Measurements are presented of the velocity structure function on axis a turbulent jet at Reynolds numbers R λ ≤ 852 and in duct flow = 515. Moments up to eighteenth order were calculated, primarily with view establish accurately dependence inertial range power-law exponent draw conclusions about distribution energy transfer range. Adequate definition probability density was achieved only for moments n 10. It is shown, however, that, although values > 10 diverges from their true values,...

The inertial-range behavior of measured temperature structure functions, up to order 12, is compared with predictions by the log-normal and $\ensuremath{\beta}$ model. Both models are unsatisfactory from a quantitative viewpoint. comparison between measurements indicates that intermittency field different velocity field.

The relation, first written by Kolmogorov, between the third-order moment of longitudinal velocity increment δu 1 and second-order is presented in a slightly more general form relating mean value product ( i ) 2 , where sum square three increments, to secondorder . In this form, relation similar that derived Yaglom for θ temperature increment. Both equations reduce ‘four-thirds’ inertialrange separations differ only through appearance molecular Prandtl number very small separations. These...

In most real or numerically simulated turbulent flows, the energy dissipated at small scales is equal to that injected very large scales, which are anisotropic. Despite this injection-scale anisotropy, one generally expects inertial-range be locally isotropic. For moderate Reynolds numbers, isotropic relations between second-order and third-order moments for temperature (Yaglom's equation) velocity increments (Kolmogorov's not respected, reflecting a non-negligible correlation responsible...

The effect of wall suction on the organized motion a tubulent boundary layer is examined experimentally both in wind tunnel and water tunnel. In windtunnel layer, which developed over slighly heated surface, temperature fluctuations were simultaneously obtained at several points, aligned either x (streamwise) or y (normal to wall) direction. traces reveal existence two spatially coherent events, characterized by sudden decrease (cooling) increase (heating) temperature. Estimates are...

Following a review of the difficulties associated with measurement and interpretation statistics small-scale motion, evidence for against local isotropy is assessed in light measurements turbulent plane jet at moderate values Reynolds Péclet numbers. These include spatial derivatives respect to different directions longitudinal velocity fluctuation temperature fluctuation. Relations between mean-square these suggest strong departures from both temperature. In contrast, locally isotropic...

Kolmogorov's equation, which relates second- and third-order moments of the velocity increment, provides a simple method for estimating mean energy dissipation rate 〈ε〉 homogeneous isotropic turbulence. However, this equation is usually not verified in small to moderate Reynolds number flows. This due partly lack isotropy either sheared or non-sheared flows, and, more importantly, influence, flow specific, inhomogeneous anisotropic large scales. These shortcomings are examined context...

Three–dimensional direct numerical simulations of unforced, incompressible, free, spatially evolving round jets are used to investigate the onset instability at low diametral Reynolds numbers (Re⩽500). Compact, coherent structures identified by means iso-surfaces vorticity and pressure fields shown be synonymous with modes. Once inflow velocity profile is fixed, as number increases from 200 500, most amplified unstable mode switches helical axisymmetric one, expected predictions viscous...

An equilibrium similarity analysis is applied to the transport equation for $\langle(\delta q)^{2}\rangle$ (${\equiv}\,\langle(\delta u)^{2}\rangle + \langle(\delta v)^{2}\rangle w)^{2}\rangle$), turbulent energy structure function, decaying homogeneous isotropic turbulence. A possible solution requires that mean $\langle q^{2}\rangle$ decays with a power-law behaviour ($\langle q^{2}\rangle\,{\sim}\,x^{m}$), and characteristic length scale, which readily identifiable Taylor microscale,...

This study concerns turbulent jets with density variations. The local statistical properties, obtained for the velocity field and mean mass fraction, are needed both better understanding of effects modeling such flows. Special attention is paid to near-field region (x/Dj≤20), where there a lack experimental results. A vertical axisymmetric jet emitted from fully developed pipe flow, weakly confined in an air coflow, investigated. Apart constant case (air/air), two situations variable treated...

Predicting the erosion resistance of saturated natural sediments requires taking into account cohesion, which results from interactions between clay particles. The current paper describes a combined experimental and theoretical examination threshold conditions for mixture clays sands. Erosion measured values are larger than those predicted noncohesive models. Beyond usual dependence on grain size, significant correlation porosity measurements is confirmed heterogenous mixtures grains with...

We investigate the dynamics of a low-density round jet, with focus on mechanisms governing turbulent momentum and mass transfers as well entrainment ambient fluid. To that purpose, we combine theoretical analysis, laboratory experiments numerical simulations. The analysis relies general formulation decomposition for case large density differences, revealing role processes contributing to entrainment: kinetic energy production variation in shape mean velocity radial profiles. spatial...

This paper is concerned with the investigation of characteristic turbulent scales in circular and plane free jets large density variations. The numerical study has been performed a second-order turbulence model to confirm analytical relations about Reynolds number effects on dynamic scalar derived from requirements pseudo-self-preservation. present results explain quantify trends previously reported visualizations variable by Pitts (NBSIR Report No. 86-3340, U.S. Department Commerce, 1986)....