User sub-routine query

MFiX How to
#1

Hi Team, please find attached mfx and usr files for your reference. Before building solver on Linux terminal by issuing mamba activate mfix-23.4.1; build_mfixsolver --batch --dmp, I edit mfx file to add call_usr = .True.
usr1.f (2.7 KB)
VIB_1100_P2S_10X.mfx (14.3 KB)

Question 1: There are 2 jobs: one with usr and another without usr (here, I use default dmp solver). usr oscillates gravity with time, also, sets constant inlet velocity – could you let me know how to ensure that gravity is oscillating? I ask you this because, till the time jobs have progressed in last two days, solution from VTK files look exactly same.

Question 2: Could you please edit this usr for me such that only gravity is oscillated? Setting constant velocity is not needed and I can do it on GUI/text editor. Please remove all unwanted lines with respect to setting velocity as these are unnecessary.

Eagerly waiting for your reply.

Best,

#2

Hi Team, @cgw, good morning. Did U find a chance to look into this request? Thank you,

#3

Hi Jagan,

I have had luck in the past using ‘usr1_des.f’ to oscillate gravity in CFDDEM.

Please find an attached example file.

Best,
Chris
usr1_des.f (2.2 KB)

#4

Hi Team, as a reminder, VTKs from SQP simulation look exactly same whether “usr1.f” is used or not-used. More details are as given in first post of this thread.
usr1.f (2.7 KB)
usr1_des.f (2.2 KB)
A flow-chart in documentation shows using usr1_des.f for DEM. Is usr1.f wrong choice to oscillate gravity? I’ve attached both usr1_des.f and usr1.f, for your reference.

Best,

#5

You are setting GRAVITY_Y in both usr1.f and usr1_des.f. You don’t need usr1.f. If you are troubleshooting, I suggest you only use a handful of particles and even start with a granular flow (this will run faster and show you if you are on the right track).