Computation of Hypersonic Turbulent and Transitional Flows Using an Extended Gas Kinetic Scheme

The kinetics of the hydrolysis and polycondensation reactions of saccharides have made the subject of numerous studies, due to their importance in several industrial sectors. The present work, presents a novel kinetic modeling framework that is specifically well-suited to reacting systems under strict moisture control that favor the polycondensation reactions towards the formation of high-degree polysaccharides. The proposed model is based on an extended and generalized kinetic scheme, including also the presence of polyols, and is formulated using two different numerical approaches, namely a deterministic one in terms of the method of moments and a stochastic kinetic Monte Carlo approach. Accordingly, the most significant advantages and drawbacks of each technique are clearly demonstrated and the most fitted one (i.e., the Monte Carlo method) is implemented for the modeling of the system under different conditions, for which experimental data were available. Through these comparisons it is shown that the model can successfully follow the evolution of the reactions up to the formation of polysaccharides of very high degrees of polymerization.

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Large-eddy simulation of wall-bounded turbulent flow with high-order discrete unified gas-kinetic scheme

Advances in Aerodynamics ◽

10.1186/s42774-020-00051-w ◽

2020 ◽

Vol 2 (1) ◽

Author(s):

Rui Zhang ◽

Chengwen Zhong ◽

Sha Liu ◽

Congshan Zhuo

Keyword(s):

Turbulent Flow ◽

Turbulent Flows ◽

Parallel Implementation ◽

Kinetic Scheme ◽

Cavity Flow ◽

Equilibrium Distribution Function ◽

Third Order ◽

Two Stage ◽

Large Eddy ◽

Unified Gas Kinetic Scheme

AbstractIn this paper, we introduce the discrete Maxwellian equilibrium distribution function for incompressible flow and force term into the two-stage third-order Discrete Unified Gas-Kinetic Scheme (DUGKS) for simulating low-speed turbulent flows. The Wall-Adapting Local Eddy-viscosity (WALE) and Vreman sub-grid models for Large-Eddy Simulations (LES) of turbulent flows are coupled within the present framework. Meanwhile, the implicit LES are also presented to verify the effect of LES models. A parallel implementation strategy for the present framework is developed, and three canonical wall-bounded turbulent flow cases are investigated, including the fully developed turbulent channel flow at a friction Reynolds number (Re) about 180, the turbulent plane Couette flow at a friction Re number about 93 and lid-driven cubical cavity flow at a Re number of 12000. The turbulence statistics, including mean velocity, the r.m.s. fluctuations velocity, Reynolds stress, etc. are computed by the present approach. Their predictions match precisely with each other, and they are both in reasonable agreement with the benchmark data of DNS. Especially, the predicted flow physics of three-dimensional lid-driven cavity flow are consistent with the description from abundant literature. The present numerical results verify that the present two-stage third-order DUGKS-based LES method is capable for simulating inhomogeneous wall-bounded turbulent flows and getting reliable results with relatively coarse grids.

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Assessment of a detailed biomass pyrolysis kinetic scheme in multiscale simulations of a single-particle pyrolyzer and a pilot-scale entrained flow pyrolyzer

Chemical Engineering Journal ◽

10.1016/j.cej.2021.129347 ◽

2021 ◽

Vol 418 ◽

pp. 129347 ◽

Cited By ~ 1

Author(s):

Xi Gao ◽

Liqiang Lu ◽

Mehrdad Shahnam ◽

William A. Rogers ◽

Kristin Smith ◽

...

Keyword(s):

Single Particle ◽

Kinetic Scheme ◽

Pilot Scale ◽

Multiscale Simulations ◽

Biomass Pyrolysis ◽

Entrained Flow ◽

Pyrolysis Kinetic

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Meshfree method based on discrete gas-kinetic scheme to simulate incompressible/compressible flows

Physics of Fluids ◽

10.1063/5.0033770 ◽

2021 ◽

Vol 33 (1) ◽

pp. 017112

Author(s):

Ningyu Zhan ◽

Rongqian Chen ◽

Yancheng You

Keyword(s):

Compressible Flows ◽

Kinetic Scheme ◽

Meshfree Method

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PLATELET AGGREGATION DOES NOT CONFORM TO SIMPLE PARTICLE COLLISION THEORY

10.1055/s-0038-1644550 ◽

1987 ◽

Author(s):

Moideen P Jamaluddin

Keyword(s):

Platelet Aggregation ◽

Rate Equation ◽

Rate Constants ◽

Kinetic Scheme ◽

Order Type ◽

Second Order ◽

Particle Collision ◽

Collision Theory ◽

Rate Law ◽

First Order

Platelet aggregation kinetics, according to the particle collision theory, generally assumed to apply, ought to conform to a second order type of rate law. But published data on the time-course of ADP-induced single platelet recruitment into aggregates were found not to do so and to lead to abnormal second order rate constants much larger than even their theoretical upper bounds. The data were, instead, found to fit a first order type of rate law rather well with rate constants in the range of 0.04 - 0.27 s-1. These results were confirmed in our laboratory employing gelfiltered calf platelets. Thus a mechanism much more complex than hithertofore recognized, is operative. The following kinetic scheme was formulated on the basis of information gleaned from the literature.where P is the nonaggregable, discoid platelet, A the agonist, P* an aggregable platelet form with membranous protrusions, and P** another aggregable platelet form with pseudopods. Taking into account the relative magnitudes of the k*s and assuming aggregation to be driven by hydrophobic interaction between complementary surfaces of P* and P** species, a rate equation was derived for aggregation. The kinetic scheme and the rate equation could account for the apparent first order rate law and other empirical observations in the literature.

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