Dipole Point Source
Use the Dipole Point Source node to add a dipole point source. A dipole is mathematically a source that corresponds to two monopoles close to each other that are completely out of phase. Dipoles appear when there are fluctuating forces in the medium; for example, a small object that vibrates back and forth. A complex acoustic source may be expanded and approximated by a collection of point sources (Monopole Point Source, Dipole Point Source, and Quadrupole Point Source). The dipole point source adds a point source term to the right-hand side of the governing Helmholtz equation such that:
where δ(x − x0) is the delta function in three dimensions and adds the source at the point where x = x0. The dipole moment vector D (SI unit: N) depends on the source type selected, as discussed below. In 2D axisymmetric models, the dipole point source is only added to the z-axis, such that x0 = (0,0,z). See Ref. 5 for details.
Figure 2-3: Schematic illustration of a dipole source.
Dipole Point Source
Select a Type: Power (the default) or User defined.
User Defined
For User defined enter a Dipole moment vector D (SI unit: N). In 2D axisymmetric components enter the z-component only.
Power
The Power option defines the following dipole moment vector in terms of the free space reference power, the dipole direction, and the source phase
Enter the following:
•
Free space reference power (RMS), Prms (SI unit: W). In a homogeneous medium, the specified power is radiated (the reference), but with other objects and boundaries present the actual power is different.
•
The source Phase (SI unit: rad).
•
Dipole moment direction eD. Defines the direction of the dipole moment vector. In 2D axisymmetric components the direction is aligned along the z-axis such that eD = ez.
Point sources in 2D components also exist. They actually correspond to infinite out-of-plane line sources, see Point Sources (for 2D Components).