Sponge Layer Model Reference

The Sponge Layer model allows you to damp fluctuations in a specified layer next to exterior boundaries. With this approach, disturbances can leave the computational domain without reflecting inside.

Theory See Sponge Layer Model
Provided By [physics continuum] > Models > Optional Models
Example Node Path Continua > Physics 1 > Models > Sponge Layer
Requires
  • Material: Gas
  • Space: Axisymmetric, Two Dimensional, or Three Dimensional
  • Time: Explicit Unsteady, Implicit Unsteady, or PISO Unsteady
  • Flow: Segregated Flow or Coupled Flow
  • Equation of State: Ideal Gas or Real Gas
Properties Key properties are:
  • Relative Amount Of Suppression
  • Sponge Layer Thickness
See Sponge Layer Properties.
Activates Boundary Inputs See Boundary Settings.
SolversOne of:
Field Functions
  • Sponge Layer Boundary Distance
  • Sponge Layer Damping Coefficient
See Field Functions.

Sponge Layer Properties

Relative Amount Of Suppression
The percentual reduction of a disturbance that travels with a the characteristic velocity through the sponge layer, α in Eqn. (4746) with 0≤α<100.
Sponge Layer Thickness
The thickness of the sponge layer, w in Eqn. (4745).
Boundary Distance Method
Specifies the method for computing the sponge layer boundary distance.
The following options are available:
  • Implicit Tree: Calculates the exact boundary distance using an implicit tree algorithm.
  • PDE: Estimates the boundary distance using a partial differential equation (PDE).
The PDE boundary distance calculation is faster, but solving for the exact boundary distance is more accurate.

Boundary Settings

Flow Boundaries
The following boundary condition is available for all boundaries of type:
  • Stagnation Inlet
  • Velocity Inlet
  • Mass Flow Inlet
  • Pressure Outlet
  • Outlet
  • Free Stream
Sponge Layer Option
When On, enables fluctuation damping in the sponge layer next to the boundary. The default is Off.

Sponge Layer Solver Properties

This solver controls the boundary distance computation for the Implicit Tree boundary distance method.

Solver Frozen
When On, the solver does not update any quantity during an iteration. It is Off by default. This is a debugging option that can result in non-recoverable errors and wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.
Verbosity
Controls the level of detail that the solver presents in the Output window.
Allows you to choose how much information Simcenter STAR-CCM+ reports in the Output window while the simulation is running. This property is useful for debugging problems when they occur. The only valid entries are 0, 1, and 2:
  • 0 = None: Leaves output at its default.
  • 1 = Low: Displays CPU time statistics across cores for calculating the boundary distance. It reports the mean, maximum, and minimum elapsed times in seconds.
  • 2 = High: Displays CPU time statistics (see low verbosity) and memory usage statistics across cores. This entry allows you to evaluate the memory consumption of all server processes that are relevant to the boundary distance calculation.

PDE Sponge Layer Solver Properties

This solver controls the boundary distance computation for the PDE boundary distance method.

Maximum Iteration
Sets the maximum number of iterations the solver can use.
Solver Tolerance
Specifies the total relative solver residual.
Under-Relaxation Factor
In order to promote convergence, this property is used to under-relax changes of the solution during the iterative process. If residuals show solution divergence and do not decrease, reduce the under-relaxation factor.
Verbosity
Allows you to choose how much information Simcenter STAR-CCM+ reports in the Output window while the simulation is running. This property is useful for debugging problems when they occur. The only valid entries are 0 and 1:
  • 0 = None: Leaves output at its default.
  • 1 = Low: Displays convergence history for boundary distance and CPU time information.
Reconstruction Frozen
When On, Simcenter STAR-CCM+ does not update reconstruction gradients with each iteration, but rather uses gradients from the last iteration in which they were updated. Activate Temporary Storage Retained in conjunction with this property. This property is Off by default.
Reconstruction Zeroed
When On, the solver sets reconstruction gradients to zero at the next iteration. This action means that face values used for upwinding (Eqn. (905)) and for computing cell gradients (Eqn. (917) and Eqn. (918)) become first-order estimates. This property is Off by default. If you turn this property Off after having it On, the solver recomputes the gradients on the next iteration.
Solver Frozen
When On, the solver does not update any quantity during an iteration. It is Off by default. This is a debugging option that can result in non-recoverable errors and wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.
Temporary Storage Retained
When On, Simcenter STAR-CCM+ retains additional field data that the solver generates during an iteration. The particular data retained depends on the solver, and becomes available as field functions during subsequent iterations. Off by default.

Under-Relaxation Factor Ramp

The PDE Sponge Layer > Under-Relaxation Factor Ramp node allows you to set and control a linear ramp for under-relaxation. For details, see Under-Relaxation Factor Ramp Reference.

AMG Linear Solver

The PDE Sponge Layer > AMG Linear Solver node allows you to set the algebraic multigrid parameters for the solver. For details, see Algebraic Multigrid and AMG Linear Solver Properties.

Field Functions

Sponge Layer Boundary Distance
The normal distance from the cell centroid to the nearest boundary face for which the Sponge Layer Option is activated.
Sponge Layer Damping Coefficient
σsl(d) in Eqn. (4745).