Acoustic Suppression Zone Model Reference

The Acoustic Suppression Zone model suppresses spurious reflective disturbances in unsteady aeroacoustic simulations.


Theory	See Acoustic Suppression Zone Model (Deprecated).
Provided By	[physics continuum] > Models > Optional Models
Example Node Path	Continua > Physics 1 > Models > Acoustic Suppression Zone (Deprecated)
Requires	Material: Gas or Liquid Space: Three Dimensional Time: Explicit Unsteady, Implicit Unsteady, or PISO Unsteady Flow: Coupled Flow or Segregated Flow Equation of State: Constant Density, Ideal Gas, or Real Gas Gradient Metrics: Gradients (selected automatically)
Properties	Key properties are: Flow Conditions Option, Relaxation Coefficient Option. See Acoustic Suppression Zone Properties.
Activates	Physics Models	Acoustic Suppression Zone Boundary Distance Model: Acoustic Suppression Zone Boundary Distance (selected automatically)
	Model Controls (child nodes)	See Computed Relaxation Coefficient.
	Boundary Inputs	See Acoustic Suppression Zone Boundary Settings.
	Region Inputs	See Acoustic Suppression Zone Region Settings.
	Field Functions	Acoustic Suppression Zone Relaxation Coefficient Acoustic Suppression Zone specific continuity source Acoustic Suppression Zone specific energy source Acoustic Suppression Zone specific momentum source See Acoustic Suppression Zone Field Functions.

Acoustic Suppression Zone Properties

Verbose

When On, displays the operations that are performed to compute Continuity, Momentum, or Energy source. The default is Off.

Continuity source

When On, the default, specifies

- σ (ρ - ρ_{r e f})

as a damping term. See Eqn. (4749).

Momentum source

When On, the default, specifies

- σ (ρ v - ρ_{r e f} v_{r e f})

as a damping term. See Eqn. (4749).

Energy source

When On, the default, specifies

- σ (ρ E - {ρ_{r e f} E}_{r e f})

as a damping term. See Eqn. (4749). Avoid using the Energy source with the segregated solver.

Flow Conditions Option

Specifies the flow conditions within the Acoustic Suppression Zone.

Specified Per-Region: Adds three nodes under Physics Values for the region: Acoustic Suppression Zone Pressure, Acoustic Suppression Zone Velocity, and Acoustic Suppression Zone Temperature. In each of these nodes, you can specify the values by Constant, Field Function, Table, or User Code. This method is the default.
Computed Average: The Acoustic Suppression Zone reference state is defined as the average per boundary of pressure, temperature, or velocity, for all boundaries using Acoustic Suppression. Useful for far-field boundary conditions, this option computes one global average for the Acoustic Suppression Zone reference pressure, velocity, or temperature, for all selected boundaries. Averaging continues for the duration of the simulation.

Relaxation Coefficient Option

Specifies the relaxation coefficient

σ

used in Eqn. (4749).

Use Boundary Distance: Computes the relaxation coefficient $σ$ , based on the boundary distance from the selected boundaries and the maximum specified value for the relaxation coefficient.
Adds a node under the Acoustic Suppression Zone model node, called Computed Relaxation Coefficient, which lets you specify Maximum Relaxation Coefficient (default value, 0) and Acoustic Suppression Zone Thickness (default value, 0).
Specify Per-Region: Specifies the relaxation coefficient $σ$ for any selection of regions, positioning the Acoustic Suppression Zone anywhere in the domain.
Adds a node under Physics Values for each region, the Acoustic Suppression Zone Relaxation Coefficient node. In each of these nodes, you can specify the values by Constant, Field Function, Table, or User Code.

When Flow Conditions Option is set to Specified Per-Region, set the values for $p$ , $v$ , and $T$ to the local flow mean values of the unsteady flow field. The pressure $p$ and temperature $T$ are used to compute the reference density $ρ_{r e f}$ . The model assumes that a statistically steady-state flow is achieved before starting to accumulate the flow-mean values.

The Acoustic Suppression Zone model is unlikely to work properly with ill-posed Flow Conditions values, or with aggressive or even discontinuous distributions (in space and time) of the relaxation coefficient $σ$ . Set the Suppression Zone to at least 5–7 (representative) wave-lengths wide and to avoid numerical instabilities in the simulation, increase the Maximum Relaxation Coefficient gradually.

Computed Relaxation Coefficient Node

The model calculates the value of the relaxation coefficient $σ$ based on the values of the properties of this node.

Maximum Relaxation Coefficient: $σ_{\max}$ , the inverse of the relaxation time. The default value is 1.0 /s. See Eqn. (4749).
Acoustic Suppression Zone Thickness: The width $w$ of the Acoustic Suppression Zone. The default value is 0.0 m. See Eqn. (4749).

Acoustic Suppression Zone Boundary Settings

Free Stream, Mass Flow, Inlet, Pressure Outlet, Stagnation Inlet, Velocity Inlet

Acoustics Suppression Zone Option: When On, enables Acoustic Suppression Zone calculations for the boundary. The default is Off.

Acoustic Suppression Zone Region Settings

Applies to fluid regions.

Acoustic Suppression Zone Pressure

Use values from a previous steady time run. This physics value has the following properties:

Method: Standard profile methods are available. The default is Constant.
Value: The pressure in the Acoustic Suppresion Zone. The default is 0.0 Pa.
Dimensions: The dimensions of the pressure. Read-only.

Acoustic Suppression Zone Velocity

Use values from a previous steady time run. This physics value has the following properties:

Method: Standard profile methods are available. The default is Constant.
Value: The fluid velocity in the Acoustic Suppression Zone. The default is [0.0, 0.0, 0.0] m/s.
Dimensions: The dimensions of the fluid velocity. Read-only.
Coordinate System: Specifies the coordinate system for defining the fluid velocity. The drop-down list of this property includes any local coordinate systems that exist in the simulation. The default is Laboratory.

Acoustic Suppression Zone Field Functions

Acoustic Suppression Zone Relaxation Coefficient: The value $σ$ in Eqn. (4749).
Acoustic Suppression Zone specific continuity source: The rate of mass transfer into the Acoustic Suppression Zone, derived from $Q$ in Eqn. (4749).
Acoustic Suppression Zone specific energy source: The rate of energy transfer into the Acoustic Suppression Zone, derived from $Q$ in Eqn. (4749).
Acoustic Suppression Zone specific momentum source: The rate of momentum transfer into the Acoustic Suppression Zone, derived from $Q$ in Eqn. (4749).