Vibration UDF for TFM model

MFiX
#1

I am trying to give a sinusoidal vibrational effect on gas phase and solid phase in a fluidized bed(2D TFM).

There will be a displacement due to vibration,
displacement, d = A * sin(2 * pi * f * time)
A: amplitude
f: frequency

and the second derivative of vibrational displacement will be vibrational acceleration.
vibrational acceleration, a = 4 * pi^2 * f^2 * A * sin(2 * pi * f * time)

Using this vibrational acceleration, I want to modify the gravity term in the momentum equation for both gas and solid phases.

g_modified = gravity - a

My question is, can anyone give me some advice/guidance on developing the udf file?
I think the approach is using “usr1.f” and change the GRAVITY_X, GRAVITY_Y, and GRAVITY_Z.
Can anyone share some example on this?

Thanks

KJ

2 Likes
TFM 2D fluizied bed, vibration and microjet effect question
#2

Yes, you can implement this in usr1.

time is accessed from the run module
pi and gravity_y etc are accessed from in the constants module

Make sure to rebuild the solver to include your changes.

1 Like
#3

Hi Jusser

I was working on UDF file for applying vibration effect.
There is too short description in MFIX web at 8.2. User-Defined Functions.
Is there any step by step UDF tutorial I can check?

KJ

1 Like
#4

Check the rotating drum legacy tutorial in legacy_tutorials/DEM_Wall_HT and look at the pdf (see attached excerpt) and study the udfs.

Rotating_gravity
Rotating_gravity1310Ă—725 121 KB

2 Likes
#5

I modified the usr1.f as below,

 SUBROUTINE USR1 

      Use usr
      Use run     
      USE constants
	
      IMPLICIT NONE
!-----------------------------------------------
!
!  Include files defining common blocks here
!
!  Define local variables here
!
!
!  Include files defining statement functions here

  CALL_USR = .TRUE. 

  CONSA = 0.0027   ! Vibration amplitude

  CONSW = 87.1478  ! Vibration angular frequency
	
  SUMA = -CONSA*CONSW*CONSW*SIN(CONSW*TIME)

  GRAVITY_Y = GRAVITY_Y - SUMA

      RETURN  
      END SUBROUTINE USR1

And my question is,

I want to give gravity_y term for both solid & gas phase like shown in attached file.

How can I give gravity_y term for both phases(with fraction and density as well) in the usr1.f?

1234
1234792Ă—173 33.2 KB

1 Like
#6

gravity_y applies to both gas and solids phases. You don’t need to touch the volume fraction and density in usr1.f, this will be handled automatically.

1 Like
#7

Firstly, I put modified usr1.f file in the project file directory.

1
1871Ă—932 140 KB

And then, I got an error message as below after clicking the build solver.

3
3491Ă—873 172 KB

Can you help me with this problem?

Thanks

KJ

#8

The error message points to the issue:

USE constants
Fatal Error: Can't open module file 'constatns.mod' for reading at (1): No such file or directory

The correct module name is constant without the s.

#9

Dear jmusser

Thank you for your reply!

I got an another error message as below,

4
4489Ă—1023 201 KB

#10

I suggest you look for and follow an intro to Fortran. You need to delcare your variables. Also, google is your friend.

#11

Hey Jeff (or anyone),

Where are these legacy tutorials stored now? A simple search for “legacy_tutorials” and “DEM_Wall_HT” comes up with nothing, at least in the mfix-19.3.1 anaconda directory. All the tutorials I’m seeing are new.

Where should the chemical reaction be written？
#12

On the Download page, please go to the “Source/Pip” tab and download the tarball. This contains all source code and legacy tests/tutorials. These are not guaranteed to run in the GUI, you may need to run from command line.

1 Like
#13

Perfect, that’s just what I needed. Thanks!