Point Sources (for 2D Components)
For 2D components, the monopole, dipole, and quadrupole point sources also exist. All the sources actually correspond to an infinite line source in the out-of-plane direction. The monopole is uniform and equally strong in all the in-plane directions — an infinitely long pulsating cylinder. The dipole source represents an infinitely long cylinder moving back and forth. The quadrupole represents two dipoles close to each other.
The point sources add the following point source term to the right-hand side of the governing Helmholtz equation — for monopole, dipole, and quadrupole point sources, respectively:
where δ(x − x0) is the delta function in 2D and adds the source at the point where (x,y) = x = x0. The monopole amplitude S (SI unit: N/m2), the dipole moment vector D (SI unit: N/m), and the quadrupole d vector (SI unit: m) and D vectors (SI unit: N/m) depend on the source type selected.
Monopole Point Source (2D Components)
Select a Type: Flow (the default), Intensity, Power, or User defined. For User defined enter a Monopole amplitude, Suser (SI unit: N/m).
Flow
Select Flow to add a monopole point 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 source defines the following monopole amplitude:
Enter values or expressions for:
•
Volume flow rate out from source, QS (SI unit: m3/s).
•
Phase ϕ (SI unit: rad).
Intensity
Select Intensity to define the source in terms of the free space reference RMS intensity Irms it radiates. In a homogeneous medium, the specified intensity is obtained (the reference), but with other objects and boundaries present, the actual intensity is different. The source defines the following monopole amplitude:
where dsrc is the distance from the source where the intensity Irms is specified and ϕ is the phase of the source. Enter values or expressions for:
•
Free space reference intensity (RMS), Irms (SI unit: W/m2).
•
Distance from source center dsrc (SI unit: m).
•
Phase ϕ (SI unit: rad).
Power
When Power is selected, specify the source’s reference RMS strength by stating the power per unit length it radiates. In a homogeneous medium, the specified power is obtained (the reference), but with other objects and boundaries present, the actual source power is different. The source defines the following monopole amplitude:
where Prms denotes the free space RMS reference power per unit length measured in W/m and ϕ is the phase of the source. Enter values or expressions for:
•
Free space reference power (RMS) per unit length, Prms (SI unit: W/m).
•
Phase ϕ (SI unit: rad).
Dipole Point Source (2D Components)
Enter a user defined Dipole-moment vector, D (SI unit: N/m).
Quadrupole Point Source (2D Components)
Enter a user defined Quadrupole d vector, d (SI unit: m), and a user-defined Quadrupole D vector, D (SI unit: N/m).
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.