V. C. Patel

Solutions of Reynolds-averaged Navier-stokes equations for three-dimensional incompressible flows

Abstract A general numerical method for the solution of complete Reynolds-averaged Navier-Stokes equations for three-dimensional flows is described. The method uses nonorthogonal body-fitted coordinates, generated either analytically or numerically, while retaining the velocity components in a triply-orthogonal curvilinear coordinate system. The convective transport equations for mean velocities and turbulence parameters (k, e) are solved by the finite-analytic method in the transformed domain. The pressure field is updated using a modified version of the SIMPLER algorithm to satisfy the equation of continuity. The capability of the method and its overall performance are demonstrated by calculations of the flow over a typical ship hull.

Longitudinal curvature effects in turbulent boundary layers

Abstract It is generally accepted that even relatively small longitudinal surface or streamline curvature has a significant affect on transport of momentum and heat in turbulent boundary layers. A review is made of experiments that elucidate the effects of curvature and turbulence models which attempt to account for these effects. While the main body of the review is concerned with two-dimensional boundary-layer flow, as is much of the available literature, attention is drawn to the much broader role of curvature in three-dimensional flows.

Prediction of turbulent flow through a transition duct using a second-moment closure

The near-wall, full Reynolds-stress closure of Launder and Shima is employed to calculate the three-dimensional turbulent flow through a circular-to-rectangular transition duct. The solutions are compared with the recent experimental data of Davis and Gessner. Dowstream of the transition region, however, the computed Reynolds stresses appear to decay at a much caster rate than observed in the measurements. These results point to the need for further refinement of Reynolds-stress models to correctly predict the relaxation of rapidly strained turbulence towards equilibrium

Viscous effects on propagation and reflection of solitary waves in shallow channels

Abstract A numerical method for the solution of the Navier-Stokes equations for flows with a free surface, with emphasis on the exact kinematic and dynamic boundary conditions at the free surface, is described. The method is used to study the propagation of a solitary wave in a shallow channel, and the reflection of such a wave from a vertical wall. The numerical results are compared with analytical solutions which neglect or simplify the effects of viscosity and surface tension.

Wake of a Self-Propelled Body, Part 1: Momentumless Wake

Experiments wereperformedin theturbulent boundary layerand nearwakeofan axisymmetricbody 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 e ows. Triple-sensor hot wires and multitube pressure probes were used to measure the mean velocity, turbulence, and pressure e 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 e 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 e ows lose their identities to become a single shear layer and the mean e ow acquires some of the characteristics of self-similar e ows. However, the momentumless wake does not conform to the assumptions and results of classical similarity analysis.

Wake of a Self-Propelled Body, Part 2: Momentumless Wake with Swirl

Experiments were performed in the near wake of an axisymmetric body propelled by a swirling jet. Comparisons with parallel experiments in the drag wake of the bare body without the jet and in the isolated swirling jet provide insights on the mixing between the component flows and their evolution into the momentumless wake with swirl. Comparisons with the momentumless wake without swirl analyze the effect of swirl in this type of wake. Comparison with experimental data in the wake of the same body propelled by a marine propeller are also presented. Hot-wire and pressure probes were used in a wind tunnel to measure the mean velocity, turbulence, and pressure fields from the jet exit to a distance of over 15 jet diameters. The wake evolves in at least three distinct stages: a zone close to the jet exit where the jet periphery mixes with the wall region of the body boundary layer, an intermediate region where the mixing between the boundary layer and the jet spreads up to the axis, and a region where the two flows lose their identities to become a single shear layer in which there is negligible turbulence production

INTERACTIVE AND LARGE-DOMAIN SOLUTIONS OF HIGHER-ORDER VISCOUS-FLOW EQUATIONS

Two approaches for the solution of the partially parabolic Reynolds equations are evaluated using the same numerical techniques and turbulence model. Comparisons are made between interactive viscous-inviscid solutions and non-interactive large-domain solutions for the flow over the tail and in the wake of axisymmetric and three-dimensional bodies to highlight the differences between the two strategies. Both approaches yield satisfactory results, though the interactive solutions appear to be computationally more efficient for the three-dimensional bodies.

Transverse curvature effects in turbulent boundary layer

Abstract The effect of transverse surface curvature on the turbulent boundary layer is reviewed by recourse to experiments on axial flow along a circular cylinder. Three flow regimes are identified depending on values of the two controlling parameters, namely, the Reynolds number and the ratio of the boundary layer thickness to cylinder radius. The boundary layer flow resembles a wake when both parameters are large. As expected, the effect of curvature is small when the Reynolds number is large and the boundary layer is thin. When the boundary layer is thick and the Reynolds number is small, which is typical of laboratory investigations, the effect of transverse curvature is felt throughout the boundary layer with evidence for relaminarization at the low Reynolds numbers. This review describes the experimental evidence and points out gaps that remain.