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R P Chhabra - One of the best experts on this subject based on the ideXlab platform.

  • natural convection in bingham Plastic Fluids from an isothermal spheroid effects of Fluid yield stress viscous dissipation and temperature dependent viscosity
    Korea-australia Rheology Journal, 2017
    Co-Authors: Sanjay Kumar Gupta, Anoop K. Gupta, R P Chhabra
    Abstract:

    In this work, the buoyancy-induced convection from an isothermal spheroid is studied in a Bingham Plastic Fluid. Extensive results on the morphology of approximate yield surfaces, temperature profiles, and the local and average Nusselt numbers are reported to elucidate the effects of the pertinent dimensionless parameters: Rayleigh number, 102 ≤ Ra ≤ 106; Prandtl number, 20 ≤ Pr ≤ 100; Bingham number, 0 ≤ Bn ≤ 103, and aspect ratio, 0.2 ≤ e ≤ 5. Due to the Fluid yield stress, Fluid-like (yielded) and solid-like (unyielded) regions coexist in the flow domain depending upon the prevailing stress levels vis-a-vis the value of the Fluid yield stress. The yielded parts progressively grow in size with the rising Rayleigh number while this tendency is countered by the increasing Bingham and Prandtl numbers. Due to these two competing effects, a limiting value of the Bingham number (Bn max) is observed beyond which heat transfer occurs solely by conduction due to the solid-like behaviour of the Fluid everywhere in the domain. Such limiting values bear a positive dependence on the Rayleigh number (Ra) and aspect ratio (e). In addition to this, oblate shapes (e 1) impede it. Finally, simple predictive expressions for the maximum Bingham number and the average Nusselt number are developed which can be used to predict a priori the overall heat transfer coefficient in a new application. Also, a criterion is developed in terms of the composite parameter Bn∙Gr-1/2 which predicts the onset of convection in such Fluids. Similarly, another criterion is developed which delineates the conditions for the onset of settling due to buoyancy effects. The paper is concluded by presenting limited results to delineate the effects of viscous dissipation and the temperature-dependent viscosity on the Nusselt number. Both these effects are seen to be rather small in Bingham Plastic Fluids.

  • the motion of a rotating circular cylinder in a stream of bingham Plastic Fluid
    Journal of Non-newtonian Fluid Mechanics, 2016
    Co-Authors: Pooja Thakur, Naveen Tiwari, Shikhar Mittal, R P Chhabra
    Abstract:

    Abstract In this work, two-dimensional, steady flow of incompressible Bingham Plastic Fluids past a rotating circular cylinder has been studied. The continuity and momentum equations have been solved numerically over the range of conditions as follows: 0.1 ≤ Re ≤ 40; Bingham number, 0 ≤ Bn ≤ 103 and non-dimensional rotational velocity 0 ≤ α ≤ 5. The objective of the detailed numerical study is to elucidate the effects of Reynolds number, Bingham number and rotational velocity on the yield surfaces, the drag and lift coefficients, and torque acting on the rotating cylinder. The present drag results have been correlated with the modified Reynolds number and rotational velocity to interpolate the intermediate values of Bingham number. In additional, shear rate and yielded/unyielded contours, and streamlines in the vicinity of the cylinder are also presented for detailed visualization of the flow field. The critical Bingham number, denoting the cessation of the flow detachment from the surface of the rotating cylinder, has been plotted as a function of the Reynolds number, and the rotational velocity is shown to suppress the propensity for flow separation.

  • Forced Convection from a Heated Equilateral Triangular Cylinder in Bingham Plastic Fluids
    Numerical Heat Transfer Part A: Applications, 2014
    Co-Authors: A. Bose, N Nirmalkar, R P Chhabra
    Abstract:

    The momentum and forced convection heat transfer characteristics of a heated equilateral triangular cylinder immersed in a Bingham Plastic Fluid have been studied numerically. The governing equations (continuity, momentum, and thermal energy) are solved for both vertex-upstream and vertex-downstream orientations, over wide ranges of the pertinent parameters, such as Reynolds number: 0.1 ≤ Re ≤30; Prandtl number: 1 ≤ Pr ≤100; and Bingham number: 0 ≤ Bn ≤200. Over the range of conditions, the flow is expected to be steady and symmetric. Detailed analysis of the flow and heat transfer phenomena in the vicinity of the cylinder is performed by a thorough inspection of the streamline and isotherm contours. Furthermore, due to the presence of the yield stress, the flow domain consists of yielded (or Fluid-like) and unyielded (or solid-like) zones. The effect of Reynolds number and Bingham number on the shape and size of these zones has been thoroughly examined in terms of the detailed velocity and shear rate pro...

  • Laminar forced convection heat transfer from a heated square cylinder in a Bingham Plastic Fluid
    International Journal of Heat and Mass Transfer, 2012
    Co-Authors: N Nirmalkar, R P Chhabra, Robert J Poole
    Abstract:

    Abstract In this work, the momentum and heat transfer characteristics of a heated cylinder of square cross-section immersed in a streaming Bingham Plastic medium have been studied. The governing differential equations (continuity, momentum and thermal energy) have been solved numerically over wide ranges of conditions as: Plastic Reynolds number, 0.1 ⩽ Re ⩽ 40 , Prandtl number, 1 ⩽ Pr ⩽ 100 and the Bingham number, 0 ⩽ Bn ⩽ 100 . Over this range of conditions, the flow is expected to be symmetric and steady. The detailed flow and temperature fields in the vicinity of the cylinder surface are examined in terms of streamline and isotherm profiles respectively. In particular, owing to the presence of the yield stress, the so-called yielded (Fluid-like) and unyielded (solid-like) regions are delineated in the flow domain as functions of the Reynolds and Bingham numbers. This objective is accomplished by a detailed examination of the velocity profiles and shear rate profiles along the center planes. Further insights are developed in terms of the distribution of the pressure and local Nusselt number along the cylinder surface together with their average values in terms of drag coefficients and mean Nusselt number. The present numerical results on drag and Nusselt number (in the form of j-factor) have been correlated to the modified Bingham and Reynolds numbers via simple expressions thereby enabling their interpolation for the intermediate values of these dimensionless parameters.

  • on creeping flow of a bingham Plastic Fluid past a square cylinder
    Journal of Non-newtonian Fluid Mechanics, 2012
    Co-Authors: N Nirmalkar, R P Chhabra, Robert J Poole
    Abstract:

    Abstract In this work, the 2-D creeping flow of Bingham Plastic Fluids past a cylinder of square cross-section has been studied numerically. The governing differential equations (continuity and momentum) have been solved over a wide range of Bingham number as 1 ⩽ Bn ⩽ 105. Similar to the case of a circular cylinder, three zones of unyielded regions are seen to be present in the vicinity of the submerged cylinder, namely, caps attached to the top and bottom surfaces of the square cylinder, two sectors situated on the lateral sides undergoing rigid-body like motion and the usual far away unyielded regions. The influence of the Bingham number on their size and on the stress (normal and shear components) field in the vicinity of the cylinder is discussed in detail. In addition, the corresponding rate of strain, pressure and stress contours are also presented to facilitate the visualization of the structure of the flow field for scores of values of Bingham number. Also, the present numerical drag results have been correlated with the Bingham number via a simple expression thereby enabling their interpolation for the intermediate values of Bingham numbers.

Waqar Khan - One of the best experts on this subject based on the ideXlab platform.

  • Laminar natural convection of non-Newtonian power-law Fluids between concentric circular cylinders
    International Communications in Heat and Mass Transfer, 2013
    Co-Authors: Meisam Habibi Matin, Waqar Khan
    Abstract:

    Abstract The two-dimensional steady-state natural convection of power-law Fluids is studied numerically between two concentric horizontal cylinders with different constant temperatures. The governing equations are discretized using finite volume technique based on second order upwind and are solved using the SIMPLE algorithm. The effects of Rayleigh number (103 ≤ Ra ≤ 105) and Prandtl number (10 ≤ Pr ≤ 103) on the dimensionless velocity and temperature are investigated for both pseudoPlastic and dilatant Fluids. Also the mean Nusselt number for various values of governing parameters is obtained and discussed. The results indicate that with increasing the power-law index from 0.6 to 1.4, the mean Nusselt number decreases. In the best case among the range of parameters considered here the heat transfer rate for pseudo-Plastic Fluid (n = 0.6) is 170% higher than the Newtonian one and for dilatant Fluid (n = 1.4) the heat transfer rate is 43% lower than the Newtonian Fluid. So the pseudoPlastic and dilatant Fluids are more efficient than Newtonian Fluids for cooling and insulating purposes, respectively. It is shown that as the Rayleigh number increases the cooling effect of pseudoPlastic Fluid and the insulating effect of dilatant Fluid become more pronounced.

Yonggang Wang - One of the best experts on this subject based on the ideXlab platform.

  • Bingham Plastic Fluid flow model for ceramic tape casting
    Materials Science and Engineering: A, 2002
    Co-Authors: Guangneng Zhang, Yonggang Wang
    Abstract:

    Abstract Multilayer ceramic substrates with conductor traces are attracting a great deal of attention for their ability to increase packaging density for large-scale integration circuits. Currently one of the main methods used for the manufacture of flat ceramic packages with precise thickness control and consistency is the tape casting technique. It is crucial that the green tape thickness is controlled precisely and consistently. The Fluid mechanics associated with the flow of a ceramic slurry during the tape casting process is analyzed. The flow of the slurry onto the casting surface can be modeled as a two-dimensional Fluid flow through a parallel channel. The material of this study is an organic-bonded glass–alumina slurry and is modeled as a Bingham Plastic Fluid with a yield stress. The proposed model accurately described the Fluid flow characteristics of the process, and has good agreement with experimental results.

N Nirmalkar - One of the best experts on this subject based on the ideXlab platform.

  • Forced Convection from a Heated Equilateral Triangular Cylinder in Bingham Plastic Fluids
    Numerical Heat Transfer Part A: Applications, 2014
    Co-Authors: A. Bose, N Nirmalkar, R P Chhabra
    Abstract:

    The momentum and forced convection heat transfer characteristics of a heated equilateral triangular cylinder immersed in a Bingham Plastic Fluid have been studied numerically. The governing equations (continuity, momentum, and thermal energy) are solved for both vertex-upstream and vertex-downstream orientations, over wide ranges of the pertinent parameters, such as Reynolds number: 0.1 ≤ Re ≤30; Prandtl number: 1 ≤ Pr ≤100; and Bingham number: 0 ≤ Bn ≤200. Over the range of conditions, the flow is expected to be steady and symmetric. Detailed analysis of the flow and heat transfer phenomena in the vicinity of the cylinder is performed by a thorough inspection of the streamline and isotherm contours. Furthermore, due to the presence of the yield stress, the flow domain consists of yielded (or Fluid-like) and unyielded (or solid-like) zones. The effect of Reynolds number and Bingham number on the shape and size of these zones has been thoroughly examined in terms of the detailed velocity and shear rate pro...

  • Laminar forced convection heat transfer from a heated square cylinder in a Bingham Plastic Fluid
    International Journal of Heat and Mass Transfer, 2012
    Co-Authors: N Nirmalkar, R P Chhabra, Robert J Poole
    Abstract:

    Abstract In this work, the momentum and heat transfer characteristics of a heated cylinder of square cross-section immersed in a streaming Bingham Plastic medium have been studied. The governing differential equations (continuity, momentum and thermal energy) have been solved numerically over wide ranges of conditions as: Plastic Reynolds number, 0.1 ⩽ Re ⩽ 40 , Prandtl number, 1 ⩽ Pr ⩽ 100 and the Bingham number, 0 ⩽ Bn ⩽ 100 . Over this range of conditions, the flow is expected to be symmetric and steady. The detailed flow and temperature fields in the vicinity of the cylinder surface are examined in terms of streamline and isotherm profiles respectively. In particular, owing to the presence of the yield stress, the so-called yielded (Fluid-like) and unyielded (solid-like) regions are delineated in the flow domain as functions of the Reynolds and Bingham numbers. This objective is accomplished by a detailed examination of the velocity profiles and shear rate profiles along the center planes. Further insights are developed in terms of the distribution of the pressure and local Nusselt number along the cylinder surface together with their average values in terms of drag coefficients and mean Nusselt number. The present numerical results on drag and Nusselt number (in the form of j-factor) have been correlated to the modified Bingham and Reynolds numbers via simple expressions thereby enabling their interpolation for the intermediate values of these dimensionless parameters.

  • on creeping flow of a bingham Plastic Fluid past a square cylinder
    Journal of Non-newtonian Fluid Mechanics, 2012
    Co-Authors: N Nirmalkar, R P Chhabra, Robert J Poole
    Abstract:

    Abstract In this work, the 2-D creeping flow of Bingham Plastic Fluids past a cylinder of square cross-section has been studied numerically. The governing differential equations (continuity and momentum) have been solved over a wide range of Bingham number as 1 ⩽ Bn ⩽ 105. Similar to the case of a circular cylinder, three zones of unyielded regions are seen to be present in the vicinity of the submerged cylinder, namely, caps attached to the top and bottom surfaces of the square cylinder, two sectors situated on the lateral sides undergoing rigid-body like motion and the usual far away unyielded regions. The influence of the Bingham number on their size and on the stress (normal and shear components) field in the vicinity of the cylinder is discussed in detail. In addition, the corresponding rate of strain, pressure and stress contours are also presented to facilitate the visualization of the structure of the flow field for scores of values of Bingham number. Also, the present numerical drag results have been correlated with the Bingham number via a simple expression thereby enabling their interpolation for the intermediate values of Bingham numbers.

Le Guer Yves - One of the best experts on this subject based on the ideXlab platform.

  • Un mélangeur actif efficace pour les Fluides à seuil de contrainte
    HAL CCSD, 2019
    Co-Authors: Moguen Yann, Younes Eliane, El Omari Kamal, Burghelea Teodor, Castelain Cathy, Le Guer Yves
    Abstract:

    National audienceWe present some results of a numerical study of the mixing of a passive scalar by chaotic advection, at low Reynolds number. The mixing is carried out by a new active open flow mixer, called RAW for Rotating Arc-Walls. A phenomenological model is proposed, making it possible to obtain a mixing criterion based on two dimensionless parameters : the Strouhal number based on the bulk velocity of the Fluids and the ratio of the transverse velocity to the bulk velocity. For a given protocol corresponding to a choice of these parameters favourable for mixing in the case of a Newtonian Fluid, the dependence on the Bingham number of the efficiency of the mixing of a Bingham Plastic Fluid is investigated. The complex role of the yield stress is evidenced.Nous présentons quelques résultats d'une étude numérique du mélange d'un scalaire passif par advection chaotique à bas nombre de Reynolds. Le mélange est effectué par un nouveau mélangeur actif en écoulement ouvert, appelé RAW pour Rotating Arc-Walls. Un modèle phénoménologique est proposé, permettant d'obtenir un critère de mélange portant sur deux paramètres adimensionnels : le nombre de Strouhal basé sur la vitesse débitante du Fluide et le rapport de la vitesse transverse d'écoulement à la vitesse débitante. Pour un protocole donné correspondant à un choix de ces paramètres favorable au mélange dans le cas d'un Fluide newtonien, nous étudions la dépendance de l'efficacité du mélange d'un Fluide de Bingham vis-à-vis du nombre de Bingham. Le rôle complexe du seuil de contrainte est mis en évidence

  • Un mélangeur actif efficace pour les Fluides à seuil de contrainte
    HAL CCSD, 2019
    Co-Authors: Moguen Yann, Younes Eliane, El Omari Kamal, Burghelea Teodor, Castelain Cathy, Le Guer Yves
    Abstract:

    International audienceWe present some results of a numerical study of the mixing of a passive scalar by chaotic advection, at low Reynolds number. The mixing is carried out by a new active open flow mixer, called RAW for Rotating Arc-Walls. A phenomenological model is proposed, making it possible to obtain a mixing criterion based on two dimensionless parameters : the Strouhal number based on the bulk velocity of the Fluids and the ratio of the transverse velocity to the bulk velocity. For a given protocol corresponding to a choice of these parameters favourable for mixing in the case of a Newtonian Fluid, the dependence on the Bingham number of the efficiency of the mixing of a Bingham Plastic Fluid is investigated. The complex role of the yield stress is evidenced.Nous présentons quelques résultats d'une étude numérique du mélange d'un scalaire passif par advection chaotique à bas nombre de Reynolds. Le mélange est effectué par un nouveau mélangeur actif en écoulement ouvert, appelé RAW pour Rotating Arc-Walls. Un modèle phénoménologique est proposé, permettant d'obtenir un critère de mélange portant sur deux paramètres adimensionnels : le nombre de Strouhal basé sur la vitesse débitante du Fluide et le rapport de la vitesse transverse d'écoulement à la vitesse débitante. Pour un protocole donné correspondant à un choix de ces paramètres favorable au mélange dans le cas d'un Fluide newtonien, nous étudions la dépendance de l'efficacité du mélange d'un Fluide de Bingham vis-à-vis du nombre de Bingham. Le rôle complexe du seuil de contrainte est mis en évidence