Fan Noise

You can solve aeroacoustic simulations of rotating fans or propellers using subsonic fluid excitations in a FEM Adaptive Order (FEMAO) acoustic solution. This method can be used to solve a variety of aeroacoustic simulations, such as marine propeller sound propagation, cooling fan noise, or HVAC blower and duct acoustic interaction.

A new technique has been implemented to solve for the acoustic or vibro-acoustic response using aeroacoustic excitations. Previously solved CFD simulation surface pressures as a function of time are imported from a CGNS (CFD General Notation System) file, converted to fan blade force excitation, and then applied as a source using an equivalent acoustic rotating force. You then apply the excitation as a fan blade load to the acoustic solution to excite the acoustic fluid.

A fan noise can have a single blade, which assumes all other blade forces are identical. If the fan noise has multiple blades, then blade forces can be unique for every blade.

You can have multiple fans at different locations in your model. Each fan must:

• Have the same number of blades

• Have the same acoustic properties (Tonal or Tonal and Broadband

• Have the same rotation speed.

• Be inside the acoustic domain (acoustic fluid mesh).

You can set each fan phase angle by selecting the X- or Y-axis of the fan CSYS and rotating the CSYS around the Z-axis.

You create a SOL108 FEMAO Acoustics solution and then include single or multiple fan noise loads in your simulation.

A fan noise load can be derived from either:

• Tonal noise, which only accounts for the blade passing frequencies where all the fan blades and forces are identical.

• Tonal and Broadband noise, which includes blade passing frequencies and broadband (turbulent) noise. The fan blades may be different and have unique forces.

For more information on Fan Noise creation, see Create a Fan Noise load and solution.

For more information on FEMAO, see Finite Element Method Adaptive Order (FEMAO) solutions.

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Intermediary elements in fan noise

Fan Noise solution quality

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Fan blade segmentation

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Fan Noise, Simcenter 3D 2021.1 Series

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