Wall BC for TFM simulation

MFiX
#1

Dear MFIX community,
I am simulating a pseudo 2D GAS-SOLID fluidized bed using MFIX-TFM 19.3.0 GUI. I have noticed a discrepancy when setting the BCs for the gas and solid phases. Ideally I would like the gas phase to be ‘NSW’ and for the solid phase ‘PSW’. However when I set the NSW for the gas phase, the same BC is duplicated for the solid phase and vice-versa. How can I go about this? I have attached a MFX file for my case sscp.mfx (29.6 KB)

Partial slip wall: velocity gradient equation
#2

I did not find any issue. Please see the definition of wall boundary condition (bold sentence), that is why you see all wall boundary conditions are set to PSW no matter what boundary condition you chose.

|FREE_SLIP_WALL| |Velocity gradients at the wall vanish. If BC_JJ_PS is equal to 1, the Johnson-Jackson boundary condition is used for solids. A FSW is equivalent to using a PSW with hw=0.|

|NO_SLIP_WALL| |All components of the velocity vanish at the wall. If BC_JJ_PS is equal to 1, the Johnson-Jackson boundary condition is used for solids. A NSW is equivalent to using a PSW with vw=0 and hw undefined.|

|PAR_SLIP_WALL| | Partial slip at the wall implemented as dv/dn + hw (v - vw) = 0, where n is the normal pointing from the fluid into the wall. The coefficients hw and vw should be specified. For free slip set hw = 0. For no slip leave hw undefined (hw=+inf) and set vw = 0. To set hw = +inf, leave it unspecified. If BC_JJ_PS is equal to 1, the Johnson-Jackson boundary condition is used for solids.|

wall_1
wall_11555×882 104 KB

wall_solid
wall_solid1466×878 87.2 KB

2 Likes
Implementing JJ BC for solid phase and NSW for gas phase
#3

Many thanks Gao Xi for the clarification!

#4

Hi,
I am setting NSW boundary condition for the gas phase and JJ PSW for the solid phase in GUI. The wall BC part of the *.mfx file is as follows.

Boundary condition 3: Left wall

bc_type(3)  = 'PSW'
bc_x_e(3)   = 0.0
bc_x_w(3)   = 0
bc_y_s(3)   = 0
bc_y_n(3)   = 0.7
bc_z_b(3)   = 0
bc_z_t(3)   = 0.015
bc_jj_ps(3) = 1
bc_uw_g(3)  = 0.0
bc_vw_g(3)  = 0.0
bc_ww_g(3)  = 0.0
# Solid 1
  bc_c_theta_m(3,1)  = 0.0
  bc_hw_s(3,1)       = 0.0
  bc_hw_theta_m(3,1) = 0.0
  bc_uw_s(3,1)       = 0
  bc_vw_s(3,1)       = 0
  bc_ww_s(3,1)       = 0

I also set the specularity coefficient value to 0.05. But, the time averaged lateral velocity profiles are the same as the case in which specularity coefficient is zero (FSW), when I compare my results with the literature. I have attached the *.mfx file. Is there anything wrong with the BC?
Laverman-2d.mfx (16.6 KB)