Problem description and model definition
The model is a simplified version of the acoustic cavity in a vehicle tire. The cross-section of the cavity is established using axisymmetric elements, and these elements are assigned material properties corresponding to air. A dummy step is used to establish the various files used in the subsequent three-dimensional analysis steps.
The complete toroidal cavity is created using a revolved symmetric model definition to form a circumferentially uniform mesh of 60 segments around the circle. Steady-state dynamic, eigenfrequency extraction, and complex frequency extraction procedures use the acoustic flow velocity to include the effects of the rotational flow.
The air cavity is analyzed at rest, at 28.0 radians per second (corresponding to 100 kilometers per hour), and at 320 radians per second (corresponding to Mach 0.3 at the outer edge of the cavity).
The steady-state dynamic results are computed at frequencies between 150 and 370 Hz. For the complex analyses, modes are requested between 45 and 1000 Hz.