Three-dimensional numerical investigation of solid particle erosion in gate valves

2013 ◽  
Vol 228 (10) ◽  
pp. 1670-1679 ◽  
Author(s):  
Zhe Lin ◽  
Xiao-Dong Ruan ◽  
Zu-Chao Zhu ◽  
Xin Fu
Keyword(s):  
Three Dimensional ◽  
Particle Diameter ◽  
Flux Ratio ◽  
Pneumatic Conveying ◽  
Cavity Depth ◽  
Fluid Analysis ◽  
Orthogonal Experiments ◽  
Total Particle ◽  
Computational Fluid Dynamics Cfd ◽  
Pass Through

Gate valves, which are widely applied in pneumatic conveying systems, are vulnerable to erosion by particles. It is thus important to investigate the erosion in gate valves from the perspective of fluid analysis, and then to predict and improve their lifetimes. The effects of valve geometry and gas–solid flow conditions on valve erosion are investigated. Since a gate valve usually operates fully open to let fluid pass through, the geometry is simplified as a cavity. As gate valves are always placed horizontally in industrial situations, investigated cavities are placed horizontally, and the erosion damage to the bottom half of the aft wall (surface T), which is most likely to be eroded, is studied. A computational fluid dynamics (CFD) based two-way Eulerian–Lagrangian procedue is used to predict the erosion severity. The simulation procedure is validated by comparing the CFD results with those obtained from experiments of a pipe and an elbow, and also with the erosion region of a damaged valve. For convenience, the total erosion ratio, defined as the ratio of the mass eroded on a particular surface to the total particle mass passing through the pipe inlet during the same time, is introduced. The results show that the total erosion ratio of surface T is largely independent of the mass flux ratio, pipe diameter and cavity depth. Meanwhile, the total erosion ratio increases with cavity width and particle diameter, while it decreases with inlet velocity. According to the fitted results, a simple erosion formula is proposed and validated by the CFD results in another 16 orthogonal experiments. Furthermore, the formula is improved for various values of Brinell hardness of carbon steel and sharpness factors of particles.

Research on the Pneumatic Conveying of the Sand in the Horizontal Pipe Based on FLUENT

2016 ◽  
Vol 11 (2) ◽  
pp. 159-165 ◽  
Author(s):  
Dan-yang Li ◽  
Shu Liu ◽  
Xiao-ning Wang
Keyword(s):  
Particle Diameter ◽  
Flow Characteristics ◽  
Axial Direction ◽  
Theoretical Research ◽  
Pneumatic Conveying ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Actual Measurement ◽  
Fluid Analysis ◽  
Euler Model

Abstract The pneumatic conveying experiment bed has been established to study the flow characteristics of air- solids two-phase flow in horizontal pipeline. Euler model was applied to simulate it based on analysis of Gambit and fluid analysis software-fluent. The simulated results indicated: under the same gas phase conveying flow and pressure, the bigger particle diameter is, the bigger pressure drop is in the horizontal pipeline. The smaller particle diameter is, the more uniform of the particle’s distribution is, and the more easily obtaining the acceleration is. Particle concentration at the bottom of the horizontal pipe is increasing in the axial direction, while close to the tail pipe it will be reduce. The simulated conclusion is consistent with the actual measurement results, herewith rendering some footing for engineering design and theoretical research on pneumatic conveying systems.

An Investigation on Ventilation of Building-Integrated Photovoltaics System Using Numerical Modeling

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Siu-Kit Lau ◽  
Yong Zhao ◽  
Stephen Siu Yu Lau ◽  
Chao Yuan ◽  
Veronika Shabunko
Keyword(s):  
Three Dimensional ◽  
Three Dimensional Model ◽  
Cell Temperature ◽  
Cavity Depth ◽  
Air Cavity ◽  
Building Integrated Photovoltaics ◽  
Geometric Configurations ◽  
Flow Disturbances ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

Abstract This study numerically investigates the thermal behavior and airflow characteristics of the building-integrated photovoltaic (BIPV) façade. A three-dimensional model is developed based on the typical BIPV façade. Computational fluid dynamics (CFD) with the shear stress transport (SST) κ-omega turbulent model is used in the study. The effects of geometric configurations on the BIPV cell temperature in steady state are evaluated including the sizes of the bottom and top openings and the depth of the back air cavity (or so-called cavity depth). When the sizes of the inlet and outlet openings are the same, the effects on the decrease of cell temperature are limited. By enlarging the bottom (inlet) opening, the impact of ventilation in the cavity behind is more significant and the cell temperature decreases. Cavity depth is also a vital factor affecting BIPV cell temperature. The paper identifies the optimal cavity depth of approximately 100–125 mm. Flow disturbance and a vortex may be observed at the bottom and top of the air cavity, respectively, as the cavity depth increases which negatively affects the ventilation causing these flow disturbances to increase the cell temperature. Thermal effects of environmental conditions are compared with regard to two selected BIPV configurations. The wind velocity and the attack angle also have an obvious impact on cell temperature. Ambient temperature and solar irradiance exhibit a linear relationship with BIPV cell temperature as expected.

3-D Euler-Lagrange CFD Simulation of Particle Impact on Carrier Fluid Through Gate Valve

2012 ◽  
Author(s):  
Zhe Lin ◽  
Xiaodong Ruan ◽  
Baoling Cui ◽  
Zuchao Zhu
Keyword(s):  
Mass Flux ◽  
Gate Valve ◽  
Particle Diameter ◽  
Flux Ratio ◽  
Flow Coefficient ◽  
Phase Flow ◽  
Pneumatic Conveying ◽  
Flow Properties ◽  
Carrier Fluid ◽  
Particle Parameters

Gate valves are widely used in dilute Pneumatic conveying systems. The flow characteristic of carrier fluid through the valve changes under the effect of particles. In this study, in order to obtain the influence of particle parameters on carrier fluid while flowing through a gate valve, a three dimensional Euler-Lagrange model is used to simulate gas-solid flow at three opening degrees of valve. Since inlet velocity of air is very small and the Mach number is less than 10%, the carrier fluid is set as incompressible Newtonian fluid. The investigated particle parameters include mass flux ratio (κ) and diameter of particles (d). An important coefficient namely flow coefficient (Cv) is calculated to express the flow properties. Our results demonstrate that the particles do little, if any, effect on the flow properties when the valve is in full open position. However, with the closure of valve, the influence of particles on carrier fluid becomes more significant. Besides, the influence extent of particles on carrier fluid increases with mass flux ratio while decreases with the increasing of particle diameter. This study gives a suggestion that for dilute phase flow of Pneumatic conveying, the influence of particles on carrier fluid can be neglected if valve is of full open condition, otherwise the effect should not be neglected. Further study will focus on two phase flow field in valves under transient conditions.

scholarly journals Computational fluid dynamics (CFD) simulation analysis on retinal gas cover rates using computational eye models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Makoto Gozawa ◽  
Yoshihiro Takamura ◽  
Tomoe Aoki ◽  
Kentaro Iwasaki ◽  
Masaru Inatani
Keyword(s):  
Cfd Simulation ◽  
Simulation Analysis ◽  
Fluid Dynamic ◽  
Fluid Analysis ◽  
Intraocular Gas ◽  
Pars Plana ◽  
Computational Fluid Dynamics Cfd ◽  
Multiple Breaks ◽  
Gas Volume ◽  
Wall Wettability

AbstractWe investigated the change in the retinal gas cover rates due to intraocular gas volume and positions using computational eye models and demonstrated the appropriate position after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Computational fluid dynamic (CFD) software was used to calculate the retinal wall wettability of a computational pseudophakic eye models using fluid analysis. The model utilized different gas volumes from 10 to 90%, in increments of 10% to the vitreous cavity in the supine, sitting, lateral, prone with closed eyes, and prone positions. Then, the gas cover rates of the retina were measured in each quadrant. When breaks are limited to the inferior retina anterior to the equator or multiple breaks are observed in two or more quadrants anterior to the equator, supine position maintained 100% gas cover rates in all breaks for the longest duration compared with other positions. When breaks are limited to either superior, nasal, or temporal retina, sitting, lower temporal, and lower nasal position were maintained at 100% gas cover rates for the longest duration, respectively. Our results may contribute to better surgical outcomes of RRDs and a reduction in the duration of the postoperative prone position.

Assessment of Unsteady Flows in Turbines

1992 ◽  
Vol 114 (1) ◽  
pp. 79-90 ◽  
Author(s):  
O. P. Sharma ◽  
G. F. Pickett ◽  
R. H. Ni
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Research Activities ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
The Impact

The impacts of unsteady flow research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations that identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.

scholarly journals Tephra4D: A Python-Based Model for High-Resolution Tephra Transport and Deposition Simulations—Applications at Sakurajima Volcano, Japan

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 331
Author(s):  
Kosei Takishita ◽  
Alexandros P. Poulidis ◽  
Masato Iguchi
Keyword(s):  
Scale Effects ◽  
Three Dimensional ◽  
Particle Diameter ◽  
Terminal Velocity ◽  
Diameter Distribution ◽  
Velocity Variation ◽  
Small Scale ◽  
Modified Model ◽  
Sakurajima Volcano ◽  
Ash Transport

Vulcanian eruptions (short-lived explosions consisting of a rising thermal) occur daily in volcanoes around the world. Such small-scale eruptions represent a challenge in numerical modeling due to local-scale effects, such as the volcano’s topography impact on atmospheric circulation and near-vent plume dynamics, that need to be accounted for. In an effort to improve the applicability of Tephra2, a commonly-used advection-diffusion model, in the case of vulcanian eruptions, a number of key modifications were carried out: (i) the ability to solve the equations over bending plume, (ii) temporally-evolving three-dimensional meteorological fields, (iii) the replacement of the particle diameter distribution with observed particle terminal velocity distribution which provides a simple way to account for the settling velocity variation due to particle shape and density. We verified the advantage of our modified model (Tephra4D) in the tephra dispersion from vulcanian eruptions by comparing the calculations and disdrometer observations of tephra sedimentation from four eruptions at Sakurajima volcano, Japan. The simulations of the eruptions show that Tephra4D is useful for eruptions in which small-scale movement contributes significantly to ash transport mainly due to the consideration for orographic winds in advection.

The Effect of Bench Arrangements on the Natural Ventilation of a Multispan Greenhouse

2013 ◽  
Author(s):  
Sunita Kruger ◽  
Leon Pretorius
Keyword(s):  
Fluid Dynamics ◽  
Natural Ventilation ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Low Velocity ◽  
Lower Velocity ◽  
Cfd Models ◽  
Temperature Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Plant Level

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably. Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.

The Lid-Driven Cavity Flow: A Synthesis of Qualitative and Quantitative Observations

1984 ◽  
Vol 106 (4) ◽  
pp. 390-398 ◽  
Author(s):  
J. R. Koseff ◽  
R. L. Street
Keyword(s):  
Heat Flux ◽  
Flow Visualization ◽  
Three Dimensional ◽  
Symmetry Plane ◽  
Lower Boundary ◽  
Thymol Blue ◽  
Width Ratio ◽  
Cavity Depth ◽  
Driven Cavity ◽  
Turbulent Characteristics

A synthesis of observations of flow in a three-dimensional lid-driven cavity is presented through the use of flow visualization pictures and velocity and heat flux measurements. The ratio of the cavity depth to width used was 1:1 and the span to width ratio was 3:1. Flow visualization was accomplished using the thymol blue technique and by rheoscopic liquid illuminated by laser-light sheets. Velocity measurements were made using a two-component laser-Doppler-anemometer and the heat flux on the lower boundary of the cavity was measured using flush mounted sensors. The flow is three-dimensional and is weaker at the symmetry plane than that predicted by accurate two-dimensional numerical simulations. Local three-dimensional features, such as corner vortices in the end-wall regions and longitudinal Taylor-Go¨rtler-like vortices, are significant influences on the flow. The flow is unsteady in the region of the downstream secondary eddy at higher Reynolds numbers (Re) and exhibits turbulent characteristics in this region at Re = 10,000.

Mechanism and Flow Control on the Mismatching of Impeller and Vaned Diffuser Caused by Inlet Prewhirl for Centrifugal Compressors

2016 ◽  
Author(s):  
Qiangqiang Huang ◽  
Xinqian Zheng ◽  
Aolin Wang
Keyword(s):  
Flow Control ◽  
Control Method ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Vaned Diffuser ◽  
Inlet Distortion ◽  
Computational Fluid Dynamics Cfd ◽  
Stagger Angle ◽  
Good Agreement ◽  
Matching Relation

Air often flows into compressors with inlet prewhirl, because it will obtain a circumferential component of velocity via inlet distortion or swirl generators such as inlet guide vanes. A lot of research has shown that inlet prewhirl does influence the characteristics of components, but the change of the matching relation between the components caused by inlet prewhirl is still unclear. This paper investigates the influence of inlet prewhirl on the matching of the impeller and the diffuser and proposes a flow control method to cure mismatching. The approach combines steady three-dimensional Reynolds-averaged Navier-Stokes (RANS) simulations with theoretical analysis and modeling. The result shows that a compressor whose impeller and diffuser match well at zero prewhirl will go to mismatching at non-zero prewhirl. The diffuser throat gets too large to match the impeller at positive prewhirl and gets too small for matching at negative prewhirl. The choking mass flow of the impeller is more sensitive to inlet prewhirl than that of the diffuser, which is the main reason for the mismatching. To cure the mismatching via adjusting the diffuser vanes stagger angle, a one-dimensional method based on incidence matching has been proposed to yield a control schedule for adjusting the diffuser. The optimal stagger angle predicted by analytical method has good agreement with that predicted by computational fluid dynamics (CFD). The compressor is able to operate efficiently in a much broader flow range with the control schedule. The flow range, where the efficiency is above 80%, of the datum compressor and the compressor only employing inlet prewhirl and no control are just 25.3% and 31.8%, respectively. For the compressor following the control schedule, the flow range is improved up to 46.5%. This paper also provides the perspective of components matching to think about inlet distortion.

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