The Experts below are selected from a list of 10500 Experts worldwide ranked by ideXlab platform
R P Chhabra - One of the best experts on this subject based on the ideXlab platform.
-
effect of inclination angle on the forced convective flow of a Power Law fluid in a 2 d planar branching channel
International Journal of Heat and Mass Transfer, 2019Co-Authors: Anamika Maurya, Naveen Tiwari, R P ChhabraAbstract:Abstract Branching T-channel is a very common element of a piping system for the transportation of liquids and gases. The brachesbranches of the T-channel can be inclined at different angles which affects the flow dynamics and heat transfer characteristics significantly. Thus, the present work focuses on the flow and thermal characteristics of the laminar forced convection of Power-Law fluids in a rectangular branching channel which have been numerically investigated over a wide range of parameters such as Reynolds number, 50 ≤ Re ≤ 300, Prandtl number, 10 ≤ Pr ≤ 50, inclination angle, 30° ≤ α ≤ 90° and Power-Law Index, 0.2 ≤ n ≤ 1.4 (includes shear-thinning, n 1 and Newtonian, n = 1 fluids). This is perhaps the first systematic study which examines the role of Power-Law fluid behaviour and of branch inclination on momentum and heat transfer characteristics. New extensive results for the flow and temperature fields are presented in terms of streamline contours and separated-flow zones, pressure coefficient, recirculation length, critical Reynolds number, isotherm contours, temperature profiles and local Nusselt number. The pressure coefficient is found to be higher for shear-thickening fluids than that for the Newtonian and shear-thinning fluids while the inclination angle has only a weak effect. The recirculation length bears a positive dependence on the Reynolds number and inclination angle while an inverse relationship is observed with Power-Law Index in both branches. The critical Reynolds number, at which the onset of flow recirculation is observed, is found to be lower for higher inclination angles and a strong influence of the Power-Law Index is also seen on the critical Reynolds number in both branches. Also, the local Nusselt number is seen to be higher at lower Prandtl numbers, low Power-Law Index values and high inclination angles for both branches. Overall, the inclination angle plays a significant role in determining the heat transfer characteristics.
-
Momentum and Heat Transfer Characteristics for the Flow of Power-Law Fluids over a Semicircular Cylinder
Numerical Heat Transfer Part A-applications, 2014Co-Authors: Anurag Kumar Tiwari, R P ChhabraAbstract:In this study, the two-dimensional steady flow of Power-Law fluids past a semicircular cylinder (flat face oriented upstream) has been investigated numerically. The governing equations (continuity, momentum, and energy) have been solved in the steady symmetric flow regime over the range of the Reynolds number (0.01 ≤ Re ≤ 25), Power-Law Index (0.2 ≤ n ≤ 1.8), and Prandtl number (0.72 ≤ Pr ≤ 100). Extensive new results reported here endeavor to elucidate the role of Power-Law Index (0.2 ≤ n ≤ 1.8) on the critical Reynolds number denoting the onset of flow separation (Re c ) and of vortex shedding (Re c ). In shear-thinning fluids, both of these transitions are seen to be delayed than that in Newtonian and shear-thickening fluids. Furthermore, the influence of the Reynolds and Prandtl numbers, Power-Law Index on drag phenomenon, and heat characteristics of semicircular cylinder have been studied in the steady flow regime. Finally, the present numerical values of the critical Reynolds numbers and the average...
-
Laminar free convection from a horizontal semi-circular cylinder to Power-Law fluids
International Journal of Heat and Mass Transfer, 2012Co-Authors: Avinash Chandra, R P ChhabraAbstract:Extensive numerical results on the flow and thermal fields are presented for free convection from a semi-circular cylinder (flat base upward) immersed in quiescent Power-Law fluids for the following ranges of conditions: Grashof number, 10 ⩽ Gr ⩽ 105, Prandtl number, 0.72 ⩽ Pr ⩽ 100, and Power-Law Index, 0.2 ⩽ n ⩽ 1.8. The heat transfer characteristics are analyzed in terms of the isotherm patterns, local and average Nusselt number as functions of the pertinent dimensionless parameters. The flow field is visualized in terms of the streamline patterns adjacent to the surface of the cylinder for a range of values of the Grashof number, Prandtl number and Power-Law Index. A separated flow region forms at as low values of the Prandtl number as Pr = 0.72 for n ⩾ 1 (Newtonian and shear-thickening fluids); whereas for shear-thinning fluids (n < 1), the flow remains attached to the cylinder surface over the range of conditions encompassed here. The bubble size grows with Grashof number and it shrinks with Prandtl number. In order to quantify the deviation from the Newtonian behaviour, the normalized values of average Nusselt number are analyzed as a function of the Power-Law Index. In addition, a correlation is proposed for average Nusselt number as a function of the Grashof number, Prandtl number and Power-Law Index. In general terms, shear-thinning fluid behaviour enhances heat transfer whereas shear-thickening has adverse influence on it.
-
influence of Power Law Index on transitional reynolds numbers for flow over a semi circular cylinder
Applied Mathematical Modelling, 2011Co-Authors: Avinash Chandra, R P ChhabraAbstract:Abstract In this work, the governing partial differential equations (continuity and Cauchy’s momentum equations) describing the flow of Power-Law type non-Newtonian fluids across a semi-circular cylinder (oriented with its curved surface in the upstream direction) have been solved numerically. In particular, consideration has been given to the delineation of the critical Reynolds numbers denoting the onset of flow separation from the surface of the cylinder and the onset of the laminar vortex shedding regime. This information is germane to establish the scaling of the macroscopic characteristics like drag coefficient and Strouhal number on the governing parameters, namely, Reynolds number and Power-Law Index. The present results clearly suggest that the transitional Reynolds numbers show a strong dependence on the type (shear-thinning and shear-thickening) of fluid behavior as well as on the severity of the shear-dependence of the viscosity. With reference to the behavior seen in Newtonian fluids, the flow remains not only attached to the surface up to higher Reynolds numbers, but shear-thinning behavior also delays the onset of the laminar vortex shedding regime. As expected, shear-thickening fluids, of course, display the opposite characteristics.
-
Momentum and heat transfer characteristics of a semi-circular cylinder immersed in Power-Law fluids in the steady flow regime
International Journal of Heat and Mass Transfer, 2011Co-Authors: Avinash Chandra, R P ChhabraAbstract:Abstract The continuity, momentum and energy equations describing the flow and heat transfer of Power-Law fluids over a semi-circular cylinder have been solved numerically in the two-dimensional steady flow regime. The influence of the Reynolds number (Re), Prandtl number (Pr) and Power-Law Index (n) on the local and global flow and heat characteristics have been studied over wide ranges of conditions as follows: 0.01 ⩽ Re ⩽ 30, 1 ⩽ Pr ⩽ 100 and 0.2 ⩽ n ⩽ 1.8. The variation of drag coefficient and Nusselt number with the Reynolds number, Prandtl number and Power-Law Index is shown over the aforementioned ranges of conditions. In addition, streamline and isotherm profiles along with the recirculation length and distribution of pressure coefficient and Nusselt number over the surface of the semi-circular cylinder are also presented to gain further insights into the nature of the underlying kinematics. The wake size (recirculation length) shows almost linear dependence on the Reynolds number (Re ⩾ 1) for all values of Power-Law Index studied herein. The drag values show the classical inverse variation with the Reynolds number, especially for shear-thinning fluids at low Reynolds numbers. The point of maximum pressure coefficient is found slightly displaced from the front stagnation point for highly shear-thinning fluids, whereas for shear-thickening and Newtonian fluids, it coincides with the front stagnation point. For fixed values of the Prandtl number and Reynolds number, the rate of heat transfer decreases with the gradual increase in Power-Law Index; this effect is particularly striking at high Prandtl numbers due to the thinning of the thermal boundary layer. Conversely, as expected, shear-thinning behavior facilitates heat transfer and shear-thickening impedes it. The effect of Power-Law Index on both momentum and heat-transfer characteristics is seen to be appreciable at low Reynolds numbers and it gradually diminishes with the increasing Reynolds number.
Gholamreza Kefayati - One of the best experts on this subject based on the ideXlab platform.
-
MHD thermosolutal natural convection and entropy generation of Carreau fluid in a heated enclosure with two inner circular cold cylinders, using LBM
International Journal of Heat and Mass Transfer, 2018Co-Authors: Gholamreza Kefayati, H. TangAbstract:In this paper, thermosolutal natural convection and entropy generation in a heated enclosure with two inner cold cylinders filled with a non-Newtonian Carreau fluid in the presence of a uniform magnetic field has been simulated by Lattice Boltzmann Method (LBM). This study has been conducted for certain pertinent parameters of Rayleigh number (Ra = 104 and 105), the Buoyancy ratio (N = −1, 0.1, 1), Hartmann number (Ha = 0, 15, 30, 60, and 90), Power-Law Indexes (n = 0.2, 1, and 1.8). Results indicate that the rise of Rayleigh number enhances heat transfer for various studied parameters. The increase in Power-Law Index provokes heat and mass transfer to drop gradually. However, the effect of Power-Law Index on heat and mass transfer declines steadily as Hartmann number rises. The enhancement of Hartmann number causes heat and mass transfer to decline significantly. The augmentation of the buoyancy ratio number enhances heat and mass transfer. The augmentation of Rayleigh number enhances different entropy generations and declines the average Bejan number. The increase in the Power-Law Index provokes various irreversibilities to drop significantly; although, the increase in Hartmann number decreases the influence of Power-Law Index on different entropy generations. The enhancement of the buoyancy ratio causes the summation entropy generations to increase considerably. It was found that the total entropy generation declines as Hartmann augments.
-
Simulation of double diffusive MHD (magnetohydrodynamic) natural convection and entropy generation in an open cavity filled with Power-Law fluids in the presence of Soret and Dufour effects (Part I: Study of fluid flow, heat and mass transfer)
Energy, 2016Co-Authors: Gholamreza KefayatiAbstract:In this paper, double diffusive natural convection of non-Newtonian Power-Law fluids in an open cavity in the presence of a horizontal magnetic field, studying Soret and Dufour parameters has been analyzed by FDLBM (Finite Difference Lattice Boltzmann method). This study has been performed for the certain pertinent parameters of Rayleigh number (Ra = 104 and 105), Hartmann number (Ha = 0, 15, and 30), Power-Law Index (n = 0.6, 1, and 1.4), Lewis number (Le = 2.5 and 5), Dufour parameter (Df = 0, 1, and 5), Soret parameter (Sr = 0, 1, and 5) and the buoyancy ratio (N = −1and 1). Results indicate that the augmentation of the Hartmann number provokes heat and mass transfer to drop for different Power-Law Indexes. As the Soret and Dufour numbers equal zero, the heat and mass transfer decrease with the increment of the Power-Law Index in different Rayleigh numbers for various Hartmann numbers. The heat transfer increases with the rise of the Dufour parameter and the mass transfer enhances as the Soret parameter increases for different Power-Law Indexes and Rayleigh numbers. The augmentation of Soret and Dufour parameters alters the behavior of heat and mass transfer against the change of the Power-Law Index.
-
Simulation of double diffusive natural convection and entropy generation of Power-Law fluids in an inclined porous cavity with Soret and Dufour effects (Part I: Study of fluid flow, heat and mass transfer)
International Journal of Heat and Mass Transfer, 2016Co-Authors: Gholamreza KefayatiAbstract:Abstract In this paper, double diffusive natural convection of non-Newtonian Power-Law fluids in an inclined porous cavity in the presence of Soret and Dufour parameters has been analyzed by Finite Difference Lattice Boltzmann Method (FDLBM). This study has been performed for the certain pertinent parameters of thermal Rayleigh number (RaT = 104 and 105), Darcy number (Da = 10−4, 10−3, and 10−2), Power-Law Index (n = 0.6–1.4), Lewis number (Le = 2.5 and 5), inclined angles (θ = 0°, 40°, 80°, and 120°), Dufour parameter (Df = 0, 1, and 5), Soret parameter (Sr = 0, 1, and 5) and the buoyancy ratio (N = −1 and 1). Results indicate that the augmentation of the Darcy number causes heat and mass transfer to rise for different Power-Law Indexes. At Da = 10−4, the heat and mass transfer increase with the augmentation of the Power-Law Index in the absence of the Soret and Dufour parameters. The rise of the inclined angle from θ = 0° to 40° and from θ = 80° to 120° provokes heat and mass transfer to augment. As the Soret and Dufour numbers equal zero, the heat transfer enhances with the increment of the Power-Law Index at Da = 10−3. The heat transfer increases with the rise of the Dufour parameter and the mass transfer enhances as the Soret parameter increases for different Power-Law Indexes and thermal Rayleigh numbers. In some cases, the augmentation of Soret and Dufour parameters alter the behavior of heat and mass transfer against the alteration of the Power-Law Index.
-
simulation of heat transfer and entropy generation of mhd natural convection of non newtonian nanofluid in an enclosure
International Journal of Heat and Mass Transfer, 2016Co-Authors: Gholamreza KefayatiAbstract:In this paper, heat transfer and entropy generation on laminar natural convection of non-Newtonian nanofluids in the presence of an external horizontal magnetic field in a square cavity has been analyzed by Finite Difference Lattice Boltzmann Method (FDLBM). The cavity is filled with water and nanoparticles of copper (Cu) while the mixture shows shear-thinning behavior. This study has been conducted for the certain pertinent parameters of Rayleigh number (Ra = 104–105), Power-Law Index (n = 0.6–1), Hartmann number (Ha = 0–90) and the volume fraction has been studied from φ = 0 to 0.04. Results indicate that the augmentation of the Power-Law Index causes heat transfer to drop in the absence of the magnetic field, by contrast, the heat transfer increases with the rise of Power-Law Index in the presence of the magnetic field. The addition of nanoparticle augments heat transfer for multifarious studied parameters. The heat transfer drops with the increase in Hartmann number generally and also affects the Power-Law Index and nanoparticles influences on heat transfer. Augmentation of the volume fraction and Rayleigh number enhance all kinds of entropy generations of heat transfer, fluid friction, and the magnetic field in different studied parameters. The increase in the Hartmann number causes the total entropy generation to drop and affects the influences of the Power-Law Index and the volume fraction on the entropy generations.
-
FDLBM simulation of magnetic field effect on mixed convection in a two sided lid-driven cavity filled with non-Newtonian nanofluid
Powder Technology, 2015Co-Authors: Gholamreza KefayatiAbstract:In this paper, laminar mixed convection of non-Newtonian nanofluids in a two sided lid-driven enclosure in the presence of a horizontal magnetic field has been analyzed by finite difference Lattice Boltzmann method (FDLBM). The cavity is filled with water and nanoparticles of Alumina (Al2O3) while the mixture shows shear-thinning behavior. This study has been conducted for the certain pertinent parameters of Richardson number (Ri = 0.001–1), Power-Law Index (n = 0.2–1), and Hartmann numbers (Ha = 0–60) and volume fraction has been studied from φ = 0 to 0.09. Results indicate that the augmentation of Richardson number decreases heat transfer. The fall of the Power Law Index declines heat transfer for different studied Richardson numbers. The addition of nanoparticle augments heat transfer for multifarious studied parameters. The increase in Hartmann number drops heat transfer generally and also affects the Power-Law Index and nanoparticle influences on heat transfer.
R F L Holanda - One of the best experts on this subject based on the ideXlab platform.
-
constraints on a possible evolution of mass density Power Law Index in strong gravitational lensing from cosmological data
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: R F L Holanda, S H Pereira, Deepak JainAbstract:In this work, by using strong gravitational lensing (SGL) observations along with Type Ia Supernovae (Union2.1) and gamma ray burst data (GRBs), we propose a new method to study a possible redshift evolution of $\gamma(z)$, the mass density Power-Law Index of strong gravitational lensing systems. In this analysis, we assume the validity of cosmic distance duality relation and the flat universe. In order to explore the $\gamma(z)$ behavior, three different parametrizations are considered, namely: (P1) $\gamma(z_l)=\gamma_0+\gamma_1 z_l$, (P2) $\gamma(z_l)=\gamma_0+\gamma_1 z_l/(1+z_l)$ and (P3) $\gamma(z_l)=\gamma_0+\gamma_1 \ln(1+z_l)$, where $z_l$ corresponds to lens redshift. If $\gamma_0=2$ and $\gamma_1=0$ the singular isothermal sphere model is recovered. Our method is performed on SGL sub-samples defined by different lens redshifts and velocity dispersions. For the former case, the results are in full agreement with each other, while a 1$\sigma$ tension between the sub-samples with low ($\leq 250$ km/s) and high ($>250$ km/s) velocity dispersions was obtained on the ($\gamma_0$-$\gamma_1$) plane. By considering the complete SGL sample, we obtain $\gamma_0 \approx 2$ and $ \gamma_1 \approx 0$ within 1$\sigma$ c.l. for all $\gamma(z)$ parametrizations. However, we find the following best fit values of $\gamma_1$: $-0.085$, $-0.16$ and $-0.12$ for P1, P2 and P3 parametrizations, respectively, suggesting a mild evolution for $\gamma(z)$. By repeating the analysis with Type Ia Supernovae from JLA compilation, GRBs and SGL systems this mild evolution is reinforced.
Ram P Bharti - One of the best experts on this subject based on the ideXlab platform.
-
Two-dimensional unsteady forced convection heat transfer in Power-Law fluids from a cylinder
International Journal of Heat and Mass Transfer, 2010Co-Authors: Vijaya K. Patnana, Ram P Bharti, Raj P. ChhabraAbstract:Abstract Forced convection heat transfer characteristics of a cylinder (maintained at a constant temperature) immersed in a streaming Power-Law fluids have been studied numerically in the two-dimensional (2-D), unsteady flow regime. The governing equations, namely, continuity, momentum and thermal energy, have been solved using a finite volume method based solver (FLUENT 6.3) over wide ranges of conditions (Power Law Index, 0.4 ⩽ n ⩽ 1.8; Reynolds number, 40 ⩽ Re ⩽ 140; Prandtl number, 1 ⩽ Pr ⩽ 100). In particular, extensive numerical results elucidating the influence of Reynolds number, Prandtl number and Power-Law Index on the isotherm patterns, local and average Nusselt numbers and their evolution with time are discussed in detail. Over the ranges of conditions considered herein, the nature of flow is fully periodic in time. The heat transfer characteristics are seen to be influenced in an intricate manner by the value of the Reynolds number (Re), Prandtl number (Pr) and the Power-Law Index (n). Depending upon the value of the Power-Law Index (n), though the flow transits from being steady to unsteady somewhere in the range ∼33 1) impedes it. Furthermore, this effect is much more pronounced in shear-thinning fluids than that in shear-thickening fluids.
-
Two-dimensional unsteady flow of Power-Law fluids over a cylinder
Chemical Engineering Science, 2009Co-Authors: Vijaya K. Patnana, Ram P Bharti, Raj P. ChhabraAbstract:Abstract The unsteady flow of incompressible Power-Law fluids over an unconfined circular cylinder in cross-flow arrangement has been studied numerically. The two-dimensional (2-D) field equations have been solved using a finite volume method based solver (FLUENT 6.3). In particular, the effects of the Power-Law Index ( 0.4 ⩽ n ⩽ 1.8 ) and Reynolds number ( 40 ⩽ Re ⩽ 140 ) on the detailed kinematics of the flow (streamline, surface pressure and vorticity patterns) and on the macroscopic parameters (drag and lift coefficients, Strouhal number) are presented in detail. The periodic vortex shedding and the evolution of detailed kinematics with time are also presented to provide insights into the nature of flow. The two-dimensional flow transits from steady to unsteady behaviour at a critical value of the Reynolds number Re ∼(40–50) and the von-Karman vortex street is observed beyond the critical Reynolds number ( Re ). Obviously, both the lift coefficient and Strouhal number values are zero for the steady flow, but their values increase with the increasing Reynolds number ( Re ) in the unsteady flow regime. For highly shear-thickening fluids ( n =1.8), the flow becomes unsteady at Re =40 and unsteadiness in the flow appears at Re =50 for all values of Power-Law Index ( n ). As expected, the evolution of the kinematics and vortex shedding show a complex dependence on the flow parameters near the transition in the flow. For a fixed value of the Reynolds number ( Re ), the drag coefficient increases and lift coefficient decreases with increasing value of the Power-Law Index ( n ). For a fixed value of the Power-Law Index ( n ), the drag coefficient gradually increases with the Reynolds number ( Re ). Similar to the drag coefficient, lift coefficient also shows a complex dependence on the Power-Law Index ( n ) near the transition zone. The value of the Strouhal number ( St ) decreases with the increasing value of the Power-Law Index ( n ) at a fixed value of the Reynolds number ( Re ).
-
Steady Flow of Power Law Fluids across a Circular Cylinder
Canadian Journal of Chemical Engineering, 2008Co-Authors: Ram P Bharti, R P Chhabra, Vinayak EswaranAbstract:The momentum equations describing the steady cross-flow of Power Law fluids past an unconfined circular cylinder have been solved numerically using a semi-implicit finite volume method. The numerical results highlighting the roles of Reynolds number and Power Law Index on the global and detailed flow characteristics have been presented over wide ranges of conditions as 5 ≤ Re ≤ 40 and 0.6 ≤ n ≤ 2. The shear-thinning behaviour (n 1) show the opposite behaviour. Furthermore, while the wake size shows non-monotonous variation with the Power Law Index, but it does not seem to influence the values of drag coefficient. The stagnation pressure coefficient and drag coefficient also show a complex dependence on the Power Law Index and Reynolds number. In addition, the pressure coefficient, vorticity and viscosity distributions on the surface of the cylinder have also been presented to gain further physical insights into the detailed flow kinematics.
-
effect of Power Law Index on critical parameters for Power Law flow across an unconfined circular cylinder
Chemical Engineering Science, 2006Co-Authors: P Sivakumar, Ram P Bharti, R P ChhabraAbstract:Abstract The conditions for the formation of a wake and for the onset of wake instability for the flow of Power-Law fluids over an unconfined circular cylinder are investigated numerically by solving the continuity and momentum equations using FLUENT (version 6.2). The effect of Power-Law Index on the critical Reynolds numbers, Strouhal number and drag coefficient has been presented over a wide range of Power-Law Index ( 0.3 ⩽ n ⩽ 1.8 ) thereby establishing the limits of the flow without separation and the steady symmetric flow regimes, respectively. While both the shear-thinning ( n 1 ) and the shear-thickening ( n > 1 ) seem to lower the value of the critical Reynolds number denoting the onset of wake instability as compared to that for Newtonian fluids, the effect is seen to be more prominent for shear-thickening fluids than that for shear-thinning fluids. The corresponding values of the critical Strouhal number ( St c ) and drag coefficient have also been presented for the critical values of the Reynolds number. Included here are also a series of streamline plots showing the onset of asymmetry and of the time-dependent flow regime.
S Mori - One of the best experts on this subject based on the ideXlab platform.
-
calculation of the Power Law Index for a time series by means of its fractal dimension
Fractals, 1996Co-Authors: S Yasue, K Munakata, Masashige Kato, S MoriAbstract:The relationship between the Power-Law Index for a time series and the fractal dimensions for both the original and the integrated time series, is investigated by using a numerical experiment. This relationship is extended and applied to the cosmic ray time series recorded at the deep underground site at Matsushiro. It is shown that we can use the present method in order to obtain the stable and reliable value of the Power-Law Index of a time series, even if the time series has relatively large statistical fluctuations.