Geen diatitel

1
Turbulence Modification by Particles in a
Vertical Grid Flow Facility - set up
measurement techniques -
C. Poelma, A. Kruizinga, H. Rotteveel, J.
Westerweel and G. Ooms ETC-9, Southampton
(UK) July 2002
2
Experimental Facility
2 Poelma, Westerweel and Ooms,
ETC-9, July 2002
Decaying Grid Turbulence
1-phase 2-phase ?
z/M
grid
Turbulence intensity ?
Single-Phase relatively well-understood Two-Phas
e turb. decay rate, length scales, correlation
lengths, dispersion ? Test case for
Felderhof-Ooms-Jansen model (analytical
model, predicts turbulence modification in
homogeneous isotropic turbulence, implemented in
Fluent)
3
Experimental Facility
3 Poelma, Westerweel and Ooms,
ETC-9, July 2002
VerMeer set up
test section
contraction
grid
diffusor
pump
4
Experimental Facility BLS
4 Poelma, Westerweel and Ooms,
ETC-9, July 2002
Boundary Layer Suction boundary layer removal
by suction through porous metal ring
segments additional advantages particle
trap due to tuneable centreline
velocity easier measurement of dispersed
phase
particle size gt pore size tracer size lt pore size
Up
Uf
5
Boundary Layer Suction
5 Poelma, Westerweel and Ooms,
ETC-9, July 2002
Effect of Boundary Layer Suction on centerline
velocity
164
0
160
156
2
152
146
Uc (mm/s)
144
140
136
5
no suction
132
2 of main flow /ring
5 of main flow /ring
128
40
50
60
70
80
90
100
110
120
z/M
6
Flow Characteristics
6 Poelma, Westerweel and Ooms,
ETC-9, July 2002
M 0.75 cm Re(pipe) 50000 Turb. Int. 5 ?
0.40 U 50 cm/s anisotropy lt 5
typical Re(turb) UL/? 600 ? 1/U dk/dx
0.1 m2/s3 fluid particles T 0.08 s U
12 cm/s tstokes 0.002 - 0.1 s L 5 mm dp
0.2 - 0.5 mm ?p/?f 1 - 7 tk 0.003 s uk
1.8 cm/s lk 0.06 mm
7
Measurement Technique
7 Poelma, Westerweel and Ooms,
ETC-9, July 2002
Combined PIV PTV Simultaneous measurement of
both phases
Nd

Yag
light sheet
fluorescent
tracer (40 micron)
L
L
PIV
R
fluid
preshift
L
L
particle (500 micron)
PTV
R
measurement region (3 cm x 3 cm)
color filter
Acquisition LaVision PIV system (2x 2000x2000
cam. _at_ 1-8Hz) Processing DaVis (initial),
PivWare and PTVWare (under development)
8
PIV/PTV Test Measurements
8 Poelma, Westerweel and Ooms,
ETC-9, July 2002
Combined two-phase PIV PTV test measurements
in thermal convection set up
top view
front view
dispersed phase
lL
Field of view
light sheet
lV
dp, ?
CCD
HEAT
9
PTV/PIV test results
9 Poelma, Westerweel and Ooms,
ETC-9, July 2002
influence of laser path length
100
90
80
70
60
percentage of valid vectors
0.3vol
50
0.4vol
40
1.0vol
30
influence of optical path length
20
100
10
0
90
0
2
4
6
8
10
12
14
16
field of view position (cm)
80
70
60
50
Measuring at 0.5vol feasible
percentage of valid vectors
40
30
0.3vol
0.4vol
20
1.0vol
10
0
2
4
6
8
10
12
14
16
18
20
depth (distance to front wall in cm)
10
PIV/PTV-examples
10 Poelma, Westerweel and Ooms,
ETC-9, July 2002
Eulerian averaging over Field of View snapshot
of both fluid flow field and particle velocities
(raw)
uy
uy,p
particles
ux
uy,f
Slip velocity
fluid
11
PIV/PTV-examples
11 Poelma, Westerweel and Ooms,
ETC-9, July 2002
Lagrangian moving with dispersed
phase matched traces of particles series of
100 images _at_ 8 Hz
t10
t5
Particle dispersion vs. Turbulent diffusion
t0
12
Summary and Outlook
12 Poelma, Westerweel and Ooms,
ETC-9, July 2002
- a grid flow facility was constructed and
characterised - the centerline velocity can be
controlled with BLS - a two-phase PTV/PIV
measurement system was developed - measurement at
0.5vol seems feasible in two-phase flows
(with particle size 300-500 microns) -
simultaneous measurement yields invaluable
information Next step systematic study of
turbulence modification