scholarly journals A laboratory and numerical study of transverse momentum exchange in vegetated channels

2020 ◽  
pp. 961-968
Author(s):  
S.H. Truong ◽  
Un Ji ◽  
W.S.J. Uijttewaal
Keyword(s):  
Transverse Momentum ◽  
Numerical Study ◽  
Momentum Exchange ◽  
Vegetated Channels

scholarly journals Discontinuous Galerkin method for solving incompressible two-phase shallow granular flow model

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987490
Author(s):  
Muhammad Rehan Saleem ◽  
Ubaid Ahmed Nisar ◽  
Shamsul Qamar
Keyword(s):  
Galerkin Method ◽  
Discontinuous Galerkin ◽  
Discontinuous Galerkin Method ◽  
Numerical Scheme ◽  
Flow Model ◽  
Numerical Study ◽  
Momentum Exchange ◽  
Two Phase ◽  
Runge Kutta ◽  
Model Equations

This article deals with the numerical study of two-phase shallow flow model describing the mixture of fluid and solid granular particles. The model under investigation consists of coupled mass and momentum equations for solid granular material and fluid particles through non-conservative momentum exchange terms. The non-conservativity of model equations poses major challenges for any numerical scheme, such as well balancing, positivity preservation, accurate approximation of non-conservative terms, and achievement of steady-state conditions. Thus, in order to approximate the present model an accurate, well-balanced, robust, and efficient numerical scheme is required. For this purpose, in this article, Runge–Kutta discontinuous Galerkin method is applied successfully for the first time to solve the model equations. Several test problems are also carried out to check the performance and accuracy of our proposed numerical method. To compare the results, the same model is solved by staggered central Nessyahu–Tadmor scheme. A good comparison is found between two schemes, but the results obtained by Runge–Kutta discontinuous Galerkin scheme are found superior over the central Nessyahu–Tadmor scheme.

A Numerical Study of Jet Propulsion of an Oblate Jellyfish Using a Momentum Exchange-Based Immersed Boundary-Lattice Boltzmann Method

2014 ◽  
Vol 6 (3) ◽  
pp. 307-326 ◽  
Author(s):  
Hai-Zhuan Yuan ◽  
Shi Shu ◽  
Xiao-Dong Niu ◽  
Mingjun Li ◽  
Yang Hu
Keyword(s):  
Reynolds Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Numerical Study ◽  
Mass Density ◽  
Density Ratio ◽  
Large Mass ◽  
Immersed Boundary ◽  
Momentum Exchange ◽  
Boltzmann Method

AbstractIn present paper, the locomotion of an oblate jellyfish is numerically investigated by using a momentum exchange-based immersed boundary-Lattice Boltzmann method based on a dynamic model describing the oblate jellyfish. The present investigation is agreed fairly well with the previous experimental works. The Reynolds number and the mass density of the jellyfish are found to have significant effects on the locomotion of the oblate jellyfish. Increasing Reynolds number, the motion frequency of the jellyfish becomes slow due to the reduced work done for the pulsations, and decreases and increases before and after the mass density ratio of the jellyfish to the carried fluid is 0.1. The total work increases rapidly at small mass density ratios and slowly increases to a constant value at large mass density ratio. Moreover, as mass density ratio increases, the maximum forward velocity significantly reduces in the contraction stage, while the minimum forward velocity increases in the relaxation stage.

Numerical Study of Instability Mechanisms Leading to Transition in Separation Bubbles

2006 ◽  
Author(s):  
B. R. McAuliffe ◽  
M. I. Yaras
Keyword(s):  
Numerical Simulation ◽  
Numerical Study ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Suction Side ◽  
Inertial Subrange ◽  
Momentum Exchange ◽  
Instability Growth ◽  
Tollmien Schlichting

In this paper, transition in a separation bubble is examined through numerical simulation. The flow Reynolds number and streamwise pressure distribution are typical of the conditions encountered on the suction side of low-pressure turbine blades of gas-turbine engines. The spatial and temporal resolutions utilized in the present computations correspond to a coarse direct numerical simulation, wherein the majority of turbulence scales, including the inertial subrange, are adequately resolved. The accuracy of the simulation results is demonstrated through favorable comparisons with experimental data corresponding to the same flow conditions. The results of the simulation show linear Tollmien-Schlichting (T-S) instability growth downstream of the point of separation, leading to the roll-up of spanwise vorticity into disctete vortical structures, characteristic of Kelvin-Helmholtz (K-H) instability growth. The extent of cross-stream momentum exchange associated with packets of amplified T-S waves is examined, along with details of the time-periodic breakdown into turbulence occurring upon the development of the K-H instability. Reynolds-averaged properties of the separation bubble are presented, and provide evidence of the strong three-dimensional nature of the reattachment process.

scholarly journals Two-Dimensional Numerical Study on the Migration of Particle in a Serpentine Channel

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Yi Liu ◽  
Qucheng Li ◽  
Deming Nie
Keyword(s):  
Lattice Boltzmann ◽  
Particle Density ◽  
Numerical Study ◽  
Density Ratio ◽  
Initial Position ◽  
Momentum Exchange ◽  
Initial Particle ◽  
Serpentine Channel ◽  
Circular Particle ◽  
Boltzmann Method

In this work, the momentum exchange scheme-based lattice Boltzmann method is adopted to numerically study the migration of a circular particle in a serpentine channel for the range of 20 ≤ Re ≤ 120. The effects of the Reynolds number, particle density, and the initial particle position are taken into account. Numerical results include the streamlines, particle trajectories, and final equilibrium positions. Close attention is also paid to the time it takes for the particle to travel in the channel. It has been found that the particle is likely to migrate to a similar equilibrium position irrespective of its initial position when Re is large. Furthermore, there exists a critical solid-to-fluid density ratio for which the particle travels fastest in the channel.

Evolution of the streamwise vortices generated between leading edge tubercles

2016 ◽  
Vol 788 ◽  
pp. 730-766 ◽  
Author(s):  
Kristy L. Hansen ◽  
Nikan Rostamzadeh ◽  
Richard M. Kelso ◽  
Bassam B. Dally
Keyword(s):  
Boundary Layer ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Surface Flux ◽  
Flow Visualisation ◽  
Streamwise Vortices ◽  
Momentum Exchange

Sinusoidal modifications to the leading edge of a foil, or tubercles, have been shown to improve aerodynamic performance under certain flow conditions. One of the mechanisms of performance enhancement is believed to be the generation of streamwise vortices, which improve the momentum exchange in the boundary layer. This experimental and numerical study investigates the formation and evolution of these streamwise vortices at a low Reynolds number of $Re=2230$, providing insight into both the averaged and time-dependent flow patterns. Furthermore, the strength of the vortices is quantified through calculation of the vorticity and circulation, and it is found that the circulation increases in the downstream direction. There is strong agreement between the experimental and numerical observations, and this allows close examination of the flow structure. The results demonstrate that the presence of strong pressure gradients near the leading edge gives rise to a significant surface flux of vorticity in this region. As soon as this vorticity is created, it is stretched, tilted and diffused in a highly three-dimensional manner. These processes lead to the generation of a pair of streamwise vortices between the tubercle peaks. A horseshoe-shaped separation zone is shown to initiate behind a tubercle trough, and this region of separation is bounded by a canopy of boundary-layer vorticity. Along the sides of this shear layer canopy, a continued influx of boundary-layer vorticity occurs, resulting in an increase in circulation of the primary streamwise vortices in the downstream direction. Flow visualisation and particle image velocimetry studies support these observations and demonstrate that the flow characteristics vary with time, particularly near the trailing edge and at a higher angle of attack. Numerical evaluation of the lift and drag coefficients reveals that, for this particular flow regime, the performance of a foil with tubercles is slightly better than that of an unmodified foil.

Numerical Study of Instability Mechanisms Leading to Transition in Separation Bubbles

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Brian R. McAuliffe ◽  
Metin I. Yaras
Keyword(s):  
Numerical Simulation ◽  
Numerical Study ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Suction Side ◽  
Inertial Subrange ◽  
Momentum Exchange ◽  
Instability Growth ◽  
Tollmien Schlichting

In this paper, transition in a separation bubble is examined through numerical simulation. The flow Reynolds number and streamwise pressure distribution are typical of the conditions encountered on the suction side of low-pressure turbine blades of gas-turbine engines. The spatial and temporal resolutions utilized in the present computations correspond to a coarse direct numerical simulation, wherein the majority of turbulence scales, including the inertial subrange, are adequately resolved. The accuracy of the simulation results is demonstrated through favorable comparisons to experimental data corresponding to the same flow conditions. The results of the simulation show linear Tollmien-Schlichting (T-S) instability growth downstream of the point of separation, leading to the roll up of spanwise vorticity into discrete vortical structures, characteristic of Kelvin-Helmholtz (K-H) instability growth. The extent of cross-stream momentum exchange associated with packets of amplified T-S waves is examined, along with details of the time-periodic breakdown into turbulence occurring upon the development of the K-H instability. Reynolds-averaged properties of the separation bubble are presented and provide evidence of the strong three-dimensional nature of the reattachment process.

Transport phenomena and evolution mechanism of the melt pool during a laser based metal melting process

2021 ◽  
pp. 1-36
Author(s):  
Qingfei Bian ◽  
Ke Tian ◽  
Kong Ling ◽  
Yitung Chen ◽  
Min Zeng ◽  
...  
Keyword(s):  
Numerical Study ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Melting Process ◽  
Numerical Results ◽  
Interface Morphology ◽  
Momentum Exchange ◽  
Interface Capturing ◽  
Melt Pool ◽  
Metal Melting

Abstract This article presents a fully three-dimensional numerical study on the process of melt pool evolution. In order to overcome the simplifications used in many existing studies, an enthalpy method is developed for the phase change, and an accurate interface capturing method, i.e., the coupled volume-of-fluid and level set (VOSET) method, is employed to track the moving gas-liquid interface. Meanwhile, corresponding experimental studies are carried out for the purpose of validation. The obtained numerical results show the formed interface morphology during the process of melt pool with its typical sizes and are quantitatively consistent with those data measured in experiments. Based on the numerical results, the thermodynamic phenomena, induced by the interaction between heat and momentum exchange, occurring in the formation of melt pool are presented and discussed. Mechanisms of the melt pool evolution revealed in the present study provide a useful guidance for better controlling the process of additive manufacturing.

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