Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4615
M. Alihosseini, P. Thamsen
In sewer sediment management, the removal of depositions using hydraulic flushing gates has recently gotten great attention. Despite numerous investigations, the complex process of sediment transport under flushing waves is not yet well understood. The present work aims to calibrate and validate a coupled computational fluid dynamics and discrete element method (CFD-DEM) to study the fluid-sediment interaction in sewers. The CFD part of the simulation was carried out in the software Ansys Fluent which is two-way coupled to the DEM software EDEM. The multiphase model volume of fluid (VOF) was used to simulate the flushing wave, while the sediments were handled as DEM particles using the discrete phase model (DPM). To validate the 3D model, experimental work has been performed in a circular laboratory pipe with sand and gravel of different size distributions. A construction of a sluice gate was installed to realize the flushing event, which is similar to a dam-break wave. The evolution of the sediment bed and the scouring efficiency of the waves were examined under different flushing conditions. The results showed that the CFD-DEM method could be used to investigate the performance of flushing devices and various features of sediment transport which are not easy to obtain in the laboratory or field.
{"title":"On Scouring Efficiency of Flush Waves in Sewers: A Numerical and Experimental Study","authors":"M. Alihosseini, P. Thamsen","doi":"10.1115/ajkfluids2019-4615","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4615","url":null,"abstract":"\u0000 In sewer sediment management, the removal of depositions using hydraulic flushing gates has recently gotten great attention. Despite numerous investigations, the complex process of sediment transport under flushing waves is not yet well understood. The present work aims to calibrate and validate a coupled computational fluid dynamics and discrete element method (CFD-DEM) to study the fluid-sediment interaction in sewers. The CFD part of the simulation was carried out in the software Ansys Fluent which is two-way coupled to the DEM software EDEM. The multiphase model volume of fluid (VOF) was used to simulate the flushing wave, while the sediments were handled as DEM particles using the discrete phase model (DPM). To validate the 3D model, experimental work has been performed in a circular laboratory pipe with sand and gravel of different size distributions. A construction of a sluice gate was installed to realize the flushing event, which is similar to a dam-break wave. The evolution of the sediment bed and the scouring efficiency of the waves were examined under different flushing conditions. The results showed that the CFD-DEM method could be used to investigate the performance of flushing devices and various features of sediment transport which are not easy to obtain in the laboratory or field.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127020259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4663
T. Kamei, T. Kanagawa
The present study theoretically elucidates an effect of the viscosity and the thermal conductivity on the propagation process of finite amplitude disturbance in bubbly liquids by deriving two types of weakly nonlinear wave equations. Appropriate choices of a set of scaling relations of physical parameters characterizing waves, that is, the wavelength, incident wave frequency, propagation speed, yield the derivation systematically. From the combination of appropriate scaling relations and the method of multiple scales, we can derive the Korteweg–de Vries–Burgers equation for the low frequency long wave and the nonlinear Schrödinger equation for slowly varying envelope wave of the quasi-monochromatic short carrier wave. As a result, the incorporation of conservation equation of energy affects nonlinear, dispersion, and dissipation terms for both long and short waves. Especially, the viscosity and the thermal conductivity lead to change considerably the form of coefficient of dissipation term.
{"title":"Two Types of Nonlinear Pressure Waves in Bubbly Liquids Incorporating Viscosity and Thermal Conductivity","authors":"T. Kamei, T. Kanagawa","doi":"10.1115/ajkfluids2019-4663","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4663","url":null,"abstract":"\u0000 The present study theoretically elucidates an effect of the viscosity and the thermal conductivity on the propagation process of finite amplitude disturbance in bubbly liquids by deriving two types of weakly nonlinear wave equations. Appropriate choices of a set of scaling relations of physical parameters characterizing waves, that is, the wavelength, incident wave frequency, propagation speed, yield the derivation systematically. From the combination of appropriate scaling relations and the method of multiple scales, we can derive the Korteweg–de Vries–Burgers equation for the low frequency long wave and the nonlinear Schrödinger equation for slowly varying envelope wave of the quasi-monochromatic short carrier wave. As a result, the incorporation of conservation equation of energy affects nonlinear, dispersion, and dissipation terms for both long and short waves. Especially, the viscosity and the thermal conductivity lead to change considerably the form of coefficient of dissipation term.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134115596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4642
A. Jaberi, M. Tadjfar
Studying of injectors with non-circular geometries has recently come to the spotlight of researchers as a potential technique to improve the liquid injection characteristics of different systems. In this work, the flow physics and breakup of two-dimensional liquid jets issued from flat slits into still air were experimentally investigated. Three injectors with aspect ratios of 30, 60 and 90 and thickness of 0.35 mm were manufactured to obtain two-dimensional liquid flow at the nozzle exit. The tests were performed for a wide range of volume flow rate, varying from 10 L/h to 240 L/h. Backlight shadowgraphy and high speed photography were employed to capture the flow dynamics of the jets. In order to capture every detail of the flow, photos of the liquid jet were taken from two views with 90° from each other. Using the visualizations, different regimes of the jet flow were explored and a regime map was proposed to distinguish these regimes based on the non-dimensional parameters of the liquid jet. Moreover, quantitative description of the main features of jet flows were obtained using an in-house image processing program. Measurements of different parameters including convergence length, maximum width, breakup length, sheet thickness to name a few, were conducted.
{"title":"Experimental Investigation on Flow and Breakup of Two-Dimensional Liquid Jets","authors":"A. Jaberi, M. Tadjfar","doi":"10.1115/ajkfluids2019-4642","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4642","url":null,"abstract":"\u0000 Studying of injectors with non-circular geometries has recently come to the spotlight of researchers as a potential technique to improve the liquid injection characteristics of different systems. In this work, the flow physics and breakup of two-dimensional liquid jets issued from flat slits into still air were experimentally investigated. Three injectors with aspect ratios of 30, 60 and 90 and thickness of 0.35 mm were manufactured to obtain two-dimensional liquid flow at the nozzle exit. The tests were performed for a wide range of volume flow rate, varying from 10 L/h to 240 L/h. Backlight shadowgraphy and high speed photography were employed to capture the flow dynamics of the jets. In order to capture every detail of the flow, photos of the liquid jet were taken from two views with 90° from each other. Using the visualizations, different regimes of the jet flow were explored and a regime map was proposed to distinguish these regimes based on the non-dimensional parameters of the liquid jet. Moreover, quantitative description of the main features of jet flows were obtained using an in-house image processing program. Measurements of different parameters including convergence length, maximum width, breakup length, sheet thickness to name a few, were conducted.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128567503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5181
J. Weber, M. Bobek, S. Rowan, Jing-Shyang Yang, R. Breault
The US Department of Energy’s National Energy Technology Laboratory is pursuing the development of advanced energy conversion technologies, many of which use gas-solid reactors such as fluidized beds and risers. To understand these units and provide high fidelity particle velocities for model development and validation efforts, particle tracking velocimetry (PTV) is typically used and remains one of only a few ways to extract particle velocities from dense multiphase flow experiments. Combined with the rapidly improving cameras (higher frame rates, higher resolutions, and lower cost) and access to high performance computers, new particle tracking tools are needed. Tracker is an opensource, cross platform particle tracking velocimetry application for tracking objects in videos and image stacks. The goal of this project is to provide a tool that is, open source, continuously developed, does not rely on expensive software, parallel, has a graphical user interface (GUI), one continuous pipeline (from reading the file to post processing), well documented, and continuously tested and verified. The application has extensive preprocessing tools, two tracking methods including poly-projection and template matching, visualization tools, and post-processing tools. The techniques are tested using both synthetic data and real experimental images. The application is extremely flexible and is easily extended to other tracking techniques, with plans to add correlation-based algorithms and optical flow algorithms. The high-fidelity data being generated is now being used to validate computational fluid dynamic models that then will be used to predict the performance of these reactors, helping to achieve the US Department of Energy’s goal of developing novel, compact gas-solid reactors.
{"title":"Tracker: An Opensource Particle Tracking Velocimetry (PTV) Application Applied to Multiphase Flow Reactors","authors":"J. Weber, M. Bobek, S. Rowan, Jing-Shyang Yang, R. Breault","doi":"10.1115/ajkfluids2019-5181","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5181","url":null,"abstract":"\u0000 The US Department of Energy’s National Energy Technology Laboratory is pursuing the development of advanced energy conversion technologies, many of which use gas-solid reactors such as fluidized beds and risers. To understand these units and provide high fidelity particle velocities for model development and validation efforts, particle tracking velocimetry (PTV) is typically used and remains one of only a few ways to extract particle velocities from dense multiphase flow experiments. Combined with the rapidly improving cameras (higher frame rates, higher resolutions, and lower cost) and access to high performance computers, new particle tracking tools are needed.\u0000 Tracker is an opensource, cross platform particle tracking velocimetry application for tracking objects in videos and image stacks. The goal of this project is to provide a tool that is, open source, continuously developed, does not rely on expensive software, parallel, has a graphical user interface (GUI), one continuous pipeline (from reading the file to post processing), well documented, and continuously tested and verified.\u0000 The application has extensive preprocessing tools, two tracking methods including poly-projection and template matching, visualization tools, and post-processing tools. The techniques are tested using both synthetic data and real experimental images. The application is extremely flexible and is easily extended to other tracking techniques, with plans to add correlation-based algorithms and optical flow algorithms.\u0000 The high-fidelity data being generated is now being used to validate computational fluid dynamic models that then will be used to predict the performance of these reactors, helping to achieve the US Department of Energy’s goal of developing novel, compact gas-solid reactors.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116822406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5291
Sufia Khatoon, J. Phirani, S. S. Bahga
In reservoir simulations, model parameters such as porosity and permeability are often uncertain and therefore better estimates of these parameters are obtained by matching the simulation predictions with the production history. Bayesian inference provides a convenient way of estimating parameters of a mathematical model, starting from a probable range of parameter values and knowing the production history. Bayesian inference techniques for history matching require computationally expensive Monte Carlo simulations, which limit their use in petroleum reservoir engineering. To overcome this limitation, we perform accelerated Bayesian inference based history matching by employing polynomial chaos (PC) expansions to represent random variables and stochastic processes. As a substitute to computationally expensive Monte Carlo simulations, we use a stochastic technique based on PC expansions for propagation of uncertainty from model parameters to model predictions. The PC expansions of the stochastic variables are obtained using relatively few deterministic simulations, which are then used to calculate the probability density of the model predictions. These results are used along with the measured data to obtain a better estimate (posterior distribution) of the model parameters using the Bayes rule. We demonstrate this method for history matching using an example case of SPE1CASE2 problem of SPEs Comparative Solution Projects. We estimate the porosity and permeability of the reservoir from limited and noisy production data.
{"title":"Polynomial Chaos Based Solution to Inverse Problems in Petroleum Reservoir Engineering","authors":"Sufia Khatoon, J. Phirani, S. S. Bahga","doi":"10.1115/ajkfluids2019-5291","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5291","url":null,"abstract":"\u0000 In reservoir simulations, model parameters such as porosity and permeability are often uncertain and therefore better estimates of these parameters are obtained by matching the simulation predictions with the production history. Bayesian inference provides a convenient way of estimating parameters of a mathematical model, starting from a probable range of parameter values and knowing the production history. Bayesian inference techniques for history matching require computationally expensive Monte Carlo simulations, which limit their use in petroleum reservoir engineering. To overcome this limitation, we perform accelerated Bayesian inference based history matching by employing polynomial chaos (PC) expansions to represent random variables and stochastic processes. As a substitute to computationally expensive Monte Carlo simulations, we use a stochastic technique based on PC expansions for propagation of uncertainty from model parameters to model predictions. The PC expansions of the stochastic variables are obtained using relatively few deterministic simulations, which are then used to calculate the probability density of the model predictions. These results are used along with the measured data to obtain a better estimate (posterior distribution) of the model parameters using the Bayes rule. We demonstrate this method for history matching using an example case of SPE1CASE2 problem of SPEs Comparative Solution Projects. We estimate the porosity and permeability of the reservoir from limited and noisy production data.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127167543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5355
Yikun Peng, Shanshan Li, Z. Pan
Evaporation of sessile droplets on superhydrophobic substrates is an important fundamental problem. Classic diffusion-based model only considers vapor diffusion and assumes an isothermal profile along the droplet interface. The diffusion based model extremely overestimates the evaporation rate for droplets evaporating on heated superhydrophobic substrates, and results in a deviation of evaporation lifetime up to 52.5%. The present 3D numerical model considers various effects including vapor diffusion, buoyancy-driven flow and evaporative cooling, etc., with conjugate heat and mass transfer solved throughout the computational domain. Evaporation of a sessile water droplet with an initial volume of 3 μL is investigated on superhydrophobic substrates (contact angle: 160 deg) with heating temperature ranging from 40 °C to 60 °C. The deviation of evaporation lifetime is less than 2% for 40 °C and 50 °C substrates. A single-roll asymmetric vortex is produced inside the droplet rather than the symmetric recirculation flow predicted by 2D axisymmetric simulation. The evaporative cooling along the droplet interface is observed, but the coolest point appears on the one side of the droplet instead of the droplet top owing to the asymmetrical rolling flow inside the droplet. It is seen that the buoyancy-driven convection significantly speeds up the evaporation as the substrate temperature increases. Influence of relative humidity is also discussed and indicates a stronger impact for low substrate temperature. The present model not only precisely predicts the instantaneous evaporation rate and the total evaporation time, but also reveals the important underlying transport characteristics, which provides new insights into evaporation of water droplets resting on heated superhydrophobic substrates.
{"title":"3D Numerical Study of the Transport Characteristics of an Evaporating Water Droplet Sessile on Heated Superhydrophobic Substrates","authors":"Yikun Peng, Shanshan Li, Z. Pan","doi":"10.1115/ajkfluids2019-5355","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5355","url":null,"abstract":"\u0000 Evaporation of sessile droplets on superhydrophobic substrates is an important fundamental problem. Classic diffusion-based model only considers vapor diffusion and assumes an isothermal profile along the droplet interface. The diffusion based model extremely overestimates the evaporation rate for droplets evaporating on heated superhydrophobic substrates, and results in a deviation of evaporation lifetime up to 52.5%. The present 3D numerical model considers various effects including vapor diffusion, buoyancy-driven flow and evaporative cooling, etc., with conjugate heat and mass transfer solved throughout the computational domain. Evaporation of a sessile water droplet with an initial volume of 3 μL is investigated on superhydrophobic substrates (contact angle: 160 deg) with heating temperature ranging from 40 °C to 60 °C. The deviation of evaporation lifetime is less than 2% for 40 °C and 50 °C substrates. A single-roll asymmetric vortex is produced inside the droplet rather than the symmetric recirculation flow predicted by 2D axisymmetric simulation. The evaporative cooling along the droplet interface is observed, but the coolest point appears on the one side of the droplet instead of the droplet top owing to the asymmetrical rolling flow inside the droplet. It is seen that the buoyancy-driven convection significantly speeds up the evaporation as the substrate temperature increases. Influence of relative humidity is also discussed and indicates a stronger impact for low substrate temperature. The present model not only precisely predicts the instantaneous evaporation rate and the total evaporation time, but also reveals the important underlying transport characteristics, which provides new insights into evaporation of water droplets resting on heated superhydrophobic substrates.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131374340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4647
Y. Murai, Daichi Saito, Daiki Ushiyama, H. Park, Y. Tasaka
How microbubbles behave inside turbulent boundary layers are investigated experimentally. Water electrolysis is applied for generation of microbubbles in water, of which electrodes are flash mounted on the solid wall in the upstream section of the measurement area. Four kinds of solid surfaces are examined to compare the microbubble distribution. For a circular cylinder of the radius R = 22 mm at Re = 5,000, we found that microbubbles depart from the surface earlier than the liquid boundary layer. For an elliptic cylinder of the curvature radius of R = 60 mm and a hydrofoil of NACA0040, microbubble injection made the separation point move downstream in the range of 9,000 < Re < 90,000. To compare the effect with the cases of flat solid surfaces (R = infinity), we visualized three-dimensional distribution of microbubbles with color-coded volumetric illumination technique. The result has shown formation of microbubble clusters intermittently, which has Coulomb potential due to negative electric charge on bubble interfaces.
{"title":"Visualization of Microbubble Distribution Inside Turbulent Boundary Layer Along Flat and Curved Solid Surfaces","authors":"Y. Murai, Daichi Saito, Daiki Ushiyama, H. Park, Y. Tasaka","doi":"10.1115/ajkfluids2019-4647","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4647","url":null,"abstract":"\u0000 How microbubbles behave inside turbulent boundary layers are investigated experimentally. Water electrolysis is applied for generation of microbubbles in water, of which electrodes are flash mounted on the solid wall in the upstream section of the measurement area. Four kinds of solid surfaces are examined to compare the microbubble distribution. For a circular cylinder of the radius R = 22 mm at Re = 5,000, we found that microbubbles depart from the surface earlier than the liquid boundary layer. For an elliptic cylinder of the curvature radius of R = 60 mm and a hydrofoil of NACA0040, microbubble injection made the separation point move downstream in the range of 9,000 < Re < 90,000. To compare the effect with the cases of flat solid surfaces (R = infinity), we visualized three-dimensional distribution of microbubbles with color-coded volumetric illumination technique. The result has shown formation of microbubble clusters intermittently, which has Coulomb potential due to negative electric charge on bubble interfaces.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131117391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5235
O. Schilling
A numerical implementation of a large number of Reynolds-averaged Navier–Stokes (RANS) models based on two-, three-, four-equation, and Reynolds stress turbulence models (using either the turbulent kinetic energy dissipation rate or the turbulent lengthscale) in an Eulerian, finite-difference shock-capturing code is described. The code uses third-order weighted essentially nonoscillatory (WENO) reconstruction of the advective fluxes, and second- or fourth-order central difference derivatives for the computation of spatial gradients. A third-order TVD Runge–Kutta time-evolution scheme is used to evolve the fields in time. Improved closures for the turbulence production terms, compressibility corrections, mixture transport coefficients, and a consistent initialization methodology for the turbulent fields are briefly summarized. The code framework allows for systematic comparisons of detailed predictions from a variety of turbulence models of increasing complexity. Applications of the code with selected K–ε based models are illustrated for each of the three instabilities. Simulations of Rayleigh–Taylor unstable flows for Atwood numbers 0.1–0.9 are shown to be consistent with previous implicit LES (ILES) results and with the expectation of increased asymmetry in the mixing layer characteristics with increasing stratification. Simulations of reshocked Richtmyer–Meshkov turbulent mixing corresponding to experiments with light-to-heavy transition in air/sulfur hexafluoride and incident shock Mach number Mas = 1.50, and heavy-to-light transition in sulfur hexafluoride/air with Mas = 1.45 are shown to be in generally good agreement with both pre- and post-reshock mixing layer widths. Finally, simulations of the seven Brown–Roshko Kelvin–Helmholtz experiments with various velocity and density ratios using nitrogen, helium, and air are shown to give mixing layer predictions in good agreement with data. The results indicate that the numerical algorithms and turbulence models are suitable for simulating these classes of inhomogeneous turbulent flows.
{"title":"Reynolds-Averaged Navier-Stokes Modeling of Turbulent Rayleigh-Taylor, Richtmyer-Meshkov, and Kelvin-Helmholtz Mixing Using a Higher-Order Shock-Capturing Method","authors":"O. Schilling","doi":"10.1115/ajkfluids2019-5235","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5235","url":null,"abstract":"\u0000 A numerical implementation of a large number of Reynolds-averaged Navier–Stokes (RANS) models based on two-, three-, four-equation, and Reynolds stress turbulence models (using either the turbulent kinetic energy dissipation rate or the turbulent lengthscale) in an Eulerian, finite-difference shock-capturing code is described. The code uses third-order weighted essentially nonoscillatory (WENO) reconstruction of the advective fluxes, and second- or fourth-order central difference derivatives for the computation of spatial gradients. A third-order TVD Runge–Kutta time-evolution scheme is used to evolve the fields in time. Improved closures for the turbulence production terms, compressibility corrections, mixture transport coefficients, and a consistent initialization methodology for the turbulent fields are briefly summarized. The code framework allows for systematic comparisons of detailed predictions from a variety of turbulence models of increasing complexity. Applications of the code with selected K–ε based models are illustrated for each of the three instabilities. Simulations of Rayleigh–Taylor unstable flows for Atwood numbers 0.1–0.9 are shown to be consistent with previous implicit LES (ILES) results and with the expectation of increased asymmetry in the mixing layer characteristics with increasing stratification. Simulations of reshocked Richtmyer–Meshkov turbulent mixing corresponding to experiments with light-to-heavy transition in air/sulfur hexafluoride and incident shock Mach number Mas = 1.50, and heavy-to-light transition in sulfur hexafluoride/air with Mas = 1.45 are shown to be in generally good agreement with both pre- and post-reshock mixing layer widths. Finally, simulations of the seven Brown–Roshko Kelvin–Helmholtz experiments with various velocity and density ratios using nitrogen, helium, and air are shown to give mixing layer predictions in good agreement with data. The results indicate that the numerical algorithms and turbulence models are suitable for simulating these classes of inhomogeneous turbulent flows.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117145349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5449
T. Fukui, M. Kawaguchi, K. Morinishi
The rheological properties of a suspension depend on particle shape, spatial arrangement of the particles and hydrodynamic interactions as well as the concentration of the particles. So far, we proposed a two-way coupling numerical scheme to evaluate the effects of particle rotation on the rheological properties. This particle rotation decreases the fluid resistance. However, these studies were conducted on the condition that suspended particles were homogeneously distributed. Therefore, the particles in this study are randomly scattered in a suspension for better practical applications. Pressure-driven suspension flow simulations were conducted to consider the effects of inertia on the relationship between spatial arrangement of the particles and the rheological properties of a suspension. The channel width and axial length were set 400 μm and 1620 μm, respectively, and periodic boundary conditions were applied in the flow direction. The rigid spherical particles whose diameter was 20 μm were randomly scattered in the channel as an initial condition. The concentration of the suspension was set 1.02% for dilute assumption, and the suspension flows with the Reynolds number from 2 to 128 were reproduced in order to investigate the inertial effects of the suspended particles on the rheological properties. The rheological properties of the suspension were evaluated in terms of power-law index (non-Newtonian index). The velocity profile of a suspension for low Reynolds number conditions exhibited almost parabolic. This indicates the suspension behaves as a Newtonian fluid. For higher Reynolds number conditions, on the other hand, the lift force on the particles increased and they migrated toward the equilibrium y-axis position, where the lift force is zero. These changes in the y-axis position of the particles caused a change in microstructure of the suspension, which were followed by a change in macroscopic rheological properties. Owing to these microstructure changes, the non-Newtonian (thixotropic) properties were enhanced as the Reynolds number increased.
{"title":"Relationship Between Macroscopic Rheological Properties and Microstructure of a Dilute Suspension by a Two-Way Coupling Numerical Scheme","authors":"T. Fukui, M. Kawaguchi, K. Morinishi","doi":"10.1115/ajkfluids2019-5449","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5449","url":null,"abstract":"\u0000 The rheological properties of a suspension depend on particle shape, spatial arrangement of the particles and hydrodynamic interactions as well as the concentration of the particles. So far, we proposed a two-way coupling numerical scheme to evaluate the effects of particle rotation on the rheological properties. This particle rotation decreases the fluid resistance. However, these studies were conducted on the condition that suspended particles were homogeneously distributed. Therefore, the particles in this study are randomly scattered in a suspension for better practical applications. Pressure-driven suspension flow simulations were conducted to consider the effects of inertia on the relationship between spatial arrangement of the particles and the rheological properties of a suspension. The channel width and axial length were set 400 μm and 1620 μm, respectively, and periodic boundary conditions were applied in the flow direction. The rigid spherical particles whose diameter was 20 μm were randomly scattered in the channel as an initial condition. The concentration of the suspension was set 1.02% for dilute assumption, and the suspension flows with the Reynolds number from 2 to 128 were reproduced in order to investigate the inertial effects of the suspended particles on the rheological properties. The rheological properties of the suspension were evaluated in terms of power-law index (non-Newtonian index). The velocity profile of a suspension for low Reynolds number conditions exhibited almost parabolic. This indicates the suspension behaves as a Newtonian fluid. For higher Reynolds number conditions, on the other hand, the lift force on the particles increased and they migrated toward the equilibrium y-axis position, where the lift force is zero. These changes in the y-axis position of the particles caused a change in microstructure of the suspension, which were followed by a change in macroscopic rheological properties. Owing to these microstructure changes, the non-Newtonian (thixotropic) properties were enhanced as the Reynolds number increased.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124544777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4917
Jiang Bian, Xuewen Cao
Condensation phenomenon has been studied actively for decades because of its extensive and significant applications in various fields of technology and engineering. The condensation phenomenon of condensable component in supersonic flows is still not understood very well as a result of the complex nucleation and droplet growth process, especially the condensation characteristic of gas mixture. In this paper, the Laval nozzle was designed based on the bi-cubic curve, state equation of real gas, arc plus straight line and viscous correction of boundary layer. The physical and mathematical models were developed to predict the condensation process in the supersonic air flows based on the nucleation and droplet growth theories, surface tension model and gas-liquid governing equations. The condensation processes of gaseous water/air binary (single condensable) gas and water/ethanol/air ternary (double condensable) gas mixture in the designed nozzle were simulated, and the reliability of the established models was verified by the experimental data. By comparing the condensation process of water/air binary gas with water/ethanol ternary gas, the influence of the second condensable component on the condensation process was analyzed. The results show that in the condensation process of gaseous water, as the pressure and temperature of water vapor decrease in the nozzle, spontaneous condensation occurs further downstream the nozzle throat. The nucleation rate grows rapidly from 0 to peak in a very short distance. With the consumption of water vapor, due to the decrease of the degree of supercooling, the nucleation environment is destroyed, and the nucleation rate quickly decreases to 0. The nucleation process is rapid in time and space, while the droplet growth process could maintain longer. The droplet number and mass fraction increase continuously till the nozzle outlet. There is a weak condensation in the nozzle due to the release of latent heat, but it is not obvious because the air acts as a heat container and absorbs the latent heat released by condensation. In the water/ethanol/air ternary system, the ethanol nucleates prior to water vapor. With the increase of supercooling, water vapor also begins to nucleate. In essence, there are two kinds of condensation nuclei (water nuclei and ethanol nuclei), and both the water and ethanol vapor can aggregate on these two kinds of condensation nuclei. Compared with the condensation process of water, the Wilson point of condensation is closer to the throat and the outlet mass fraction of liquid phase is greater in the condensation process of water/ethanol mixture, which shows that the water and ethanol can affect and promote each other. The maximum nucleation rate, droplet growth rate, droplet radius and outlet mass fraction of liquid phase of water/air binary and water/ethanol/air ternary mixture are about 9.46 × 1026 m−3s−1 and 2.57 × 1027 m−3s−1, 1.65 × 10−5 m/s and 1.02 × 10−5m/s, 1.32 × 10−7m and 1.63 ×
{"title":"Research on the Condensation Process of Gaseous Water and Water/Ethanol Mixture in the Laval Nozzle","authors":"Jiang Bian, Xuewen Cao","doi":"10.1115/ajkfluids2019-4917","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4917","url":null,"abstract":"\u0000 Condensation phenomenon has been studied actively for decades because of its extensive and significant applications in various fields of technology and engineering. The condensation phenomenon of condensable component in supersonic flows is still not understood very well as a result of the complex nucleation and droplet growth process, especially the condensation characteristic of gas mixture. In this paper, the Laval nozzle was designed based on the bi-cubic curve, state equation of real gas, arc plus straight line and viscous correction of boundary layer. The physical and mathematical models were developed to predict the condensation process in the supersonic air flows based on the nucleation and droplet growth theories, surface tension model and gas-liquid governing equations. The condensation processes of gaseous water/air binary (single condensable) gas and water/ethanol/air ternary (double condensable) gas mixture in the designed nozzle were simulated, and the reliability of the established models was verified by the experimental data. By comparing the condensation process of water/air binary gas with water/ethanol ternary gas, the influence of the second condensable component on the condensation process was analyzed. The results show that in the condensation process of gaseous water, as the pressure and temperature of water vapor decrease in the nozzle, spontaneous condensation occurs further downstream the nozzle throat. The nucleation rate grows rapidly from 0 to peak in a very short distance. With the consumption of water vapor, due to the decrease of the degree of supercooling, the nucleation environment is destroyed, and the nucleation rate quickly decreases to 0. The nucleation process is rapid in time and space, while the droplet growth process could maintain longer. The droplet number and mass fraction increase continuously till the nozzle outlet. There is a weak condensation in the nozzle due to the release of latent heat, but it is not obvious because the air acts as a heat container and absorbs the latent heat released by condensation.\u0000 In the water/ethanol/air ternary system, the ethanol nucleates prior to water vapor. With the increase of supercooling, water vapor also begins to nucleate. In essence, there are two kinds of condensation nuclei (water nuclei and ethanol nuclei), and both the water and ethanol vapor can aggregate on these two kinds of condensation nuclei. Compared with the condensation process of water, the Wilson point of condensation is closer to the throat and the outlet mass fraction of liquid phase is greater in the condensation process of water/ethanol mixture, which shows that the water and ethanol can affect and promote each other. The maximum nucleation rate, droplet growth rate, droplet radius and outlet mass fraction of liquid phase of water/air binary and water/ethanol/air ternary mixture are about 9.46 × 1026 m−3s−1 and 2.57 × 1027 m−3s−1, 1.65 × 10−5 m/s and 1.02 × 10−5m/s, 1.32 × 10−7m and 1.63 ×","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"30 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124615223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：