Line Source
Use the Line Source node to add a source on a line/edge in 3D components. This type of source corresponds to a radially vibrating cylinder in the limit where its radius tends to zero. The line source adds a source term to the right-hand side of the governing Helmholtz equation such that:
where δ(x − x0) is the delta function in 3D that adds the source on the edge where x = x0 and dl is the line element along the edge (SI unit: m). The monopole amplitude S (SI unit: N/m2) depends on the source type selected, as discussed below.
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Frequency Domain Study
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Solution (datasets) in the COMSOL Multiphysics Reference Manual
For the Pressure Acoustics, Transient interface, only the Flow (no phase specification), User defined, and the Gaussian pulse source types are available. The Gaussian pulse source type has no effect in the frequency domain. See The Gaussian Pulse Source Type Settings.
Line Source
Select a Type: Flow (the default), Intensity, Power, or User defined.
For User defined, enter a Monopole amplitude, S = Suser (SI unit: N/m2). Otherwise, enter details as follows.
Flow
Select Flow to add an edge source located at r = r0 defined in terms of the volume flow rate per unit length out from source QS and the phase ϕ of the source. The flow edge source defines the following monopole amplitude:
A flow edge source with the strength QS represents an area flow out from the source (the source is a very thin cylinder with a surface that pulsates).
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Enter a Volume flow rate per unit length out from source, QS (SI unit: m2/s) for the source-strength amplitude in the field.
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Enter a Phase ϕ (SI unit: rad).
When defining a Solution dataset and plotting the results, specify a nonzero phase ϕ to produce a nonzero result when visualizing the resulting pressure field using the default value (0) in the Solution at angle (phase).
Intensity
Select Intensity to add an edge source located at r = r0 defined in terms of the source intensity radiated Irms and the phase ϕ of the source. Set a desired free space reference intensity (RMS) Irms at a specified distance dsrc from the source. In a homogeneous medium, the specified intensity is obtained when the edge is a straight line (this is the reference). With other objects and boundaries present, or if the edge is curved, the actual radiated intensity is different. This source type defines the following monopole amplitude:
where Ledge is the length of the source line (automatically determined) and dsrc is the distance from the source where free space reference intensity (RMS) Irms is specified. Enter values or expressions for:
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Free space reference intensity (RMS), Irms (SI unit: W/m2).
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Distance from source center dsrc (SI unit: m).
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Phase ϕ (SI unit: rad).
Power
Select Power to add an edge source located at r = r0 specified in terms of the source’s reference RMS strength by stating the total power Prms a straight line source would radiate into a homogeneous medium. This source type defines the following monopole amplitude:
where Ledge is the length of the source line (automatically determined) and Prms denotes the free space reference RMS power (in the reference homogeneous case) per unit length measured in W/m. Enter values or expressions for:
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Free space reference power (RMS), Prms (SI unit: W).
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Phase ϕ (SI unit: rad).