For the relatively high frequencies relevant in a turbofan engine duct, the modes of a lined section may be classified in two categories: genuine acoustic 3D duct modes resulting from the finiteness of the duct geometry, and 2D surface waves that exist only near the wall surface in a way essentially independent of the rest of the duct. Per frequency and circumferential order there are at most f...

For the relatively high frequencies relevant in a turbofan engine duct the modes of a lined section may be classified in two categories: genuine acoustic 3D duct modes resulting from the finiteness of the duct geometry, and 2D surface waves that exist only near the wall surface in a way essentially independent of the rest of the duct. Per frequency and circumferential order there are at most 4 ...

This paper develops a method for analyzing the change of surface, a continuous function defined over the two-dimensional space. The surface change is represented by a scalar field in a spatio-temporal region. The region is divided into subregions called hills and waves which are based on the local form of the surface. They are both threedimensional tessellations of the spatio-temporal region, a...

Wind stress, waves, stratification, velocity profiles, and surface fields of radial velocity and acoustic backscatter intensity were measured along a drift track 50 to 150 km off Point Arguello, California. On March 8, 1995, the wind increased from calm to 12 rn/s from the SE, opposing swell from the NW. It increased to15 rn/s at noon UTC on March 9, remained steady over the next 12 hours, brie...