Perturbed Convective Wave Model Reference

The Perturbed Convective Wave model is a hybrid aeroacoustics models that solves a wave equation for the acoustic potential.


Theory	See Perturbed Convective Wave Model.
Provided By	[physics continuum] > Models > Aeroacoustics Models
Example Node Path	Continua > Physics 1 > Models > Perturbed Convective Wave
Requires	Space: Three Dimensional Time: Implicit Unsteady Material: any but Solid or Multi-Component Solid Flow: any Equation of State: Constant Density Optional Models: Aeroacoustics
Properties	See Perturbed Convective Wave Properties.
Activates	Materials	See Material Properties.
	Boundary Inputs	See Boundary Settings.
	Region Inputs	See Region Settings.
	Interface Inputs	See Interface Settings.
	Solvers	Perturbed Convective Wave See Perturbed Convective Wave Solver Properties.
	Field Functions	Acoustic Density Acoustic Potential Acoustic Pressure Acoustic Source Acoustic Velocity Incompressible Pressure Fluctuation Pressure Perturbation See Field Functions.

Perturbed Convective Wave Properties

Reference Speed of Sound

The speed of sound,

c_{0}

in Eqn. (4735).

Secondary Gradients

Neglect or include the boundary secondary gradients for diffusion and/or the interior secondary gradients at mesh faces.

On: Include both secondary gradients.
Off: Exclude both secondary gradients.
Interior Only: Include the interior secondary gradients only.
Boundaries Only: Include the boundary secondary gradients only.

Material Properties

Speed of Sound

The speed of sound,

c_{0}

in Eqn. (4735).


Method	Corresponding Method Node
Constant Specifes the speed of sound using a scalar profile value.	Constant Specifies the speed of sound $c_{0}$ .
Ideal Gas (Density and Reference Pressure) Calculates the speed of sound using the ideal gas law as: $c_{0} = \sqrt{\frac{γ p_{0}}{ρ}}$ with: $γ = \frac{C_{p}}{(C_{p} - \frac{R}{M})}$ where: $p_{0}$ is the reference pressure $ρ$ is the density. $C_{p}$ is the specific heat capacity. $R$ is the universal gas constant. $M$ is the molecular weight.	Ideal Gas (Density and Reference Pressure) This node provides no properties. Selecting this method adds the following material property: Molecular Weight Specifies the molecular weight $M$ . Heat Capacity Specifies the specific heat capacity $C_{p}$ .
Ideal Gas (Reference Temperature) Calculates the speed of sound using the ideal gas law as: $c_{0} = \sqrt{γ R T_{0}}$ with: $γ = \frac{C_{p}}{(C_{p} - \frac{R}{M})}$ where $T_{0}$ is the reference temperature.	Ideal Gas (Reference Temperature) Exposes the following property: Reference Temperature Specifies the reference temperature $T_{0}$ . Selecting this method adds the following material property: Molecular Weight Specifies the molecular weight $M$ . Heat Capacity Specifies the specific heat capacity $C_{p}$ .

Boundary Settings

Wall

Acoustic Specification

Specifies how the wall boundary acts on the acoustic potential.

Method	Corresponding Physics Value Nodes
None The wall boundary has no specific acoustic potential but is a reflecting boundary.	None
Specified Sets a specified acoustic potential at the wall boundary.	Acoustic Potential Specifies the acoustic potential at the wall.
Non-reflecting The wall is a non-reflecting boundary. The acoustic potential is absorbed at the boundary.	None
Partially Absorbing The wall boundary partially absorbs the acoustic potential.	Partial Wall Absorption Coefficient Specifies the fraction of acoustic potential that is absorbed at the wall as a value between 0 and 1.

Symmetry Plane

Acoustic Specification

Specifies how the symmetry plane boundary acts on the acoustic potential.

Non-reflecting	Corresponding Physics Value Nodes
On The symmetry plane boundary is non-reflecting. The acoustic potential is absorbed at the boundary.	None
Off The symmetry plane boundary is a reflecting boundary.	None

Flow Boundaries

The following boundary condition is available for all boundaries of type:

Mass Flow Inlet
Stagnation Inlet
Velocity Inlet
Pressure Outlet
Outlet

Acoustic Specification

Specifies how the flow boundary acts on the acoustic potential.

Profile
On Sets a specified acoustic potential profile at the boundary.	Acoustic Potential Specifies the acoustic potential at the boundary.
Off The flow boundary is a non-reflective boundary. The acoustic potential is absorbed at the boundary.	None

Region Settings

Applies to fluid regions.

Acoustic Damping Coefficient: $b_{d}$ in Eqn. (4736) (0 for no damping and 1 for maximum damping).
Noise Source Weighting Coefficient: Specifies a weighting coefficient in the calculation of the incompressible pressure fluctuation $p_{i n c}^{f}$ (1 for computing $p_{i n c}^{f}$ and 0 for removing $p_{i n c}^{f}$ ).
User Defined Noise Source: $S_{ϕ^{a}}$ in Eqn. (4735).

Interface Settings

Applies to porous baffle interfaces.

Porous Baffle Acoustic Option

Specifies how the porous baffle interface acts on acoustic waves.


Porous Baffle Acoustic Option	Corresponding Physics Value Nodes
Reflecting Acoustic waves reflect from the porous baffle interface interface as they reflect from a solid wall. The acoustic source terms are calculated assuming zero velocity at the interface.	None
Transparent Acoustic waves travel through the porous baffle interface as they travel through an internal interface. No reflections occur. The sound sources are calculated assuming a continuous, smooth velocity field across the interface.	None

Perturbed Convective Wave Solver Properties

Similar to the flow solvers, the Perturbed Convective Wave solver uses the AMG Linear Solver infrastructure that is provided in Simcenter STAR-CCM+.

Start Time: The elapsed simulation time before the Perturbed Convective Wave solver begins calculating.
Acoustic Sub Time-Step: When Off, performs one acoustic time-step after each flow time-step.; When On, performs two acoustic time-steps after each flow time-step.; Activate this option when you encounter instabilites of the Perturbed Convective Wave solution.
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.
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.
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.
Newmark-Alpha Parameter: The parameter value for the Newmark-alpha method of numerical time integration that is used in the Perturbed Convective Wave solver, $α$ in Eqn. (4743).
Maximum Number of Iterations: Maximum number of inner iterations executed by the Perturbed Convective Wave solver.
Convergence Tolerance: The solver convergence limit to break out of the inner iterations.

Field Functions

Acoustic Density: $ρ_{a}$ in Eqn. (4739).
Acoustic Potential: $ϕ^{a}$ in Eqn. (4735).
Acoustic Pressure: $p^{a}$ in Eqn. (4738).
Acoustic Source: The right-hand side of Eqn. (4735).; This field is only available when the Temporary Storage Retained option is activated for the Perturbed Convective Wave solver.
Acoustic Velocity: $v^{a}$ in Eqn. (4740).
Incompressible Pressure Fluctuation: $p_{i n c}^{f}$ in Eqn. (4735).; This field is only available when the Temporary Storage Retained option is activated for the Perturbed Convective Wave solver.
Pressure Perturbation: The pressure perturbation $p^{p}$ , calculated as:; $p^{p} = p_{i n c}^{f} + p^{a}$; where $p_{i n c}^{f}$ is the incompressible pressure fluctuation and $p^{a}$ is the acoustic pressure.