Numerical Investigation of Near-Wall Turbulent Heat Transfer Taking Into Account the Unsteady Heat Conduction in the Solid Wall

1989 ◽  
Vol 111 (2) ◽  
pp. 385-392 ◽  
Author(s):  
N. Kasagi ◽  
A. Kuroda ◽  
M. Hirata
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Solid Wall ◽  
Wall Turbulence ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Turbulence Structure ◽  
Temperature Variance ◽  
Unsteady Heat Conduction ◽  
Near Wall

The deterministic near-wall turbulence model developed by Kasagi et al. (1984b) is used in a numerical analysis of turbulent heat transfer, in which the unsteady heat conduction inside the wall associated with the turbulent flow unsteadiness is taken into account. Unlike the typical methodology based on Reynolds decomposition, the algebraic expressions for the three fluctuating velocities given by the model are directly introduced into the governing energy equation. From the numerical results of the unsteady conjugate heat transfer, the statistical quantities, such as temperature variance, turbulent heat flux, and turbulent Prandtl number, are obtained for fluids of various Prandtl numbers. It is demonstrated that the near-wall behavior of these quantities is strongly influenced by the thermal properties and thickness of the wall. In addition, the budget of the temperature variance associated with coherent turbulence structure is calculated and, except for dissipation, each budget term is in qualitative agreement with the experiment.

Heat Transfer Modeling and the Assumption of Zero Wall Temperature Fluctuations

1994 ◽  
Vol 116 (4) ◽  
pp. 855-863 ◽  
Author(s):  
T. P. Sommer ◽  
R. M. C. So ◽  
H. S. Zhang
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Transfer Problem ◽  
Solid Wall ◽  
Temperature Fluctuations ◽  
Wall Turbulence ◽  
Turbulent Heat ◽  
Fluctuating Temperature ◽  
Temperature Variance ◽  
Near Wall

At present, it is not clear how the fluctuating temperature at the wall can be properly specified for near-wall turbulent heat-flux models. The conventional approach is to assume zero fluctuating temperature or zero gradient for the temperature variance at the wall. These are idealized specifications and the latter condition could lead to an ill-posed problem for fully developed pipe and channel flows. In this paper, the validity and extent of the zero fluctuating wall temperature condition for heat transfer calculations are examined. The approach taken is to assume Taylor series expansions in the wall normal coordinate for the fluctuating quantities that are general enough to account for both zero and nonzero temperature fluctuations at the wall and to develop a near-wall turbulence model allowing finite values of the wall temperature variance. As for the wall temperature variance boundary condition, it is estimated by solving the coupled heat transfer problem between the fluid and the solid wall. The eddy thermal conductivity is calculated from the temperature variance and its dissipation rate. Heat transfer calculations assuming both zero and nonzero fluctuating wall temperature reveal that the zero fluctuating wall temperature assumption is quite valid for the mean field and the associated integral heat transfer properties. The effects of nonzero fluctuating wall temperature on the fluctuating field are limited only to a small region near the wall for most fluid/solid combinations considered.

Coherent motions and heat transfer in a wall turbulent shear flow

1995 ◽  
Vol 305 ◽  
pp. 127-157 ◽  
Author(s):  
Y. Nagano ◽  
M. Tagawa
Keyword(s):  
Heat Transfer ◽  
Heat Transport ◽  
Phase Relationship ◽  
Transport Processes ◽  
Wall Turbulence ◽  
Ar Model ◽  
Turbulent Heat Transfer ◽  
Good Time ◽  
Turbulent Shear ◽  
Turbulent Heat

In wall turbulence, it is widely accepted that the coherent motions determine the essential features of turbulent transport phenomena. In the present study, we have refined a trajectory-based detection algorithm for coherent motions and have investigated the relationship between coherent motions and scalar (heat) transfer from a structural point of view, i. e. trajectory analysis of the VITA heat transfer events, extraction of key flow modules and the relevant heat transport, and the prediction of passive scalar transfer by means of an autoregressive (AR) model. As a result, it is shown that the phase relationship of fluctuating velocity components dominates the essential characteristics of the transport processes of heat and momentum in wall turbulence and there exist distinct differences in individual correspondence between the coherent motions and heat transport processes, neither of which can be revealed by the widely used VITA technique. Also, the AR model is shown to provide good time-series predictions for turbulent heat transfer associated with coherent structures near the wall.

A Stochastic Lagrangian Model for Near-Wall Turbulent Heat Transfer

1997 ◽  
Vol 119 (1) ◽  
pp. 46-52 ◽  
Author(s):  
S. Mazumder ◽  
M. F. Modest
Keyword(s):  
Heat Transfer ◽  
Joint Probability ◽  
Molecular Transport ◽  
Temperature Fluctuations ◽  
Reynolds Stress Model ◽  
Constant Heat Flux ◽  
Lagrangian Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Near Wall

The modeling of near-wall turbulent heat transfer necessitates appropriate description of near-wall effects, namely, molecular transport, production of turbulence by inhomogeneities, and dissipation of the temperature fluctuations by viscosity. A stochastic Lagrangian model, based on the velocity-composition joint probability density function (PDF) method, has been proposed. The proposed model, when compared with experimental and direct numerical simulation (DNS) data, overdamps the dissipation of the temperature fluctuations in the inertial sublayer, but reaches the correct limit at the wall. The performance of the model has also been compared to the standard k-ε and the algebraic Reynolds stress model (ARSM) for both constant heat flux and constant temperature boundary conditions at large Reynolds numbers. The Lagrangian nature of the model helps eliminate numerical diffusion completely.

Turbulent Heat Transfer in Plane Couette Flow

2004 ◽  
Author(s):  
Phuong M. Le ◽  
Dimitrios V. Papavassiliou
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Prandtl Number ◽  
Couette Flow ◽  
Channel Flow ◽  
Turbulent Dispersion ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Turbulence Structure ◽  
Plane Couette Flow

Direct numerical simulations of a turbulent plane Couette flow are combined with Lagrangian scalar tracking of thermal markers that are released in the flow field to determine the behavior of an instantaneous scalar line source located at the wall. The resulting probability density functions are used to calculate the behavior of instantaneous line sources of heat at the wall of the channel. The method is applied for fluids with a range of molecular Prandtl number, Pr, between 0.1 and 15,000, giving emphasis on the high Pr cases. The issues that are investigated are the effect of the Pr on turbulent dispersion, and the effect of the turbulence structure on turbulent heat transfer. The flow field for plane Couette flow is fundamentally different than that for channel flow, because the whole Couette flow domain is a constant stress region that forms an extensive logarithmic layer. For an instantaneous source at the wall, it is found that in both the channel flow and the Couette flow cases there are similar stages of development of the marker cloud that depend on the Prandtl number. This dependence becomes stronger as the Pr increases. However, this similarity is only qualitative.

Numerical Investigation of a Heated Sodium Jet in a Co-Flow

2007 ◽  
Author(s):  
I. Otic´ ◽  
A. G. Class
Keyword(s):  
Heat Transfer ◽  
Pipe Wall ◽  
Experimental Studies ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Velocity ◽  
Temperature Variance ◽  
Physical Mechanisms ◽  
Insight Into ◽  
Good Agreement

Results of a numerical simulation of turbulent heated sodium jet in a co-flow using a combined LES-DNS approach are presented. The calculations correspond to the experiment of Knebel, Krebs, Muller and Axcell [1]. In agreement with the experimental results co-flow suppresses flow reversal along the outlet pipe wall. Comparisons of mean velocity, mean temperature, and temperature variance between experimental and numerical results show fairly good agreement. The results support the applicability of the combined LES-DNS approach for this type of flows. Simulations using this approach may complement experimental studies, allowing for better insight into the physical mechanisms of liquid metal turbulent heat transfer.

Turbulent Heat Transfer Augmentation Using Microscale Disturbances Inside the Viscous Sublayer

1992 ◽  
Vol 114 (2) ◽  
pp. 348-353 ◽  
Author(s):  
H. Kozlu ◽  
B. B. Mikic ◽  
A. T. Patera
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Heat Removal ◽  
Channel Flows ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Two Dimensional ◽  
Optimal Position ◽  
Heat Transfer Augmentation ◽  
Near Wall

We report here on an experimental study of heat transfer augmentation in turbulent flow. Enhancement strategies employed in this investigation are based on the near-wall mixing processes induced in the sublayer through appropriate wall and near-wall streamwise-periodic disturbances. Experiments are performed in a low-turbulence wind-tunnel with a high-aspect-ratio rectangular channel having either (a) two-dimensional periodic microgrooves on the wall, or (b) two-dimensional microcylinders placed in the immediate vicinity of the wall. It is found that micro-disturbances placed inside the sublayer induce favorable heat-transport augmentation with respect to the smooth-wall case, in that near-analogous momentum and heat transfer behavior are preserved; a roughly commensurate increase in heat and momentum transport is termed favorable in that it leads to a reduction in the pumping power penalty at fixed heat removal rate. The study shows that this favorable performance of microcylinder-equipped channel flows is achieved for microcylinders placed inside y+ ≃20, implying a dependence of the optimal position and size on Reynolds number. For microgrooved channel flows, favorable augmentation is obtained for a wider range of Reynolds numbers; however, optimal enhancement still requires a matching of geometric perturbation with the sublayer scale.

Sign in / Sign up

Export Citation Format

Share Document