THE BOUNDARY CONDITION AT AN IMPEDANCE WALL IN A NON-UNIFORM DUCT WITH POTENTIAL MEAN FLOW

✍ Scribed by W. EVERSMAN

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 221 KB
• Volume: 246
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.2000.3607

✦ Synopsis

The boundary condition at an impedance wall in a duct with a steady mean #ow requiring the speci"cation of the normal component of acoustic particle velocity is examined. It is found that when implemented in the weak formulation of the "nite element method it can be considerably simpli"ed. The boundary condition would appear to require data which includes the tangential derivative of the tangential mean #ow velocity, the normal derivative of the normal component of mean #ow velocity, and the derivatives of the mean #ow density and the boundary admittance along the boundary. It is shown that with suitable rearrangement the normal and tangential velocity derivatives can be eliminated, as can the derivatives of the mean #ow density and admittance. The boundary condition becomes only slightly more complicated than the corresponding boundary condition when mean #ow is absent, and is no more di$cult to implement, requiring only local values of tangential mean #ow velocity, density, and admittance which are already required as data for the weak formulation of the "eld equation.

2001 Academic Press