Mixing Tank: Exercise 5—Assigning Boundary Conditions
For boundary conditions, the fluid behavior and properties are specified at all bounding surfaces of the fluid domain.
Specifying Boundary Conditions
1. Under Boundary Conditions, select FLUID_ROTOR.
2. In the Model tab, select the following values for the options listed:
◦ Flow — Rotating Wall
◦ Rotational Direction — Counterclockwise
◦ Rotational Speed — 12.57 rad/s
◦ Rotational Axis Vector — 0,0,1
◦ Rotational Center — 0,0,0
Specifying Volume Conditions
1. Under
Domains, select
FLUID_ROTOR.
2. In the Model tab, select the following values for the options listed:
◦ Common > Volume Remesh— Volume Remesh
◦ Method — Rotation
◦ Rotational Direction — Counterclockwise
◦ Rotational Speed — 12.57 rad/s
◦ Rotational Axis Vector — 0,0,1
◦ Rotational Center — 0,0,0
Specifying Volume Conditions for Materials
1. To set the fluid, click
Materials. The
Material Selection dialog box opens. The fluid properties are set automatically when you select a new fluid.
2. For all the fluid domains, select water.
3. Select
Domains in the Flow Analysis Tree
4. In the Model tab, for Flow, set the following values for the options listed:
◦ Viscosity — Constant Dynamic Viscosity
◦ Value — 0.001003 Pa-s
Specifying Initial Conditions for Species
1. In the Flow Analysis Tree, select
Physics.
2. In the
Operations group, click
Expression Editor.
3. In the Expression Editor box, enter the following:
# Species initial condition
species_initial_level= (z>1.00) ? 1 : 0
##############################################################################
# Output Volume Weighted Uniformity Index #
# ------------------------------------------------------------------------ #
# In this example, the volume weighted uniformity index for concentration of "1" on whole volume were calculated and added as XY-plot variable #
# The variable is plotted by selecting "Common" in the Flow Analysis tree. #
##############################################################################
# interested variable
phi = species.01.C
# Volume Weighted Uniformity Index
# ==============================
# step 0: calculate total volume
# ------------------------------------
#vol_t = integral(1, volume.FLUID_ROTOR)+integral(1, volume.FLUID_STATOR)
vol_t = 1.08811
# step 1: calculate volume averaged phi for all volumes
# --------------------------------------------------
phi_t = integral(phi, volume.FLUID_ROTOR)+integral(phi, volume.FLUID_STATOR)
phi_a = phi_t/vol_t
# step 2: calculate volume weighted uniformity index
# ------------------------------------------------
phi_awui = 1 - 0.5*( integral(abs(phi-phi_a), volume.FLUID_ROTOR)+
integral(abs(phi-phi_a), volume.FLUID_STATOR) )/ phi_a /vol_t
# step 3: add plot variable
# -------------------------
plot.phi_awui = phi_awui
#plot.phi_awui: Volume Weighted Uniformity Index Species 1 [-]
4. Click OK.
5. Select
Domains in the Flow Analysis Tree
6. In the Model tab, for Species 01.
7. For Initial Condition, set Value to species_initial_level
Uniformity Index
Generally, mixing performance is evaluated by visual uniformity and quantitative change in local concentration as a function of time and average concentration. The
Expression Editor in
Creo Flow Analysis evaluates the quantitative change in the Volume Weighted Uniformity Index of Species and Volume Average Species.
The volume averaged phi and weighted uniformity index are calculated using the following equations:
volume averaged phi: phi_a = Sum(phi)/volume
volume weighted uniformity index: u_i = sum(abs(phi-phi_a))/volume/phi_a