A TURBULENT PLUME UNDER DIFFERENT EXPERIMENTAL CONDITIONS: ENTRAINMENT, VELOCITY AND VORTICITY FIELDS

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24 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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A TURBULENT PLUME UNDER DIFFERENT EXPERIMENTAL
CONDITIONS
:
ENTRAINMENT,
VELOCITY AND VORTICITY
FIELDS

Matulka, A.
1
, López González
-
Nieto, P.
1,2
,

Redondo,

J.
M
.
1,3

Tarquis Alfonso, A.
4

(1) Pluridisciplinar Institute. UCM. 28040 Madrid. Spain.
E
-
mail: anna.
magdalena.matulka@upc.edu

(2) Applied Mathematics Dpto. UCM. 28040 Madrid.
Spain
. E
-
mail: maplopez@bio.ucm.es


(3
) Applied
Physics

Dpto.
U
PC
.
Barcelona
.
Spain
.
E
-
mail:
redondo@edu.upc.es

(4
) Applied Mathematics Dp
to. U
P
M. 28040 Madrid.
Spain.
E
-
mail: anamaria.tarquis@upm.es



ABSTRACT


Turbulent plumes are fluid motions whose primary source of kinetic energy and
momentum flux is body forces derived from density inhomogeneities. The plume
boundary acts as a phase bo
undary across which ambient fluid is entrained
.

The
difference between the plume
-
fluid radial velocity and the total fluid velocity quantifies
in a natural way the purely horizontal entrainment flux of ambient fluid into the plume
across the phase boundary

at the plume edge.

At geophysics,

it is usual the generation of turbulent plumes as a part of a dispersion
process.
For example,

there are eruptionc plumes, river plumes (into a lake, sea or
ocean), mantle plumes
, hydrothermal plumes or

contaminant plumes
, for example
.

They
also are important in engineering (building ventilation processes).

Present
paper

describes

an initial research

on
a
turbulent plume
in different
experimental
configurations

(Atwood number and initial potential energy).
Th
is

work is
bas
ed on experiments

in a confined geomtry

that have been performed in laboratory

utilizing visualizations methods
.

We aim to understand the behaviour of a turbulent plume looking at its velocity and
vorticity fields, using the PIV method. We calculate veloci
ty and vorticity PDFs and the
evolution of the structure of stratified decaying, with DigFlow program (Matulka,
2010
).

Present paper shows results of velocity and vorticity for different Atwood
number in the evolution of time.

We also explore the mixing of

the ambient fluid
produced by plume analyzing
the evolution of the plume radius
b(z
)

under different
experimental conditions
.
C
ommonly onedimensional

models incorporating a constant
entrainment coefficient
are used; we verify experimentally this assumptio
n and study
the possibility of
a variable entrainment, also related to the modification of the initial
experimental conditions.


REFERENCES


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Fackrell, J. E. and Robins, A. G.: C
oncentration fluctuations and fluxes in plumes from a point source in a
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-
26, 1982.

List, E. J.: Turbulent jets and plumes. Ann. Rev. Fluid Mech., 14, 189
-
212, 1982.

López, P., Cano, J. L. and Redo
ndo, J. M.: An experimental model of mixing processes generated by an
array of top
-
heavy turbulent plumes. Il Nuovo Cimento, 31C (5
-
6), 679
-
698, 2008.

Matulka, A., The Turbulent Structure in Environmental Flows: Effects of Stratification and Rotation,
2010
.

Redondo J.M., R. Castilla, A. Carillo, A. Matulka and A. Babiano; Taxonomy of 2D
-
3D Decaying Non
-
Homogeneous Turbulence. Topical Problems of Fluid Mechanics, Prague (ISBN 978
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80
-
87012
-
19
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2),
2009.

Woods, A. W; Turbulent plumes in nature. Annual Review o
f Fluid Mechanics, 42, 391
-
412, 2010.