Simcenter STAR-CCM+ Evaluate Residence Time Distributions on Outlets

For many Lagrangian evaluations in Simcenter STAR-CCM+ the boundary sampling is a very good choice. It stores all the particles in contact with a boundary for one time step (or iteration in steady state mode). This is important as Lagrangian particles use a different time step as the CFD solver. In transient simulations the information needs to be accumulated for more than one time step. 

For particle size distributions more simple methodologies should be preferred. These are discussed in Evaluate Particle Size Distribution on Outlets. These methods use a second evaluation Lagrangian Phase to store the data. A parcel transfer injector is used to re-create the particles. Unfortunately, this injector cannot be used for the residence time.

Please find an example simulation attached. In this picture you can see how the residence time distribution is very different for the two outlets. BS1 is the bottom surface. Particles hit it very quickly. BS 2 is the upper outlet facing the camera. Here particles need at least one revolution before hitting the outlet.

An alternative to the parcel transfer injector is described in this article. A table is used to store the particle data and a table injector is used to inject the exact same parcels into the evaluation phase for accumulation.

1. Copy the original Lagrangian Phase 1.
   • Rename the new phase to 'evaluation'.
   • Remove Two-Way Coupling model if applicable.
   • Remove additional models not needed for the evaluation.
   • (Add model Parcel Depletion and Residence Time model.) see below
2. In the original Lagrangian Phase activate the Boundary Sampling model.
   • Add the outlets to the boundaries.
   • Add all relevant field functions (Parcel Mass, Particle Diameter, Particle Residence Time and possibly Injector Index).
3. Create a new User Field Function and name it 'ParticleMassFlowRate'. This calculates the necessary injection mass flow rate.
   • Definition: $ParcelMass / $TimeStep
4. Do the next steps for the newly created Lagrangian Phase.
   • Change the boundary interaction type on the outlets to phase impermeable
     Regions > Region 1 > Boundaries > Outlet > Phase Conditions > Phase 1 > Type > phase impermeable
   • A new boundary condition is created for the Lagrangian phases. Change the mode on the Phase Impermeable boundaries to Stick.
     Continua > Physics 1 > Models > Lagrangian Multiphase > Lagrangian Phases > Phase 1 > Boundary Conditions > Phase Impermeable > Physics Conditions > Mode > Stick
   • Add the Passive Scalar model and create a new passive scalar.
   • rename it to Residence_Time 
   • You may repeat these two steps for more information like Injector index, particle temperature or other passive scalars
5. Create a new XYZ-Table
   • Parts > The boundary sampling created in 2.
   • Scalars > The field functions selected in 2 and the function created in 3.
   • Activate the Auto Extract Update for each time step.
6. Create new injector
   • Lagrangian Phase > 'evaluation'
   • Type > Table Injector
   • Input > All Regions
   • Conditions > Flow Rate Distribution > Per Injection Point
   • Under Values > Injection Points Table > select the table created in 5.
   • Values >  Particle Diameter > Injection Table  > Track: Particle Diameter
   • Values > Mass Flow Rate > Injection Table > ParticleMassFlowRate
   • Values > Velocity > Injection Table > Track: Particle Velocity X ...
   • Values > Passive Scalar > Injection Table > Match the Data Names
     •  Residence_Time > Track: Particle Residence Time
7. You can identify the particles on the outlet easily as they are in the 'evaluation' phase. The particles sticking to a boundary also get the 'Boundary Index' Field Function which might be used in a Threshold Derived Part.