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Acoustic Streaming in a Microchannel Cross Section
Recent advances in the fabrication of microfluidic systems require handling of live cells and other micro particles as well as mixing. All this can, for example, be achieved using acoustic radiation forces and the viscous drag from the streaming flow. Streaming: Due to the nonlinear terms in the Navier-Stokes equations, harmonic perturbation of the flow will lead to a net time-averaged flow ...
Acoustic Levitator
An ultrasonic standing wave levitator, also called acoustic levitator, is a device used for levitating fluid and solid particles in an acoustic field. The standing acoustic waves exert an acoustic radiation force on the particles. The force is a second order effect and stems from a combination of the time averaged pressure and inertial interaction between the particles and the acoustic field. ...
Loudspeaker Driver in a Vented Enclosure
This model of a boxed loudspeaker lets you apply a nominal driving voltage and extract the resulting sound pressure level in the outside room as a function of the frequency. The sensitivity, both on-axis and spatial, is determined as function of frequency. These are some of the most important design parameters for a loudspeaker. The electromagnetic properties of the driver are supplied from the ...
Cylindrical Subwoofer
In this model, the acoustic field inside and outside a down-firing subwoofer is computed. This model is set up in 2D axisymmetry using the Pressure Acoustics application mode. The modeled physical domain is a hemisphere with a radius of 1 m. To minimize the effect of non-physical reflections at the exterior boundary of this domain, an absorbing Perfectly Matched Layer (PML) is added. The ...
Transient Gaussian Explosion
An ellipse with sound-hard walls has the interesting property that an acoustic signal emanating from one of the foci refocuses at the other focal point b/c seconds later, where b (in meters) is the major axis length and c (m/s) is the speed of sound. This model involves a Gaussian explosion at one focus of an ellipse to illustrate some properties of time-dependent acoustic problems. The ...
Helmholtz Resonator Analyzed with Different Frequency Domain Solvers
This model simulates a simple three-dimensional axisymmetric Helmholtz resonator, a classic acoustics model of a resonating circuit with a known theoretical solution. The idealized version considered here consists of a tube and a closed volume in series which are exposed to a pulsatile pressure. Real-world phenomena explained by the resonator include amongst others the resonance from blowing ...
Open Pipe
In this model, sound created by a vibrating piston radiates through a baffled pipe. The impedance is measured and then used in an impedance boundary condition that replaces the surrounding air domain. This technique can be employed to reduce solution time and memory usage for large models with pipe openings.
Acoustic-Structure Interaction with a Perfectly Matched Layer (PML)
This small tutorial model shows how to set up a model with a solid mechanics and a pressure acoustics domain including a common perfectly matched layer (PML). The PML is used to model an open or infinite domain for both the elastic waves and the pressure waves. Two configurations of PMLs exist (this model describes the first case which is also the most difficult to handle): 1. One PML should ...
Acoustic Scattering off an Ellipsoid
This is a tutorial model that illustrates the use of the scattered field formulation in acoustics. A solid object (here an ellipsoid) is hit by an incident plane wave field (background pressure field). The model solves for the scattered field. The model uses a PML and a far-field calculation is also added. The mesh is set up to enhance the PML and the far-field performance.
Transfer Impedance of a Perforate
Perforates are plates with a distribution of small perforations or holes. They are used in muffler systems, sound absorbing panels, and in many other places as liners, where it is important to control attenuation precisely. As the perforations become smaller and smaller, viscous and thermal losses become more important. The attenuation behavior, which is also frequency dependent, can be ...
