Journal articles: 'VOF simulace'

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Zhang, Hong Qing, Xian Tang Zhang, Yi Long Lou, and Wei Ping Xing. "Comparative Analysis of Wind Speed in Ventilation Hole Simulated by VOF and Euler Model." Applied Mechanics and Materials 624 (August 2014): 643–46. http://dx.doi.org/10.4028/www.scientific.net/amm.624.643.

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In order to analysis the applicability of VOF and Euler models to simulate water-air two-phase flow, VOF model and Euler model, respectively combining turbulent model, were used to simulate wind speed in ventilation hole of working gate in a hydropower station spillway tunnel with high head and large discharge in China. The results show that the dragging force simulated by Euler model is much more effective than that simulated by VOF model, causing significant increase of airflow in ventilation hole. It is obviously that wind speed simulated by Euler model is more close to the measured one, which may also provide evidence for design of ventilation hole. So Euler model is a better method to simulate the characteristic of aerated flow than VOF model. Meanwhile, the maximum wind speed occur near the inlet of ventilation hole, and the maximum value of wind speed is close to 120 m/s, which can cause loud noise. And wind speed distribution on the inlet section and outlet section of ventilation hole is respectively the most non-uniform and uniform. The conclusions obtained can improve the design of ventilation hole.

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Zhang, Hong Qing, Yi Long Lou, Wei Ping Xing, and Jun Jun Tan. "Numerical Simulation of Ventilation Characteristics in a Hydropower Station Spillway Tunnel with High Head and Large Discharge." Advanced Materials Research 926-930 (May 2014): 3527–30. http://dx.doi.org/10.4028/www.scientific.net/amr.926-930.3527.

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High wind speedandloudnoise usually occur in the hydropower station spillway tunnel, which will impact the producing environment of operators. In this paper, turbulent model and VOF modelwere combinedto simulate wind speed and the volume of ventilated airin ventilation holeandthreeaeratorsin the spillway tunnel on the right bank of a hydropower station in China. The results show thatVOF modelcan well simulate ventilated air induced by water drag, andthe volume of ventilated air in ventilation hole is the largest.Wind speed distribution on the longitudinal sectionof the inlet of ventilation hole is non-uniform,and loud noisewill occurthere. Wind speed on the left side of three aerators is higher than that on the right side. The results of the volume of ventilated airin threeaerators simulated by VOF modelare credible, but we should improve the VOF model to more accurately simulate aerated flow.

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Yang, Jie, Yu Xin Ren, and Shou Mei Xiong. "Numerical Simulation of Die-Casting Mold Filling Process by Using Fractional Step Method." Materials Science Forum 575-578 (April 2008): 104–8. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.104.

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In the numerical simulation of mold filling process, the calculation efficiency has been a key point for practical applications due to the complexity and thin-section of die castings. In current research work, a fractional step method was applied in the solution of the unsteady Navier-Stokes equations, which can be implemented with a single solution to the momentum/pressure equations at each time step. This method may avoid the decrease in efficiency induced by iteration. A water analog system was designed and developed to simulate the die casting process. The flow patterns were recorded by a high speed camera with a capturing rate of 500 frames per second. The simulation results were consistent with the experimental ones. Besides, the fluid flow patterns of several components were simulated by the fractional step and VOF algorithm, and the SOLA-VOF algorithm respectively. The simulation results showed that the combination of the fractional step method and VOF method can improve the computational efficiency to some extent in numerical simulation of mold filling process.

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Samuel, Samuel, Andi Trimulyono, and Ari Wibawa Budi Santosa. "Simulasi CFD pada Kapal Planing Hull." Kapal: Jurnal Ilmu Pengetahuan dan Teknologi Kelautan 16, no. 3 (November 13, 2019): 123–28. http://dx.doi.org/10.14710/kapal.v16i3.26397.

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Akurasi dalam memprediksi hambatan kapal adalah salah satu aspek penting dalam mendesain lambung kapal. Secara umum, hambatan kapal dengan type planing lebih rumit daripada type displacement. Planing hull memiliki karakteristik unik seperti trim, heave, hard-chine, Froude number tinggi dan dead-rise angle. Gaya hidrodinamik pada planing hull lebih dominan daripada gaya hidrostatik. Analisis numerik menggunakan Finite Volume Method (FVM) dipilih untuk menyelesaikan masalah hidrodinamik. Dalam penelitian ini, persamaan (RANS Reynolds-Averaged Navier-Stokes) digunakan untuk menggambarkan model turbulensi dengan k-ε. Secara umum, pemodelan Volume of Fluid (VOF) menggunakan aliran multiphase Euler yang diasumsikan air dan udara sebagai phase. Tujuan dari penelitian ini adalah untuk memperkenalkan perhitungan kapal type planing hull untuk memprediksi hambatan kapal dan seakeeping. Studi validasi ini dilakukan dengan menggunakan eksperimen Fridsma hullform. Hasil pada penelitian ini menunjukkan bahwa simulasi numerik pada jenis planing hull dapat diprediksi dengan akurasi yang cukup baik.

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Liu, Y. L., B. Lv, and W. L. Wei. "Large Eddy Simulation of Gas-Liquid Two-Phase Flow for a Nested Type Fixed-Cone Valve." Applied Mechanics and Materials 170-173 (May 2012): 2458–63. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.2458.

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large eddy simulation cooperated with a physical fractional-step method is applied to simulate steady flow around a nested type fixed-cone valve; and the equations are solved with the finite volume method. The free fluid surface is simulated by the VOF method. The pressure contours and vorticity magnitude are obtained. The modeling results conform to physical law, and show that the large eddy simulation theory has powerful capacity in simulation of microstructures of turbulent flows, and the function of the nested type fixed-cone valve for energy dissipating is good.

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Cao, Wen Jiong, Shou Bin Dong, Xin Wei Lu, and Zhao Yao Zhou. "Numerical Simulation of Filling Process in HPDC by Lattice Boltzmann Method." Advanced Materials Research 717 (July 2013): 354–58. http://dx.doi.org/10.4028/www.scientific.net/amr.717.354.

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A general lattice Boltzmann Method (LBM) to simulate filling process of high pressure die casting (HPDC) is investigated. Boundary conditions are studied and the free surface model is established by combine the LBM with VOF method. The final model was substantiated by simulating filling process in HPDC in three dimensions. The simulated results from LBM and finite difference method (FDM) were compared with the experiments. The results show the former is in a better agreement with experiments. It demonstrates the efficiency and precision of this LBM model in describing flow pattern in filling process.

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Rahaman, Md Mashiur, Hiromichi Akimoto, and Md Ashim Ali. "Numerical simulation of 2D hydrodynamic impact of wedge and ship section at variable velocity." Journal of Naval Architecture and Marine Engineering 10, no. 1 (June 29, 2013): 49–58. http://dx.doi.org/10.3329/jname.v10i1.14383.

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A commercial CFD code Fluent 6.3® is used to simulate non-linear free surface flow and compute the impact load during variable velocity water entry of 2D wedge and ship section. The code uses the finite volume method to solve the conservation of mass and momentum equations to obtain simulated flow field. The interface between water and air was modeled using volume of fluid (VOF) method. Wedge section with 30 degree dead-rise angle and a ship section are numerically simulated. Time history of impact force and pressures at distinct locations are predicted; and compared with existing experimental results and other numerical methods. Present numerical results compare well with experimental measurements.DOI: http://dx.doi.org/10.3329/jname.v10i1.14383

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8

Shang, Zhi, Jing Lou, and Hongying Li. "Simulations of Flow Transitions in a Vertical Pipe Using Coupled Level Set and VOF Method." International Journal of Computational Methods 14, no. 02 (February 22, 2017): 1750013. http://dx.doi.org/10.1142/s021987621750013x.

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The level set (LS) and volume-of-fluid (VOF) methods are usually employed to simulate the two-phase flow. However every single method of them will face the mass conservative or accurate issues during the simulation. The coupled level set and volume-of-fluid (CLSVOF) method was not only able to conquer the shortages of the LS and VOF methods but also simultaneously keep the merits of both of the methods. In CLSVOF method the geometry reconstruction technology was employed to realize the coupling between LS and VOF. After the validation of single bubble rising cases, the CLSVOF method was used to simulate the complex transitional two-phase flows in a vertical pipe and the simulation results were compared to experiments.

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Zhang, Wei, You Hong Tang, Cheng Bi Zhao, and Cheng Zhang. "A Two-Phase Flow Model with VOF for Free Surface Flow Problems." Applied Mechanics and Materials 232 (November 2012): 279–83. http://dx.doi.org/10.4028/www.scientific.net/amm.232.279.

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A numerical model based on the two-phase flow model for incompressible viscous fluid with a complex free surface has been developed in this study. The two-step projection method is employed to solve the Navier–Stokes equations in the numerical solutions, and finite difference method on a staggered grid is used throughout the computation. The two-order accurate volume of fluid (VOF) method is used to track the distorted and broken free surfaces. The two-phase model is first validated by simulating the dam break over a dry bed, in which the numerical results and experimental data agree well. Then 2-D fluid sloshing in a horizontally excited rectangular tank at different excitation frequencies is simulated using this two-phase model. The results of this study show that the two-phase flow model with VOF method is a potential tool for the simulation of nonlinear fluid sloshing. These studies demonstrate the capability of the two-phase model to simulate free surface flow problems with considering air movement effects.

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Suthanarak, Nawaporn, and Navaphattra Nunak. "A CFD study on wall shear stress of falling water film on food contact surface." MATEC Web of Conferences 192 (2018): 03052. http://dx.doi.org/10.1051/matecconf/201819203052.

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This paper proposes a CFD model to simulate the wall shear stress of the falling water film on the hydrophilic surface (aluminum) of the inclined flat plate in the range of 30°, 60° and 90° at a flow rate of 100, 200 and 300 L/h. Wall shear stress simulated from the CFD using SST k-ω with the VOF model was compared with the real data obtained from the experiment. It was found that both inclined angle and water flow rate had an effect to the wall shear stress and the CFD with the proposed model had the potential to predict it with the maximum averaged error of 2.9%.

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Jouvet, Guillaume, Marco Picasso, Jacques Rappaz, and Heinz Blatter. "A new algorithm to simulate the dynamics of a glacier: theory and applications." Journal of Glaciology 54, no. 188 (2008): 801–11. http://dx.doi.org/10.3189/002214308787780049.

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AbstractWe propose a novel Eulerian algorithm to compute the changes of a glacier geometry for given mass balances. The surface of a glacier is obtained by solving a transport equation for the volume of fluid (VOF). The surface mass balance is taken into account by adding an interfacial term in the transport equation. An unstructured mesh with standard stabilized finite elements is used to solve the non-linear Stokes problem. The VOF function is computed on a structured grid with a high resolution. The algorithm is stable for Courant numbers larger than unity and conserves mass to a high accuracy. To demonstrate the potential of the algorithm, we apply it to reconstructed Late-glacial states of a small valley glacier, Vadret Muragl, in the Swiss Alps.

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Qiu, Ruofan, Anlin Wang, Qiwei Gong, and Tao Jiang. "Simulation of two-phase fluid mixture flow in rectangular two-inlet cavity using lattice Boltzmann method." International Journal of Modern Physics C 25, no. 04 (March 6, 2014): 1450004. http://dx.doi.org/10.1142/s0129183114500041.

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In this paper, two-phase fluid mixture flow in rectangular two-inlet cavity is studied using lattice Boltzmann method (LBM). To simulate two-phase fluids with large viscosity difference, the pseudo-potential model is improved. The improved model is verified for surface tension through Laplace's law and shown much better performance in simulating fluids with large viscosity difference than pseudo-potential model. The multiple-relaxation-time (MRT) scheme is used to enhance numerical stability. Then the two-phase fluid mixture flow with same and different viscosity in two-inlet cavity is simulated by present lattice Boltzmann (LB) model, pseudo-potential LB model and volume-of-fluid (VOF) method, respectively. The comparison of these numerical results shows that LB model is more suitable for such kind of flow than VOF method, since it can reflect repulsive forces and transitional region of two-phase fluids in dynamic process. Moreover, it also shows that present LB model has better dynamic stability than pseudo-potential model. Furthermore, simulations of the two-phase fluid mixture flow with different fluid viscosities, inlet velocities, inlet heights and outlet positions using present LB model are presented, exhibiting their effect to contact area of fluids.

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von Boetticher, Albrecht, Jens M. Turowski, Brian W. McArdell, Dieter Rickenmann, and James W. Kirchner. "DebrisInterMixing-2.3: a finite volume solver for three-dimensional debris-flow simulations with two calibration parameters – Part 1: Model description." Geoscientific Model Development 9, no. 9 (August 31, 2016): 2909–23. http://dx.doi.org/10.5194/gmd-9-2909-2016.

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Abstract. Here, we present a three-dimensional fluid dynamic solver that simulates debris flows as a mixture of two fluids (a Coulomb viscoplastic model of the gravel mixed with a Herschel–Bulkley representation of the fine material suspension) in combination with an additional unmixed phase representing the air and the free surface. We link all rheological parameters to the material composition, i.e., to water content, clay content, and mineral composition, content of sand and gravel, and the gravel's friction angle; the user must specify only two free model parameters. The volume-of-fluid (VoF) approach is used to combine the mixed phase and the air phase into a single cell-averaged Navier–Stokes equation for incompressible flow, based on code adapted from standard solvers of the open-source CFD software OpenFOAM. This effectively single-phase mixture VoF method saves computational costs compared to the more sophisticated drag-force-based multiphase models. Thus, complex three-dimensional flow structures can be simulated while accounting for the pressure- and shear-rate-dependent rheology.

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von Boetticher, A., J. M. Turowski, B. W. McArdell, D. Rickenmann, and J. W. Kirchner. "DebrisInterMixing-2.3: a Finite Volume solver for three dimensional debris flow simulations based on a single calibration parameter – Part 1: Model description." Geoscientific Model Development Discussions 8, no. 8 (August 13, 2015): 6349–78. http://dx.doi.org/10.5194/gmdd-8-6349-2015.

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Abstract. Here we present a three-dimensional fluid dynamic solver that simulates debris flows as a mixture of two phases (gravel and fine material suspension) with a third unmixed phase representing the air and the free surface. We link all rheological parameters to the material composition, i.e., to water content, clay content and mineral composition, content of sand and gravel, and the gravel's friction angle; the user must specify only a single free model parameter. The Volume-Of-Fluid (VOF) approach is used to combine the three phases into a single cell-averaged Navier–Stokes equation for incompressible flow, based on code adapted from standard solvers of the Open-Source CFD software OpenFOAM. We present a stable implementation of a Coulomb-Viscoplastic model that represents the pressure-dependent flow behavior of the granular phase, and a Herschel–Bulkley representation of the interstitial fluid. The VOF method saves computational costs compared to drag-force based multiphase models. Thus depth-averaging is not necessary and complex three-dimensional flow structures can be simulated.

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Dong, Xu, Ya Xing Wang, Ye Li, and Li Zeng. "Numerical Simulation of Underwater Ellipsoid Motion near Free Surface." Applied Mechanics and Materials 275-277 (January 2013): 502–7. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.502.

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To analyze hydrodynamic characteristics of small scale body motion near free surface, finite volume method was adopt to compute incompressible Reynolds Averaged N-S (RANS) equations, numerical methods were conducted to simulate changes of drag coefficient and surface shape when moving near free surface. VOF method with Geo-Reconstruct form was used to deal with free surface. Fully developed turbulent flow can be solved by RNG k-ε model, and near wall region by near-wall functions. Quick upwind schemes were used to overcome instability problem when simulating high Reynolds flow. The results showed that VOF method, combined with RNG k-ε model, can be put to use to numerically simulate underwater body moving near free surface, and catch shape change of free surface in high Froude number.

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Chu, Chia-Ren, Truc Thi Thu Tran, and Tso-Ren Wu. "Numerical Analysis of Free-Surface Flows over Rubber Dams." Water 13, no. 9 (April 30, 2021): 1271. http://dx.doi.org/10.3390/w13091271.

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This study integrates a large eddy simulation (LES) model and volume of fluid (VOF) method to simulate the free-surface flows over inflexible circular-crested dams of different shapes. The simulated water depths and pressures on the dam surface are validated by the results of laboratory experiments. Then the numerical model examines the effects of the water depths and the Reynolds number on the hydrodynamic force and the discharge coefficient. The simulation results reveal that the time-averaged drag coefficient decreases as the downstream water depth H2 increases, while the influence of water depth H2 on the lift coefficients is less significant. Furthermore, the discharge coefficients of circular and elliptical dams, computed from the simulated velocity profiles over the crest of the dam, agree with the formulae suggested by previous studies when the downstream depth H2/H1 < 0.90. In contrast, the discharge coefficient of a tear-shape dam is slightly larger than those of circular dams.

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Zhang, Hong Qing, Yi Long Lou, Qian Zhao, and Wei Kai Tan. "Analysis the Response of Aerated Flow Depth to the VOF Model." Applied Mechanics and Materials 716-717 (December 2014): 767–70. http://dx.doi.org/10.4028/www.scientific.net/amm.716-717.767.

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In order to analysis the response of aerated flow depth to the VOF model, in this paper, we used VOF combining turbulent model to simulate aerated flow depth in a hydropower station spillway tunnel with high head and large discharge in China. The results show that aerated flow depth is slightly larger than the experiment water depth, but the maximum deviation are not greater than 5% (except the pile number 0+605.236 m). So, using empirical formula to converse the calculate value of water depth into aerated flow depth can make up for the defects of the VOF model which cannot directly get aerated flow depth of the cross section inside the spillway tunnel. But the section water depth can’t be obtained by empirical formula calculation value conversion when cavity exists in the spillway tunnel.

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Chen, Yen-Lung, Jing-Bo Hung, Shih-Lun Hsu, Shih-Chun Hsiao, and Yuan-Chieh Wu. "Interaction of Water Waves and a Submerged Parabolic Obstacle in the Presence of a Following Uniform/Shear Current Using RANS Model." Mathematical Problems in Engineering 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/896723.

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This paper simulates regular waves propagating over a submerged parabolic obstacle in the presence of a uniform/shear current using a two-dimensional numerical model, named COBRAS (Cornell Breaking and Structure). The numerical model solves the Reynolds-Averaged Navier-Stokes (RANS) equations and the free surface deformation is tracked using the volume of fluid method (VOF). The capability of the numerical model to simulate regular waves with a uniform or shear current over a constant water depth is first validated with available analytical solutions and experimental data. Comparisons among the experimental data, analytical solutions, and present numerical results show good agreements. Then, regular waves propagating over a submerged parabolic obstacle with a following current are investigated. Detailed discussions including those on the velocity and vorticity fields and the relation between free surface and vorticity are given.

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Jing, Shu Guang, Xue Ping Gao, Lai Fei Jia, and Li Ping Xu. "Three-Dimensional Numerical Simulation of the Hydraulic Characteristics of Spillway in Gushitan Reservoir." Applied Mechanics and Materials 256-259 (December 2012): 2403–6. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.2403.

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Based on standard k-ε turbulence model and the VOF method for tracking free surface, hydraulic characteristics of the spillway in Gushitan Reservoir are simulated with a 3-D numerical model. The discharge capacity, water surface profiles, bottom pressure distribution and flow pattern are studied. Numerical simulation results have been in good agreement with experimental results, showing fine feasibility to study hydraulic characteristics of the spillway with the VOF method. The hydraulic characteristics acquired by the numerical simulation method can be used for spillway design.

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Lubin, Pierre, and Stéphane Glockner. "NUMERICAL SIMULATIONS OF BREAKING SOLITARY WAVES." Coastal Engineering Proceedings 1, no. 33 (September 28, 2012): 59. http://dx.doi.org/10.9753/icce.v33.waves.59.

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This paper presents the application of a parallel numerical code to breaking solitary waves impacting a seawall structure. The three-dimensional Navier-Stokes equations are solved in air and water, coupled with a subgrid-scale model to take turbulence into account. We compared three numerical methods for the free-surface description, using the classical VOF-PLIC and VOF-TVD methods, and an original VOF-SM method recently developed in our numerical tool (Vincent et al., 2010). Some experimental data for solitary waves impinging and overtopping coastal structures are available in literature (Hsiao et al., 2010). Solitary waves are often used to model tsunami behaviors because of their hydrodynamic similarities. From a numerical point of view, it allows shorter CPU time simulations, as only one wave breaks. Here we apply the model to simulate three-dimensional solitary waves and compare qualitatively our results with the experimental data. We investigate three configurations of solitary waves impinging and overtopping an impermeable seawall on a 1:20 sloping beach.

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Suo, Xiao Yong. "Numerical Simulation of Droplet Ejection Based on VOF Method." Applied Mechanics and Materials 548-549 (April 2014): 1257–64. http://dx.doi.org/10.4028/www.scientific.net/amm.548-549.1257.

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Taking ejection process of the ink droplets from ink-jet nozzle as the prototype, a similar numerical model of droplet ejection was established. The VOF method was applied to track the interface of droplet ejection process and it is shown that the numerical results simulated by the VOF method were accurate and reliable. Six kinds of liquid with different physical properties were chosen as the research object. The numerical results were analyzed and compared. Finally, the effect of the surface tension, viscosity and density on the droplet ejection process was discussed.

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Ganzeveld, L., G. Eerdekens, G. Feig, H. Fischer, H. Harder, R. Königstedt, D. Kubistin, et al. "Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL campaign." Atmospheric Chemistry and Physics 8, no. 20 (October 27, 2008): 6223–43. http://dx.doi.org/10.5194/acp-8-6223-2008.

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Abstract. We present an evaluation of sources, sinks and turbulent transport of nitrogen oxides, ozone and volatile organic compounds (VOC) in the boundary layer over French Guyana and Suriname during the October 2005 GABRIEL campaign by simulating observations with a single-column chemistry and climate model (SCM) along a zonal transect. Simulated concentrations of O3 and NO as well as NO2 photolysis rates over the forest agree well with observations when a small soil-biogenic NO emission flux was applied. This suggests that the photochemical conditions observed during GABRIEL reflect a pristine tropical low-NOx regime. The SCM uses a compensation point approach to simulate nocturnal deposition and daytime emissions of acetone and methanol and produces daytime boundary layer mixing ratios in reasonable agreement with observations. The area average isoprene emission flux, inferred from the observed isoprene mixing ratios and boundary layer height, is about half the flux simulated with commonly applied emission algorithms. The SCM nevertheless simulates too high isoprene mixing ratios, whereas hydroxyl concentrations are strongly underestimated compared to observations, which can at least partly explain the discrepancy. Furthermore, the model substantially overestimates the isoprene oxidation products methlyl vinyl ketone (MVK) and methacrolein (MACR) partly due to a simulated nocturnal increase due to isoprene oxidation. This increase is most prominent in the residual layer whereas in the nocturnal inversion layer we simulate a decrease in MVK and MACR mixing ratios, assuming efficient removal of MVK and MACR. Entrainment of residual layer air masses, which are enhanced in MVK and MACR and other isoprene oxidation products, into the growing boundary layer poses an additional sink for OH which is thus not available for isoprene oxidation. Based on these findings, we suggest pursuing measurements of the tropical residual layer chemistry with a focus on the nocturnal depletion of isoprene and its oxidation products.

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Ganzeveld, L., G. Eerdekens, G. Feig, H. Fischer, H. Harder, R. Königstedt, D. Kubistin, et al. "Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL Campaign." Atmospheric Chemistry and Physics Discussions 8, no. 3 (June 16, 2008): 11909–65. http://dx.doi.org/10.5194/acpd-8-11909-2008.

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Abstract. We present an evaluation of sources, sinks and turbulent transport of nitrogen oxides, ozone and volatile organic compounds (VOC) in the boundary layer over French Guyana and Suriname during the October 2005 GABRIEL campaign by simulating observations with a single-column chemistry and climate model (SCM) along a zonal transect. Simulated concentrations of O3 and NO as well as NO2 photolysis rates over the forest agree well with observations when a small soil-biogenic NO emission flux was applied. This suggests that the photochemical conditions observed during GABRIEL reflect a pristine tropical low-NOx regime. The SCM uses a compensation point approach to simulate nocturnal deposition and daytime emissions of acetone and methanol and produces daytime boundary layer mixing ratios in reasonable agreement with observations. The area average isoprene emission flux, inferred from the observed isoprene mixing ratios and boundary layer height, is about half the flux simulated with commonly applied emission algorithms. The SCM nevertheless simulates too high isoprene mixing ratios, whereas hydroxyl concentrations are strongly underestimated compared to observations, which can at least partly explain the discrepancy. Furthermore, the model substantially overestimates the isoprene oxidation products methlyl vinyl ketone (MVK) and methacrolein (MACR) partly due to a simulated nocturnal increase due to isoprene oxidation. This increase is most prominent in the residual layer whereas in the nocturnal inversion layer we simulate a decrease in MVK and MACR mixing ratios, assuming efficient removal of MVK and MACR. Entrainment of residual layer air masses, which are enhanced in MVK and MACR and other isoprene oxidation products, into the growing boundary layer poses an additional sink for OH which is thus not available for isoprene oxidation. Based on these findings, we suggest pursuing measurements of the tropical residual layer chemistry with a focus on the nocturnal depletion of isoprene and its oxidation products.

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Johnson, D., S. R. Utembe, and M. E. Jenkin. "Simulating the detailed chemical composition of secondary organic aerosol formed on a regional scale during the TORCH 2003 campaign in the southern UK." Atmospheric Chemistry and Physics 6, no. 2 (February 8, 2006): 419–31. http://dx.doi.org/10.5194/acp-6-419-2006.

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Abstract. Following on from the companion study (Johnson et al., 2006), a photochemical trajectory model (PTM) has been used to simulate the chemical composition of organic aerosol for selected events during the 2003 TORCH (Tropospheric Organic Chemistry Experiment) field campaign. The PTM incorporates the speciated emissions of 124 non-methane anthropogenic volatile organic compounds (VOC) and three representative biogenic VOC, a highly-detailed representation of the atmospheric degradation of these VOC, the emission of primary organic aerosol (POA) material and the formation of secondary organic aerosol (SOA) material. SOA formation was represented by the transfer of semi- and non-volatile oxidation products from the gas-phase to a condensed organic aerosol-phase, according to estimated thermodynamic equilibrium phase-partitioning characteristics for around 2000 reaction products. After significantly scaling all phase-partitioning coefficients, and assuming a persistent background organic aerosol (both required in order to match the observed organic aerosol loadings), the detailed chemical composition of the simulated SOA has been investigated in terms of intermediate oxygenated species in the Master Chemical Mechanism, version 3.1 (MCM v3.1). For the various case studies considered, 90% of the simulated SOA mass comprises between ca. 70 and 100 multifunctional oxygenated species derived, in varying amounts, from the photooxidation of VOC of anthropogenic and biogenic origin. The anthropogenic contribution is dominated by aromatic hydrocarbons and the biogenic contribution by α- and β-pinene (which also constitute surrogates for other emitted monoterpene species). Sensitivity in the simulated mass of SOA to changes in the emission rates of anthropogenic and biogenic VOC has also been investigated for 11 case study events, and the results have been compared to the detailed chemical composition data. The role of accretion chemistry in SOA formation, and its implications for the results of the present investigation, is discussed.

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Johnson, D., S. R. Utembe, and M. E. Jenkin. "Simulating the detailed chemical composition of secondary organic aerosol formed on a regional scale during the TORCH 2003 campaign in the southern UK." Atmospheric Chemistry and Physics Discussions 5, no. 4 (August 30, 2005): 7875–902. http://dx.doi.org/10.5194/acpd-5-7875-2005.

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Abstract. Following on from the companion study (Johnson et al., 2005a), a photochemical trajectory model (PTM) has been used to simulate the chemical composition of organic aerosol for selected events during the 2003 TORCH (Tropospheric Organic Chemistry Experiment) field campaign. The PTM incorporates the speciated emissions of 124 non-methane anthropogenic volatile organic compounds (VOC) and three representative biogenic VOC, a highly-detailed representation of the atmospheric degradation of these VOC, the emission of primary organic aerosol (POA) material and the formation of secondary organic aerosol (SOA) material. SOA formation was represented by the transfer of semi- and non-volatile oxidation products from the gas-phase to a condensed organic aerosol-phase, according to estimated thermodynamic equilibrium phase-partitioning characteristics for around 2000 reaction products. After significantly scaling all phase-partitioning coefficients, and assuming a persistent background organic aerosol (both required in order to match the observed organic aerosol loadings), the detailed chemical composition of the simulated SOA has been investigated in terms of intermediate oxygenated species in the Master Chemical Mechanism, version 3.1 (MCM v3.1). For the various case studies considered, 90% of the simulated SOA mass comprises between ca. 70 and 100 multifunctional oxygenated species derived, in varying amounts, from the photooxidation of VOC of anthropogenic and biogenic origin. The anthropogenic contribution is dominated by aromatic hydrocarbons and the biogenic contribution by α- and β-pinene (which also constitute surrogates for other emitted monoterpene species). Sensitivity in the simulated mass of SOA to changes in the emission rates of anthropogenic and biogenic VOC has also been investigated for 11 case study events, and the results have been compared to the detailed chemical composition data. The role of accretion chemistry in SOA formation, and its implications for the results of the present investigation, is discussed.

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Xu, Qi, Jiakuan Yang, Huijie Hou, Yuchen Hu, Sha Liang, Keke Xiao, Xu Wu, et al. "Simulation on flow field and gas hold-up of a pilot-scale oxidation ditch by using liquid-gas CFD model." Water Science and Technology 78, no. 9 (November 12, 2018): 1956–65. http://dx.doi.org/10.2166/wst.2018.472.

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Abstract A liquid–gas two-phase computational fluid dynamics (CFD) model was developed to simulate flow field and gas hold-up in a pilot-scale oxidation ditch (OD). The volume of fluid (VOF) model and the mass flow inlet boundary condition for gas injection were introduced in this model. The simulated values of the flow velocities and the gas hold-up were verified by experimental measurements in the pilot-scale OD. The results showed that the gas hold-up at test-site 3, immediately downstream of the surface aerator, was the highest among all three test-sites. Most of the gas existed in the upper portion of the ditch and was close to the inner side of the channel. Based on the liquid–gas two-phase CFD model, three operating conditions with different setting height ratios of the submerged impellers were simulated. The simulated results suggested that the setting heights of the submerged impellers have significant impacts on the flow velocity distribution. Lowering the setting height could increase the flow velocity in the pilot-scale OD. An optimal setting height ratio of 0.273 was proposed, which would be beneficial for minimizing sludge sedimentation, especially near the inner side of the curve bend.

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Wang, Jiantao, Gang Liu, Xiong Jiang, and Bin Mou. "ρ-VOF: An interface sharpening method for gas–liquid flow simulation." Modern Physics Letters B 32, no. 12n13 (May 10, 2018): 1840017. http://dx.doi.org/10.1142/s0217984918400171.

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The study on simulation of compressible gas–liquid flow remains open. Popular methods are either confined to incompressible flow regime, or inevitably induce smear of the free interface. A new finite volume method for compressible two-phase flow simulation is contributed for this subject. First, the “heterogeneous equilibrium” assumption is introduced to the control volume, by hiring free interface reconstruction technology, the distribution of each component in the control volume is achieved. Next, AUSM[Formula: see text]-up (advection upstream splitting method) scheme is employed to calculate the convective fluxes and pressure fluxes, with the contact discontinuity characteristic considered, followed by the update of the whole flow field. The new method features on density-based pattern and interface reconstruction technology from VOF (volume of fluid), thus we name it “[Formula: see text]-VOF method”. Inherited from AUSM families and VOF, [Formula: see text]-VOF behaves as an all-speed method, capable of simulating shock in gas–liquid flow, and preserving the sharpness of the free interface. Gas–liquid shock tube is simulated to evaluate the method, from which good agreement is obtained between the predicted results and those of the cited literature, meanwhile, sharper free interface is identified. Finally, the capability and validity of [Formula: see text]-VOF method can be concluded in compressible gas–liquid flow simulation.

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Zhang, Zheng Fu, Jun Wei Wang, and Feng Bao. "Numerical Simulation of the Nozzle with Self-Oscillating Flow Using the VOF Model." Advanced Materials Research 479-481 (February 2012): 2380–82. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.2380.

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The jet water shape of the nozzle will become a self-oscillating shape, if the triangle and U shape models are made into the normal nozzle. Using the VOF model , the jet shape of the nozzle will be simulated through a commercial CFD software 'FLUENT'. The VOF model (Volume of Fluid) is a surface-tracking technique applied to a fixed Eulerian mesh. It is designed for two or more immiscible fluids where the position of the interface between the fluids is of interest. The CFD simulation results shows that the jet shape of the nozzle is oscillate in a fixed period.

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Azimi, Hamed, Saeid Shabanlou, Isa Ebtehaj, and Hossein Bonakdari. "Discharge Coefficient of Rectangular Side Weirs on Circular Channels." International Journal of Nonlinear Sciences and Numerical Simulation 17, no. 7-8 (December 1, 2016): 391–99. http://dx.doi.org/10.1515/ijnsns-2016-0033.

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AbstractIn this study, the flow turbulence and variations of the supercritical free surface flow in a circular channel along a side weir are simulated as three dimensional using the RNG k-ε turbulence model and volume of fluid (VOF) scheme. Comparison between the numerical model and experimental measurements shows that the numerical model simulates the free surface flow with good accuracy. According to the numerical model results, the specific energy variations along the side weir for the supercritical flow regime are almost constant and the energy drop is not significant but by increasing the side weir length the energy difference between the side weir upstream and downstream increases. Next, using the nonlinear regression (NLR) and analysis of the simulation results, some relationships for calculating the discharge coefficient of side weir on circular channels in supercritical flow regime are provided.

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Prinos, Panayotis, Maria Tsakiri, and Dimitris Souliotis. "A NUMERICAL SIMULATION OF THE WOS AND THE WAVE PROPAGATION ALONG A COASTAL DIKE." Coastal Engineering Proceedings 1, no. 33 (October 25, 2012): 49. http://dx.doi.org/10.9753/icce.v33.waves.49.

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Wave overtopping and the propagation of the waves on the crest and the landward slope of a coastal dike is investigated numerically. Wave overtopping conditions are simulated using the concept of the Wave Overtopping Simulator (WOS). Two numerical models of the WOS are constructed using the FLUENT 6.0.12 (FLUENT Inc. 2001) and the FLOW 3D 9.4 (FLOW 3D 2010) CFD codes. The former simulates the WOS without accounting for air entrainment while the latter accounts for air entrainment. The unsteady RANS equations, the RNG k-ε turbulence model and the VOF method are solved numerically, for "tracking" the free surface and the head of the "current" from the dike crest to the landward dike slope. The computed results from the two models are compared with each other and also against field measurements and proposed empirical relationships (Van der Meer et al. 2010).

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El Ouafa, Mohamed, Stephane Vincent, and Vincent Le Chenadec. "Monolithic Solvers for Incompressible Two-Phase Flows at Large Density and Viscosity Ratios." Fluids 6, no. 1 (January 5, 2021): 23. http://dx.doi.org/10.3390/fluids6010023.

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In this paper, we investigate the accuracy and robustness of three classes of methods for solving two-phase incompressible flows on a staggered grid. Here, the unsteady two-phase flow equations are simulated by finite volumes and penalty methods using implicit and monolithic approaches (such as the augmented Lagrangian and the fully coupled methods), where all velocity components and pressure variables are solved simultaneously (as opposed to segregated methods). The interface tracking is performed with a Volume-of-Fluid (VOF) method, using the Piecewise Linear Interface Construction (PLIC) technique. The home code Fugu is used for implementing the various methods. Our target application is the simulation of two-phase flows at high density and viscosity ratios, which are known to be challenging to simulate. The resulting strategies of monolithic approaches will be proven to be considerably better suited for these two-phase cases, they also allow to use larger time step than segregated methods.

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Yang, A. S. "Attitude-Adjustment-Induced Sloshing Characteristics in a Satellite Propellant Tank." Journal of Mechanics 28, no. 2 (May 8, 2012): 261–68. http://dx.doi.org/10.1017/jmech.2012.29.

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AbstractThe fluid sloshing behavior in a propellant tank is a major concern for the control and stabilization of a spacecraft. This research aims to investigate the attitude-adjustment-induced sloshing phenomenon in a satellite propellant tank under microgravities. In the analysis, the complicated interfacial flow was simulated using the transient three-dimensional conservation equations of mass and momentum with treatment of the surface tension effect at the interface boundary by the continuum surface force (CSF) model. The volume-of-fluid (VOF) method in conjunction with the piecewise linear interface construction (PLIC) technique was also utilized to describe the fluid interface motions. Computations were performed to simulate the sloshing process in the FORMOSAT-2 propellant tank for determining the impact disturbance properties generated during the pitch maneuver. Because the predicted disturbance moments were well below the design control moments, the attitude-adjustment-induced sloshing effect would not cause any performance deterioration for satisfactory attitude modification of the satellite.

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Yu, Yue, Zhi Wen, Xun Liang Liu, Fu Yong Su, Hai Peng Lan, and Xiao Hong Hao. "Hydraulic Model Experiment and Numerical Simulation of Bottom-Blowing Copper Smelting Furnace." Applied Mechanics and Materials 602-605 (August 2014): 546–53. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.546.

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A hydraulic model is used to study the flowing process within a bottom-blowing furnace designed by a company, and the VOF model is adopted to simulate its process. The VOF method can describe the formation, growing up and separation actions in theorizing process by comparing the simulation and experimental results, and this is a foundation of using a model to research the thermal process of the bottom-blowing furnace. It is indicated that a nozzle with disperse spouts can stir a larger zone, by comparing the influence on flowing process of four nozzles with different structures. The disperse spouts are benefit to increase the stirring and reaction efficiencies, but the pressure fluctuations near the nozzle export is more obvious, and it may affect the lifespan of the nozzle.

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Han, Shuang, Runhua Yang, Chaobo Li, and Lixin Yang. "The Wettability and Numerical Model of Different Silicon Microstructural Surfaces." Applied Sciences 9, no. 3 (February 8, 2019): 566. http://dx.doi.org/10.3390/app9030566.

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Wettability is an important property of solid surfaces and is widely used in many industries. In this work, seven silicon microstructure surfaces were made by plasma immersion ion implantation (PIII) technology. The experimental contact angles and theoretical contact angles of various surfaces were compared, which indicated that the classical theory had great limitations in predicting the static contact angles of complex structures. A parameterized microstructure surface was established by computational fluid dynamics (CFD) with a volume-of-fluid (VOF) model to analyze the reasons for the differences between experimental and theoretical contact angles. Comparing the results of experiments and simulations, it was found that the VOF model can simulate the contact angle of these surfaces very well. The geometrical models of the different microstructures were simplified, and waveforms of the surfaces were obtained.

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Gao, Donghong, Neil B. Morley, and Vijay Dhir. "Understanding Magnetic Field Gradient Effect From a Liquid Metal Droplet Movement." Journal of Fluids Engineering 126, no. 1 (January 1, 2004): 120–24. http://dx.doi.org/10.1115/1.1637638.

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A two-dimensional liquid metal droplet moving into magnetic field gradient regions in a vacuum space in the absence of gravity has been simulated in VOF-CSF method. The general one-fluid VOF model for tracking free surfaces, and associated CSF model for applying surface tension to free surfaces are formulated. The calculations show us that the droplet encounters strong magnetohydrodynamics (MHD) drag from the field gradient along moving path. Interaction of liquid motion with a magnetic field induces electrical currents and Lorentz force on the droplet. The force is always to oppose the liquid motion in both increased and decreased field conditions. More attention is given to understanding the MHD equations and numerical results.

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36

Zulkefle, Ahmad Aizan, Maslan Zainon, Zaihasraf Zakaria, Mohd Ariff Mat Hanafiah, Nurul Huda Abdul Razak, Seyed Ahmad Shahahmadi, Md Akhtaruzzaman, Kamaruzzaman Sopian, and Nowshad Amin. "A Comparative Study between Silicon Germanium and Germanium Solar Cells by Numerical Simulation." Applied Mechanics and Materials 761 (May 2015): 341–46. http://dx.doi.org/10.4028/www.scientific.net/amm.761.341.

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This paper presents the performance between silicon germanium (SiGe) and crystalline germanium (Ge) solar cells in terms of their simulated open circuit voltage, short circuit current density, fill factor and efficiency. The PC1D solar cell modeling software has been used to simulate and analyze the performance for both solar cells, and the total thickness is limited to 1μm of both SiGe and Ge solar cells. The Si0.1Ge0.9 thickness is varied from 10nm to 100nm to examine the effect of Si0.1Ge0.9 thickness on SiGe solar cell. The result of simulation exhibits the SiGe solar cell give a better performance compared to Ge solar cell. The efficiency of 9.74% (VOC = 0.48V, JSC = 27.86mA/cm2, FF =0.73) is achieved with Si0.1Ge0.9 layer of 0.1μm in thickness whilst 2.73% (VOC = 0.20V, JSC = 27.31mA/cm2, FF =0.50) efficiency is obtained from Ge solar cell.

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37

Alammari, Ammar, Ammar A. Alkahtani, Mohd Riduan Ahmad, Fuad Noman, Mona Riza Mohd Esa, Muhammad Haziq Mohammad Sabri, Sulaiman Ali Mohammad, Ahmed Salih Al-Khaleefa, Zen Kawasaki, and Vassilios Agelidis. "Kalman Filter and Wavelet Cross-Correlation for VHF Broadband Interferometer Lightning Mapping." Applied Sciences 10, no. 12 (June 20, 2020): 4238. http://dx.doi.org/10.3390/app10124238.

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Lightning mapping systems based on perpendicular crossed baseline interferometer (ITF) technology have been developed rapidly in recent years. Several processing methods have been proposed to estimate the temporal location and spatial map of lightning strikes. In this paper, a single very high frequency (VHF) ITF is used to simulate and augment the lightning maps. We perform a comparative study of using different processing techniques and procedures to enhance the localization and mapping of lightning VHF radiation. The benchmark environment involves the use of different noise reduction and cross-correlation methods. Moreover, interpolation techniques are introduced to smoothen the correlation peaks for more accurate lightning localization. A positive narrow bipolar event (NBE) lightning discharge is analyzed and the mapping procedure is confirmed using both simulated and measured lightning signals. The results indicate that a good estimation of lightning radiation sources is achieved when using wavelet denoising and cross-correlations in wavelet-domain (CCWD) with a minimal error of 3.46°. The investigations carried out in this study confirm that the ITF mapping system could effectively map the lightning VHF radiation source.

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Hu, Li-fen, Hao Wu, Qingtao Gong, Xiangyang Wang, and Wenbin Lv. "Time-Domain Flooding Simulation of a Damaged Warship." Marine Technology Society Journal 54, no. 2 (March 1, 2020): 69–78. http://dx.doi.org/10.4031/mtsj.54.2.7.

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AbstractUnderstanding of the complex dynamic behavior of damaged ships and floodwater remains limited for ship designers and safety authorities. In this work, a Navier-Stokes (NS) solver that combines the volume of fluid (VOF) method with overset mesh techniques is developed to simulate the flooding process of a damaged ship. The VOF method captures the fluid interface, and the turbulence effect on flows is considered with the k-ω model. The overset mesh techniques are employed to handle the mesh update following transient ship motions. Then, the results of a damaged barge with dynamic and overset mesh are compared with the experimental data. On the basis of this validation, the solver is applied to the flooding problems of a damaged warship. This research is intended to be a useful step toward the establishment of a stability criterion for damaged ships in the future.

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Wang, Ren Ping, Yong Ping Lei, and Yao Wu Shi. "Numerical Simulation of the Formation Process of the Keyhole in Laser Deep Penetration Welding." Advanced Materials Research 113-116 (June 2010): 1779–81. http://dx.doi.org/10.4028/www.scientific.net/amr.113-116.1779.

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In order to simulate accurately the formation process of the keyhole in laser deep penetration welding. Multiple reflection and Fresnel absorption are implemented simultaneously with the ray tracing technique in the keyhole. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Simulation results are compared with the experimental ones to verify its validity.

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Zhang, Lei, Ling Ling Wang, Zhen Zhen Yu, Yuan Bao Leng, Wan Zeng Song, and Bin Zhang. "Characteristics of Non-Linear Internal Waves in a Three-Dimensional Numerical Wave Tank." Applied Mechanics and Materials 212-213 (October 2012): 1123–30. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.1123.

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Internal waves have a significant impact on the hydrodynamic and stratification characteristics in the density stratified lakes and oceans. In order to reveal the features of internal waves, a three-dimensional numerical wave tank in regular terrain based on the computational fluid dynamics (CFD) model was established to simulate the processes of non-linear internal solitary waves propagation and evolution. The concept of a fraction volume of fluid (VOF) was employed to track the interface of the two-layer fluid. Comparisons were made between CFD model and weakly non-linear KdV theory, it was shown that the wave amplitude predictions by the CFD model agreed well with the KdV equation. On the other hand, the convergence flow and divergence flow at the water surface were captured successfully by the simulated spatial and temporal distributions of velocity. Some peculiar hydrodynamic characteristics, e. g. turbulence kinetic energy and its dissipation rate in the numerical wave tank were also identified and examined. Consequently, this paper provides a reliable method for understanding the phenomenon of internal waves in stratified water bodies.

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Zhang, Jun Xia, and Xiao Lin Xu. "Application of VOF Interfacial Tracking Model to Condensation Heat Transfer." Advanced Materials Research 619 (December 2012): 139–42. http://dx.doi.org/10.4028/www.scientific.net/amr.619.139.

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Condensation heat transfer used to the condenser as an important way of heat transfer is a phenomenon that involves flowing and heat and mass transfer of both gas and liquid phases. Thus, the development of its numerical prediction helps to the design of the condenser. At the present work, a VOF model was used to numerically simulate condensation heat transfer in a V-shape tube, obtaining volume fraction of vapor, location of liquid film and parameters of heat transfer. Results show that the VOF model may predict flow pattern of condensation and mass flux of condensation of vapor on the liquid film well. From computations, mass flux of condensation of vapor on the liquid film increases along vapor flowing, however, it tends to steady at the back part of the condenser tube. Flow pattern of condensation develops from annular flow at the inlet of the condenser tube to stratified flow, finally to plug flow at its back part. Velocity decreases along the tube length.

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42

Li-Fen, Hu, Qi Huibo, Li Yuemeng, Li Wubin, and Chen Shude. "The CFD Method-Based Research on Damaged Ship’s Flooding Process in Time-Domain." Polish Maritime Research 26, no. 1 (March 1, 2019): 72–81. http://dx.doi.org/10.2478/pomr-2019-0009.

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Abstract The flooding process is one of the main concerns of damaged ship stability. This paper combines the volume of fluid (VOF) method incorporated in the Navier-Stokes (NS) solver with dynamic mesh techniques to simulate the flooding of a damaged ship. The VOF method is used to capture the fluid interface, while the dynamic mesh techniques are applied to update the mesh as a result of transient ship motions. The time-domain flooding processes of a damaged barge and a rectangular cabin model are carried out based on the abovementioned method, and the computational results appear compatible with the experimental data. During the flooding process, the motion of the flooding flow at different stages is observed and compared with that observed in real conditions. The time-domain research of the flooding process is the starting point for subsequent establishment of damaged ship’s roll movement and capsizing the mechanism of dead ship condition in wave.

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43

Taamneh, Yazan. "Influence of Jordanian zeolite on the performance of a solar still: experiments and CFD simulation studies." Water Supply 16, no. 6 (June 2, 2016): 1700–1709. http://dx.doi.org/10.2166/ws.2016.091.

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Computational fluid dynamics (CFD) simulations were performed for experiments carried out with two identical pyramid-shaped solar stills. One was filled with Jordanian zeolite-seawater and the second was filled with seawater only. This work is focused on CFD analysis validation with experimental data conducted using a model of phase change interaction (evaporation-condensation model) inside the solar still. A volume-of-fluid (VOF) model was used to simulate the inter phase change through evaporation-condensation between zeolite-water and water vapor inside the two solar stills. The effect of the volume fraction of the zeolite particles (0 ≤ ϕ ≤ 0.05) on the heat and distillate yield inside the solar still was investigated. Based on the CFD simulation results, the hourly quantity of freshwater showed a good agreement with the corresponding experimental data. The present study has established the utility of using the VOF two phase flow model to provide a reasonable solution to the complicated inter phase mass transfer in a solar still.

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Johnson, D., S. R. Utembe, M. E. Jenkin, R. G. Derwent, G. D. Hayman, M. R. Alfarra, H. Coe, and G. McFiggans. "Simulating regional scale secondary organic aerosol formation during the TORCH 2003 campaign in the southern UK." Atmospheric Chemistry and Physics 6, no. 2 (February 8, 2006): 403–18. http://dx.doi.org/10.5194/acp-6-403-2006.

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Abstract. A photochemical trajectory model has been used to simulate the chemical evolution of air masses arriving at the TORCH field campaign site in the southern UK during late July and August 2003, a period which included a widespread and prolonged photochemical pollution episode. The model incorporates speciated emissions of 124 non-methane anthropogenic VOC and three representative biogenic VOC, coupled with a comprehensive description of the chemistry of their degradation. A representation of the gas/aerosol absorptive partitioning of ca. 2000 oxygenated organic species generated in the Master Chemical Mechanism (MCM v3.1) has been implemented, allowing simulation of the contribution to organic aerosol (OA) made by semi- and non-volatile products of VOC oxidation; emissions of primary organic aerosol (POA) and elemental carbon (EC) are also represented. Simulations of total OA mass concentrations in nine case study events (optimised by comparison with observed hourly-mean mass loadings derived from aerosol mass spectrometry measurements) imply that the OA can be ascribed to three general sources: (i) POA emissions; (ii) a "ubiquitous" background concentration of 0.7 µg m-3; and (iii) gas-to-aerosol transfer of lower volatility products of VOC oxidation generated by the regional scale processing of emitted VOC, but with all partitioning coefficients increased by a species-independent factor of 500. The requirement to scale the partitioning coefficients, and the implied background concentration, are both indicative of the occurrence of chemical processes within the aerosol which allow the oxidised organic species to react by association and/or accretion reactions which generate even lower volatility products, leading to a persistent, non-volatile secondary organic aerosol (SOA). The contribution of secondary organic material to the simulated OA results in significant elevations in the simulated ratio of organic carbon (OC) to EC, compared with the ratio of 1.1 assigned to the emitted components. For the selected case study events, [OC]/[EC] is calculated to lie in the range 2.7-9.8, values which are comparable with the high end of the range reported in the literature.

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45

Johnson, D., S. R. Utembe, M. E. Jenkin, R. G. Derwent, G. D. Hayman, M. R. Alfarra, H. Coe, and G. McFiggans. "Simulating regional scale secondary organic aerosol formation during the TORCH 2003 campaign in the southern UK." Atmospheric Chemistry and Physics Discussions 5, no. 4 (August 30, 2005): 7829–74. http://dx.doi.org/10.5194/acpd-5-7829-2005.

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Abstract. A photochemical trajectory model has been used to simulate the chemical evolution of air masses arriving at the TORCH field campaign site in the southern UK during late July and August 2003, a period which included a widespread and prolonged photochemical pollution episode. The model incorporates speciated emissions of 124 non-methane anthropogenic VOC and three representative biogenic VOC, coupled with a comprehensive description of the chemistry of their degradation. A representation of the gas/aerosol absorptive partitioning of ca. 2000 oxygenated organic species generated in the Master Chemical Mechanism (MCM v3.1) has been developed and implemented, allowing simulation of the contribution to organic aerosol (OA) made by semi- and non-volatile products of VOC oxidation; emissions of primary organic aerosol (POA) and elemental carbon (EC) are also represented. Simulations of total OA mass concentrations in nine case study events (optimised by comparison with observed mass loadings derived from aerosol mass spectrometry measurements) imply that the OA can be ascribed to three general sources: (i) POA emissions; (ii) a ubiquitous background concentration of 0.7 µg m−3; and (iii) gas-to-aerosol transfer of lower volatility products of VOC oxidation generated by the regional scale processing of emitted VOC, but with all partitioning coefficients increased by a species-independent factor of 500. The requirement to scale the partitioning coefficients, and the implied background concentration, are both indicative of the occurrence of chemical processes within the aerosol which allow the oxidised organic species to react by association and/or accretion reactions which generate even lower volatility products, leading to a persistent, non-volatile secondary organic aerosol (SOA). The contribution of secondary organic material to the simulated OA results in significant elevations in the simulated ratio of organic carbon (OC) to EC, compared with the ratio of 1.1 assigned to the emitted components. For the selected case study events, [OC]/[EC] is calculated to lie in the range 2.7–9.8, values which are comparable with the high end of the range reported in the literature.

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46

Gleed, R. D., and J. P. Mortola. "Ventilation in newborn rats after gestation at simulated high altitude." Journal of Applied Physiology 70, no. 3 (March 1, 1991): 1146–51. http://dx.doi.org/10.1152/jappl.1991.70.3.1146.

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Pregnant rats were kept at a simulated altitude of 4,500 m (PO2 91 Torr) for the whole of gestation and returned to sea level 1 day after giving birth. During pregnancy, body weight gain and food intake were approximately 30% less than in controls at sea level. Measurements were made on the 1-day-old (HYPO) pups after a few hours at sea level. In normoxia, ventilation (VE) measured by flow plethysmography was more (+17%) and O2 consumption (VO2) measured by a manometric method was less (-19%) than in control (CONT) pups; in HYPO pups VE/VO2 was 44% greater than in CONT pups. In acute hyperoxia, VE/VO2 of HYPO and CONT pups decreased by a similar amount (15-20%), indicating some limitation in O2 availability for both groups of pups in normoxia. However, VE/VO2 of HYPO pups, even in hyperoxia, remained above (+34%) that of CONT pups. HYPO pups weighed slightly less than CONT pups, their lungs were hypoplastic, and their hearts were a larger fraction of body weight. An additional group of female rats was acclimatized (8 days) to high altitude before insemination. During pregnancy, body weight gain and food intake of these females were similar to those of pregnant rats at sea level. Measurements on the 1-day-old pups of this group were similar to those of HYPO pups. We conclude that newborn rats born after hypoxic gestation present metabolic adaptation (low VO2) and acclimatization (high VE/VO2), possibly because of hypoxemia. Maternal acclimatization before insemination substantially alters maternal growth in hypoxia but does not affect neonatal outcome.

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Xu, Rang Shu, Xiao Wen Chen, Jian Ming Yang, Zhi Wei Dong, and Min Li Bai. "Research on a Scheme of Real-Time Measuring of Lubrication Oil Quantity in an Aero-Engine Tank." Advanced Materials Research 317-319 (August 2011): 2079–84. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.2079.

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The composition and principles of the digital measuring system was investigated on the basis of digital oil measuring method. Fly attitude-oil quality - measuring height data tables were generated by using UG software calculation of oil quantity characteristics. Then the oil surface angle under different fly attitude and overload was calculated through coordinate transformation method. Finally the amount of oil was calculated by three-dimensional liner interpolation method. Meanwhile, the free surface movement of lubricating oil tank under different overload was simulated through VOF numerical model. The results showed that using UG software to build model and generate fly attitude-oil quantity-measuring height data tables is accurate and useful. The VOF model method is a complement to digital measurement, which can track the phase interface of continuum, analyze the movement of oil qualitatively and calculate the dead volume of digital method.

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Yu, Qun, Xiao Dong Hu, Long Huan Huang, and Yue Lin. "Optimum Design and Analysis of Metal Delivery System for Magnesium Alloy Plates with Twin-Roll Casting Process." Applied Mechanics and Materials 395-396 (September 2013): 1150–53. http://dx.doi.org/10.4028/www.scientific.net/amm.395-396.1150.

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Using physical and numerical simulation method，metal delivery system of twin-roll casting magnesium alloy process was researched. The Anycasting software was used to simulate different flow systems by VOF method. And based on similar principles, an acrylic experimental model with the ratio of 1:1 was designed. The dam’s size and position were optimized by simulations and experiments. The flow distribution is uniform along the horizontal of the casting roller. Numerical simulation and physical simulation are in good coincidence.

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Li, Chuan Qi, Jie Gong, and Xiang Fu Li. "Numerical Simulation of Flow over a Spillway with Turbulence Model." Applied Mechanics and Materials 90-93 (September 2011): 2511–15. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.2511.

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In this paper, the Standard k- ε equation turbulence model was used to simulate three-dimensional flow over a spillway. The volume of fluid method (VOF) was introduced into the iteration of calculation to solve the free water surface, and segregated solver was used with the PISO pressure-velocity coupling scheme. The free surface, the magnitude and distribution of the velocity, the pressure on the spillway surface and so on were obtained. The simulation results were in good agreement with the experiment data.

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Feng, Xing, Wan Qing Wu, and Feng Li Zhang. "The Deflection Angle Impact on the Oil Containment by Boom Based on the Numerical Wave Flume." Advanced Materials Research 183-185 (January 2011): 495–99. http://dx.doi.org/10.4028/www.scientific.net/amr.183-185.495.

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The 2-D numerical wave flume, based on the Reynolds Averaged Navier-Stokes equations and the standard turbulence model, was developed to simulate the turbulent flows with the free surface, in which the volume of fluid (VOF) method was used to handle the large deformation of the free surface and the relaxation approach of combined wave generation and absorbing was implemented, utilizing the commercial CFD software-FLUENT. The relationship of the wave parameters, initial failure velocity and the deflection angle was investigated.

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Journal articles on the topic 'VOF simulace'

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