scholarly journals The investigation of the cavitation processes in the radial labyrinth pump

2018 ◽  
Vol 8 (1) ◽  
pp. 322-328
Author(s):  
Moloshnyi Oleksandr ◽  
Szulc Przemyslaw
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Volume Fraction ◽  
Mechanical Energy ◽  
Circular Cross Section ◽  
Back Side ◽  
Numerical Investigations ◽  
Numerical Research ◽  
The Moment ◽  
Velocity Pressure

Abstract The paper concerns the analysis of the cavitation processes in the flow passages of the radial labyrinth pump. The object of the analysis contains the active (moving) and the passive (stationary) discs with straight channels trajectory and semi-circular cross-section. The conversion of the mechanical energy into hydraulic based on the exchange of the momentum between the liquid remaining in the moving and the stationary areas of the discs as well as on the centrifugal increase of the moment of momentum. The analysis of the cavitation processes was realized by the experimental research and the numerical simulation. In the article, the comparison of the cavitation characteristics was carried out. The numerical simulation had given similar results to the experimental one, the process of the cavitation was visualized. Furthermore, numerical investigations helped to describe the cavitation development. The results of the numerical research such as the distributions of the velocity, pressure and vapor volume fraction in the passages were presented. At first, cavitation starts on the back side and on the top of the wall between channels of the active disc. Further, the cavitation areas are growing along the axis of the channels. Eventually, they separation was observed and vortices of the vapour-gas mixture in the middle of the channels were formed. This phenomenon is so-called super cavitation vortices.

Hydrodynamic Predictions of Dense Gas-Solids Flow in CFB Riser

2012 ◽  
Vol 516-517 ◽  
pp. 917-920
Author(s):  
Xue Yao Wang ◽  
Xue Zhi Wu ◽  
Sheng Dian Wang ◽  
Xiang Xu ◽  
Yun Han Xiao
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Circular Cross Section ◽  
Deep Understanding ◽  
Experimental Methods ◽  
Concentration Profiles ◽  
Simulation Research ◽  
Solids Concentration ◽  
High Efficient ◽  
2D Numerical Simulation

The flow character in riser is important for deep understanding the steady and high-efficient running of CFBs. In this paper, the 2D numerical simulation research for bench-scale circular cross-section riser based on EMMS methods is carried out. The solids’ transient moving profiles are captured. By analyzing the axial solids concentration profiles by simulation and experimental methods, the practicability of the EMMS model is verified.

scholarly journals Numerical simulation of minor losses coefficient on the example of elbows

2018 ◽  
Vol 180 ◽  
pp. 02093
Author(s):  
Smyk Emil ◽  
Mrozik Dariusz ◽  
Olszewski Łukasz ◽  
Peszyński Kazimierz
Keyword(s):  
Numerical Simulation ◽  
Numerical Methods ◽  
Numerical Method ◽  
Cross Section ◽  
Analytical Methods ◽  
Circular Cross Section ◽  
Experimental Methods ◽  
Loss Coefficient ◽  
Complicated Problem ◽  
Minor Losses

Determining of minor losses coefficient is very complicated problem. Analytical methods are often very difficult and experimental methods are very expensive and time-consuming. Consequently, the use of numerical methods seems to be a good solution, but there are no publications describing this issue. Therefore, the paper is describing the numerical method of determining the minor loss coefficient ξ on the example of elbows with circular cross-section.

Velocity Field and Energy Dissipation in Viscoplastic Flow in Tubes of Non-Circular Cross-Section

2014 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Felipe Godoy
Keyword(s):  
Energy Dissipation ◽  
Velocity Field ◽  
Yield Stress ◽  
Cross Section ◽  
Mechanical Energy ◽  
Longitudinal Velocity ◽  
Circular Cross Section ◽  
Viscoplastic Flow ◽  
Entire Cross Section ◽  
Cross Sectional

An analytical method for determining the velocity field, shear stress and energy dissipation in viscoplastic flow in non-circular straight tubes is presented. Bingham’s model of fluid is used for the case of tubes with several cross-sectional contours that can be arbitrarily chosen through a shape factor imposed in the solution for the longitudinal velocity. The analysis is extended to steady flow in tubes in which the cross-section contour exhibits sharp corners. In these cases three flow zones are distinguished: stagnant, non-zero deformation, and plug zones. The method provides the expressions for determining the boundaries and characteristics of those three zones for a wide variety of cross-section shapes. In particular the dynamics of plug-zones for large values of the yield stress and for contours that markedly differ from circumferences is analyzed. Energy dissipation is determined throughout the entire cross-section, so that the effect of shape on mechanical energy loss is assessed in terms of the yield stress and viscosity of the fluid. Some general expressions that help understand energy dissipation mechanisms are derived by using natural coordinates for the velocity field and related variables. These results draw on several recent works from other researchers and the present authors, which have highlighted the significant difficulty of determining the zones of zero deformation in viscoplastic flow when the related solid boundaries are not elementary.

scholarly journals An integral equation method for the homogenization of unidirectional fibre-reinforced media; antiplane elasticity and other potential problems

2017 ◽  
Vol 473 (2201) ◽  
pp. 20170080 ◽  
Author(s):  
Duncan Joyce ◽  
William J. Parnell ◽  
Raphaël C. Assier ◽  
I. David Abrahams
Keyword(s):  
Cross Section ◽  
Volume Fraction ◽  
Effective Properties ◽  
Circular Cross Section ◽  
Rational Functions ◽  
High Volume ◽  
Cross Sectional ◽  
Antiplane Elasticity ◽  
Unidirectional Fibre ◽  
Explicit Expressions

In Parnell & Abrahams (2008 Proc. R. Soc. A 464 , 1461–1482. ( doi:10.1098/rspa.2007.0254 )), a homogenization scheme was developed that gave rise to explicit forms for the effective antiplane shear moduli of a periodic unidirectional fibre-reinforced medium where fibres have non-circular cross section. The explicit expressions are rational functions in the volume fraction. In that scheme, a (non-dilute) approximation was invoked to determine leading-order expressions. Agreement with existing methods was shown to be good except at very high volume fractions. Here, the theory is extended in order to determine higher-order terms in the expansion. Explicit expressions for effective properties can be derived for fibres with non-circular cross section, without recourse to numerical methods. Terms appearing in the expressions are identified as being associated with the lattice geometry of the periodic fibre distribution, fibre cross-sectional shape and host/fibre material properties. Results are derived in the context of antiplane elasticity but the analogy with the potential problem illustrates the broad applicability of the method to, e.g. thermal, electrostatic and magnetostatic problems. The efficacy of the scheme is illustrated by comparison with the well-established method of asymptotic homogenization where for fibres of general cross section, the associated cell problem must be solved by some computational scheme.

Numerical Investigation of Turbulent Magnetic Nanofluid Flow inside Straight Channels

2016 ◽  
Vol 819 ◽  
pp. 382-391 ◽  
Author(s):  
Nor Azwadi Che Sidik ◽  
Mohammed Raad Abdulwahab
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Section ◽  
Volume Fraction ◽  
Numerical Study ◽  
Circular Cross Section ◽  
Average Diameter ◽  
Turbulent Regime ◽  
Reynolds Number Increase ◽  
Number Increase

A numerical study using computational fluid dynamics method with an approach of single phase has been presented in order to determine the effects of the concentration of the nanoparticles and flow rate on the convective heat transfer and friction factor in turbulent regime flowing through three different straight channels (straight, circular and triangular) with different Reynolds number (5000 ≤ Re ≤ 20000) using constant applied heat flux. The nanofluid was used consist of Fe3O4 magnetic nanoparticles with average diameter of (13nm) dispersed in water with four volume fraction (0, 0.2, 0.4, 0.6%). The results revealed that as volume fraction and Reynolds number increase Nusselt number increase and the heat transfer rate in circular cross section tube is better than that in square and triangular cross section channels.

Rapid motions of free-surface avalanches down curved and twisted channels and their numerical simulation

2005 ◽  
Vol 363 (1832) ◽  
pp. 1551-1571 ◽  
Author(s):  
Shiva P Pudasaini ◽  
Yongqi Wang ◽  
Kolumban Hutter
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Circular Cross Section ◽  
Hyperbolic Partial Differential Equations ◽  
Finite Mass ◽  
Governing Equations ◽  
Cross Sectional ◽  
Variation Diminishing ◽  
Cross Sectional Profile ◽  
Sectional Profile

This paper presents a new model and discussions about the motion of avalanches from initiation to run-out over moderately curved and twisted channels of complicated topography and its numerical simulations. The model is a generalization of a well established and widely used depth-averaged avalanche model of Savage & Hutter and is published with all its details in Pudasaini & Hutter (Pudasaini & Hutter 2003 J. Fluid Mech. 495 , 193–208). The intention was to be able to describe the flow of a finite mass of snow, gravel, debris or mud, down a curved and twisted corrie of nearly arbitrary cross-sectional profile. The governing equations for the distribution of the avalanche thickness and the topography-parallel depth-averaged velocity components are a set of hyperbolic partial differential equations. They are solved for different topographic configurations, from simple to complex, by applying a high-resolution non-oscillatory central differencing scheme with total variation diminishing limiter. Here we apply the model to a channel with circular cross-section and helical talweg that merges into a horizontal channel which may or may not become flat in cross-section. We show that run-out position and geometry depend strongly on the curvature and twist of the talweg and cross-sectional geometry of the channel, and how the topography is shaped close to run-out zones.

scholarly journals Study on Retrofitting of RC Column Using Ferrocement Full and Strip Wrapping

2019 ◽  
Vol 5 (11) ◽  
pp. 2472-2485
Author(s):  
Balamuralikrishnan R. ◽  
M. Al Madhani ◽  
R. Al Madhani
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Volume Fraction ◽  
Single Layer ◽  
Longitudinal Reinforcement ◽  
Element Analysis ◽  
Rc Columns ◽  
Rc Column ◽  
Concrete Form ◽  
Wrapping Technique

Ferrocement is one of the cement-based composites used for retrofitting and rehabilitation among many applications. Ferrocement is one of the reinforced concrete form with lightweight and thin composite with durability and environmental resistant that strengthen the conventional RC columns to increase its strength and serviceability. This paper examines the performance of the ferrocement wrapping in RC columns experimentally with numerical simulation using ANSYS19. Totally sixteen number of RC column of size 150 mm × 150 mm in cross section and 450 mm in length were cast and tested in laboratory. Twelve are retrofitted columns with respect to volume fraction and wrapping technique. Six columns were retrofitted by full wrapping technique and six columns of strip wrapping technique. The remaining four columns are control columns in virgin condition to compare with the retrofitted columns. Concerning the volume fraction of each specimen, the number of pre-woven mesh layers were single layer, double layer and three layers. C30 concrete grade adopted in all specimens as per ACI Committee 211-1.91 with 4H8 longitudinal reinforcement and H6 of 75mm c/c ties. As the previous researchers examined the ferrocement and proved its efficiency. This study aims to examine the ferrocement in full and strip wrapping technique to compare their efficiency to increase the strength. Finite element analysis using ANSYS19 adopted to compare the experimental data with the numerical simulation. The results are analyzed and observed that the ferrocement has increased the confinement and strength of the RC columns. 

Numerical simulation of in-pipe particle transportation in CO2 foam

2017 ◽  
Vol 5 (2) ◽  
pp. SF243-SF249
Author(s):  
Cheng Huang ◽  
Xiao Sun ◽  
Jinqiao Wu
Keyword(s):  
Numerical Simulation ◽  
Critical Point ◽  
Cross Section ◽  
Particle Distribution ◽  
Settling Velocity ◽  
Volume Fraction ◽  
Two Phase ◽  
Multiple Phase ◽  
Full Development ◽  
Fracturing Fluids

Proppant-carrying foam fracturing fluids have complex rheological and transportation properties. Current studies on these fluids often focus on experimental phenomena. However, due to the limitation of experimental research, only macroscopic properties, such as the critical settling velocity, can be obtained. Transportation mechanisms and volume fraction distributions are poorly understood as well. In our study, the liquid-solid drag coefficient is corrected, and the mathematical physical model of non-Newtonian fluids of the particle-foam multiple phase is established by using a two-phase model. Proppant settling and transport properties in foam fracturing fluids are numerically studied, particle distribution on pipe cross section is obtained at various conditions, and a criterion for full development of fluid flow in pipe is set. We also find that when the Reynolds number (Re) is less than 190, the critical point of full development of flow increases with Re, whereas when Re is greater than 190, the critical point of full development decreases exponentially with the increasing of Re before stabilizing at approximately 45.

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