scholarly journals Prediction of drop size of natural gas condensates using molecular simulation and Young growth model

2018 ◽  
Vol 8 (1) ◽  
pp. 67-75
Author(s):  
Arlex Chaves-Guerrero
Keyword(s):  
Molecular Simulation ◽  
Drop Size ◽  
Sampling Technique ◽  
Nucleation And Growth ◽  
Umbrella Sampling ◽  
Gas Condensates ◽  
Droplet Nucleation ◽  
The Monte Carlo Method ◽  
Young Growth ◽  
Good Agreement

This paper describes the development and implementation of a molecular simulation model to predict the nucleation process during the condensation of heavy components of the gas natural mixtures of linear alkane (C1 - C6 and C9) at transport conditions (10-40 bar). Specifically, it was used the Monte Carlo method with configurational-bias, the united-atom  force field known as “Transferable Potentials for Phase Equilibria (TraPPE-UA)," and the Umbrella sampling technique. The growth of the droplets was evaluated with the model of Young considering numbers of Knudsen below 0.1. The simulation results obtained for the droplet nucleation and growth were compared with experimental data reported in the literature with the aim of validating the implemented models. The simulations predict a droplets size of 2.09 μm which is in good agreement with the experimental results.

Determination of Base Flipping Free Energy Landscapes from Nonequilibrium Stratification

2019 ◽  
Author(s):  
Xiaohui Wang ◽  
Zhaoxi Sun
Keyword(s):  
Free Energy ◽  
Energy Landscape ◽  
Sampling Technique ◽  
Umbrella Sampling ◽  
Energy Simulation ◽  
Nonlinear Dependence ◽  
Free Energy Landscape ◽  
Convergence Criterion ◽  
Base Flipping ◽  
Convergence Behavior

<p>Correct calculation of the variation of free energy upon base flipping is crucial in understanding the dynamics of DNA systems. The free energy landscape along the flipping pathway gives the thermodynamic stability and the flexibility of base-paired states. Although numerous free energy simulations are performed in the base flipping cases, no theoretically rigorous nonequilibrium techniques are devised and employed to investigate the thermodynamics of base flipping. In the current work, we report a general nonequilibrium stratification scheme for efficient calculation of the free energy landscape of base flipping in DNA duplex. We carefully monitor the convergence behavior of the equilibrium sampling based free energy simulation and the nonequilibrium stratification and determine the empirical length of time blocks required for converged sampling. Comparison between the performances of equilibrium umbrella sampling and nonequilibrium stratification is given. The results show that nonequilibrium free energy simulation is able to give similar accuracy and efficiency compared with the equilibrium enhanced sampling technique in the base flipping cases. We further test a convergence criterion we previously proposed and it comes out that the convergence behavior determined by this criterion agrees with those given by the time-invariant behavior of PMF and the nonlinear dependence of standard deviation on the sample size. </p>

scholarly journals Measuring Hydrometeors Using a Precipitation Microphysical Characteristics Sensor: Sampling Effect of Different Bin Sizes on Drop Size Distribution Parameters

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xichuan Liu ◽  
Taichang Gao ◽  
Yuntao Hu ◽  
Xiaojian Shu
Keyword(s):  
Drop Size ◽  
Rain Rate ◽  
Monte Carlo Model ◽  
Rain Gauge ◽  
Sampling Schemes ◽  
Distribution Parameters ◽  
Optimum Sampling ◽  
Simulation Results ◽  
The Impact ◽  
Good Agreement

In order to improve the measurement of precipitation microphysical characteristics sensor (PMCS), the sampling process of raindrops by PMCS based on a particle-by-particle Monte-Carlo model was simulated to discuss the effect of different bin sizes on DSD measurement, and the optimum sampling bin sizes for PMCS were proposed based on the simulation results. The simulation results of five sampling schemes of bin sizes in four rain-rate categories show that the raw capture DSD has a significant fluctuation variation influenced by the capture probability, whereas the appropriate sampling bin size and width can reduce the impact of variation of raindrop number on DSD shape. A field measurement of a PMCS, an OTT PARSIVEL disdrometer, and a tipping bucket rain Gauge shows that the rain-rate and rainfall accumulations have good consistencies between PMCS, OTT, and Gauge; the DSD obtained by PMCS and OTT has a good agreement; the probability of N0, μ, and Λ shows that there is a good agreement between the Gamma parameters of PMCS and OTT; the fitted μ-Λ and Z-R relationship measured by PMCS is close to that measured by OTT, which validates the performance of PMCS on rain-rate, rainfall accumulation, and DSD related parameters.

scholarly journals On the Shape–Slope Relation of Drop Size Distributions in Convective Rain

2005 ◽  
Vol 44 (7) ◽  
pp. 1146-1151 ◽  
Author(s):  
Axel Seifert
Keyword(s):  
Size Distribution ◽  
Gamma Distribution ◽  
Drop Size ◽  
Empirical Relation ◽  
Size Distributions ◽  
Shape Parameters ◽  
Raindrop Size Distribution ◽  
Raindrop Size ◽  
Drop Size Distributions ◽  
Good Agreement

Abstract The relation between the slope and shape parameters of the raindrop size distribution parameterized by a gamma distribution is examined. The comparison of results of a simple rain shaft model with an empirical relation based on disdrometer measurements at the surface shows very good agreement, but a more detailed discussion reveals some difficulties—for example, deviations from the gamma shape and the overestimation of collisional breakup.

scholarly journals Alignment of Dust Grains by Magnetic Relaxation: A Comparison Between Results Obtained by Two Different Methods

1973 ◽  
Vol 52 ◽  
pp. 187-189
Author(s):  
P. Cugnon
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Magnetic Relaxation ◽  
Planck Equation ◽  
Dust Grains ◽  
Fokker Planck Equation ◽  
The Monte Carlo Method ◽  
Good Agreement ◽  
Fokker Planck

This paper is devoted to a comparison between results obtained by Purcell and Spitzer (1971) using a Monte-Carlo method and by the author (1971) using a Fokker-Planck equation. It is shown that there is a good agreement between the results within the dispersion expected from the Monte-Carlo method.

Secondary Fluorescence of 3D Heterogeneous Materials Using a Hybrid Model

2020 ◽  
Vol 26 (3) ◽  
pp. 484-496
Author(s):  
Yu Yuan ◽  
Hendrix Demers ◽  
Xianglong Wang ◽  
Raynald Gauvin
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Analytical Model ◽  
Hybrid Model ◽  
Three Dimensional ◽  
Heterogeneous Materials ◽  
X Ray ◽  
The Monte Carlo Method ◽  
Secondary Fluorescence ◽  
Good Agreement

AbstractIn electron probe microanalysis or scanning electron microscopy, the Monte Carlo method is widely used for modeling electron transport within specimens and calculating X-ray spectra. For an accurate simulation, the calculation of secondary fluorescence (SF) is necessary, especially for samples with complex geometries. In this study, we developed a program, using a hybrid model that combines the Monte Carlo simulation with an analytical model, to perform SF correction for three-dimensional (3D) heterogeneous materials. The Monte Carlo simulation is performed using MC X-ray, a Monte Carlo program, to obtain the 3D primary X-ray distribution, which becomes the input of the analytical model. The voxel-based calculation of MC X-ray enables the model to be applicable to arbitrary samples. We demonstrate the derivation of the analytical model in detail and present the 3D X-ray distributions for both primary and secondary fluorescence to illustrate the capability of our program. Examples for non-diffusion couples and spherical inclusions inside matrices are shown. The results of our program are compared with experimental data from references and with results from other Monte Carlo codes. They are found to be in good agreement.

scholarly journals A representative density profile of the North Greenland snowpack

2016 ◽  
Vol 10 (5) ◽  
pp. 1991-2002 ◽  
Author(s):  
Christoph Florian Schaller ◽  
Johannes Freitag ◽  
Sepp Kipfstuhl ◽  
Thomas Laepple ◽  
Hans Christian Steen-Larsen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Density Profile ◽  
Accumulation Rate ◽  
Sampling Technique ◽  
Data Sets ◽  
Accumulation Rates ◽  
The North ◽  
North Greenland ◽  
Good Agreement

Abstract. Along a traverse through North Greenland in May 2015 we collected snow cores up to 2 m depth and analyzed their density and water isotopic composition. A new sampling technique and an adapted algorithm for comparing data sets from different sites and aligning stratigraphic features are presented. We find good agreement of the density layering in the snowpack over hundreds of kilometers, which allows the construction of a representative density profile. The results are supported by an empirical statistical density model, which is used to generate sets of random profiles and validate the applied methods. Furthermore we are able to calculate annual accumulation rates, align melt layers and observe isotopic temperatures in the area back to 2010. Distinct relations of δ18O with both accumulation rate and density are deduced. Inter alia the depths of the 2012 melt layers and high-resolution densities are provided for applications in remote sensing.

A New Kinetic Model for The Nucleation and Growth of Self-Interstitial Clusters in Silicon

2001 ◽  
Vol 669 ◽  
Author(s):  
Christophe J. Ortiz ◽  
Daniel Mathiot
Keyword(s):  
Kinetic Model ◽  
Inverse Modeling ◽  
Nucleation And Growth ◽  
Experimental Results ◽  
Physical Parameters ◽  
Formation Energies ◽  
Good Agreement

ABSTRACTA model for nucleation and growth of {311} defects is proposed on the basis of thermodynamic and kinetic considerations. Simulated results are discussed and compared to experimental results found in the literature. According to our model it is found that formation energies of self-interstitial clusters depends on the local interstitial supersaturation. Physical parameters extracted from experimental results by inverse modeling are in good agreement with recent values published in the literature.

A Comparison of a Spray Penetration Correlation by an Optical Obscuration Technique to Other Correlations Obtained by Different Techniques

2002 ◽  
Author(s):  
Badih A. Jawad
Keyword(s):  
Drop Size ◽  
Optical Measurement ◽  
Sampling Technique ◽  
Optical Signal ◽  
Spray Penetration ◽  
Spray Formation ◽  
Diesel Fuels ◽  
Liquid Immersion ◽  
Cylindrical Volume ◽  
Collimated Beam

Previous studies dealing with sprays have used a variety of techniques to determine spray droplets and spray penetration. In particular, the sedimentation tower method and the liquid immersion sampling technique were most popular. However, in these techniques sampling is done after spray formation is complete. The completion time of spray formation appears to vary with the conditions of injection and ambient factors, thus making measurements under transient conditions during injection difficult. A pulsed Malvern drop-size analyzer, based on Fraunhofer diffraction, was utilized to determine spray penetrations of diesel fuels under different conditions of injection, along with the effects of fuel properties. In these study, the spray is formed by injecting a calibrated amount of fuel into air. A two mm diameter collimated beam illuminated a cylindrical volume perpendicular to the axis of the fuel spray, and its attenuation was recorded and stored on the oscilloscope. With the optical measurement being synchronized to the needle lift of the injector, the output of the needle lift transducer and the optical signal was recorded simultaneously. Thus, the arrival and the duration of the spray at various positions along its axis were measured. A spray penetration correlation is obtained, and is compared to other existing correlations in the literature.

A Simple and Fast Method for Calculating Properties Across a Condensation Shock

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
V. Babu
Keyword(s):  
Experimental Data ◽  
Steam Turbine ◽  
Simple Procedure ◽  
Nucleation And Growth ◽  
Fast Method ◽  
Algebraic Equations ◽  
Gas Dynamic ◽  
Droplet Nucleation ◽  
Condensation Shock ◽  
Steam Turbine Blade

A simple procedure for calculating the pressure at the onset and termination of condensation shocks that occur in steam nozzles and steam turbine blade passages is presented. In addition, the location of the termination of the condensation shock with reference to the throat location is also predicted. The procedure is based entirely on thermodynamic and gas dynamic considerations, without using a model for droplet nucleation and growth and the nozzle profile. The only input required is the stagnation condition at the inlet to the nozzle. The procedure requires the solution of a system of algebraic equations which can be accomplished quite easily. Calculations have been carried out for several inlet stagnation conditions and the predictions are compared with the available experimental data. The agreement is seen to be reasonable considering the simplicity of the procedure.

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