A second-order moment particle–wall collision model accounting for the wall roughness

2005 ◽  
Vol 159 (2) ◽  
pp. 111-120 ◽  
Author(s):  
Xia Zhang ◽  
Lixing Zhou
Keyword(s):  
Second Order ◽  
Order Moment ◽  
Wall Roughness ◽  
Collision Model ◽  
Wall Collision

Simulation of Gas-Particle Channel Flows Using a Two-Fluid Particle-Wall Collision Model Accounting for Wall Roughness

2003 ◽  
Author(s):  
X. Zhang ◽  
L. X. Zhou
Keyword(s):  
Kinetic Energy ◽  
Channel Flows ◽  
Fluid Particle ◽  
Wall Friction ◽  
Wall Roughness ◽  
Reynolds Stresses ◽  
Collision Model ◽  
Wall Collision ◽  
Pdpa Measurement ◽  
Two Fluid

A two-fluid particle-wall collision model accounting for wall roughness is proposed. It accounts for the effects of wall friction, restitution, in particular the wall roughness, and hence the redistribution of particle Reynolds stresses in different directions at the wall, the absorption of turbulent kinetic energy from the kinetic energy of mean motion at the wall and the attenuation of particle motion by the wall. It gives the effect of wall roughness on the particle turbulence. The proposed model is applied to simulate gas-particle horizontal channel flows and is validated using PDPA measurement results. It is shown that presently used zero-gradient boundary conditions and other collision models of particle phase might give false results.

scholarly journals Method for Measuring the Second-Order Moment of Atmospheric Turbulence

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 564
Author(s):  
Hong Shen ◽  
Longkun Yu ◽  
Xu Jing ◽  
Fengfu Tan
Keyword(s):  
Atmospheric Turbulence ◽  
Weighting Function ◽  
Structure Constant ◽  
Turbulence Models ◽  
Second Order ◽  
Index Structure ◽  
Order Moment ◽  
Site Testing ◽  
Optical Effects ◽  
Novel Method

The turbulence moment of order m (μm) is defined as the refractive index structure constant Cn2 integrated over the whole path z with path-weighting function zm. Optical effects of atmospheric turbulence are directly related to turbulence moments. To evaluate the optical effects of atmospheric turbulence, it is necessary to measure the turbulence moment. It is well known that zero-order moments of turbulence (μ0) and five-thirds-order moments of turbulence (μ5/3), which correspond to the seeing and the isoplanatic angles, respectively, have been monitored as routine parameters in astronomical site testing. However, the direct measurement of second-order moments of turbulence (μ2) of the whole layer atmosphere has not been reported. Using a star as the light source, it has been found that μ2 can be measured through the covariance of the irradiance in two receiver apertures with suitable aperture size and aperture separation. Numerical results show that the theoretical error of this novel method is negligible in all the typical turbulence models. This method enabled us to monitor μ2 as a routine parameter in astronomical site testing, which is helpful to understand the characteristics of atmospheric turbulence better combined with μ0 and μ5/3.

A second-order moment method applied to gas-solid risers

AIChE Journal ◽  
2012 ◽  
Vol 58 (12) ◽  
pp. 3653-3675 ◽  
Author(s):  
Juhui Chen ◽  
Shuyan Wang ◽  
Dan Sun ◽  
Huilin Lu ◽  
Dimitri Gidaspow ◽  
...  
Keyword(s):  
Moment Method ◽  
Second Order ◽  
Order Moment

Shape Interpretation of Second-Order Moment Invariants

2016 ◽  
Vol 56 (1) ◽  
pp. 125-136 ◽  
Author(s):  
Joviša Žunić ◽  
Dragiša Žunić
Keyword(s):  
Second Order ◽  
Order Moment ◽  
Moment Invariants

scholarly journals Distributionally robust joint chance constraints with second-order moment information

2011 ◽  
Vol 137 (1-2) ◽  
pp. 167-198 ◽  
Author(s):  
Steve Zymler ◽  
Daniel Kuhn ◽  
Berç Rustem
Keyword(s):  
Chance Constraints ◽  
Second Order ◽  
Order Moment ◽  
Distributionally Robust

Three-Dimensional Simulation of Cross-Flow Microfilter Fouling in Tortuous Pore Profiles With Semisynthetic Metalworking Fluids

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Bingyi Yu ◽  
Shiv G. Kapoor ◽  
Richard E. DeVor
Keyword(s):  
Colloidal Particles ◽  
Three Dimensional ◽  
Particle Trapping ◽  
Collision Model ◽  
Flux Decline ◽  
Cake Layer ◽  
Trapping Model ◽  
Wall Collision ◽  
Dimensional Simulation ◽  
Layer Development

Fouling mechanisms and models for flux decline are investigated with a three-dimensional simulation of the tortuous, verisimilar geometry of an α-alumina microfilter. Reconstruction of the three-dimensional geometry was accomplished from two-dimensional cross-sectional cuts. A wall collision model and a particle trapping model are developed for the investigation of fouling mechanisms. The reconstructed geometry and the two models were used in computational fluid dynamics to simulate metalworking colloidal particles travelling through and becoming trapped in the tortuous pore paths of a microfilter. Results reveal sharp flux decline initiating from partial pore blocking and subdued flux decline transitioning to cake layer development with steady-state flow. This flow behavior is in agreement with experimental data from earlier studies. The inclusion of the wall collision model and particle trapping model enabled the revelation of cake layer development as a fouling mechanism. Additional simulations of microfilters at different particle size distributions were conducted and discussed.

Simulation of Swirl Combustion and NO Formation Using Various Second Order Moment Turbulent Combustion Models and DNS Verification

2008 ◽  
Author(s):  
F. Wang ◽  
Y. Huang ◽  
L. X. Zhou ◽  
C. X. Xu ◽  
J. Cao
Keyword(s):  
Turbulent Combustion ◽  
Reaction Rate ◽  
Rate Coefficient ◽  
Second Order ◽  
Concentration Fluctuation ◽  
Order Moment ◽  
Combustion Model ◽  
Reaction Rate Coefficient ◽  
No Formation ◽  
Swirl Combustion

If the instantaneous chemistry reaction rate is taken as ws = Bρ2Y1Y2 exp(−E/RT) = ρ2Y1Y2K, here K is a contraction for the exponential term. Then, ignoring the three order fluctuation correlation term, the average reaction rate could be ws = ρ2(Y1Y2K + Y1′Y2′K + Y1K′Y2′ + Y2K′Y1′). The authors have simulated jet combustion and swirl combustion using this kind of second order moment (SOM) turbulent combustion model. The predictions are close to experimental data in most regions. In order to improve the SOM turbulent combustion model, the effect of various correlation moments in the simulation of turbulent swirl combustion and NO formation is studied by comparing different SOM turbulence-chemistry models, including the unified second-order moment (USM) model, the model accounting for only the time-averaged reaction-rate coefficient, the model accounting for only the concentration fluctuation and the model accounting for both the time-averaged reaction-rate coefficient and the concentration fluctuation. These models are incorporated into the FLUENT code for a methane-air swirling combustion and NO formation under various swirl numbers. The magnitude of various correlations and their effect on the time-averaged reaction rate are analyzed, and the simulation results are compared with the corresponding measurement results. The results showed that the USM model gives the best agreement with the experimental results and among various correlation moments the correlation of reaction-rate coefficient fluctuation with the concentration fluctuation is most important. Additionally, a direct numerical simulation (DNS) of three-dimensional channel turbulent reacting flows with consideration of buoyancy effect using a spectral method was carried out. The statistical results are shown that K′Y′ are larger than Y1′Y2′.

Sign in / Sign up

Export Citation Format

Share Document