Scanning LDV System for Modeling Vibration and Acoustics

Nomura Enterprise Inc. (NEI) proposes to extend a novel research technology, Laser-Based Spatial Dynamics Modeling (LSDM) for the solution of 3-D velocity fields over submerged structures using a scanning laser Doppler vibrometer (SLDV). NEI will be assisted by the Structural Imaging and Modal Analysis Laboratory of Virginia Tech. LSDM technology exploits high spatial density noncontact SLDV measurement capability coupled with a new finite element to solve for complex-valued 3-D velocity fields. This research has already been demonstrated on shell and tire structures. Five fundamental concepts uniquely separate LSDM from other approaches: (1) the 3-D result is a spatially continuous field, (2) the finite element mesh solves for the 3-D velocity field over a structure simultaneously, (3) the solution is converged by mesh refinement and statistically qualified, (4) arbitrary geometries are naturally accommodated through finite element meshing, and (5) the technology can be taken into the field. The 3-D field solution allows postprocessing to extract angular velocities, displacements, dynamics strains, and structural intensity. A very powerful LSDM application uses the 3-D velocity field solution as the prescribed velocity boundary condition for acoustic analysis. This application of LSDM will be developed and demonstrated on structures at a U.S. Navy facility.