Mathematical Theory of Compressible Viscous, and Heat Conducting Fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2007-01-01
Roč. 33, č. 4 (2007), s. 461-490 ISSN 0898-1221 R&D Projects: GA ČR GA201/05/0164 Institutional research plan: CEZ:AV0Z10190503 Keywords : compressible fluid * viscous fluid * entropy Subject RIV: BA - General Mathematics Impact factor: 0.720, year: 2007
Dimension reduction for compressible viscous fluids
Czech Academy of Sciences Publication Activity Database
Bella, P.; Feireisl, Eduard; Novotný, A.
2014-01-01
Roč. 134, č. 1 (2014), s. 111-121 ISSN 0167-8019 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes system * dimension reduction * thin rod Subject RIV: BA - General Mathematics Impact factor: 1.047, year: 2014 http://link.springer.com/article/10.1007%2Fs10440-014-9872-5
Spectral analysis of viscous static compressible fluid equilibria
Energy Technology Data Exchange (ETDEWEB)
Nunez, Manuel [Departamento de Analisis Matematico, Universidad de Valladolid, Valladolid (Spain)
2001-05-25
It is generally assumed that the study of the spectrum of the linearized Navier-Stokes equations around a static state will provide information about the stability of the equilibrium. This is obvious for inviscid barotropic compressible fluids by the self-adjoint character of the relevant operator, and rather easy for viscous incompressible fluids by the compact character of the resolvent. The viscous compressible linearized system, both for periodic and homogeneous Dirichlet boundary problems, satisfies neither condition, but it does turn out to be the generator of an immediately continuous, almost stable semigroup, which justifies the analysis of the spectrum as predictive of the initial behaviour of the flow. As for the spectrum itself, except for a unique negative finite accumulation point, it is formed by eigenvalues with negative real part, and nonreal eigenvalues are confined to a certain bounded subset of complex numbers. (author)
Mathematical theory of compressible viscous fluids analysis and numerics
Feireisl, Eduard; Pokorný, Milan
2016-01-01
This book offers an essential introduction to the mathematical theory of compressible viscous fluids. The main goal is to present analytical methods from the perspective of their numerical applications. Accordingly, we introduce the principal theoretical tools needed to handle well-posedness of the underlying Navier-Stokes system, study the problems of sequential stability, and, lastly, construct solutions by means of an implicit numerical scheme. Offering a unique contribution – by exploring in detail the “synergy” of analytical and numerical methods – the book offers a valuable resource for graduate students in mathematics and researchers working in mathematical fluid mechanics. Mathematical fluid mechanics concerns problems that are closely connected to real-world applications and is also an important part of the theory of partial differential equations and numerical analysis in general. This book highlights the fact that numerical and mathematical analysis are not two separate fields of mathematic...
The motion of a compressible viscous fluid around rotating body
Czech Academy of Sciences Publication Activity Database
Kračmar, S.; Nečasová, Šárka; Novotný, A.
2014-01-01
Roč. 60, č. 1 (2014), s. 189-208 ISSN 0430-3202 R&D Projects: GA ČR(CZ) GAP201/11/1304 Institutional support: RVO:67985840 Keywords : compressible fluids * rotating fluids * Navier-Stokes equations Subject RIV: BA - General Mathematics http://link.springer.com/article/10.1007%2Fs11565-014-0212-5
Self-propelled motion in a viscous compressible fluid
Czech Academy of Sciences Publication Activity Database
Mácha, Václav; Nečasová, Šárka
2016-01-01
Roč. 146, č. 2 (2016), s. 415-433 ISSN 0308-2105 R&D Projects: GA ČR(CZ) GAP201/11/1304; GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : self-propelled motion * compressible fluid * deformable structure Subject RIV: BA - General Mathematics Impact factor: 1.158, year: 2016 http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=10065194&fileId=S0308210515000487
Linear study of Kelvin-Helmholtz instability for a viscous compressible fluid
International Nuclear Information System (INIS)
Hallo, L.; Gauthier, S.
1992-01-01
The linear phase of the process leading to a developed turbulence is particularly important for the study of flow stability. A Galerkin spectral method adapted to the study of the mixture layer of one fluid is proposed from a sheared initial velocity profile. An algebraic mapping is developed to improve accuracy near high gradient zone. Validation is obtained by analytic methods for non-viscous flow and multi-domain spectral methods for viscous and compressible flow. Rates of growth are presented for subsonic and slightly supersonic flow. An extension of the method is presented for the study of the linear stability of a mixture with variable concentration and transport properties
Efficient Simulation of Compressible, Viscous Fluids using Multi-rate Time Integration
Mikida, Cory; Kloeckner, Andreas; Bodony, Daniel
2017-11-01
In the numerical simulation of problems of compressible, viscous fluids with single-rate time integrators, the global timestep used is limited to that of the finest mesh point or fastest physical process. This talk discusses the application of multi-rate Adams-Bashforth (MRAB) integrators to an overset mesh framework to solve compressible viscous fluid problems of varying scale with improved efficiency, with emphasis on the strategy of timescale separation and the application of the resulting numerical method to two sample problems: subsonic viscous flow over a cylinder and a viscous jet in crossflow. The results presented indicate the numerical efficacy of MRAB integrators, outline a number of outstanding code challenges, demonstrate the expected reduction in time enabled by MRAB, and emphasize the need for proper load balancing through spatial decomposition in order for parallel runs to achieve the predicted time-saving benefit. This material is based in part upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0002374.
Steady fall of isothermal, resistive-viscous, compressible fluid across magnetic field
Energy Technology Data Exchange (ETDEWEB)
Low, B. C., E-mail: low@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80301 (United States); Egan, A. K., E-mail: andrea.egan@colorado.edu [Barnard College, New York, New York 10027, USA and Department of Physics, Colorado University, Boulder, Colorado 80309 (United States)
2014-06-15
This is a basic MHD study of the steady fall of an infinite, vertical slab of isothermal, resistive-viscous, compressible fluid across a dipped magnetic field in uniform gravity. This double-diffusion steady flow in unbounded space poses a nonlinear but numerically tractable, one-dimensional (1D) free-boundary problem, assuming constant coefficients of resistivity and viscosity. The steady flow is determined by a dimensionless number μ{sub 1} proportional to the triple product of the two diffusion coefficients and the square of the linear total mass. For a sufficiently large μ{sub 1}, the Lorentz, viscous, fluid-pressure, and gravitational forces pack and collimate the fluid into a steady flow of a finite width defined by the two zero-pressure free-boundaries of the slab with vacuum. The viscous force is essential in this collimation effect. The study conjectures that in the regime μ{sub 1}→0, the 1D steady state exists only for μ{sub 1}∈Ω, a spectrum of an infinite number of discrete values, including μ{sub 1} = 0 that corresponds to two steady states, the classical zero-resistivity static slab of Kippenhahn and Schlüter [R. Kippenhahn and A. Schlüter, Z. Astrophys. 43, 36 (1957)] and its recent generalization [B. C. Low et al., Astrophys. J. 755, 34 (2012)] to admit an inviscid resistive flow. The pair of zero-pressure boundaries of each of the μ{sub 1}→0 steady-state slabs are located at infinity. Computational evidence suggests that the Ω steady-states are densely distributed around μ{sub 1} = 0, as an accumulation point, but are sparsely separated by open intervals of μ{sub 1}-values for which the slab must be either time-dependent or spatially multi-dimensional. The widths of these intervals are vanishingly small as μ{sub 1}→0. This topological structure of physical states is similar to that described by Landau and Liftshitz [L. D. Landau and E. M. Lifshitz, Fluid Mechanics (Addison-Wesley, Reading, MA, 1959)] to explain the onset
Self-propelled motion in a viscous compressible fluid –unbounded domains
Czech Academy of Sciences Publication Activity Database
Mácha, Václav; Nečasová, Šárka
2016-01-01
Roč. 26, č. 4 (2016), s. 627-643 ISSN 0218-2025 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : self-propelled motion * compressible fluid * deformable structure Subject RIV: BA - General Mathematics Impact factor: 2.860, year: 2016 http://www.worldscientific.com/doi/10.1142/S0218202516500123
Czech Academy of Sciences Publication Activity Database
Penel, P.; Straškraba, Ivan
2010-01-01
Roč. 134, č. 3 (2010), s. 278-294 ISSN 0007-4497 R&D Projects: GA ČR GA201/08/0012 Institutional research plan: CEZ:AV0Z10190503 Keywords : compressible fluid * Navier-Stokes equations * asymptotic behavior Subject RIV: BA - General Mathematics Impact factor: 0.722, year: 2010 http://www.sciencedirect.com/science/article/pii/S0007449709000153
Sudden viscous dissipation in compressing plasma turbulence
Davidovits, Seth; Fisch, Nathaniel
2015-11-01
Compression of a turbulent plasma or fluid can cause amplification of the turbulent kinetic energy, if the compression is fast compared to the turnover and viscous dissipation times of the turbulent eddies. The consideration of compressing turbulent flows in inviscid fluids has been motivated by the suggestion that amplification of turbulent kinetic energy occurred on experiments at the Weizmann Institute of Science Z-Pinch. We demonstrate a sudden viscous dissipation mechanism whereby this amplified turbulent kinetic energy is rapidly converted into thermal energy, which further increases the temperature, feeding back to further enhance the dissipation. Application of this mechanism in compression experiments may be advantageous, if the plasma can be kept comparatively cold during much of the compression, reducing radiation and conduction losses, until the plasma suddenly becomes hot. This work was supported by DOE through contract 67350-9960 (Prime # DOE DE-NA0001836) and by the DTRA.
On the Motion of a Viscous, Compressible, and Meat Conducting Fluid
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2004-01-01
Roč. 53, č. 4 (2004), s. 1707-1740 ISSN 0022-2518 R&D Projects: GA AV ČR(CZ) IAA1019302 Institutional research plan: CEZ:AV0Z1019905 Keywords : compressible Navier-Stokes equations * temperature dependent viscosity * global existence Subject RIV: BA - General Mathematics Impact factor: 0.784, year: 2004
Czech Academy of Sciences Publication Activity Database
Ducomet, B.; Nečasová, Šárka
2013-01-01
Roč. 6, č. 5 (2013), s. 1193-1213 ISSN 1937-1632 R&D Projects: GA ČR(CZ) GAP201/11/1304 Institutional support: RVO:67985840 Keywords : motion of rigid bodies * incompressible fluid * compressible fluid Subject RIV: BA - General Mathematics https://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=8331
Handbook of mathematical analysis in mechanics of viscous fluids
Novotný, Antonín
2018-01-01
Mathematics has always played a key role for researches in fluid mechanics. The purpose of this handbook is to give an overview of items that are key to handling problems in fluid mechanics. Since the field of fluid mechanics is huge, it is almost impossible to cover many topics. In this handbook, we focus on mathematical analysis on viscous Newtonian fluid. The first part is devoted to mathematical analysis on incompressible fluids while part 2 is devoted to compressible fluids.
Singular limits in thermodynamics of viscous fluids
Feireisl, Eduard
2017-01-01
This book is about singular limits of systems of partial differential equations governing the motion of thermally conducting compressible viscous fluids. "The main aim is to provide mathematically rigorous arguments how to get from the compressible Navier-Stokes-Fourier system several less complex systems of partial differential equations used e.g. in meteorology or astrophysics. However, the book contains also a detailed introduction to the modelling in mechanics and thermodynamics of fluids from the viewpoint of continuum physics. The book is very interesting and important. It can be recommended not only to specialists in the field, but it can also be used for doctoral students and young researches who want to start to work in the mathematical theory of compressible fluids and their asymptotic limits." Milan Pokorný (zbMATH) "This book is of the highest quality from every point of view. It presents, in a unified way, recent research material of fundament al importance. It is self-contained, thanks to Chapt...
Self-consistent viscous heating of rapidly compressed turbulence
Campos, Alejandro; Morgan, Brandon
2017-11-01
Given turbulence subjected to infinitely rapid deformations, linear terms representing interactions between the mean flow and the turbulence dictate the evolution of the flow, whereas non-linear terms corresponding to turbulence-turbulence interactions are safely ignored. For rapidly deformed flows where the turbulence Reynolds number is not sufficiently large, viscous effects can't be neglected and tend to play a prominent role, as shown in the study of Davidovits & Fisch (2016). For such a case, the rapid increase of viscosity in a plasma-as compared to the weaker scaling of viscosity in a fluid-leads to the sudden viscous dissipation of turbulent kinetic energy. As shown in Davidovits & Fisch, increases in temperature caused by the direct compression of the plasma drive sufficiently large values of viscosity. We report on numerical simulations of turbulence where the increase in temperature is the result of both the direct compression (an inviscid mechanism) and the self-consistent viscous transfer of energy from the turbulent scales towards the thermal energy. A comparison between implicit large-eddy simulations against well-resolved direct numerical simulations is included to asses the effect of the numerical and subgrid-scale dissipation on the self-consistent viscous This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Directory of Open Access Journals (Sweden)
Ivo Stachiv
2015-11-01
Full Text Available Vibrating micro-/nanosized cantilever beams under an applied axial force are the key components of various devices used in nanotechnology. In this study, we perform a complete theoretical investigation of the cantilever beams under an arbitrary value of the axial force vibrating in a specific environment such as vacuum, air or viscous fluid. Based on the results easy accessible expressions enabling one the fast and highly accurate estimations of changes in the Q-factor and resonant frequencies of beam oscillating in viscous fluid caused by the applied axial force are derived and analyzed. It has been also shown that for beam-to-string and string vibrational regimes the mode shape starts to significantly deviate from the one known for a beam without axial force. Moreover, a linear dependency of the vibrational amplitude in resonance on the dimensionless tension parameter has been found. We revealed that only a large axial force, i.e. the string vibrational regime, significantly improves the Q-factor of beams submerged in fluid, while an increase of the axial force in beam and beam-to-string transition regimes has a negligibly small impact on the Q-factor enhancement. Experiments carried out on the carbon nanotubes and nanowires are in a good agreement with present theoretical predictions.
Multidomain spectral solution of compressible viscous flows
International Nuclear Information System (INIS)
Kopriva, D.A.
1994-01-01
We develop a nonoverlapping mutidomain spectral collocation method to solve compressible viscous flows. At the interfaces, the advection terms are treated with a characteristic correction method. The diffusion terms are treated with a penalty method. Spectral accuracy is demonstrated on linear model problems in one and two space dimensions. The method is applied to a subsonic and supersonic flow over a flat plate. The results are compared to solutions of the boundary-layer equations which show that two digit accuracy in the adiabatic plate temperature is obtained with 16 points in the boundary layer for a freestream Mach number of two. A second application is to a transonic flow in a two-dimensional converging-diverging nozzle, where the computed results are compared to experimental data
On compressible and piezo-viscous flow in thin porous media.
Pérez-Ràfols, F; Wall, P; Almqvist, A
2018-01-01
In this paper, we study flow through thin porous media as in, e.g. seals or fractures. It is often useful to know the permeability of such systems. In the context of incompressible and iso-viscous fluids, the permeability is the constant of proportionality relating the total flow through the media to the pressure drop. In this work, we show that it is also relevant to define a constant permeability when compressible and/or piezo-viscous fluids are considered. More precisely, we show that the corresponding nonlinear equation describing the flow of any compressible and piezo-viscous fluid can be transformed into a single linear equation. Indeed, this linear equation is the same as the one describing the flow of an incompressible and iso-viscous fluid. By this transformation, the total flow can be expressed as the product of the permeability and a nonlinear function of pressure, which represents a generalized pressure drop.
Compressed gas domestic aerosol valve design using high viscous product
Directory of Open Access Journals (Sweden)
A Nourian
2016-10-01
Full Text Available Most of the current universal consumer aerosol products using high viscous product such as cooking oil, antiperspirants, hair removal cream are primarily used LPG (Liquefied Petroleum Gas propellant which is unfriendly environmental. The advantages of the new innovative technology described in this paper are: i. No butane or other liquefied hydrocarbon gas is used as a propellant and it replaced with Compressed air, nitrogen or other safe gas propellant. ii. Customer acceptable spray quality and consistency during can lifetime iii. Conventional cans and filling technology There is only a feasible energy source which is inert gas (i.e. compressed air to replace VOCs (Volatile Organic Compounds and greenhouse gases, which must be avoided, to improve atomisation by generating gas bubbles and turbulence inside the atomiser insert and the actuator. This research concentrates on using "bubbly flow" in the valve stem, with injection of compressed gas into the passing flow, thus also generating turbulence. The new valve designed in this investigation using inert gases has advantageous over conventional valve with butane propellant using high viscous product (> 400 Cp because, when the valving arrangement is fully open, there are negligible energy losses as fluid passes through the valve from the interior of the container to the actuator insert. The use of valving arrangement thus permits all pressure drops to be controlled, resulting in improved control of atomising efficiency and flow rate, whereas in conventional valves a significant pressure drops occurs through the valve which has a complex effect on the corresponding spray.
Viscous Flow with Large Fluid-Fluid Interface Displacement
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz; Hassager, Ole; Saasen, Arild
1998-01-01
The arbitrary Lagrange-Euler (ALE) kinematic description has been implemented in a 3D transient finite element program to simulate multiple fluid flows with fluid-fluid interface or surface displacements. The description of fluid interfaces includes variable interfacial tension, and the formulation...... is useful in the simulation of low and intermediate Reynolds number viscous flow. The displacement of two immiscible Newtonian fluids in a vertical (concentric and eccentric) annulus and a (vertical and inclined)tube is simulated....
Compressible generalized Newtonian fluids
Czech Academy of Sciences Publication Activity Database
Málek, Josef; Rajagopal, K.R.
2010-01-01
Roč. 61, č. 6 (2010), s. 1097-1110 ISSN 0044-2275 Institutional research plan: CEZ:AV0Z20760514 Keywords : power law fluid * uniform temperature * compressible fluid Subject RIV: BJ - Thermodynamics Impact factor: 1.290, year: 2010
Design method for fluid viscous dampers
Energy Technology Data Exchange (ETDEWEB)
Jia, Jiuhong; Hua, Hongxing [Shanghai Jiaotong University, State Key Laboratory of Mechanical System and Vibration, Shanghai (China); Du, Jianye; Wang, Yu [Naval Arming Academy, Institute of Naval Vessels, Beijing (China)
2008-09-15
A basic design method of doubly acting fluid viscous dampers with double guide bars is presented. The flow of the viscoelastic fluid between two parallel plates, one of which is started suddenly and the other of which is still, is analyzed. According to this solution, the velocity and the shear stress of the fluid at the fringe of the piston are solved approximately. A mathematical model of viscous dampers is derived, and the shock test is carried out. From experimental results, the parameters of the mathematical model are determined. Consequently, a semi-empirical design equation is obtained. Applying this equation to a certain practical damper, the damping material is chosen and the physical dimensions of the damper are determined. Shock tests using this damper are performed. Theoretical results are in good agreement with experimental results, which validates the reliability of the calculated physical dimensions of the specimen damper and the validity of the basic design equation. (orig.)
A dynamic counterpart of Lamb vector in viscous compressible aerodynamics
International Nuclear Information System (INIS)
Liu, L Q; Wu, J Z; Shi, Y P; Zhu, J Y
2014-01-01
The Lamb vector is known to play a key role in incompressible fluid dynamics and vortex dynamics. In particular, in low-speed steady aerodynamics it is solely responsible for the total force acting on a moving body, known as the vortex force, with the classic two-dimensional (exact) Kutta–Joukowski theorem and three-dimensional (linearized) lifting-line theory as the most famous special applications. In this paper we identify an innovative dynamic counterpart of the Lamb vector in viscous compressible aerodynamics, which we call the compressible Lamb vector. Mathematically, we present a theorem on the dynamic far-field decay law of the vorticity and dilatation fields, and thereby prove that the generalized Lamb vector enjoys exactly the same integral properties as the Lamb vector does in incompressible flow, and hence the vortex-force theory can be generalized to compressible flow with exactly the same general formulation. Moreover, for steady flow of polytropic gas, we show that physically the force exerted on a moving body by the gas consists of a transverse force produced by the original Lamb vector and a new longitudinal force that reflects the effects of compression and irreversible thermodynamics. (paper)
Viscous and gravitational fingering in multiphase compositional and compressible flow
Moortgat, Joachim
2016-03-01
Viscous and gravitational fingering refer to flow instabilities in porous media that are triggered by adverse mobility or density ratios, respectively. These instabilities have been studied extensively in the past for (1) single-phase flow (e.g., contaminant transport in groundwater, first-contact-miscible displacement of oil by gas in hydrocarbon production), and (2) multi-phase immiscible and incompressible flow (e.g., water-alternating-gas (WAG) injection in oil reservoirs). Fingering in multiphase compositional and compressible flow has received much less attention, perhaps due to its high computational complexity. However, many important subsurface processes involve multiple phases that exchange species. Examples are carbon sequestration in saline aquifers and enhanced oil recovery (EOR) by gas or WAG injection below the minimum miscibility pressure. In multiphase flow, relative permeabilities affect the mobility contrast for a given viscosity ratio. Phase behavior can also change local fluid properties, which can either enhance or mitigate viscous and gravitational instabilities. This work presents a detailed study of fingering behavior in compositional multiphase flow in two and three dimensions and considers the effects of (1) Fickian diffusion, (2) mechanical dispersion, (3) flow rates, (4) domain size and geometry, (5) formation heterogeneities, (6) gravity, and (7) relative permeabilities. Results show that fingering in compositional multiphase flow is profoundly different from miscible conditions and upscaling techniques used for the latter case are unlikely to be generalizable to the former.
Compressible Fluid Suspension Performance Testing
National Research Council Canada - National Science Library
Hoogterp, Francis
2003-01-01
... compressible fluid suspension system that was designed and installed on the vehicle by DTI. The purpose of the tests was to evaluate the possible performance benefits of the compressible fluid suspension system...
Development of a Model Foamy Viscous Fluid
Directory of Open Access Journals (Sweden)
Vial C.
2013-08-01
Full Text Available The objective is to develop a model viscous foamy fluid, i.e. below the very wet limit, the rheological and stability properties of which can be tuned. First, the method used for the preparation of foamy fluids is detailed, including process and formulation. Then, experimental results highlight that stable foamy fluids with a monomodal bubble size distribution can be prepared with a void fraction between 25% and 50% (v/v. Their viscoelastic properties under flow and low-strain oscillatory conditions are shown to result from the interplay between the formulation of the continuous phase, void fraction and bubble size. Their apparent viscosity can be described using the Cross equation and zero-shear Newtonian viscosity may be predicted by a Mooney equation up to a void fraction about 40%. The Cox-Merz and the Laun’s rules apply when the capillary number Ca is lower than 0.1. The upper limit of the zero-shear plateau region decreases when void fraction increases or bubble size decreases. In the shear-thinning region, shear stress varies with Ca1/2, as in wet foams with immobile surfaces. Finally, foamy fluids can be sheared up to Ca about 0.1 without impairing their microstructure. Their stability at rest achieves several hours and increases with void fraction due to compact packing constraints. These constitute, therefore, versatile model fluids to investigate the behaviour of foamy fluids below the very wet limit in process conditions.
Asymptotic stability of steady compressible fluids
Padula, Mariarosaria
2011-01-01
This volume introduces a systematic approach to the solution of some mathematical problems that arise in the study of the hyperbolic-parabolic systems of equations that govern the motions of thermodynamic fluids. It is intended for a wide audience of theoretical and applied mathematicians with an interest in compressible flow, capillarity theory, and control theory. The focus is particularly on recent results concerning nonlinear asymptotic stability, which are independent of assumptions about the smallness of the initial data. Of particular interest is the loss of control that sometimes results when steady flows of compressible fluids are upset by large disturbances. The main ideas are illustrated in the context of three different physical problems: (i) A barotropic viscous gas in a fixed domain with compact boundary. The domain may be either an exterior domain or a bounded domain, and the boundary may be either impermeable or porous. (ii) An isothermal viscous gas in a domain with free boundaries. (iii) A h...
Diffusion on Viscous Fluids, Existence and Asymptotic Properties of Solutions,
1983-09-01
Matematica - Politecuico di Milano (1982). 11.* P. Secchi "On the Initial Value ProbleM for the Nquations of Notion of Viscous Incompressible Fluids In...of two viscous Incompressible Fluids’, preprint DepartLmento dl matematica - Politecuico di Milano (1982). -15- 11. P. Secchi 00n the XnitiaI Value
Hydrodynamic response of viscous fluids under seismic excitation
International Nuclear Information System (INIS)
Ma, D.C.
1993-01-01
Hydrodynamic response of liquid-tank systems, such as reactor vessels, spent-fuel pools and liquid storage tanks have been studied extensively in the last decade (Chang et al. 1988; Ma et al. 1991). However, most of the studies are conducted with the assumption of an inviscid fluid. In recent years, the hydrodynamic response of viscous fluids has received increasing attention in high level waste storage tanks containing viscous waste material. This paper presents a numerical study on the hydrodynamic response of viscous fluids in a large 2-D fluid-tank system under seismic excitation. Hydrodynamic responses (i.e. sloshing wave height, fluid pressures, shear stress, etc.) are calculated for a fluid with various viscosities. Four fluid viscosities are considered. They are 1 cp, 120 cp, 1,000 cp and 12,000 cp (1 cp = 1.45 x 10 -7 lb-sec/in 2 ). Note that the liquid sodium of the Liquid-Metal Reactor (LMR) reactor has a viscosity of 1.38 x 10 -5 lb-sec/in 2 (about 95 cp) at an operational temperature of 900 degree F. Section 2 describes the pertinent features of the mathematical model. In Section 3, the fundamental sloshing phenomena of viscous fluid are examined. Sloshing wave height and shear stress for fluid with different viscosities are compared. The conclusions are given in Section 4
Combined Effect of Pressure and Temperature on the Viscous Behaviour of All-Oil Drilling Fluids
Directory of Open Access Journals (Sweden)
Hermoso J.
2014-12-01
Full Text Available The overall objective of this research was to study the combined influence of pressure and temperature on the complex viscous behaviour of two oil-based drilling fluids. The oil-based fluids were formulated by dispersing selected organobentonites in mineral oil, using a high-shear mixer, at room temperature. Drilling fluid viscous flow characterization was performed with a controlled-stress rheometer, using both conventional coaxial cylinder and non-conventional geometries for High Pressure/High Temperature (HPHT measurements. The rheological data obtained confirm that a helical ribbon geometry is a very useful tool to characterise the complex viscous flow behaviour of these fluids under extreme conditions. The different viscous flow behaviours encountered for both all-oil drilling fluids, as a function of temperature, are related to changes in polymer-oil pair solvency and oil viscosity. Hence, the resulting structures have been principally attributed to changes in the effective volume fraction of disperse phase due to thermally induced processes. Bingham’s and Herschel-Bulkley’s models describe the rheological properties of these drilling fluids, at different pressures and temperatures, fairly well. It was found that Herschel-Bulkley’s model fits much better B34-based oil drilling fluid viscous flow behaviour under HPHT conditions. Yield stress values increase linearly with pressure in the range of temperature studied. The pressure influence on yielding behaviour has been associated with the compression effect of different resulting organoclay microstructures. A factorial WLF-Barus model fitted the combined effect of temperature and pressure on the plastic viscosity of both drilling fluids fairly well, being this effect mainly influenced by the piezo-viscous properties of the continuous phase.
Microjet Generator for Highly Viscous Fluids
Onuki, Hajime; Oi, Yuto; Tagawa, Yoshiyuki
2018-01-01
This paper describes a simple system for generating a highly viscous microjet. The jet is produced inside a wettable thin tube partially submerged in a liquid. The gas-liquid interface inside the tube, which is initially concave, is kept much deeper than that outside the tube. An impulsive force applied at the bottom of a liquid container leads to significant acceleration of the liquid inside the tube followed by flow focusing due to the concave interface. The jet generation process can be divided into two parts that occur in different time scales, i.e., the impact interval [impact duration ≤O (10-4) s ] and the focusing interval [focusing duration ≫O (10-4) s ]. During the impact interval, the liquid accelerates suddenly due to the impact. During the focusing interval, the microjet emerges due to flow focusing. In order to explain the sudden acceleration inside the tube during the impact interval, we develop a physical model based on a pressure impulse approach. Numerical simulations confirm the proposed model, indicating that the basic mechanism of the acceleration of the liquid due to the impulsive force is elucidated. Remarkably, the viscous effect is negligible during the impact interval. In contrast, during the focusing interval, the viscosity plays an important role in the microjet generation. We experimentally and numerically investigate the velocity of microjets with various viscosities. We find that higher viscosities lead to reduction of the jet velocity, which can be described by using the Reynolds number (the ratio between the inertia force and the viscous force). This device may be a starting point for next-generation technologies, such as high-viscosity inkjet printers including bioprinters and needle-free injection devices for minimally invasive medical treatments.
Simulation of swimming strings immersed in a viscous fluid flow
Huang, Wei-Xi; Sung, Hyung Jin
2006-11-01
In nature, many phenomena involve interactions between flexible bodies and their surrounding viscous fluid, such as a swimming fish or a flapping flag. The intrinsic dynamics is complicate and not well understood. A flexible string can be regarded as a one-dimensional flag model. Many similarities can be found between the flapping string and swimming fish, although different wake speed results in a drag force for the flapping string and a propulsion force for the swimming fish. In the present study, we propose a mathematical formulation for swimming strings immersed in a viscous fluid flow. Fluid motion is governed by the Navier-Stokes equations and a momentum forcing is added in order to bring the fluid to move at the same velocity with the immersed surface. A flexible inextensible string model is described by another set of equations with an additional momentum forcing which is a result of the fluid viscosity and the pressure difference across the string. The momentum forcing is calculated by a feedback loop. Simulations of several numerical examples are carried out, including a hanging string which starts moving under gravity without ambient fluid, a swinging string immersed in a quiescent viscous fluid, a string swimming within a uniform surrounding flow, and flow over two side-by-side strings. The numerical results agree well with the theoretical analysis and previous experimental observations. Further simulation of a swimming fish is under consideration.
Nonlinear Thermal Instability in Compressible Viscous Flows Without Heat Conductivity
Jiang, Fei
2018-04-01
We investigate the thermal instability of a smooth equilibrium state, in which the density function satisfies Schwarzschild's (instability) condition, to a compressible heat-conducting viscous flow without heat conductivity in the presence of a uniform gravitational field in a three-dimensional bounded domain. We show that the equilibrium state is linearly unstable by a modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further construct the initial data of linearly unstable solutions to be the one of the original nonlinear problem, and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we finally show that the equilibrium state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap instability argument.
Effective description of dark matter as a viscous fluid
Floerchinger, S.; Tetradis, N.; Wiedemann, U.A.
2016-10-28
Treating dark matter at large scales as an effectively viscous fluid provides an improved framework for the calculation of the density and velocity power spectra compared to the standard assumption of an ideal pressureless fluid. We discuss how this framework can be made concrete through an appropriate coarse-graining procedure. We also review results that demonstrate that it improves the convergence of cosmological perturbation theory.
A Thermodynamically Consistent Approach to Phase-Separating Viscous Fluids
Anders, Denis; Weinberg, Kerstin
2018-04-01
The de-mixing properties of heterogeneous viscous fluids are determined by an interplay of diffusion, surface tension and a superposed velocity field. In this contribution a variational model of the decomposition, based on the Navier-Stokes equations for incompressible laminar flow and the extended Korteweg-Cahn-Hilliard equations, is formulated. An exemplary numerical simulation using C1-continuous finite elements demonstrates the capability of this model to compute phase decomposition and coarsening of the moving fluid.
Effective description of dark matter as a viscous fluid
International Nuclear Information System (INIS)
Floerchinger, Stefan; Garny, Mathias; Tetradis, Nikolaos; Wiedemann, Urs Achim
2016-01-01
Treating dark matter at large scales as an effectively viscous fluid provides an improved framework for the calculation of the density and velocity power spectra compared to the standard assumption of an ideal pressureless fluid. We discuss how this framework can be made concrete through an appropriate coarse-graining procedure. We also review results that demonstrate that it improves the convergence of cosmological perturbation theory
Viscous coupled fluids in inflationary cosmology
Energy Technology Data Exchange (ETDEWEB)
Brevik, I., E-mail: iver.h.brevik@ntnu.no [Norwegian University of Science and Technology (Norway); Timoshkin, A. V., E-mail: timoshkinAV@tspu.edu.ru [Tomsk State Pedagogical University (Russian Federation)
2016-04-15
We consider the inflation produced by two coupled fluids in a flat Friedmann–Robertson–Walker universe. Different cosmological models for describing inflation with the use of an inhomogeneous equation of state for the fluid are investigated. The gravitational equations for energy and matter are solved, and analytic representations for the Hubble parameter and the energy density are obtained. Corrections to the energy density for matter inducing the inflation and the coupling to energy are discussed. We analyze the description of inflation induced by nonconstant equation-of-state parameters from fluid viscosity. The correspondence between the spectral index and the tensor-to-scalar ratio recently observed by the Planck satellite is considered.
Instabilities in a Relativistic Viscous Fluid
Corona-Galindo, M. G.; Klapp, J.; Vazquez, A.
1990-11-01
RESUMEN. Las ecuaciones hidrodinamicas de un fluido imperfecto relativista son resueltas, y los modos hidrodinamicos son analizados con el prop6sito de estabiecer correlaciones con las estructuras cosmol6gicas. ABSTRACT The hydrodynamical equations of a relativistic imperfect fluid are solved, and the hydrodynamical modes are analysed with the aim to establish correlations with cosmological structures. Ke, words: COSMOLOGY - HYDRODYNAMICS - RELATIVITY
Viscous-elastic dynamics of power-law fluids within an elastic cylinder
Boyko, Evgeniy; Bercovici, Moran; Gat, Amir D.
2017-07-01
In a wide range of applications, microfluidic channels are implemented in soft substrates. In such configurations, where fluidic inertia and compressibility are negligible, the propagation of fluids in channels is governed by a balance between fluid viscosity and elasticity of the surrounding solid. The viscous-elastic interactions between elastic substrates and non-Newtonian fluids are particularly of interest due to the dependence of viscosity on the state of the system. In this work, we study the fluid-structure interaction dynamics between an incompressible non-Newtonian fluid and a slender linearly elastic cylinder under the creeping flow regime. Considering power-law fluids and applying the thin shell approximation for the elastic cylinder, we obtain a nonhomogeneous p-Laplacian equation governing the viscous-elastic dynamics. We present exact solutions for the pressure and deformation fields for various initial and boundary conditions for both shear-thinning and shear-thickening fluids. We show that in contrast to Stokes' problem where a compactly supported front is obtained for shear-thickening fluids, here the role of viscosity is inversed and such fronts are obtained for shear-thinning fluids. Furthermore, we demonstrate that for the case of a step in inlet pressure, the propagation rate of the front has a tn/n +1 dependence on time (t ), suggesting the ability to indirectly measure the power-law index (n ) of shear-thinning liquids through measurements of elastic deformation.
Capillary waves of compressible fluids
International Nuclear Information System (INIS)
Falk, Kerstin; Mecke, Klaus
2011-01-01
The interplay of thermal noise and molecular forces is responsible for surprising features of liquids on sub-micrometer lengths-in particular at interfaces. Not only does the surface tension depend on the size of an applied distortion and nanoscopic thin liquid films dewet faster than would be expected from hydrodynamics, but also the dispersion relation of capillary waves differ at the nanoscale from the familiar macroscopic behavior. Starting with the stochastic Navier-Stokes equation we study the coupling of capillary waves to acoustic surface waves which is possible in compressible fluids. We find propagating 'acoustic-capillary waves' at nanometer wavelengths where in incompressible fluids capillary waves are overdamped.
Shear waves in inhomogeneous, compressible fluids in a gravity field.
Godin, Oleg A
2014-03-01
While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere.
Steady fall of a rigid body in viscous fluid
Czech Academy of Sciences Publication Activity Database
Nečasová, Šárka
2005-01-01
Roč. 63, Sp. Is. (2005), s. 2113-2119 ISSN 0362-546X. [Invited Talks from the Fourth World Congress of Nonlinear Analysts (WCNA 2004). Orlando , 30.7.2004-7.8.2004] R&D Projects: GA ČR(CZ) GA201/02/0684 Institutional research plan: CEZ:AV0Z1019905 Keywords : steady fall * rigid body * viscous fluid Subject RIV: BA - General Mathematics Impact factor: 0.519, year: 2005
Mathematical theory of viscous fluids: retrospective and future perspectives
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2010-01-01
Roč. 27, č. 2 (2010), s. 533-555 ISSN 1078-0947 R&D Projects: GA ČR GA201/08/0315 Institutional research plan: CEZ:AV0Z10190503 Keywords : viscous fluid * Navier-Stokes-Fourier system * global-intime solutions Subject RIV: BA - General Mathematics Impact factor: 0.986, year: 2010 http://www.aimsciences.org/journals/displayArticles.jsp?paperID=4942
Dynamics of two coaxial cylindrical shells containing viscous fluid
International Nuclear Information System (INIS)
Yeh, T.T.; Chen, S.S.
1976-09-01
This study was motivated by the need to design the thermal shield in reactor internals and other system components to avoid detrimental flow-induced vibrations. The system component is modeled as two coaxial shells separated by a viscous fluid. In the analysis, Flugge's shell equations of motion and linearized Navier-Stokes equation for viscous fluid are employed. First, a traveling-wave type solution is taken for shells and fluid. Then, from the interface conditions between the shells and fluid, the solution for the fluid medium is expressed in terms of shell displacements. Finally, using the shell equations of motion gives the frequency equation, from which the natural frequency, mode shape, and modal damping ratio of coupled modes can be calculated. The analytical results show a fairly good qualitative agreement with the published experimental data. Some important conclusions are as follows: (1) In computing the natural frequencies and mode shapes of uncoupled modes and coupled modes, the fluid may be considered inviscid and incompressible. (2) There exists out-of-phase and in-phase modes. The lowest natural frequency is always associated with the out-of-phase mode. (3) The lowest natural frequency of coupled modes is lower than the uncoupled modes. (4) The fluid viscosity contributes significantly to damping, in particular, the modal damping of the out-of-phase modes isrelatively large for small gaps. (5) If the fluid gap is small, or the fluid viscosity is relatively high, the simulation of the vibration Reynolds number should be included to ensure that modal damping of the model is properly accounted for. With the presented analysis and results, the frequency and damping characteristics can be analyzed and design parameters can be related to frequency and damping
Rheology of granular flows immersed in a viscous fluid
International Nuclear Information System (INIS)
Amarsid, Lhassan
2015-01-01
We investigate the behavior of granular materials immersed in a viscous fluid by means of extensive simulations based on the Discrete Element Method for particle dynamics coupled with the Lattice Boltzmann method for the fluid. We show that, for a broad range of parameters such as shear rate, confining stress and viscosity, the internal friction coefficient and packing fraction are well described by a single 'visco-inertial' dimensionless parameter combining inertial and Stokes numbers. The frictional behavior under constant confining pressure is mapped into a viscous behavior under volume-controlled conditions, leading to the divergence of the effective normal and shear viscosities in inverse square of the distance to the critical packing fraction. The results are in excellent agreement with the experimental data of Boyer et al. (2011). The evolution of the force network in terms of connectivity and anisotropy as a function of the visco-inertial number, indicates that the increase of frictional strength is a direct consequence of structural anisotropy enhanced by both fluid viscosity and grain inertia. In view of application to a potential nuclear accident, we also study the fragmentation and flow of confined porous aggregates in a fluid under the action of local overpressures and pressure gradients as well as gravity-driven flow of immersed particles in an hourglass. (author)
On some Approximation Schemes for Steady Compressible Viscous Flow
Bause, M.; Heywood, J. G.; Novotny, A.; Padula, M.
This paper continues our development of approximation schemes for steady compressible viscous flow based on an iteration between a Stokes like problem for the velocity and a transport equation for the density, with the aim of improving their suitability for computations. Such schemes seem attractive for computations because they offer a reduction to standard problems for which there is already highly refined software, and because of the guidance that can be drawn from an existence theory based on them. Our objective here is to modify a recent scheme of Heywood and Padula [12], to improve its convergence properties. This scheme improved upon an earlier scheme of Padula [21], [23] through the use of a special ``effective pressure'' in linking the Stokes and transport problems. However, its convergence is limited for several reasons. Firstly, the steady transport equation itself is only solvable for general velocity fields if they satisfy certain smallness conditions. These conditions are met here by using a rescaled variant of the steady transport equation based on a pseudo time step for the equation of continuity. Another matter limiting the convergence of the scheme in [12] is that the Stokes linearization, which is a linearization about zero, has an inevitably small range of convergence. We replace it here with an Oseen or Newton linearization, either of which has a wider range of convergence, and converges more rapidly. The simplicity of the scheme offered in [12] was conducive to a relatively simple and clearly organized proof of its convergence. The proofs of convergence for the more complicated schemes proposed here are structured along the same lines. They strengthen the theorems of existence and uniqueness in [12] by weakening the smallness conditions that are needed. The expected improvement in the computational performance of the modified schemes has been confirmed by Bause [2], in an ongoing investigation.
Special Fluid Viscous Dampers For The Messina Strait Bridge
International Nuclear Information System (INIS)
Colato, Gian Paolo; Infanti, Samuele; Castellano, Maria Gabriella
2008-01-01
The Messina Strait Bridge would be the world's longest suspension bridge, with a design earthquake characterised by a PGA value of 0.58 g and a distance between the ipocenter and the bridge of 15 km. Said critical structure of course would need a suitable restraint system for traffic braking loads, wind and seismic actions. Each type of load requires a specific behaviour of the restraint system, making its design a big challenge.The restraint system comprises special types of fluid viscous dampers, installed both in longitudinal and transverse direction, both at the towers and at the anchorages. In seismic conditions they behave as viscous dampers, to reduce the forces on the structural elements and the movements of the bridge deck. But in service dynamic conditions, e.g. under traffic or wind load, the devices shall behave like shock transmission units, thus preventing the longitudinal and transverse movements of the deck.FIP Industriale cooperated with the selected General Contractor, a consortium lead by Impregilo, in the design of said viscous dampers. This paper describes the main features of said devices
Slow Waves in Fractures Filled with Viscous Fluid
Energy Technology Data Exchange (ETDEWEB)
Korneev, Valeri
2008-01-08
Stoneley guided waves in a fluid-filled fracture generally have larger amplitudes than other waves, and therefore, their properties need to be incorporated in more realistic models. In this study, a fracture is modeled as an infinite layer of viscous fluid bounded by two elastic half-spaces with identical parameters. For small fracture thickness, I obtain a simple dispersion equation for wave-propagation velocity. This velocity is much smaller than the velocity of a fluid wave in a Biot-type solution, in which fracture walls are assumed to be rigid. At seismic prospecting frequencies and realistic fracture thicknesses, the Stoneley guided wave has wavelengths on the order of several meters and an attenuation Q factor exceeding 10, which indicates the possibility of resonance excitation in fluid-bearing rocks. The velocity and attenuation of Stoneley guided waves are distinctly different at low frequencies for water and oil. The predominant role of fractures in fluid flow at field scales is supported by permeability data showing an increase of several orders of magnitude when compared to values obtained at laboratory scales. These data suggest that Stoneley guided waves should be taken into account in theories describing seismic wave propagation in fluid-saturated rocks.
Performance of a viscous damper using electro-rheological fluid
International Nuclear Information System (INIS)
Otani, A.; Kobayashi, H.; Kobayashi, N.; Tadaishi, Y.
1994-01-01
A new damper has been developed that suppresses small-amplitude vibrations over a wide frequency range. The damper has been tested using both an electro-rheological fluid (ERF) and a highly viscous liquid, which are enclosed in the damper's casing (a metal bellows). The apparent viscosity of the ERF can be changed by varying the strength of the applied electrical field. Initially, a simple L-shaped piping model excited by a rotary-type exciter was used to investigate the performance of the damper, utilizing both fluids. The experimental results demonstrate the effectiveness of the passive damper. Based on the experimental results, application of the damper to an actual piping system with a big pump was carried out analytical
Multiscale Behavior of Viscous Fluids Dynamics: Experimental Observations
Arciniega-Ceballos, Alejandra; Spina, Laura; Scheu, Bettina; Dingwell, Donald B.
2016-04-01
The dynamics of Newtonian fluids with viscosities of mafic to intermediate silicate melts (10-1000 Pa s) during slow decompression present multi-time scale processes. To observe these processes we have performed several experiments on silicon oil saturated with Argon gas for 72 hours, in a Plexiglas autoclave. The slow decompression, dropping from 10 MPa to ambient pressure, acting as the excitation mechanism, triggered several processes with their own distinct timescales. These processes generate complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit flanked by high-speed video recordings. The analysis in time and frequency of these time series and their correlation with the associated high-speed imaging enables the characterization of distinct phases and the extraction of the individual processes during the evolution of decompression of these viscous fluids. We have observed fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution along the conduit. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the conduit system. Our observations point to the great potential of this experimental approach in the understanding of volcanic conduit dynamics and volcanic seismicity.
Non self-propelled swimmer in a confined viscous fluid
Choudhary, Priyanka; Mandal, Subhayan
2018-05-01
As we know that in a low Reynolds number regime, the swimming strategies that are used in high Reynolds number swimming are inefficient because of the dominating viscous forces. Therefore, micro-swimmers have developed different moving strategies that have fruitfully overcome and have exploited drag. Hydrodynamic interactions due to the objects in the vicinity are also one of the ingredients that can make a micro-swimmer motile. To show the importance of such kind of hydrodynamic interactions, here we investigate a 2-D scallop near no-slip boundaries in a viscous fluid using bead spring model together with multi-particle collision dynamics. Here, we show that if we place a scallop near a wall, it gets rotated and the direction of rotation depends upon the orientation of the scallop as expected. Instead of one wall, if we place the scallop between two closely spaced walls, initially it rotates and then slowly starts moving in backward direction due to the hydrodynamic interaction with the walls. Then we show that how the speed of the scallop is affected as we change the width of the channel. Our results can endue important guidance in the construction of robotic micro-swimmers.
Introduction to compressible fluid flow
Oosthuizen, Patrick H
2013-01-01
IntroductionThe Equations of Steady One-Dimensional Compressible FlowSome Fundamental Aspects of Compressible FlowOne-Dimensional Isentropic FlowNormal Shock WavesOblique Shock WavesExpansion Waves - Prandtl-Meyer FlowVariable Area FlowsAdiabatic Flow with FrictionFlow with Heat TransferLinearized Analysis of Two-Dimensional Compressible FlowsHypersonic and High-Temperature FlowsHigh-Temperature Gas EffectsLow-Density FlowsBibliographyAppendices
The stochastic dynamics of tethered microcantilevers in a viscous fluid
Energy Technology Data Exchange (ETDEWEB)
Robbins, Brian A.; Paul, Mark R. [Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Radiom, Milad; Ducker, William A. [Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Walz, John Y. [Department of Chemical Engineering, University of Kentucky, Lexington, Kentucky 40506 (United States)
2014-10-28
We explore and quantify the coupled dynamics of a pair of micron scale cantilevers immersed in a viscous fluid that are also directly tethered to one another at their tips by a spring force. The spring force, for example, could represent the molecular stiffness or elasticity of a biomolecule or material tethered between the cantilevers. We use deterministic numerical simulations with the fluctuation-dissipation theorem to compute the stochastic dynamics of the cantilever pair for the conditions of experiment when driven only by Brownian motion. We validate our approach by comparing directly with experimental measurements in the absence of the tether which shows excellent agreement. Using numerical simulations, we quantify the correlated dynamics of the cantilever pair over a range of tether stiffness. Our results quantify the sensitivity of the auto- and cross-correlations of equilibrium fluctuations in cantilever displacement to the stiffness of the tether. We show that the tether affects the magnitude of the correlations which can be used in a measurement to probe the properties of an attached tethering substance. For the configurations of current interest using micron scale cantilevers in water, we show that the magnitude of the fluid coupling between the cantilevers is sufficiently small such that the influence of the tether can be significant. Our results show that the cross-correlation is more sensitive to tether stiffness than the auto-correlation indicating that a two-cantilever measurement has improved sensitivity when compared with a measurement using a single cantilever.
Scale interactions in compressible rotating fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Novotný, A.
2014-01-01
Roč. 193, č. 6 (2014), s. 1703-1725 ISSN 0373-3114 Keywords : compressible fluid * rotating fluid * singular limit Subject RIV: BA - General Mathematics Impact factor: 1.065, year: 2014 http://link.springer.com/article/10.1007%2Fs10231-013-0353-7
Vapour and air bubble collapse analysis in viscous compressible water
Directory of Open Access Journals (Sweden)
Gil Bazanini
2001-01-01
Full Text Available Numerical simulations of the collapse of bubbles (or cavities are shown, using the finite difference method, taking into account the compressibility of the liquid, expected to occur in the final stages of the collapse process. Results are compared with experimental and theoretical data for incompressible liquids, to see the influence of the compressibility of the water in the bubble collapse. Pressure fields values are calculated in an area of 800 x 800 mm, for the case of one bubble under the hypothesis of spherical symmetry. Results are shown as radius versus time curves for the collapse (to compare collapse times, and pressure curves in the plane, for pressure fields. Such calculations are new because of their general point of view, since the existing works do not take into account the existence of vapour in the bubble, neither show the pressure fields seen here. It is also expected to see the influence of the compressibility of the water in the collapse time, and in the pressure field, when comparing pressure values.
Rotational friction coefficient of a permeable cylinder in a viscous fluid
Wiegel, F.W.
1979-01-01
An exact expression is derived for the rotational friction coefficient of a cylinder of infinite length and constant permeability immersed in an incompressible viscous fluid. An asymptotic expression for the translational friction coefficient of a permeable cylinder moving in a sheet of viscous
Cross-coupling effects in chemically non-equilibrium viscous compressible flows
International Nuclear Information System (INIS)
Kustova, E.V.; Giordano, D.
2011-01-01
Graphical abstract: Self-cosistent kinetic-theory description of chemical-reaction rates and mean normal stress in one-temperature viscous compressible gas flows. Reaearch highlights: → In chemically non-equilibrium viscous compressible flows, the rate of each reaction depends on the velocity divergence and rates of all other reactions. → Cross effects between the rates of chemical reactions and normal mean stress can be found in the symmetric form and expressed in terms of the reaction affinities. → In the case of small affinities, the entropy production is unconditionally non-negative; in the case of finite affinities, the entropy production related to the scalar forces has no definite sign. - Abstract: A closed self-consistent description of a one-temperature non-equilibrium reacting flow is presented on the basis of the kinetic theory methods. A general case including internal degrees of freedom, dissociation-recombination and exchange reactions, and arbitrary values of affinities of chemical reactions is considered. Chemical-reaction rates and mean normal stress in viscous compressible flows are studied and a symmetric cross coupling between these terms is found. It is shown that the rate of each chemical reaction and the mean normal stress depend on velocity divergence and affinities of all chemical reactions; the law of mass action is violated in viscous flows. The results obtained in the frame of linear irreversible thermodynamics can be deduced from the proposed model for the particular case of small affinities. The reciprocal Onsager-Casimir relations are verified, the symmetry of kinetic coefficients is demonstrated, and the entropy production in a viscous flow is studied.
Computational fluid dynamics study of viscous fingering in supercritical fluid chromatography.
Subraveti, Sai Gokul; Nikrityuk, Petr; Rajendran, Arvind
2018-01-26
Axi-symmetric numerical simulations are carried out to study the dynamics of a plug introduced through a mixed-stream injection in supercritical fluid chromatographic columns. The computational fluid dynamics model developed in this work takes into account both the hydrodynamics and adsorption equilibria to describe the phenomena of viscous fingering and plug effect that contribute to peak distortions in mixed-stream injections. The model was implemented into commercial computational fluid dynamics software using user-defined functions. The simulations describe the propagation of both the solute and modifier highlighting the interplay between the hydrodynamics and plug effect. The simulated peaks showed good agreement with experimental data published in the literature involving different injection volumes (5 μL, 50 μL, 1 mL and 2 mL) of flurbiprofen on Chiralpak AD-H column using a mobile phase of CO 2 and methanol. The study demonstrates that while viscous fingering is the main source of peak distortions for large-volume injections (1 mL and 2 mL) it has negligible impact on small-volume injections (5 μL and 50 μL). Band broadening in small-volume injections arise mainly due to the plug effect. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.
Study of the motion of a vertically falling sphere in a viscous fluid
International Nuclear Information System (INIS)
Soares, A A; Caramelo, L; Andrade, M A P M
2012-01-01
This paper aims at contributing to a better understanding of the motion of spherical particles in viscous fluids. The classical problem of spheres falling through viscous fluids for small Reynolds numbers was solved taking into account the effects of added mass. The analytical solution for the motion of a falling sphere, from the beginning to the end of the fall, was combined with an iterative numerical method to determine the fluid viscosity coefficient, diameter of the sphere and terminal velocity. The proposed solution was validated with experimental literature data. The study presented may also help understanding the fluid-particle interactions from both theoretical and educational standpoints. (paper)
Rotating compressible fluids under strong stratification
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Lu, Y.; Novotný, A.
2014-01-01
Roč. 19, October (2014), s. 11-18 ISSN 1468-1218 Keywords : rotating fluid * compressible Navier-Stokes * strong stratification Subject RIV: BA - General Mathematics Impact factor: 2.519, year: 2014 http://www.sciencedirect.com/science/article/pii/S1468121814000212#
Chen, Yong; Huang, Yiyong; Chen, Xiaoqian
2013-02-01
Ultrasonic flow meter with non-invasive no-moving-parts construction has good prospective application for space on-orbit fluid gauging. In traditional pulse transit time flow meter, inconsistency of ultrasonic transducers leads to measurement error and plane wave theory, bases of transit time flow meter, is valuable only for low-frequency wave propagation in inviscid fluid and will lose feasibility when fluid viscosity is considered. In this paper, based on the hydrodynamics of viscous fluid, wave propagation with uniform flow profile is mathematically formulated and a novel solution for viscous fluid using potential theory is firstly presented. Then a novel design methodology of continuous ultrasonic flow meter is proposed, where high measurement rangeability and accuracy are guaranteed individually by solving the integral ambiguity using multi-tone wide laning strategy and the fractional phase shift using phase lock loop tracking method. A comparison with transit time ultrasonic flow meter shows the advantage of proposed methodology. In the end, parametric analysis of viscosity on wave propagation and ultrasonic flow meter is compressively investigated. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.
Spatiotemporal resonances in mixing of open viscous fluids
DEFF Research Database (Denmark)
Okkels, Fridolin; Tabeling, Patrick
2004-01-01
In this Letter, we reveal a new dynamical phenomenon, called "spatiotemporal resonance," which is expected to take place in a broad range of viscous, periodically forced, open systems. The observation originates from a numerical and theoretical analysis of a micromixer, and is supported...
Mathematical theory of compressible fluid flow
von Mises, Richard
2004-01-01
A pioneer in the fields of statistics and probability theory, Richard von Mises (1883-1953) made notable advances in boundary-layer-flow theory and airfoil design. This text on compressible flow, unfinished upon his sudden death, was subsequently completed in accordance with his plans, and von Mises' first three chapters were augmented with a survey of the theory of steady plane flow. Suitable as a text for advanced undergraduate and graduate students - as well as a reference for professionals - Mathematical Theory of Compressible Fluid Flow examines the fundamentals of high-speed flows, with
Moortgat, J.; Amooie, M. A.; Soltanian, M. R.
2016-12-01
Problems in hydrogeology and hydrocarbon reservoirs generally involve the transport of solutes in a single solvent phase (e.g., contaminants or dissolved injection gas), or the flow of multiple phases that may or may not exchange mass (e.g., brine, NAPL, oil, gas). Often, flow is viscously and gravitationally unstable due to mobility and density contrasts within a phase or between phases. Such instabilities have been studied in detail for single-phase incompressible fluids and for two-phase immiscible flow, but to a lesser extent for multiphase multicomponent compressible flow. The latter is the subject of this presentation. Robust phase stability analyses and phase split calculations, based on equations of state, determine the mass exchange between phases and the resulting phase behavior, i.e., phase densities, viscosities, and volumes. Higher-order finite element methods and fine grids are used to capture the small-scale onset of flow instabilities. A full matrix of composition dependent coefficients is considered for each Fickian diffusive phase flux. Formation heterogeneity can have a profound impact and is represented by realistic geostatistical models. Qualitatively, fingering in multiphase compositional flow is different from single-phase problems because 1) phase mobilities depend on rock wettability through relative permeabilities, and 2) the initial density and viscosity ratios between phases may change due to species transfer. To quantify mixing rates in different flow regimes and for varying degrees of miscibility and medium heterogeneities, we define the spatial variance, scalar dissipation rate, dilution index, skewness, and kurtosis of the molar density of introduced species. Molar densities, unlike compositions, include compressibility effects. The temporal evolution of these measures shows that, while transport at the small-scale (cm) is described by the classical advection-diffusion-dispersion relations, scaling at the macro-scale (> 10 m) shows
Compressible fluid flows driven by stochastic forcing
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Maslowski, B.; Novotný, A.
2013-01-01
Roč. 254, č. 3 (2013), s. 1342-1358 ISSN 0022-0396 R&D Projects: GA ČR GA201/09/0917 Institutional research plan: CEZ:AV0Z10190503 Institutional support: RVO:67985840 Keywords : stochastic Navier-Stokes equations * compressible fluid * random driving force Subject RIV: BA - General Mathematics Impact factor: 1.570, year: 2013 http://www.sciencedirect.com/science/article/pii/S0022039612004135
Exact Theory of Compressible Fluid Turbulence
Drivas, Theodore; Eyink, Gregory
2017-11-01
We obtain exact results for compressible turbulence with any equation of state, using coarse-graining/filtering. We find two mechanisms of turbulent kinetic energy dissipation: scale-local energy cascade and ``pressure-work defect'', or pressure-work at viscous scales exceeding that in the inertial-range. Planar shocks in an ideal gas dissipate all kinetic energy by pressure-work defect, but the effect is omitted by standard LES modeling of pressure-dilatation. We also obtain a novel inverse cascade of thermodynamic entropy, injected by microscopic entropy production, cascaded upscale, and removed by large-scale cooling. This nonlinear process is missed by the Kovasznay linear mode decomposition, treating entropy as a passive scalar. For small Mach number we recover the incompressible ``negentropy cascade'' predicted by Obukhov. We derive exact Kolmogorov 4/5th-type laws for energy and entropy cascades, constraining scaling exponents of velocity, density, and internal energy to sub-Kolmogorov values. Although precise exponents and detailed physics are Mach-dependent, our exact results hold at all Mach numbers. Flow realizations at infinite Reynolds are ``dissipative weak solutions'' of compressible Euler equations, similarly as Onsager proposed for incompressible turbulence.
Algebraic mesh generation for large scale viscous-compressible aerodynamic simulation
International Nuclear Information System (INIS)
Smith, R.E.
1984-01-01
Viscous-compressible aerodynamic simulation is the numerical solution of the compressible Navier-Stokes equations and associated boundary conditions. Boundary-fitted coordinate systems are well suited for the application of finite difference techniques to the Navier-Stokes equations. An algebraic approach to boundary-fitted coordinate systems is one where an explicit functional relation describes a mesh on which a solution is obtained. This approach has the advantage of rapid-precise mesh control. The basic mathematical structure of three algebraic mesh generation techniques is described. They are transfinite interpolation, the multi-surface method, and the two-boundary technique. The Navier-Stokes equations are transformed to a computational coordinate system where boundary-fitted coordinates can be applied. Large-scale computation implies that there is a large number of mesh points in the coordinate system. Computation of viscous compressible flow using boundary-fitted coordinate systems and the application of this computational philosophy on a vector computer are presented
Balance equations for a viscous fluid from a Hamilton type variational principle
International Nuclear Information System (INIS)
Fierros Palacios, A.
1992-01-01
The partial differential field equations for any viscous fluid are obtained from the Lagrangian formalism as in classical field theory. An action functional is introduced as a space-time integral over a region of three-dimensional Euclidean space, of a Lagrangian density function of certain field variables. A Hamilton type extremum action principle is postulated with adequate boundary conditions, and a set of differential field equations is derived. With an appropriate Lagrangian density of the T-V type, the equation of motion for any viscous fluid is reproduced. A theorem referring to the invariance of the action under time variations lead to the generalized energy balance equation for the viscous fluid and to the energy balance equation proper. The same theoretical approach can be used to solve the problem of potential flow. (Author)
Bulk viscous Zel'dovich fluid model and its asymptotic behavior
Energy Technology Data Exchange (ETDEWEB)
Nair, K.R.; Mathew, Titus K. [Cochin University of Science and Technology, Department of Physics, Kochi (India)
2016-10-15
In this paper we consider a flat FLRW universe with bulk viscous Zel'dovich fluid as the cosmic component. Considering the bulk viscosity as characterized by a constant bulk viscous coefficient, we analyze the evolution of the Hubble parameter. Type Ia Supernovae data is used for constraining the model and for extracting the constant bulk viscous parameter and present the Hubble parameter. We also present the analysis of the scale factor, equation of state, and deceleration parameter. The model predicts the later time acceleration and is also compatible with the age of the universe as given by the oldest globular clusters. Study of the phase-space behavior of the model shows that a universe dominated by bulk viscous Zel'dovich fluid is stable. But the inclusion of a radiation component in addition to the Zel'dovich fluid makes the model unstable. Hence, even though the bulk viscous Zel'dovich fluid dominated universe is a feasible one, the model as such fails to predict a prior radiation dominated phase. (orig.)
Modelling the normal bouncing dynamics of spheres in a viscous fluid
Directory of Open Access Journals (Sweden)
Izard Edouard
2017-01-01
Full Text Available Bouncing motions of spheres in a viscous fluid are numerically investigated by an immersed boundary method to resolve the fluid flow around solids which is combined to a discrete element method for the particles motion and contact resolution. Two well-known configurations of bouncing are considered: the normal bouncing of a sphere on a wall in a viscous fluid and a normal particle-particle bouncing in a fluid. Previous experiments have shown the effective restitution coefficient to be a function of a single parameter, namely the Stokes number which compares the inertia of the solid particle with the fluid viscous dissipation. The present simulations show a good agreement with experimental observations for the whole range of investigated parameters. However, a new definition of the coefficient of restitution presented here shows a dependence on the Stokes number as in previous works but, in addition, on the fluid to particle density ratio. It allows to identify the viscous, inertial and dry regimes as found in experiments of immersed granular avalanches of Courrech du Pont et al. Phys. Rev. Lett. 90, 044301 (2003, e.g. in a multi-particle configuration.
One-Dimensional Problem of a Conducting Viscous Fluid with One Relaxation Time
Directory of Open Access Journals (Sweden)
Angail A. Samaan
2011-01-01
Full Text Available We introduce a magnetohydrodynamic model of boundary-layer equations for conducting viscous fluids. This model is applied to study the effects of free convection currents with thermal relaxation time on the flow of a viscous conducting fluid. The method of the matrix exponential formulation for these equations is introduced. The resulting formulation together with the Laplace transform technique is applied to a variety problems. The effects of a plane distribution of heat sources on the whole and semispace are studied. Numerical results are given and illustrated graphically for the problem.
Bulk viscous cosmological model with interacting dark fluids
International Nuclear Information System (INIS)
Kremer, Gilberto M.; Sobreiro, Octavio A.S.
2012-01-01
We study a cosmological model for a spatially flat Universe whose constituents are a dark energy field and a matter field comprising baryons and dark matter. The constituents are assumed to interact with each other, and a non-equilibrium pressure is introduced to account for irreversible processes. We take the nonequilibrium pressure to be proportional to the Hubble parameter within the framework of a first-order thermodynamic theory. The dark energy and matter fields are coupled by their barotropic indexes, which depend on the ratio between their energy densities. We adjust the free parameters of the model to optimize the fits to the Hubble parameter data. We compare the viscous model with the non-viscous one, and show that the irreversible processes cause the dark-energy and matter-density parameters to become equal and the decelerated-accelerated transition to occur at earlier times. Furthermore, the density and deceleration parameters and the distance modulus have the correct behavior, consistent with a viable scenario of the present status of the Universe . (author)
Initial value problem for Rayleigh--Taylor instability of viscous fluids
International Nuclear Information System (INIS)
Menikoff, R.; Mjolsness, R.C.; Sharp, D.H.; Zemach, C.; Doyle, B.J.
1978-01-01
The initial value problem associated with the development of small amplitude disturbances in Rayleigh--Taylor unstable, viscous, incompressible fluids is studied. Solutions to the linearized equations of motion which satisfy general initial conditions are obtained in terms of Fourier--Laplace transforms of the hydrodynamic variables, without restriction on the density or viscosity of either fluid. When the two fluids have equal kinematic viscosities, these transforms can be inverted explicitly to express the fluid variables as integrals of Green's functions multiplied by initial data. In addition to normal modes, a set of continuum modes, not treated explicitly in the literature, makes an important contribution to the development of the fluid motion
Viscous dipping, application to the capture of fluids in living organisms
Lechantre, Amandine; Michez, Denis; Damman, Pascal
Some insects, birds and mammals use flower nectar as their energy resources. For this purpose, they developed specific skills to ingest viscous fluids. Depending on the sugar content, i.e., the viscosity, different strategies are observed in vivo. Indeed, butterflies use simple suction for low viscosity nectars; hummingbirds have a tongue made from two thin flexible sheets that bend to form a tube when immersed in a fluid; other animals exhibit in contrast complex papillary structures. We focus on this last method generally used for very viscous nectars. More specifically, bees and bats possess a tongue decorated with microstructures that, according to biologists, would be optimized for fluid capture by viscous dipping. In this talk, we will discuss this assumption by comparing physical models of viscous dipping to in vivo measurements. To mimic the tongue morphology, we used various rod shapes obtained by 3D printing. The influence of the type and size of lateral microstructures was then investigated and used to build a global framework describing viscous dipping for structured rods/tongues.
Yang, L. M.; Shu, C.; Wang, Y.; Sun, Y.
2016-08-01
The sphere function-based gas kinetic scheme (GKS), which was presented by Shu and his coworkers [23] for simulation of inviscid compressible flows, is extended to simulate 3D viscous incompressible and compressible flows in this work. Firstly, we use certain discrete points to represent the spherical surface in the phase velocity space. Then, integrals along the spherical surface for conservation forms of moments, which are needed to recover 3D Navier-Stokes equations, are approximated by integral quadrature. The basic requirement is that these conservation forms of moments can be exactly satisfied by weighted summation of distribution functions at discrete points. It was found that the integral quadrature by eight discrete points on the spherical surface, which forms the D3Q8 discrete velocity model, can exactly match the integral. In this way, the conservative variables and numerical fluxes can be computed by weighted summation of distribution functions at eight discrete points. That is, the application of complicated formulations resultant from integrals can be replaced by a simple solution process. Several numerical examples including laminar flat plate boundary layer, 3D lid-driven cavity flow, steady flow through a 90° bending square duct, transonic flow around DPW-W1 wing and supersonic flow around NACA0012 airfoil are chosen to validate the proposed scheme. Numerical results demonstrate that the present scheme can provide reasonable numerical results for 3D viscous flows.
Bounds on fluid permeability for viscous flow through porous media
International Nuclear Information System (INIS)
Berryman, J.G.
1985-01-01
General properties of variational bounds on Darcy's constant for slow viscous flow through porous media are studied. The bounds are also evaluated numerically for the penetrable sphere model. The bound of Doi depending on two-point correlations and the analytical bound of Weissberg and Prager give comparable results in the low density limit but the analytical bound is superior for higher densities. Prager's bound depending on three-point correlation functions is worse than the analytical bound at low densities but better (although comparable to it) at high densities. A procedure for methodically improving Prager's three point bound is presented. By introducing a Gaussian trial function, the three-point bound is improved by an order of magnitude for moderate values of porosity. The new bounds are comparable in magnitude to the Kozeny--Carman empirical relation for porous materials
Alekseev, P. S.; Dmitriev, A. P.; Gornyi, I. V.; Kachorovskii, V. Yu.; Narozhny, B. N.; Titov, M.
2018-02-01
Ultrapure conductors may exhibit hydrodynamic transport where the collective motion of charge carriers resembles the flow of a viscous fluid. In a confined geometry (e.g., in ultra-high-quality nanostructures), the electronic fluid assumes a Poiseuille-type flow. Applying an external magnetic field tends to diminish viscous effects leading to large negative magnetoresistance. In two-component systems near charge neutrality, the hydrodynamic flow of charge carriers is strongly affected by the mutual friction between the two constituents. At low fields, the magnetoresistance is negative, however, at high fields the interplay between electron-hole scattering, recombination, and viscosity results in a dramatic change of the flow profile: the magnetoresistance changes its sign and eventually becomes linear in very high fields. This nonmonotonic magnetoresistance can be used as a fingerprint to detect viscous flow in two-component conducting systems.
Survey of numerical methods for compressible fluids
Energy Technology Data Exchange (ETDEWEB)
Sod, G A
1977-06-01
The finite difference methods of Godunov, Hyman, Lax-Wendroff (two-step), MacCormack, Rusanov, the upwind scheme, the hybrid scheme of Harten and Zwas, the antidiffusion method of Boris and Book, and the artificial compression method of Harten are compared with the random choice known as Glimm's method. The methods are used to integrate the one-dimensional equations of gas dynamics for an inviscid fluid. The results are compared and demonstrate that Glimm's method has several advantages. 16 figs., 4 tables.
MHD flow and heat transfer of a viscous reacting fluid over a ...
African Journals Online (AJOL)
This paper presents a boundary layer flow analysis for a viscous, incompressible, electrically conducting reacting fluid over a stretching sheet in the presence of a magnetic field. It is shown that the Hartmann, Prandtl and the Eckert numbers have effect on the velocity and temperature fields. Journal of the Nigerian ...
Energy Technology Data Exchange (ETDEWEB)
Costa, V.A.F. [Departamento de Engenharia Mecanica, Universidade de Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro (Portugal)
2006-07-15
Care needs to be taken when considering the viscous dissipation in the energy conservation formulation of the natural convection problem in fluid-saturated porous media. The unique energy formulation compatible with the First Law of Thermodynamics informs us that if the viscous dissipation term is taken into account, also the work of pressure forces term needs to be taken into account. In integral terms, the work of pressure forces must equal the energy dissipated by viscous effects, and the net energy generation in the overall domain must be zero. If only the (positive) viscous dissipation term is considered in the energy conservation equation, the domain behaves as a heat multiplier, with an heat output greater than the heat input. Only the energy formulation consistent with the First Law of Thermodynamics leads to the correct flow and temperature fields, as well as of the heat transfer parameters characterizing the involved porous device. Attention is given to the natural convection problem in a square enclosure filled with a fluid-saturated porous medium, using the Darcy Law to describe the fluid flow, but the main ideas and conclusions apply equally for any general natural or mixed convection heat transfer problem. It is also analyzed the validity of the Oberbeck-Boussinesq approximation when applied to natural convection problems in fluid-saturated porous media. (author)
Improving total-building seismic performance using linear fluid viscous dampers
Del Gobbo, GM; Blakeborough, A; Williams, MS
2018-01-01
Previous research has revealed that Eurocode-compliant structures can experience structural and nonstructural damage during earthquakes. Retrofitting buildings with fluid viscous dampers (FVDs) can improve interstorey drifts and floor accelerations, two structural parameters that characterize seismic demand. Previous research focusing on FVD applications for improving seismic performance has focused on structural performance. Structural parameters such as interstorey drifts and floor accelera...
Keslerová, Radka; Trdlička, David
2015-09-01
This work deals with the numerical modelling of steady flows of incompressible viscous and viscoelastic fluids through the three dimensional channel with T-junction. The fundamental system of equations is the system of generalized Navier-Stokes equations for incompressible fluids. This system is based on the system of balance laws of mass and momentum for incompressible fluids. Two different mathematical models for the stress tensor are used for simulation of Newtonian and Oldroyd-B fluids flow. Numerical solution of the described models is based on cetral finite volume method using explicit Runge-Kutta time integration.
Mixed convective flow of immiscible viscous fluids confined between ...
African Journals Online (AJOL)
user
International Journal of Engineering, Science and Technology ... finite difference methods to analyze the problem of natural convection boundary layer flow along a complex vertical surface ... analyzed the flow of two immiscible fluids in a parallel plate channel ... wavy and flat walls are maintained at constant temperatures w.
Numerical Study on Mass Transfer of a Vapor Bubble Rising in Very High Viscous Fluid
Directory of Open Access Journals (Sweden)
T. Kunugi
2014-09-01
Full Text Available This study focused on a bubble rising behavior in a molten glass because it is important to improve the efficiency of removal of bubbles from the molten glass. On the other hand, it is expected that some gas species which exists in a bubble are transferred into the molten glass through the bubble interface, i.e., the mass transfer, subsequently, it may cause a bubble contraction in the molten glass. In this paper, in order to understand the bubble rising behavior with its contraction caused by the mass transfer through the bubble interface in the very high viscous fluid such as the molten glass, a bubble contraction model has been developed. The direct numerical simulations based on the MARS (Multi-interface Advection and Reconstruction Solver coupled with the mass transfer equation and the bubble contraction model regarding the mass transfer from the rising bubble in very high viscous fluid have been performed. Here, the working fluids were water vapor as the gas species and the molten glass as the very high viscous fluid. Also, the jump conditions at the bubble interface for the mass transfer were examined. Furthermore, the influence of the bubble contraction for the bubble rising compared to that in the water as a normal viscous fluid was investigated. From the result of the numerical simulations, it was found that the bubble rising behavior was strongly affected not only by the viscosity of the working fluid but also by the bubble contraction due to the mass transfer through the bubble interface.
Computational modelling of the flow of viscous fluids in carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Khosravian, N [Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Rafii-Tabar, H [Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of)
2007-11-21
Carbon nanotubes will have extensive application in all areas of nano-technology, and in particular in the field of nano-fluidics, wherein they can be used for molecular separation, nano-scale filtering and as nano-pipes for conveying fluids. In the field of nano-medicine, nanotubes can be functionalized with various types of receptors to act as bio-sensors for the detection and elimination of cancer cells, or be used as bypasses and even neural connections. Modelling fluid flow inside nanotubes is a very challenging problem, since there is a complex interplay between the motion of the fluid and the stability of the walls. A critical issue in the design of nano-fluidic devices is the induced vibration of the walls, due to the fluid flow, which can promote structural instability. It has been established that the resonant frequencies depend on the flow velocity. We have studied, for the first time, the flow of viscous fluids through multi-walled carbon nanotubes, using the Euler-Bernoulli classical beam theory to model the nanotube as a continuum structure. Our aim has been to compute the effect of the fluid flow on the structural stability of the nanotubes, without having to consider the details of the fluid-walls interaction. The variations of the resonant frequencies with the flow velocity are obtained for both unembedded nanotubes, and when they are embedded in an elastic medium. It is found that a nanotube conveying a viscous fluid is more stable against vibration-induced buckling than a nanotube conveying a non-viscous fluid, and that the aspect ratio plays the same role in both cases.
Computational modelling of the flow of viscous fluids in carbon nanotubes
International Nuclear Information System (INIS)
Khosravian, N; Rafii-Tabar, H
2007-01-01
Carbon nanotubes will have extensive application in all areas of nano-technology, and in particular in the field of nano-fluidics, wherein they can be used for molecular separation, nano-scale filtering and as nano-pipes for conveying fluids. In the field of nano-medicine, nanotubes can be functionalized with various types of receptors to act as bio-sensors for the detection and elimination of cancer cells, or be used as bypasses and even neural connections. Modelling fluid flow inside nanotubes is a very challenging problem, since there is a complex interplay between the motion of the fluid and the stability of the walls. A critical issue in the design of nano-fluidic devices is the induced vibration of the walls, due to the fluid flow, which can promote structural instability. It has been established that the resonant frequencies depend on the flow velocity. We have studied, for the first time, the flow of viscous fluids through multi-walled carbon nanotubes, using the Euler-Bernoulli classical beam theory to model the nanotube as a continuum structure. Our aim has been to compute the effect of the fluid flow on the structural stability of the nanotubes, without having to consider the details of the fluid-walls interaction. The variations of the resonant frequencies with the flow velocity are obtained for both unembedded nanotubes, and when they are embedded in an elastic medium. It is found that a nanotube conveying a viscous fluid is more stable against vibration-induced buckling than a nanotube conveying a non-viscous fluid, and that the aspect ratio plays the same role in both cases
Three-dimensional viscous fingering of miscible fluids in porous media
Suekane, Tetsuya; Ono, Jei; Hyodo, Akimitsu; Nagatsu, Yuichiro
2017-10-01
Viscous fingering is a flow instability that is induced at the displacement front when a less-viscous fluid (LVF) displaces a more-viscous fluid (MVF). Because of the opaque nature of porous media, most experimental investigations of the structure of viscous fingering and its development in time have been limited to two-dimensional porous media or Hele-Shaw cells. In this study, we investigate the three-dimensional characteristics of viscous fingering in porous media using a microfocused x-ray computer tomography (CT) scanner. Similar to two-dimensional experiments, characteristic events such as tip-splitting, shielding, and coalescence were observed in three-dimensional viscous fingering as well. With an increase in the Péclet number at a fixed viscosity ratio, M , the fingers appearing on the interface tend to be fine; however, the locations of the tips of the fingers remain the same for the same injected volume of the LVF. The finger extensions increase in proportion to ln M , and the number of fingers emerging at the initial interface increases with M . This fact agrees qualitatively with linear stability analyses. Within the fingers, the local concentration of NaI, which is needed for the x-ray CT scanner, linearly decreases, whereas it sharply decreases at the tips of the fingers. A locally high Péclet number as well as unsteady motions in lateral directions may enhance the dispersion at the tips of the fingers. As the viscosity ratio increases, the efficiency of each sweep monotonically decreases and reaches an asymptotic state; in addition, the degree of mixing increases with the viscosity ratio. For high flow rates, the asymptotic value of the sweep efficiency is low for high viscosity ratios, while there is no clear dependence of the asymptotic value on the Péclet number.
Roll and Yaw of Paramecium swimming in a viscous fluid
Jung, Sunghwan; Jana, Saikat; Giarra, Matt; Vlachos, Pavlos
2012-11-01
Many free-swimming microorganisms like ciliates, flagellates, and invertebrates exhibit helical trajectories. In particular, the Paramecium spirally swims along its anterior direction by the beating of cilia. Due to the oblique beating stroke of cilia, the Paramecium rotates along its long axis as it swims forward. Simultaneously, this long axis turns toward the oral groove side. Combined roll and yaw motions of Paramecium result in swimming along a spiral course. Using Particle Image Velocimetry, we measure and quantify the flow field and fluid stress around Paramecium. We will discuss how the non-uniform stress distribution around the body induces this yaw motion.
Linear and nonlinear viscous flow in two-dimensional fluids
International Nuclear Information System (INIS)
Gravina, D.; Ciccotti, G.; Holian, B.L.
1995-01-01
We report on molecular dynamics simulations of shear viscosity η of a dense two-dimensional fluid as a function of the shear rate γ. We find an analytic dependence of η on γ, and do not find any evidence whatsoever of divergence in the Green-Kubo (GK) value that would be caused by the well-known long-time tail for the shear-stress autocorrelation function, as predicted by the mode-coupling theory. In accordance with the linear response theory, the GK value of η agrees remarkably well with nonequilibrium values at small shear rates. (c) 1995 The American Physical Society
Compression in Working Memory and Its Relationship With Fluid Intelligence.
Chekaf, Mustapha; Gauvrit, Nicolas; Guida, Alessandro; Mathy, Fabien
2018-06-01
Working memory has been shown to be strongly related to fluid intelligence; however, our goal is to shed further light on the process of information compression in working memory as a determining factor of fluid intelligence. Our main hypothesis was that compression in working memory is an excellent indicator for studying the relationship between working-memory capacity and fluid intelligence because both depend on the optimization of storage capacity. Compressibility of memoranda was estimated using an algorithmic complexity metric. The results showed that compressibility can be used to predict working-memory performance and that fluid intelligence is well predicted by the ability to compress information. We conclude that the ability to compress information in working memory is the reason why both manipulation and retention of information are linked to intelligence. This result offers a new concept of intelligence based on the idea that compression and intelligence are equivalent problems. Copyright © 2018 Cognitive Science Society, Inc.
Data on mixing of viscous fluids by helical screw impellers in cylindrical vessels
Directory of Open Access Journals (Sweden)
Houari Ameur
2016-09-01
Full Text Available In this article, the data assembled regarding the mixing of Newtonian and shear thinning fluids by screw impellers in a cylindrical tank is disclosed. The data summarizing some information on the efficiency of such impellers are obtained via 3D calculations of velocities and viscous dissipation in the whole vessel volume. The data presented herein may be useful for those who want to outline the mixing characteristics in terms of fluid circulation and power consumption for this kind of impellers, therefore, avoiding a great effort for achieving a high number of experiments. Keyword: Mixing, Helical screw agitator, Power consumption, Fluid circulation, Cylindrical tanks
International Nuclear Information System (INIS)
Tupper, B.O.J.
1983-01-01
The work of a previous article is extended to show that space-times which are the exact solutions of the field equations for a perfect fluid also may be exact solutions of the field equations for a viscous magnetohydrodynamic fluid. Conditions are found for this equivalence to exist and viscous magnetohydrodynamic solutions are found for a number of known perfect fluid space-times. (author)
Flow of viscous fluid along an exponentially stretching curved surface
Directory of Open Access Journals (Sweden)
N.F. Okechi
Full Text Available In this paper, we present the boundary layer analysis of flow induced by rapidly stretching curved surface with exponential velocity. The governing boundary value problem is reduced into self-similar form using a new similarity transformation. The resulting equations are solved numerically using shooting and Runge-Kutta methods. The numerical results depicts that the fluid velocity as well as the skin friction coefficient increases with the surface curvature, similar trend is also observed for the pressure. The dimensionless wall shear stress defined for this problem is greater than that of a linearly stretching curved surface, but becomes comparably less for a surface stretching with a power-law velocity. In addition, the result for the plane surface is a special case of this study when the radius of curvature of the surface is sufficiently large. The numerical investigations presented in terms of the graphs are interpreted with the help of underlying physics of the fluid flow and the consequences arising from the curved geometry. Keywords: Boundary layer flow, Curved surface, Exponential stretching, Curvature
Compressions of electrorheological fluids under different initial gap distances.
Tian, Yu; Wen, Shizhu; Meng, Yonggang
2003-05-01
Compressions of electrorheological (ER) fluids have been carried out under different initial gap distances and different applied voltages. The nominal yield stresses of the compressed ER fluid under different conditions, according to the mechanics of compressing continuous fluids considering the yield stress of the plastic fluid, have been calculated. Curves of nominal yield stress under different applied voltages at an initial gap distance of 4 mm overlapped well and were shown to be proportional to the square of the external electric field and agree well with the traditional description. With the decrease of the initial gap distance, the difference between the nominal yield stress curves increased. The gap distance effect on the compression of ER fluids could not be explained by the traditional description based on the Bingham model and the continuous media theory. An explanation based on the mechanics of particle chain is proposed to describe the gap distance effect on the compression of ER fluids.
Dong, Guanyu
2018-03-01
In order to analyze the microscopic stress field acting on residual oil droplets in micro pores, calculate its deformation, and explore the hydrodynamic mechanism of viscous-elastic fluids displacing oil droplets, the viscous-elastic fluid flow equations in micro pores are established by choosing the Upper Convected Maxwell constitutive equation; the numerical solutions of the flow field are obtained by volume control and Alternate Direction Implicit methods. From the above, the velocity field and microscopic stress field; the forces acting on residual oil droplets; the deformations of residual oil droplets by various viscous-elastic displacing fluids and at various Wiesenberg numbers are calculated and analyzed. The result demonstrated that both the normal stress and horizontal force acting on the residual oil droplets by viscous-elastic fluids are much larger compared to that of inelastic fluid; the distribution of normal stress changes abruptly; under the condition of the same pressure gradient in the system under investigation, the ratio of the horizontal forces acting on the residual oil droplets by different displacing fluids is about 1:8:20, which means that under the above conditions, the driving force on a oil droplet is 20 times higher for a viscous-elastic fluid compared to that of a Newtonian Fluid. The conclusions are supportive of the mechanism that viscous-elastic driving fluids can increase the Displacement Efficiency. This should be of help in designing new chemicals and selecting Enhanced Oil Recovery systems.
Pulsatile flow of viscous and viscoelastic fluids in constricted tubes
Energy Technology Data Exchange (ETDEWEB)
Javadzadegan, A.; Esmaeili, M.; Majidi, S. [University of Tehran, Tehran (Iran, Islamic Republic of); Fakhimghanbarzadeh, B. [Sharif University of Technology, Tehran (Iran, Islamic Republic of)
2009-09-15
The unsteady flow of blood through stenosed artery, driven by an oscillatory pressure gradient, is studied. An appropriate shape of the time-dependent stenoses which are overlapped in the realm of the formation of arterial narrowing is constructed mathematically. A mathematical model is developed by treating blood as a non-Newtonian fluid characterized by the Oldroyd-B and Cross models. A numerical scheme has been used to solve the unsteady nonlinear Navier- stokes equations in cylindrical coordinate system governing flow, assuming axial symmetry under laminar flow condition so that the problem effectively becomes two-dimensional. Finite difference technique was used to investigate the effects of parameters such as pulsatility, non-Newtonian properties and the flow time on the velocity components, the rate of flow, and the wall shear stress through their graphical representations quantitatively at the end of the paper in order to validate the applicability of the present improved mathematical model under consideration
Pulsatile flow of viscous and viscoelastic fluids in constricted tubes
International Nuclear Information System (INIS)
Javadzadegan, A.; Esmaeili, M.; Majidi, S.; Fakhimghanbarzadeh, B.
2009-01-01
The unsteady flow of blood through stenosed artery, driven by an oscillatory pressure gradient, is studied. An appropriate shape of the time-dependent stenoses which are overlapped in the realm of the formation of arterial narrowing is constructed mathematically. A mathematical model is developed by treating blood as a non-Newtonian fluid characterized by the Oldroyd-B and Cross models. A numerical scheme has been used to solve the unsteady nonlinear Navier- stokes equations in cylindrical coordinate system governing flow, assuming axial symmetry under laminar flow condition so that the problem effectively becomes two-dimensional. Finite difference technique was used to investigate the effects of parameters such as pulsatility, non-Newtonian properties and the flow time on the velocity components, the rate of flow, and the wall shear stress through their graphical representations quantitatively at the end of the paper in order to validate the applicability of the present improved mathematical model under consideration
Lagrangian particle method for compressible fluid dynamics
Samulyak, Roman; Wang, Xingyu; Chen, Hsin-Chiang
2018-06-01
A new Lagrangian particle method for solving Euler equations for compressible inviscid fluid or gas flows is proposed. Similar to smoothed particle hydrodynamics (SPH), the method represents fluid cells with Lagrangian particles and is suitable for the simulation of complex free surface/multiphase flows. The main contributions of our method, which is different from SPH in all other aspects, are (a) significant improvement of approximation of differential operators based on a polynomial fit via weighted least squares approximation and the convergence of prescribed order, (b) a second-order particle-based algorithm that reduces to the first-order upwind method at local extremal points, providing accuracy and long term stability, and (c) more accurate resolution of entropy discontinuities and states at free interfaces. While the method is consistent and convergent to a prescribed order, the conservation of momentum and energy is not exact and depends on the convergence order. The method is generalizable to coupled hyperbolic-elliptic systems. Numerical verification tests demonstrating the convergence order are presented as well as examples of complex multiphase flows.
Robustness of one-dimensional viscous fluid motion under multidimensional perturbations
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Sun, Y.
2015-01-01
Roč. 259, č. 12 (2015), s. 7529-7539 ISSN 0022-0396 EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes equations * 1-D compressible fluid flow * relative energy Subject RIV: BA - General Mathematics Impact factor: 1.821, year: 2015 http://www.sciencedirect.com/science/article/pii/S0022039615004325
Directory of Open Access Journals (Sweden)
Sami Ul Haq
2015-01-01
Full Text Available The objective of this study is to explore the influence of wall slip condition on a free convection flow of an incompressible viscous fluid with heat transfer and ramped wall temperature. Exact solution of the problem is obtained by using Laplace transform technique. Graphical results to see the effects of Prandtl number Pr, time t, and slip parameter η on velocity and skin friction for the case of ramped and constant temperature of the plate are provided and discussed.
Londono, J.M.; Wagg, D.; Neild, S.A.
2014-01-01
Viscous fluid dampers have proved to be effective in suppressing unwanted vibrations in a range of engineering structures. When dampers are fitted in a structure, a brace is typically used to attach them to the main structure. The stiffness of this brace can significantly alter the effectiveness of the damper, and in structures with multiple dampers, this can be a complex scenario to model. In this paper, we demonstrate that the effects of the brace compliance on the damper performance can be...
A Thermodynamical Theory with Internal Variables Describing Thermal Effects in Viscous Fluids
Ciancio, Vincenzo; Palumbo, Annunziata
2018-04-01
In this paper the heat conduction in viscous fluids is described by using the theory of classical irreversible thermodynamics with internal variables. In this theory, the deviation from the local equilibrium is characterized by vectorial internal variables and a generalized entropy current density expressed in terms of so-called current multipliers. Cross effects between heat conduction and viscosity are also considered and some phenomenological generalizations of Fourier's and Newton's laws are obtained.
Vapor-Gas Bubble Evolution and Growth in Extremely Viscous Fluids Under Vacuum
Kizito, John; Balasubramaniam, R.; Nahra, Henry; Agui, Juan; Truong, Duc
2008-01-01
Formation of vapor and gas bubbles and voids is normal and expected in flow processes involving extremely viscous fluids in normal gravity. Practical examples of extremely viscous fluids are epoxy-like filler materials before the epoxy fluids cure to their permanent form to create a mechanical bond between two substrates. When these fluids flow with a free liquid interface exposed to vacuum, rapid bubble expansion process may ensue. Bubble expansion might compromise the mechanical bond strength. The potential sources for the origin of the gases might be incomplete out-gassing process prior to filler application; regasification due to seal leakage in the filler applicator; and/or volatiles evolved from cure reaction products formed in the hardening process. We embarked on a study that involved conducting laboratory experiments with imaging diagnostics in order to deduce the seriousness of bubbling caused by entrained air and volatile fluids under space vacuum and low gravity environment. We used clear fluids with the similar physical properties as the epoxy-like filler material to mimic the dynamics of bubbles. Another aspect of the present study was to determine the likelihood of bubbling resulting from dissolved gases nucleating from solution. These experimental studies of the bubble expansion are compared with predictions using a modified Rayleigh- Plesset equation, which models the bubble expansion.
International Nuclear Information System (INIS)
Kubo, S; Ishioka, T; Fukutomi, J; Shigemitsu, T
2012-01-01
Fluid machines for fluid food have been used in wide variety of fields i.e. transportation, the filling, and for the improvement of quality of fluid foods. However, flow conditions of it are quite complicated because fluid foods are different from water. Therefore, design methods based on internal flow conditions have not been conducted. In this research, turbo-pumps having a small number of blades were used to decrease shear loss and keep wide flow passage. The influence of the tip clearance was investigated by the numerical analysis using the model with and without the tip clearance. In this paper, the influence of tip clearance on performances and internal flow conditions of turbo-pump using low viscous fluid were clarified by experimental and numerical analysis results. In addition, design methods based on the internal flow were considered. Further, the influences of viscosity on the performance characteristic and internal flow were investigated.
VBM with viscous fluid registration of grey matter segments in SPM.
Directory of Open Access Journals (Sweden)
João M. S. Pereira
2013-07-01
Full Text Available Improved registration of grey matter segments in SPM has been achieved with the DARTEL algorithm. Previous work from our group suggested, however, that such improvements may not translate to studies of clinical groups. To address the registration issue in atrophic brains, this paper relaxed the condition of diffeomorphism, central to DARTEL, and made use of a viscous fluid registration model with limited regularisation constraints to register the modulated grey matter probability maps to an intra-population template. Quantitative analysis of the registration results after the additional viscous fluid step showed no worsening of co-localisation of fiducials compared to DARTEL or unified segmentation methods, and the resulting voxel based morphometry (VBM analyses were able to better identify atrophic regions and to produce results with fewer apparent false positives. DARTEL showed great sensitivity to atrophy, but the resulting VBM maps presented broad, amorphous regions of significance that are hard to interpret. We propose that the condition of diffeomorphism is not necessary for basic VBM studies in atrophic populations, but also that it has disadvantages that must be taken into consideration before a study. The presented viscous fluid registration method is proposed for VBM studies to enhance sensitivity and localizing power.
A ghost fluid method for sharp interface simulations of compressible multiphase flows
International Nuclear Information System (INIS)
Majidi, Sahand; Afshari, Asghar
2016-01-01
A ghost fluid based computational tool is developed to study a wide range of compressible multiphase flows involving strong shocks and contact discontinuities while accounting for surface tension, viscous stresses and gravitational forces. The solver utilizes constrained reinitialization method to predict the interface configuration at each time step. Surface tension effect is handled via an exact interface Riemann problem solver. Interfacial viscous stresses are approximated by considering continuous velocity and viscous stress across the interface. To assess the performance of the solver several benchmark problems are considered: One-dimensional gas-water shock tube problem, shock-bubble interaction, air cavity collapse in water, underwater explosion, Rayleigh-Taylor Instability, and ellipsoidal drop oscillations. Results obtained from the numerical simulations indicate that the numerical methodology performs reasonably well in predicting flow features and exhibit a very good agreement with prior experimental and numerical observations. To further examine the accuracy of the developed ghost fluid solver, the obtained results are compared to those by a conventional diffuse interface solver. The comparison shows the capability of our ghost fluid method in reproducing the experimentally observed flow characteristics while revealing more details regarding topological changes of the interface.
A ghost fluid method for sharp interface simulations of compressible multiphase flows
Energy Technology Data Exchange (ETDEWEB)
Majidi, Sahand; Afshari, Asghar [University of Tehran, Teheran (Iran, Islamic Republic of)
2016-04-15
A ghost fluid based computational tool is developed to study a wide range of compressible multiphase flows involving strong shocks and contact discontinuities while accounting for surface tension, viscous stresses and gravitational forces. The solver utilizes constrained reinitialization method to predict the interface configuration at each time step. Surface tension effect is handled via an exact interface Riemann problem solver. Interfacial viscous stresses are approximated by considering continuous velocity and viscous stress across the interface. To assess the performance of the solver several benchmark problems are considered: One-dimensional gas-water shock tube problem, shock-bubble interaction, air cavity collapse in water, underwater explosion, Rayleigh-Taylor Instability, and ellipsoidal drop oscillations. Results obtained from the numerical simulations indicate that the numerical methodology performs reasonably well in predicting flow features and exhibit a very good agreement with prior experimental and numerical observations. To further examine the accuracy of the developed ghost fluid solver, the obtained results are compared to those by a conventional diffuse interface solver. The comparison shows the capability of our ghost fluid method in reproducing the experimentally observed flow characteristics while revealing more details regarding topological changes of the interface.
Analysis on the Viscous Pumping in a Magnetic Fluid Seal Under a Rotating Load and the Seal Design
長屋, 幸助; 大沼, 浩身; 佐藤, 淳
1990-01-01
This paper discusses effects of viscous pumping in a magnetic fluid seal under a rotating load. The Reynolds equation was presented for the seal based on magnetic fluid mechanics, and the expressions for obtaining pressures in the seal, eccentricities of the rotating shaft due to the viscous pumping and seal pressures were given. Numerical Calculations were carried out for some sample problems, and the effect of magnetic flux densities on the pressure in the seal and the seal pressures were c...
On the sound attenuation in fluid due to the thermal diffusion and viscous dissipation
Energy Technology Data Exchange (ETDEWEB)
Hu, Hanping, E-mail: hphu@ustc.edu.cn; Wang, Yandong; Wang, Dongdong
2015-09-11
We review the sound attenuation in fluid due to the thermal diffusion and viscous dissipation and derive the formula of the sound attenuation coefficient in fluid by solving a fully thermally–mechanically coupled equation set. Problem occurring in Stokes–Kirchhoff relation, the well-known and widely used classical formula for sound attenuation coefficient, is therefore found and pointed out. The reason for its generation is analyzed and verified. An improved formula to replace Stokes–Kirchhoff relation is suggested and the typical case for the error in calculating sound pressure level (SPL) of attenuated sound wave in fluid between the two formulas is also given. - Highlights: • Problem with Stokes–Kirchhoff relation. • Generation reason of defect in Stokes–Kirchhoff relation. • An improved formula for sound attenuation coefficient in fluid. • Typical cases of the calculation error by Stokes–Kirchhoff relation.
How to dip nectar: optimal time apportionment in natural viscous fluid transport
Wu, Jianing; Shi, Guanya; Zhao, Yiwei; Yan, Shaoze
2018-06-01
The mouthparts of some animals are highly evolved fluid transporters. Most honeybees dip viscous nectar in a cyclic fashion by using protrusible tongues with active hairs that can erect rhythmically. The glossal hairs flatten when the tongue extends into the nectar, and then erect outwards like an umbrella to catch nectar while retracting. This paper examines the potential capability of honeybees in allocating the duration of the tongue protraction and retraction phases for the sake of energy saving. A physical model is established to analyze energy consumption induced by viscous drag, considering tongue kinematics and variation of the surface profile in different phases of tongue movements. The results indicate that the theoretically optimal time apportionment ratio at which the energy consumption is the minimum, is directly related to the square root of the tongue’s diameter ratio between the protraction and retraction phase. Through dipping observations, we validate that the duration for the protraction and retraction phases show high accordance with the theoretical prediction. These findings not only broaden the insights into honeybee’s foraging strategy but inspire the design of high-performance microfluidic pumps with dynamic surfaces to transport viscous fluid.
Directory of Open Access Journals (Sweden)
S. Srinivas
2016-01-01
Full Text Available The present work investigates the effects of thermal-diffusion and diffusion-thermo on MHD flow of viscous fluid between expanding or contracting rotating porous disks with viscous dissipation. The partial differential equations governing the flow problem under consideration have been transformed by a similarity transformation into a system of coupled nonlinear ordinary differential equations. An analytical approach, namely the homotopy analysis method is employed in order to obtain the solutions of the ordinary differential equations. The effects of various emerging parameters on flow variables have been discussed numerically and explained graphically. Comparison of the HAM solutions with the numerical solutions is performed.
Simulations of viscous and compressible gas-gas flows using high-order finite difference schemes
Capuano, M.; Bogey, C.; Spelt, P. D. M.
2018-05-01
A computational method for the simulation of viscous and compressible gas-gas flows is presented. It consists in solving the Navier-Stokes equations associated with a convection equation governing the motion of the interface between two gases using high-order finite-difference schemes. A discontinuity-capturing methodology based on sensors and a spatial filter enables capturing shock waves and deformable interfaces. One-dimensional test cases are performed as validation and to justify choices in the numerical method. The results compare well with analytical solutions. Shock waves and interfaces are accurately propagated, and remain sharp. Subsequently, two-dimensional flows are considered including viscosity and thermal conductivity. In Richtmyer-Meshkov instability, generated on an air-SF6 interface, the influence of the mesh refinement on the instability shape is studied, and the temporal variations of the instability amplitude is compared with experimental data. Finally, for a plane shock wave propagating in air and impacting a cylindrical bubble filled with helium or R22, numerical Schlieren pictures obtained using different grid refinements are found to compare well with experimental shadow-photographs. The mass conservation is verified from the temporal variations of the mass of the bubble. The mean velocities of pressure waves and bubble interface are similar to those obtained experimentally.
Advanced Fluid Reduced Order Models for Compressible Flow.
Energy Technology Data Exchange (ETDEWEB)
Tezaur, Irina Kalashnikova [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Fike, Jeffrey A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carlberg, Kevin Thomas [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Barone, Matthew F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Maddix, Danielle [Stanford Univ., CA (United States); Mussoni, Erin E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Balajewicz, Maciej [Univ. of Illinois, Urbana-Champaign, IL (United States)
2017-09-01
This report summarizes fiscal year (FY) 2017 progress towards developing and implementing within the SPARC in-house finite volume flow solver advanced fluid reduced order models (ROMs) for compressible captive-carriage flow problems of interest to Sandia National Laboratories for the design and qualification of nuclear weapons components. The proposed projection-based model order reduction (MOR) approach, known as the Proper Orthogonal Decomposition (POD)/Least- Squares Petrov-Galerkin (LSPG) method, can substantially reduce the CPU-time requirement for these simulations, thereby enabling advanced analyses such as uncertainty quantification and de- sign optimization. Following a description of the project objectives and FY17 targets, we overview briefly the POD/LSPG approach to model reduction implemented within SPARC . We then study the viability of these ROMs for long-time predictive simulations in the context of a two-dimensional viscous laminar cavity problem, and describe some FY17 enhancements to the proposed model reduction methodology that led to ROMs with improved predictive capabilities. Also described in this report are some FY17 efforts pursued in parallel to the primary objective of determining whether the ROMs in SPARC are viable for the targeted application. These include the implemen- tation and verification of some higher-order finite volume discretization methods within SPARC (towards using the code to study the viability of ROMs on three-dimensional cavity problems) and a novel structure-preserving constrained POD/LSPG formulation that can improve the accuracy of projection-based reduced order models. We conclude the report by summarizing the key takeaways from our FY17 findings, and providing some perspectives for future work.
Farsoiya, Palas Kumar; Dasgupta, Ratul
2017-11-01
When the interface between two radially unbounded, viscous fluids lying vertically in a stable configuration (denser fluid below) at rest, is perturbed, radially propagating capillary-gravity waves are formed which damp out with time. We study this process analytically using a recently developed linearised theory. For small amplitude initial perturbations, the analytical solution to the initial value problem, represented as a linear superposition of Bessel modes at time t = 0 , is found to agree very well with results obtained from direct numerical simulations of the Navier-Stokes equations, for a range of initial conditions. Our study extends the earlier work by John W. Miles who studied this initial value problem analytically, taking into account, a single viscous fluid only. Implications of this study for the mechanistic understanding of droplet impact into a deep pool, will be discussed. Some preliminary, qualitative comparison with experiments will also be presented. We thank SERB Dept. Science & Technology, Govt. of India, Grant No. EMR/2016/000830 for financial support.
On the viscous dissipation modeling of thermal fluid flow in a porous medium
Salama, Amgad
2011-02-24
The problem of viscous dissipation and thermal dispersion in saturated porous medium is numerically investigated for the case of non-Darcy flow regime. The fluid is induced to flow upward by natural convection as a result of a semi-infinite vertical wall that is immersed in the porous medium and is kept at constant higher temperature. The boundary layer approximations were used to simplify the set of the governing, nonlinear partial differential equations, which were then non-dimensionalized and solved using the finite elements method. The results for the details of the governing parameters are presented and investigated. It is found that the irreversible process of transforming the kinetic energy of the moving fluid to heat energy via the viscosity of the moving fluid (i.e.; viscous dissipation) resulted in insignificant generation of heat for the range of parameters considered in this study. On the other hand, thermal dispersion has shown to disperse heat energy normal to the wall more effectively compared with the normal diffusion mechanism. © 2011 Springer-Verlag.
Hydrodynamic instability of compressible fluid in porous medium
International Nuclear Information System (INIS)
Argal, Shraddha; Tiwari, Anita; Sharma, P K; Prajapati, R P
2014-01-01
The hydrodynamic Rayleigh -Taylor instability of two superposed compressible fluids in porous medium has been studied. The dispersion relation is derived for such a medium by using normal mode analysis. The RT instability is discussed for various simplified configuration. The effect of porosity and dynamic viscosity has been analyzed and it is observed that porosity and dynamic viscosity have stabilizing effect on the Rayleigh- Taylor instability of compressible fluids.
A Modeling of Compressible Droplets in a Fluid
Boudin, Laurent; Desvilletter, Laurent; Motte, Renaud
2003-01-01
In this work, we are interested in a complex fluid-kinetic model that aims to take into account the compressibility of the droplets of the spray. The ambient fluid is described by Euler-like equations, in which the transfer of momentum and energy form the droplets is taken into account, while the spray is represented by a probability density function satisfying a Vlasov-like equation. Implicit terms crop up because of the compressibility of the droplets. After having derived...
Unstable oscillation of tubular cantilevered beams conveying a compressible fluid
International Nuclear Information System (INIS)
Johnson, R.O.; Stoneking, J.E.; Carley, T.G.
1986-01-01
This paper is concerned with establishing the conditions of stability of a cantilevered tube conveying a compressible fluid. Solutions to Niordson's eigenvalue problem associated with the equations of motion are computed using Muller's method. The effects on critical velocity of compressibility which are accommodated by specifying the tube aspect ratio and fluid sonic velocity are parametrically studied. Aspect ratio is found to have a more pronounced effect on critical velocity than sonic velocity over the parameter range that was considered. (orig.)
Bianchi I cosmology in the presence of a causally regularized viscous fluid
Energy Technology Data Exchange (ETDEWEB)
Montani, Giovanni [ENEA, FSN-FUSPHY-TSM, R.C. Frascati, Frascati (Italy); Universita degli Studi di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); Venanzi, Marta [Universita degli Studi di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); University of Southampton, Department of Physics and Astronomy, Southampton (United Kingdom)
2017-07-15
We analyze the dynamics of a Bianchi I cosmology in the presence of a viscous fluid, causally regularized according to the Lichnerowicz approach. We show how the effect induced by shear viscosity is still able to produce a matter creation phenomenon, meaning that also in the regularized theory we address, the Universe is emerging from a singularity with a vanishing energy density value. We discuss the structure of the singularity in the isotropic limit, when bulk viscosity is the only retained contribution. We see that, as far as viscosity is not a dominant effect, the dynamics of the isotropic Universe possesses the usual non-viscous power-law behaviour but in correspondence to an effective equation of state, depending on the bulk viscosity coefficient. Finally, we show that, in the limit of a strong non-thermodynamical equilibrium of the Universe mimicked by a dominant contribution of the effective viscous pressure, a power-law inflation behaviour of the Universe appears, the cosmological horizons are removed and a significant amount of entropy is produced. (orig.)
Numerical simulation of energy equation with viscous dissipation for compressible flow over cones
International Nuclear Information System (INIS)
Asif, M.; Chughtai, I.R.
1998-01-01
A finite volume discretization technique has been used to solve the energy equation with viscous dissipation. The effects of viscous heat dissipation for Mach numbers 1.5 and 2.0, at an angle of attack of 0 degree, over sharp and blunt cones have been studied. Algebraic equations have been solved using line-by-line Tda method. Supersonic flow over cones has been analyzed and discussed with and without considering the viscous dissipation effects. It has been found that the effects of viscous dissipation increase with the increase in Mach number. Viscous dissipation affects the temperature distribution of the body. However, the temperature difference in these cases was insignificant. This may be due to the fact that these analysis have been done at 0 km altitude. (author)
Swimming of a sphere in a viscous incompressible fluid with inertia
International Nuclear Information System (INIS)
Felderhof, B U; Jones, R B
2017-01-01
The swimming of a sphere immersed in a viscous incompressible fluid with inertia is studied for surface modulations of small amplitude on the basis of the Navier–Stokes equations. The mean swimming velocity and the mean rate of dissipation are expressed as quadratic forms in term of the surface displacements. With a choice of a basis set of modes the quadratic forms correspond to two Hermitian matrices. Optimization of the mean swimming velocity for given rate of dissipation requires the solution of a generalized eigenvalue problem involving the two matrices. It is found for surface modulations of low multipole order that the optimal swimming efficiency depends in intricate fashion on a dimensionless scale number involving the radius of the sphere, the period of the cycle, and the kinematic viscosity of the fluid. (paper)
International Nuclear Information System (INIS)
Sharma, R.C.; Kumar, Pardeep
1998-01-01
The Rayleigh-Taylor instability of two superposed electrically conducting Walters elastico-viscous fluids (Model B') of uniform densities when the whole system is immersed in a uniform horizontal magnetic field has been studied. The stability analysis has been carried out, for mathematical simplicity, for two highly viscoelastic fluids of equal kinematic viscosities and equal kinematic viscoelasticities. For the stable configuration as in hydrodynamic case, the system is found to be stable or unstable for the wave-number range k (2v') -12 depending on kinematic viscoelasticity v'. For the unstable configuration, the magnetic field has got stabilizing effect and completely stabilizes certain wave-number range which was always unstable in the absence of magnetic field. The behaviour of growth rates with respect kinematic viscosity and kinematic viscoelasticity parameters are examined analytically. (author)
Swimming of a sphere in a viscous incompressible fluid with inertia
Energy Technology Data Exchange (ETDEWEB)
Felderhof, B U [Institut für Theorie der Statistischen Physik RWTH Aachen University, Templergraben 55, D-52056 Aachen (Germany); Jones, R B, E-mail: ufelder@physik.rwth-aachen.de, E-mail: r.b.jones@qmul.ac.uk [Queen Mary University of London, The School of Physics and Astronomy, Mile End Road, London E1 4NS (United Kingdom)
2017-08-15
The swimming of a sphere immersed in a viscous incompressible fluid with inertia is studied for surface modulations of small amplitude on the basis of the Navier–Stokes equations. The mean swimming velocity and the mean rate of dissipation are expressed as quadratic forms in term of the surface displacements. With a choice of a basis set of modes the quadratic forms correspond to two Hermitian matrices. Optimization of the mean swimming velocity for given rate of dissipation requires the solution of a generalized eigenvalue problem involving the two matrices. It is found for surface modulations of low multipole order that the optimal swimming efficiency depends in intricate fashion on a dimensionless scale number involving the radius of the sphere, the period of the cycle, and the kinematic viscosity of the fluid. (paper)
Swimming of a sphere in a viscous incompressible fluid with inertia
Felderhof, B. U.; Jones, R. B.
2017-08-01
The swimming of a sphere immersed in a viscous incompressible fluid with inertia is studied for surface modulations of small amplitude on the basis of the Navier-Stokes equations. The mean swimming velocity and the mean rate of dissipation are expressed as quadratic forms in term of the surface displacements. With a choice of a basis set of modes the quadratic forms correspond to two Hermitian matrices. Optimization of the mean swimming velocity for given rate of dissipation requires the solution of a generalized eigenvalue problem involving the two matrices. It is found for surface modulations of low multipole order that the optimal swimming efficiency depends in intricate fashion on a dimensionless scale number involving the radius of the sphere, the period of the cycle, and the kinematic viscosity of the fluid.
Nonlinear hydromagnetic Rayleigh-Taylor instability for strong viscous fluids in porous media
El-Dib, Y O
2003-01-01
In the present work a weakly nonlinear stability for magnetic fluid is discussed. The research of an interface between two strong viscous homogeneous incompressible fluids through porous medium is investigated theoretically and graphically. The effect of the vertical magnetic field has been demonstrated in this study. The linear form of equation of motion is solved in the light of the nonlinear boundary conditions. The boundary value problem leads to construct nonlinear characteristic equation having complex coefficients in elevation function. The nonlinearity is kept to third-order expansion. The nonlinear characteristic equation leads to derive the well-known nonlinear Schroedinger equation. This equation having complex coefficients of the disturbance amplitude varies in both space and time. Stability criteria have been performed for nonlinear Chanderasekhar dispersion relation including the porous effects. Stability conditions are discussed through the assumption of equal kinematic viscosity. The calculati...
Hydromagnetic stability of rotating stratified compressible fluid flows
Energy Technology Data Exchange (ETDEWEB)
Srinivasan, V; Kandaswamy, P [Dept. of Mathematics, Bharathiar University, Coimbatore, Tamil Nadu, India; Debnath, L [Dept. of Mathematics, University of Central Florida, Orlando, USA
1984-09-01
The hydromagnetic stability of a radially stratified compressible fluid rotating between two coaxial cylinders is investigated. The stability with respect to axisymmetric disturbances is examined. The fluid system is found to be thoroughly stable to axisymmetric disturbances provided the fluid rotates very rapidly. The system is shown to be unstable to non-axisymmetric disturbances, and the slow amplifying hydromagnetic wave modes propagate against the basic rotation. The lower and upper bounds of the azimuthal phase speeds of the amplifying waves are determined. A quadrant theorem on the slow waves characteristic of a rapidly rotating fluid is derived. Special attention is given to the effects of compressibility of the fluid. Some results concerning the stability of an incompressible fluid system are obtained as special cases of the present analysis.
Nonlocal vibration of Y-shaped CNT conveying nano-magnetic viscous fluid under magnetic field
Directory of Open Access Journals (Sweden)
A. Ghorbanpour Arani
2015-06-01
Full Text Available This study deals with the vibration and stability analysis of a Y-shaped single-walled carbon nanotube (SWCNT embedded in visco-Pasternak foundation and conveying nano-magnetic viscous fluid (NMF based on nonlocal elasticity theory and Euler–Bernoulli beam model. The fluid is two-phases due to the existence of magnetic nanoparticles which its volume fraction is much little in comparison with the base fluid where the influence of 2D magnetic field is taken into account. Also, Knudsen number is used to correct the velocity profile of fluid. The Galerkin method is applied to solve the equation of motion which is obtained by employing Hamilton’s principle. The detail parametric study is conducted, focusing on the combined effects of carbon nanotube and Y-shaped junction fitted at the downstream end, fluid velocity, Knudsen number and elastic medium. The results indicate that increasing the angle between centerline of the CNT and the downstream elbows decreases stability of system.
Arciniega-Ceballos, A.; Spina, L.; Scheu, B.; Dingwell, D. B.
2015-12-01
We have investigated the dynamics of Newtonian fluids with viscosities (10-1000 Pa s; corresponding to mafic to intermediate silicate melts) during slow decompression, in a Plexiglas shock tube. As an analogue fluid we used silicon oil saturated with Argon gas for 72 hours. Slow decompression, dropping from 10 MPa to ambient pressure, acts as the excitation mechanism, initiating several processes with their own distinct timescales. The evolution of this multi-timescale phenomenon generates complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit. Correlation analysis of these time series with the associated high-speed imaging enables characterization of distinct phases of the dynamics of these viscous fluids and the extraction of the time and the frequency characteristics of the individual processes. We have identified fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution in space. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the system. Our observations point to the great potential of this experimental approach in the understanding of volcanic processes and volcanic seismicity.
Yang, L M; Shu, C; Wang, Y
2016-03-01
In this work, a discrete gas-kinetic scheme (DGKS) is presented for simulation of two-dimensional viscous incompressible and compressible flows. This scheme is developed from the circular function-based GKS, which was recently proposed by Shu and his co-workers [L. M. Yang, C. Shu, and J. Wu, J. Comput. Phys. 274, 611 (2014)]. For the circular function-based GKS, the integrals for conservation forms of moments in the infinity domain for the Maxwellian function-based GKS are simplified to those integrals along the circle. As a result, the explicit formulations of conservative variables and fluxes are derived. However, these explicit formulations of circular function-based GKS for viscous flows are still complicated, which may not be easy for the application by new users. By using certain discrete points to represent the circle in the phase velocity space, the complicated formulations can be replaced by a simple solution process. The basic requirement is that the conservation forms of moments for the circular function-based GKS can be accurately satisfied by weighted summation of distribution functions at discrete points. In this work, it is shown that integral quadrature by four discrete points on the circle, which forms the D2Q4 discrete velocity model, can exactly match the integrals. Numerical results showed that the present scheme can provide accurate numerical results for incompressible and compressible viscous flows with roughly the same computational cost as that needed by the Roe scheme.
International Nuclear Information System (INIS)
Shirani, E.; Zirak, S.
2001-01-01
Compressible flows for unsteady, inviscid and viscous cases have been studied. Important features of flows such as formation of shock waves across the flow in an unsteady flow as well as interaction of shock waves with boundary layers and their effects on the flow around the blades have been analyzed. Jameson control volume approach was used to spatially integrate the flow equations and the fourth order Runge-Kutta method was used for time integration. The obtained finite difference equations were used to simulate inviscid and viscous flows in V KI cascades and the effects of viscosity, angle of attack, bal de pitches and back pressure on the flow were obtained. It was shown that when the flow was assumed inviscid, the error on the distribution of pressure on the blades were about ten percent. Finally, unsteady flow were simulated and formation of shock waves and their motions were analyzed
Energy Technology Data Exchange (ETDEWEB)
Boualit, A.; Boualit, S. [Unite de recherche appliquee en energies renouvelables, Ghardaia (Algeria); Zeraibi, N. [Universite de Boumerdes, Faculte des hydrocarbures dept. Transport et equipement, Boumerdes (Algeria); Amoura, M. [Universite des Sciences et de la Technologie Houari Boumedienne, Faculte de Physique, Dept. Energetique, Alger (Algeria)
2011-01-15
The thermal development of the hydrodynamically developing laminar flow of a viscoplastic fluid (fluid of Bingham) between two plane plates maintained at a constant temperature has been studied numerically. This analysis has shown the effect caused by inertia and the rheological behaviour of the fluid on the velocity, pressure and temperature fields. The effects of Bingham and Peclet numbers on the Nusselt values with the inclusion of viscous dissipation are also discussed. (authors)
Stability of horizontal viscous fluid layers in a vertical arbitrary time periodic electric field
Bandopadhyay, Aditya; Hardt, Steffen
2017-12-01
The stability of a horizontal interface between two viscous fluids, one of which is conducting and the other is dielectric, acted upon by a vertical time-periodic electric field is considered theoretically. The two fluids are bounded by electrodes separated by a finite distance. For an applied ac electric field, the unstable interface deforms in a time periodic manner, owing to the time dependent Maxwell stress, and is characterized by the oscillation frequency which may or may not be the same as the frequency of the ac electric field. The stability curve, which relates the critical voltage, manifested through the Mason number—the ratio of normal electric stress and viscous stress, and the instability wavenumber at the onset of the instability, is obtained by means of the Floquet theory for a general arbitrary time periodic electric field. The limit of vanishing viscosities is shown to be in excellent agreement with the marginal stability curves predicted by means of a Mathieu equation. The influence of finite viscosity and electrode separation is discussed in relation to the ideal case of inviscid fluids. The methodology to obtain the marginal stability curves developed here is applicable to any arbitrary but time periodic signal, as demonstrated for the case of a signal with two different frequencies, and four different frequencies with a dc offset. The mode coupling in the interfacial normal stress leads to appearance of harmonic and subharmonic modes, characterized by the frequency of the oscillating interface at an integral or half-integral multiple of the applied frequency, respectively. This is in contrast to the application of a voltage with a single frequency which always leads to a harmonic mode oscillation of the interface. Whether a harmonic or subharmonic mode is the most unstable one depends on details of the excitation signal.
Magnetohydrodynamics of unsteady viscous fluid on boundary layer past a sliced sphere
Nursalim, Rahmat; Widodo, Basuki; Imron, Chairul
2017-10-01
Magnetohydrodynamics (MHD) is important study in engineering and industrial fields. By study on MHD, we can reach the fluid flow characteristics that can be used to minimize its negative effect to an object. In decades, MHD has been widely studied in various geometry forms and fluid types. The sliced sphere is a geometry form that has not been investigated. In this paper we study magnetohydrodynamics of unsteady viscous fluid on boundary layer past a sliced sphere. Assumed that the fluid is incompressible, there is no magnetic field, there is no electrical voltage, the sliced sphere is fix and there is no barrier around the object. In this paper we focus on velocity profile at stagnation point (x = 0°). Mathematical model is governed by continuity and momentum equation. It is converted to non-dimensional, stream function, and similarity equation. Solution of the mathematical model is obtained by using Keller-Box numerical method. By giving various of slicing angle and various of magnetic parameter we get the simulation results. The simulation results show that increasing the slicing angle causes the velocity profile be steeper. Also, increasing the value of magnetic parameter causes the velocity profile be steeper. On the large slicing angle there is no significant effect of magnetic parameter to velocity profile, and on the high the value of magnetic parameter there is no significant effect of slicing angle to velocity profile.
Damage in agitated vessels of large visco-elastic particles dispersed in a highly viscous fluid.
Bouvier, Laurent; Moreau, Anne; Line, Alain; Fatah, Nouria; Delaplace, Guillaume
2011-01-01
Many food recipes entail several homogenization steps for solid particles in hot or cold viscous liquids, such as pureed fruit and sugar, jam or sauce with mushroom pieces. Unfortunately, these unavoidable processes induce damage to the solid particles. To date, little is known of the extent and nature of the damage caused. Consequently, few clear guidelines are available for monitoring solid particle integrity when mixing solid/liquid suspensions in an agitated tank. In this study, an attempt is made to quantify the impact of various physical parameters including the influence of the rotational speed of the impeller and the processing time on particle attrition, when a suspension of large visco-elastic particles in a highly viscous fluid is mixed under isothermal condition. Pectin gel particles were immerged in a viscous liquid and homogenized for various times and rotational speeds, while the evolution of the particle's morphological parameters was monitored. Then, a set of dimensionless numbers governing the attrition mechanism is established and some empirical process relationships are proposed to correlate these numbers to the morphological characteristics and mass balance ratios. From the conditions observed, it is clear that 2 dimensionless ratios could be responsible for a change in the damaging mechanisms. These 2 ratios are the Froude and impeller rotation numbers. Finally, in the conditions tested, mass balance ratios appear to be mainly sensitive to the impeller rotational number, while the shape ratios are both impacted by the Froude and impeller rotational numbers. Damage to solid particles suspended in a stirred vessel reduce the final product quality in industrial cooking processes. Examples of this are fruit in jam or sauces with mushroom pieces. The attrition phenomenon was measured and the influences of the impeller rotational speed and processing time were evaluated quantitatively in function of dimensionless numbers. This study contributes key
Rapid depressurization of a compressible fluid
International Nuclear Information System (INIS)
Dang, M.; Dupont, J.F.; Weber, H.
1978-08-01
The rapid depressurization of a plenum is a situation frequently encountered in the dynamical analysis of nuclear gas cycles of the HHT type. Various methods of numerical analyses for a 1-dimensional flow model are examined: finite difference method; control volume method; method of characteristics. Based on the shallow water analogy to compressible flow, the numerical results are compared with those from a water table set up to simulate a standard problem. (Auth.)
International Nuclear Information System (INIS)
Brandão, P V; Alves, L S de B; Barletta, A
2014-01-01
The present paper investigates the transition from convective to absolute instability induced by viscous dissipation. As far as the authors are aware, this is the first time such a study is reported in the literature. Its framework is provided by the Poiseuille-Darcy-Benard convection of a Newtonian fluid. We found the same behaviour observed in the absence of viscous dissipation whenever the Gebhart number is smaller than Ge < 0.95, which is the stabilising effect of the cross flow. When 0.95 < Ge < 4.31, weak cross flows still stabilise the onset of absolute instability but stronger cross flows destabilise it. For a stronger viscous dissipation, i.e. Ge > 4.31, the cross flow always destabilises this onset. The latter two conditions create a scenario where viscous dissipation is capable of inducing a transition to absolute instability in the absence of wall heating, i.e. with a zero Rayleigh number
Energy Technology Data Exchange (ETDEWEB)
York, A.R. II [Sandia National Labs., Albuquerque, NM (United States). Engineering and Process Dept.
1997-07-01
The material point method (MPM) is an evolution of the particle in cell method where Lagrangian particles or material points are used to discretize the volume of a material. The particles carry properties such as mass, velocity, stress, and strain and move through a Eulerian or spatial mesh. The momentum equation is solved on the Eulerian mesh. Modifications to the material point method are developed that allow the simulation of thin membranes, compressible fluids, and their dynamic interactions. A single layer of material points through the thickness is used to represent a membrane. The constitutive equation for the membrane is applied in the local coordinate system of each material point. Validation problems are presented and numerical convergence is demonstrated. Fluid simulation is achieved by implementing a constitutive equation for a compressible, viscous, Newtonian fluid and by solution of the energy equation. The fluid formulation is validated by simulating a traveling shock wave in a compressible fluid. Interactions of the fluid and membrane are handled naturally with the method. The fluid and membrane communicate through the Eulerian grid on which forces are calculated due to the fluid and membrane stress states. Validation problems include simulating a projectile impacting an inflated airbag. In some impact simulations with the MPM, bodies may tend to stick together when separating. Several algorithms are proposed and tested that allow bodies to separate from each other after impact. In addition, several methods are investigated to determine the local coordinate system of a membrane material point without relying upon connectivity data.
International Nuclear Information System (INIS)
Yamaguchi, Hiroshi; Zhang, Xin-Rong; Niu, Xiao-Dong
2010-01-01
The damping characteristics and flow behaviors of ER fluids inside a piston–cylinder viscous damper subjected to external electric fields are studied based on experiment, theoretical analysis and numerical simulation. The viscous damper is a closed system with an inner piston and an outer cylinder, which is designed and constructed in our laboratory. In the experiment, the test ER fluid is enclosed in the gap of a piston–cylinder system. To examine the damping characteristics of the test ER fluid, a piston sine vibration experiment is performed with accompanying theoretical analyses. In addition, in order to investigate the ER flow behaviors inside the damper, a numerical simulation is carried out. The present study discloses the damping characteristics and the fluid mechanism of the ER fluid in the piston–cylinder damper with an applied external electric field
Thin-Film Magnetic-Field-Response Fluid-Level Sensor for Non-Viscous Fluids
Woodard, Stanley E.; Shams, Qamar A.; Fox, Robert L.; Taylor, Bryant D.
2008-01-01
An innovative method has been developed for acquiring fluid-level measurements. This method eliminates the need for the fluid-level sensor to have a physical connection to a power source or to data acquisition equipment. The complete system consists of a lightweight, thin-film magnetic-field-response fluid-level sensor (see Figure 1) and a magnetic field response recorder that was described in Magnetic-Field-Response Measurement-Acquisition System (LAR-16908-1), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 28. The sensor circuit is a capacitor connected to an inductor. The response recorder powers the sensor using a series of oscillating magnetic fields. Once electrically active, the sensor responds with its own harmonic magnetic field. The sensor will oscillate at its resonant electrical frequency, which is dependent upon the capacitance and inductance values of the circuit.
Conveyor belt effect in the flow through a tube of a viscous fluid with spinning particles.
Felderhof, B U
2012-04-28
The extended Navier-Stokes equations describing the steady-state hydrodynamics of a viscous fluid with spinning particles are solved for flow through a circular cylindrical tube. The flow caused by an applied torque density in the azimuthal direction and linear in the radial distance from the axis is compared with the flow caused by a uniform applied force density directed along the axis of the tube. In both cases the flow velocity is of Poiseuille type plus a correction. In the first case the flow velocity is caused by the conveyor belt effect of spinning particles. The corrections to the Poiseuille flow pattern in the two cases differ only by a proportionality factor. The spin velocity profiles in the two cases are also proportional.
Spherical top-hat collapse of a viscous unified dark fluid
Energy Technology Data Exchange (ETDEWEB)
Li, Wei [Bohai University, Department of Physics, Jinzhou (China); Dalian University of Technology, Institute of Theoretical Physics, Dalian (China); Xu, Lixin [Dalian University of Technology, Institute of Theoretical Physics, Dalian (China)
2014-05-15
In this paper, we test the spherical collapse of a viscous unified dark fluid (VUDF) which has constant adiabatic sound speed and show the nonlinear collapse for VUDF, baryons, and darkmatter, which are important in forming the large-scale structure of our Universe. By varying the values of the model parameters α and ζ{sub 0}, we discuss their effects on the nonlinear collapse of the VUDF model, and we compare its result to the ΛCDM model. The results of the analysis show that, within the spherical top-hat collapse framework, larger values of α and smaller values of ζ{sub 0} make the structure formation earlier and faster, and the other collapse curves are almost distinguished with the curve of ΛCDM model if the bulk viscosity coefficient ζ{sub 0} is less than 10{sup -3}. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Tuttle, R.F.; Loyalka, S.K.
1985-06-01
The collisional dynamics of nonspherical aerosols is modeled by the introduction of a shape factor, US . Mechanistic calculation of US requires knowledge of the flow fields around the aerosols. Since actual aerosols can be complicated in shape and since the computation of flow fields can be quite difficult, insights into the nature of US are gained by using the superposition technique and studying aerosols that have tractable flow fields. The motion of an oblate spheroid in a viscous fluid is considered. The Navier-Stokes equations and associated boundary conditions are represented in oblate spheroidal coordinates. A combination of finite differences and spline-interpolation techniques is used to transform these equations to a form suitable for numerical computations. Converged results for the flow fields are obtained for a 0 to 5 range of Reynolds numbers. In the limit of zero Reynolds number, the results are found to be in agreement with the analytical solutions of Oberbeck.
Nonlinear electrorheological instability of two Rivlin-Ericksen elastico-viscous fluids
El-Dib, Y O
2003-01-01
The behaviour of surface waves propagating between two Rivlin-Ericksen elastico-viscous fluids is examined. The investigation is made in the presence of a vertical electric field and a relative horizontal constant velocity. The influence of both surface tension and gravity force is taken into account. Due to the inclusion of streaming flow a mathematical simplification is considered. The viscoelastic contribution is demonstrated in the boundary conditions. From this point of view the approximation equations of motion are solved in the absence of viscoelastic effects. The solutions of the linearized equations of motion under nonlinear boundary conditions lead to derivation of a nonlinear equation governing the interfacial displacement and having damping terms with complex coefficients. This equation is accomplished by utilizing the cubic nonlinearity. The use of the Gardner-Morikawa transformation yields a simplified linear dispersion relation so that the periodic solution for the linear form is utilized. The ...
Anisotropic Bianchi Type-III Bulk Viscous Fluid Universe in Lyra Geometry
Directory of Open Access Journals (Sweden)
Priyanka Kumari
2013-01-01
Full Text Available An anisotropic Bianchi type-III cosmological model is investigated in the presence of a bulk viscous fluid within the framework of Lyra geometry with time-dependent displacement vector. It is shown that the field equations are solvable for any arbitrary function of a scale factor. To get the deterministic model of the universe, we have assumed that (i a simple power-law form of a scale factor and (ii the bulk viscosity coefficient are proportional to the energy density of the matter. The exact solutions of the Einstein’s field equations are obtained which represent an expanding, shearing, and decelerating model of the universe. Some physical and kinematical behaviors of the cosmological model are briefly discussed.
Quantifying the chiral magnetic effect from anomalous-viscous fluid dynamics
Jiang, Yin; Shi, Shuzhe; Yin, Yi; Liao, Jinfeng
2018-01-01
The Chiral Magnetic Effect (CME) is a macroscopic manifestation of fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as an anomalous transport current in the fluid dynamics framework. Experimental observation of the CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to look for the CME in heavy ion collisions. Critically needed for such a search is the theoretical prediction for the CME signal. In this paper we report a first quantitative modeling framework, Anomalous Viscous Fluid Dynamics (AVFD), which computes the evolution of fermion currents on top of realistic bulk evolution in heavy ion collisions and simultaneously accounts for both anomalous and normal viscous transport effects. AVFD allows a quantitative understanding of the generation and evolution of CME-induced charge separation during the hydrodynamic stage, as well as its dependence on theoretical ingredients. With reasonable estimates of key parameters, the AVFD simulations provide the first phenomenologically successful explanation of the measured signal in 200 AGeV AuAu collisions. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, within the framework of the Beam Energy Scan Theory (BEST) Topical Collaboration. The work is also supported in part by the National Science Foundation under Grant No. PHY-1352368 (SS and JL), by the National Science Foundation of China under Grant No. 11735007 (JL) and by the U.S. Department of Energy under grant Contract Number No. DE- SC0012704 (BNL)/DE-SC0011090 (MIT) (YY). JL is grateful to the Institute for Nuclear Theory for hospitality during the INT-16-3 Program. The computation of this research was performed on IU’s Big Red II cluster, supported in part by Lilly Endowment, Inc. (through its support for the Indiana University Pervasive Technology Institute) and in part by the Indiana METACyt
Nonisothermal flow of a non-Newtonian fluid with viscous heating between two parallel plates
International Nuclear Information System (INIS)
Imal, M.; Pinarbasi, A.
2004-01-01
In this study the pressure gradient-flow rate relationship for steady-state nonisothermal pressure-driven flow of a non-Newtonian fluid in a channel is investigated including the effect of viscous heating is taken into account. The viscosity of the fluid depends on both temperature and shear-rate. Exponential dependence of viscosity on temperature is modelled through Arrhenius law. Non-Newtonian behaviour of the fluid is modelled according to the Carreau rheological equation, which reflects the characteristics of most polymers adequately with an exponential temperature dependence of viscosity. Flow governing motion and energy balance equations are coupled and solution of this non-linear boundary value problem is found iteratively using a pseudo spectral method based on Chebyshev polynomials. The effect of activation energy parameter and Brinkman number, as well as the power-law index and material time constant on the flow is studied. It is found that while the pressure gradient-flow rate graph is monotonic for certain ranges of flow controlling parameters, there is a large jump in the graph under certain values of these parameters.(1 table and 5 figures are included.)
Directory of Open Access Journals (Sweden)
I. J. Uwanta
2014-01-01
Full Text Available This study investigates the unsteady natural convection and mass transfer flow of viscous reactive, heat generating/absorbing fluid in a vertical channel formed by two infinite parallel porous plates having temperature dependent thermal conductivity. The motion of the fluid is induced due to natural convection caused by the reactive property as well as the heat generating/absorbing nature of the fluid. The solutions for unsteady state temperature, concentration, and velocity fields are obtained using semi-implicit finite difference schemes. Perturbation techniques are used to get steady state expressions of velocity, concentration, temperature, skin friction, Nusselt number, and Sherwood number. The effects of various flow parameters such as suction/injection (γ, heat source/sinks (S, Soret number (Sr, variable thermal conductivity δ, Frank-Kamenetskii parameter λ, Prandtl number (Pr, and nondimensional time t on the dynamics are analyzed. The skin friction, heat transfer coefficients, and Sherwood number are graphically presented for a range of values of the said parameters.
Low Mach number limits of compressible rotating fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2012-01-01
Roč. 14, č. 1 (2012), s. 61-78 ISSN 1422-6928 R&D Projects: GA ČR GA201/08/0315 Institutional research plan: CEZ:AV0Z10190503 Keywords : low Mach number limit * rotating fluid * compressible fluid Subject RIV: BA - General Mathematics Impact factor: 1.415, year: 2012 http://www.springerlink.com/content/635r1116j40t6428/
Substance advection by a steady 2D stream of the viscous fluid in a lengthy free-surfaced canal
Hanjalic, K.; Nadolin, K.A.; Peeters, T.W.J; Bochev, Mikhail A.; Nicolayev, I.A.
1997-01-01
Spreading of a low-concentrated admixture in the 2D (length - depth) stream of the viscous fluid in an open lengthy canal is considered; the admixture's dissipation and diffusion are taken into account. Apart from being long, the canal is assumed to be low-sloping, with a given shape of the
About the stability of the rotational motion of a top with a cavity filled up with a viscous fluid
International Nuclear Information System (INIS)
Parada, R.F.; Collar, A.F.
1995-09-01
The linear stability problem of the rotational motion of a top around a fixed point containing an inner cavity filled up with a viscous fluid is considered. The effect of the viscosity in the stability problem is studied. (author). 15 refs
Gupta, Sumeet; Poulikakos, Dimos; Kurtcuoglu, Vartan
2008-09-01
We present here the analytical solution of transient, laminar, viscous flow of an incompressible, Newtonian fluid driven by a harmonically oscillating pressure gradient in a straight elliptic annulus. The analytical formulation is based on the exact solution of the governing fluid flow equations known as Navier-Stokes equations. We validate the analytical solution using a finite-volume computational fluid dynamics approach. As the analytical solution includes Mathieu and modified Mathieu functions, we also present a stepwise procedure for their evaluation for large complex arguments typically associated with viscous flows. We further outline the procedure for evaluating the associated Fourier coefficients and their eigenvalues. We finally apply the analytical solution to investigate the cerebrospinal fluid flow in the human spinal cavity, which features a shape similar to an elliptic annulus.
A new formulation of equations of compressible fluids by analogy with Maxwell's equations
International Nuclear Information System (INIS)
Kambe, Tsutomu
2010-01-01
A compressible ideal fluid is governed by Euler's equation of motion and equations of continuity, entropy and vorticity. This system can be reformulated in a form analogous to that of electromagnetism governed by Maxwell's equations with source terms. The vorticity plays the role of magnetic field, while the velocity field plays the part of a vector potential and the enthalpy (of isentropic flows) plays the part of a scalar potential in electromagnetism. The evolution of source terms of fluid Maxwell equations is determined by solving the equations of motion and continuity. The equation of sound waves can be derived from this formulation, where time evolution of the sound source is determined by the equation of motion. The theory of vortex sound of aeroacoustics is included in this formulation. It is remarkable that the forces acting on a point mass moving in a velocity field of an inviscid fluid are analogous in their form to the electric force and Lorentz force in electromagnetism. The significance of the reformulation is interpreted by examples taken from fluid mechanics. This formulation can be extended to viscous fluids without difficulty. The Maxwell-type equations are unchanged by the viscosity effect, although the source terms have additional terms due to viscosities.
Directory of Open Access Journals (Sweden)
Svetlana S. Vlasova
2016-09-01
Full Text Available The exact stationary solution of the boundary-value problem that describes the convective motion of an incompressible viscous fluid in the two-dimensional layer with the square heating of a free surface in Stokes's approach is found. The linearization of the Oberbeck–Boussinesq equations allows one to describe the flow of fluid in extreme points of pressure and temperature. The condition under which the counter-current flows (two counter flows in the fluid can be observed, is introduced. If the stagnant point in the fluid exists, six non-closed whirlwinds can be observed.
Coupled Viscous Fluid Flow and Joint Deformation Analysis for Grout Injection in a Rock Joint
Kim, Hyung-Mok; Lee, Jong-Won; Yazdani, Mahmoud; Tohidi, Elham; Nejati, Hamid Reza; Park, Eui-Seob
2018-02-01
Fluid flow modeling is a major area of interest within the field of rock mechanics. The main objective of this study is to gain insight into the performance of grout injection inside jointed rock masses by numerical modeling of grout flow through a single rock joint. Grout flow has been widely simulated using non-Newtonian Bingham fluid characterized by two main parameters of dynamic viscosity and shear yield strength both of which are time dependent. The increasing value of these properties with injection time will apparently affect the parameters representing the grouting performance including grout penetration length and volumetric injection rate. In addition, through hydromechanical coupling a mutual influence between the injection pressure from the one side and the joint opening/closing behavior and the aperture profile variation on the other side is anticipated. This is capable of producing a considerable impact on grout spread within the rock joints. In this study based on the Bingham fluid model, a series of numerical analysis has been conducted using UDEC to simulate the flow of viscous grout in a single rock joint with smooth parallel surfaces. In these analyses, the time-dependent evolution of the grout fluid properties and the hydromechanical coupling have been considered to investigate their impact on grouting performance. In order to verify the validity of these simulations, the results of analyses including the grout penetration length and the injection flow rate were compared with a well-known analytical solution which is available for the simple case of constant grout properties and non-coupled hydraulic analysis. The comparison demonstrated that the grout penetration length can be overestimated when the time-dependent hardening of grout material is not considered. Moreover, due to the HM coupling, it was shown that the joint opening induced by injection pressure may have a considerable increasing impression on the values of penetration length and
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
Cross, M. F.
2011-01-01
A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.
Viscous-Fluid-Spring Damper Retrofit of a Steel Moment Frame Structure
International Nuclear Information System (INIS)
Hussain, Saif; Van Benschoten, Paul; Al Satari, Mohamed; Lin, Silian
2008-01-01
The subject building is a peculiar pre-Northridge steel moment resisting frame building. Upon investigating the existing lateral resisting system, numerous significant deficiencies were identified; inherent lack of redundancy, poor geometry and inadequate stiffness of the lateral resisting system. All of which resulted in an extremely soft 5-story structure with a primary torsional mode of vibration at T 1 = 5.46 s. Significant structural modifications were deemed necessary to meet the ''life-safety'' performance objective as outlined in rehabilitation standards such as ASCE 41. Both increased stiffness and damping were required to adequately retrofit the building. Furthermore, adjacent building separation as well as deformation compatibility issues needed to be addressed and resolved. A three-dimensional computer model of the building was created using ETABS mathematically simulating the building's dynamic characteristics in its current condition. Multiple seismic retrofit systems were investigated such as Buckling Restrained Braced Frames (BRBF's). However, based on the performance effectiveness and constructability of the retrofit schemes studied, the Viscous-Fluid-Spring Damper (VFSD) system was proposed as the ''optimum'' solution for the building. The VFSD, was chosen because it combines the relatively compact size and minimally invasive constructability with the required properties (an elastomeric spring in parallel with a nonlinear velocity dependent viscous damper). A site-specific response spectrum was developed for the Design Basis Earthquake (DBE, 475 year return period) event, and three pairs of representative earthquake horizontal ground motion time-histories were scaled to match this DBE. The proposed scheme reduced the building maximum inter-story drift ratio from 5.4% to about 1%. Similarly, the maximum roof displacement was reduced by about 70% (23'' to 7'')
The Correlated Dynamics of Micron-Scale Cantilevers in a Viscous Fluid
Robbins, Brian A.
A number of microcantilever systems of fundamental importance are explored using theoretical and numerical methods to quantify and provide physical insights into the dynamics of experimentally accessible systems that include a variety of configurations and viscous fluids. It is first shown that the correlated dynamics of both a laterally and vertically offset cantilever pair can be accurately predicted by numerical simulations. This is verified by comparing the correlated dynamics yielded by numerical simulations with experimental measurement. It is also demonstrated that in order to obtain these accurate predictions, geometric details of the cantilever must be included in the numerical simulation to directly reflect the experimental cantilever. A microrheology technique that utilizes the fluctuation-dissipation theorem is proposed. It is shown that by including the frequency dependence of the fluid damping, improvements in accuracy of the predictions of the rheological properties of the surrounding fluid are observed over current techniques. The amplitude spectrum of a 2-D cantilever in a power-law fluid is studied. The resulting amplitude spectrum yielded a curve similar to an overdamped system. It is observed that the amplitude and noise spectrum yield the same qualitative response for a 2-D cantilever in a shear-thinning, power-law fluid. The correlated dynamics of a tethered vertically offset cantilever pair is investigated. It is shown that for a range of stiffness ratios, which is the ratio of the spring constant of the tethering relative to the cantilever spring constant, the change in the correlated dynamics of a Hookean spring tethered cantilever pair can be seen in the presence of fluid coupling. The dynamics of a spring-mass tethered, vertically offset cantilever pair is qualitatively studied by simplifying the model to an array of springs and masses. The resulting study found that the correlated dynamics of the displacement of mass of the tethered
Improved seismic response of rc frame structures by using fluid viscous dampers
International Nuclear Information System (INIS)
Khan, Q.S.; Qazi, A.U.; Ilyas, M.
2013-01-01
In modern era passive control devices are used to improve the seismic response of structures during large magnitude earthquakes. In this research an analytical study is carried out on commercial FEM program SAP 2000 by modeling five, seven and nine storey RC frame structures. Response to four earthquake ground motions on modeled frame structures is studied and is effectively controlled by varying the characteristic properties of Fluid viscous dampers (FVD). Response in terms of frequency, displacement, velocity, acceleration, storey drift, base shear and energy dissipation is studied. Quantitatively in the modeled frames damage in terms of percentage change in global stiffness and natural frequency is determined. Qualitatively damage in terms of performance levels as per ATC-40 and FEMA-440 is considered. With an increase in Additional Stiffness Ratio of FVD corresponding increase in natural frequency and reduction in dynamic response is observed. FVDs significantly improve structural performance level of frames from Completely Damage to Immediate Occupancy/Operational Level during large magnitude earthquakes. (author)
Motion of two spheres translating and rotating through a viscous fluid with slip surfaces
International Nuclear Information System (INIS)
Saad, E I
2012-01-01
The axisymmetrical motion of two spherical particles translating along and rotating about a common line that joins their centers in viscous fluid with slip flow boundary conditions on their surfaces has been studied numerically. The particles may differ in radius and in translational and angular velocities. Under the Stokesian approximation, a general solution is constructed from the superposition of the basic functions in the two spherical coordinate systems based on the centers of the particles. The boundary conditions at their surfaces are satisfied by the collocation technique. Numerical results for the normalized drag force and couple acting on each sphere are obtained for various values of the slip coefficients, size ratio, separation parameter, and velocity ratio of the particles. The normalized force and couple on each particle reach the single particle limit as the distance between the centers grows large enough and each particle may then be translated and rotated independently of each other. The accuracy of the numerical technique has been tested against the known analytical solution for two spheres with no-slip surfaces. (paper)
Seismic energy dissipation study of linear fluid viscous dampers in steel structure design
Directory of Open Access Journals (Sweden)
A. Ras
2016-09-01
Full Text Available Energy dissipation systems in civil engineering structures are sought when it comes to removing unwanted energy such as earthquake and wind. Among these systems, there is combination of structural steel frames with passive energy dissipation provided by Fluid Viscous Dampers (FVD. This device is increasingly used to provide better seismic protection for existing as well as new buildings and bridges. A 3D numerical investigation is done considering the seismic response of a twelve-storey steel building moment frame with diagonal FVD that have linear force versus velocity behaviour. Nonlinear time history, which is being calculated by Fast nonlinear analysis (FNA, of Boumerdes earthquake (Algeria, May 2003 is considered for the analysis and carried out using the SAP2000 software and comparisons between unbraced, braced and damped structure are shown in a tabulated and graphical format. The results of the various systems are studied to compare the structural response with and without this device of the energy dissipation thus obtained. The conclusions showed the formidable potential of the FVD to improve the dissipative capacities of the structure without increasing its rigidity. It is contributing significantly to reduce the quantity of steel necessary for its general stability.
Seismic Retrofitting of an Existing Steel Railway Bridge by Fluid Viscous Dampers
Gangopadhyay, Avijit; Ghosh, Aparna Dey
2016-09-01
There are over a lakh of bridges in the Indian Railways, many of which have become seismically deficient, either through aging or due to inadequate seismic design considerations. The extensive damage of bridges all over the world in recent earthquakes has propelled significant advancement in earthquake protection and retrofitting of bridges. Amongst various passive control systems that are reliable as well as cost-effective, Fluid Viscous Dampers (FVDs) are proving to be successful in bridge vibration control. Orificed FVDs, commercially available as Taylor Devices, have already been successfully installed in several bridges worldwide. However, there has been no such application or study related to Indian railway bridges. In this paper, an existing thirty years' old railway bridge in Jharkhand, India, has been analyzed in SAP2000v14 considering reduced stiffness and found deficient when subjected to spectrum-compatible accelerograms. Subsequent retrofitting of the bridge superstructure with FVDs has been carried out and the results indicate substantial reductions in the responses of the bridge deck.
Probabilistic analysis of wind-induced vibration mitigation of structures by fluid viscous dampers
Chen, Jianbing; Zeng, Xiaoshu; Peng, Yongbo
2017-11-01
The high-rise buildings usually suffer from excessively large wind-induced vibrations, and thus vibration control systems might be necessary. Fluid viscous dampers (FVDs) with nonlinear power law against velocity are widely employed. With the transition of design method from traditional frequency domain approaches to more refined direct time domain approaches, the difficulty of time integration of these systems occurs sometimes. In the present paper, firstly the underlying reason of the difficulty is revealed by identifying that the equations of motion of high-rise buildings installed with FVDs are sometimes stiff differential equations. Thus, an approach effective for stiff differential systems, i.e., the backward difference formula (BDF), is then introduced, and verified to be effective for the equation of motion of wind-induced vibration controlled systems. Comparative studies are performed among some methods, including the Newmark method, KR-alpha method, energy-based linearization method and the statistical linearization method. Based on the above results, a 20-story steel frame structure is taken as a practical example. Particularly, the randomness of structural parameters and of wind loading input is emphasized. The extreme values of the responses are examined, showing the effectiveness of the proposed approach, and also necessitating the refined probabilistic analysis in the design of wind-induced vibration mitigation systems.
Research on Fluid Viscous Damper Parameters of Cable-Stayed Bridge in Northwest China
Directory of Open Access Journals (Sweden)
Xiongjun He
2017-01-01
Full Text Available To optimize the aseismic performance of nonlinear fluid viscous dampers (FVD of cable-stayed bridge in the highly seismic zone, Xigu Yellow River Bridge in northwest China is taken as an example. Nonlinear time-history analysis method is used to research on the relation among the internal forces, displacements, and damping parameters of the 650 tonnage FVD. The method of getting the minimum of binary functions is used to obtain the optimal parameters of FVD. Also, the 1 : 1 full-scale FVD model is made and used in the constitutive relation test. Then the test result of the damping parameters can be got by normal equation method. The optimized method to obtain the damping parameters is further verified. The results indicate that seismic response in key positions of the cable-stayed bridge can be reduced by installing longitudinal nonlinear FVD between the towers and girders if choosing reasonable damping parameters C and ξ. The optimal damping parameters can be calculated accurately by the proposed method of optimizing damping parameters of nonlinear FVD, and the constitutive relation test verifies the correctness of the optimization analysis method. Conclusions concerned can be applied to the design of nonlinear FVD for cable-stayed bridges.
Directory of Open Access Journals (Sweden)
Norfifah Bachok
Full Text Available The steady boundary layer flow of a viscous and incompressible fluid over a moving vertical flat plate in an external moving fluid with viscous dissipation is theoretically investigated. Using appropriate similarity variables, the governing system of partial differential equations is transformed into a system of ordinary (similarity differential equations, which is then solved numerically using a Maple software. Results for the skin friction or shear stress coefficient, local Nusselt number, velocity and temperature profiles are presented for different values of the governing parameters. It is found that the set of the similarity equations has unique solutions, dual solutions or no solutions, depending on the values of the mixed convection parameter, the velocity ratio parameter and the Eckert number. The Eckert number significantly affects the surface shear stress as well as the heat transfer rate at the surface.
Directory of Open Access Journals (Sweden)
Tasawar Hayat
Full Text Available The present article has been arranged to study the Hall current and Joule heating effects on peristaltic flow of viscous fluid in a channel with flexible walls. Both fluid and channel are in a state of solid body rotation. Convective conditions for heat transfer in the formulation are adopted. Viscous dissipation in energy expression is taken into account. Resulting differential systems after invoking small Reynolds number and long wavelength considerations are numerically solved. Runge-Kutta scheme of order four is implemented for the results of axial and secondary velocities, temperature and heat transfer coefficient. Comparison with previous limiting studies is shown. Outcome of new parameters of interest is analyzed. Keywords: Rotating frame, Hall current, Joule heating, Convective conditions, Wall properties
Kruep, Stephanie Jean
2007-01-01
This thesis presents the details of a study regarding both the use of linear viscous fluid dampers in controlling the interstory drift in steel moment frames, and the use of incremental dynamic analysis as a method of visualizing the behavior of these moment frames when subjected to seismic load effects. Models of three story and nine story steel moment frames were designed to meet typical strength requirements for office buildings in Seattle, Washington. These models were intentionally des...
Hadjeb Abdessalam; Bouzit Mohamed; Kamla Youcef; Ameur Houari
2017-01-01
Mixing processes are becoming today a huge concern for industrialists in various domains like the pharmaceutical production, oil refining, food industry and manufacture of cosmetic products especially when the processes are related to the mixing of highly viscous products. So the choice of a stirring system for this category of products or fluids must be rigorously examined before use because of the flows which are laminar in the most cases, something that is not good to obtain homogeneous pa...
International Nuclear Information System (INIS)
Kraenkel, R.A.; Pereira, J.G.; Manna, M.A.
1991-01-01
The (2+1)-dimensional Burgers equation is obtained as the equation of motion governing the surface perturbations of a shallow viscous fluid heated from below, provided the Rayleigh number of the system satisfy the condition R ≠ 30. A solution to this equation is explicity exhibited and it is argued that it describes the nonlinear evolution of a nearly one-dimensional kink. (author)
Mahanthesh, B.; Gireesha, B. J.
2018-03-01
The impact of Marangoni convection on dusty Casson fluid boundary layer flow with Joule heating and viscous dissipation aspects is addressed. The surface tension is assumed to vary linearly with temperature. Physical aspects of magnetohydrodynamics and thermal radiation are also accounted. The governing problem is modelled under boundary layer approximations for fluid phase and dust particle phase and then Runge-Kutta-Fehlberg method based numeric solutions are established. The momentum and heat transport mechanisms are focused on the result of distinct governing parameters. The Nusselt number is also calculated. It is established that the rate of heat transfer can be enhanced by suspending dust particles in the base fluid. The temperature field of fluid phase and temperature of dust phase are quite reverse for thermal dust parameter. The radiative heat, viscous dissipation and Joule heating aspects are constructive for thermal fields of fluid and dust phases. The velocity of dusty Casson fluid dominates the velocity of dusty fluid while this trend is opposite in the case of temperature. Moreover qualitative behaviour of fluid phase and dust phase temperature/velocity are similar.
Directory of Open Access Journals (Sweden)
Yu Bai
2017-12-01
Full Text Available This paper investigates the incompressible fractional MHD Maxwell fluid due to a power function accelerating plate with the first order slip, and the numerical analysis on the flow and heat transfer of fractional Maxwell fluid has been done. Moreover the deformation motion of fluid micelle is simply analyzed. Nonlinear velocity equation are formulated with multi-term time fractional derivatives in the boundary layer governing equations, and convective heat transfer boundary condition and viscous dissipation are both taken into consideration. A newly finite difference scheme with L1-algorithm of governing equations are constructed, whose convergence is confirmed by the comparison with analytical solution. Numerical solutions for velocity and temperature show the effects of pertinent parameters on flow and heat transfer of fractional Maxwell fluid. It reveals that the fractional derivative weakens the effects of motion and heat conduction. The larger the Nusselt number is, the greater the heat transfer capacity of fluid becomes, and the temperature gradient at the wall becomes more significantly. The lower Reynolds number enhances the viscosity of the fluid because it is the ratio of the viscous force and the inertia force, which resists the flow and heat transfer.
Bai, Yu; Jiang, Yuehua; Liu, Fawang; Zhang, Yan
2017-12-01
This paper investigates the incompressible fractional MHD Maxwell fluid due to a power function accelerating plate with the first order slip, and the numerical analysis on the flow and heat transfer of fractional Maxwell fluid has been done. Moreover the deformation motion of fluid micelle is simply analyzed. Nonlinear velocity equation are formulated with multi-term time fractional derivatives in the boundary layer governing equations, and convective heat transfer boundary condition and viscous dissipation are both taken into consideration. A newly finite difference scheme with L1-algorithm of governing equations are constructed, whose convergence is confirmed by the comparison with analytical solution. Numerical solutions for velocity and temperature show the effects of pertinent parameters on flow and heat transfer of fractional Maxwell fluid. It reveals that the fractional derivative weakens the effects of motion and heat conduction. The larger the Nusselt number is, the greater the heat transfer capacity of fluid becomes, and the temperature gradient at the wall becomes more significantly. The lower Reynolds number enhances the viscosity of the fluid because it is the ratio of the viscous force and the inertia force, which resists the flow and heat transfer.
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G Rana
2016-09-01
Full Text Available The thermosolutal instability of compressible Walters' (model B' elastico-viscous rotating fluid permeated with suspended particles (fine dust in the presence of vertical magnetic field in porous medium is considered. By applying normal mode analysis method, the dispersion relation has been derived and solved analytically. It is observed that the rotation, magnetic field, suspended particles and viscoelasticity introduce oscillatory modes. For stationary convection the Walters' (model B' fluid behaves like an ordinary Newtonian fluid and it is observed that the rotation and stable solute gradient has stabilizing effects and suspended particles are found to have destabilizing effect on the system, whereas the medium permeability has stabilizing or destabilizing effect on the system under certain conditions. The magnetic field has destabilizing effect in the absence of rotation, whereas in the presence of rotation, magnetic field has stabilizing or destabilizing effect under certain conditions.
Two-fluid and parallel compressibility effects in tokamak plasmas
International Nuclear Information System (INIS)
Sugiyama, L.E.; Park, W.
1998-01-01
The MHD, or single fluid, model for a plasma has long been known to provide a surprisingly good description of much of the observed nonlinear dynamics of confined plasmas, considering its simple nature compared to the complexity of the real system. On the other hand, some of the supposed agreement arises from the lack of the detailed measurements that are needed to distinguish MHD from more sophisticated models that incorporate slower time scale processes. At present, a number of factors combine to make models beyond MHD of practical interest. Computational considerations still favor fluid rather than particle models for description of the full plasma, and suggest an approach that starts from a set of fluid-like equations that extends MHD to slower time scales and more accurate parallel dynamics. This paper summarizes a set of two-fluid equations for toroidal (tokamak) geometry that has been developed and tested as the MH3D-T code [1] and some results from the model. The electrons and ions are described as separate fluids. The code and its original MHD version, MH3D [2], are the first numerical, initial value models in toroidal geometry that include the full 3D (fluid) compressibility and electromagnetic effects. Previous nonlinear MHD codes for toroidal geometry have, in practice, neglected the plasma density evolution, on the grounds that MHD plasmas are only weakly compressible and that the background density variation is weaker than the temperature variation. Analytically, the common use of toroidal plasma models based on aspect ratio expansion, such as reduced MHD, has reinforced this impression, since this ordering reduces plasma compressibility effects. For two-fluid plasmas, the density evolution cannot be neglected in principle, since it provides the basic driving energy for the diamagnetic drifts of the electrons and ions perpendicular to the magnetic field. It also strongly influences the parallel dynamics, in combination with the parallel thermal
On the motion of viscous, compressible and heat-conducting liquids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Novotný, A.; Sun, Y.
2016-01-01
Roč. 57, č. 8 (2016), s. 083101 ISSN 0022-2488 EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes equations * weak solution * relative energy Subject RIV: BA - General Mathematics Impact factor: 1.077, year: 2016 http://scitation.aip.org/content/aip/journal/jmp/57/8/10.1063/1.4959772
Czech Academy of Sciences Publication Activity Database
Petrov, A. G.; Kharlamov, Alexander A.
2013-01-01
Roč. 48, č. 5 (2013), s. 577-587 ISSN 0015-4628 R&D Projects: GA ČR(CZ) GA103/09/2066 Grant - others:Development of the Scientific Potential of the Higher Schoo(RU) 2.1.2/3604; Russian Foundation for Basic Research (RU) 11- 01-005355 Institutional support: RVO:67985874 Keywords : lubrication layer theory * viscous and inviscid fluids * thin layer * vicinity of a contact * three-dimensional problems Subject RIV: BK - Fluid Dynamics Impact factor: 0.320, year: 2013
Pressure and compressibility factor of bidisperse magnetic fluids
Minina, Elena S.; Blaak, Ronald; Kantorovich, Sofia S.
2018-04-01
In this work, we investigate the pressure and compressibility factors of bidisperse magnetic fluids with relatively weak dipolar interactions and different granulometric compositions. In order to study these properties, we employ the method of diagram expansion, taking into account two possible scenarios: (1) dipolar particles repel each other as hard spheres; (2) the polymer shell on the surface of the particles is modelled through a soft-sphere approximation. The theoretical predictions of the pressure and compressibility factors of bidisperse ferrofluids at different granulometric compositions are supported by data obtained by means of molecular dynamics computer simulations, which we also carried out for these systems. Both theory and simulations reveal that the pressure and compressibility factors decrease with growing dipolar correlations in the system, namely with an increasing fraction of large particles. We also demonstrate that even if dipolar interactions are too weak for any self-assembly to take place, the interparticle correlations lead to a qualitative change in the behaviour of the compressibility factors when compared to that of non-dipolar spheres, making the dependence monotonic.
Magneto thermal convection in a compressible couple-stress fluid
Energy Technology Data Exchange (ETDEWEB)
Singh, Mahinder [Lovely School of Science, Dept. of Mathematics, Lovely Professional Univ., Phagwara (India); Kumar, Pardeep [Dept. of Mathematics, ICDEOL, H.P. Univ., Shimla (India)
2010-03-15
The problem of thermal instability of compressible, electrically conducting couple-stress fluids in the presence of a uniform magnetic field is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, couple-stress, and magnetic field postpone the onset of convection. Graphs have been plotted by giving numerical values of the parameters to depict the stability characteristics. The principle of exchange of stabilities is found to be satisfied. The magnetic field introduces oscillatory modes in the system that were non-existent in its absence. The case of overstability is also studied wherein a sufficient condition for the non-existence of overstability is obtained. (orig.)
Two-Phase Flow in Wire Coating with Heat Transfer Analysis of an Elastic-Viscous Fluid
Directory of Open Access Journals (Sweden)
Zeeshan Khan
2016-01-01
Full Text Available This work considers two-phase flow of an elastic-viscous fluid for double-layer coating of wire. The wet-on-wet (WOW coating process is used in this study. The analytical solution of the theoretical model is obtained by Optimal Homotopy Asymptotic Method (OHAM. The expression for the velocity field and temperature distribution for both layers is obtained. The convergence of the obtained series solution is established. The analytical results are verified by Adomian Decomposition Method (ADM. The obtained velocity field is compared with the existing exact solution of the same flow problem of second-grade fluid and with analytical solution of a third-grade fluid. Also, emerging parameters on the solutions are discussed and appropriate conclusions are drawn.
International Nuclear Information System (INIS)
Dumbser, Michael; Peshkov, Ilya; Romenski, Evgeniy; Zanotti, Olindo
2016-01-01
Highlights: • High order schemes for a unified first order hyperbolic formulation of continuum mechanics. • The mathematical model applies simultaneously to fluid mechanics and solid mechanics. • Viscous fluids are treated in the frame of hyper-elasticity as generalized visco-plastic solids. • Formal asymptotic analysis reveals the connection with the Navier–Stokes equations. • The distortion tensor A in the model appears to be well-suited for flow visualization. - Abstract: This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell–Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic–parabolic Navier
Energy Technology Data Exchange (ETDEWEB)
Dumbser, Michael, E-mail: michael.dumbser@unitn.it [Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento (Italy); Peshkov, Ilya, E-mail: peshkov@math.nsc.ru [Open and Experimental Center for Heavy Oil, Université de Pau et des Pays de l' Adour, Avenue de l' Université, 64012 Pau (France); Romenski, Evgeniy, E-mail: evrom@math.nsc.ru [Sobolev Institute of Mathematics, 4 Acad. Koptyug Avenue, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 2 Pirogova Str., 630090 Novosibirsk (Russian Federation); Zanotti, Olindo, E-mail: olindo.zanotti@unitn.it [Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento (Italy)
2016-06-01
Highlights: • High order schemes for a unified first order hyperbolic formulation of continuum mechanics. • The mathematical model applies simultaneously to fluid mechanics and solid mechanics. • Viscous fluids are treated in the frame of hyper-elasticity as generalized visco-plastic solids. • Formal asymptotic analysis reveals the connection with the Navier–Stokes equations. • The distortion tensor A in the model appears to be well-suited for flow visualization. - Abstract: This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell–Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic–parabolic Navier
Karlsen, Jonas; Bruus, Henrik
2015-11-01
We present a theoretical analysis (arxiv.org/abs/1507.01043) of the acoustic radiation force on a single small particle, either a thermoviscous fluid droplet or a thermoelastic solid particle, suspended in a viscous and heat-conducting fluid. Our analysis places no restrictions on the viscous and thermal boundary layer thicknesses relative to the particle radius, but it assumes the particle to be small in comparison to the acoustic wavelength. This is the limit relevant to scattering of ultrasound waves from sub-micrometer particles. For particle sizes smaller than the boundary layer widths, our theory leads to profound consequences for the acoustic radiation force. For example, for liquid droplets and solid particles suspended in gasses we predict forces orders of magnitude larger than expected from ideal-fluid theory. Moreover, for certain relevant choices of materials, we find a sign change in the acoustic radiation force on different-sized but otherwise identical particles. These findings lead to the concept of a particle-size-dependent acoustophoretic contrast factor, highly relevant to applications in acoustic levitation or separation of micro-particles in gases, as well as to handling of μm- and nm-sized particles such as bacteria and vira in lab-on-a-chip systems.
Directory of Open Access Journals (Sweden)
Ahmed M. Elsayed
2013-01-01
Full Text Available Film cooling is vital to gas turbine blades to protect them from high temperatures and hence high thermal stresses. In the current work, optimization of film cooling parameters on a flat plate is investigated numerically. The effect of film cooling parameters such as inlet velocity direction, lateral and forward diffusion angles, blowing ratio, and streamwise angle on the cooling effectiveness is studied, and optimum cooling parameters are selected. The numerical simulation of the coolant flow through flat plate hole system is carried out using the “CFDRC package” coupled with the optimization algorithm “simplex” to maximize overall film cooling effectiveness. Unstructured finite volume technique is used to solve the steady, three-dimensional and compressible Navier-Stokes equations. The results are compared with the published numerical and experimental data of a cylindrically round-simple hole, and the results show good agreement. In addition, the results indicate that the average overall film cooling effectiveness is enhanced by decreasing the streamwise angle for high blowing ratio and by increasing the lateral and forward diffusion angles. Optimum geometry of the cooling hole on a flat plate is determined. In addition, numerical simulations of film cooling on actual turbine blade are performed using the flat plate optimal hole geometry.
DEFF Research Database (Denmark)
Cutanda Henriquez, Vicente; Juhl, Peter Møller
2013-01-01
are solved using extended boundary conditions that account for: i) negligible temperature fluctuations at the boundary, and ii) normal and tangential matching of the boundary’s particle velocity. The proposed model does not require constructing a special mesh for the viscous and thermal boundary layers...
International Nuclear Information System (INIS)
Mazlan, S A; Ekreem, N B; Olabi, A G
2008-01-01
This paper presents an experimental investigation of two different magnetorheological (MR) fluids, namely, water-based and hydrocarbon-based MR fluids in compression mode under various applied currents. Finite element method magnetics was used to predict the magnetic field distribution inside the MR fluids generated by a coil. A test rig was constructed where the MR fluid was sandwiched between two flat surfaces. During the compression, the upper surface was moved towards the lower surface in a vertical direction. Stress-strain relationships were obtained for arrangements of equipment where each type of fluid was involved, using compression test equipment. The apparent compressive stress was found to be increased with the increase in magnetic field strength. In addition, the apparent compressive stress of the water-based MR fluid showed a response to the compressive strain of greater magnitude. However, during the compression process, the hydrocarbon-based MR fluid appeared to show a unique behaviour where an abrupt pressure drop was discovered in a region where the apparent compressive stress would be expected to increase steadily. The conclusion is drawn that the apparent compressive stress of MR fluids is influenced strongly by the nature of the carrier fluid and by the magnitude of the applied current
The velocity of the arterial pulse wave: a viscous-fluid shock wave in an elastic tube.
Painter, Page R
2008-07-29
The arterial pulse is a viscous-fluid shock wave that is initiated by blood ejected from the heart. This wave travels away from the heart at a speed termed the pulse wave velocity (PWV). The PWV increases during the course of a number of diseases, and this increase is often attributed to arterial stiffness. As the pulse wave approaches a point in an artery, the pressure rises as does the pressure gradient. This pressure gradient increases the rate of blood flow ahead of the wave. The rate of blood flow ahead of the wave decreases with distance because the pressure gradient also decreases with distance ahead of the wave. Consequently, the amount of blood per unit length in a segment of an artery increases ahead of the wave, and this increase stretches the wall of the artery. As a result, the tension in the wall increases, and this results in an increase in the pressure of blood in the artery. An expression for the PWV is derived from an equation describing the flow-pressure coupling (FPC) for a pulse wave in an incompressible, viscous fluid in an elastic tube. The initial increase in force of the fluid in the tube is described by an increasing exponential function of time. The relationship between force gradient and fluid flow is approximated by an expression known to hold for a rigid tube. For large arteries, the PWV derived by this method agrees with the Korteweg-Moens equation for the PWV in a non-viscous fluid. For small arteries, the PWV is approximately proportional to the Korteweg-Moens velocity divided by the radius of the artery. The PWV in small arteries is also predicted to increase when the specific rate of increase in pressure as a function of time decreases. This rate decreases with increasing myocardial ischemia, suggesting an explanation for the observation that an increase in the PWV is a predictor of future myocardial infarction. The derivation of the equation for the PWV that has been used for more than fifty years is analyzed and shown to yield
Directory of Open Access Journals (Sweden)
Hadjeb Abdessalam
2017-09-01
Full Text Available Mixing processes are becoming today a huge concern for industrialists in various domains like the pharmaceutical production, oil refining, food industry and manufacture of cosmetic products especially when the processes are related to the mixing of highly viscous products. So the choice of a stirring system for this category of products or fluids must be rigorously examined before use because of the flows which are laminar in the most cases, something that is not good to obtain homogeneous particles or suspensions after the mixing operation. This CFD study allows developing a new geometrical model of mechanical agitator with high performance for mixing of highly viscous fluids. It consists of a combination of two bladed and helical screw agitators. The investigations of the flow structure generated in the vessel are made by using the computer code ANSYS CFX (version 13.0, which allows us to realize and test the effectiveness of the new stirrer on the resulting mixture and power consumption.
Felderhof, B. U.
2017-09-01
Translational and rotational swimming at small Reynolds numbers of a planar assembly of identical spheres immersed in an incompressible viscous fluid is studied on the basis of a set of equations of motion for the individual spheres. The motion of the spheres is caused by actuating forces and forces derived from a direct interaction potential, as well as hydrodynamic forces exerted by the fluid as frictional and added mass hydrodynamic interactions. The translational and rotational swimming velocities of the assembly are deduced from momentum and angular momentum balance equations. The mean power required during a period is calculated from an instantaneous power equation. Expressions are derived for the mean swimming velocities and the mean power, valid to second order in the amplitude of displacements from the relative equilibrium positions. Hence these quantities can be evaluated for prescribed periodic displacements. Explicit calculations are performed for three spheres interacting such that they form an equilateral triangle in the rest frame of the configuration.
Cascades and Dissipative Anomalies in Compressible Fluid Turbulence
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Gregory L. Eyink
2018-02-01
Full Text Available We investigate dissipative anomalies in a turbulent fluid governed by the compressible Navier-Stokes equation. We follow an exact approach pioneered by Onsager, which we explain as a nonperturbative application of the principle of renormalization-group invariance. In the limit of high Reynolds and Péclet numbers, the flow realizations are found to be described as distributional or “coarse-grained” solutions of the compressible Euler equations, with standard conservation laws broken by turbulent anomalies. The anomalous dissipation of kinetic energy is shown to be due not only to local cascade but also to a distinct mechanism called pressure-work defect. Irreversible heating in stationary, planar shocks with an ideal-gas equation of state exemplifies the second mechanism. Entropy conservation anomalies are also found to occur via two mechanisms: an anomalous input of negative entropy (negentropy by pressure work and a cascade of negentropy to small scales. We derive “4/5th-law”-type expressions for the anomalies, which allow us to characterize the singularities (structure-function scaling exponents required to sustain the cascades. We compare our approach with alternative theories and empirical evidence. It is argued that the “Big Power Law in the Sky” observed in electron density scintillations in the interstellar medium is a manifestation of a forward negentropy cascade or an inverse cascade of usual thermodynamic entropy.
Cascades and Dissipative Anomalies in Compressible Fluid Turbulence
Eyink, Gregory L.; Drivas, Theodore D.
2018-02-01
We investigate dissipative anomalies in a turbulent fluid governed by the compressible Navier-Stokes equation. We follow an exact approach pioneered by Onsager, which we explain as a nonperturbative application of the principle of renormalization-group invariance. In the limit of high Reynolds and Péclet numbers, the flow realizations are found to be described as distributional or "coarse-grained" solutions of the compressible Euler equations, with standard conservation laws broken by turbulent anomalies. The anomalous dissipation of kinetic energy is shown to be due not only to local cascade but also to a distinct mechanism called pressure-work defect. Irreversible heating in stationary, planar shocks with an ideal-gas equation of state exemplifies the second mechanism. Entropy conservation anomalies are also found to occur via two mechanisms: an anomalous input of negative entropy (negentropy) by pressure work and a cascade of negentropy to small scales. We derive "4 /5 th-law"-type expressions for the anomalies, which allow us to characterize the singularities (structure-function scaling exponents) required to sustain the cascades. We compare our approach with alternative theories and empirical evidence. It is argued that the "Big Power Law in the Sky" observed in electron density scintillations in the interstellar medium is a manifestation of a forward negentropy cascade or an inverse cascade of usual thermodynamic entropy.
DEFF Research Database (Denmark)
Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri
Accurate multi-phase flow solvers at low Reynolds number are of particular interest for the simulation of interface instabilities in the co-processing of multilayered material. We present a two-phase flow solver for incompressible viscous fluids which uses the streamfunction as the primary variable...... of the flow. Contrary to fractional step methods, the streamfunction formulation eliminates the pressure unknowns, and automatically fulfills the incompressibility constraint by construction. As a result, the method circumvents the loss of temporal accuracy at low Reynolds numbers. The interface is tracked...
DEFF Research Database (Denmark)
Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri
2014-01-01
Accurate multi-phase flow solvers at low Reynolds number are of particular interest for the simulation of interface instabilities in the co-processing of multilayered material. We present a two-phase flow solver for incompressible viscous fluids which uses the streamfunction as the primary variable...... of the flow. Contrary to fractional step methods, the streamfunction formulation eliminates the pressure unknowns, and automatically fulfills the incompressibility constraint by construction. As a result, the method circumvents the loss of temporal accuracy at low Reynolds numbers. The interface is tracked...
Peco, C.; Rosolen, A.; Arroyo, M.
2013-01-01
We present a Lagrangian phase-field method to study the low Reynolds number dynamics of vesicles embedded in a viscous fluid. In contrast to previous approaches, where the field variables are the phase-field and the fluid velocity, here we exploit the fact that the phasefield tracks a material interface to reformulate the problem in terms of the Lagrangian motion of a background medium, containing both the biomembrane and the fluid. We discretize the equations in space with maximum-entr...
International Nuclear Information System (INIS)
McHugh, P.R.; Ramshaw, J.D.
1991-11-01
MAGMA is a FORTRAN computer code designed to viscous flow in in situ vitrification melt pools. It models three-dimensional, incompressible, viscous flow and heat transfer. The momentum equation is coupled to the temperature field through the buoyancy force terms arising from the Boussinesq approximation. All fluid properties, except density, are assumed variable. Density is assumed constant except in the buoyancy force terms in the momentum equation. A simple melting model based on the enthalpy method allows the study of the melt front progression and latent heat effects. An indirect addressing scheme used in the numerical solution of the momentum equation voids unnecessary calculations in cells devoid of liquid. Two-dimensional calculations can be performed using either rectangular or cylindrical coordinates, while three-dimensional calculations use rectangular coordinates. All derivatives are approximated by finite differences. The incompressible Navier-Stokes equations are solved using a new fully implicit iterative technique, while the energy equation is differenced explicitly in time. Spatial derivatives are written in conservative form using a uniform, rectangular, staggered mesh based on the marker and cell placement of variables. Convective terms are differenced using a weighted average of centered and donor cell differencing to ensure numerical stability. Complete descriptions of MAGMA governing equations, numerics, code structure, and code verification are provided. 14 refs
Energy Technology Data Exchange (ETDEWEB)
McHugh, P.R.; Ramshaw, J.D.
1991-11-01
MAGMA is a FORTRAN computer code designed to viscous flow in in situ vitrification melt pools. It models three-dimensional, incompressible, viscous flow and heat transfer. The momentum equation is coupled to the temperature field through the buoyancy force terms arising from the Boussinesq approximation. All fluid properties, except density, are assumed variable. Density is assumed constant except in the buoyancy force terms in the momentum equation. A simple melting model based on the enthalpy method allows the study of the melt front progression and latent heat effects. An indirect addressing scheme used in the numerical solution of the momentum equation voids unnecessary calculations in cells devoid of liquid. Two-dimensional calculations can be performed using either rectangular or cylindrical coordinates, while three-dimensional calculations use rectangular coordinates. All derivatives are approximated by finite differences. The incompressible Navier-Stokes equations are solved using a new fully implicit iterative technique, while the energy equation is differenced explicitly in time. Spatial derivatives are written in conservative form using a uniform, rectangular, staggered mesh based on the marker and cell placement of variables. Convective terms are differenced using a weighted average of centered and donor cell differencing to ensure numerical stability. Complete descriptions of MAGMA governing equations, numerics, code structure, and code verification are provided. 14 refs.
Translational friction coefficient of a permeable cylinder in a sheet of viscous fluid
Wiegel, F.W.
1979-01-01
The author calculates the translational friction coefficient and the translational diffusion coefficient of a permeable cylinder moving in a sheet of fluid which is embedded on both sides in a fluid of much lower viscosity. The result, which is an asymptotic expression valid in the limit of small
Samanta, Gauranga Charan; Myrzakulov, Ratbay; Shah, Parth
2017-04-01
The authors considered the bulk viscous fluid in f(R, T) gravity within the framework of Kaluza-Klein space time. The bulk viscous coefficient (ξ) expressed as ξ = {ξ_0} + {ξ_1}{{\\dot a} \\over a} + {ξ_2}{{\\ddot a} \\over {\\dot a}}, where ξ0, ξ1, and ξ2 are positive constants. We take p=(γ-1)ρ, where 0≤γ≤2 as an equation of state for perfect fluid. The exact solutions to the corresponding field equations are given by assuming a particular model of the form of f(R, T)=R+2f(T), where f(T)=λT, λ is constant. We studied the cosmological model in two stages, in first stage: we studied the model with no viscosity, and in second stage: we studied the model involve with viscosity. The cosmological model involve with viscosity is studied by five possible scenarios for bulk viscous fluid coefficient (ξ). The total bulk viscous coefficient seems to be negative, when the bulk viscous coefficient is proportional to {ξ _2}{{\\ddot a} \\over {\\dot a}}, hence, the second law of thermodynamics is not valid; however, it is valid with the generalised second law of thermodynamics. The total bulk viscous coefficient seems to be positive, when the bulk viscous coefficient is proportional to ξ = {ξ _1}{{\\dot a} \\over a} + {ξ _2}{{\\ddot a} \\over {\\dot a}} and ξ = {ξ _0} + {ξ _1}{{\\dot a} \\over a} + {ξ _2}{{\\ddot a} \\over {\\dot a}}, so the second law of thermodynamics and the generalised second law of thermodynamics is satisfied throughout the evolution. We calculate statefinder parameters of the model and observed that it is different from the ∧CDM model. Finally, some physical and geometrical properties of the models are discussed.
Felderhof, B. U.
2015-11-01
A mechanical model of swimming and flying in an incompressible viscous fluid in the absence of gravity is studied on the basis of assumed equations of motion. The system is modeled as an assembly of rigid spheres subject to elastic direct interactions and to periodic actuating forces which sum to zero. Hydrodynamic interactions are taken into account in the virtual mass matrix and in the friction matrix of the assembly. An equation of motion is derived for the velocity of the geometric center of the assembly. The mean power is calculated as the mean rate of dissipation. The full range of viscosity is covered, so that the theory can be applied to the flying of birds, as well as to the swimming of fish or bacteria. As an example a system of three equal spheres moving along a common axis is studied.
Stability with respect to domain of the low Mach number limit of compressible viscous fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Karper, T.; Kreml, Ondřej; Stebel, Jan
2013-01-01
Roč. 23, č. 13 (2013), s. 2465-2493 ISSN 0218-2025 R&D Projects: GA ČR GA201/09/0917 Institutional research plan: CEZ:AV0Z10190503 Keywords : incompressible limit * domain dependence * Navier-Stokes system Subject RIV: BA - General Mathematics Impact factor: 2.351, year: 2013 http://www.worldscientific.com/doi/abs/10.1142/S0218202513500371
Suitable weak solutions: from compressible viscous to incompressible inviscid fluid flows
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Novotný, A.; Petzeltová, Hana
2013-01-01
Roč. 356, č. 2 (2013), s. 683-702 ISSN 0025-5831 R&D Projects: GA ČR GA201/09/0917 Institutional research plan: CEZ:AV0Z10190503 Keywords : relative entropy * incompressible limit * inviscid limit Subject RIV: BA - General Mathematics Impact factor: 1.201, year: 2013 http://link.springer.com/article/10.1007%2Fs00208-012-0862-5
Gupta, Anoop Kumar; Gupta, Sanjay; Chhabra, Rajendra Prasad
2017-08-01
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.
Time-asymptotic interaction of flocking particles and an incompressible viscous fluid
International Nuclear Information System (INIS)
Bae, Hyeong-Ohk; Choi, Young-Pil; Ha, Seung-Yeal; Kang, Moon-Jin
2012-01-01
We present a new coupled kinetic-fluid model for the interactions between Cucker–Smale (C–S) flocking particles and incompressible fluid on the periodic spatial domain T d . Our coupled system consists of the kinetic C–S equation and the incompressible Navier–Stokes equations, and these two systems are coupled through the drag force. For the proposed model, we provide a global existence of weak solutions and a priori time-asymptotic exponential flocking estimates for any smooth flow, when the kinematic viscosity of the fluid is sufficiently large. The velocity of individual C–S particles and fluid velocity tend to the averaged time-dependent particle velocities exponentially fast
Dynamic viscous behavior of magneto-rheological fluid in coupled mode operation
International Nuclear Information System (INIS)
Kaluvan, Suresh; Park, JinHyuk; Choi, Seung-Hyun; Kim, Pyunghwa; Choi, Seung-Bok
2015-01-01
A new method of measuring the coupled mode viscosity behavior of magneto-rheological (MR) fluid using the resonance concept is proposed. The coupled mode viscosity measurement device is designed as a resonant system using a cantilever beam probing with the rotating shaft mechanism. The ‘C’ shaped iron core of an electromagnetic coil, mounted in a resonating cantilever beam is used as a probing tip. The MR fluid between the probing tip and the rotating shaft mechanism experiences both squeeze and shear force. The vibration induced by the resonating cantilever beam creates only squeeze force on the MR fluid when the shaft is stationary. When the cantilever beam is vibrating at resonance and the shaft is rotating, the MR fluid experiences coupled (shear and squeeze) force. The cantilever beam is vibrated at its resonant frequency using the piezoelectric actuation technique and the resonance is maintained using simple closed loop resonator electronics. The input current to the probing coil is varied to produce a variable magnetic field which causes the viscosity change of the MR fluid. The viscosity change of the MR fluid produces a coupled force, which induces an additional stiffness on the resonating cantilever beam and alters its initial resonant frequency. The shift in resonant frequency due to the change in viscosity of the MR fluid is measured with the help of a resonator electronics circuit and its viscosity is related to the field dependent coupled mode yield stress of the MR fluid. The proposed measurement device is analytically derived and experimentally evaluated. (technical note)
Shams, Mosayeb; Raeini, Ali Q; Blunt, Martin J; Bijeljic, Branko
2018-07-15
This paper examines the role of momentum transfer across fluid-fluid interfaces in two-phase flow. A volume-of-fluid finite-volume numerical method is used to solve the Navier-Stokes equations for two-phase flow at the micro-scale. The model is applied to investigate viscous coupling effects as a function of the viscosity ratio, the wetting phase saturation and the wettability, for different fluid configurations in simple pore geometries. It is shown that viscous coupling effects can be significant for certain pore geometries such as oil layers sandwiched between water in the corner of mixed wettability capillaries. A simple parametric model is then presented to estimate general mobility terms as a function of geometric properties and viscosity ratio. Finally, the model is validated by comparison with the mobilities computed using direct numerical simulation. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.
Thermo-fluid dynamic analysis of wet compression process
International Nuclear Information System (INIS)
Mohan, Abhay; Kim, Heuy Dong; Chidambaram, Palani Kumar; Suryan, Abhilash
2016-01-01
Wet compression systems increase the useful power output of a gas turbine by reducing the compressor work through the reduction of air temperature inside the compressor. The actual wet compression process differs from the conventional single phase compression process due to the presence of latent heat component being absorbed by the evaporating water droplets. Thus the wet compression process cannot be assumed isentropic. In the current investigation, the gas-liquid two phase has been modeled as air containing dispersed water droplets inside a simple cylinder-piston system. The piston moves in the axial direction inside the cylinder to achieve wet compression. Effects on the thermodynamic properties such as temperature, pressure and relative humidity are investigated in detail for different parameters such as compression speeds and overspray. An analytical model is derived and the requisite thermodynamic curves are generated. The deviations of generated thermodynamic curves from the dry isentropic curves (PV γ = constant) are analyzed
Thermo-fluid dynamic analysis of wet compression process
Energy Technology Data Exchange (ETDEWEB)
Mohan, Abhay; Kim, Heuy Dong [School of Mechanical Engineering, Andong National University, Andong (Korea, Republic of); Chidambaram, Palani Kumar [FMTRC, Daejoo Machinery Co. Ltd., Daegu (Korea, Republic of); Suryan, Abhilash [Dept. of Mechanical Engineering, College of Engineering Trivandrum, Kerala (India)
2016-12-15
Wet compression systems increase the useful power output of a gas turbine by reducing the compressor work through the reduction of air temperature inside the compressor. The actual wet compression process differs from the conventional single phase compression process due to the presence of latent heat component being absorbed by the evaporating water droplets. Thus the wet compression process cannot be assumed isentropic. In the current investigation, the gas-liquid two phase has been modeled as air containing dispersed water droplets inside a simple cylinder-piston system. The piston moves in the axial direction inside the cylinder to achieve wet compression. Effects on the thermodynamic properties such as temperature, pressure and relative humidity are investigated in detail for different parameters such as compression speeds and overspray. An analytical model is derived and the requisite thermodynamic curves are generated. The deviations of generated thermodynamic curves from the dry isentropic curves (PV{sup γ} = constant) are analyzed.
Feeding of swimming Paramecium with fore-aft asymmetry in viscous fluid
Zhang, Peng; Jana, Saikat; Giarra, Matthew; Vlachos, Pavlos; Jung, Sunghwan
2013-11-01
Swimming behaviours and feeding efficiencies of Paramecium Multimicronucleatum with fore-aft asymmetric body shapes are studied experimentally and numerically. Among various possible swimming ways, ciliates typically exhibit only one preferred swimming directions in favorable conditions. Ciliates, like Paramecia, with fore-aft asymmetric shapes preferably swim towards the slender anterior while feeding fluid to the oral groove located at the center of the body. Since both feeding and swimming efficiencies are influenced by fluid motions around the body, it is important to reveal the fluid mechanics around a moving object. Experimentally, μ-PIV methods are employed to characterize the source-dipole streamline patterns and fluid motions around Paramecium. Numerical simulations by boundary element methods are also used to evaluate surface stresses and velocities, which give insights into the efficiencies of swimming and feeding depending on body asymmetry. It is concluded that a slender anterior and fat posterior increases the combined efficiency of swimming and feeding, which matches well with actual shapes of Paramecium. Discrepancies between experiments and simulations are also discussed.
The magnetic interaction of Janus magnetic particles suspended in a viscous fluid
Seong, Y.; Kang, T.G.; Hulsen, M.A.; den Toonder, J.M.J.; Anderson, P.D.
2016-01-01
We studied the magnetic interaction between circular Janus magnetic particles suspended in a Newtonian fluid under the influence of an externally applied uniform magnetic field. The particles are equally compartmentalized into paramagnetic and non-magnetic sides. A direct numerical scheme is
CSIR Research Space (South Africa)
Bogaers, Alfred EJ
2015-01-01
Full Text Available In this paper we introduce the idea of combining artificial compressibility (AC) with quasi-Newton (QN) methods to solve strongly coupled, fully/quasi-enclosed fluid-structure interaction (FSI) problems. Partitioned, incompressible, FSI based...
Blockage effects on viscous fluid flow and heat transfer past a magnetic obstacle in a duct
International Nuclear Information System (INIS)
Zhang Xi-Dong; Huang Hu-Lin
2013-01-01
The effect of lateral walls on fluid flow and heat transfer is investigated when a fluid passes a magnetic obstacle. The blockage ratio β that represents the ratio between the width of external magnet M y and the spanwise width L y is employed to depict the effect. The finite volume method (FVM) based on the PISO algorithm is applied for the blockage ratios of 0.2, 0.3, and 0.4. The results show that the value of Strouhal number St increases as the blockage ratio β increases, and for small β, the variation of St is very small when the interaction parameter and Reynolds number are increasing. Moreover, the cross-stream mixing induced by the magnetic obstacle can enhance the wall-heat transfer and the maximum value of the overall heat transfer increment is about 50.5%
Shrestha, Bishwash; Ahsan, Syed N.; Aureli, Matteo
2018-01-01
In this paper, we present a comprehensive experimental study on harmonic oscillations of a submerged rigid plate in a quiescent, incompressible, Newtonian, viscous fluid. The fluid-structure interaction problem is analyzed from both qualitative and quantitative perspectives via a detailed particle image velocimetry (PIV) experimental campaign conducted over a broad range of oscillation frequency and amplitude parameters. Our primary goal is to identify the effect of the oscillation characteristics on the mechanisms of fluid-structure interaction and on the dynamics of vortex shedding and convection and to elucidate the behavior of hydrodynamic forces on the oscillating structure. Towards this goal, we study the flow in terms of qualitative aspects of its pathlines, vortex shedding, and symmetry breaking phenomena and identify distinct hydrodynamic regimes in the vicinity of the oscillating structure. Based on these experimental observations, we produce a novel phase diagram detailing the occurrence of distinct hydrodynamic regimes as a function of relevant governing nondimensional parameters. We further study the hydrodynamic forces associated with each regime using both PIV and direct force measurement via a load cell. Our quantitative results on experimental estimation of hydrodynamic forces show good agreement against predictions from the literature, where numerical and semi-analytical models are available. The findings and observations in this work shed light on the relationship between flow physics, vortex shedding, and convection mechanisms and the hydrodynamic forces acting on a rigid oscillating plate and, as such, have relevance to various engineering applications, including energy harvesting devices, biomimetic robotic system, and micro-mechanical sensors and actuators.
Theory of errors in Coriolis flowmeter readings due to compressibility of the fluid being metered
Kutin, Jože; Hemp, John
2015-01-01
The compressibility of fluids in a Coriolis mass flowmeter can cause errors in the meter's measurements of density and mass flow rate. These errors may be better described as errors due to the finite speed of sound in the fluid being metered, or due to the finite wavelength of sound at the operating frequency of the meter. In this paper, they are investigated theoretically and calculated to a first approximation (small degree of compressibility). The investigation is limited to straight beam-...
Gong, Yuezheng; Zhao, Jia; Wang, Qi
2017-10-01
A quasi-incompressible hydrodynamic phase field model for flows of fluid mixtures of two incompressible viscous fluids of distinct densities and viscosities is derived by using the generalized Onsager principle, which warrants the variational structure, the mass conservation and energy dissipation law. We recast the model in an equivalent form and discretize the equivalent system in space firstly to arrive at a time-dependent ordinary differential and algebraic equation (DAE) system, which preserves the mass conservation and energy dissipation law at the semi-discrete level. Then, we develop a temporal discretization scheme for the DAE system, where the mass conservation and the energy dissipation law are once again preserved at the fully discretized level. We prove that the fully discretized algorithm is unconditionally energy stable. Several numerical examples, including drop dynamics of viscous fluid drops immersed in another viscous fluid matrix and mixing dynamics of binary polymeric solutions, are presented to show the convergence property as well as the accuracy and efficiency of the new scheme.
Modeling of fiber orientation in viscous fluid flow with application to self-compacting concrete
Kolařík, Filip; Patzák, Bořek
2013-10-01
In recent years, unconventional concrete reinforcement is of growing popularity. Especially fiber reinforcement has very wide usage in high performance concretes like "Self Compacting Concrete" (SCC). The design of advanced tailor-made structures made of SCC can take advantage of anisotropic orientation of fibers. Tools for fiber orientation predictions can contribute to design of tailor made structure and allow to develop casting procedures that enable to achieve the desired fiber distribution and orientation. This paper deals with development and implementation of suitable tool for prediction of fiber orientation in a fluid based on the knowledge of the velocity field. Statistical approach to the topic is employed. Fiber orientation is described by a probability distribution of the fiber angle.
Gangadhar, K.; Kumar, Sathies; Lakshmi Narayana, K.; Subhakar, M. J.; Rushi Kumar, B.
2017-11-01
In this paper, MHD flow and heat transfer of electrically conducting micro polar fluid over a permeable stretching surface with slip flow in the existence of viscous dissipation and temperature dependent slip flow are investigated. With the help of similarity transformations, the fundamental equations have been altered into a system of ordinary differential equations. It is difficult to solve these equations methodically. That’s why we used bvp4c MATLAB solver. We found the Numerical values for the wall couple stress, skin-friction coefficient, and the local Nusselt number in addition to the micro rotation, velocity, and temperature reports for diverse values of the principal parameters like thermal slip parameter, material parameter, magnetic parameter, heat generation/absorption parameter, velocity slip parameter and Eckert number It is observed that the values of suction/injection parameters rise corresponding to the lessening in the values of velocity, angular velocity, and temperature. Moreover, the change in the values of the Eckert number is opposite to the change in the values of the local Nusselt number.
Dholey, S.
2018-04-01
In this paper, we have investigated numerically the laminar unsteady separated stagnation-point flow and heat transfer of a viscous fluid over a moving flat surface in the presence of a time dependent free stream velocity which causes the unsteadiness of this flow problem. The plate is assumed to move in the same or opposite direction of the free stream velocity. The flow is therefore governed by the velocity ratio parameter λ (ratio of the plate velocity to the free stream velocity) and the unsteadiness parameter β. When the plate surface moves in the same direction of the free stream velocity (i.e., when λ > 0), the solution of this flow problem continues for any given value of β. On the other hand, when they move in opposite directions (i.e., when λ heat transfer analysis is that for a given value of λ(= 0), first the heat transfer rate increases with the increase of the Prandtl number Pr and after attaining a maximum value, it decreases and finally tends to be zero for large values of Pr depending upon the values of β > 0. On the contrary, for a given value of β(≤ 0), the rate of heat transfer increases consistently with the increase of Pr.
Casado-Pascual, Jesús
2018-03-01
The emergence of directed motion is investigated in a system consisting of a sphere immersed in a viscous fluid and subjected to time-periodic forces of zero average. The directed motion arises from the combined action of a nonlinear drag force and the applied driving forces, in the absence of any periodic substrate potential. Necessary conditions for the existence of such directed motion are obtained and an analytical expression for the average terminal velocity is derived within the adiabatic approximation. Special attention is paid to the case of two mutually perpendicular forces with sinusoidal time dependence, one with twice the period of the other. It is shown that, although neither of these two forces induces directed motion when acting separately, when added together, the resultant force generates directed motion along the direction of the force with the shortest period. The dependence of the average terminal velocity on the system parameters is analyzed numerically and compared with that obtained using the adiabatic approximation. Among other results, it is found that, for appropriate parameter values, the direction of the average terminal velocity can be reversed by varying the forcing strength. Furthermore, certain aspects of the observed phenomenology are explained by means of symmetry arguments.
Magri, Fabien; Cacace, Mauro; Fischer, Thomas; Kolditz, Olaf; Wang, Wenqing; Watanabe, Norihiro
2017-04-01
In contrast to simple homogeneous 1D and 2D systems, no appropriate analytical solutions exist to test onset of thermal convection against numerical models of complex 3D systems that account for variable fluid density and viscosity as well as permeability heterogeneity (e.g. presence of faults). Owing to the importance of thermal convection for the transport of energy and minerals, the development of a benchmark test for density/viscosity driven flow is crucial to ensure that the applied numerical models accurately simulate the physical processes at hands. The presented study proposes a 3D test case for the simulation of thermal convection in a faulted system that accounts for temperature dependent fluid density and viscosity. The linear stability analysis recently developed by Malkovsky and Magri (2016) is used to estimate the critical Rayleigh number above which thermal convection of viscous fluids is triggered. The numerical simulations are carried out using the finite element technique. OpenGeoSys (Kolditz et al., 2012) and Moose (Gaston et al., 2009) results are compared to those obtained using the commercial software FEFLOW (Diersch, 2014) to test the ability of widely applied codes in matching both the critical Rayleigh number and the dynamical features of convective processes. The methodology and Rayleigh expressions given in this study can be applied to any numerical model that deals with 3D geothermal processes in faulted basins as by example the Tiberas Basin (Magri et al., 2016). References Kolditz, O., Bauer, S., Bilke, L., Böttcher, N., Delfs, J. O., Fischer, T., U. J. Görke, T. Kalbacher, G. Kosakowski, McDermott, C. I., Park, C. H., Radu, F., Rink, K., Shao, H., Shao, H.B., Sun, F., Sun, Y., Sun, A., Singh, K., Taron, J., Walther, M., Wang,W., Watanabe, N., Wu, Y., Xie, M., Xu, W., Zehner, B., 2012. OpenGeoSys: an open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media. Environmental
International Nuclear Information System (INIS)
Maniyeri, Ranjith; Kang, Sang Mo
2012-01-01
We present a three dimensional computational model based on an immersed boundary (IB) method to study the hydrodynamic features of a solid flexible cylindrical rod in a viscous fluid driven at one side by a tiny motor. The elastic rod is modelled by a number of circular cross-sections with twelve IB points on each cross-section. Three types of elastic links are created from each IB point to obtain an elastic network model of the rod and the first cross-section is modelled as the motor part. The elastic forces are computed based on an elastic energy approach and the motor forces are obtained from the applied angular frequency of rotation of the motor. The Stokes equations governing the fluid are solved on a staggered Cartesian grid system using the fractional-step based finite-volume method. Numerical simulations are performed to demonstrate the three dynamical stages of rod motion- twirling, whirling and overwhirling for different rotational frequency of the motor. It is revealed that for low rotational frequencies, the rod undergoes stable rigid body motion known as twirling. For high rotational frequencies of the motor, it is observed that the rod initially undergoes whirling motion and attains an unstable helical shape. Further, it is noticed that a discontinuous shape transition occurs for the rod and it folds back on itself. This unstable motion is referred to as overwhirling. It is also found that there exists a critical value of angular frequency of rotation of the motor below which the rod is subjected to twirling motion and above which it undergoes overwhirling motion
Sakuraba, A.
2015-12-01
I made a linear analysis of flow-induced oscillations along an underground cylindrical conduit with an elliptical cross section on the basis of the hypothesis that volcanic tremor is a result of magma movement through a conduit. As a first step to understand how the self oscillation occurs because of magma flow, I investigated surface wave propagation and attenuation along an infinitely long fluid-filled elliptic cylinder in an elastic medium. The boundary element method is used to obtain the two-dimensional wave field around the ellipse in the frequency-wavenumber domain. When the major axis is much greater than the minor axis of the ellipse, we obtain the analytic form of the dispersion relation of both the crack-wave mode (Korneev 2008, Lipovsky & Dunham 2015) and the Rayleigh-wave mode with flexural deformation. The crack-wave mode generally has a slower phase speed and a higher attenuation than the Rayleigh-wave mode. In the long-wavelength limit, the crack-wave mode disappears because of fluid viscosity, but the Rayleigh-wave mode exists with a constant Q-value that depends on viscosity. When the aspect ratio of the ellipse is finite, the surface waves can basically be understood as those propagating along a fluid pipe. The flexural mode does exist even when the wavelength is much longer than the major axis, but its phase speed coincides with that of the surrounding S-wave (Randall 1991). As its attenuation is zero in the long-wavelength limit, the flexural mode differs in nature from surface wave. I also obtain a result on linear stability of viscous flow through an elliptic cylinder. In this analysis, I made an assumption that the fluid inertia is so small that the Stokes equation can be used. As suggested by the author's previous study (Sakuraba & Yamauchi 2014), the flexural (Rayleigh-wave) mode is destabilized at a critical flow speed that decreases with the wavelength. However, when the wavelength is much greater than the major axis of the ellipse, the
Tip Effect of the Tapping Mode of Atomic Force Microscope in Viscous Fluid Environments.
Shih, Hua-Ju; Shih, Po-Jen
2015-07-28
Atomic force microscope with applicable types of operation in a liquid environment is widely used to scan the contours of biological specimens. The contact mode of operation allows a tip to touch a specimen directly but sometimes it damages the specimen; thus, a tapping mode of operation may replace the contact mode. The tapping mode triggers the cantilever of the microscope approximately at resonance frequencies, and so the tip periodically knocks the specimen. It is well known that the cantilever induces extra liquid pressure that leads to drift in the resonance frequency. Studies have noted that the heights of protein surfaces measured via the tapping mode of an atomic force microscope are ~25% smaller than those measured by other methods. This discrepancy may be attributable to the induced superficial hydrodynamic pressure, which is worth investigating. In this paper, we introduce a semi-analytical method to analyze the pressure distribution of various tip geometries. According to our analysis, the maximum hydrodynamic pressure on the specimen caused by a cone-shaped tip is ~0.5 Pa, which can, for example, pre-deform a cell by several nanometers in compression before the tip taps it. Moreover, the pressure calculated on the surface of the specimen is 20 times larger than the pressure without considering the tip effect; these results have not been motioned in other papers. Dominating factors, such as surface heights of protein surface, mechanical stiffness of protein increasing with loading velocity, and radius of tip affecting the local pressure of specimen, are also addressed in this study.
Multiple-relaxation-time lattice Boltzmann model for compressible fluids
International Nuclear Information System (INIS)
Chen Feng; Xu Aiguo; Zhang Guangcai; Li Yingjun
2011-01-01
We present an energy-conserving multiple-relaxation-time finite difference lattice Boltzmann model for compressible flows. The collision step is first calculated in the moment space and then mapped back to the velocity space. The moment space and corresponding transformation matrix are constructed according to the group representation theory. Equilibria of the nonconserved moments are chosen according to the need of recovering compressible Navier-Stokes equations through the Chapman-Enskog expansion. Numerical experiments showed that compressible flows with strong shocks can be well simulated by the present model. The new model works for both low and high speeds compressible flows. It contains more physical information and has better numerical stability and accuracy than its single-relaxation-time version. - Highlights: → We present an energy-conserving MRT finite-difference LB model. → The moment space is constructed according to the group representation theory. → The new model works for both low and high speeds compressible flows. → It has better numerical stability and wider applicable range than its SRT version.
Cochlear Outer-Hair-Cell Power Generation and Viscous Fluid Loss
Wang, Yanli; Steele, Charles R.; Puria, Sunil
2016-01-01
Since the discovery of otoacoustic emissions and outer hair cell (OHC) motility, the fundamental question of whether the cochlea produces mechanical power remains controversial. In the present work, direct calculations are performed on power loss due to fluid viscosity and power generated by the OHCs. A three-dimensional box model of the mouse cochlea is used with a feed-forward/feed-backward approximation representing the organ of Corti cytoarchitecture. The model is fit to in vivo basilar membrane motion with one free parameter for the OHCs. The calculations predict that the total power output from the three rows of OHCs can be over three orders of magnitude greater than the acoustic input power at 10 dB sound pressure level (SPL). While previous work shows that the power gain, or the negative damping, diminishes with intensity, we show explicitly based on our model that OHC power output increases and saturates with SPL. The total OHC power output is about 2 pW at 80 dB SPL, with a maximum of about 10 fW per OHC.
Performance of Twin-Fluid Atomizers for Atomization of Viscous Solutions
Directory of Open Access Journals (Sweden)
Mlkvik Marek
2015-01-01
Full Text Available Presented paper deals with a comparison of two internally mixing twin fluid atomizers. The well - known Y- jet atomizer and so called outside-in-liquid effervescent atomizer (OUIL were investigated. The working regimes were defined by the pressure drop (Δp and the gas to the liquid ratio (GLR. The internal and the external two-phase flows of both atomizers were studied. The influence of the mixing mechanism on the internal flow was evaluated by the gas to the liquid momentum ratio (Φ. In advance, the stability of the separated flow (liquid film was examined in term of the critical wavelength of the surface disturbances (λc. The external flow was observed by the high – speed camera. The influence of the basic forces on the deformation of the liquid was determined by a dimensionless criterion w·μ / σ. The values of Φ 3, where the liquid momentum overcomes the gas momentum. The values of w·μ / σ> 20 for both atomizers indicates the dominant influence of the viscosity and the drag force on the breakup process.
Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions
International Nuclear Information System (INIS)
Zhang, Rui; Schweizer, Kenneth S.
2015-01-01
We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant
International Nuclear Information System (INIS)
Khosravian, N; Rafii-Tabar, H
2008-01-01
In the design of nanotube-based fluidic devices, a critical issue is the effect of the induced vibrations in the nanotube arising from the fluid flow, since these vibrations can promote structural instabilities, such as buckling transitions. It is known that the induced resonant frequencies depend on the fluid flow velocity in a significant manner. We have studied, for the first time, the flow of a non-viscous fluid in stubby multi-walled carbon nanotubes, using the Timoshenko classical beam theory to model the nanotubes as a continuum structure. We have obtained the variations of the resonant frequencies with the fluid flow velocity under several experimentally interesting boundary conditions and aspect ratios of the nanotube. The main finding from our work is that, compared to an Euler-Bernoulli classical beam model of a nanotube, the Timoshenko beam predicts the loss of stability at lower fluid flow velocities
Energy Technology Data Exchange (ETDEWEB)
Khosravian, N; Rafii-Tabar, H [Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Research in Fundamental Sciences (IPM), PO Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: rafii-tabar@nano.ipm.ac.ir
2008-07-09
In the design of nanotube-based fluidic devices, a critical issue is the effect of the induced vibrations in the nanotube arising from the fluid flow, since these vibrations can promote structural instabilities, such as buckling transitions. It is known that the induced resonant frequencies depend on the fluid flow velocity in a significant manner. We have studied, for the first time, the flow of a non-viscous fluid in stubby multi-walled carbon nanotubes, using the Timoshenko classical beam theory to model the nanotubes as a continuum structure. We have obtained the variations of the resonant frequencies with the fluid flow velocity under several experimentally interesting boundary conditions and aspect ratios of the nanotube. The main finding from our work is that, compared to an Euler-Bernoulli classical beam model of a nanotube, the Timoshenko beam predicts the loss of stability at lower fluid flow velocities.
Czech Academy of Sciences Publication Activity Database
Petrov, A. G.; Kharlamov, Alexander
2013-01-01
Roč. 48, č. 2 (2013), s. 179-191 ISSN 0015-4628 R&D Projects: GA ČR GA103/09/2066 Grant - others:Russian Foundation for Basic Research (RU) 11-01-00535; Russian Foundation for Basic Research (RU) 11-01-00857; Target Analytical Program; Development of the Scientific Potential of the Higher School(RU) 2.1.2/3604 Institutional support: RVO:67985874 Keywords : lubrication layer theory * viscous and inviscid fluids * thin layer * contact vicinity Subject RIV: BK - Fluid Dynamics Impact factor: 0.320, year: 2013
Numerical solver for compressible two-fluid flow
J. Naber (Jorick)
2005-01-01
textabstractThis report treats the development of a numerical solver for the simulation of flows of two non-mixing fluids described by the two-dimensional Euler equations. A level-set equation in conservative form describes the interface. After each time step the deformed level-set function is
Motions of deformable inclusions in a horizontally oscillating vessel with a compressible fluid
DEFF Research Database (Denmark)
Demidov, I.V.; Sorokin, Vladislav
2016-01-01
The paper is concerned with the analysis of rigid particle and compressible gas bubble motion in a horizontally oscillating vessel with a compressible fluid. A nonlinear differential equation describing motion of inclusions with respect to the vessel is derived and solved by the method of direct...... of the bubbles which are affected by the negligible vibrational force is found. Also an approximate expression has been obtained for the average velocity of bubble׳s motion in the fluid; relationship between this velocity and bubble radius and vibration parameters has been revealed. A simple physical explanation...
Simulating coupled dynamics of a rigid-flexible multibody system and compressible fluid
Hu, Wei; Tian, Qiang; Hu, HaiYan
2018-04-01
As a subsequent work of previous studies of authors, a new parallel computation approach is proposed to simulate the coupled dynamics of a rigid-flexible multibody system and compressible fluid. In this approach, the smoothed particle hydrodynamics (SPH) method is used to model the compressible fluid, the natural coordinate formulation (NCF) and absolute nodal coordinate formulation (ANCF) are used to model the rigid and flexible bodies, respectively. In order to model the compressible fluid properly and efficiently via SPH method, three measures are taken as follows. The first is to use the Riemann solver to cope with the fluid compressibility, the second is to define virtual particles of SPH to model the dynamic interaction between the fluid and the multibody system, and the third is to impose the boundary conditions of periodical inflow and outflow to reduce the number of SPH particles involved in the computation process. Afterwards, a parallel computation strategy is proposed based on the graphics processing unit (GPU) to detect the neighboring SPH particles and to solve the dynamic equations of SPH particles in order to improve the computation efficiency. Meanwhile, the generalized-alpha algorithm is used to solve the dynamic equations of the multibody system. Finally, four case studies are given to validate the proposed parallel computation approach.
Low Mach number asymptotics for reacting compressible fluid flows
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Petzeltová, Hana
2010-01-01
Roč. 26, č. 2 (2010), s. 455-480 ISSN 1078-0947 R&D Projects: GA ČR GA201/05/0164 Institutional research plan: CEZ:AV0Z10190503 Keywords : low Mach number * Navier-Stokes-Fourier system * reacting fluids Subject RIV: BA - General Mathematics Impact factor: 0.986, year: 2010 http://www.aimsciences.org/journals/displayArticles.jsp?paperID=4660
Directory of Open Access Journals (Sweden)
Mohammad M. Rahman
2016-11-01
Full Text Available The aim of the present study is to analyze numerically the steady boundary layer flow and heat transfer characteristics of Casson fluid with variable temperature and viscous dissipation past a permeable shrinking sheet with second order slip velocity. Using appropriate similarity transformations, the basic nonlinear partial differential equations have been transformed into ordinary differential equations. These equations have been solved numerically for different values of the governing parameters namely: shrinking parametersuction parameterCasson parameterfirst order slip parametersecond order slip parameter Prandtl number and the Eckert number using the bvp4c function from MATLAB. A stability analysis has also been performed. Numerical results have been obtained for the reduced skin-friction, heat transfer and the velocity and temperature profiles. The results indicate that dual solutions exist for the shrinking surface for certain values of the parameter space. The stability analysis indicates that the lower solution branch is unstable, while the upper solution branch is stable and physically realizable. In addition, it is shown that for a viscous fluida very good agreement exists between the present numerical results and those reported in the open literature. The present results are original and new for the boundary-layer flow and heat transfer past a shrinking sheet in a Casson fluid. Therefore, this study has importance for researchers working in the area of non-Newtonian fluids, in order for them to become familiar with the flow behavior and properties of such fluids.
Energy Technology Data Exchange (ETDEWEB)
Richard C. Martineau; Ray A. Berry
2003-04-01
A new semi-implicit pressure-based Computational Fluid Dynamics (CFD) scheme for simulating a wide range of transient and steady, inviscid and viscous compressible flow on unstructured finite elements is presented here. This new CFD scheme, termed the PCICEFEM (Pressure-Corrected ICE-Finite Element Method) scheme, is composed of three computational phases, an explicit predictor, an elliptic pressure Poisson solution, and a semiimplicit pressure-correction of the flow variables. The PCICE-FEM scheme is capable of second-order temporal accuracy by incorporating a combination of a time-weighted form of the two-step Taylor-Galerkin Finite Element Method scheme as an explicit predictor for the balance of momentum equations and the finite element form of a time-weighted trapezoid rule method for the semi-implicit form of the governing hydrodynamic equations. Second-order spatial accuracy is accomplished by linear unstructured finite element discretization. The PCICE-FEM scheme employs Flux-Corrected Transport as a high-resolution filter for shock capturing. The scheme is capable of simulating flows from the nearly incompressible to the high supersonic flow regimes. The PCICE-FEM scheme represents an advancement in mass-momentum coupled, pressurebased schemes. The governing hydrodynamic equations for this scheme are the conservative form of the balance of momentum equations (Navier-Stokes), mass conservation equation, and total energy equation. An operator splitting process is performed along explicit and implicit operators of the semi-implicit governing equations to render the PCICE-FEM scheme in the class of predictor-corrector schemes. The complete set of semi-implicit governing equations in the PCICE-FEM scheme are cast in this form, an explicit predictor phase and a semi-implicit pressure-correction phase with the elliptic pressure Poisson solution coupling the predictor-corrector phases. The result of this predictor-corrector formulation is that the pressure Poisson
Compressible fluid flow through rocks of variable permeability
International Nuclear Information System (INIS)
Lin, W.
1977-01-01
The effectiveness of course-grained igneous rocks as shelters for burying radioactive waste can be assessed by determining the rock permeabilities at their in situ pressures and stresses. Analytical and numerical methods were used to solve differential equations of one-dimensional fluid flow through rocks with permeabilities from 10 4 to 1 nD. In these calculations, upstream and downstream reservoir volumes of 5, 50, and 500 cm 3 were used. The optimal size combinations of the two reservoirs were determined for measurements of permeability, stress, strain, acoustic velocity, and electrical conductivity on low-porosity, coarse-grained igneous rocks
Analysis of time integration methods for the compressible two-fluid model for pipe flow simulations
B. Sanderse (Benjamin); I. Eskerud Smith (Ivar); M.H.W. Hendrix (Maurice)
2017-01-01
textabstractIn this paper we analyse different time integration methods for the two-fluid model and propose the BDF2 method as the preferred choice to simulate transient compressible multiphase flow in pipelines. Compared to the prevailing Backward Euler method, the BDF2 scheme has a significantly
Compressibility effects in packed and open tubular gas and supercritical fluid chromatography
Janssen, J.G.M.; Snijders, H.M.J.; Cramers, C.A.; Schoenmakers, P.J.
1992-01-01
The influence of the pressure drop on the efficiency and speed of anal. in packed and open tubular supercrit. fluid chromatog. (SFC) is described: methods previously developed to describe the effects of mobile phase compressibility on the performance of open tubular columns in SFC have been extended
Bunton, Patrick H.; Tullier, Michael P.; Meiburg, Eckart; Pojman, John A.
2017-10-01
Viscous fingering can occur in fluid motion whenever a high mobility fluid displaces a low mobility fluid in a Darcy type flow. When the mobility difference is primarily attributable to viscosity (e.g., flow between the two horizontal plates of a Hele-Shaw cell), viscous fingering (VF) occurs, which is sometimes termed the Saffman-Taylor instability. Alternatively, in the presence of differences in density in a gravity field, buoyancy-driven convection can occur. These instabilities have been studied for decades, in part because of their many applications in pollutant dispersal, ocean currents, enhanced petroleum recovery, and so on. More recent interest has emerged regarding the effects of chemical reactions on fingering instabilities. As chemical reactions change the key flow parameters (densities, viscosities, and concentrations), they may have either a destabilizing or stabilizing effect on the flow. Hence, new flow patterns can emerge; moreover, one can then hope to gain some control over flow instabilities through reaction rates, flow rates, and reaction products. We report effects of chemical reactions on VF in a Hele-Shaw cell for a reactive step-growth cross-linking polymerization system. The cross-linked reaction product results in a non-monotonic viscosity profile at the interface, which affects flow stability. Furthermore, three-dimensional internal flows influence the long-term pattern that results.
The Taylor-Proudman column in a rapidly-rotating compressible fluid I. energy transports
International Nuclear Information System (INIS)
Park, Jun Sang
2014-01-01
A theoretical study is made of the steady flow of a compressible fluid in a rapidly rotating finite cylinder. Flow is generated by imposing mechanical and/or thermal disturbances at the rotating endwall disks. Both the Ekman and Rossby numbers are small. An examination is made of the energy budget for a control volume in the Ekman boundary layer. A combination of physical variables, which is termed the energy flux content, consisting of temperature and modified angular momentum, emerges to be relevant. The distinguishing features of a compressible fluid, in contrast to those of an incompressible fluid, are noted. A plausible argument is given to explain the difficulty in achieving the Taylor-Proudman column in a compressible rotating fluid. For the Taylor-Proudman column to be sustained, in the interior, it is shown that the net energy transport between the solid disk wall and the interior fluid should vanish. Physical rationalizations are facilitated by resorting to the concept of the afore-stated energy flux content.
International Nuclear Information System (INIS)
Karpp, R.R.
1980-10-01
This report treats analytically the problem of the symmetric impact of two compressible fluid streams. The flow is assumed to be steady, plane, inviscid, and subsonic and that the compressible fluid is of the Chaplygin (tangent gas) type. In the analysis, the governing equations are first transformed to the hodograph plane where an exact, closed-form solution is obtained by standard techniques. The distributions of fluid properties along the plane of symmetry as well as the shapes of the boundary streamlines are exactly determined by transforming the solution back to the physical plane. The problem of a compressible fluid jet penetrating into an infinite target of similar material is also exactly solved by considering a limiting case of this solution. This new compressible flow solution reduces to the classical result of incompressible flow theory when the sound speed of the fluid is allowed to approach infinity. Several illustrations of the differences between compressible and incompressible flows of the type considered are presented
Rayleigh Taylor instability of two superposed compressible fluids in un-magnetized plasma
International Nuclear Information System (INIS)
Sharma, P K; Tiwari, A; Argal, S; Chhajlani, R K
2014-01-01
The linear Rayleigh Taylor instability of two superposed compressible Newtonian fluids is discussed with the effect of surface tension which can play important roles in space plasma. As in both the superposed Newtonian fluids, the system is stable for potentially stable case and unstable for potentially unstable case in the present problem also. The equations of the problem are solved by normal mode method and a dispersion relation is obtained for such a system. The behaviour of growth rate is examined in the presence of surface tension and it is found that the surface tension has stabilizing influence on the Rayleigh Taylor instability of two superposed compressible fluids. Numerical analysis is performed to show the effect of sound velocity and surface tension on the growth rate of Rayleigh Taylor instability. It is found that both parameters have stabilizing influence on the growth rate of Rayleigh Taylor instability.
Directory of Open Access Journals (Sweden)
Natal'ya V. Burmasheva
2017-12-01
Full Text Available In this paper a new exact solution of an overdetermined system of Oberbeck–Boussinesq equations that describes a stationary shear flow of a viscous incompressible fluid in an infinite layer is under study. The given exact solution is a generalization of the Ostroumov–Birich class for a layered unidirectional flow. In the proposed solution, the horizontal velocities depend only on the transverse coordinate z. The temperature field and the pressure field are three-dimensional. In contradistinction to the Ostroumov–Birich solution, in the solution presented in the paper the horizontal temperature gradients are linear functions of the $z$ coordinate. This structure of the exact solution allows us to find a nontrivial solution of the Oberbeck–Boussinesq equations by means of the identity zero of the incompressibility equation. This exact solution is suitable for investigating large-scale flows of a viscous incompressible fluid by quasi-two-dimensional equations. Convective fluid motion is caused by the setting of tangential stresses on the free boundary of the layer. Inhomogeneous thermal sources are given on both boundaries. The pressure in the fluid at the upper boundary coincides with the atmospheric pressure. The paper focuses on the study of temperature and pressure fields, which are described by polynomials of three variables. The features of the distribution of the temperature and pressure profiles, which are polynomials of the seventh and eighth degree, respectively, are discussed in detail. To analyze the properties of temperature and pressure, algebraic methods are used to study the number of roots on a segment. It is shown that the background temperature and the background pressure are nonmonotonic functions. The temperature field is stratified into zones that form the thermocline and the thermal boundary layer near the boundaries of the fluid layer. Investigation of the properties of the pressure field showed that it is stratified
Effect of pore geometry on the compressibility of a confined simple fluid
Dobrzanski, Christopher D.; Maximov, Max A.; Gor, Gennady Y.
2018-02-01
Fluids confined in nanopores exhibit properties different from the properties of the same fluids in bulk; among these properties is the isothermal compressibility or elastic modulus. The modulus of a fluid in nanopores can be extracted from ultrasonic experiments or calculated from molecular simulations. Using Monte Carlo simulations in the grand canonical ensemble, we calculated the modulus for liquid argon at its normal boiling point (87.3 K) adsorbed in model silica pores of two different morphologies and various sizes. For spherical pores, for all the pore sizes (diameters) exceeding 2 nm, we obtained a logarithmic dependence of fluid modulus on the vapor pressure. Calculation of the modulus at saturation showed that the modulus of the fluid in spherical pores is a linear function of the reciprocal pore size. The calculation of the modulus of the fluid in cylindrical pores appeared too scattered to make quantitative conclusions. We performed additional simulations at higher temperature (119.6 K), at which Monte Carlo insertions and removals become more efficient. The results of the simulations at higher temperature confirmed both regularities for cylindrical pores and showed quantitative difference between the fluid moduli in pores of different geometries. Both of the observed regularities for the modulus stem from the Tait-Murnaghan equation applied to the confined fluid. Our results, along with the development of the effective medium theories for nanoporous media, set the groundwork for analysis of the experimentally measured elastic properties of fluid-saturated nanoporous materials.
International Nuclear Information System (INIS)
Bonfiglio, Andrea; Repetto, Rodolfo; Stocchino, Alessandro; Siggers, Jennifer H
2013-01-01
Intravitreal drug delivery is a commonly used treatment for several retinal diseases. The objective of this research is to characterize and quantify the role of the vitreous humor motion, induced by saccadic movements, on drug transport processes in the vitreous chamber. A Perspex model of the human vitreous chamber was created, and filled with a purely viscous fluid, representing eyes with a liquefied vitreous humor or those containing viscous tamponade fluids. Periodic movements were applied to the model and the resulting three-dimensional (3D) flow fields were measured. Drug delivery within the vitreous chamber was investigated by calculating particle trajectories using integration over time of the experimental velocity fields. The motion of the vitreous humor generated by saccadic eye movements is intrinsically 3D. Advective mass transport largely overcomes molecular diffusive transport and is significantly anisotropic, leading to a much faster drug dispersion than in the case of stationary vitreous humor. Disregarding the effects of vitreous humor motion due to eye movements when predicting the efficiency of drug delivery treatments leads to significant underestimation of the drug transport coefficients, and this, in turn, will lead to significantly erroneous predictions of the concentration levels on the retina. (paper)
International Nuclear Information System (INIS)
Dehkordi, Asghar Molaei; Mohammadi, Ali Asghar
2009-01-01
A numerical investigation was conducted on the transient behavior of a hydrodynamically, fully developed, laminar flow of power-law fluids in the thermally developing entrance region of circular ducts taking into account the effect of viscous dissipation but neglecting the effect of axial conduction. In this regard, the unsteady state thermal energy equation was solved by using a finite difference method, whereas the steady state thermal energy equation without wall heat flux was solved analytically as the initial condition of the former. The effects of the power-law index and wall heat flux on the local Nusselt number and thermal entrance length were investigated. Moreover, the local Nusselt number of steady state conditions was correlated in terms of the power-law index and wall heat flux and compared with literature data, which were obtained by an analytic solution for Newtonian fluids. Furthermore, a relationship was proposed for the thermal entrance length
Lyapunov stability of ideal compressible and incompressible fluid equilibria in three dimensions
International Nuclear Information System (INIS)
Holm, D.D.
1985-08-01
Linearized stability of ideal compressible and incompressible fluid equilibria in three dimensions is analyzed using Lyapunov's direct method. An action principle is given for the Eulerian and Lagrangian fluid descriptions and the family of constants of motion due to symmetry under fluid-particle relabelling is derived in the form of Ertel's theorem for each description. In an augmented Euleriah description, the steady equilibrium flows of these two fluids theories are identified as critical points of the conserved Lyapunov functionals defined by the sum, H + C, of the energy H, and the Ertel constants of motion, C. It turns out that unconditional linear Lyapunov stability of these flows in the norm provided by the second variation of H + C is precluded by vortex-particle stretching, even for otherwise shear-stable flows. Conditional Lyapunov stability of these flows is discussed. 24 refs
Introduction of small velocity and pressure variation into a stationary compressible fluid
Energy Technology Data Exchange (ETDEWEB)
Trancong, Ton [Defence Science and Technology Organisation Australia, Fishermens Bend (Australia). Aeronautical Research Lab.
1992-06-01
This work formulates the aerodynamic time-dependent Coulomb and Biot-Savart laws with inherent transmission retardation. It generalizes the theory by Baskin et al. (for only the isentropic propagation of small vortex disturbances) to deal with the propagation of small disturbances caused by a distributed system of both vortices and variation in specific entropy of a thermodynamically simple compressible fluid. The proof here uses an alternative, more appealing derivation with the help of a novel wave-cone transformation (which changes Kirchhoff's retarded potentials into Newtonian potentials). The results suggest the possibility of using a focused laser spot to simulate the effect of a source in a compressible fluid; the source may even move at a supersonic speed to create a shock wave. They also suggest a time-dependent, three-dimensional formula for lifts caused by small disturbances that is in agreement with Blasius' formula for two-dimensional, time-independent, inviscid flows. (orig.).
Compressible fluids driven by stochastic forcing: The relative energy inequality and applications
Czech Academy of Sciences Publication Activity Database
Breit, D.; Feireisl, Eduard; Hofmanová, M.
2017-01-01
Roč. 350, č. 2 (2017), s. 443-473 ISSN 0010-3616 EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : compressible fluids * Navier-Stokes system Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 2.500, year: 2016 http://link.springer.com/article/10.1007%2Fs00220-017-2833-x
The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection
Li, Xiaocan; Guo, Fan; Li, Hui; Birn, Joachim
2018-03-01
Particle acceleration in space and astrophysical reconnection sites is an important unsolved problem in studies of magnetic reconnection. Earlier kinetic simulations have identified several acceleration mechanisms that are associated with particle drift motions. Here, we show that, for sufficiently large systems, the energization processes due to particle drift motions can be described as fluid compression and shear, and that the shear energization is proportional to the pressure anisotropy of energetic particles. By analyzing results from fully kinetic simulations, we show that the compression energization dominates the acceleration of high-energy particles in reconnection with a weak guide field, and the compression and shear effects are comparable when the guide field is 50% of the reconnecting component. Spatial distributions of those energization effects reveal that reconnection exhausts, contracting islands, and island-merging regions are the three most important regions for compression and shear acceleration. This study connects particle energization by particle guiding-center drift motions with that due to background fluid motions, as in the energetic particle transport theory. It provides foundations for building particle transport models for large-scale reconnection acceleration such as those in solar flares.
Analysis of a discrete element method and coupling with a compressible fluid flow method
International Nuclear Information System (INIS)
Monasse, L.
2011-01-01
This work aims at the numerical simulation of compressible fluid/deformable structure interactions. In particular, we have developed a partitioned coupling algorithm between a Finite Volume method for the compressible fluid and a Discrete Element method capable of taking into account fractures in the solid. A survey of existing fictitious domain methods and partitioned algorithms has led to choose an Embedded Boundary method and an explicit coupling scheme. We first showed that the Discrete Element method used for the solid yielded the correct macroscopic behaviour and that the symplectic time-integration scheme ensured the preservation of energy. We then developed an explicit coupling algorithm between a compressible inviscid fluid and an un-deformable solid. Mass, momentum and energy conservation and consistency properties were proved for the coupling scheme. The algorithm was then extended to the coupling with a deformable solid, in the form of a semi implicit scheme. Finally, we applied this method to unsteady inviscid flows around moving structures: comparisons with existing numerical and experimental results demonstrate the excellent accuracy of our method. (author) [fr
Li, X.; Guo, F.; Li, G.; Li, H.
2016-12-01
Theories of particle transport and acceleration have shown that fluid compression is the leading mechanism for particle acceleration and plasma energization. However, the role of compression in particle acceleration during magnetic reconnection is unclear. We use two approaches to study this issue. First, using fully kinetic simulations, we quantitatively calculate the effect of compression in energy conversion and particle energization during magnetic reconnection for a range of plasma beta and guide field. We show that compression has an important contribution for the energy conversion between the bulk kinetic energy and the internal energy when the guide field is smaller than the reconnecting component. Based on this result, we then study the large-scale reconnection acceleration by solving the Parker's transport equation in a background reconnecting flow provided by MHD simulations. Due to the compression effect, the simulations suggest fast particle acceleration to high energies in the reconnection layer. This study clarifies the nature of particle acceleration in reconnection layer, and may be important to understand particle acceleration and plasma energization during solar flares.
International Nuclear Information System (INIS)
Soltani, P; Farshidianfar, A; Taherian, M M
2010-01-01
In this study, for the first time, the transverse vibrational model of a viscous-fluid-conveying single-walled carbon nanotube (SWCNT) embedded in biological soft tissue is developed. Nonlocal Euler-Bernoulli beam theory has been used to investigate fluid-induced vibration of the SWCNT while visco-elastic behaviour of the surrounding tissue is simulated by the Kelvin-Voigt model. The results indicate that the resonant frequencies and the critical flow velocity at which structural instability of nanotubes emerges are significantly dependent on the properties of the medium around the nanotube, the boundary conditions, the viscosity of the fluid and the nonlocal parameter. Detailed results are demonstrated for the dependence of damping and elastic properties of the medium on the resonant frequencies and the critical flow velocity. Three standard boundary conditions, namely clamped-clamped, clamped-pinned and pinned-pinned, are applied to study the effect of the supported end conditions. Furthermore, it is found that the visco-elastic foundation causes an obvious reduction in the critical velocity in comparison with the elastic foundation, in particular for a compliant medium, pinned-pinned boundary condition, high viscosity of the fluid and small values of the nonlocal coefficient.
Directory of Open Access Journals (Sweden)
T. M. Ajayi
2017-01-01
Full Text Available The problem of a non-Newtonian fluid flow past an upper surface of an object that is neither a perfect horizontal/vertical nor inclined/cone in which dissipation of energy is associated with temperature-dependent plastic dynamic viscosity is considered. An attempt has been made to focus on the case of two-dimensional Casson fluid flow over a horizontal melting surface embedded in a thermally stratified medium. Since the viscosity of the non-Newtonian fluid tends to take energy from the motion (kinetic energy and transform it into internal energy, the viscous dissipation term is accommodated in the energy equation. Due to the existence of internal space-dependent heat source; plastic dynamic viscosity and thermal conductivity of the non-Newtonian fluid are assumed to vary linearly with temperature. Based on the boundary layer assumptions, suitable similarity variables are applied to nondimensionalized, parameterized and reduce the governing partial differential equations into a coupled ordinary differential equations. These equations along with the boundary conditions are solved numerically using the shooting method together with the Runge-Kutta technique. The effects of pertinent parameters are established. A significant increases in Rex1/2Cfx is guaranteed with St when magnitude of β is large. Rex1/2Cfx decreases with Ec and m.
Mathematical modelling and numerical resolution of multi-phase compressible fluid flows problems
International Nuclear Information System (INIS)
Lagoutiere, Frederic
2000-01-01
This work deals with Eulerian compressible multi-species fluid dynamics, the species being either mixed or separated (with interfaces). The document is composed of three parts. The first parts devoted to the numerical resolution of model problems: advection equation, Burgers equation, and Euler equations, in dimensions one and two. The goal is to find a precise method, especially for discontinuous initial conditions, and we develop non dissipative algorithms. They are based on a downwind finite-volume discretization under some stability constraints. The second part treats of the mathematical modelling of fluids mixtures. We construct and analyse a set of multi-temperature and multi-pressure models that are entropy, symmetrizable, hyperbolic, not ever conservative. In the third part, we apply the ideas developed in the first part (downwind discretization) to the numerical resolution of the partial differential problems we have constructed for fluids mixtures in the second part. We present some numerical results in dimensions one and two. (author) [fr
An Embedded Ghost-Fluid Method for Compressible Flow in Complex Geometry
Almarouf, Mohamad Abdulilah Alhusain Alali; Samtaney, Ravi
2016-01-01
We present an embedded ghost-fluid method for numerical solutions of the compressible Navier Stokes (CNS) equations in arbitrary complex domains. The PDE multidimensional extrapolation approach of Aslam [1] is used to reconstruct the solution in the ghost-fluid regions and impose boundary conditions at the fluid-solid interface. The CNS equations are numerically solved by the second order multidimensional upwind method of Colella [2] and Saltzman [3]. Block-structured adaptive mesh refinement implemented under the Chombo framework is utilized to reduce the computational cost while keeping high-resolution mesh around the embedded boundary and regions of high gradient solutions. Numerical examples with different Reynolds numbers for low and high Mach number flow will be presented. We compare our simulation results with other reported experimental and computational results. The significance and advantages of our implementation, which revolve around balancing between the solution accuracy and implementation difficulties, are briefly discussed as well. © 2016 Trans Tech Publications.
An Embedded Ghost-Fluid Method for Compressible Flow in Complex Geometry
Almarouf, Mohamad Abdulilah Alhusain Alali
2016-06-03
We present an embedded ghost-fluid method for numerical solutions of the compressible Navier Stokes (CNS) equations in arbitrary complex domains. The PDE multidimensional extrapolation approach of Aslam [1] is used to reconstruct the solution in the ghost-fluid regions and impose boundary conditions at the fluid-solid interface. The CNS equations are numerically solved by the second order multidimensional upwind method of Colella [2] and Saltzman [3]. Block-structured adaptive mesh refinement implemented under the Chombo framework is utilized to reduce the computational cost while keeping high-resolution mesh around the embedded boundary and regions of high gradient solutions. Numerical examples with different Reynolds numbers for low and high Mach number flow will be presented. We compare our simulation results with other reported experimental and computational results. The significance and advantages of our implementation, which revolve around balancing between the solution accuracy and implementation difficulties, are briefly discussed as well. © 2016 Trans Tech Publications.
Directory of Open Access Journals (Sweden)
Khilap Singh
2016-01-01
Full Text Available A numerical model is developed to examine the effects of thermal radiation on unsteady mixed convection flow of a viscous dissipating incompressible micropolar fluid adjacent to a heated vertical stretching surface in the presence of the buoyancy force and heat generation/absorption. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The model contains nonlinear coupled partial differential equations which have been converted into ordinary differential equation by using the similarity transformations. The dimensionless governing equations for this investigation are solved by Runge-Kutta-Fehlberg fourth fifth-order method with shooting technique. Numerical solutions are then obtained and investigated in detail for different interesting parameters such as the local skin-friction coefficient, wall couple stress, and Nusselt number as well as other parametric values such as the velocity, angular velocity, and temperature.
Directory of Open Access Journals (Sweden)
Aftab Ahmed
2018-01-01
Full Text Available The aim of the present study is to investigate the combined effects of the thermal radiation, viscous dissipation, suction/injection and internal heat generation/absorption on the boundary layer flow of a non-Newtonian power law fluid over a semi infinite permeable flat plate moving in parallel or reversely to a free stream. The resulting system of partial differential equations (PDEs is first transformed into a system of coupled nonlinear ordinary differential equations (ODEs which are then solved numerically by using the shooting technique. It is found that the dual solutions exist when the flat plate and the free stream move in the opposite directions. Dimensionless boundary layer velocity and temperature distributions are plotted and discussed for various values of the emerging physical parameters. Finally, the tables of the relevant boundary derivatives are presented for some values of the governing physical parameters.
Methods for compressible fluid simulation on GPUs using high-order finite differences
Pekkilä, Johannes; Väisälä, Miikka S.; Käpylä, Maarit J.; Käpylä, Petri J.; Anjum, Omer
2017-08-01
We focus on implementing and optimizing a sixth-order finite-difference solver for simulating compressible fluids on a GPU using third-order Runge-Kutta integration. Since graphics processing units perform well in data-parallel tasks, this makes them an attractive platform for fluid simulation. However, high-order stencil computation is memory-intensive with respect to both main memory and the caches of the GPU. We present two approaches for simulating compressible fluids using 55-point and 19-point stencils. We seek to reduce the requirements for memory bandwidth and cache size in our methods by using cache blocking and decomposing a latency-bound kernel into several bandwidth-bound kernels. Our fastest implementation is bandwidth-bound and integrates 343 million grid points per second on a Tesla K40t GPU, achieving a 3 . 6 × speedup over a comparable hydrodynamics solver benchmarked on two Intel Xeon E5-2690v3 processors. Our alternative GPU implementation is latency-bound and achieves the rate of 168 million updates per second.
International Nuclear Information System (INIS)
Kambe, Tsutomu
2013-01-01
A new representation of the solution to Euler's equation of motion is presented by using a system of expressions for compressible rotational flows of an ideal fluid. This is regarded as a generalization of Bernoulli's theorem to compressible rotational flows. The present expressions are derived from the variational principle. The action functional for the principle consists of the main terms of the total kinetic, potential and internal energies, together with three additional terms yielding the equations of continuity, entropy and a third term that provides the rotational component of velocity field. The last term has the form of scalar product satisfying gauge symmetry with respect to both translation and rotation. This is a generalization of the Clebsch transformation from a physical point of view. It is verified that the system of new expressions, in fact, satisfies Euler's equation of motion. (paper)
Brehm, Christoph; Barad, Michael F.; Kiris, Cetin C.
2016-01-01
An immersed boundary method for the compressible Navier-Stokes equation and the additional infrastructure that is needed to solve moving boundary problems and fully coupled fluid-structure interaction is described. All the methods described in this paper were implemented in NASA's LAVA solver framework. The underlying immersed boundary method is based on the locally stabilized immersed boundary method that was previously introduced by the authors. In the present paper this method is extended to account for all aspects that are involved for fluid structure interaction simulations, such as fast geometry queries and stencil computations, the treatment of freshly cleared cells, and the coupling of the computational fluid dynamics solver with a linear structural finite element method. The current approach is validated for moving boundary problems with prescribed body motion and fully coupled fluid structure interaction problems in 2D and 3D. As part of the validation procedure, results from the second AIAA aeroelastic prediction workshop are also presented. The current paper is regarded as a proof of concept study, while more advanced methods for fluid structure interaction are currently being investigated, such as geometric and material nonlinearities, and advanced coupling approaches.
Static, Dynamic, and Thermal Properties of Compressible Fluid Film Journal Bearings
DEFF Research Database (Denmark)
Paulsen, Bo Terp; Morosi, Stefano; Santos, Ilmar
2011-01-01
fluid film journal bearing, in order to identify when this type of analysis should be of concern. Load capacity, stiffness, and damping coefficients are determined by the solution of the standard Reynolds equation coupled to the energy equation. Numerical investigations show how bearing geometry......, and work great efficiency. A great deal of literature has concentrated on the analysis and prediction of the static and dynamic performance of gas bearings, assuming isothermal conditions. The present contribution presents a detailed mathematical modeling for nonisothermal lubrication of a compressible...
STEADY-STATE modeling and simulation of pipeline networks for compressible fluids
Directory of Open Access Journals (Sweden)
A.L.H. Costa
1998-12-01
Full Text Available This paper presents a model and an algorithm for the simulation of pipeline networks with compressible fluids. The model can predict pressures, flow rates, temperatures and gas compositions at any point of the network. Any network configuration can be simulated; the existence of cycles is not an obstacle. Numerical results from simulated data on a proposed network are shown for illustration. The potential of the simulator is explored by the analysis of a pressure relief network, using a stochastic procedure for the evaluation of system performance.
Energy Technology Data Exchange (ETDEWEB)
Klimachkov, D. A., E-mail: klimchakovdmitry@gmail.com; Petrosyan, A. S., E-mail: apetrosy@iki.rssi.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation)
2016-09-15
Shallow water magnetohydrodynamic (MHD) theory describing incompressible flows of plasma is generalized to the case of compressible flows. A system of MHD equations is obtained that describes the flow of a thin layer of compressible rotating plasma in a gravitational field in the shallow water approximation. The system of quasilinear hyperbolic equations obtained admits a complete simple wave analysis and a solution to the initial discontinuity decay problem in the simplest version of nonrotating flows. In the new equations, sound waves are filtered out, and the dependence of density on pressure on large scales is taken into account that describes static compressibility phenomena. In the equations obtained, the mass conservation law is formulated for a variable that nontrivially depends on the shape of the lower boundary, the characteristic vertical scale of the flow, and the scale of heights at which the variation of density becomes significant. A simple wave theory is developed for the system of equations obtained. All self-similar discontinuous solutions and all continuous centered self-similar solutions of the system are obtained. The initial discontinuity decay problem is solved explicitly for compressible MHD equations in the shallow water approximation. It is shown that there exist five different configurations that provide a solution to the initial discontinuity decay problem. For each configuration, conditions are found that are necessary and sufficient for its implementation. Differences between incompressible and compressible cases are analyzed. In spite of the formal similarity between the solutions in the classical case of MHD flows of an incompressible and compressible fluids, the nonlinear dynamics described by the solutions are essentially different due to the difference in the expressions for the squared propagation velocity of weak perturbations. In addition, the solutions obtained describe new physical phenomena related to the dependence of the
Directory of Open Access Journals (Sweden)
Mahmood H. Ali
2015-02-01
Full Text Available A numerical study of non-Darcian natural convection heat transfer in a rectangular enclosure filled with porous medium saturated with viscous fluid was carried out. The effects of medium Rayleigh number, porosity, particle to fluid thermal conductivity ratio, Darcy number and enclosure aspect ratio on heat transfer were examined to demonstrate the ability of using this construction in thermal insulation of buildings walls.A modified Brinkman-Forchheimer-extended Darcy flow model was used and no-slip boundary conditions were imposed for velocity at the walls and the governing equations were expressed in dimensionless stream function, vorticity, and temperature formulation. The resulting algebraic equations obtained from finite difference discritization of vorticity and temperature equations are solved using (ADI method which uses Three Diagonal Matrix Algorithm (TDMA in each direction, while that of the stream function equation solved using successive iteration method.The study was done for the range of enclosure aspect ratio ( which is in the tall layers region at medium Rayleigh number ( , Darcy number (Da=10-3, 10-4, 10-5 , porosity (e=0.35, 0.45, 0.55, particle to fluid thermal conductivity (kS/kf=5.77, 38.5, 1385.5.The results showed that the Nusselt number is direct proportional to medium Rayleigh number and porosity and reversely proportional to Darcy number, ratio of particle to fluid thermal conductivity and enclosure aspect ratio. The variables that affect the heat transfer in the above arrangement was correlated in a mathematical equation that account better for their affects on heat transfer which is represented by mean Nusselt number (Nu.
International Nuclear Information System (INIS)
Kondoh, Yoshiomi; Serizawa, Shunsuke; Nakano, Akihiro; Takahashi, Toshiki; Van Dam, James W.
2004-01-01
The final self-similar state of decaying two-dimensional (2D) turbulence in 2D incompressible viscous flow is analytically and numerically investigated for the case with periodic boundaries. It is proved by theoretical analysis and simulations that the sinh-Poisson state cω=-sinh(βψ) is not realized in the dynamical system of interest. It is shown by an eigenfunction spectrum analysis that a sufficient explanation for the self-organization to the decaying self-similar state is the faster energy decay of higher eigenmodes and the energy accumulation to the lowest eigenmode for given boundary conditions due to simultaneous normal and inverse cascading by nonlinear mode couplings. The theoretical prediction is demonstrated to be correct by simulations leading to the lowest eigenmode of {(1,0)+(0,1)} of the dissipative operator for the periodic boundaries. It is also clarified that an important process during nonlinear self-organization is an interchange between the dominant operators, which leads to the final decaying self-similar state
A numerical study of bubble interactions in Rayleigh--Taylor instability for compressible fluids
International Nuclear Information System (INIS)
Glimm, J.; Li, X.L.; Menikoff, R.; Sharp, D.H.; Zhang, Q.
1990-01-01
The late nonlinear and chaotic stage of Rayleigh--Taylor instability is characterized by the evolution of bubbles of the light fluid and spikes of the heavy fluid, each penetrating into the other phase. This paper is focused on the numerical study of bubble interactions and their effect on the statistical behavior and evolution of the bubble envelope. Compressible fluids described by the two-fluid Euler equations are considered and the front tracking method for numerical simulation of these equations is used. Two major phenomena are studied. One is the dynamics of the bubbles in a chaotic environment and the interaction among neighboring bubbles. Another one is the acceleration of the overall bubble envelope, which is a statistical consequence of the interactions of bubbles. The main result is a consistent analysis, at least in the approximately incompressible case of these two phenomena. The consistency encompasses the analysis of experiments, numerical simulation, simple theoretical models, and variation of parameters. Numerical simulation results that are in quantitative agreement with laboratory experiment for one-and-one-half (1 1/2) generations of bubble merger are presented. To the authors' knowledge, computations of this accuracy have not previously been obtained
International Nuclear Information System (INIS)
Anand, Vishal
2016-01-01
Highlights: • Exponential formulation of s-PTT model used. • Heat transfer and entropy generation characteristics studied. • Effects of three slip laws examined. • Exponential formulation more accurate than linear formulation. - Abstract: This study concerns the heat transfer and entropy generation characteristics of viscoelastic fluid flow modeled by the exponential formulation of simplified Phan-Thien–Tanner (s-PTT) model. This is the first such study in literature of thermal behavior of viscoelastic fluids modeled by the exponential formulation of s-PTT model. The flow between two parallel plates is laminar, hydrodynamically and thermally fully developed, viscous dissipative and subject to uniform heat flux on the walls. The slip velocity boundary condition is imposed on the fluid–solid interface and the slip is captured by three slip laws, namely, Navier's non-linear slip law, Hatzikiriakos slip law, and asymptotic slip law. The governing equations have been solved analytically. Closed form solutions for the velocity distribution have been derived while the temperature distribution is presented in terms of an infinite but convergent series. The results pertaining to the three slip laws have been presented in detail. Finally, a comparison has been made between the results for exponential formulation and those for the linear formulation of the s-PTT model. The comparison shows that results for linear formulation deviate significantly from those for exponential formulation and thus the accuracy of the exponential formulation justifies the extra mathematical complexity which it entails.
Gnaneswara Reddy, Machireddy
2017-12-01
The problem of micropolar fluid flow over a nonlinear stretching convective vertical surface in the presence of Lorentz force and viscous dissipation is investigated. Due to the nature of heat transfer in the flow past vertical surface, Cattaneo-Christov heat flux model effect is properly accommodated in the energy equation. The governing partial differential equations for the flow and heat transfer are converted into a set of ordinary differential equations by employing the acceptable similarity transformations. Runge-Kutta and Newton's methods are utilized to resolve the altered governing nonlinear equations. Obtained numerical results are compared with the available literature and found to be an excellent agreement. The impacts of dimensionless governing flow pertinent parameters on velocity, micropolar velocity and temperature profiles are presented graphically for two cases (linear and nonlinear) and analyzed in detail. Further, the variations of skin friction coefficient and local Nusselt number are reported with the aid of plots for the sundry flow parameters. The temperature and the related boundary enhances enhances with the boosting values of M. It is found that fluid temperature declines for larger thermal relaxation parameter. Also, it is revealed that the Nusselt number declines for the hike values of Bi.
Dissipative measure-valued solutions to the compressible Navier-Stokes system
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Gwiazda, P.; Swierczewska-Gwiazda, A.; Wiedemann, E.
2016-01-01
Roč. 55, č. 6 (2016), č. článku 141. ISSN 0944-2669 EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : singular limit * compressible fluid * viscous fluid Subject RIV: BA - General Mathematics Impact factor: 1.532, year: 2016 http://link.springer.com/article/10.1007/s00526-016-1089-1
Banerjee, Supratik; Kritsuk, Alexei G.
2018-02-01
Three-dimensional, compressible, magnetohydrodynamic turbulence of an isothermal, self-gravitating fluid is analyzed using two-point statistics in the asymptotic limit of large Reynolds numbers (both kinetic and magnetic). Following an alternative formulation proposed by Banerjee and Galtier [Phys. Rev. E 93, 033120 (2016), 10.1103/PhysRevE.93.033120; J. Phys. A: Math. Theor. 50, 015501 (2017), 10.1088/1751-8113/50/1/015501], an exact relation has been derived for the total energy transfer. This approach results in a simpler relation expressed entirely in terms of mixed second-order structure functions. The kinetic, thermodynamic, magnetic, and gravitational contributions to the energy transfer rate can be easily separated in the present form. By construction, the new formalism includes such additional effects as global rotation, the Hall term in the induction equation, etc. The analysis shows that solid-body rotation cannot alter the energy flux rate of compressible turbulence. However, the contribution of a uniform background magnetic field to the flux is shown to be nontrivial unlike in the incompressible case. Finally, the compressible, turbulent energy flux rate does not vanish completely due to simple alignments, which leads to a zero turbulent energy flux rate in the incompressible case.
Czech Academy of Sciences Publication Activity Database
Nečasová, Šárka; Takahashi, T.; Tucsnak, M.
2011-01-01
Roč. 116, č. 3 (2011), s. 329-352 ISSN 0167-8019 R&D Projects: GA ČR(CZ) GAP201/11/1304 Institutional research plan: CEZ:AV0Z10190503 Keywords : Navier-Stokes equations * fluid-structure integration * weak solutions * free boundary Subject RIV: BA - General Mathematics Impact factor: 0.899, year: 2011 http://rd.springer.com/article/10.1007/s10440-011-9646-2#
Directory of Open Access Journals (Sweden)
Douglas P. Taylor
1995-01-01
Full Text Available Today's economic climate demands that conversion of military technology for commerical applications be a part of an aerospace and defense company's strategic planning. Toward this goal, a successful defense conversion has occurred recently with the application of high capacity fluid damping devices from the defense community for use as seismic energy dissipation elements in commercial buildings, bridges, and related structures. These products have been used by the military for many years for attenuation of weapons grade shock, typically applied to shipboard equipment or land based strategic weapons. Commercial energy dissipation devices historically have involved heavy yielding sections or hysteretic joints.
Rhodes, J. A.; Tiwari, S. N.; Vonlavante, E.
1988-01-01
A comparison of flow separation in transonic flows is made using various computational schemes which solve the Euler and the Navier-Stokes equations of fluid mechanics. The flows examined are computed using several simple two-dimensional configurations including a backward facing step and a bump in a channel. Comparison of the results obtained using shock fitting and flux vector splitting methods are presented and the results obtained using the Euler codes are compared to results on the same configurations using a code which solves the Navier-Stokes equations.
Langlois, William E
2014-01-01
Leonardo wrote, 'Mechanics is the paradise of the mathematical sciences, because by means of it one comes to the fruits of mathematics' ; replace 'Mechanics' by 'Fluid mechanics' and here we are." - from the Preface to the Second Edition Although the exponential growth of computer power has advanced the importance of simulations and visualization tools for elaborating new models, designs and technologies, the discipline of fluid mechanics is still large, and turbulence in flows remains a challenging problem in classical physics. Like its predecessor, the revised and expanded Second Edition of this book addresses the basic principles of fluid mechanics and solves fluid flow problems where viscous effects are the dominant physical phenomena. Much progress has occurred in the nearly half a century that has passed since the edition of 1964. As predicted, aspects of hydrodynamics once considered offbeat have risen to importance. For example, the authors have worked on problems where variations in viscosity a...
Energy Technology Data Exchange (ETDEWEB)
Etienne, St.
1999-09-01
To compute the viscous flow around flexible circular cylinders arrays, a numerical model has been set up so solve the Reynolds averaged Navier-Stokes equations (RANSE). A domain decomposition method has been chosen to ensure the great flexibility of structures in the fluid domain. It consists in solving the RANS equations in a Eulerian way near the bodies and in a Lagrangian way in the wake(s). Then, we concentrate calculations in interest areas and we avoid mesh distortions. The resolution in the turbulent regime has been realized with k - {omega} and k - {epsilon} models. Compared with experiments, mix k - {omega} and k - {epsilon} models give the best results. Applications concern with the modeling of shielding and vortex-induced vibrations (VIV) phenomena in arrays of flexible cylinders. Results are validated by comparisons with experimental data. (authors)
Felderhof, B U
2013-08-01
Recently, a critical test of the Navier-Stokes-Fourier equations for compressible fluid continua was proposed [H. Brenner, Phys. Rev. E 87, 013014 (2013)]. It was shown that the equations of bivelocity hydrodynamics imply that a compressible fluid in an isolated rotating circular cylinder attains a nonequilibrium steady state with a nonuniform temperature increasing radially with distance from the axis. We demonstrate that statistical mechanical arguments, involving Hamiltonian dynamics and ergodicity due to irregularity of the wall, lead instead to a thermal equilibrium state with uniform temperature. This is the situation to be expected in experiment.
Bandyopadhyay, Alak; Majumdar, Alok
2007-01-01
The present paper describes the verification and validation of a quasi one-dimensional pressure based finite volume algorithm, implemented in Generalized Fluid System Simulation Program (GFSSP), for predicting compressible flow with friction, heat transfer and area change. The numerical predictions were compared with two classical solutions of compressible flow, i.e. Fanno and Rayleigh flow. Fanno flow provides an analytical solution of compressible flow in a long slender pipe where incoming subsonic flow can be choked due to friction. On the other hand, Raleigh flow provides analytical solution of frictionless compressible flow with heat transfer where incoming subsonic flow can be choked at the outlet boundary with heat addition to the control volume. Nonuniform grid distribution improves the accuracy of numerical prediction. A benchmark numerical solution of compressible flow in a converging-diverging nozzle with friction and heat transfer has been developed to verify GFSSP's numerical predictions. The numerical predictions compare favorably in all cases.
Poppe, Christian; Dörr, Dominik; Henning, Frank; Kärger, Luise
2018-05-01
Wet compression moulding (WCM) provides large-scale production potential for continuously fiber reinforced components as a promising alternative to resin transfer moulding (RTM). Lower cycle times are possible due to parallelization of the process steps draping, infiltration and curing during moulding (viscous draping). Experimental and theoretical investigations indicate a strong mutual dependency between the physical mechanisms, which occur during draping and mould filling (fluid-structure-interaction). Thus, key process parameters, like fiber orientation, fiber volume fraction, cavity pressure and the amount and viscosity of the resin are physically coupled. To enable time and cost efficient product and process development throughout all design stages, accurate process simulation tools are desirable. Separated draping and mould filling simulation models, as appropriate for the sequential RTM-process, cannot be applied for the WCM process due to the above outlined physical couplings. Within this study, a two-dimensional Darcy-Propagation-Element (DPE-2D) based on a finite element formulation with additional control volumes (FE/CV) is presented, verified and applied to forming simulation of a generic geometry, as a first step towards a fluid-structure-interaction model taking into account simultaneous resin infiltration and draping. The model is implemented in the commercial FE-Solver Abaqus by means of several user subroutines considering simultaneous draping and 2D-infiltration mechanisms. Darcy's equation is solved with respect to a local fiber orientation. Furthermore, the material model can access the local fluid domain properties to update the mechanical forming material parameter, which enables further investigations on the coupled physical mechanisms.
Gaik*, Tay Kim; Demiray, Hilmi; Tiong, Ong Chee
In the present work, treating the artery as a prestressed thin-walled and long circularly cylindrical elastic tube with a mild symmetrical stenosis and the blood as an incompressible Newtonian fluid, we have studied the pro pagation of weakly nonlinear waves in such a composite medium, in the long wave approximation, by use of the reductive perturbation method. By intro ducing a set of stretched coordinates suitable for the boundary value type of problems and expanding the field variables into asymptotic series of the small-ness parameter of nonlinearity and dispersion, we obtained a set of nonlinear differential equations governing the terms at various order. By solving these nonlinear differential equations, we obtained the forced perturbed Korteweg-de Vries equation with variable coefficient as the nonlinear evolution equation. By use of the coordinate transformation, it is shown that this type of nonlinear evolution equation admits a progressive wave solution with variable wave speed.
Compressible Analysis of Bénard Convection of Magneto Rotatory Couple-Stress Fluid
Directory of Open Access Journals (Sweden)
Mehta C.B.
2018-02-01
Full Text Available Thermal Instability (Benard’s Convection in the presence of uniform rotation and uniform magnetic field (separately is studied. Using the linearized stability theory and normal mode analyses the dispersion relation is obtained in each case. In the case of rotatory Benard’s stationary convection compressibility and rotation postpone the onset of convection whereas the couple-stress have duel character onset of convection depending on rotation parameter. While in the absence of rotation couple-stress always postpones the onset of convection. On the other hand, magnetic field on thermal instability problem on couple-stress fluid for stationary convection couple-stress parameter and magnetic field postpones the onset of convection. The effect of compressibility also postpones the onset of convection in both cases as rotation and magnetic field. Graphs have been plotted by giving numerical values to the parameters to depict the stationary characteristics. Further, the magnetic field and rotation are found to introduce oscillatory modes which were non-existent in their absence and then the principle of exchange of stability is valid. The sufficient conditions for non-existence of overstability are also obtained.
Directory of Open Access Journals (Sweden)
Mustapha Lahmar
2015-04-01
Full Text Available On the basis of the V. K. Stokes micro-continuum theory, the effects of couple stresses on the nonlinear dynamic response of the unbalanced Jeffcott’s flexible rotor supported by layered hydrodynamic journal bearings is presented in this paper. A nonlinear transient modified Reynolds’ equation is derived and discretized by the finite element method to obtain the fluid-film pressure field as well as the film thickness by means of the implicit Euler method. The nonlinear orbits of the rotor center are determined by solving the nonlinear differential equations of motion with the explicit Euler’s scheme taking into account the flexibility of rotor. According to the obtained results, the combined effects of couple stresses due to the presence of polymer additives in lubricant and the pressure dependent viscosity on the nonlinear dynamic response of the rotor-bearing system are significant and cannot be ignored or overlooked. As expected, these effects are more noticeable for polymers characterized by higher length molecular chains.
Directory of Open Access Journals (Sweden)
M.C. Raju
2015-03-01
Full Text Available A theoretical analysis is performed to study induced magnetic field effects on free convection flow past a vertical plate. The x¯-axis is taken vertically upwards along the plate, y¯-axis normal to the plate into the fluid region. It is assumed that the plate is electrically non-conducting and the applied magnetic field is of uniform strength (H0 and perpendicular to the plate. The magnetic Reynolds number of the flow is not taken to be small enough so that the induced magnetic field is taken into account. The coupled nonlinear partial differential equations are solved by Perturbation technique and the effects of various physical parameters on velocity, temperature, and induced magnetic fields are studied through graphs and tables. Variations in Skin friction and rate of heat transfer are also studied. It is observed that an increase in magnetic parameter decreases the velocity for both water and air. It is also seen that there is a fall in induced magnetic field as magnetic Prandtl number, and magnetic field parameter increase.
Low-Reynolds number flow of a viscous fluid in a channel partially filled with a porous medium
International Nuclear Information System (INIS)
Deng, C.; Martinez, D.M.
2003-01-01
Steady flow inside a rectangular channel with wall suction and partially filled with a porous material is examined. We solve the Navier-Stokes equations in the clear fluid region of the channel and the Brinkman extended Darcy's law in the porous material. The stress jump conditions outlined by Ochoa-Tapia and Whitaker are employed at the interface between these two regions. Ochoa-Tapia and Whitaker's conditions contain an empirical constant β which is unknown a priori. In this work we propose a method to estimate β. To do so, we solve for the flow field using two different approaches. In the first approach, the flow is assumed to be of similarity form and a new asymmetric solution is reported; β is retained in this formulation. In the second approach, we re-pose the equations of motion over the entire domain by considering the porous medium as a sink-term (which can be turned on and off); β is not required in this formulation. We estimate the value of β by comparing the resulting flow fields. (author)
Lagrangian fluid description with simple applications in compressible plasma and gas dynamics
International Nuclear Information System (INIS)
Schamel, Hans
2004-01-01
The Lagrangian fluid description, in which the dynamics of fluids is formulated in terms of trajectories of fluid elements, not only presents an alternative to the more common Eulerian description but has its own merits and advantages. This aspect, which seems to be not fully explored yet, is getting increasing attention in fluid dynamics and related areas as Lagrangian codes and experimental techniques are developed utilizing the Lagrangian point of view with the ultimate goal of a deeper understanding of flow dynamics. In this tutorial review we report on recent progress made in the analysis of compressible, more or less perfect flows such as plasmas and dilute gases. The equations of motion are exploited to get further insight into the formation and evolution of coherent structures, which often exhibit a singular or collapse type behavior occurring in finite time. It is argued that this technique of solution has a broad applicability due to the simplicity and generality of equations used. The focus is on four different topics, the physics of which being governed by simple fluid equations subject to initial and/or boundary conditions. Whenever possible also experimental results are mentioned. In the expansion of a semi-infinite plasma into a vacuum the energetic ion peak propagating supersonically towards the vacuum--as seen in laboratory experiments--is interpreted by means of the Lagrangian fluid description as a relic of a wave breaking scenario of the corresponding inviscid ion dynamics. The inclusion of viscosity is shown numerically to stabilize the associated density collapse giving rise to a well defined fast ion peak reminiscent of adhesive matter. In purely convection driven flows the Lagrangian flow velocity is given by its initial value and hence the Lagrangian velocity gradient tensor can be evaluated accurately to find out the appearance of singularities in density and vorticity and the emergence of new structures such as wavelets in one
Lagrangian fluid description with simple applications in compressible plasma and gas dynamics
Schamel, Hans
2004-03-01
The Lagrangian fluid description, in which the dynamics of fluids is formulated in terms of trajectories of fluid elements, not only presents an alternative to the more common Eulerian description but has its own merits and advantages. This aspect, which seems to be not fully explored yet, is getting increasing attention in fluid dynamics and related areas as Lagrangian codes and experimental techniques are developed utilizing the Lagrangian point of view with the ultimate goal of a deeper understanding of flow dynamics. In this tutorial review we report on recent progress made in the analysis of compressible, more or less perfect flows such as plasmas and dilute gases. The equations of motion are exploited to get further insight into the formation and evolution of coherent structures, which often exhibit a singular or collapse type behavior occurring in finite time. It is argued that this technique of solution has a broad applicability due to the simplicity and generality of equations used. The focus is on four different topics, the physics of which being governed by simple fluid equations subject to initial and/or boundary conditions. Whenever possible also experimental results are mentioned. In the expansion of a semi-infinite plasma into a vacuum the energetic ion peak propagating supersonically towards the vacuum-as seen in laboratory experiments-is interpreted by means of the Lagrangian fluid description as a relic of a wave breaking scenario of the corresponding inviscid ion dynamics. The inclusion of viscosity is shown numerically to stabilize the associated density collapse giving rise to a well defined fast ion peak reminiscent of adhesive matter. In purely convection driven flows the Lagrangian flow velocity is given by its initial value and hence the Lagrangian velocity gradient tensor can be evaluated accurately to find out the appearance of singularities in density and vorticity and the emergence of new structures such as wavelets in one-dimension (1D
Formation of Hydro-acoustic Waves in Dissipative Coupled Weakly Compressible Fluids
Abdolali, A.; Kirby, J. T., Jr.; Bellotti, G.
2014-12-01
Recent advances in deep sea measurement technology provide an increasing opportunity to detect and interpret hydro-acoustic waves as a component in improved Tsunami Early Warning Systems (TEWS). For the idealized case of a homogeneous water column above a moving but otherwise rigid bottom (in terms of assessing acoustic wave interaction), the description of the infinite family of acoustic modes is characterized by local water depth at source area; i.e. the period of the first acoustic mode is given by four times the required time for sound to travel from the seabed to the surface. Spreading off from earthquake zone, the dominant spectrum is filtered and enriched by seamounts and barriers. This study focuses on the characteristics of hydro-acoustic waves generated by sudden sea bottom motion in a weakly compressible fluid coupled with an underlying sedimentary layer, where the added complexity of the sediment layer rheology leads to both the lowering of dominant spectral peaks and wave attenuation across the full spectrum. To overcome the computational difficulties of three-dimensional models, we derive a depth integrated equation valid for varying water depth and sediment thickness. Damping behavior of the two layered system is initially taken into account by introducing the viscosity of fluid-like sedimentary layer. We show that low frequency pressure waves which are precursor components of tsunamis contain information of seafloor motion.
Viscous Fingering in Deformable Systems
Guan, Jian Hui; MacMinn, Chris
2017-11-01
Viscous fingering is a classical hydrodynamic instability that occurs when an invading fluid is injected into a porous medium or a Hele-Shaw cell that contains a more viscous defending fluid. Recent work has shown that viscous fingering in a Hele-Shaw cell is supressed when the flow cell is deformable. However, the mechanism of suppression relies on a net volumetric expansion of the flow area. Here, we study flow in a novel Hele-Shaw cell consisting of a rigid bottom plate and a flexible top plate that deforms in a way that is volume-conserving. In other words, fluid injection into the flow cell leads to a local expansion of the flow area (outward displacement of the flexible surface) that must be coupled to non-local contraction (inward displacement of the flexible surface). We explore the impact of this volumetric confinement on steady viscous flow and on viscous fingering. We would like to thank EPSRC for the funding for this work.
Proposal of a critical test of the Navier-Stokes-Fourier paradigm for compressible fluid continua
Brenner, Howard
2013-01-01
A critical, albeit simple experimental and/or molecular-dynamic (MD) simulation test is proposed whose outcome would, in principle, establish the viability of the Navier-Stokes-Fourier (NSF) equations for compressible fluid continua. The latter equation set, despite its longevity as constituting the fundamental paradigm of continuum fluid mechanics, has recently been criticized on the basis of its failure to properly incorporate volume transport phenomena—as embodied in the proposed bivelocity paradigm [H. Brenner, Int. J. Eng. Sci.IJESAN0020-722510.1016/j.ijengsci.2012.01.006 54, 67 (2012)]—into its formulation. Were the experimental or simulation results found to accord, even only qualitatively, with bivelocity predictions, the temperature distribution in a gas-filled, thermodynamically and mechanically isolated circular cylinder undergoing steady rigid-body rotation in an inertial reference frame would not be uniform; rather, the temperature would be higher at the cylinder wall than along the axis of rotation. This radial temperature nonuniformity contrasts with the uniformity of the temperature predicted by the NSF paradigm for these same circumstances. Easily attainable rates of rotation in centrifuges and readily available tools for measuring the expected temperature differences render experimental execution of the proposed scheme straightforward in principle. As such, measurement—via experiment or MD simulation—of, say, the temperature difference ΔT between the gas at the wall and along the axis of rotation would provide quantitative tests of both the NSF and bivelocity hydrodynamic models, whose respective solutions for the stated set of circumstances are derived in this paper. Independently of the correctness of the bivelocity model, any temperature difference observed during the proposed experiment or simulation, irrespective of magnitude, would preclude the possibility of the NSF paradigm being correct for fluid continua, except for
Proposal of a critical test of the Navier-Stokes-Fourier paradigm for compressible fluid continua.
Brenner, Howard
2013-01-01
A critical, albeit simple experimental and/or molecular-dynamic (MD) simulation test is proposed whose outcome would, in principle, establish the viability of the Navier-Stokes-Fourier (NSF) equations for compressible fluid continua. The latter equation set, despite its longevity as constituting the fundamental paradigm of continuum fluid mechanics, has recently been criticized on the basis of its failure to properly incorporate volume transport phenomena-as embodied in the proposed bivelocity paradigm [H. Brenner, Int. J. Eng. Sci. 54, 67 (2012)]-into its formulation. Were the experimental or simulation results found to accord, even only qualitatively, with bivelocity predictions, the temperature distribution in a gas-filled, thermodynamically and mechanically isolated circular cylinder undergoing steady rigid-body rotation in an inertial reference frame would not be uniform; rather, the temperature would be higher at the cylinder wall than along the axis of rotation. This radial temperature nonuniformity contrasts with the uniformity of the temperature predicted by the NSF paradigm for these same circumstances. Easily attainable rates of rotation in centrifuges and readily available tools for measuring the expected temperature differences render experimental execution of the proposed scheme straightforward in principle. As such, measurement-via experiment or MD simulation-of, say, the temperature difference ΔT between the gas at the wall and along the axis of rotation would provide quantitative tests of both the NSF and bivelocity hydrodynamic models, whose respective solutions for the stated set of circumstances are derived in this paper. Independently of the correctness of the bivelocity model, any temperature difference observed during the proposed experiment or simulation, irrespective of magnitude, would preclude the possibility of the NSF paradigm being correct for fluid continua, except for incompressible flows.
DEFF Research Database (Denmark)
Larsen, Jon Steffen; Santos, Ilmar
2015-01-01
An efficient finite element scheme for solving the non-linear Reynolds equation for compressible fluid coupled to compliant structures is presented. The method is general and fast and can be used in the analysis of airfoil bearings with simplified or complex foil structure models. To illustrate...
International Nuclear Information System (INIS)
Feng Chaojun; Li Xinzhou
2009-01-01
We investigate the viscous Ricci dark energy (RDE) model by assuming that there is bulk viscosity in the linear barotropic fluid and the RDE. In the RDE model without bulk viscosity, the universe is younger than some old objects at certain redshifts. Since the age of the universe should be longer than any objects living in the universe, the RDE model suffers the age problem, especially when we consider the object APM 08279+5255 at z=3.91 with age t=2.1 Gyr. In this Letter, we find that once the viscosity is taken into account, this age problem is alleviated.
Nonlinear waves in bipolar complex viscous astroclouds
Karmakar, P. K.; Haloi, A.
2017-05-01
A theoretical evolutionary model to analyze the dynamics of strongly nonlinear waves in inhomogeneous complex astrophysical viscous clouds on the gravito-electrostatic scales of space and time is procedurally set up. It compositionally consists of warm lighter electrons and ions (Boltzmanian); and cold massive bi-polar dust grains (inertial fluids) alongside vigorous neutral dynamics in quasi-neutral hydrodynamic equilibrium. Application of the Sagdeev pseudo-potential method reduces the inter-coupled structure equations into a pair of intermixed forced Korteweg-de Vries-Burgers (f-KdVB) equations. The force-terms are self-consistently sourced by inhomogeneous gravito-electrostatic interplay. A numerical illustrative shape-analysis based on judicious astronomical parametric platform shows the electrostatic waves evolving as compressive dispersive shock-like eigen-modes. A unique transition from quasi-monotonic to non-monotonic oscillatory compressive shock-like patterns is found to exist. In contrast, the self-gravitational and effective perturbations grow purely as non-monotonic compressive oscillatory shock-like structures with no such transitory features. It is seen that the referral frame velocity acts as amplitude-reducing agent (stabilizing source) for the electrostatic fluctuations solely. A comparison in the prognostic light of various earlier satellite-based observations and in-situ measurements is presented. The paper ends up with synoptic highlights on the main implications and non-trivial applications in the interstellar space and cosmic plasma environments leading to bounded structure formation.
Periodic folding of viscous sheets
Ribe, Neil M.
2003-09-01
The periodic folding of a sheet of viscous fluid falling upon a rigid surface is a common fluid mechanical instability that occurs in contexts ranging from food processing to geophysics. Asymptotic thin-layer equations for the combined stretching-bending deformation of a two-dimensional sheet are solved numerically to determine the folding frequency as a function of the sheet’s initial thickness, the pouring speed, the height of fall, and the fluid properties. As the buoyancy increases, the system bifurcates from “forced” folding driven kinematically by fluid extrusion to “free” folding in which viscous resistance to bending is balanced by buoyancy. The systematics of the numerically predicted folding frequency are in good agreement with laboratory experiments.
Thermodynamic bounds for existence of normal shock in compressible fluid flow in pipes
Directory of Open Access Journals (Sweden)
SERGIO COLLE
Full Text Available Abstract The present paper is concerned with the thermodynamic theory of the normal shock in compressible fluid flow in pipes, in the lights of the pioneering works of Lord Rayleigh and G. Fanno. The theory of normal shock in pipes is currently presented in terms of the Rayleigh and Fanno curves, which are shown to cross each other in two points, one corresponding to a subsonic flow and the other corresponding to a supersonic flow. It is proposed in this paper a novel differential identity, which relates the energy flux density, the linear momentum flux density, and the entropy, for constant mass flow density. The identity so obtained is used to establish a theorem, which shows that Rayleigh and Fanno curves become tangent to each other at a single sonic point. At the sonic point the entropy reaches a maximum, either as a function of the pressure and the energy density flux or as a function of the pressure and the linear momentum density flux. A Second Law analysis is also presented, which is fully independent of the Second Law analysis based on the Rankine-Hugoniot adiabatic carried out by Landau and Lifshitz (1959.
Soni, V.; Hadjadj, A.; Roussel, O.
2017-12-01
In this paper, a fully adaptive multiresolution (MR) finite difference scheme with a time-varying tolerance is developed to study compressible fluid flows containing shock waves in interaction with solid obstacles. To ensure adequate resolution near rigid bodies, the MR algorithm is combined with an immersed boundary method based on a direct-forcing approach in which the solid object is represented by a continuous solid-volume fraction. The resulting algorithm forms an efficient tool capable of solving linear and nonlinear waves on arbitrary geometries. Through a one-dimensional scalar wave equation, the accuracy of the MR computation is, as expected, seen to decrease in time when using a constant MR tolerance considering the accumulation of error. To overcome this problem, a variable tolerance formulation is proposed, which is assessed through a new quality criterion, to ensure a time-convergence solution for a suitable quality resolution. The newly developed algorithm coupled with high-resolution spatial and temporal approximations is successfully applied to shock-bluff body and shock-diffraction problems solving Euler and Navier-Stokes equations. Results show excellent agreement with the available numerical and experimental data, thereby demonstrating the efficiency and the performance of the proposed method.
Czech Academy of Sciences Publication Activity Database
Ducomet, B.; Nečasová, Šárka
2013-01-01
Roč. 11, č. 1 (2013), s. 1350003 ISSN 0219-5305 R&D Projects: GA ČR GA201/08/0012 Institutional research plan: CEZ:AV0Z10190503 Keywords : compressible fluids * viscous * conducting fluids Subject RIV: BA - General Mathematics Impact factor: 1.500, year: 2013 http://www.worldscientific.com/doi/abs/10.1142/S0219530513500036
Viscous entrainment on hairy surfaces
Nasto, Alice; Brun, P.-T.; Hosoi, A. E.
2018-02-01
Nectar-drinking bats and honeybees have tongues covered with hairlike structures, enhancing their ability to take up viscous nectar by dipping. Using a combination of model experiments and theory, we explore the physical mechanisms that govern viscous entrainment in a hairy texture. Hairy surfaces are fabricated using laser cut molds and casting samples with polydimethylsiloxane (PDMS) elastomer. We model the liquid trapped within the texture using a Darcy-Brinkmann-like approach and derive the drainage flow solution. The amount of fluid that is entrained is dependent on the viscosity of the fluid, the density of the hairs, and the withdrawal speed. Both experiments and theory reveal an optimal hair density to maximize fluid uptake.
Energy Technology Data Exchange (ETDEWEB)
Paolucci, S.
1982-12-01
An approximation leading to anelastic equations capable of describing thermal convection in a compressible fluid is given. These equations are more general than the Oberbeck-Boussinesq equations and different than the standard anelastic equations in that they can be used for the computation of convection in a fluid with large density gradients present. We show that the equations do not contain acoustic waves, while at the same time they can still describe the propagation of internal waves. Throughout we show that the filtering of acoustic waves, within the limits of the approximation, does not appreciably alter the description of the physics.
International Nuclear Information System (INIS)
Li, X.L.
1993-01-01
Computation of three-dimensional (3-D) Rayleigh--Taylor instability in compressible fluids is performed on a MIMD computer. A second-order TVD scheme is applied with a fully parallelized algorithm to the 3-D Euler equations. The computational program is implemented for a 3-D study of bubble evolution in the Rayleigh--Taylor instability with varying bubble aspect ratio and for large-scale simulation of a 3-D random fluid interface. The numerical solution is compared with the experimental results by Taylor
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-04-20
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a non-perturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely...
CSIR Research Space (South Africa)
Heyns, Johan A
2012-06-01
Full Text Available combines a blended higher resolution scheme with the addition of an artificial compressive term to the volume-of-fluid equation. This reduces the numerical smearing of the interface associated with explicit higher resolution schemes while limiting...
1978-01-01
The proposed magnetically anchored viscous fluid damper can maintain the Skylab in a gravity-gradient stabilized mode at the anticipated reboost altitudes. The parameters influencing damper performance (and thereby affecting the degree of risk) are: (1) amount of skylab pitch bias in the orbit plane which will result from aerodynamic trim conditions of the post-reboost configuration Skylab; (2) the lowest altitude to which the post-reboost Skylab will be allowed to decay prior to the next rendezvous; (3) maximum allowable weight and size of the proposed damper in order to match shuttle/TRS mission constraints; (4) the amount of magnetic materials expected to be in the vicinity of the damper.
Pesch, L.; van der Vegt, Jacobus J.W.
2008-01-01
Using the generalized variable formulation of the Euler equations of fluid dynamics, we develop a numerical method that is capable of simulating the flow of fluids with widely differing thermodynamic behavior: ideal and real gases can be treated with the same method as an incompressible fluid. The
Influence of viscous dissipation and radiation on MHD Couette flow ...
African Journals Online (AJOL)
The overall analysis of the study of these parameters in various degrees show an increase in the velocity profile of the fluid, while radiation parameter decreases the temperature profile; viscous dissipation and Reynolds number increase the temperature profile of the fluid. Key word: Couette flow, viscous dissipation, ...
Caroff, Jildaz; Mihalea, Cristian; Da Ros, Valerio; Yagi, Takanobu; Iacobucci, Marta; Ikka, Léon; Moret, Jacques; Spelle, Laurent
2017-07-01
Recent reports have revealed a worsening of aneurysm occlusion between WEB treatment baseline and angiographic follow-up due to "compression" of the device. We utilized computational fluid dynamics (CFD) in order to determine whether the underlying mechanism of this worsening is flow related. We included data from all consecutive patients treated in our institution with a WEB for unruptured aneurysms located either at the middle cerebral artery or basilar tip. The CFD study was performed using pre-operative 3D rotational angiography. From digital subtraction follow-up angiographies patients were dichotomized into two groups: one with WEB "compression" and one without. We performed statistical analyses to determine a potential correlation between WEB compression and CFD inflow ratio. Between July 2012 and June 2015, a total of 22 unruptured middle cerebral artery or basilar tip aneurysms were treated with a WEB device in our department. Three patients were excluded from the analysis and the mean follow-up period was 17months. Eleven WEBs presented "compression" during follow-up. Interestingly, device "compression" was statistically correlated to the CFD inflow ratio (P=0.018), although not to aneurysm volume, aspect ratio or neck size. The mechanisms underlying the worsening of aneurysm occlusion in WEB-treated patients due to device compression are most likely complex as well as multifactorial. However, it is apparent from our pilot study that a high arterial inflow is, at least, partially involved. Further theoretical and animal research studies are needed to increase our understanding of this phenomenon. Copyright © 2017 Elsevier Masson SAS. All rights reserved.
Vibrational spectroscopy of shock-compressed fluid N2 and O2
International Nuclear Information System (INIS)
Schmidt, S.C.; Moore, D.S.; Shaw, M.S.; Johnson, J.D.
1987-01-01
Single-pulse multiplex coherent anti-Stokes Raman scattering (CARS) was used to observe the vibrational spectra of liquid N 2 shock-compressed to several pressures and temperatures up to 41 GPa and 5200 K and liquid O 2 shock-compressed to several pressures and temperatures up to 10 GPa and 1000 K. For N 2 , the experimental spectra were compared to synthetic spectra calculated using a semiclassical model for CARS intensities and estimated vibrational frequencies, peak Raman susceptibilities, and Raman line widths. The question of excited state populations in the shock-compressed state is addressed
Ganesh Kumar, K.; Rudraswamy, N. G.; Gireesha, B. J.; Krishnamurthy, M. R.
2017-09-01
Present exploration discusses the combined effect of viscous dissipation and Joule heating on three dimensional flow and heat transfer of a Jeffrey nanofluid in the presence of nonlinear thermal radiation. Here the flow is generated over bidirectional stretching sheet in the presence of applied magnetic field by accounting thermophoresis and Brownian motion of nanoparticles. Suitable similarity transformations are employed to reduce the governing partial differential equations into coupled nonlinear ordinary differential equations. These nonlinear ordinary differential equations are solved numerically by using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. Graphically results are presented and discussed for various parameters. Validation of the current method is proved by comparing our results with the existing results under limiting situations. It can be concluded that combined effect of Joule and viscous heating increases the temperature profile and thermal boundary layer thickness.
Dynamic compressibility of air in porous structures at audible frequencies
DEFF Research Database (Denmark)
Lafarge, Denis; Lemarinier, Pavel; Allard, Jean F.
1997-01-01
Measurements of dynamic compressibility of air-filled porous sound-absorbing materials are compared with predictions involving two parametere, the static thermal permeability k'_0 and the thermal characteristic dimension GAMMA'. Emphasis on the notion of dynamic and static thermal permeability...... of the viscous forces. Using both parameters, a simple model is constructed for the dynamic thermal permeability k', which is completely analogous to the Johnson et al. [J. Fluid Mech. vol. 176, 379 (1987)] model of dynamic viscous permeability k. The resultant modeling of dynamic compressibility provides...... predictions which are closer to the experimental results than the previously used simpler model where the compressibility is the same as in identical circular cross-sectional shaped pores, or distributions of slits, related to a given GAMMA'....
Zheng, H. W.; Shu, C.; Chew, Y. T.
2008-07-01
In this paper, an object-oriented and quadrilateral-mesh based solution adaptive algorithm for the simulation of compressible multi-fluid flows is presented. The HLLC scheme (Harten, Lax and van Leer approximate Riemann solver with the Contact wave restored) is extended to adaptively solve the compressible multi-fluid flows under complex geometry on unstructured mesh. It is also extended to the second-order of accuracy by using MUSCL extrapolation. The node, edge and cell are arranged in such an object-oriented manner that each of them inherits from a basic object. A home-made double link list is designed to manage these objects so that the inserting of new objects and removing of the existing objects (nodes, edges and cells) are independent of the number of objects and only of the complexity of O( 1). In addition, the cells with different levels are further stored in different lists. This avoids the recursive calculation of solution of mother (non-leaf) cells. Thus, high efficiency is obtained due to these features. Besides, as compared to other cell-edge adaptive methods, the separation of nodes would reduce the memory requirement of redundant nodes, especially in the cases where the level number is large or the space dimension is three. Five two-dimensional examples are used to examine its performance. These examples include vortex evolution problem, interface only problem under structured mesh and unstructured mesh, bubble explosion under the water, bubble-shock interaction, and shock-interface interaction inside the cylindrical vessel. Numerical results indicate that there is no oscillation of pressure and velocity across the interface and it is feasible to apply it to solve compressible multi-fluid flows with large density ratio (1000) and strong shock wave (the pressure ratio is 10,000) interaction with the interface.
Energy Technology Data Exchange (ETDEWEB)
De Rossi, Filippo; Mastrullo, Rita; Mazzei, Pietro [Naples Univ. (Italy)
1993-05-01
A software package for both the computation of thermodynamic properties and the analysis of the usual vapour compression plant schemes is a useful tool for air conditioning and refrigeration researchers and manufacturers. At present, it could make an important contribution to the search for CFC substitutes; in fact, comparisons between two or more working fluids could be accomplished more easily. A program created by the authors is presented by means of some demonstrative diagrams referring to a comparison between the ''ozone killer'' R12 and its substitute R134a. An R134a exergy-enthalpy chart is also provided. (Author)
Nguyen, Quynhhoa T; Wong, Benjamin L; Chun, June; Yoon, Yeoung C; Talke, Frank E; Sah, Robert L
2010-06-18
During joint articulation, cartilage is subjected to compression, shear, and sliding, mechanical factors that regulate and affect cartilage metabolism. The objective of this study was to use an in vitro material-on-cartilage shear test to elucidate the effects of counter-surface roughness (Polished, Mildly rough, and Rough), lubricants (phosphate buffered saline (PBS) and bovine synovial fluid (bSF)), and compression offset on the shearing and sliding of normal human talar cartilage under dynamic lateral displacement. Peak shear stress (sigma(xz,m)) and strain (E(xz,m)) increased with increasing platen roughness and compression offset, and were 30% higher with PBS than with bSF. Compared to PBS, bSF was more effective as a lubricant for P than for M and R platens as indicated by the higher reduction in kinetic friction coefficient (-60% vs. -20% and -19%, respectively), sigma(xz,m) (-50% vs. -14% and -17%) and E(xz,m) (-54% vs. -19% and -17%). Cartilage shear and sliding were evident for all counter-surfaces either at low compression offset (10%) or with high lateral displacement (70%), regardless of lubricant. An increase in tissue shear occurred with either increased compression offset or increased surface roughness. This material and biomechanical test system allow control of cartilage sigma(xz,m) and E(xz,m), and hence, sliding magnitude, for an imposed lateral displacement. It therefore can facilitate study of cartilage mechanobiological responses to distinct regimes of cartilage loading and articulation, such as shear with variable amounts of sliding. Copyright (c) 2010 Elsevier Ltd. All rights reserved.
Multiple scales and singular limits for compressible rotating fluids with general initial data
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Novotný, A.
2014-01-01
Roč. 39, č. 6 (2014), s. 1104-1127 ISSN 0360-5302 Keywords : compressible Navier-Stokes equations * multiple scales * oscillatory integrals Subject RIV: BA - General Mathematics Impact factor: 1.013, year: 2014 http://www.tandfonline.com/doi/full/10.1080/03605302.2013.856917
DGFEM for dynamical systems describing interaction of compressible fluid and structures
Czech Academy of Sciences Publication Activity Database
Feistauer, M.; Hasnedlová, J.; Horáček, Jaromír; Kosík, A.; Kučera, V.
2013-01-01
Roč. 254, December 2013 (2013), s. 17-30 ISSN 0377-0427 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : compressible Navier–Stokes equations * dynamic elasticity equations * newmark method * flow-induced vibrations of vocal folds Subject RIV: BI - Acoustics Impact factor: 1.077, year: 2013
Directory of Open Access Journals (Sweden)
Janet Douglass
2017-09-01
Full Text Available When normal lymphatic function is hampered, imperceptible subcutaneous edema can develop and progress to overt lymphedema. Low-cost reliable devices for objective assessment of lymphedema are well accepted in clinical practice and research on breast-cancer related lymphedema but are untested in populations with lymphatic filariasis (LF. This is a cross-sectional analysis of baseline data in a longitudinal study on asymptomatic, LF antigen-positive and -negative young people in Myanmar. Rapid field screening was used to identify antigen-positive cases and a group of antigen-negative controls of similar age and gender were invited to continue in the study. Tissue compressibility was assessed with three tissue tonometers, and free fluids were assessed using bio-impedance spectroscopy (BIS. Infection status was confirmed by Og4C3 antigen assay. At baseline (n = 98, antigen-positive cases had clinically relevant increases in tissue compressibility at the calf using a digital Indurometer (11.1%, p = 0.021, and in whole-leg free fluid using BIS (9.2%, p = 0.053. Regression analysis for moderating factors (age, gender, hydration reinforced the between-infection group differences. Results demonstrate that sub-clinical changes associated with infection can be detected in asymptomatic cases. Further exploration of these low-cost devices in clinical and research settings on filariasis-related lymphedema are warranted.
A Level-set based framework for viscous simulation of particle-laden supersonic flows
Das, Pratik; Sen, Oishik; Jacobs, Gustaaf; Udaykumar, H. S.
2017-06-01
Particle-laden supersonic flows are important in natural and industrial processes, such as, volcanic eruptions, explosions, pneumatic conveyance of particle in material processing etc. Numerical study of such high-speed particle laden flows at the mesoscale calls for a numerical framework which allows simulation of supersonic flow around multiple moving solid objects. Only a few efforts have been made toward development of numerical frameworks for viscous simulation of particle-fluid interaction in supersonic flow regime. The current work presents a Cartesian grid based sharp-interface method for viscous simulations of interaction between supersonic flow with moving rigid particles. The no-slip boundary condition is imposed at the solid-fluid interfaces using a modified ghost fluid method (GFM). The current method is validated against the similarity solution of compressible boundary layer over flat-plate and benchmark numerical solution for steady supersonic flow over cylinder. Further validation is carried out against benchmark numerical results for shock induced lift-off of a cylinder in a shock tube. 3D simulation of steady supersonic flow over sphere is performed to compare the numerically obtained drag co-efficient with experimental results. A particle-resolved viscous simulation of shock interaction with a cloud of particles is performed to demonstrate that the current method is suitable for large-scale particle resolved simulations of particle-laden supersonic flows.
Viscous fingering with permeability heterogeneity
International Nuclear Information System (INIS)
Tan, C.; Homsy, G.M.
1992-01-01
Viscous fingering in miscible displacements in the presence of permeability heterogeneities is studied using two-dimensional simulations. The heterogeneities are modeled as stationary random functions of space with finite correlation scale. Both the variance and scale of the heterogeneities are varied over modest ranges. It is found that the fingered zone grows linearly in time in a fashion analogous to that found in homogeneous media by Tan and Homsy [Phys. Fluids 31, 1330 (1988)], indicating a close coupling between viscous fingering on the one hand and flow through preferentially more permeable paths on the other. The growth rate of the mixing zone increases monotonically with the variance of the heterogeneity, as expected, but shows a maximum as the correlation scale is varied. The latter is explained as a ''resonance'' between the natural scale of fingers in homogeneous media and the correlation scale
Computation of Viscous Incompressible Flows
Kwak, Dochan
2011-01-01
This monograph is intended as a concise and self-contained guide to practitioners and graduate students for applying approaches in computational fluid dynamics (CFD) to real-world problems that require a quantification of viscous incompressible flows. In various projects related to NASA missions, the authors have gained CFD expertise over many years by developing and utilizing tools especially related to viscous incompressible flows. They are looking at CFD from an engineering perspective, which is especially useful when working on real-world applications. From that point of view, CFD requires two major elements, namely methods/algorithm and engineering/physical modeling. As for the methods, CFD research has been performed with great successes. In terms of modeling/simulation, mission applications require a deeper understanding of CFD and flow physics, which has only been debated in technical conferences and to a limited scope. This monograph fills the gap by offering in-depth examples for students and engine...
Laser driven single shock compression of fluid deuterium from 45 to 220 GPa
Energy Technology Data Exchange (ETDEWEB)
Hicks, D; Boehly, T; Celliers, P; Eggert, J; Moon, S; Meyerhofer, D; Collins, G
2008-03-23
The compression {eta} of liquid deuterium between 45 and 220 GPa under laser-driven shock loading has been measured using impedance matching to an aluminum (Al) standard. An Al impedance match model derived from a best fit to absolute Hugoniot data has been used to quantify and minimize the systematic errors caused by uncertainties in the high-pressure Al equation of state. In deuterium below 100 GPa results show that {eta} {approx_equal} 4.2, in agreement with previous impedance match data from magnetically-driven flyer and convergent-explosive shock wave experiments; between 100 and 220 GPa {eta} reaches a maximum of {approx}5.0, less than the 6-fold compression observed on the earliest laser-shock experiments but greater than expected from simple extrapolations of lower pressure data. Previous laser-driven double-shock results are found to be in good agreement with these single-shock measurements over the entire range under study. Both sets of laser-shock data indicate that deuterium undergoes an abrupt increase in compression at around 110 GPa.
Pasquariello, Vito; Hammerl, Georg; Örley, Felix; Hickel, Stefan; Danowski, Caroline; Popp, Alexander; Wall, Wolfgang A.; Adams, Nikolaus A.
2016-02-01
We present a loosely coupled approach for the solution of fluid-structure interaction problems between a compressible flow and a deformable structure. The method is based on staggered Dirichlet-Neumann partitioning. The interface motion in the Eulerian frame is accounted for by a conservative cut-cell Immersed Boundary method. The present approach enables sub-cell resolution by considering individual cut-elements within a single fluid cell, which guarantees an accurate representation of the time-varying solid interface. The cut-cell procedure inevitably leads to non-matching interfaces, demanding for a special treatment. A Mortar method is chosen in order to obtain a conservative and consistent load transfer. We validate our method by investigating two-dimensional test cases comprising a shock-loaded rigid cylinder and a deformable panel. Moreover, the aeroelastic instability of a thin plate structure is studied with a focus on the prediction of flutter onset. Finally, we propose a three-dimensional fluid-structure interaction test case of a flexible inflated thin shell interacting with a shock wave involving large and complex structural deformations.
Energy Technology Data Exchange (ETDEWEB)
Tautz, R. C., E-mail: robert.c.tautz@gmail.com [Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin (Germany); Lerche, I., E-mail: lercheian@yahoo.com [Institut für Geowissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther-Universität Halle, D-06099 Halle (Germany)
2015-11-15
This note considers the evolution of steady isothermal flow across a uniform magnetic field from an analytic standpoint. This problem is of concern in developments of magnetic fields in the solar corona and for prominence dynamics. Limiting behaviors are obtained to the nonlinear equation describing the flow depending on the value of a single parameter. For the situation where the viscous drag is a small correction to the inviscid flow limiting structures are also outlined. The purpose of the note is to show how one can evaluate some of the analytic properties of the highly nonlinear equation that are of use in considering the numerical evolution as done in Low and Egan [Phys. Plasmas 21, 062105 (2014)].
Energy Technology Data Exchange (ETDEWEB)
Goubel-Lenoel, A
1999-10-01
In order to provide complementary means for measurement of water levels in pressurized vessels of nuclear reactors, the possibilities of an immersed torsional wave sensor are being looked into. It has already been modeled, considering an incompressible fluid. Yet, because the fluid can turn into a two-phase fluid, we have investigated how to extend the existing model. As a first step, we have taken into account the compressibility of the surrounding fluid. We focus on a cylindrical waveguide with an elliptic cross-section. Its transverse dimensions are small compared with its length and the wavelengths in the fluid. We start with the elasticity equations for the waveguide. Then, from the exact expression of the pressure exerted by the fluid on the waveguide boundary, a long wavelength approximation is obtained. We end by applying Hamilton's principle of energy conservation, which leads to an approximate equation governing the fluid-loaded waveguide motion, and to an expression of the apparent phase velocity of the torsional wave in the immersed waveguide. Finally, fluid level measurement is possible. Some simulations are made, highlighting the influence of the compressibility. (author)
CSIR Research Space (South Africa)
Malan, AG
2011-08-01
Full Text Available to modelling both forced convection as well as heat transfer and fluid flow through heterogeneous saturated porous materials via an edge-based finite volume discretization scheme. A volume-averaged set of local thermal disequilibrium governing equations...
Incompressible limit of compressible Navier-Stokes equations
International Nuclear Information System (INIS)
Bessaih, H.
1994-01-01
In this paper we study the system which describes the motion of compressible viscous fluid in a bounded domain Ω of R 3 . When we introduce a parameter λ, that is the inverse of the Mach number, we prove, under small initial data and external force (for barotropic flows), that the solution of Navier-Stokes equations is the incompressible limit of the solution of compressible Navier-Stokes equations, as the Mach number becomes small. For this, we show the existence of a solution verifying estimates independent of λ. Compactness argument allow us to pass to the limit on λ in the nonlinear terms. (author). 17 refs
Numerical simulation of fluid-structure interaction of compressible flow and elastic structure
Czech Academy of Sciences Publication Activity Database
Hasnedlová, J.; Feistauer, M.; Horáček, Jaromír; Kosík, A.; Kučera, V.
2013-01-01
Roč. 95, Suppl 1 (2013), s. 343-361 ISSN 0010-485X R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional research plan: CEZ:AV0Z20760514 Institutional support: RVO:61388998 Keywords : fluid–structure interaction * compressible flow * discontinuous Galerkin finite element method * coupling algorithms Subject RIV: BI - Acoustics Impact factor: 1.055, year: 2013 http://link.springer.com/article/10.1007%2Fs00607-012-0240-x
International Nuclear Information System (INIS)
Ricard, J.
1979-01-01
In the relativity theory, the variation of a certain amount of energy supplied to a body, according to its speed, has been a matter of controversy. We study this variation either for a fluid that is submitted by a compression, or for a gas receiving heat from outward. It is shown that the problem is solved by a simple matter of definition of the energy received in the system of coordinate where the body is moving. Besides, we establish the impulse-energy tensor for a compressible fluid [fr
International Nuclear Information System (INIS)
Cowie, L.L.
1981-01-01
In this, the second paper of a series on the galactodynamics of the cloudy interstellar medium, we consider the response of such a gas to a forcing potential in the tight-winding density wave theory. The cloud fluid is treated in the hydrodynamic limit with an equation of state which softens at high densities. It is shown that in the inner regions of the galaxy, cooling of the cloud fluid in the arms can result in gravitational instability and the formation of large bound complexes of clouds which we identify with the giant molecular clouds (GMCs). Masses dimensions, distributions, and scale heights of the GMCs are predicted by the theory. It is suggested that the interstellar gas density in the disk is regulated by the gravitational instability mechanism in the arms which siphons material into star formation. Implications for the evolution of individual GMCs and for galactic morphology are discussed
Analysis of a Compressible Fluid Soft Recoil (CFSR) Concept Applied to a 155 MM Howitzer
1979-03-01
Nitrile or Buna-N ( NBR ) rubber with ’ backup rings of nylotron. HITRILE NVLOTRON Piston seals An unresolved problem is that the coefficient of...fluid at atmospheric pressure Poisson’s ratio for Nitrile rubber dynamic coefficient of friction for rubber mass of recoiling parts weight of...Greene, tweed 5 Co. Palmetto catalog.) 43 [i^ - 0.50 = coefficient of friction (An approximate figure for rubber supplied by RIA Rubber
An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows
International Nuclear Information System (INIS)
Pantano, C.; Saurel, R.; Schmitt, T.
2017-01-01
Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-known pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. As a result, the combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement.
Delayed Capillary Breakup of Falling Viscous Jets
Javadi, A.; Eggers, J.; Bonn, D.; Habibi, M.; Ribe, N.M.
2013-01-01
Thin jets of viscous fluid like honey falling from capillary nozzles can attain lengths exceeding 10 m before breaking up into droplets via the Rayleigh-Plateau (surface tension) instability. Using a combination of laboratory experiments and WKB analysis of the growth of shape perturbations on a jet
Barth, Timothy J.; Chan, Tony F.; Tang, Wei-Pai
1998-01-01
This paper considers an algebraic preconditioning algorithm for hyperbolic-elliptic fluid flow problems. The algorithm is based on a parallel non-overlapping Schur complement domain-decomposition technique for triangulated domains. In the Schur complement technique, the triangulation is first partitioned into a number of non-overlapping subdomains and interfaces. This suggests a reordering of triangulation vertices which separates subdomain and interface solution unknowns. The reordering induces a natural 2 x 2 block partitioning of the discretization matrix. Exact LU factorization of this block system yields a Schur complement matrix which couples subdomains and the interface together. The remaining sections of this paper present a family of approximate techniques for both constructing and applying the Schur complement as a domain-decomposition preconditioner. The approximate Schur complement serves as an algebraic coarse space operator, thus avoiding the known difficulties associated with the direct formation of a coarse space discretization. In developing Schur complement approximations, particular attention has been given to improving sequential and parallel efficiency of implementations without significantly degrading the quality of the preconditioner. A computer code based on these developments has been tested on the IBM SP2 using MPI message passing protocol. A number of 2-D calculations are presented for both scalar advection-diffusion equations as well as the Euler equations governing compressible fluid flow to demonstrate performance of the preconditioning algorithm.
Donkov, Sava; Stefanov, Ivan Z.
2018-03-01
We have set ourselves the task of obtaining the probability distribution function of the mass density of a self-gravitating isothermal compressible turbulent fluid from its physics. We have done this in the context of a new notion: the molecular clouds ensemble. We have applied a new approach that takes into account the fractal nature of the fluid. Using the medium equations, under the assumption of steady state, we show that the total energy per unit mass is an invariant with respect to the fractal scales. As a next step we obtain a non-linear integral equation for the dimensionless scale Q which is the third root of the integral of the probability distribution function. It is solved approximately up to the leading-order term in the series expansion. We obtain two solutions. They are power-law distributions with different slopes: the first one is -1.5 at low densities, corresponding to an equilibrium between all energies at a given scale, and the second one is -2 at high densities, corresponding to a free fall at small scales.
Buckling and stretching of thin viscous sheets
O'Kiely, Doireann; Breward, Chris; Griffiths, Ian; Howell, Peter; Lange, Ulrich
2016-11-01
Thin glass sheets are used in smartphone, battery and semiconductor technology, and may be manufactured by producing a relatively thick glass slab and subsequently redrawing it to a required thickness. The resulting sheets commonly possess undesired centerline ripples and thick edges. We present a mathematical model in which a viscous sheet undergoes redraw in the direction of gravity, and show that, in a sufficiently strong gravitational field, buckling is driven by compression in a region near the bottom of the sheet, and limited by viscous resistance to stretching of the sheet. We use asymptotic analysis in the thin-sheet, low-Reynolds-number limit to determine the centerline profile and growth rate of such a viscous sheet.
Czech Academy of Sciences Publication Activity Database
Stachiv, Ivo; Fang, T.-H.; Chen, T.-H.
2015-01-01
Roč. 5, č. 11 (2015), s. 1-14, č. článku 117140. ISSN 2158-3226 R&D Projects: GA ČR GC15-13174J Institutional support: RVO:68378271 Keywords : nanomechanical resonators * carbon nanotubes * tensile force * real-time * frequency * spectrometry * liquid Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.444, year: 2015
Hansen, J S; Daivis, Peter J; Todd, B D
2009-10-01
In this paper we present equilibrium molecular-dynamics results for the shear, rotational, and spin viscosities for fluids composed of linear molecules. The density dependence of the shear viscosity follows a stretched exponential function, whereas the rotational viscosity and the spin viscosities show approximately power-law dependencies. The frequency-dependent shear and spin viscosities are also studied. It is found that viscoelastic behavior is first manifested in the shear viscosity and that the real part of the spin viscosities features a maximum for nonzero frequency. The calculated transport coefficients are used together with the extended Navier-Stokes equations to investigate the effect of the coupling between the intrinsic angular momentum and linear momentum for highly confined fluids. Both steady and oscillatory flows are studied. It is shown, for example, that the fluid flow rate for Poiseuille flow is reduced by up to 10% in a 2 nm channel for a buta-triene fluid at density 236 kg m(-3) and temperature 306 K. The coupling effect may, therefore, become very important for nanofluidic applications.
Variational form for a viscous plasma
International Nuclear Information System (INIS)
Ishida, A.; Steinhauer, L.C.; Berk, H.L.
1991-01-01
The variational formulation for a fluid plasma including the parallel and gyroviscosities is developed using the basic approach of Berk et al. [Phys. Fluids 24, 2245 (1981)]. The equivalence of the variational problem to the original viscous fluid equations of motion is shown. The theory is developed for an axisymmetric plasma with no magnetic field in the azimuthal direction and therefore applies to field-reversed configurations and axisymmetric mirrors. This theory offers the advantage of describing both parallel and transverse ion kinetic effects within the simplicity afforded by a variational fluid model
Directory of Open Access Journals (Sweden)
Zeeshan Khan
Full Text Available Modern optical fibers require a double-layer coating on the glass fiber in order to provide protection from signal attenuation and mechanical damage. The most important plastic resins used in wires and optical fibers are plastic polyvinyl chloride (PVC and low and high density polyethylene (LDPE/HDPE, nylon and Polysulfone. One of the most important things which affect the final product after processing is the design of the coating die. In the present study, double-layer optical fiber coating is performed using melt polymer satisfying Oldroyd 8-constant fluid model in a pressure type die with the effect of magneto-hydrodynamic (MHD. Wet-on-wet coating process is applied for double-layer optical fiber coating. The coating process in the coating die is modeled as a simple two-layer Couette flow of two immiscible fluids in an annulus with an assigned pressure gradient. Based on the assumptions of fully developed laminar and MHD flow, the Oldroyd 8-constant model of non-Newtonian fluid of two immiscible resin layers is modeled. The governing nonlinear equations are solved analytically by the new technique of Optimal Homotopy Asymptotic Method (OHAM. The convergence of the series solution is established. The results are also verified by the Adomian Decomposition Method (ADM. The effect of important parameters such as magnetic parameter Mi, the dilatant constant α, the Pseodoplastic constant β, the radii ratio δ, the pressure gradient Ω, the speed of fiber optics V, and the viscosity ratio κ on the velocity profiles, thickness of coated fiber optics, volume flow rate, and shear stress on the fiber optics are investigated. At the end the result of the present work is also compared with the experimental results already available in the literature by taking non-Newtonian parameters tends to zero. Keywords: Non-Newtonian fluid, Oldroyd 8-constant fluid, MHD flow, Double-layer fiber coating, OHAM, ADM, Wet-on-wet coating process
Energy Technology Data Exchange (ETDEWEB)
Zhou, Yijie [ORNL; Lim, Hyun-Kyung [ORNL; de Almeida, Valmor F [ORNL; Navamita, Ray [State University of New York, Stony Brook; Wang, Shuqiang [State University of New York, Stony Brook; Glimm, James G [ORNL; Li, Xiao-lin [State University of New York, Stony Brook; Jiao, Xiangmin [ORNL
2012-06-01
This progress report describes the development of a front tracking method for the solution of the governing equations of motion for two-phase micromixing of incompressible, viscous, liquid-liquid solvent extraction processes. The ability to compute the detailed local interfacial structure of the mixture allows characterization of the statistical properties of the two-phase mixture in terms of droplets, filaments, and other structures which emerge as a dispersed phase embedded into a continuous phase. Such a statistical picture provides the information needed for building a consistent coarsened model applicable to the entire mixing device. Coarsening is an undertaking for a future mathematical development and is outside the scope of the present work. We present here a method for accurate simulation of the micromixing dynamics of an aqueous and an organic phase exposed to intense centrifugal force and shearing stress. The onset of mixing is the result of the combination of the classical Rayleigh- Taylor and Kelvin-Helmholtz instabilities. A mixing environment that emulates a sector of the annular mixing zone of a centrifugal contactor is used for the mathematical domain. The domain is small enough to allow for resolution of the individual interfacial structures and large enough to allow for an analysis of their statistical distribution of sizes and shapes. A set of accurate algorithms for this application requires an advanced front tracking approach constrained by the incompressibility condition. This research is aimed at designing and implementing these algorithms. We demonstrate verification and convergence results for one-phase and unmixed, two-phase flows. In addition we report on preliminary results for mixed, two-phase flow for realistic operating flow parameters.
Entropy Stable Summation-by-Parts Formulations for Compressible Computational Fluid Dynamics
Carpenter, M.H.
2016-11-09
A systematic approach based on a diagonal-norm summation-by-parts (SBP) framework is presented for implementing entropy stable (SS) formulations of any order for the compressible Navier–Stokes equations (NSE). These SS formulations discretely conserve mass, momentum, energy and satisfy a mathematical entropy equality for smooth problems. They are also valid for discontinuous flows provided sufficient dissipation is added at shocks and discontinuities to satisfy an entropy inequality. Admissible SBP operators include all centred diagonal-norm finite-difference (FD) operators and Legendre spectral collocation-finite element methods (LSC-FEM). Entropy stable multiblock FD and FEM operators follows immediately via nonlinear coupling operators that ensure conservation, accuracy and preserve the interior entropy estimates. Nonlinearly stable solid wall boundary conditions are also available. Existing SBP operators that lack a stability proof (e.g. weighted essentially nonoscillatory) may be combined with an entropy stable operator using a comparison technique to guarantee nonlinear stability of the pair. All capabilities extend naturally to a curvilinear form of the NSE provided that the coordinate mappings satisfy a geometric conservation law constraint. Examples are presented that demonstrate the robustness of current state-of-the-art entropy stable SBP formulations.
Densimetry in compressed fluids by combining hydrostatic weighing and magnetic levitation
International Nuclear Information System (INIS)
Masui, R.; Haynes, W.M.; Chang, R.F.; Davis, H.A.; Sengers, J.M.H.L.
1984-01-01
A magnetic suspension densimeter is described that has been built for measuring the density of compressed liquids at pressures up to 15 MPa in the temperature range 20 0 --200 0 C with an uncertainty of 0.1%. The densimeter combines the principle of magnetic levitation of a buoy with that of liquid density determination by hydrostatic weighing. To accomplish this, the support coil is suspended from an electronic balance, and the balance readings are recorded (1) with the buoy at rest, and (2) with the buoy in magnetic suspension. Details are given of the construction of the cell, coil, buoy, and thermostat. The procedure is described by which cell and buoy are aligned so that the suspended buoy does not touch the cell wall. Test data on the densities of seven different liquids were obtained at room temperature. They agree with reliable literature values to within 0.1%. In a separate experiment, the bulk thermal expansion coefficient of the buoy material was determined. This experiment and its results are also given here
One-dimensional reduction of viscous jets. II. Applications
Pitrou, Cyril
2018-04-01
In a companion paper [Phys. Rev. E 97, 043115 (2018), 10.1103/PhysRevE.97.043115], a formalism allowing to describe viscous fibers as one-dimensional objects was developed. We apply it to the special case of a viscous fluid torus. This allows to highlight the differences with the basic viscous string model and with its viscous rod model extension. In particular, an elliptic deformation of the torus section appears because of surface tension effects, and this cannot be described by viscous string nor viscous rod models. Furthermore, we study the Rayleigh-Plateau instability for periodic deformations around the perfect torus, and we show that the instability is not sufficient to lead to the torus breakup in several droplets before it collapses to a single spherical drop. Conversely, a rotating torus is dynamically attracted toward a stationary solution, around which the instability can develop freely and split the torus in multiple droplets.
On the motion of a compressible fluid in a rotating cylinder
International Nuclear Information System (INIS)
Brouwers, J.J.H.
1976-06-01
The secondary flow of an incompressible fluid or a perfect gas in a rotating cylinder is taken as a small perturbation on the isothermal state of rigid body rotation. Three types of flow are identified by increasing length-to-radius ratio L. These correspond to Esup(1/2) -1 and E -1 approximately L, where E is the Ekman number based on the radius and taken to be small. In the first range a geostrophic flow in the interior extended by Ekman layers near the end caps and Stewartson layers near the cylinder wall is found. For L approximately Esup(-1/2) and L approximately E -1 both Stewartson layers successively expand to the interior. For L approximately> E -1 radial diffusion of momentum is an important parameter describing the flow in the main section of the cylinder. For the perfect gas, special attention is focussed on strong radial density gradients. The modified Ekman number Esub(m) based on the density at the cylinder wall and on the density scale height is taken to be small. Increasing the ratio of the length to the radial density scale height Lsub(m) again three types of flow are distinguished. These correspond to Esub(m)sup(1/2) -1 and Esub(m)sup(-1) approximately Lsub(m). Compared to the incompressible fluid, two essential differences are found. (i) An inviscid flow characteristic for the first range is only observed in a limited region near the cylinder wall. Diffusive processes are important in the core of the cylinder. (ii) A change of the flow type appears when both Stewartson layers successively expand over the small radial density scale height. Diffusive regions come up from the centre of the cylinder and join. A change of the flow type appears at relatively small values of L. The theory discusses the efficiency of gas ultracentrifuges for isotope separation
Czech Academy of Sciences Publication Activity Database
Nečasová, Šárka; Wolf, J.
2016-01-01
Roč. 36, č. 3 (2016), s. 1539-1562 ISSN 1078-0947 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : incompressible fluid * motion of rigid body * strong solutions Subject RIV: BA - General Mathematics Impact factor: 1.099, year: 2016 http://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=11589
Theory of the shock process in dense fluids
International Nuclear Information System (INIS)
Wallace, D.C.
1991-01-01
A shock is assumed to be a steady plane wave, and irreversible thermodynamics is assumed valid. The fluid is characterized by heat conduction and by viscous or viscoelastic response, according to the strain rate. It is shown that setting the viscosity zero produces a solution which constitutes a lower bound through the shock process for the shear stress, and upper bounds for the temperature, entropy, pressure, and heat current. It is shown that there exists an upper bound to the dynamic stresses which can be achieved during shock compression, that this bound corresponds to a purely elastic response of the fluid, and that solution for the shock process along this bound constitutes lower bounds for the temperature and entropy. It is shown that a continuous steady shock is possible only if the heat current is positive and the temperature is an increasing function of compression almost everywhere. In his theory of shocks in gases, Rayleigh showed that there is a maximum shock strength for which a continuous steady solution can exist with heat conduction but without viscosity. Two more limits are shown to exist for dense fluids, based on the fluid response in the leading edge of the shock: for shocks at the overdriven threshold and above, no solution is possible without heat transport; for shocks near the viscous fluid limit and above, viscous fluid theory is not valid, and the fluid response in the leading edge of the shock is approximately that of a nonplastic solid. The viscous fluid limit is estimated to be 13 kbar for water and 690 kbar for mercury
A Blast Wave Model With Viscous Corrections
Yang, Z.; Fries, R. J.
2017-04-01
Hadronic observables in the final stage of heavy ion collision can be described well by fluid dynamics or blast wave parameterizations. We improve existing blast wave models by adding shear viscous corrections to the particle distributions in the Navier-Stokes approximation. The specific shear viscosity η/s of a hadron gas at the freeze-out temperature is a new parameter in this model. We extract the blast wave parameters with viscous corrections from experimental data which leads to constraints on the specific shear viscosity at kinetic freeze-out. Preliminary results show η/s is rather small.
A Blast Wave Model With Viscous Corrections
International Nuclear Information System (INIS)
Yang, Z; Fries, R J
2017-01-01
Hadronic observables in the final stage of heavy ion collision can be described well by fluid dynamics or blast wave parameterizations. We improve existing blast wave models by adding shear viscous corrections to the particle distributions in the Navier-Stokes approximation. The specific shear viscosity η/s of a hadron gas at the freeze-out temperature is a new parameter in this model. We extract the blast wave parameters with viscous corrections from experimental data which leads to constraints on the specific shear viscosity at kinetic freeze-out. Preliminary results show η/s is rather small. (paper)
International Nuclear Information System (INIS)
Gawusu, S.
2015-07-01
Oil extraction represents an important investment and the control of a rational exploitation of a field means mastering various scientific techniques including the understanding of the dynamics of fluids in place. This thesis presents a theoretical investigation of the dynamic behaviour of an oil reservoir during its exploitation. The study investigated the dynamics of fluid flow patterns in a homogeneous oil reservoir using the Radial Diffusivity Equation (RDE) as well as two phase oil-water flow equations. The RDE model was solved analytically and numerically for pressure using the Constant Terminal Rate Solution (CTRS) and the fully implicit Finite Difference Method (FDM) respectively. The mathematical derivations of the models and their solution procedures were presented to allow for easy utilization of the techniques for reservoir and engineering applications. The study predicted that the initial oil reservoir pressure will be able to do the extraction for a very long time before any other recovery method will be used to aid in the extraction process depending on the rate of production. Reservoir simulation describing a one dimensional radial flow of a compressible fluid in porous media may be adequately performed using ordinary laptop computers as revealed by the study. For the simulation of MATLAB, the case of the Jubilee Fields, Tano Basin was studied, an algorithm was developed for the simulation of pressure in the reservoir. It ensues from the analysis of the plots of pressure vrs time and space that the Pressure Transient Analysis (PTA) was duly followed. The approximate solutions of the analytical and numerical solutions to the Radial Diffusivity Equation (RDE) were in excellent agreement, thus the reservoir simulation model developed can be used to describe typical pressure-time relationships that are used in conventional Pressure Transient Analysis (PTA). The study was extended to two phase oil-water flow in reservoirs. The flow of fluids in multi
Interpretation of Fermion system equilibration by energy fluid motion
International Nuclear Information System (INIS)
Jang, S.
1990-01-01
We study the equilibration of fermion system with the help of both linear and non-linear master equations which are originated from the extended time-dependent Hartree-Fock equation of motion. We show how the non-linear master equation for nucleon occupation number transforms into the Navier-Stokes type of one dimensional equation for non-stationary flow of a compressible and viscous fluid. Physical consequences of these equations are investigated by providing illustrative examples
The thinning of viscous liquid threads.
Castrejon-Pita, J. Rafael; Castrejon-Pita, Alfonso A.; Hutchings, Ian M.
2012-11-01
The thinning neck of dripping droplets is studied experimentally for viscous Newtonian fluids. High speed imaging is used to measure the minimum neck diameter in terms of the time τ to breakup. Mixtures of water and glycerol with viscosities ranging from 20 to 363 mPa s are used to model the Newtonian behavior. The results show the transition from potential to inertial-viscous regimes occurs at the predicted values of ~Oh2. Before this transition the neck contraction rate follows the inviscid scaling law ~τ 2 / 3 . After the transition, the neck thinning tends towards the linear viscous scaling law ~ τ . Project supported by the EPSRC-UK (EP/G029458/1) and Cambridge-KACST.
Defining the best parallelization strategy for a diphasic compressible fluid mechanics code
International Nuclear Information System (INIS)
Berthou, Jean-Yves; Fayolle, Eric; Faucher, Eric; Scliffet, Laurent
2000-01-01
Nuclear plants use steam generator safety valves in order to regulate possible large pressure variations of fluids. In case of an incident these valves may be fed with pressurized liquid water (for instance a pressure of 9 MPa at a temperature of 300degC). When a pressurized liquid is submitted to a strong pressure drop, it will start evaporating. This phenomena is called flashing. Z. Bilicki and co-authors proposed the homogeneous relaxation model (HRM) to compute critical flashing water flows. Its computation in the case of non stationary one-dimensional flashing flows has been carried out with the development of a dedicated time dependent Finite Volume scheme based on a simplified version of the Godunov approach. Electricite De France Research and Development division have developed a monodimensional implementation of the HRM model: ECOSS, a 11000 lines FORTRAN 90. Applied to a shock tube test case with a 20000 elements monodimensional mesh, the simulation of the physical phenomenon during 2.5 seconds requires at least 100 days of computation on a SUN Sparc-Ultra60. This execution time justifies the ECOSS parallelization. Furthermore, we plan a modeling on 2D meshes for the next few years. Knowing that multiplying the mesh dimension by a factor 10 multiplies the execution time by a factor 100, ECOSS would take years of computation with small 2D meshes (1000 x 1000) on a conventional workstation. This paper describes the parallelization analysis we have conducted and we presents the experimental results we have obtained applying different programming model (MPI, OpenMP, HPF) on various platforms (a Compaq Proliant 6000 4 processors, a Cray T3E-750 300 processors, a HP class V 16 processors, a SGI Origin2000 32 processors, a cluster of PCs and a COMPAQ SC 232 processors). These experimental results will be discussed according to the following criteria: efficiency, salability, maintainability, developing costs and portability. As a conclusion, we will present the
Defining the best parallelization strategy for a diphasic compressible fluid mechanics code
Energy Technology Data Exchange (ETDEWEB)
Berthou, Jean-Yves; Fayolle, Eric [Electricite de France, Research and Development division, Modeling and Information Technologies Department, CLAMART CEDEX (France); Faucher, Eric; Scliffet, Laurent [Electricite de France, Research and Development Division, Mechanics and Component Technology Branch Department, Moret sur Loing (France)
2000-09-01
Nuclear plants use steam generator safety valves in order to regulate possible large pressure variations of fluids. In case of an incident these valves may be fed with pressurized liquid water (for instance a pressure of 9 MPa at a temperature of 300degC). When a pressurized liquid is submitted to a strong pressure drop, it will start evaporating. This phenomena is called flashing. Z. Bilicki and co-authors proposed the homogeneous relaxation model (HRM) to compute critical flashing water flows. Its computation in the case of non stationary one-dimensional flashing flows has been carried out with the development of a dedicated time dependent Finite Volume scheme based on a simplified version of the Godunov approach. Electricite De France Research and Development division have developed a monodimensional implementation of the HRM model: ECOSS, a 11000 lines FORTRAN 90. Applied to a shock tube test case with a 20000 elements monodimensional mesh, the simulation of the physical phenomenon during 2.5 seconds requires at least 100 days of computation on a SUN Sparc-Ultra60. This execution time justifies the ECOSS parallelization. Furthermore, we plan a modeling on 2D meshes for the next few years. Knowing that multiplying the mesh dimension by a factor 10 multiplies the execution time by a factor 100, ECOSS would take years of computation with small 2D meshes (1000 x 1000) on a conventional workstation. This paper describes the parallelization analysis we have conducted and we presents the experimental results we have obtained applying different programming model (MPI, OpenMP, HPF) on various platforms (a Compaq Proliant 6000 4 processors, a Cray T3E-750 300 processors, a HP class V 16 processors, a SGI Origin2000 32 processors, a cluster of PCs and a COMPAQ SC 232 processors). These experimental results will be discussed according to the following criteria: efficiency, salability, maintainability, developing costs and portability. As a conclusion, we will present the
Czech Academy of Sciences Publication Activity Database
Punčochářová-Pořízková, P.; Kozel, K.; Horáček, Jaromír
2011-01-01
Roč. 46, č. 1 (2011), s. 404-410 ISSN 0045-7930 R&D Projects: GA MŠk OC09019 Institutional research plan: CEZ:AV0Z20760514 Keywords : finite volume method * unsteady flow * low Mach number * viscous compressible fluid Subject RIV: BI - Acoustics Impact factor: 1.810, year: 2011 http://www.sciencedirect.com/science/article/pii/S0045793010003439
Effect of viscous dissipation and radiation in an annular cone
International Nuclear Information System (INIS)
Ahmed, N. J. Salman; Kamangar, Sarfaraz; Khan, T. M. Yunus; Azeem
2016-01-01
The viscous dissipation is an effect due to which heat is generated inside the medium. The presence of radiation further complicates the heat transfer behavior inside porous medium. The present paper discusses the combined effect of viscous dissipation and radiation inside a porous medium confined in an annular cone with inner radius r_i. The viscous dissipation and radiation terms are included in the energy equation thereby solving the coupled momentum and energy equations with the help of finite element method. The results are presented in terms of isothermal and streamline indicating the thermal and fluid flow behavior of porous medium. It is found that the combination of viscous dissipation and radiation parameter and the cone angle has significant effect on the heat transfer and fluid flow behavior inside the porous medium. The fluid velocity is found to increase with the increase in Raleigh number
Effect of viscous dissipation and radiation in an annular cone
Energy Technology Data Exchange (ETDEWEB)
Ahmed, N. J. Salman; Kamangar, Sarfaraz [Centre for Energy Sciences, Dept. of Mechanical Engineering, University of Malaya, Kuala Lumpur, 50603 Malaysia (Malaysia); Khan, T. M. Yunus, E-mail: yunus.tatagar@gmail.com [Centre for Energy Sciences, Dept. of Mechanical Engineering, University of Malaya, Kuala Lumpur, 50603 Malaysia (Malaysia); Dept. of Mechanical Engineering, BVB College of Engineering & Technology, Hubli (India); Azeem [Dept. of Computer System & Technology, University of Malaya, Kuala Lumpur (Malaysia)
2016-06-21
The viscous dissipation is an effect due to which heat is generated inside the medium. The presence of radiation further complicates the heat transfer behavior inside porous medium. The present paper discusses the combined effect of viscous dissipation and radiation inside a porous medium confined in an annular cone with inner radius r{sub i}. The viscous dissipation and radiation terms are included in the energy equation thereby solving the coupled momentum and energy equations with the help of finite element method. The results are presented in terms of isothermal and streamline indicating the thermal and fluid flow behavior of porous medium. It is found that the combination of viscous dissipation and radiation parameter and the cone angle has significant effect on the heat transfer and fluid flow behavior inside the porous medium. The fluid velocity is found to increase with the increase in Raleigh number.
Shinbrot, Marvin
2012-01-01
Readable and user-friendly, this high-level introduction explores the derivation of the equations of fluid motion from statistical mechanics, classical theory, and a portion of the modern mathematical theory of viscous, incompressible fluids. 1973 edition.
Directory of Open Access Journals (Sweden)
A. M. Salem
2013-01-01
Full Text Available A numerical model is developed to study the effects of temperature-dependent viscosity on heat and mass transfer flow of magnetohydrodynamic(MHD micropolar fluids with medium molecular weight along a permeable stretching surface embedded in a non-Darcian porous medium in the presence of viscous dissipation and chemical reaction. The governing boundary equations for momentum, angular momentum (microrotation, and energy and mass transfer are transformed to a set of nonlinear ordinary differential equations by using similarity solutions which are then solved numerically by shooting technique. A comparison between the analytical and the numerical solutions has been included. The effects of the various physical parameters entering into the problem on velocity, microrotation, temperature and concentration profiles are presented graphically. Finally, the effects of pertinent parameters on local skin-friction coefficient, local Nusselt number and local Sherwood number are also presented graphically. One important observation is that for some kinds of mixtures (e.g., H2, air with light and medium molecular weight, the magnetic field and temperature-dependent viscosity effects play a significant role and should be taken into consideration as well.
Denisova, Irina Vlad.
2015-03-01
The paper deals with the motion of two immiscible viscous fluids in a container, one of the fluids being compressible while another one being incompressible. The interface between the fluids is an unknown closed surface where surface tension is neglected. We assume the compressible fluid to be barotropic, the pressure being given by an arbitrary smooth increasing function. This problem is considered in anisotropic Sobolev-Slobodetskiǐ spaces. We show that the L 2-norms of the velocity and deviation of compressible fluid density from the mean value decay exponentially with respect to time. The proof is based on a local existence theorem (Denisova, Interfaces Free Bound 2:283-312, 2000) and on the idea of constructing a function of generalized energy, proposed by Padula (J Math Fluid Mech 1:62-77, 1999). In addition, we eliminate the restrictions for the viscosities which appeared in Denisova (Interfaces Free Bound 2:283-312, 2000).
Mathematical models of viscous friction
Buttà, Paolo; Marchioro, Carlo
2015-01-01
In this monograph we present a review of a number of recent results on the motion of a classical body immersed in an infinitely extended medium and subjected to the action of an external force. We investigate this topic in the framework of mathematical physics by focusing mainly on the class of purely Hamiltonian systems, for which very few results are available. We discuss two cases: when the medium is a gas and when it is a fluid. In the first case, the aim is to obtain microscopic models of viscous friction. In the second, we seek to underline some non-trivial features of the motion. Far from giving a general survey on the subject, which is very rich and complex from both a phenomenological and theoretical point of view, we focus on some fairly simple models that can be studied rigorously, thus providing a first step towards a mathematical description of viscous friction. In some cases, we restrict ourselves to studying the problem at a heuristic level, or we present the main ideas, discussing only some as...
Viscous Design of TCA Configuration
Krist, Steven E.; Bauer, Steven X. S.; Campbell, Richard L.
1999-01-01
The goal in this effort is to redesign the baseline TCA configuration for improved performance at both supersonic and transonic cruise. Viscous analyses are conducted with OVERFLOW, a Navier-Stokes code for overset grids, using PEGSUS to compute the interpolations between overset grids. Viscous designs are conducted with OVERDISC, a script which couples OVERFLOW with the Constrained Direct Iterative Surface Curvature (CDISC) inverse design method. The successful execution of any computational fluid dynamics (CFD) based aerodynamic design method for complex configurations requires an efficient method for regenerating the computational grids to account for modifications to the configuration shape. The first section of this presentation deals with the automated regridding procedure used to generate overset grids for the fuselage/wing/diverter/nacelle configurations analysed in this effort. The second section outlines the procedures utilized to conduct OVERDISC inverse designs. The third section briefly covers the work conducted by Dick Campbell, in which a dual-point design at Mach 2.4 and 0.9 was attempted using OVERDISC; the initial configuration from which this design effort was started is an early version of the optimized shape for the TCA configuration developed by the Boeing Commercial Airplane Group (BCAG), which eventually evolved into the NCV design. The final section presents results from application of the Natural Flow Wing design philosophy to the TCA configuration.
Attractors of dissipative structure in three dissipative fluids
International Nuclear Information System (INIS)
Kondoh, Yoshiomi
1993-10-01
A general theory with use of auto-correlations for distributions is presented to derive that realization of coherent structures in general dissipative dynamic systems is equivalent to that of self-organized states with the minimum dissipation rate for instantaneously contained energy. Attractors of dissipative structure are shown to be given by eigenfunctions for dissipative dynamic operators of the dynamic system and to constitute the self-organized and self-similar decay phase. Three typical examples applied to incompressible viscous fluids, to incompressible viscous and resistive magnetohydrodynamic (MHD) fluids and to compressible resistive MHD plasmas are presented to lead to attractors in the three dissipative fluids and to describe a common physical picture of self-organization and bifurcation of the dissipative structure. (author)
Lyutyy, T. V.; Reva, V. V.
2018-05-01
Ferrofluid heating by an external alternating field is studied based on the rigid dipole model, where the magnetization of each particle in a fluid is supposed to be firmly fixed in the crystal lattice. Equations of motion, employing Newton's second law for rotational motion, the condition of rigid body rotation, and the assumption that the friction torque is proportional to angular velocity are used. This oversimplification permits us to expand the model easily: to take into account the thermal noise and interparticle interaction that allows us to estimate from unified positions the role of thermal activation and dipole interaction in the heating process. Our studies are conducted in three stages. The exact expressions for the average power loss of a single particle are obtained within the dynamical approximation. Then, in the stochastic case, the power loss of a single particle is estimated analytically using the Fokker-Planck equation and numerically using the effective Langevin equation. Finally, the power loss for the particle ensemble is obtained using the molecular dynamics method. Here, the local dipole fields are calculated approximately based on the Barnes-Hut algorithm. The revealed trends in the behavior of both a single particle and the particle ensemble suggest the way of choosing the conditions for obtaining the maximum heating efficiency. The competitiveness character of the interparticle interaction and thermal noise is investigated in detail. Two situations, when the thermal noise rectifies the power loss reduction caused by the interaction, are described. The first of them is related to the complete destruction of dense clusters at high noise intensity. The second one originates from the rare switching of the particles in clusters due to thermal activation, when the noise intensity is relatively weak. In this way, the constructive role of noise appears in the system.
Bulk viscous cosmology with causal transport theory
International Nuclear Information System (INIS)
Piattella, Oliver F.; Fabris, Júlio C.; Zimdahl, Winfried
2011-01-01
We consider cosmological scenarios originating from a single imperfect fluid with bulk viscosity and apply Eckart's and both the full and the truncated Müller-Israel-Stewart's theories as descriptions of the non-equilibrium processes. Our principal objective is to investigate if the dynamical properties of Dark Matter and Dark Energy can be described by a single viscous fluid and how such description changes when a causal theory (Müller-Israel-Stewart's, both in its full and truncated forms) is taken into account instead of Eckart's non-causal one. To this purpose, we find numerical solutions for the gravitational potential and compare its behaviour with the corresponding ΛCDM case. Eckart's and the full causal theory seem to be disfavoured, whereas the truncated theory leads to results similar to those of the ΛCDM model for a bulk viscous speed in the interval 10 −11 || cb 2 ∼ −8
Enhanced Compressible Fluids Investigation
1983-04-01
tetramethyldisiloxane and 1,1,3,3-Tetrakis (3,3,3-trifluoropropyl) dimethyldisiloxane, were synthesized by Silar Laboratories (Scotia, New York). If these showed...hypothesis, hexakis(trimethylsiloxy)disiloxane was synthesized by Silar Laboratories. The structure of the compound as inferred by its method of
Jablonská, Jana
2014-03-01
The presence of air in the liquid causes the dynamic system behaviour. When solve to issue of the dynamics we often meet problems of cavitation. Cavitation is an undesirable phenomenon, since it causes a disruption of the surrounding material and material destruction. Cavitation is accompanied by loud sound effects and reduces the efficiency of such pumps, etc. Therefore, it is desirable to model systems in which the cavitation might occur. A typical example is a solution of water hammer.
Directory of Open Access Journals (Sweden)
Jablonská Jana
2014-03-01
Full Text Available The presence of air in the liquid causes the dynamic system behaviour. When solve to issue of the dynamics we often meet problems of cavitation. Cavitation is an undesirable phenomenon, since it causes a disruption of the surrounding material and material destruction. Cavitation is accompanied by loud sound effects and reduces the efficiency of such pumps, etc. Therefore, it is desirable to model systems in which the cavitation might occur. A typical example is a solution of water hammer.
The partially filled viscous ring damper.
Alfriend, K. T.
1973-01-01
The problem of a spinning satellite with a partially filled viscous ring damper is investigated. It is shown that there are two distinct modes of motion, the nutation-synchronous mode and spin-synchronous mode. From an approximate solution of the equations of motion a time constant is obtained for each mode. From a consideration of the fluid dynamics several methods are developed for determining the damping constant.
Viscous, Resistive Magnetorotational Modes
DEFF Research Database (Denmark)
Pessah, Martin Elias; Chan, Chi-kwan
2008-01-01
We carry out a comprehensive analysis of the behavior of the magnetorotational instability (MRI) in viscous, resistive plasmas. We find exact, non-linear solutions of the non-ideal magnetohydrodynamic (MHD) equations describing the local dynamics of an incompressible, differentially rotating...
DEFF Research Database (Denmark)
Dyre, Jeppe
1999-01-01
Recent NMR experiments on supercooled toluene and glycerol by Hinze and Böhmer show that small rotation angles dominate with only a few large molecular rotations. These results are here interpreted by assuming that viscous liquids are solidlike on short length scales. A characteristic length...
Leapfrogging of multiple coaxial viscous vortex rings
International Nuclear Information System (INIS)
Cheng, M.; Lou, J.; Lim, T. T.
2015-01-01
A recent theoretical study [Borisov, Kilin, and Mamaev, “The dynamics of vortex rings: Leapfrogging, choreographies and the stability problem,” Regular Chaotic Dyn. 18, 33 (2013); Borisov et al., “The dynamics of vortex rings: Leapfrogging in an ideal and viscous fluid,” Fluid Dyn. Res. 46, 031415 (2014)] shows that when three coaxial vortex rings travel in the same direction in an incompressible ideal fluid, each of the vortex rings alternately slips through (or leapfrogs) the other two ahead. Here, we use a lattice Boltzmann method to simulate viscous vortex rings with an identical initial circulation, radius, and separation distance with the aim of studying how viscous effect influences the outcomes of the leapfrogging process. For the case of two identical vortex rings, our computation shows that leapfrogging can be achieved only under certain favorable conditions, which depend on Reynolds number, vortex core size, and initial separation distance between the two rings. For the case of three coaxial vortex rings, the result differs from the inviscid model and shows that the second vortex ring always slips through the leading ring first, followed by the third ring slipping through the other two ahead. A simple physical model is proposed to explain the observed behavior
Zhang, Jianwen; Zhao, Xiaokui
2015-01-01
In general, the resistivity is inversely proportional to the electrical conductivity, and is usually taken to be zero when the conducting fluid is of extremely high conductivity (e.g., ideal conductors). In this paper, we first establish the global well-posedness of strong solution to an initial-boundary value problem of the one-dimensional compressible, viscous, heat-conductive, non-resistive MHD equations with general heat-conductivity coefficient and large data. Then, the non-resistive lim...
Viscous flows the practical use of theory
Brenner, Howard
1988-01-01
Representing a unique approach to the study of fluid flows, Viscous Flows demonstrates the utility of theoretical concepts and solutions for interpreting and predicting fluid flow in practical applications. By critically comparing all relevant classes of theoretical solutions with experimental data and/or general numerical solutions, it focuses on the range of validity of theoretical expressions rather than on their intrinsic character.This book features extensive use of dimensional analysis on both models and variables, and extensive development of theoretically based correlating equations.
Directory of Open Access Journals (Sweden)
H. Shokrollahi
2016-03-01
Full Text Available The purpose of this work is to investigate the effects of the volume fraction and bimodal distribution of solid particles on the compression and tension behavior of the Co-ferrite-based magneto-rheological fluids (MRFs containing silicon oil as a carrier. Hence, Co-ferrite particles (CoFe2O4 with two various sizes were synthesized by the chemical co-precipitation method and mixed so as to prepare the bimodal MRF. The X-Ray Diffraction (XRD analysis, Fourier Transform Infrared Spectroscopy (FTIR, Laser Particle Size Analysis (LPSA and Vibrating Sample Magnetometer (VSM were conducted to examine the structural and magnetic properties, respectively. The results indicated that the increase of the volume fraction has a direct increasing influence on the values of the compression and tension strengths of fluids. In addition, the compression and tension strengths of the mixed MRF sample (1.274 and 0.647 MPa containing 60 and 550 nm samples were higher than those of the MRF sample with the same volume fraction and uniform particle size of 550 nm.
Safaei, Hadi; Emami, Mohsen Davazdah; Jazi, Hamidreza Salimi; Mostaghimi, Javad
2017-12-01
Applications of hollow spherical particles in thermal spraying process have been developed in recent years, accompanied by attempts in the form of experimental and numerical studies to better understand the process of impact of a hollow droplet on a surface. During such process, volume and density of the trapped gas inside droplet change. The numerical models should be able to simulate such changes and their consequent effects. The aim of this study is to numerically simulate the impact of a hollow ZrO2 droplet on a flat surface using the volume of fluid technique for compressible flows. An open-source, finite-volume-based CFD code was used to perform the simulations, where appropriate subprograms were added to handle the studied cases. Simulation results were compared with the available experimental data. Results showed that at high impact velocities ( U 0 > 100 m/s), the compression of trapped gas inside droplet played a significant role in the impact dynamics. In such velocities, the droplet splashed explosively. Compressibility effects result in a more porous splat, compared to the corresponding incompressible model. Moreover, the compressible model predicted a higher spread factor than the incompressible model, due to planetary structure of the splat.
Experimental study of highly viscous impinging jets
Energy Technology Data Exchange (ETDEWEB)
Gomon, M. [Univ. of Texas, Austin, TX (United States). Dept. of Mechanical Engineering
1998-12-01
The objective of this research is to study the behavior of highly viscous gravity-driven jets filling a container. Matters of interest are the formation of voids in the fluid pool during the filling process and the unstable behavior of the fluid in the landing region which manifests itself as an oscillating motion. The working fluids used in this research are intended to simulate the flow behavior of molten glass. Qualitative and quantitative results are obtained in a parametric study. The fraction of voids present in the fluid pool after the filling of the container is measured for different parameter values of viscosity and mass flow rate. Likewise, frequencies of the oscillating jet are measured. Results are inconclusive with regard to a correlation between parameter settings and void fractions. As for frequencies, power law correlations are established.
Experimental study of highly viscous impinging jets
International Nuclear Information System (INIS)
Gomon, M.
1998-12-01
The objective of this research is to study the behavior of highly viscous gravity-driven jets filling a container. Matters of interest are the formation of voids in the fluid pool during the filling process and the unstable behavior of the fluid in the landing region which manifests itself as an oscillating motion. The working fluids used in this research are intended to simulate the flow behavior of molten glass. Qualitative and quantitative results are obtained in a parametric study. The fraction of voids present in the fluid pool after the filling of the container is measured for different parameter values of viscosity and mass flow rate. Likewise, frequencies of the oscillating jet are measured. Results are inconclusive with regard to a correlation between parameter settings and void fractions. As for frequencies, power law correlations are established
Daude, F.; Galon, P.
2018-06-01
A Finite-Volume scheme for the numerical computations of compressible single- and two-phase flows in flexible pipelines is proposed based on an approximate Godunov-type approach. The spatial discretization is here obtained using the HLLC scheme. In addition, the numerical treatment of abrupt changes in area and network including several pipelines connected at junctions is also considered. The proposed approach is based on the integral form of the governing equations making it possible to tackle general equations of state. A coupled approach for the resolution of fluid-structure interaction of compressible fluid flowing in flexible pipes is considered. The structural problem is solved using Euler-Bernoulli beam finite elements. The present Finite-Volume method is applied to ideal gas and two-phase steam-water based on the Homogeneous Equilibrium Model (HEM) in conjunction with a tabulated equation of state in order to demonstrate its ability to tackle general equations of state. The extensive application of the scheme for both shock tube and other transient flow problems demonstrates its capability to resolve such problems accurately and robustly. Finally, the proposed 1-D fluid-structure interaction model appears to be computationally efficient.
International Nuclear Information System (INIS)
Roskosch, Dennis; Atakan, Burak
2015-01-01
Fluid selection for thermodynamic cycles like refrigeration cycles, heat pumps or organic Rankine cycles remains an actual topic. Generally the search for a working fluid is based on experimental approaches or on a not very systematic trial and error approach, far from being elegant. An alternative method may be a theory based reverse engineering approach, proposed and investigated here: The design process should start with an optimal process and with (abstract) properties of the fluid needed to fit into this optimal process, best described by some general equation of state and the corresponding fluid-describing parameters. These should be analyzed and optimized with respect to the defined model process, which also has to be optimized simultaneously. From this information real fluids can be selected or even synthesized which have fluid defining properties in the optimum regime like critical temperature or ideal gas capacities of heat, allowing to find new working fluids, not considered so far. The number and kind of the fluid-defining parameters is mainly based on the choice of the used EOS (equation of state). The property model used in the present work is based on the cubic Peng–Robinson equation, chosen due to its moderate numerical expense, sufficient accuracy as well as a general availability of the fluid-defining parameters for many compounds. The considered model-process works between the temperature levels of 273.15 and 333.15 K and can be used as heat pump for supplying buildings with heat, typically. The objective functions are the COP (coefficient of performance) and the VHC (volumetric heating capacity) as a function of critical pressure, critical temperature, acentric factor and two coefficients for the temperature-dependent isobaric ideal gas heat capacity. Also, the steam quality at the compressor entrance has to be regarded as a problem variable. The results give clear hints regarding optimal fluid parameters of the analyzed process and deepen
International Nuclear Information System (INIS)
Mu, Tiancheng; Liu, Zhimin; Han, Buxing.; Li, Zhonghao; Zhang, Jianling; Zhang, Xiaogang
2003-01-01
The phase behavior, density, and constant-volume molar heat capacity (C v,m ) of ethane + n-pentane binary mixtures have been measured in the supercritical region and subcritical region at T=309.45 K. In addition, the isothermal compressibility (κ T ) has been calculated using the density data determined. For a mixed fluid with a composition close to the critical composition, C v,m and κ T increase sharply as the pressure approaches the critical point (CP), the dew point (DP), or the bubble point (BP). However, C v,m is not sensitive to pressure in the entire pressure range if the composition of the mixed fluid is far from the critical composition. To tune the properties of the binary mixtures effectively by pressure, both the composition and the pressure should be close to the critical point of the mixture. The intermolecular interactions in the mixture are also discussed on the basis of the experimental results
The boundary data immersion method for compressible flows with application to aeroacoustics
Energy Technology Data Exchange (ETDEWEB)
Schlanderer, Stefan C., E-mail: stefan.schlanderer@unimelb.edu.au [Faculty for Engineering and the Environment, University of Southampton, SO17 1BJ Southampton (United Kingdom); Weymouth, Gabriel D., E-mail: G.D.Weymouth@soton.ac.uk [Faculty for Engineering and the Environment, University of Southampton, SO17 1BJ Southampton (United Kingdom); Sandberg, Richard D., E-mail: richard.sandberg@unimelb.edu.au [Department of Mechanical Engineering, University of Melbourne, Melbourne VIC 3010 (Australia)
2017-03-15
This paper introduces a virtual boundary method for compressible viscous fluid flow that is capable of accurately representing moving bodies in flow and aeroacoustic simulations. The method is the compressible extension of the boundary data immersion method (BDIM, Maertens & Weymouth (2015), ). The BDIM equations for the compressible Navier–Stokes equations are derived and the accuracy of the method for the hydrodynamic representation of solid bodies is demonstrated with challenging test cases, including a fully turbulent boundary layer flow and a supersonic instability wave. In addition we show that the compressible BDIM is able to accurately represent noise radiation from moving bodies and flow induced noise generation without any penalty in allowable time step.
A non-oscillatory energy-splitting method for the computation of compressible multi-fluid flows
Lei, Xin; Li, Jiequan
2018-04-01
This paper proposes a new non-oscillatory energy-splitting conservative algorithm for computing multi-fluid flows in the Eulerian framework. In comparison with existing multi-fluid algorithms in the literature, it is shown that the mass fraction model with isobaric hypothesis is a plausible choice for designing numerical methods for multi-fluid flows. Then we construct a conservative Godunov-based scheme with the high order accurate extension by using the generalized Riemann problem solver, through the detailed analysis of kinetic energy exchange when fluids are mixed under the hypothesis of isobaric equilibrium. Numerical experiments are carried out for the shock-interface interaction and shock-bubble interaction problems, which display the excellent performance of this type of schemes and demonstrate that nonphysical oscillations are suppressed around material interfaces substantially.
Kumar, V. R. Sanal; Sankar, Vigneshwaran; Chandrasekaran, Nichith; Saravanan, Vignesh; Natarajan, Vishnu; Padmanabhan, Sathyan; Sukumaran, Ajith; Mani, Sivabalan; Rameshkumar, Tharikaa; Nagaraju Doddi, Hema Sai; Vysaprasad, Krithika; Sharan, Sharad; Murugesh, Pavithra; Shankar, S. Ganesh; Nejaamtheen, Mohammed Niyasdeen; Baskaran, Roshan Vignesh; Rahman Mohamed Rafic, Sulthan Ariff; Harisrinivasan, Ukeshkumar; Srinivasan, Vivek
2018-02-01
A closed-form analytical model is developed for estimating the 3D boundary-layer-displacement thickness of an internal flow system at the Sanal flow choking condition for adiabatic flows obeying the physics of compressible viscous fluids. At this unique condition the boundary-layer blockage induced fluid-throat choking and the adiabatic wall-friction persuaded flow choking occur at a single sonic-fluid-throat location. The beauty and novelty of this model is that without missing the flow physics we could predict the exact boundary-layer blockage of both 2D and 3D cases at the sonic-fluid-throat from the known values of the inlet Mach number, the adiabatic index of the gas and the inlet port diameter of the internal flow system. We found that the 3D blockage factor is 47.33 % lower than the 2D blockage factor with air as the working fluid. We concluded that the exact prediction of the boundary-layer-displacement thickness at the sonic-fluid-throat provides a means to correctly pinpoint the causes of errors of the viscous flow solvers. The methodology presented herein with state-of-the-art will play pivotal roles in future physical and biological sciences for a credible verification, calibration and validation of various viscous flow solvers for high-fidelity 2D/3D numerical simulations of real-world flows. Furthermore, our closed-form analytical model will be useful for the solid and hybrid rocket designers for the grain-port-geometry optimization of new generation single-stage-to-orbit dual-thrust-motors with the highest promising propellant loading density within the given envelope without manifestation of the Sanal flow choking leading to possible shock waves causing catastrophic failures.
Directory of Open Access Journals (Sweden)
V. R. Sanal Kumar
2018-02-01
Full Text Available A closed-form analytical model is developed for estimating the 3D boundary-layer-displacement thickness of an internal flow system at the Sanal flow choking condition for adiabatic flows obeying the physics of compressible viscous fluids. At this unique condition the boundary-layer blockage induced fluid-throat choking and the adiabatic wall-friction persuaded flow choking occur at a single sonic-fluid-throat location. The beauty and novelty of this model is that without missing the flow physics we could predict the exact boundary-layer blockage of both 2D and 3D cases at the sonic-fluid-throat from the known values of the inlet Mach number, the adiabatic index of the gas and the inlet port diameter of the internal flow system. We found that the 3D blockage factor is 47.33 % lower than the 2D blockage factor with air as the working fluid. We concluded that the exact prediction of the boundary-layer-displacement thickness at the sonic-fluid-throat provides a means to correctly pinpoint the causes of errors of the viscous flow solvers. The methodology presented herein with state-of-the-art will play pivotal roles in future physical and biological sciences for a credible verification, calibration and validation of various viscous flow solvers for high-fidelity 2D/3D numerical simulations of real-world flows. Furthermore, our closed-form analytical model will be useful for the solid and hybrid rocket designers for the grain-port-geometry optimization of new generation single-stage-to-orbit dual-thrust-motors with the highest promising propellant loading density within the given envelope without manifestation of the Sanal flow choking leading to possible shock waves causing catastrophic failures.
Manipulation of viscous fingering in a radially tapered cell geometry
Bongrand, Grégoire; Tsai, Peichun Amy
2018-06-01
When a more mobile fluid displaces another immiscible one in a porous medium, viscous fingering propagates with a partial sweep, which hinders oil recovery and soil remedy. We experimentally investigate the feasibility of tuning such fingering propagation in a nonuniform narrow passage with a radial injection, which is widely used in various applications. We show that a radially converging cell can suppress the common viscous fingering observed in a uniform passage, and a full sweep of the displaced fluid is then achieved. The injection flow rate Q can be further exploited to manipulate the viscous fingering instability. For a fixed gap gradient α , our experimental results show a full sweep at a small Q but partial displacement with fingering at a sufficient Q . Finally, by varying α , we identify and characterize the variation of the critical threshold between stable and unstable displacements. Our experimental results reveal good agreement with theoretical predictions by a linear stability analysis.
Computer simulation of viscous fingering in a lifting Hele-Shaw cell
Indian Academy of Sciences (India)
We simulate viscous fingering generated by separating two plates with a constant force, in a lifting Hele-Shaw cell. Variation in the patterns for different fluid viscosity and lifting force is studied. Viscous fingering is strongly affected by anisotropy. We report a computer simulation study of fingering patterns, where circular or ...
Czech Academy of Sciences Publication Activity Database
Dell'Oro, Filippo; Feireisl, Eduard
2015-01-01
Roč. 128, November (2015), s. 136-148 ISSN 0362-546X R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes equations * unbounded domain * weak solutions * energy inequality Subject RIV: BA - General Mathematics Impact factor: 1.125, year: 2015 http://www.sciencedirect.com/science/article/pii/S0362546X15002692
Energy Technology Data Exchange (ETDEWEB)
Mendes, Albert C.R., E-mail: albert@fisica.ufjf.br [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330, Juiz de Fora - MG (Brazil); Takakura, Flavio I., E-mail: takakura@fisica.ufjf.br [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330, Juiz de Fora - MG (Brazil); Abreu, Everton M.C., E-mail: evertonabreu@ufrrj.br [Grupo de Física Teórica e Matemática Física, Departamento de Física, Universidade Federal Rural do Rio de Janeiro, 23890-971, Seropédica - RJ (Brazil); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330, Juiz de Fora - MG (Brazil); Neto, Jorge Ananias, E-mail: jorge@fisica.ufjf.br [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330, Juiz de Fora - MG (Brazil)
2017-05-15
In this work we have obtained a higher-derivative Lagrangian for a charged fluid coupled with the electromagnetic fluid and the Dirac’s constraints analysis was discussed. A set of first-class constraints fixed by noncovariant gauge condition were obtained. The path integral formalism was used to obtain the partition function for the corresponding higher-derivative Hamiltonian and the Faddeev–Popov ansatz was used to construct an effective Lagrangian. Through the partition function, a Stefan–Boltzmann type law was obtained. - Highlights: • Higher-derivative Lagrangian for a charged fluid. • Electromagnetic coupling and Dirac’s constraint analysis. • Partition function through path integral formalism. • Stefan–Boltzmann-kind law through the partition function.
Second law analysis of a reacting temperature dependent viscous ...
African Journals Online (AJOL)
In this paper, entropy generation during the flow of a reacting viscous fluid through an inclined Channel with isothermal walls are investigated. The coupled energy and momentum equations were solved numerically. Previous results in literature (Adesanya et al 2006 [[17]) showed both velocity and temperature have two ...
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
This paper investigates double diffusive convection MHD flow past a vertical porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic ...
Unsteady Viscous Flow Past an Impulsively Started Porous Vertical ...
African Journals Online (AJOL)
This paper presents a new numerical approach for solving unsteady two dimensional boundary layer flow past an infinite vertical porous surface with the flow generated by Newtonian heating and impulsive motion in the presence of viscous dissipation and temperature dependent viscosity. The viscosity of the fluid under ...
Vieira, Sheila Lopes; de Arruda, Antonio Celso Fonseca
In the majority of published articles on the topic, ER fluids have been studied as if they were viscous liquids. In this work, electrorheological fluids were characterized as solids and their mechanical properties were determined. The results infer that ER materials are controllably resistant to compression, tensile and shear stress, in this order of magnitude. More precisely, fluids made of starch have elasticity modulus similar to that of rubber, they have tensile strength 103 to 5×104 times lower than that of low density polyethylene (LDPE), static yield stress 4×104 to 8×105 times lower than that of acrylonitrile-butadiene-styrene terpolymer (ABS) and fatigue life similar to some polymers like polyethylene(PE) and polypropylene (PP).
CSIR Research Space (South Africa)
Heyns, Johan A
2013-05-01
Full Text Available of the gas has a noteworthy effect on predicted pressure loads in liquid–gas flow in certain instances. With the aim of providing a more accurate numerical representation of dynamic two-fluid flow, the solver is subsequently extended to account for variations...
Bulk viscous matter and recent acceleration of the universe based on causal viscous theory
Energy Technology Data Exchange (ETDEWEB)
Mohan, N.D.J.; Sasidharan, Athira; Mathew, Titus K. [Cochin University of Science and Technology, Department of Physics, Kochi (India)
2017-12-15
The evolution of the bulk viscous matter dominated universe has been analysed using the full causal theory for the evolution of the viscous pressure in the context of the recent acceleration of the universe. The form of the viscosity is taken as ξ = αρ{sup 1/2}. We obtained analytical solutions for the Hubble parameter and scale factor of the universe. The model parameters have been computed using the observational data. The evolution of the prominent cosmological parameters was obtained. The age of the universe for the best estimated model parameters is found to be less than observational value. The viscous matter behaves like a stiff fluid in the early phase and evolves to a negative pressure fluid in the later phase. The equation of state is found to be stabilised with value ω > -1. The local as well as generalised second law of thermodynamics is satisfied. The statefinder diagnostic shows that this model is distinct from the standard ΛCDM. One of the marked deviations seen in this model to be compared with the corresponding model using the Eckart approach is that in this model the bulk viscosity decreases with the expansion of the universe, while in the Eckart formalism it increases from negative values in the early universe towards positive values. (orig.)
Bulk viscous matter and recent acceleration of the universe based on causal viscous theory
International Nuclear Information System (INIS)
Mohan, N.D.J.; Sasidharan, Athira; Mathew, Titus K.
2017-01-01
The evolution of the bulk viscous matter dominated universe has been analysed using the full causal theory for the evolution of the viscous pressure in the context of the recent acceleration of the universe. The form of the viscosity is taken as ξ = αρ 1/2 . We obtained analytical solutions for the Hubble parameter and scale factor of the universe. The model parameters have been computed using the observational data. The evolution of the prominent cosmological parameters was obtained. The age of the universe for the best estimated model parameters is found to be less than observational value. The viscous matter behaves like a stiff fluid in the early phase and evolves to a negative pressure fluid in the later phase. The equation of state is found to be stabilised with value ω > -1. The local as well as generalised second law of thermodynamics is satisfied. The statefinder diagnostic shows that this model is distinct from the standard ΛCDM. One of the marked deviations seen in this model to be compared with the corresponding model using the Eckart approach is that in this model the bulk viscosity decreases with the expansion of the universe, while in the Eckart formalism it increases from negative values in the early universe towards positive values. (orig.)
Grundland, A. M.; Lalague, L.
1996-04-01
This paper presents a new method of constructing, certain classes of solutions of a system of partial differential equations (PDEs) describing the non-stationary and isentropic flow for an ideal compressible fluid. A generalization of the symmetry reduction method to the case of partially-invariant solutions (PISs) has been formulated. We present a new algorithm for constructing PISs and discuss in detail the necessary conditions for the existence of non-reducible PISs. All these solutions have the defect structure 0305-4470/29/8/019/img1 and are computed from four-dimensional symmetric subalgebras. These theoretical considerations are illustrated by several examples. Finally, some new classes of invariant solutions obtained by the symmetry reduction method are included. These solutions represent central, conical, rational, spherical, cylindrical and non-scattering double waves.
International Nuclear Information System (INIS)
Gudjonsdottir, V.; Infante Ferreira, C.A.; Rexwinkel, Glenn; Kiss, Anton A.
2017-01-01
Upgrading waste heat by compression resorption heat pumps (CRHP) has the potential to make a strong impact in industry. The efficiency of CRHP can be further improved by using alternative working fluids. In this work, the addition of carbon dioxide to aqueous ammonia solutions for application in CRHP is investigated. The previously published thermodynamic models for the ternary mixture are evaluated by comparing their results with experimental thermodynamic data, and checking their advantages and disadvantages. Then the models are used to investigate the impact of adding CO_2 to NH_3-H_2O in wet compression resorption heat pump applications. For an application where a waste stream is heated from 60 to 105 °C, a COP increase of up to 5% can be attained by adding CO_2 to the ammonia-water mixture, without any risk of salt formation. Additional advantages of adding CO_2 to the ammonia-water mixture in that case are decreased pressure ratio, as well as an increase in the lower pressure level. When practical pressure restrictions are considered the benefits of the added CO_2 become even larger or around 25% increase in the COP. Nonetheless, when the waste stream was considered to be additionally cooled down, no significant benefits were observed. - Highlights: • NH_3-CO_2-H_2O mixture is proposed as a working fluid for CRHP. • COP improvements of 5% are achieved compared to NH_3-H_2O. • Additional advantages of the added CO_2 are decreased pressure ratio.
Viscous Regularization of the Euler Equations and Entropy Principles
Guermond, Jean-Luc
2014-03-11
This paper investigates a general class of viscous regularizations of the compressible Euler equations. A unique regularization is identified that is compatible with all the generalized entropies, à la [Harten et al., SIAM J. Numer. Anal., 35 (1998), pp. 2117-2127], and satisfies the minimum entropy principle. A connection with a recently proposed phenomenological model by [H. Brenner, Phys. A, 370 (2006), pp. 190-224] is made. © 2014 Society for Industrial and Applied Mathematics.
International Nuclear Information System (INIS)
Novello, M.; Salim, J.M.; Torres, J.; Oliveira, H.P. de
1989-01-01
A set of spatially homogeneous and isotropic cosmological geometries generated by a class of non-perfect is investigated fluids. The irreversibility if this system is studied in the context of causal thermodynamics which provides a useful mechanism to conform to the non-violation of the causal principle. (author) [pt
Kameyama, Masanori; Yamamoto, Mayumi
2018-01-01
We conduct a series of numerical experiments of thermal convection of highly compressible fluids in a two-dimensional rectangular box, in order to study the mantle convection on super-Earths. The thermal conductivity and viscosity are assumed to exponentially depend on depth and temperature, respectively, while the variations in thermodynamic properties (thermal expansivity and reference density) with depth are taken to be relevant for the super-Earths with 10 times the Earth's. From our experiments we identified a distinct regime of convecting flow patterns induced by the interplay between the adiabatic temperature change and the spatial variations in viscosity and thermal conductivity. That is, for the cases with strong temperature-dependent viscosity and depth-dependent thermal conductivity, a "deep stratosphere" of stable thermal stratification is formed at the base of the mantle, in addition to thick stagnant lids at their top surfaces. In the "deep stratosphere", the fluid motion is insignificant particularly in the vertical direction in spite of smallest viscosity owing to its strong dependence on temperature. Our finding may further imply that some of super-Earths which are lacking in mobile tectonic plates on their top surfaces may have "deep stratospheres" at the base of their mantles.
Directory of Open Access Journals (Sweden)
Tahmina Akhter
2014-01-01
Full Text Available The flow of a compressible fluid with slip through a cylinder with an asymmetric local constriction has been considered both numerically, as well as analytically. For the numerical work, a particle-based method whose dynamics is governed by the multiparticle collision (MPC rule has been used together with a generalized boundary condition that allows for slip at the wall. Since it is well known that an MPC system corresponds to an ideal gas and behaves like a compressible, viscous flow on average, an approximate analytical solution has been derived from the compressible Navier–Stokes equations of motion coupled to an ideal gas equation of state using the Karman–Pohlhausen method. The constriction is assumed to have a polynomial form, and the location of maximum constriction is varied throughout the constricted portion of the cylinder. Results for centerline densities and centerline velocities have been compared for various Reynolds numbers, Mach numbers, wall slip values and flow geometries.
International Nuclear Information System (INIS)
Sturtevant, B.
1986-01-01
The purpose of this research program is to investigate fluid dynamic instabilities and mixing initiated by the interaction of shock waves with interfaces between light and heavy gases. In particular, the nonlinear stage of shock-initiated Rayleigh-Taylor instability (also known as the Richtmeyer-Meshkov instability), the secondary instabilities (e.g., the Kelvin-Helmholtz instability) arising therefrom and the resulting mixing of the two gases are of interest. This report describes activities during the performance period 1 October 1985 to 30 September 1986
Energy Technology Data Exchange (ETDEWEB)
Kim, Seong Gu; Baik, Seungjoon; Cho, Seong Kuk; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Kwon, Jinsu [Hanyang University, Seoul (Korea, Republic of)
2015-10-15
The authors compared flow parameters of S-CO{sub 2} compressor with various fluids to investigate fluid characteristic of S-CO{sub 2}, and performance of pump-derived type (shrouded impeller) compressor. The CFD results showed that the isentropic efficiency of CO{sub 2} case has a comparable performance in comparison to the water since S-CO{sub 2} has a meta-incompressible characteristic near the critical point. Because of the low rotating speed and non-optimized geometry of impeller, the pressure ratio of the compressor is low. However, the authors confirmed that this shrouded type impeller for S-CO{sub 2} compressor showed good performance as much as water case. This results will be reflected in the future S-CO{sub 2} compressor design. As the generation IV reactors are being researched, the supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle is identified as one of the promising power conversion cycles. The S-CO{sub 2} cycle has several advantages: high efficiency it has compact cycle components and simple layout. It can be also used for a power conversion system of sodium-cooled fast reactor (SFR) since it can eliminate potential safety issue of the sodium-water reactions. Moreover, the S-CO{sub 2} cycle can be used for small modular reactors (SMR) application since it occupies small footprint and it can designed as an economical dry-cooling system for SMRs. Design of a compressor is the major technical issue in development of S-CO{sub 2} cycle. Main purposes of this experiment are to accumulate operating experience of the S-CO{sub 2} loop, and to obtain fundamental data for the compressor design optimization near the critical point. However, inside the compressor, it is hard to know flow parameters by measurements. Therefore, the authors performed a CFD analysis to obtain useful flow parameters inside the compressor. The main goal of this paper is studying the flow parameters of pump-derived type compressor with S-CO{sub 2}, water, and air fluids to
Thermal radiation from an evolving viscous quark gluon plasma
International Nuclear Information System (INIS)
Mitra, Sukanya; Mohanty, Payal; Sarkar, Sourav; Alam, Jan-E
2013-01-01
The effects of viscosity on the space-time evolution of quark gluon plasma produced in nuclear collisions at relativistic heavy ion collider energies have been studied. The entropy generated due to the viscous motion of the fluid has been taken into account in constraining the initial temperature by the final multiplicity (measured at the freeze-out point). The viscous effects on the photon spectra has been introduced consistently through the evolution dynamics and phase space factors of all the participating partons/hadrons in the production process. In contrast to some of the recent calculations the present work includes the contribution from the hadronic phase. A small change in the transverse momentum (p T ) distribution of photons is observed due to viscous effects. (author)
Directory of Open Access Journals (Sweden)
Bruno C. Silva
2017-05-01
Full Text Available IntroductionObstructive sleep apnea (OSA is common in edematous states, notably in hemodialysis patients. In this population, overnight fluid shift can play an important role on the pathogenesis of OSA. The effect of compression stockings (CS and continuous positive airway pressure (CPAP on fluid shift is barely known. We compared the effects of CS and CPAP on fluid dynamics in a sample of patients with OSA in hemodialysis, through a randomized crossover study.MethodsEach participant performed polysomnography (PSG at baseline, during CPAP titration, and after 1 week of wearing CS. Neck circumference (NC and segmental bioelectrical impedance were done before and after PSG.ResultsFourteen patients were studied (53 ± 9 years; 57% men; body mass index 29.7 ± 6.8 kg/m2. Apnea–hypopnea index (AHI decreased from 20.8 (14.2; 39.6 at baseline to 7.9 (2.8; 25.4 during CPAP titration and to 16.7 (3.5; 28.9 events/h after wearing CS (CPAP vs. baseline, p = 0.004; CS vs. baseline, p = 0.017; and CPAP vs. CS, p = 0.017. Nocturnal intracellular trunk water was higher after wearing CS in comparison to baseline and CPAP (p = 0.03. CS reduced the fluid accumulated in lower limbs during the day, although not significantly. Overnight fluid shift at baseline, CPAP, and CS was −183 ± 72, −343 ± 220, and −290 ± 213 ml, respectively (p = 0.006. Overnight NC increased at baseline (0.7 ± 0.4 cm, decreased after CPAP (−1.0 ± 0.4 cm, and while wearing CS (−0.4 ± 0.8 cm (CPAP vs. baseline, p < 0.0001; CS vs. baseline, p = 0.001; CPAP vs. CS, p = 0.01.ConclusionCS reduced AHI by avoiding fluid retention in the legs, favoring accumulation of water in the intracellular component of the trunk, thus avoiding fluid shift to reach the neck. CPAP improved OSA by exerting local pressure on upper airway, with no impact on fluid redistribution. CPAP performed significantly better than CS
The effect of diffusion in a new viscous continuum traffic model
International Nuclear Information System (INIS)
Yu Lei; Li Tong; Shi Zhongke
2010-01-01
In this Letter, we propose a new continuum traffic model with a viscous term. The linear stability condition for viscous shock waves is derived. We derive the Korteweg-de Vries (KdV) equation near the neutral stability line. Then we investigate the effect of the viscous term by numerical simulations. The results show that viscosity may induce oscillations and the amplitude of the oscillation increases as the viscosity coefficient increases. This agrees with the linear stability condition. The local clusters are compressed by increasing the viscosity coefficient in the cluster study.
The effect of diffusion in a new viscous continuum traffic model
Energy Technology Data Exchange (ETDEWEB)
Yu Lei, E-mail: yuleijk@126.co [College of Automation, Northwestern Polytechnical University, Xi' an, ShaanXi (China); Li Tong [Department of Mathematics, University of Iowa, Iowa City, IA (United States); Shi Zhongke [College of Automation, Northwestern Polytechnical University, Xi' an, ShaanXi (China)
2010-05-10
In this Letter, we propose a new continuum traffic model with a viscous term. The linear stability condition for viscous shock waves is derived. We derive the Korteweg-de Vries (KdV) equation near the neutral stability line. Then we investigate the effect of the viscous term by numerical simulations. The results show that viscosity may induce oscillations and the amplitude of the oscillation increases as the viscosity coefficient increases. This agrees with the linear stability condition. The local clusters are compressed by increasing the viscosity coefficient in the cluster study.
International Nuclear Information System (INIS)
Kreider, J.F.
1985-01-01
This book is an introduction on fluid mechanics incorporating computer applications. Topics covered are as follows: brief history; what is a fluid; two classes of fluids: liquids and gases; the continuum model of a fluid; methods of analyzing fluid flows; important characteristics of fluids; fundamentals and equations of motion; fluid statics; dimensional analysis and the similarity principle; laminar internal flows; ideal flow; external laminar and channel flows; turbulent flow; compressible flow; fluid flow measurements
Lagrangian finite element formulation for fluid-structure interaction and application
International Nuclear Information System (INIS)
Hautfenne, M.H.
1983-01-01
The aim of this communication is to present a new finite element software (FLUSTRU) for fluid-structure interaction in a lagrangian formulation. The stiffness and damping matrices of the fluid are computed from the governing laws of the medium: the fluid is supposed to be viscous and compressible (Stokes' equations). The main problem stated by the lagrangian formulation of the fluid is the presence of spurious free-vibration modes (zero energy modes) in the fluid. Those modes are generated by the particular form of the matrix. These spurious modes have been examined and two particular methods to eliminate them have been developed: industrial applications prove the efficiency of the proposed methods. (orig./GL)
Relic gravitons and viscous cosmologies
International Nuclear Information System (INIS)
Cataldo, Mauricio; Mella, Patricio
2006-01-01
Previously it was shown that there exists a class of viscous cosmological models which violate the dominant energy condition for a limited amount of time after which they are smoothly connected to the ordinary radiation era (which preserves the dominant energy conditions). This violation of the dominant energy condition at an early cosmological epoch may influence the slopes of energy spectra of relic gravitons that might be of experimental relevance. However, the bulk viscosity coefficient of these cosmologies became negative during the ordinary radiation era, and then the entropy of the sources driving the geometry decreases with time. We show that in the presence of viscous sources with a linear barotropic equation of state p=γρ we get viscous cosmological models with positive bulk viscous stress during all their evolution, and hence the matter entropy increases with the expansion time. In other words, in the framework of viscous cosmologies, there exist isotropic models compatible with the standard second law of thermodynamics which also may influence the slopes of energy spectra of relic gravitons
Ludwig Prandtl and Boundary Layers in Fluid Flow
Indian Academy of Sciences (India)
His research is ... research in fluid mechan- ... For common fluids the viscous force is proportional to .... that the analogy is only a very crude, qualitative one. ..... separation is turbulent and the fluid in the wake is nearly stagnant. Method of.
Directory of Open Access Journals (Sweden)
WU Renchao
2016-06-01
Full Text Available In this paper, we consider three dimensional compressible viscous magnetohydro dynamic equations(MHD with external potentialforce. We first derive the corresponding non-constantstationary solutions. Then we show global well-posedness of the initial value problem for the three dimensional compressible viscous magnetohydrodynamic equations, provided that rescribed initial data is close to the stationary solution.
Energy Technology Data Exchange (ETDEWEB)
Abishev, S K; Bulgakov, R R; Sakharov, V A
1981-01-01
Basic features are presented of a new experimental-research unit of gas-lift recovery of oil UGDN-2 for conditions of lifting the highly viscous oil. It is proposed that this unit be used to conduct experiments and to determine the calculated relationships of a gas-liquid lifter on fluids simulating highly viscous oil.
Microfluidic System Simulation Including the Electro-Viscous Effect
Rojas, Eileen; Chen, C. P.; Majumdar, Alok
2007-01-01
This paper describes a practical approach using a general purpose lumped-parameter computer program, GFSSP (Generalized Fluid System Simulation Program) for calculating flow distribution in a network of micro-channels including electro-viscous effects due to the existence of electrical double layer (EDL). In this study, an empirical formulation for calculating an effective viscosity of ionic solutions based on dimensional analysis is described to account for surface charge and bulk fluid conductivity, which give rise to electro-viscous effect in microfluidics network. Two dimensional slit micro flow data was used to determine the model coefficients. Geometry effect is then included through a Poiseuille number correlation in GFSSP. The bi-power model was used to calculate flow distribution of isotropically etched straight channel and T-junction microflows involving ionic solutions. Performance of the proposed model is assessed against experimental test data.
Scaling the viscous circular hydraulic jump
Argentina, Mederic; Cerda, Enrique; Duchesne, Alexis; Limat, Laurent
2017-11-01
The formation mechanism of hydraulic jumps has been proposed by Belanger in 1828 and rationalised by Lord Rayleigh in 1914. As the Froude number becomes higher than one, the flow super criticality induces an instability which yields the emergence of a steep structure at the fluid surface. Strongly deformed liquid-air interface can be observed as a jet of viscous fluid impinges a flat boundary at high enough velocity. In this experimental setup, the location of the jump depends on the viscosity of the liquid, as shown by T. Bohr et al. in 1997. In 2014, A. Duchesne et al. have established the constancy of the Froude number at jump. Hence, it remains a contradiction, in which the radial hydraulic jump location might be explained through inviscid theory, but is also viscosity dependent. We present a model based on the 2011 Rojas et al. PRL, which solves this paradox. The agreement with experimental measurements is excellent not only for the prediction of the position of the hydraulic jump, but also for the determination of the fluid thickness profile. We predict theoretically the critical value of the Froude number, which matches perfectly to that measured by Duchesne et al. We acknowledge the support of the CNRS and the Universit Cte d'Azur, through the IDEX funding.
Nanoconfined ionic liquids: Disentangling electrostatic and viscous forces
Lhermerout, Romain; Perkin, Susan
2018-01-01
Recent reports of surface forces across nanoconfined ionic liquids have revealed the existence of an anomalously long-ranged interaction apparently of electrostatic origin. Ionic liquids are viscous, and therefore it is important to inspect rigorously whether the observed repulsive forces are indeed equilibrium forces or, rather, arise from the viscous force during drainage of the fluid between two confining surfaces. In this paper we present our direct measurements of surface forces between mica sheets approaching in the ionic liquid [C2C1Im ] [NTf2] , exploring three orders of magnitude in approach velocity. Trajectories are systematically fitted by solving the equation of motion, allowing us to disentangle the viscous and equilibrium contributions. First, we find that the drainage obeys classical hydrodynamics with a negative slip boundary condition in the range of the structural force, implying that a nanometer -thick portion of the liquid in the vicinity of the solid surface is composed of ordered molecules that do not contribute to the flow. Second, we show that a long-range static force must indeed be invoked, in addition to the viscous force, in order to describe the data quantitatively. This equilibrium interaction decays exponentially and with decay length in agreement with the screening length reported for the same system in previous studies. In those studies the decay was simply checked to be independent of velocity and measured at a low approach rate, rather than explicitly taking account of viscous effects: we explain why this gives indistinguishable outcomes for the screening length by noting that the viscous force is linear to very good approximation over a wide range of distances.
Stokes’ and Lamb's viscous drag laws
International Nuclear Information System (INIS)
Eames, I; Klettner, C A
2017-01-01
Since Galileo used his pulse to measure the time period of a swinging chandelier in the 17th century, pendulums have fascinated scientists. It was not until Stokes' (1851 Camb. Phil. Soc. 9 8–106) (whose interest was spurred by the pendulur time pieces of the mid 19th century) treatise on viscous flow that a theoretical framework for the drag on a sphere at low Reynolds number was laid down. Stokes' famous drag law has been used to determine two fundamental physical constants—the charge on an electron and Avogadro's constant—and has been used in theories which have won three Nobel prizes. Considering its illustrious history it is then not surprising that the flow past a sphere and its two-dimensional analog, the flow past a cylinder, form the starting point of teaching flow past a rigid body in undergraduate level fluid mechanics courses. Usually starting with the two-dimensional potential flow past a cylinder, students progress to the three-dimensional potential flow past a sphere. However, when the viscous flow past rigid bodies is taught, the three-dimensional example of a sphere is first introduced, and followed by (but not often), the two-dimensional viscous flow past a cylinder. The reason why viscous flow past a cylinder is generally not taught is because it is usually explained from an asymptotic analysis perspective. In fact, this added mathematical complexity is why the drag on a cylinder was only solved in 1911, 60 years after the drag on a sphere. In this note, we show that the viscous flow past a cylinder can be explained without the need to introduce any asymptotic analysis while still capturing all the physical insight of this classic fluid mechanics problem. (paper)
Osmosis-driven viscous fingering of oil-in-water emulsions
Liu, Ying; Rallabandi, Bhargav; Baskaran, Mrudhula; Stone, Howard
2017-11-01
Viscous fingering occurs when a low viscosity fluid invades a more viscous fluid. Fingering of two miscible fluids is more complicated than that of immiscible fluids in that there is no sharp fluid-fluid interface and diffusion occurs between the phases. We experimentally studied the fingering of two miscible fluids: an oil-in-water emulsion and a sodium chloride solution. When the concentration of sodium chloride in the water phase in the emulsion exceeds that in the sodium chloride solution, the consequent osmotic flow automatically facilitates the occurrence of the fingering. On the contrary, when the sodium chloride solution has higher concentration, the spreading of emulsion is more uniform than the case without the concentration difference. We provide a model to rationalize and quantify these observations.
Establishment of the technical basis to apply the viscous damper in nuclear power plant
Energy Technology Data Exchange (ETDEWEB)
Nakajima, J.; Suezono, N.; Higuchi, T. [Toshiba Corp., Isogo Nuclear Engineering Center, Isogo-ku, Yokohama (Japan); Katayama, H. [Toshiba Corp., Power and Industrial Systems Research and Development Center, Isogo-ku, Yokohama (Japan)
2014-07-01
In recent years, the technical development of the damper using viscous fluid (hereinafter called 'the viscous damper') for the structures, bridges and components in the general industrial field is remarkable, and the experiences of the application to mitigate influence in an earthquake is being gathered now. In this paper, purpose of the whole activity, schedule, the research and test results carried out so far, and future plan to establish the technical basis to apply the viscous damper in nuclear power plant are reported. (author)
Daripa, Prabir
2011-11-01
We numerically investigate the optimal viscous profile in constant time injection policy of enhanced oil recovery. In particular, we investigate the effect of a combination of interfacial and layer instabilities in three-layer porous media flow on the overall growth of instabilities and thereby characterize the optimal viscous profile. Results based on monotonic and non-monotonic viscous profiles will be presented. Time permitting. we will also present results on multi-layer porous media flows for Newtonian and non-Newtonian fluids and compare the results. The support of Qatar National Fund under a QNRF Grant is acknowledged.
Establishment of the technical basis to apply the viscous damper in nuclear power plant
International Nuclear Information System (INIS)
Nakajima, J.; Suezono, N.; Higuchi, T.; Katayama, H.
2014-01-01
In recent years, the technical development of the damper using viscous fluid (hereinafter called 'the viscous damper') for the structures, bridges and components in the general industrial field is remarkable, and the experiences of the application to mitigate influence in an earthquake is being gathered now. In this paper, purpose of the whole activity, schedule, the research and test results carried out so far, and future plan to establish the technical basis to apply the viscous damper in nuclear power plant are reported. (author)
Simulation of compressible viscous flow in time-dependent domains
Czech Academy of Sciences Publication Activity Database
Česenek, J.; Feistauer, M.; Horáček, Jaromír; Kučera, V.; Prokopova, J.
2013-01-01
Roč. 219, č. 13 (2013), s. 7139-7150 ISSN 0096-3003 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : time dependent domain * ALE method * semi-implicit time discretization * shock indicator Subject RIV: BI - Acoustics Impact factor: 1.600, year: 2013
Improvements for rotary viscous dampers used in spacecraft deployment mechanisms
Stewart, Alphonso; Powers, Charles; Lyons, Ron
1998-01-01
During component level thermal-vacuum deployment testing of eight rotary viscous dampers for the Tropical Rainfall Measuring Mission (TRMM) satellite, all the dampers failed to provide damping during a region of the deployment. Radiographic examination showed that air in the damping fluid caused the undamped motion when the dampers were operated in a vacuum environment. Improvements in the procedure used to fill the dampers with damping fluid, the installation of a Viton vacuum seal in the damper cover, and improved screening techniques eliminated the problem.
Numerical solution of inviscid and viscous laminar and turbulent flow around the airfoil
Directory of Open Access Journals (Sweden)
Slouka Martin
2016-01-01
Full Text Available This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox k-omega model. Calculations are done for NACA 0012 and RAE 2822 airfoil profile for the different angles of upstream flow. Numerical results are compared and discussed with experimental data.
Large scale structure from viscous dark matter
Blas, Diego; Garny, Mathias; Tetradis, Nikolaos; Wiedemann, Urs Achim
2015-01-01
Cosmological perturbations of sufficiently long wavelength admit a fluid dynamic description. We consider modes with wavevectors below a scale $k_m$ for which the dynamics is only mildly non-linear. The leading effect of modes above that scale can be accounted for by effective non-equilibrium viscosity and pressure terms. For mildly non-linear scales, these mainly arise from momentum transport within the ideal and cold but inhomogeneous fluid, while momentum transport due to more microscopic degrees of freedom is suppressed. As a consequence, concrete expressions with no free parameters, except the matching scale $k_m$, can be derived from matching evolution equations to standard cosmological perturbation theory. Two-loop calculations of the matter power spectrum in the viscous theory lead to excellent agreement with $N$-body simulations up to scales $k=0.2 \\, h/$Mpc. The convergence properties in the ultraviolet are better than for standard perturbation theory and the results are robust with respect to varia...
Streng, Martin; Streng, M.; ten Cate, Eric; ten Cate, Eric (H.H.); Geurts, Bernardus J.; Kuerten, Johannes G.M.
1998-01-01
We consider several aspects of efficient numerical simulation of viscous compressible flow on both homogeneous and heterogeneous workstation-clusters. We consider dedicated systems, as well as clusters operating in a multi-user environment. For dedicated homogeneous clusters, we show that with
Renormalization group approach to causal bulk viscous cosmological models
International Nuclear Information System (INIS)
Belinchon, J A; Harko, T; Mak, M K
2002-01-01
The renormalization group method is applied to the study of homogeneous and flat Friedmann-Robertson-Walker type universes, filled with a causal bulk viscous cosmological fluid. The starting point of the study is the consideration of the scaling properties of the gravitational field equations, the causal evolution equation of the bulk viscous pressure and the equations of state. The requirement of scale invariance imposes strong constraints on the temporal evolution of the bulk viscosity coefficient, temperature and relaxation time, thus leading to the possibility of obtaining the bulk viscosity coefficient-energy density dependence. For a cosmological model with bulk viscosity coefficient proportional to the Hubble parameter, we perform the analysis of the renormalization group flow around the scale-invariant fixed point, thereby obtaining the long-time behaviour of the scale factor
Thermal and viscous effects on sound waves: revised classical theory.
Davis, Anthony M J; Brenner, Howard
2012-11-01
In this paper the recently developed, bi-velocity model of fluid mechanics based on the principles of linear irreversible thermodynamics (LIT) is applied to sound propagation in gases taking account of first-order thermal and viscous dissipation effects. The results are compared and contrasted with the classical Navier-Stokes-Fourier results of Pierce for this same situation cited in his textbook. Comparisons are also made with the recent analyses of Dadzie and Reese, whose molecularly based sound propagation calculations furnish results virtually identical with the purely macroscopic LIT-based bi-velocity results below, as well as being well-supported by experimental data. Illustrative dissipative sound propagation examples involving application of the bi-velocity model to several elementary situations are also provided, showing the disjoint entropy mode and the additional, evanescent viscous mode.
IUTAM Symposium on Lubricated Transport of Viscous Materials
1998-01-01
The main objective of the First International Symposium on Lubricated Transport of Viscous Materials was to bring together scientists and engineers from academia and industryto discuss current research work and exchange ideas in this newly emerging field. It is an area offluid dynamics devoted to laying bare the principlesofthe lubricated transport of viscous materials such as crude oil, concentrated oil/water emulsion, slurries and capsules. It encompasses several types of problem. Studies of migration of particulates away from walls, Segre-Silverberg effects, lubrication versus lift and shear-induced migration belong to one category. Some of the technological problems are the fluid dynamics ofcore flows emphasizing studies ofstability, problems of start-up, lift-off and eccentric flow where gravity causes the core flow to stratify. Another category of problems deals with the fouling of pipe walls with oil, with undesirable increases in pressure gradients and even blocking. This study involves subjects like ...
Viscous dissipation and Joule heating effects in MHD 3D flow with heat and mass fluxes
Muhammad, Taseer; Hayat, Tasawar; Shehzad, Sabir Ali; Alsaedi, Ahmed
2018-03-01
The present research explores the three-dimensional stretched flow of viscous fluid in the presence of prescribed heat (PHF) and concentration (PCF) fluxes. Mathematical formulation is developed in the presence of chemical reaction, viscous dissipation and Joule heating effects. Fluid is electrically conducting in the presence of an applied magnetic field. Appropriate transformations yield the nonlinear ordinary differential systems. The resulting nonlinear system has been solved. Graphs are plotted to examine the impacts of physical parameters on the temperature and concentration distributions. Skin friction coefficients and local Nusselt and Sherwood numbers are computed and analyzed.
Measuring viscosity with a levitating magnet: application to complex fluids
International Nuclear Information System (INIS)
Even, C; Bouquet, F; Deloche, B; Remond, J
2009-01-01
As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-10 6 mPa s are obtained. This experiment is used as an introduction to complex fluids and soft matter physics
Modeling of brittle-viscous flow using discrete particles
Thordén Haug, Øystein; Barabasch, Jessica; Virgo, Simon; Souche, Alban; Galland, Olivier; Mair, Karen; Abe, Steffen; Urai, Janos L.
2017-04-01
Many geological processes involve both viscous flow and brittle fractures, e.g. boudinage, folding and magmatic intrusions. Numerical modeling of such viscous-brittle materials poses challenges: one has to account for the discrete fracturing, the continuous viscous flow, the coupling between them, and potential pressure dependence of the flow. The Discrete Element Method (DEM) is a numerical technique, widely used for studying fracture of geomaterials. However, the implementation of viscous fluid flow in discrete element models is not trivial. In this study, we model quasi-viscous fluid flow behavior using Esys-Particle software (Abe et al., 2004). We build on the methodology of Abe and Urai (2012) where a combination of elastic repulsion and dashpot interactions between the discrete particles is implemented. Several benchmarks are presented to illustrate the material properties. Here, we present extensive, systematic material tests to characterize the rheology of quasi-viscous DEM particle packing. We present two tests: a simple shear test and a channel flow test, both in 2D and 3D. In the simple shear tests, simulations were performed in a box, where the upper wall is moved with a constant velocity in the x-direction, causing shear deformation of the particle assemblage. Here, the boundary conditions are periodic on the sides, with constant forces on the upper and lower walls. In the channel flow tests, a piston pushes a sample through a channel by Poisseuille flow. For both setups, we present the resulting stress-strain relationships over a range of material parameters, confining stress and strain rate. Results show power-law dependence between stress and strain rate, with a non-linear dependence on confining force. The material is strain softening under some conditions (which). Additionally, volumetric strain can be dilatant or compactant, depending on porosity, confining pressure and strain rate. Constitutive relations are implemented in a way that limits the
Mirzadeh, Mohammad; Bazant, Martin
2017-11-01
Interfacial instabilities are ubiquitous in Fluid Mechanics and have been one of the main the subjects of pattern formation. However, these instabilities could lead to inefficiencies which are undesired in many applications. For instance, viscous fingering results in residual trapping of oil during secondary recovery when a low-viscosity fluid, e.g. water, is used for injection. In their seminal work, Saffman and Taylor showed that the onset of this instability is controlled by the viscosity ratio of the two fluids. However, other physiochemical processes could enhance or suppress viscous fingering. Here we consider the role of salinity effects on the front stability. Our recent theory suggests that viscous fingering could be controlled, and even suppressed, by appropriately injecting electric currents. However, even in the absence of any external currents, strong electrokinetic coupling (present in small pores when the electric double layers overlap) can reduce viscous fingering by increasing the ``effective viscosity'' of the injected fluid. These findings suggest that it might be possible to improve extraction efficiencies by appropriately controlling the salt concentration of the injected fluid.
Lectures on Mathematical Foundation of Turbulent Viscous Flows
Miyakawa, Tetsuro
2006-01-01
Five leading specialists reflect on different and complementary approaches to fundamental questions in the study of the Fluid Mechanics and Gas Dynamics equations. Constantin presents the Euler equations of ideal incompressible fluids and discusses the blow-up problem for the Navier-Stokes equations of viscous fluids, describing some of the major mathematical questions of turbulence theory. These questions are connected to the Caffarelli-Kohn-Nirenberg theory of singularities for the incompressible Navier-Stokes equations that is explained in Gallavotti's lectures. Kazhikhov introduces the theory of strong approximation of weak limits via the method of averaging, applied to Navier-Stokes equations. Y. Meyer focuses on several nonlinear evolution equations - in particular Navier-Stokes - and some related unexpected cancellation properties, either imposed on the initial condition, or satisfied by the solution itself, whenever it is localized in space or in time variable. Ukai presents the asymptotic analysis th...
Prandtl, Ludwig
1953-01-01
Equilibrium of liquids and gases ; kinematics : dynamics of frictionless fluids ; motion of viscous fluids : turbulence : fluid resistance : practical applications ; flow with appreciable volume changes (dynamics of gases) ; miscellaneous topics.
Evidence of nonuniqueness and oscillatory solutions in computational fluid mechanics
International Nuclear Information System (INIS)
Nunziato, J.W.; Gartling, D.K.; Kipp, M.E.
1985-01-01
We will review some of our recent experiences in computing solutions for nonlinear fluids in relatively simple, two-dimensional geometries. The purpose of this discussion will be to display by example some of the interesting but difficult questions that arise when ill-behaved solutions are obtained numerically. We will consider two examples. As the first example, we will consider a nonlinear elastic (compressible) fluid with chemical reactions and discuss solutions for detonation and detonation failure in a two-dimensional cylinder. In this case, the numerical algorithm utilizes a finite-difference method with artificial viscosity (von Neumann-Richtmyer method) and leads to two, distinctly different, stable solutions depending on the time step criterion used. The second example to be considered involves the convection of a viscous fluid in a rectangular container as a result of an exothermic polymerization reaction. A solidification front develops near the top of the container and propagates down through the fluid, changing the aspect ratio of the region ahead of the front. Using a Galerkin-based finite element method, a numerical solution of the partial differential equations is obtained which tracks the front and correctly predicts the fluid temperatures near the walls. However, the solution also exhibits oscillatory behavior with regard to the number of cells in the fluid ahead of the front and in the strength of the cells. More definitive experiments and analysis are required to determine whether this oscillatory phenomena is a numerical artifact or a physical reality. 20 refs., 14 figs
Friedmann model with viscous cosmology in modified f(R,T) gravity theory
Energy Technology Data Exchange (ETDEWEB)
Singh, C.P.; Kumar, Pankaj [Delhi Technological University, Department of Applied Mathematics, Delhi (India)
2014-10-15
In this paper, we introduce the bulk viscosity in the formalism of modified gravity theory in which the gravitational action contains a general function f(R,T), where R and T denote the curvature scalar and the trace of the energy.momentum tensor, respectively, within the framework of a flat Friedmann-Robertson-Walker model. As an equation of state for a prefect fluid, we take p = (γ - 1)ρ, where 0 ≤ γ ≤ 2 and a viscous term as a bulk viscosity due to the isotropic model, of the form ξ = ξ{sub 0} + ξ{sub 1}H, where ξ{sub 0} and ξ{sub 1} are constants, and H is the Hubble parameter. The exact non-singular solutions to the corresponding field equations are obtained with non-viscous and viscous fluids, respectively, by assuming a simplest particular model of the form of f(R,T) = R + 2f(T), where f(T) = αT (α is a constant). A big-rip singularity is also observed for γ < 0 at a finite value of cosmic time under certain constraints. We study all possible scenarios with the possible positive and negative ranges of α to analyze the expansion history of the universe. It is observed that the universe accelerates or exhibits a transition from a decelerated phase to an accelerated phase under certain constraints of ξ{sub 0} and ξ{sub 1}. We compare the viscous models with the non-viscous one through the graph plotted between the scale factor and cosmic time and find that the bulk viscosity plays a major role in the expansion of the universe. A similar graph is plotted for the deceleration parameter with non-viscous and viscous fluids and we find a transition from decelerated to accelerated phase with some form of bulk viscosity. (orig.)
Brownian motion in a flowing fluid revisited
International Nuclear Information System (INIS)
Ramshaw, J.D.
1981-01-01
It is shown how the phenomenon of osmosis may be treated using the phenomenological theory of Brownian motion in a flowing fluid. The theory is also generalized to include viscous stresses in the particle and mixture momentum equations
Hussaini, M. Y. (Editor); Kumar, A. (Editor); Salas, M. D. (Editor)
1993-01-01
The purpose here is to assess the state of the art in the areas of numerical analysis that are particularly relevant to computational fluid dynamics (CFD), to identify promising new developments in various areas of numerical analysis that will impact CFD, and to establish a long-term perspective focusing on opportunities and needs. Overviews are given of discretization schemes, computational fluid dynamics, algorithmic trends in CFD for aerospace flow field calculations, simulation of compressible viscous flow, and massively parallel computation. Also discussed are accerelation methods, spectral and high-order methods, multi-resolution and subcell resolution schemes, and inherently multidimensional schemes.
Alternating currents and shear waves in viscous electronics
Semenyakin, M.; Falkovich, G.
2018-02-01
Strong interaction among charge carriers can make them move like viscous fluid. Here we explore alternating current (ac) effects in viscous electronics. In the Ohmic case, incompressible current distribution in a sample adjusts fast to a time-dependent voltage on the electrodes, while in the viscous case, momentum diffusion makes for retardation and for the possibility of propagating slow shear waves. We focus on specific geometries that showcase interesting aspects of such waves: current parallel to a one-dimensional defect and current applied across a long strip. We find that the phase velocity of the wave propagating along the strip respectively increases/decreases with the frequency for no-slip/no-stress boundary conditions. This is so because when the frequency or strip width goes to zero (alternatively, viscosity go to infinity), the wavelength of the current pattern tends to infinity in the no-stress case and to a finite value in a general case. We also show that for dc current across a strip with a no-stress boundary, there are only one pair of vortices, while there is an infinite vortex chain for all other types of boundary conditions.
Cardy-Verlinde entropy formula in viscous cosmology
International Nuclear Information System (INIS)
Brevik, I.; Odintsov, S.D.
2002-01-01
The results of a paper by Verlinde (hep-th/0008140), discussing the holographic principle in a radiation dominated universe, are extended when allowing the cosmic fluid to possess a bulk viscosity. This corresponds to a nonconformally invariant theory. The generalization of the Cardy-Verlinde entropy formula to the case of a viscous universe seems from a formal point of view to be possible, although we question on physical grounds some elements of this kind of theory, especially the manner in which the Casimir energy is evaluated. Our discussion suggests that for nonconformally invariant theories the holographic definition of Casimir energy should be modified
Viscous fingering and channeling in chemical enhanced oil recovery
Daripa, Prabir; Dutta, Sourav
2017-11-01
We have developed a hybrid numerical method based on discontinuous finite element method and modified method of characteristics to compute the multiphase multicomponent fluid flow in porous media in the context of chemical enhanced oil recovery. We use this method to study the effect of various chemical components on the viscous fingering and channeling in rectilinear and radial flow configurations. We will also discuss about the efficiency of various flooding schemes based on these understandings. Time permitting, we will discuss about the effect of variable injection rates in these practical setting. U.S. National Science Foundation Grant DMS-1522782.
Fluid mechanics in fluids at rest.
Brenner, Howard
2012-07-01
Using readily available experimental thermophoretic particle-velocity data it is shown, contrary to current teachings, that for the case of compressible flows independent dye- and particle-tracer velocity measurements of the local fluid velocity at a point in a flowing fluid do not generally result in the same fluid velocity measure. Rather, tracer-velocity equality holds only for incompressible flows. For compressible fluids, each type of tracer is shown to monitor a fundamentally different fluid velocity, with (i) a dye (or any other such molecular-tagging scheme) measuring the fluid's mass velocity v appearing in the continuity equation and (ii) a small, physicochemically and thermally inert, macroscopic (i.e., non-Brownian), solid particle measuring the fluid's volume velocity v(v). The term "compressibility" as used here includes not only pressure effects on density, but also temperature effects thereon. (For example, owing to a liquid's generally nonzero isobaric coefficient of thermal expansion, nonisothermal liquid flows are to be regarded as compressible despite the general perception of liquids as being incompressible.) Recognition of the fact that two independent fluid velocities, mass- and volume-based, are formally required to model continuum fluid behavior impacts on the foundations of contemporary (monovelocity) fluid mechanics. Included therein are the Navier-Stokes-Fourier equations, which are now seen to apply only to incompressible fluids (a fact well-known, empirically, to experimental gas kineticists). The findings of a difference in tracer velocities heralds the introduction into fluid mechanics of a general bipartite theory of fluid mechanics, bivelocity hydrodynamics [Brenner, Int. J. Eng. Sci. 54, 67 (2012)], differing from conventional hydrodynamics in situations entailing compressible flows and reducing to conventional hydrodynamics when the flow is incompressible, while being applicable to both liquids and gases.
Viscous forces and bulk viscoelasticity near jamming
Baumgarten, K.; Tighe, B.P.
2017-01-01
When weakly jammed packings of soft, viscous, non-Brownian spheres are probed mechanically, they respond with a complex admixture of elastic and viscous effects. While many of these effects are understood for specific, approximate models of the particles' interactions, there are a number of proposed
Ten themes of viscous liquid dynamics
DEFF Research Database (Denmark)
Dyre, J. C.
2007-01-01
Ten ‘themes' of viscous liquid physics are discussed with a focus on how they point to a general description of equilibrium viscous liquid dynamics (i.e., fluctuations) at a given temperature. This description is based on standard time-dependent Ginzburg-Landau equations for the density fields...
Viscous bursting of suspended films
Debrégeas, G.; Martin, P.; Brochard-Wyart, F.
1995-11-01
Soap films break up by an inertial process. We present here the first observations on freely suspended films of long-chain polymers, where viscous effects are dominant and no surfactant is present. A hole is nucleated at time 0 and grows up to a radius R(t) at time t. A surprising feature is that the liquid from the hole is not collected into a rim (as it is in soap films): The liquid spreads out without any significant change of the film thickness. The radius R(t) grows exponentially with time, R~exp(t/τ) [while in soap films R(t) is linear]. The rise time τ~ηe/2γ where η is viscosity, e is thickness (in the micron range), and γ is surface tension. A simple model is developed to explain this growth law.
Electrokinetic Control of Viscous Fingering
Mirzadeh, Mohammad; Bazant, Martin Z.
2017-10-01
We present a theory of the interfacial stability of two immiscible electrolytes under the coupled action of pressure gradients and electric fields in a Hele-Shaw cell or porous medium. Mathematically, our theory describes a phenomenon of "vector Laplacian growth," in which the interface moves in response to the gradient of a vector-valued potential function through a generalized mobility tensor. Physically, we extend the classical Saffman-Taylor problem to electrolytes by incorporating electrokinetic (EK) phenomena. A surprising prediction is that viscous fingering can be controlled by varying the injection ratio of electric current to flow rate. Beyond a critical injection ratio, stability depends only upon the relative direction of flow and current, regardless of the viscosity ratio. Possible applications include porous materials processing, electrically enhanced oil recovery, and EK remediation of contaminated soils.
Three-dimensional lattice Boltzmann model for compressible flows.
Sun, Chenghai; Hsu, Andrew T
2003-07-01
A three-dimensional compressible lattice Boltzmann model is formulated on a cubic lattice. A very large particle-velocity set is incorporated in order to enable a greater variation in the mean velocity. Meanwhile, the support set of the equilibrium distribution has only six directions. Therefore, this model can efficiently handle flows over a wide range of Mach numbers and capture shock waves. Due to the simple form of the equilibrium distribution, the fourth-order velocity tensors are not involved in the formulation. Unlike the standard lattice Boltzmann model, no special treatment is required for the homogeneity of fourth-order velocity tensors on square lattices. The Navier-Stokes equations were recovered, using the Chapman-Enskog method from the Bhatnagar-Gross-Krook (BGK) lattice Boltzmann equation. The second-order discretization error of the fluctuation velocity in the macroscopic conservation equation was eliminated by means of a modified collision invariant. The model is suitable for both viscous and inviscid compressible flows with or without shocks. Since the present scheme deals only with the equilibrium distribution that depends only on fluid density, velocity, and internal energy, boundary conditions on curved wall are easily implemented by an extrapolation of macroscopic variables. To verify the scheme for inviscid flows, we have successfully simulated a three-dimensional shock-wave propagation in a box and a normal shock of Mach number 10 over a wedge. As an application to viscous flows, we have simulated a flat plate boundary layer flow, flow over a cylinder, and a transonic flow over a NACA0012 airfoil cascade.
DNABIT Compress - Genome compression algorithm.
Rajarajeswari, Pothuraju; Apparao, Allam
2011-01-22
Data compression is concerned with how information is organized in data. Efficient storage means removal of redundancy from the data being stored in the DNA molecule. Data compression algorithms remove redundancy and are used to understand biologically important molecules. We present a compression algorithm, "DNABIT Compress" for DNA sequences based on a novel algorithm of assigning binary bits for smaller segments of DNA bases to compress both repetitive and non repetitive DNA sequence. Our proposed algorithm achieves the best compression ratio for DNA sequences for larger genome. Significantly better compression results show that "DNABIT Compress" algorithm is the best among the remaining compression algorithms. While achieving the best compression ratios for DNA sequences (Genomes),our new DNABIT Compress algorithm significantly improves the running time of all previous DNA compression programs. Assigning binary bits (Unique BIT CODE) for (Exact Repeats, Reverse Repeats) fragments of DNA sequence is also a unique concept introduced in this algorithm for the first time in DNA compression. This proposed new algorithm could achieve the best compression ratio as much as 1.58 bits/bases where the existing best methods could not achieve a ratio less than 1.72 bits/bases.
Implementation aspects of the Boundary Element Method including viscous and thermal losses
DEFF Research Database (Denmark)
Cutanda Henriquez, Vicente; Juhl, Peter Møller
2014-01-01
The implementation of viscous and thermal losses using the Boundary Element Method (BEM) is based on the Kirchhoff’s dispersion relation and has been tested in previous work using analytical test cases and comparison with measurements. Numerical methods that can simulate sound fields in fluids...
Directory of Open Access Journals (Sweden)
Anna Maria Pellegrino
2017-12-01
Full Text Available This paper refers to complex granular-fluid mixtures involved into geophysical flows, such as debris and hyper-concentrated flows. For such phenomena, the interstitial fluids play a role when they are in the viscous regime. Referring to experiments on granular-fluid mixture carried out with pressure imposed annular shear cell, we study the rheological behaviour of dense mixture involving both spheres and irregular-shaped particles. For the case of viscous suspensions with irregular grains, a significant scatter of data from the trend observed for mixtures with spherical particles was evident. In effect, the shape of the particles likely plays a fundamental role in the flow dynamics, and the constitutive laws proposed by the frictional theory for the spheres are no longer valid. Starting from the frictional approach successfully applied to suspension of spheres, we demonstrate that also in case of irregular particles the mixture rheology may be fully characterized by the two relationships involving friction coefficient µ and volume concentration Ф as a function of the dimensionless viscous number Iv. To this goal, we provided a new consistent general model, referring to the volume fraction law and friction law, which accounts for the particle shape. In this way, the fitting parameters reduce just to the static friction angle µ1, and the two parameters, k and fs related to the grain shape. The resulting general model may apply to steady fully developed flows of saturated granular fluid mixture in the viscous regime, no matter of granular characteristics.
Viscous damping of solitary waves in the mud banks of Kerala, West coast of India
Digital Repository Service at National Institute of Oceanography (India)
Shenoi, S.S.C.; Murty, C.S.
Analysis of wave damping in mud bank region following the process of transfer of wave energy to the interior of fluid column through the boundary layer and the energy loss computations owing to viscous shear beneath the solitary wave over a smooth...
Effect of viscous dissipation on mixed convection flow in a vertical ...
African Journals Online (AJOL)
The reference temperature of the external fluid is considered to be equal and different. The perturbation method which is valid for small values of perturbation parameter is used to find the combined effects of buoyancy forces and viscous dissipation. The limitation imposed on the perturbation parameter is relaxed by solving ...
Effect of constant heat flux at outer cylinder on stability of viscous ...
African Journals Online (AJOL)
In this paper, the stability of the Couette flow of a viscous incompressible fluid between two concentric rotating cylinders is studied in the presence of a radial temperature gradient, when the outer cylinder is maintained at a constant heat flux. The analytical solution of the eigen-value problem is obtained by using the ...
Call your health insurance or prescription plan: Find out if they pay for compression stockings. Ask if your durable medical equipment benefit pays for compression stockings. Get a prescription from your doctor. Find a medical equipment store where they can ...
Saintillan, David
2018-01-01
An active fluid denotes a viscous suspension of particles, cells, or macromolecules able to convert chemical energy into mechanical work by generating stresses on the microscale. By virtue of this internal energy conversion, these systems display unusual macroscopic rheological signatures, including a curious transition to an apparent superfluid-like state where internal activity exactly compensates viscous dissipation. These behaviors are unlike those of classical complex fluids and result from the coupling of particle configurations with both externally applied flows and internally generated fluid disturbances. Focusing on the well-studied example of a suspension of microswimmers, this review summarizes recent experiments, models, and simulations in this area and highlights the critical role played by the rheological response of these active materials in a multitude of phenomena, from the enhanced transport of passive suspended objects to the emergence of spontaneous flows and collective motion.
Kannan, R. M.; Pullepu, Bapuji; Immanuel, Y.
2018-04-01
A two dimensional mathematical model is formulated for the transient laminar free convective flow with heat transfer over an incompressible viscous fluid past a vertical cone with uniform surface heat flux with combined effects of viscous dissipation and radiation. The dimensionless boundary layer equations of the flow which are transient, coupled and nonlinear Partial differential equations are solved using the Network Simulation Method (NSM), a powerful numerical technique which demonstrates high efficiency and accuracy by employing the network simulator computer code Pspice. The velocity and temperature profiles have been investigated for various factors, namely viscous dissipation parameter ε, Prandtl number Pr and radiation Rd are analyzed graphically.
DYNAMICS OF THIN VISCOUS LAYERS
ROJAS, NICOLAS
2011-01-01
As Isaac Newton discovered in Mechanics, and published in his Principia Mathematica in 1687, inertial effects are essential to describe natural phenomena. In the case of Fluid Dynamics, inertia was included by Claude-Louis Navier and George Gabriel Stokes almost two centuries after in 1822 when calculating the mass and momentum conservation of au infinitesimal fluid elemeut. Although Navier-Stokes equations are very useful for describing any event of any liquid or gas and there...
Metode Penurunan Respon Dinamik Sistem Poros-rotor dengan Peredam Viscous Rotary
Nusyirwan, Nusyirwan
2014-01-01
Viscosity or viscosity is one of the quantities that are very important in the analysis of the behavior and movement of fluids that come into contact with other objects such as solids {solid body). Viscous dampers can be used to reduce the amplitude of the response due to the unbalanced mass, rotation critically, noise and shock loads. Absorbers working with fluid film bearing securities which are placed at a certain point, which is connected to the shaft-rotating rotor. Certain viscosity flu...
Viscous shear in the Kerr metric
International Nuclear Information System (INIS)
Anderson, M.R.; Lemos, J.P.S.
1988-01-01
Models of viscous flows on to black holes commonly assume a zero-torque boundary condition at the radius of the last stable Keplerian orbit. It is here shown that this condition is wrong. The viscous torque is generally non-zero at both the last stable orbit and the horizon itself. The existence of a non-zero viscous torque at the horizon does not require the transfer of energy or angular momentum across any spacelike distance, and so does not violate causality. Further, in comparison with the viscous torque in the distant, Newtonian regime, the viscous torque on the horizon is often reversed, so that angular momentum is viscously advected inwards rather than outwards. This phenomenon is first suggested by an analysis of the quasi-stationary case, and then demonstrated explicitly for a series of cold, dynamical flows which fall freely from the last stable orbit in the Schwarzschild and Kerr metrics. In the steady flows constructed here, the net torque on the hole is always directed in the usual sense; any reversal in the viscous torque is offset by an increase in the convected flux of angular momentum. (author)
Effects of viscous pressure on warm inflationary generalized cosmic Chaplygin gas model
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Saleem, Rabia, E-mail: msharif.math@pu.edu.pk, E-mail: rabiasaleem1988@yahoo.com [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan)
2014-12-01
This paper is devoted to study the effects of bulk viscous pressure on an inflationary generalized cosmic Chaplygin gas model using FRW background. The matter contents of the universe are assumed to be inflaton and imperfect fluid. We evaluate inflaton fields, potentials and entropy density for variable as well as constant dissipation and bulk viscous coefficients in weak as well as high dissipative regimes during intermediate era. In order to discuss inflationary perturbations, we evaluate entropy density, scalar (tensor) power spectra, their corresponding spectral indices, tensor-scalar ratio and running of spectral index in terms of inflaton which are constrained using recent Planck, WMAP7 and Bicep2 probes.
Effects of viscous pressure on warm inflationary generalized cosmic Chaplygin gas model
International Nuclear Information System (INIS)
Sharif, M.; Saleem, Rabia
2014-01-01
This paper is devoted to study the effects of bulk viscous pressure on an inflationary generalized cosmic Chaplygin gas model using FRW background. The matter contents of the universe are assumed to be inflaton and imperfect fluid. We evaluate inflaton fields, potentials and entropy density for variable as well as constant dissipation and bulk viscous coefficients in weak as well as high dissipative regimes during intermediate era. In order to discuss inflationary perturbations, we evaluate entropy density, scalar (tensor) power spectra, their corresponding spectral indices, tensor-scalar ratio and running of spectral index in terms of inflaton which are constrained using recent Planck, WMAP7 and Bicep2 probes
Directory of Open Access Journals (Sweden)
Mukesh Kumar Awasthi
2013-01-01
Full Text Available The instability of a thin sheet of viscous and dielectric liquid moving in the same direction as an air stream in the presence of a uniform horizontal electric field has been carried out using viscous potential flow theory. It is observed that aerodynamic-enhanced instability occurs if the Weber number is much less than a critical value related to the ratio of the air and liquid stream velocities, viscosity ratio of two fluids, the electric field, and the dielectric constant values. Liquid viscosity has stabilizing effect in the stability analysis, while air viscosity has destabilizing effect.
Viscous and Joule heating effects on MHD free convection flow with variable plate temperature
International Nuclear Information System (INIS)
Hossain, M.A.
1990-09-01
A steady two-dimensional laminar boundary layer flow of a viscous incompressible and electrically conducting fluid past a vertical heated plate with variable temperature in the presence of a transverse uniform magnetic field has been investigated by bringing the effect of viscous and Joules heating. The non-dimensional boundary layer equations are solved using the implicit finite difference method along with Newton's approximation for small Prandtl number chosen as typical of coolant liquid metals at operating temperature. (author). 10 refs, 2 figs, 1 tab
Bianchi Type-I bulk viscous fluid string dust magnetized ...
Indian Academy of Sciences (India)
It is interesting to note that magnetic field present in galactic and inter galactic spaces plays a significant role at cosmological scale. Melvin [3] in the cosmological solution for dust and electromagnetic field suggested that during the evolution of the universe, the matter was in highly ionized state and is smoothly coupled with.
Low moduli elastomers with low viscous dissipation
DEFF Research Database (Denmark)
Bejenariu, Anca Gabriela; Yu, Liyun; Skov, Anne Ladegaard
2012-01-01
A controlled reaction schema for addition curing silicones leads to both significantly lower elastic modulus and lower viscous dissipation than for the chemically identical network prepared by the traditional reaction schema....
Paramecia swimming in viscous flow
Zhang, P.; Jana, S.; Giarra, M.; Vlachos, P. P.; Jung, S.
2015-12-01
Ciliates like Paramecia exhibit fore-aft asymmetry in their body shapes, and preferentially swim in the direction of the slender anterior rather than the wider posterior. However, the physical reasons for this preference are not well understood. In this work, we propose that specific features of the fluid flow around swimming Paramecia confer some energetic advantage to the preferred swimming direction. Therefore, we seek to understand the effects of body asymmetry and swimming direction on the efficiency of swimming and the flux of fluid into the cilia layer (and thus of food into the oral groove), which we assumed to be primary factors in the energy budgets of these organisms. To this end, we combined numerical techniques (the boundary element method) and laboratory experiments (micro particle image velocimetry) to develop a quantitative model of the flow around a Paramecium and investigate the effect of the body shape on the velocity fields, as well as on the swimming and feeding behaviors. Both simulation and experimental results show that velocity fields exhibit fore-aft asymmetry. Moreover, the shape asymmetry revealed an increase of the fluid flux into the cilia layer compared to symmetric body shapes. Under the assumption that cilia fluid intake and feeding efficiency are primary factors in the energy budgets of Paramecia, our model predicts that the anterior swimming direction is energetically favorable to the posterior swimming direction.
Reduced viscosity interpreted for fluid/gas mixtures
Lewis, D. H.
1981-01-01
Analysis predicts decrease in fluid viscosity by comparing pressure profile of fluid/gas mixture with that of power-law fluid. Fluid is taken to be viscous, non-Newtonian, and incompressible; the gas to be ideal; the flow to be inertia-free, isothermal, and one dimensional. Analysis assists in design of flow systems for petroleum, coal, polymers, and other materials.
Salama, Amgad
2013-02-01
Some sort of controversy is associated with the problem of viscous dissipation in saturated porous media for which we try to present a comparison study between the influences of the different terms contributing to this phenomenon. We consider viscous dissipation by studying the case of semi-infinite flat plate embedded in saturated porous medium and is kept at constant, higher temperature compared with the surrounding fluid. The fluid is induced to move upwards by natural convection during which viscous dissipation is considered. The boundary layer assumptions are considered to simplify the treatment and to highlight the influencing parameters. The behavior of temperature, and velocity fields in the neighborhood of the vertical flat plate were used to highlight the effects of these parameters. Three terms were considered to contribute to viscous dissipation, namely Darcy\\'s term, the Forchheimer term and Al-Hadharami\\'s term. Although there are no unanimous agreements between researchers to include the Forchhemier term in the dissipation function, some researchers argued it might have an indirect effect and hence for this sake and for completion purposes, we include it in this comparison study. Dimensional considerations reveal that Darcy\\'s term is influenced by Gebhart number, the Forchheimer term is controlled by the non-Darcy parameter and Al-Hadharami\\'s term is influenced by Darcy\\'s number. The governing, non-dimensional set of equations together with the imposed boundary conditions is numerically investigated by finite element method. The results for the details of the governing parameters are presented and investigated. It is found that the irreversible process of transforming the kinetic energy of the moving fluid to heat energy via the viscosity of the moving fluid (i.e., viscous dissipation) is very much influenced by the relative magnitude of these dimensionless parameters. © 2012 Elsevier Masson SAS. All rights reserved.
Mukherjee, Debraj; Pressman, Barry D; Krakow, Deborah; Rimoin, David L; Danielpour, Moise
2014-09-01
Achondroplasia may be associated with compression at the cervicomedullary junction. Determining which patients are at greatest risk for neurological complications of cervicomedullary compression can be difficult. In the current study the authors reviewed their records to determine the incidence and clinical significance of dynamic cervicomedullary stenosis and obstruction of CSF flow along with surgical outcomes following posterior fossa decompression. The authors reviewed 34 consecutive cases involving symptomatic children with achondroplasia undergoing cervicomedullary decompression performed by a single surgeon over 11 years. Of these patients, 29 had undergone preoperative dynamic MRI of the cervicomedullary junction with cine (cinema) CSF flow studies; 13 of these patients underwent postoperative dynamic MRI studies. Clinical outcomes included changes in polysomnography, head circumference percentile, and fontanel characteristics. Radiographic outcomes included changes in dynamic spinal cord diameter, improvement in CSF flow at the foramen magnum, and change in the Evans ratio. Patients were predominantly female, with a mean age at presentation of 6.6 years and mean follow-up of 3.7 years (range 1-10 years). All patients had moderate to excellent improvement in postoperative polysomnography, slight decrease in average head circumference percentile (from 46.9th percentile to 45.7th percentile), and no subjective worsening of fontanel characteristics. The Evans ratio decreased by 2%, spinal cord diameter increased an average of 3.1 mm, 5.2 mm, and 0.2 mm in the neutral, flexed, and extended positions, respectively, and CSF flow improved qualitatively in all 3 positions. There were no postoperative infections, CSF leaks, or other major complications. None of the patients undergoing initial foramen magnum decompression performed at our medical center required reoperation. Patients with achondroplasia and symptomatic cervicomedullary compression have increased risk
Flow of conductive fluid between parallel disks in an axial magnetic field, (2)
International Nuclear Information System (INIS)
Koike, Kazuo; Kamiyama, Shin-ichi
1981-01-01
The basic characteristics of the flow in a disc type non-equilibrium MHD power generator were studied. The flow of conductive fluid between parallel disks in an axial magnetic field was analyzed as the subsonic MHD turbulent approach flow of viscous compressible fluid, taking the electron temperature dependence of conductivity into account. The equations for the flow between disks are described by ordinary electromagnetic hydrodynamic approximation. Practical numerical calculation was performed for the non-equilibrium argon plasma seeded with potassium. The effects of the variation of characteristics of non-equilibrium plasma in main flow and boundary layer on the flow characteristics became clear. The qualitative tendency of the properties of MHD generators can be well explained. (Kato, T.)
A fluid-solid finite element method for the analysis of reactor safety problems
International Nuclear Information System (INIS)
Mitra, Santanu; Kumar, Ashutosh; Sinhamahapatra, K.P.
2006-01-01
The work presented herein can broadly be categorized as a fluid-structure interaction problem. The response of a circular cylindrical structure subjected to cross flow is examined using the finite element method for both the liquid and the structure domains. The cylindrical tube is mounted elastically at the ends and is free to move under the action of the unsteady flow-induced forces. The fluid is considered to be acoustic compressible and viscous. A Galerkin finite element method implemented on a triangular mesh is used to solve the time-dependent Navier-Stokes equations. The cylinder motion is modeled using a five-degrees of freedom generalized shell element structural dynamics model. The numerical simulations of the response of the calandria tubes/pressure tubes, adjustor rod and shut-off rod of a nuclear reactor are presented. A few typical results are presented to assess the accuracy and applicability of the developed modules
Fluids and vortex from constrained fluctuations around C-metric black holes
Hao, Xin; Wu, Bin; Zhao, Liu
2017-08-01
By foliating the four-dimensional C-metric black hole spacetime, we consider a kind of initial-value-like formulation of the vacuum Einstein's equation, the holographic initial data is a double consisting of the induced metric and the Brown-York energy momentum tensor on an arbitrary initial hypersurface. Then by perturbing the initial data that generates the background spacetime, it is shown that, in an appropriate limit, the fluctuation modes are governed by the continuity equation and the compressible Navier-Stokes equation which describe the momentum transport in non-relativistic viscous fluid on a flat Newtonian space. It turns out that the flat space fluid behaves as a pure vortex and the viscosity to entropy ratio is subjected to the black hole acceleration.
Huang, Xiangdi; Li, Jing
2018-03-01
For the three-dimensional full compressible Navier-Stokes system describing the motion of a viscous, compressible, heat-conductive, and Newtonian polytropic fluid, we establish the global existence and uniqueness of classical solutions with smooth initial data which are of small energy but possibly large oscillations where the initial density is allowed to vanish. Moreover, for the initial data, which may be discontinuous and contain vacuum states, we also obtain the global existence of weak solutions. These results generalize previous ones on classical and weak solutions for initial density being strictly away from a vacuum, and are the first for global classical and weak solutions which may have large oscillations and can contain vacuum states.
On the continuum theory of the one-fluid solar wind for small Prandtl number
International Nuclear Information System (INIS)
Johnson, R.S.
1976-01-01
The continuum theory for a single-species gas expanding into a vacuum (or near vacuum) is considered. The gas is assumed compressible, viscous and heat conducting with a constant Prandtl number and viscosity proportional to (temperature) sup(ω), ω > 1. The gas is under the influence of a gravitational field centred on the Sun. For small Prandtl number (which is realistic for the one-fluid solar wind), the method of matched asymptotic expansions is used to construct a solution describing the complete flow field from the surface of the Sun to infinity. The first two regions correspond to those found by Roberts and Soward (Proc. R. Soc. Lond.; A328:185 (1972)) for large thermal conductivity; the next involves the viscous terms, and in the fourth the viscous terms dominate. It it shown from the fourth region that either the flow remains supersonic but terminates at a finite point, or the flow becomes subsonic through a diffuse shock layer and approaches a non-zero pressure at infinity. It is seen that the existence of a critical point (subsonic/supersonic transition) together with a known pressure at infinity can uniquely determine the complete solution. However, to correspond with typical results near the Sun and at the Earth's orbit the pressure at infinity is found to be very much larger than that generally accepted. (author)
Theers, Mario; Winkler, Roland G
2014-08-28
We investigate the emergent dynamical behavior of hydrodynamically coupled microrotors by means of multiparticle collision dynamics (MPC) simulations. The two rotors are confined in a plane and move along circles driven by active forces. Comparing simulations to theoretical results based on linearized hydrodynamics, we demonstrate that time-dependent hydrodynamic interactions lead to synchronization of the rotational motion. Thermal noise implies large fluctuations of the phase-angle difference between the rotors, but synchronization prevails and the ensemble-averaged time dependence of the phase-angle difference agrees well with analytical predictions. Moreover, we demonstrate that compressibility effects lead to longer synchronization times. In addition, the relevance of the inertia terms of the Navier-Stokes equation are discussed, specifically the linear unsteady acceleration term characterized by the oscillatory Reynolds number ReT. We illustrate the continuous breakdown of synchronization with the Reynolds number ReT, in analogy to the continuous breakdown of the scallop theorem with decreasing Reynolds number.
Measuring Viscosity with a Levitating Magnet: Application to Complex Fluids
Even, C.; Bouquet, F.; Remond, J.; Deloche, B.
2009-01-01
As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-10[superscript 6] mPa s are obtained. This experiment is used as an introduction to complex…
A sharp interface Cartesian grid method for viscous simulation of shocked particle-laden flows
Das, Pratik; Sen, Oishik; Jacobs, Gustaaf; Udaykumar, H. S.
2017-09-01
A Cartesian grid-based sharp interface method is presented for viscous simulations of shocked particle-laden flows. The moving solid-fluid interfaces are represented using level sets. A moving least-squares reconstruction is developed to apply the no-slip boundary condition at solid-fluid interfaces and to supply viscous stresses to the fluid. The algorithms developed in this paper are benchmarked against similarity solutions for the boundary layer over a fixed flat plate and against numerical solutions for moving interface problems such as shock-induced lift-off of a cylinder in a channel. The framework is extended to 3D and applied to calculate low Reynolds number steady supersonic flow over a sphere. Viscous simulation of the interaction of a particle cloud with an incident planar shock is demonstrated; the average drag on the particles and the vorticity field in the cloud are compared to the inviscid case to elucidate the effects of viscosity on momentum transfer between the particle and fluid phases. The methods developed will be useful for obtaining accurate momentum and heat transfer closure models for macro-scale shocked particulate flow applications such as blast waves and dust explosions.
Shear-Induced Membrane Fusion in Viscous Solutions
Kogan, Maxim
2014-05-06
Large unilamellar lipid vesicles do not normally fuse under fluid shear stress. They might deform and open pores to relax the tension to which they are exposed, but membrane fusion occurring solely due to shear stress has not yet been reported. We present evidence that shear forces in a viscous solution can induce lipid bilayer fusion. The fusion of 1,2-dioleoyl-sn-glycero-3- phosphocholine (DOPC) liposomes is observed in Couette flow with shear rates above 3000 s-1 provided that the medium is viscous enough. Liposome samples, prepared at different viscosities using a 0-50 wt % range of sucrose concentration, were studied by dynamic light scattering, lipid fusion assays using Förster resonance energy transfer (FRET), and linear dichroism (LD) spectroscopy. Liposomes in solutions with 40 wt % (or more) sucrose showed lipid fusion under shear forces. These results support the hypothesis that under suitable conditions lipid membranes may fuse in response to mechanical-force- induced stress. © 2014 American Chemical Society.
Treatment of fully enclosed FSI using artificial compressibility
CSIR Research Space (South Africa)
Bogaers, Alfred EJ
2013-07-01
Full Text Available artificial compressibility (AC), whereby the fluid equations are modified to allow for compressibility which internally incorporates an approximation of the system volume change as a function of pressure....
Fast fluid registration of medical images
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Gramkow, Claus
1996-01-01
This paper offers a new fast algorithm for non-rigid viscous fluid registration of medical images that is at least an order of magnitude faster than the previous method by (Christensen et al., 1994). The core algorithm in the fluid registration method is based on a linear elastic deformation...
Technical fluid dynamics. 7. rev. ed.
International Nuclear Information System (INIS)
Becker, E.; Piltz, E.
1993-01-01
An introductory textbook for students of engineering containing the following subjects: Definition and properties of fluids, hydrostatics, Bernoulli's equation, theorem of momentum for steadystate flows, wing lattice and single wing, plane parallel flow of a viscous fluid, pipe flow, boundary layers, gas flows. (orig.) [de
Energy recovery during expansion of compressed gas using power plant low-quality heat sources
Ochs, Thomas L [Albany, OR; O'Connor, William K [Lebanon, OR
2006-03-07
A method of recovering energy from a cool compressed gas, compressed liquid, vapor, or supercritical fluid is disclosed which includes incrementally expanding the compressed gas, compressed liquid, vapor, or supercritical fluid through a plurality of expansion engines and heating the gas, vapor, compressed liquid, or supercritical fluid entering at least one of the expansion engines with a low quality heat source. Expansion engines such as turbines and multiple expansions with heating are disclosed.
Laminar motion of the incompressible fluids in self-acting thrust bearings with spiral grooves.
Velescu, Cornel; Popa, Nicolae Calin
2014-01-01
We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the "pumping" direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances) and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc.), for the laminar and permanent motion regime.
Laminar Motion of the Incompressible Fluids in Self-Acting Thrust Bearings with Spiral Grooves
Directory of Open Access Journals (Sweden)
Cornel Velescu
2014-01-01
Full Text Available We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the “pumping” direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc., for the laminar and permanent motion regime.
Simultaneous viscous-inviscid coupling via transpiration
International Nuclear Information System (INIS)
Yiu, K.F.C.; Giles, M.B.
1995-01-01
In viscous-inviscid coupling analysis, the direct coupling technique and the inverse coupling technique are commonly adopted. However, stability and convergence of the algorithms derived are usually very unsatisfactory. Here, by using the transpiration technique to simulate the effect of the displacement thickness, a new simultaneous coupling method is derived. The integral boundary layer equations and the full potential equation are chosen to be the viscous-inviscid coupled system. After discretization, the Newton-Raphson technique is proposed to solve the coupled nonlinear system. Several numerical results are used to demonstrate the accuracy and efficiency of the proposed method. 15 refs., 23 figs
Fully-developed heat transfer in annuli with viscous dissipation
Energy Technology Data Exchange (ETDEWEB)
Coelho, P.M. [Universidade do Porto, Porto (Portugal). Centro de Estudos de Fenomenos de Transporte, DEMEGI, Faculdade de Engenharia; Pinho, F.T. [Universidade do Porto, Porto (Portugal). Centro de Estudos de Fenomenos de Transporte, Faculdade de Engenharia
2006-09-15
For Newtonian concentric annular flows analytical solutions are obtained under imposed asymmetric constant wall heat fluxes as well as under imposed asymmetric constant wall temperatures, taking into account viscous dissipation and for fluid dynamic and thermally fully-developed conditions. Results for the special case of the heat flux ratio for identical wall temperatures and the critical Brinkman numbers marking changes of sign in wall heat fluxes are also derived. Equations are presented for the Nusselt numbers at the inner and outer walls, bulk temperature and normalised temperature distribution as a function of all relevant non-dimensional numbers. Given the complexity of the derived equations, simpler exact expressions are presented for the Nusselt numbers for ease of use, with their coefficients given in tables as a function of the radius ratio. (author)
Two-particle microrheology of quasi-2D viscous systems.
Prasad, V; Koehler, S A; Weeks, Eric R
2006-10-27
We study the spatially correlated motions of colloidal particles in a quasi-2D system (human serum albumin protein molecules at an air-water interface) for different surface viscosities eta s. We observe a transition in the behavior of the correlated motion, from 2D interface dominated at high eta s to bulk fluid dependent at low eta s. The correlated motions can be scaled onto a master curve which captures the features of this transition. This master curve also characterizes the spatial dependence of the flow field of a viscous interface in response to a force. The scale factors used for the master curve allow for the calculation of the surface viscosity eta s that can be compared to one-particle measurements.
Energy and Transmissibility in Nonlinear Viscous Base Isolators
Markou, Athanasios A.; Manolis, George D.
2016-09-01
High damping rubber bearings (HDRB) are the most commonly used base isolators in buildings and are often combined with other systems, such as sliding bearings. Their mechanical behaviour is highly nonlinear and dependent on a number of factors. At first, a physical process is suggested here to explain the empirical formula introduced by J.M. Kelly in 1991, where the dissipated energy of a HDRB under cyclic testing, at constant frequency, is proportional to the amplitude of the shear strain, raised to a power of approximately 1.50. This physical process is best described by non-Newtonian fluid behaviour, originally developed by F.H. Norton in 1929 to describe creep in steel at high-temperatures. The constitutive model used includes a viscous term, that depends on the absolute value of the velocity, raised to a non-integer power. The identification of a three parameter Kelvin model, the simplest possible system with nonlinear viscosity, is also suggested here. Furthermore, a more advanced model with variable damping coefficient is implemented to better model in this complex mechanical process. Next, the assumption of strain-rate dependence in their rubber layers under cyclic loading is examined in order to best interpret experimental results on the transmission of motion between the upper and lower surfaces of HDRB. More specifically, the stress-relaxation phenomenon observed with time in HRDB can be reproduced numerically, only if the constitutive model includes a viscous term, that depends on the absolute value of the velocity raised to a non-integer power, i. e., the Norton fluid previously mentioned. Thus, it becomes possible to compute the displacement transmissibility function between the top and bottom surfaces of HDRB base isolator systems and to draw engineering-type conclusions, relevant to their design under time-harmonic loads.
Alfriend, K. T.
1973-01-01
A ring partially filled with a viscous fluid has been analyzed as a nutation damper for a spinning satellite. The fluid has been modelled as a rigid slug of finite length moving in a tube and resisted by a linear viscous force. It is shown that there are two distinct modes of motion, called the spin synchronous mode and the nutation synchronous mode. Time constants for each mode are obtained for both the symmetric and asymmetric satellite. The effects of a stop in the tube and an offset of the ring from the spin axis are also investigated. An analysis of test results is also given including a determination of the effect of gravity on the time constants in the two modes.
The application of finite element method for mhd viscous flow over a porous stretching sheet
International Nuclear Information System (INIS)
Mahmood, R.; Sajid, M.
2007-01-01
This work is concerned with the magnetohydrodynamic (MHD) viscous flow due to a porous stretching sheet. The similarity solution of the problem is obtained using finite element method. The physical quantities of interest like the fluid velocity and skin friction coefficient is obtained and discussed under the influence of suction parameter and Hartman number. It is evident from the results that MHD can be used to control the boundary layer thickness. (author)
Magnetic power piston fluid compressor
Gasser, Max G. (Inventor)
1994-01-01
A compressor with no moving parts in the traditional sense having a housing having an inlet end allowing a low pressure fluid to enter and an outlet end allowing a high pressure fluid to exit is described. Within the compressor housing is at least one compression stage to increase the pressure of the fluid within the housing. The compression stage has a quantity of magnetic powder within the housing, is supported by a screen that allows passage of the fluid, and a coil for selectively providing a magnetic field across the magnetic powder such that when the magnetic field is not present the individual particles of the powder are separated allowing the fluid to flow through the powder and when the magnetic field is present the individual particles of the powder pack together causing the powder mass to expand preventing the fluid from flowing through the powder and causing a pressure pulse to compress the fluid.
Magnetic Viscous Drag for Friction Labs
Gaffney, Chris; Catching, Adam
2016-01-01
The typical friction lab performed in introductory mechanics courses is usually not the favorite of either the student or the instructor. The measurements are not all that easy to make, and reproducibility is usually a troublesome issue. This paper describes the augmentation of such a friction lab with a study of the viscous drag on a magnet…
Dilepton production in schematic causal viscous hydrodynamics
International Nuclear Information System (INIS)
Song, Taesoo; Han, Kyong Chol; Ko, Che Ming
2011-01-01
Assuming that in the hot dense matter produced in relativistic heavy-ion collisions, the energy density, entropy density, and pressure as well as the azimuthal and space-time rapidity components of the shear tensor are uniform in the direction transversal to the reaction plane, we derive a set of schematic equations from the Isreal-Stewart causal viscous hydrodynamics. These equations are then used to describe the evolution dynamics of relativistic heavy-ion collisions by taking the shear viscosity to entropy density ratio of 1/4π for the initial quark-gluon plasma (QGP) phase and of 10 times this value for the later hadron-gas (HG) phase. Using the production rate evaluated with particle distributions that take into account the viscous effect, we study dilepton production in central heavy-ion collisions. Compared with results from the ideal hydrodynamics, we find that although the dilepton invariant mass spectra from the two approaches are similar, the transverse momentum spectra are significantly enhanced at high transverse momenta by the viscous effect. We also study the transverse momentum dependence of dileptons produced from QGP for a fixed transverse mass, which is essentially absent in the ideal hydrodynamics, and find that this so-called transverse mass scaling is violated in the viscous hydrodynamics, particularly at high transverse momenta.
Directory of Open Access Journals (Sweden)
Hayley Letson
Full Text Available Systemic inflammation and coagulopathy are major drivers of injury progression following hemorrhagic trauma. Our aim was to examine the effect of small-volume 3% NaCl adenosine, lidocaine and Mg2+ (ALM bolus and 0.9% NaCl/ALM 'drip' on inflammation and coagulation in a rat model of hemorrhagic shock.Sprague-Dawley rats (429±4 g were randomly assigned to: 1 shams, 2 no-treatment, 3 saline-controls, 4 ALM-therapy, and 5 Hextend®. Hemorrhage was induced in anesthetized-ventilated animals by liver resection (60% left lateral lobe and 50% medial lobe. After 15 min, a bolus of 3% NaCl ± ALM (0.7 ml/kg was administered intravenously (Phase 1 followed 60 min later by 4 hour infusion of 0.9% NaCl ± ALM (0.5 ml/kg/hour with 1-hour monitoring (Phase 2. Plasma cytokines were measured on Magpix® and coagulation using Stago/Rotational Thromboelastometry.After Phase 1, saline-controls, no-treatment and Hextend® groups showed significant falls in white and red cells, hemoglobin and hematocrit (up to 30%, whereas ALM animals had similar values to shams (9-15% losses. After Phase 2, these deficits in non-ALM groups were accompanied by profound systemic inflammation. In contrast, after Phase 1 ALM-treated animals had undetectable plasma levels of IL-1α and IL-1β, and IL-2, IL-6 and TNF-α were below baseline, and after Phase 2 they were less or similar to shams. Non-ALM groups (except shams also lost their ability to aggregate platelets, had lower plasma fibrinogen levels, and were hypocoagulable. ALM-treated animals had 50-fold higher ADP-induced platelet aggregation, and 9.3-times higher collagen-induced aggregation compared to saline-controls, and had little or no coagulopathy with significantly higher fibrinogen shifting towards baseline. Hextend® had poor outcomes.Small-volume ALM bolus/drip mounted a frontline defense against non-compressible traumatic hemorrhage by defending immune cell numbers, suppressing systemic inflammation, improving platelet
Directory of Open Access Journals (Sweden)
A. V. Rusanov
2016-12-01
Full Text Available The results of numerical investigation of spatial flow of viscous incompressible fluid in flow part of Kaplan turbine PL20 Kremenchug HPP at optimum setting angle of runner blade φb = 15° and at maximum setting angle φb = 35° are shown. The flow simulation has been carried out on basis of numerical integration of the Reynolds equations with an additional term containing artificial compressibility. The differential two-parameter model of Menter (SST has been applied to take into account turbulent effects. Numerical integration of the equations is carried out using an implicit quasi-monotone Godunov type scheme of second - order accuracy in space and time. The calculations have been conducted with the help of the software system IPMFlow. The analysis of fluid flow in the flow part elements is shown and the values of hydraulic losses and local cavitation coefficient have been obtained. Comparison of calculated and experimental results has been carried out.
Finite approximations in fluid mechanics
International Nuclear Information System (INIS)
Hirschel, E.H.
1986-01-01
This book contains twenty papers on work which was conducted between 1983 and 1985 in the Priority Research Program ''Finite Approximations in Fluid Mechanics'' of the German Research Society (Deutsche Forschungsgemeinschaft). Scientists from numerical mathematics, fluid mechanics, and aerodynamics present their research on boundary-element methods, factorization methods, higher-order panel methods, multigrid methods for elliptical and parabolic problems, two-step schemes for the Euler equations, etc. Applications are made to channel flows, gas dynamical problems, large eddy simulation of turbulence, non-Newtonian flow, turbomachine flow, zonal solutions for viscous flow problems, etc. The contents include: multigrid methods for problems from fluid dynamics, development of a 2D-Transonic Potential Flow Solver; a boundary element spectral method for nonstationary viscous flows in 3 dimensions; navier-stokes computations of two-dimensional laminar flows in a channel with a backward facing step; calculations and experimental investigations of the laminar unsteady flow in a pipe expansion; calculation of the flow-field caused by shock wave and deflagration interaction; a multi-level discretization and solution method for potential flow problems in three dimensions; solutions of the conservation equations with the approximate factorization method; inviscid and viscous flow through rotating meridional contours; zonal solutions for viscous flow problems
Instrumentation, measurements, and experiments in fluids
Rathakrishnan, E
2007-01-01
NEED AND OBJECTIVE OF EXPERIMENTAL STUDY Some Fluid Mechanics MeasurementsMeasurement SystemsSome of the Important Quantities Associated with FluidFlow MeasurementsFUNDAMENTALS OF FLUID MECHANICSProperties of FluidsThermodynamic PropertiesSurface TensionAnalysis of Fluid FlowBasic and Subsidiary Laws for Continuous MediaKinematics of Fluid FlowStreamlinesPotential FlowViscous FlowsGas DynamicsWIND TUNNELSLow-Speed Wind TunnelsPower Losses in a Wind TunnelHigh-Speed Wind TunnelsHypersonic TunnelsInstrume
Numerical study of fluid motion in bioreactor with two mixers
Energy Technology Data Exchange (ETDEWEB)
Zheleva, I., E-mail: izheleva@uni-ruse.bg [Department of Heat Technology, Hydraulics and Ecology, Angel Kanchev University of Rousse, 8 Studentska str., 7017 Rousse (Bulgaria); Lecheva, A., E-mail: alecheva@uni-ruse.bg [Department of Mathematics, Angel Kanchev University of Rousse, 8 Studentska str., 7017 Rousse (Bulgaria)
2015-10-28
Numerical study of hydrodynamic laminar behavior of a viscous fluid in bioreactor with multiple mixers is provided in the present paper. The reactor is equipped with two disk impellers. The fluid motion is studied in stream function-vorticity formulation. The calculations are made by a computer program, written in MATLAB. The fluid structure is described and numerical results are graphically presented and commented.
International Nuclear Information System (INIS)
Blake, B.; Zumbrun, K.; Lafitte, O.
2010-01-01
For the two-dimensional Navier Stokes equations of isentropic magnetohydrodynamics (MHD) with γ-law gas equation of state, γ≥1, and infinite electrical resistivity, we carry out a global analysis categorizing all possible viscous shock profiles. Precisely, we show that the phase portrait of the Crave ling-wave ODE generically consists of either two rest points connected by a viscous Lax profile, or else four rest points, two saddles and two nodes. In the latter configuration, which rest points are connected by profiles depends on the ratio of viscosities, and can involve Lax, over-compressive, or under-compressive shock profiles. Considered as three-dimensional solutions, under-compressive shocks are Lax-type (Alfven) waves. For the monatomic and diatomic cases γ=5/3 and γ=7/5, with standard viscosity ratio for a nonmagnetic gas, we find numerically that the the nodes are connected by a family of over-compressive profiles bounded by Lax profiles connecting saddles to nodes, with no under-compressive shocks occurring. We carry out a systematic numerical Evans function analysis indicating that all of these two-dimensional shock profiles are linearly and nonlinearly stable, both with respect to two- and three-dimensional perturbations. For the same gas constants, but different viscosity ratios, we investigate also cases for which under-compressive shocks appear; these are seen numerically to be stable as well, both with respect to two-dimensional and (in the neutral sense of convergence to nearby Riemann solutions) three-dimensional perturbations. (authors)
A Gas-kinetic Discontinuous Galerkin Method for Viscous Flow Equations
International Nuclear Information System (INIS)
Liu, Hongwei; Xu, Kun
2007-01-01
This paper presents a Runge-Kutta discontinuous Galerkin (RKDG) method for viscous flow computation. The construction of the RKDG method is based on a gas-kinetic formulation, which not only couples the convective and dissipative terms together, but also includes both discontinuous and continuous representation in the flux evaluation at the cell interface through a simple hybrid gas distribution function. Due to the intrinsic connection between the gaskinetic BGK model and the Navier-Stokes equations, the Navier-Stokes flux is automatically obtained by the present method. Numerical examples for both one dimensional (10) and two dimensional(20) compressible viscous flows are presented to demonstrate the accuracy and shock capturing capability of the current RKDG method