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Heat and Mass Transfer

, Volume 46, Issue 1, pp 107–112 | Cite as

The influence of the periodic disturbance on the local heat transfer in separated and reattached flow

  • Zouhaier MehrezEmail author
  • Mourad Bouterra
  • Afif El Cafsi
  • Ali Belghith
  • Patrick Le Quere
Original

Abstract

A numerical study based on the large eddy simulation methodology was made of heat transfer in locally disturbed turbulent separated and reattached flow over a backward facing step. The local disturbance was given to the flow by a sinusoidally blowing/suction of the fluid into a separated shear layer. The Reynolds number was fixed at 33,000 and Richardson number at 0.5. The disturbance frequency was varied in the range 0  St  2, where St is the Strouhal number of disturbance. The obtained results revealed the existence of an optimum perturbation frequency value, St = 0.25, in terms of the reduced reattachment length. At this frequency the heat transfer is significantly enhanced in the recirculation zone. The influence of the frequency and the amplitude of disturbance, in the maximum heat transfer positions and the maximum local Nusselt number, is analysed.

Keywords

Nusselt Number Recirculation Zone Strouhal Number Local Nusselt Number Disturbance Frequency 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

A

Amplitude of disturbance

f

Frequency of disturbance

g

Gravitational acceleration

H

Computational domain width

h

Step height

Nu

Local Nusselt number H(−∂θ/∂y)w

Numax

Maximum local Nusselt number

Re

Reynolds number (U o H/ν)

Ra

Rayleigh number (gβ(T h − T c)H 3/νκ)

Ri

Richardson number (Ra/Re 2·Pr)

P

Pressure

Pr

Prandtl number

St

Strouhal number (fh/U o)

ui

Velocity vector

u

Longitudinal velocity

Uo

Maximum velocity in the inlet

v

Transverse velocity

t

Time

T

Temperature

x, y

Cartesian coordinates

Xr

Reattachment length

Xmax

Maximum heat transfer abscissa

Greek symbols

β

Thermal expansion coefficient

κ

Thermal diffusivity

ν

Kinematic viscosity

νt

Turbulent viscosity

θ

Dimensionless temperature (T  T C/T h − T C)

σc

Turbulent Prandtl number

Subscripts

C

Cold

h

Hot

w

Wall

o

Non-disturbed case

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Zouhaier Mehrez
    • 1
    Email author
  • Mourad Bouterra
    • 1
  • Afif El Cafsi
    • 1
  • Ali Belghith
    • 1
  • Patrick Le Quere
    • 2
  1. 1.Faculté des Sciences de TunisCampus UniversitaireTunisTunisia
  2. 2.LIMSI-CNRS Bat. 508Orsay CedexFrance

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