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Sample records for two-dimensional peristaltic flow

  1. Particle motion in unsteady two-dimensional peristaltic flow with application to the ureter

    Science.gov (United States)

    Jiménez-Lozano, Joel; Sen, Mihir; Dunn, Patrick F.

    2009-04-01

    Particle motion in an unsteady peristaltic fluid flow is analyzed. The fluid is incompressible and Newtonian in a two-dimensional planar geometry. A perturbation method based on a small ratio of wave height to wavelength is used to obtain a closed-form solution for the fluid velocity field. This analytical solution is used in conjunction with an equation of motion for a small rigid sphere in nonuniform flow taking Stokes drag, virtual mass, Faxén, Basset, and gravity forces into account. Fluid streamlines and velocity profiles are calculated. Theoretical values for pumping rates are compared with available experimental data. An application to ureteral peristaltic flow is considered since fluid flow in the ureter is sometimes accompanied by particles such as stones or bacteriuria. Particle trajectories for parameters that correspond to calcium oxalates for calculosis and Escherichia coli type for bacteria are analyzed. The findings show that retrograde or reflux motion of the particles is possible and bacterial transport can occur in the upper urinary tract when there is a partial occlusion of the wave. Dilute particle mixing is also investigated, and it is found that some of the particles participate in the formation of a recirculating bolus, and some of them are delayed in transit and eventually reach the walls. This can explain the failure of clearing residuals from the upper urinary tract calculi after successful extracorporeal shock wave lithotripsy. The results may also be relevant to the transport of other physiological fluids and industrial applications in which peristaltic pumping is used.

  2. Motility and peristaltic flow in maintaining microbiome populations

    Science.gov (United States)

    Mirbagheri, Seyed Amir; Fu, Henry C.

    2016-11-01

    Bacteria are an important component of the microbiome in the digestive tract, and must be able to maintain their population despite the fact that the contents of the intestines are constantly flowing towards evacuation. Many bacteria accomplish this by colonizing the surfaces of the intestines where flows diminish, but some species live in the lumen. We attempt to address whether swimming motility of these species plays an important role in maintaining bacterial population in the face of peristaltic pumping out of the intestine. Using a two-dimensional model of peristaltic flows induced by small-amplitude traveling waves we examine the Lagrangian trajectories of passive bacteria as well as motile bacteria, which are treated as Brownian particles undergoing enhanced diffusion due to the bacteria's run-and-tumble motility. We examine how the densities of growing populations of bacteria depend on the combination of motility and peristaltic flow.

  3. Streamline topologies and their bifurcations for mixed convective peristaltic flow

    Directory of Open Access Journals (Sweden)

    Z. Asghar

    2015-09-01

    Full Text Available In this work our focus is on streamlines patterns and their bifurcations for mixed convective peristaltic flow of Newtonian fluid with heat transfer. The flow is considered in a two dimensional symmetric channel and the governing equations are simplified under widely taken assumptions of large wavelength and low Reynolds number in a wave frame of reference. In order to study the streamlines patterns, a system of nonlinear autonomous differential equations are established and dynamical systems approach is used to discuss the local bifurcations and their topological changes. We have discussed all types of bifurcations and their topological changes are presented graphically. We found that the vortices contract along the vertical direction whereas they expand along horizontal direction. A global bifurcations diagram is used to summarize the bifurcations. The trapping and backward flow regions are mainly affected by increasing Grashof number and constant heat source parameter in such a way that trapping region increases whereas backward flow region shrinks.

  4. Janus Spectra in Two-Dimensional Flows

    Science.gov (United States)

    Liu, Chien-Chia; Cerbus, Rory T.; Chakraborty, Pinaki

    2016-09-01

    In large-scale atmospheric flows, soap-film flows, and other two-dimensional flows, the exponent of the turbulent energy spectra, α , may theoretically take either of two distinct values, 3 or 5 /3 , but measurements downstream of obstacles have invariably revealed α =3 . Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which α transitions from 3 to 5 /3 for the streamwise fluctuations but remains equal to 3 for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows.

  5. Janus spectra in two-dimensional flows

    CERN Document Server

    Liu, Chien-Chia; Chakraborty, Pinaki

    2016-01-01

    In theory, large-scale atmospheric flows, soap-film flows and other two-dimensional flows may host two distinct types of turbulent energy spectra---in one, $\\alpha$, the spectral exponent of velocity fluctuations, equals $3$ and the fluctuations are dissipated at the small scales, and in the other, $\\alpha=5/3$ and the fluctuations are dissipated at the large scales---but measurements downstream of obstacles have invariably revealed $\\alpha = 3$. Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which $\\alpha$ has transitioned from $3$ to $5/3$ for the streamwise fluctuations but remains equal to $3$ for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows...

  6. Endoscopic Effects on Peristaltic Flow of a Nanofluid

    Institute of Scientific and Technical Information of China (English)

    Noreen Sher Akbart; S. Nadeem

    2011-01-01

    In the present investigation we have studied the peristaltic flow of a nanofluid in an endoscope. The flow is investigated in a wave frame of reference moving with velocity of the wave c. Analytical solutions have been calculated using Homotopy perturbation method (HPM) for temperature and nanoparticle equation while exact solutions have been calculated for velocity and pressure gradient. Numerical integration have been used to obtain the graphical results for pressure rise and frictional forces. The effects of various emerging parameters are investigated for five different peristaltic waves. Streamlines have been plotted at the end of the article.

  7. Peristaltic flow in non-uniform vessels of the micro-circulatory system

    CERN Document Server

    Maiti, S

    2013-01-01

    Of concern in the paper is generalized a theoretical study concerning the peristaltic flow of blood in the micro-circulatory system. The vessel is considered to be of non-uniform cross-section and blood to be a non-Newtonian fluid. The progressive wave front of the peristaltic flow is supposed sinusoidal/straight section dominated (SSD) (expansion/contraction type); Reynolds number is considered to be small with reference to the flow of physiological fluids. The non-Newtonian behaviour of blood is illustrated by considering the Herschel-Bulkley fluid model. The objective of the study has been to examine the effect of the effects of amplitude ratio, mean pressure gradient, yield stress and the power law index on the velocity distribution, wall shear stress, streamline pattern and trapping. Considerable quantitative differences between the results obtained for transport in two dimensional channel and an axisymmetric circular tube are noticed. The study shows that peristaltic pumping, flow velocity and wall shea...

  8. Two dimensional axisymmetric smooth lattice Ricci flow

    CERN Document Server

    Brewin, Leo

    2015-01-01

    A lattice based method will be presented for numerical investigations of Ricci flow. The method will be applied to the particular case of 2-dimensional axially symmetric initial data on manifolds with S^2 topology. Results will be presented that show that the method works well and agrees with results obtained using contemporary finite difference methods.

  9. Phase separation under two-dimensional Poiseuille flow.

    Science.gov (United States)

    Kiwata, H

    2001-05-01

    The spinodal decomposition of a two-dimensional binary fluid under Poiseuille flow is studied by numerical simulation. We investigated time dependence of domain sizes in directions parallel and perpendicular to the flow. In an effective region of the flow, the power-law growth of a characteristic length in the direction parallel to the flow changes from the diffusive regime with the growth exponent alpha=1/3 to a new regime. The scaling invariance of the growth in the perpendicular direction is destroyed after the diffusive regime. A recurrent prevalence of thick and thin domains which determines log-time periodic oscillations has not been observed in our model. The growth exponents in the infinite system under two-dimensional Poiseuille flow are obtained by the renormalization group.

  10. Dynamics of vortex interactions in two-dimensional flows

    DEFF Research Database (Denmark)

    Juul Rasmussen, J.; Nielsen, A.H.; Naulin, V.

    2002-01-01

    a critical value, a(c). Using the Weiss-field, a(c) is estimated for vortex patches. Introducing an effective radius for vortices with distributed vorticity, we find that 3.3 a(c) ...The dynamics and interaction of like-signed vortex structures in two dimensional flows are investigated by means of direct numerical solutions of the two-dimensional Navier-Stokes equations. Two vortices with distributed vorticity merge when their distance relative to their radius, d/R-0l. is below...

  11. Numerical Study of Two-Dimensional Viscous Flow over Dams

    Institute of Scientific and Technical Information of China (English)

    王利兵; 刘宇陆; 涂敏杰

    2003-01-01

    In this paper, the characteristics of two-dimensional viscous flow over two dams were numerically investigated. The results show that the behavior of the vortices is closely related to the space between two dams, water depth, Fr number and Reynolds number. In addition, the flow properties behind each dam are different, and the changes over two dams are more complex than over one dam. Finally, the relevant turbulent characteristics were analyzed.

  12. Mean flow generation in rotating anelastic two-dimensional convection

    CERN Document Server

    Currie, Laura K

    2016-01-01

    We investigate the processes that lead to the generation of mean flows in two-dimensional anelastic convection. The simple model consists of a plane layer that is rotating about an axis inclined to gravity. The results are two-fold: firstly we numerically investigate the onset of convection in three-dimensions, paying particular attention to the role of stratification and highlight a curious symmetry. Secondly, we investigate the mechanisms that drive both zonal and meridional flows in two dimensions. We find that, in general, non-trivial Reynolds stresses can lead to systematic flows and, using statistical measures, we quantify the role of stratification in modifying the coherence of these flows.

  13. Statistical mechanics of two-dimensional and geophysical flows

    CERN Document Server

    Bouchet, Freddy

    2011-01-01

    The theoretical study of the self-organization of two-dimensional and geophysical turbulent flows is addressed based on statistical mechanics methods. This review is a self-contained presentation of classical and recent works on this subject; from the statistical mechanics basis of the theory up to applications to Jupiter's troposphere and ocean vortices and jets. Emphasize has been placed on examples with available analytical treatment in order to favor better understanding of the physics and dynamics. The equilibrium microcanonical measure is built from the Liouville theorem. On this theoretical basis, we predict the output of the long time evolution of complex turbulent flows as statistical equilibria. This is applied to make quantitative models of two-dimensional turbulence, the Great Red Spot and other Jovian vortices, ocean jets like the Gulf-Stream, and ocean vortices. We also present recent results for non-equilibrium situations, for the studies of either the relaxation towards equilibrium or non-equi...

  14. Two Dimensional Lattice Boltzmann Method for Cavity Flow Simulation

    Directory of Open Access Journals (Sweden)

    Panjit MUSIK

    2004-01-01

    Full Text Available This paper presents a simulation of incompressible viscous flow within a two-dimensional square cavity. The objective is to develop a method originated from Lattice Gas (cellular Automata (LGA, which utilises discrete lattice as well as discrete time and can be parallelised easily. Lattice Boltzmann Method (LBM, known as discrete Lattice kinetics which provide an alternative for solving the Navier–Stokes equations and are generally used for fluid simulation, is chosen for the study. A specific two-dimensional nine-velocity square Lattice model (D2Q9 Model is used in the simulation with the velocity at the top of the cavity kept fixed. LBM is an efficient method for reproducing the dynamics of cavity flow and the results which are comparable to those of previous work.

  15. AN APPROACH IN MODELING TWO-DIMENSIONAL PARTIALLY CAVITATING FLOW

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An approach of modeling viscosity, unsteady partially cavitating flows around lifting bodies is presented. By employing an one-fluid Navier-Stokers solver, the algorithm is proved to be able to handle two-dimensional laminar cavitating flows at moderate Reynolds number. Based on the state equation of water-vapor mixture, the constructive relations of densities and pressures are established. To numerically simulate the cavity wall, different pseudo transition of density models are presumed. The finite-volume method is adopted and the algorithm can be extended to three-dimensional cavitating flows.

  16. Phase Transitions in Two-Dimensional Traffic Flow Models

    CERN Document Server

    Cuesta, J A; Molera, J M; Cuesta, José A; Martinez, Froilán C; Molera, Juan M

    1993-01-01

    Abstract: We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.

  17. Phase Transitions in Two-Dimensional Traffic Flow Models

    CERN Document Server

    Cuesta, José A; Molera, Juan M; Escuela, Angel Sánchez; 10.1103/PhysRevE.48.R4175

    2009-01-01

    We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.

  18. Nonclassical Symmetry Analysis of Heated Two-Dimensional Flow Problems

    Science.gov (United States)

    Naeem, Imran; Naz, Rehana; Khan, Muhammad Danish

    2015-12-01

    This article analyses the nonclassical symmetries and group invariant solution of boundary layer equations for two-dimensional heated flows. First, we derive the nonclassical symmetry determining equations with the aid of the computer package SADE. We solve these equations directly to obtain nonclassical symmetries. We follow standard procedure of computing nonclassical symmetries and consider two different scenarios, ξ1≠0 and ξ1=0, ξ2≠0. Several nonclassical symmetries are reported for both scenarios. Furthermore, numerous group invariant solutions for nonclassical symmetries are derived. The similarity variables associated with each nonclassical symmetry are computed. The similarity variables reduce the system of partial differential equations (PDEs) to a system of ordinary differential equations (ODEs) in terms of similarity variables. The reduced system of ODEs are solved to obtain group invariant solution for governing boundary layer equations for two-dimensional heated flow problems. We successfully formulate a physical problem of heat transfer analysis for fluid flow over a linearly stretching porous plat and, with suitable boundary conditions, we solve this problem.

  19. Epi-two-dimensional flow and generalized enstrophy

    CERN Document Server

    Yoshida, Zensho

    2016-01-01

    The conservation of the enstrophy ($L^2$ norm of the vorticity $\\omega$) plays an essential role in the physics and mathematics of two-dimensional (2D) Euler fluids. Generalizing to compressible ideal (inviscid and barotropic) fluids, the generalized enstrophy $\\int_{\\Sigma(t)} f(\\omega/\\rho)\\rho\\, d^2 x$, ($f$ an arbitrary smooth function, $\\rho$ the density, and $\\Sigma(t)$ an arbitrary 2D domain co-moving with the fluid) is a constant of motion, and plays the same role. On the other hand, for the three-dimensional (3D) ideal fluid, the helicity $\\int_{M} {V}\\cdot\\omega\\,d^3x$, ($V$ the flow velocity, $\\omega=\

  20. Flow of foams in two-dimensional disordered porous media

    Science.gov (United States)

    Dollet, Benjamin; Geraud, Baudouin; Jones, Sian A.; Meheust, Yves; Cantat, Isabelle; Institut de Physique de Rennes Team; Geosciences Rennes Team

    2015-11-01

    Liquid foams are a yield stress fluid with elastic properties. When a foam flow is confined by solid walls, viscous dissipation arises from the contact zones between soap films and walls, giving very peculiar friction laws. In particular, foams potentially invade narrow pores much more efficiently than Newtonian fluids, which is of great importance for enhanced oil recovery. To quantify this effect, we study experimentally flows of foam in a model two-dimensional porous medium, consisting of an assembly of circular obstacles placed randomly in a Hele-Shaw cell, and use image analysis to quantify foam flow at the local scale. We show that bubbles split as they flow through the porous medium, by a mechanism of film pinching during contact with an obstacle, yielding two daughter bubbles per split bubble. We quantify the evolution of the bubble size distribution as a function of the distance along the porous medium, the splitting probability as a function of bubble size, and the probability distribution function of the daughter bubbles. We propose an evolution equation to model this splitting phenomenon and compare it successfully to the experiments, showing how at long distance, the porous medium itself dictates the size distribution of the foam.

  1. ACCRETION DISKS IN TWO-DIMENSIONAL HOYLE-LYTTLETON FLOW

    Energy Technology Data Exchange (ETDEWEB)

    Blondin, John M., E-mail: John_Blondin@ncsu.edu [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States)

    2013-04-20

    We investigate the flip-flop instability observed in two-dimensional planar hydrodynamic simulations of Hoyle-Lyttleton accretion in the case of an accreting object with a radius much smaller than the nominal accretion radius, as one would expect in astrophysically relevant situations. Contrary to previous results with larger accretors, accretion from a homogenous medium onto a small accretor is characterized by a robust, quasi-Keplerian accretion disk. For gas with a ratio of specific heats of 5/3, such a disk remains locked in one direction for a uniform ambient medium. The accretion flow is more variable for gas with a ratio of specific heats of 4/3, with more dynamical interaction of the disk flow with the bow shock leading to occasional flips in the direction of rotation of the accretion disk. In both cases the accretion of angular momentum is determined by the flow pattern behind the accretion shock rather than by the parameters of the upstream flow.

  2. Thin films flowing down inverted substrates: two dimensional flow

    CERN Document Server

    Lin, Te-sheng

    2009-01-01

    We consider free surface instabilities of films flowing on inverted substrates within the framework of lubrication approximation. We allow for the presence of fronts and related contact lines, and explore the role which they play in instability development. It is found that a contact line, modeled by a commonly used precursor film model, leads to free surface instabilities of convective type without any additional natural or excited perturbations. A single parameter D=(3Ca)^{1/3}cot\\alpha, where Ca is the capillary number and \\alpha is the inclination angle, is identified as a governing parameter in the problem. This parameter may be interpreted to reflect the combined effect of inclination angle, film thickness, Reynolds number and the fluid flux. Variation of D leads to change of the wave-like properties of the instabilities, allowing to observe traveling wave behavior, mixed waves, and the waves resembling solitary ones.

  3. Effects of heat and mass transfer on peristaltic flow of a Bingham fluid in the presence of inclined magnetic field and channel with different wave forms

    Energy Technology Data Exchange (ETDEWEB)

    Akram, Safia, E-mail: safia_akram@yahoo.com [Department of Basic Sciences, MCS, National University of Sciences and Technology, Rawalpindi 46000 (Pakistan); Nadeem, S.; Hussain, Anwar [Department of Mathematics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    2014-08-01

    In the present analysis we discussed the influence of heat and mass transfer on the peristaltic flow of a Bingham in an inclined magnetic field and channel with different wave forms. The governing two dimensional equations of momentum, heat and mass transfer are simplified under the assumptions of long wavelength and low Reynolds number approximation. The exact solutions of momentum, heat and mass transfer are calculated. Finally, graphical behaviors of various physical parameters are also discussed through the graphical behavior of pressure rise, pressure gradient, temperature concentration and stream functions. - Highlights: • Combine effects of heat and mass transfer on peristaltic flow problem is discussed. • Effects of inclined magnetic field and channel on new fluid model are discussed. • Effects of different wave forms are also discussed in the present flow problem.

  4. Endoscopy analysis for the peristaltic flow of nanofluids containing carbon nanotubes with heat transfer

    Energy Technology Data Exchange (ETDEWEB)

    Akbar, Noreen Sher [National University of Sciences and Technology, Islamabad (Pakistan)

    2015-07-01

    Cu-water nanofluid with carbon nanotubes is considered for the peristaltic flow in an endoscope. The peristaltic flow for nanofluid is modelled considering that the peristaltic rush wave is a sinusoidal wave that propagates along the walls of the tube. The governing equations for the proposed model are simplified by using the assumptions of long-wavelength and low Reynolds number. Exact solutions have been evaluated for velocity, temperature, and pressure gradient. Graphical results for the numerical values of the flow parameters, i.e. Hartmann number M, the solid volume fraction φ of the nanoparticles, Grashof number Gr, heat absorption parameter β, and radius of the inner tube ε, have been presented for the pressure difference, frictional forces, velocity profile, and temperature profile, and trapping phenomena have been discussed at the end of the article.

  5. Flow Rate Driven by Peristaltic Movement in Plasmodial Tube of Physarum Polycephalum

    Science.gov (United States)

    Yamada, Hiroyasu; Nakagaki, Toshiyuki

    2008-07-01

    We report a theoretical analysis of protoplasmic streaming driven by peristaltic movement in an elastic tube of an amoeba-like organism. The Plasmodium of Physarum polycephalum, a true slime mold, is a large amoeboid organism that adopts a sheet-like form with a tubular network. The network extends throughout the Plasmodium and enables the transport and circulation of chemical signals and nutrients. This tubular flow is driven by periodically propagating waves of active contraction of the tube cortex, a process known as peristaltic movement. We derive the relationship between the phase velocity of the contraction wave and the flow rate, and we discuss the physiological implications of this relationship.

  6. The two-dimensional Godunov scheme and what it means for macroscopic pedestrian flow models

    NARCIS (Netherlands)

    Van Wageningen-Kessels, F.L.M.; Daamen, W.; Hoogendoorn, S.P.

    2015-01-01

    An efficient simulation method for two-dimensional continuum pedestrian flow models is introduced. It is a two-dimensional and multi-class extension of the Go-dunov scheme for one-dimensional road traffic flow models introduced in the mid 1990’s. The method can be applied to continuum pedestrian flo

  7. Elliptic Length Scales in Laminar, Two-Dimensional Supersonic Flows

    Science.gov (United States)

    2015-06-01

    adiabatic wall flows over compression ramps and flows with shock impingements. The new correlations are derived from existing numerical data and...developed for 2D, laminar adiabatic wall flows over compression ramps and flows with shock impingements. These correlations are derived from existing...characterizing the influence of shocks and compression ramps on flat plate flows is presented. New correlations for laminar compressive interactions on

  8. Peristaltic Flow of Phan-Thien-Tanner Fluid in an Asymmetric Channel with Porous Medium

    Directory of Open Access Journals (Sweden)

    Kuppalapalle Vajravelu

    2016-01-01

    Full Text Available This paper deals with peristaltic transport of Phan-Thien-Tanner fluid in an asymmetric channel induced by sinusoidal peristaltic waves traveling down the flexible walls of the channel. The flow is investigated in a wave frame of reference moving with the velocity of the waveby using the long wavelength and low Reynolds number approximations.The nonlinear governing equations are solved employing a perturbation method by choosing as the perturbation parameter. The expressions for velocity, stream function and pressure gradient are obtained. The features of the flow characteristics are analyzed through graphs and the obtained results are discussed in detail. It is noticed that the peristaltic pumping gets reduced due to an increase in the phase difference of the traveling waves. It is also observed that the size of the trapping bolus is a decreasing function of the permeability parameter and the Weissenberg number. Furthermore, the results obtained for the flow characteristics reveal many interesting behaviors that warrant further study on the non-Newtonian fluid phenomena, especially the Peristaltic flow phenomena.

  9. Flow Modelling for partially Cavitating Two-dimensional Hydrofoils

    DEFF Research Database (Denmark)

    Krishnaswamy, Paddy

    2001-01-01

    The present work addresses te computational analysis of partial sheet hydrofoil cavitation in two dimensions. Particular attention is given to the method of simulating the flow at the end of the cavity. A fixed-length partially cavitating panel method is used to predict the height of the re...... of the model and comparing the present calculations with numerical results. The flow around the partially cavitating hydrofoil with a re-entrant jet has also been treated with a viscous/inviscid interactive method. The viscous flow model is based on boundary layer theory applied on the compound foil......, consisting of the union of the cavity and the hydrofoil surface. The change in the flow direction in the cavity closure region is seen to have a slightly adverse effect on the viscous pressure distribution. Otherwise, it is seen that the viscous re-entrant jet solution compares favourably with experimental...

  10. Two-Dimensional Turbulent Separated Flow. Volume 1

    Science.gov (United States)

    1985-06-01

    of detached turbulent boundary layers, even when the sign of U is changed to account for mean backflows. Thus, earlier researchers, such as Kuhn and...Turbulent Shear Layer," Third Symposium on Turbulent Shear Flows, pp. 16.23-16.29. Hillier, R., Latour , M.E.M.P., and Cherry, N.J. (1983), "Unsteady...344. Kuhn , G.D. and Nielsen, J.N. (1971), "An Analytical Method for Calculating Turbulent Separated Flows Due to Adverse Pressure Gradients

  11. Bubbly flows around a two-dimensional circular cylinder

    Science.gov (United States)

    Lee, Jubeom; Park, Hyungmin

    2016-11-01

    Two-phase cross flows around a bluff body occur in many thermal-fluid systems like steam generators, heat exchangers and nuclear reactors. However, our current knowledge on the interactions among bubbles, bubble-induced flows and the bluff body are limited. In the present study, the gas-liquid bubbly flows around a solid circular cylinder are experimentally investigated while varying the mean void fraction from 5 to 27%. The surrounding liquid (water) is initially static and the liquid flow is only induced by the air bubbles. For the measurements, we use the high-speed two-phase particle image velocimetry techniques. First, depending on the mean void fraction, two regimes are classified with different preferential concentration of bubbles in the cylinder wake, which are explained in terms of hydrodynamic force balances acting on rising bubbles. Second, the differences between the two-phase and single-phase flows (while matching their Reynolds numbers) around a circular cylinder will be discussed in relation to effects of bubble dynamics and the bubble-induced turbulence on the cylinder wake. Supported by a Grant (MPSS-CG-2016-02) through the Disaster and Safety Management Institute funded by Ministry of Public Safety and Security of Korean government.

  12. Numerical study for MHD peristaltic flow in a rotating frame.

    Science.gov (United States)

    Hayat, T; Zahir, Hina; Tanveer, Anum; Alsaedi, A

    2016-12-01

    The aim of present investigation is to model and analyze the magnetohydrodynamic (MHD) peristaltic transport of Prandtl fluid in a channel with flexible walls. The whole system consisting of fluid and channel are in a rotating frame of reference with uniform angular velocity. Viscous dissipation in thermal equation is not ignored. The channel boundaries satisfy the convective conditions in terms of temperature. The arising complicated problems are reduced in solvable form using large wavelength and small Reynolds number assumptions. Numerical solution for axial and secondary velocities, temperature and heat transfer coefficient are presented. Main emphasis is given to the outcome of rotation and material parameters of Prandtl fluid on the physical quantities of interest.

  13. Two-dimensional nonlinear travelling waves in magnetohydrodynamic channel flow

    CERN Document Server

    Hagan, Jonathan

    2013-01-01

    The present study is concerned with the stability of a flow of viscous conducting liquid driven by pressure gradient in the channel between two parallel walls subject to a transverse magnetic field. Although the magnetic field has a strong stabilizing effect, this flow, similarly to its hydrodynamic counterpart -- plane Poiseuille flow, is known to become turbulent significantly below the threshold predicted by linear stability theory. We investigate the effect of the magnetic field on 2D nonlinear travelling-wave states which are found at substantially subcritical Reynolds numbers starting from $Re_n=2939$ without the magnetic field and from $Re_n\\sim6.50\\times10^3Ha$ in a sufficiently strong magnetic field defined by the Hartmann number $Ha.$ Although the latter value is by a factor of seven lower than the linear stability threshold $Re_l\\sim4.83\\times10^4Ha$,it is still more by an order of magnitude higher than the experimentally observed value for the onset of turbulence in this flow.

  14. Two-Dimensional Graphs Moving by Mean Curvature Flow

    Institute of Scientific and Technical Information of China (English)

    CHEN Jing Yi; LI Jia Yu; TIAN Gang

    2002-01-01

    A surface Σ is a graph in R4 if there is a unit constant 2-form ω on R4 such that initial surface, then the mean curvature flow has a global solution and the scaled surfaces converge to a self-similar solution. A surface ∑ is a graph in M1 × M2 where M1 and M2 are Riemann surfaces,surface with scalar curvature R, v0 ≥1/√2 on the initial surface, then the mean curvature flow has a global solution and it sub-converges to a minimal surface, if, in addition, R ≥ 0 it converges to a totally geodesic surface which is holomorphic.

  15. Two dimensional RG flows and Yang-Mills instantons

    CERN Document Server

    Gava, Edi; Narain, K S

    2010-01-01

    We study RG flow solutions in (1,0) six dimensional supergravity coupled to an anti-symmetric tensor and Yang-Mills multiplets corresponding to a semisimple group $G$. We turn on $G$ instanton gauge fields, with instanton number $N$, in the conformally flat part of the 6D metric. The solution interpolates between two (4,0) supersymmetric $AdS_3\\times S^3$ backgrounds with two different values of $AdS_3$ and $S^3$ radii and describes an RG flow in the dual 2D SCFT. For the single instanton case and $G=SU(2)$, there exist a consistent reduction ansatz to three dimensions, and the solution in this case can be interpreted as an uplifted 3D solution. Correspondingly, we present the solution in the framework of N=4 $(SU(2)\\ltimes \\mathbf{R}^3)^2$ three dimensional gauged supergravity. The flows studied here are of v.e.v. type, driven by a vacuum expectation value of a (not exactly) marginal operator of dimension two in the UV. We give an interpretation of the supergravity solution in terms of the D1/D5 system in ty...

  16. Efficient solution of two-dimensional steady separated flows

    Science.gov (United States)

    Napolitano, M.

    This work is concerned with the numerical solution of 2D incompressible steady laminar separated flows at moderate-to-high values of Re. The vorticity-stream function Navier-Stokes equations, as well as approximate models based upon the boundary-layer theory, will be considered. The main objective of the paper is to present the development of an efficient approach for solving a class of problems usually referred to as high Re weakly separated flows. A description is given of a block-alternating-direction-implicit method, which applies the approximate factorization scheme of Beam and Warming to the vorticity-stream function equations, using the delta form of the deferred correction procedure of Khosla and Rubin to combine the stability of upwind schemes with the accuracy of central differences. The logical steps which led to the development of a more efficient incremental block-line Gauss-Seidel method and to a simple multigrid strategy particularly suited for this kind of numerical scheme are then outlined. Finally, benchmark-quality solutions for separated flows inside diffusers and channels with smooth as well as sudden expansions are presented.

  17. The Characteristics Method Applied to Stationary Two-Dimensional and Rotationally Symmetrical Gas Flows

    Science.gov (United States)

    Pfeiffer, F.; Meyer-Koenig, W.

    1949-01-01

    By means of characteristics theory, formulas for the numerical treatment of stationary compressible supersonic flows for the two-dimensional and rotationally symmetrical cases have been obtained from their differential equations.

  18. Endoscope effects on MHD peristaltic flow of a power-law fluid

    Directory of Open Access Journals (Sweden)

    T. Hayat

    2006-01-01

    Full Text Available To understand the influence of an inserted endoscope and magnetohydrodynamic (MHD power-law fluid on peristaltic motion, an attempt has been made for flow through tubes. The magnetic field of uniform strength is applied in the transverse direction to the flow. The analysis has been performed under long wavelength at low-Reynolds number assumption. The velocity fields and axial pressure gradient have been evaluated analytically. Numerical results are also presented and discussed.

  19. Blast shocks in quasi-two-dimensional supersonic granular flows.

    Science.gov (United States)

    Boudet, J F; Cassagne, J; Kellay, H

    2009-11-27

    In a thin, dilute, and fast flowing granular layer, the impact of a small sphere generates a fast growing hole devoid of matter. The growth of this hole is studied in detail, and its dynamics is found to mimic that of blast shocks in gases. This dynamics can be decomposed into two stages: a fast initial stage (the blast) and a slower growth regime whose growth velocity is given by the speed of sound in the medium used. A simple model using ingredients already invoked for the case of blast shocks in gases but including the inelastic nature of collisions between grains accounts accurately for our results. The system studied here allows for a detailed study of the full dynamics of a blast as it relaxes from a strong to a weak shock and later to an acoustic disturbance.

  20. Topology of streamlines and vorticity contours for two - dimensional flows

    DEFF Research Database (Denmark)

    Andersen, Morten

    Considering a coordinate-free formulation of helical symmetry rather than more traditional definitions based on coordinates, we discuss basic properties of helical vector fields and compare results from the literature. For inviscid flow where a velocity field is generated by a sum of helical vortex...... generated by a helical vortex filament in an ideal fluid. The classical expression for the stream function obtained by Hardin (Phys. Fluids 25, 1982) contains an infinite sum of modified Bessel functions. Using the approach by Okulov (Russ. J. Eng. Thermophys. 5, 1995) we obtain a closed-form approximation...... by a point vortex above a wall in inviscid fluid. There is no reason to a priori expect equivalent results of the three vortex definitions. However, the study is mainly motivated by the findings of Kudela & Malecha (Fluid Dyn. Res. 41, 2009) who find good agreement between the vorticity and streamlines...

  1. Numerical simulation of two-dimensional steady granular flows in rotating drum: On surface flow rheology

    Science.gov (United States)

    Renouf, M.; Bonamy, D.; Dubois, F.; Alart, P.

    2005-10-01

    The rheology of two-dimensional steady surface flow of cohesionless cylinders in a rotating drum is investigated through nonsmooth contact dynamics simulations. Profiles of volume fraction, translational and angular velocity, rms velocity, strain rate, and stress tensor are measured at the midpoint along the length of the surface-flowing layer, where the flow is generally considered as steady and homogeneous. Analysis of these data and their interrelations suggest the local inertial number—defined as the ratio between local inertial forces and local confinement forces—to be the relevant dimensionless parameter to describe the transition from the quasistatic part of the packing to the flowing part at the surface of the heap. Variations of the components of the stress tensor as well as the ones of rms velocity as a function of the inertial number are analyzed within both the quasistatic and the flowing phases. Their implications are discussed.

  2. Stability of a Two-Dimensional Poiseuille-Type Flow for a Viscoelastic Fluid

    Science.gov (United States)

    Endo, Masakazu; Giga, Yoshikazu; Götz, Dario; Liu, Chun

    2017-03-01

    A viscoelastic flow in a two-dimensional layer domain is considered. An L 2-stability of the Poiseuille-type flow is established provided that both Poiseuille flow and perturbation is sufficiently small. Our analysis is based on a stream function formulation introduced by Lin et al. (Commun Pure Appl Math 58(11):1437-1471, 2005).

  3. Mixed Convection Peristaltic Flow of Third Order Nanofluid with an Induced Magnetic Field

    OpenAIRE

    Saima Noreen

    2013-01-01

    This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quant...

  4. Local approximation for contour dynamics in effectively two-dimensional ideal electron-magnetohydrodynamic flows

    DEFF Research Database (Denmark)

    Ruban, V.P.; Senchenko, Sergey

    2004-01-01

    The evolution of piecewise constant distributions of a conserved quantity related to the frozen-in canonical vorticity in effectively two-dimensional incompressible ideal EMHD flows is analytically investigated by the Hamiltonian method. The study includes the case of axisymmetric flows with zero...

  5. Computation of two-dimensional isothermal flow in shell-and-tube heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Carlucci, L.N.; Galpin, P.F.; Brown, J.D.; Frisina, V.

    1983-07-01

    A computational procedure is outlined whereby two-dimensional isothermal shell-side flow distributions can be calculated for tube bundles having arbitrary boundaries and flow blocking devices, such as sealing strips, defined in arbitrary locations. The procedure is described in some detail and several computed results are presented to illustrate the robustness and generality of the method. 11 figs.

  6. Design considerations for pulsed-flow comprehensive two-dimensional GC: dynamic flow model approach.

    Science.gov (United States)

    Harvey, Paul McA; Shellie, Robert A; Haddad, Paul R

    2010-04-01

    A dynamic flow model, which maps carrier gas pressures and carrier gas flow rates through the first dimension separation column, the modulator sample loop, and the second dimension separation column(s) in a pulsed-flow modulation comprehensive two-dimensional gas chromatography (PFM-GCxGC) system is described. The dynamic flow model assists design of a PFM-GCxGC modulator and leads to rapid determination of pneumatic conditions, timing parameters, and the dimensions of the separation columns and connecting tubing used to construct the PFM-GCxGC system. Three significant innovations are introduced in this manuscript, which were all uncovered by using the dynamic flow model. A symmetric flow path modulator improves baseline stability, appropriate selection of the flow restrictors in the first dimension column assembly provides a generally more stable and robust system, and these restrictors increase the modulation period flexibility of the PFM-GCxGC system. The flexibility of a PFM-GCxGC system resulting from these innovations is illustrated using the same modulation interface to analyze Special Antarctic Blend (SAB) diesel using 3 s and 9 s modulation periods.

  7. New insight into flow development and two dimensionality of turbulent channel flows

    Science.gov (United States)

    Vinuesa, Ricardo; Bartrons, Eduard; Chiu, Daniel; Dressler, Kristofer M.; Rüedi, J.-D.; Suzuki, Yasumasa; Nagib, Hassan M.

    2014-06-01

    The experimental conditions required for a turbulent channel flow to be considered fully developed and nominally two dimensional remain a challenging objective. In this study, we show that the flow obtained in a high-aspect-ratio channel facility cannot be reproduced by direct numerical simulations (DNSs) of spanwise-periodic channel flows; therefore, we reserve the term "channel" for spanwise-periodic DNSs and denote the experimental flow by the term "duct." Oil film interferometry (OFI) and static pressure measurements were carried out over the range in an adjustable-geometry duct flow facility. Three-dimensional effects were studied by considering different aspect ratio (AR) configurations and also by fixing the AR and modifying the hydraulic diameter of the section. The conditions at the centerplane of the duct were characterized through the local skin friction from the OFI and the centerline velocity at four different streamwise locations and through the wall shear based on the streamwise global pressure gradient. The skin friction obtained from pressure gradient overestimated the local shear measurements obtained from the OFI and did not reproduce the same AR dependence observed with OFI. Differences between the local and global techniques were also reflected in the flow development. For the range of Reynolds numbers tested, the development length of high-aspect-ratio ducts scales with the duct full-height and is around , much larger than the values of around 100-150 H previously reported in the literature.

  8. Interaction of two-dimensional turbulence with a sheared channel flow: a numerical study

    Science.gov (United States)

    Kamp, Leon; Marques Rosas Fernandes, Vitor; van Heijst, Gertjan; Clercx, Herman

    2015-11-01

    Interaction of large-scale flows with turbulence is of fundamental and widespread importance in geophysical fluid dynamics and also, more recently for the dynamics of fusion plasma. More specifically the interplay between two-dimensional turbulence and so-called zonal flows has gained considerable interest because of its relevance for transport and associated barriers. We present numerical results on the interaction of driven two-dimensional turbulence with typical sheared channel flows (Couette and Poiseuille). It turns out that a linear shear rate that is being sustained by moving channel walls (Couette flow) is far more effective in suppressing turbulence and associated transport than a Poiseuille flow. We explore the mechanisms behind this in relation to the width of the channel and the strength of the shear of the background flow. Also the prominent role played by the no-slip boundaries and the Reynolds stress is discussed.

  9. On the existence of two-dimensional nonlinear steady states in plane Couette flow

    CERN Document Server

    Rincon, Francois

    2007-01-01

    The problem of two-dimensional steady nonlinear dynamics in plane Couette flow is revisited using homotopy from either plane Poiseuille flow or from plane Couette flow perturbed by a small symmetry-preserving identity operator. Our results show that it is not possible to obtain the nonlinear plane Couette flow solutions reported by Cherhabili and Ehrenstein [Eur. J. Mech. B/Fluids, 14, 667 (1995)] using their Poiseuille-Couette homotopy. We also demonstrate that the steady solutions obtained by Mehta and Healey [Phys. Fluids, 17, 4108 (2005)] for small symmetry-preserving perturbations are influenced by an artefact of the modified system of equations used in their paper. However, using a modified version of their model does not help to find plane Couette flow solution in the limit of vanishing symmetry-preserving perturbations either. The issue of the existence of two-dimensional nonlinear steady states in plane Couette flow remains unsettled.

  10. Numerical simulation of peristaltic flow of a Carreau nanofluid in an asymmetric channel

    Directory of Open Access Journals (Sweden)

    Noreen Sher Akbar

    2014-03-01

    Full Text Available In this article, we studied MHD peristaltic flow of a Carreau nanofluid in an asymmetric channel. The flow development is carried out in a wave frame of reference moving with velocity of the wave c1. The governing nonlinear partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations using similarity transformations and then tackled numerically using the fourth and fifth order Runge–Kutta–Fehlberg. Numerical results are obtained for dimensionless velocity, stream function, pressure rise, temperature and nanoparticle volume fraction. It is found that the pressure rise increases with increase in Hartmann Number and thermophoresis parameter.

  11. Influences of Hall current and chemical reaction in mixed convective peristaltic flow of Prandtl fluid

    Science.gov (United States)

    Hayat, T.; Zahir, Hina; Tanveer, Anum; Alsaedi, A.

    2016-06-01

    The objective of present analysis is to address the mixed convective peristaltic flow of Prandtl fluid in a planar channel with compliant walls. Effects of applied magnetic field and Hall current are retained. Heat transfer in fluid flow is characterized through convective boundary conditions. Impact of first order chemical reaction together with Soret effect is examined. Problems formulation in view of long wavelength and low Reynolds number consideration is developed. The graphs are obtained numerically for the velocity, temperature, concentration and heat transfer coefficient. Results for Hall parameter and Hartman number on velocity have opposite characteristics.

  12. Magnetohydrodynamic peristaltic flow of a hyperbolic tangent fluid in a vertical asymmetric channel with heat transfer

    Institute of Scientific and Technical Information of China (English)

    Sohail Nadeem; Safia Akram

    2011-01-01

    In the present paper we discuss the magnetohydrodynamic (MHD) peristaltic flow of a hyperbolic tangent fluid model in a vertical asymmetric channel under a zero Reynolds number and long wavelength approximation. Exact solution of the temperature equation in the absence of dissipation term has been computed and the analytical expression for stream function and axial pressure gradient are established. The flow is analyzed in a wave frame of reference moving with the velocity of wave. The expression for pressure rise has been computed numerically. The physical features of pertinent parameters are analyzed by plotting graphs and discussed in detail.

  13. Two-dimensional cellular automaton model of traffic flow with open boundaries

    CERN Document Server

    Tadaki, S I

    1996-01-01

    A two-dimensional cellular automaton model of traffic flow with open boundaries are investigated by computer simulations. The outflow of cars from the system and the average velocity are investigated. The time sequences of the outflow and average velocity have flicker noises in a jamming phase. The low density behavior are discussed with simple jam-free approximation.

  14. Streamline topologies near simple degenerate critical points in two-dimensional flow away from boundaries

    DEFF Research Database (Denmark)

    Brøns, Morten; Hartnack, Johan Nicolai

    1999-01-01

    Streamline patterns and their bifurcations in two-dimensional incompressible flow are investigated from a topological point of view. The velocity field is expanded at a point in the fluid, and the expansion coefficients are considered as bifurcation parameters. A series of nonlinear coordinate...

  15. Streamline topologies near simple degenerate critical points in two-dimensional flow away from boundaries

    DEFF Research Database (Denmark)

    Brøns, Morten; Hartnack, Johan Nicolai

    1998-01-01

    Streamline patterns and their bifurcations in two-dimensional incompressible flow are investigated from a topological point of view. The velocity field is expanded at a point in the fluid, and the expansion coefficients are considered as bifurcation parameters. A series of non-linear coordinate...

  16. Williamson Fluid Model for the Peristaltic Flow of Chyme in Small Intestine

    Directory of Open Access Journals (Sweden)

    Sohail Nadeem

    2012-01-01

    Full Text Available Mathematical model for the peristaltic flow of chyme in small intestine along with inserted endoscope is considered. Here, chyme is treated as Williamson fluid, and the flow is considered between the annular region formed by two concentric tubes (i.e., outer tube as small intestine and inner tube as endoscope. Flow is induced by two sinusoidal peristaltic waves of different wave lengths, traveling down the intestinal wall with the same speed. The governing equations of Williamson fluid in cylindrical coordinates have been modeled. The resulting nonlinear momentum equations are simplified using long wavelength and low Reynolds number approximations. The resulting problem is solved using regular perturbation method in terms of a variant of Weissenberg number We. The numerical solution of the problem is also computed by using shooting method, and comparison of results of both solutions for velocity field is presented. The expressions for axial velocity, frictional force, pressure rise, stream function, and axial pressure gradient are obtained, and the effects of various emerging parameters on the flow characteristics are illustrated graphically. Furthermore, the streamlines pattern is plotted, and it is observed that trapping occurs, and the size of the trapped bolus varies with varying embedded flow parameters.

  17. Numerical Investigation of Dynamic Effects on Unsteady Flow Measurements Using a Two-Dimensional Probe

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The dynamic effects in measurements of unsteady flow when using a probe with quasi-steady calibration curves has been investigated in this paper by numerical simulation of the compressible flow around a fixed two-dimensional 3-hole probe. The unsteady velocity and pressure distributions, as well as the hole-pressures, are calculated for high frequency flow variations. The measurement errors caused by the dynamic effects indicate that considerable measurement errors may occur for high frequency flow fluctuation, e.g., 2000Hz, especially, when the flow around the probe head approaches separation. This work shows how numerical simulation can be used to investigate and correct for the dynamic effects.

  18. On the origins of vortex shedding in two-dimensional incompressible flows

    Science.gov (United States)

    Boghosian, M. E.; Cassel, K. W.

    2016-12-01

    An exegesis of a novel mechanism leading to vortex splitting and subsequent shedding that is valid for two-dimensional incompressible, inviscid or viscous, and external or internal or wall-bounded flows, is detailed in this research. The mechanism, termed the vortex shedding mechanism (VSM) is simple and intuitive, requiring only two coincident conditions in the flow: (1) the existence of a location with zero momentum and (2) the presence of a net force having a positive divergence. Numerical solutions of several model problems illustrate causality of the VSM. Moreover, the VSM criteria is proved to be a necessary and sufficient condition for a vortex splitting event in any two-dimensional, incompressible flow. The VSM is shown to exist in several canonical problems including the external flow past a circular cylinder. Suppression of the von Kármán vortex street is demonstrated for Reynolds numbers of 100 and 400 by mitigating the VSM.

  19. Electrokinetic transport in unsteady flow through peristaltic microchannel

    Science.gov (United States)

    Tripathi, Dharmendra; Mulchandani, Janak; Jhalani, Shubham

    2016-04-01

    We analyze the electrokinetic transport of aqueous electrolyte fluids with Newtonian model in presence of peristalsis through microchannel. Debye-Hückel linearization is employed to simplify the problem. Low Reynolds number and large wavelength approximations are taken into account subjected to microfluidics applications. Electrical double layer (EDL) is considered very thin and electroosmotic slip velocity (i.e. Helmholtz-Smoluchowski velocity) at the wall is subjected to study the effect of applied electrical field. The solutions for axial velocity and pressure difference along the channel length are obtained analytically and the effects of adding and opposing the flow by applied electric field have been discussed. It is revealed that the axial velocity and pressure gradient enhances with adding electric field and an opposite behavior is found in the flow direction on opposing the electric field. These results may also help towards designing organ-on-a-chip like devices for better drug design.

  20. Coexistence of two dissipative mechanisms in two-dimensional turbulent flows

    Energy Technology Data Exchange (ETDEWEB)

    Yen, Romain Nguyen van [FB Mathematik und Informatik, Freie Universitaet, Berlin (Germany); Farge, Marie [LMD-CNRS-IPSL, ENS Paris (France); Schneider, Kai, E-mail: rnguyen@zedat.fu-berlin.de [M2P2-CNRS, Universite d' Aix-Marseille (France)

    2011-12-22

    Two distinct dissipative mechanisms occurring in two-dimensional fully developed turbulent flows in the limit of vanishing viscosity have been highlighted by means of direct numerical simulation. First, molecular energy dissipation is triggered by the production of localized vortices at the walls. Second, instabilities intrinsic to the flow itself generate a noisy component which can be quantified by wavelet analysis. The possibilities of competition and coexistence of the two mechanisms are discussed.

  1. Two-Dimensional Automatic Measurement for Nozzle Flow Distribution Using Improved Ultrasonic Sensor

    OpenAIRE

    Changyuan Zhai; Chunjiang Zhao; Xiu Wang; Ning Wang; Wei Zou; Wei Li

    2015-01-01

    Spray deposition and distribution are affected by many factors, one of which is nozzle flow distribution. A two-dimensional automatic measurement system, which consisted of a conveying unit, a system control unit, an ultrasonic sensor, and a deposition collecting dish, was designed and developed. The system could precisely move an ultrasonic sensor above a pesticide deposition collecting dish to measure the nozzle flow distribution. A sensor sleeve with a PVC tube was designed for the ultras...

  2. Transition to two-dimensionality in magnetohydrodynamic turbulent Taylor-Couette flow.

    Science.gov (United States)

    Zhao, Yurong; Tao, Jianjun; Zikanov, Oleg

    2014-03-01

    Transition from a Taylor-Couette turbulent flow to a completely two-dimensional axisymmetric turbulent state is realized numerically by increasing gradually the strength of the azimuthal magnetic field produced by electric current flowing through the axial rod. With the increase of the Hartmann number, the Taylor-vortex-like structures shrink, move closer to the inner cylinder, and turn into unsteady but perfect tori at sufficiently high Hartmann numbers.

  3. TWO-DIMENSIONAL PLANE WATER FLOW AND WATER QUALITY DISTRIBUTION IN BOSTEN LAKE

    Institute of Scientific and Technical Information of China (English)

    Feng Min-quan; Zhou Xiao-de; Zheng Bang-min; Min Tao; Zhao Ke-yu

    2003-01-01

    The two-dimensional plane water flow and water quality was developed by using the techniques of coordinate transformation, alternating directions, staggered grid, linear recurrence, and implicit scheme in the study of large water body in lakes. The model was proved to be suitable for treating the irregular boundary and predicting quickly water flow and water quality. The application of the model to the Bosten Lake in Xinjiang Uygur Autonomous Region of China shows that it is reasonable and practicable.

  4. Double-Humped Transverse Density Profile in Two-Dimensional Chute Flow with Rough Sidewalls

    Institute of Scientific and Technical Information of China (English)

    HU Guo-Qi; ZHANG Xun-Sheng; BAO De-Song; TANG Xiao-Wei

    2006-01-01

    @@ We study a two-dimensional granular rapid flow with rough sidewalls stuck with the same size discs by molecular dynamics simulation. A transient state of the double-humped density profile in the flowing process has been found, which appears and moves as travelling wave and is the same as the phenomena in the recent experiments [Acta Phys. Sin. 53 (2004) 3389 (in Chinese)].

  5. Soret and Dufour Effects on MHD Peristaltic Flow of Jeffrey Fluid in a Rotating System with Porous Medium

    Science.gov (United States)

    Hayat, Tasawar; Rafiq, Maimona; Ahmad, Bashir

    2016-01-01

    The objective of present paper is to examine the peristaltic flow of magnetohydrodynamic (MHD) Jeffrey fluid saturating porous space in a channel through rotating frame. Unlike the previous attempts, the flow formulation is based upon modified Darcy's law porous medium effect in Jeffrey fluid situation. In addition the impacts due to Soret and Dufour effects in the radiative peristaltic flow are accounted. Rosseland’s approximation has been utilized for the thermal radiative heat flux. Lubrication approach is implemented for the simplification. Resulting problems are solved for the stream function, temperature and concentration. Graphical results are prepared and analyzed for different parameters of interest entering into the problems. PMID:26808387

  6. Soret and Dufour Effects on MHD Peristaltic Flow of Jeffrey Fluid in a Rotating System with Porous Medium.

    Directory of Open Access Journals (Sweden)

    Tasawar Hayat

    Full Text Available The objective of present paper is to examine the peristaltic flow of magnetohydrodynamic (MHD Jeffrey fluid saturating porous space in a channel through rotating frame. Unlike the previous attempts, the flow formulation is based upon modified Darcy's law porous medium effect in Jeffrey fluid situation. In addition the impacts due to Soret and Dufour effects in the radiative peristaltic flow are accounted. Rosseland's approximation has been utilized for the thermal radiative heat flux. Lubrication approach is implemented for the simplification. Resulting problems are solved for the stream function, temperature and concentration. Graphical results are prepared and analyzed for different parameters of interest entering into the problems.

  7. Mixed convection peristaltic flow of third order nanofluid with an induced magnetic field.

    Science.gov (United States)

    Noreen, Saima

    2013-01-01

    This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quantities such as velocity, pressure rise, temperature, induced magnetic field and concentration distributions are discussed.

  8. The Mathematical Analysis for Peristaltic Flow of Hyperbolic Tangent Fluid in a Curved Channel

    Institute of Scientific and Technical Information of China (English)

    S.Nadeem; E.N.Maraj

    2013-01-01

    In the present paper,we have investigated the peristaltic flow of hyperbolic tangent fluid in a curved channel.The governing equations of hyperbolic tangent fluid model for curved channel are derived including the effects of curvature.The highly nonlinear partial differential equations are simplified by using the wave frame transformation,long wave length and low Reynolds number assumptions.The reduced nonlinear partial differential equation is solved analytically with the help of homotopy perturbation method (HPM).The physical features of pertinent parameters have been discussed by plotting the graphs of pressure rise and stream functions.

  9. Radiative Peristaltic Flow of Jeffrey Nanofluid with Slip Conditions and Joule Heating.

    Directory of Open Access Journals (Sweden)

    Tasawar Hayat

    Full Text Available Mixed convection peristaltic flow of Jeffrey nanofluid in a channel with compliant walls is addressed here. The present investigation includes the viscous dissipation, thermal radiation and Joule heating. Whole analysis is performed for velocity, thermal and concentration slip conditions. Related problems through long wavelength and low Reynolds number are examined for stream function, temperature and concentration. Impacts of thermal radiation, Hartman number, Brownian motion parameter, thermophoresis, Joule heating and slip parameters are explored in detail. Clearly temperature is a decreasing function of Hartman number and radiation parameter.

  10. Hall and ion slip effects on peristaltic flow of Jeffrey nanofluid with Joule heating

    Science.gov (United States)

    Hayat, T.; Shafique, Maryam; Tanveer, A.; Alsaedi, A.

    2016-06-01

    This paper addresses mixed convective peristaltic flow of Jeffrey nanofluid in a channel with complaint walls. The present investigation includes the viscous dissipation, thermal radiation and Joule heating. Hall and ion slip effects are also taken into account. Related problems through long wavelength and low Reynolds number are examined for stream function, temperature and concentration. Impacts of thermal radiation, Hartman number, Brownian motion parameter, thermophoresis, Joule heating, Hall and ion slip parameters are investigated in detail. It is observed that velocity increases and temperature decreases with Hall and ion slip parameters. Further the thermal radiation on temperature has qualitatively similar role to that of Hall and ion slip effects.

  11. Peristaltic flow in an asymmetric channel with convective boundary conditions and Joule heating

    Institute of Scientific and Technical Information of China (English)

    Abbasi Fahad Munir; Hayat Tasawar; Ahmad Bashir

    2014-01-01

    The peristaltic transport of viscous fluid in an asymmetric channel is concentrated. The channel walls exhibit convective boundary conditions. Both cases of hydrodynamic and magnetohydrodynamic (MHD) fluids are considered. Mathematical analysis has been presented in a wave frame of reference. The resulting problems are non-dimensionalized. Long wavelength and low Reynolds number approximations are employed. Joule heating effect on the thermal equation is retained. Analytic solutions for stream function and temperature are constructed. Numerical integration is carried out for pressure rise per wavelength. Effects of influential flow parameters have been pointed out through graphs.

  12. Peristaltic flow of a Johnson-Segalman fluid through a deformable tube

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yongqi [Darmstadt University of Technology, Department of Mechanical Engineering, Darmstadt (Germany); Universitaet fuer Bodenkultur, Institute of Geotechnical Engineering, Vienna (Austria); Hayat, Tasawar [Quaid-i-Azam University, Mathematics Department, Islamabad (Pakistan); Hutter, Kolumban [ETH Zuerich, VAW, Zuerich (Switzerland)

    2007-09-15

    To understand theoretically the flow properties of physiological fluids we have considered as a model the peristaltic motion of a Johnson-Segalman fluid in a tube with a sinusoidal wave traveling down its wall. The perturbation solution for the stream function is obtained for large wavelength and small Weissenberg number. The expressions for the axial velocity, pressure gradient, and pressure rise per wavelength are also constructed. The general solution of the governing nonlinear partial differential equation is given using a transformation method. The numerical solution is also obtained and is compared with the perturbation solution. Numerical results are demonstrated for various values of the physical parameters of interest. (orig.)

  13. Mixed convection peristaltic flow of third order nanofluid with an induced magnetic field.

    Directory of Open Access Journals (Sweden)

    Saima Noreen

    Full Text Available This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quantities such as velocity, pressure rise, temperature, induced magnetic field and concentration distributions are discussed.

  14. Modeling two-dimensional water flow and bromide transport in a heterogeneous lignitic mine soil

    Energy Technology Data Exchange (ETDEWEB)

    Buczko, U.; Gerke, H.H. [Brandenburg University of Technology, Cottbus (Germany)

    2006-02-15

    Water and solute fluxes in lignitic mine soils and in many other soils are often highly heterogeneous. Here, heterogeneity reflects dumping-induced inclined structures and embedded heterogeneous distributions of sediment mixtures and of lignitic fragments. Such two-scale heterogeneity effects may be analyzed through the application of two-dimensional models for calculating water and solute fluxes. The objective of this study was to gain more insight to what extent spatial heterogeneity of soil hydraulic parameters contributes to preferential flow at a lignitic mine soil. The simulations pertained to the 'Barenbrucker Hohe' site in Germany where previously water fluxes and applied tracers had been monitored with a cell lysimeter, and from where a soil block had been excavated for detailed two-dimensional characterization of the hydraulic parameters using pedotransfer functions. Based on those previous studies, scenarios with different distributions of hydraulic parameters were simulated. The results show that spatial variability of hydraulic parameters alone can hardly explain the observed flow patterns. The observed preferential flow at the site was probably caused by additional factors such as hydrophobicity, the presence of root channels, anisotropy in the hydraulic conductivity, and heterogeneous root distributions. To study the relative importance of these other factors by applying two-dimensional flow models to such sites, the experimental database must be improved. Single-continuum model approaches may be insufficient for such sites.

  15. Characterizing Mixing in a Quasi-Two-Dimensional Flow using Persistent Homology

    Science.gov (United States)

    Tithof, Jeffrey; Kelley, Douglas

    2016-11-01

    Fluid mixing is a tremendously important phenomenon present in numerous physical systems, both natural and human-made. Describing, understanding, and predicting the mixing behavior of fluid flows poses an immense challenge. In this work, we explore the utility of topological data analysis in quantifying fluid mixing. We analyze Eulerian and Lagrangian quantities obtained from a quasi-two-dimensional flow realized by driving a thin layer of fluid with electromagnetic forces. Our analysis employs persistent homology, which offers a unique framework for quantifying topological features associated with connectivity in the fluid flow. Preliminary results suggest that this topological approach offers new physical insight, complementing existing methods for quantifying fluid mixing.

  16. EXPERIMENTAL INVESTIGATION ON TWO-DIMENSIONAL UNSTEADY COLD FLOW IN MPC EXHAUST MANIFOLD

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The gas flow in exhaust manifolds has much effect on scavenge, pumping loss and exhaust energy utilization of turbocharged diesel engines. This paper presented experimental investigation on two-dimensional unsteady flow in MPC(modular pulse converter) exhaust manifold model. The pressure and velocity distributions in six sections of the manifold model were measured when the diesel engine was motored. The probe with slitted sleeve was used to determine flow direction. The experimental results show that velocity distributions vary with place and time; the pressure traces at different points of the same section are not different obviously.

  17. Two Dimensional Subsonic Euler Flows Past a Wall or a Symmetric Body

    Science.gov (United States)

    Chen, Chao; Du, Lili; Xie, Chunjing; Xin, Zhouping

    2016-08-01

    The existence and uniqueness of two dimensional steady compressible Euler flows past a wall or a symmetric body are established. More precisely, given positive convex horizontal velocity in the upstream, there exists a critical value {ρ_cr} such that if the incoming density in the upstream is larger than {ρ_cr}, then there exists a subsonic flow past a wall. Furthermore, {ρ_cr} is critical in the sense that there is no such subsonic flow if the density of the incoming flow is less than {ρ_cr}. The subsonic flows possess large vorticity and positive horizontal velocity above the wall except at the corner points on the boundary. Moreover, the existence and uniqueness of a two dimensional subsonic Euler flow past a symmetric body are also obtained when the incoming velocity field is a general small perturbation of a constant velocity field and the density of the incoming flow is larger than a critical value. The asymptotic behavior of the flows is obtained with the aid of some integral estimates for the difference between the velocity field and its far field states.

  18. Numerical and analytical treatment on peristaltic flow of Williamson fluid in the occurrence of induced magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Akram, Safia, E-mail: safia_akram@yahoomail.com [Department of Basic Sciences, Military College of Signals, National University of Sciences and Technology (Pakistan); Nadeem, S. [Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000 (Pakistan); Hanif, M. [Department of Basic Sciences, Military College of Signals, National University of Sciences and Technology (Pakistan)

    2013-11-15

    In this paper the effects of induced magnetic field on the peristaltic transport of a Williamson fluid model in an asymmetric channel has been investigated. The problem is simplified by using long wave length and low Reynolds number approximations. The perturbation and numerical solutions have been presented. The expressions for pressure rise, pressure gradient, stream function, magnetic force function, current density distribution have been computed. The results of pertinent parameters have been discussed graphically. The trapping phenomena for different wave forms have been also discussed. - highlights: • The main motivation of this work is that we want to see the behavior of peristaltic flow of Williamson fluid in the occurrence of induced magnetic field. In literature no attempt is taken to discuss the lateral Numerical and analytical treatment on peristaltic flow of Williamson fluid in the occurrence of induced magnetic field. • We do not want to fill the gap in literature after studying this.

  19. Flow pattern transition accompanied with sudden growth of flow resistance in two-dimensional curvilinear viscoelastic flows

    OpenAIRE

    Yatou, Hiroki

    2010-01-01

    We find three types of steady solutions and remarkable flow pattern transitions between them in a two-dimensional wavy-walled channel for low to moderate Reynolds (Re) and Weissenberg (Wi) numbers using direct numerical simulations with spectral element method. The solutions are called "convective", "transition", and "elastic" in ascending order of Wi. In the convective region in the Re-Wi parameter space, the convective effect and the pressure gradient balance on average. As Wi increases, th...

  20. Group classification of steady two-dimensional boundary-layer stagnation-point flow equations

    OpenAIRE

    Nadjafikhah, Mehdi; Hejazi, Seyed Reza

    2010-01-01

    Lie symmetry group method is applied to study the boundary-layer equations for two-dimensional steady flow of an incompressible, viscous fluid near a stagnation point at a heated stretching sheet placed in a porous medium equation. The symmetry group and its optimal system are given, and group invariant solutions associated to the symmetries are obtained. Finally the structure of the Lie algebra symmetries is determined.

  1. Analytical Studies of Two-Dimensional Channel Turbulent Flow Subjected to Coriolis Force

    OpenAIRE

    鬼頭, 修己; 中林, 功一; キトウ, オサミ; Kito, Osami

    1992-01-01

    Coriolis effects on fully developed turbulent flow in a two-dimensional channel rotating about an axis perpendicular to its axis are considered. The Coriolis force has stabilizing/destabilizing effects on turbulence, and the mean velocity distribution changes accordingly. Experimental and numerical studies on the velocity characteristics have already been conducted by other researchers for various conditions. However, we cannot assemble the overall picture of the Coriolis effect on the veloci...

  2. An immersed interface method for two-dimensional modelling of stratified flow in pipes

    OpenAIRE

    Berthelsen, Petter Andreas

    2004-01-01

    This thesis deals with the construction of a numerical method for solving two-dimensional elliptic interface problems, such as fully developed stratified flow in pipes. Interface problems are characterized by its non-smooth and often discontinuous behaviour along a sharp boundary separating the fluids or other materials. Classical numerical schemes are not suitable for these problems due to the irregular geometry of the interface. Standard finite difference discretization across the interface...

  3. Spatial statistics of magnetic field in two-dimensional chaotic flow in the resistive growth stage

    Science.gov (United States)

    Kolokolov, I. V.

    2017-03-01

    The correlation tensors of magnetic field in a two-dimensional chaotic flow of conducting fluid are studied. It is shown that there is a stage of resistive evolution where the field correlators grow exponentially with time. The two- and four-point field correlation tensors are computed explicitly in this stage in the framework of Batchelor-Kraichnan-Kazantsev model. They demonstrate strong temporal intermittency of the field fluctuations and high level of non-Gaussianity in spatial field distribution.

  4. Determination of two-dimensional magnetostatic equilibria and analogous Euler flows

    Science.gov (United States)

    Linardatos, D.

    1993-01-01

    A modified computational procedure with an improved time-stepping algorithm for two-dimensional magnetic relaxation is developed. The procedure is used to determine a family of flows in a closed (square) domain with a single elliptic stagnation point. In addition, the problem of saddle point collapse is investigated, and the tendency to form discontinuities is confirmed in the manner described by Bajer (1989).

  5. Prandtl's Boundary Layer Equation for Two-Dimensional Flow: Exact Solutions via the Simplest Equation Method

    Directory of Open Access Journals (Sweden)

    Taha Aziz

    2013-01-01

    Full Text Available The simplest equation method is employed to construct some new exact closed-form solutions of the general Prandtl's boundary layer equation for two-dimensional flow with vanishing or uniform mainstream velocity. We obtain solutions for the case when the simplest equation is the Bernoulli equation or the Riccati equation. Prandtl's boundary layer equation arises in the study of various physical models of fluid dynamics. Thus finding the exact solutions of this equation is of great importance and interest.

  6. Flow Rate in the Discharge of a Two-dimensional Silo

    Science.gov (United States)

    Zuriguel, I.; Janda, A.; Garcimartín, A.; Maza, D.

    2009-06-01

    We present an experimental study of the flow rate in the discharge of a flat bottomed two-dimensional silo. The results of the flow rate dependence on the size of the orifice evidence that the Beverloo expression is not valid for small outlet sizes. This behavior is related with the properties of the flow rate which has been found to fluctuate in a gaussian like form for large orifices. On the contrary, for small orifices extreme events appear at zero flow rates causing a significant slow down of the average flow rate. These events are explained in terms of the existence of arches that block the outlet instantaneously but are unstable to permanently halt the flow.

  7. Two-dimensional surface river flow patterns measured with paired RiverSondes

    Science.gov (United States)

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.

    2008-01-01

    Two RiverSondes were operated simultaneously in close proximity in order to provide a two-dimensional map of river surface velocity. The initial test was carried out at Threemile Slough in central California. The two radars were installed about 135 m apart on the same bank of the channel. Each radar used a 3-yagi antenna array and determined signal directions using direction finding. The slough is approximately 200 m wide, and each radar processed data out to about 300 m, with a range resolution of 15 m and an angular resolution of 1 degree. Overlapping radial vector data from the two radars were combined to produce total current vectors at a grid spacing of 10 m, with updates every 5 minutes. The river flow in the region, which has a maximum velocity of about 0.8 m/s, is tidally driven with flow reversals every 6 hours, and complex flow patterns were seen during flow reversal. The system performed well with minimal mutual interference. The ability to provide continuous, non-contact two-dimensional river surface flow measurements will be useful in several unique settings, such as studies of flow at river junctions where impacts to juvenile fish migration are significant. Additional field experiments are planned this year on the Sacramento River. ?? 2007 IEEE.

  8. Two-dimensional hydrodynamic flow focusing in a microfluidic platform featuring a monolithic integrated glass micronozzle

    Science.gov (United States)

    Liu, Yifan; Shen, Yusheng; Duan, Lian; Yobas, Levent

    2016-10-01

    Two-dimensional hydrodynamic flow focusing is demonstrated through a microfluidic device featuring a monolithic integrated glass micronozzle inside a flow-focusing geometry. Such a coaxial configuration allows simple one-step focusing of a sample fluid stream, jetted from the micronozzle tip, in both in-plane and out-of-plane directions. The width of the focused filament can be precisely controlled and further scaled down to the submicrometer regime to facilitate rapid hydrodynamic mixing. Fluorescence quenching experiments reveal ultra-fast microsecond mixing of the denaturant into the focused filament. This device offers new possibilities to a set of applications such as the study of protein folding kinetics.

  9. Critical behavior in the inverse to forward energy transition in two-dimensional magnetohydrodynamic flow.

    Science.gov (United States)

    Seshasayanan, Kannabiran; Alexakis, Alexandros

    2016-01-01

    We investigate the critical transition from an inverse cascade of energy to a forward energy cascade in a two-dimensional magnetohydrodynamic flow as the ratio of magnetic to mechanical forcing amplitude is varied. It is found that the critical transition is the result of two competing processes. The first process is due to hydrodynamic interactions and cascades the energy to the large scales. The second process couples small-scale magnetic fields to large-scale flows, transferring the energy back to the small scales via a nonlocal mechanism. At marginality the two cascades are both present and cancel each other. The phase space diagram of the transition is sketched.

  10. Flow of an aqueous foam through a two-dimensional porous medium: a pore scale investigation

    Science.gov (United States)

    Meheust, Y.; Jones, S. A.; Dollet, B.; Cox, S.; Cantat, I.

    2012-12-01

    Flowing foams are used in many engineering and technical applications. A well-known application is oil recovery. Another one is the remediation of polluted soil: the foam is injected into the ground in order to mobilize chemical species present in the medium. Apart from potential interesting physico-chemical and biochemical properties, foams have peculiar flow properties that might be of benefit to the application. We address here this physical aspect of the topic. As a precursor to the study of foam flow through a complex porous material, we first study the behavior of an aqueous two-dimensional foam flowing through a medium consisting of two parallel channels with different widths, at fixed medium porosity, that is, at fixed total combined width of the two channels. The flow velocity, and hence flux, in each channel is measured by analyzing images of the flowing foam. It is then compared to a theoretical model, the basic assumption of which is that the pressure drop along a channel is identical for both channels. This pressure drop both consists of (i) a dynamic pressure drop, which is controlled by bubble-wall friction and depends on the foam velocity in the channel, and (ii) a capillary pressure drop over the bubble films that emerge at the channel outlet, the latter pressure drop being controlled by the radius of curvature of the bubble film. Based on this assumption, the dependence of the ratio of the foam velocities in the two channels is inferred as a function of the channel width ratio. It compares well to the measurements and shows that the flow behavior is highly dependent on the foam structure within the narrowest of the two channels, especially when a "bamboo" structure is obtained. Consequently, the flux in a channel is found to have a more complicated relation to the channel width than expected for the flow of a standard Newtonian fluid in the same geometry. We provide a comparison to this reference configuration. We then study the flow of the same

  11. Effect of induced magnetic field on peristaltic flow of a micropolar fluid in an asymmetric channel

    CERN Document Server

    Shit, G C; Ng, E Y K; 10.1002/cnm.1397

    2010-01-01

    Of concern in this paper is an investigation of peristaltic transport of a physiological fluid in an asymmetric channel under long wave length and low-Reynolds number assumptions. The flow is assumed to be incompressible, viscous, electrically conducting micropolar fluid and the effect of induced magnetic field is taken into account. Exact analytical solutions obtained for the axial velocity, microrotation component, stream line pattern, magnetic force function, axial-induced magnetic field as well as the current density distribution across the channel. The flow phenomena for the pumping characteristics, trapping and reflux are also investigated. The results presented reveal that the velocity decreases with the increase of magnetic field as well as the coupling parameter. Moreover, the trapping fluid can be eliminated by the application of an external magnetic field. Thus, the study bears the promise of important applications in physiological systems.

  12. Peristaltic flow of a reactive viscous fluid through a porous saturated channel and convective cooling conditions

    Science.gov (United States)

    Asghar, S.; Hussain, Q.; Hayat, T.; Alsaedi, A.

    2015-07-01

    This article addresses the heat transfer in a peristaltic flow of a reactive combustible viscous fluid through a porous saturated medium. The flow here is induced because of travelling waves along the channel walls. It is assumed that exothermic chemical reactions take place within the channel under the Arrhenius kinetics and the convective heat exchange with the ambient medium at the surfaces of the channel walls follows Newton's law of cooling. The analysis is carried out in the presence of viscous dissipation and without consumption of the material. The governing equations are formulated by employing the long-wavelength approximation. Closed-form solutions for the stream function, axial velocity, and axial pressure gradient are obtained. It is found that the temperature decreases at high Biot numbers, and the Nusselt number increases with increasing reaction parameter. The Biot number and reaction parameter produce the opposite effects on the Nusselt number.

  13. Peristaltic flow of a micropolar fluid with nano particles in small intestine

    Science.gov (United States)

    Akbar, Noreen Sher; Nadeem, S.

    2013-12-01

    The present article analyzed the peristaltic flow of a nanofluid in a uniform tube for micropolar fluid. The governing equations for proposed model are developed in cylindrical coordinates system. The flow is discussed in a wave frame of reference moving with velocity of the wave c. Under the assumptions of longwave length the reduced coupled nonlinear differential equations of momentum, energy, and concentrations are solved by Homotopy perturbation method is used to get the solutions for velocity, temperature, nano particle, microrotation component. The solutions consists Brownian motion number N b, thermophoresis number N t, local temperature Grashof number B r and local nano particle Grashof number G r . The effects of various parameters involved in the problem are investigated for pressure rise, pressure gradient, temperature and concentration profile. Five different waves are taken into account for analysis. Streamlines have been plotted at the end of the article.

  14. Implementation of the Log-Conformation Formulation for Two-Dimensional Viscoelastic Flow

    CERN Document Server

    Jensen, K E; Okkels, F

    2015-01-01

    We have implemented the log-conformation method for two-dimensional viscoelastic flow in COMSOL, a commercial high-level finite element package. The code is verified for an Oldroyd-B fluid flowing past a confined cylinder. We are also able to describe the well-known bistability of the viscoelastic flow in a cross-slot geometry for a FENE-CR fluid, and we describe the changes required for performing simulations with the Phan-Thien-Tanner (PTT), Giesekus and FENE-P models. Finally, we calculate the flow of a FENE-CR fluid in a geometry with three in- and outlets. The implementation is included in the supplementary material, and we hope that it can inspire new as well as experienced researchers in the field of differential constitutive equations for viscoelastic flow.

  15. Experimental study on two-dimensional film flow with local measurement methods

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jin-Hwa, E-mail: evo03@snu.ac.kr [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Cho, Hyoung-Kyu [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Seok [Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Euh, Dong-Jin, E-mail: djeuh@kaeri.re.kr [Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Park, Goon-Cherl [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of)

    2015-12-01

    Highlights: • An experimental study on the two-dimensional film flow with lateral air injection was performed. • The ultrasonic thickness gauge was used to measure the local liquid film thickness. • The depth-averaged PIV (Particle Image Velocimetry) method was applied to measure the local liquid film velocity. • The uncertainty of the depth-averaged PIV was quantified with a validation experiment. • Characteristics of two-dimensional film flow were classified following the four different flow patterns. - Abstract: In an accident condition of a nuclear reactor, multidimensional two-phase flows may occur in the reactor vessel downcomer and reactor core. Therefore, those have been regarded as important issues for an advanced thermal-hydraulic safety analysis. In particular, the multi-dimensional two-phase flow in the upper downcomer during the reflood phase of large break loss of coolant accident appears with an interaction between a downward liquid and a transverse gas flow, which determines the bypass flow rate of the emergency core coolant and subsequently, the reflood coolant flow rate. At present, some thermal-hydraulic analysis codes incorporate multidimensional modules for the nuclear reactor safety analysis. However, their prediction capability for the two-phase cross flow in the upper downcomer has not been validated sufficiently against experimental data based on local measurements. For this reason, an experimental study was carried out for the two-phase cross flow to clarify the hydraulic phenomenon and provide local measurement data for the validation of the computational tools. The experiment was performed in a 1/10 scale unfolded downcomer of Advanced Power Reactor 1400 (APR1400). Pitot tubes, a depth-averaged PIV method and ultrasonic thickness gauge were applied for local measurement of the air velocity, the liquid film velocity and the liquid film thickness, respectively. The uncertainty of the depth-averaged PIV method for the averaged

  16. A study of unsteady physiological magneto-fluid flow and heat transfer through a finite length channel by peristaltic pumping.

    Science.gov (United States)

    Tripathi, Dharmendra; Bég, O Anwar

    2012-08-01

    Magnetohydrodynamic peristaltic flows arise in controlled magnetic drug targeting, hybrid haemodynamic pumps and biomagnetic phenomena interacting with the human digestive system. Motivated by the objective of improving an understanding of the complex fluid dynamics in such flows, we consider in the present article the transient magneto-fluid flow and heat transfer through a finite length channel by peristaltic pumping. Reynolds number is small enough and the wavelength to diameter ratio is large enough to negate inertial effects. Analytical solutions for temperature field, axial velocity, transverse velocity, pressure gradient, local wall shear stress, volume flowrate and averaged volume flowrate are obtained. The effects of the transverse magnetic field, Grashof number and thermal conductivity on the flow patterns induced by peristaltic waves (sinusoidal propagation along the length of channel) are studied using graphical plots. The present study identifies that greater pressure is required to propel the magneto-fluid by peristaltic pumping in comparison to a non-conducting Newtonian fluid, whereas, a lower pressure is required if heat transfer is effective. The analytical solutions further provide an important benchmark for future numerical simulations.

  17. One- and two-dimensional Stirling machine simulation using experimentally generated reversing flow turbuulence models

    Energy Technology Data Exchange (ETDEWEB)

    Goldberg, L.F. [Univ. of Minnesota, Minneapolis, MN (United States)

    1990-08-01

    The activities described in this report do not constitute a continuum but rather a series of linked smaller investigations in the general area of one- and two-dimensional Stirling machine simulation. The initial impetus for these investigations was the development and construction of the Mechanical Engineering Test Rig (METR) under a grant awarded by NASA to Dr. Terry Simon at the Department of Mechanical Engineering, University of Minnesota. The purpose of the METR is to provide experimental data on oscillating turbulent flows in Stirling machine working fluid flow path components (heater, cooler, regenerator, etc.) with particular emphasis on laminar/turbulent flow transitions. Hence, the initial goals for the grant awarded by NASA were, broadly, to provide computer simulation backup for the design of the METR and to analyze the results produced. This was envisaged in two phases: First, to apply an existing one-dimensional Stirling machine simulation code to the METR and second, to adapt a two-dimensional fluid mechanics code which had been developed for simulating high Rayleigh number buoyant cavity flows to the METR. The key aspect of this latter component was the development of an appropriate turbulence model suitable for generalized application to Stirling simulation. A final-step was then to apply the two-dimensional code to an existing Stirling machine for which adequate experimental data exist. The work described herein was carried out over a period of three years on a part-time basis. Forty percent of the first year`s funding was provided as a match to the NASA funds by the Underground Space Center, University of Minnesota, which also made its computing facilities available to the project at no charge.

  18. Water-channel study of flow and turbulence past a two-dimensional array of obstacles

    CERN Document Server

    Di Bernardino, Annalisa; Leuzzi, Giovanni; Querzoli, Giorgio

    2016-01-01

    A neutral boundary layer was generated in the laboratory to analyze the mean velocity field and the turbulence field within and above an array of two-dimensional obstacles simulating an urban canopy. Different geometrical configurations were considered in order to investigate the main characteristics of the flow as a function of the aspect ratio (AR) of the canopy. To this end, a summary of the two-dimensional fields of the fundamental turbulence parameters is given for AR ranging from 1 to 2. The results show that the flow field depends strongly on AR only within the canyon, while the outer flow seems to be less sensitive to this parameter. This is not true for the vertical momentum flux, which is one of the parameters most affected by AR, both within and outside the canyon. The experiments also indicate that, when (i.e. the skimming flow regime), the roughness sub-layer extends up to a height equal to 1.25 times the height of the obstacles (H), surmounted by an inertial sub-layer that extends up to 2.7 H. I...

  19. Hydrodynamic aspects of premixed flame stripes in two-dimensional stagnation-point flows

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.; Sohrab, S.H. [Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering

    1995-06-01

    The behavior of cellular premixed flames of rich butane-air in the two-dimensional stagnation-point flow configuration has been investigated. It is found that the stretching of the cellular flame results in the alignment f the ridge (extinction) and the trough (combustion) zones of the individual cells such as to form a series of parallel flame stripes. The number of flame stripes as a function of the equivalence ratio for three different mean velocities at the nozzle have been determined. Through the introduction of a generalized form of the stream function periodic velocity fields are obtained as the exact solutions of the Euler equation for the nonreactive finite-jet two-dimensional stagnation flow. The predicted periodic velocity profiles are confirmed by the experimental observation of the streamlines in nonreactive flow made visible by laser-sheet lighting. The observed average size of the flame stripes is found to be in good agreement with the predicted value. Similar periodic velocity profiles are also obtained for the viscous flow within the laminar boundary layer by treatment of the unsteady vorticity equation first described by Taylor. The results support an earlier prediction by Williams that cellular flame structures that are affected mainly by diffusive-thermal phenomena may in fact be initiated by the hydrodynamic instability.

  20. Two-dimensional confocal laser scanning microscopy image correlation for nanoparticle flow velocimetry

    Science.gov (United States)

    Jun, Brian; Giarra, Matthew; Golz, Brian; Main, Russell; Vlachos, Pavlos

    2016-11-01

    We present a methodology to mitigate the major sources of error associated with two-dimensional confocal laser scanning microscopy (CLSM) images of nanoparticles flowing through a microfluidic channel. The correlation-based velocity measurements from CLSM images are subject to random error due to the Brownian motion of nanometer-sized tracer particles, and a bias error due to the formation of images by raster scanning. Here, we develop a novel ensemble phase correlation with dynamic optimal filter that maximizes the correlation strength, which diminishes the random error. In addition, we introduce an analytical model of CLSM measurement bias error correction due to two-dimensional image scanning of tracer particles. We tested our technique using both synthetic and experimental images of nanoparticles flowing through a microfluidic channel. We observed that our technique reduced the error by up to a factor of ten compared to ensemble standard cross correlation (SCC) for the images tested in the present work. Subsequently, we will assess our framework further, by interrogating nanoscale flow in the cell culture environment (transport within the lacunar-canalicular system) to demonstrate our ability to accurately resolve flow measurements in a biological system.

  1. NUMERICAL SIMULATION OF TWO-DIMENSIONAL DAM-BREAK FLOWS IN CURVED CHANNELS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Two-dimensional transient dam-break flows in a river with bends were theoretically studied. The river was modeled as a curved channel with a constant width and a flat bottom. The water was assumed to be an incompressible and homogeneous fluid. A channel-fitted orthogonal curvilinear coordinate system was established and the corresponding two-dimensional shallow-water equations were derived for this system. The governing equations with well-posed initial and boundary conditions were numerically solved in a rectangular domain by use of the Godunov-type finite-difference scheme, which can capture the hydraulic jump of dam-break flows. The comparison between the obtained numerical results and the experimental data of Miller and Chaudry in a semicircle channel shows the validity of the present numerical scheme. The mathematical model and the numerical method were applied to the dam-break flows in channels with various curvatures. Based on the numerical results, the influence of river curvatures on the dam-break flows was analyzed in details.

  2. Electrohydrodynamic peristaltic flow of a viscoelastic Oldroyd fluid with a mild stenosis: Application of an endoscope

    Science.gov (United States)

    El-dabe, N. T. M.; Moatimid, G. M.; Hassan, M. A.; Mostapha, D. R.

    2016-01-01

    The effect of a vertical alternating current, electric field, and heat transfer on a peristaltic flow of a dielectric viscoelastic Oldroyd fluid is studied. This analysis involves uniform and nonuniform annuli having a mild stenosis. The analytical solutions of equations of motion are based on the perturbation technique. This technique depends on two parameters: amplitude ratio and small wave number. Numerical calculations are performed to obtain the effects of several parameters, such as the electrical Rayleigh number, temperature gradient, Reynolds number, wave number, maximum height of stenosis, and Weissenberg numbers, on the distributions of velocity, temperature, electric potential, and wall shear stress. It is found that the above-mentioned distributions in the case of a convergent tapered tube are larger than those in the case of a non-tapered one as well as a diverging tapered tube.

  3. Characteristics of Jeffrey fluid model for peristaltic flow of chyme in small intestine with magnetic field

    Science.gov (United States)

    Akbar, Noreen Sher; Nadeem, S.; Lee, Changhoon

    In the present article we have analyzed the Jeffrey fluid model for the peristaltic flow of chyme in the small intestine. We have formulated the problem using two non-periodic sinusoidal waves of different wavelengths propagating with same speed c along the outer wall of the tube. Governing equations for the problem under consideration have been simplified under the assumptions of long wavelength and low Reynolds number approximation (such assumptions are consistent since Re (Reynolds number) is very small and long wavelength approximation also exists in the small intestine). Exact solutions have been calculated for velocity and pressure rise. Physical behavior of different parameters of Jeffrey fluid has been presented graphically for velocity, pressure rise, pressure gradient and frictional forces. The trapping phenomenon is also discussed at the end of the article.

  4. Hall and ion slip effects on peristaltic flow of Jeffrey nanofluid with Joule heating

    Energy Technology Data Exchange (ETDEWEB)

    Hayat, T. [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); NAAM Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Shafique, Maryam [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); Tanveer, A., E-mail: anum@math.qau.edu.pk [Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan); Alsaedi, A. [NAAM Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2016-06-01

    This paper addresses mixed convective peristaltic flow of Jeffrey nanofluid in a channel with complaint walls. The present investigation includes the viscous dissipation, thermal radiation and Joule heating. Hall and ion slip effects are also taken into account. Related problems through long wavelength and low Reynolds number are examined for stream function, temperature and concentration. Impacts of thermal radiation, Hartman number, Brownian motion parameter, thermophoresis, Joule heating, Hall and ion slip parameters are investigated in detail. It is observed that velocity increases and temperature decreases with Hall and ion slip parameters. Further the thermal radiation on temperature has qualitatively similar role to that of Hall and ion slip effects. - Highlights: • Peristalsis in the presence of Jeffery nanofluid is formulated. • Compliant properties of channel walls are addressed. • Impact of Hall and ion slip effects is outlined. • Influence of Joule heating and radiation is investigated. • Mixed convection for both heat and mass transfer is present.

  5. Wake structure and thrust generation of a flapping foil in two-dimensional flow

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; Bohr, Tomas; Schnipper, Teis

    2017-01-01

    We present a combined numerical (particle vortex method) and experimental (soap film tunnel) study of a symmetric foil undergoing prescribed oscillations in a two-dimensional free stream. We explore pure pitching and pure heaving, and contrast these two generic types of kinematics. We compare...... measurements and simulations when the foil is forced with pitching oscillations, and we find a close correspondence between flow visualisations using thickness variations in the soap film and the numerically determined vortex structures. Numerically, we determine wake maps spanned by oscillation frequency...

  6. Two-dimensional motion of unstable steps induced by flow in solution

    OpenAIRE

    Sato, Masahide

    2011-01-01

    By carrying out Monte Carlo simulation, we study step instabilities during crystal growth from solution. In previous studies [M. Sato. J. Phys. Soc. Jpn. 79 (2010) 064606; M. Sato, J. Cryst. Growth 318 (2011) 5; M. Sato. J. Phys. Soc. Jpn. 80 (2011) 024604], we used a one-dimensional model, so that we were unable to study another type of instability, step wandering. In this research, we use a two-dimensional model to study both step wandering and step bunching. When the flow of solutes is in ...

  7. Spatial statistics of magnetic field in two-dimensional chaotic flow in the resistive growth stage

    CERN Document Server

    Kolokolov, Igor

    2016-01-01

    The correlation tensors of magnetic field in a two-dimensional chaotic flow of conducting fluid are studied. It is shown that there is a stage of resistive evolution where the field correlators grow exponentially with time what contradicts to the statements present in literature. The two- and four-point field correlation tensors are computed explicitly in this stage in the framework of Batchelor-Kraichnan-Kazantsev model. These tensors demonstrate highly intermittent statistics of the field fluctuations both in space and time.

  8. Two-dimensional numerical simulation of flow around three-stranded rope

    Science.gov (United States)

    Wang, Xinxin; Wan, Rong; Huang, Liuyi; Zhao, Fenfang; Sun, Peng

    2016-08-01

    Three-stranded rope is widely used in fishing gear and mooring system. Results of numerical simulation are presented for flow around a three-stranded rope in uniform flow. The simulation was carried out to study the hydrodynamic characteristics of pressure and velocity fields of steady incompressible laminar and turbulent wakes behind a three-stranded rope. A three-cylinder configuration and single circular cylinder configuration are used to model the three-stranded rope in the two-dimensional simulation. The governing equations, Navier-Stokes equations, are solved by using two-dimensional finite volume method. The turbulence flow is simulated using Standard κ-ɛ model and Shear-Stress Transport κ-ω (SST) model. The drag of the three-cylinder model and single cylinder model is calculated for different Reynolds numbers by using control volume analysis method. The pressure coefficient is also calculated for the turbulent model and laminar model based on the control surface method. From the comparison of the drag coefficient and the pressure of the single cylinder and three-cylinder models, it is found that the drag coefficients of the three-cylinder model are generally 1.3-1.5 times those of the single circular cylinder for different Reynolds numbers. Comparing the numerical results with water tank test data, the results of the three-cylinder model are closer to the experiment results than the single cylinder model results.

  9. On the use of wall functions as boundary conditions for two-dimensional separated compressible flows

    Science.gov (United States)

    Viegas, J. R.; Rubesin, M. W.; Horstman, C. C.

    1985-01-01

    A new and improved wall function method for compressible turbulent flows has been developed and tested. This method is applicable to attached and separated flows, to both high- and low-Reynolds number flows, and to flows with adiabatic and nonadiabatic surfaces. This wall function method has been applied to the Launder-Spalding k-epsilon two-equation model of turbulence. The tests consist of comparisons of calculated and experimental results for: (1) an axisymmetrical transonic shock-wave/boundary-wave interaction flow at low Reynolds number in an adiabatic tube, (2) an axisymmetrical high-Reynolds number transonic flow over a nonadiabatic bump, and (3) a two-dimensional supersonic high-Reynolds number flow on a nonadiabatic deflected flap. Each of these experiments had significant regions of flow separation. The calculations are performed with an implicit algorithm that solves the Reynolds-averaged Navier-Stokes equations. It is shown that the results obtained agree very well with the data for the complex compressible flows tested.

  10. The direct enstrophy cascade of two-dimensional soap film flows

    CERN Document Server

    Rivera, Mike; Ecke, Robert

    2013-01-01

    We investigate the direct enstrophy cascade of two-dimensional decaying turbulence in a flowing soap film channel. We use a coarse-graining approach that allows us to resolve the nonlinear dynamics and scale-coupling simultaneously in scale and in space. From our data, we calculate the transfer of enstrophy across scale $\\ell$ at every point $\\bx$ in the flow domain. We verify an exact relation due to Eyink (1995) between traditional 3rd-order structure function and the enstrophy flux obtained by coarse-graining. We also present experimental evidence that enstrophy cascades to smaller (larger) scales with a 60% (40%) probability, in support of theoretical predictions by Merilees & Warn (1975). Using an Eulerian coherent structure identification technique, we then determine the effect of flow topology on the enstrophy cascade. A key finding is that "centers" are inefficient at transferring enstrophy between scales, in contrast to "saddle" regions which transfer enstrophy to small scales with high efficienc...

  11. Solvable phase diagrams and ensemble inequivalence for two-dimensional and geophysical turbulent flows

    CERN Document Server

    Venaille, Antoine

    2010-01-01

    Using explicit analytical computations, generic occurrence of inequivalence between two or more statistical ensembles is obtained for a large class of equilibrium states of two-dimensional and geophysical turbulent flows. The occurrence of statistical ensemble inequivalence is shown to be related to previously observed phase transitions in the equilibrium flow topology. We find in these turbulent flow equilibria, two mechanisms for the appearance of ensemble equivalences, that were not observed in any physical systems before. These mechanisms are associated respectively with second-order azeotropy (simultaneous appearance of two second-order phase transitions), and with bicritical points (bifurcation from a first-order to two second-order phase transition lines). The important roles of domain geometry, of topography, and of a screening length scale (the Rossby radius of deformation) are discussed. It is found that decreasing the screening length scale (making interactions more local) surprisingly widens the r...

  12. Gas-kinetic numerical schemes for one- and two-dimensional inner flows

    Institute of Scientific and Technical Information of China (English)

    Zhi-hui LI; Lin BI; Zhi-gong TANG

    2009-01-01

    Several kinds of explicit and implicit finite-difference schemes directly solving the discretized velocity distribution functions are designed with precision of different orders by analyzing the inner characteristics of the gas-kinetic numerical algorithm for Boltzmann model equation.The peculiar flow phenomena and mechanism from various flow regimes are revealed in the numerical simulations of the unsteady Sod shock-tube problems and the two-dimensional channel flows with different Knudsen numbers.The numerical remainder-effects of the difference schemes are investigated and analyzed based on the computed results.The ways of improving the computational efficiency of the gaskinetic numerical method and the computing principles of difference discretization are discussed.

  13. A characteristic mapping method for two-dimensional incompressible Euler flows

    Science.gov (United States)

    Yadav, Badal; Mercier, Olivier; Nave, Jean-Christophe; Schneider, Kai

    2016-11-01

    We propose an efficient semi-Lagrangian method for solving the two-dimensional incompressible Euler equations with high precision on a coarse grid. The new approach evolves the flow map using the gradient-augmented level set method (GALSM). Since the flow map can be decomposed into submaps (each over a finite time interval), the error can be controlled by choosing the remapping times appropriately. This leads to a numerical scheme that has exponential resolution in linear time. The computational efficiency and the high precision of the method are illustrated for a vortex merger and a four mode flow. Comparisons with a Cauchy-Lagrangian method are also presented. KS thankfully acknowledges financial support from the French Research Federation for Fusion Studies within the framework of the European Fusion Development Agreement (EFDA).

  14. Solution of Two-Dimensional Viscous Flow Driven by Motion of Flexible Walls

    Directory of Open Access Journals (Sweden)

    Mohamed Gad-el-Hak

    2010-03-01

    Full Text Available An exact solution of the Navier–Stokes equations for a flow driven by motion of flexible wall is developed. A simple two-dimensional channel with deforming walls is considered as domain. The governing equations are linearized for low Reynolds number and large Womersley number Newtonian flows. Appropriate boundary conditions for general deformation are decomposed into harmonic excitations in space by Fourier series decomposition. A model of harmonic boundary deformation is considered and results are compared with computational fluid dynamics predictions. The results of velocity profiles across the channel and the centerline velocities of the channel are in good agreement with CFD solution. The analytical model developed provides quantitative descriptions of the flow field for a wide spectrum of actuating frequnecy and boundary conditions. The presented model can be used as an effective framework for preliminary design and optimization of displacement micropumps and other miniature applications.

  15. An incompressible two-dimensional multiphase particle-in-cell model for dense particle flows

    Energy Technology Data Exchange (ETDEWEB)

    Snider, D.M. [SAIC, Albuquerque, NM (United States); O`Rourke, P.J. [Los Alamos National Lab., NM (United States); Andrews, M.J. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering

    1997-06-01

    A two-dimensional, incompressible, multiphase particle-in-cell (MP-PIC) method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to a Eulerian grid and then mapping back computed stress tensors to particle positions. This approach utilizes the best of Eulerian/Eulerian continuum models and Eulerian/Lagrangian discrete models. The solution scheme allows for distributions of types, sizes, and density of particles, with no numerical diffusion from the Lagrangian particle calculations. The computational method is implicit with respect to pressure, velocity, and volume fraction in the continuum solution thus avoiding courant limits on computational time advancement. MP-PIC simulations are compared with one-dimensional problems that have analytical solutions and with two-dimensional problems for which there are experimental data.

  16. A two-dimensional CA model for traffic flow with car origin and destination

    Science.gov (United States)

    In-nami, Junji; Toyoki, Hiroyasu

    2007-05-01

    Dynamic phase transitions in a two-dimensional traffic flow model defined on a decorated square-lattice are studied numerically. The square-lattice point and the decorated site denote intersections and roads, respectively. In the present model, a car has a finite deterministic path between the origin and the destination, which is assigned to the car from the beginning. In this new model, we found a new phase between the free-flow phase and the frozen-jam phase that is absent from previous models. The new model is characterized by the persistence of a macroscopic cluster. Furthermore, the behavior in this macroscopic cluster phase is classified into three regions characterized by the shape of the cluster. The boundary of the three regions is phenomenologically estimated. When the trip length is short and the car density is high, both ends of the belt-like cluster connect to each other through the periodic boundary with some probability. This type of cluster is classified topologically as a string on a two-dimensional torus.

  17. A two-dimensional adaptive spectral element method for the direct simulation of incompressible flow

    Science.gov (United States)

    Hsu, Li-Chieh

    The spectral element method is a high order discretization scheme for the solution of nonlinear partial differential equations. The method draws its strengths from the finite element method for geometrical flexibility and spectral methods for high accuracy. Although the method is, in theory, very powerful for complex phenomena such as transitional flows, its practical implementation is limited by the arbitrary choice of domain discretization. For instance, it is hard to estimate the appropriate number of elements for a specific case. Selection of regions to be refined or coarsened is difficult especially as the flow becomes more complex and memory limits of the computer are stressed. We present an adaptive spectral element method in which the grid is automatically refined or coarsened in order to capture underresolved regions of the domain and to follow regions requiring high resolution as they develop in time. The objective is to provide the best and most efficient solution to a time-dependent nonlinear problem by continually optimizing resource allocation. The adaptivity is based on an error estimator which determines which regions need more resolution. The solution strategy is as follows: compute an initial solution with a suitable initial mesh, estimate errors in the solution locally in each element, modify the mesh according to the error estimators, interpolate old mesh solutions onto the new elements, and resume the numerical solution process. A two-dimensional adaptive spectral element method for the direct simulation of incompressible flows has been developed. The adaptive algorithm effectively diagnoses and refines regions of the flow where complexity of the solution requires increased resolution. The method has been demonstrated on two-dimensional examples in heat conduction, Stokes and Navier-Stokes flows.

  18. The flow of an aqueous foam through a two-dimensional porous medium

    Science.gov (United States)

    Dollet, B.; Jones, S. A.; Géraud, B.; Meheust, Y.; Cox, S. J.; Cantat, I.

    2013-12-01

    Flowing foams are used in many engineering and technical applications. A well-known application is oil recovery. Another one is the remediation of polluted soils: the foam is injected into the ground in order to mobilize chemical species present in the medium. Apart from potential interesting physico-chemical and biochemical properties, foams have peculiar flow properties that applications might benefit of. In particular, viscous dissipation arises mostly from the contact zones between the soap films and the walls, which results in peculiar friction laws allowing the foam to invade narrow pores more efficiently than Newtonian fluids would. We investigate the flow of a two-dimensional foam in three geometrical configurations. The flow velocity field and pressure field can both be reconstructed from the kinematics of the foam bubbles. We first consider a medium consisting of two parallel channels with different widths, at fixed medium porosity, that is, at fixed total combined width of the two channels. The flow behavior is highly dependent on the foam structure within the narrowest of the two channels [1]; consequently, the flux ratio between the two channels exhibits a non-monotonic dependence on the ratio of their widths. We then consider two parallel channels that are respectively convergent and divergent. The resulting flow kinematics imposes asymmetric bubble deformations in the two channels; these deformations strongly impact the foam/wall friction, and consequently the flux distribution between the two channels, causing flow irreversibility. We quantitatively predict the flux ratio as a function of the channel widths by modeling pressure drops of both viscous and capillary origins. This study reveals the crucial importance of boundary-induced bubble deformation on the mobility of a flowing foam. We then study how film-wall friction, capillary pressures and bubble deformation impact the flow of a foam in a two-dimensional porous medium consisting of randomly

  19. Nonlinear transverse cascade and two-dimensional magnetohydrodynamic subcritical turbulence in plane shear flows.

    Science.gov (United States)

    Mamatsashvili, G R; Gogichaishvili, D Z; Chagelishvili, G D; Horton, W

    2014-04-01

    We find and investigate via numerical simulations self-sustained two-dimensional turbulence in a magnetohydrodynamic flow with a maximally simple configuration: plane, noninflectional (with a constant shear of velocity), and threaded by a parallel uniform background magnetic field. This flow is spectrally stable, so the turbulence is subcritical by nature and hence it can be energetically supported just by a transient growth mechanism due to shear flow non-normality. This mechanism appears to be essentially anisotropic in the spectral (wave-number) plane and operates mainly for spatial Fourier harmonics with streamwise wave numbers less than the ratio of flow shear to Alfvén speed, kymagnetohydrodynamic (MHD) turbulence research. We find similarity of the nonlinear dynamics to the related dynamics in hydrodynamic flows: to the bypass concept of subcritical turbulence. The essence of the analyzed nonlinear MHD processes appears to be a transverse redistribution of kinetic and magnetic spectral energies in the wave-number plane [as occurs in the related hydrodynamic flow; see Horton et al., Phys. Rev. E 81, 066304 (2010)] and differs fundamentally from the existing concepts of (anisotropic direct and inverse) cascade processes in MHD shear flows.

  20. Flow pattern transition accompanied with sudden growth of flow resistance in two-dimensional curvilinear viscoelastic flows

    CERN Document Server

    Yatou, Hiroki

    2010-01-01

    We find three types of steady solutions and remarkable flow pattern transitions between them in a two-dimensional wavy-walled channel for low to moderate Reynolds (Re) and Weissenberg (Wi) numbers using direct numerical simulations with spectral element method. The solutions are called "convective", "transition", and "elastic" in ascending order of Wi. In the convective region in the Re-Wi parameter space, the convective effect and the pressure gradient balance on average. As Wi increases, the elastic effect becomes suddenly comparable and the first transition sets in. Through the transition, a separation vortex disappears and a jet flow induced close to the wall by the viscoelasticity moves into the bulk; The viscous drag significantly drops and the elastic wall friction rises sharply. This transition is caused by an elastic force in the streamwise direction due to the competition of the convective and elastic effects. In the transition region, the convective and elastic effects balance. When the elastic eff...

  1. Finite-time barriers to front propagation in two-dimensional fluid flows

    CERN Document Server

    Mahoney, John R

    2015-01-01

    Recent theoretical and experimental investigations have demonstrated the role of certain invariant manifolds, termed burning invariant manifolds (BIMs), as one-way dynamical barriers to reaction fronts propagating within a flowing fluid. These barriers form one-dimensional curves in a two-dimensional fluid flow. In prior studies, the fluid velocity field was required to be either time-independent or time-periodic. In the present study, we develop an approach to identify prominent one-way barriers based only on fluid velocity data over a finite time interval, which may have arbitrary time-dependence. We call such a barrier a burning Lagrangian coherent structure (bLCS) in analogy to Lagrangian coherent structures (LCSs) commonly used in passive advection. Our approach is based on the variational formulation of LCSs using curves of stationary "Lagrangian shear", introduced by Farazmand, Blazevski, and Haller [Physica D 278-279, 44 (2014)] in the context of passive advection. We numerically validate our techniqu...

  2. Flow-rate fluctuations in the outpouring of grains from a two-dimensional silo.

    Science.gov (United States)

    Janda, A; Harich, R; Zuriguel, I; Maza, D; Cixous, P; Garcimartín, A

    2009-03-01

    We present experimental results obtained with a two-dimensional silo discharging under gravity through an orifice at the flat bottom. High-speed measurements provide enough time resolution to detect every single bead that goes out and this allows the measurement of the flow rate in short-time windows. Two different regimes are clearly distinguished: one for large orifices, which can be described by Gaussian fluctuations, and another for small orifices, in which extreme events appear. The frontier between those two regimes coincides with the outlet size below which jamming events are frequent. Moreover, it is shown that the power spectrum of the flow-rate oscillations is not dominated by any particular frequency.

  3. A Hybrid Nodal Method for Time-Dependent Incompressible Flow in Two-Dimensional Arbitrary Geometries

    Energy Technology Data Exchange (ETDEWEB)

    Toreja, A J; Uddin, R

    2002-10-21

    A hybrid nodal-integral/finite-analytic method (NI-FAM) is developed for time-dependent, incompressible flow in two-dimensional arbitrary geometries. In this hybrid approach, the computational domain is divided into parallelepiped and wedge-shaped space-time nodes (cells). The conventional nodal integral method (NIM) is applied to the interfaces between adjacent parallelepiped nodes (cells), while a finite analytic approach is applied to the interfaces between parallelepiped and wedge-shaped nodes (cells). In this paper, the hybrid method is formally developed and an application of the NI-FAM to fluid flow in an enclosed cavity is presented. Results are compared with those obtained using a commercial computational fluid dynamics code.

  4. Improved modeling and numerics to solve two-dimensional elliptic fluid flow and heat transfer problems

    Science.gov (United States)

    Chan, B. C.

    1986-05-01

    A basic, limited scope, fast-running computer model is presented for the solution of two-dimensional, transient, thermally-coupled fluid flow problems. This model is to be the module in the SSC (an LMFBR thermal-hydraulic systems code) for predicting complex flow behavior, as occurs in the upper plenum of the loop-type design or in the sodium pool of the pool-type design. The nonlinear Navier-Stokes equations and the two-equation (two-variable) transport model of turbulence are reduced to a set of linear algebraic equations in an implicit finite difference scheme, based on the control volume approach. These equations are solved iteratively in a line-by-line procedure using the tri-diagonal matrix algorithm. The results of calculational examplers are shown in the computer-generated plots.

  5. Numerical Algorithms for Two-Dimensional Dry Granular Flow with Deformable Elastic Grain

    Energy Technology Data Exchange (ETDEWEB)

    Boateng, H A; Elander, V; Jin, C; Li, Y; Vasquez, P; Fast, P

    2005-08-11

    The authors consider the dynamics of interacting elastic disks in the plane. This is an experimentally realizable two-dimensional model of dry granular flow where the stresses can be visualized using the photoelastic effect. As the elastic disks move in a vacuum, they interact through collisions with each other and with the surrounding geometry. Because of the finite propagation speed of deformations inside each grain it can be difficult to capture computationally even simple experiments involving just a few interacting grains. The goal of this project is to improve our ability to simulate dense granular flow in complex geometry. They begin this process by reviewing some past work, how they can improve upon previous work. the focus of this project is on capturing the elastic dynamics of each grain in an approximate, computationally tractable, model that can be coupled to a molecular dynamics scheme.

  6. A minimum action method for small random perturbations of two-dimensional parallel shear flows

    Science.gov (United States)

    Wan, Xiaoliang

    2013-02-01

    In this work, we develop a parallel minimum action method for small random perturbations of Navier-Stokes equations to solve the optimization problem given by the large deviation theory. The Freidlin-Wentzell action functional is discretized by hp finite elements in time direction and spectral methods in physical space. A simple diagonal preconditioner is constructed for the nonlinear conjugate gradient solver of the optimization problem. A hybrid parallel strategy based on MPI and OpenMP is developed to improve numerical efficiency. Both h- and p-convergence are obtained when the discretization error from physical space can be neglected. We also present preliminary results for the transition in two-dimensional Poiseuille flow from the base flow to a non-attenuated traveling wave.

  7. Laboratory setup and results of experiments on two-dimensional multiphase flow in porous media

    Energy Technology Data Exchange (ETDEWEB)

    McBride, J.F. (ed.) (Pacific Northwest Lab., Richland, WA (USA)); Graham, D.N. (ed.); Schiegg, H.O. (SIMULTEC Ltd., Meilen/Zurich (Switzerland))

    1990-10-01

    In the event of an accidental release into earth's subsurface of an immiscible organic liquid, such as a petroleum hydrocarbon or chlorinated organic solvent, the spatial and temporal distribution of the organic liquid is of great interest when considering efforts to prevent groundwater contamination or restore contaminated groundwater. An accurate prediction of immiscible organic liquid migration requires the incorporation of relevant physical principles in models of multiphase flow in porous media; these physical principles must be determined from physical experiments. This report presents a series of such experiments performed during the 1970s at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland. The experiments were designed to study the transient, two-dimensional displacement of three immiscible fluids in a porous medium. This experimental study appears to be the most detailed published to date. The data obtained from these experiments are suitable for the validation and test calibration of multiphase flow codes. 73 refs., 140 figs.

  8. Enhanced Transport of Passive Tracers In A Time Periodic Two-dimensional Flow

    Science.gov (United States)

    Boffetta, G.; Cencini, M.; Espa, S.; Musacchio, S.

    , investigating systems in which the second condition is violated is much more inter- esting. With this purpose, some experiments have shown how superdiffusion arises in a two-dimensional quasi-geostrophic (planetary-type) flow, where particles can jump for very long time in the same direction performing a Levy flight (Castiglione et al., 2001 ). Moreover, two recent papers (Vulpiani, 1998; Solomon, 2001) show how, also in very simple two-dimensional, time and space periodic cellular flows,anomalous diffusive behaviours can appear. In this paper we present an experimental study of transport in an electromagnetically forced time periodic two-dimensional flow. The flow is generated by applying an electromagnetic forcing on a thin layer of an elec- trolyte solution and reveals in a square grid of alternating vortices. Time dependence can be easily obtained by changing the time dependence of the electric fields. In par- ticular, considering certain values of the imposed oscillation frequencies, particles can display very long jump. Particle Tracking Velocimetry (PTV) is used to measure the flow field. This technique is the most suitable for studying dispersion phenomena in a Lagrangian framework allowing the direct evaluation of particle displacements and related quantities (Cenedese, Querzoli; 2000). Moreover, due to the characteristics of the analyzed flow and to the improvement of the tracking procedure, we have been able to track a great number of particles for time intervals greater than the charac- teristic time-scales of the flow. In order to characterize the time correlations we will evaluate the so-called jumps probabilities with memory which represent the probabil- ities to jump in a given direction conditioned to having experienced jumps in the same direction at previous times. Such statistics will revealed very useful and suitable for detecting the onset of the aforementioned correlations. 2

  9. Uncertainty analysis of quasi-two-dimensional flow simulation in compound channels with overbank flows

    OpenAIRE

    Riahi-Madvar, Hossien; Ayyoubzadeh, Seyed Ali; Namin, Masoud Montazeri; Seifi, Akram

    2011-01-01

    Flow in compound channels with overbank flows becomes more complex because of shear interactions between flows in main channel and flood plains, lateral momentum transfer and secondary flows. Compound channels have interesting applications in flood control, civil engineering and environmental management. Because it is difficult to obtain sufficiently accurate and comprehensive understandings of flow in natural compound rivers, the developed models of flow in overbank flows have many uncertain...

  10. GIS-based two-dimensional numerical simulation of rainfall-induced debris flow

    Directory of Open Access Journals (Sweden)

    C. Wang

    2008-02-01

    Full Text Available This paper aims to present a useful numerical method to simulate the propagation and deposition of debris flow across the three dimensional complex terrain. A depth-averaged two-dimensional numerical model is developed, in which the debris and water mixture is assumed to be continuous, incompressible, unsteady flow. The model is based on the continuity equations and Navier-Stokes equations. Raster grid networks of digital elevation model in GIS provide a uniform grid system to describe complex topography. As the raster grid can be used as the finite difference mesh, the continuity and momentum equations are solved numerically using the finite difference method. The numerical model is applied to simulate the rainfall-induced debris flow occurred in 20 July 2003, in Minamata City of southern Kyushu, Japan. The simulation reproduces the propagation and deposition and the results are in good agreement with the field investigation. The synthesis of numerical method and GIS makes possible the solution of debris flow over a realistic terrain, and can be used to estimate the flow range, and to define potentially hazardous areas for homes and road section.

  11. GIS-based two-dimensional numerical simulation of rainfall-induced debris flow

    Science.gov (United States)

    Wang, C.; Li, S.; Esaki, T.

    2008-02-01

    This paper aims to present a useful numerical method to simulate the propagation and deposition of debris flow across the three dimensional complex terrain. A depth-averaged two-dimensional numerical model is developed, in which the debris and water mixture is assumed to be continuous, incompressible, unsteady flow. The model is based on the continuity equations and Navier-Stokes equations. Raster grid networks of digital elevation model in GIS provide a uniform grid system to describe complex topography. As the raster grid can be used as the finite difference mesh, the continuity and momentum equations are solved numerically using the finite difference method. The numerical model is applied to simulate the rainfall-induced debris flow occurred in 20 July 2003, in Minamata City of southern Kyushu, Japan. The simulation reproduces the propagation and deposition and the results are in good agreement with the field investigation. The synthesis of numerical method and GIS makes possible the solution of debris flow over a realistic terrain, and can be used to estimate the flow range, and to define potentially hazardous areas for homes and road section.

  12. Two-Dimensional Automatic Measurement for Nozzle Flow Distribution Using Improved Ultrasonic Sensor

    Directory of Open Access Journals (Sweden)

    Changyuan Zhai

    2015-10-01

    Full Text Available Spray deposition and distribution are affected by many factors, one of which is nozzle flow distribution. A two-dimensional automatic measurement system, which consisted of a conveying unit, a system control unit, an ultrasonic sensor, and a deposition collecting dish, was designed and developed. The system could precisely move an ultrasonic sensor above a pesticide deposition collecting dish to measure the nozzle flow distribution. A sensor sleeve with a PVC tube was designed for the ultrasonic sensor to limit its beam angle in order to measure the liquid level in the small troughs. System performance tests were conducted to verify the designed functions and measurement accuracy. A commercial spray nozzle was also used to measure its flow distribution. The test results showed that the relative error on volume measurement was less than 7.27% when the liquid volume was 2 mL in trough, while the error was less than 4.52% when the liquid volume was 4 mL or more. The developed system was also used to evaluate the flow distribution of a commercial nozzle. It was able to provide the shape and the spraying width of the flow distribution accurately.

  13. Two-dimensional automatic measurement for nozzle flow distribution using improved ultrasonic sensor.

    Science.gov (United States)

    Zhai, Changyuan; Zhao, Chunjiang; Wang, Xiu; Wang, Ning; Zou, Wei; Li, Wei

    2015-10-16

    Spray deposition and distribution are affected by many factors, one of which is nozzle flow distribution. A two-dimensional automatic measurement system, which consisted of a conveying unit, a system control unit, an ultrasonic sensor, and a deposition collecting dish, was designed and developed. The system could precisely move an ultrasonic sensor above a pesticide deposition collecting dish to measure the nozzle flow distribution. A sensor sleeve with a PVC tube was designed for the ultrasonic sensor to limit its beam angle in order to measure the liquid level in the small troughs. System performance tests were conducted to verify the designed functions and measurement accuracy. A commercial spray nozzle was also used to measure its flow distribution. The test results showed that the relative error on volume measurement was less than 7.27% when the liquid volume was 2 mL in trough, while the error was less than 4.52% when the liquid volume was 4 mL or more. The developed system was also used to evaluate the flow distribution of a commercial nozzle. It was able to provide the shape and the spraying width of the flow distribution accurately.

  14. Experimental Observation of Exact Coherent Structures in a Weakly Turbulent Quasi-Two-Dimensional Flow

    Science.gov (United States)

    Suri, Balachandra; Tithof, Jeffrey; Pallantla, Ravi Kumar; Grigoriev, Roman; Schatz, Michael

    2015-11-01

    The dynamical systems approach to fluid turbulence relies on understanding the role of unstable, non-chaotic solutions - such as equilibria, traveling waves, and periodic orbits - of the Navier-Stokes equations. These solutions, called Exact Coherent Structures, exist in the same parameter regime as turbulence, but being unstable, are observed in experiments only as short transients. In this talk, we present experimental evidence for the existence and dynamical relevance of unstable equilibria in a weakly turbulent quasi-two-dimensional (Q2D) Kolmogorov flow. In the experiment, this Q2D flow is generated in an electromagnetically driven shallow layer of electrolyte. The numerical simulations, however, use a strictly 2D model which incorporates the effects of the finite thickness of the fluid layer in the experiment. During its evolution, there are instances when the dynamics of a weakly turbulent flow slow down, rather dramatically. Using experimental flow fields from such instances, and by means of a Newton-Solver, we numerically compute several unstable equilibria. Additionally, using numerical simulations, we show that the dynamics of a turbulent flow in the neighbourhood of an equilibrium are accurately described by the unstable manifold of the equilibrium. This work is supported in part by the National Science Foundation under grants CBET-0900018, and CMMI-1234436.

  15. Coherent Structures in Turbulent Flow over Two-Dimensional River Dunes

    CERN Document Server

    Omidyeganeh, Mohammad

    2011-01-01

    We performed large-eddy simulations of the flow over a typical two-dimensional dune geometry at laboratory scale (the Reynolds number based on the average channel height and mean velocity is 18,900) using the Lagrangian dynamic eddy-viscosity subgrid-scale model. The flow separates at the dune crest and reattaches downstream on the bed (at x=5.7h). A favorable pressure gradient accelerates the flow over the stoss-side (the upward-sloping region for x > 8h) and an unfavorable gradient for x < 8h decelerates the flow over the lee-side of the dune. Due to the separation of the flow, a shear layer is generated after the crest that expands in the wake region towards the next dune. The outer-layer turbulence structures are visualized through isosurfaces of pressure fluctuations colored by distance to the surface. Spanwise vortices are generated in the shear layer separating from the crest due to the Kelvin-Helmholtz instability. They are convected downstream and either interact with the wall or rise to the surfa...

  16. Three dimensional peristaltic flow of hyperbolic tangent fluid in non-uniform channel having flexible walls

    Directory of Open Access Journals (Sweden)

    M. Ali Abbas

    2016-03-01

    Full Text Available In this present analysis, three dimensional peristaltic flow of hyperbolic tangent fluid in a non-uniform channel has been investigated. We have considered that the pressure is uniform over the whole cross section and the interial effects have been neglected. For this purpose we consider laminar flow under the assumptions of long wavelength (λ→∞ and creeping flow (Re→0 approximations. The attained highly nonlinear equations are solved with the help of Homotopy perturbation method. The influence of various physical parameters of interest is demonstrated graphically for wall tension, mass characterization, damping nature of the wall, wall rigidity, wall elastance, aspect ratio and the Weissenberg number. In this present investigation we found that the magnitude of the velocity is maximum in the center of the channel whereas it is minimum near the walls. Stream lines are also drawn to discuss the trapping mechanism for all the physical parameters. Comparison has also been presented between Newtonian and non-Newtonian fluid.

  17. Flow of a two-dimensional aqueous foam in two parallel channels

    Science.gov (United States)

    Jones, S.; Cantat, I.; Dollet, B.; Meheust, Y.

    2012-04-01

    Flowing foams are used in many engineering and technical applications. A well-known application is oil recovery. Another one is the remediation of polluted soil: the foam is injected into the ground in order to mobilize chemical species that are initially present in the medium. Apart from potential interesting physico-chemical and biochemical properties, foams have pecular flow properties that might be used in order to reach regions of the medium that are normally the least permeable. We study here this physical aspect of the topic. As a precursor to the study of foam flow through a complex porous material, we study the behaviour of an aqueous two-dimensional foam flowing through a medium consisting of two parallel channels with different widths, at fixed medium porosity, that is, at fixed total combined width of the two channels. The flow velocity, and hence flux, in each channel is measured by analyzing images of the flowing foam. The corresponding pressure drop along each channel is calculated based on theoretical arguments involving both (i) a dynamic pressure drop, which is controlled by bubble-wall friction, and (ii) possibly a capillary pressure drop over the bubble films that emerge at the channel outlet, the latter pressure drop being controlled by the radius of curvature of the bubble film. The flow behaviour of the foam happens to not uniquely be determined by the channel width, as would be the case for a Newtonian fluid, but also to be highly dependent on the foam structure within the narrowest of the two channel, especially when a "bamboo" structure is obtained. Consequently, the flux in a channel is found to have a more complicated relation to the channel width than expected. We try to define a corresponding medium permeability and compare it to the permeability expected for the flow of a standard newtonian fluid in the same geometry.

  18. Numerical Investigation on Two-dimensional Boundary Layer Flow with Transition

    Institute of Scientific and Technical Information of China (English)

    Yong Zhao; Tianlin Wang; Zhi Zong

    2014-01-01

    As a basic problem in many engineering applications, transition from laminar to turbulence still remains a difficult problem in computational fluid dynamics (CFD). A numerical study of one transitional flow in two-dimensional is conducted by Reynolds averaged numerical simulation (RANS) in this paper. Turbulence model plays a significant role in the complex flows’ simulation, and four advanced turbulence models are evaluated. Numerical solution of frictional resistance coefficient is compared with the measured one in the transitional zone, which indicates that Wilcox (2006) k-ω model with correction is the best candidate. Comparisons of numerical and analytical solutions for dimensionless velocity show that averaged streamwise dimensionless velocity profiles correct the shape rapidly in transitional region. Furthermore, turbulence quantities such as turbulence kinetic energy, eddy viscosity, and Reynolds stress are also studied, which are helpful to learn the transition’s behavior.

  19. A numerical study of the alpha model for two-dimensional magnetohydrodynamic turbulent flows

    CERN Document Server

    Mininni, P D; Pouquet, A G

    2004-01-01

    We explore some consequences of the ``alpha model,'' also called the ``Lagrangian-averaged'' model, for two-dimensional incompressible magnetohydrodynamic (MHD) turbulence. This model is an extension of the smoothing procedure in fluid dynamics which filters velocity fields locally while leaving their associated vorticities unsmoothed, and has proved useful for high Reynolds number turbulence computations. We consider several known effects (selective decay, dynamic alignment, inverse cascades, and the probability distribution functions of fluctuating turbulent quantities) in magnetofluid turbulence and compare the results of numerical solutions of the primitive MHD equations with their alpha-model counterparts' performance for the same flows, in regimes where available resolution is adequate to explore both. The hope is to justify the use of the alpha model in regimes that lie outside currently available resolution, as will be the case in particular in three-dimensional geometry or for magnetic Prandtl number...

  20. Experimental Analysis of Two-Dimensional Pedestrian Flow in front of the Bottleneck

    CERN Document Server

    cek, Marek Buká\\v; Krbálek, Milan

    2014-01-01

    This contribution presents experimental study of two-dimensional pedestrian flow with the aim to capture the pedestrian behaviour within the cluster formed in front of the bottleneck. Two experiments of passing through a room with one entrance and one exit were arranged according to phase transition study in Ezaki et al. (2012), the inflow rate was regulated to obtain different walking modes. By means of automatic image processing, pedestrians' paths are extracted from camera records to get actual velocity and local density. Macroscopic information is extracted by means of virtual detector and leaving times of pedestrians. The pedestrian's behaviour is evaluated by means of density and velocity. Different approaches of measurement are compared using several fundamental diagrams. Two phases of crowd behaviour have been recognized and the phase transition was described.

  1. Two-dimensional behavior of three-dimensional magnetohydrodynamic flow with a strong guiding field.

    Science.gov (United States)

    Alexakis, Alexandros

    2011-11-01

    The magnetohydrodynamic (MHD) equations in the presence of a guiding magnetic field are investigated by means of direct numerical simulations. The basis of the investigation consists of nine runs forced at the small scales. The results demonstrate that for a large enough uniform magnetic field the large scale flow behaves as a two-dimensional (2D) (non-MHD) fluid exhibiting an inverse cascade of energy in the direction perpendicular to the magnetic field, while the small scales behave like a three-dimensional (3D) MHD fluid cascading the energy forwards. The amplitude of the inverse cascade is sensitive to the magnetic field amplitude, the domain size, the forcing mechanism, and the forcing scale. All these dependences are demonstrated by the varying parameters of the simulations. Furthermore, in the case that the system is forced anisotropically in the small parallel scales an inverse cascade in the parallel direction is observed that is feeding the 2D modes k(//)=0.

  2. Two-Dimensional River Flow Patterns Observed with a Pair of UHF Radar System

    Directory of Open Access Journals (Sweden)

    Yidong Hou

    2017-01-01

    Full Text Available A pair of ultrahigh-frequency (UHF radars system for measuring the two-dimensional river flow patterns is presented. The system consists of two all-digital UHF radars with exactly the same hardware structure, operating separately at 329–339 MHz and 341–351 MHz. The adoption of direct radio frequency (RF sampling technique and digital pulse compression simplifies the structure of radar system and eliminates the distortion introduced by the analog mixer, which improves the SNR and dynamic range of the radar. The field experiment was conducted at Hanjiang River, Hubei province, China. Over a period of several weeks, the radar-derived surface velocity has been very highly correlated with the measurements of EKZ-I, with a correlation coefficient of 0.958 and a mean square error of 0.084 m/s.

  3. Simulations of Viscous Accretion Flow around Black Holes in Two-Dimensional Cylindrical Geometry

    CERN Document Server

    Lee, Seong-Jae; Kumar, Rajiv; Hyung, Siek; Ryu, Dongsu

    2016-01-01

    We simulate shock-free and shocked viscous accretion flow onto a black hole in a two dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian Total Variation Diminishing (LTVD) and remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. Inviscid shock-free accretion disk solution produced a thick disk structure, while the viscous shock-free solution attained a Bondi-like structure, but in either case, no jet activity nor any QPO-like activity developed. The steady state shocked solution in the inviscid, as well as, in the viscous regime, matched theoretical predictions well. However, increasing viscosity renders the accretion shock unstable. Large amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. Such oscillation of the inner part of disk is interpreted as the source of QPO in hard X-rays observed in micro-qua...

  4. Turbulence models and Reynolds analogy for two-dimensional supersonic compression ramp flow

    Science.gov (United States)

    Wang, Chi R.; Bidek, Maleina C.

    1994-01-01

    Results of the application of turbulence models and the Reynolds analogy to the Navier-Stokes computations of Mach 2.9 two-dimensional compression ramp flows are presented. The Baldwin-Lomax eddy viscosity model and the kappa-epsilon turbulence transport equations for the turbulent momentum flux modeling in the Navier-Stokes equations are studied. The Reynolds analogy for the turbulent heat flux modeling in the energy equation was also studied. The Navier-Stokes equations and the energy equation were numerically solved for the flow properties. The Reynolds shear stress, the skin friction factor, and the surface heat transfer rate were calculated and compared with their measurements. It was concluded that with a hybrid kappa-epsilon turbulence model for turbulence modeling, the present computations predicted the skin friction factors of the 8 deg and 16 deg compression ramp flows and with the turbulent Prandtl number Pr(sub t) = 0.93 and the ratio of the turbulent thermal and momentum transport coefficients mu(sub q)/mu(sub t) = 2/Prt, the present computations also predicted the surface heat transfer rates beneath the boundary layer flow of the 16 compression ramp.

  5. Wake Effects on Drift in Two-Dimensional Inviscid Incompressible Flows

    CERN Document Server

    Melkoumian, Sergei

    2014-01-01

    This investigation analyzes the effect of vortex wakes on the Lagrangian displacement of particles induced by the passage of an obstacle in a two-dimensional incompressible and inviscid fluid. In addition to the trajectories of individual particles, we also study their drift and the corresponding total drift areas in the F\\"oppl and Kirchhoff potential flow models. Our findings, which are obtained numerically and in some regimes are also supported by asymptotic analysis, are compared to the wakeless potential flow which serves as a reference. We show that in the presence of the F\\"oppl vortex wake some of the particles follow more complicated trajectories featuring a second loop. The appearance of an additional stagnation point in the F\\"oppl flow is identified as a source of this effect. It is also demonstrated that, while the total drift area increases with the size of the wake for large vortex strengths, it is actually decreased for small circulation values. On the other hand, the Kirchhoff flow model is s...

  6. The onset of thermal instability of a two-dimensional hydromagnetic stagnation point flow

    Energy Technology Data Exchange (ETDEWEB)

    Amaouche, Mustapha; Bouda, Faical Nait [Laboratoire de physique theorique, Universite de Bejaia, Route de Targua Ouzemour Bejaia (Algeria); Sadat, Hamou [Laboratoire d' Etudes Thermiques, Universite de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers (France)

    2005-10-01

    The aim of the present paper is to examine the effects of a constant magnetic field on the thermal instability of a two-dimensional stagnation point flow. First, it is shown that a basic flow, described by an exact solution of the full Navier-Stokes equations exists under some conditions relating the orientation of the magnetic field in the plane of motion to the obliqueness of free stream. The stability of the basic flow is then investigated in the usual fashion by making use of the normal mode decomposition. The resulting eigenvalue problem is solved numerically by means of a pseudo spectral collocation method based upon Laguerre's functions. The use of this procedure is warranted by the exponential damping of disturbances far from the boundary layer and the appropriate distribution of the roots of Laguerre's polynomials to treat boundary layer problems. It is found through the calculation of neutral stability curves that magnetic field acts to increase the stability of the basic flow. (author)

  7. Numerical simulation of two-dimensional fluid flow with strong shocks

    Energy Technology Data Exchange (ETDEWEB)

    Woodward, P.; Colella, P.

    1984-04-01

    Results of an extensive comparison of numerical methods for simulating hydrodynamics are presented and discussed. This study focuses on the simulation of fluid flows with strong shocks in two dimensions. By ''strong shocks,'' we here refer to shocks in which there is substantial entropy production. For the case of shocks in air, we therefore refer to Mach numbers of three and greater. For flows containing such strong shocks we find that a careful treatment of flow discontinuities is of greatest importance in obtaining accurate numerical results. Three aproaches to treating discontinuities in the flow are discussed-artificial viscosity, blending of low- and high-order-accurate fluxes, and the use of nonlinear solutions to Riemann's problem. The advantages and disadvantages of each approach are discussed and illustrated by computed results for three test problems. In this comparison we have focused our attention entirely upon the performance of schemes for differencing the hydrodynamic equations. We have regarded the nature of the grid upon which such differencing schemes are applied as an independent issue outside the scope of this work. Therefore we have restricted our study to the case of uniform, square computational zones in Cartesian coordinates. For simplicity we have further restricted our attention to two-dimensional difference schemes which are built out of symmetrized products of one-dimensional difference operators.

  8. Transient magneto-peristaltic flow of couple stress biofluids: a magneto-hydro-dynamical study on digestive transport phenomena.

    Science.gov (United States)

    Tripathi, Dharmendra; Anwar Bég, O

    2013-11-01

    Magnetic fields are increasingly being utilized in endoscopy and gastric transport control. In this regard, the present study investigates the influence of a transverse magnetic field in the transient peristaltic rheological transport. An electrically-conducting couple stress non-Newtonian model is employed to accurately simulate physiological fluids in peristaltic flow through a sinusoidally contracting channel of finite length. This model is designed for computing the intra-bolus oesophageal and intestinal pressures during the movement of food bolus in the digestive system under magneto-hydro-dynamic effects. Long wavelength and low Reynolds number approximations have been employed to reduce the governing equations from nonlinear to linear form, this being a valid approach for creeping flows which characterizes physiological dynamics. Analytical approximate solutions for axial velocity, transverse velocity, pressure gradient, local wall shear stress and volumetric flow rate are obtained for the non-dimensional conservation equations subject to appropriate boundary conditions. The effects of couple stress parameter and transverse magnetic field on the velocity profile, pressure distribution, local wall shear stress and the averaged flow rate are discussed with the aid of computational results. The comparative study of non-integral and integral number of waves propagating along the finite length channel is also presented. Magnetic field and non-Newtonian properties are found to strongly influence peristaltic transport.

  9. Dual-RiverSonde measurements of two-dimensional river flow patterns

    Science.gov (United States)

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.; Stumpner, P.; Burau, J.R.

    2008-01-01

    Two-dimensional river flow patterns have been measured using a pair of RiverSondes in two experiments in the Sacramento-San Joaquin River Delta system of central California during April and October 2007. An experiment was conducted at Walnut Grove, California in order to explore the use of dual RiverSondes to measure flow patterns at a location which is important in the study of juvenile fish migration. The data available during the first experiment were limited by low wind, so a second experiment was conducted at Threemile Slough where wind conditions and surface turbulence historically have resulted in abundant data. Both experiments included ADCP near-surface velocity measurements from either manned or unmanned boats. Both experiments showed good comparisons between the RiverSonde and ADCP measurements. The flow conditions at both locations are dominated by tidal effects, with partial flow reversal at Walnut Grove and complete flow reversal at Threemile Slough. Both systems showed complex flow patterns during the flow reversals. Quantitative comparisons between the RiverSondes and an ADCP on a manned boat at Walnut Grove showed mean differences of 4.5 cm/s in the u (eastward) and 7.6 cm/s in the v (northward) components, and RMS differences of 14.7 cm/s in the u component and 21.0 cm/s in the v component. Quantitative comparisons between the RiverSondes and ADCPs on autonomous survey vessels at Threemile Slough showed mean differences of 0.007 cm/s in the u component and 0.5 cm/s in the v component, and RMS differences of 7.9 cm/s in the u component and 13.5 cm/s in the v component after obvious outliers were removed. ?? 2008 IEEE.

  10. The flow of a foam in a two-dimensional porous medium

    Science.gov (United States)

    Géraud, Baudouin; Jones, Siân. A.; Cantat, Isabelle; Dollet, Benjamin; Méheust, Yves

    2016-02-01

    Foams have been used for decades as displacing fluids for enhanced oil recovery and aquifer remediation, and more recently, for remediation of the vadose zone, in which case foams carry chemical amendments. Foams are better injection fluids than aqueous solutions due to their low sensitivity to gravity and because they are less sensitive to permeability heterogeneities, thus allowing a more uniform sweep. The latter aspect results from their peculiar rheology, whose understanding motivates the present study. We investigate foam flow through a two-dimensional porous medium consisting of circular obstacles positioned randomly in a horizontal transparent Hele-Shaw cell. The local foam structure is recorded in situ, which provides a measure of the spatial distribution of bubble velocities and sizes at regular time intervals. The flow exhibits a rich phenomenology including preferential flow paths and local flow nonstationarity (intermittency) despite the imposed permanent global flow rate. Moreover, the medium selects the bubble size distribution through lamella division-triggered bubble fragmentation. Varying the mean bubble size of the injected foam, its water content, and mean velocity, we characterize those processes systematically. In particular, we measure the spatial evolution of the distribution of bubble areas, and infer the efficiency of bubble fragmentation depending on the various control parameters. We furthermore show that the distributions of bubble sizes and velocities are correlated. This study sheds new light on the local rheology of foams in porous media and opens the way toward quantitative characterization of the relationship between medium geometry and foam flow properties. It also suggests that large-scale models of foam flows in the subsurface should account for the correlation between bubble sizes and velocities.

  11. One- and two-dimensional modelling of overland flow in semiarid shrubland, Jornada basin, New Mexico

    Science.gov (United States)

    Howes, David A.; Abrahams, Athol D.; Pitman, E. Bruce

    2006-03-01

    Two distributed parameter models, a one-dimensional (1D) model and a two-dimensional (2D) model, are developed to simulate overland flow in two small semiarid shrubland watersheds in the Jornada basin, southern New Mexico. The models are event-based and represent each watershed by an array of 1-m2 cells, in which the cell size is approximately equal to the average area of the shrubs.Each model uses only six parameters, for which values are obtained from field surveys and rainfall simulation experiments. In the 1D model, flow volumes through a fixed network are computed by a simple finite-difference solution to the 1D kinematic wave equation. In the 2D model, flow directions and volumes are computed by a second-order predictor-corrector finite-difference solution to the 2D kinematic wave equation, in which flow routing is implicit and may vary in response to flow conditions.The models are compared in terms of the runoff hydrograph and the spatial distribution of runoff. The simulation results suggest that both the 1D and the 2D models have much to offer as tools for the large-scale study of overland flow. Because it is based on a fixed flow network, the 1D model is better suited to the study of runoff due to individual rainfall events, whereas the 2D model may, with further development, be used to study both runoff and erosion during multiple rainfall events in which the dynamic nature of the terrain becomes an important consideration.

  12. Mixed convection peristaltic flow of Eyring-Powell nanofluid in a curved channel with compliant walls.

    Science.gov (United States)

    Tanveer, Anum; Hayat, T; Alsaadi, Fuad; Alsaedi, A

    2017-03-01

    The novel features of nanofluids made them potentially significant in heat transfer mechanism occurring in medical and industrial processes like microelectronics, pharmaceutical processes, hybrid engines, thermal management of vehicles, refrigerator, chiller, gas temperature reduction and so forth. These processes bear tendency to enhance thermal conductivity and the convective heat transfer more efficiently than base fluid. This unique aspect made nanofluids the topic of interest in recent time via different fluid flow models. The problem in hand is one such application of nanofluids in peristaltic flow through curved channel. Thus peristalsis of Eyring-Powell nanofluid followed through conservation principles of mass, momentum, energy and concentration has been modeled. The whole system is made coupled via viscous dissipation, mixed convection, thermophoresis and Brownian motion. The complexity of system has been executed through a numerical approach after utilizing small Reynolds number and large wavelength concepts. A striking feature of this study is the activation of velocity and temperature with larger Brownian diffusion, whereas reduction is noticed with advancement in thermophoresis. Moreover the numerically obtained results for compliant walls are compatible with those obtained through other techniques.

  13. Simultaneous effects of Hall and convective conditions on peristaltic flow of couple-stress fluid in an inclined asymmetric channel

    Indian Academy of Sciences (India)

    T Hayat; Maryam Iqbal; Humaira Yasmin; Fuad E Alsaadi; Huijun Gao

    2015-07-01

    A mathematical model is developed to analyse the peristaltic flow of couple-stress fluid in an inclined asymmetric channel with convective conditions. Soret and Dufour and Hall effects are taken into account. Analysis has been carried out in a wave frame of reference. Expressions for velocity, pressure gradient, temperature and concentration are constructed. Pumping and trapping phenomena are examined. Impact of sundry parameters on the velocity, temperature and concentration is discussed.

  14. Flow pattern transition accompanied with sudden growth of flow resistance in two-dimensional curvilinear viscoelastic flows.

    Science.gov (United States)

    Yatou, Hiroki

    2010-09-01

    We numerically find three types of steady solutions of viscoelastic flows and flow pattern transitions between them in a two-dimensional wavy-walled channel for low to moderate Weissenberg (Wi) and Reynolds (Re) numbers using a spectral element method. The solutions are called "convective," "transition," and "elastic" in ascending order of Wi. In the convective region in the Wi-Re parameter space, convective effect and pressure gradient balance on average. As Wi increases, elastic effect becomes comparable, and the first transition sets in. Through the transition, a separation vortex disappears, and a jet flow induced close to the wall by the viscoelasticity moves into the bulk; the viscous drag significantly drops, and the elastic wall friction rises sharply. This transition is caused by an elastic force in the streamwise direction due to the competition of the convective and elastic effects. In the transition region, the convective and elastic effects balance. When the elastic effect becomes greater than the convective effect, the second transition occurs but it is relatively moderate. The second transition seems to be governed by the so-called Weissenberg effect. These transitions are not sensitive to driving forces. By a scaling analysis, it is shown that the stress component is proportional to the Reynolds number on the boundary of the first transition in the Wi-Re space. This scaling coincides well with the numerical result.

  15. Effect of a levee setback on aquatic resources using two-dimensional flow and bioenergetics models

    Science.gov (United States)

    Black, Robert W.; Czuba, Christiana R.; Magirl, Christopher S.; McCarthy, Sarah; Berge, Hans; Comanor, Kyle

    2016-04-05

    Watershed restoration is the focus of many resource managers and can include a multitude of restoration actions each with specific restoration objectives. For the White River flowing through the cities of Pacific and Sumner, Washington, a levee setback has been proposed to reconnect the river with its historical floodplain to help reduce flood risks, as well as provide increased habitat for federally listed species of salmonids. The study presented here documents the use of a modeling framework that integrates two-dimensional hydraulic modeling with process-based bioenergetics modeling for predicting how changes in flow from reconnecting the river with its floodplain affects invertebrate drift density and the net rate of energy intake of juvenile salmonids. Modeling results were calculated for flows of 25.9 and 49.3 cubic meters per second during the spring, summer, and fall. Predicted hypothetical future mean velocities and depths were significantly lower and more variable when compared to current conditions. The abundance of low energetic cost and positive growth locations for salmonids were predicted to increase significantly in the study reach following floodplain reconnection, particularly during the summer. This modeling framework presents a viable approach for evaluating the potential fisheries benefits of reconnecting a river to its historical floodplain that integrates our understanding of hydraulic, geomorphology, and organismal biology.

  16. Unsteady Free-surface Waves Due to a Submerged Body in Two-dimensional Oseen Flows

    Institute of Scientific and Technical Information of China (English)

    LUDong-qiang; AllenT.CHWANG

    2004-01-01

    The two-dimensional unsteady free-surface waves due to a submerged body moving in an incompressible viscous fluid of infinite depth is considered.The disturbed flow is governed by the unsteadyOseen equations with the kinematic and dynamic boundary conditions linearized for the free-surface waves.Accordingly, the body is mathematically simulated by an Oseenlet with a periodically oscillating strength.By means of Fourier transforms,the exact solution for the free-surface waves is expressed by an integral with a complex dispersion function, which explicitly shows that the wave dynamics is characterized by a Reynolds number and a Strouhal number.By applying Lighthill's theorem, asymptotic representations are derived for the far-field waves with a sub-critical and a super-critical Strouhal number. It is found that the generated waves due to the oscillating Oseenlet consist of the steady-state and transient responses. For the viscous flow with a sub-critical Strouhal number, there exist four waves: three propagate downstream while one propagates upstream.However, for the viscous flow with a super-critical Strouhal number, there exist two waves only,which propagate downstream.

  17. Two-dimensional relativistic space charge limited current flow in the drift space

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y. L.; Chen, S. H., E-mail: chensh@ncu.edu.tw [Department of Physics, National Central University, Jhongli 32001, Taiwan (China); Koh, W. S. [A-STAR Institute of High Performance Computing, Singapore 138632 (Singapore); Ang, L. K. [Engineering Product Development, Singapore University of Technology and Design, Singapore 138682 (Singapore)

    2014-04-15

    Relativistic two-dimensional (2D) electrostatic (ES) formulations have been derived for studying the steady-state space charge limited (SCL) current flow of a finite width W in a drift space with a gap distance D. The theoretical analyses show that the 2D SCL current density in terms of the 1D SCL current density monotonically increases with D/W, and the theory recovers the 1D classical Child-Langmuir law in the drift space under the approximation of uniform charge density in the transverse direction. A 2D static model has also been constructed to study the dynamical behaviors of the current flow with current density exceeding the SCL current density, and the static theory for evaluating the transmitted current fraction and minimum potential position have been verified by using 2D ES particle-in-cell simulation. The results show the 2D SCL current density is mainly determined by the geometrical effects, but the dynamical behaviors of the current flow are mainly determined by the relativistic effect at the current density exceeding the SCL current density.

  18. Visualization of three-dimensional incompressible flows by quasi-two-dimensional divergence-free projections in arbitrary flow regions

    Science.gov (United States)

    Gelfgat, Alexander Yu.

    2016-08-01

    A visualization of three-dimensional incompressible flows by divergence-free quasi-two-dimensional projections of the velocity field onto three coordinate planes is revisited. An alternative and more general way to compute the projections is proposed. The approach is based on the Chorin projection combined with a SIMPLE-like iteration. Compared to the previous methodology based on divergence-free Galerkin-Chebyshev bases, this technique, formulated in general curvilinear coordinates, is applicable to any flow region and allows for faster computations. To illustrate this visualization method, examples in Cartesian and spherical coordinates, as well as post-processing of experimental 3D-PTV data, are presented.

  19. Two-dimensional Rarefaction Waves in the High-speed Two-phase Flow

    Science.gov (United States)

    Nakagawa, Masafumi; Harada, Atsushi

    Two-phase flow nozzles are used in the total flow system for geothermal power plants and in the ejector of the refrigerant cycle, etc. One of the most important functions of a two-phase flow nozzle is to convert the thermal energy to the kinetic energy of the two-phase flow. The kinetic energy of the two-phase flow exhausted from a nozzle is available for all applications of this type. There exist the shock waves or rarefaction waves at the outlet of a supersonic nozzle in the case of non-best fitting expansion conditions when the operation conditions of the nozzle are widely chosen. The purpose of the present study is to elucidate theoretically the character of the rarefaction waves at the outlet of the supersonic two-phase flow nozzle. Two-dimensional basic equations for the compressible two-phase flow are introduced considering the inter-phase momentum transfer. Sound velocities are obtained from these equations by using monochromatic wave approximation. Those depend on the relaxation time that determines the momentum transfer. The two-phase flow with large relaxation times has a frozen sound velocity, and with small one has an equilibrium sound velocity. Rarefaction waves which occurred behind the two-phase flow nozzle are calculated by the CIP method. Although the frozen Mach number, below one, controls these basic equations, the rarefaction waves appeared for small relaxation time. The Mach line behind which the expansion starts depends on the inlet velocity and the relaxation time. Those relationships are shown in this paper. The pressure expansion curves are only a function of the revolution angle around the corner of the nozzle outlet for the relaxation time less than 0.1. For the larger relaxation time, the pressure decays because of internal friction caused by inter phase momentum transfer, and the expansion curves are a function of not only the angle but also the flow direction. The calculated expansion curves are compared with the experimental ones

  20. Two dimensional analysis of low pressure flows in the annulus region between two concentric cylinders.

    Science.gov (United States)

    Al-Kouz, Wael; Alshare, Aiman; Alkhalidi, Ammar; Kiwan, Suhil

    2016-01-01

    A numerical simulation of the steady two-dimensional laminar natural convection heat transfer for the gaseous low-pressure flows in the annulus region between two concentric horizontal cylinders is carried out. This type of flow occurs in "evacuated" solar collectors and in the receivers of the solar parabolic trough collectors. A finite volume code is used to solve the coupled set of governing equations. Boussinesq approximation is utilized to model the buoyancy effect. A correlation for the thermal conductivity ratio (k r = k eff/k) in terms of Knudsen number and the modified Rayleigh number is proposed for Prandtl number (Pr = 0.701). It is found that as Knudsen number increases then the thermal conductivity ratio decreases for a given Rayleigh number. Also, it is shown that the thermal conductivity ratio k r increases as Rayleigh number increases. It appears that there is no consistent trend for varying the dimensionless gap spacing between the inner and the outer cylinder ([Formula: see text]) on the thermal conductivity ratio (k r) for the considered spacing range.

  1. Two dimensional heat transfer problem in flow boiling in a rectangular minichannel

    Directory of Open Access Journals (Sweden)

    Hożejowska Sylwia

    2015-01-01

    Full Text Available The paper presents mathematical modelling of flow boiling heat transfer in a rectangular minichannel asymmetrically heated by a thin and one-sided enhanced foil. Both surfaces are available for observations due to the openings covered with glass sheets. Thus, changes in the colour of the plain foil surface can be registered and then processed. Plain side of the heating foil is covered with a base coat and liquid crystal paint. Observation of the opposite, enhanced surface of the minichannel allows for identification of the gas-liquid two-phase flow patterns and vapour quality. A two-dimensional mathematical model of heat transfer in three subsequent layers (sheet glass, heating foil, liquid was proposed. Heat transfer in all these layers was described with the respective equations: Laplace equation, Poisson equation and energy equation, subject to boundary conditions corresponding to the observed physical process. The solutions (temperature distributions in all three layers were obtained by Trefftz method. Additionally, the temperature of the boiling liquid was obtained by homotopy perturbation method (HPM combined with Trefftz method. The heat transfer coefficient, derived from Robin boundary condition, was estimated in both approaches. In comparison, the results by both methods show very good agreement especially when restricted to the thermal sublayer.

  2. Effect of rotation on peristaltic flow of a micropolar fluid through a porous medium with an external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Alla, A.M., E-mail: mohmrr@yahoo.com [Maths Department, Faculty of Science, Taif University (Saudi Arabia); Abo-Dahab, S.M., E-mail: sdahb@yahoo.com [Maths Department, Faculty of Science, Taif University (Saudi Arabia); Maths Department, Faculty of Science, SVU, Qena 83523 (Egypt); Al-Simery, R.D. [Maths Department, Faculty of Science, Taif University (Saudi Arabia)

    2013-12-15

    In this paper, the effects of both rotation and magnetic field of a micropolar fluid through a porous medium induced by sinusoidal peristaltic waves traveling down the channel walls are studied analytically and computed numerically. Closed-form solutions under the consideration of long wavelength and low-Reynolds number is presented. The analytical expressions for axial velocity, pressure rise per wavelength, mechanical efficiency, spin velocity, stream function and pressure gradient are obtained in the physical domain. The effect of the rotation, density, Hartmann number, permeability, coupling number, micropolar parameter and the non-dimensional wave amplitude in the wave frame is analyzed theoretically and computed numerically. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of rotation and magnetic field. The results indicate that the effect of rotation, density, Hartmann number, permeability, coupling number, micropolar parameter and the non-dimensional wave amplitude are very pronounced in the phenomena. - Highlights: • The effects of induced magnetic field and rotation in peristaltic motion of a two dimensional of a micropolar fluid through a porous medium • The exact and closed form solutions are presented • Different wave shapes are considered to observe the behavior of the axial velocity, pressure rise, mechanical efficiency, spin velocity, stream function and pressure gradient.

  3. The Two-Dimensional Supersonic Flow and Mixing with a Perpendicular Injection in a Scramjet Combustor

    Institute of Scientific and Technical Information of China (English)

    Mohammad Ali; S.Ahmed; A.K.M.Sadrul Islam

    2003-01-01

    A numerical investigation has been performed on supersonic mixing of hydrogen with air in a Scramjet(Supersonic Combustion Ramjet) combustor and its flame holding capability by solving Two-Dimensional full Navier-Stokes equations. The main flow is air entering through a finite width of inlet and gaseous hydrogen is injected perpendicularly from the side wall. An explicit Harten-Yee Non-MUSCL Modified-flux-type TVD scheme has been used to solve the system of equations, and a zero-equation algebraic turbulence model to calculate the eddy viscosity coefficient. In this study the enhancement of mixing and good flame holding capability of a supersonic combustor have been investigated by varying the distance of injector position from left boundary keeping constant the backward-facing step height and other calculation parameters. The results show that the configuration for small distance of injector position has high mixing efficiency but the upstream recirculation can not evolved properly which is an important factor for flame holding capability. On the other hand, the configuration for very long distance has lower mixing efficiency due to lower gradient of hydrogen mass concentration on the top of injector caused by the expansion of side jet in both upstream and downstream of injector. For moderate distance of injector position, large and elongated upstream recirculation can evolve which might be activated as a good flame holder.

  4. Simulations of Viscous Accretion Flow around Black Holes in a Two-dimensional Cylindrical Geometry

    Science.gov (United States)

    Lee, Seong-Jae; Chattopadhyay, Indranil; Kumar, Rajiv; Hyung, Siek; Ryu, Dongsu

    2016-11-01

    We simulate shock-free and shocked viscous accretion flows onto a black hole in a two-dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian total variation diminishing plus remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. The inviscid shock-free accretion disk solution produced a thick disk structure, while the viscous shock-free solution attained a Bondi-like structure, but in either case, no jet activity nor any quasi-periodic oscillation (QPO)-like activity developed. The steady-state shocked solution in the inviscid as well as in the viscous regime matched theoretical predictions well. However, increasing viscosity renders the accretion shock unstable. Large-amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. This oscillation of the inner part of the disk is interpreted as the source of QPO in hard X-rays observed in micro-quasars. Strong shock oscillation induces strong episodic jet emission. The jets also show the existence of shocks, which are produced as one shell hits the preceding one. The periodicities of the jets and shock oscillation are similar; the jets for the higher viscosity parameter appear to be stronger and faster.

  5. PHYSALIS: a new method for particle flow simulation. Part III: convergence analysis of two-dimensional flows

    Science.gov (United States)

    Huang, Huaxiong; Takagi, Shu

    2003-08-01

    In this paper, we study the convergence property of PHYSALIS when it is applied to incompressible particle flows in two-dimensional space. PHYSALIS is a recently proposed iterative method which computes the solution without imposing the boundary conditions on the particle surfaces directly. Instead, a consistency equation based on the local (near particle) representation of the solution is used as the boundary conditions. One of the important issues needs to be addressed is the convergence properties of the iterative procedure. In this paper, we present the convergence analysis using Laplace and biharmonic equations as two model problems. It is shown that convergence of the method can be achieved but the rate of convergence depends on the relative locations of the cages. The results are directly related to potential and Stokes flows. However, they are also relevant to Navier-Stokes flows, heat conduction in composite media, and other problems.

  6. Convective heat and mass transfer on MHD peristaltic flow of Williamson fluid with the effect of inclined magnetic field

    Science.gov (United States)

    Veera Krishna, M.; Swarnalathamma, B. V.

    2016-05-01

    In this paper, we discussed the peristaltic MHD flow of an incompressible and electrically conducting Williamson fluid in a symmetric planar channel with heat and mass transfer under the effect of inclined magnetic field. Viscous dissipation and Joule heating are also taken into consideration. Mathematical model is presented by using the long wavelength and low Reynolds number approximations. The differential equations governing the flow are highly nonlinear and thus perturbation solution for small Weissenberg number (We Effects of the heat and mass transfer on the longitudinal velocity, temperature and concentration are studied in detail. Main observations are presented in the concluding section. The streamlines pattern is also given due attention.

  7. Self Organized Criticality in a two dimensional Cellular Automaton model of a magnetic flux tube with background flow

    CERN Document Server

    Danila, Bogdan; Mocanu, Gabriela

    2015-01-01

    We investigate the transition to Self Organized Criticality in a two-dimensional model of a flux tube with a background flow. The magnetic induction equation, represented by a partial differential equation with a stochastic source term, is discretized and implemented on a two dimensional cellular automaton. The energy released by the automaton during one relaxation event is the magnetic energy. As a result of the simulations we obtain the time evolution of the energy release, of the system control parameter, of the event lifetime distribution and of the event size distribution, respectively, and we establish that a Self Organized Critical state is indeed reached by the system. Moreover, energetic initial impulses in the magnetohydrodynamic flow can lead to one dimensional signatures in the magnetic two dimensional system, once the Self Organized Critical regime is established. The applications of the model for the study of Gamma Ray Bursts is briefly considered, and it is shown that some astrophysical paramet...

  8. Adjustment of roughness sublayer in turbulent flows over two-dimensional idealised roughness elements

    Science.gov (United States)

    HO, Yat-Kiu; LIU, Chun-Ho

    2015-04-01

    The atmospheric boundary layer (ABL) immediately above the urban canopy is the roughness sublayer (RSL). In this layer, flows and turbulence are strongly affected by the roughness elements beneath, e.g. building obstacles. The wind flows over urban areas could be represented by conventional logarithmic law of the wall (log-law) in the neutrally stratified ABL. However, in the RSL region, the vertical wind profile deviates from that predicted from log-law and the effect could be extended from ground level up to several canopy heights. As a result, the Monin-Obukhov similarity theory (MOST) fails and an additional length scale is required to describe the flows. The key aim of this study is to introduce a simple wind profile model which accounts for the effect of the RSL in neutral stratification using wind tunnel experiments. Profile measurements of wind speeds and turbulence quantities over various two-dimensional (2D) idealised roughness elements are carried out in an open-circuit wind tunnel with test section of size 560 mm (width) × 560 mm (height) × 6 m (length). The separation between the roughness elements is varied systematically so that ten different types of surface forms are adopted. The velocity measurements are obtained by hot-wire anemometry using X-probe design (for UW- measurements) with a constant temperature anemometer. For each configuration, eight vertical profiles are collected over the canopy, including solid boundaries and cavities of the roughness elements. Firstly, we compute the measurement results using conventional MOST to determine different roughness parameters. Afterwards, we derive the RSL height from the Reynolds stress profiles. Since the profiles taken from different locations of the canopy are eventually converged with increasing height, we use this 'congregated height' to define the RSL height. Next, we introduce an alternative function, i.e. power-law function, instead of MOST, to describe the velocity profile in attempt to

  9. The Second Las Cruces Trench Experiment: Experimental Results and Two-Dimensional Flow Predictions

    Science.gov (United States)

    Hills, R. G.; Wierenga, P. J.; Hudson, D. B.; Kirkland, M. R.

    1991-10-01

    As part of a comprehensive field study designed to provide data to test stochastic and deterministic models of water flow and contaminant transport in the vadose zone, several trench experiments were performed in the semiarid region of southern New Mexico. The first trench experiment is discussed by Wierenga et al. (this issue). During the second trench experiment, a 1.2 m wide by 12 m long area on the north side of and parallel to a 26.4 m long by 4.8 m wide by 6m deep trench was irrigated with water containing tracers using a carefully controlled drip irrigation system. The irrigated area was heavily instrumented with tensiometers and neutron probe access tubes to monitor water movement, and with suction samplers to monitor solute transport. Water containing tritium and bromide was. applied during the first 11.5 days of the study. Thereafter, water was applied without tracers for an additional 64 days. Both water movement and tracer movement were monitored in the subsoil during infiltration and redistribution. The experimental results indicate that water and bromide moved fairly uniformly during infiltration and the bromide moved ahead of the tritium due to anion exclusion during redistribution. Comparisons between measurements and predictions made with a two-dimensional model show qualitative agreement for two of the three water content measurement planes. Model predictions of tritium and bromide transport were not as satisfactory. Measurements of both tritium and bromide show localized areas of high relative concentrations and a large downward motion of bromide relative to tritium during redistribution. While the simple deterministic model does show larger downward motions for bromide than for tritium during redistribution, it does not predict the high concentrations of solute observed during infiltration, nor can it predict the heterogeneous behavior observed for tritium during infiltration and for bromide during redistribution.

  10. Bouncing, rolling, energy flows, and cluster formation in a two-dimensional vibrated granular gas

    Science.gov (United States)

    Pérez-Ángel, Gabriel; Nahmad-Molinari, Yuri

    2011-10-01

    We study the formation of crystalline clusters for a two-dimensional (2D) sinusoidally vibrated granular gas, with maximum vertical acceleration smaller than gravity, using fully 3D simulations. It is found that this phenomenon arises from the spontaneous segregation of the granulate into two dynamical modes: one of grains that bounce in synchrony with the motion of the sustaining plate (“bouncers”) and another of grains that cease to bounce and simply rolls on the plate, without ever loosing contact with it (“rollers”). These two dynamical categories are quite robust with respect to perturbations. The populations for bouncers and rollers depend on the preparation of the granulate and can be made to take arbitrary values in all the range of accelerations where both dynamical modes are present. It is found that the dynamical mode with the largest population coalesces in clusters under the influence of the other mode, whose grains act as a higher pressure gas that compresses the clusters. In this way it is possible to produce clusters of rollers or clusters of bouncers. A gas made of grains from only one dynamical class shows only weak density fluctuations. When the occupation fractions for both modes are similar, one observes segregation and clusters of both types. The clustering of the gas is monitored using both the average coordination number and the local hexatic order parameter ψ6. Energy flows in the plane are monitored, and it is shown that roller-bouncer collisions increase horizontal kinetic energy, while all other types of collisions reduce this energy. We find that friction with the substrate is the main sink of horizontal energy for these granular gases.

  11. Fast chemical reaction in two-dimensional Navier-Stokes flow: initial regime.

    Science.gov (United States)

    Ait-Chaalal, Farid; Bourqui, Michel S; Bartello, Peter

    2012-04-01

    This paper studies an infinitely fast bimolecular chemical reaction in a two-dimensional biperiodic Navier-Stokes flow. The reactants in stoichiometric quantities are initially segregated by infinite gradients. The focus is placed on the initial stage of the reaction characterized by a well-defined one-dimensional material contact line between the reactants. Particular attention is given to the effect of the diffusion κ of the reactants. This study is an idealized framework for isentropic mixing in the lower stratosphere and is motivated by the need to better understand the effect of resolution on stratospheric chemistry in climate-chemistry models. Adopting a Lagrangian straining theory approach, we relate theoretically the ensemble mean of the length of the contact line, of the gradients along it, and of the modulus of the time derivative of the space-average reactant concentrations (here called the chemical speed) to the joint probability density function of the finite-time Lyapunov exponent λ with two times τ and τ[over ̃]. The time 1/λ measures the stretching time scale of a Lagrangian parcel on a chaotic orbit up to a finite time t, while τ measures it in the recent past before t, and τ[over ̃] in the early part of the trajectory. We show that the chemical speed scales like κ(1/2) and that its time evolution is determined by rare large events in the finite-time Lyapunov exponent distribution. The case of smooth initial gradients is also discussed. The theoretical results are tested with an ensemble of direct numerical simulations (DNSs) using a pseudospectral model.

  12. The TUBES algorithm for the exact representation of advective transport in a two-dimensional discretized flow field

    Energy Technology Data Exchange (ETDEWEB)

    Costa-Cabral, M.C. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Hydrophysik

    1999-07-01

    Current Lagrangian models for simulating advective transport of trace species in a discretized two-dimensional flow field use simplified descriptions of tracer sources, receptors and flow paths. When 'forward trajectories' are used, a diffuse source spread over a two-dimensional grid cell is treated as a single point source located at the cell's center, and its flow is projected in the downflow direction by a line. When 'backward trajectories' are used, each cell is treated as a point receptor and flow is projected back in time in the upflow direction by a line. In both cases, two-dimensional sources or receptors are treated as zero dimensional, and two-dimensional flow tubes are replaced by one-dimensional lines. While these simplifications may be acceptable in some cases, they can generate large errors when the flow field contains regions of considerable divergence of flow directions, or when fine scales are used. A new algorithm is introduced, called TUBES, which provides an exact solution to advective transport in a discretized two-dimensional flow field. TUBES uses two-dimensional flow tubes whose width expands and contracts over directionally divergent and convergent regions of the flow field, respectively. TUBES has applications in a wide variety of the earth sciences, including atmospheric science, oceanography, and surface and groundwater hydrology. (orig.) [German] Gegenwaertige Lagrange-Modelle zur Simulation advektiver Transporte von Tracern in einem diskretisierten zweidimensionalen Stroemungsfeld verwenden vereinfachte Beschreibungen der Quellen, Rezeptoren und Transportwege. Bei der Verwendung vorwaerts gerichteter Trajektorien ('forward trajectories') werden diffusive Quellen, die ueber eine zweidimensionale Gitterzelle verteilt sind, als Punktquelle behandelt, und der Transport mit der Stroemung erfolgt entlang einer Linie. Bei der Verwendung rueckwaerts gerichteter Trajektorien ('backward trajectories

  13. Viscous/potential flow about multi-element two-dimensional and infinite-span swept wings - Theory and experiment

    Science.gov (United States)

    Olson, L. E.; Dvorak, F. A.

    1976-01-01

    The viscous subsonic flow past two-dimensional and infinite-span swept multi-component airfoils is studied theoretically and experimentally. The computerized analysis is based on iteratively coupled boundary-layer and potential-flow analysis. The method, which is restricted to flows with only slight separation, gives surface pressure distribution, chordwise and spanwise boundary-layer characteristics, lift, drag, and pitching moment for airfoil configurations with up to four elements. Merging confluent boundary layers are treated. Theoretical predictions are compared with an exact theoretical potential flow solution and with experimental measures made in the Ames 40- by 80-Foot Wind Tunnel for both two-dimensional and infinite-span swept wing configurations. Section lift characteristics are accurately predicted for zero and moderate sweep angles where flow separation effects are negligible.

  14. Viscous/potential flow about multi-element two-dimensional and infinite-span swept wings: Theory and experiment

    Science.gov (United States)

    Olson, L. E.; Dvorak, F. A.

    1975-01-01

    The viscous subsonic flow past two-dimensional and infinite-span swept multi-component airfoils is studied theoretically and experimentally. The computerized analysis is based on iteratively coupled boundary layer and potential flow analysis. The method, which is restricted to flows with only slight separation, gives surface pressure distribution, chordwise and spanwise boundary layer characteristics, lift, drag, and pitching moment for airfoil configurations with up to four elements. Merging confluent boundary layers are treated. Theoretical predictions are compared with an exact theoretical potential flow solution and with experimental measures made in the Ames 40- by 80-Foot Wind Tunnel for both two-dimensional and infinite-span swept wing configurations. Section lift characteristics are accurately predicted for zero and moderate sweep angles where flow separation effects are negligible.

  15. A Numerical Investigation of Peristaltic Waves in Circular Tubes

    Science.gov (United States)

    Xiao, Q.; Damodaran, M.

    Peristaltic pumping is a process of fluid transport arising from the progressive waves, which travel along the walls of a flexible channel. It is a primary physiological transport mechanism that is inherent in many tubular organs of the human body such as the ureter, the gastro-intestinal tract, the urethra, and so on. Many studies exist in literature with the aim of understanding the characteristics of peristaltic flow under the assumption of low Reynolds number and infinitely long wavelength in a two-dimensional channel. However, peristaltic pumping is also the mechanism used in other industrial applications such as the blood pump for which the Reynolds number has a moderately high value. As studies concerning moderate to high Reynolds number flow in the circular tube are rare in literature, in the present study, the peristaltic flow of an incompressible fluid is numerically simulated using the finite volume method for solving the incompressible Navier-Stokes equations in primitive variable formulation by means of an infinite train of sinusoidal waves traveling along the wall of an axi-symmetric tube. The computational model presented in this work covers a wider range of Reynolds number (0.01-100), wave amplitude (0-0.8), and wavelength (0.01-0.4) than the those attempted in previous studies reported in literature and some new results pertaining to the distribution of velocity, pressure, wall shear stress for different peristaltic flow conditions characterizing flow at moderately higher Reynolds number have been obtained. The effect of the wave amplitude, wavelength, and Reynolds number on the "flow trapping" mechanism induced by peristalsis has also been investigated here for higher ranges of values of the parameters characterizing peristalsis.

  16. Copper oxide nanoparticles analysis with water as base fluid for peristaltic flow in permeable tube with heat transfer.

    Science.gov (United States)

    Akbar, Noreen Sher; Raza, M; Ellahi, R

    2016-07-01

    The peristaltic flow of a copper oxide water fluid investigates the effects of heat generation and magnetic field in permeable tube is studied. The mathematical formulation is presented, the resulting equations are solved exactly. The obtained expressions for pressure gradient, pressure rise, temperature, velocity profile are described through graphs for various pertinent parameters. It is found that pressure gradient is reduce with enhancement of particle concentration and velocity profile is upturn, beside it is observed that temperature increases as more volume fraction of copper oxide. The streamlines are drawn for some physical quantities to discuss the trapping phenomenon.

  17. Combined effect of couple stresses and heat and mass transfer on peristaltic flow with slip conditions in a tube.

    Science.gov (United States)

    Sobh, Ayman M

    2013-10-01

    In this article, the influence of heat and mass transfer on peristaltic transport of a couple stress fluid in a uniform tube with slip conditions on the wall is studied. The problem can model the blood flow in living creatures. Under long wavelength approximation and zero Reynolds number, exact solutions for the axial velocity component, pressure gradient, and both temperature and concentration fields are derived. The pressure rise is computed numerically and explained graphically. Moreover, effects of various physical parameters of the problem on temperature distribution, concentration field, and trapping are studied and discussed graphically.

  18. Wind Tunnel Study on Flows over Various Two-dimensional Idealized Urban-liked Surfaces

    Science.gov (United States)

    Ho, Yat-Kiu; Liu, Chun-Ho

    2013-04-01

    Extensive human activities (e.g. increased traffic emissions) emit a wide range of pollutants resulting in poor urban area air quality. Unlike open, flat and homogenous rural terrain, urban surface is complicated by the presence of buildings, obstacles and narrow streets. The irregular urban surfaces thus form a random roughness that further modifies the near-surface flows and pollutant dispersion. In this study, a physical modelling approach is employed to commence a series of wind tunnel experiments to study the urban-area air pollution problems. The flow characteristics over different hypothetical urban roughness surfaces were studied in a wind tunnel in isothermal conditions. Preliminary experiments were conducted based on six types of idealized two-dimensional (2D) street canyon models with various building-height-to-street-width (aspect) ratios (ARs) 1, 1/2, 1/4, 1/8, 1/10 and 1/12. The main instrumentation is an in-house 90o X-hotwire anemometry. In each set of configuration, a sampling street canyon was selected near the end of the streamwise domain. Its roof level, i.e. the transverse between the mid points of the upstream and downstream buildings, was divided into eight segments. The measurements were then recorded on the mid-plane of the spannwise domain along the vertical profile (from building roof level to the ceiling of wind tunnel) of the eight segments. All the data acquisition processes were handled by the NI data acquisition modules, NI 9239 and CompactDAQ-9188 hardware. Velocity calculation was carried out in the post-processing stage on a digital computer. The two-component flow velocities and velocity fluctuations were calculated at each sampling points, therefore, for each model, a streamwise average of eight vertical profiles of mean velocity and velocity fluctuations was presented. A plot of air-exchange rate (ACH) against ARs was also presented in order to examine the ventilation performance of different tested models. Preliminary results

  19. Evaporation, Heat Transfer, and Velocity Distribution in Two-Dimensional and Rotationally Symmetrical Laminar Boundary-Layer Flow

    Science.gov (United States)

    Froessling, Nils

    1958-01-01

    The fundamental boundary layer equations for the flow, temperature and concentration fields are presented. Two dimensional symmetrical and unsymmetrical and rotationally symmetrical steady boundary layer flows are treated as well as the transfer boundary layer. Approximation methods for the calculation of the transfer layer are discussed and a brief survey of an investigation into the validity of the law that the Nusselt number is proportional to the cube root of the Prandtl number is presented.

  20. 水坝绕流的数值研究%Numerical Study of Two-Dimensional Viscous Flow over Dams

    Institute of Scientific and Technical Information of China (English)

    王利兵; 刘宇陆; 涂敏杰

    2003-01-01

    In this paper, the characteristics of two-dimensional viscous flow over two dams were numerically investigated. The results show that the behavior of the vortices is closely related to the space between two dams, water depth, Fr number and Reynolds number. In addition, the flow properties behind each dam are different, and the changes over two dams are more complex than over one dam. Finally, the relevant turbulent characteristics were analyzed.

  1. Exact two-dimensionalization of low-magnetic-Reynolds-number flows subject to a strong magnetic field

    CERN Document Server

    Gallet, Basile

    2015-01-01

    We investigate the behavior of flows, including turbulent flows, driven by a horizontal body-force and subject to a vertical magnetic field, with the following question in mind: for very strong applied magnetic field, is the flow mostly two-dimensional, with remaining weak three-dimensional fluctuations, or does it become exactly 2D, with no dependence along the vertical? We first focus on the quasi-static approximation, i.e. the asymptotic limit of vanishing magnetic Reynolds number Rm << 1: we prove that the flow becomes exactly 2D asymptotically in time, regardless of the initial condition and provided the interaction parameter N is larger than a threshold value. We call this property "absolute two-dimensionalization": the attractor of the system is necessarily a (possibly turbulent) 2D flow. We then consider the full-magnetohydrodynamic equations and we prove that, for low enough Rm and large enough N, the flow becomes exactly two-dimensional in the long-time limit provided the initial vertically-de...

  2. Simultaneous effects of slip and MHD on peristaltic blood flow of Jeffrey fluid model through a porous medium

    Directory of Open Access Journals (Sweden)

    M.M. Bhatti

    2016-06-01

    Full Text Available In this article, the simultaneous effects of slip and Magnetohydrodynamics (MHD on peristaltic blood flow of Jeffrey fluid model have been investigated in a non-uniform porous channel. The governing equation of blood flow for Jeffrey fluid model is solved with the help of long wavelength and creeping flow regime. The solution of the resulting differential equation is solved analytically and a closed form solution is presented. The impact of all the physical parameters is plotted for velocity profile and pressure rise. Nowadays, Magnetohydrodynamics is applicable in various magnetic drug targeting for cancer diseases and also very helpful to control the flow. The present analysis is also described for Newtonian fluid (λ1→0 as a special case of our study. It is observed that magnitude of the velocity is opposite near the walls due to slip effects whereas similar behavior has been observed for magnetic field.

  3. Second-order phase transition in two-dimensional cellular automaton model of traffic flow containing road sections

    Science.gov (United States)

    Shi, Xiao-Qiu; Wu, Yi-Qi; Li, Hong; Zhong, Rui

    2007-11-01

    Two-dimensional cellular automaton model has been broadly researched for traffic flow, as it reveals the main characteristics of the traffic networks in cities. Based on the BML models, a first-order phase transition occurs between the low-density moving phase in which all cars move at maximal speed and the high-density jammed phase in which all cars are stopped. However, it is not a physical result of a realistic system. We propose a new traffic rule in a two-dimensional traffic flow model containing road sections, which reflects that a car cannot enter into a road crossing if the road section in front of the crossing is occupied by another car. The simulation results reveal a second-order phase transition that separates the free flow phase from the jammed phase. In this way the system will not be entirely jammed (“don’t block the box” as in New York City).

  4. Flow of a Burger’s Fluid in a Channel Induced by Peristaltic Compliant Walls

    Directory of Open Access Journals (Sweden)

    I. Ahmad

    2014-01-01

    Full Text Available A theoretical analysis is presented for the peristaltic motion of a magneto-hydrodynamic (MHD non-Newtonian fluid in channel with complaint walls. The fluid obeys viscoelastic non-Newtonian model with Burger’s constitutive equation. The relevant equations are first developed and then solved using perturbation technique. Expressions of stream function and velocity components are constructed under the assumption that δ (characteristic ratio of transversal and axial scales of peristaltic motion is small. The results indicate the strong effects of Burger’s fluid parameter, Hartman number, Reynolds number, and complaint wall parameters on the velocity field and stream function. The obtained solutions are shown graphically for the different values of involved parameters.

  5. Adaptivity techniques for the computation of two-dimensional viscous flows using structured meshes

    Science.gov (United States)

    Szmelter, J.; Evans, A.; Weatherill, N. P.

    In this paper three different adaptivity techniques have been investigated on the base of structured meshes. All the techniques indicate the significance of using adaptivity for improving computational results. In particular, the technique of combining point enrichment and node movement strategies offers the best compromise. Although, the work presented here used two-dimensional structured meshes, the techniques can be readily applied to hybrid and unstructured meshes. Also, preliminary three-dimensional numerical results have been already obtained by coauthors.

  6. Hydromagnetic Blood Flow of Sisko Fluid in a Non-uniform Channel Induced by Peristaltic Wave

    Science.gov (United States)

    Zeeshan, A.; Bhatti, M. M.; Akbar, N. S.; Sajjad, Y.

    2017-07-01

    In this paper, a smooth repetitive oscillating wave traveling down the elastic walls of a non-uniform two-dimensional channels is considered. It is assumed that the fluid is electrically conducting and a uniform magnetic field is perpendicular to flow. The Sisko fluid is grease thick non-Newtonian fluid can be considered equivalent to blood. Taking long wavelength and low Reynolds number, the equations are reduced. The analytical solution of the emerging non-linear differential equation is obtained by employing Homotopy Perturbation Method (HPM). The outcomes for dimensionless flow rate and dimensionless pressure rise have been computed numerically with respect to sundry concerning parameters amplitude ratio ϕ, Hartmann number M, and Sisko fluid parameter b 1. The behaviors for pressure rise and average friction have been discussed in details and displayed graphically. Numerical and graphical comparison of Newtonian and non-Newtonian has also been evaluated for velocity and pressure rise. It is observed that the magnitude of pressure rise is maximum in the middle of the channel whereas for higher values of fluid parameter it increases. Further, it is also found that the velocity profile shows converse behavior along the walls of the channel against multiple values of fluid parameter.

  7. Numerical method of the Riemann problem for two-dimensional multi-fluid flows with general equation of state

    Institute of Scientific and Technical Information of China (English)

    Bai Jing-Song; Zhang Zhan-Ji; Li Ping; Zhong Min

    2006-01-01

    Based on the classical Roe method, we develop an interface capture method according to the general equation of state, and extend the single-fluid Roe method to the two-dimensional (2D) multi-fluid flows, as well as construct the continuous Roe matrix for the whole flow field. The interface capture equations and fluid dynamic conservative equations are coupled together and solved by using any high-resolution schemes that usually suit for the single-fluid flows. Some numerical examples are given to illustrate the solution of 1D and 2D multi-fluid Riemann problems.

  8. On calculation of quasi-two-dimensional divergence-free projections for visualization of three-dimensional incompressible flows

    OpenAIRE

    Gelfgat, Alexander

    2015-01-01

    A visualization of three-dimensional incompressible flows by divergence-free quasi-two-dimensional projections of the velocity field on three coordinate planes was recently proposed. The projections were calculated using divergence-free Galerkin bases, which resulted in the whole procedure being complicated and CPU-time consuming. Here we propose an alternative way based on the Chorin projection combined with a SIMPLE-like iteration. The approach proposed is much easier in realization, allows...

  9. Remark on Single Exponential Bound of the Vorticity Gradient for the Two-Dimensional Euler Flow Around a Corner

    Science.gov (United States)

    Itoh, Tsubasa; Miura, Hideyuki; Yoneda, Tsuyoshi

    2016-09-01

    In this paper, we consider the two-dimensional Euler flow under a simple symmetry condition, with hyperbolic structure in a unit square {D = {(x_1,x_2):0 < x_1+x_2 < √{2},0 < -x_1+x_2 < √{2}}}. It is shown that the Lipschitz estimate of the vorticity on the boundary is at most a single exponential growth near the stagnation point.

  10. Coupling Navier-stokes and Cahn-hilliard Equations in a Two-dimensional Annular flow Configuration

    KAUST Repository

    Vignal, Philippe

    2015-06-01

    In this work, we present a novel isogeometric analysis discretization for the Navier-Stokes- Cahn-Hilliard equation, which uses divergence-conforming spaces. Basis functions generated with this method can have higher-order continuity, and allow to directly discretize the higher- order operators present in the equation. The discretization is implemented in PetIGA-MF, a high-performance framework for discrete differential forms. We present solutions in a two- dimensional annulus, and model spinodal decomposition under shear flow.

  11. Two-dimensional modeling of a polymer electrolyte membrane fuel cell with long flow channel. Part I. Model development

    OpenAIRE

    2015-01-01

    A two-dimensional single-phase model is developed for the steady-state and transient analysis of polymer electrolyte membrane fuel cells (PEMFC). Based on diluted and concentrated solution theories, viscous flow is introduced into a phenomenological multi-component modeling framework in the membrane. Characteristic variables related to the water uptake are discussed. A ButlereVolmer formulation of the current-overpotential relationship is developed based on an elementary mechanism of elect...

  12. Numerical simulation of peristaltic flow of a biorheological fluid with shear-dependent viscosity in a curved channel.

    Science.gov (United States)

    Ali, N; Javid, K; Sajid, M; Anwar Bég, O

    2016-01-01

    Peristaltic motion of a non-Newtonian Carreau fluid is analyzed in a curved channel under the long wavelength and low Reynolds number assumptions, as a simulation of digestive transport. The flow regime is shown to be governed by a dimensionless fourth-order, nonlinear, ordinary differential equation subject to no-slip wall boundary conditions. A well-tested finite difference method based on an iterative scheme is employed for the solution of the boundary value problem. The important phenomena of pumping and trapping associated with the peristaltic motion are investigated for various values of rheological parameters of Carreau fluid and curvature of the channel. An increase in Weissenberg number is found to generate a small eddy in the vicinity of the lower wall of the channel, which is enhanced with further increase in Weissenberg number. For shear-thinning bio-fluids (power-law rheological index, n Weissenberg number displaces the maximum velocity toward the upper wall. For shear-thickening bio-fluids, the velocity amplitude is enhanced markedly with increasing Weissenberg number.

  13. Fourier solution of two-dimensional Navier Stokes equation with periodic boundary conditions and incompressible flow

    CERN Document Server

    Kuiper, Logan K

    2016-01-01

    An approximate solution to the two dimensional Navier Stokes equation with periodic boundary conditions is obtained by representing the x any y components of fluid velocity with complex Fourier basis vectors. The chosen space of basis vectors is finite to allow for numerical calculations, but of variable size. Comparisons of the resulting approximate solutions as they vary with the size of the chosen vector space allow for extrapolation to an infinite basis vector space. Results suggest that such a solution, with the full basis vector space and which would give the exact solution, would fail for certain initial velocity configurations when initial velocity and time t exceed certain limits.

  14. Numerical Simulation of the Flow around Two-dimensional Partially Cavitating Hydrofoils

    Institute of Scientific and Technical Information of China (English)

    Fahri Celik; Yasemin Arikan Ozden; Sakir Bal

    2014-01-01

    In the present study, a new approach is applied to the cavity prediction for two-dimensional (2D) hydrofoils by the potential based boundary element method (BEM). The boundary element method is treated with the source and doublet distributions on the panel surface and cavity surface by the use of the Dirichlet type boundary conditions. An iterative solution approach is used to determine the cavity shape on partially cavitating hydrofoils. In the case of a specified cavitation number and cavity length, the iterative solution method proceeds by addition or subtraction of a displacement thickness on the cavity surface of the hydrofoil. The appropriate cavity shape is obtained by the dynamic boundary condition of the cavity surface and the kinematic boundary condition of the whole foil surface including the cavity. For a given cavitation number the cavity length of the 2D hydrofoil is determined according to the minimum error criterion among different cavity lengths, which satisfies the dynamic boundary condition on the cavity surface. The NACA 16006, NACA 16012 and NACA 16015 hydrofoil sections are investigated for two angles of attack. The results are compared with other potential based boundary element codes, the PCPAN and a commercial CFD code (FLUENT). Consequently, it has been shown that the results obtained from the two dimensional approach are consistent with those obtained from the others.

  15. Numerical simulation of the flow around two-dimensional partially cavitating hydrofoils

    Science.gov (United States)

    Celik, Fahri; Ozden, Yasemin Arikan; Bal, Sakir

    2014-09-01

    In the present study, a new approach is applied to the cavity prediction for two-dimensional (2D) hydrofoils by the potential based boundary element method (BEM). The boundary element method is treated with the source and doublet distributions on the panel surface and cavity surface by the use of the Dirichlet type boundary conditions. An iterative solution approach is used to determine the cavity shape on partially cavitating hydrofoils. In the case of a specified cavitation number and cavity length, the iterative solution method proceeds by addition or subtraction of a displacement thickness on the cavity surface of the hydrofoil. The appropriate cavity shape is obtained by the dynamic boundary condition of the cavity surface and the kinematic boundary condition of the whole foil surface including the cavity. For a given cavitation number the cavity length of the 2D hydrofoil is determined according to the minimum error criterion among different cavity lengths, which satisfies the dynamic boundary condition on the cavity surface. The NACA 16006, NACA 16012 and NACA 16015 hydrofoil sections are investigated for two angles of attack. The results are compared with other potential based boundary element codes, the PCPAN and a commercial CFD code (FLUENT). Consequently, it has been shown that the results obtained from the two dimensional approach are consistent with those obtained from the others.

  16. Mathematical Analysis for Peristaltic Flow of Two Phase Nanofluid in a Curved Channel

    Science.gov (United States)

    Nadeem, S.; Iqra, Shahzadi

    2015-11-01

    This paper describes the theoretical analysis for peristaltic motion of water base nanofluid containing distinct types of the nanoparticles like Cu, TiO2, and Al2O3. Equations of nano fluid are modelled and simplified by constructing the suppositions of low Reynolds number as well as long wave length. The reduced equations are solved exactly. Solutions are represented through graphs. Outcomes for the velocity, temperature, pressure rise and stream lines are analyzed graphically. The work presented here is based on the fictitious values, however some other values can be tested experimentally.

  17. Peristaltic flow of Johnson-Segalman fluid in asymmetric channel with convective boundary conditions

    Institute of Scientific and Technical Information of China (English)

    H YASMIN; T HAYAT; A ALSAEDI; HH ALSULAMI

    2014-01-01

    This work is concerned with the peristaltic transport of the Johnson-Segalman fluid in an asymmetric channel with convective boundary conditions. The mathematical modeling is based upon the conservation laws of mass, linear momentum, and energy. The resulting equations are solved after long wavelength and low Reynolds number are used. The results for the axial pressure gradient, velocity, and temperature profiles are obtained for small Weissenberg number. The expressions of the pressure gra-dient, velocity, and temperature are analyzed for various embedded parameters. Pumping and trapping phenomena are also explored.

  18. A solution of two-dimensional magnetohydrodynamic flow using the finite volume method

    Directory of Open Access Journals (Sweden)

    Naceur Sonia

    2014-01-01

    Full Text Available This paper presents the two dimensional numerical modeling of the coupling electromagnetic-hydrodynamic phenomena in a conduction MHD pump using the Finite volume Method. Magnetohydrodynamic problems are, thus, interdisciplinary and coupled, since the effect of the velocity field appears in the magnetic transport equations, and the interaction between the electric current and the magnetic field appears in the momentum transport equations. The resolution of the Maxwell's and Navier Stokes equations is obtained by introducing the magnetic vector potential A, the vorticity z and the stream function y. The flux density, the electromagnetic force, and the velocity are graphically presented. Also, the simulation results agree with those obtained by Ansys Workbench Fluent software.

  19. Water Impact of Rigid Wedges in Two-Dimensional Fluid Flow

    Directory of Open Access Journals (Sweden)

    Sawan Shah

    2015-01-01

    Full Text Available A combined experimental and numerical investigation was conducted into impact of rigid wedges on water in two-dimensional fluid conditions. Drop test experiments were conducted involving symmetric rigid wedges of varying angle and mass impacted onto water. The kinematic behaviour of the wedge and water was characterised using high-speed video. Numerical models were analysed in LS-DYNA® that combined regions of Smoothed Particle Hydrodynamics particles and a Lagrangian element mesh. The analysis captured the majority of experimental results and trends, within the bounds of experimental variance. Further, the combined modelling technique presented a highly attractive combination of computational efficiency and accuracy, making it a suitable candidate for aircraft ditching investigations.

  20. A new technique for calculating reentry base heating. [analysis of laminar base flow field of two dimensional reentry body

    Science.gov (United States)

    Meng, J. C. S.

    1973-01-01

    The laminar base flow field of a two-dimensional reentry body has been studied by Telenin's method. The flow domain was divided into strips along the x-axis, and the flow variations were represented by Lagrange interpolation polynomials in the transformed vertical coordinate. The complete Navier-Stokes equations were used in the near wake region, and the boundary layer equations were applied elsewhere. The boundary conditions consisted of the flat plate thermal boundary layer in the forebody region and the near wake profile in the downstream region. The resulting two-point boundary value problem of 33 ordinary differential equations was then solved by the multiple shooting method. The detailed flow field and thermal environment in the base region are presented in the form of temperature contours, Mach number contours, velocity vectors, pressure distributions, and heat transfer coefficients on the base surface. The maximum heating rate was found on the centerline, and the two-dimensional stagnation point flow solution was adquate to estimate the maximum heating rate so long as the local Reynolds number could be obtained.

  1. Two-dimensionalization of the flow driven by a slowly rotating impeller in a rapidly rotating fluid

    CERN Document Server

    Machicoane, Nathanaël; Cortet, Pierre-Philippe

    2016-01-01

    We characterize the two-dimensionalization process in the turbulent flow produced by an impeller rotating at a rate $\\omega$ in a fluid rotating at a rate $\\Omega$ around the same axis for Rossby number $Ro=\\omega/\\Omega$ down to $10^{-2}$. The flow can be described as the superposition of a large-scale vertically invariant global rotation and small-scale shear layers detached from the impeller blades. As $Ro$ decreases, the large-scale flow is subjected to azimuthal modulations. In this regime, the shear layers can be described in terms of wakes of inertial waves traveling with the blades, originating from the velocity difference between the non-axisymmetric large-scale flow and the blade rotation. The wakes are well defined and stable at low Rossby number, but they become disordered at $Ro$ of order of 1. This experiment provides insight into the route towards pure two-dimensionalization induced by a background rotation for flows driven by a non-axisymmetric rotating forcing.

  2. Analytical solution for peristaltic flow of conducting nanofluids in an asymmetric channel with slip effect of velocity, temperature and concentration

    Directory of Open Access Journals (Sweden)

    S. Sreenadh

    2016-06-01

    Full Text Available The Peristaltic transport of conducting nanofluids under the effect of slip condition in an asymmetric channel is reported in the present work. The mathematical modelling has been carried out under long wavelength and low Reynolds number approximations. The analytical solutions are obtained for pressure rise, nanoparticle concentration, temperature distribution, velocity profiles and stream function. Influence of various parameters on the flow characteristics has been discussed with the help of graphs. The results showed that the pressure rise increases with increasing magnetic effect and decreases with increasing slip parameter. The effects of thermophoresis parameter and Brownian motion parameter on the nanoparticle concentration and temperature distribution are studied. It is observed that the pressure gradient increases with increasing slip parameter and magnetic effect. The trapping phenomenon for different parameters is presented.

  3. Multi-scale coupling strategy for fully two-dimensional and depth-averaged models for granular flows

    Science.gov (United States)

    Pudasaini, Shiva P.; Domnik, Birte; Miller, Stephen A.

    2013-04-01

    We developed a full two-dimensional Coulomb-viscoplastic model and applied it for inclined channel flows of granular materials from initiation to their deposition. The model includes the basic features and observed phenomena in dense granular flows like the exhibition of a yield strength and a non-zero slip velocity. A pressure-dependent yield strength is proposed to account for the frictional nature of granular materials. The yield strength can be related to the internal friction angle of the material and plays an important role, for example, in deposition processes. The interaction of the flow with the solid boundary is modelled by a pressure and rate-dependent Coulomb-viscoplastic sliding law. We developed an innovative multi-scale strategy to couple the full two-dimensional, non depth-averaged model (N-DAM) with a one-dimensional, depth-averaged model (DAM). The coupled model reduces computational complexity dramatically by using DAM only in regions with smooth changes of flow variables. The numerics uses N-DAM in regions where depth-averaging becomes inaccurate, for instance, in the initiation and deposition regions, and (particularly) when the flow hits an obstacle or a defense structure. In these regions, momentum transfer must be, and is, considered in all directions. We observe very high coupling performance, and show that the numerical results deviate only slightly from results of the much more cumbersome full two-dimensional model. This shows that the coupled model, which retains all the basic physics of the flow, is an attractive alternative to an expensive, full two-dimensional simulations. We compare simulation results with different experimental data for shock waves appearing in rapid granular flows down inclined channels and impacting a wall. The model predicts the evolution of the strong shock wave and the impact force on a rigid wall for different inclination angles and sliding surfaces. It is demonstrated that the internal friction angle plays an

  4. Jamming of particles in a two-dimensional fluid-driven flow

    Science.gov (United States)

    Guariguata, Alfredo; Pascall, Masika A.; Gilmer, Matthew W.; Sum, Amadeu K.; Sloan, E. Dendy; Koh, Carolyn A.; Wu, David T.

    2012-12-01

    The jamming of particles under flow is of critical importance in a broad range of natural and industrial settings, such as the jamming of ice in rivers, or the plugging of suspended solids in pipeline transport. Relatively few studies have been carried out on jamming of suspended particles under flow, in comparison to the many studies on jamming in gravity-driven flows that have revealed various features of the jamming process. Fluid-driven particle flows differ in several aspects from gravity-driven flows, particularly in being compatible with a range of particle concentrations and velocities. Additionally, there are fluid-particle interactions and hydrodynamic effects. To investigate particle jamming in fluid-driven flows, we have performed both experiments and computer simulations on the flow of circular particles floating over water in an open channel with a restriction. We determined the flow-rate boundary for a dilute-to-dense flow transition, similar to that seen in gravity-driven flows. The maximum particle throughput increased for larger restriction sizes consistent with a Beverloo equation form over the entire range of particle mixtures and restriction sizes. The exponent of ˜3/2 in the Beverloo equation is consistent with approximately constant acceleration of grains due to fluid drag in the immediate region of the opening. We verified that the jamming probability from the dense flow gave a geometric distribution in the number of particles escaping before a jam. The probability of jamming in both experiments and simulations was found to be dependent on the ratio of channel opening to particle size, but only weakly dependent on the fluid flow velocity. Flow entrance effects were measured and observed to affect the jamming probability, and dependence on particle friction coefficient was determined from simulation. A comprehensive model for the jamming probability integrating these observations from the different flow regimes was shown to be in good

  5. ONE- AND TWO-DIMENSIONAL COUPLED HYDRODYNAMICS MODEL FOR DAM BREAK FLOW

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    1-D and 2-D mathematical models for dam break flow were established and verified with the measured data in laboratory. The 1-D and 2-D models were then coupled, and used to simulate the dam break flow from the reservoir tail to the dam site, the propagation of dam break waves in the downstream channel, and the submergence of dam break flow in the downstream town with the hydrodynamics method. As a numerical example, the presented model was employed to simulate dam break flow of a hydropower station under construction. In simulation, different dam-break durations, upstream flows and water levels in front of dam were considered, and these influencing factors of dam break flow were analyzed, which could be referenced in planning and designing hydropower stations.

  6. Two-Dimensional Spectroscopy of Photospheric Shear Flows in a Small delta Spot

    CERN Document Server

    Denker, C; Tritschler, A; Yurchyshyn, V

    2007-01-01

    In recent high-resolution observations of complex active regions, long-lasting and well-defined regions of strong flows were identified in major flares and associated with bright kernels of visible, near-infrared, and X-ray radiation. These flows, which occurred in the proximity of the magnetic neutral line, significantly contributed to the generation of magnetic shear. Signatures of these shear flows are strongly curved penumbral filaments, which are almost tangential to sunspot umbrae rather than exhibiting the typical radial filamentary structure. Solar active region NOAA 10756 was a moderately complex, beta-delta sunspot group, which provided an opportunity to extend previous studies of such shear flows to quieter settings. We conclude that shear flows are a common phenomenon in complex active regions and delta spots. However, they are not necessarily a prerequisite condition for flaring. Indeed, in the present observations, the photospheric shear flows along the magnetic neutral line are not related to a...

  7. The CABARET method for a weakly compressible fluid flows in one- and two-dimensional implementations

    Science.gov (United States)

    Kulikov, Yu M.; Son, E. E.

    2016-11-01

    The CABARET method implementation for a weakly compressible fluid flow is in the focus of present paper. Testing both one-dimensional pressure balancing problem and a classical plane Poiseuille flow, we analyze this method in terms of discontinuity resolution, dispersion and dissipation. The method is proved to have an adequate convergence to an analytical solution for a velocity profile. We also show that a flow formation process represents a set of self-similar solutions under varying pressure differential and sound speed.

  8. Unstable shear flows in two dimensional strongly correlated liquids - a hydrodynamic and molecular dynamics study

    Science.gov (United States)

    Gupta, Akanksha; Ganesh, Rajaraman; Joy, Ashwin

    2016-11-01

    In Navier-Stokes fluids, shear flows are known to become unstable leading to instability and eventually to turbulence. A class of flow namely, Kolmogorov Flows (K-Flows) exhibit such transition at low Reynolds number. Using fluid and molecular dynamics, we address the physics of transition from laminar to turbulent regime in strongly correlated-liquids such as in multi-species plasmas and also in naturally occurring plasmas with K-Flows as initial condition. A 2D phenomenological generalized hydrodynamic model is invoked wherein the effect of strong correlations is incorporated via a viscoelastic memory. To study the stability of K-Flows or in general any shear flow, a generalized eigenvalue solver has been developed along with a spectral solver for the full nonlinear set of fluid equations. A study of the linear and nonlinear features of K-Flow in incompressible and compressible limit exhibits cyclicity and nonlinear pattern formation in vorticity. A first principles based molecular dynamics simulation of particles interacting via Yukawa potential is performed with features such as configurational and kinetic thermostats for K-Flows. This work reveals several interesting similarities and differences between hydrodynamics and molecular dynamics studies.

  9. Temperature and velocity field of the two-dimensional transverse hot-air jet in a freestream flow.

    Science.gov (United States)

    Tatom, J. W.; Cooper, M. A.; Hayden, T. K.

    1972-01-01

    Experimental investigation of the low subsonic, two-dimensional transverse hot-air jet. In the study jet-to-freestream angles of 90, 120, 135, and 150 deg and jet-to-freestream velocity ratios of 5, 10, and 20 were investigated. In the tests the jet velocity and temperature fields were measured using a temperature-compensated hot-wire anemometer. Photographs of the flowfield were also made. The tests results are compared with the available data and analysis. Results indicate a relatively minor deflection of the freestream by the jet and the presence of a large separated flow region behind the jet.

  10. Single-particle detection of virus simulants under microfluidic flow with two-dimensional photonic crystals (Conference Presentation)

    Science.gov (United States)

    Miller, Benjamin L.; Baker, James E.; Sriram, Rashmi

    2017-05-01

    Because of their compatibility with standard CMOS fabrication, small footprint, and exceptional sensitivity, Two-Dimensional Photonic Crystals (2D PhCs) have been posited as attractive components for the development of real-time integrated photonic virus sensors. While detection of single virus-sized particles by 2D PhCs has been demonstrated, specific recognition of a virus simulant under conditions relevant to sensor use (including aqueous solution and microfluidic flow) has remained an unsolved challenge. This talk will describe the design and testing of a W1 waveguide-coupled 2D PhC in the context of addressing that challenge.

  11. Wake Behavior behind Turbine Cascades in Compressible Two-Dimensional Flows

    Directory of Open Access Journals (Sweden)

    Kurz Rainer

    2005-01-01

    Full Text Available The goal of the paper is to describe wake parameters of wakes from turbine cascades in compressible flows especially in planes where the leading edge of the following blade row would be located. Data from experiments with turbine cascades in compressible flow will be used to derive a theoretical approach which describes the wake growth and the recovery of the velocity deficit. The theory is based on similarity assumptions. The derived equations depend on simple and readily available parameters such as overall losses, exit angle, and Mach or Laval number. In compressible turbine flows, the influence of the inviscid flow field is of great importance. In this paper, an approach to take this influence into account when determining the behavior of the wake is presented. Correlations for basic characteristics of wakes in compressible flows are not readily available. Such correlations are necessary as input to unsteady flow and heat transfer calculation procedures for turbomachine blades. Based on available data on wake behavior in the compressible flow behind turbine blades, the correlations presented describe the wake behavior from the trailing edge to the confluence of the wakes of adjacent blades.

  12. The effect of magnetic field on mean flow generation by rotating two-dimensional convection

    CERN Document Server

    Currie, Laura K

    2016-01-01

    Motivated by the significant interaction of convection, rotation and magnetic field in many astrophysical objects, we investigate the interplay between large-scale flows driven by rotating convection and an imposed magnetic field. We utilise a simple model in two dimensions comprised of a plane layer that is rotating about an axis inclined to gravity. It is known that this setup can result in strong mean flows; we numerically examine the effect of an imposed horizontal magnetic field on such flows. We show that increasing the field strength in general suppresses the time-dependent mean flows, but in some cases it organises them leading to stronger time-averaged flows. Further, we discuss the effect of the field on the correlations responsible for driving the flows and the competition between Reynolds and Maxwell stresses. A change in behaviour is observed when the (fluid and magnetic) Prandtl numbers are decreased. In the smaller Prandtl number regime, it is shown that significant mean flows can persist even ...

  13. Two-Dimensional Stagnation-Point Velocity-Slip Flow and Heat Transfer over Porous Stretching Sheet

    Directory of Open Access Journals (Sweden)

    FEROZ AHMED SOOMRO

    2016-10-01

    Full Text Available Present paper investigates 2D (Two-Dimensional stagnation-point velocity-slip flow over porous stretching sheet. The governing non-linear PDEs (Partial Differential Equations are non-dimensionlized by using the similarity transformation technique that results into coupled non-linear ODEs (Ordinary Differential Equations. Such ODEs are then solved by using shooting technique with fourth-order Runge-Kutta method. Since the behavior of boundary layer stagnation-point flow depends on the rate of cooling and stretching. Therefore, the main objective of this paper is to analyze the effects of different working parameters on shear stress, heat transfer, velocity and temperature of fluid. The results revealed that the velocity-slip has significant effect on the fluid flow as well as on the heat transfer. The numerical results are also compared with existing work for no-slip condition and found to have good agreement with improved asymptotic behavior.

  14. Cross-flow blowing of a two-dimensional stationary arc.

    Science.gov (United States)

    Bose, T. K.

    1971-01-01

    It is demonstrated in an analysis that the electrons emitted from the cathode undergo collisions with the heavy particles and are deflected in the flow direction by the component of a collisional force associated with the relative difference in flow velocities between electrons and heavy particles. The resultant motion of the electrons describing the arc is thus caused by a combined action of the collisional force that results from the externally applied electric field. An expression is given which enables computation of the arc shape to be made provided the velocity distribution of the cross-flow and the distribution of the externally applied electric field are prescribed.

  15. Nonparallel stability of two-dimensional nonuniformly heated boundary-layer flows

    Science.gov (United States)

    Nayfeh, A. H.; El-Hady, N. M.

    1979-01-01

    An analysis is presented for the linear stability of water boundary-layer flows over nonuniformly flat plates. Included in the analysis are disturbances due to velocity, pressure, temperatures, density, and transport properties as well as variations of the liquid properties with temperature. The method of multiple scales is used to account for the nonparallelism of the mean flow. In contrast with previous analyses, the nonsimilarity of the mean flow is taken into account. No analysis agrees, even qualitatively, with the experimental data when similar profiles are used. However, both the parallel and nonparallel results qualitatively agree with the experimental results of Strazisar and Reshotko when nonsimilar profiles are used.

  16. Numerical simulation of two-dimensional corner flows in a circulating water channel with guide vanes

    Energy Technology Data Exchange (ETDEWEB)

    Hung, Y.; Nishimoto, H.; Tamashima, M.; Yamazaki, R. [West Japan Fluid Engineering Co. Ltd., Nagasaki (Japan); Wang, G.

    1998-09-04

    A Navier-Stokes procedure is developed based on the Finite Volume Method to simulate the 2-D comer flows in a CWC. The staggered grid is adopted and a new method is presented to coupling the velocities and the pressure when the grid lines change direction by 90deg. The turbulince is approximated using {kappa} - {epsilon} model and a transfinite algebraic method is used to generate the body fitted coordinates. After validation of the computer code, the corner flows in a CWC was calculated and the effect of guide vanes was investigated. For laminar flows, the guide vanes may restrain the separations on the inner side but not so effective on the outside; for turbulent flows, separations on the inner side disappeared even without guide vanes but still remained on the outside. By incorporating guide vanes, the separation can be effectively controlled. 6 refs., 13 figs.

  17. A two-dimensional parabolic model for vertical annular two-phase flow

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, F.M.; Toledo, A. Alvarez; Paladino, E.E. [Graduate Program in Mechanical Engineering, Universidade Federal de Rio Grande do Norte, Natal, RN (Brazil)], e-mail: emilio@ct.ufrn.br

    2010-07-01

    This work presents a solution algorithm for predicting hydrodynamic parameters for developing and equilibrium, adiabatic, annular, vertical two-phase flow. It solves mass and momentum transport differential equations for both the core and the liquid film across their entire domains. Thus, the velocity and shear stress distributions from the tube center to the wall are obtained, together with the average film thickness and the pressure gradient, making no use of empirical closure relations nor assuming any known velocity profile to solve the triangular relationship in the liquid film. The model was developed using the Finite Volume Method and an iterative procedure is proposed to solve all flow variables for given phase superficial velocities. The procedure is validated against the analytical solution for laminar flow and experimental data for gas-liquid turbulent flow with entrainment. For the last case, an algebraic turbulence model is used for turbulent viscosity calculation for both, liquid film and gas core. (author)

  18. Least Squares Shadowing Sensitivity Analysis of Chaotic Flow Around a Two-Dimensional Airfoil

    Science.gov (United States)

    Blonigan, Patrick J.; Wang, Qiqi; Nielsen, Eric J.; Diskin, Boris

    2016-01-01

    Gradient-based sensitivity analysis has proven to be an enabling technology for many applications, including design of aerospace vehicles. However, conventional sensitivity analysis methods break down when applied to long-time averages of chaotic systems. This breakdown is a serious limitation because many aerospace applications involve physical phenomena that exhibit chaotic dynamics, most notably high-resolution large-eddy and direct numerical simulations of turbulent aerodynamic flows. A recently proposed methodology, Least Squares Shadowing (LSS), avoids this breakdown and advances the state of the art in sensitivity analysis for chaotic flows. The first application of LSS to a chaotic flow simulated with a large-scale computational fluid dynamics solver is presented. The LSS sensitivity computed for this chaotic flow is verified and shown to be accurate, but the computational cost of the current LSS implementation is high.

  19. Shunt flow evaluation in congenital heart disease based on two-dimensional speckle tracking.

    Science.gov (United States)

    Fadnes, Solveig; Nyrnes, Siri Ann; Torp, Hans; Lovstakken, Lasse

    2014-10-01

    High-frame-rate ultrasound speckle tracking was used for quantification of peak velocity in shunt flows resulting from septal defects in congenital heart disease. In a duplex acquisition scheme implemented on a research scanner, unfocused transmit beams and full parallel receive beamforming were used to achieve a frame rate of 107 frames/s for full field-of-view flow images with high accuracy, while also ensuring high-quality focused B-mode tissue imaging. The setup was evaluated in vivo for neonates with atrial and ventricular septal defects. The shunt position was automatically tracked in B-mode images and further used in blood speckle tracking to obtain calibrated shunt flow velocities throughout the cardiac cycle. Validation toward color flow imaging and pulsed wave Doppler with manual angle correction indicated that blood speckle tracking could provide accurate estimates of shunt flow velocities. The approach was less biased by clutter filtering compared with color flow imaging and was able to provide velocity estimates beyond the Nyquist range. Possible placements of sample volumes (and angle corrections) for conventional Doppler resulted in a peak shunt velocity variations of 0.49-0.56 m/s for the ventricular septal defect of patient 1 and 0.38-0.58 m/s for the atrial septal defect of patient 2. In comparison, the peak velocities found from speckle tracking were 0.77 and 0.33 m/s for patients 1 and 2, respectively. Results indicated that complex intraventricular flow velocity patterns could be quantified using high-frame-rate speckle tracking of both blood and tissue movement. This could potentially help increase diagnostic accuracy and decrease inter-observer variability when measuring peak velocity in shunt flows. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  20. Measuring two-dimensional components of a flow velocity vector using a hot-wire probe.

    Science.gov (United States)

    Kiełbasa, Jan

    2007-08-01

    The article presents a single-hot-wire probe adapted to detect the direction of flow velocity. The modification consists of the introduction of a third support which allows to measure voltage at the central point of the wire. The sign of voltage difference DeltaU between both parts of the wire is the measure of the direction of flow velocity in a system of coordinates associated with the probe.

  1. Wake Behavior behind Turbine Cascades in Compressible Two-Dimensional Flows

    OpenAIRE

    2005-01-01

    The goal of the paper is to describe wake parameters of wakes from turbine cascades in compressible flows especially in planes where the leading edge of the following blade row would be located. Data from experiments with turbine cascades in compressible flow will be used to derive a theoretical approach which describes the wake growth and the recovery of the velocity deficit. The theory is based on similarity assumptions. The derived equations depend on simple and readily available parameter...

  2. Ensemble Distribution for Immiscible Two-Phase Flow in Two-Dimensional Networks

    CERN Document Server

    Savani, Isha; Kjelstrup, Signe; Vassvik, Morten; Sinha, Santanu; Hansen, Alex

    2016-01-01

    An ensemble distribution has been constructed to describe steady immiscible two-phase flow of two incompressible fluids in a network. The system is ergodic. The distribution relates the time that a bubble of the non-wetting fluid spends in a link to the local volume flow. The properties of the ensemble distribution are tested by two-phase flow simulations at the pore-scale for capillary numbers ranging from 0.1 to 0.001. It is shown that the distribution follows the postulated dependence on the local flow for Ca = 0.01 and 0.001. The distribution is used to compute the global flow performance of the network. In particular, we find the expression for the overall mobility of the system using the ensemble distribution. The entropy production at the scale of the network is shown to give the expected product of the average flow and its driving force, obtained from a black-box description. The distribution can be used to obtain macroscopic variables from local network information, for a practical range of capillary...

  3. A two-dimensional flow sensor with integrated micro thermal sensing elements and a back propagation neural network.

    Science.gov (United States)

    Que, Ruiyi; Zhu, Rong

    2013-12-31

    This paper demonstrates a novel flow sensor with two-dimensional 360° direction sensitivity achieved with a simple structure and a novel data fusion algorithm. Four sensing elements with roundabout wires distributed in four quadrants of a circle compose the sensor probe, and work in constant temperature difference (CTD) mode as both Joule heaters and temperature detectors. The magnitude and direction of a fluid flow are measured by detecting flow-induced temperature differences among the four elements. The probe is made of Ti/Au thin-film with a diameter of 2 mm, and is fabricated using micromachining techniques. When a flow goes through the sensor, the flow-induced temperature differences are detected by the sensing elements that also serve as the heaters of the sensor. By measuring the temperature differences among the four sensing elements symmetrically distributed in the sensing area, a full 360° direction sensitivity can be obtained. By using a BP neural network to model the relationship between the readouts of the four sensor elements and flow parameters and execute data fusion, the magnitude and direction of the flow can be deduced. Validity of the sensor design was proven through both simulations and experiments. Wind tunnel experimental results show that the measurement accuracy of the airflow speed reaches 0.72 m/s in the range of 3 m/s-30 m/s and the measurement accuracy of flow direction angle reaches 1.9° in the range of 360°.

  4. A Two-Dimensional Flow Sensor with Integrated Micro Thermal Sensing Elements and a Back Propagation Neural Network

    Directory of Open Access Journals (Sweden)

    Ruiyi Que

    2013-12-01

    Full Text Available This paper demonstrates a novel flow sensor with two-dimensional 360° direction sensitivity achieved with a simple structure and a novel data fusion algorithm. Four sensing elements with roundabout wires distributed in four quadrants of a circle compose the sensor probe, and work in constant temperature difference (CTD mode as both Joule heaters and temperature detectors. The magnitude and direction of a fluid flow are measured by detecting flow-induced temperature differences among the four elements. The probe is made of Ti/Au thin-film with a diameter of 2 mm, and is fabricated using micromachining techniques. When a flow goes through the sensor, the flow-induced temperature differences are detected by the sensing elements that also serve as the heaters of the sensor. By measuring the temperature differences among the four sensing elements symmetrically distributed in the sensing area, a full 360° direction sensitivity can be obtained. By using a BP neural network to model the relationship between the readouts of the four sensor elements and flow parameters and execute data fusion, the magnitude and direction of the flow can be deduced. Validity of the sensor design was proven through both simulations and experiments. Wind tunnel experimental results show that the measurement accuracy of the airflow speed reaches 0.72 m/s in the range of 3 m/s–30 m/s and the measurement accuracy of flow direction angle reaches 1.9° in the range of 360°.

  5. Simultaneous effects of radial magnetic field and wall properties on peristaltic flow of Carreau-Yasuda fluid in curved flow configuration

    Science.gov (United States)

    Hayat, T.; Tanveer, A.; Alsaadi, F.

    2015-12-01

    The objective of present article is to address the magnetohydrodynamic (MHD) peristaltic flow of Carreau-Yasuda fluid in a curved geometry. The channel boundaries satisfy wall slip and compliant properties. The fluid is electrically conducting through an applied magnetic field in the radial direction. Heat transfer is also studied. Governing equation comprised the viscous dissipation effects. The non-linear expressions are first obtained and then approximated using long wavelength and low Reynolds number considerations. The resulting systems are solved for the series solutions. The expressions of velocity, temperature, heat transfer coefficient and stream function are obtained and analyzed via graphical illustrations.

  6. Simultaneous effects of radial magnetic field and wall properties on peristaltic flow of Carreau-Yasuda fluid in curved flow configuration

    Directory of Open Access Journals (Sweden)

    T. Hayat

    2015-12-01

    Full Text Available The objective of present article is to address the magnetohydrodynamic (MHD peristaltic flow of Carreau-Yasuda fluid in a curved geometry. The channel boundaries satisfy wall slip and compliant properties. The fluid is electrically conducting through an applied magnetic field in the radial direction. Heat transfer is also studied. Governing equation comprised the viscous dissipation effects. The non-linear expressions are first obtained and then approximated using long wavelength and low Reynolds number considerations. The resulting systems are solved for the series solutions. The expressions of velocity, temperature, heat transfer coefficient and stream function are obtained and analyzed via graphical illustrations.

  7. Moderately converging ion and electron flows in two-dimensional diodes

    Science.gov (United States)

    Cavenago, M.

    2012-11-01

    Flow of particles in diodes is solved selfconsistently assuming an approximated system of flow lines, that can be easily represented by an analytic transformation in a complex plane, with assumed uniformity in the third spatial direction. Beam current compression is tunable by an angle parameter α0; transformed coordinate lines are circular arcs, exactly matching to the curved cathode usually considered by rectilinear converging flows. The curvature of flow lines allows to partly balance the transverse effect of space charge. A self-contained discussion of the whole theory is reported, ranging from analytical solution for selfconsistent potential to electrode drawing to precise numerical simulation, which serves as a verification and as an illustration of typical electrode shapes. Motion and Poisson equation are written in a curved flow line system and their approximate consistency is shown to imply an ordinary differential equation for the beam edge potential. Transformations of this equation and their series solutions are given and discussed, showing that beam edge potential has a maximum, so supporting both diode (with α0 ≅ π/3) and triode design. Numerical simulations confirm the consistency of these solution. Geometrical details of diode design are discussed: the condition of a zero divergence beam, with the necessary anode lens effect included, is written and solved, as a function of beam compression; accurate relations for diode parameters and perveance are given. Weakly relativistic effects including self-magnetic field are finally discussed as a refinement.

  8. Periodic dislocation dynamics in two-dimensional concentrated emulsion flowing in a tapered microchannel

    Science.gov (United States)

    Gai, Ya; Leong, Chia Min; Cai, Wei; Tang, Sindy K. Y.

    2016-11-01

    Here we report a surprising order in concentrated emulsion when flowing as a monolayer in a tapered microfluidic channel. The flow of droplets in micro-channels can be non-trivial, and may lead to unexpected phenomena such as long-period oscillations and chaos. Previously, there have been studies on concentrated emulsions in straight channels and channels with bends. The dynamics of how drops flow and rearrange in a tapered geometry has not yet been characterized. At sufficiently slow flow rates, the drops arrange into a hexagonal lattice. At a given x-position, the time-averaged droplet velocities are uniform. The instantaneous drop velocities, however, reveal a different, wave-like pattern. Within the rearrangement zone where the number of rows of drops decreases from N to N-1, there is always a drop moved faster than the others. Close examination reveals the anomalous velocity profile arises from a series of dislocations that are both spatial and temporal periodic. To our knowledge, such reproducible dislocation motion has not been reported before. Our results are useful in novel flow control and mixing strategies in droplet microfluidics as well as modeling crystal plasticity in low-dimensional nanomaterials.

  9. New families of flows between two-dimensional conformal field theories

    CERN Document Server

    Dorey, P; Tateo, R; Dorey, Patrick; Dunning, Clare; Tateo, Roberto

    2000-01-01

    We present evidence for the existence of infinitely-many new families of renormalisation group flows between the nonunitary minimal models of conformal field theory. These are associated with perturbations by the $\\phi_{21}$ and In all of the new flows, the finite-volume effective central charge is a non-monotonic function of the system size. The evolution of this effective central charge is studied by means of a nonlinear integral equation, a massless variant of an equation recently found to describe certain massive perturbations of these same models. We also observe that a similar non-monotonicity arises in the more familiar $\\phi_{13}$ perturbations, when the flows induced are between nonunitary minimal models.

  10. Exact two-dimensionalization of rapidly rotating large-Reynolds-number flows

    CERN Document Server

    Gallet, Basile

    2015-01-01

    We consider the flow of a Newtonian fluid in a three-dimensional domain, rotating about a vertical axis and driven by a vertically invariant horizontal body-force. This system admits vertically invariant solutions that satisfy the 2D Navier-Stokes equation. At high Reynolds number and without global rotation, such solutions are usually unstable to three-dimensional perturbations. By contrast, for strong enough global rotation, we prove rigorously that the 2D (and possibly turbulent) solutions are stable to vertically dependent perturbations: the flow becomes 2D in the long-time limit. These results shed some light on several fundamental questions of rotating turbulence: for arbitrary Reynolds number and small enough Rossby number, the system is attracted towards purely 2D flow solutions, which display no energy dissipation anomaly and no cyclone-anticyclone asymmetry. Finally, these results challenge the applicability of wave turbulence theory to describe stationary rotating turbulence in bounded domains.

  11. Two dimensional analytical solution for a partially vegetated compound channel flow

    Institute of Scientific and Technical Information of China (English)

    HUAI Wen-xin; XU Zhi-gang; YANG Zhong-hua; ZENG Yu-hong

    2008-01-01

    The theory of an eddy viscosity model is applied to the study of the flow in a compound channel which is partially vegetated. The governing equation is constituted by analyzing the longitudinal forces acting on the unit volume where the effect of the vegetation on the flow is considered as a drag force item. The compound channel is di- vided into 3 sub-regions in the transverse direction, and the coefficients in every region's differential equations were solved simultaneously. Thus, the analytical solution of the transverse distribution of the depth-averaged velocity for uniform flow in a partially vege- tated compound channel was obtained. The results can be used to predict the transverse distribution of bed shear stress, which has an important effect on the transportation of sediment. By comparing the analytical results with the measured data, the analytical so- lution in this paper is shown to be sufficiently accurate to predict most hydraulic features for engineering design purposes.

  12. A Finite-Element Solution of the Navier-Stokes Equations for Two-Dimensional and Axis-Symmetric Flow

    Directory of Open Access Journals (Sweden)

    Sven Ø. Wille

    1980-04-01

    Full Text Available The finite element formulation of the Navier-Stokes equations is derived for two-dimensional and axis-symmetric flow. The simple triangular, T6, isoparametric element is used. The velocities are interpolated by quadratic polynomials and the pressure is interpolated by linear polynomials. The non-linear simultaneous equations are solved iteratively by the Newton-Raphson method and the element matrix is given in the Newton-Raphson form. The finite element domain is organized in substructures and an equation solver which works on each substructure is specially designed. This equation solver needs less storage in the computer and is faster than the traditional banded equation solver. To reduce the amount of input data an automatic mesh generator is designed. The input consists of the coordinates of eight points defining each substructure with the corresponding boundary conditions. In order to interpret the results they are plotted on a calcomp plotter. Examples of plots of the velocities, the streamlines and the pressure inside a two-dimensional flow divider and an axis-symmetric expansion of a tube are shown for various Reynolds numbers.

  13. MOFAT: A two-dimensional finite element program for multiphase flow and multicomponent transport. Program documentation and user's guide

    Science.gov (United States)

    Katyal, A. K.; Kaluarachchi, J. J.; Parker, J. C.

    1991-05-01

    The manual describes a two-dimensional finite element model for coupled multiphase flow and multicomponent transport in planar or radially symmetric vertical sections. Flow and transport of three fluid phases, including water, nonaqueous phase liquid (NAPL), and gas are considered by the program. The program can simulate flow only or coupled flow and transport. The flow module can be used to analyze two phases, water and NAPL, with the gas phase held at constant pressure, or explicit three-phase flow of water, NAPL, and gas at various pressures. The transport module can handle up to five components which partition among water, NAPL, gas and solid phases assuming either local equilibrium or first-order mass transfer. Three phase permeability-saturation-capillary pressure relations are defined by an extension of the van Genuchten model. The governing equations are solved using an efficient upstream-weighted finite element scheme. The required inputs for flow and transport analysis are described. Detailed instructions for creating data files needed to run the program and examples of input and output files are given in appendices.

  14. Fundamental interactions of vortical structures with boundary layers in two-dimensional flows

    DEFF Research Database (Denmark)

    Coutsias, E.A.; Lynov, Jens-Peter

    1991-01-01

    in the vorticity-stream function representation for bounded geometries. Fundamental processes connected to vorticity detachment from the boundary layers caused by the proximity of vortical structures are described. These processes include enstrophy enhancement of the main flow during bursting events, and pinning...

  15. On calculation of quasi-two-dimensional divergence-free projections for visualization of three-dimensional incompressible flows

    CERN Document Server

    Gelfgat, Alexander

    2015-01-01

    A visualization of three-dimensional incompressible flows by divergence-free quasi-two-dimensional projections of the velocity field on three coordinate planes was recently proposed. The projections were calculated using divergence-free Galerkin bases, which resulted in the whole procedure being complicated and CPU-time consuming. Here we propose an alternative way based on the Chorin projection combined with a SIMPLE-like iteration. The approach proposed is much easier in realization, allows for faster computations, and can be generalized for arbitrary curvilinear orthogonal coordinates. To illustrate the visualization method, examples of flow visualization in cylindrical and spherical coordinates, as well as post-processing of experimental 3D-PTV data are presented.

  16. Programmed automation of modulator cold jet flow for comprehensive two-dimensional gas chromatographic analysis of vacuum gas oils.

    Science.gov (United States)

    Rathbun, Wayne

    2007-01-01

    A method is described for automating the regulation of cold jet flow of a comprehensive two-dimensional gas chromatograph (GCxGC) configured with flame ionization detection. This new capability enables the routine automated separation, identification, and quantitation of hydrocarbon types in petroleum fractions extending into the vacuum gas oil (VGO) range (IBP-540 degrees C). Chromatographic data acquisition software is programmed to precisely change the rate of flow from the cold jet of a nitrogen cooled loop modulator of a GCxGC instrument during sample analysis. This provides for the proper modulation of sample compounds across a wider boiling range. The boiling point distribution of the GCxGC separation is shown to be consistent with high temperature simulated distillation results indicating recovery of higher boiling semi-volatile VGO sample components. GCxGC configured with time-of-flight mass spectrometry is used to determine the molecular identity of individual sample components and boundaries of different molecular types.

  17. Sound generated by instability waves of supersonic flows. I Two-dimensional mixing layers. II - Axisymmetric jets

    Science.gov (United States)

    Tam, C. K. W.; Burton, D. E.

    1984-01-01

    An investigation is conducted of the phenomenon of sound generation by spatially growing instability waves in high-speed flows. It is pointed out that this process of noise generation is most effective when the flow is supersonic relative to the ambient speed of sound. The inner and outer asymptotic expansions corresponding to an excited instability wave in a two-dimensional mixing layer and its associated acoustic fields are constructed in terms of the inner and outer spatial variables. In matching the solutions, the intermediate matching principle of Van Dyke and Cole is followed. The validity of the theory is tested by applying it to an axisymmetric supersonic jet and comparing the calculated results with experimental measurements. Very favorable agreements are found both in the calculated instability-wave amplitude distribution (the inner solution) and the near pressure field level contours (the outer solution) in each case.

  18. ANALYSIS OF WATER QUALITY IN SHALLOW LAKES WITH A TWO-DIMENSIONAL FLOW-SEDIMENT MODEL

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The governing equation for sediment pollutions was derived based on the turbulent diffusion of pollutants in shallow lakes. Coupled with shallow water equations, a depth-averaged 2-D flow and water quality model was developed. By means of the conservation law, a proposed differential equation for the change of sediment pollutants was linked to the 2-D equations. Under the framework of the finite volume method, the Osher approximate Riemann solver was employed to solve the equations. An analytical resolution was used to examine the model capabilities. Simulated results matched the exact solutions especially well. As an example, the simulation of CODMn in the Wuli Lake, a part of the Taihu lake, was conducted, which led to reasonable results. This study provides a new approach and a practical tool for the simulation of flow and water quality in shallow lakes.

  19. Unstable manifold computations for the two-dimensional plane Poiseuille flow

    Energy Technology Data Exchange (ETDEWEB)

    Casas, Pablo S. [Universidad Politecnica de Cataluna, Departamento de Matematica Aplicada I, Barcelona (Spain); Jorba, Angel [Universidad de Barcelona, Departamento de Matematica Aplicada y Analisis, Barcelona (Spain)

    2004-11-01

    We follow the unstable manifold of periodic and quasi-periodic solutions in time for the Poiseuille problem, using two formulations: holding a constant flux or mean pressure gradient. By means of a numerical integrator of the Navier-Stokes equations, we let the fluid evolve from an initially perturbed unstable solution until the fluid reaches an attracting state. Thus, we detect several connections among different configurations of the flow such as laminar, periodic, quasi-periodic with two or three basic frequencies, and more complex sets that we have not been able to classify. These connections make possible the location of new families of solutions, usually hard to find by means of numerical continuation of curves, and show the richness of the dynamics of the Poiseuille flow. (orig.)

  20. Two-dimensional nonstationary flow of a conducting fluid, induced by a rotating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kapusta, A.B.

    1977-07-01

    An examination is made of a full induction problem on the planar movement of a conducting fluid in a rotating magnetic field. The solution to this problem is sought by the method of degradation into Fourier series by harmonics of the rotating field. The initial system of partial differential equations is reduced to the system 2+1 of normal differential equations that bind the amplitudes of function harmonics and electrical vector potential. A solution to the problem for small anti ..omega.. was found with an accuracy up to the second approximation. The unsteadiness of flow was found to be manifested in a form of induced cross-sectional waves, traveling along the stream tubes of this flow at a speed that is equal to the phase velocity of the magnetic field. The appearance of wave effects is explained by considerations of symmetry. 5 references, 1 figure.

  1. Identifying the Flow Physics and Modeling Transient Forces on Two-Dimensional Wings

    Science.gov (United States)

    2016-09-02

    becomes smaller relative to the random component of the error (indicated by the size of the confidence ellipse). This means that the modifications to...understanding the dynamics of these unsteady flows, and uses state-of-the-art techniques, both for measuring these phenomena in experiments (using an...art techniques, both for measuring these phenomena in experiments (using an unsteady wind tunnel at IIT), and for analyzing the data and developing

  2. Finite-Difference Lattice Boltzmann Scheme for High-Speed Compressible Flow: Two-Dimensional Case

    Science.gov (United States)

    Gan, Yan-Biao; Xu, Ai-Guo; Zhang, Guang-Cai; Zhang, Ping; Zhang, Lei; Li, Ying-Jun

    2008-07-01

    Lattice Boltzmann (LB) modeling of high-speed compressible flows has long been attempted by various authors. One common weakness of most of previous models is the instability problem when the Mach number of the flow is large. In this paper we present a finite-difference LB model, which works for flows with flexible ratios of specific heats and a wide range of Mach number, from 0 to 30 or higher. Besides the discrete-velocity-model by Watari [Physica A 382 (2007) 502], a modified Lax Wendroff finite difference scheme and an artificial viscosity are introduced. The combination of the finite-difference scheme and the adding of artificial viscosity must find a balance of numerical stability versus accuracy. The proposed model is validated by recovering results of some well-known benchmark tests: shock tubes and shock reflections. The new model may be used to track shock waves and/or to study the non-equilibrium procedure in the transition between the regular and Mach reflections of shock waves, etc.

  3. Two-dimensional intraventricular flow pattern visualization using the image-based computational fluid dynamics.

    Science.gov (United States)

    Doost, Siamak N; Zhong, Liang; Su, Boyang; Morsi, Yosry S

    2016-10-31

    The image-based computational fluid dynamics (IB-CFD) technique, as the combination of medical images and the CFD method, is utilized in this research to analyze the left ventricle (LV) hemodynamics. The research primarily aims to propose a semi-automated technique utilizing some freely available and commercial software packages in order to simulate the LV hemodynamics using the IB-CFD technique. In this research, moreover, two different physiological time-resolved 2D models of a patient-specific LV with two different types of aortic and mitral valves, including the orifice-type valves and integrated with rigid leaflets, are adopted to visualize the process of developing intraventricular vortex formation and propagation. The blood flow pattern over the whole cardiac cycle of two models is also compared to investigate the effect of utilizing different valve types in the process of the intraventricular vortex formation. Numerical findings indicate that the model with integrated valves can predict more complex intraventricular flow that can match better the physiological flow pattern in comparison to the orifice-type model.

  4. Molecular dynamics computations of two dimensional supersonic rarefied gas flow past blunt bodies

    Science.gov (United States)

    Greber, Isaac; Wachman, Harold Y.; Woo, Myeung-Jouh

    1991-01-01

    This paper presents results of molecular dynamics computations of supersonic flow past a circular cylinder and past a flat plate perpendicular to a supersonic stream. The results are for Mach numbers of approximately 5 and 10, for several Knudsen numbers and several ratios of surface to free stream temperatures. A special feature of the computations is the use of relatively small numbers of particles in the molecular dynamics simulation, and an examination of the adequacy of using small numbers of particles to obtain physically useful results.

  5. Numerical Solutions for Supersonic Flow of an Ideal Gas Around Blunt Two-Dimensional Bodies

    Science.gov (United States)

    Fuller, Franklyn B.

    1961-01-01

    The method described is an inverse one; the shock shape is chosen and the solution proceeds downstream to a body. Bodies blunter than circular cylinders are readily accessible, and any adiabatic index can be chosen. The lower limit to the free-stream Mach number available in any case is determined by the extent of the subsonic field, which in turn depends upon the body shape. Some discussion of the stability of the numerical processes is given. A set of solutions for flows about circular cylinders at several Mach numbers and several values of the adiabatic index is included.

  6. Analytic Approximate Solutions for Unsteady Two-Dimensional and Axisymmetric Squeezing Flows between Parallel Plates

    Directory of Open Access Journals (Sweden)

    Mohammad Mehdi Rashidi

    2008-01-01

    Full Text Available The flow of a viscous incompressible fluid between two parallel plates due to the normal motion of the plates is investigated. The unsteady Navier-Stokes equations are reduced to a nonlinear fourth-order differential equation by using similarity solutions. Homotopy analysis method (HAM is used to solve this nonlinear equation analytically. The convergence of the obtained series solution is carefully analyzed. The validity of our solutions is verified by the numerical results obtained by fourth-order Runge-Kutta.

  7. Statistical theory of reversals in two-dimensional confined turbulent flows

    CERN Document Server

    Shukla, Vishwanath; Brachet, Marc

    2016-01-01

    It is shown that the Truncated Euler Equations, i.e. a finite set of ordinary differential equations for the amplitude of the large-scale modes, can correctly describe the complex transitional dynamics that occur within the turbulent regime of a confined 2D Navier-Stokes flow with bottom friction and a spatially periodic forcing. In particular, the random reversals of the large scale circulation on the turbulent background involve bifurcations of the probability distribution function of the large-scale circulation velocity that are described by the related microcanonical distribution which displays transitions from gaussian to bimodal and broken ergodicity. A minimal 13-mode model reproduces these results.

  8. Molecular dynamics computations of two dimensional supersonic rarefied gas flow past blunt bodies

    Science.gov (United States)

    Greber, Isaac; Wachman, Harold Y.; Woo, Myeung-Jouh

    1991-01-01

    This paper presents results of molecular dynamics computations of supersonic flow past a circular cylinder and past a flat plate perpendicular to a supersonic stream. The results are for Mach numbers of approximately 5 and 10, for several Knudsen numbers and several ratios of surface to free stream temperatures. A special feature of the computations is the use of relatively small numbers of particles in the molecular dynamics simulation, and an examination of the adequacy of using small numbers of particles to obtain physically useful results.

  9. The orientation field of fibers advected by a two-dimensional chaotic flow

    Science.gov (United States)

    Hejazi, Bardia; Mehlig, Bernhard; Voth, Greg

    2016-11-01

    We examine the orientation of slender fibers advected by a 2D chaotic flow. The orientation field of these fibers show fascinating structures called scar lines, where they rotate by π over short distances. We use the standard map as a convenient model to represent a time-periodic 2D incompressible fluid flow. To understand the fiber orientation field, we consider the stretching field, given by the eigenvalues and eigenvectors of the Cauchy-Green strain tensors. The eigenvector field is strongly aligned with the fibers over almost the entire field, but develops topological singularities at certain points which do not exist in the advected fiber field. The singularities are points that have experienced zero stretching, and the number of such points increases rapidly with time. A key feature of both the fiber orientation and the eigenvector field are the scar lines. We show that certain scar lines form from fluid elements that are initially stretched in one direction and then stretched in an orthogonal direction to cancel the initial stretching. The scar lines that satisfy this condition contain the singularities of the eigenvector field. These scar lines highlight the major differences between the passive director field and the much more widely studied passive scalar field.

  10. AQMAN; linear and quadratic programming matrix generator using two-dimensional ground-water flow simulation for aquifer management modeling

    Science.gov (United States)

    Lefkoff, L.J.; Gorelick, S.M.

    1987-01-01

    A FORTRAN-77 computer program code that helps solve a variety of aquifer management problems involving the control of groundwater hydraulics. It is intended for use with any standard mathematical programming package that uses Mathematical Programming System input format. The computer program creates the input files to be used by the optimization program. These files contain all the hydrologic information and management objectives needed to solve the management problem. Used in conjunction with a mathematical programming code, the computer program identifies the pumping or recharge strategy that achieves a user 's management objective while maintaining groundwater hydraulic conditions within desired limits. The objective may be linear or quadratic, and may involve the minimization of pumping and recharge rates or of variable pumping costs. The problem may contain constraints on groundwater heads, gradients, and velocities for a complex, transient hydrologic system. Linear superposition of solutions to the transient, two-dimensional groundwater flow equation is used by the computer program in conjunction with the response matrix optimization method. A unit stress is applied at each decision well and transient responses at all control locations are computed using a modified version of the U.S. Geological Survey two dimensional aquifer simulation model. The program also computes discounted cost coefficients for the objective function and accounts for transient aquifer conditions. (Author 's abstract)

  11. Statistical mechanics of two-dimensional Euler flows and minimum enstrophy states

    CERN Document Server

    Naso, A; Dubrulle, B

    2009-01-01

    A simplified thermodynamic approach of the incompressible 2D Euler equation is considered based on the conservation of energy, circulation and microscopic enstrophy. Statistical equilibrium states are obtained by maximizing the Miller-Robert-Sommeria (MRS) entropy under these sole constraints. The vorticity fluctuations are Gaussian while the mean flow is characterized by a linear $\\overline{\\omega}-\\psi$ relationship. Furthermore, the maximization of entropy at fixed energy, circulation and microscopic enstrophy is equivalent to the minimization of macroscopic enstrophy at fixed energy and circulation. This provides a justification of the minimum enstrophy principle from statistical mechanics when only the microscopic enstrophy is conserved among the infinite class of Casimir constraints. A new class of relaxation equations towards the statistical equilibrium state is derived. These equations can provide an effective description of the dynamics towards equilibrium or serve as numerical algorithms to determin...

  12. Inversion for basal friction coefficients with a two-dimensional flow line model using Tikhonov regularization

    Directory of Open Access Journals (Sweden)

    Yuri V. Konovalov

    2012-09-01

    Full Text Available We present results of basal friction coefficient inversion. The inversion was performed by a 2D flow line model for one of the four fast flowing ice streams on the southern side of the Academy of Sciences Ice Cap in the Komsomolets Island, Severnaya Zemlya archipelago. The input data for the performance of both the forward and the inverse problems included synthetic aperture radar interferometry ice surface velocities, ice surface elevations and ice thicknesses obtained by airborne measurements (all were taken from Dowdeswell et al., 2002. Numerical experiments with: i different sea level shifts; and ii randomly perturbed friction coefficient have been carried out in the forward problem. The impact of sea level changes on vertical distribution of horizontal velocity and on shear stress distribution near the ice front has been investigated in experiments with different sea level shifts. The experiments with randomly perturbed friction coefficient have revealed that the modeled surface velocity is weakly sensitive to the perturbations and, therefore, the inverse problem should be considered ill posed. To mitigate ill posedness of the inverse problem, Tikhonov’s regularization was applied. The regularization parameter was determined from the relation of the discrepancy between observed and modeled velocities to the regularization parameter. The inversion was performed for both linear and non-linear sliding laws. The inverted spatial distributions of the basal friction coefficient are similar for both sliding laws. The similarity between these inverted distributions suggests that the changes in the friction coefficient are accompanied by appropriate water content variations at the glacier base.

  13. Two-dimensional finite volume method for dam-break flow simulation

    Institute of Scientific and Technical Information of China (English)

    M.ALIPARAST

    2009-01-01

    A numerical model based upon a second-order upwind cell-center finite volume method on unstructured triangular grids is developed for solving shallow water equations.The assumption of a small depth downstream instead of a dry bed situation changes the wave structure and the propagation speed of the front which leads to incorrect results.The use of Harten-Lax-vau Leer (HLL) allows handling of wet/dry treatment.By usage of the HLL approximate Riemann solver,also it make possible to handle discontinuous solutions.As the assumption of a very small depth downstream of the dam can change the nature of the dam break flow problem which leads to incorrect results,the HLL approximate Riemann solver is used for the computation of inviscid flux functions,which makes it possible to handle discontinuous solutions.A multidimensional slope-limiting technique is applied to achieve second-order spatial accuracy and to prevent spurious oscillations.To alleviate the problems associated with numerical instabilities due to small water depths near a wet/dry boundary,the friction source terms are treated in a fully implicit way.A third-order Runge-Kutta method is used for the time integration of semi-discrete equations.The developed numerical model has been applied to several test cases as well as to real flows.The tests are tested in two cases:oblique hydraulic jump and experimental dam break in converging-diverging flume.Numerical tests proved the robustness and accuracy of the model.The model has been applied for simulation of dam break analysis of Torogh in Irun.And finally the results have been used in preparing EAP (Emergency Action Plan).

  14. Critical Stokes number for the capture of inertial particles by recirculation cells in two-dimensional quasisteady flows

    Science.gov (United States)

    Verjus, Romuald; Angilella, Jean-Régis

    2016-05-01

    Inertial particles are often observed to be trapped, temporarily or permanently, by recirculation cells which are ubiquitous in natural or industrial flows. In the limit of small particle inertia, determining the conditions of trapping is a challenging task, as it requires a large number of numerical simulations or experiments to test various particle sizes or densities. Here, we investigate this phenomenon analytically and numerically in the case of heavy particles (e.g., aerosols) at low Reynolds number, to derive a trapping criterion that can be used both in analytical and numerical velocity fields. The resulting criterion allows one to predict the characteristics of trapped particles as soon as single-phase simulations of the flow are performed. Our analysis is valid for two-dimensional particle-laden flows in the vertical plane, in the limit where the particle inertia, the free-fall terminal velocity, and the flow unsteadiness can be treated as perturbations. The weak unsteadiness of the flow generally induces a chaotic tangle near heteroclinic or homoclinic cycles if any, leading to the apparent diffusion of fluid elements through the boundary of the cell. The critical particle Stokes number Stc below which aerosols also enter and exit the cell in a complex manner has been derived analytically, in terms of the flow characteristics. It involves the nondimensional curvature-weighted integral of the squared velocity of the steady fluid flow along the dividing streamline of the recirculation cell. When the flow is unsteady and St>Stc , a regular motion takes place due to gravity and centrifugal effects, like in the steady case. Particles driven towards the interior of the cell are trapped permanently. In contrast, when the flow is unsteady and St

  15. VNAP2: a computer program for computation of two-dimensional, time-dependent, compressible, turbulent flow

    Energy Technology Data Exchange (ETDEWEB)

    Cline, M.C.

    1981-08-01

    VNAP2 is a computer program for calculating turbulent (as well as laminar and inviscid), steady, and unsteady flow. VNAP2 solves the two-dimensional, time-dependent, compressible Navier-Stokes equations. The turbulence is modeled with either an algebraic mixing-length model, a one-equation model, or the Jones-Launder two-equation model. The geometry may be a single- or a dual-flowing stream. The interior grid points are computed using the unsplit MacCormack scheme. Two options to speed up the calculations for high Reynolds number flows are included. The boundary grid points are computed using a reference-plane-characteristic scheme with the viscous terms treated as source functions. An explicit artificial viscosity is included for shock computations. The fluid is assumed to be a perfect gas. The flow boundaries may be arbitrary curved solid walls, inflow/outflow boundaries, or free-jet envelopes. Typical problems that can be solved concern nozzles, inlets, jet-powered afterbodies, airfoils, and free-jet expansions. The accuracy and efficiency of the program are shown by calculations of several inviscid and turbulent flows. The program and its use are described completely, and six sample cases and a code listing are included.

  16. A Numerical Scheme Based on an Immersed Boundary Method for Compressible Turbulent Flows with Shocks: Application to Two-Dimensional Flows around Cylinders

    Directory of Open Access Journals (Sweden)

    Shun Takahashi

    2014-01-01

    Full Text Available A computational code adopting immersed boundary methods for compressible gas-particle multiphase turbulent flows is developed and validated through two-dimensional numerical experiments. The turbulent flow region is modeled by a second-order pseudo skew-symmetric form with minimum dissipation, while the monotone upstream-centered scheme for conservation laws (MUSCL scheme is employed in the shock region. The present scheme is applied to the flow around a two-dimensional cylinder under various freestream Mach numbers. Compared with the original MUSCL scheme, the minimum dissipation enabled by the pseudo skew-symmetric form significantly improves the resolution of the vortex generated in the wake while retaining the shock capturing ability. In addition, the resulting aerodynamic force is significantly improved. Also, the present scheme is successfully applied to moving two-cylinder problems.

  17. Proteomic Analysis of Colorectal Cancer: Prefractionation Strategies Using two-Dimensional Free-Flow Electrophoresis

    Directory of Open Access Journals (Sweden)

    Richard J. Simpson

    2006-04-01

    Full Text Available This review deals with the application of a new prefractionation tool, free-flow electrophoresis (FFE, for proteomic analysis of colorectal cancer (CRC. CRC is a leading cause of cancer death in the Western world. Early detection is the single most important factor influencing outcome of CRC patients. If identified while the disease is still localized, CRC is treatable. To improve outcomes for CRC patients there is a pressing need to identify biomarkers for early detection (diagnostic markers, prognosis (prognostic indicators, tumour responses (predictive markers and disease recurrence (monitoring markers. Despite recent advances in the use of genomic analysis for risk assessment, in the area of biomarker identification genomic methods alone have yet to produce reliable candidate markers for CRC. For this reason, attention is being directed towards proteomics as a complementary analytical tool for biomarker identification. Here we describe a proteomics separation tool, which uses a combination of continuous FFE, a liquid-based isoelectric focusing technique, in the first dimension, followed by rapid reversed-phase HPLC (1–6 min/analysis in the second dimension. We have optimized imaging software to present the FFE/RP-HPLC data in a virtual 2D gel-like format. The advantage of this liquid based fractionation system over traditional gel-based fractionation systems is the ability to fractionate large quantity protein samples. Unlike 2D gels, the method is applicable to both high-Mr proteins and small peptides, which are difficult to separate, and in the case of peptides, are not retained in standard 2D gels.

  18. Numerical solutions of peristaltic flow of a Newtonian fluid under the effects of magnetic field and heat transfer in a porous concentric tubes

    Energy Technology Data Exchange (ETDEWEB)

    Nadeem, Sohail; Akbar, Noreen Sher; Malik, Muhammad Yousaf [Dept. of Mathematics, Quaid-i-Azam Univ., Islamabad (Pakistan)

    2010-05-15

    In the present article, we have studied the effects of heat transfer on a peristaltic flow of a magnetohydrodynamic (MHD) Newtonian fluid in a porous concentric horizontal tube (an application of an endoscope). The problem under consideration is formulated under the assumptions of long wave-length and neglecting the wave number. A closed form of Adomian solutions and numerical solutions are presented which show a complete agreement with each other. The influence of pertinent parameters is analyzed through graphs. (orig.)

  19. PHYSALIS: a new method for particle simulation. Part II: two-dimensional Navier-Stokes flow around cylinders

    Science.gov (United States)

    Takagi, S.; Og˜uz, H. N.; Zhang, Z.; Prosperetti, A.

    2003-05-01

    This paper presents a new approach to the direct numerical simulation of particle flows. The basic idea is to use a local analytic representation valid near the particle to "transfer" the no-slip condition from the particle surface to the adjacent grid nodes. In this way the geometric complexity arising from the irregular relation between the particle boundary and the underlying mesh is avoided and fast solvers can be used. The results suggest that the computational effort increases very slowly with the number of particles so that the method is efficient for large-scale simulations. The focus here is on the two-dimensional case (cylindrical particles), but the same procedure, to be developed in forthcoming papers, applies to three dimensions (spherical particles). Several extensions are briefly discussed.

  20. Wall interference in a two-dimensional-flow wind tunnel, with consideration of the effect of compressibility

    Science.gov (United States)

    Allen, H Julian; Vincenti, Walter G

    1944-01-01

    Theoretical tunnel-wall corrections are derived for an airfoil of finite thickness and camber in a two-dimensional-flow wind tunnel. The theory takes account of the effects of the wake of the airfoil and of the compressibility of the fluid, and is based upon the assumption that the chord of the airfoil is small in comparison with the height of the tunnel. Consideration is given to the phenomenon of choking at high speeds and its relation to the tunnel-wall corrections. The theoretical results are compared with the small amount of low-speed experimental data available and the agreement is seen to be satisfactory, even for relatively large values of the chord-height ratio.

  1. Considerations on the effect of wind-tunnel walls on oscillating air forces for two-dimensional subsonic compressible flow

    Science.gov (United States)

    Runyan, Harry L; Watkins, Charles E

    1953-01-01

    This report treats the effect of wind-tunnel walls on the oscillating two-dimensional air forces in a compressible medium. The walls are simulated by the usual method of placing images at appropriate distances above and below the wing. An important result shown is that, for certain conditions of wing frequency, tunnel height, and Mach number, the tunnel and wing may form a resonant system so that the forces on the wing are greatly changed from the condition of no tunnel walls. It is pointed out that similar conditions exist for three-dimensional flow in circular and rectangular tunnels and apparently, within certain Mach number ranges, in tunnels of nonuniform cross section or even in open tunnels or jets.

  2. Random attractors in $H^1$ for stochastic two dimensional micropolar fluid flows with spatial-valued noises

    Directory of Open Access Journals (Sweden)

    Wenqiang Zhao

    2014-11-01

    Full Text Available This work studies the long-time behavior of two-dimensional micropolar fluid flows perturbed by the generalized time derivative of the infinite dimensional Wiener processes. Based on the omega-limit compactness argument as well as some new estimates of solutions, it is proved that the generated random dynamical system admits an H^1-random attractor which is compact in H^1 space and attracts all tempered random subsets of L^2 space in H^1 topology. We also give a general abstract result which shows that the continuity condition and absorption of the associated random dynamical system in H^1 space is not necessary for the existence of random attractor in H^1 space.

  3. Global Structure of Three Distinct Accretion Flows and Outflows around Black Holes through Two-Dimensional Radiation-Magnetohydrodynamic Simulations

    CERN Document Server

    Ohsuga, Ken

    2011-01-01

    We present the detailed global structure of black hole accretion flows and outflows through newly performed two-dimensional radiation-magnetohydrodynamic simulations. By starting from a torus threaded with weak toroidal magnetic fields and by controlling the central density of the initial torus, rho_0, we can reproduce three distinct modes of accretion flow. In model A with the highest central density, an optically and geometrically thick supercritical accretion disk is created. The radiation force greatly exceeds the gravity above the disk surface, thereby driving a strong outflow (or jet). Because of the mild beaming, the apparent (isotropic) photon luminosity is ~22L_E (where L_E is the Eddington luminosity) in the face-on view. Even higher apparent luminosity is feasible if we increase the flow density. In model B with a moderate density, radiative cooling of the accretion flow is so efficient that a standard-type, cold, and geometrically thin disk is formed at radii greater than ~7R_S (where R_S is the S...

  4. 1r2dinv: A finite-difference model for inverse analysis of two dimensional linear or radial groundwater flow

    Science.gov (United States)

    Bohling, G.C.; Butler, J.J.

    2001-01-01

    We have developed a program for inverse analysis of two-dimensional linear or radial groundwater flow problems. The program, 1r2dinv, uses standard finite difference techniques to solve the groundwater flow equation for a horizontal or vertical plane with heterogeneous properties. In radial mode, the program simulates flow to a well in a vertical plane, transforming the radial flow equation into an equivalent problem in Cartesian coordinates. The physical parameters in the model are horizontal or x-direction hydraulic conductivity, anisotropy ratio (vertical to horizontal conductivity in a vertical model, y-direction to x-direction in a horizontal model), and specific storage. The program allows the user to specify arbitrary and independent zonations of these three parameters and also to specify which zonal parameter values are known and which are unknown. The Levenberg-Marquardt algorithm is used to estimate parameters from observed head values. Particularly powerful features of the program are the ability to perform simultaneous analysis of heads from different tests and the inclusion of the wellbore in the radial mode. These capabilities allow the program to be used for analysis of suites of well tests, such as multilevel slug tests or pumping tests in a tomographic format. The combination of information from tests stressing different vertical levels in an aquifer provides the means for accurately estimating vertical variations in conductivity, a factor profoundly influencing contaminant transport in the subsurface. ?? 2001 Elsevier Science Ltd. All rights reserved.

  5. Turbulent Friction in the Boundary Layer of a Flat Plate in a Two-Dimensional Compressible Flow at High Speeds

    Science.gov (United States)

    Frankl, F.; Voishel, V.

    1943-01-01

    In the present report an investigation is made on a flat plate in a two-dimensional compressible flow of the effect of compressibility and heating on the turbulent frictional drag coefficient in the boundary layer of an airfoil or wing radiator. The analysis is based on the Prandtl-Karman theory of the turbulent boundary later and the Stodola-Crocco, theorem on the linear relation between the total energy of the flow and its velocity. Formulas are obtained for the velocity distribution and the frictional drag law in a turbulent boundary later with the compressibility effect and heat transfer taken into account. It is found that with increase of compressibility and temperature at full retardation of the flow (the temperature when the velocity of the flow at a given point is reduced to zero in case of an adiabatic process in the gas) at a constant R (sub x), the frictional drag coefficient C (sub f) decreased, both of these factors acting in the same sense.

  6. Exact Analytical Solution of the Peristaltic Nanofluids Flow in an Asymmetric Channel with Flexible Walls and Slip Condition: Application to the Cancer Treatment

    Directory of Open Access Journals (Sweden)

    Abdelhalim Ebaid

    2013-01-01

    Full Text Available In the cancer treatment, magnetic nanoparticles are injected into the blood vessel nearest to the cancer’s tissues. The dynamic of these nanoparticles occurs under the action of the peristaltic waves generated on the flexible walls of the blood vessel. Studying such nanofluid flow under this action is therefore useful in treating tissues of the cancer. In this paper, the mathematical model describing the slip peristaltic flow of nanofluid was analytically investigated. Exact expressions were deduced for the temperature distribution and nano-particle concentration. In addition, the effects of the slip, thermophoresis, and Brownian motion parameters on the temperature and nano-particle concentration profiles were discussed and further compared with other approximate results in the literatures. In particular, these results have been obtained at the same values of the physical examined parameters that was considered in Akbar et al., “Peristaltic flow of a nanofluid with slip effects,” 2012. The results reveal that remarkable differences are detected between the exact current results and those approximately obtained in the literatures for behaviour of the temperature profile and nano-particles concentration. Accordingly, the current analysis and results are considered as optimal and therefore may be taken as a base for any future comparisons.

  7. Characterization of the left atrial vortex flow by two-dimensional transesophageal contrast echocardiography using particle image velocimetry.

    Science.gov (United States)

    Park, Kyu-Hwan; Son, Jang-Won; Park, Won-Jong; Lee, Sang-Hee; Kim, Ung; Park, Jong-Seon; Shin, Dong-Gu; Kim, Young-Jo; Choi, Jung-Hyun; Houle, Helene; Vannan, Mani A; Hong, Geu-Ru

    2013-01-01

    This article is the first clinical investigation of the quantitative left atrial (LA) vortex flow by two-dimensional (2-D) transesophageal contrast echocardiography (2-D-TECE) using vector particle image velocimetry (PIV). The aims of this study were to assess the feasibility of LA vortex flow analysis and to characterize and quantify the LA vortex flow in controls and in patients with atrial fibrillation (AF). Thirty-five controls and 30 patients with AF underwent transesophageal contrast echocardiography. The velocity vector was estimated by particle image velocimetry. The morphology and pulsatility of the LA vortex flow were compared between the control and AF groups. In all patients, quantitative LA vortex flow analysis was feasible. In the control group, multiple, pulsatile, compact and elliptical-shaped vortices were seen in the periphery of the LA. These vortices were persistently maintained and vectors were directed toward the atrioventricular inflow. In the AF group, a large, merged, lower pulsatile and round-shaped vortex was observed in the center of the LA. In comparisons of vortex parameters, the relative strength was significantly lower in the AF group (1.624 ± 0.501 vs. 2.105 ± 0.226, p < 0.001). It is feasible to characterize and quantify the LA vortex flow by transesophageal contrast echocardiography in patients with AF, which offers a new method to obtain additional information on LA hemodynamics. The approach has the potential for early detection of the LA dysfunction and in decisions regarding treatment strategy and guiding anticoagulation treatment in patients with AF.

  8. Direct experimental visualization of the global Hamiltonian progression of two-dimensional Lagrangian flow topologies from integrable to chaotic state.

    Science.gov (United States)

    Baskan, O; Speetjens, M F M; Metcalfe, G; Clercx, H J H

    2015-10-01

    Countless theoretical/numerical studies on transport and mixing in two-dimensional (2D) unsteady flows lean on the assumption that Hamiltonian mechanisms govern the Lagrangian dynamics of passive tracers. However, experimental studies specifically investigating said mechanisms are rare. Moreover, they typically concern local behavior in specific states (usually far away from the integrable state) and generally expose this indirectly by dye visualization. Laboratory experiments explicitly addressing the global Hamiltonian progression of the Lagrangian flow topology entirely from integrable to chaotic state, i.e., the fundamental route to efficient transport by chaotic advection, appear non-existent. This motivates our study on experimental visualization of this progression by direct measurement of Poincaré sections of passive tracer particles in a representative 2D time-periodic flow. This admits (i) accurate replication of the experimental initial conditions, facilitating true one-to-one comparison of simulated and measured behavior, and (ii) direct experimental investigation of the ensuing Lagrangian dynamics. The analysis reveals a close agreement between computations and observations and thus experimentally validates the full global Hamiltonian progression at a great level of detail.

  9. Direct experimental visualization of the global Hamiltonian progression of two-dimensional Lagrangian flow topologies from integrable to chaotic state

    Energy Technology Data Exchange (ETDEWEB)

    Baskan, O.; Clercx, H. J. H [Fluid Dynamics Laboratory, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Speetjens, M. F. M. [Energy Technology Laboratory, Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Metcalfe, G. [Commonwealth Scientific and Industrial Research Organisation, Melbourne, Victoria 3190 (Australia); Swinburne University of Technology, Department of Mechanical Engineering, Hawthorn VIC 3122 (Australia)

    2015-10-15

    Countless theoretical/numerical studies on transport and mixing in two-dimensional (2D) unsteady flows lean on the assumption that Hamiltonian mechanisms govern the Lagrangian dynamics of passive tracers. However, experimental studies specifically investigating said mechanisms are rare. Moreover, they typically concern local behavior in specific states (usually far away from the integrable state) and generally expose this indirectly by dye visualization. Laboratory experiments explicitly addressing the global Hamiltonian progression of the Lagrangian flow topology entirely from integrable to chaotic state, i.e., the fundamental route to efficient transport by chaotic advection, appear non-existent. This motivates our study on experimental visualization of this progression by direct measurement of Poincaré sections of passive tracer particles in a representative 2D time-periodic flow. This admits (i) accurate replication of the experimental initial conditions, facilitating true one-to-one comparison of simulated and measured behavior, and (ii) direct experimental investigation of the ensuing Lagrangian dynamics. The analysis reveals a close agreement between computations and observations and thus experimentally validates the full global Hamiltonian progression at a great level of detail.

  10. Simultaneous effects of single wall carbon nanotube and effective variable viscosity for peristaltic flow through annulus having permeable walls

    Science.gov (United States)

    Shahzadi, Iqra; Nadeem, S.; Rabiei, Faranak

    The current article deals with the combine effects of single wall carbon nanotubes and effective viscosity for the peristaltic flow of nanofluid through annulus. The nature of the walls is assumed to be permeable. The present theoretical model can be considered as mathematical representation to the motion of conductive physiological fluids in the existence of the endoscope tube which has many biomedical applications such as drug delivery system. The outer tube has a wave of sinusoidal nature that is travelling along its walls while the inner tube is rigid and uniform. Lubrication approach is used for the considered analysis. An empirical relation for the effective variable viscosity of nanofluid is proposed here interestingly. The viscosity of nanofluid is the function of radial distance and the concentration of nanoparticles. Exact solution for the resulting system of equations is displayed for various quantities of interest. The outcomes show that the maximum velocity of SWCNT-blood nanofluid enhances for larger values of viscosity parameter. The pressure gradient in the more extensive part of the annulus is likewise found to increase as a function of variable viscosity parameter. The size of the trapped bolus is also influenced by variable viscosity parameter. The present examination also revealed that the carbon nanotubes have many applications related to biomedicine.

  11. A numerical model for density-and-viscosity-dependent flows in two-dimensional variably saturated porous media

    Science.gov (United States)

    Boufadel, Michel C.; Suidan, Makram T.; Venosa, Albert D.

    1999-04-01

    We present a formulation for water flow and solute transport in two-dimensional variably saturated media that accounts for the effects of the solute on water density and viscosity. The governing equations are cast in a dimensionless form that depends on six dimensionless groups of parameters. These equations are discretized in space using the Galerkin finite element formulation and integrated in time using the backward Euler scheme with mass lumping. The modified Picard method is used to linearize the water flow equation. The resulting numerical model, the MARUN model, is verified by comparison to published numerical results. It is then used to investigate beach hydraulics at seawater concentration (about 30 g l -1) in the context of nutrients delivery for bioremediation of oil spills on beaches. Numerical simulations that we conducted in a rectangular section of a hypothetical beach revealed that buoyancy in the unsaturated zone is significant in soils that are fine textured, with low anisotropy ratio, and/or exhibiting low physical dispersion. In such situations, application of dissolved nutrients to a contaminated beach in a freshwater solution is superior to their application in a seawater solution. Concentration-engendered viscosity effects were negligible with respect to concentration-engendered density effects for the cases that we considered.

  12. A two-dimensional continuum model of biofilm growth incorporating fluid flow and shear stress based detachment

    KAUST Repository

    Duddu, Ravindra

    2009-05-01

    We present a two-dimensional biofilm growth model in a continuum framework using an Eulerian description. A computational technique based on the eXtended Finite Element Method (XFEM) and the level set method is used to simulate the growth of the biofilm. The model considers fluid flow around the biofilm surface, the advection-diffusion and reaction of substrate, variable biomass volume fraction and erosion due to the interfacial shear stress at the biofilm-fluid interface. The key assumptions of the model and the governing equations of transport, biofilm kinetics and biofilm mechanics are presented. Our 2D biofilm growth results are in good agreement with those obtained by Picioreanu et al. (Biotechnol Bioeng 69(5):504-515, 2000). Detachment due to erosion is modeled using two continuous speed functions based on: (a) interfacial shear stress and (b) biofilm height. A relation between the two detachment models in the case of a 1D biofilm is established and simulated biofilm results with detachment in 2D are presented. The stress in the biofilm due to fluid flow is evaluated and higher stresses are observed close to the substratum where the biofilm is attached. © 2008 Wiley Periodicals, Inc.

  13. Two dimensional modelling of flood flows and suspended sedimenttransport: the case of the Brenta River, Veneto (Italy

    Directory of Open Access Journals (Sweden)

    P. Martini

    2004-01-01

    Full Text Available The paper presents a numerical model for the simulation of flood waves and suspended sediment transport in a lowland river basin of North Eastern Italy. The two dimensional depth integrated momentum and continuity equations are modified to take into account the bottom irregularities that strongly affect the hydrodynamics in partially dry areas, as for example, in the first stages of an inundation process or in tidal flow. The set of equations are solved with a standard Galerkin finite element method using a semi-implicit numerical scheme where the effects of both the small channel network and the regulation devices on the flood wave propagation are accounted for. Transport of suspended sediment and bed evolution are coupled with the hydrodynamics using an appropriate form of the advection-dispersion equation and Exner's equation. Applications to a case study are presented in which the effects of extreme flooding on the Brenta River (Italy are examined. Urban and rural flood risk areas are identified and the effects of a alleviating action based on a diversion channel flowing into Venice Lagoon are simulated. The results show that this solution strongly reduces the flood risk in the downstream areas and can provide an important source of sediment for the Venice Lagoon. Finally, preliminary results of the sediment dispersion due to currents and waves in the Venice Lagoon are presented.

  14. Peristaltic particle transport using the Lattice Boltzmann method

    Energy Technology Data Exchange (ETDEWEB)

    Connington, Kevin William [Los Alamos National Laboratory; Kang, Qinjun [Los Alamos National Laboratory; Viswanathan, Hari S [Los Alamos National Laboratory; Abdel-fattah, Amr [Los Alamos National Laboratory; Chen, Shiyi [JOHNS HOPKINS UNIV.

    2009-01-01

    Peristaltic transport refers to a class of internal fluid flows where the periodic deformation of flexible containing walls elicits a non-negligible fluid motion. It is a mechanism used to transport fluid and immersed solid particles in a tube or channel when it is ineffective or impossible to impose a favorable pressure gradient or desirous to avoid contact between the transported mixture and mechanical moving parts. Peristaltic transport occurs in many physiological situations and has myriad industrial applications. We focus our study on the peristaltic transport of a macroscopic particle in a two-dimensional channel using the lattice Boltzmann method. We systematically investigate the effect of variation of the relevant dimensionless parameters of the system on the particle transport. We find, among other results, a case where an increase in Reynolds number can actually lead to a slight increase in particle transport, and a case where, as the wall deformation increases, the motion of the particle becomes non-negative only. We examine the particle behavior when the system exhibits the peculiar phenomenon of fluid trapping. Under these circumstances, the particle may itself become trapped where it is subsequently transported at the wave speed, which is the maximum possible transport in the absence of a favorable pressure gradient. Finally, we analyze how the particle presence affects stress, pressure, and dissipation in the fluid in hopes of determining preferred working conditions for peristaltic transport of shear-sensitive particles. We find that the levels of shear stress are most hazardous near the throat of the channel. We advise that shear-sensitive particles should be transported under conditions where trapping occurs as the particle is typically situated in a region of innocuous shear stress levels.

  15. Modeling performance of a two-dimensional capsule in a microchannel flow: long-term lateral migration.

    Science.gov (United States)

    Li, Hua; Ma, Gang

    2010-08-01

    The long-term lateral migration of a two-dimensional elastic capsule in a microchannel is studied numerically in this paper. The numerical method combines a finite volume technique for solving the fluid problem with a front tracking technique for capturing and tracking the capsule membrane. The capsule is modeled as a liquid medium enclosed by a thin membrane which has linear elastic properties. The capsule, whose initial shape is circle and which starts from a near-center position or a near-wall position, experiences tilting and membrane tank-treading, and migrates laterally when moving along the surrounding flow. The lateral migration demonstrates the existence of lift effect of surrounding flow on moving capsule. Before capsule approaches to the microchannel centerline closely, lower membrane dilation modulus and lower viscosity ratio tend to result in faster lateral migration. The initial position also influences the performance behavior of capsule, despite the lateral migration of capsule is a quasisteady process. Small difference in capsule behavior when capsule is not near to the microchannel centerline might lead to significant difference in capsule behavior when capsule approaches closely to the centerline. When capsules are near to microchannel wall, the effect of the wall on capsule behavior might dominate, leading to relatively faster lateral migration. When capsules are not far from microchannel centerline, the effect of the nonlinearity of Poiseuille flow might dominate, resulting in relatively slower lateral movement. When capsules are located closely to the centerline, they behave differently, where the reason still remains poorly understood and it will be one of our future studies. The comparison between the capsule behavior from the present simulation and that by the migration law proposed by Coupier [Phys. Fluids 20, 111702 (2008)] shows that the behavioral agreement for near-wall capsule is better than that for near-center capsule, and the best

  16. Two-dimensional aligned-field magnetofluiddynamic flow. I Steady incompressible flow with non-zero charge density

    Science.gov (United States)

    Yin, W.-L.

    1984-04-01

    It is shown that, in the case of non-zero charge density, the class of steady, plane, incompressible, aligned-fluid magnetofluiddynamic flows contains no rotational motions. Therefore, this class of flows is exhausted by the irrotational solutions of Kingston and Power.

  17. Numerical Simulation of Particle Flow Motion in a Two-Dimensional Modular Pebble-Bed Reactor with Discrete Element Method

    Directory of Open Access Journals (Sweden)

    Guodong Liu

    2013-01-01

    Full Text Available Modular pebble-bed nuclear reactor (MPBNR technology is promising due to its attractive features such as high fuel performance and inherent safety. Particle motion of fuel and graphite pebbles is highly associated with the performance of pebbled-bed modular nuclear reactor. To understand the mechanism of pebble’s motion in the reactor, we numerically studied the influence of number ratio of fuel and graphite pebbles, funnel angle of the reactor, height of guide ring on the distribution of pebble position, and velocity by means of discrete element method (DEM in a two-dimensional MPBNR. Velocity distributions at different areas of the reactor as well as mixing characteristics of fuel and graphite pebbles were investigated. Both fuel and graphite pebbles moved downward, and a uniform motion was formed in the column zone, while pebbles motion in the cone zone was accelerated due to the decrease of the cross sectional flow area. The number ratio of fuel and graphite pebbles and the height of guide ring had a minor influence on the velocity distribution of pebbles, while the variation of funnel angle had an obvious impact on the velocity distribution. Simulated results agreed well with the work in the literature.

  18. NUMERICAL SIMULATION OF UNSTEADY TURBULENT FLOW INDUCED BY TWO-DIMENSIONAL ELEVATOR CAR AND COUNTER WEIGHT SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A two-dimensional model of unsteady turbulent flow induced by high-speed elevator system was established in the present study. The research was focused on the instantaneous variation of the aerodynamic force on the car structure during traversing motion of the counter weight in the hoistway. A dynamic meshing method was employed to treat the multi-body motion system to avoid poor distortion of meshes. A comprehensive understanding of this significant aspect was obtained by varying the horizontal gap (δ=0.1m, 0.2m, and 0.3m) between the elevator car and the counter weight, and the moving speed (U0=2m/s, 6m/s, and 10m/s) of the elevator system. A pulsed intensification of the aerodynamic force on the elevator car and subsequent appearance of large valley with negative aerodynamic force were clearly observed in the numerical results. In parameters studied (δ=0.1m, U0=2m/s, 6m/s, 10m/s), the peaked horizontal and vertical forces are respectively 7-11 and 4.3-5.65 times of that when the counter weight is far from the car. These results demonstrated the prominent influence of the traversing counter weight on aerodynamic force on the elevator car, which is of great significance to designers of high-speed elevator system.

  19. Diverse effects of two-dimensional and step flow growth mode induced microstructures on the magnetic anisotropies of SrRuO[subscript3] thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Y.Z.; Chmaissem, O.; Kolesnik, S.; Ullah, A.; Lurio, L.B.; Brown, D.E.; Brady, J.; Dabrowski, B.; Kimball, C.W.; Haji-Sheikh, M.; Genis, A.P. (NIU)

    2010-12-03

    Geometrical anisotropy axes of diverse SrRuO{sub 3} (SRO) films grown by random and directional two-dimensional and step flow modes are determined and their characteristic angular magnetizations are understood in terms of growth mode induced structural effects. Two-dimensional SRO films possess single-crystal-like structural qualities. Angular magnetization measurements show sharp minima and indicate the films easy axis to be in the [310] direction. In contrast, examination of step flow SRO films shows the presence of degenerate multiple in-plane domains and the anisotropy axis in a direction close to [110] even though directional surface steps are clearly visible.

  20. Hall and radial magnetic field effects on radiative peristaltic flow of Carreau-Yasuda fluid in a channel with convective heat and mass transfer

    Science.gov (United States)

    Hayat, T.; Farooq, S.; Alsaedi, A.; Ahmad, B.

    2016-08-01

    The purpose of present investigation is to study the Hall and MHD effects on peristaltic flow of Carreau-Yasuda fluid in a convectively curved configuration. Thermal radiation, Soret and Dufour effects are also accounted. The channel walls comprised the no slip and compliant properties. Constitutive equations for mass, momentum, energy and concentration are first modeled in view of considered assumptions and then simplified under long wavelength and low Reynolds number approximation. Solution of the resulting system of equations is carried out via a regular perturbation technique. Physical behaviors of velocity, temperature, concentration and streamlines are discussed with the help of graphical representation.

  1. LLUVIA-II: A program for two-dimensional, transient flow through partially saturated porous media; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, R.R.; Hopkins, P.L.

    1992-08-01

    LLUVIA-II is a program designed for the efficient solution of two- dimensional transient flow of liquid water through partially saturated, porous media. The code solves Richards equation using the method-of-lines procedure. This document describes the solution procedure employed, input data structure, output, and code verification.

  2. Model the nonlinear instability of wall-bounded shear flows as a rare event: a study on two-dimensional Poiseuille flow

    Science.gov (United States)

    Wan, Xiaoliang; Yu, Haijun; Weinan, E.

    2015-05-01

    In this work, we study the nonlinear instability of two-dimensional (2D) wall-bounded shear flows from the large deviation point of view. The main idea is to consider the Navier-Stokes equations perturbed by small noise in force and then examine the noise-induced transitions between the two coexisting stable solutions due to the subcritical bifurcation. When the amplitude of the noise goes to zero, the Freidlin-Wentzell (F-W) theory of large deviations defines the most probable transition path in the phase space, which is the minimizer of the F-W action functional and characterizes the development of the nonlinear instability subject to small random perturbations. Based on such a transition path we can define a critical Reynolds number for the nonlinear instability in the probabilistic sense. Then the action-based stability theory is applied to study the 2D Poiseuille flow in a short channel.

  3. Hydrologic Analysis and Two-Dimensional Simulation of Flow at State Highway 17 crossing the Gasconade River near Waynesville, Missouri

    Science.gov (United States)

    Huizinga, Richard J.

    2008-01-01

    In cooperation with the Missouri Department of Transportation, the U.S. Geological Survey determined hydrologic and hydraulic parameters for the Gasconade River at the site of a proposed bridge replacement and highway realignment of State Highway 17 near Waynesville, Missouri. Information from a discontinued streamflow-gaging station on the Gasconade River near Waynesville was used to determine streamflow statistics for analysis of the 25-, 50-, 100-, and 500-year floods at the site. Analysis of the streamflow-gaging stations on the Gasconade River upstream and downstream from Waynesville indicate that flood peaks attenuate between the upstream gaging station near Hazelgreen and the Waynesville gaging station, such that the peak discharge observed on the Gasconade River near Waynesville will be equal to or only slightly greater (7 percent or less) than that observed near Hazelgreen. A flood event occurred on the Gasconade River in March 2008, and a flood measurement was obtained near the peak at State Highway 17. The elevation of high-water marks from that event indicated it was the highest measured flood on record with a measured discharge of 95,400 cubic feet per second, and a water-surface elevation of 766.18 feet near the location of the Waynesville gaging station. The measurements obtained for the March flood resulted in a shift of the original stage-discharge relation for the Waynesville gaging station, and the streamflow statistics were modified based on the new data. A two-dimensional hydrodynamic flow model was used to simulate flow conditions on the Gasconade River in the vicinity of State Highway 17. A model was developed that represents existing (2008) conditions on State Highway 17 (the 'model of existing conditions'), and was calibrated to the floods of March 20, 2008, December 4, 1982, and April 14, 1945. Modifications were made to the model of existing conditions to create a model that represents conditions along the same reach of the Gasconade

  4. Two-Dimensional Rotorcraft Downwash Flow Field Measurements by Lidar-Based Wind Scanners with Agile Beam Steering

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Angelou, Nikolas; Hansen, Per

    2014-01-01

    position; all points in space within a cone with a full opening angle of 1208 can be reached from about 8mout to some hundred meters depending on the range resolution required. The first two-dimensional mean wind fields measured in a horizontal plane and in a vertical plane below a hovering search...

  5. Stability of a flow down an incline with respect to two-dimensional and three-dimensional disturbances for Newtonian and non-Newtonian fluids.

    Science.gov (United States)

    Allouche, M H; Millet, S; Botton, V; Henry, D; Ben Hadid, H; Rousset, F

    2015-12-01

    Squire's theorem, which states that the two-dimensional instabilities are more dangerous than the three-dimensional instabilities, is revisited here for a flow down an incline, making use of numerical stability analysis and Squire relationships when available. For flows down inclined planes, one of these Squire relationships involves the slopes of the inclines. This means that the Reynolds number associated with a two-dimensional wave can be shown to be smaller than that for an oblique wave, but this oblique wave being obtained for a larger slope. Physically speaking, this prevents the possibility to directly compare the thresholds at a given slope. The goal of the paper is then to reach a conclusion about the predominance or not of two-dimensional instabilities at a given slope, which is of practical interest for industrial or environmental applications. For a Newtonian fluid, it is shown that, for a given slope, oblique wave instabilities are never the dominant instabilities. Both the Squire relationships and the particular variations of the two-dimensional wave critical curve with regard to the inclination angle are involved in the proof of this result. For a generalized Newtonian fluid, a similar result can only be obtained for a reduced stability problem where some term connected to the perturbation of viscosity is neglected. For the general stability problem, however, no Squire relationships can be derived and the numerical stability results show that the thresholds for oblique waves can be smaller than the thresholds for two-dimensional waves at a given slope, particularly for large obliquity angles and strong shear-thinning behaviors. The conclusion is then completely different in that case: the dominant instability for a generalized Newtonian fluid flowing down an inclined plane with a given slope can be three dimensional.

  6. Enhancement of plume dilution in two-dimensional and three-dimensional porous media by flow focusing in high-permeability inclusions

    Science.gov (United States)

    Ye, Yu; Chiogna, Gabriele; Cirpka, Olaf A.; Grathwohl, Peter; Rolle, Massimo

    2015-07-01

    In porous media, lateral mass exchange exerts a significant influence on the dilution of solute plumes in quasi steady state. This process is one of the main mechanisms controlling transport of continuously emitted conservative tracers in groundwater and is fundamental for the understanding of many degradation processes. We investigate the effects of high-permeability inclusions on transverse mixing in three-dimensional versus two-dimensional systems by experimental, theoretical, and numerical analyses. Our results show that mixing enhancement strongly depends on the system dimensionality and on the parameterization used to model transverse dispersion. In particular, no enhancement of transverse mixing would occur in three-dimensional media if the local transverse dispersion coefficient was uniform and flow focusing in both transverse directions was identical, which is fundamentally different from the two-dimensional case. However, the velocity and grain size dependence of the transverse dispersion coefficient and the correlation between hydraulic conductivity and grain size lead to prevailing mixing enhancement within the inclusions, regardless of dimensionality. We perform steady state bench-scale experiments with multiple tracers in three-dimensional and quasi two-dimensional flow-through systems at two different velocities (1 and 5 m/d). We quantify transverse mixing by the flux-related dilution index and compare the experimental results with model simulations. The experiments confirm that, although dilution is larger in three-dimensional systems, the enhancement of transverse mixing due to flow focusing is less effective than in two-dimensional systems. The spatial arrangement of the high-permeability inclusions significantly affects the degree of mixing enhancement. We also observe more pronounced compound-specific effects in the dilution of solute plumes in three-dimensional porous media than in two-dimensional ones.

  7. Peristaltic transport of Conducting Bingham fluid in contact with a Newtonian fluid in a channel

    Directory of Open Access Journals (Sweden)

    M.Arun kumar

    2013-04-01

    Full Text Available Peristaltic pumping by a sinusoidal traveling wave in the walls of a two dimensional channel filled with two immiscible fluids with magnetic effect is investigated. The core region of the channel is occupied by a Bingham fluid where as the peripheral region is occupied by a Newtonian fluid. The flow is examined in a wave frame of reference moving with the velocity of the wave. The expressions for the stream function, the velocity and the pressure rise are obtained. The equation for the interface separating the two fluids is obtained. Numerical results are reported for several of the physical parameters of interest. We observed that the lower values of

  8. Linear stability of horizontal, laminar fully developed, quasi-two-dimensional liquid metal duct flow under a transverse magnetic field and heated from below

    Science.gov (United States)

    Vo, Tony; Pothérat, Alban; Sheard, Gregory J.

    2017-03-01

    This study considers the linear stability of Poiseuille-Rayleigh-Bénard flows subjected to a transverse magnetic field, to understand the instabilities that arise from the complex interaction between the effects of shear, thermal stratification, and magnetic damping. This fundamental study is motivated in part by the desire to enhance heat transfer in the blanket ducts of nuclear fusion reactors. In pure magnetohydrodynamic flows, the imposed transverse magnetic field causes the flow to become quasi-two-dimensional and exhibit disturbances that are localized to the horizontal walls. However, the vertical temperature stratification in Rayleigh-Bénard flows feature convection cells that occupy the interior region, and therefore the addition of this aspect provides an interesting point for investigation. The linearized governing equations are described by the quasi-two-dimensional model proposed by Sommeria and Moreau [J. Fluid Mech. 118, 507 (1982), 10.1017/S0022112082001177], which incorporates a Hartmann friction term, and the base flows are considered fully developed and one-dimensional. The neutral stability curves for critical Reynolds and Rayleigh numbers, Rec and Rac, respectively, as functions of Hartmann friction parameter H have been obtained over 10-2≤H ≤104 . Asymptotic trends are observed as H →∞ following Rec∝H1 /2 and Rac∝H . The linear stability analysis reveals multiple instabilities which alter the flow both within the Shercliff boundary layers and the interior flow, with structures consistent with features from plane Poiseuille and Rayleigh-Bénard flows.

  9. Hall and Joule heating effects on peristaltic flow of Powell-Eyring liquid in an inclined symmetric channel

    Science.gov (United States)

    Hayat, T.; Aslam, Naseema; Rafiq, M.; Alsaadi, Fuad E.

    This article is intended to investigate the influence of Hall current on peristaltic transport of conducting Eyring-Powell fluid in an inclined symmetric channel. Energy equation is modeled by taking Joule heating effect into consideration. Velocity and thermal slip conditions are imposed. Lubrication approximation is considered for the analysis. Fundamental equations are non-linear due to fluid parameter A. Regular perturbation technique is employed to find the solution of systems of equations. The key roles of different embedded parameters on velocity, temperature and heat transfer coefficient in the problem are discussed graphically. Trapping phenomenon is analyzed carefully.

  10. Peristaltic flow of a couple stress fluid under the effect of induced magnetic field in an asymmetric channel

    Energy Technology Data Exchange (ETDEWEB)

    Nadeem, Sohail; Akram, Safia [Quaid-i-Azam University, Department of Mathematics, Islamabad (Pakistan)

    2011-01-15

    The present paper investigates the peristaltic transport of a couple stress fluid in an asymmetric channel with the effect of the induced magnetic field. The exact solutions of momentum and the magnetic field equations have been calculated under the assumptions of long wave length and low but finite Reynolds number. The expression for pressure rise has been computed numerically using mathematics software Mathematica. The graphical results have been presented to discuss the physical behavior of various physical parameters of interest. Finally, the trapping phenomena have been discussed for various physical parameters. (orig.)

  11. Effect of velocity boundary conditions on the heat transfer and flow topology in two-dimensional Rayleigh-Bénard convection.

    Science.gov (United States)

    van der Poel, Erwin P; Ostilla-Mónico, Rodolfo; Verzicco, Roberto; Lohse, Detlef

    2014-07-01

    The effect of various velocity boundary condition is studied in two-dimensional Rayleigh-Bénard convection. Combinations of no-slip, stress-free, and periodic boundary conditions are used on both the sidewalls and the horizontal plates. For the studied Rayleigh numbers Ra between 10(8) and 10(11) the heat transport is lower for Γ=0.33 than for Γ=1 in case of no-slip sidewalls. This is, surprisingly, the opposite for stress-free sidewalls, where the heat transport increases for a lower aspect ratio. In wider cells the aspect-ratio dependence is observed to disappear for Ra ≥ 10(10). Two distinct flow types with very different dynamics can be seen, mostly dependent on the plate velocity boundary condition, namely roll-like flow and zonal flow, which have a substantial effect on the dynamics and heat transport in the system. The predominantly horizontal zonal flow suppresses heat flux and is observed for stress-free and asymmetric plates. Low aspect-ratio periodic sidewall simulations with a no-slip boundary condition on the plates also exhibit zonal flow. In all the other cases, the flow is roll like. In two-dimensional Rayleigh-Bénard convection, the velocity boundary conditions thus have large implications on both roll-like and zonal flow that have to be taken into consideration before the boundary conditions are imposed.

  12. An efficient, direct finite difference method for computing sound propagation in arbitrarily shaped two-dimensional and axisymmetric ducts without flow

    Science.gov (United States)

    Chakravarthy, S.

    1978-01-01

    An efficient, direct finite difference method is presented for computing sound propagation in non-stepped two-dimensional and axisymmetric ducts of arbitrarily varying cross section without mean flow. The method is not restricted by axial variation of acoustic impedance of the duct wall linings. The non-uniform two-dimensional or axisymmetric duct is conformally mapped numerically into a rectangular or cylindrical computational domain using a new procedure based on a method of fast direct solution of the Cauchy-Riemann equations. The resulting Helmholtz equation in the computational domain is separable. The solution to the governing equation and boundary conditions is expressed as a linear combination of fundamental solutions. The fundamental solutions are computed only once for each duct shape by means of the fast direct cyclic reduction method for the discrete solution of separable elliptic equations. Numerical results for several examples are presented to show the applicability and efficiency of the method.

  13. Peristaltic Flow and Heat Transfer of a Conducting Phan-Thien-Tanner Fluid in an Asymmetric Channel - Application to Chyme Movement in Small Intestine

    Science.gov (United States)

    Vajravelu, K.; Sreenadh, S.; Dhananjaya, S.; Lakshminarayana, P.

    2016-08-01

    In this paper, the influence of heat transfer on the peristaltic flow of a conducting Phan-Thien-Tanner fluid in an asymmetric channel with porous medium is studied. The coupled nonlinear governing differential equations are solved by a perturbation technique. The expressions for the temperature field, the stream function, the axial velocity, and the pressure gradient are obtained. The effects of the various physical parameters such as the magnetic parameter M, the permeability parameter σ, the Brinkman number Br and the Weissenberg number We on the pumping phenomenon are analyzed through graphs and the results are discussed in detail. It is observed that the velocity and the pressure are decreased with increasing the magnetic parameter M whereas the effect of the parameter M on the temperature field is quite the opposite.

  14. Role of Inclined Magnetic Field and Copper Nanoparticles on Peristaltic Flow of Nanofluid through Inclined Annulus: Application of the Clot Model

    Science.gov (United States)

    Shahzadi, Iqra; Nadeem, S.

    2017-06-01

    A genuine neurotic condition is experienced when some blood constituents accumulate on the wall of the artery get withdrew from the wall, again join the circulatory system and coagulation occur. Role of copper nanoparticles and inclined magnetic field on the peristaltic flow of a nanofluid in an annular region of inclined annulus is investigated. We represent the clot model by considering the small artery as an annulus whose outer tube has a wave of sinusoidal nature and inner tube has a clot on its walls. Lubrication approach is used to simplify the problem. Close form solutions are determined for temperature and velocity profile. Impact of related parameters on pressure rise, pressure gradient, velocity and streamlines are interpreted graphically. Comparison among the pure blood and copper blood is presented and analyzed. One main finding of the considered analysis is that the inclusion of copper nanoparticles enlarges the amplitude of the velocity. Therefore, the considered study plays a dominant role in biomedical applications.

  15. Heat transfer in the flow of a cold, two-dimensional vertical liquid jet against a hot, horizontal plate

    CERN Document Server

    Shu, Jian-Jun

    2014-01-01

    A cold, thin film of liquid impinging on an isothermal hot, horizontal surface has been investigated. An approximate solution for the velocity and temperature distributions in the flow along the horizontal surface is developed, which exploits the hydrodynamic similarity solution for thin film flow. The approximate solution may provide a valuable basis for assessing flow and heat transfer in more complex settings.

  16. Effect of wall suction on the stability of compressible subsonic flows over smooth two-dimensional backward-facing steps

    Science.gov (United States)

    Al-Maaitah, Ayman A.; Nayfeh, Ali H.; Ragab, Saad A.

    1989-01-01

    The effect of suction on the stability of compressible flows over backward-facing steps is investigated. Mach numbers up to 0.8 are considered. The results show that continuous suction stabilizes the flow outside the separation bubble, but it destabilizes the flow inside it. Nevertheless, the overall N factor decreases as the suction level increases due to the considerable reduction of the separation bubble. For the same suction flow rate, properly distributed suction strips stabilize the flow more than continuous suction. The size of the separation bubble, and hence its effect on the instability can be considerably reduced by placing strips with high suction velocities in the separation region.

  17. Coupled One and Two Dimensional Model for River Network Flow and Sediment Transport%一二维耦合河网水沙模型研究

    Institute of Scientific and Technical Information of China (English)

    吕文丽; 张旭

    2011-01-01

    Based on previous research, a new one and two-dimensional coupled model of river water and sediment was proposed.With reference to the three-level solution for one-dimensional river network water mode, the two-dimensional river section will be generalized to river section within the river network.One and two dimensional coupled river network sediment model will be established with the balance of flow amount and sediment transport.The model sets up the chasing relationship between variables of water level and sediment content at the end and first section to further establish matrix equations of the whole one and two-dimensional river network node water level and sediment content.Though the verification and calculation for generalized river network from Datong to Zhenjiang in the lower reaches of the Yangtze River, it is found that the model is of great practical value.%借鉴河网水流的三级解法,将二维河段概化为河网内部河段,通过河网节点流量和输沙量的平衡,建立一二维耦合河网水沙模型.模型采用全隐式方法建立二维河段以首末断面的水位和含沙量为中间变量的矩阵追赶关系,进而建立整个一二维河网的节点水位及含沙量的矩阵方程组.对方程组的求解,可实现一二维水沙模型的耦合求解.通过对长江下游大通至镇江概化河网的验证计算,表明模型具有很好的实用价值.

  18. Two-dimensional simulation of Poiseuille-Rayleigh-Bénard flows in binary fluids with Soret effect

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Poiseuille-Rayleigh-Bénard flows in binary fluids with Soret effect are directly simulated by a mixed finite element method.A temperature perturbation is used as an initial disturbed source for the basic parallel flows.The whole spatio-temporal evolution of the binary fluid flows is exhibited:initially only the disturbed mode with the wavenumber k=π is amplified while others are damped.and continuously the amplified mode grows further and the nonlinear effect becomes important;after a nonlinear evolution transition the flow system evolves finally into a periodic right traveling wave.

  19. A Unified Two-Dimensional Approach to the Calculation of Three- Dimensional Hypersonic Flows, with Application to Bodies of Revolution

    Science.gov (United States)

    1955-01-01

    8217rinRE-DifMENSONAL HtYPERtSONIC 15.W indicated-flow-separation oin the leewardl side of (lie body for excellent agreemelnt in tlie plano of symmlletry...REIMARKS b~ound~ary layers may, inl like imanner, prove useful il- pie - A mnethod of characteristics employing p)ressure and-flow deigdrednesoa

  20. Smoothed particle hydrodynamics method applied to pulsatile flow inside a rigid two-dimensional model of left heart cavity.

    Science.gov (United States)

    Shahriari, S; Kadem, L; Rogers, B D; Hassan, I

    2012-11-01

    This paper aims to extend the application of smoothed particle hydrodynamics (SPH), a meshfree particle method, to simulate flow inside a model of the heart's left ventricle (LV). This work is considered the first attempt to simulate flow inside a heart cavity using a meshfree particle method. Simulating this kind of flow, characterized by high pulsatility and moderate Reynolds number using SPH is challenging. As a consequence, validation of the computational code using benchmark cases is required prior to simulating the flow inside a model of the LV. In this work, this is accomplished by simulating an unsteady oscillating flow (pressure amplitude: A = 2500 N ∕ m(3) and Womersley number: W(o)  = 16) and the steady lid-driven cavity flow (Re = 3200, 5000). The results are compared against analytical solutions and reference data to assess convergence. Then, both benchmark cases are combined and a pulsatile jet in a cavity is simulated and the results are compared with the finite volume method. Here, an approach to deal with inflow and outflow boundary conditions is introduced. Finally, pulsatile inlet flow in a rigid model of the LV is simulated. The results demonstrate the ability of SPH to model complex cardiovascular flows and to track the history of fluid properties. Some interesting features of SPH are also demonstrated in this study, including the relation between particle resolution and sound speed to control compressibility effects and also order of convergence in SPH simulations, which is consistently demonstrated to be between first-order and second-order at the moderate Reynolds numbers investigated.

  1. Use of variable weighting to eliminate numerical diffusion in two-dimensional two-phase flow in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Lasseter, T.J.; Karakas, M.

    1982-01-01

    A simple numerical method has been developed that largely eliminates numerical diffusion errors associated with saturation discontinuities or shocks for two-phase flow in one and two dimensions. The important aspect of the approach is the computation of a variable weighting factor for the interface fractional flow between grid blocks. The approach appears to be generalizable to the multicomponent, multidimensional case including gravity and capilarity. 5 refs.

  2. MOFAT: A two-dimensional finite-element program for multiphase flow and multicomponent transport. Program documentation and user's guide

    Energy Technology Data Exchange (ETDEWEB)

    Katyal, A.K.; Kaluarachchi, J.J.; Parker, J.C.

    1991-05-01

    The manual describes a two-dimensional finite element model for coupled multiphase flow and multicomponent transport in planar or radially symmetric vertical sections. Flow and transport of three fluid phases, including water, nonaqueous phase liquid (NAPL), and gas are considered by the program. The program can simulate flow only or coupled flow and transport. The flow module can be used to analyze two phases, water and NAPL, with the gas phase held at constant pressure, or explicit three-phase flow of water, NAPL, and gas at various pressures. The transport module can handle up to five components which partition among water, NAPL, gas and solid phases assuming either local equilibrium or first-order mass transfer. Three phase permeability-saturation-capillary pressure relations are defined by an extension of the van Genuchten model. The governing equations are solved using an efficient upstream-weighted finite element scheme. The report describes the required inputs for flow analysis and transport analysis. Time dependent boundary conditions for flow and transport analysis can be handled by the program and are described in the report. Detailed instructions for creating data files needed to run the program and example input and output files are given in appendices.

  3. Magneto-Hydrodynamic Flow in a Two-Dimensional Inclined Rectangular Enclosure Heated and Cooled on Adjacent Walls

    Directory of Open Access Journals (Sweden)

    M.N Kherief

    2016-01-01

    Full Text Available Steady, laminar, natural-convection flow in the presence of a magnetic field in an inclined rectangular enclosure heated from one side and cooled from the adjacent side was considered. The governing equations were solved numerically for the stream function, vorticity and temperature using the finite-volume method for various Grashof and Hartman numbers and inclination angles and magnetic field directions. The results show that the orientation and the strength and direction of the magnetic field have significant effects on the flow and temperature fields. Counterclockwise inclination induces the formation of multiple eddies inside the enclosure significantly affecting the temperature field. Circulation inside the enclosure and therefore the convection become stronger as the Grashof number increases while the magnetic field suppresses the convective flow and the heat transfer rate.

  4. History independence of steady state in simultaneous two-phase flow through two-dimensional porous media.

    Science.gov (United States)

    Erpelding, Marion; Sinha, Santanu; Tallakstad, Ken Tore; Hansen, Alex; Flekkøy, Eirik Grude; Måløy, Knut Jørgen

    2013-11-01

    It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.

  5. Numerical Model of Formaldehyde Photo-Oxidation in a Two Dimensional Flow Field Over Cylindrical UV Light Sources

    Science.gov (United States)

    2012-05-10

    light (Schmelzle, 1994 and Albano , 1994). The kinetic mechanisms were incorporated into the flow field model by introducing the species mass... Albano , M., 1994. Computer Simulation of a Photolytic Reactor to Study the Effects of a Variety of Wavelengths, A Thesis in Environmental Pollution

  6. PHYSALIS: a new method for particle simulation: Part II: two-dimensional Navier–Stokes flow around cylinders

    NARCIS (Netherlands)

    Takagi, S.; Oguz, H.N.; Zhang, Z.; Prosperetti, A.

    2003-01-01

    This paper presents a new approach to the direct numerical simulation of particle flows. The basic idea is to use a local analytic representation valid near the particle to “transfer” the no-slip condition from the particle surface to the adjacent grid nodes. In this way the geometric complexity ari

  7. Two-Dimensional Flow Nanometry of Biological Nanoparticles for Accurate Determination of Their Size and Emission Intensity

    CERN Document Server

    Block, Stephan; Lundgren, Anders; Zhdanov, Vladimir P; Höök, Fredrik

    2016-01-01

    Biological nanoparticles (BNPs) are of high interest due to their key role in various biological processes and use as biomarkers. BNP size and molecular composition are decisive for their functions, but simultaneous determination of both properties with high accuracy remains challenging, which is a severe limitation. Surface-sensitive microscopy allows one to precisely determine fluorescence or scattering intensity, but not the size of individual BNPs. The latter is better determined by tracking their random motion in bulk, but the limited illumination volume for tracking this motion impedes reliable intensity determination. We here show that attaching BNPs (specifically, vesicles and functionalized gold NPs) to a supported lipid bilayer, subjecting them to a hydrodynamic flow, and tracking their motion via surface-sensitive imaging enable to determine their diffusion coefficients and flow-induced drift velocities and to accurately quantify both BNP size and emission intensity. For vesicles, the high accuracy...

  8. Two-dimensional flow nanometry of biological nanoparticles for accurate determination of their size and emission intensity

    Science.gov (United States)

    Block, Stephan; Fast, Björn Johansson; Lundgren, Anders; Zhdanov, Vladimir P.; Höök, Fredrik

    2016-09-01

    Biological nanoparticles (BNPs) are of high interest due to their key role in various biological processes and use as biomarkers. BNP size and composition are decisive for their functions, but simultaneous determination of both properties with high accuracy remains challenging. Optical microscopy allows precise determination of fluorescence/scattering intensity, but not the size of individual BNPs. The latter is better determined by tracking their random motion in bulk, but the limited illumination volume for tracking this motion impedes reliable intensity determination. Here, we show that by attaching BNPs to a supported lipid bilayer, subjecting them to hydrodynamic flows and tracking their motion via surface-sensitive optical imaging enable determination of their diffusion coefficients and flow-induced drifts, from which accurate quantification of both BNP size and emission intensity can be made. For vesicles, the accuracy of this approach is demonstrated by resolving the expected radius-squared dependence of their fluorescence intensity for radii down to 15 nm.

  9. Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

    Science.gov (United States)

    Gai, Ya; Leong, Chia Min; Cai, Wei; Tang, Sindy K. Y.

    2016-10-01

    When a many-body system is driven away from equilibrium, order can spontaneously emerge in places where disorder might be expected. Here we report an unexpected order in the flow of a concentrated emulsion in a tapered microfluidic channel. The velocity profiles of individual drops in the emulsion show periodic patterns in both space and time. Such periodic patterns appear surprising from both a fluid and a solid mechanics point of view. In particular, when the emulsion is considered as a soft crystal under extrusion, a disordered scenario might be expected based on the stochastic nature of dislocation dynamics in microscopic crystals. However, an orchestrated sequence of dislocation nucleation and migration is observed to give rise to a highly ordered deformation mode. This discovery suggests that nanocrystals can be made to deform more controllably than previously thought. It can also lead to novel flow control and mixing strategies in droplet microfluidics.

  10. A pore scale study on fluid flow through two dimensional dual scale porous media with small number of intraparticle pores

    Directory of Open Access Journals (Sweden)

    Sabet Safa

    2016-03-01

    Full Text Available In the present study, the fluid flow in a periodic, non-isotropic dual scale porous media consisting of permeable square rods in inline arrangement is analyzed to determine permeability, numerically. The continuity and Navier-Stokes equations are solved to obtain the velocity and pressure distributions in the unit structures of the dual scale porous media for flows within Darcy region. Based on the obtained results, the intrinsic inter and intraparticle permeabilities and the bulk permeability tensor of the dual scale porous media are obtained for different values of inter and intraparticle porosities. The study is performed for interparticle porosities between 0.4 and 0.75 and for intraparticle porosities from 0.2 to 0.8. A correlation based on Kozeny-Carman relationship in terms of inter and intraparticle porosities and permeabilities is proposed to determine the bulk permeability tensor of the dual scale porous media.

  11. Image analysis method for the measurement of water saturation in a two-dimensional experimental flow tank

    Science.gov (United States)

    Belfort, Benjamin; Weill, Sylvain; Lehmann, François

    2017-07-01

    A novel, non-invasive imaging technique is proposed that determines 2D maps of water content in unsaturated porous media. This method directly relates digitally measured intensities to the water content of the porous medium. This method requires the classical image analysis steps, i.e., normalization, filtering, background subtraction, scaling and calibration. The main advantages of this approach are that no calibration experiment is needed, because calibration curve relating water content and reflected light intensities is established during the main monitoring phase of each experiment and that no tracer or dye is injected into the flow tank. The procedure enables effective processing of a large number of photographs and thus produces 2D water content maps at high temporal resolution. A drainage/imbibition experiment in a 2D flow tank with inner dimensions of 40 cm × 14 cm × 6 cm (L × W × D) is carried out to validate the methodology. The accuracy of the proposed approach is assessed using a statistical framework to perform an error analysis and numerical simulations with a state-of-the-art computational code that solves the Richards' equation. Comparison of the cumulative mass leaving and entering the flow tank and water content maps produced by the photographic measurement technique and the numerical simulations demonstrate the efficiency and high accuracy of the proposed method for investigating vadose zone flow processes. Finally, the photometric procedure has been developed expressly for its extension to heterogeneous media. Other processes may be investigated through different laboratory experiments which will serve as benchmark for numerical codes validation.

  12. Impulse transfer in a turbulent flow with two-dimensional structure of disturbances in a homogeneous shear region

    Energy Technology Data Exchange (ETDEWEB)

    Votsish, A.D.

    1977-07-01

    Results are given for experimental studies of the effect that a cross-sectional magnetic field has on longitudinal and cross-sectional velocity pulsations and the coefficient of their correlation in a homogeneous shear region of averaged flow velocity. An opposite sign change for turbulent friction was obtained as the magnetic field was increased. In this connection an identification was made of an impulse transfer from regions with lower speeds to regions with high speeds. 4 references, 1 figure.

  13. Heat transfer in the flow of a cold, two-dimensional draining sheet over a hot, horizontal cylinder

    CERN Document Server

    Shu, Jian-Jun

    2014-01-01

    The paper considers heat transfer characteristics of thin film flow over a hot horizontal cylinder resulting from a cold vertical sheet of liquid falling onto the surface. The underlying physical features of the developing film thickness, velocity and temperature distributions have been illustrated by numerical solutions of high accuracy for large Reynolds numbers using the modified Keller box method. The solutions for film thickness distribution are good agreement with those obtained using the Pohlhausen integral momentum technique thus providing a basic confirmation of the validity of the results presented.

  14. Asymptotic Behaviour of Solutions to the Navier-stokes Equations of a Two-dimensional Compressible Flow

    Institute of Scientific and Technical Information of China (English)

    Ying-hui ZHANG; Zhong TAN

    2011-01-01

    In this paper,we are concerned with the asymptotic behaviour of a weak solution to the NavierStokes equations for compressible barotropic flow in two space dimensions with the pressure function satisfying p(ρ) =a(ρ)logd(ρ) for large (ρ).Here d > 2,a > 0.We introduce useful tools from the theory of Orlicz spaces and construct a suitable function which approximates the density for time going to infinity.Using properties of this function,we can prove the strong convergence of the density to its limit state.The behaviour of the velocity field and kinetic energy is also briefly discussed.

  15. Effects of rotation and magnetic field on the nonlinear peristaltic flow of a second-order fluid in an asymmetric channel through a porous medium

    Institute of Scientific and Technical Information of China (English)

    A.M.Abd-Alla; S.M.Abo-Dahab; H.D.El-Shahrany

    2013-01-01

    In this paper,the effects of both rotation and magnetic field of the peristaltic transport of a second-order fluid through a porous medium in a channel are studied analytically and computed numerically.The material is represented by the constitutive equations for a second-order fluid.Closed-form solutions under the consideration of long wavelength and low Reynolds number is presented.The analytical expressions for the pressure gradient,pressure rise,friction force,stream function,shear stress,and velocity are obtained in the physical domain.The effects of the non-dimensional wave amplitude,porosity,magnetic field,rotation,and the dimensionless time-mean flow in the wave frame are analyzed theoretically and computed numerically.Numerical results are given and illustrated graphically in each case considered.Comparison was made with the results obtained in the presence and absence of rotation,magnetic field,and porosity.The results indicate that the effects of the non-dimensional wave amplitude,porosity,magnetic field,rotation,and the dimensionless time-mean flow are very pronounced in the phenomena.

  16. Numerical Simulation for Two-Phase Water Hammer Flows in Pipe by Quasi-Two-Dimensional Model

    Institute of Scientific and Technical Information of China (English)

    Tae Uk Jang; Yuebin Wu; Ying Xu; Qiang Sun

    2016-01-01

    The features of a quasi⁃two⁃dimensional ( quasi⁃2D) model for simulating two⁃phase water hammer flows with vaporous cavity in a pipe are investigated. The quasi⁃2D model with discrete vaporous cavity in the pipe is proposed in this paper. This model uses the quasi⁃2D model for pure liquid zone and one⁃dimensional ( 1D ) discrete vapor cavity model for vaporous cavity zone. The quasi⁃2D model solves two⁃dimensional equations for both axial and radial velocities and 1D equations for both pressure head and discharge by the method of characteristics. The 1D discrete vapor cavity model is used to simulate the vaporous cavity occurred when the pressure in the local pipe is lower than the vapor pressure of the liquid. The proposed model is used to simulate two⁃phase water flows caused by the rapid downstream valve closure in a reservoir⁃pipe⁃valve system. The results obtained by the proposed model are compared with those by the corresponding 1D model and the experimental ones provided by the literature, respectively. The comparison shows that the maximum pressure heads simulated by the proposed model are more accurate than those by the corresponding 1D model.

  17. Development of a Semi-Automatic Technique for Flow Estimation using Optical Flow Registration and k-means Clustering on Two Dimensional Cardiovascular Magnetic Resonance Flow Images

    DEFF Research Database (Denmark)

    Brix, Lau; Christoffersen, Christian P. V.; Kristiansen, Martin Søndergaard

    of the aorta. Methods: 2D phase contrast flow images of the aorta were acquired from a patient with an enlarged pulmonary artery on a Philips Achieva 1.5T CMR system. The cardiac motion was removed from the data set using the Cornelius/Kanade registration algorithm. The time resolved flow data...... promising because it saves time for post-processing. However, the k-means cluster approach is not comprehensive for quantitative flow estimations as it is but seems feasible for a subsequent segmentation algorithm like deformable contours (i.e. snakes). Future work may overcome this manual part and make...

  18. Hydraulic validation of two-dimensional simulations of braided river flow with spatially continuous aDcp data

    Science.gov (United States)

    Williams, R. D.; Brasington, J.; Hicks, M.; Measures, R.; Rennie, C. D.; Vericat, D.

    2013-09-01

    Gravel-bed braided rivers are characterized by shallow, branching flow across low relief, complex, and mobile bed topography. These conditions present a major challenge for the application of higher dimensional hydraulic models, the predictions of which are nevertheless vital to inform flood risk and ecosystem management. This paper demonstrates how high-resolution topographic survey and hydraulic monitoring at a density commensurate with model discretization can be used to advance hydrodynamic simulations in braided rivers. Specifically, we detail applications of the shallow water model, Delft3d, to the Rees River, New Zealand, at two nested scales: a 300 m braid bar unit and a 2.5 km reach. In each case, terrestrial laser scanning was used to parameterize the topographic boundary condition at hitherto unprecedented resolution and accuracy. Dense observations of depth and velocity acquired from a mobile acoustic Doppler current profiler (aDcp), along with low-altitude aerial photography, were then used to create a data-rich framework for model calibration and testing at a range of discharges. Calibration focused on the estimation of spatially uniform roughness and horizontal eddy viscosity, νH, through comparison of predictions with distributed hydraulic data. Results revealed strong sensitivity to νH, which influenced cross-channel velocity and localization of high shear zones. The high-resolution bed topography partially accounts for form resistance, and the recovered roughness was found to scale by 1.2-1.4 D84 grain diameter. Model performance was good for a range of flows, with minimal bias and tight error distributions, suggesting that acceptable predictions can be achieved with spatially uniform roughness and νH.

  19. A finite difference technique for solving a time strain separable K-BKZ constitutive equation for two-dimensional moving free surface flows

    Science.gov (United States)

    Tomé, M. F.; Bertoco, J.; Oishi, C. M.; Araujo, M. S. B.; Cruz, D.; Pinho, F. T.; Vynnycky, M.

    2016-04-01

    This work is concerned with the numerical solution of the K-BKZ integral constitutive equation for two-dimensional time-dependent free surface flows. The numerical method proposed herein is a finite difference technique for simulating flows possessing moving surfaces that can interact with solid walls. The main characteristics of the methodology employed are: the momentum and mass conservation equations are solved by an implicit method; the pressure boundary condition on the free surface is implicitly coupled with the Poisson equation for obtaining the pressure field from mass conservation; a novel scheme for defining the past times t‧ is employed; the Finger tensor is calculated by the deformation fields method and is advanced in time by a second-order Runge-Kutta method. This new technique is verified by solving shear and uniaxial elongational flows. Furthermore, an analytic solution for fully developed channel flow is obtained that is employed in the verification and assessment of convergence with mesh refinement of the numerical solution. For free surface flows, the assessment of convergence with mesh refinement relies on a jet impinging on a rigid surface and a comparison of the simulation of a extrudate swell problem studied by Mitsoulis (2010) [44] was performed. Finally, the new code is used to investigate in detail the jet buckling phenomenon of K-BKZ fluids.

  20. Time-Dependent Parabolic Finite Difference Formulation for Harmonic Sound Propagation in a Two-Dimensional Duct with Flow

    Science.gov (United States)

    Kreider, Kevin L.; Baumeister, Kenneth J.

    1996-01-01

    An explicit finite difference real time iteration scheme is developed to study harmonic sound propagation in aircraft engine nacelles. To reduce storage requirements for future large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable for a harmonic monochromatic sound field, a parabolic (in time) approximation is introduced to reduce the order of the governing equation. The analysis begins with a harmonic sound source radiating into a quiescent duct. This fully explicit iteration method then calculates stepwise in time to obtain the 'steady state' harmonic solutions of the acoustic field. For stability, applications of conventional impedance boundary conditions requires coupling to explicit hyperbolic difference equations at the boundary. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

  1. Improving Peak Capacity in Fast On-Line Comprehensive Two-Dimensional Liquid Chromatography with Post First Dimension Flow-Splitting

    Science.gov (United States)

    Filgueira, Marcelo R.; Huang, Yuan; Witt, Klaus; Castells, Cecilia; Carr, Peter W.

    2011-01-01

    The use of flow splitters between the two dimensions in on-line comprehensive two dimensional liquid chromatography (LC×LC) has not received very much attention in comparison to their use in GC×GC where they are quite common. In principle, splitting the flow after the first dimension column and performing on-line LC×LC on this constant fraction of the first dimension effluent should allow the two dimensions to be optimized almost independently. When there is no flow splitting any change in the first dimension flow rate has an immediate impact on the second dimension. With a flow splitter one could for example double the flow rate into the first dimension column and do a 1:1 flow split without changing the sample loop size or the sampler’s collection time. Of course, the sensitivity would be diminished but this can be partially compensated by use of a larger injection; this will likely only amount to a small price to pay for this increased resolving power and system flexibility. Among other benefits, we found a 2-fold increase in the corrected 2D peak capacity and the number of observed peaks for a 15 min analysis time by using a post first dimension flow splitter. At a fixed analysis time this improvement results primarily from an increase in the gradient time resulting from the reduced system re-equilibration time and to a smaller extent it is due to the increased peak capacity achieved by full optimization of the first dimension. PMID:22017622

  2. Numerical simulation of two-dimensional granular shearing flows and the friction force of a moving slab on the granular media

    Institute of Scientific and Technical Information of China (English)

    Cai Qing-Dong; Chen Shi-Yi; Sheng Xiao-Wei

    2011-01-01

    This paper studies some interesting features of two-dimensional granular shearing flow by using molecular dynamic approach for a specific granular system. The obtained results show that the probability distribution function of velocities of particles is Gaussian at the central part, but diverts from Gaussian distribution nearby the wall. The macroscopic stress along the vertical direction has large fluctuation around a constant value, the non-zero average velocity occurs mainly near the moving wall, which forms a shearing zone. . In the shearing movement, the volume of the granular material behaves in a random manner. The equivalent friction coefficient between moving slab and granular material correlates with the moving speed at low velocity, and approaches constant as the velocity is large enough.

  3. The effect of velocity boundary conditions on the heat transfer and flow topology in two-dimensional Rayleigh-B\\'enard convection

    CERN Document Server

    van der Poel, Erwin P; Verzicco, Roberto; Lohse, Detlef

    2015-01-01

    The effect of various velocity boundary condition is studied in two-dimensional Rayleigh-B\\'enard convection. Combinations of no-slip, stress-free and periodic boundary conditions are used on both the sidewalls and the horizontal plates. For the studied Rayleigh numbers Ra between $10^8$ and $10^{11}$ the heat transport is lower for $\\Gamma = 0.33$ than for $\\Gamma = 1$ in case of no-slip sidewalls. This is surprisingly opposite for stress-free sidewalls, where the heat transport increases for lower aspect-ratio. In wider cells the aspect-ratio dependence is observed to disappear for $\\text{Ra} \\ge 10^{10}$. Two distinct flow types with very different dynamics can be seen, mostly dependent on the plate velocity boundary condition, namely roll-like flow and horizontal zonal flow, which have a substantial effect on the dynamics and heat transport in the system. The predominantly horizontal zonal flow suppresses heat flux and is observed for stress-free and asymmetric plates. Low aspect-ratio periodic sidewall s...

  4. Two-Dimensional Cutting (TDC) Vitrectome: In Vitro Flow Assessment and Prospective Clinical Study Evaluating Core Vitrectomy Efficiency versus Standard Vitrectome.

    Science.gov (United States)

    Pavlidis, Mitrofanis

    2016-01-01

    Purpose. To evaluate comparative aspiration flow performance and also vitrectomy operating time efficiency using a double-cutting open port vitreous cutting system incorporated in a two-dimensional cutting (TDC, DORC International) vitrectome design versus standard vitreous cutter. Methods. In vitro investigations compared aspiration flow rates in artificial vitreous humor at varying cutter speeds and vacuum levels using a TDC vitrectome and a standard vitrectome across different aspiration pump systems. A prospective single-centre clinical study evaluated duration of core vitrectomy in 80 patients with macular pucker undergoing 25-gauge or 27-gauge vitrectomy using either a TDC vitrectome at 16,000 cuts per minute (cpm) or standard single-cut vitrectome, combined with a Valve Timing intelligence (VTi) pump system (EVA, DORC International). Results. Aspiration flow rates remained constant independent of TDC vitrectome cut rate, while flow rates decreased linearly at higher cutter speeds using a classic single-blade vitrectome. Mean duration of core vitrectomy surgeries using a TDC vitreous cutter system was significantly (p < 0.001) shorter than the mean duration of core vitrectomy procedures using a single-cut vitrectome of the same diameter (reduction range, 34%-50%). Conclusion. Vitrectomy surgery performed using a TDC vitrectome was faster than core vitrectomy utilizing a standard single-action vitrectome at similar cut speeds.

  5. Two-Dimensional Cutting (TDC Vitrectome: In Vitro Flow Assessment and Prospective Clinical Study Evaluating Core Vitrectomy Efficiency versus Standard Vitrectome

    Directory of Open Access Journals (Sweden)

    Mitrofanis Pavlidis

    2016-01-01

    Full Text Available Purpose. To evaluate comparative aspiration flow performance and also vitrectomy operating time efficiency using a double-cutting open port vitreous cutting system incorporated in a two-dimensional cutting (TDC, DORC International vitrectome design versus standard vitreous cutter. Methods. In vitro investigations compared aspiration flow rates in artificial vitreous humor at varying cutter speeds and vacuum levels using a TDC vitrectome and a standard vitrectome across different aspiration pump systems. A prospective single-centre clinical study evaluated duration of core vitrectomy in 80 patients with macular pucker undergoing 25-gauge or 27-gauge vitrectomy using either a TDC vitrectome at 16,000 cuts per minute (cpm or standard single-cut vitrectome, combined with a Valve Timing intelligence (VTi pump system (EVA, DORC International. Results. Aspiration flow rates remained constant independent of TDC vitrectome cut rate, while flow rates decreased linearly at higher cutter speeds using a classic single-blade vitrectome. Mean duration of core vitrectomy surgeries using a TDC vitreous cutter system was significantly (p<0.001 shorter than the mean duration of core vitrectomy procedures using a single-cut vitrectome of the same diameter (reduction range, 34%–50%. Conclusion. Vitrectomy surgery performed using a TDC vitrectome was faster than core vitrectomy utilizing a standard single-action vitrectome at similar cut speeds.

  6. Stokesian peristaltic pumping in a three-dimensional tube with a phase-shifted asymmetry

    Science.gov (United States)

    Aranda, Vivian; Cortez, Ricardo; Fauci, Lisa

    2011-08-01

    Many physiological flows are driven by waves of muscular contractions passed along a tubular structure. This peristaltic pumping plays a role in ovum transport in the oviduct and in rapid sperm transport through the uterus. As such, flow due to peristalsis has been a central theme in classical biological fluid dynamics. Analytical approaches and numerical methods have been used to study flow in two-dimensional channels and three-dimensional tubes. In two dimensions, the effect of asymmetry due to a phase shift between the channel walls has been examined. However, in three dimensions, peristalsis in a non-axisymmetric tube has received little attention. Here, we present a computational model of peristaltic pumping of a viscous fluid in three dimensions based upon the method of regularized Stokeslets. In particular, we study the flow structure and mean flow in a three-dimensional tube whose asymmetry is governed by a single phase-shift parameter. We view this as a three-dimensional analog of the phase-shifted two-dimensional channel. We find that the maximum mean flow rate is achieved for the parameter that results in an axisymmetric tube. We also validate this approach by comparing our computational results with classical long-wavelength theory for the three-dimensional axisymmetric tube. This computational framework is easily implemented and may be adapted to more comprehensive physiological models where the kinematics of the tube walls are not specified a priori, but emerge due to the coupling of its passive elastic properties, force generating mechanisms, and the surrounding viscous fluid.

  7. Existence of shocklets in a two-dimensional supersonic mixing layer and its influence on the flow structure

    Institute of Scientific and Technical Information of China (English)

    CAO; Wei

    2001-01-01

    .0, MNRAS,1992, 256: 349.[25]Hazard, C. , Morton, D. C., Terlevich, R. et al. , Nine new quasi-stellar objects with borad absorption lines, Astrophys.J. , 1984, 282: 33.[26]Osmer, P. S. , Q0353-383: The best case yet for abundance anomalies in quasars, Astrophys. J. , 1980, 237, 666.[27]Hamann, F. , Zuo, L., Tytler, D. , Broad Ne VIII λ774 emission from quasars in the HST-Fos snapshot survey (ABSNAP),Astrophys. J., 1995, 444: L69.[28]Laor, A. , Bahcall, J. N., Jannuzi, B. T. , The ultraviolet emission properties of five low-redshift active galactic unclei at high signal-to-noise ratio and spectral resolution, Astrophys. J., 1994, 420: 110.[29]Barthel, P. D., Tytler, D. R., Thomson, B., Optical spectra of distant radio loud quasars, A&AS, 1990, 82: 339.[30]Schmidt, M., Schneider, D. P., Gunn, J. E., Pc0910 + 5625: An optically selected quasar with a redshift of 4.04, Astro-phys. J., 1987, 321: L7.[31]Adams, M. T., Coleman, G. D., Stockman, H. S. et al., The spectrum of Markarian 132, Astrophys. J., 1978, 228:758.[32]Hammann, F. , Shields, J. C. , Ferland, G. J. et al. , Broad NE VIII lambda 744 emission from the Quasar PG 148 + 549,Astrophys. J., 1995, 454: 688.[33]Baldwin, J. A., McMahon, R., Hazard, C. et al., QSOs with narrow emission lines, Astrophys. J., 1988, 327: 103.[34]Baldwin, J. A. , Burbidge, E. M. , Hazard, C. et al. , A spectroscopic surrvey of 92 QSO candidates, Astrophys. J. ,1973, 185: 739.[35]Baldwin, J. A. , Ferland, G. J. , Korista, K. T., Very high density clumps and out flowing winds in QSO broad-line re-gions, Astrophys. J., 1996, 461: 664.[36]Ferland, G. J., Baldwin, J. A., Korista, K. T., High metal enrichments in luminous quasars, Astrophys. J., 461: 683.[37]Bceker, R. H., Helfand, D. J., White, R. L., The discovery of an X-ray selected radio-loud quasar at z = 3.9 AJ, 1992,104: 531.[38]Schneider, D. P., Lawrence, C. R., Schmide, M. et al., Deep optical and radio observations of the

  8. Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap: future modeled histories obtained for the reference surface mass balance

    Directory of Open Access Journals (Sweden)

    Y. V. Konovalov

    2015-11-01

    Full Text Available The prognostic experiments for fast-flowing ice streams on the southern side of the Academy of Sciences Ice Cap in the Komsomolets Island, Severnaya Zemlya archipelago, are implemented in this study. These experiments are based on inversions of basal friction coefficients using a two-dimensional flow-line thermo-coupled model and the Tikhonov's regularization method. The modeled ice temperature distributions in the cross-sections were obtained using the ice surface temperature histories that were inverted previously from the borehole temperature profiles derived at the Academy of Sciences Ice Cap. Input data included InSAR ice surface velocities, ice surface elevations, and ice thicknesses obtained from airborne measurements and the surface mass balance, were adopted from the prior investigations for the implementation of both the forward and inverse problems. The prognostic experiments reveal that both ice mass and ice stream extents decline for the reference time-independent surface mass balance. Specifically, the grounding line retreats (a along the B–B' flow line from ~ 40 to ~ 30 km (the distance from the summit, (b along the C–C' flow line from ~ 43 to ~ 37 km, and (c along the D–D' flow line from ~ 41 to ~ 32 km considering a time period of 500 years and assuming time-independent surface mass balance. Ice flow velocities in the ice streams decrease with time and this trend results in the overall decline of the outgoing ice flux. Generally, the modeled histories are in agreement with observations of sea ice extent and thickness indicating a continual ice decline in the Arctic.

  9. Kinetic Monte Carlo simulations of one-dimensional and two-dimensional traffic flows: Comparison of two look-ahead rules

    Science.gov (United States)

    Sun, Yi; Timofeyev, Ilya

    2014-05-01

    We employ an efficient list-based kinetic Monte Carlo (KMC) method to study traffic flow models on one-dimensional (1D) and two-dimensional (2D) lattices based on the exclusion principle and Arrhenius microscopic dynamics. This model implements stochastic rules for cars' movements based on the configuration of the traffic ahead of each car. In particular, we compare two different look-ahead rules: one is based on the distance from the car under consideration to the car in front of it, and the other one is based on the density of cars ahead. The 1D numerical results of these two rules suggest different coarse-grained macroscopic limits in the form of integro-differential Burgers equations. The 2D results of both rules exhibit a sharp phase transition from freely flowing to fully jammed, as a function of the initial density of cars. However, the look-ahead rule based on the density of the traffic produces more realistic results. The KMC simulations reported in this paper are compared with those from other well-known traffic flow models and the corresponding empirical results from real traffic.

  10. Flow-modulated comprehensive two-dimensional gas chromatography combined with a vacuum ultraviolet detector for the analysis of complex mixtures.

    Science.gov (United States)

    Zoccali, Mariosimone; Schug, Kevin A; Walsh, Phillip; Smuts, Jonathan; Mondello, Luigi

    2017-05-12

    The present paper is focused on the use of a vacuum ultraviolet absorption spectrometer (VUV) for gas chromatography (GC), within the context of flow modulated comprehensive two-dimensional gas chromatography (FM GC×GC). The features of the VUV detector were evaluated through the analysis of petrochemical and fatty acids samples. Besides responding in a predictable fashion via Beer's law principles, the detector provides additional spectroscopic information for qualitative analysis. Virtually all chemical species absorb and have unique gas phase absorption features in the 120-240nm wavelength range monitored. The VUV detector can acquire up to 90 full range absorption spectra per second, allowing its coupling with comprehensive two-dimensional gas chromatography. This recent form of detection can address specific limitations related to mass spectrometry (e.g., identification of isobaric and isomeric species with very similar mass spectra or labile chemical compounds), and it is also able to deconvolute co-eluting peaks. Moreover, it is possible to exploit a pseudo-absolute quantitation of analytes based on pre-recorded absorption cross-sections for target analytes, without the need for traditional calibration. Using this and the other features of the detector, particular attention was devoted to the suitability of the FM GC×GC-VUV system toward qualitative and quantitative analysis of bio-diesel fuel and different kinds of fatty acids. Satisfactory results were obtained in terms of tailing factor (1.1), asymmetry factor (1.1), and similarity (average value 97%), for the FAMEs mixtures analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Two-dimensional hydrodynamic modeling to quantify effects of peak-flow management on channel morphology and salmon-spawning habitat in the Cedar River, Washington

    Science.gov (United States)

    Czuba, Christiana; Czuba, Jonathan A.; Gendaszek, Andrew S.; Magirl, Christopher S.

    2010-01-01

    The Cedar River in Washington State originates on the western slope of the Cascade Range and provides the City of Seattle with most of its drinking water, while also supporting a productive salmon habitat. Water-resource managers require detailed information on how best to manage high-flow releases from Chester Morse Lake, a large reservoir on the Cedar River, during periods of heavy precipitation to minimize flooding, while mitigating negative effects on fish populations. Instream flow-management practices include provisions for adaptive management to promote and maintain healthy aquatic habitat in the river system. The current study is designed to understand the linkages between peak flow characteristics, geomorphic processes, riverine habitat, and biological responses. Specifically, two-dimensional hydrodynamic modeling is used to simulate and quantify the effects of the peak-flow magnitude, duration, and frequency on the channel morphology and salmon-spawning habitat. Two study reaches, representative of the typical geomorphic and ecologic characteristics of the Cedar River, were selected for the modeling. Detailed bathymetric data, collected with a real-time kinematic global positioning system and an acoustic Doppler current profiler, were combined with a LiDAR-derived digital elevation model in the overbank area to develop a computational mesh. The model is used to simulate water velocity, benthic shear stress, flood inundation, and morphologic changes in the gravel-bedded river under the current and alternative flood-release strategies. Simulations of morphologic change and salmon-redd scour by floods of differing magnitude and duration enable water-resource managers to incorporate model simulation results into adaptive management of peak flows in the Cedar River. PDF version of a presentation on hydrodynamic modelling in the Cedar River in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.

  12. Two-dimensional hydrodynamic modeling to quantify effects of peak-flow management on channel morphology and salmon-spawning habitat in the Cedar River, Washington

    Science.gov (United States)

    Barnas, C. R.; Czuba, J. A.; Gendaszek, A. S.; Magirl, C. S.

    2010-12-01

    The Cedar River in Washington State originates on the western slope of the Cascade Range and provides the City of Seattle with most of its drinking water, while also supporting a productive salmon habitat. Water-resource managers require detailed information on how best to manage high-flow releases from Chester Morse Lake, a large reservoir on the Cedar River, during periods of heavy precipitation to minimize flooding, while mitigating negative effects on fish populations. Instream flow-management practices include provisions for adaptive management to promote and maintain healthy aquatic habitat in the river system. The current study is designed to understand the linkages between peak flow characteristics, geomorphic processes, riverine habitat, and biological responses. Specifically, two-dimensional hydrodynamic modeling is used to simulate and quantify the effects of the peak-flow magnitude, duration, and frequency on the channel morphology and salmon-spawning habitat. Two study reaches, representative of the typical geomorphic and ecologic characteristics of the Cedar River, were selected for the modeling. Detailed bathymetric data, collected with a real-time kinematic global positioning system and an acoustic Doppler current profiler, were combined with a LiDAR-derived digital elevation model in the overbank area to develop a computational mesh. The model is used to simulate water velocity, benthic shear stress, flood inundation, and morphologic changes in the gravel-bedded river under the current and alternative flood-release strategies. Simulations of morphologic change and salmon-redd scour by floods of differing magnitude and duration enable water-resource managers to incorporate model simulation results into adaptive management of peak flows in the Cedar River.

  13. Application of adjustment calculus in the nodeless Trefftz method for a problem of two-dimensional temperature field of the boiling liquid flowing in a minichannel

    Directory of Open Access Journals (Sweden)

    Hożejowska Sylwia

    2014-03-01

    Full Text Available The paper presents application of the nodeless Trefftz method to calculate temperature of the heating foil and the insulating glass pane during continuous flow of a refrigerant along a vertical minichannel. Numerical computations refer to an experiment in which the refrigerant (FC-72 enters under controlled pressure and temperature a rectangular minichannel. Initially its temperature is below the boiling point. During the flow it is heated by a heating foil. The thermosensitive liquid crystals allow to obtain twodimensional temperature field in the foil. Since the nodeless Trefftz method has very good performance for providing solutions to such problems, it was chosen as a numerical method to approximate two-dimensional temperature distribution in the protecting glass and the heating foil. Due to known temperature of the refrigerant it was also possible to evaluate the heat transfer coefficient at the foil-refrigerant interface. For expected improvement of the numerical results the nodeless Trefftz method was combined with adjustment calculus. Adjustment calculus allowed to smooth the measurements and to decrease the measurement errors. As in the case of the measurement errors, the error of the heat transfer coefficient decreased.

  14. Numerical simulation of nematic liquid crystalline flow in two-dimensional L-shaped channels; Nijigen L gata ryuro ni okeru nematic ekisho no nagare no suchi simulation

    Energy Technology Data Exchange (ETDEWEB)

    Chono, S.; Tsuji, T. [Fukui University, Fukui (Japan). Faculty of Engineering

    1995-05-25

    Finite difference solutions to the Leslie-Ericksen equations were obtained for flows in two-dimensional L-shaped channels with various contraction ratios of the upstream to downstream channel width. A streamline shift toward the outer wall occurs upstream of the reentrant corner. Such behavior is similar to that of viscoelastic fluids. With increasing contraction ratio, the streamline shift occurs further upstream. The effect of the wall anchoring angle for the director is remarkable; for example, when the anchoring angle along the downstream walls is set to be opposite to the main flow direction, a distortion of streamlines is produced in the corner region and the director moves to the downstream region upside down. At small Ericksen numbers, the orientation angle for the director is varied over a wide area so as to suppress its local deformation. In contrast, when the Ericksen number is large, the director profile in the upstream region is retained close to the corner region where the director turns rapidly to the downstream direction. 7 refs., 9 figs., 1 tab.

  15. Study on the flow behavior of ferrofluids in a two-dimensional channel (1st report). Magnetic field of various derections

    Energy Technology Data Exchange (ETDEWEB)

    Tomita, Yukio; Ishibashi, Yukio; Saito, Eiji; Saito, Toshio

    1988-02-25

    For elucidation of the flow behavior of a magnetic fluid as a one-phase fluid, water base ferrofluids were introduced in a two-dimensional channel and the action of a uniform vertical magnetic field axial magnetic field, and both fields inclined at various angles to examine the laminar flow region. The ferrofluids used in the experiment were prepared by dispersing 17.5 weight % of Fe/sub 3/ O/sub 4/ fine particles of about 100A in diameter into ion-exchange water, and adding an anionic sodium oleate to stabilize the dispersion. Under no action of the magnetic fields, ferrofluids having a higher concentration than the above value exhibited plastic fluid. As the direction of the magnetic field acting on the fluid approached the vertical, so the pressure loss was increased. The pipe friction coefficient could be expressed by the empirical formula of which the variables are the ratios of inertia force/viscous force and magnetic force/viscous force, and the inclination of the magnetic poles. (15 figs, 14 refs)

  16. Two-dimensional calculus

    CERN Document Server

    Osserman, Robert

    2011-01-01

    The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o

  17. Two dimensional vernier

    Science.gov (United States)

    Juday, Richard D. (Inventor)

    1992-01-01

    A two-dimensional vernier scale is disclosed utilizing a cartesian grid on one plate member with a polar grid on an overlying transparent plate member. The polar grid has multiple concentric circles at a fractional spacing of the spacing of the cartesian grid lines. By locating the center of the polar grid on a location on the cartesian grid, interpolation can be made of both the X and Y fractional relationship to the cartesian grid by noting which circles coincide with a cartesian grid line for the X and Y direction.

  18. Cerebral blood flow volume measurements of the carotid artery and ipsilateral branches using two-dimensional phase-contrast magnetic resonance angiography

    Institute of Scientific and Technical Information of China (English)

    Gang Guo; Yonggui Yang; Weiqun Yang

    2011-01-01

    The optimal velocity encoding of phase-contrast magnetic resonance angiography (PC MRA) in measuring cerebral blood flow volume (BFV) ranges from 60 to 80 cm/s. To verify the accuracy of two-dimensional (2D) PC MRA, the present study localized the region of interest at blood vessels of the neck using PC MRA based on three-dimensional time-of-flight sequences, and the velocity encodingwas set to 80 cm/s. Results of the measurements showed that the error rate was 7.0 ± 6.0%in the estimation of BFV in the internal carotid artery, the external carotid artery and the ipsilateralcommon carotid artery. There was no significant difference, and a significant correlation in BFV between internal carotid artery + external carotid artery and ipsilateral common carotid artery. Inaddition, the BFV of the common carotid artery was correlated with that of the ipsilateral internal carotid artery. The main error was attributed to the external carotid artery and its branches. Therefore,after selecting the appropriate scanning parameters and protocols, 2D PC MRA is more accuratein the determination of BFV in the carotid arteries.

  19. Determination of aromatic sulphur compounds in heavy gas oil by using (low-)flow modulated comprehensive two-dimensional gas chromatography-triple quadrupole mass spectrometry.

    Science.gov (United States)

    Franchina, Flavio Antonio; Machado, Maria Elisabete; Tranchida, Peter Quinto; Zini, Cláudia Alcaraz; Caramão, Elina Bastos; Mondello, Luigi

    2015-03-27

    The present research is focused on the development of a flow-modulated comprehensive two-dimensional gas chromatography-triple quadrupole mass spectrometry (FM GC × GC-MS/MS) method for the determination of classes of aromatic organic sulphur compounds (benzothiophenes, dibenzothiophenes, and benzonaphthothiophene) in heavy gas oil (HGO). The MS/MS instrument was used to provide both full-scan and multiple-reaction-monitoring (MRM) data. Linear retention index (LRI) ranges were used to define the MRM windows for each chemical class. Calibration solutions (internal standard: 1-fluoronaphthalene) were prepared by using an HGO sample, depleted of S compounds. Calibration information was also derived for the thiophene class (along with MRM and LRI data), even though such constituents were not present in the HGO. Linearity was satisfactory over the analyzed concentration range (1-100 mg/L); intra-day precision for the lowest calibration point was always below 17%. Accuracy was also satisfactory, with a maximum percentage error of 3.5% (absolute value) found among the S classes subjected to (semi-)quantification. The highest limit of quantification was calculated to be 299 μg/L (for the C1-benzothiophene class), while the lowest was 21 μg/L (for the C4-benzothiophene class).

  20. Assessment of left and right ventricular diastolic and systolic functions using two-dimensional speckle-tracking echocardiography in patients with coronary slow-flow phenomenon.

    Directory of Open Access Journals (Sweden)

    Yonghuai Wang

    Full Text Available Coronary slow-flow phenomenon (CSFP is an angiographic diagnosis characterised by a low rate of flow of contrast agent in the normal or near-normal epicardial coronary arteries. Many of the patients with CSFP may experience recurrent acute coronary syndromes. However, current clinical practice tends to underestimate the impact of CSFP due to the yet unknown effect on the cardiac function. This study was performed to evaluate left ventricular (LV and right ventricular (RV diastolic and systolic functions, using two-dimensional (2D longitudinal strain and strain rate, in patients with CSFP, and to determine the relationships between the thrombolysis in myocardial infarction (TIMI frame count (TFC and LV and RV diastolic and systolic functions.Sixty-three patients with CSFP and 45 age- and sex-matched controls without CSFP were enrolled in the study. Diagnosis of CSFP was made by TFC. LV and RV diastolic and systolic functions were assessed by 2D speckle-tracking echocardiography.LV peak early diastolic longitudinal strain rate (LSRe was lower in patients with CSFP than in controls (P = 0.01. LV peak systolic longitudinal strain (LS and LV peak systolic longitudinal strain rate (LSRs were lower in patients with CSFP than in controls (P = 0.004 and P = 0.03, respectively. There was no difference in LV ejection fraction. RV peak early diastolic longitudinal strain rate (RSRe was lower in patients with CSFP than in controls (P = 0.03. There were no differences in RV peak systolic longitudinal strain (RS, RV peak systolic longitudinal strain rate (RSRs, or RV fractional area change among the groups. The mean TFC correlated negatively with LSRe and RSRe in patients with CSFP (r = -0.26, P = 0.04 and r = -0.32, P = 0.01, respectively.LV diastolic and systolic functions were impaired in patients with CSFP. CSFP also affected RV diastolic function, but not RV systolic function.

  1. Combine effects of Magnetohydrodynamics (MHD and partial slip on peristaltic Blood flow of Ree–Eyring fluid with wall properties

    Directory of Open Access Journals (Sweden)

    M.M. Bhatti

    2016-09-01

    Full Text Available In this article, combine effects of Magnetohydrodynamics and partial slip on Blood flow of Ree–Eyring fluid through a porous medium have been investigated. The walls of the non-uniform porous channel are considered as compliant. The governing equation of Ree–Eyring fluid for blood flow are simplified using long wavelength and low Reynolds number approximation. The obtained resulting equation are solved analytically and exact solution has been obtained. The impact of different physical parameters such as Hartmann number, slip parameter, porous parameter, wall rigidity parameter, wall tension and mass characterization parameter are taken into account. It is found that velocity distribution increases due to slip effects while its behavior is opposite for Hartmann number. Trapping mechanism has also taken under consideration by drawing contour streamlines.

  2. Effects of nanoparticles on the peristaltic motion of tangent hyperbolic fluid model in an annulus

    Directory of Open Access Journals (Sweden)

    S. Nadeem

    2015-12-01

    Full Text Available In the present article, effects of nanoparticles on the peristaltic flow of tangent hyperbolic fluid in an annulus are described. The two-dimensional equations of tangent hyperbolic fluid are solved by using the assumptions of low Reynolds number and long wavelength. Analytical solution is obtained with the help of homotopy perturbation and Adomian decomposition method for velocity, temperature and nanoparticles concentration. Solutions are discussed through graphs. Solutions for pressure rise, temperature, nanoparticles concentration, pressure gradient and streamlines are plotted for various emerging parameters. It is found that the temperature profile increases with increase in Brownian motion and thermophoresis parameter. It is also found that the size of the trapped bolus in triangular wave is smaller as compared to other waves. Further, the comparison of both analytical solutions is presented.

  3. Joule heating effects on electromagnetohydrodynamic flow through a peristaltically induced micro-channel with different zeta potential and wall slip

    Science.gov (United States)

    Ranjit, N. K.; Shit, G. C.

    2017-09-01

    This paper aims to develop a mathematical model for magnetohydrodynamic flow of biofluids through a hydrophobic micro-channel with periodically contracting and expanding walls under the influence of an axially applied electric field. The velocity slip effects have been taken into account at the channel walls by employing different slip lengths due to hydrophobic gating. Different temperature jump factors have also been used to investigate the thermomechanical interactions at the fluid-solid interface. The electromagnetohydrodynamic flow in a microchannel is simplified under the framework of Debye-Hückel linearization approximation. We have derived the closed-form solutions for the linearized dimensionless boundary value problem under the assumptions of long wave length and low Reynolds number. The axial velocity, temperature, pressure distribution, stream function, wall shear stress and the Nusselt number have been appraised for diverse values of the parameters approaching into the problem. Our main focus is to determine the effects of different zeta potential on the axial velocity and temperature distribution under electromagnetic environment. This study puts forward an important observation that the different zeta potential plays an important role in controlling fluid velocity. The study further reveals that the temperature increases significantly with the Joule heating parameter and the Brinkman number (arises due to the dissipation of energy).

  4. Two-dimensional optical spectroscopy

    CERN Document Server

    Cho, Minhaeng

    2009-01-01

    Discusses the principles and applications of two-dimensional vibrational and optical spectroscopy techniques. This book provides an account of basic theory required for an understanding of two-dimensional vibrational and electronic spectroscopy.

  5. Numerical Modeling and Investigation of Fluid-Driven Fracture Propagation in Reservoirs Based on a Modified Fluid-Mechanically Coupled Model in Two-Dimensional Particle Flow Code

    Directory of Open Access Journals (Sweden)

    Jian Zhou

    2016-09-01

    Full Text Available Hydraulic fracturing is a useful tool for enhancing rock mass permeability for shale gas development, enhanced geothermal systems, and geological carbon sequestration by the high-pressure injection of a fracturing fluid into tight reservoir rocks. Although significant advances have been made in hydraulic fracturing theory, experiments, and numerical modeling, when it comes to the complexity of geological conditions knowledge is still limited. Mechanisms of fluid injection-induced fracture initiation and propagation should be better understood to take full advantage of hydraulic fracturing. This paper presents the development and application of discrete particle modeling based on two-dimensional particle flow code (PFC2D. Firstly, it is shown that the modeled value of the breakdown pressure for the hydraulic fracturing process is approximately equal to analytically calculated values under varied in situ stress conditions. Furthermore, a series of simulations for hydraulic fracturing in competent rock was performed to examine the influence of the in situ stress ratio, fluid injection rate, and fluid viscosity on the borehole pressure history, the geometry of hydraulic fractures, and the pore-pressure field, respectively. It was found that the hydraulic fractures in an isotropic medium always propagate parallel to the orientation of the maximum principal stress. When a high fluid injection rate is used, higher breakdown pressure is needed for fracture propagation and complex geometries of fractures can develop. When a low viscosity fluid is used, fluid can more easily penetrate from the borehole into the surrounding rock, which causes a reduction of the effective stress and leads to a lower breakdown pressure. Moreover, the geometry of the fractures is not particularly sensitive to the fluid viscosity in the approximate isotropic model.

  6. On a two-dimensional mode-matching technique for sound generation and transmission in axial-flow outlet guide vanes

    Science.gov (United States)

    Bouley, Simon; François, Benjamin; Roger, Michel; Posson, Hélène; Moreau, Stéphane

    2017-09-01

    The present work deals with the analytical modeling of two aspects of outlet guide vane aeroacoustics in axial-flow fan and compressor rotor-stator stages. The first addressed mechanism is the downstream transmission of rotor noise through the outlet guide vanes, the second one is the sound generation by the impingement of the rotor wakes on the vanes. The elementary prescribed excitation of the stator is an acoustic wave in the first case and a hydrodynamic gust in the second case. The solution for the response of the stator is derived using the same unified approach in both cases, within the scope of a linearized and compressible inviscid theory. It is provided by a mode-matching technique: modal expressions are written in the various sub-domains upstream and downstream of the stator as well as inside the inter-vane channels, and matched according to the conservation laws of fluid dynamics. This quite simple approach is uniformly valid in the whole range of subsonic Mach numbers and frequencies. It is presented for a two-dimensional rectilinear-cascade of zero-staggered flat-plate vanes and completed by the implementation of a Kutta condition. It is then validated in sound generation and transmission test cases by comparing with a previously reported model based on the Wiener-Hopf technique and with reference numerical simulations. Finally it is used to analyze the tonal rotor-stator interaction noise in a typical low-speed fan architecture. The interest of the mode-matching technique is that it could be easily transposed to a three-dimensional annular cascade in cylindrical coordinates in a future work. This makes it an attractive alternative to the classical strip-theory approach.

  7. Two-Dimensional Simulation of Flow and Evaluation of Bridge Scour at Structure A-1700 on Interstate 155 over the Mississippi River near Caruthersville, Missouri

    Science.gov (United States)

    Huizinga, Richard J.

    2007-01-01

    The evaluation of scour at bridges throughout the State of Missouri has been ongoing since 1991, and most of these evaluations have used one-dimensional hydraulic analysis and application of conventional scour depth prediction equations. Occasionally, the complex conditions of a site dictate a more thorough assessment of the stream hydraulics beyond a one-dimensional model. This was the case for structure A-1700, the Interstate 155 bridge crossing the Mississippi River near Caruthersville, Missouri. To assess the complex hydraulics at this site, a two-dimensional hydrodynamic flow model was used to simulate flow conditions on the Mississippi River in the vicinity of the Interstate 155 structure A-1700. The model was used to simulate flow conditions for three discharges: a flood that occurred on April 4, 1975 (the calibration flood), which had a discharge of 1,658,000 cubic feet per second; the 100-year flood, which has a discharge of 1,960,000 cubic feet per second; and the project design flood, which has a discharge of 1,974,000 cubic feet per second. The project design flood was essentially equivalent to the flood that would cause impending overtopping of the mainline levees along the Mississippi River in the vicinity of structure A-1700. Discharge and river-stage readings from the flood of April 4, 1975, were used to calibrate the flow model. The model was then used to simulate the 100-year and project design floods. Hydraulic flow parameters obtained from the three flow simulations were applied to scour depth prediction equations to determine contraction, local pier, and abutment scour depths at structure A-1700. Contraction scour and local pier scour depths computed for the project design discharge generally were the greatest, whereas the depths computed for the calibration flood were the least. The maximum predicted total scour depth (contraction and local pier scour) for the calibration flood was 66.1 feet; for the 100-year flood, the maximum predicted total

  8. A Peristaltic Meso-Scale Mixer

    Science.gov (United States)

    Bau, Haim; Yi, Mingqiang; Hu, Howard H.

    2000-11-01

    In recent years, there has been a growing interest in developing minute laboratories on a "chip". Often, in order to facilitate chemical and biological reactions, one needs to mix various reagents and chemicals. Although the characteristic lengths associated with micro-devices are small, typically on the order of 100mm, in the case of large molecules, diffusion alone does not provide a sufficiently rapid means for mixing. Recent experimental[1] and theoretical[2] studies suggested the use of surface waves to induce peristaltic motion and enhance fluid stirring. We considered incompressible, viscous fluid confined in a rectangular cavity. One or two of the cavity walls were made of a thin membrane. Electric conductors were printed on the membrane. By passing appropriately phased alternating electric currents through these conductors in the presence of a magnetic field, relatively large amplitude travelling waves could be transmitted in cavity's walls and induce peristaltic motion. We describe the results of a theoretical study. We extended Selverov and Stone[2] theory to account for the presence of lateral boundaries. The induced velocity profiles were determined analytically for small amplitude waves (e) and numerically for waves of arbitrary amplitude. The effect of the peristaltic motion on the stretching and deformation of material lines were quantified. The work was supported, in part, by DARPA through grant N66001-97-1-8911 to the University of Pennsylvania. [1] Moroney, R. M., White, R., M., Howe, R., T., 1991, Ultrasonically Induced Microtransport, Proceedings IEEE Workshop Micro Electro Mechanical Systems, MEMS 95 Amsterdam, 277-282. [2] Selverov, K., and Stone, H., A., 2000, Peristaltically Driven Flows for Micro Mixers, to appear in Physics of Fluids.

  9. Transient peristaltic transport of grains in a liquid

    Directory of Open Access Journals (Sweden)

    Marconati Marco

    2017-01-01

    Full Text Available Pumping suspensions and pastes has always been a significant technological challenge in a number of industrial applications ranging from food processing to mining. Peristaltic pumps have become popular to pump and/or dose complex fluids, due to their robustness. During the transport of suspensions with peristaltic pumps, clogging issues may arise, particularly during transient operations. That is a matter of particular concern whenever the pumping device is used intermittently to generate flow only on demand. Further understanding of the transient dynamics of such systems and of the conditions that can lead to jamming would result in more robust peristaltic pump design. To achieve these goals, an experimental setup that simplifies the statorrotor assembly of a peristaltic hose pump was used. In this setup, a roller transfers momentum to a liquid suspension, upon application of a constant load. The evolution of the velocity of the roller was recorded for different concentrations of mono-dispersed spheres of different diameters. The flow is found not to be strongly dependent on the dispersed particle volume fraction, if the size of the suspended phase is comparable with the hose diameter. Conversely, the flow is strongly slowed down when their size is small and the particle concentration is increased. These findings could help improving the design of peristaltic pumps by a more appropriate sizing, given the diameter of the hose and that of the particles to be transported.

  10. Transient peristaltic transport of grains in a liquid

    Science.gov (United States)

    Marconati, Marco; Rault, Sharvari; Charkhi, Farshad; Burbidge, Adam; Engmann, Jan; Ramaioli, Marco

    2017-06-01

    Pumping suspensions and pastes has always been a significant technological challenge in a number of industrial applications ranging from food processing to mining. Peristaltic pumps have become popular to pump and/or dose complex fluids, due to their robustness. During the transport of suspensions with peristaltic pumps, clogging issues may arise, particularly during transient operations. That is a matter of particular concern whenever the pumping device is used intermittently to generate flow only on demand. Further understanding of the transient dynamics of such systems and of the conditions that can lead to jamming would result in more robust peristaltic pump design. To achieve these goals, an experimental setup that simplifies the statorrotor assembly of a peristaltic hose pump was used. In this setup, a roller transfers momentum to a liquid suspension, upon application of a constant load. The evolution of the velocity of the roller was recorded for different concentrations of mono-dispersed spheres of different diameters. The flow is found not to be strongly dependent on the dispersed particle volume fraction, if the size of the suspended phase is comparable with the hose diameter. Conversely, the flow is strongly slowed down when their size is small and the particle concentration is increased. These findings could help improving the design of peristaltic pumps by a more appropriate sizing, given the diameter of the hose and that of the particles to be transported.

  11. Effect of radiation and magnetic field on peristaltic transport of nanofluids through a porous space in a tapered asymmetric channel

    Energy Technology Data Exchange (ETDEWEB)

    Kothandapani, M., E-mail: mkothandapani@gmail.com [Department of Mathematics, University College of Engineering Arni, (A Constituent College of Anna University Chennai), Arni 632326, Tamil Nadu (India); Prakash, J., E-mail: prakashjayavel@yahoo.co.in [Department of Mathematics, Arulmigu Meenakshi Amman College of Engineering, Vadamavandal 604410, Tamil Nadu (India)

    2015-03-15

    Theoretical analyses on the effect of radiation and MHD on the peristaltic flow of a nanofluid through a porous medium in a two dimensional tapered asymmetric channel has been made. The nanofluid is assumed to be electrically conducting in the presence of a uniform magnetic field. The transport equation accounts the both Brownian motion and thermophoresis along with the radiation reaction. The problem has been further simplified with the authentic assumptions of long wavelength and small Reynolds number. The analytical expressions obtained for the axial velocity, stream function, temperature field, nanoparticle fraction field and pressure gradient provide satisfactory explanation. Influence of various parameters on the flow characteristics have been discussed with the help of graphical results. The trapping phenomenon has also been discussed in detail. - Highlights: • Combine effect of thermal radiation and MHD on the peristaltic flow of a Newtonian nanofluid are discussed. • This work may be first attempt dealing the study of Newtonian nanofluid flow in the porous tapered asymmetric channel. • The velocity, stream function, temperature field and nanoparticle fraction field provide satisfactory explanation with help of graphs.

  12. Heat Transfer Analysis for Peristaltic Mechanism in Variable Viscosity Fluid

    Institute of Scientific and Technical Information of China (English)

    T.Hayat; F.M.Abbasi; Awatif A.Hendi

    2011-01-01

    An analysis is carried out for a peristaltic flow of a third-order fluid with heat transfer and variable viscosity when no-slip condition does not hold. Perturbation solution is discussed and a comparative study between the cases of constant and variable viscosities is presented and analyzed.%@@ An analysis is carried out for a peristaltic flow of a third-order fluid with heat transfer and variable viscosity when no-slip condition does not hold.Perturbation solution is discussed and a comparative stuity between the cases of constant and variable viscosities is presented and analyzed.

  13. Peristaltic ion source

    Energy Technology Data Exchange (ETDEWEB)

    Brown, I.G.; Anders, A.; Anders, S.; Dickinson, M.R.; MacGill, R.A.

    1995-08-01

    Conventional ion sources generate energetic ion beams by accelerating the plasma-produced ions through a voltage drop at the extractor, and since it is usual that the ion beam is to propagate in a space which is at ground potential, the plasma source is biased at extractor voltage. For high ion beam energy the plasma source and electrical systems need to be raised to high voltage, a task that adds considerable complexity and expense to the total ion source system. The authors have developed a system which though forming energetic ion beams at ground potential as usual, operates with the plasma source and electronics at ground potential also. Plasma produced by a nearby source streams into a grided chamber that is repetitively pulsed from ground to high positive potential, sequentially accepting plasma into its interior region and ejecting it energetically. They call the device a peristaltic ion source. In preliminary tests they`ve produced nitrogen and titanium ion beams at energies from 1 to 40 keV. Here they describe the philosophy behind the approach, the test embodiment that they have made, and some preliminary results.

  14. Two-dimensional magma-repository interactions

    NARCIS (Netherlands)

    Bokhove, O.

    2001-01-01

    Two-dimensional simulations of magma-repository interactions reveal that the three phases --a shock tube, shock reflection and amplification, and shock attenuation and decay phase-- in a one-dimensional flow tube model have a precursor. This newly identified phase ``zero'' consists of the impact of

  15. Numerical modeling method on the movement of water flow and suspended solids in two-dimensional sedimentation tanks in the wastewater treatment plant

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Taking the distributing calculation of velocity and concentration as an example, the paper established a series of governing equations by the vorticity-stream function method, and dispersed the equations by the finite differencing method. After figuring out the distribution field of velocity, the paper also calculated the concentration distribution in sedimentation tank by using the two-dimensional concentration transport equation. The validity and feasibility of the numerical method was verified through comparing with experimental data. Furthermore, the paper carried out a tentative exploration into the application of numerical simulation of sedimentation tanks.

  16. Peristaltic transport of MHD Williamson fluid in an inclined asymmetric channel through porous medium with heat transfer

    Institute of Scientific and Technical Information of China (English)

    K. Ramesh; M. Devakar

    2015-01-01

    The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.

  17. Correlation between DNAPL distribution area and dissolved concentration in surfactant enhanced aquifer remediation effluent: a two-dimensional flow cell study

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Bin; Li, Huiying; Du, Xiaoming; Zhong, Lirong; Yang, Bin; Du, Ping; Gu, Qingbao; Li, Fasheng

    2016-02-01

    During the process of surfactant enhanced aquifer remediation (SEAR), free phase dense non-aqueous phase liquid (DNAPL) may be mobilized and spread. The understanding of the impact of DNAPL spreading on the SEAR remediation is not sufficient with its positive effect infrequently mentioned. To evaluate the correlation between DNAPL spreading and remediation efficiency, a two-dimensional sandbox apparatus was used to simulate the migration and dissolution process of 1,2-DCA (1,2-dichloroethane) DNAPL in SEAR. Distribution area of DNAPL in the sandbox was determined by digital image analysis and correlated with effluent DNAPL concentration. The results showed that the effluent DNAPL concentration has significant positive linear correlation with the DNAPL distribution area, indicating the mobilization of DNAPL could improve remediation efficiency by enlarging total NAPL-water interfacial area for mass transfer. Meanwhile, the vertical migration of 1,2-DCA was limited within the boundary of aquifer in all experiments, implying that by manipulating injection parameters in SEAR, optimal remediation efficiency can be reached while the risk of DNAPL vertical migration is minimized. This study provides a convenient visible and quantitative method for the optimization of parameters for SEAR project, and an approach of rapid predicting the extent of DNAPL contaminant distribution based on the dissolved DNAPL concentration in the extraction well.

  18. Correlation between DNAPL distribution area and dissolved concentration in surfactant enhanced aquifer remediation effluent: A two-dimensional flow cell study.

    Science.gov (United States)

    Wu, Bin; Li, Huiying; Du, Xiaoming; Zhong, Lirong; Yang, Bin; Du, Ping; Gu, Qingbao; Li, Fasheng

    2016-02-01

    During the process of surfactant enhanced aquifer remediation (SEAR), free phase dense non-aqueous phase liquid (DNAPL) may be mobilized and spread. The understanding of the impact of DNAPL spreading on the SEAR remediation is not sufficient with its positive effect infrequently mentioned. To evaluate the correlation between DNAPL spreading and remediation efficiency, a two-dimensional sandbox apparatus was used to simulate the migration and dissolution process of 1,2-DCA (1,2-dichloroethane) DNAPL in SEAR. Distribution area of DNAPL in the sandbox was determined by digital image analysis and correlated with effluent DNAPL concentration. The results showed that the effluent DNAPL concentration has significant positive linear correlation with the DNAPL distribution area, indicating the mobilization of DNAPL could improve remediation efficiency by enlarging total NAPL-water interfacial area for mass transfer. Meanwhile, the vertical migration of 1,2-DCA was limited within the boundary of aquifer in all experiments, implying that by manipulating injection parameters in SEAR, optimal remediation efficiency can be reached while the risk of DNAPL vertical migration is minimized. This study provides a convenient visible and quantitative method for the optimization of parameters for SEAR project, and an approach of rapid predicting the extent of DNAPL contaminant distribution based on the dissolved DNAPL concentration in the extraction well.

  19. Peristaltic flow of a fluid in a porous channel: A study having relevance to flow of bile within ducts in a pathological state

    CERN Document Server

    Maiti, S; 10.1016/j.ijengsci.2011.05.006

    2011-01-01

    The paper deals with a theoretical study of the transport of a fluid in a channel, which takes place by the phenomenon of peristalsis. A mathematical analysis of the said problem has been presented. The analysis involves the application of a suitable perturbation technique. The velocity profile and the critical pressure for the occurrence of reflux are investigated with particular emphasis by using appropriate numerical methods. The effects of various parameters, such as Reynolds number, pressure gradient, porosity parameter, Darcy number, slip parameter, amplitude ratio and wave number on velocity and critical pressure for reflux are investigated in detail. The computed results are compared with a previous analytical work and an experimental investigation reported earlier in existing scientific literatures. The results of the present study are in conformity to both of them. The study has got some relevance to the physiological flow of bile in the common bile duct in a pathological state. It reveals that in t...

  20. Lymphocyte profiles in multiple myeloma and monoclonal gammopathy of undetermined significance: flow-cytometric characterization and analysis in a two-dimensional correlation biplot.

    Science.gov (United States)

    Van den Hove, L E; Meeus, P; Derom, A; Demuynck, H; Verhoef, G E; Vandenberghe, P; Boogaerts, M A

    1998-06-01

    The distribution of 27 T-, B-, and natural killer-cell subsets in the peripheral blood of 40 patients with multiple myeloma (MM), ten patients with monoclonal gammopathy of undetermined significance (MGUS), and 40 healthy donors was investigated by means of classical univariate statistics and advanced multivariate data-analytical techniques. The latter approach was used to describe, represent, and analyze lymphocyte subset distribution in a two-dimensional correlation biplot, allowing comparison of complex lymphocyte profiles (i.e., compound lymphocyte subset distributions) of individual subjects rather than isolated subset values of selected patient and/or donor groups. The correlation biplot revealed that, in accordance with the univariate statistics, the MM patients were characterized by marked shifts towards CD8+, CD57+, CD62L-, CD(16+56)+, and HLA-DR+ T cells, suggesting in vivo immune activation. The activation profile was most markedly observed in treated MM patients in the advanced disease stage category. The lymphocyte profiles of MGUS patients were heterogeneous, with approximately half of them located in the swarm of MM patients and the other half in the swarm of healthy donors. Although the univariate statistics revealed significant differences between MGUS patients and healthy donors only within the B-cell compartment, the correlation biplot revealed that two MGUS patients clearly had a typical T-cell activation profile similar to that of the MM patients. One MGUS patient with a T-cell activation profile progressed 13 months later to a stage IA MM and required chemotherapy. A marked lymphocyte profile shift in one MM patient was associated with terminal and aggressive disease transformation. Our study illustrates further the practical use of correlation biplots for the detection of aberrant lymphocyte profiles and/or profile shifts in individual patients.

  1. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    of this thesis is on online comprehensive two-dimensional liquid chromatography (online LC×LC) with reverse phase in both dimensions (online RP×RP). Since online RP×RP has not been attempted before within this research group, a significant part of this thesis consists of knowledge and experience gained...

  2. Saturation of the response to stochastic forcing in two-dimensional backward-facing step flow: A self-consistent approximation

    Science.gov (United States)

    Mantič-Lugo, Vladislav; Gallaire, François

    2016-12-01

    Selective noise amplifiers are characterized by large linear amplification to external perturbations in a particular frequency range despite their global linear stability. Applying a stochastic forcing with increasing amplitude, the response undergoes a strong nonlinear saturation when compared to the linear estimation. Building upon our previous work, we introduce a predictive model that describes this nonlinear dynamics, and we apply it to a canonical example of selective noise amplifiers: the backward-facing step flow. Rewriting conveniently the stochastic forcing and response in the frequency domain, the model consists in a mean flow equation coupled to the linear response to forcing at each frequency. This coupling is attained by the Reynolds stress, which is constructed by the integral in frequency of the independent responses. We generalize the model for a response to a white noise forcing δ -correlated in space and time restricting the flow dynamics to its most energetic patterns calculated from the optimal harmonic forcing and response of the flow. The model estimates accurately the response saturation when compared to direct numerical simulations, and it correctly approximates the structure of the response and the mean flow modification. It also shows that the response undergoes a selective process governed by the nonlinear gain, which promotes a response structure with an approximately single frequency and wavelength in the whole domain. These results suggest that the mean flow modification by the Reynolds stress is the key nonlinearity in the saturation process of the response to white noise.

  3. Towards two-dimensional search engines

    CERN Document Server

    Ermann, Leonardo; Shepelyansky, Dima L

    2011-01-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Information flow properties on PageRank-CheiRank plane are analyzed for networks of British, French and Italian Universities, Wikipedia, Linux Kernel, gene regulation and other networks. Methods of spam links control are also analyzed.

  4. Toward two-dimensional search engines

    Science.gov (United States)

    Ermann, L.; Chepelianskii, A. D.; Shepelyansky, D. L.

    2012-07-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank-CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed.

  5. Effects of Ramped Wall Temperature on Unsteady Two-Dimensional Flow Past a Vertical Plate with Thermal Radiation and Chemical Reaction

    Directory of Open Access Journals (Sweden)

    V. Rajesh

    2014-08-01

    Full Text Available The interaction of free convection with thermal radiation of a viscous incompressible unsteady flow past a vertical plate with ramped wall temperature and mass diffusion is presented here, taking into account the homogeneous chemical reaction of first order. The fluid is gray, absorbing-emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative flux in the energy equation. The dimensionless governing equations are solved using an implicit finite-difference method of the Crank-Nicolson type, which is stable and convergent. The velocity profiles are compared with the available theoretical solution and are found to be in good agreement. Numerical results for the velocity, the temperature, the concentration, the local and average skin friction, the Nusselt number and Sherwood number are shown graphically. This work has wide application in chemical and power engineering and also in the study of vertical air flow into the atmosphere. The present results can be applied to an important class of flows in which the driving force for the flow is provided by combination of the thermal and chemical species diffusion effects.

  6. Two-dimensional simulation by regularization of free surface viscoplastic flows with Drucker-Prager yield stress and application to granular collapse

    Science.gov (United States)

    Lusso, Christelle; Ern, Alexandre; Bouchut, François; Mangeney, Anne; Farin, Maxime; Roche, Olivier

    2017-03-01

    This work is devoted to numerical modeling and simulation of granular flows relevant to geophysical flows such as avalanches and debris flows. We consider an incompressible viscoplastic fluid, described by a rheology with pressure-dependent yield stress, in a 2D setting with a free surface. We implement a regularization method to deal with the singularity of the rheological law, using a mixed finite element approximation of the momentum and incompressibility equations, and an arbitrary Lagrangian Eulerian (ALE) formulation for the displacement of the domain. The free surface is evolved by taking care of its deposition onto the bottom and of preventing it from folding over itself. Several tests are performed to assess the efficiency of our method. The first test is dedicated to verify its accuracy and cost on a one-dimensional simple shear plug flow. On this configuration we setup rules for the choice of the numerical parameters. The second test aims to compare the results of our numerical method to those predicted by an augmented Lagrangian formulation in the case of the collapse and spreading of a granular column over a horizontal rigid bed. Finally we show the reliability of our method by comparing numerical predictions to data from experiments of granular collapse of both trapezoidal and rectangular columns over horizontal rigid or erodible granular bed made of the same material. We compare the evolution of the free surface, the velocity profiles, and the static-flowing interface. The results show the ability of our method to deal numerically with the front behavior of granular collapses over an erodible bed.

  7. Two dimensional unstable scar statistics.

    Energy Technology Data Exchange (ETDEWEB)

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)

    2006-12-01

    This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.

  8. Two-Dimensional Vernier Scale

    Science.gov (United States)

    Juday, Richard D.

    1992-01-01

    Modified vernier scale gives accurate two-dimensional coordinates from maps, drawings, or cathode-ray-tube displays. Movable circular overlay rests on fixed rectangular-grid overlay. Pitch of circles nine-tenths that of grid and, for greatest accuracy, radii of circles large compared with pitch of grid. Scale enables user to interpolate between finest divisions of regularly spaced rule simply by observing which mark on auxiliary vernier rule aligns with mark on primary rule.

  9. Simulating high Reynolds number flow in two-dimensional lid-driven cavity by multi-relaxation-time lattice Boltzmann method

    Institute of Scientific and Technical Information of China (English)

    Chai Zhen-Hua; Shi Bao-Chang; Zheng Lin

    2006-01-01

    By coupling the non-equilibrium extrapolation scheme for boundary condition with the multi-relaxation-time lattice Boltzmann method, this paper finds that the stability of the multi-relaxation-time model can be improved greatly, especially on simulating high Reynolds number (Re) flow. As a discovery, the super-stability analysed by Lallemand and Luo is verified and the complex structure of the cavity flow is also exhibited in our numerical simulation when Re is high enough. To the best knowledge of the authors, the maximum of Re which has been investigated by direct numerical simulation is only around 50 000 in the literature; however, this paper can readily extend the maximum to 1000 000 with the above combination.

  10. A Novel Method for the Numerical Solution of the Navier-Stokes Equations in Two-Dimensional Flow Using a Pressure Poisson Equation

    Science.gov (United States)

    Messaris, G. T.; Papastavrou, C. A.; Loukopoulos, V. C.; Karahalios, G. T.

    2009-08-01

    A new finite-difference method is presented for the numerical solution of the Navier-Stokes equations of motion of a viscous incompressible fluid in two (or three) dimensions and in the primitive-variable formulation. Introducing two auxiliary functions of the coordinate system and considering the form of the initial equation on lines passing through the nodal point (x0, y0) and parallel to the coordinate axes, we can separate it into two parts that are finally reduced to ordinary differential equations, one for each dimension. The final system of linear equations in n-unknowns is solved by an iterative technique and the method converges rapidly giving satisfactory results. For the pressure variable we consider a pressure Poisson equation with suitable Neumann boundary conditions. Numerical results, confirming the accuracy of the proposed method, are presented for configurations of interest, like Poiseuille flow and the flow between two parallel plates with step under the presence of a pressure gradient.

  11. 层流炉二维PIV自动控制系统%Design and Experiment of the Two-dimensional PIV Automatic Control System for Laminar Entrained Flow Reactor

    Institute of Scientific and Technical Information of China (English)

    杨延强; 易维明; 李志合; 柏雪源; 李永军

    2012-01-01

    In the cold PIV (particle image velocimetry) system of the laminar entrained flow reactor, the relative position between the camera and the measuring tube was an important condition to ensure accurate test data. To make the PIV operation more convenient, accurate, and fast in the test, two-dimensional PIV automatic control system was designed. And the reliability of the system was tested in the cold simulation equipment of laminar flow furnace, compared with no using two-dimensional PIV automatic control system, the results showed that in different sections of the measuring tube, the particle speed of the axial center achieves a smooth transition, and eliminates the jump change; when collection distance is 350mm and main air flow rate is 1. 5 mVh, the relative error of particle residence time is 9. 218% ; and the operation saves time and effort in the test process. These suggested that the two-dimensional PIV automatic control system could satisfy the cold test of the laminar entrained flow reactor needs, achieve uniform and continuous test, reduce human error and improve the accuracy of test data.%在层流炉冷态粒子图像测速( PIV)系统中,相机与测量管的相对位置是保证试验数据精确的重要条件.为使试验过程中整个PIV系统操作起来更加方便、准确、快捷,设计了二维PIV自动控制系统,并在层流炉冷态模拟装置上对该系统的可靠性进行了试验验证.与没有使用二维PIV自动控制系统之前的试验结果相比:各测量段颗粒的轴向中心速度相互之间的衔接实现了平滑过渡,消除了跳跃性变化;收集距离为350 mm,主气流流量为1.5 m3/h时,层流炉内颗粒停留时间的相对误差为9.218%.说明该二维PIV自动控制系统能够满足层流炉冷态试验需要,实现了均匀、连续拍摄,减少了人为误差,提高了试验数据的准确性.

  12. Effects of Magnetic Field and an Endoscope on Peristaltic Motion

    Directory of Open Access Journals (Sweden)

    V. P. Rathod

    2011-01-01

    Full Text Available The Problem of peristaltic transport of a magnetic fluid with variable viscosity through the gap between coaxial tubes where the outer tube is nonuniform with sinusoidal wave traveling down its wall and the inner tube is rigid. The relation between the pressure gradient and friction force on the inner and outer tubes is obtained in terms of magnetic and viscosity parameter. The numerical solutions of pressure gradient, outer friction and inner friction force, and flow rate are shown graphically.

  13. An Evaluation of Recently Developed RANS-Based Turbulence Models for Flow Over a Two-Dimensional Block Subjected to Different Mesh Structures and Grid Resolutions

    Science.gov (United States)

    Kardan, Farshid; Cheng, Wai-Chi; Baverel, Olivier; Porté-Agel, Fernando

    2016-04-01

    Understanding, analyzing and predicting meteorological phenomena related to urban planning and built environment are becoming more essential than ever to architectural and urban projects. Recently, various version of RANS models have been established but more validation cases are required to confirm their capability for wind flows. In the present study, the performance of recently developed RANS models, including the RNG k-ɛ , SST BSL k-ω and SST ⪆mma-Reθ , have been evaluated for the flow past a single block (which represent the idealized architecture scale). For validation purposes, the velocity streamlines and the vertical profiles of the mean velocities and variances were compared with published LES and wind tunnel experiment results. Furthermore, other additional CFD simulations were performed to analyze the impact of regular/irregular mesh structures and grid resolutions based on selected turbulence model in order to analyze the grid independency. Three different grid resolutions (coarse, medium and fine) of Nx × Ny × Nz = 320 × 80 × 320, 160 × 40 × 160 and 80 × 20 × 80 for the computational domain and nx × nz = 26 × 32, 13 × 16 and 6 × 8, which correspond to number of grid points on the block edges, were chosen and tested. It can be concluded that among all simulated RANS models, the SST ⪆mma-Reθ model performed best and agreed fairly well to the LES simulation and experimental results. It can also be concluded that the SST ⪆mma-Reθ model provides a very satisfactory results in terms of grid dependency in the fine and medium grid resolutions in both regular and irregular structure meshes. On the other hand, despite a very good performance of the RNG k-ɛ model in the fine resolution and in the regular structure grids, a disappointing performance of this model in the coarse and medium grid resolutions indicates that the RNG k-ɛ model is highly dependent on grid structure and grid resolution. These quantitative validations are essential

  14. 微极流体蠕动泵经由滑移边界管道输送的Stokes流动%Study on Stokes Flow of Micro-Polar Fluids by Peristaltic Pumping Through a Tube With Slip Boundary Condition

    Institute of Scientific and Technical Information of China (English)

    D·特里帕蒂; M·K·乔伯; P·K·古泊塔; 吴承平

    2011-01-01

    The Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of slip boundary condition was studied. The motion of wall was governed by the sinusoidal wave equation. Analytical and numerical solutions for axial velocity, micro-polar vector, stream function, pressure gradient, friction force and mechanical efficiency were obtained by using the lubrication theory. The impacts of emerging parameters such as coupling number, micro-polar parameter and slip parameter on pumping characteristic, friction force and trapping phenomena were depicted graphically. Numerical computation infers that more pressure requires for peristaltic pumping when coupling number is large while opposite behavior is found for micro-polar parameter and the slip parameter. The size of trapped bolus reduces with coupling number and micro-polar parameter whereas it blows up with slip parameter.%计及管道边界条件滑移的影响,研究微极流体蠕动泵,经由圆柱形管道输运的Stokes流动.壁面运动的控制方程为正弦波方程.使用润滑理论,得到了轴向速度、微转动向量、流函数、压力梯度、摩擦力和机械效率的解析数值解.用图形表示出构成参数,如像耦合参数、微极参数和表征蠕流泵特性的滑移参数、摩擦力和俘获现象的影响.数值计算表明,当耦合参数较大时,需要蠕动泵的压力更大,而微极参数和滑移参数正相反.俘获团块的大小随耦合参数和微极参数的减小而缩小,而随滑移参数的增大而缩小.

  15. Examples of numerical simulations of two-dimensional unsaturated flow with VS2DI code using different interblock conductivity averaging schemes

    Directory of Open Access Journals (Sweden)

    Szymkiewicz Adam

    2015-09-01

    Full Text Available Flow in unsaturated porous media is commonly described by the Richards equation. This equation is strongly nonlinear due to interrelationships between water pressure head (negative in unsaturated conditions, water content and hydraulic conductivity. The accuracy of numerical solution of the Richards equation often depends on the method used to estimate average hydraulic conductivity between neighbouring nodes or cells of the numerical grid. The present paper discusses application of the computer simulation code VS2DI to three test problems concerning infiltration into an initially dry medium, using various methods for inter-cell conductivity calculation (arithmetic mean, geometric mean and upstream weighting. It is shown that the influence of the averaging method can be very large for coarse grid, but that it diminishes as cell size decreases. Overall, the arithmetic average produced the most reliable results for coarse grids. Moreover, the difference between results obtained with various methods is a convenient indicator of the adequacy of grid refinement.

  16. Examples of numerical simulations of two-dimensional unsaturated flow with VS2DI code using different interblock conductivity averaging schemes

    Science.gov (United States)

    Szymkiewicz, Adam; Tisler, Witold; Burzyński, Kazimierz

    2015-09-01

    Flow in unsaturated porous media is commonly described by the Richards equation. This equation is strongly nonlinear due to interrelationships between water pressure head (negative in unsaturated conditions), water content and hydraulic conductivity. The accuracy of numerical solution of the Richards equation often depends on the method used to estimate average hydraulic conductivity between neighbouring nodes or cells of the numerical grid. The present paper discusses application of the computer simulation code VS2DI to three test problems concerning infiltration into an initially dry medium, using various methods for inter-cell conductivity calculation (arithmetic mean, geometric mean and upstream weighting). It is shown that the influence of the averaging method can be very large for coarse grid, but that it diminishes as cell size decreases. Overall, the arithmetic average produced the most reliable results for coarse grids. Moreover, the difference between results obtained with various methods is a convenient indicator of the adequacy of grid refinement.

  17. Two-dimensional liquid chromatography

    DEFF Research Database (Denmark)

    Græsbøll, Rune

    Two-dimensional liquid chromatography has received increasing interest due to the rise in demand for analysis of complex chemical mixtures. Separation of complex mixtures is hard to achieve as a simple consequence of the sheer number of analytes, as these samples might contain hundreds or even...... dimensions. As a consequence of the conclusions made within this thesis, the research group has, for the time being, decided against further development of online LC×LC systems, since it was not deemed ideal for the intended application, the analysis of the polar fraction of oil. Trap-and...

  18. A new numerical method to calculate inhomogeneous and time-dependent large deformation of two-dimensional geodynamic flows with application to diapirism

    Science.gov (United States)

    Fuchs, L.; Schmeling, H.

    2013-08-01

    A key to understand many geodynamic processes is studying the associated large deformation fields. Finite deformation can be measured in the field by using geological strain markers giving the logarithmic strain f = log 10(R), where R is the ellipticity of the strain ellipse. It has been challenging to accurately quantify finite deformation of geodynamic models for inhomogeneous and time-dependent large deformation cases. We present a new formulation invoking a 2-D marker-in-cell approach. Mathematically, one can describe finite deformation by a coordinate transformation to a Lagrangian reference frame. For a known velocity field the deformation gradient tensor, F, can be calculated by integrating the differential equation DtFij = LikFkj, where L is the velocity gradient tensor and Dt the Lagrangian derivative. The tensor F contains all information about the minor and major semi-half axes and orientation of the strain ellipse and the rotation. To integrate the equation centrally in time and space along a particle's path, we use the numerical 2-D finite difference code FDCON in combination with a marker-in-cell approach. For a sufficiently high marker density we can accurately calculate F for any 2-D inhomogeneous and time-dependent creeping flow at any point for a deformation f up to 4. Comparison between the analytical and numerical solution for the finite deformation within a Poiseuille-Couette flow shows an error of less than 2 per cent for a deformation up to f = 1.7. Moreover, we determine the finite deformation and strain partitioning within Rayleigh-Taylor instabilities (RTIs) of different viscosity and layer thickness ratios. These models provide a finite strain complement to the RTI benchmark of van Keken et al. Large finite deformation of up to f = 4 accumulates in RTIs within the stem and near the compositional boundaries. Distinction between different stages of diapirism shows a strong correlation between a maximum occurring deformation of f = 1, 3 and

  19. Two-dimensional modeling of a polymer electrolyte membrane fuel cell with long flow channel. Part II. Physics-based electrochemical impedance analysis

    Science.gov (United States)

    Bao, Cheng; Bessler, Wolfgang G.

    2015-03-01

    The state-of-the-art electrochemical impedance spectroscopy (EIS) calculations have not yet started from fully multi-dimensional modeling. For a polymer electrolyte membrane fuel cell (PEMFC) with long flow channel, the impedance plot shows a multi-arc characteristic and some impedance arcs could merge. By using a step excitation/Fourier transform algorithm, an EIS simulation is implemented for the first time based on the full 2D PEMFC model presented in the first part of this work. All the dominant transient behaviors are able to be captured. A novel methodology called 'configuration of system dynamics', which is suitable for any electrochemical system, is then developed to resolve the physical meaning of the impedance spectra. In addition to the high-frequency arc due to charge transfer, the Nyquist plots contain additional medium/low-frequency arcs due to mass transfer in the diffusion layers and along the channel, as well as a low-frequency arc resulting from water transport in the membrane. In some case, the impedance spectra appear partly inductive due to water transport, which demonstrates the complexity of the water management of PEMFCs and the necessity of physics-based calculations.

  20. Two-dimensional capillary origami

    Energy Technology Data Exchange (ETDEWEB)

    Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu

    2016-01-08

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

  1. Two-dimensional quantum repeaters

    Science.gov (United States)

    Wallnöfer, J.; Zwerger, M.; Muschik, C.; Sangouard, N.; Dür, W.

    2016-11-01

    The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.

  2. Two-dimensional capillary origami

    Science.gov (United States)

    Brubaker, N. D.; Lega, J.

    2016-01-01

    We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid.

  3. Two-dimensional cubic convolution.

    Science.gov (United States)

    Reichenbach, Stephen E; Geng, Frank

    2003-01-01

    The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.

  4. 沟道二维泥石流运动和冲淤数值模型研究%Two-dimensional numerical model for debris flow motion and gully bed evolution

    Institute of Scientific and Technical Information of China (English)

    张万顺; 赵琰鑫; 崔鹏; 彭虹; 陈雪娇

    2012-01-01

    以水沙混合流模型为基础,采用混合流沙量动态变化模式,提出泥石流运动控制方程组,建立适用于模拟泥石流在天然沟道中的运动和冲淤过程的二维数值模型.模型基于水动力学理论、水沙两相混合流理论和宾汉体模型理论,考虑了泥石流运动、泥沙输移、沟床变形、泥石流宾汉体流变特性等主要动力学过程.将模型应用于云南东川蒋家沟实测泥石流过程的模拟研究,结果较好地反映了泥石流运动不连续性的特征和泥石流沟道冲淤随时间演变的实际规律.%A two-dimensional mathematical model of debris flow in natural gully is developed. Based on the hydrodynamic theory, the water-sediments two-phase flow theory and the Bingham rheological theory, the dynamic processes of debris flow movement, sediment transport, bed evolution and rheological properties of the debris flow are considered. The model is applied to simulate debris flow event in Jiangjia Gully, Yunnan Province and predict the flow pattern and bed erosion-deposition processes. The results show the effectiveness of the proposed model.

  5. Peristaltic transport of Carreau-Yasuda fluid in a curved channel with slip effects.

    Directory of Open Access Journals (Sweden)

    Tasawar Hayat

    Full Text Available The wide occurrence of peristaltic pumping should not be surprising at all since it results physiologically from neuro-muscular properties of any tubular smooth muscle. Of special concern here is to predict the rheological effects on the peristaltic motion in a curved channel. Attention is focused to develop and simulate a nonlinear mathematical model for Carreau-Yasuda fluid. The progressive wave front of peristaltic flow is taken sinusoidal (expansion/contraction type. The governing problem is challenge since it has nonlinear differential equation and nonlinear boundary conditions even in the long wavelength and low Reynolds number regime. Numerical solutions for various flow quantities of interest are presented. Comparison for different flow situations is also made. Results of physical quantities are interpreted with particular emphasis to rheological characteristics.

  6. Classifying Two-dimensional Hyporeductive Triple Algebras

    CERN Document Server

    Issa, A Nourou

    2010-01-01

    Two-dimensional real hyporeductive triple algebras (h.t.a.) are investigated. A classification of such algebras is presented. As a consequence, a classification of two-dimensional real Lie triple algebras (i.e. generalized Lie triple systems) and two-dimensional real Bol algebras is given.

  7. Peristaltic pumping in an elastic tube: feeding the hungry python

    Science.gov (United States)

    Takagi, Daisuke; Balmforth, Neil

    2010-11-01

    Biological ducts convey contents like food in the digestive system by peristaltic action, propagating waves of muscular contraction and relaxation. The motion is investigated theoretically by considering a radial force of sinusoidal or Gaussian form moving steadily down a fluid-filled axisymmetric tube. Effects of the prescribed force on the resultant fluid flow and elastic deformation of the tube wall are presented. The flow can induce a rigid object suspended in the fluid to propel in different ways, as demonstrated in numerous examples.

  8. Interpreting the cross-sectional flow field in a river bank based on a genetic-algorithm two-dimensional heat-transport method (GA-VS2DH)

    Science.gov (United States)

    Su, Xiaoru; Shu, Longcang; Chen, Xunhong; Lu, Chengpeng; Wen, Zhonghui

    2016-12-01

    Interactions between surface waters and groundwater are of great significance for evaluating water resources and protecting ecosystem health. Heat as a tracer method is widely used in determination of the interactive exchange with high precision, low cost and great convenience. The flow in a river-bank cross-section occurs in vertical and lateral directions. In order to depict the flow path and its spatial distribution in bank areas, a genetic algorithm (GA) two-dimensional (2-D) heat-transport nested-loop method for variably saturated sediments, GA-VS2DH, was developed based on Microsoft Visual Basic 6.0. VS2DH was applied to model a 2-D bank-water flow field and GA was used to calibrate the model automatically by minimizing the difference between observed and simulated temperatures in bank areas. A hypothetical model was developed to assess the reliability of GA-VS2DH in inverse modeling in a river-bank system. Some benchmark tests were conducted to recognize the capability of GA-VS2DH. The results indicated that the simulated seepage velocity and parameters associated with GA-VS2DH were acceptable and reliable. Then GA-VS2DH was applied to two field sites in China with different sedimentary materials, to verify the reliability of the method. GA-VS2DH could be applied in interpreting the cross-sectional 2-D water flow field. The estimates of horizontal hydraulic conductivity at the Dawen River and Qinhuai River sites are 1.317 and 0.015 m/day, which correspond to sand and clay sediment in the two sites, respectively.

  9. Interpreting the cross-sectional flow field in a river bank based on a genetic-algorithm two-dimensional heat-transport method (GA-VS2DH)

    Science.gov (United States)

    Su, Xiaoru; Shu, Longcang; Chen, Xunhong; Lu, Chengpeng; Wen, Zhonghui

    2016-08-01

    Interactions between surface waters and groundwater are of great significance for evaluating water resources and protecting ecosystem health. Heat as a tracer method is widely used in determination of the interactive exchange with high precision, low cost and great convenience. The flow in a river-bank cross-section occurs in vertical and lateral directions. In order to depict the flow path and its spatial distribution in bank areas, a genetic algorithm (GA) two-dimensional (2-D) heat-transport nested-loop method for variably saturated sediments, GA-VS2DH, was developed based on Microsoft Visual Basic 6.0. VS2DH was applied to model a 2-D bank-water flow field and GA was used to calibrate the model automatically by minimizing the difference between observed and simulated temperatures in bank areas. A hypothetical model was developed to assess the reliability of GA-VS2DH in inverse modeling in a river-bank system. Some benchmark tests were conducted to recognize the capability of GA-VS2DH. The results indicated that the simulated seepage velocity and parameters associated with GA-VS2DH were acceptable and reliable. Then GA-VS2DH was applied to two field sites in China with different sedimentary materials, to verify the reliability of the method. GA-VS2DH could be applied in interpreting the cross-sectional 2-D water flow field. The estimates of horizontal hydraulic conductivity at the Dawen River and Qinhuai River sites are 1.317 and 0.015 m/day, which correspond to sand and clay sediment in the two sites, respectively.

  10. Two-dimensional function photonic crystals

    CERN Document Server

    Wu, Xiang-Yao; Liu, Xiao-Jing; Liang, Yu

    2016-01-01

    In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed into the appropriate band gaps structures by the two-dimensional function photonic crystals.

  11. Optimal excitation of two dimensional Holmboe instabilities

    CERN Document Server

    Constantinou, Navid C

    2010-01-01

    Highly stratified shear layers are rendered unstable even at high stratifications by Holmboe instabilities when the density stratification is concentrated in a small region of the shear layer. These instabilities may cause mixing in highly stratified environments. However these instabilities occur in tongues for a limited range of parameters. We perform Generalized Stability analysis of the two dimensional perturbation dynamics of an inviscid Boussinesq stratified shear layer and show that Holmboe instabilities at high Richardson numbers can be excited by their adjoints at amplitudes that are orders of magnitude larger than by introducing initially the unstable mode itself. We also determine the optimal growth that obtains for parameters for which there is no instability. We find that there is potential for large transient growth regardless of whether the background flow is exponentially stable or not and that the characteristic structure of the Holmboe instability asymptotically emerges for parameter values ...

  12. Two-dimensional lattice Boltzmann model for magnetohydrodynamics.

    Science.gov (United States)

    Schaffenberger, Werner; Hanslmeier, Arnold

    2002-10-01

    We present a lattice Boltzmann model for the simulation of two-dimensional magnetohydro dynamic (MHD) flows. The model is an extension of a hydrodynamic lattice Boltzman model with 9 velocities on a square lattice resulting in a model with 17 velocities. Earlier lattice Boltzmann models for two-dimensional MHD used a bidirectional streaming rule. However, the use of such a bidirectional streaming rule is not necessary. In our model, the standard streaming rule is used, allowing smaller viscosities. To control the viscosity and the resistivity independently, a matrix collision operator is used. The model is then applied to the Hartmann flow, giving reasonable results.

  13. Infusion of iloprost without a peristaltic pump: Safety and tolerability

    Directory of Open Access Journals (Sweden)

    Paola Faggioli

    2013-04-01

    Full Text Available Introduction: Iloprost is a potent prostacyclin (PGI2 analogue that is effective in the treatment of peripheral arterial disease, vasculitis, pulmonary hypertension, and secondary Raynaud’s phenomenon. Intravenous infusions are generally administered with the aid of a peristaltic pump to reduce the risk of adverse reactions caused by unintentional increases in the infusion rate. This increases the cost of care in terms of equipment and personnel and may limit the use of this drug. Materials and methods: We retrospectively analyzed 18,432 iloprost infusions administered between 1999 and 2009 to 272 patients with systemic sclerosis (n = 253 and 19 with peripheral arterial disease (n = 19. All infusions were administered in the day hospital over 6 h with a normal IV set-up with a roller flow regulator. Flow rates were set to deliver iloprost at 1-2 ng/kg/min. Rates were verified by direct drop counts during the first 15-20 minutes of the infusion and at each subsequent check. Results: There were no adverse events that were fatal, life-threatening, or associated with prolongation of hospitalization and very few events requiring intensive care or continuous monitoring. The latter included 4 cases of tachycardia/arrhythmia (extrasystoles in most cases, 3 cases of hypotension (systolic pressure < 80 mmHg, and 2 cases of hypertension (BP > 170/100 mmHg. All other adverse reactions were mild, reversible, and similar to those seen with iloprost infusion with peristaltic pump. Only one patient had to be switched to another prostanoid (due to intolerance. Discussion: Iloprost infusion administered with a normal IV flow regulator appears to be as safe, well tolerated, and effective as traditional infusion with a peristaltic pump.

  14. Hadamard States and Two-dimensional Gravity

    CERN Document Server

    Salehi, H

    2001-01-01

    We have used a two-dimensional analog of the Hadamard state-condition to study the local constraints on the two-point function of a linear quantum field conformally coupled to a two-dimensional gravitational background. We develop a dynamical model in which the determination of the state of the quantum field is essentially related to the determination of a conformal frame. A particular conformal frame is then introduced in which a two-dimensional gravitational equation is established.

  15. Topological defects in two-dimensional crystals

    OpenAIRE

    Chen, Yong; Qi, Wei-Kai

    2008-01-01

    By using topological current theory, we study the inner topological structure of the topological defects in two-dimensional (2D) crystal. We find that there are two elementary point defects topological current in two-dimensional crystal, one for dislocations and the other for disclinations. The topological quantization and evolution of topological defects in two-dimensional crystals are discussed. Finally, We compare our theory with Brownian-dynamics simulations in 2D Yukawa systems.

  16. Use of on-line stop-flow heart-cutting two-dimensional high performance liquid chromatography for simultaneous determination of 12 major constituents in tartary buckwheat (Fagopyrum tataricum Gaertn).

    Science.gov (United States)

    Ren, Qiang; Wu, Caisheng; Zhang, Jinlan

    2013-08-23

    The use of two-dimensional liquid chromatography (2D-LC) for quantification studies presents challenges with respect to repeatability, precision, and robustness. The present study used an on-line stop-flow heart-cutting 2D-LC system to determine 12 chemical constituents in tartary buckwheat. A combination of various stationary phases was developed and bridged using two switch valves as the interface. Hydrophilic interaction chromatography was chosen for separation in the first dimension ((1)D), and mixed mode stationary phases (an amide polar-embedded phase and alkyl-phenyl phase) were used in parallel for separation in the second dimension ((2)D). The mobile phase comprised acetonitrile and water containing 0.03% aqueous phosphoric acid. The sample was separated into two fractions on the (1)D column (HILIC-10 column) using 5% acetonitrile. One fraction, mainly comprising flavonoids, was directly eluted onto the head of (2)D column (Polar Advantage II column) and further separated using a linear gradient of 11-23% acetonitrile. The second fraction, containing phenylpropanoid glycosides, was trapped on the (1)D column. This retained fraction was back-flushed onto the (2)D column (Phenyl-1 column) and separated using a linear gradient of 35-43% acetonitrile. An on-line stop-flow heart-cutting 2D-LC system was successfully developed with column switching and back-flush. This 2D-LC system was validated and was able to simultaneously determine 12 major components in tartary buckwheat: seven flavonoids, four phenylpropanoid glycosides, and N-trans-feruloyltyramine. The system showed good performance with respect to linearity (r>0.996), repeatability (RSD, relative standard deviation<3.4%), intra-day and inter-day precision (RSD<4.6%), recovery (91.2-108%), limit of detection (LOD) (0.05-0.21μg/mL), and limit of quantification (LOQ) (0.10-0.41μg/mL). The on-line stop-flow heart-cutting 2D-LC system offers a potential approach to analyze compounds, which have similar

  17. The partition function of two-dimensional string theory

    Science.gov (United States)

    Dijkgraaf, Robbert; Moore, Gregory; Plesser, Ronen

    1993-04-01

    We derive a compact and explicit expression for the generating functional of all correlation functions of tachyon operators in two-dimensional string theory. This expression makes manifest relations of the c = 1 system to KP flow nd W 1 + ∞ constraints. Moreover we derive a Kontsevich-Penner integral representation of this generating functional.

  18. The partition function of two-dimensional string theory

    Energy Technology Data Exchange (ETDEWEB)

    Dijkgraaf, R. (School of Natural Sciences, Inst. for Advanced Study, Princeton, NJ (United States) Dept. of Mathematics, Univ. Amsterdam (Netherlands)); Moore, G.; Plesser, R. (Dept. of Physics, Yale Univ., New Haven, CT (United States))

    1993-04-12

    We derive a compact and explicit expression for the generating functional of all correlation functions of tachyon operators in two-dimensional string theory. This expression makes manifest relations of the c=1 system to KP flow and W[sub 1+[infinity

  19. Strongly interacting two-dimensional Dirac fermions

    NARCIS (Netherlands)

    Lim, L.K.; Lazarides, A.; Hemmerich, Andreas; de Morais Smith, C.

    2009-01-01

    We show how strongly interacting two-dimensional Dirac fermions can be realized with ultracold atoms in a two-dimensional optical square lattice with an experimentally realistic, inherent gauge field, which breaks time reversal and inversion symmetries. We find remarkable phenomena in a temperature

  20. Topology optimization of two-dimensional waveguides

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard; Sigmund, Ole

    2003-01-01

    In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....

  1. 两种空化模型计算二维水翼空化流动研究%Study of cavitating flows around two-dimensional hydrofoil using two cavitation models

    Institute of Scientific and Technical Information of China (English)

    刘艳; 赵鹏飞; 王晓放

    2012-01-01

    Cavitating flows around a two-dimensional NACA66 hydrofoil with an angle of attack of 6.5° are studied using the mixture multiphase model and cavitation model.The Singhal′s full cavitation model(FCM) and the Zwart-Gerber-Belamri(Z-G-B) cavitation model are applied,and based on experimental data,results obtained from the two models are compared in terms of pressure distribution coefficient on the surface of the hydrofoil,lift and drag coefficients and flow field structures.The experimental results show that for the FCM,the value of mass fraction of noncondensible gases has some effects on computational results.The length of cavitation zone becomes smaller with the mass fraction of noncondensible gases decreasing.For the Z-G-B model,both vaporization and condensation coefficients have influence on results.In general,both cavitation models give satisfactory prediction results by choosing reasonable empirical coefficients.%采用混合多相流模型和空化模型对攻角为6.5°的NACA66型二维水翼的空化流动进行数值研究.使用Singhal全空化模型(FCM)和Zwart-Gerber-Belamri(Z-G-B)空化模型,以实验数据为基准,对这两种空化模型得到的翼型表面压力分布系数和升、阻力系数以及流场结构进行了比较和分析,结果表明:FCM中,不凝结气体质量分数对计算结果影响较大,空化区长度随着不凝结气体质量分数的减小而变小;Z-G-B空化模型中,蒸发系数和凝结系数对结果有较大影响.总体说来,通过选取合理的经验系数,两种空化模型都给出了令人满意的空化流动结果.

  2. Transport behavior of water molecules through two-dimensional nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Chongqin; Li, Hui; Meng, Sheng, E-mail: smeng@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-11-14

    Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.

  3. Transport behavior of water molecules through two-dimensional nanopores

    Science.gov (United States)

    Zhu, Chongqin; Li, Hui; Meng, Sheng

    2014-11-01

    Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.

  4. Hamiltonian formalism of two-dimensional Vlasov kinetic equation.

    Science.gov (United States)

    Pavlov, Maxim V

    2014-12-08

    In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented.

  5. One-and Two-dimensional Integrated Simulation of Urban Storm Pipe Network and Surface Flow%城市雨水管网与地面流的一、二维集成模拟研究

    Institute of Scientific and Technical Information of China (English)

    徐速

    2011-01-01

    Taking Beijing Yizhuang economic development area as example, the MIKE Flood integrated simulation model was used for one- and two-dimensional integrated simulation of storm pipe network and surface flow for the existing condition and constructed wetland built in the future in 1, 5, and 10 year storm return periods. The results show that under the existing condition, there are flooded areas in all 3 storm return periods, especially in more than 5 year return periods, the flooded area exceeds 10% of the total area. The constructed wetland built in the future can reduce about 20% flooded area,which locates at the upstream of the wetland, than the existing condition. The results can be utilized to do further research including risk assessment and comparison among emergency response plans to find an optimal way to reduce loss from storm.%采用MTKE n00d集成模型,以北京市亦庄经济技术开发区为案例,针对现状和未来建设人工湿地两种情景,对1年、5年、10年暴雨重现期下的淹没特性进行了雨水管网和地面流的一、二维集成模拟.模拟结果表明,在现状条件下,3种暴雨重现期都会产生淹没区域,尤其是在5年以上重现期时整个区域的10%都会被淹没;未来建设人工湿地可比现状减少20%左右的淹没面积,但其作用范围是人工湿地上游区域,对其他区域则没有明显作用.利用这些结果可进行暴雨危害的风险评估,并对各种工程方案进行比较分析,以寻找减轻暴雨淹没损失的最佳途径.

  6. Two Dimensional Plasmonic Cavities on Moire Surfaces

    Science.gov (United States)

    Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla

    2010-03-01

    We investigate surface plasmon polariton (SPP) cavitiy modes on two dimensional Moire surfaces in the visible spectrum. Two dimensional hexagonal Moire surface can be recorded on a photoresist layer using Interference lithography (IL). Two sequential exposures at slightly different angles in IL generate one dimensional Moire surfaces. Further sequential exposure for the same sample at slightly different angles after turning the sample 60 degrees around its own axis generates two dimensional hexagonal Moire cavity. Spectroscopic reflection measurements have shown plasmonic band gaps and cavity states at all the azimuthal angles (omnidirectional cavity and band gap formation) investigated. The plasmonic band gap edge and the cavity states energies show six fold symmetry on the two dimensional Moire surface as measured in reflection measurements.

  7. Two-dimensional function photonic crystals

    Science.gov (United States)

    Liu, Xiao-Jing; Liang, Yu; Ma, Ji; Zhang, Si-Qi; Li, Hong; Wu, Xiang-Yao; Wu, Yi-Heng

    2017-01-01

    In this paper, we have studied two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , that can become true easily by electro-optical effect and optical kerr effect. We calculated the band gap structures of TE and TM waves, and found the TE (TM) wave band gaps of function photonic crystals are wider (narrower) than the conventional photonic crystals. For the two-dimensional function photonic crystals, when the dielectric constant functions change, the band gaps numbers, width and position should be changed, and the band gap structures of two-dimensional function photonic crystals can be adjusted flexibly, the needed band gap structures can be designed by the two-dimensional function photonic crystals, and it can be of help to design optical devices.

  8. Two-Dimensional Planetary Surface Lander

    Science.gov (United States)

    Hemmati, H.; Sengupta, A.; Castillo, J.; McElrath, T.; Roberts, T.; Willis, P.

    2014-06-01

    A systems engineering study was conducted to leverage a new two-dimensional (2D) lander concept with a low per unit cost to enable scientific study at multiple locations with a single entry system as the delivery vehicle.

  9. Interpolation by two-dimensional cubic convolution

    Science.gov (United States)

    Shi, Jiazheng; Reichenbach, Stephen E.

    2003-08-01

    This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.

  10. CORPORATE VALUATION USING TWO-DIMENSIONAL MONTE CARLO SIMULATION

    Directory of Open Access Journals (Sweden)

    Toth Reka

    2010-12-01

    Full Text Available In this paper, we have presented a corporate valuation model. The model combine several valuation methods in order to get more accurate results. To determine the corporate asset value we have used the Gordon-like two-stage asset valuation model based on the calculation of the free cash flow to the firm. We have used the free cash flow to the firm to determine the corporate market value, which was calculated with use of the Black-Scholes option pricing model in frame of the two-dimensional Monte Carlo simulation method. The combined model and the use of the two-dimensional simulation model provides a better opportunity for the corporate value estimation.

  11. Comparative Analysis on Two-dimensional and Three-dimensional Numerical Simulation of Internal Flow of Volute, Guide Vane and Turning Wheel of Axial Flow Turbine%混流式水轮机蜗壳·导叶及转轮内部水流的二维与三维数值模拟比较分析

    Institute of Scientific and Technical Information of China (English)

    肖玉红

    2011-01-01

    Based on N-S equation and standard k-ε turbulence model, CFD computational fluid dynamics software was adapted in two-di mensional steady numerical simulation for internal flow of volute, guide vane and turning wheel of HLA616-WJ-55 axial flow turbine, and the results were compared and analyzed with three-dimensional numerical simulation of the same turbine type. The results showed that the internal flow rule of volute of two-dimensional was consistent with three-dimensional numerical simulation, and the distribution of pressure and speed were uniform, the flow condition was better. Two-dimensional CFD analysis could predict the structures of internal flows of volute, guide vane and turning wheel roundly, and numerical simulation results had important directive significance to turbines selection and optimization design.%基于N-S方程和标准k-ε紊流模型,采用CFD计算流体力学软件对HLA616 -W J-55混流式水轮机原型机的蜗壳、导叶及转轮内部水流进行二维定常数值模拟,并与同型式水轮机的蜗壳、导叶及转轮内部流动三维数值模拟结果进行比较分析.结果表明,二维与三维蜗壳内部流动的规律基本一致,压力分布和速度分布比较均匀,流动状况较为理想.二维CFD分析能较全面地预测水轮机蜗壳、导叶及转轮内部流场的结构,数值模拟结果对水轮机选型和优化设计均具有重要的指导意义.

  12. Statistical study of approximations to two dimensional inviscid turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Glaz, H.M.

    1977-09-01

    A numerical technique is developed for studying the ergodic and mixing hypotheses for the dynamical systems arising from the truncated Fourier transformed two-dimensional inviscid Navier-Stokes equations. This method has the advantage of exactly conserving energy and entropy (i.e., total vorticity) in the inviscid case except for numerical error in solving the ordinary differential equations. The development of the mathematical model as an approximation to a real physical (turbulent) flow and the numerical results obtained are discussed.

  13. TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yougang; Xu, Yidong; Chen, Xuelei [Key Laboratory of Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 China (China); Park, Changbom [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); Kim, Juhan, E-mail: wangyg@bao.ac.cn, E-mail: cbp@kias.re.kr [Center for Advanced Computation, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of)

    2015-11-20

    We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array.

  14. Two dimensional topology of cosmological reionization

    CERN Document Server

    Wang, Yougang; Xu, Yidong; Chen, Xuelei; Kim, Juhan

    2015-01-01

    We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two dimensional genus curve for the early, middle and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometer Array.

  15. Linear peristaltic pump based on electromagnetic actuators

    Directory of Open Access Journals (Sweden)

    Maddoui Lotfi

    2014-01-01

    Full Text Available In this paper a study and design of a linear peristaltic pump are presented. A set of electromagnetic (solenoid actuators is used as the active tools to drag the liquid by crushing an elastic tube. The pump consists of six serially-connected electromagnetic actuators controlled via an electronic board. This may be considered as a simulated peristalsis action of intestines. The dynamic performances of the pump are investigated analytically and experimentally.

  16. Two-dimensional x-ray diffraction

    CERN Document Server

    He, Bob B

    2009-01-01

    Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea

  17. Matching Two-dimensional Gel Electrophoresis' Spots

    DEFF Research Database (Denmark)

    Dos Anjos, António; AL-Tam, Faroq; Shahbazkia, Hamid Reza

    2012-01-01

    This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches. This ar......This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches...

  18. Mobility anisotropy of two-dimensional semiconductors

    Science.gov (United States)

    Lang, Haifeng; Zhang, Shuqing; Liu, Zhirong

    2016-12-01

    The carrier mobility of anisotropic two-dimensional semiconductors under longitudinal acoustic phonon scattering was theoretically studied using deformation potential theory. Based on the Boltzmann equation with the relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was derived, showing that the influence of effective mass on mobility anisotropy is larger than those of deformation potential constant or elastic modulus. Parameters were collected for various anisotropic two-dimensional materials (black phosphorus, Hittorf's phosphorus, BC2N , MXene, TiS3, and GeCH3) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio is overestimated by the previously described method.

  19. Towards two-dimensional search engines

    OpenAIRE

    Ermann, Leonardo; Chepelianskii, Alexei D.; Shepelyansky, Dima L.

    2011-01-01

    We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Statistical properties of inf...

  20. Magnetic Field and Gravity Effects on Peristaltic Transport of a Jeffrey Fluid in an Asymmetric Channel

    Directory of Open Access Journals (Sweden)

    A. M. Abd-Alla

    2014-01-01

    Full Text Available In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric channel has been investigated. Mathematical modeling is carried out by utilizing long wavelength and low Reynolds number assumptions. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity, and shear stress on the channel walls have been computed numerically. Effects of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity, and shear stress are discussed in detail and shown graphically. The results indicate that the effect of Hartmann number, ratio of relaxation to retardation times, time-mean flow, phase angle, and gravity field are very pronounced in the peristaltic transport phenomena. Comparison was made with the results obtained in the presence and absence of magnetic field and gravity field.

  1. Piezoelectricity in Two-Dimensional Materials

    KAUST Repository

    Wu, Tao

    2015-02-25

    Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

  2. Kronecker Product of Two-dimensional Arrays

    Institute of Scientific and Technical Information of China (English)

    Lei Hu

    2006-01-01

    Kronecker sequences constructed from short sequences are good sequences for spread spectrum communication systems. In this paper we study a similar problem for two-dimensional arrays, and we determine the linear complexity of the Kronecker product of two arrays. Our result shows that similar good property on linear complexity holds for Kronecker product of arrays.

  3. Two-Dimensional Toda-Heisenberg Lattice

    Directory of Open Access Journals (Sweden)

    Vadim E. Vekslerchik

    2013-06-01

    Full Text Available We consider a nonlinear model that is a combination of the anisotropic two-dimensional classical Heisenberg and Toda-like lattices. In the framework of the Hirota direct approach, we present the field equations of this model as a bilinear system, which is closely related to the Ablowitz-Ladik hierarchy, and derive its N-soliton solutions.

  4. A novel two dimensional particle velocity sensor

    NARCIS (Netherlands)

    Pjetri, Olti; Wiegerink, Remco J.; Lammerink, Theo S.; Krijnen, Gijs J.

    2013-01-01

    In this paper we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0x2.5x0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to fabrica

  5. Two-dimensional microstrip detector for neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Oed, A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.

  6. Two-dimensional subwavelength plasmonic lattice solitons

    CERN Document Server

    Ye, F; Hu, B; Panoiu, N C

    2010-01-01

    We present a theoretical study of plasmonic lattice solitons (PLSs) formed in two-dimensional (2D) arrays of metallic nanowires embedded into a nonlinear medium with Kerr nonlinearity. We analyze two classes of 2D PLSs families, namely, fundamental and vortical PLSs in both focusing and defocusing media. Their existence, stability, and subwavelength spatial confinement are studied in detai

  7. A two-dimensional Dirac fermion microscope

    DEFF Research Database (Denmark)

    Bøggild, Peter; Caridad, Jose; Stampfer, Christoph

    2017-01-01

    in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2...

  8. Peristaltic Transport of a Couple Stress Fluid : Some Physiological Applications

    CERN Document Server

    Maiti, S

    2010-01-01

    The present paper deals with a theoretical investigation of the peristaltic transport of a couple stress fluid in a porous channel. The study is motivated towards the physiological flow of blood in the micro-circulatory system, by taking account of the particle size effect. The velocity, pressure gradient, stream function and frictional force of blood are investigated, when the Reynolds number is small and the wavelength is large, by using appropriate analytical and numerical methods. Effects of different physical parameters reflecting porosity, Darcy number, couple stress parameter as well as amplitude ratio on velocity profiles, pumping action and frictional force, streamlines pattern and trapping of blood are studied with particular emphasis. The computational results are presented in graphical form. The results are found to be in good agreement with those of Shapiro et. al \\cite{r25} that was carried out for a non-porous channel in the absence of couple stress effect. The present study puts forward an imp...

  9. Consistent theory of turbulent transport in two-dimensional magnetohydrodynamics.

    Science.gov (United States)

    Kim, Eun-jin

    2006-03-03

    A theory of turbulent transport is presented in two-dimensional magnetohydrodynamics with background shear and magnetic fields. We provide theoretical predictions for the transport of magnetic flux, momentum, and particles and turbulent intensities, which show stronger reduction compared with the hydrodynamic case, with different dependences on shearing rate, magnetic field, and values of viscosity, Ohmic diffusion, and particle diffusivity. In particular, particle transport is more severely suppressed than momentum transport, effectively leading to a more efficient momentum transport. The role of magnetic fields in quenching transport without altering the amplitude of flow velocity and in inhibiting the generation of shear flows is elucidated. Implications of the results are discussed.

  10. Packaged peristaltic micropump for controlled drug delivery application

    Science.gov (United States)

    Vinayakumar, K. B.; Nadiger, Girish; R. Shetty, Vikas; Dinesh, N. S.; Nayak, M. M.; Rajanna, K.

    2017-01-01

    Micropump technology has evolved significantly in the last two decades and is finding a variety of applications ranging from μTAS (micro Total Analysis System) to drug delivery. However, the application area of the micropump is limited owing to: simple pumping mechanism, ease of handling, controlled (microliter to milliliter) delivery, continuous delivery, and accuracy in flow rate. Here, the author presents the design, development, characterization, and precision flow controlling of a DC-motor driven peristaltic pump for controlled drug delivery application. All the micropump components were fabricated using the conventional fabrication technique. The volume flow variation of the pump has been characterized for different viscous fluids. The change in volume flow due to change in back pressure has been presented in detail. The fail-safe mode operation of the pump has been tested and leak rate was measured (˜0.14% leak for an inlet pressure of 140 kPa) for different inlet pressures. The precision volume flow of the pump has been achieved by measuring the pinch cam position and load current. The accuracy in the volume flow has been measured after 300 rotations. Finally, the complete system has been integrated with the necessary electronics and an android application has been developed for the self-administration of bolus and basal delivery of insulin.

  11. Electronics based on two-dimensional materials.

    Science.gov (United States)

    Fiori, Gianluca; Bonaccorso, Francesco; Iannaccone, Giuseppe; Palacios, Tomás; Neumaier, Daniel; Seabaugh, Alan; Banerjee, Sanjay K; Colombo, Luigi

    2014-10-01

    The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

  12. Two-dimensional ranking of Wikipedia articles

    Science.gov (United States)

    Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.

    2010-10-01

    The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.

  13. Two-Dimensional NMR Lineshape Analysis

    Science.gov (United States)

    Waudby, Christopher A.; Ramos, Andres; Cabrita, Lisa D.; Christodoulou, John

    2016-04-01

    NMR titration experiments are a rich source of structural, mechanistic, thermodynamic and kinetic information on biomolecular interactions, which can be extracted through the quantitative analysis of resonance lineshapes. However, applications of such analyses are frequently limited by peak overlap inherent to complex biomolecular systems. Moreover, systematic errors may arise due to the analysis of two-dimensional data using theoretical frameworks developed for one-dimensional experiments. Here we introduce a more accurate and convenient method for the analysis of such data, based on the direct quantum mechanical simulation and fitting of entire two-dimensional experiments, which we implement in a new software tool, TITAN (TITration ANalysis). We expect the approach, which we demonstrate for a variety of protein-protein and protein-ligand interactions, to be particularly useful in providing information on multi-step or multi-component interactions.

  14. A two-dimensional Dirac fermion microscope

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M.; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-01

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  15. A two-dimensional Dirac fermion microscope.

    Science.gov (United States)

    Bøggild, Peter; Caridad, José M; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads

    2017-06-09

    The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.

  16. Two-Dimensional Scheduling: A Review

    Directory of Open Access Journals (Sweden)

    Zhuolei Xiao

    2013-07-01

    Full Text Available In this study, we present a literature review, classification schemes and analysis of methodology for scheduling problems on Batch Processing machine (BP with both processing time and job size constraints which is also regarded as Two-Dimensional (TD scheduling. Special attention is given to scheduling problems with non-identical job sizes and processing times, with details of the basic algorithms and other significant results.

  17. Two dimensional fermions in four dimensional YM

    CERN Document Server

    Narayanan, R

    2009-01-01

    Dirac fermions in the fundamental representation of SU(N) live on a two dimensional torus flatly embedded in $R^4$. They interact with a four dimensional SU(N) Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the size of the torus in units of $\\frac{1}{\\Lambda_{SU(N)}}$ is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit.

  18. Two-dimensional Kagome photonic bandgap waveguide

    DEFF Research Database (Denmark)

    Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou;

    2000-01-01

    The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....

  19. String breaking in two-dimensional QCD

    CERN Document Server

    Hornbostel, K J

    1999-01-01

    I present results of a numerical calculation of the effects of light quark-antiquark pairs on the linear heavy-quark potential in light-cone quantized two-dimensional QCD. I extract the potential from the Q-Qbar component of the ground-state wavefunction, and observe string breaking at the heavy-light meson pair threshold. I briefly comment on the states responsible for the breaking.

  20. Two-dimensional supramolecular electron spin arrays.

    Science.gov (United States)

    Wäckerlin, Christian; Nowakowski, Jan; Liu, Shi-Xia; Jaggi, Michael; Siewert, Dorota; Girovsky, Jan; Shchyrba, Aneliia; Hählen, Tatjana; Kleibert, Armin; Oppeneer, Peter M; Nolting, Frithjof; Decurtins, Silvio; Jung, Thomas A; Ballav, Nirmalya

    2013-05-07

    A bottom-up approach is introduced to fabricate two-dimensional self-assembled layers of molecular spin-systems containing Mn and Fe ions arranged in a chessboard lattice. We demonstrate that the Mn and Fe spin states can be reversibly operated by their selective response to coordination/decoordination of volatile ligands like ammonia (NH3). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Two dimensional echocardiographic detection of intraatrial masses.

    Science.gov (United States)

    DePace, N L; Soulen, R L; Kotler, M N; Mintz, G S

    1981-11-01

    With two dimensional echocardiography, a left atrial mass was detected in 19 patients. Of these, 10 patients with rheumatic mitral stenosis had a left atrial thrombus. The distinctive two dimensional echocardiographic features of left atrial thrombus included a mass of irregular nonmobile laminated echos within an enlarged atrial cavity, usually with a broad base of attachment to the posterior left atrial wall. Seven patients had a left atrial myxoma. Usually, the myxoma appeared as a mottled ovoid, sharply demarcated mobile mass attached to the interatrial septum. One patient had a right atrial angiosarcoma that appeared as a nonmobile mass extending from the inferior vena caval-right atrial junction into the right atrial cavity. One patient had a left atrial leiomyosarcoma producing a highly mobile mass attached to the lateral wall of the left atrium. M mode echocardiography detected six of the seven myxomas, one thrombus and neither of the other tumors. Thus, two dimensional echocardiography appears to be the technique of choice in the detection, localization and differentiation of intraatrial masses.

  2. Analysis of peristaltic waves and their role in migrating Physarum plasmodia

    Science.gov (United States)

    Lewis, Owen L.; Guy, Robert D.

    2017-07-01

    The true slime mold Physarum polycephalum exhibits a vast array of sophisticated manipulations of its intracellular cytoplasm. Growing microplasmodia of Physarum have been observed to adopt an elongated tadpole shape, then contract in a rhythmic, traveling wave pattern that resembles peristaltic pumping. This contraction drives a fast flow of non-gelated cytoplasm along the cell longitudinal axis. It has been hypothesized that this flow of cytoplasm is a driving factor in generating motility of the plasmodium. In this work, we use two different mathematical models to investigate how peristaltic pumping within Physarum may be used to drive cellular motility. We compare the relative phase of flow and deformation waves predicted by both models to similar phase data collected from in vivo experiments using Physarum plasmodia. The first is a PDE model based on a dimensional reduction of peristaltic pumping within a finite length chamber. The second is a more sophisticated computational model which accounts for more general shape changes, more complex cellular mechanics, and dynamically modulated adhesion to the underlying substrate. This model allows us to directly compute cell crawling speed. Both models suggest that a mechanical asymmetry in the cell is required to reproduce the experimental observations. Such a mechanical asymmetry is also shown to increase the potential for cellular migration, as measured by both stress generation and migration velocity.

  3. Confinement and dynamical regulation in two-dimensional convective turbulence

    DEFF Research Database (Denmark)

    Bian, N.H.; Garcia, O.E.

    2003-01-01

    In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low-frequency bur......In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low......-frequency bursting in the fluctuation level and the convective heat flux integral, both resulting in a state of large-scale intermittency. The first one involves the control of convective transport by sheared mean flows. This regulation relies on the conservative transfer of kinetic energy from tilted fluctuations...... to the mean component of the flow. Bursting can also result from the quasi-linear modification of the linear instability drive which is the mean pressure gradient. For each bursting process the relevant zero-dimensional model equations are given. These are finally coupled in a minimal model of convection...

  4. Configuration of Shock Waves in Two-Dimensional Overexpanded Jets

    Institute of Scientific and Technical Information of China (English)

    Masashi Kashitani; Yutaka Yamaguchi; Yoshiaki Miyazato; Mitsuharu Masuda; Kazuyasu Matsuo

    2003-01-01

    An experimental and analytical study has been carried out to obtain the clear understanding of a shock wave transition associated with a steady two-dimensional overexpanded flow. Two-dimensional inviscid theory with respect to a shock wave reflection is used in the present study on the characteristic of shock waves. The results obtained from the flow analysis are compared with those obtained from flow visualizations. It is shown that in the region of regular reflection, the angle of an incident shock wave becomes lower than that calculated by two shock theory with an increment in the ratio pe/pb of the nozzle exit pressure pe to the back pressure pb. It is indicated that the configuration of shock waves in overexpanded jets is influenced by the divergent angle at the nozzle exit. Also it is shown from the flow visualization that a series of shock waves move into the nozzle inside with a decrease in pressure ratio pe/pb, even if the pe/pb is under overexpanded conditions.

  5. Positivity-preserving cell-centered Lagrangian schemes for multi-material compressible flows: From first-order to high-orders. Part II: The two-dimensional case

    Science.gov (United States)

    Vilar, François; Shu, Chi-Wang; Maire, Pierre-Henri

    2016-05-01

    This paper is the second part of a series of two. It follows [44], in which the positivity-preservation property of methods solving one-dimensional Lagrangian gas dynamics equations, from first-order to high-orders of accuracy, was addressed. This article aims at extending this analysis to the two-dimensional case. This study is performed on a general first-order cell-centered finite volume formulation based on polygonal meshes defined either by straight line edges, conical edges, or any high-order curvilinear edges. Such formulation covers the numerical methods introduced in [6,32,5,41,43]. This positivity study is then extended to high-orders of accuracy. Through this new procedure, scheme robustness is highly improved and hence new problems can be tackled. Numerical results are provided to demonstrate the effectiveness of these methods. It is important to point out that even if this paper is concerned with purely Lagrangian schemes, the theory developed is of fundamental importance for any methods relying on a purely Lagrangian step, as ALE methods or non-direct Euler schemes.

  6. PDMS气动微泵的研制%Development of a PDMS Pneumatic Peristaltic Micropump

    Institute of Scientific and Technical Information of China (English)

    关艳霞; 凌宇

    2012-01-01

    聚二甲聚硅氧烷(PDMS)气动微泵具有结构简单、易于制作、造价低和易于集成的特点.对微泵的结构进行了分析、设计与制作,较详细地讨论了关键制作工艺,并对影响流速的主要因素进行了分析,通过对结构参数的优化,使微泵的最大流速达到0.55μL/min,较相关文献中的微泵的流速提高4倍,使微泵更具有实用性.%A PDMS pneumatic peristaltic micropump has features of simplicity in structures and fabricating technique,fast in replication,low in cost,easy in integrating with other microfluidic component. In this paper,the development of a PDMS pneumatic peristaltic micropump has been done by analyzing the structure of a PDMS pneumatic peristaltic micropump, and the key process and the main factors affecting velocity have been discussed. By optimizing the structural parameters of the pump,the flow rate has been to 0. 55 μL/min,5 times of the flow rate of the micopump reported in the related literature,and that make it more practical.

  7. Thermally developing MHD peristaltic transport of nanofluids with velocity and thermal slip effects

    Science.gov (United States)

    Sher Akbar, Noreen; Bintul Huda, A.; Tripathi, D.

    2016-09-01

    We investigate the velocity slip and thermal slip effects on peristaltically driven thermal transport of nanofluids through the vertical parallel plates under the influence of transverse magnetic field. The wall surface is propagating with sinusoidal wave velocity c. The flow characteristics are governed by the mass, momentum and energy conservation principle. Low Reynolds number and large wavelength approximations are taken into consideration to simplify the non-linear terms. Analytical solutions for axial velocity, temperature field, pressure gradient and stream function are obtained under certain physical boundary conditions. Two types of nanoparticles, SiO2 and Ag, are considered for analysis with water as base fluid. This is the first article in the literature that discusses the SiO2 and Ag nanoparticles for a peristaltic flow with variable viscosity. The effects of physical parameters on velocity, temperature, pressure and trapping are discussed. A comparative study of SiO2 nanofluid, Ag nanofluid and pure water is also presented. This model is applicable in biomedical engineering to make thermal peristaltic pumps and other pumping devices like syringe pumps, etc. It is observed that pressure for pure water is maximum and pressure for Ag nanofluid is minimum.

  8. Weakly disordered two-dimensional Frenkel excitons

    Science.gov (United States)

    Boukahil, A.; Zettili, Nouredine

    2004-03-01

    We report the results of studies of the optical properties of weakly disordered two- dimensional Frenkel excitons in the Coherent Potential Approximation (CPA). An approximate complex Green's function for a square lattice with nearest neighbor interactions is used in the self-consistent equation to determine the coherent potential. It is shown that the Density of States is very much affected by the logarithmic singularities in the Green's function. Our CPA results are in excellent agreement with previous investigations by Schreiber and Toyozawa using the Monte Carlo simulation.

  9. Two-dimensional photonic crystal surfactant detection.

    Science.gov (United States)

    Zhang, Jian-Tao; Smith, Natasha; Asher, Sanford A

    2012-08-07

    We developed a novel two-dimensional (2-D) crystalline colloidal array photonic crystal sensing material for the visual detection of amphiphilic molecules in water. A close-packed polystyrene 2-D array monolayer was embedded in a poly(N-isopropylacrylamide) (PNIPAAm)-based hydrogel film. These 2-D photonic crystals placed on a mirror show intense diffraction that enables them to be used for visual determination of analytes. Binding of surfactant molecules attaches ions to the sensor that swells the PNIPAAm-based hydrogel. The resulting increase in particle spacing red shifts the 2-D diffracted light. Incorporation of more hydrophobic monomers increases the sensitivity to surfactants.

  10. Theory of two-dimensional transformations

    OpenAIRE

    Kanayama, Yutaka J.; Krahn, Gary W.

    1998-01-01

    The article of record may be found at http://dx.doi.org/10.1109/70.720359 Robotics and Automation, IEEE Transactions on This paper proposes a new "heterogeneous" two-dimensional (2D) transformation group ___ to solve motion analysis/planning problems in robotics. In this theory, we use a 3×1 matrix to represent a transformation as opposed to a 3×3 matrix in the homogeneous formulation. First, this theory is as capable as the homogeneous theory, Because of the minimal size, its implement...

  11. Two-dimensional ranking of Wikipedia articles

    CERN Document Server

    Zhirov, A O; Shepelyansky, D L

    2010-01-01

    The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists {\\it ab aeterno}. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. We analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.

  12. Mobility anisotropy of two-dimensional semiconductors

    CERN Document Server

    Lang, Haifeng; Liu, Zhirong

    2016-01-01

    The carrier mobility of anisotropic two-dimensional (2D) semiconductors under longitudinal acoustic (LA) phonon scattering was theoretically studied with the deformation potential theory. Based on Boltzmann equation with relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was deduced, which shows that the influence of effective mass to the mobility anisotropy is larger than that of deformation potential constant and elastic modulus. Parameters were collected for various anisotropic 2D materials (black phosphorus, Hittorf's phosphorus, BC$_2$N, MXene, TiS$_3$, GeCH$_3$) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio was overestimated in the past.

  13. Sums of two-dimensional spectral triples

    DEFF Research Database (Denmark)

    Christensen, Erik; Ivan, Cristina

    2007-01-01

    construct a sum of two dimensional modules which reflects some aspects of the topological dimensions of the compact metric space, but this will only give the metric back approximately. At the end we make an explicit computation of the last module for the unit interval in. The metric is recovered exactly......, the Dixmier trace induces a multiple of the Lebesgue integral but the growth of the number of eigenvalues is different from the one found for the standard differential operator on the unit interval....

  14. Binding energy of two-dimensional biexcitons

    DEFF Research Database (Denmark)

    Singh, Jai; Birkedal, Dan; Vadim, Lyssenko;

    1996-01-01

    Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....

  15. Dynamics of film. [two dimensional continua theory

    Science.gov (United States)

    Zak, M.

    1979-01-01

    The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets. The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles. The theory is illustrated by examples.

  16. MHD peristaltic transport of spherical and cylindrical magneto-nanoparticles suspended in water

    Directory of Open Access Journals (Sweden)

    F. M. Abbasi

    2015-07-01

    Full Text Available Advancements in the biomedical engineering have enhanced the usage of magnto-nanoparticles in improving the precision and efficiency of the magneto-drug delivery systems. Such systems make use of the externally applied magnetic fields to direct the drug towards a specific target in the human body. Peristalsis of magneto-nanofluids is of significant importance in such considerations. Hence peristaltic transport of Fe3O4-water nanofluid through a two-dimensional symmetric channel is analyzed in the presence of an externally applied constant magnetic field. Hamilton-Crosser’s model of the thermal conductivity is utilized in the problem development. The nanofluid saturates a non-uniform porous medium in which the porosity of the porous medium varies with the distance from the channel walls. Analysis is performed for the spherical and the cylindrical nanoparticles. Resulting system of equations is numerically solved. Impacts of sundry parameters on the axial velocity, temperature, pressure gradient and heat transfer rate at the boundary are examined. Comparison between the results for spherical and cylindrical nanoparticles is also presented. Results show that the nanoparticles volume fraction and the Hartman number have increasing effect on the pressure gradient throughout the peristaltic tract. Effective heat transfer rate at the boundary tends to enhance with an increase in the nanoparticles volume fraction. Use of spherical nanoparticles results in a higher value of axial velocity and the temperature at the center of channel when compared with the case of cylindrical nanoparticles.

  17. Two-dimensional gauge theoretic supergravities

    Science.gov (United States)

    Cangemi, D.; Leblanc, M.

    1994-05-01

    We investigate two-dimensional supergravity theories, which can be built from a topological and gauge invariant action defined on an ordinary surface. One is the N = 1 supersymmetric extension of the Jackiw-Teitelboim model presented by Chamseddine in a superspace formalism. We complement the proof of Montano, Aoaki and Sonnenschein that this extension is topological and gauge invariant, based on the graded de Sitter algebra. Not only do the equations of motion correspond to the supergravity ones and do gauge transformations encompass local supersymmetries, but we also identify the ∫-theory with the superfield formalism action written by Chamseddine. Next, we show that the N = 1 supersymmetric extension of string-inspired two-dimensional dilaton gravity put forward by Park and Strominger cannot be written as a ∫-theory. As an alternative, we propose two topological and gauge theories that are based on a graded extension of the extended Poincaré algebra and satisfy a vanishing-curvature condition. Both models are supersymmetric extensions of the string-inspired dilaton gravity.

  18. Two-Dimensional Theory of Scientific Representation

    Directory of Open Access Journals (Sweden)

    A Yaghmaie

    2013-03-01

    Full Text Available Scientific representation is an interesting topic for philosophers of science, many of whom have recently explored it from different points of view. There are currently two competing approaches to the issue: cognitive and non-cognitive, and each of them claims its own merits over the other. This article tries to provide a hybrid theory of scientific representation, called Two-Dimensional Theory of Scientific Representation, which has the merits of the two accounts and is free of their shortcomings. To do this, we will argue that although scientific representation needs to use the notion of intentionality, such a notion is defined and realized in a simply structural form contrary to what cognitive approach says about intentionality. After a short introduction, the second part of the paper is devoted to introducing theories of scientific representation briefly. In the third part, the structural accounts of representation will be criticized. The next step is to introduce the two-dimensional theory which involves two key components: fixing and structural fitness. It will be argued that fitness is an objective and non-intentional relation, while fixing is intentional.

  19. Two-dimensional shape memory graphene oxide

    Science.gov (United States)

    Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe

    2016-06-01

    Driven by the increasing demand for micro-/nano-technologies, stimuli-responsive shape memory materials at nanoscale have recently attracted great research interests. However, by reducing the size of conventional shape memory materials down to approximately nanometre range, the shape memory effect diminishes. Here, using density functional theory calculations, we report the discovery of a shape memory effect in a two-dimensional atomically thin graphene oxide crystal with ordered epoxy groups, namely C8O. A maximum recoverable strain of 14.5% is achieved as a result of reversible phase transition between two intrinsically stable phases. Our calculations conclude co-existence of the two stable phases in a coherent crystal lattice, giving rise to the possibility of constructing multiple temporary shapes in a single material, thus, enabling highly desirable programmability. With an atomic thickness, excellent shape memory mechanical properties and electric field stimulus, the discovery of a two-dimensional shape memory graphene oxide opens a path for the development of exceptional micro-/nano-electromechanical devices.

  20. Existence and Stability of Two-Dimensional Compact-Like Discrete Breathers in Discrete Two-Dimensional Monatomic Square Lattices

    Institute of Scientific and Technical Information of China (English)

    XU Quan; TIAN Qiang

    2007-01-01

    Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generafized discrete two-dimensional monatomic model.It is proven that the twodimensional compact-like discrete breathers exist not only in two-dimensional soft Ф4 potentials but also in hard two-dimensional Ф4 potentials and pure two-dimensional K4 lattices.The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Ф4 potential are determined by coupling parameter K4,while those in pure two-dimensional K4 lattices have no coupling with parameter K4.The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.

  1. Microbionic and peristaltic robots in a pipe

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A microbionic and peristaltic robot that simulates the motion of an earthworm to move within a micropipe is proposed. The robot consists of three flexible units. Each unit is composed of two plates connected with three shape memory alloys (SMA) 120°apart, the rubber gasbag around the SMA wires inflated with air inside. Each unit corresponds to a segment of an earthworm, and the SMA and rubber gasbag have the same functions as the cricoid and longitudinal muscles of the earthworm. A control system is designed to fulfill the control of the three flexible units motions, such as stretching, shrinking and bending, so the microrobot can walk forward and backward, and choose the direction.

  2. Phonon hydrodynamics in two-dimensional materials.

    Science.gov (United States)

    Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola

    2015-03-06

    The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.

  3. Probabilistic Universality in two-dimensional Dynamics

    CERN Document Server

    Lyubich, Mikhail

    2011-01-01

    In this paper we continue to explore infinitely renormalizable H\\'enon maps with small Jacobian. It was shown in [CLM] that contrary to the one-dimensional intuition, the Cantor attractor of such a map is non-rigid and the conjugacy with the one-dimensional Cantor attractor is at most 1/2-H\\"older. Another formulation of this phenomenon is that the scaling structure of the H\\'enon Cantor attractor differs from its one-dimensional counterpart. However, in this paper we prove that the weight assigned by the canonical invariant measure to these bad spots tends to zero on microscopic scales. This phenomenon is called {\\it Probabilistic Universality}. It implies, in particular, that the Hausdorff dimension of the canonical measure is universal. In this way, universality and rigidity phenomena of one-dimensional dynamics assume a probabilistic nature in the two-dimensional world.

  4. Two-dimensional position sensitive neutron detector

    Indian Academy of Sciences (India)

    A M Shaikh; S S Desai; A K Patra

    2004-08-01

    A two-dimensional position sensitive neutron detector has been developed. The detector is a 3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Å neutrons. The detector is tested with 0.5 bar 3He + 1.5 bar krypton gas mixture in active chamber and 2 bar 4He in compensating chamber. The pulse height spectrum recorded at an anode potential of 2000 V shows energy resolution of ∼ 25% for the 764 keV peak. A spatial resolution of 8 mm × 6 mm is achieved. The detector is suitable for SANS studies in the range of 0.02–0.25 Å-1.

  5. Two-dimensional heterostructures for energy storage

    Science.gov (United States)

    Pomerantseva, Ekaterina; Gogotsi, Yury

    2017-07-01

    Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. We also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.

  6. Rationally synthesized two-dimensional polymers.

    Science.gov (United States)

    Colson, John W; Dichtel, William R

    2013-06-01

    Synthetic polymers exhibit diverse and useful properties and influence most aspects of modern life. Many polymerization methods provide linear or branched macromolecules, frequently with outstanding functional-group tolerance and molecular weight control. In contrast, extending polymerization strategies to two-dimensional periodic structures is in its infancy, and successful examples have emerged only recently through molecular framework, surface science and crystal engineering approaches. In this Review, we describe successful 2D polymerization strategies, as well as seminal research that inspired their development. These methods include the synthesis of 2D covalent organic frameworks as layered crystals and thin films, surface-mediated polymerization of polyfunctional monomers, and solid-state topochemical polymerizations. Early application targets of 2D polymers include gas separation and storage, optoelectronic devices and membranes, each of which might benefit from predictable long-range molecular organization inherent to this macromolecular architecture.

  7. Local doping of two-dimensional materials

    Science.gov (United States)

    Wong, Dillon; Velasco, Jr, Jairo; Ju, Long; Kahn, Salman; Lee, Juwon; Germany, Chad E.; Zettl, Alexander K.; Wang, Feng; Crommie, Michael F.

    2016-09-20

    This disclosure provides systems, methods, and apparatus related to locally doping two-dimensional (2D) materials. In one aspect, an assembly including a substrate, a first insulator disposed on the substrate, a second insulator disposed on the first insulator, and a 2D material disposed on the second insulator is formed. A first voltage is applied between the 2D material and the substrate. With the first voltage applied between the 2D material and the substrate, a second voltage is applied between the 2D material and a probe positioned proximate the 2D material. The second voltage between the 2D material and the probe is removed. The first voltage between the 2D material and the substrate is removed. A portion of the 2D material proximate the probe when the second voltage was applied has a different electron density compared to a remainder of the 2D material.

  8. Two-dimensional fourier transform spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    DeFlores, Lauren; Tokmakoff, Andrei

    2016-10-25

    The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

  9. Two-dimensional fourier transform spectrometer

    Science.gov (United States)

    DeFlores, Lauren; Tokmakoff, Andrei

    2013-09-03

    The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.

  10. FACE RECOGNITION USING TWO DIMENSIONAL LAPLACIAN EIGENMAP

    Institute of Scientific and Technical Information of China (English)

    Chen Jiangfeng; Yuan Baozong; Pei Bingnan

    2008-01-01

    Recently,some research efforts have shown that face images possibly reside on a nonlinear sub-manifold. Though Laplacianfaces method considered the manifold structures of the face images,it has limits to solve face recognition problem. This paper proposes a new feature extraction method,Two Dimensional Laplacian EigenMap (2DLEM),which especially considers the manifold structures of the face images,and extracts the proper features from face image matrix directly by using a linear transformation. As opposed to Laplacianfaces,2DLEM extracts features directly from 2D images without a vectorization preprocessing. To test 2DLEM and evaluate its performance,a series of ex-periments are performed on the ORL database and the Yale database. Moreover,several experiments are performed to compare the performance of three 2D methods. The experiments show that 2DLEM achieves the best performance.

  11. Equivalency of two-dimensional algebras

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Gildemar Carneiro dos; Pomponet Filho, Balbino Jose S. [Universidade Federal da Bahia (UFBA), BA (Brazil). Inst. de Fisica

    2011-07-01

    Full text: Let us consider a vector z = xi + yj over the field of real numbers, whose basis (i,j) satisfy a given algebra. Any property of this algebra will be reflected in any function of z, so we can state that the knowledge of the properties of an algebra leads to more general conclusions than the knowledge of the properties of a function. However structural properties of an algebra do not change when this algebra suffers a linear transformation, though the structural constants defining this algebra do change. We say that two algebras are equivalent to each other whenever they are related by a linear transformation. In this case, we have found that some relations between the structural constants are sufficient to recognize whether or not an algebra is equivalent to another. In spite that the basis transform linearly, the structural constants change like a third order tensor, but some combinations of these tensors result in a linear transformation, allowing to write the entries of the transformation matrix as function of the structural constants. Eventually, a systematic way to find the transformation matrix between these equivalent algebras is obtained. In this sense, we have performed the thorough classification of associative commutative two-dimensional algebras, and find that even non-division algebra may be helpful in solving non-linear dynamic systems. The Mandelbrot set was used to have a pictorial view of each algebra, since equivalent algebras result in the same pattern. Presently we have succeeded in classifying some non-associative two-dimensional algebras, a task more difficult than for associative one. (author)

  12. Anomaly matching condition in two-dimensional systems

    CERN Document Server

    Dubinkin, O; Gubankova, E

    2016-01-01

    Based on Son-Yamamoto relation obtained for transverse part of triangle axial anomaly in ${\\rm QCD}_4$, we derive its analog in two-dimensional system. It connects the transverse part of mixed vector-axial current two-point function with diagonal vector and axial current two-point functions. Being fully non-perturbative, this relation may be regarded as anomaly matching for conductivities or certain transport coefficients depending on the system. We consider the holographic RG flows in holographic Yang-Mills-Chern-Simons theory via the Hamilton-Jacobi equation with respect to the radial coordinate. Within this holographic model it is found that the RG flows for the following relations are diagonal: Son-Yamamoto relation and the left-right polarization operator. Thus the Son-Yamamoto relation holds at wide range of energy scales.

  13. Material line fluctuations slaved to bulk correlations in two-dimensional turbulence

    Science.gov (United States)

    Odijk, Theo

    2017-02-01

    An analogy is pointed out between a polymer chain fluctuating in a two-dimensional nematic background and a freely floating material line buffeted by a two-dimensional turbulent fluid in the inertial (Kraichnan) regime. Under certain conditions, the back-reaction of the line on the turbulent flow may be neglected. The fractal exponent related to the size-contour relation of the material line is connected to a "nematic" correlation function in the bulk.

  14. Two dimensional hydrodynamic modeling of a high latitude braided river

    Science.gov (United States)

    Humphries, E.; Pavelsky, T.; Bates, P. D.

    2014-12-01

    Rivers are a fundamental resource to physical, ecologic and human systems, yet quantification of river flow in high-latitude environments remains limited due to the prevalence of complex morphologies, remote locations and sparse in situ monitoring equipment. Advances in hydrodynamic modeling and remote sensing technology allow us to address questions such as: How well can two-dimensional models simulate a flood wave in a highly 3-dimensional braided river environment, and how does the structure of such a flood wave differ from flow down a similar-sized single-channel river? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate flood waves, discharge, water surface height, and velocity measurements over a ~70 km reach of the Tanana River in Alaska. In order to use LISFLOOD-FP a digital elevation model (DEM) fused with detailed bathymetric data is required. During summer 2013, we surveyed 220,000 bathymetric points along the study reach using an echo sounder system connected to a high-precision GPS unit. The measurements are interpolated to a smooth bathymetric surface, using Topo to Raster interpolation, and combined with an existing five meter DEM (Alaska IfSAR) to create a seamless river terrain model. Flood waves are simulated using varying complexities in model solvers, then compared to gauge records and water logger data to assess major sources of model uncertainty. Velocity and flow direction maps are also assessed and quantified for detailed analysis of braided channel flow. The most accurate model output occurs with using the full two-dimensional model structure, and major inaccuracies appear to be related to DEM quality and roughness values. Future work will intercompare model outputs with extensive ground measurements and new data from AirSWOT, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.

  15. Numerical Experiment on Two-Dimensional Line Thermal

    Institute of Scientific and Technical Information of China (English)

    J.H.W.LEE; G.Q.CHEN(陈国谦)

    2002-01-01

    The time evolution of a two-dimensional line thermal-a turbulent flow produced by an initial element with signifi-cant buoyancy released in a large water body, is numerically studied with the two-equation k - s model for turbulenceclosure. The numerical results show that the thermal is characterized by a vortex pair flow and a kidney shaped concentra-tion structure with double peak maxima; the computed flow details and scalar mixing characteristics can be described byself-similar relations beyond a dimensionless time around 10. There are two regions in the flow field of a line thermal: amixing region where the concentration of tracer fluid is high and the flow is turbulent and rotational with a pair of vortexeyes, and an ambient region where the concentration is zero and the flow is potential and well-described by a model ofdoublet with strength very close to those given by early experimental and analytical studies. The added virtual mass coeffi-cient of the thermal motion is found to be approximately 1. The aspect ratio for the kidney-shaped sectional thermal isfound to be around 1.45 for the self-similar phase. The predicted thermal spreading and mixing rate compares well withexperimental data.

  16. On numerical evaluation of two-dimensional phase integrals

    DEFF Research Database (Denmark)

    Lessow, H.; Rusch, W.; Schjær-Jacobsen, Hans

    1975-01-01

    The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated.......The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated....

  17. Integral transformation of the Navier-Stokes equations for laminar flow in channels of arbitrary two-dimensional geometry; Transformacao integral das equacoes de Navier-Stokes para escoamento laminar em canais de geometria bidimensional arbitraria

    Energy Technology Data Exchange (ETDEWEB)

    Perez Guerrero, Jesus Salvador

    1995-12-31

    Laminar developing flow in channels of arbitrary geometry was studied by solving the Navier-Stokes equations in the stream function-only formulation through the Generalized Integral Transform Technique (GITT). The stream function is expanded in an infinite system based on eigenfunctions obtained by considering solely the diffusive terms of the original formulation. The Navier-Stokes equations are transformed into an infinite system of ordinary differential equations, by using the transformation and inversion formulae. For computational purposes, the infinite series is truncated, according to an automatic error control procedure. The ordinary differential is solved through well-established scientific subroutines from widely available mathematical libraries. The classical problem of developing flow between parallel-plates is analysed first, as for both uniform and irrotational inlet conditions. The effect of truncating the duct length in the accuracy of the obtained solution is studied. A convergence analysis of the results obtained by the GITT is performed and compared with results obtained by finite difference and finite element methods, for different values of Reynolds number. The problem of flow over a backward-facing step then follows. Comparisons with experimental results in the literature indicate an excellent agreement. The numerical co-validation was established for a test case, and perfect agreement is reached against results considered as benchmarks in the recent literature. The results were shown to be physically more reasonable than others obtained by purely numerical methods, in particular for situations where three-dimensional effects are identified. Finally, a test problem for an irregular by shoped duct was studied and compared against results found in the literature, with good agreement and excellent convergence rates for the stream function field along the whole channel, for different values of Reynolds number. (author) 78 refs., 24 figs., 14 tabs.

  18. Quantum creep in a highly crystalline two-dimensional superconductor

    Science.gov (United States)

    Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu

    Conventional studies on quantum phase transitions, especially on superconductor-insulator or superconductor-metal-insulator transitions have been performed in deposited metallic thin films such as Bismuth or MoGe. Although the techniques of thin films deposition have been considerably improved, unintentional disorder such as impurities and deficiencies, generating the pinning centers, seems to still exist in such systems. The mechanical exfoliated highly crystalline two-dimensional material can be a good candidate to realize a less-disordered 2D superconductor with extremely weak pinning, combined with transfer method or ionic-liquid gating. We report on the quantum metal, namely, magnetic-field-induced metallic state observed in an ion-gated two-dimensional superconductor based on an ultra-highly crystalline layered band insulator, ZrNCl. We found that the superconducting state is extremely fragile against external magnetic fields; that is, zero resistance state immediately disappears, once an external magnetic field switches on. This is because the present system is relatively clean and the pinning potential is extremely weak, which cause quantum tunneling and flux flow of vortices, resulting in metallic ground state.

  19. Two-Dimensional turbulence in the inverse cascade range

    CERN Document Server

    Yakhot, V

    1999-01-01

    A theory of two-dimensional turbulence in the inverse energy cascade range is presented. Strong time-dependence of the large-scale features of the flow ($\\bar{u^{2}}\\propto t$) results in decoupling of the large-scale dynamics from statistically steady-state small-scale random processes. This time-dependence is also a reason for the localness of the pressure-gradient terms in the equations governing the small-scale velocity difference PDF's. The derived expressions for the pressure gradient contributions lead to a gaussian statistics of transverse velocity differences. The solution for the PDF of longitudinal velocity differences is based on a smallness of the energy flux in two-dimensional turbulence. The theory makes a few quantitative predictions which can be tested experimentally. One of the most surprising results, derived in this paper, is that the small-scale transverse velocity differences are governed by a linear Langevin-like equation, strirred by a non-local universal gaussian random force. This ex...

  20. Perspective: Two-dimensional resonance Raman spectroscopy

    Science.gov (United States)

    Molesky, Brian P.; Guo, Zhenkun; Cheshire, Thomas P.; Moran, Andrew M.

    2016-11-01

    Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in complex systems. The 2DRR method can leverage electronic resonance enhancement to selectively probe chromophores embedded in complex environments (e.g., a cofactor in a protein). In addition, correlations between the two dimensions of the 2DRR spectrum reveal information that is not available in traditional Raman techniques. For example, distributions of reactant and product geometries can be correlated in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this perspective article, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide and myoglobin. We also address key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopies. Most notably, it has been shown that these two techniques are subject to a tradeoff between sensitivity to anharmonicity and susceptibility to artifacts. Overall, recent experimental developments and applications of the 2DRR method suggest great potential for the future of the technique.

  1. Comparative Two-Dimensional Fluorescence Gel Electrophoresis.

    Science.gov (United States)

    Ackermann, Doreen; König, Simone

    2018-01-01

    Two-dimensional comparative fluorescence gel electrophoresis (CoFGE) uses an internal standard to increase the reproducibility of coordinate assignment for protein spots visualized on 2D polyacrylamide gels. This is particularly important for samples, which need to be compared without the availability of replicates and thus cannot be studied using differential gel electrophoresis (DIGE). CoFGE corrects for gel-to-gel variability by co-running with the sample proteome a standardized marker grid of 80-100 nodes, which is formed by a set of purified proteins. Differentiation of reference and analyte is possible by the use of two fluorescent dyes. Variations in the y-dimension (molecular weight) are corrected by the marker grid. For the optional control of the x-dimension (pI), azo dyes can be used. Experiments are possible in both vertical and horizontal (h) electrophoresis devices, but hCoFGE is much easier to perform. For data analysis, commercial software capable of warping can be adapted.

  2. Two-dimensional hexagonal semiconductors beyond graphene

    Science.gov (United States)

    Nguyen, Bich Ha; Hieu Nguyen, Van

    2016-12-01

    The rapid and successful development of the research on graphene and graphene-based nanostructures has been substantially enlarged to include many other two-dimensional hexagonal semiconductors (THS): phosphorene, silicene, germanene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) such as MoS2, MoSe2, WS2, WSe2 as well as the van der Waals heterostructures of various THSs (including graphene). The present article is a review of recent works on THSs beyond graphene and van der Waals heterostructures composed of different pairs of all THSs. One among the priorities of new THSs compared to graphene is the presence of a non-vanishing energy bandgap which opened up the ability to fabricate a large number of electronic, optoelectronic and photonic devices on the basis of these new materials and their van der Waals heterostructures. Moreover, a significant progress in the research on TMDCs was the discovery of valley degree of freedom. The results of research on valley degree of freedom and the development of a new technology based on valley degree of freedom-valleytronics are also presented. Thus the scientific contents of the basic research and practical applications os THSs are very rich and extremely promising.

  3. Two-Dimensional Phononic Crystals: Disorder Matters.

    Science.gov (United States)

    Wagner, Markus R; Graczykowski, Bartlomiej; Reparaz, Juan Sebastian; El Sachat, Alexandros; Sledzinska, Marianna; Alzina, Francesc; Sotomayor Torres, Clivia M

    2016-09-14

    The design and fabrication of phononic crystals (PnCs) hold the key to control the propagation of heat and sound at the nanoscale. However, there is a lack of experimental studies addressing the impact of order/disorder on the phononic properties of PnCs. Here, we present a comparative investigation of the influence of disorder on the hypersonic and thermal properties of two-dimensional PnCs. PnCs of ordered and disordered lattices are fabricated of circular holes with equal filling fractions in free-standing Si membranes. Ultrafast pump and probe spectroscopy (asynchronous optical sampling) and Raman thermometry based on a novel two-laser approach are used to study the phononic properties in the gigahertz (GHz) and terahertz (THz) regime, respectively. Finite element method simulations of the phonon dispersion relation and three-dimensional displacement fields furthermore enable the unique identification of the different hypersonic vibrations. The increase of surface roughness and the introduction of short-range disorder are shown to modify the phonon dispersion and phonon coherence in the hypersonic (GHz) range without affecting the room-temperature thermal conductivity. On the basis of these findings, we suggest a criteria for predicting phonon coherence as a function of roughness and disorder.

  4. Two-dimensional topological photonic systems

    Science.gov (United States)

    Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng

    2017-09-01

    The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.

  5. Radiation effects on two-dimensional materials

    Energy Technology Data Exchange (ETDEWEB)

    Walker, R.C. II; Robinson, J.A. [Department of Materials Science, Penn State, University Park, PA (United States); Center for Two-Dimensional Layered Materials, Penn State, University Park, PA (United States); Shi, T. [Department of Mechanical and Nuclear Engineering, Penn State, University Park, PA (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States); Silva, E.C. [GlobalFoundries, Malta, NY (United States); Jovanovic, I. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States)

    2016-12-15

    The effects of electromagnetic and particle irradiation on two-dimensional materials (2DMs) are discussed in this review. Radiation creates defects that impact the structure and electronic performance of materials. Determining the impact of these defects is important for developing 2DM-based devices for use in high-radiation environments, such as space or nuclear reactors. As such, most experimental studies have been focused on determining total ionizing dose damage to 2DMs and devices. Total dose experiments using X-rays, gamma rays, electrons, protons, and heavy ions are summarized in this review. We briefly discuss the possibility of investigating single event effects in 2DMs based on initial ion beam irradiation experiments and the development of 2DM-based integrated circuits. Additionally, beneficial uses of irradiation such as ion implantation to dope materials or electron-beam and helium-beam etching to shape materials have begun to be used on 2DMs and are reviewed as well. For non-ionizing radiation, such as low-energy photons, we review the literature on 2DM-based photo-detection from terahertz to UV. The majority of photo-detecting devices operate in the visible and UV range, and for this reason they are the focus of this review. However, we review the progress in developing 2DMs for detecting infrared and terahertz radiation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Photodetectors based on two dimensional materials

    Science.gov (United States)

    Zheng, Lou; Zhongzhu, Liang; Guozhen, Shen

    2016-09-01

    Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on. Project supported by the National Natural Science Foundation of China (Nos. 61377033, 61574132, 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.

  7. Asymptotics for Two-dimensional Atoms

    DEFF Research Database (Denmark)

    Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip

    2012-01-01

    We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....

  8. Predicting Two-Dimensional Silicon Carbide Monolayers.

    Science.gov (United States)

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.

  9. Measurements of fiber orientation in two-dimensional fiber suspension flow using image-processing method; Gazo shoriho ni yoru sen`i gan`yutai no nijigen nagare ni okeru sen`i haiko no sokutei

    Energy Technology Data Exchange (ETDEWEB)

    Chono, S.; Tanoue, S.; Iemoto, Y. [Fukui University, Fukui (Japan). Faculty of Engineering

    1998-10-25

    Orientation profiles of fibers in fiber suspension flow between two parallel plates with a square cylinder on the center axis was studied by using the computer image analysis. The orientational order parameter S decreases near the square cylinder because the flow changes its direction and also a wake is developed, while it is large near the channel wall owing to high shear deformation. The preferred angle and S decrease in the downstream vicinity of the square cylinder, and reach fully-developed values at a farther area. S along the channel center axis increases with increasing a fiber concentration and the Reynolds number. The size of a square cylinder has an effect on the fiber orientation near the cylinder. Since a stagnation region and a large wake are developed before and after a cylinder for a viscoelastic fluid, a lower value of S near the cylinder is obtained for the viscoelastic fluid compared to that for a Newtonian fluid. At a downstream area, however, the viscoelastic fluid gives a higher values of S. 21 refs., 14 figs., 1 tab.

  10. Spallation of Small Particles From Peristaltic Pump Tube Segments.

    Science.gov (United States)

    Liu, Yi; Faria, Monica; Leonard, Edward

    2017-07-01

    In most extracorporeal filtration devices such as hemodialysis a peristaltic pump is used to circulate blood. Pump function requires the repeated compression of an elastomeric tube from which particles may be shed into the circulatory system, a process called spallation. Earlier studies are likely to have missed the large number of small particles (particles down to 0.6 µm. As polyvinyl chloride (PVC) tubing is commonly used for this process, a series of studies was conducted on three different types to study its spallation characteristics, along with a co-extruded PVC/polyurethane tubing known for its enhanced biocompatibility properties. For all types of PVC tubes, the average size of the spallated particles was 0.83 ± 0.03 µm; for the PVC/polyurethane tubing the average size of the spallated particles was approximately twice that reported for PVC tubing. For PVC tubes with equal inner diameter, those with less plasticizer released fewer particles; for tubes with the same Shore hardness, tubes with larger internal diameters released fewer particles. It was also shown that PVC tubes operating at a slower flow rate does not reduce the total number of particles released per volume pumped. The total number of particles spallated from the PVC/polyurethane tubing was 10 times lower than from the lowest spallating PVC tubing. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  11. Peristaltic motion of third grade fluid in curved channel

    Institute of Scientific and Technical Information of China (English)

    S.HINA; M.MUSTAFA; T.HAYAT; F.E.ALSAADI

    2014-01-01

    Analysis is performed to study the slip effects on the peristaltic flow of non-Newtonian fluid in a curved channel with wall properties. The resulting nonlinear partial differential equations are transformed to a single ordinary differential equation in a stream function by using the assumptions of long wavelength and low Reynolds number. This differential equation is solved numerically by employing the built-in routine for solving nonlinear boundary value problems (BVPs) through the software Mathematica. In addition, the analytic solutions for small Deborah number are computed with a regular perturbation technique. It is noticed that the symmetry of bolus is destroyed in a curved channel. An intensification in the slip effect results in a larger magnitude of axial velocity. Further, the size and circulation of the trapped boluses increase with an increase in the slip parameter. Different from the case of planar channel, the axial velocity profiles are tilted towards the lower part of the channel. A comparative study between analytic and numerical solutions shows excellent agreement.

  12. Calculation of two-dimensional wetland plant-impacted flow field in Dianchi lake%计入湿地植物影响的滇池二维流场计算

    Institute of Scientific and Technical Information of China (English)

    程浩亮; 杨具瑞; 芦振爱; 凌祯; 李君宁

    2012-01-01

    A depth-averaged 2D hydrodynamic model of ecosystem was developed in this work based on the comprehensive roughness of wetland determined by a flume experiment and some available information about Dianchi lake,such as the planning of ecological environment construction,the lake′s conditions of wetland plants and water area variation,and the previous studies.With this model,three types of flow fields were simulated to evaluate the effects of breakwater removing and ecological wetland construction and to analyze the flow field changes caused by wetland plants and different water boundaries.Results show that the breakwater removal for water area expansion produced little effect on the global water,but it caused significant changes in the local flow,due to its effects on the boundary location and the direction of wind-driven current.In the region between Fubao and Xishan of the north Dianchi,the average flow velocity was increased from 0.73cm/s to 1.18cm/s or by 61.6%,while in Kunyang of the south Dianchi,the velocity from 0.34cm/s to 0.57cm/s or by 67.6%.Velocity increase in the rest lake regions was quite small,from 1.22cm/s to 1.32cm/s or only by 8.2%.The impact of ecological wetland is limited within the wetland region of average flow velocity decreased by 67.4%(from 0.43cm/s to 0.14cm/s),while this impact is little in the rest regions with only a 4.7% decrease in their flow velocity(from 1.27cm/s to 1.21cm/s) on average.These results are valuable to the ecological environment restoring and construction of Dianchi lake.%依据滇池生态环境建设规划,在以前研究工作的基础上,综合考虑湿地植物和湖泊水域条件变化,在水槽实验确定湿地植物综合糙率基础上,根据水动力学原理建立垂向平均化的二维水动力学模型。模拟研究了拆除防浪堤前后滇池水体及滇池生态湿地建成后湿地水体3种情况的流场,分析了湿地植物以及湖泊水体边界条件改变对滇池流场的影响。模

  13. Interaction of two-dimensional magnetoexcitons

    Science.gov (United States)

    Dumanov, E. V.; Podlesny, I. V.; Moskalenko, S. A.; Liberman, M. A.

    2017-04-01

    We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector k→∥ = 0 , taking into account the influence of the excited Landau levels (ELLs) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field. It is shown that the account of the ELLs gives rise to the repulsion between the spinless magnetoexcitons with k→∥ = 0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g (0) ∼ 1 / B) . In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 2D magnetoexcitons with k→∥ = 0 . The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g (0) 1 /√{ B} .

  14. Two-dimensional materials and their prospects in transistor electronics.

    Science.gov (United States)

    Schwierz, F; Pezoldt, J; Granzner, R

    2015-05-14

    During the past decade, two-dimensional materials have attracted incredible interest from the electronic device community. The first two-dimensional material studied in detail was graphene and, since 2007, it has intensively been explored as a material for electronic devices, in particular, transistors. While graphene transistors are still on the agenda, researchers have extended their work to two-dimensional materials beyond graphene and the number of two-dimensional materials under examination has literally exploded recently. Meanwhile several hundreds of different two-dimensional materials are known, a substantial part of them is considered useful for transistors, and experimental transistors with channels of different two-dimensional materials have been demonstrated. In spite of the rapid progress in the field, the prospects of two-dimensional transistors still remain vague and optimistic opinions face rather reserved assessments. The intention of the present paper is to shed more light on the merits and drawbacks of two-dimensional materials for transistor electronics and to add a few more facets to the ongoing discussion on the prospects of two-dimensional transistors. To this end, we compose a wish list of properties for a good transistor channel material and examine to what extent the two-dimensional materials fulfill the criteria of the list. The state-of-the-art two-dimensional transistors are reviewed and a balanced view of both the pros and cons of these devices is provided.

  15. Finite amplitude waves in two-dimensional lined ducts

    Science.gov (United States)

    Nayfeh, A. H.; Tsai, M.-S.

    1974-01-01

    A second-order uniform expansion is obtained for nonlinear wave propagation in a two-dimensional duct lined with a point-reacting acoustic material consisting of a porous sheet followed by honeycomb cavities and backed by the impervious wall of the duct. The waves in the duct are coupled with those in the porous sheet and the cavities. An analytical expression is obtained for the absorption coefficient in terms of the sound frequency, the physical properties of the porous sheet, and the geometrical parameters of the flow configuration. The results show that the nonlinearity flattens and broadens the absorption vs. frequency curve, irrespective of the geometrical dimensions or the porous material acoustic properties, in agreement with experimental observations.

  16. Molecular-dynamics simulation of two-dimensional thermophoresis

    Science.gov (United States)

    Paredes; Idler; Hasmy; Castells; Botet

    2000-11-01

    A numerical technique is presented for the thermal force exerted on a solid particle by a gaseous medium between two flat plates at different temperatures, in the free molecular or transition flow. This is a two-dimensional molecular-dynamics simulation of hard disks in a inhomogeneous thermal environment. All steady-state features exhibited by the compressible hard-disk gas are shown to be consistent with the expected behaviors. Moreover the thermal force experienced by a large solid disk is investigated, and compared to the analytical case of cylinders moving perpendicularly to the constant temperature gradient for an infinite Knudsen number and in an infinite medium. We show precise examples of how this technique can be used simply to investigate more difficult practical problems, in particluar the influence of nonlinear gradients for large applied differences of temperature, of proximity of the walls, and of smaller Knudsen numbers.

  17. A renormalization group analysis of two-dimensional magnetohydrodynamic turbulence

    Science.gov (United States)

    Liang, Wenli Z.; Diamond, P. H.

    1993-01-01

    The renormalization group (RNG) method is used to study the physics of two-dimensional (2D) magnetohydrodynamic (MHD) turbulence. It is shown that, for a turbulent magnetofluid in two dimensions, no RNG transformation fixed point exists on account of the coexistence of energy transfer to small scales and mean-square magnetic flux transfer to large scales. The absence of a fixed point renders the RNG method incapable of describing the 2D MHD system. A similar conclusion is reached for 2D hydrodynamics, where enstrophy flows to small scales and energy to large scales. These analyses suggest that the applicability of the RNG method to turbulent systems is intrinsically limited, especially in the case of systems with dual-direction transfer.

  18. Development of two-dimensional hot pool model

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yong Bum; Hahn, H. D

    2000-05-01

    During a normal reactor scram, the heat generation is reduced almost instantaneously while the coolant flow rate follows the pump coast-down. This mismatch between power and flow results in a situation where the core flow entering the hot pool is at a lower temperature than the temperature of the bulk pool sodium. This temperature difference leads to thermal stratification. Thermal stratification can occur in the hot pool region if the entering coolant is colder than the existing hot pool coolant and the flow momentum is not large enough to overcome the negative buoyancy force. Since the fluid of hot pool enters IHX{sub s}, the temperature distribution of hot pool can alter the overall system response. Hence, it is necessary to predict the pool coolant temperature distribution with sufficient accuracy to determine the inlet temperature conditions for the IHX{sub s} and its contribution to the net buoyancy head. Therefore, in this study two-dimensional hot pool model is developed instead of existing one-dimensional model to predict the hot pool coolant temperature and velocity distribution more accurately and is applied to the SSC-K code.

  19. Two-Dimensional Rotating Stall Analysis in a Wide Vaneless Diffuser

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available We report a numerical study on the vaneless diffuser core flow instability in centrifugal compressors. The analysis is performed for the purpose of better understanding of the rotating stall flow mechanism in radial vaneless diffusers. Since the analysis is restricted to the two-dimensional core flow, the effect of the wall boundary layers is neglected. A commercial code with the standard incompressible viscous flow solver is applied to model the vaneless diffuser core flow in the plane parallel to the diffuser walls. At the diffuser inlet, rotating jet-wake velocity pattern is prescribed and at the diffuser outlet constant static pressure is assumed. Under these circumstances, two-dimensional rotating flow instability similar to rotating stall is found to exist. Performed parameter analysis reveals that this instability is strongly influenced by the diffuser geometry and the inlet and outlet flow conditions.

  20. Ultrafast two dimensional infrared chemical exchange spectroscopy

    Science.gov (United States)

    Fayer, Michael

    2011-03-01

    The method of ultrafast two dimensional infrared (2D IR) vibrational echo spectroscopy is described. Three ultrashort IR pulses tuned to the frequencies of the vibrational transitions of interest are directed into the sample. The interaction of these pulses with the molecular vibrational oscillators produces a polarization that gives rise to a fourth pulse, the vibrational echo. The vibrational echo pulse is combined with another pulse, the local oscillator, for heterodyne detection of the signal. For fixed time between the second and third pulses, the waiting time, the first pulse is scanned. Two Fourier transforms of the data yield a 2D IR spectrum. The waiting time is increased, and another spectrum is obtained. The change in the 2D IR spectra with increased waiting time provides information on the time evolution of the structure of the molecular system under observation. In a 2D IR chemical exchange experiment, two species A and B, are undergoing chemical exchange. A's are turning into B's, and B's are turning into A's, but the overall concentrations of the species are not changing. The kinetics of the chemical exchange on the ground electronic state under thermal equilibrium conditions can be obtained 2D IR spectroscopy. A vibration that has a different frequency for the two species is monitored. At very short time, there will be two peaks on the diagonal of the 2D IR spectrum, one for A and one for B. As the waiting time is increased, chemical exchange causes off-diagonal peaks to grow in. The time dependence of the growth of these off-diagonal peaks gives the chemical exchange rate. The method is applied to organic solute-solvent complex formation, orientational isomerization about a carbon-carbon single bond, migration of a hydrogen bond from one position on a molecule to another, protein structural substate interconversion, and water hydrogen bond switching between ions and water molecules. This work was supported by the Air Force Office of Scientific