Fluids

10049 KiB

Open AccessArticle

Heat Transfer and Dissipation Effects in the Flow of a Drilling Fluid

by Wei-Tao Wu and Mehrdad Massoudi

Fluids 2016, 1(1), 4; https://doi.org/10.3390/fluids1010004 - 18 Mar 2016

Cited by 17 | Viewed by 4268

In this paper we study the effects of dissipation in the Couette flow and heat transfer in a drilling fluid, and explore the effects of concentration and the shear-rate and temperature-dependent viscosity, along with a variable thermal conductivity. A brief discussion on the constitutive relations for the stress tensor, the diffusive particle flux vector, and the heat flux vector is presented. The one-dimensional forms of the governing equations are solved numerically and the results are presented through a parametric study by varying the dimensionless numbers. Full article

(This article belongs to the Special Issue Rheology and the Thermo-Mechanics of Non-Newtonian Fluids)

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10858 KiB

Open AccessArticle

A Volume Averaging Theory for Convective Flow in a Nanofluid Saturated Metal Foam

by Wenhao Zhang, Wenhao Li, Chen Yang and Akira Nakayama

Fluids 2016, 1(1), 8; https://doi.org/10.3390/fluids1010008 - 08 Mar 2016

Cited by 2 | Viewed by 4652

Abstract

A rigorous derivation of the macroscopic governing equations for convective flow in a nanofluid saturated metal foam has been conducted using the volume averaging theory originally developed for analyzing heat and fluid flow in porous media. The nanoparticle conservation equation at a pore scale based on the Buongiorno model has been integrated over a local control volume together with the equations of continuity, Navier–Stokes and energy conservation. The unknown terms resulting from the volume averaging procedure were modeled mathematically to obtain a closed set of volume averaged versions of the governing equations. This set of the volume averaged governing equations was analytically solved to find the velocity, temperature and nanoparticle distributions and heat transfer characteristics resulting from both thermal and nanoparticle mechanical dispersions in a nanofluid saturated metal foam. Eventually, the analysis revealed that an unconventionally high level of the heat transfer rate (about 80 times as high as the case of base fluid convection without a metal foam) can be attained by combination of metal foam and nanofluid. Full article

(This article belongs to the Special Issue Fundamental Studies in Flow and Heat Transfer in Nanofluids)

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270 KiB

Open AccessArticle

On Objectivity, Irreversibility and Non-Newtonian Fluids

by A. D. Kirwan

Fluids 2016, 1(1), 3; https://doi.org/10.3390/fluids1010003 - 01 Mar 2016

Cited by 7 | Viewed by 4013

Abstract

Early progress in non-Newtonian fluid mechanics was facilitated by the emergence of two fundamental and complementary principles: objective constitutive characterizations and unambiguous identification of irreversible processes. Motivated by practical and economic concerns in recent years, this line of fluid research has expanded to include debris flows, slurries, biofluids and fluid-solid mixtures; i.e., complex nonlinear fluids with disparate flow properties. Phenomenological descriptions of these fluids now necessarily include strong nonlinear coupling between the fluxes of mass, energy and momentum. Here, I review these principles, illustrate how they constrain the constitutive equations for non-Newtonian fluids and demonstrate how they have impacted other areas of fluid research. Full article

(This article belongs to the Special Issue Rheology and the Thermo-Mechanics of Non-Newtonian Fluids)

736 KiB

Open AccessArticle

Simulation of Individual Polymer Chains and Polymer Solutions with Smoothed Dissipative Particle Dynamics

by Sergey Litvinov, Qingguang Xie, Xiangyu Hu, Nikolaus Adams and Marco Ellero

Fluids 2016, 1(1), 7; https://doi.org/10.3390/fluids1010007 - 06 Feb 2016

Cited by 20 | Viewed by 6235

Abstract

In an earlier work (Litvinov et al., Phys.Rev.E 77, 066703 (2008)), a model for a polymer molecule in solution based on the smoothed dissipative particle dynamics method (SDPD) has been presented. In the present paper, we show that the model can be extended to three-dimensional situations and simulate effectively diluted and concentrated polymer solutions. For an isolated suspended polymer, calculated static and dynamic properties agree well with previous numerical studies and theoretical predictions based on the Zimm model. This implies that hydrodynamic interactions are fully developed and correctly reproduced under the current simulated conditions. Simulations of polymer solutions and melts are also performed using a reverse Poiseuille flow setup. The resulting steady rheological properties (viscosity, normal stress coefficients) are extracted from the simulations and the results are compared with the previous numerical studies, showing good results. Full article

(This article belongs to the Special Issue Rheology and the Thermo-Mechanics of Non-Newtonian Fluids)

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141 KiB

Open AccessEditorial

The Journal of Fluids: An International and Interdisciplinary Scientific Open Access Journal

by Bekir Sami Yilbas

Fluids 2016, 1(1), 1; https://doi.org/10.3390/fluids1010001 - 04 Jan 2016

Cited by 2 | Viewed by 2912

Abstract

The science of fluids started from early civilizations when mankind understood the nature of channel flow. Archimedes discovered the hydrodynamics of floating bodies in early 250 B.C. [...] Full article

391 KiB

Open AccessArticle

A Simple Stochastic Parameterization for Reduced Models of Multiscale Dynamics

by Rafail Abramov

Fluids 2016, 1(1), 2; https://doi.org/10.3390/fluids1010002 - 24 Dec 2015

Cited by 11 | Viewed by 3533

Abstract

Multiscale dynamics are frequently present in real-world processes, such as the atmosphere-ocean and climate science. Because of time scale separation between a small set of slowly evolving variables and much larger set of rapidly changing variables, direct numerical simulations of such systems are difficult to carry out due to many dynamical variables and the need for an extremely small time discretization step to resolve fast dynamics. One of the common remedies for that is to approximate a multiscale dynamical systems by a closed approximate model for slow variables alone, which reduces the total effective dimension of the phase space of dynamics, as well as allows for a longer time discretization step. Recently, we developed a new method for constructing a deterministic reduced model of multiscale dynamics where coupling terms were parameterized via the Fluctuation-Dissipation theorem. In this work we further improve this previously developed method for deterministic reduced models of multiscale dynamics by introducing a new method for parameterizing slow-fast interactions through additive stochastic noise in a systematic fashion. For the two-scale Lorenz 96 system with linear coupling, we demonstrate that the new method is able to recover additional features of multiscale dynamics in a stochastically forced reduced model, which the previously developed deterministic method could not reproduce. Full article

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Fluids, Volume 1, Issue 1 (March 2016) – 6 articles

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