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Turbulent Mixed Convection

Electronic Theses of Indian Institute of Science

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Field Value
 
Title Turbulent Mixed Convection
 
Creator Ramesh Chandra, D S
 
Subject Mechanical Enginering
Shear Flow
Convection Model
Near Wall Dynamics
Flow Regimes
Monin-Obukhov Theory
Wall Shear Stress
Low Speed Mixed Convection LSM)
High Speed Mixed Convection (HSM)
 
Description Turbulent mixed convection is a complicated flow where the buoyancy and shear forces compete with each other in affecting the flow dynamics. This thesis deals with the near wall dynamics in a turbulent mixed convection flow over an isothermal horizontal heated plate. We distinguish between two types of mixed convection ; low-speed mixed convection (LSM) and high-speed mixed convection (HSM). In LSM the entire boundary layer, including the near-wall region, is dominated by buoyancy; in HSM the near-wall region, is dominated by shear and the outer region by buoyancy. We show that the value of the parameter (* = ^ determines whether the flow is LSM or HSM. Here yr is the friction length scale and L is the Monin-Obukhov length scale.

In the present thesis we proposed a model for the near-wall dynamics in LSM. We assume the coherent structure near-wall for low-speed mixed convection to be streamwise aligned periodic array of laminar plumes and give a 2d model for the near wall dynamics, Here the equation to solve for the streamwise velocity is linear with the vertical and spanwise velocities given by the free convection model of Theerthan and Arakeri [1]. We determine the profiles of streamwise velocity, Reynolds shear stress and RMS of the fluctuations of the three components of velocity. From the model we obtain the scaling for wall shear stress rw as rw oc (UooAT*), where Uoo is the free-stream velocity and AT is the temperature difference between the free-stream and the horizontal surface.A similar scaling for rw was obtained in the experiments of Ingersoll [5] and by Narasimha et al [11] in the atmospheric boundary layer under low wind speed conditions. We also derive a formula for boundary layer thickness 5(x) which predicts the boundary layer growth for the combination free-stream velocity Uoo and AT in the low-speed mixed convection regime.
 
Publisher Indian Institute of Science
 
Contributor Arakeri, J H
 
Date 2006-08-28T05:26:19Z
2006-08-28T05:26:19Z
2006-08-28T05:26:19Z
2000-04
 
Type Electronic Thesis and Dissertation
 
Format 7489124 bytes
application/pdf
 
Identifier http://hdl.handle.net/2005/236
null
 
Language en
 
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