This numerical study explores the physical processes involved in breaking waves. The two-dimensional, incompressible, unsteady Navier-Stokes equations are solved in sufficiently refined grids to capture viscous and capillary effects. The immiscible interface, characterized by a jump in density and viscosity, is embedded in the domain and a hybrid front tracking/capturing method is used to characterize the moving interface of this multiphase flow. A parametric study is conducted to assess the role of surface tension, Reynolds number, density, and viscosity on the breaking process, as well as their role in the vorticity redistribution and energy dissipation beneath the surface.

This paper presents the influence of injected polymer solutions on turbulence in fully developed channel flows. In particular, it investigates the impact of concentration and mixing of the polymer solution on drag reduction. It is observed, via flow visualization and birefringence measurements, that for large injection concentrations macromolecular polymer structures exist in the flow. They are found to be mostly located in the neighborhood of the channel centerline. Laser Doppler velocimetry was used to characterize the mean and turbulent flow with and without the presence of macromolecular polymer structures.

Experiments were performed in the turbulent boundary layer and near wake of an axisymmetric body propelled by a jet to study the evolution of the momentumless wake. Comparisons with measurements in the drag wake of the body (without the jet) and in the isolated jet provide an understanding of initial mixing between the two ows. Triple-sensor hot wires and multitube pressure probes were used to measure the mean velocity, turbulence, and pressure elds from the jet exit to a distance of over 15 jet diameters. It is found that the evolution of the wake takes place in three distinct stages: a zone close to the jet exit, about 4 jet diameters long, where the jet shear layer mixes with uid from the wall region of the boundary layer; an intermediate region, about 12 jet diameters long, where there is mixing between the boundary layer and the jet up to the axis; and the third region where the two ows lose their identities to become a single shear layer and the mean ow acquires some of the characteristics of self-similar ows. However, the momentumless wake does not conform to the assumptions and results of classical similarity analysis.

SUMMARYA complementary set of Reynolds-averaged Navier-Stokes (RANS) equations has been developed for steady incompressible, turbulent ows. The method is based on the Helmholtz decomposition of the velocity vector ÿeld into a viscous and a potential components. In the complementary RANS solver a potential solution coexists with a viscous solution with the purpose of contributing to a fastest decay of the viscous solution in the far ÿeld. The proposed complementary RANS equations have been validated for steady laminar and turbulent ows. The computational results show that the complementary RANS solver is able to produce less grid-dependent solutions than a conventional RANS solver.

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