A Study of Silt Erosion on Inner Buckets of Pelton Turbines

2014 ◽  
Vol 716-717 ◽  
pp. 644-649
Author(s):  
Su Wei ◽  
Wen Wu Song ◽  
Fu Jie ◽  
Cao Yong
Keyword(s):  
Flow Velocity ◽  
Sediment Concentration ◽  
Continuous Phase ◽  
Two Phase ◽  
Pelton Turbine ◽  
Coupled Calculation ◽  
Sediment Size ◽  
Fluid Analysis ◽  
Motion Characteristics ◽  
Silt Erosion

A 3-D model of pelton turbine bucket was built to investigate the motion characteristics of sediment particles in pelton turbines and the erosion caused by the movement. With the assistance of fluid analysis software FLUENT, A continuous phase turbulence model was estimated by the Euler equation which achieved convergence and the selected coupled calculation for solid-liquid two-phase flow with DPM model was built. It can be draw from the numerical analysis that, with the same size and sediment concentration, the inner bucket wall would suffer from the greater erosion by the relatively greater flow velocity; under the same condition of flow velocity and sediment concentration, the more serious erosion was caused by the bigger sized sediments; and the greater sediment concentration led to greater erosion, given the same flow velocity and sediment size. Based on the study, it showed that the erosion of inner wall of buckets was mainly affected by sediment size and concentration, as well as flow velocity.

scholarly journals Numerical Study for Near-Bed Variables in Velocity-Skewed Oscillatory Sheet Flow Transport

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Xin Chen ◽  
Zichao Zhang ◽  
Yong Li ◽  
Xiaoyan Shi
Keyword(s):  
Sediment Concentration ◽  
Sediment Flux ◽  
Phase Model ◽  
Phase Lag ◽  
Bed Sediment ◽  
Sheet Flow ◽  
Fall Velocity ◽  
Two Phase ◽  
Sediment Size ◽  
Flow Transport

The near-bed sediment concentration and vertical sediment flux are important in sediment transport mechanics, but they are known much less than the horizontal sediment flux, especially for fine sediment in unsteady flows. A developed two-phase model is applied to study the near-bed sediment concentration, vertical sediment flux, and the relevant total sediment amount for the velocity-skewed oscillatory sheet flow transport. With the sediment concentration hindered fall velocity, the classical reference concentration formulas conducted by Engelund and Fredsoe (1976) and Zyserman and Fredsoe (1994) are utilized for the comparison with the two-phase model and illustration of the phase-lag and sediment size effects in near-bed sediment concentration and vertical sediment flux. The concentration and vertical flux predicted by the two-phase model agree well with experimental data and are better than empirical formulas. Furthermore, the sediment size effect for pick-up flux function over starved bed is shown to be quite different from that containing sufficient sediment in oscillatory flows.

Phase Inversion in Two-Phase Liquid Systems

1992 ◽  
Vol 57 (7) ◽  
pp. 1419-1423
Author(s):  
Jindřich Weiss
Keyword(s):  
Interfacial Tension ◽  
Phase Inversion ◽  
Continuous Phase ◽  
Considerable Effect ◽  
Weak Dependence ◽  
Dispersed Phase ◽  
Two Phase ◽  
Liquid Systems ◽  
Phase Liquid

New data on critical holdups of dispersed phase were measured at which the phase inversion took place. The systems studied differed in the ratio of phase viscosities and interfacial tension. A weak dependence was found of critical holdups on the impeller revolutions and on the material contactor; on the contrary, a considerable effect of viscosity was found out as far as the viscosity of continuous phase exceeded that of dispersed phase.

scholarly journals Getting information on suspended sediments in a large river from acoustic backscatter

2018 ◽  
Vol 40 ◽  
pp. 04017
Author(s):  
Adrien Vergne ◽  
Céline Berni ◽  
Jérôme Le Coz
Keyword(s):  
Suspended Sediment Concentration ◽  
Spatial Information ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Large River ◽  
Acoustic Backscatter ◽  
Qualitative Information ◽  
Sediment Size ◽  
The Common

There has been a growing interest in the last decade in extracting information on Suspended Sediment Concentration (SSC) from acoustic backscatter in rivers. Quantitative techniques are not yet effective, but acoustic backscatter already provides qualitative information on suspended sediments. In particular, in the common case of a bi-modal sediment size distribution, corrected acoustic backscatter can be used to look for sand particles in suspension and provide spatial information on their distribution throughout a river crosssection. This paper presents a case-study where these techniques have been applied.

scholarly journals Two-Phase Turbulence Statistics from High Fidelity Dispersed Droplet Flow Simulations in a Pressurized Water Reactor (PWR) Sub-Channel with Mixing Vanes

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 72
Author(s):  
Nadish Saini ◽  
Igor A. Bolotnov
Keyword(s):  
Continuous Phase ◽  
System Level ◽  
Data Repository ◽  
High Fidelity ◽  
Turbulence Statistics ◽  
Two Phase ◽  
Pressurized Water ◽  
Droplet Dynamics ◽  
High Resolution Data ◽  
Spacer Grids

In the dispersed flow film boiling regime (DFFB), which exists under post-LOCA (loss-of-coolant accident) conditions in pressurized water reactors (PWRs), there is a complex interplay between droplet dynamics and turbulence in the surrounding steam. Experiments have accredited particular significance to droplet collision with the spacer-grids and mixing vane structures and their consequent positive feedback to the heat transfer recorded in the immediate downstream vicinity. Enabled by high-performance computing (HPC) systems and a massively parallel finite element-based flow solver—PHASTA (Parallel Hierarchic Adaptive Stabilized Transient Analysis)—this work presents high fidelity interface capturing, two-phase, adiabatic simulations in a PWR sub-channel with spacer grids and mixing vanes. Selected flow conditions for the simulations are informed by the experimental data found in the literature, including the steam Reynolds number and collision Weber number (Wec={40,80}), and are characteristic of the DFFB regime. Data were collected from the simulations at an unprecedented resolution, which provides detailed insights into the continuous phase turbulence statistics, highlighting the effects of the presence of droplets and the comparative effect of different Weber numbers on turbulence in the surrounding steam. Further, axial evolution of droplet dynamics was analyzed through cross-sectionally averaged quantities, including droplet volume, surface area and Sauter mean diameter (SMD). The downstream SMD values agree well with the existing empirical correlations for the selected range of Wec. The high-resolution data repository from the simulations herein is expected to be of significance to guide model development for system-level thermal hydraulic codes.

Formation of Two-Phase Multiple Emulsions by Inclusion of Continuous Phase into Dispersed Phase

Langmuir ◽  
2002 ◽  
Vol 18 (20) ◽  
pp. 7334-7340 ◽  
Author(s):  
Jong-Moon Lee ◽  
Kyung-Hee Lim ◽  
Duane H. Smith
Keyword(s):  
Continuous Phase ◽  
Dispersed Phase ◽  
Two Phase ◽  
Multiple Emulsions

scholarly journals NUMERICAL SIMULATION OF AIR – WATER FLOWS IN AN EVAPORATIVE CONDENSER

2009 ◽  
Vol 8 (1) ◽  
pp. 24 ◽  
Author(s):  
I. C. Acunha Jr ◽  
P. S. Schneider
Keyword(s):  
Turbulent Flows ◽  
Simple Algorithm ◽  
Continuous Phase ◽  
Velocity Fields ◽  
Temperature Fields ◽  
Two Phase ◽  
Equipment Manufacturer ◽  
Functional Aspects ◽  
Water Behavior ◽  
Complex Phenomena

Evaporative condensers present a hard problem for numerical modeling because of the complex phenomena of heat and mass transfer outside of the bundle tubes in turbulent flows. The goal of this work is to study the air and water behavior inside an evaporative condenser operating with ammonia as the refrigerant fluid. A commercial CFD software package (FLUENT) is employed to predict the two-phase flow of air and water droplets in this equipment. The air flow is modeled as a continuous phase using the Eulerian approach while the droplets water flow is modeled as a disperse phase with Lagrangian approach. The coupling between pressure and velocity fields is performed by the SIMPLE algorithm. The pressure, velocity and temperature fields are used to perform qualitative analyses to identify functional aspects of the condenser, while the temperature and the relative humidity evolution contributed to verify the agreement between the results obtained with the numerical model and those presented by equipment manufacturer.

scholarly journals MAGNITUDE OF THE B-FACTOR UNDER WAVE ACTION

1986 ◽  
Vol 1 (20) ◽  
pp. 67
Author(s):  
J. Van de Graaff ◽  
R.C. Steijn
Keyword(s):  
Velocity Distribution ◽  
Water Depth ◽  
Sediment Concentration ◽  
Wave Action ◽  
Practical Applications ◽  
Wave Flume ◽  
Sediment Size ◽  
Flume Tests ◽  
Waves And Currents ◽  
The Moment

The sediment transport due to waves and currents depends on the distribution of sediment concentration and on the distribution of the velocity over the water depth. Our knowledge of both phenomena for practical applications is still rather poor. Some results of wave flume tests concerning the distribution of sediment concentrations due to wave action will be discussed. It turns out that the sediment size of the bottom material has a rather unexpected effect hereupon. With respect to the velocity distribution only some qualitative remarks can be made at the moment.

scholarly journals Prediction Models of Droplet Characteristics Based on the Locally Convergent Configurations in PMMA Microchips

2021 ◽  
Vol 2097 (1) ◽  
pp. 012027
Author(s):  
Zhongxin Liu ◽  
Zhiliang Wang ◽  
Chao Wang ◽  
Jinsong Zhang
Keyword(s):  
Flow Rate ◽  
Relative Position ◽  
Prediction Models ◽  
Continuous Phase ◽  
Lubricating Oil ◽  
Flow Rate Ratio ◽  
Phase Flow ◽  
Exponential Relationship ◽  
Two Phase ◽  
Relationship Of

Abstract This paper novel designed the local convergence configuration in the coaxial channels to study the two-phase flow (lubricating oil (continuous phase, flow rate Q c)/deionized water (dispersed phase, flow rate Q d)). Two geometric control variables, the relative position (x) and tapering characteristics (α), had the different effects on the droplet formation. The increase of relative position x caused the higher frequency and finer droplets, and the increase of convergence angle α, took the opposite effects. The results indicated that the equivalent dimensionless droplet length Ld/Wout and the flow rate ratio Qd/Qc had an exponential relationship of about 1/2. Similarly, it was found that the dispersed droplets generating frequency and the two-phase capillary number, CaTP = uTPμc/σ, had an exponential relationship. The advantage of the convergent configurations in micro-channel was the size and efficiency of droplet generation was very favorable to be controlled by α and x.

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