Approved for public release; distribution is unlimited / Langmuir circulations in a coastal environment at an inner shelf site with strong tidal forcing were examined using a 4-month observation of high-resolution velocity profiles during the ONR-sponsored CBLAST-Low air-sea interaction experiment. Because of their potential contributions to mixing processes in the surface boundary layer, Langmuir circulations are important for naval operations such as ASW, MCM and Amphibious operations in littoral waters. A detection algorithm for upwelling / downwelling velocities due to Langmuir circulations was developed. Analyses focused on long-fetch, unstratified water column conditions with locally developed seas. The observations showed that strong Langmuir circulations greatly reduced water column shear arising from the tidally forced bottom boundary layer, while there was no significant effect from the strong tidal boundary layer on the formation of Langmuir cells. Long fetch conditions had the strongest vertical velocities with Langmuir number 0.1-0.4, while short fetch conditions have weaker vertical velocities with Langmuir number greater than 0.5. Cell vertical velocities were correlated with the water friction velocity, but penetration depths did not depend on forcing mechanisms. Spacing and penetration depths were correlated for increasing wind speed and wave heights whereas this correlation was not seen for constant high wind speed and wave heights. / Lieutenant Junior Grade, Turkish Navy

No description available.

Thesis (M.App.Sc.) - Carleton University, 2002. / Includes bibliographical references (p. 221-225). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: David B. Goldstein. Vita. Includes bibliographical references. Also available from UMI.

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, Sept. 2004. / Thesis advisor(s): Timothy P. Stanton. Includes bibliographical references (p. 95-99). Also available online.

Thesis (Ph. D.)--Massachusetts Institute of Thechnology / Woods Hole Oceanographic Institution, 1980. / Grant no: OCE 76-81190. Photocopy of typescript. Includes bibliographical references (p. 92-98).

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 134-137). Also available on the World Wide Web.

In order to improve the state of turbulence modeling for three-dimensional flows, more detailed information on the fundamental physics of the flow is required. It has been recognized for some time now that organized motions or coherent structures in the flow play a large part in determining the flow characteristics, and there is now a large body of literature dealing with various aspects of coherent structures. However, almost all of the existing literature deal with mean two-dimensional flows with very little reported for mean three-dimensional flows. In the present study, measurements were performed in a three-dimensional, pressure-driven turbulent boundary layer (<i>Re</i>_θ = 5936) in the flow around a wing-body junction with a variety of multiple-sensor probes, to examine the features of the coherent structures in the flow. This test flow has a number of practical applications and was selected because of its strong three-dimensional nature and the availability of an extensive set of mean-flow measurements from previous investigations. The measurements were carried out with a hot-wire rake with sixteen sensors spaced approximately logarithmically over 25.4 mm (1 inch), a parallel-sensor probe with two parallel sensors spaced approximately 4.8 mm apart, a rotatable wall-sensor probe with two wall-mounted hot-film sensors spaced 6.93 mm apart and a traversable wall-sensor probe with two variable-spacing wall-mounted hot-film sensors. The hot-wire rake was used to examine the structure of the flow in both the Y (normal to the wall) and Z (spanwise) directions. The parallel and rotatable wall-sensor probes were used to look at the angular characteristics of the coherent structures in the flow and at the wall, respectively, and the spanwise structure of the flow at the wall was examined through the traversable wall-sensor probe. The results of the measurements show that the spectral characteristics of the flow are affected by three-dimensional effects. The direction of motion of the coherent structures lags behind the local mean-velocity vectors in the X-Z plane (parallel to the wall) with very little variation with frequency (structure size). Unlike two-dimensional boundary layers, the spectral variation of the convective wave speed does not collapse when normalized with the local mean velocity and friction velocity in the outer and inner regions, respectively. In the outer region of the boundary layer, the distribution of the intermittency with Y appears to agree quite closely with previously reported results for two-dimensional boundary layers. The mean ejection frequency in the near-wall flow and the frequency at the peak of the first moment of the wall shear-stress power spectrum show fairly close agreement, consistent with previously reported results for a two dimensional boundary layer. The measurements with the traversable wall-sensor probe indicate the presence of an organized structure, probably low-speed streaks in the near-wall region, with a preferred spanwise spacing. This spanwise spacing was found to be Î Î * = 85 and 135 at two different measurement stations. somewhat different from the well accepted value of Î Î * = 100 for two-dimensional boundary layers. Time-delayed correlations of the velocity signal over a range of Y locations reveal an inclined linear wavefront similar to previously reported results for a two-dimensional boundary layer. / Ph. D.

Some important Computational Fluid Dynamics (CFD) applications and flow solvers are strongly influenced by the effects of low Mach number and/or high heat transfer rates. The present study focuses on the validation of a new flow solver over a range of Mach numbers and heat transfer rates of practical interest. The validation study addresses both algorithm performance via convergence rate and accuracy via comparisons with an analytical similarity solution, for flow past a flat plate held at a constant temperature. The ranges of flow conditions investigated in this study are (0.1 <= Mref <= 3.0) and (0.1 <= Twall <= 10.0). The algorithm has been found to converge well for most flow conditions tested. Optimal convergence rate is more strongly influenced by choice of time step in subsonic flows than in supersonic flows. Validation comparisons show the algorithm to maintain a consistent and acceptable level of accuracy for most tested flow speeds and wall temperatures, with most deviations attributable to flow physics constraints imposed by the theoretical result or to grid resolution. One possible exception, where the outer range of capability of the present algorithm may have been reached, is noted.

Numerical simulations of incompressible, two-dimensional, monochromatically and bichromatically forced laminar free shear layers are performed on the basis of a vorticity-velocity formulation of the complete Navier-Stokes equations employing central finite differences. Spatially periodic shear layers developing in time (temporal model) are compared with shear layers developing in the stream-wise direction (spatial model). The regimes of linear growth and saturation of the fundamental are quantitatively scrutinized, the saturation of the subharmonic and vortex merging are investigated, and the effects of a forcing phase-shift between fundamental and subharmonic. For the spatial model the appearance of an unforced subharmonic was also examined. It was found that contrary to temporal shear layers a significant control of vortex merging by means of a forcing phase-shift and vortex shredding are not possible in spatial shear layers due to strong dispersion.