The ultimate limitations to the performance of long-range sonar are due to ocean sound speed perturbations and the characteristics of the ambient acoustic noise field. Scattering and diffraction resulting from internal waves and other ocean processes limit the temporal and spatial coherence of the received signal, while the ambient noise field is in direct competition with the received signal. ...

An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow fie ld are modeled with the aid of Spalart-Alimaras one-equation turbulence modeL Appropriate acoustic and outflow boundary conditions were implemented to ...

A processing approach for the collection and retention of mammalian cells within a high porosity polyester mesh having millimeter-sized pores has been studied. Cell retention occurs via energizing the mesh with a low intensity, resonant acoustic field. The resulting acoustic field induces the interaction of cells with elements of the mesh or with each other and effectively prevents the entrainm...

The dynamic characteristics of near-field levitation bearings have been investigated in this study. Through theoretical analysis, two different types system stiffness are defined and derived analytically. relates the excitation amplitude to force amplitude, while effective governs time-averaged force-displacement relationship. results indicate non-linear asymmetric spring constants that can eff...