Natural Convection On The Cylindrical Enclosure With Localized Heating From Below

Perm State University

Natural Convection On The Cylindrical Natural Convection On The Cylindrical Enclosure With Localized Heating From BelowEnclosure With Localized Heating From Below..

Perm 2010

A.V. Evgrafova

Scientific advisers

P. G. Phrick

A. N. Sukhanovsky

The goal of this work is investigation of transverse rolls in natural convection flow over localized heat source in a cylindrical fluid layer.

Importance of the work and its aims

Morning Glory Clouds Over Australia (Photo by M. Petroff, 11 August 2009)

Thermal – chemical vapor deposition system

Experimental set-up

1-heater,2-vessel, 3- fluid,4-divergent flow,5-convergent flow

2R2

4

5

h, mm

1

1

2

h 3

z

R1 = 52 mm ,R2 = 150 mm, h = 30 mm, the fluid is silicon oil

R1R1

Numeric simulation

In numeric simulation laminar natural convection has been studied in a horizontal cylindrical enclosure with a free upper surface and heating source at the bottom. For simulation Ansys Cfx is used.

z

r

Secondary structures. Experiment.

ΔТ,0С1 2 3

z, mm

Т, 0С

Distribution of temperature over vertical coordinate

1. r=10 mm, 2. r=30 mm, 3. r=50 mm.

Gr =9.8*104

Instantaneous temperature distribution over radial coordinate, z=1mm

Temperature distribution over time, z=1mm, r=30 mm

Radial and time distribution of temperature. Experiment.

Т, 0С

0 50 100 150 200 250 300 350 400 450 50023.6

23.8

24

24.2

24.4

24.6

24.8

X: 268Y: 24.38

Зависимость температуры от времени на 30 мм от центра(область квазистационара - эксперимент)

t, с

Т,

град

X: 281Y: 24.38

r, mm

t, s

Gr =9.8*104

Т, 0С

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

X: 0.06885Y: 0.1612

Спектр пульсация температуры (30 мм от центра-эксперимент)

частота, Гц

E,K

2 *с

X: 0.1377Y: 0.02147

0 0.02 0.04 0.06 0.08 0.1 0.12 0.140

0.1

0.2

0.3

0.4

0.5

0.6

0.7

X: 0.06641Y: 0.5177

Спектр пульсаций температуры в области квазистационара(40 мм от центра-численный расчет)

частота, Гц

E,K

2 *сE, К2 *s

E, К2 *s

ν, Hz

ν, Hz

Spectral analysis of temperature fluctuations

Experimentr=30 mm

ν=0.0688 Hz

Numeric simulationr=30 mm

ν=0.0664 Hz

Gr =9.8*104

Secondary structures. Numeric simulation.

Instantaneous temperature field in heated region

Dynamics of secondary rolls

Gr =9.8*104

Z, mm

r, mm

Conclusion• Secondary structures generation in the form of transverse rolls is studied both numerically and experimentally in cylindrical fluid layer with localized heating.• Results obtained numerically and the experimental data correlated well because the frequencies of rolls generation are equal. • Basing on the good correlation a lot of flow characteristics are obtained, such as instantaneous temperature fields. Also the origin and dynamics of the secondary structures were traced.

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