 ## Fluids

• yyds4092
Subscriber
Hi guys When we turn on the DEM model in Fluent, we can have particle variables like total force and collision force in X Y Z direction and their magnitudes.
In Ansys_Fluent_Users_Guide_2022R1, the total force is defined as:
the total force (body force and volume force) acting on the DEM particle during the DEM collision
and the collision force is defined as:
the body force acting on the DEM particle during the DEM collision
Therefore, I try to figure out what body force and volume force refer to and what differences they have. I looked them up in Ansys theory and users guide but I cannot find any clear definition to distinguish them. Moreover, the book called Engineering fluid mechanics by Graebel William said ''Body forces (sometimes called volume forces) '', which makes this question a little bit silly. However, I compared these two forces in my simulation and they are quite different. I am wondering if anybody could help me out?
• yyds4092
Subscriber
Hi Dr Amine I am wondering if you could give me any advice about this problem or suggest how Fluent DEM calculated these forces.

Sincerely
Yyds4092
• DrAmine
Ansys Employee
• yyds4092 Do you mean the total force is the sum of the forces in the equation above (including collision force) and the collision force is just the force calculated from Collision Laws? I am wondering if there is any reference I could refer to as I want to put these results in my work. 