Effect of Fine Sediments on the Performance of Axial Pumps

2008 ◽  
Author(s):  
Abdullah Saeed Al-Ghamdi
Keyword(s):  
Fine Sand ◽  
Sediment Concentration ◽  
Input Power ◽  
Fine Sediment ◽  
Motor Speed ◽  
Fine Sediments ◽  
Axial Pump ◽  
Axial Pumps ◽  
Work Done ◽  
Commercial Size

This study presents experimental work done to investigate the effect of fine sediment concentration on the performance of axial pumps. The pump was tested at three different motor speeds of 1000 rpm, 1150 rpm and 1350 rpm. At each motor speed, the pump was tested at three different sediment concentrations by weight of 0%, 2.485% and 8.10%. The sediment used in the investigation consists of a mixture of fine sand, silt and clay (16% fine sand, 38% silt and 46% clay). Results show that the efficiency of the axial pump is negatively influenced by the presence of fine sediments in the flow. As the sediment concentration increases to 8.10% the maximum reduction in axial pump’s efficiency for the range tested reached about 30% for motor speed of 1350 rpm and up to 40% for the lower motor speed of 1000 rpm. The reduction in the efficiency may be attributed to the change in the viscosity of the fluid that required higher torque (hence higher input power) to produce the same discharge. These results provide an evidence of a considerable reduction of axial pumps efficiency when used to pump water with fine sediment of silt and clay. However, further investigation is recommended for commercial size pumps and at different sediment concentrations and different composition of sediment.

scholarly journals TURBULENCE-RESOLVING NUMERICAL SIMULATION OF FINE SEDIMENT TRANSPORT OVER BEDFORMS

2018 ◽  
pp. 24
Author(s):  
Liangyi Yue ◽  
Zhen Cheng ◽  
Tian-Jian Hsu ◽  
Alexander R. Horner-Devine ◽  
Andrew J. Manning
Keyword(s):  
Sediment Transport ◽  
Fine Sand ◽  
Fine Sediment ◽  
Density Stratification ◽  
Numerical Accuracy ◽  
Sand Fraction ◽  
Fine Sediments ◽  
Shelf Sediment ◽  
Transport Modes ◽  
Turbulent Wave

Wave-supported gravity currents in turbulent wave bottom boundary layer (WBBL) are one of the most important processes causing cross-continental shelf sediment transport. The high numerical accuracy 3D numerical model has been used to investigate the fine sediment transport in the WBBL and several different transport modes have been found due to sedimentinduced density stratification (Ozdemir et al., 2010; Cheng et al., 2015). However, laboratory experiments suggest the presence of a small amount of sand fraction and the formation of ripple bed alter the structure of WBBL significantly (Hooshmand, et al., 2015). The purpose of this study is to understand the interplay of fine sand, bedforms, and sediment-induced density stratification in determining the transport modes of fine sediments in WBBL through turbulence-resolving numerical simulations.

Gravel Bed Composition in Oregon Coastal Streams

1980 ◽  
Vol 37 (10) ◽  
pp. 1514-1521 ◽  
Author(s):  
J. N. Adams ◽  
R. L. Beschta
Keyword(s):  
Regression Analysis ◽  
Fine Sediment ◽  
Low Flow ◽  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Gravel Bed ◽  
Fine Sediments ◽  
High Flows ◽  
The Impact

The amount of fine sediments (generally < 1 mm in diameter) in gravel bedded streams is often used as an indicator of habitat quality and also as a measure of the impact from accelerated sedimentation resulting from land disturbance. Five streams in the Oregon Coast Range were studied to evaluate temporal and spatial variability of streambed composition, as well as the factors affecting the amount of fine sediment within the bed. The amount of fine sediments (< 1 mm) contained in frozen streambed cores and expressed as a percentage (by weight) of the total sample proved highly variable in time and space. During a 19-mo sampling period, temporal variability was caused by an occasional flushing of fines from the gravel beds during high flows. Percent fines also varied greatly between streams, between locations in the same stream, and between locations in the same riffle. Streams on 21 Coast Range watersheds were sampled during summer low flow. The amount of fines averaged 19.4% for all watersheds and ranged from 10.6 to 29.4% for streams on undisturbed watersheds. Regression analysis indicated that the watershed slope, area, relief, and land use influenced the amount of fine sediment in the bed. Bed composition varied greatly between locations in the same stream with about 75% of the within-stream comparisons indicating a significant (α = 0.05) difference. Within a single stream, gravel bed composition correlated significantly with channel sinuosity and bank-full stage. Regression analysis and field observations suggested that road construction and logging operations can increase the amount of fines; however, such increases may be temporary if high flows flush the gravelsKey words: bed sediments, forest harvesting, Oregon Coast Range, sedimentation, spawning gravels, stream channels, water quality

Erodibility of fine sediment deposits in gravel bed rivers: investigation of the spatial variability

2021 ◽  
Author(s):  
Hanna Haddad ◽  
Magali Jodeau ◽  
Germain Antoine ◽  
Cédric Legoût
Keyword(s):  
Spatial Variability ◽  
Spatial Organization ◽  
Fine Sediment ◽  
Aquatic Life ◽  
Vegetation Growth ◽  
Gravel Bed ◽  
Fine Sediments ◽  
Sediment Deposits ◽  
Low Altitude ◽  
Gravel Bed Rivers

&lt;p&gt;Fine sediments exhibit various stages of deposition and erosion during their transport from hillslopes to the ocean. In mountainous environments, high fine sediment load during runoff or dam flushing events can lead to important amounts of deposits in gravel bed rivers. Massive deposits may lead to bar elevation, riparian vegetation growth and consequently to bar stabilization, which can increase flood risks. High amount of fine sediment deposits alters also aquatic life and habitat.&lt;/p&gt;&lt;p&gt;In order to better understand the dynamics of re-suspension of these deposits, and to accurately predict it with numerical modelling, field monitoring campaigns were performed to assess both the spatial variability and the controlling factors of the erodibility of fine deposits. The cohesive strength-meter (CSM) device, a pocket penetrometer and a pocket shear vane were used to evaluate the erodibility of fine sediments deposited in two rivers in the French Alps: The Is&amp;#232;re and Galabre.&lt;/p&gt;&lt;p&gt;The results highlight the specificity of gravel bed rivers with an abundance of areas of deposition of fine sediments, which are discontinuous compared to estuaries and lowland rivers. A high spatial variability of the erodibility was observed and related to the spatial organization of the deposits. The location of the deposit and its elevation, the moisture and the grain sizes are inter-related and have important correlations with the erodibility. Measurements show that high altitude dry deposits and low altitude humid deposits are more easily eroded than intermediate deposits with medium moisture. The measured variables explain part of the variability of the erodibility but other processes such as the history or the origin of the deposit might also be important factors to consider.&lt;/p&gt;

scholarly journals Fine Sediment Modeling During Storm-Based Events in the River Bandon, Ireland

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1523 ◽  
Author(s):  
Juan T. García ◽  
Joseph R. Harrington
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Storm Event ◽  
Storm Events ◽  
Event Scale ◽  
Model Based ◽  
Sediment Volume ◽  
Bed Erosion

The River Bandon located in County Cork (Ireland) has been time-continuously monitored by turbidity probes, as well as automatic and manual suspended sediment sampling. The current work evaluates three different models used to estimate the fine sediment concentration during storm-based events over a period of one year. The modeled suspended sediment concentration is compared with that measured at an event scale. Uncertainty indices are calculated and compared with those presented in the bibliography. An empirically-based model was used as a reference, as this model has been previously applied to evaluate sediment behavior over the same time period in the River Bandon. Three other models have been applied to the gathered data. First is an empirically-based storm events model, based on an exponential function for calculation of the sediment output from the bed. A statistically-based approach first developed for sewers was also evaluated. The third model evaluated was a shear stress erosion-based model based on one parameter. The importance of considering the fine sediment volume stored in the bed and its consolidation to predict the suspended sediment concentration during storm events is clearly evident. Taking into account dry weather periods and the bed erosion in previous events, knowledge on the eroded volume for each storm event is necessary to adjust the parameters for each model.

scholarly journals Numerical Simulation for Flow of Rolling Piston Type of Rotary Compressor

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2526
Author(s):  
Li-Chieh Hsu ◽  
Guo-Wei Wong ◽  
Po-Jui Lu ◽  
Fu-Shun Hsu ◽  
Ying-Chien Chen
Keyword(s):  
Numerical Study ◽  
Input Power ◽  
Rotary Compressor ◽  
Additional Resistance ◽  
Potential Factors ◽  
Reed Valve ◽  
Rolling Piston ◽  
Inlet Angle ◽  
Work Done ◽  
Design Margin

In this numerical study, the temperature, pressure and flow structure inside the rotary compressor are obtained to analyze the work consumption and efficiency. The geometry of the compressor such as volume, inlet angle, and mass of reed valve are varied to look for optimal performance and design margin as the suggestions for manufacturing. The work done on refrigerant increases proportionally with the volume of the compressor. However, there is an optimal volume for efficiency. The design margin for inlet angle is determined. The best efficiency exists in a specific inlet angle. Larger mass of reed valve leads to the increase of input power due to the additional resistance from greater inertia, which causes a decrease of efficiency. The flow visualization by simulation diagnoses the potential factors, which may cause noise problem.

scholarly journals Time Evolution of Estuarine Turbidity Maxima in Well-Mixed, Tidally Dominated Estuaries: The Role of Availability- and Erosion-Limited Conditions

2018 ◽  
Vol 48 (8) ◽  
pp. 1629-1650 ◽  
Author(s):  
Ronald L. Brouwer ◽  
George P. Schramkowski ◽  
Yoeri M. Dijkstra ◽  
Henk M. Schuttelaars
Keyword(s):  
River Discharge ◽  
Suspended Sediment Concentration ◽  
Time Lag ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Time Varying ◽  
Hydrodynamic Conditions ◽  
Good Qualitative Agreement ◽  
Estuarine Turbidity Maxima

AbstractUsing an idealized width-averaged process-based model, the role of a mud pool on the bed and time-varying river discharge on the trapping of fine sediment is systematically investigated. For this purpose, a dynamically and physically motivated description of erodibility is presented, which relates the amount of sediment on the bed to the suspended sediment concentration (SSC). We can distinguish between two states: in the availability-limited state, the SSC is limited by the amount of erodible sediment at the bed. Over time, under constant forcing conditions, the estuary evolves to morphodynamic equilibrium. In the erosion-limited state, there is an abundant amount of sediment at the bed so that sediment pickup occurs at the maximum possible rate. The SSC is then limited by the local hydrodynamic conditions. In this state, the estuary keeps importing sediment, forming an erodible bottom pool that grows in time. These two states can be used to explain the response of an estuary to changing river discharge. Under availability-limited conditions, periods of high river discharge push estuarine turbidity maxima (ETMs) downstream, while drier periods allow ETMs to move upstream. However, when the estuary is in an erosion-limited state during low river discharge, a bottom pool is formed. When the discharge then increases, it takes time to deplete this pool, so that an ETM located over a bottom pool moves with a significant time lag relative to changes in the river discharge. Good qualitative agreement is found between model results and observations in the Scheldt Estuary of surface SSC using a representative year of discharge conditions.

Theoretical Analyses of the Number of Backflow Vortices on an Axial Pump or Compressor

2019 ◽  
Author(s):  
Yu Ito ◽  
Yuhei Sato ◽  
Takao Nagasaki
Keyword(s):  
Contact Surface ◽  
Tip Clearance ◽  
The Other ◽  
Vortex Center ◽  
Secondary Vortex ◽  
Axial Pump ◽  
Cylindrical Casing ◽  
Axial Pumps ◽  
Secondary Vortices ◽  
Theoretical Analyses

Abstract This paper presents theoretical analyses of flow fields on an axial pump or compressor, where the main flow enters from one side of the cylindrical casing, whereas an axially reverse and tangentially whirling flow enters from the tip clearance between the casing and the impeller, which sucks in the mixed flow. In this flow field, several secondary vortices exist in the mixing zone across the contact surface between the main and the axially reverse tangentially whirling flow. This type of secondary vortex is called a “backflow vortex.” The backflow vortices are tornado-like, parallel to the casing axis, and periodically distributed on the contact surface; they revolve around the casing axis and rotate around themselves. Regarding the backflow vortices, the relationships between their number (N), revolving diameter (d), revolving angular velocity (ω), and the ratio of the forced vortex region to the distance between the secondary-vortex center and the cylindrical wall (f) were all theoretically investigated. The five major findings are as follows: First, between d, ω, N, and f, any parameter can be determined if the other three are specified. Second, ω decreases, N increases, or f increases when d is increased and the other two are fixed. Third, d decreases, N increases, or f increases when ω is increased and the other two are fixed. Fourth, d increases, ω increases, or f decreases when N is increased and the other two are fixed. Fifth, d increases, ω increases, or N decreases when f is increased and the other two are fixed. To validate these theoretical results, “backflow vortex cavitation,” which occurs around the center of the backflow vortices on a rotating inducer as a representative of axial pumps or compressors, was observed. The backflow vortex cavitation is visible; therefore, d, ω, and N become quantitatively measurable. The test inducer was a triple-threaded helical inducer with a diameter of 65.3 mm and a rotational speed range of 3000–6000 rpm. It was experimentally confirmed that the proposed theoretical analysis is true.

Fine sediment retention in storage chambers: an assessment of time-dependent effects

2002 ◽  
Vol 45 (7) ◽  
pp. 123-131 ◽  
Author(s):  
V.R. Stovin ◽  
J.P. Grimm ◽  
A.J. Saul
Keyword(s):  
Fine Sediment ◽  
Multiphase Model ◽  
Storm Events ◽  
Dimensional Model ◽  
Flow Conditions ◽  
Sediment Retention ◽  
Fine Sediments ◽  
Storage Chamber ◽  
Flow Hydraulics ◽  
The Uk

The optimisation of the design of a storage chamber is generally based upon some measure of the chamber's sedimentation efficiency. In the UK, chambers that minimise the deposition of fine sediments are preferred. Previous laboratory and CFD-based studies to measure efficiency have focused on steady flow conditions. However, both the flow hydraulics within a storage chamber and the pollutant loading in the incoming sewage vary markedly during storm events. This paper outlines a CFD-based approach for determining “overall” chamber efficiency. The approach employs an unsteady volume-of-fluid multiphase model and stochastic particle tracking. Preliminary results from a simplified two-dimensional model are presented.

scholarly journals The Prediction of Fine Sediment Distribution in Gravel-Bed Rivers Using a Combination of DEM and FNN

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1515
Author(s):  
Van Hieu Bui ◽  
Minh Duc Bui ◽  
Peter Rutschmann
Keyword(s):  
Feedforward Neural Networks ◽  
Fine Sediment ◽  
Sediment Distribution ◽  
Gravel Bed ◽  
Fine Sediments ◽  
Porosity Variation ◽  
Sediment Sorting ◽  
Gravel Bed Rivers ◽  
Bed Material ◽  
The Relationship

Large amounts of fine sediment infiltration into void spaces of coarse bed material have the ability to alter the morphodynamics of rivers and their aquatic ecosystems. Modelling the mechanisms of fine sediment infiltration in gravel-bed is therefore of high significance. We proposed a framework for calculating the sediment exchange in two layers. On the basis of the conventional approaches, we derived a two-layer fine sediment sorting, which considers the transportation of fine sediment in the form of infiltration into the void spaces of the gravel-bed. The relationship between the fine sediment exchange and the affected factors was obtained by using the discrete element method (DEM) in combination with feedforward neural networks (FNN). The DEM model was validated and applied for gravel-bed flumes with different sizes of fine sediments. Further, we developed algorithms for extracting information in terms of gravel-bed packing, grain size distribution, and porosity variation. On the basis of the DEM results with this extracted information, we developed an FNN model for fine sediment sorting. Analyzing the calculated results and comparing them with the available measurements showed that our framework can successfully simulate the exchange of fine sediment in gravel-bed rivers.

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