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Spatial distribution and settling velocity of heavy particles in synthetic turbulent ﬁelds

Łuniewski M., Pozorski J.

Transactions of the Institute of Fluid-Flow Machinery

2017

nr 135

87--100

We analyse numerically the motion of small inertial particles, subject to gravity, in two simple velocity ﬁelds: two-dimensional cellular ﬂow, and a three-dimensional ﬂow being the superposition of random Fourier velocity modes. The latter, also known as the kinematic simulation or synthetic turbulence, has often been applied in various studies, including those aiming to predict particle dispersion. The interplay of the particle inertia and the acceleration of gravity has non-trivial consequences for trajectories of particles and their spatial distribution, known as a preferential concentration. Also, we compute the average settling velocity of particles in function of their inertia and the number of ﬂuid velocity modes used in simulations. The present paper aims to study these efects, as the synthetic turbulence represents an interesting option for subﬁlter modeling in particle-laden large-eddy simulation.

Numerical study of a polydisperse two-phase jet

Barata J., Perestrelo N.

Archiwum Motoryzacji

2000

Nr 2

113-125

Low emissions gas turbine combustors will demand fuel injection systems that are efficient in the accomplishment of the mixing of fuel and air in the shortest possible residence time. This paper describes a computational study of a polydisperse two-phase turbulent jet, which is the basic configuration to analyze how the various parameters influence the size distribution and the dispersion of the droplets in the injection process. An Eulerian frame for the for the gas phase was used in conjunction with a Lagrangian approach to describe both interphase slip and turbulence on particle motion. Good agreement of the computations with the experimental data is obtained for both the gas and the particles turbulence modulation and anisotropy effects were introduced and were found to be very important to the successful performance of the computational method. The exchange of monumentum and turbulence energy between the two phases was shown to play a decisive role on the flow development. The predictions confirmed the measurements and showed that the particles do not follow the turbulent gas flow, but they affect it significantly. Considerably high values of the radial velocity were detected around the centerline far from the jet exit where the velocity of the particles lags that of the fluid, that seems to be associated with the effect of shear induced lift forces.

Przedstawiono studium komputerowe polidyspersyjnej dwufazowej strugi turbulentnej, które jest bazą wyjściową do oceny wpływu różnych parametrów na rozkład średnicy kropel podczas wtrysku do ośrodka gazowego. Wykorzystano Eulerowską analizę do fazy gazowej oraz analizę Lagrange'a do obliczania drogi cząstek. Uzyskane wyniki obliczeniowe są zgodne z eksperymentalnymi. Turbulencja i niejednorodność średnic kropel mają istotny wpływ na rozwój strumienia. Stwierdzono także, że składowe promieniowe prędkości z daleka od otworu rozpylacza uzyskują wysokie wartości.