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You are here: Tutorials > Mixing Tank > Setting up the model > Defining Physics and Conditions

Defining Physics and Conditions

The physics and conditions are specified as follows.

Add Modules
  1. Click Select Modules in the Model Panel. The Physical Model Selection dialog box opens.
  2. Select Turbulence in the Available Modules list and click Add.
  3. Select Species in the Available Modules list. Enter 1 in the Module Name and click Add.

  4. Click Close to close the Physical Model Selection dialog box.

  

Figure 11.289 - Adding modules
Operating Parameters
Common
  1. Select Common in the Model Panel.
  2. Select Transient from the Time Definition drop-down list in the Model Tab of Properties Panel.
  3. Enter 20 for Number of Iterations.
  4. Enter Simulation Time (Duration) as 10 s and Number of Time Steps as 400 for the Time Definition list.
  5. Enter 100 for Result Saving Frequency.
  

Figure 11.290 - Common Operating parameters
Boundary Conditions

The boundary conditions are specified as follows.

Rotor Volume
  1. Select mixingtank_rotor from the Volumes list in the Geometric Entities Panel.
  2. Select Volume Remesh for Common drop-down list in the Model Tab of Properties Panel.
  3. Select Counter Clockwise for Rotational Direction.
  4. Enter 120 rpm for Rotational Speed under the Flow.
  5. Enter 0, 0, 0 for Rotational Center and 0, 0, 1 for Rotational Axis Vector.
  

Figure 11.291 - Rotor Volume conditions

 

Rotor Boundary
  1. Select mixingtank_rotor and mixingtank_stator_shaft from the Boundaries list in the Geometric Entities Panel.
  2. Select Rotating Wall under Flow drop-down list in the Model Tab of Properties Panel.
  3. Select Counterclockwise for Rotational Direction.
  4. Enter 120 rpm for Rotational Speed.
  5. Enter 0, 0, 0 for Rotational Center and 0, 0, 1 for Rotational Axis Vector.
  

Figure 11.292 - Rotor Boundary conditions
Fluid Properties
  1. Select Volumes in the Geometric Entities Panel.
  2. Enter 998 kg/m3 for Value under the Common list in the Model Tab of Properties Panel.

  3. Enter 0.001003 Pa-s for Value under Viscosity in the Flow list.

Initial Conditions
  1. Click Edit Expressions icon on the View Toolbar or in the Value under Initial Condition drop-down list, to open the Expression Editor dialog box.
  2. Enter the following for Global Expressions, (see Figure 11.293).
    species_initial_level= (z>1) ? 1 : 0.
  3. Click OK, to close the Expression Editor dialog box.
  4. Enter species_initial_level for Value under Initial Condition drop-down list in the Species list.
  5. The user needs to copy and paste the sample expression written under Description drop-down list for Global Expressions editor of Simerics-MP under the Uniformity Index expressions .

 

  

Figure 11.293 - Fluid properties and Initial condition
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 Simerics-MP is used to evaluate the quantitative change in the Volume Weighted Uniformity Index of Species and Volume Average Species.

The volume averaged phi for and weighted uniformity index is calculated using following equation.

volume averaged phi: phi_a = Sum(phi)/volume

volume weighted uniformity index: u_i = sum(abs(phi-phi_a))/volume/phi_a

ClosedDescription

 

# 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 variables will show in XY-plot variable list when click on "Common" in "Model" panel. #

##############################################################################

# interested variable

phi = species.1.C

# Volume Weighted Uniformity Index

# ==============================

# step 0: calculate total volume

# ------------------------------------

#vol_t = integral(1, volume.mixingtank_rotor)+integral(1, volume.mixingtank_stator)

vol_t = 1.08811

# step 1: calculate volume averaged phi for all volumes

# --------------------------------------------------

phi_t = integral(phi, volume.mixingtank_rotor)+integral(phi, volume.mixingtank_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.mixingtank_rotor)+

integral(abs(phi-phi_a), volume.mixingtank_stator) )/ phi_a /vol_t

# step 3: add plot variable

# -------------------------

plot.phi_awui = phi_awui

#plot.phi_awui: Volume Weighted Uniformity Index Species 1 [-]

  Note:For more information, refer Expression Editor.

 

 

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