Turbulent flows are ubiquitous both in nature and in engineering applications, with far-reaching implications. Turbulence in wall bounded shear flows such as that in pipes, channels and boundary layers feature turbulent transition at Reynolds numbers for which the laminar flow is linearly stable [1], and often do so in the form of discrete patches of turbulence surrounded by quiescent fluid [2]...

The purpose of this study was to determine the total resistance and investigate flow around a full-scale kayak. Utilizing Computational Fluid Dynamics(CFD), it deter-mined how presence rudder affects kayak hydrodynamic performance. To an-alyse flow, computational fluid dynamics based on RANS-VOF solver em-ployed. volume approach k-ω turbulence model were used in two-phase steady simulations hul...

A numerical study based on large eddy simulation is performed to investigate a bottom boundary layer under an oscillating tidal current. The focus is on the boundary layer response to an external stratification. The thermal field shows a mixed layer that is separated from the external stratified fluid by a thermocline. The mixed layer grows slowly in time with an oscillatory modulation by the t...

We present an introductory overview of several challenging problems in the statistical characterisation of turbulence. We provide examples from fluid turbulence in three and two dimensions, from the turbulent advection of passive scalars, turbulence in the one-dimensional Burgers equation, and fluid turbulence in the presence of polymer additives.

We studied thermal turbulence in a low Prandtl number, Pr, fluid using liquid Hg (Pr ­ 0.024). For Rayleigh numbers (106 , Ra , 108), the histogram of temperature fluctuations at the center of the cell (aspect ratio 1), and the scaling laws for the Nusselt number and the large scale flow, all showed He-like hard turbulence. However, the cascade range of the frequency spectrum of the temperature...

Cavitation and turbulence in a diesel injector nozzle has a great effect on the development and primary breakup of spray. However, the mechanism of the cavitation flow inside the nozzle and its influence on spray characteristics have not been clearly known yet because of the internal nozzle flow complexities. In this paper, a comprehensive numerical simulation is carried out to study the intern...

The basic element of Lighthill's "sandwich model" of tropical cyclones is the existence of "ocean spray," a layer intermediate between air and sea made up of a cloud of droplets that can be viewed as a "third fluid." We propose a mathematical model of the flow in the ocean spray based on a semiempirical turbulence theory and demonstrate that the availability of the ocean spray over the waves in...

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