Streamwise vorticity generation in a compound meandering channel

2014 ◽  
pp. 47-53
Author(s):  
I Mera ◽  
J Anta ◽  
E Peña
Keyword(s):  
Streamwise Vorticity ◽  
Meandering Channel ◽  
Vorticity Generation

FLOOD HYDRAULICS DUE TO EMERGENT VEGETATION ALONG A RIPARIAN ZONE IN MEANDERING CHANNELS

2016 ◽  
Vol 78 (9-4) ◽  
Author(s):  
Zulkiflee Ibrahim ◽  
Zulhilmi Ismail ◽  
Sobri Harun ◽  
Koji Shiono ◽  
Nazirah Mohd. Zuki ◽  
...  
Keyword(s):  
Shear Stress ◽  
Flow Resistance ◽  
Riparian Zone ◽  
Streamwise Vorticity ◽  
Floodplain Vegetation ◽  
Meandering Channel ◽  
Meandering Channels ◽  
Boundary Shear ◽  
Residential Properties ◽  
Boundary Shear Stress

Frequent floods around the globe including recent events in several states in Malaysia have damaged the residential properties, infrastructures and crops or even deaths. Clearing vegetations or trees on the floodplain has been pointed out as a contributing factor to the damages. Thus, the influence of floodplain vegetation on the river hydraulics during flooding must be better understood. The hydraulics of flood flows in non-erodible vegetated meandering channel was experimented in the laboratory where two-lined steel rods were installed along a riparian zone to simulate as trees. The stage-discharge relationship, flow resistance, depth-averaged velocity, streamwise vorticity and boundary shear stress patterns during shallow and deep flood inundations were studied. The findings showed that floodplain vegetation had increased the channel flow depth by 32% and its flow resistance. The velocity in vegetated zone was lowered and the shear stress reduced by 86.5% to 91% along the river meander. In addition, the trees also limit flow interaction between main channel and floodplain

Simultaneous Dual-Doppler and Mobile Mesonet Observations of Streamwise Vorticity Currents in Three Supercells

2020 ◽  
Vol 148 (12) ◽  
pp. 4859-4874
Author(s):  
Shawn S. Murdzek ◽  
Paul M. Markowski ◽  
Yvette P. Richardson
Keyword(s):  
High Resolution ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Cross Sections ◽  
The Other ◽  
Streamwise Vorticity ◽  
Vorticity Generation ◽  
Southern Fringe

AbstractRecent high-resolution numerical simulations of supercells have identified a feature referred to as the streamwise vorticity current (SVC). Some have presumed the SVC to play a role in tornadogenesis and maintenance, though observations of such a feature have been limited. To this end, 125-m dual-Doppler wind syntheses and mobile mesonet observations are used to examine three observed supercells for evidence of an SVC. Two of the three supercells are found to contain a feature similar to an SVC, while the other supercell contains an antistreamwise vorticity ribbon on the southern fringe of the forward flank. A closer examination of the two supercells with SVCs reveals that the SVCs are located on the cool side of boundaries within the forward flank that separate colder, more turbulent flow from warmer, more laminar flow, similar to numerical simulations. Furthermore, the observed SVCs are similar to those in simulations in that they appear to be associated with baroclinic vorticity generation and have similar appearances in vertical cross sections. Aside from some apparent differences in the location of the maximum streamwise vorticity between simulated and observed SVCs, the SVCs seen in numerical simulations are indeed similar to reality. The SVC, however, may not be essential for tornadogenesis, at least for weak tornadoes, because the supercell that did not have a well-defined SVC produced at least one brief, weak tornado during the analysis period.

scholarly journals Roles of Streamwise and Transverse Partial-Vorticity Components in Steady Inviscid Isentropic Supercell-Like Flows

2017 ◽  
Vol 74 (9) ◽  
pp. 3021-3041 ◽  
Author(s):  
Robert Davies-Jones
Keyword(s):  
Temperature Gradients ◽  
Streamwise Vorticity ◽  
Flow Vorticity ◽  
Unstable Environment ◽  
Vorticity Component ◽  
Analytical Formulas ◽  
Transverse Temperature ◽  
Vorticity Generation ◽  
Strong Vortex ◽  
River Bend

Abstract Investigations of tornadogenesis in supercells attempt to find the origin of the tornado’s large vorticity by determining vorticity generation and amplification along trajectories that enter the tornado from a horizontally uniform unstable environment. Insights into tornadogenesis are provided by finding analytical formulas for vorticity variations along streamlines in idealized, steady, inviscid, isentropic inflows of dry air imported from the environment. The streamlines and vortex lines lie in the stationary isentropic surfaces so the vorticity is 2D. The transverse vorticity component (positive leftward of the streamlines) arises from imported transverse vorticity and from baroclinic vorticity accumulated in streamwise temperature gradients. The streamwise component stems from imported streamwise vorticity, from baroclinic vorticity accrued in transverse temperature gradients, and from positive transverse vorticity that is turned streamwise in cyclonically curved flow by a “river-bend process.” It is amplified in subsiding air as it approaches the ground. Streamwise stretching propagates a parcel’s streamwise vorticity forward in time. In steady flow, vorticity decomposes into baroclinic vorticity and two barotropic parts ωBTIS and ωBTIC arising from imported storm-relative streamwise vorticity (directional shear) and storm-relative crosswise vorticity (speed shear), respectively. The Beltrami vorticity ωBTIS is purely streamwise. It explains why abundant environmental storm-relative streamwise vorticity close to ground favors tornadic supercells. It flows directly into the updraft base unmodified apart from streamwise stretching, establishing mesocyclonic rotation and strong vortex suction at low altitudes. Increase (decrease) in storm-relative environmental wind speed with height near the ground accelerates (delays) tornadogenesis as positive (negative) ωBTIC is turned into streamwise (antistreamwise) vorticity within cyclonically curved flow around the mesocyclone.

Measured and Predicted Secondary Flows in a Centrifugal Impeller

1971 ◽  
Vol 93 (1) ◽  
pp. 126-131 ◽  
Author(s):  
J. H. G. Howard ◽  
E. Lennemann
Keyword(s):  
Secondary Flows ◽  
Centrifugal Impeller ◽  
Streamwise Vorticity ◽  
Complex Flow ◽  
Primary Flow ◽  
Slip Rings ◽  
Rotating Impeller ◽  
Vorticity Generation ◽  
Hot Film ◽  
Simple Combination

The complete velocity distribution, including both primary and secondary velocities, has been measured in passages of centrifugal impellers of simple shape. Comparison is made with theoretically predicted secondary vorticities based on a simple combination of an inviscid primary flow and a streamwise vorticity generation analysis. The measured velocities were obtained in a water-flow impeller rig using a miniature, cylindrical, hot-film probe positioned on the rotating impeller and traversed and controlled remotely through slip rings. The understanding of the complex flow patterns was assisted by a photographic study employing a hydrogen bubble, flow visualization technique.

SHORT-TERM EVOLUTION OF FLOW & MORPHOLOGY IN AN ERODIBLE MEANDERING CHANNEL WITH & WITHOUT GROYNES

2018 ◽  
Vol 74 (4) ◽  
pp. I_1147-I_1152
Author(s):  
Saroj KARKI ◽  
Yuji HASEGAWA ◽  
Masakazu HASHIMOTO ◽  
Hajime NAKAGAWA ◽  
Kenji KAWAIKE
Keyword(s):  
Short Term ◽  
Meandering Channel ◽  
Term Evolution ◽  
Flow Morphology

scholarly journals Analog-based meandering channel simulation

2014 ◽  
Vol 50 (2) ◽  
pp. 836-854 ◽  
Author(s):  
Gregoire Mariethoz ◽  
Alessandro Comunian ◽  
Inigo Irarrazaval ◽  
Philippe Renard
Keyword(s):  
Channel Simulation ◽  
Meandering Channel
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