Working with FW-H Surfaces

FW-H Surfaces define the source locations of the noise.

FW-H surfaces can be thought of as being similar to radio speakers—they are the source of noise. Greschner and others [61] suggest that there are two types of FW-H Surfaces: impermeable and permeable. Surfaces can be renamed, copied, and deleted in the same way as other simulation objects.

Impermeable FW-H Surfaces

An impermeable FW-H surface acts as a filter of wall boundary conditions from which noise originates. Locate impermeable surfaces at one or more wall boundaries.

Note	For the Ffowcs Williams-Hawkings steady model, use only impermeable surfaces.

Permeable FW-H Surfaces

A permeable FW-H surface acts as a filter of internal interface boundaries. Locate permeable surfaces on a fine region of the mesh that surrounds all sources of noise: monopoles, dipoles, and quadrupoles.

When you select a Permeable FW-H surface, the On-the-Fly and Post FWH models calculate the sound pressure at receiver locations using Farassat's Formulation 1A or Dunn-Farassat-Padula Formulation 1A.

The Permeable FW-H formulations include all sources of noise, distributed on the surface as monopole and dipole terms, and also the contribution from the volumetric sources inside by the integration surface. The formulations assume that the contribution to the total noise of volumetric sources outside the integration surface is negligible.

Since the evaluation of the FW-H surface sources is independent of FW-H volume sources, you do not need to select regions for each point receiver.

Creating Surfaces

To add a surface to the simulation, right-click the FW-H Surfaces manager node and select Impermeable Surface or Permeable Surface from the New submenu.

FW-H Surfaces Manger

The FW-H Surfaces manager node is available for the Ffowcs Williams-Hawkings steady model and the On-the-Fly FW-H model. The FW-H Surfaces node is the manager node for all FW-H surfaces (impermeable and permeable) in the Simcenter STAR-CCM+ simulation tree.

This manager can hold any number of surfaces up to the memory limits of the computer.

Surface Properties

Boundaries

List of boundaries used for FW-H surfaces. Edit this property to add or remove boundaries with the in-place object selector.

Periodic Domain

When On, the default, the FW-H solver copies and rotates data from a domain sector into a full-sized domain and works with the resulting data. An example is the model of a fan with a perfect correlation between the blades, then the domain sector copied and rotated into the full domain volume. When On, this option gives the ability to enable computation of the sector domain as a full 360 degrees domain to compare with experimental data. For a full domain model, the Periodic Domain property is disregarded and therefore does not affect the results.

When Off, the solver enables computation only in the sector domain, working with data from that sector for the acoustic beamforming method.

Note	Periodic Domain treats the noise sources for FW-H surface as coming from periodic computational domains.

Pop-Up Menu of the FW-H Surfaces Manager

New: Adds a surface (impermeable or permeable) to the object tree, depending on your choice from the submenu.