Heat the initial portion in a plane channel in the flow medium in the regime of ideal displacement with boundary conditions of first kind

2015 ◽  
Vol 3 (5) ◽  
pp. 188-190
Author(s):  
A. Boger ◽  
A. Makarovskiy
Keyword(s):  
Boundary Conditions ◽  
Plane Channel ◽  
Initial Portion ◽  
Ideal Displacement ◽  
Flow Medium

scholarly journals Investigation of the Wall Scalar Fluctuations Effect on Passive Scalar Turbulent Fields at Several Prandtl Numbers by Means of Direct Numerical Simulations

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Bruno Chaouat ◽  
Christophe Peyret
Keyword(s):  
Boundary Condition ◽  
Heat Flux ◽  
Scalar Field ◽  
Boundary Conditions ◽  
Plane Channel ◽  
Passive Scalar ◽  
Wall Region ◽  
Turbulent Heat ◽  
The Mean ◽  
Prandtl Numbers

Abstract We investigate the effect of the wall-scalar fluctuations on passive scalar turbulent fields for a moderate Reynolds number Rτ = 395 and for several Prandtl numbers ranging from the very low value Pr = 0.01 to the high value Pr = 10 by means of direct numerical simulation (DNS) simulations. Several cases of plane channel flows are considered. Case I is a channel flow heated on both walls with a constant imposed heat flux qw. We consider for this case two different types of boundary conditions. For the first one, the isoscalar boundary condition θw = 0 is imposed at the wall implying that its fluctuation and therefore its rms scalar fluctuations θrms=⟨θ′θ′⟩ is zero at the wall whereas in the second type, θw is not prescribed to a fixed value so that it is fluctuating in time at the wall leading to nonzero rms fluctuations. In this latter case, as the heat flux is maintained constant in time at the wall, the fluctuating heat flux q′w reduces to zero at the wall. For illustration purpose, in addition to case I, we also consider case II, which is a plane channel heated only from one wall but cooled from the other one at the same rate taking into account of the freestream scalar boundary condition at the wall θ′w≠0 with q′w=0. The distributions of the mean scalar field, root-mean-square fluctuations, turbulent heat flux, correlation coefficient, turbulent Prandtl number, and Nusselt number are examined in detail. Moreover, some insights into the flow structure of the scalar fields are provided. As a result of interest, it is found that the mean scalar field ⟨θ⟩ is not affected by the scalar fluctuations at the wall. But owing to the different boundary conditions applied at the wall, significant differences in the evolution of the rms scalar fluctuations θrms are observed in the immediate vicinity of the wall. Surprisingly, the maximum rms intensity remains almost unchanged in the near wall region whatever the type of boundary condition is applied at the wall. In addition, the turbulent heat fluxes that play a major role in heat transfer are found to be independent of the wall scalar fluctuations. This study demonstrates that the impact of the wall scalar fluctuations is appreciable mainly in the near wall region. This outcome must be taken into account when simulating industrial flows with thermal boundary conditions involving different fluid/solid combinations.

scholarly journals Artificial boundary conditions for the ILES modeling of plane channel flow using the Cabaret scheme

2019 ◽  
pp. 12-20
Author(s):  
Д.Г. Асфандияров
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Channel Flow ◽  
Plane Channel ◽  
Pseudospectral Method ◽  
Artificial Boundary ◽  
Cabaret Scheme ◽  
Artificial Boundary Conditions ◽  
Wide Range ◽  
Plane Channel Flow

Представлены результаты ILES-моделирования классической задачи течения вязкой несжимаемой жидкости в плоском канале по схеме Кабаре. Рассматривается возможность модификации расчета течения возле стенки для более точного определения средних характеристик. Предложено введение "искусственных" граничных условий путем использования в первом слое ячеек вблизи стенки специальной модели вихревой вязкости для корректного учета сдвиговых эффектов. Приводится сравнение результатов расчета течения в плоском канале по схеме Кабаре с предложенными искусственными граничными условиями и без в широком диапазоне чисел Рейнольдса. Показано, что введенные модификации в пристеночном слое позволяют повысить точность определения средних характеристик течения, в особенности вторых моментов. Полученные данные также сравниваются с результатами LES-моделирования с использованием псевдоспектрального метода и с данными прямого численного моделирования. Some results of ILES modeling of the plane channel flow of a viscous incompressible fluid using the Cabaret scheme are discussed. The possibility of modifying the calculation of flow near the wall is considered to determine the average characteristics more accurately. The "artificial" boundary conditions are introduced by using a special eddy viscosity model in the first layer of cells near the wall to correctly account for shear effects. The results of numerical simulation of plane channel flow obtained using the Cabaret scheme with and without artificial boundary conditions are compared in a wide range of Reynolds numbers. It is shown that the introduced modifications in the near-wall layer improve the accuracy of determining the average flow characteristics, especially the second moments. The obtained data are also compared with the results of LES modeling by the pseudospectral method and with the data from direct numerical simulation.

Computational Modeling of the Effects of Viscous Dissipation on Polymer Melt Flow Behavior During Injection Molding Process in Plane Channels

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
M. Tutar ◽  
A. Karakus
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Boundary Conditions ◽  
Viscous Dissipation ◽  
Plane Channel ◽  
Polymer Melt ◽  
Viscous Heating ◽  
Melt Flow ◽  
Flow And Heat Transfer ◽  
Volume Method

The present finite volume method based fluid flow solutions investigate the boundary-layer flow and heat transfer characteristics of polymer melt flow in a rectangular plane channel in the presence of the effect of viscous dissipation and heat transfer by considering the viscosity and density variations in the flow. For different inflow velocity boundary conditions and the injection polymer melt temperatures, the viscous dissipation effects on the velocity and temperature distributions are studied extensively to analyze the degree of interactions of thermal flow field dominated by the viscous heating and momentum diffusion mechanism with varying boundary conditions. The modified forms of Cross constitutive equation and Tait equation of state are adopted for the representation of viscosity variations and density change, respectively, in the polymer melt flow. These models together with the viscous dissipation terms are successfully incorporated into the finite volume method based fluid flow solutions to realistically represent the heat effects in the plane channel. The numerical results presented for two different commercial polymer melt flows, namely, polymer Polyacetal POM-M90-44 and polypropylene (PP), demonstrate that proposed mathematical formulations for viscosity and density variations including viscous heating terms into the energy equations, which are fully coupled with momentum equations, lead to more accurate representation of the fluid flow and heat transfer phenomena for the polymer melt flows in plane channels.

Use of the Magnetostatic Analogue In Electromagnetic Lens Engineering

1970 ◽  
Vol 28 ◽  
pp. 360-361
Author(s):  
John W. Coleman
Keyword(s):  
Boundary Conditions ◽  
High Performance ◽  
Force Fields ◽  
Optical Design ◽  
Direct Conversion ◽  
Design Engineering ◽  
Design Data ◽  
Scalar Potentials ◽  
Geometric Elements ◽  
At Will

In the design engineering of high performance electromagnetic lenses, the direct conversion of electron optical design data into drawings for reliable hardware is oftentimes difficult, especially in terms of how to mount parts to each other, how to tolerance dimensions, and how to specify finishes. An answer to this is in the use of magnetostatic analytics, corresponding to boundary conditions for the optical design. With such models, the magnetostatic force on a test pole along the axis may be examined, and in this way one may obtain priority listings for holding dimensions, relieving stresses, etc..The development of magnetostatic models most easily proceeds from the derivation of scalar potentials of separate geometric elements. These potentials can then be conbined at will because of the superposition characteristic of conservative force fields.

A digital vocal tract simulator with boundary conditions at lips and glottis

1981 ◽  
Vol 64 (11) ◽  
pp. 18-26 ◽  
Author(s):  
Tetsuya Nomura ◽  
Nobuhiro Miki ◽  
Nobuo Nagai
Keyword(s):  
Boundary Conditions ◽  
Vocal Tract

Exploring the affective impact, boundary conditions, and antecedents of leader humility.

2018 ◽  
Vol 103 (9) ◽  
pp. 1019-1038 ◽  
Author(s):  
Lin Wang ◽  
Bradley P. Owens ◽  
Junchao (Jason) Li ◽  
Lihua Shi
Keyword(s):  
Boundary Conditions ◽  
Affective Impact ◽  
Leader Humility
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