Relating Integral Length Scale to Turbulent Time Scale and Comparing k-ε and RNG k-ε Turbulence Models in Diesel Combustion Simulation

2002 ◽  
Author(s):  
Ossi Kaario ◽  
Martti Larmi ◽  
Franz Tanner
Keyword(s):  
Time Scale ◽  
Turbulence Models ◽  
Integral Length Scale ◽  
Length Scale ◽  
Diesel Combustion ◽  
Combustion Simulation

Development of a reduced mechanism of a three components surrogate fuel for the coal-to-liquid and diesel combustion simulation

Fuel ◽  
2021 ◽  
Vol 294 ◽  
pp. 120370
Author(s):  
Shaodian Lin ◽  
Wanchen Sun ◽  
Liang Guo ◽  
Peng Cheng ◽  
Yuxiang Sun ◽  
...  
Keyword(s):  
Diesel Combustion ◽  
Reduced Mechanism ◽  
Combustion Simulation ◽  
Surrogate Fuel ◽  
Three Components

Time scale of dynamic heterogeneity in model ionic liquids and its relation to static length scale and charge distribution

2015 ◽  
Vol 17 (43) ◽  
pp. 29281-29292 ◽  
Author(s):  
Sang-Won Park ◽  
Soree Kim ◽  
YounJoon Jung
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Charge Distribution ◽  
Power Law ◽  
Structural Relaxation ◽  
Time Scale ◽  
Length Scale ◽  
Dynamic Heterogeneity ◽  
General Power

We find a general power-law behavior: , where ζdh ≈ 1.2 for all the ionic liquid models, regardless of charges and the length scale of structural relaxation.

Particle Collision Effect on Turbulent Prandtl Number in Gas-Solid Flows

2006 ◽  
Author(s):  
Zohreh Mansoori ◽  
Majid Saffar-Avval ◽  
Hasan Basirat-Tabrizi ◽  
Goodarz Ahmadi ◽  
Payam Ramezani
Keyword(s):  
Prandtl Number ◽  
Turbulent Flow ◽  
Time Scale ◽  
Turbulence Models ◽  
Flow Region ◽  
Eddy Diffusivity ◽  
Particle Collision ◽  
Turbulent Prandtl Number ◽  
Particle Collisions ◽  
Particle Properties

Traditional gas-solid turbulence models using constant or the single-phase gas turbulent Prandtl number cause error in the thermal eddy diffusivity and thermal turbulent intensity fields calculation. The thermo-mechanical turbulence model is based on solving the hydrodynamic transport equations of the turbulent kinetic energy and turbulent time scale, beside the thermal turbulent equations of temperature variance and thermal turbulence time scale. This model has the ability to calculate the turbulent Prandtl number directly by computing the eddy viscosity and the thermal eddy diffusivity through the values of turbulence fluctuation velocity and thermal variances and time scales. A four way Eulerian/Lagrangian formulation was used to study the effect of particle properties on the turbulent flow and thermal fields, as well as on turbulent Prandtl number in a gas-solid developing pipe flow. Inter-particle collisions were included and the Lagrangian trajectory analysis was used. The earlier results showed that turbulent Prandtl number is influenced by the variations of gas and particle properties and also inter-particle collisions in a fully-developed riser. In the current study, the developing gas-solid flow region in a pipe was considered and the variation of turbulent flow field due to inter-particle collision was evaluated.

scholarly journals Effect of red blood cell shape changes on haemoglobin interactions and dynamics: a neutron scattering study

2020 ◽  
Vol 7 (10) ◽  
pp. 201507
Author(s):  
Keyun Shou ◽  
Mona Sarter ◽  
Nicolas R. de Souza ◽  
Liliana de Campo ◽  
Andrew E. Whitten ◽  
...  
Keyword(s):  
Blood Cell ◽  
Neutron Scattering ◽  
Protein Interactions ◽  
Red Blood Cell ◽  
Small Angle ◽  
Time Scale ◽  
Small Angle Neutron Scattering ◽  
Length Scale ◽  
Elastic Neutron ◽  
Shape Changes

By using a combination of experimental neutron scattering techniques, it is possible to obtain a statistical perspective on red blood cell (RBC) shape in suspensions, and the inter-relationship with protein interactions and dynamics inside the confinement of the cell membrane. In this study, we examined the ultrastructure of RBC and protein–protein interactions of haemoglobin (Hb) in them using ultra-small-angle neutron scattering and small-angle neutron scattering (SANS). In addition, we used the neutron backscattering method to access Hb motion on the ns time scale and Å length scale. Quasi-elastic neutron scattering (QENS) experiments were performed to measure diffusive motion of Hb in RBCs and in an RBC lysate. By using QENS, we probed both internal Hb dynamics and global protein diffusion, on the accessible time scale and length scale by QENS. Shape changes of RBCs and variation of intracellular Hb concentration were induced by addition of the Na + -selective ionophore monensin and the K + -selective one, valinomycin. The experimental SANS and QENS results are discussed within the framework of crowded protein solutions, where free motion of Hb is obstructed by mutual interactions.

Lateral dispersion in random cylinder arrays at high Reynolds number

2008 ◽  
Vol 600 ◽  
pp. 339-371 ◽  
Author(s):  
YUKIE TANINO ◽  
HEIDI M. NEPF
Keyword(s):  
Turbulence Intensity ◽  
Turbulent Diffusion ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Laboratory Data ◽  
Integral Length Scale ◽  
Length Scale ◽  
Linear Superposition ◽  
Cylinder Diameter ◽  
The Mean

Laser-induced fluorescence was used to measure the lateral dispersion of passive solute in random arrays of rigid, emergent cylinders of solid volume fraction φ=0.010–0.35. Such densities correspond to those observed in aquatic plant canopies and complement those in packed beds of spheres, where φ≥0.5. This paper focuses on pore Reynolds numbers greater than Res=250, for which our laboratory experiments demonstrate that the spatially averaged turbulence intensity and Kyy/(Upd), the lateral dispersion coefficient normalized by the mean velocity in the fluid volume, Up, and the cylinder diameter, d, are independent of Res. First, Kyy/(Upd) increases rapidly with φ from φ =0 to φ=0.031. Then, Kyy/(Upd) decreases from φ=0.031 to φ=0.20. Finally, Kyy/(Upd) increases again, more gradually, from φ=0.20 to φ=0.35. These observations are accurately described by the linear superposition of the proposed model of turbulent diffusion and existing models of dispersion due to the spatially heterogeneous velocity field that arises from the presence of the cylinders. The contribution from turbulent diffusion scales with the mean turbulence intensity, the characteristic length scale of turbulent mixing and the effective porosity. From a balance between the production of turbulent kinetic energy by the cylinder wakes and its viscous dissipation, the mean turbulence intensity for a given cylinder diameter and cylinder density is predicted to be a function of the form drag coefficient and the integral length scale lt. We propose and experimentally verify that lt=min{d, 〈sn〉A}, where 〈sn〉A is the average surface-to-surface distance between a cylinder in the array and its nearest neighbour. We farther propose that only turbulent eddies with mixing length scale greater than d contribute significantly to net lateral dispersion, and that neighbouring cylinder centres must be farther than r* from each other for the pore space between them to contain such eddies. If the integral length scale and the length scale for mixing are equal, then r*=2d. Our laboratory data agree well with predictions based on this definition of r*.

scholarly journals LOCAL OBSERVED TIME AND REDSHIFT IN CURVED SPACE–TIME

2001 ◽  
Vol 16 (21) ◽  
pp. 1385-1393 ◽  
Author(s):  
SZE-SHIANG FENG
Keyword(s):  
Cosmological Constant ◽  
Time Scale ◽  
Space Time ◽  
Local Observable ◽  
Length Scale ◽  
De Sitter ◽  
Perfect Agreement ◽  
Curved Space ◽  
De Sitter Universe ◽  
Changing Rate

Using the observed time and spatial intervals defined originally by Einstein and the observational frame in the vierbein formalism, we propose that in curved space–time, for a wave received in laboratories, the observed frequency is the changing rate of the phase of the wave relative to the local observable time scale and the momentum is the changing rate of the phase relative to the local observable spatial length scale. The case of Robertson–Walker universe is especially considered and the application to de Sitter universe results in a cosmological constant in perfect agreement with the observational data.

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