Lorentz Centre, 19 Sep. 2006 Particle transport and flow modification in planar temporally evolving...

Lorentz Centre, 19 Sep. 2006

Particle transport and flow modification in planar temporally evolving mixing layers

Djamel Lakehal, Chidambaram Narayanan(G. Yadigaroglu, ETH Zurich)

Adjunct Lecturer at ETH & Manager of ASCOMP GmbH(www.ascomp.ch)

Outline

Motivations: environmental concerns

Mixing layer basic flow features

Transport under 1-way coupling

Transport under 2-way coupling

Summary

Transport & dispersion of sandVolcanic ash dispersion

CO2

H20

Environmental flows with particles and droplets

Simulation: Eulerian-Lagrangian formulation

fpi

j

Fx

u

x

p

x

uu

t

u

x

u

j

j

j

j

j

j

j

2

21

0

Re

FLUID

PARTICLE

3/2

2

Re15.01

)(2

9

pd

pippp

dp

f

txuud

fdt

dvi

i

Details

Re=400, 64 X 129 Fourier Chebyshev collocation; Lx=4/Km

Tangent-hyperbolic U velocity fieldAmplitude of Fund. & Sub. modes Ef = 10-2; Es = 10-4

Rep < 1; Np = 2-4.105 particles; St= 0.3 - 5; M = 0.1-0.52nd order Runge-Kutta for Particle Equation

4th order Lagrangian ploynomial velocity interpolation

DNS of Particle dispersion in a mixing layer; St = 1.0

2D particle-laden mixing layer under 1- and 2-way Coupling: What is new ?

The analysis is Eulerian-Eulerian based

The controlling mechanisms

The mean vertical particle-phase velocity induced by KH

The correlation between particle-phase and fluid-phase modal (KH induced) stress

The effect of particle-phase modal velocity on the growth of the particle-phase mixing layer

Basic Flow Features:

1. flow evolution

2. Kinetic energy balances

Particle Transport under One-way

1. centrifuging effect

2. statistics

3. momentum balance

I- Outline: Particle Transport under 1-way Coupling

Saturation of fund. mode at t=48

initiation of pairing at t=72

end of pairing at t=96

single vortex at t=120

u=<u> +u’

u=<u> +u’

t=72 t=96

t=72 t=96

St=0.3 St=0.6 St=1

t=72

St=0.3 St=0.6 St=1

t=96

Analysis: Continuum formulation

cdz

pppp

dcz

dpppp

pppp

dcx

dpppp

p

Fz

pww

z

wwwwnz

nFwwnz

wnt

wuuwnz

nFuwnz

unt

wnzt

n

''

][

1

][

1

0

CONTINUM

FIELD

FLUID

W

t=48 t=96

t=48 t=96t=72

Only the sub-harmonic is “really” nutating:effective St have diminished; L has increased

t=96, St=0.6 t=96, St=1

momentum depletion region

accumulation region

II- Outline: Particle Transport under 2-way Coupling

Computational parameters

Particle accumulation patterns

Fundamental mode saturation & pairing

Particle Statistics

1. Generation of small scales

2. Evolution of average modal stress

3. Mean kinetic energy balance

St=1

St=0.3

St=0.6

M=0.2t=72

St=0.3M=0

M=0.5M=0.2

St=1t=96

St=2M=0.2

No new instability forms for low M and uniformly distributed particles: rather drag effect

t=72 t=96

St=1, time=72

M=0

M=0.2 M=0.5

M=0.1

M=0

M=0.5M=0.2

M=0.1

St=1, time=96

t=48 t=96

Centrifuging effect of KH is lower in 2-way coupling

t=48 t=96

St=0.3 St=1

Summary

Particle transport in turbulent mixing layers was analyzed using DNS + Lagrangian particle tracking.

Particles modify the flow evolution dramatically even at mass loadings of 0.5; generation of small scales.

Intricate undulating patterns are formed.

Effect of preferential concentration on particle statistics was emphasized.

Related publications

Related publications

Narayanan C., Lakehal, D.: DNS of particle-laden mixing-layers. Part I: One-way coupled flow and dispersed-phase features. Phys. Fluids, 18(9), pp. 15, 2006.

Narayanan C., Lakehal, D.: DNS of particle-laden mixing-layers. Part II: Two-way coupled induced generation of small-scale vorticity, Phys. Fluids, 18(9), 2006.

Botto L., Narayanan C., Fulgosi M., Lakehal D.: Effect of near-wall turbulence enhancement on the mechanism of particle deposition, Int. J. Multiphase Flow, 31(8), 2005.

Lakehal D., Narayanan C.: Numerical Analysis of the continuum formulation for the Initial Evolution of Mixing Layers with Particles, Int. J. Multiphase Flow, 29(6), 2003. 

Narayanan C., Lakehal D., Botto L., Soldati A.: Mechanisms of particle deposition in a fully-developed turbulent open channel flow, Phys. of Fluids, 15(3), pp. 763, (2003).

Narayanan C., Lakehal D.: Temporal instabilities of a mixing-layer with uniform and non-uniform particle loadings, Physics of Fluids, 14(11), pp. 3775, (2002).

Narayanan C., Lakehal D.: Linear Stabilities Analysis of Particle-Laden Mixing Layers using Lagrangian Particle Tracking, Powder Technology, 125, pp. 122,  (2002).