:08
#3
New Member

shuqichang
Join Date: Feb 2022
Posts: 22
Rep Power: 4
Quote:
 Originally Posted by kamath 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)

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?
Attached Images
 1.jpg (105.1 KB, 12 views)

 May 6, 2022, 03:21 #4 Super Moderator   Arun Kamath Join Date: Nov 2014 Location: Trondheim, Norway Posts: 250 Rep Power: 12 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 __________________ Arun X years with REEF3D

May 6, 2022, 08:56
#5
New Member

shuqichang
Join Date: Feb 2022
Posts: 22
Rep Power: 4
Quote:
 Originally Posted by kamath 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.