Simulating the Soot Loading in Wall-flow DPF Using a Three-Dimensional Macroscopic Model

2006 ◽  
Author(s):  
Yong Yi
Keyword(s):  
Three Dimensional ◽  
Macroscopic Model ◽  
Soot Loading ◽  
Wall Flow

A Comparison Between Experimental and Predicted Flow Profiles Beneath a Semi-Confined Axisymmetric Impinging Jet

2003 ◽  
Author(s):  
C. Y. Cheong ◽  
P. T. Ireland ◽  
S. Ashforth-Frost
Keyword(s):  
Viscous Flow ◽  
Flow Model ◽  
Three Dimensional ◽  
Impinging Jet ◽  
Theoretical Models ◽  
Velocity Profiles ◽  
Axisymmetric Case ◽  
Air Jet ◽  
Wall Flow ◽  
Near Wall

Theoretical predictions have been compared with experiment for a single semi-confined impinging jet. The turbulent air jet discharged at Re = 20 000 and impinged at nozzle-to-plate spacings (z/d) of 2 and 6.5. Experimental velocity profiles were obtained using hot-wire anemometry. Theoretical velocity profiles were derived using stagnation three-dimensional flow model and viscous flow model for an axisymmetric case. For z/d = 2, velocity profiles in the inviscid region of the near wall flow can be predicted accurately using the stagnation flow model. As the edge of the jet is approached, the flow becomes complex and, as expected, cannot be predicted using the model. Prediction of boundary layer profiles using the viscous flow solution for an axisymmetric case is also reasonable. For z/d = 6.5, the developing impinging jet is essentially turbulent on impact and consequently predictions of near wall flow field, using both the theoretical models, are inappropriate.

Instability in a viscous flow driven by streamwise vortices

2001 ◽  
Vol 432 ◽  
pp. 127-166 ◽  
Author(s):  
K. W. BRINCKMAN ◽  
J. D. A. WALKER
Keyword(s):  
Boundary Layer ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Wall Layer ◽  
External Flow ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Wall Flow ◽  
Turbulent Wall ◽  
Near Wall

Unsteady separation processes at large finite, Reynolds number, Re, are considered, as well as the possible relation to existing descriptions of boundary-layer separation in the limit Re → ∞. The model problem is a fundamental vortex-driven three-dimensional flow, believed to be relevant to bursting near the wall in a turbulent boundary layer. Bursting is known to be associated with streamwise vortex motion, but the vortex/wall interactions that drive the near-wall flow toward breakdown have not yet been fully identified. Here, a simulation of symmetric counter-rotating vortices is used to assess the influence of sustained pumping action on the development of a viscous wall layer. The calculated solutions describe a three-dimensional flow at finite Re that is independent of the streamwise coordinate and consists of a crossflow plane motion, with a developing streamwise flow. The unsteady problem is constructed to mimic a typical cycle in turbulent wall layers and numerical solutions are obtained over a range of Re. Recirculating eddies develop rapidly in the near-wall flow, but these eddies are eventually bisected by alleyways which open up from the external flow region to the wall. At sufficiently high Re, an oscillation was found to develop in the streamwise vorticity field near the alleyways with a concurrent evolution of a local spiky behaviour in the wall shear. Above a critical value of Re, the oscillation grows rapidly in amplitude and eventually penetrates the external flow field, suggesting the onset of an unstable wall-layer breakdown. Local zones of severely retarded streamwise velocity are computed which are reminiscent of the low-speed streaks commonly observed in turbulent boundary layers. A number of other features also bear a resemblance to observed coherent structure in the turbulent wall layer.

Direct Force Wall Shear Measurements in Pressure-Driven Three-Dimensional Turbulent Boundary Layers

1982 ◽  
Vol 104 (2) ◽  
pp. 150-155 ◽  
Author(s):  
J. E. McAllister ◽  
F. J. Pierce ◽  
M. H. Tennant
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Three Dimensional ◽  
Turbulent Boundary Layers ◽  
Direct Measurements ◽  
Stress Directions ◽  
Wall Flow ◽  
Wall Shear ◽  
Pressure Driven

Unique, simultaneous direct measurements of the magnitude and direction of the local wall shear stress in a pressure-driven three-dimensional turbulent boundary layer are presented. The flow is also described with an oil streak wall flow pattern, a map of the wall shear stress-wall pressure gradient orientations, a comparison of the wall shear stress directions relative to the directions of the nearest wall velocity as measured with a typical, small boundary layer directionally sensitive claw probe, as well as limiting wall streamline directions from the oil streak patterns, and a comparison of the freestream streamlines and the wall flow streamlines. A review of corrections for direct force sensing shear meters for two-dimensional flows is presented with a brief discussion of their applicability to three-dimensional devices.

scholarly journals A Jones matrix formalism for simulating three-dimensional polarized light imaging of brain tissue

2015 ◽  
Vol 12 (111) ◽  
pp. 20150734 ◽  
Author(s):  
M. Menzel ◽  
K. Michielsen ◽  
H. De Raedt ◽  
J. Reckfort ◽  
K. Amunts ◽  
...  
Keyword(s):  
Myelin Sheath ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Polarized Light ◽  
Microscopic Model ◽  
Macroscopic Model ◽  
Jones Matrix ◽  
Matrix Formalism ◽  
Nerve Fibres ◽  
Polarized Light Imaging

The neuroimaging technique three-dimensional polarized light imaging (3D-PLI) provides a high-resolution reconstruction of nerve fibres in human post-mortem brains. The orientations of the fibres are derived from birefringence measurements of histological brain sections assuming that the nerve fibres—consisting of an axon and a surrounding myelin sheath—are uniaxial birefringent and that the measured optic axis is oriented in the direction of the nerve fibres (macroscopic model). Although experimental studies support this assumption, the molecular structure of the myelin sheath suggests that the birefringence of a nerve fibre can be described more precisely by multiple optic axes oriented radially around the fibre axis (microscopic model). In this paper, we compare the use of the macroscopic and the microscopic model for simulating 3D-PLI by means of the Jones matrix formalism. The simulations show that the macroscopic model ensures a reliable estimation of the fibre orientations as long as the polarimeter does not resolve structures smaller than the diameter of single fibres. In the case of fibre bundles, polarimeters with even higher resolutions can be used without losing reliability. When taking the myelin density into account, the derived fibre orientations are considerably improved.

A limit problem for three-dimensional ideal compressible radiation magneto-hydrodynamics

2017 ◽  
Vol 16 (01) ◽  
pp. 85-102 ◽  
Author(s):  
Feng Xie ◽  
Christian Klingenberg
Keyword(s):  
Three Dimensional ◽  
Limit Problem ◽  
Mhd Equations ◽  
Macroscopic Model ◽  
Radiation Hydrodynamics ◽  
Approximation Model ◽  
Speed Of Light ◽  
Additional Radiation ◽  
Radiation Magnetohydrodynamics ◽  
The Ideal

General radiation magnetic hydrodynamics models include two main parts that are coupled: one part is the macroscopic magnetic fluid part, which is governed by the ideal compressible magnetohydrodynamic (MHD) equations with additional radiation terms; another part is the radiation field, which is described by a transfer equation. It is well known that in radiation hydrodynamics without a magnetic field there are two physical approximations: one is the so-called P1 approximation and the other is the so-called gray approximation. Starting out with a general radiation MHD model one can derive the so-called MHD-P1 approximation model. In this paper, we study the non-relativistic type limit for this MHD-P1 approximation model since the speed of light is much larger than the speed of the macroscopic fluid. This way we achieve a rigorous derivation of a widely used macroscopic model in radiation magnetohydrodynamics.

Simulating the Flow and Soot Loading in Wall- Flow DPF Using a Two-Dimensional Mesoscopic Model

2018 ◽  
Author(s):  
Xiangjin Kong ◽  
Zhijun Li ◽  
Xingyu Liang ◽  
Boxi Shen ◽  
Li He ◽  
...  
Keyword(s):  
Two Dimensional ◽  
Mesoscopic Model ◽  
Soot Loading ◽  
Wall Flow

Numerical Analysis of Plume Structures of Fluids on a Horizontal Heated Plate

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
T. Praphul ◽  
P. J. Joshy ◽  
P. S. Tide
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Three Dimensional ◽  
Boussinesq Approximation ◽  
Cube Root ◽  
Heated Plate ◽  
Steady State Model ◽  
Increasing Trend ◽  
Wall Flow ◽  
Near Wall

Numerical investigations have been carried out to predict the near-wall dynamics in indirect natural convection for air (Pr = 0.7) and water (Pr = 5.2). Near-wall flow structures appear to be line plumes. Three-dimensional laminar, steady-state model was used to model the problem. Density was formulated using the Boussinesq approximation. Flux scaling, plume spacing and plume lengths obtained numerically are found to have the same trend with the results available in the literature. Plume length and Nusselt number, Nu exhibits an increasing trend with an increase in Rayleigh number, RaH for both Pr fluids. The plume spacing is found to have an inverse relationship with RaH. The cube root of Rayleigh number based on plume spacing, Raλ1/3 is found to have a slight dependence on the dimensionless plume spacing, λ/H. Nu scales as Nu∼CRaHn, n = 0.26 for air and n = 0.3 for water. Heat transfer is thus found to be dominated by near-wall phenomenon. Nu shows a nonlinear relationship with LpH/A and is found to be an accurate representation of heat transfer.

scholarly journals Cardboard Dinosaur: The Use of Simple Three-Dimensionality and Macroscopy Tools as a Low-Cost Strategy for Presentation of Classical Biological Themes

2020 ◽  
Author(s):  
Aixa Hafsha
Keyword(s):  
Biological Sciences ◽  
Undergraduate Students ◽  
Computational Models ◽  
Low Cost ◽  
Three Dimensional ◽  
Visual Exploration ◽  
Macroscopic Model ◽  
Student Interest ◽  
Low Cost Strategy ◽  
Dino Model

According to the literature, materials that explore visual effects are being more produced for teaching purposes, especially the computational ones. The application of these materials has significantly increased at different educational levels, from elementary to post-graduation. In this study, we aim to evaluate the level of student interest in the presentation of a classical theme of the biological sciences, Dinosaurs, by using Two-dimensional (2D), Three-dimensional (3D) or computational models. Therefore, we built three models of an Allosaurus skeleton including: 1) a 3D macroscopic “Dino” model (1 m per 1.5 m long) made with cardboard; 2) a 2D colorful Dino figure printed on an A4 size paper, and 3) a computational dancing dinosaur simulation, a “Virtual Dino” model, made with six sequential photographic repeated frames. A questionnaire and an in loco dynamic evaluation were created and applied to analyze the students’ preference. Thirty-seven undergraduate students of Biological Sciences and Medicine courses had their reaction (choice) filmed and analyzed after looking at these three models. The results show that there is a high preference for the 3D-macroscopic “Dino”, suggesting that visual exploration is still more attractive than a computational tool to stimulate interest in a topic. The preference for the three-dimensional macroscopic model still raises applicable perspectives and further challenges that may and should be explored in the area of science education, not only for deaf, blind and/or visually impaired people, but for each and every student.

scholarly journals Macroscopic constitutive model for ergodic and non-ergodic lead-free relaxors

2021 ◽  
pp. 1045389X2110386
Author(s):  
Friedemann A Streich ◽  
Alexander Martin ◽  
Kyle G Webber ◽  
Marc Kamlah
Keyword(s):  
Constitutive Model ◽  
Time Integration ◽  
Three Dimensional ◽  
Solution Procedure ◽  
Ferroelectric Materials ◽  
Lead Free ◽  
Macroscopic Model ◽  
Internal Variables ◽  
Integration Scheme ◽  
Predictor Corrector

A fully electromechanically coupled, three dimensional phenomenological constitutive model for relaxor ferroelectric materials was developed for the use in a finite-element-method (FEM) solution procedure. This macroscopic model was used to simulate the macroscopic electromechanical response of lead-free ergodic [Formula: see text] and non-ergodic [Formula: see text] relaxor materials. The presented constitutive model is capable of accounting for the observed pinched hysteretic response as well as non-deviatoric polarization induced strain and internal order transitions. Time integration of the history dependent internal variables is done with a predictor-corrector integration scheme. The adaptability of the constitutive model regarding the pinching of the hystereses is shown. Simulations are compared to experimental observations.

scholarly journals A three-dimensional meso-macroscopic model for Li-Ion intercalation batteries

2016 ◽  
Vol 325 ◽  
pp. 42-50 ◽  
Author(s):  
S. Allu ◽  
S. Kalnaus ◽  
S. Simunovic ◽  
J. Nanda ◽  
J.A. Turner ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Macroscopic Model ◽  
Li Ion ◽  
Ion Intercalation
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