scholarly journals Topics in fluvial and lagoon morphodynamics

2002 ◽  
Author(s):  
Luca Solari
Keyword(s):  
Flow Field ◽  
Bedload Transport ◽  
Observational Evidence ◽  
Field Pattern ◽  
Tidal Channels ◽  
New Model ◽  
Bed Topography ◽  
Meandering Channels ◽  
Present Book ◽  
Transverse Slope

The present book covers topics both on fluvial and lagoon morphodynamics. The first part is dedicated to tidal environments. Topics include an overview of main morphological features and mechanisms of estuaries and tidal channels and a model devoted to investigate flow field pattern and bed topography in tidal meandering channels and a comparison with recent observational evidence of meanders within different tidal environments. The general failure of Bagnold hypothesis when applied to equilibrium bedload transport at even relatively modest transverse slope is demonstrated. A new model is then proposed based on an empirical entrainment formulation of bed grains.

scholarly journals Experiments on Longitudinal and Transverse Bedload Transport in Sine-Generated Meandering Channels

2021 ◽  
Vol 11 (14) ◽  
pp. 6560
Author(s):  
Li He ◽  
Dong Chen ◽  
Donatella Termini ◽  
Shiyan Zhang ◽  
Zhenhui Zhu
Keyword(s):  
Longitudinal Direction ◽  
Bedload Transport ◽  
Bed Topography ◽  
Bed Deformation ◽  
Meandering Channels ◽  
Curved Channels ◽  
Initial Location ◽  
Moving Direction ◽  
Point Bars ◽  
Gain Loss

Bedload grains in consecutive meandering bends either move longitudinally or across the channel centerline. This study traces and quantifies the grains’ movement in two laboratorial sine-generated channels, i.e., one with deflection angle θ0 = 30° and the other 110°. The grains originally paved along the channels are uniform in size with D = 1 mm and are dyed in various colors, according to their initial location. The experiments recorded the changes in the flow patterns, bed deformation, and the gain-loss distribution of the colored grains in the pool-bar complexes. We observed the formation of two types of erosion zones during the process of the bed deformation, i.e., Zone 1 in the foreside of the point bars and Zone 2 near the concave bank downstream of the bend apexes. Most grains eroded from Zone 1 are observed moving longitudinally as opposed to crossing the channel centerline. Contrastingly, the dominant moving direction of the grains eroded from Zone 2 changes from the longitudinal direction to the transversal one as the bed topography evolves. Besides, most building material of the point bars comes from the upstream bends, although low- and highly curved channels behave differently.

Investigation on Laminar Flow Field Performances in a Dual-Impeller Stirred Tank

2012 ◽  
Vol 550-553 ◽  
pp. 2964-2967
Author(s):  
De Yu Luan ◽  
Shen Jie Zhou ◽  
Song Ying Chen
Keyword(s):  
Laminar Flow ◽  
Flow Field ◽  
Velocity Distribution ◽  
Radial Velocity ◽  
Velocity Vector ◽  
Equations Of Motion ◽  
Stirred Tank ◽  
Field Pattern ◽  
3D Flow ◽  
Multiple Reference

Abstract: The 3D flow field generated by a dual-impeller in the agitation of glycerin fluid was simulated using the commercial CFD package. The flow was modeled as laminar and a multiple reference frame (MRF) approach was used to solve the discretized equations of motion. The velocity profiles with a dual-impeller rotating at constant speed of 200r/min and at different layer clearances were obtained. By analysis to their axial and radial velocity vector plots and velocity distribution curves, it is found that the velocity distributions of the dual 6-bladed radial disc turbines (2-6DT) are better when the clearance is bigger or equal to the T/2, accompanied with the flow field pattern of parallel flow. Moreover，when the clearance is smaller or equal to the T/3, there are more advantages for 6-bladed radial disc turbines + pitch 4-bladed turbines (6DT+PTB) than other combinations，followed by the flow field pattern of connected flow.

scholarly journals Vortex valve

2018 ◽  
Vol 180 ◽  
pp. 02001 ◽  
Author(s):  
Karel Adámek ◽  
Jan Kolář ◽  
Pavel Peukert
Keyword(s):  
Flow Field ◽  
Flow Characteristic ◽  
Flow Simulation ◽  
New Model ◽  
Numerical Flow Simulation ◽  
Moving Parts

The paper deals with a flow field inside the so-called vortex valve, used as an outlet device on retention reservoirs for retention of rainstorms and later slow outflow into sewerage etc. The system is very simple, without moving parts. Using the method of numerical flow simulation, the unusual flow characteristic Δp = f(Q), containing two branches, is explained. Further, there it is studied influence of both inlet/outlet opening sizes on the form of the characteristic. Results can be used for designing the new model series of valves for various flows.

scholarly journals 3D Flow Field Measurement Around a Rotating Stall Cell

1998 ◽  
Author(s):  
C. Palomba ◽  
P. Puddu ◽  
F. Nurzia
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Field Pattern ◽  
Mean Flow ◽  
Axial Section ◽  
Average Technique ◽  
Compressor Rotor ◽  
Flow Compressor

Rotating stall is an unsteady phenomenon that arises in axial and radial flow compressors. Under certain operating conditions a more or less regular cell of turbulent flow develops and propagates around the annulus at a speed lower than rotor speed. Recently little work has been devoted to the understanding of the flow field pattern inside a rotating cell. However, this knowledge could be of help in the understanding of the interaction between the cell and the surrounding flow. Such information could be extremely important during the modelling process when some hypothesis have to be made about the cell behaviour. A detailed experimental investigation has been conducted during one cell operation of an isolated low-speed axial flow compressor rotor using a slanted hot wire and an ensemble average technique based on the cell revolution time. The three flow field components have been measured on 9 axial section for 800 circumferential points and on 21 radial stations to give a complete description of the flow field upstream and downstream of the rotor. Interpretation of data can give a description of the mean flow field patterns inside and around the rotating cell.

The Influence of a Novel Bio-Cell Flow Field Pattern on the Performance and Operating Conditions for a PEM Fuel Cell

2005 ◽  
Author(s):  
Fang-Bor Weng ◽  
Ay Su ◽  
Kai-Fan Lo ◽  
Cheng-Hsin Tu
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Gas Diffusion ◽  
Cell System ◽  
Operating Conditions ◽  
Cell Performance ◽  
Channel Structure ◽  
Field Pattern ◽  
Fuel Cell Performance ◽  
Stable Performance

A novel bio-cell flow field pattern is experimentally investigated by determining fuel cell performance and optimal operating conditions. The cell performance is analyzed by the polarization curve and the long-term stability. The bio-cell flow channel structure has a main feed track, a secondary branch track, and repeats to promote water removal from gas diffusion layer. The performance of the bio-cell flow field pattern is optimal performance when the cell is operated with low humidity gases and low cell temperature. In addition, the bio-cell flow field exhibits stable performance for non-humidified air. The fuel cell with the novel bio-cell flow field has advantages for low relative humidity operations. The results of the bio-cell flow field could potentially simplify fuel cell system design without humidifiers.

Responses to Continuously Changing Optic Flow in Area MST

2000 ◽  
Vol 84 (2) ◽  
pp. 730-743 ◽  
Author(s):  
Monica Paolini ◽  
Claudia Distler ◽  
Frank Bremmer ◽  
Markus Lappe ◽  
Klaus-Peter Hoffmann
Keyword(s):  
Flow Field ◽  
Flow Fields ◽  
Complete Characterization ◽  
Field Pattern ◽  
Temporal Context ◽  
Field Stimulation ◽  
Independence Test ◽  
Symmetry Test ◽  
Mst Neurons ◽  
Temporal Symmetry

We studied the temporal behavior and tuning properties of medial superior temporal (MST) neurons in response to constant flow-field stimulation and continuously changing flow-field stimulation (transitions), which were obtained by morphing one flow field into another. During transitions, the flow fields resembled the motion pattern seen by an observer during changing ego-motion. Our aim was to explore the behavior of MST cells in response to changes in the flow-field pattern and to establish whether the responses of MST cells are temporally independent or if they are affected by contextual information from preceding stimulation. We first tested whether the responses obtained during transitions were linear with respect to the two stimuli defining the transition. In over half of the transitions, the cell response was nonlinear: the response during the transition could not be predicted by the linear interpolation between the stimulus before and after the transition. Nonlinearities in the responses could arise from a dependence on temporal context or from nonlinearities in the tuning to flow-field patterns. To distinguish between these two hypotheses, we fit the responses during transitions and during continuous stimuli to the predictions of a temporally independent model (temporal-independence test) and we compared the responses during transitions to the responses elicited by inverse transitions (temporal-symmetry test). The effect of temporal context was significant in only 7.2% and 5.5% of cells in the temporal-independence test and in the temporal-symmetry test, respectively. Most of the nonlinearities in the cell responses could be accounted for by nonlinearities in the tuning to flow-field stimuli (i.e., the responses to a restricted set of flow fields did not predict the responses to other flow fields). Tuning nonlinearities indicate that a complete characterization of the tuning properties of MST neurons cannot be obtained by testing only a small number of flow fields. Because the cells' responses do not depend on temporal context, continuously changing stimulation can be used to characterize the receptive field properties of cells more efficiently than constant stimulation. Temporal independence in the responses to transitions indicates that MST cells do not code for second-order temporal properties of flow-field stimuli, i.e., for changes in the flow field through time that can be construed as paths through the environment. Information about ego-motion three-dimensional paths through the environment may either be processed at the population level in MST or in other cortical areas.

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