Requesting equivalent radiated power (ERP) output

In Simcenter Nastran Vibro-Acoustic solutions and Simcenter 3D Noise and Vibration ATV Response solutions, you can request output for equivalent radiated power (ERP). You can use ERP results to identify the areas of a structure that are the primary sources of the noise due to structural vibration.

To request output:

• In a Simcenter Nastran vibro-acoustics solution, use the Vibro-Acoustic Output Requests modeling object. You can specify the coefficient used to scale the ERP, the frequencies to calculate the ERP, and the panels for which ERP is output.

• In a Simcenter 3D Noise and Vibration ATV Response solution, use the ATV Vibro-Acoustic Output Requests modeling object. You must specify the speed of sound and the density of the acoustic fluid to be used in the calculation of the ERP

For both solutions, you can request output of ERP by element for elements that comprise the selected panels.

When you request ERP output, you can then post-process the results using the Equivalent Radiated Power post-processing scenario and the Scenario Based Data-Visualization Navigator. For more information, see Equivalent Radiated Power scenario.

Calculating ERP

ERP is a measure of the normal velocity distribution over the face of an element. The ERP attributable to the ith element at frequency ωk is given by:

ERP{E_i}\left( {{\omega k}} \right) = \frac{1}{2}c\int\limits{{S_i}} {{v_n}\left( {{\rm{x}},{\omega _k}} \right)v_n^*\left( {{\rm{x}},{\omega _k}} \right)ds}

where:

• c is the scaling coefficient, which is usually the product of density and speed of sound in the fluid medium.

• {v_n}\left( {{\rm{x}},{\omega _k}} \right) is the normal velocity as a function of position, {\rm{x}}, at frequency \omega _k.

• Frequencies ωk are the solution frequencies (or a subset of frequencies as specified by the SOLUTION describer).

• v_n^*\left( {{\rm{x}},{\omega _k}} \right) is the complex conjugate of {v_n}\left( {{\rm{x}},{\omega _k}} \right).

• SI is the surface area of the ith element.

In an ATV response solution, because you must specify the speed of sound and the density of the acoustic fluid, the ERP attributable to the ith element at frequency ωk is given by:

ERP{E_i}\left( {{\omega k}} \right) = \frac{1}{2}\rho c\int\limits{{S_i}} {{v_n}\left( {{\rm{x}},{\omega _k}} \right)v_n^*\left( {{\rm{x}},{\omega _k}} \right)ds}

where:

• \rho\ is the density of the acoustic fluid.

• c is the speed of sound in the acoustic fluid.

For more information on calculating ERP, see Equivalent Radiated Power Output in the Simcenter Nastran Basic Dynamic Analysis User's Guide.

Where do I find it?

Requesting ERP in Simcenter Nastran vibro-acoustic solutions

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter Nastran as the specified solverVibro-Acoustic as the specified analysis typeOne of the following as the specified solution type:SOL 108 Direct Frequency ResponseSOL 108 Vibro-Acoustic Transfer Vector ResponseSOL 111 Modal Frequency Response
Command Finder	Modeling Objects
Location in dialog box	Type list→Vibro-Acoustic Output Requests→Create→Equivalent Radiated Power page→Enable ERP Request

Requesting ERP in Simcenter 3D Noise and Vibration ATV Response solutions

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter 3D Noise and Vibration as the specified solverVibro-Acoustic as the specified analysis typeAcoustic Transfer Vector (ATV) Response as the specified solution type
Command Finder	Modeling Objects
Location in dialog box	Type list→ATV Vibro-Acoustic Output Requests→Create→Structural Results group→Equivalent Radiated Power

Learn more

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Requesting equivalent radiated power (ERP) output, Simcenter 3D 2021.1 Series

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