A three-dimensional total variation diminishing (TVD) algorithm is developed for computing unsteady/steady flows in pulsed lasers. The general approach utilizes a three-dimensional thin-layer Navier-Stokes/Euler solver with source terms in the main channel, a one-dimensional Euler solver with source terms in the sidewall-muffler backing volume, and a quasisteady channel to backing volume flow-exchange model. Explicit time integration of these equations is accomplished via symmetric TVD formulations in an effort to enhance accuracy of the computed solution. Shock-tube experiments are performed to generate a data base for generic laser related problems and are shown to compare well with the computed solutions. Some aspects of laser flow/acoustic design are then discussed to demonstrate the capability of the code to supplement an overall flow system design effort. Nomenclature a -acoustic speed C d = discharge coefficient (muffler wall) K ml = normalized linear resistance in muffler backing volume, K m Llp r u r K mn = normalized nonlinear resistance in muffler backing volume, K mn L K r = normalized linear resistance of muffler wall, KJp r u r L = reference length p -dimensional pressure t -dimensional time u r -reference velocity, a 0 a = open area ratio (muffler wall) y = ratio of specific heats p r = reference density, p 0

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This paper describes an in-house experiment that was perfonned at the Avco Research LabsfFextron to test a proprietary atmospheric phase compensation algorithm. Since the laser energies of interest were small enough that thermal blooming was not an issue, it was only necessary to simulate the effect of atmospheric turbulence. This was achieved by fabricating phase screens that mimicked Kolmogorov phase statistics. A simulated atmosphere was constructed from these phase screens and the phase at the simulated ground was measured with a digital heterodyne interferometer. The result of this effort was an initial verification of our proprietary algorithm two years before the field experiment.

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