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Goodarz Ahmadi - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of effects of inner cone on flow field performance and Erosion Rate of cyclone separators
Separation and Purification Technology, 2018Co-Authors: Farzad Parvaz, Seyyed Hossein Hosseini, Khairy Elsayed, Goodarz AhmadiAbstract:Abstract Gas cyclones have many industrial applications for separation of solids and liquids from gases. The geometry of the cyclone is the most influential parameter for its performance. This study investigates the effect of presence of an inner cone located at the bottom of the cyclone on the performance of the cyclone separator. Several CFD simulations in cyclones with inner cones with different diameters and heights were performed using the Reynolds stress turbulence model (RSM). The collection efficiency of the cyclone was studied using the Eulerian-Lagrangian approach. The results showed that the maximum tangential velocity is 1.6–1.7 times the inlet velocity. On the other hand, in the radial sections crossing the inner cone, the gradients of the axial and tangential velocities are zero. The maximum axial and tangential velocities occurred in the region between the top of the inner cone to the vortex finder. It was found that by increasing the inner cone height at constant diameter, the cyclone collection performance improves. An increase in the diameter of the inner cone, however, leads to a decrease in the cyclone performance. In overall, with an increase in the inner cone height and diameter, the pressure loss decreases. Finally, the Erosion study was conducted using the Det Norske Veritas (DNV) Erosion model. It was found that the value of coefficient of restitution affects the predicted Erosion Rate. In addition, the collection efficiency decreases when the Erosion effect was included in the CFD model especially for higher velocities.
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the effects of wall roughness on Erosion Rate in gas solid turbulent annular pipe flow
Powder Technology, 2015Co-Authors: M Jafari, Z Mansoori, Saffar M Avval, Goodarz AhmadiAbstract:Abstract In the present study, the effects of wall roughness on Erosion Rate for gas–solid flows in horizontal annular pipes for different ratios of inner to outer radii and also for different values of solid particle concentration are investigated. The results are compared with earlier studies, and the effect of various parameters is discussed. The impingement angles and impact velocities of solid particles, which are needed for using the comprehensive Erosion model, are evaluated using a four-way coupled Eulerian–Lagrangian simulation approach of gas–solid flows. The turbulent gas phase flow is solved using the k–e model. For the simulation of particle movement, the fluctuations of gas phase velocity are evaluated by the eddy interaction method. The numerical results indicate that the solid particle induced Erosion Rate at the outer wall of annular pipes is considerably larger in comparison with a simple circular pipe with the same outer radius, and the Erosion Rate further increases as the radius ratio increases. The results also show that the Erosion Rates at both inner and outer walls increase as wall roughness increases and are much higher compared with those for smooth walls or walls with a small roughness.
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modeling and numerical investigation of Erosion Rate for turbulent two phase gas solid flow in horizontal pipes
Powder Technology, 2014Co-Authors: M Jafari, Z Mansoori, Saffar M Avval, Goodarz Ahmadi, A EbadiAbstract:Abstract A modified model for prediction of Erosion Rate in pipe flows is presented based on the simulation of the fluid fluctuating velocities with the Discrete Random Walk model. Turbulence modulation of gas–solid flow in a horizontal pipe is investigated numerically using a four-way coupled Eulerian–Lagrangian approach. The particle impingement angle and impact velocity are evaluated and used for predicting the Erosion Rate by the available and newly developed models. The gas–solid flow simulation results are validated by comparison of the model predictions with the earlier experimental data for two-phase pipe flows. A modified model for Erosion was developed that accounts for the effect of particle size to simulate the wall impact velocity caused by fluid turbulence. It is demonstRated that, when compared to the previous simplified Erosion models, the new model can estimate Erosion Rate more accuRately, especially for small particles in gas–solid flows.
Sean D Willett - One of the best experts on this subject based on the ideXlab platform.
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some analytical methods for converting thermochronometric age to Erosion Rate
Geochemistry Geophysics Geosystems, 2013Co-Authors: Sean D Willett, Mark T BrandonAbstract:[1] An analytical method is presented for converting thermochronometric ages to surface Erosion or, equivalently, exhumation Rate. The method incorpoRates the two most important thermal processes during cooling by Erosion: the dependence of closure temperature on cooling Rate and the advection of heat by rock motion toward the Earth's surface. Two thermal models are considered: (1) a steady state model, valid for low Erosion Rates; and (2) an eroding half-space model, which has no steady state, but captures the transient increase of geothermal gradient with Erosion. In each case, it is assumed that data consist of one or more thermochronometric ages, present-day surface geothermal gradient, and topographic information including the elevation at which the age was obtained. Analytical solutions are provided to derive the Erosion Rate from these data either as an explicit expression for the steady case or as a root-finding problem for the transient case. A graphical method for plotting age against Erosion Rate and geothermal gradient is presented as a method for solving the root finding problem and for tracking analytical errors in observations of age and surface geothermal gradient. The graphical method is also appropriate for comparing data from different elevations or from different thermochronometric systems. Examples are provided using synthetic data or published data from the literature.
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controls on the patterns of topography and Erosion Rate in a critical orogen
Journal of Geophysical Research, 2007Co-Authors: Drew B Stolar, Gerard H Roe, Sean D WillettAbstract:[1] We solve for the steady state patterns of Erosion Rate and topography in a critical wedge to understand the mutual adjustment of tectonics, Erosion, and topography in the absence and presence of spatial variations in precipitation Rate. We consider steady state systems in which tectonics favors a critical topographic form, assumed to be the mean elevation across the range, and in which surface Erosion by rivers and hillslopes opeRates on a two-dimensional landscape. We find that (1) a nonuniform critical topographic form implies a nonuniform pattern of ridge-valley relief and hence a nonuniform pattern of Erosion Rate, and (2) when the system is forced by local variations in precipitation Rate, maintenance of the critical topographic form requires a local response of rock uplift that greatly dampens changes in topography. We apply these concepts to the western side of the Olympic Mountains of Washington State, where mean elevation, ridge-valley relief, and precipitation Rates increase from the coast to the topographic crest of the range. We find that the main control on the Erosion Rate pattern is the pattern in mean elevation and the amount of precipitation. In contrast, the pattern of precipitation is only a minor control. As a whole, our work demonstRates an approach for developing the theoretical context that is necessary for interpreting spatial associations between patterns in topography, precipitation, and Erosion in natural orogens.
Susan L Brantley - One of the best experts on this subject based on the ideXlab platform.
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chemical reactions porosity and microfracturing in shale during weathering the effect of Erosion Rate
Geochimica et Cosmochimica Acta, 2020Co-Authors: Daniella M Rempe, William E Dietrich, Joshua A West, Teng Chiu Lin, Lixin Jin, Susan L BrantleyAbstract:Abstract The Rate of chemical weathering has been observed to increase with the Rate of physical Erosion in published comparisons of many catchments, but the mechanisms that couple these processes are not well understood. We investigated this question by examining the chemical weathering and porosity profiles from catchments developed on marine shale located in Pennsylvania, USA (Susquehanna Shale Hills Critical Zone Observatory, SSHCZO); California, USA (Eel River Critical Zone Observatory, ERCZO); and Taiwan (Fushan Experimental Forest). The protolith compositions, protolith porosities, and the depths of regolith at these sites are roughly similar while the catchments are characterized by large differences in Erosion Rate (1–3 mm yr−1 in Fushan ≫ 0.2–0.4 mm yr−1 in ERCZO ≫ 0.01–0.025 mm yr−1 in SSHCZO). The natural experiment did not totally isolate Erosion as a variable: mean annual precipitation varied along the Erosion gradient (4.2 m yr−1 in Fushan > 1.9 m yr−1 in ERCZO > 1.1 m yr−1 in SSHCZO), so the fastest eroding site experiences nearly twice the mean annual temperature of the other two. Even though Erosion Rates varied by about 100×, the depth of pyrite and carbonate depletion (defined here as regolith thickness) is roughly the same, consistent with chemical weathering of those minerals keeping up with Erosion at the three sites. These minerals were always observed to be the deepest to react, and they reacted until 100% depletion. In two of three of the catchments where borehole observations were available for ridges, these minerals weathered across narrow reaction fronts. On the other hand, for the rock-forming clay mineral chlorite, the depth interval of weathering was wide and the extent of depletion observed at the land surface decreased with increasing Erosion/precipitation. Thus, chemical weathering of the clay did not keep pace with Erosion Rate. But perhaps the biggest difference among the shales is that in the fast-eroding sites, microfractures account for 30–60% of the total porosity while in the slow-eroding shale, dissolution could be directly related to secondary porosity. We argue that the microfractures increase the influx of oxygen at depth and decrease the size of diffusion-limited internal domains of matrix, accelerating weathering of pyrite and carbonate under high Erosion-Rate conditions. Thus, microfracturing is a process that can couple physical Erosion and chemical weathering in shales.
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a mathematical model for steady state regolith production at constant Erosion Rate
Earth Surface Processes and Landforms, 2010Co-Authors: Marina I Lebedeva, Raymond C Fletcher, Susan L BrantleyAbstract:It has been hypothesized that many soil profiles reach a steady-state thickness. In this work, such profiles were simulated using a one-dimensional model of reaction with advective and diffusive solute transport. A model ‘rock’ is considered, consisting of albite that weathers to kaolinite in the presence of chemically inert quartz. The model yields three different steady-state regimes of weathering. At the lowest Erosion Rates, a local-equilibrium regime is established where albite is completely depleted in the weathering zone. This regime is equivalent to the transport-limited regime described in the literature. With an increase in Erosion Rate, transition and kinetic regimes are established. In the transition regime, both albite and kaolinite are present in the weathering zone, but albite does not persist to the soil–air interface. In the weathering-limited regime, here called the kinetic regime, albite persists to the soil–air interface. The steady-state thickness of regolith decreases with increasing Erosion Rate in the local equilibrium and transition regimes, but in the kinetic regime, this thickness is independent of Erosion Rate. Analytical expressions derived from the model are used to show that regolith production Rates decrease exponentially with regolith thickness. The steady-state regolith thickness increases with the Darcy velocity of the pore fluid, and in the local equilibrium regime may vary markedly with small variations in this velocity and Erosion Rate. In the weathering-limited regime, the temperature dependences for chemical weathering Rates are related to the activation energy for the Rate constant for mineral reaction and to the ΔH of dissolution, while for local equilibrium regimes they are related to the ΔH only. The model illustRates how geochemical and geomorphological observations are related for a simple compositional system. The insights provided will be useful in interpreting natural regolith profiles. Copyright © 2010 John Wiley & Sons, Ltd.
Xian Xue - One of the best experts on this subject based on the ideXlab platform.
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potential wind Erosion Rate response to climate and land use changes in the watershed of the ningxia inner mongolia reach of the yellow river china 1986 2013
Earth Surface Processes and Landforms, 2017Co-Authors: Tao Wang, Xian XueAbstract:Climate and land-use changes could strongly affect wind Erosion and in turn cause a series of environmental problems. Thus, the objective of this study was to assess potential wind Erosion Rate (PWER) response to climate and land-use changes in the watershed of the Ningxia–Inner Mongolia Reach of the Yellow River (NIMRYR), China. The watershed of NIMRYR suffers from serious wind Erosion hazards, and over recent decades, wind Erosion intensity and distribution has changed, following climate and land-use changes. To understand these processes in the NIMRYR watershed, the IntegRated Wind Erosion Modelling System (IWEMS) and the Revised Wind Erosion Equation (RWEQ) were used to calculate the PWER under different climate conditions and land-use scenarios, and to assess the influences of climate and land-use changes on the PWER. The results show the PWER in the whole watershed had a significant declining trend from 1986 to 2013. The results of the relationship among PWER, climate change, and land-use changes showed that climate change was the dominant control on the PWER change in this watershed. Compared to the period 1986–1995, the average PWER decreased 23.32% and 64.98% as a result of climate change in the periods 1996–2005 and 2006–2013, respectively. In contrast with climate change, the effects of land-use changes on the average PWER were much lower, and represented a change in PWER of less than 3.3% across the whole watershed. The study method we used could provide some valuable reference for wind Erosion modelling, and the research results should help climate and land-use researchers to develop stRategies to reduce wind Erosion. Copyright © 2017 John Wiley & Sons, Ltd.
M Jafari - One of the best experts on this subject based on the ideXlab platform.
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the effects of wall roughness on Erosion Rate in gas solid turbulent annular pipe flow
Powder Technology, 2015Co-Authors: M Jafari, Z Mansoori, Saffar M Avval, Goodarz AhmadiAbstract:Abstract In the present study, the effects of wall roughness on Erosion Rate for gas–solid flows in horizontal annular pipes for different ratios of inner to outer radii and also for different values of solid particle concentration are investigated. The results are compared with earlier studies, and the effect of various parameters is discussed. The impingement angles and impact velocities of solid particles, which are needed for using the comprehensive Erosion model, are evaluated using a four-way coupled Eulerian–Lagrangian simulation approach of gas–solid flows. The turbulent gas phase flow is solved using the k–e model. For the simulation of particle movement, the fluctuations of gas phase velocity are evaluated by the eddy interaction method. The numerical results indicate that the solid particle induced Erosion Rate at the outer wall of annular pipes is considerably larger in comparison with a simple circular pipe with the same outer radius, and the Erosion Rate further increases as the radius ratio increases. The results also show that the Erosion Rates at both inner and outer walls increase as wall roughness increases and are much higher compared with those for smooth walls or walls with a small roughness.
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modeling and numerical investigation of Erosion Rate for turbulent two phase gas solid flow in horizontal pipes
Powder Technology, 2014Co-Authors: M Jafari, Z Mansoori, Saffar M Avval, Goodarz Ahmadi, A EbadiAbstract:Abstract A modified model for prediction of Erosion Rate in pipe flows is presented based on the simulation of the fluid fluctuating velocities with the Discrete Random Walk model. Turbulence modulation of gas–solid flow in a horizontal pipe is investigated numerically using a four-way coupled Eulerian–Lagrangian approach. The particle impingement angle and impact velocity are evaluated and used for predicting the Erosion Rate by the available and newly developed models. The gas–solid flow simulation results are validated by comparison of the model predictions with the earlier experimental data for two-phase pipe flows. A modified model for Erosion was developed that accounts for the effect of particle size to simulate the wall impact velocity caused by fluid turbulence. It is demonstRated that, when compared to the previous simplified Erosion models, the new model can estimate Erosion Rate more accuRately, especially for small particles in gas–solid flows.