Log in

Relevant bibliographies by topics / Random flow field / Journal articles

Journal articles on the topic 'Random flow field'

To see the other types of publications on this topic, follow the link: Random flow field.

Author: Grafiati

Published: 4 June 2021

Last updated: 19 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Random flow field.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Breyer, L. A., and G. O. Roberts. "A New Method for Coupling Random Fields." LMS Journal of Computation and Mathematics 5 (2002): 77–94. http://dx.doi.org/10.1112/s146115700000070x.

Full text

Abstract:

AbstractGiven a Markov chain, a stochastic flow that simultaneously constructs sample paths started at each possible initial value can be constructed as a composition of random fields. Here, a method is described for coupling flows by modifying an arbitrary field (consistent with the Markov chain of interest) by an independence Metropolis-Hastings iteration. The resulting stochastic flow is shown to have many desirable coalescence properties, regardless of the form of the original flow.

APA, Harvard, Vancouver, ISO, and other styles

2

IJZERMANS, RUTGER H. A., ELENA MENEGUZ, and MICHAEL W. REEKS. "Segregation of particles in incompressible random flows: singularities, intermittency and random uncorrelated motion." Journal of Fluid Mechanics 653 (April 13, 2010): 99–136. http://dx.doi.org/10.1017/s0022112010000170.

Full text

Abstract:

The results presented here are part of a long-term study in which we analyse the segregation of inertial particles in turbulent flows using the so called full Lagrangian method (FLM) to evaluate the ‘compressibility’ of the particle phase along a particle trajectory. In the present work, particles are advected by Stokes drag in a random flow field consisting of counter-rotating vortices and in a flow field composed of 200 random Fourier modes. Both flows are incompressible and, like turbulence, have structure and a distribution of scales with finite lifetime. The compressibility is obtained by first calculating the deformation tensor Jij associated with an infinitesimally small volume of particles following the trajectory of an individual particle. The fraction of the initial volume occupied by the particles centred around a position x at time t is denoted by |J|, where J ≡ det(Jij) and Jij ≡ ∂xi(x0, t)/∂x0,j, x0 denoting the initial position of the particle. The quantity d〈ln|J|〉/dt is shown to be equal to the particle averaged compressibility of the particle velocity field 〈∇ · v〉, which gives a measure of the rate-of-change of the total volume occupied by the particle phase as a continuum. In both flow fields the compressibility of the particle velocity field is shown to decrease continuously if the Stokes number St (the dimensionless particle relaxation time) is below a threshold value Stcr, indicating that the segregation of particles continues indefinitely. We show analytically and numerically that the long-time limit of 〈∇ · v〉 for sufficiently small values of St is proportional to St2 in the flow field composed of random Fourier modes, and to St in the flow field consisting of counter-rotating vortices. If St > Stcr, however, the particles are ‘mixed’. The level of mixing can be quantified by the degree of random uncorrelated motion (RUM) of particles which is a measure of the decorrelation of the velocities of two nearby particles. RUM is zero for fluid particles and increases rapidly with the Stokes number if St > Stcr, approaching unity for St ≫ 1. The spatial averages of the higher-order moments of the particle number density are shown to diverge with time indicating that the spatial distribution of particles may be very intermittent, being associated with non-zero values of RUM and the occurrence of singularities in the particle velocity field. Our results are consistent with previous observations of the radial distribution function in Chun et al. (J. Fluid Mech., vol. 536, 2005, p. 219).

APA, Harvard, Vancouver, ISO, and other styles

3

S&z.xl;luż;alec, Andrzej. "Temperature field in random conditions." International Journal of Heat and Mass Transfer 34, no. 1 (January 1991): 55–58. http://dx.doi.org/10.1016/0017-9310(91)90172-b.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Kawaguchi, Takaaki. "Plastic flow in a driven random-field XY model." Physics Letters A 251, no. 1 (January 1999): 73–78. http://dx.doi.org/10.1016/s0375-9601(98)00851-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Smirnov, A., S. Shi, and I. Celik. "Random Flow Generation Technique for Large Eddy Simulations and Particle-Dynamics Modeling." Journal of Fluids Engineering 123, no. 2 (February 16, 2001): 359–71. http://dx.doi.org/10.1115/1.1369598.

Full text

Abstract:

A random flow generation (RFG) technique is presented, which can be used for initial/inlet boundary generation in LES (Large-Eddy-Simulations) or particle tracking in LES/RANS (Reynolds-Averaged Navier-Stokes) computations of turbulent flows. The technique is based on previous methods of synthesizing divergence-free vector fields from a sample of Fourier harmonics and allows to generate non-homogeneous anisotropic flow field representing turbulent velocity fluctuations. It was validated on the cases of boundary layer and flat plate flows. Applications of the technique to LES and particle tracking are considered.

APA, Harvard, Vancouver, ISO, and other styles

6

Kolokolov, I. V., V. V. Lebedev, and G. A. Sizov. "Magnetic field correlations in random flow with strong steady shear." Journal of Experimental and Theoretical Physics 113, no. 2 (August 2011): 339–51. http://dx.doi.org/10.1134/s1063776111060033.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

SIGURGEIRSSON, H., and A. M. STUART. "INERTIAL PARTICLES IN A RANDOM FIELD." Stochastics and Dynamics 02, no. 02 (June 2002): 295–310. http://dx.doi.org/10.1142/s021949370200042x.

Full text

Abstract:

The motion of an inertial particle in a Gaussian random field is studied. This is a model for the phenomenon of preferential concentration, whereby inertial particles in a turbulent flow can correlate significantly. Mathematically the motion is described by Newton's second law for a particle on a 2-D torus, with force proportional to the difference between a background fluid velocity and the particle velocity itself. The fluid velocity is defined through a linear stochastic PDE of Ornstein–Uhlenbeck type. The properties of the model are studied in terms of the covariance of the noise which drives the stochastic PDE. Sufficient conditions are found for almost sure existence and uniqueness of particle paths, and for a random dynamical system with a global random attractor. The random attractor is illustrated by means of a numerical experiment, and the relevance of the random attractor for the understanding of particle distributions is highlighted.

APA, Harvard, Vancouver, ISO, and other styles

8

ZIRBEL, CRAIG L., and WOJBOR A. WOYCZYŃSKI. "ROTATION OF PARTICLES IN POLARIZED BROWNIAN FLOWS." Stochastics and Dynamics 02, no. 01 (March 2002): 109–29. http://dx.doi.org/10.1142/s0219493702000339.

Full text

Abstract:

We consider the rotation of tangent vectors and the mutual rotation of two particles undergoing motion in a random two-dimensional velocity field. We look at random fields whose laws are invariant under translations and rotations, but not reflections. These polarized fields are intermediate between homogeneous and isotropic fields, and may possess a preferred sense of rotation. The covariance of such a field must have a certain form which we describe. In a Brownian flow based on a polarized random field, we show that tangent vectors can rotate at a constant asymptotic rate, and that under certain conditions, two particles will rotate about each other at the same asymptotic rate. For illustration we present simulations of a polarized Gaussian field and of particles moving in a polarized Brownian flow.

APA, Harvard, Vancouver, ISO, and other styles

9

van Gogh, M. A., T. Bauer, L. De Angelis, and L. Kuipers. "Poynting singularities in the transverse flow-field of random vector waves." Optics Letters 45, no. 9 (April 28, 2020): 2600. http://dx.doi.org/10.1364/ol.389301.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Adhikari, Sondipon, Akshat Rastogi, and Bishakh Bhattacharya. "Piezoelectric vortex induced vibration energy harvesting in a random flow field." Smart Materials and Structures 29, no. 3 (February 19, 2020): 035034. http://dx.doi.org/10.1088/1361-665x/ab519f.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Maier, Robert S., D. M. Kroll, H. Ted Davis, and Robert S. Bernard. "Pore-Scale Flow and Dispersion." International Journal of Modern Physics C 09, no. 08 (December 1998): 1523–33. http://dx.doi.org/10.1142/s0129183198001370.

Full text

Abstract:

Pore-scale simulations of fluid flow and mass transport offer a direct means to reproduce and verify laboratory measurements in porous media. We have compared lattice-Boltzmann (LB) flow simulations with the results of NMR spectroscopy from several published flow experiments. Although there is qualitative agreement, the differences highlight numerical and experimental issues, including the rate of spatial convergence, and the effect of signal attenuation near solid surfaces. For the range of Reynolds numbers relevant to groundwater investigations, the normalized distribution of fluid velocities in random sphere packings collapse onto a single curve, when scaled with the mean velocity. Random-walk particle simulations in the LB flow fields have also been performed to study the dispersion of an ideal tracer. These simulations show an encouraging degree of quantitative agreement with published NMR measurements of hydrodynamic and molecular dispersion, and the simulated dispersivities scale in accordance with published experimental and theoretical results for the Peclet number rangek 1 ≤ Pe ≤1500. Experience with the random-walk method indicates that the mean properties of conservative transport, such as the first and second moments of the particle displacement distribution, can be estimated with a number of particles comparable to the spatial discretization of the velocity field. However, the accurate approximation of local concentrations, at a resolution comparable to that of the velocity field, requires significantly more particles. This requirement presents a significant computational burden and hence a numerical challenge to the simulation of non-conservative transport processes.

APA, Harvard, Vancouver, ISO, and other styles

12

Last, G., and R. Schassberger. "A flow conservation law for surface processes." Advances in Applied Probability 28, no. 01 (March 1996): 13–28. http://dx.doi.org/10.1017/s0001867800027269.

Full text

Abstract:

The object studied in this paper is a pair (Φ, Y), where Φ is a random surface in and Y a random vector field on . The pair is jointly stationary, i.e. its distribution is invariant under translations. The vector field Y is smooth outside Φ but may have discontinuities on Φ. Gauss' divergence theorem is applied to derive a flow conservation law for Y. For this specializes to a well-known rate conservation law for point processes. As an application, relationships for the linear contact distribution of Φ are derived.

APA, Harvard, Vancouver, ISO, and other styles

13

Last, G., and R. Schassberger. "A flow conservation law for surface processes." Advances in Applied Probability 28, no. 1 (March 1996): 13–28. http://dx.doi.org/10.2307/1427911.

Full text

Abstract:

The object studied in this paper is a pair (Φ, Y), where Φ is a random surface in and Y a random vector field on . The pair is jointly stationary, i.e. its distribution is invariant under translations. The vector field Y is smooth outside Φ but may have discontinuities on Φ. Gauss' divergence theorem is applied to derive a flow conservation law for Y. For this specializes to a well-known rate conservation law for point processes. As an application, relationships for the linear contact distribution of Φ are derived.

APA, Harvard, Vancouver, ISO, and other styles

14

Kostecki, Stanisław. "Random Vortex Method in Numerical Analysis of 2D Flow Around Circular Cylinder." Studia Geotechnica et Mechanica 36, no. 4 (February 28, 2015): 57–63. http://dx.doi.org/10.2478/sgem-2014-0036.

Full text

Abstract:

Abstract A combination of the vortex method and the boundary element method is used here to predict the two-dimensional flow field around a circular cylinder. Cylindrical structures experience strong hydrodynamic loading, due to vortex detachment from the both sides of cylinder during the flow. Thus, the practical meaning of such calculation is significant particularly in offshore oil and gas engineering as well as in the bridge and hydraulic structure engineering. This paper presents the mathematical formulation of the vortex method for the velocity and vorticity field calculation. The calculated velocity and vorticity fields are then used to predict the pressure distribution on the cylinder surface by the boundary element method. The resulting pressure on the cylinder, the Strouhal number and the length of the base recirculation zone are compared with solutions of other numerical methods and experiments, and a good agreement is achieved.

APA, Harvard, Vancouver, ISO, and other styles

15

Zhang, Ningbo, Changyou Liu, Xiaojie Wu, and Tingxiang Ren. "Dynamic Random Arching in the Flow Field of Top-Coal Caving Mining." Energies 11, no. 5 (May 1, 2018): 1106. http://dx.doi.org/10.3390/en11051106.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Schmidhuber, Christof. "RG flow on random surfaces with handles and closed string field theory." Nuclear Physics B 453, no. 1-2 (October 1995): 156–80. http://dx.doi.org/10.1016/0550-3213(95)00436-v.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Coscarella, Francesco, Nadia Penna, Aldo Pedro Ferrante, Paola Gualtieri, and Roberto Gaudio. "Turbulent Flow through Random Vegetation on a Rough Bed." Water 13, no. 18 (September 17, 2021): 2564. http://dx.doi.org/10.3390/w13182564.

Full text

Abstract:

River vegetation radically modifies the flow field and turbulence characteristics. To analyze the vegetation effects on the flow, most scientific studies are based on laboratory tests or numerical simulations with vegetation stems on smooth beds. Nevertheless, in this manner, the effects of bed sediments are neglected. The aim of this paper is to experimentally investigate the effects of bed sediments in a vegetated channel and, in consideration of that, comparative experiments of velocity measures, performed with an Acoustic Doppler Velocimeter (ADV) profiler, were carried out in a laboratory flume with different uniform bed sediment sizes and the same pattern of randomly arranged emergent rigid vegetation. To better comprehend the time-averaged flow conditions, the time-averaged velocity was explored. Subsequently, the analysis was focused on the energetic characteristics of the flow field with the determination of the Turbulent Kinetic Energy (TKE) and its components, as well as of the energy spectra of the velocity components immediately downstream of a vegetation element. The results show that both the vegetation and bed roughness surface deeply affect the turbulence characteristics. Furthermore, it was revealed that the roughness influence becomes predominant as the grain size becomes larger.

APA, Harvard, Vancouver, ISO, and other styles

18

Ahlström, Ulf, and Erik Börjesson. "Segregation of Motion Structure from Random Visual Noise." Perception 25, no. 3 (March 1996): 279–91. http://dx.doi.org/10.1068/p250279.

Full text

Abstract:

A potential source of information about spatial layout, surface slant, and self-motion is provided by transformations of the optic flow field. Theoretical analyses have demonstrated that such flow fields can be decomposed into translation, rotation, expansion, and deformation components. The objective in this study was to investigate the effectiveness of these motions as visual primitives for preattentive scene segregation. The stimuli consisted of two-frame patterns containing 998 dots. A variable number of these dots (5 to 50) were defined as target dots, representing a specific motion structure, with the residual dots defined as a noise field. The observers' task was to identify the location and type of motion structure. On the basis of the number of target dots needed to detect and correctly identify the target structure, it was determined that translation was the most easily detected structure, followed by rotation, expansion, and compression. Deformation was found to have a detection threshold as high as compression. The results are related to other studies of these motion components.

APA, Harvard, Vancouver, ISO, and other styles

19

Lynov, J. P., A. H. Nielsen, H. L. Pécseli, and J. Juul Rasmussen. "Studies of the Eulerian–Lagrangian transformation in two-dimensional random flows." Journal of Fluid Mechanics 224 (March 1991): 485–505. http://dx.doi.org/10.1017/s0022112091001842.

Full text

Abstract:

Two-dimensional, incompressible flows are discussed by a generalization of the line-vortex model. A large number of structures are randomly distributed initially. Each individual structure is convected by the superposed flow field of all the others. The statistical properties of the resulting space–time varying random flow are studied. Analytical expressions for both Eulerian and Lagrangian correlation functions are obtained for the limit where the density of structures is large. The analytical results compare favourably with numerical simulations. The study serves as a special test on proposed relations between Eulerian and Lagrangian averages which can be generally valid, i.e. also for three-dimensional, turbulent flows.

APA, Harvard, Vancouver, ISO, and other styles

20

Pereira, Rodrigo M., Christophe Garban, and Laurent Chevillard. "A dissipative random velocity field for fully developed fluid turbulence." Journal of Fluid Mechanics 794 (April 4, 2016): 369–408. http://dx.doi.org/10.1017/jfm.2016.166.

Full text

Abstract:

We investigate the statistical properties, based on numerical simulations and analytical calculations, of a recently proposed stochastic model for the velocity field (Chevillardet al.,Europhys. Lett., vol. 89, 2010, 54002) of an incompressible, homogeneous, isotropic and fully developed turbulent flow. A key step in the construction of this model is the introduction of some aspects of the vorticity stretching mechanism that governs the dynamics of fluid particles along their trajectories. An additional further phenomenological step aimed at including the long range correlated nature of turbulence makes this model dependent on a single free parameter,${\it\gamma}$, that can be estimated from experimental measurements. We confirm the realism of the model regarding the geometry of the velocity gradient tensor, the power-law behaviour of the moments of velocity increments (i.e. the structure functions) including the intermittent corrections and the existence of energy transfer across scales. We quantify the dependence of these basic properties of turbulent flows on the free parameter${\it\gamma}$and derive analytically the spectrum of exponents of the structure functions in a simplified non-dissipative case. A perturbative expansion in power of${\it\gamma}$shows that energy transfer, at leading order, indeed take place, justifying the dissipative nature of this random field.

APA, Harvard, Vancouver, ISO, and other styles

21

Ruzmaikin, A. A. "Dynamo in Astrophysics." Symposium - International Astronomical Union 140 (1990): 83–89. http://dx.doi.org/10.1017/s0074180900189636.

Full text

Abstract:

The fast dynamo acting in a turbulent flow explains the origin of magnetic fields in astrophysical objects. Stellar cycles and large-scale magnetic fields in spiral galaxies reflect the behaviour of a mean magnetic field. Intermittent magnetic structures in clusters of galaxies are associated with random magnetic field.

APA, Harvard, Vancouver, ISO, and other styles

22

VENTURI, DANIELE, XIAOLIANG WAN, and GEORGE EM KARNIADAKIS. "Stochastic low-dimensional modelling of a random laminar wake past a circular cylinder." Journal of Fluid Mechanics 606 (July 10, 2008): 339–67. http://dx.doi.org/10.1017/s0022112008001821.

Full text

Abstract:

We present a new compact expansion of a random flow field into stochastic spatial modes, hence extending the proper orthogonal decomposition (POD) to noisy (non-coherent) flows. As a prototype problem, we consider unsteady laminar flow past a circular cylinder subject to random inflow characterized as a stationary Gaussian process. We first obtain random snapshots from full stochastic simulations (based on polynomial chaos representations), and subsequently extract a small number of deterministic modes and corresponding stochastic modes by solving a temporal eigenvalue problem. Finally, we determine optimal sets of random projections for the stochastic Navier–Stokes equations, and construct reduced-order stochastic Galerkin models. We show that the number of stochastic modes required in the reconstruction does not directly depend on the dimensionality of the flow system. The framework we propose is general and it may also be useful in analysing turbulent flows, e.g. in quantifying the statistics of energy exchange between coherent modes.

APA, Harvard, Vancouver, ISO, and other styles

23

Field, R. V., and M. Grigoriu. "Level cut Gaussian random field models for transitions from laminar to turbulent flow." Probabilistic Engineering Mechanics 28 (April 2012): 91–102. http://dx.doi.org/10.1016/j.probengmech.2011.08.023.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Liu, Wenwei, Sheng Chen, and Shuiqing Li. "Random adhesive loose packings of micron-sized particles under a uniform flow field." Powder Technology 335 (July 2018): 70–76. http://dx.doi.org/10.1016/j.powtec.2018.04.072.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Olcay, Ali B., Tait S. Pottebaum, and Paul S. Krueger. "Sensitivity of Lagrangian coherent structure identification to flow field resolution and random errors." Chaos: An Interdisciplinary Journal of Nonlinear Science 20, no. 1 (March 2010): 017506. http://dx.doi.org/10.1063/1.3276062.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Zhao, Y., and K. Anastasiou. "Bottom friction effects in the combined flow field of random waves and currents." Coastal Engineering 19, no. 3-4 (May 1993): 223–43. http://dx.doi.org/10.1016/0378-3839(93)90030-c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Jenkins, A. D. "Simulation of turbulent dispersion using a simple random model of the flow field." Applied Mathematical Modelling 9, no. 4 (August 1985): 239–45. http://dx.doi.org/10.1016/0307-904x(85)90060-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Wang, Jingbo, and Nicholas Zabaras. "A Markov random field model of contamination source identification in porous media flow." International Journal of Heat and Mass Transfer 49, no. 5-6 (March 2006): 939–50. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2005.09.016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Ostoja-Starzewski, Martin. "Plastic Flow of Random Media: Micromechanics, Markov Property and Slip-Lines." Applied Mechanics Reviews 45, no. 3S (March 1, 1992): S75—S81. http://dx.doi.org/10.1115/1.3121394.

Full text

Abstract:

The classical method of slip-lines (characteristics) of planar flow of perfectly-plastic media is generalized to a stochastic setting. The media are charaterized by space-homogeneous statistics of the yield limit k, whose derivation is outlined on the basis of micromechanics. The field equations of the random continuum approximation lead to a stochastic hyperbolic system. This system, when stated in a finite difference form, displays a Markov property for the forward evolution. On that basis, two methods of solution of boundary value problems - an exact one and a mean-field one - are outlined through an example of a Cauchy problem. The principal observation is that even for a weak material randomness the stochastic solution may differ qualitatively from that of a homogeneous deterministic medium and have a strong scatter.

APA, Harvard, Vancouver, ISO, and other styles

30

Steinberg, Victor. "Elastic Turbulence: An Experimental View on Inertialess Random Flow." Annual Review of Fluid Mechanics 53, no. 1 (January 5, 2021): 27–58. http://dx.doi.org/10.1146/annurev-fluid-010719-060129.

Full text

Abstract:

A viscous solvent laminar flow may be strongly modified by the addition of a tiny amount of long polymer molecules, resulting in a chaotic flow called elastic turbulence (ET). ET is attributed to polymer stretching, which generates elastic stress and its back reaction on the flow. Its properties are analogous to those observed in hydrodynamic turbulence, although the formal similarity does not imply a similarity in physical mechanisms underlining these two types of random motion. Here we review the statistical and spectral properties and the spatial structure of the velocity field, the statistical and spectral properties of pressure fluctuations, and scaling of the friction factor of ET in wall-bounded and unbounded flow geometries, as observed in experiments and numerical simulations and described by theory for a wide range of control parameters and polymer concentrations.

APA, Harvard, Vancouver, ISO, and other styles

31

CHERTKOV, M., G. FALKOVICH, I. KOLOKOLOV, and V. LEBEDEV. "THEORY OF RANDOM ADVECTION IN TWO DIMENSIONS." International Journal of Modern Physics B 10, no. 18n19 (August 30, 1996): 2273–309. http://dx.doi.org/10.1142/s0217979296001033.

Full text

Abstract:

The steady statistics of a passive scalar advected by a random two-dimensional flow of an incompressible fluid is described at scales less than the correlation length of the flow and larger than the diffusion scale. The probability distribution of the scalar is expressed via the probability distribution of the line stretching rate. The description of the line stretching can be reduced to the classical problem of studying the product of many matrices with a unit determinant. We found a change of variables which allows one to map the matrix problem into a scalar one and to prove thus a central limit theorem for the statistics of the stretching rate. The proof is valid for any finite correlation time of the velocity field. Whatever be the statistics of the velocity field, the statistics of the passive scalar in the inertial interval of scales is shown to approach Gaussianity as one increases the Peclet number Pe (the ratio of the pumping scale to the diffusion one). The first n < ln (Pe) simultaneous correlation functions are expressed via the flux of the squared scalar and only one unknown factor depending on the velocity field: the mean stretching rate. That factor can be calculated analytically for the limiting cases. The non-Gaussian tails of the probability distributions at finite Pe are found to be exponential.

APA, Harvard, Vancouver, ISO, and other styles

32

He, X. S., and J. G. Georgiadis. "Pressure Propagation in Pulsatile Flow Through Random Microvascular Networks." Journal of Biomechanical Engineering 115, no. 2 (May 1, 1993): 180–86. http://dx.doi.org/10.1115/1.2894119.

Full text

Abstract:

A microvascular network with random dimensions of vessels is built on the basis of statistical analysis of conjuctival beds reported in the literature. Our objective is to develop a direct method of evaluating the statistics of the pulsatile hydrodynamic field starting from a priori statistics which mimic the large-scale heterogeneity of the network. The model consists of a symmetric diverging-converging dentritic network of ten levels of vessels, each level described by a truncated Gaussian distribution of vessel diameters and lengths. In each vascular segment, the pressure distribution is given by a diffusion equation with random parameters, while the blood flow rate depends linearly on the pressure gradient. The results are presented in terms of the mean value and standard deviation of the pressure and flow rate waveforms at two positions along the network. It is shown that the assumed statistical variation of vessel lengths results in flow rate deviations as high as 50 percent of the mean, while the corresponding effect of vessel diameter variation is much smaller. For a given pressure drop, the statistical variation of lengths increases the mean flow while the effect on the mean pressure distribution is negligible.

APA, Harvard, Vancouver, ISO, and other styles

33

Worsley, K. J. "Local Maxima and the Expected Euler Characteristic of Excursion Sets of χ 2, F and t Fields." Advances in Applied Probability 26, no. 1 (March 1994): 13–42. http://dx.doi.org/10.2307/1427576.

Full text

Abstract:

The maximum of a Gaussian random field was used by Worsley et al. (1992) to test for activation at an unknown point in positron emission tomography images of blood flow in the human brain. The Euler characteristic of excursion sets was used as an estimator of the number of regions of activation. The expected Euler characteristic of excursion sets of stationary Gaussian random fields has been derived by Adler and Hasofer (1976) and Adler (1981). In this paper we extend the results of Adler (1981) to χ2, F and t fields. The theory is applied to some three-dimensional images of cerebral blood flow from a study on pain perception.

APA, Harvard, Vancouver, ISO, and other styles

34

SYROS, C. "ON THE RANDOM QFT FOUNDATIONS OF STATISTICAL MECHANICS." International Journal of Modern Physics B 05, no. 18 (November 10, 1991): 2909–34. http://dx.doi.org/10.1142/s0217979291001139.

Full text

Abstract:

The Statistical Mechanics of the N-particle system is derived from Quantum Random Field Theory. An asymptotically measure preserving, flow operator has been obtained from the QFT evolution operator. A basic assumption is that the field Lagrangian is a generalized, infinitely divisible random field, and the interaction Hamiltonian varies in time in a step-wise manner at the transition lattice space-time points. Macroscopic boundary conditions are imposed on the wave functions. The density matrix, the partition function, the Bose-Einstein, the Fermi-Dirac distributions and the thermodynamic temperature follow. The equilibrium or non-equilibrium temperature have been obtained as functionals of the interaction Hamiltonian. The chemical potential has also been derived from the theory.

APA, Harvard, Vancouver, ISO, and other styles

35

Kolyukhin, Dmitriy. "Global sensitivity analysis for a stochastic flow problem." Monte Carlo Methods and Applications 24, no. 4 (December 1, 2018): 263–70. http://dx.doi.org/10.1515/mcma-2018-2022.

Full text

Abstract:

Abstract The paper is devoted to the modeling of a single-phase flow through saturated porous media. A statistical approach where permeability is considered as a lognormal random field is applied. The impact of permeability, random boundary conditions and wells pressure on the flow in a production well is studied. A numerical procedure to generate an ensemble of realizations of the numerical solution of the problem is developed. A global sensitivity analysis is performed using Sobol indices. The impact of different model parameters on the total model uncertainty is studied.

APA, Harvard, Vancouver, ISO, and other styles

36

Su Tao, Feng Yao-Dong, Zhao Hong-Wu, Huang De-Cai, and Sun Gang. "Control of the fluctuation in the uniform granular flow by a random force field." Acta Physica Sinica 62, no. 16 (2013): 164502. http://dx.doi.org/10.7498/aps.62.164502.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Esmonde, H., and H. See. "Identification of an ER Fluid in Unsteady Flow with Random Electric Field and Solidification." Journal of Intelligent Material Systems and Structures 20, no. 2 (June 10, 2008): 205–15. http://dx.doi.org/10.1177/1045389x08091119.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Vanderborght, J., D. Jacques, D. Mallants, P. H. Tseng, and J. Feyen. "Comparison between field measurements and numerical simulation of steady-state solute transport in a heterogeneous soil profile." Hydrology and Earth System Sciences 1, no. 4 (December 31, 1997): 853–71. http://dx.doi.org/10.5194/hess-1-853-1997.

Full text

Abstract:

Abstract. Abstract: Field-scale solute dispersion is determined by water flow heterogeneity which results from spatial variability of soil hydraulic properties and soil moisture state. Measured variabilities of soil hydraulic properties are highly sensitive to the experimental method. Field-scale dispersion derived from leaching experiments in a macroporous loam soil was compared with field-scale dispersion obtained with numerical simulations in heterogeneous random fields. Four types of random fields of hydraulic properties having statistical properties derived from four different types of laboratory measurements were considered. Based on this comparison, the measurement method depicting heterogeneities of hydraulic properties most relevant to field-scale solute transport was identified. For unsaturated flow, the variability of the hydraulic conductivity characteristic measured on a small soil volume was the most relevant parameter. For saturated flow, simulated dispersion underestimated the measured dispersion and it was concluded that heterogeneity of macroscopic hydraulic properties could not represent solute flow heterogeneity under these flow conditions. Field-scale averaged solute concentrations depend both on the detection method and the averaging procedure. Flux-averaged concentrations (relevant to practical applications) differ from volume-averaged or resident concentrations (easy to measure), especially when water flow is more heterogeneous. Simulated flux and resident concentrations were subsequently used to test two simple one-dimensional transport models in predicting flux concentrations when they are calibrated on resident concentrations. In the first procedure, solute transport in a heterogeneous soil is represented by a 1-D convection dispersion process. The second procedure was based on the relation between flux and resident concentrations for a stochastic convective process. Better predictions of flux concentrations were obtained using the second procedure, especially when water flow and solute transport are very heterogeneous.

APA, Harvard, Vancouver, ISO, and other styles

39

Xu, Feng, and Oliver E. Jensen. "Drop spreading with random viscosity." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2194 (October 2016): 20160270. http://dx.doi.org/10.1098/rspa.2016.0270.

Full text

Abstract:

We examine theoretically the spreading of a viscous liquid drop over a thin film of uniform thickness, assuming the liquid’s viscosity is regulated by the concentration of a solute that is carried passively by the spreading flow. The solute is assumed to be initially heterogeneous, having a spatial distribution with prescribed statistical features. To examine how this variability influences the drop’s motion, we investigate spreading in a planar geometry using lubrication theory, combining numerical simulations with asymptotic analysis. We assume diffusion is sufficient to suppress solute concentration gradients across but not along the film. The solute field beneath the bulk of the drop is stretched by the spreading flow, such that the initial solute concentration immediately behind the drop’s effective contact lines has a long-lived influence on the spreading rate. Over long periods, solute swept up from the precursor film accumulates in a short region behind the contact line, allowing patches of elevated viscosity within the precursor film to hinder spreading. A low-order model provides explicit predictions of the variances in spreading rate and drop location, which are validated against simulations.

APA, Harvard, Vancouver, ISO, and other styles

40

Li, Tong Zhuo, Peng Fei Bi, and Nan Jiang. "To Simulate the Flow Field of Jet Pumps of Plane Model by Using Monte Carlo Method." Advanced Materials Research 295-297 (July 2011): 1829–33. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.1829.

Full text

Abstract:

First numeric computation of fluid field inside jet pump is conducted with continuity equation and momentum equation of steady fluid under right-angled two-dimension coordinates, and the random walk model is given. As for the method of integrating coupling pressure and momentum equation is adopted. The result is conforming to the flow of reality. Furthermore, the relation of random walk times and computing time and computing errors is analyzed in-depth. The relation of iterative times and computing errors is analyzed. It establishes a foundation for studying the flow field of jet pumps to use the Monte Carlo Method. At the meantime it develops a new field.

APA, Harvard, Vancouver, ISO, and other styles

41

Worsley, K. J. "Local Maxima and the Expected Euler Characteristic of Excursion Sets of χ 2, F and t Fields." Advances in Applied Probability 26, no. 01 (March 1994): 13–42. http://dx.doi.org/10.1017/s0001867800025970.

Full text

Abstract:

The maximum of a Gaussian random field was used by Worsley et al. (1992) to test for activation at an unknown point in positron emission tomography images of blood flow in the human brain. The Euler characteristic of excursion sets was used as an estimator of the number of regions of activation. The expected Euler characteristic of excursion sets of stationary Gaussian random fields has been derived by Adler and Hasofer (1976) and Adler (1981). In this paper we extend the results of Adler (1981) toχ2,Fandtfields. The theory is applied to some three-dimensional images of cerebral blood flow from a study on pain perception.

APA, Harvard, Vancouver, ISO, and other styles

42

Cherrett, M. A., J. D. Bryce, and R. B. Ginder. "Unsteady Three-Dimensional Flow in a Single-Stage Transonic Fan: Part I—Unsteady Rotor Exit Flow Field." Journal of Turbomachinery 117, no. 4 (October 1, 1995): 506–13. http://dx.doi.org/10.1115/1.2836562.

Full text

Abstract:

Detailed unsteady aerodynamic measurements have been taken in a single-stage transonic fan with a very high stator-hub loading. Two-dimensional dynamic yawmeter probes, capable of measuring mean and fluctuating levels of stagnation pressure, static pressure, and yaw angle have been traversed at rotor exit, and downstream of the stator along with several types of pneumatic three-dimensional probe. Part I of this paper describes the dynamic yawmeters and their performance, and presents ensemble-averaged stagnation pressure and random stagnation pressure unsteadiness measurements taken at rotor exit. These are used to illustrate the salient features of the rotor flow field, and the effects of compressor aerodynamic loading. Part II presents measurements taken at stator exit.

APA, Harvard, Vancouver, ISO, and other styles

43

Shi, Cong, Zhuoran Dong, Shrinivas Pundlik, and Gang Luo. "A Hardware-Friendly Optical Flow-Based Time-to-Collision Estimation Algorithm." Sensors 19, no. 4 (February 16, 2019): 807. http://dx.doi.org/10.3390/s19040807.

Full text

Abstract:

This work proposes a hardware-friendly, dense optical flow-based Time-to-Collision (TTC) estimation algorithm intended to be deployed on smart video sensors for collision avoidance. The algorithm optimized for hardware first extracts biological visual motion features (motion energies), and then utilizes a Random Forests regressor to predict robust and dense optical flow. Finally, TTC is reliably estimated from the divergence of the optical flow field. This algorithm involves only feed-forward data flows with simple pixel-level operations, and hence has inherent parallelism for hardware acceleration. The algorithm offers good scalability, allowing for flexible tradeoffs among estimation accuracy, processing speed and hardware resource. Experimental evaluation shows that the accuracy of the optical flow estimation is improved due to the use of Random Forests compared to existing voting-based approaches. Furthermore, results show that estimated TTC values by the algorithm closely follow the ground truth. The specifics of the hardware design to implement the algorithm on a real-time embedded system are laid out.

APA, Harvard, Vancouver, ISO, and other styles

44

Wu, Chunrui, Tiechen Zhang, Jiale Fu, Xiaori Liu, and Boxiong Shen. "Random pore structure and REV scale flow analysis of engine particulate filter based on LBM." Open Physics 18, no. 1 (December 5, 2020): 881–96. http://dx.doi.org/10.1515/phys-2020-0208.

Full text

Abstract:

Abstract In this article, lattice Boltzmann method (LBM) is used to simulate the multi-scale flow characteristics of the engine particulate filter at the pore scale and the representative elementary volume (REV) scale, respectively. Four kinds of random wall-pore structures are considered, which are circular random structure, square random structure, isotropic quartet structure generation set (QSGS), and anisotropic QSGS, with difference analysis done. In terms of the REV scale, the influence of different inlet flow velocities and wall permeabilities on the flow in single channel is analyzed. The result indicates that the internal seepage laws of random structures constructed in this article and single channel are in accordance with Darcy’s law. Circular random structure has better permeability than square random structure. Isotropic QSGS has better fluidity than anisotropic one. The flow in single channel is similar to Poiseuille flow. The flow lines in the channel are complicated and a large number of vortices appear at the ends of channel with high inlet flow rate. With the increase of inlet velocity, the static pressure in channel gradually increases along the axial direction as well as the seepage velocity. The temperature field in the channel becomes more uniform as the flow velocity increases, and the higher temperature distribution appears on the wall of the porous media.

APA, Harvard, Vancouver, ISO, and other styles

45

WANG, Jun-wei, Chang-sheng ZHU, Zhi-ping WANG, Li FENG, and Rong-zhen XIAO. "Phase-field simulation of forced flow effect on random preferred growth direction of multiple grains." Transactions of Nonferrous Metals Society of China 21, no. 7 (July 2011): 1620–26. http://dx.doi.org/10.1016/s1003-6326(11)60905-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Elperin, Tov, Nathan Kleeorin, Igor Rogachevskii, and Dmitry Sokoloff. "Passive scalar transport in a random flow with a finite renewal time: Mean-field equations." Physical Review E 61, no. 3 (March 1, 2000): 2617–25. http://dx.doi.org/10.1103/physreve.61.2617.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Peiffer, D. G., M. W. Kim, and R. D. Lundberg. "Influence of an elongational flow field on random coil and rod-like polymers in solution." Polymer 27, no. 4 (April 1986): 493–502. http://dx.doi.org/10.1016/0032-3861(86)90232-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Bin, Liu, Wang Bo, Li Zhuo, and Lv Yanfang. "The diffusion of CO2-brine storage based on stochastic partial differential equations." E3S Web of Conferences 206 (2020): 03031. http://dx.doi.org/10.1051/e3sconf/202020603031.

Full text

Abstract:

The migration of CO2 is stochastic in heterogeneous porous media. This paper considers the CO2 diffusion with the case of steady flow in heterogeneous porous media. The partial differential equations of CO2 diffusion in random velocity field are established based on the mass conservation equations of CO2- brine two-phase flow with the change of time scale and spatial scale under the influence of heterogeneity such as permeability and porosity. The random travel process of CO2 is quantified by joint probability distributions and joint statistical moments (mean and variance), and the diffusion model of CO2 particle in random velocity field is established under the condition of non-linear and immiscibility in heterogeneous porous media. The micro mechanism of diffusion in heterogeneous porous media is revealed by numerical simulation. The general conclusion of steady state flow of CO2 diffusion in heterogeneous porous media was verified by simulating Sleipner CO2-brine storage in Norway.

APA, Harvard, Vancouver, ISO, and other styles

49

Ounis, H., and G. Ahmadi. "Analysis of Dispersion of Small Spherical Particles in a Random Velocity Field." Journal of Fluids Engineering 112, no. 1 (March 1, 1990): 114–20. http://dx.doi.org/10.1115/1.2909358.

Full text

Abstract:

The equation of motion of a small spherical rigid particle in a turbulent flow field, including the Stokes drag, the Basset force, and the virtual mass effects, is considered. For an isotropic field, the lift force and the velocity gradient effects are neglected. Using the spectral method, responses of the resulting constant coefficient stochastic integrao-differential equation are studied. Analytical expressions relating the Lagrangian energy spectra of particle velocity to that of the fluid are developed and the results are used to evaluate various response statistics. Variations of the mean-square particle velocity and particle diffusivity with size, density ratio and response time are studied. The theoretical predictions are compared with the digital simulation results and the available data and good agreement is observed.

APA, Harvard, Vancouver, ISO, and other styles

50

Fan, Fa-Gung, and Goodarz Ahmadi. "Dispersion of Ellipsoidal Particles in an Isotropic Pseudo-Turbulent Flow Field." Journal of Fluids Engineering 117, no. 1 (March 1, 1995): 154–61. http://dx.doi.org/10.1115/1.2816805.

Full text

Abstract:

Dispersion of ellipsoidal particles in a simulated isotropic pseudo-turbulent field is studied. A procedure using Euler’s four parameters in describing the particle orientations is used, and the governing equations for the translational and rotational motions of particles are outlined. Turbulence fluctuation velocity field is simulated by a Gaussian random model. Motions of ellipsoidal particles of different sizes and lengths are analyzed. Ensemble and time averagings are used for evaluating various statistics of particle motion. Effects of size, shape, and density ratio on the mean-square particle velocities and the relative particle diffusivities are studied. By applying the orientation-averaging procedure, an analytical model for estimating the mean-square particle velocities and the relative diffusivities is developed. The predictions of the approximate model are compared with the simulation results and discussed.

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!