A New Monte-Carlo Scheme for Simulating Lagrangian Particle Diffusion with Wind Shear Effects

1984 ◽  
pp. 99-111 ◽  
Author(s):  
Paolo Zannetti
Keyword(s):  
Monte Carlo ◽  
Wind Shear ◽  
Particle Diffusion ◽  
Lagrangian Particle ◽  
Shear Effects

scholarly journals Wind Shear Effects on Radiatively and Evaporatively Driven Stratocumulus Tops

2018 ◽  
Vol 75 (9) ◽  
pp. 3245-3263 ◽  
Author(s):  
Bernhard Schulz ◽  
Juan Pedro Mellado
Keyword(s):  
Critical Velocity ◽  
Wind Shear ◽  
Radiative Cooling ◽  
Entrainment Rate ◽  
Entrainment Velocity ◽  
Velocity Jump ◽  
Individual Contributions ◽  
Shear Effects ◽  
The Mean ◽  
The Individual

Abstract Direct numerical simulations resolving meter and submeter scales in the cloud-top region of stratocumulus are used to investigate the interactions between a mean vertical wind shear and in-cloud turbulence driven by evaporative and radiative cooling. There are three major results. First, a critical velocity jump exists, above which shear significantly broadens the entrainment interfacial layer (EIL), enhances cloud-top cooling, and increases the mean entrainment velocity; shear effects are negligible when the velocity jump is below . Second, a depletion velocity jump exists, above which shear-enhanced mixing reduces cloud-top radiative cooling, thereby weakening the large convective motions; shear effects remain localized within the EIL when the velocity jump is below . The critical velocity jump and depletion velocity jump are provided as a function of in-cloud and free-tropospheric conditions, and one finds and for typical subtropical conditions. Third, the individual contributions to the mean entrainment velocity from mixing, radiative cooling, and evaporative cooling strongly depend on the choice of the reference height where the entrainment velocity is calculated. This result implies that the individual contributions to the mean entrainment velocity should be estimated at a comparable height while deriving entrainment-rate parameterizations. A strong shear alters substantially the magnitude and the height where these individual contributions reach their maxima, which further demonstrates the importance of shear on the dynamics of stratocumulus clouds.

Lagrangian particle tracking with new weighted fraction Monte Carlo method for studying the soot particle size distributions in premixed flames

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiao Jiang ◽  
Tat Leung Chan
Keyword(s):  
Particle Size ◽  
Monte Carlo ◽  
Soot Formation ◽  
Particle Size Distributions ◽  
Lagrangian Particle ◽  
Content Type ◽  
Soot Particles ◽  
Stochastic Error ◽  
Formation And Evolution ◽  
Size Interval

Purpose The purpose of this paper is to study the soot formation and evolution by using this newly developed Lagrangian particle tracking with weighted fraction Monte Carlo (LPT-WFMC) method. Design/methodology/approach The weighted soot particles are used in this MC framework and is tracked using Lagrangian approach. A detailed soot model based on the LPT-WFMC method is used to study the soot formation and evolution in ethylene laminar premixed flames. Findings The LPT-WFMC method is validated by both experimental and numerical results of the direct simulation Monte Carlo (DSMC) and Multi-Monte Carlo (MMC) methods. Compared with DSMC and MMC methods, the stochastic error analysis shows this new LPT-WFMC method could further extend the particle size distributions (PSDs) and improve the accuracy for predicting soot PSDs at larger particle size regime. Originality/value Compared with conventional weighted particle schemes, the weight distributions in LPT-WFMC method are adjustable by adopting different fraction functions. As a result, the number of numerical soot particles in each size interval could be also adjustable. The stochastic error of PSDs in larger particle size regime can also be minimized by increasing the number of numerical soot particles at larger size interval.

Investigation of Horizontal and Vertical Wind Shear Effects Using a Wind Turbine Emulator

2019 ◽  
Vol 10 (3) ◽  
pp. 1206-1216 ◽  
Author(s):  
Ebrahim Mohammadi ◽  
Roohollah Fadaeinedjad ◽  
Hamid Reza Naji ◽  
Gerry Moschopoulos
Keyword(s):  
Wind Turbine ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Shear Effects
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