Post FW-H Model
The Post FW-H model is an unsteady time model that allows you to export flow field data from noise emitting surfaces to a .simh file, so that you can use the data for a subsequent analysis of the sound pressure at far-field point receivers.
The model calculates the far-field noise contribution at each point receiver on request. To account for the time delay between the emission time and reception time, the Post FW-H model uses the advanced time approach as described for the FW-H Unsteady Solver. For each surface and each receiver, at each collected flow field time-step, the model:
- Computes the thickness and loading terms. It computes all surface integrals that are based on reading pressure surface data at the required time levels for accurate time derivatives.
- Accumulates the contribution of each individual integral in discrete time bins, where each bin correspond with an actual reception time.
The noise level at each individual receiver is a superposition of the signals from sound sources on the noise emitting surfaces lagged in time.
Post FW-H Surfaces
Post FW-H surfaces define the boundaries or surface derived parts from which the flow field data are exported to the .simh file. The surfaces define the source locations of noise for the far-field noise prediction.
There are two types of Post FW-H surfaces—permeable and impermeable. Depending on the surface type, the Post FW-H model exports the following field data from the surfaces:
| Surface Type | Surface Field Data |
|---|---|
| Impermeable (defined by boundaries) | For stationary regions:
|
| Permeable (defined by interface boundaries or surface derived parts) |
|
Post FW-H Receivers
Post FW-H receivers define locations in the far-field where acoustic data from the Post FW-H surfaces are collected for noise prediction. The location is defined by a point probe representing a single microphone.
Post FW-H receivers can collect acoustic data from multiple FW-H surfaces stored in a single .simh file.
By default, the sources of acoustic data are the flow field variables pressure, density, and velocity as provided by the Segregated or Coupled Flow model. Alternatively, you can use the respective field functions from the Acoustic Wave model or the Pertubed Convective Wave model.
Stationary and Rotating Cases
The Post FW-H model can be used for the following cases:
- Stationary cases with multiple permeable and impermeable Post FW-H surfaces.
- Transient rotating cases with multiple impermeable Post FW-H surfaces.
For domains of rotational symmetry, you can model a sector of the domain using periodic interfaces and repeating interfaces. If you use a repeating interface, you must model half the domain (180 deg sector)—sectors that represent less than 180 deg of the domain are not supported.
For stationary cases, the Post FW-H model exports pressure, density, and velocity flow field data from the selected Post FW-H surfaces. For rotating cases with periodic domains, the model also exports the Rotation Angle (deg) as specified at the periodic interface.