Turbulent dispersed multiphase flows are common in many engineering and environmental applications. The stochastic nature of both the carrier-phase turbulence dispersed-phase distribution makes problem turbulent flow far more complex than its single-phase counterpart. In this article we first review current state-of-the-art experimental computational techniques for flows, their strengths limitations, opportunities future. then focuses on three important aspects flows: preferential...

Direct numerical simulation of isotropic turbulence was used to investigate the effect on concentration fields heavy particles. The hydrodynamic field computed using 643 points and a statistically stationary flow obtained by forcing low-wave-number components velocity field. particles in simulations were time advanced according Stokes drag law also assumed be much more dense than fluid. Properties particle cloud following trajectories 1 000 through simulated fields. Three values ratio...

Preferential concentration describes the accumulation of dense particles within specific regions instantaneous turbulence field. This phenomenon occurs in dilute particle-laden flows with particle time constants same order as an appropriately chosen scale. The mechanisms which drive preferential are centrifuging away from vortex cores and convergence zones. Experimental numerical studies reviewed demonstrate that a wide range including plane axisymmetric free shear flows, wall-bounded...

Despite extensive study, there remain significant questions about the Reynolds-number scaling of zero-pressure-gradient flat-plate turbulent boundary layer. While mean flow is generally accepted to follow law wall, little consensus Reynolds normal stresses, except that are effects even very close wall. Using a low-speed, high-Reynolds-number facility and high-resolution laser-Doppler anemometer, we have measured stresses for layer from Re θ = 1430 31 000. Profiles u ′ 2 , v show reasonably...

The effect of turbulence on particle concentration fields and the modification by particles has been investigated using direct numerical simulations isotropic turbulence. motion was computed Stokes’ law resistance it also assumed volume fraction negligible. For in which do not modify field found that light collect preferentially regions low vorticity high strain rate. increased mass loading attenuated an increasing energy. Examination spatial energy spectra showed kinetic wave numbers...

The interactions between small dense particles and fluid turbulence have been investigated in a downflow fully developed channel air. Particle velocities of, the presence 50 μm glass, 90 glass 70 copper spherical beads were measured by laser Doppler anemometry, at particle mass loadings up to 80%. These smaller than Kolmogorov lengthscale of flow could respond some but not all scales turbulent motion. Streamwise mean velocity profiles flatter profile, which was unmodified loading....

An investigation of the instantaneous particle concentration at centerline a turbulent channel flow has been conducted. The field was obtained by digitizing photographs particles illuminated spanwise laser sheet and identifying individual particles. resulting distribution then compared to expected for same number randomly distributed throughout volume. Significant departures from randomness have found differences are strongly dependent on time constants Five different classes were...

Combined heat transfer and fluid dynamic measurements in a separated reattaching boundary layer, with emphasis on the near-wall region, are presented. A constant heat-flux surface behind single-sided sudden expansion is used to obtain Stanton number profiles as function of Reynolds boundary-layer thickness at separation. Fluctuating skin-friction temperature demonstrate importance region controlling rate. The fluctuating skin friction controls rate near reattachment, while conventional...

The interaction of solid particles with the temporal features a turbulent flow has direct relevance to problems in particle and spray combustion processing particulate solids. object present study was examine behaviour jet dominated by vortex ring structures. An axisymmetric air laden 55 μm glass forced axially an acoustic speaker organize structures rolling up free shear layer downstream nozzle exit. Visualization studies unforced Reynolds number order 20000 were completed using pulsed...

We present results from a direct numerical simulation of the passive transport solid particles by fully developed turbulent channel flow with Reynolds number 180 based on friction velocity and half-width. Three particle sets are studied, ranging in diameter 0.5 to 1.4 viscous wall units aerodynamic time constant 0.6 56 centreline Kolmogorov scales. use density histograms fractal dimensions show that level order spatial distribution peaks near Stokes unity scale. then quantify relationship...

Measurements of heavy particle dispersion have been made using direct numerical simulations isotropic turbulence. The parameters affecting the solid particles, namely inertia and drift due to body forces were investigated separately. In agreement with theoretical studies Reeks, Pismen & Nir, effect is increase eddy diffusivity over that fluid (in absence drift). in particles was between 2 16%, reasonable increases reported Nir. a deterministic shown decrease unequally directions normal...

The mean streamwise development of pairs longitudinal vortices embedded in an otherwise two-dimensional turbulent boundary layer was studied. Planes closely spaced measurements the three components velocity were obtained at several locations, and vorticity circulation calculated. Skin-friction also made. It found that rate spreading a vortex greatly increased by close proximity other vortices. decrease significantly greater for corotating than counter rotating Boundary-layer thinning skin...

The current study investigates turbulence modification by particles in a backward-facing step flow with fully developed channel inlet. This provides range of regimes which to compare under the same experimental conditions. Gas-phase velocities presence 3–40% mass loadings three different particle classes (90 and 150 μm diameter glass 70 copper spheres) were measured. Attenuation streamwise fluid up 35% was observed channel-flow extension region for 40% loading largest particles. level...

The interaction between a fixed particle and decaying homogeneous isotropic turbulence is studied numerically using an overset grid that provides resolution of all scales fluid motion. A description the numerical technique validation solution procedure are presented. An ensemble 64 simulations with in different regions flow computed. diameter approximately twice size unladen Kolmogorov length scale, maximum value Reynolds numbers due to turbulent fluctuations close 20. Ensemble averages...

Abstract We present wall-modelled large-eddy simulations (WLES) of oblique shock waves interacting with the turbulent boundary layers (TBLs) (nominal $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq \ge =\geqslant \geq \def \Pr {\mathit {Pr}}\def \Fr {Fr}}\def \Rey {Re}}\delta _{99}=5.4\ \mathrm{mm}$ and ${\mathit{Re}}_{\theta }\approx 1.4\times 10^4$ ) developed inside a duct an almost-square cross-section ( $45\ \mathrm{mm}\times 47.5\ to...

The heat transfer effects of an isolated longitudinal vortex embedded in a turbulent boundary layer were examined experimentally for circulations ranging from Γ/U∞δ99 = 0.12 to 0.86. test facility consisted two-dimensional boundary-layer wind tunnel, with introduced into the flow by half-delta wing protruding surface. In all cases, size was same order as thickness. Heat measurements made using constant-heat-flux surface 160 thermocouples provide high resolution surface-temperature...

This paper describes the result of both an experimental and analytical investigation response a two-dimensional, turbulent boundary layer in air to presence particles. Copper shot, 70 μm diameter, were uniformly introduced into vertical layer, at momentum thickness Reynolds number about 1000. The particle mass flux was set 20% fluid flux, all measurements made using single-component, forward-scatter laser Doppler anemometer. clearly demonstrated that particles damped turbulence, apparently...