scholarly journals Morphodynamics and sedimentary structures of bedforms under supercritical-flow conditions: New insights from flume experiments

Sedimentology ◽  
2013 ◽  
Vol 61 (3) ◽  
pp. 712-748 ◽  
Author(s):  
Matthieu J.B. Cartigny ◽  
Dario Ventra ◽  
George Postma ◽  
Jan H. van Den Berg
Keyword(s):  
Flow Conditions ◽  
Flume Experiments ◽  
Supercritical Flow ◽  
Sedimentary Structures

Performance and Flow Characteristics of an Optimized Supercritical Compressor Stator Cascade

2005 ◽  
Vol 128 (3) ◽  
pp. 435-443 ◽  
Author(s):  
Bo Song ◽  
Wing F. Ng
Keyword(s):  
Boundary Layer ◽  
Numerical Study ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Supercritical Flow ◽  
Gradient Distribution ◽  
Controlled Diffusion ◽  
Mach Numbers

An experimental and numerical study was performed on an optimized compressor stator cascade designed to operate efficiently at high inlet Mach numbers (M1) ranging from 0.83 to 0.93 (higher supercritical flow conditions). Linear cascade tests confirmed that low losses and high turning were achieved at normal supercritical flow conditions (0.7<M1<0.8), as well as higher supercritical flow conditions (0.83<M1<0.93), both at design and off-design incidences. The performance of this optimized stator cascade is better than those reported in the literature based on Double Circular Arc (DCA) and Controlled Diffusion Airfoil (CDA) blades, where losses increase rapidly for M1>0.83. A two-dimensional (2D) Navier-Stokes solver was applied to the cascade to characterize the performance and flow behavior. Good agreement was obtained between the CFD and the experiment. Experimental loss characteristics, blade surface Mach numbers, shadowgraphs, along with CFD flowfield simulations, were presented to elucidate the flow physics. It is found that low losses are due to the well-controlled boundary layer, which is attributed to an optimum flow structure associated with the blade profile. The multishock pattern and the advantageous pressure gradient distribution on the blade are the key reasons of keeping the boundary layer from separating, which in turn accounts for the low losses at the higher supercritical flow conditions.

scholarly journals LAG EFFECTS IN MORPHODYNAMIC MODELLING OF ENGINEERING IMPACTS

2012 ◽  
Vol 1 (33) ◽  
pp. 45 ◽  
Author(s):  
Michiel A.F. Knaapen ◽  
David M. Kelly
Keyword(s):  
Sediment Transport ◽  
Sediment Concentration ◽  
Flow Conditions ◽  
Flume Experiments ◽  
Lag Effects ◽  
Morphodynamic Modelling ◽  
Morphology Model ◽  
Bed Exchange ◽  
Morphodynamic Modeling ◽  
Concentration Equation

This paper details the extension of the sediment transport and morphology model SISYPHE to include a lag term within the bed exchange source term of the, depth-averaged, continuity of sediment concentration equation. This lag term represents the time it takes for a sediment concentration profile to adapt to spatial or temporal changes in the flow. The inclusion of a lag term means that the settling velocity is no longer the only scaling factor for the exchange of sediment between the water and the bed. The modified sediment transport and morphodynamics model is tested against field data from the Thames estuary (UK) and on the morphodynamic development of a dredged trench in flume experiments. It is illustrated that the lag factor introduced is essential to model the sediment transport and morphodynamics, especially when considering engineered situations, where the bed is out of equilibrium with the flow conditions. Moreover, with this lag factor included, there is evidence that SISYPHE can be used for morphodynamic modeling of engineered situations.

Transport of adsorbing metals from stream water to a stationary sand-bed in a laboratory flume

1995 ◽  
Vol 46 (1) ◽  
pp. 209 ◽  
Author(s):  
H Eylers ◽  
NH Brooks ◽  
JJ Morgan
Keyword(s):  
Metal Ions ◽  
Stream Water ◽  
Flow Conditions ◽  
Advective Flow ◽  
Flume Experiments ◽  
Lithium Ions ◽  
Overlying Water ◽  
Experimental Conditions ◽  
Sediment Bed ◽  
Laboratory Flume

The transport of zinc and lithium ions between the overlying water column and the stationary sand-bed in a laboratory flume with bottom bedforms is investigated. Experiments have been performed under simplified conditions in a recirculating laboratory flume with straight impermeable walls and a sand-bed. The sand is well sorted and acid-washed to provide reproducible experimental conditions. The chemical composition of the recirculating water is controlled and steady flow conditions are maintained in the experiments. The concentrations of initially added metal ions are monitored both in the circulating overlying water and in the pore water of the sediment bed. Batch experiments were performed to investigate the chemical partitioning of the metal ions to the sand grain surfaces, and the data were compared with adsorption values obtained from the flume experiments. A model based on pressure-driven advective flow and linear partitioning of the pollutant to the sediment has been developed and accurately predicts the rate of transfer of the metal ions (zinc and lithium) into the bed in the case of stationary bedforms.

Hydraulic behaviour of junction manholes under supercritical flow conditions

2012 ◽  
Vol 50 (6) ◽  
pp. 631-636 ◽  
Author(s):  
Juan Saldarriaga ◽  
Nataly Bermúdez ◽  
Diva P. Rubio
Keyword(s):  
Flow Conditions ◽  
Supercritical Flow ◽  
Hydraulic Behaviour
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