scholarly journals A Two-Dimensional Simulation of Flow Field in Lakes under Wind Acting on the Water Surface and the Impact of Aquatic Plants on the Flow Patterns

10.5109/4703 ◽  
2006 ◽  
Vol 51 (1) ◽  
pp. 13-18
Author(s):  
Bui Quoc Lap ◽  
Ken Mori
Keyword(s):  
Flow Field ◽  
Aquatic Plants ◽  
Water Surface ◽  
Flow Patterns ◽  
Two Dimensional ◽  
Dimensional Simulation ◽  
The Impact

scholarly journals A Stochastic Model of Atmospheric Rime Icing

1988 ◽  
Vol 34 (116) ◽  
pp. 26-30 ◽  
Author(s):  
E.M. Gates ◽  
A. Liu ◽  
E.P. Lozowski
Keyword(s):  
Stochastic Process ◽  
Flow Field ◽  
Diameter Ratio ◽  
Two Dimensional ◽  
Small Water ◽  
Ice Accumulation ◽  
Discrete Structures ◽  
Random Position ◽  
Air Speed ◽  
The Impact

Abstract The accumulation of rime ice on structures, due to the impact and freezing of small water droplets, has been modelled as a stochastic process. Individual droplets are introduced into the flow field about the structure at a random position. Their trajectories are then calculated to determine the position of impact on the structure, or on previously impacted droplets. By assuming that the droplets maintain their shape on impact, the modelled accretion is gradually built up, one droplet at a time. In the present paper, attention has been limited to a circular cylinder as the collecting structure, and it has been assumed that the flow field and the ice accumulation are strictly two-dimensional. With these assumptions, the influence of the droplet/cylinder diameter ratio and of the air speed upon the resulting predictions has been investigated. The main feature of interest in the model prediction is the development, near the edges of the accumulation, of discrete structures called “rime feathers”. The mechanism for the growth of these rime feathers is described, and a comparison is made between the characteristics of the predicted structures and of some natural rime feathers grown in an icing wind tunnel.

Impact of Cavity on Sunroof Buffeting: A Two Dimensional CFD Study

2004 ◽  
Author(s):  
Chang-Fa An ◽  
Seyed Mehdi Alaie ◽  
Michael S. Scislowicz
Keyword(s):  
Fluid Dynamics ◽  
Wind Tunnel ◽  
Three Dimensional ◽  
Leading Edge ◽  
Two Dimensional ◽  
Deep Insight ◽  
Simulation Results ◽  
Dimensional Simulation ◽  
The Impact ◽  
Insight Into

Driven by fluid dynamics principles, the concept for buffeting reduction, a cavity installed at the leading edge of the sunroof opening, is analyzed. The cavity provides a room to hold the vortex, shed from upstream, and prevents the vortex from escaping and from directly intruding into the cabin. The concept has been verified by means of a two dimensional simulation for a production SUV using the CFD software — FLUENT. The simulation results show that the impact of the cavity is crucial to reduce buffeting. It is shown that the buffeting level may be reduced by 3 dB by adding a cavity to the sunroof configuration. Therefore, the cavity could be considered as a means of buffeting reduction, in addition to the three currently-known concepts: wind deflector, sunroof glass comfort position and cabin venting. Thorough understanding of the buffeting mechanism helps explain why and how the cavity works to reduce buffeting. Investigation of the buffeting-related physics provides a deep insight into the flow nature and, therefore, a useful hint to geometry modification for buffeting reduction. The buffeting level may be further reduced by about 4 dB or more by cutting the corners of the sunroof opening into smooth ramps, guided by ideas coming from careful examining the physics of flow. More work including three dimensional simulation and wind tunnel experiment should follow in order to develop more confidence in the functionality of the cavity to hopefully promote this idea to the level that it can be utilized in a feasible way to address sunroof buffeting.

Hydroelastic Modeling of Wet Deck Slamming on Multihull Vessels

2021 ◽  
Vol 39 (03) ◽  
pp. 225-239
Author(s):  
Jan Kvalsvold ◽  
Odd M. Faltinsen
Keyword(s):  
Water Surface ◽  
Normal Modes ◽  
Two Dimensional ◽  
Sea Waves ◽  
Rotatory Inertia ◽  
Shear Deformations ◽  
Inertia Effects ◽  
Elastic Stresses ◽  
The Impact ◽  
Impact Region

Slamming against the wet deck of a multihull vessel in head sea waves is studied analytically and numerically. The theoretical slamming model is a two-dimensional, asymptotic method valid for small local angles between the undisturbed water surface and the wet deck in the impact region. The disturbance of the water surface as well as the local hydroelastic effects in the slamming area are accounted for. The elastic deflections of the wet deck are expressed in terms of "dry" normal modes. The structural formu­lation accounts for the shear deformations and the rotatory inertia effects in the wet deck. The findings show that the slamming loads on the wet deck and the resulting elastic stresses in the wet deck are strongly influenced by the elasticity of the wet deck structure.

Fluid Dynamics of Hydrophilous Pollination in Ruppia (Widgeon Grass)

2016 ◽  
Author(s):  
Naga Musunuri ◽  
Ian Fischer ◽  
Pushpendra Singh ◽  
Daniel E. Bunker ◽  
Susan Pell
Keyword(s):  
Fluid Dynamics ◽  
Aquatic Plants ◽  
Water Surface ◽  
Pollen Dispersal ◽  
Pollen Grain ◽  
Air Bubbles ◽  
Ruppia Maritima ◽  
Two Dimensional ◽  
Brackish Waters ◽  
Hydrophilous Pollination

The aim of this work is to understand the physics underlying the mechanisms of two-dimensional aquatic pollen dispersal, known as hydrophily, that have evolved in several genera of aquatic plants, including Halodule, Halophila, Lepilaena, and Ruppia. We selected Ruppia maritima, which is native to salt and brackish waters circumglobally, for this study. We observed two mechanisms by which the pollen released from male inflorescences of Ruppia is adsorbed on a water surface: 1) inflorescences rise above the water surface and after they mature their pollen mass falls onto the surface as clumps and disperses as it comes in contact with the surface; 2) inflorescences remain below the surface and produce air bubbles which carry pollen mass to the surface where it disperses. In both cases dispersed pollen masses combined with others under the action of lateral capillary forces to form pollen rafts. The formation of porous pollen rafts increases the probability of pollination since the attractive capillary force on a pollen raft toward a stigma is much larger than on a single pollen grain. The presence of a trace amount of surfactant can disrupt the pollination process as the pollen is not captured or transported on the water surface.

scholarly journals A Stochastic Model of Atmospheric Rime Icing

1988 ◽  
Vol 34 (116) ◽  
pp. 26-30 ◽  
Author(s):  
E.M. Gates ◽  
A. Liu ◽  
E.P. Lozowski
Keyword(s):  
Stochastic Process ◽  
Flow Field ◽  
Diameter Ratio ◽  
Two Dimensional ◽  
Small Water ◽  
Ice Accumulation ◽  
Discrete Structures ◽  
Random Position ◽  
Air Speed ◽  
The Impact

AbstractThe accumulation of rime ice on structures, due to the impact and freezing of small water droplets, has been modelled as a stochastic process. Individual droplets are introduced into the flow field about the structure at a random position. Their trajectories are then calculated to determine the position of impact on the structure, or on previously impacted droplets. By assuming that the droplets maintain their shape on impact, the modelled accretion is gradually built up, one droplet at a time.In the present paper, attention has been limited to a circular cylinder as the collecting structure, and it has been assumed that the flow field and the ice accumulation are strictly two-dimensional. With these assumptions, the influence of the droplet/cylinder diameter ratio and of the air speed upon the resulting predictions has been investigated. The main feature of interest in the model prediction is the development, near the edges of the accumulation, of discrete structures called “rime feathers”. The mechanism for the growth of these rime feathers is described, and a comparison is made between the characteristics of the predicted structures and of some natural rime feathers grown in an icing wind tunnel.

scholarly journals Swath-altimetry measurements of the main stem Amazon River: measurement errors and hydraulic implications

2015 ◽  
Vol 19 (4) ◽  
pp. 1943-1959 ◽  
Author(s):  
M. D. Wilson ◽  
M. Durand ◽  
H. C. Jung ◽  
D. Alsdorf
Keyword(s):  
Surface Water ◽  
Water Surface ◽  
Hydraulic Model ◽  
Two Dimensions ◽  
Main Stem ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Temporal Sampling ◽  
Spatio Temporal ◽  
The Impact

Abstract. The Surface Water and Ocean Topography (SWOT) mission, scheduled for launch in 2020, will provide a step-change improvement in the measurement of terrestrial surface-water storage and dynamics. In particular, it will provide the first, routine two-dimensional measurements of water-surface elevations. In this paper, we aimed to (i) characterise and illustrate in two dimensions the errors which may be found in SWOT swath measurements of terrestrial surface water, (ii) simulate the spatio-temporal sampling scheme of SWOT for the Amazon, and (iii) assess the impact of each of these on estimates of water-surface slope and river discharge which may be obtained from SWOT imagery. We based our analysis on a virtual mission for a ~260 km reach of the central Amazon (Solimões) River, using a hydraulic model to provide water-surface elevations according to SWOT spatio-temporal sampling to which errors were added based on a two-dimensional height error spectrum derived from the SWOT design requirements. We thereby obtained water-surface elevation measurements for the Amazon main stem as may be observed by SWOT. Using these measurements, we derived estimates of river slope and discharge and compared them to those obtained directly from the hydraulic model. We found that cross-channel and along-reach averaging of SWOT measurements using reach lengths greater than 4 km for the Solimões and 7.5 km for Purus reduced the effect of systematic height errors, enabling discharge to be reproduced accurately from the water height, assuming known bathymetry and friction. Using cross-sectional averaging and 20 km reach lengths, results show Nash–Sutcliffe model efficiency values of 0.99 for the Solimões and 0.88 for the Purus, with 2.6 and 19.1 % average overall error in discharge, respectively. We extend the results to other rivers worldwide and infer that SWOT-derived discharge estimates may be more accurate for rivers with larger channel widths (permitting a greater level of cross-sectional averaging and the use of shorter reach lengths) and higher water-surface slopes (reducing the proportional impact of slope errors on discharge calculation).

Instantaneous water surface and bed scour profiles using video image analysis

1998 ◽  
Vol 25 (4) ◽  
pp. 662-667 ◽  
Author(s):  
R Balachandar ◽  
J A Kells
Keyword(s):  
Image Analysis ◽  
Flow Field ◽  
Water Surface ◽  
Surface Profile ◽  
Steady Flows ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Two Dimensional Flow ◽  
Water Surface Profile ◽  
Bed Scour

In steady open-channel flow, the use of a conventional point gauge to obtain the water surface profile yields reasonably accurate results. However, in unsteady and quasi-steady flows, the point gauge is not of much use. Furthermore, in flow fields where there is significant bed scour, it is often of interest to the hydraulic engineer to obtain the instantaneous bed scour profile during the scouring process. In most quasi-steady flows involving bed scour, the water surface profile continuously readjusts itself in response to the changes in the bed profile. To carry out a proper analysis of the entire flow field, it is necessary to obtain both the instantaneous water surface and the corresponding bed scour profiles. The development of a nonintrusive video image analysis procedure to simultaneously obtain the water surface and bed scour profiles in a two-dimensional flow field is presented in this paper. A computer program entitled PROSCAN has been developed to extract the water surface and bed scour profiles from digitized video images of the flow field. The use of PROSCAN is demonstrated by obtaining the instantaneous water surface and bed scour profiles for a two-dimensional flow field downstream of a sluice gate.Key words: image analysis, software development, water surface profile, bed scour profile, scour dynamics.

Observation and Analysis of a Non-Uniform Avalanche Phenomenon in 4H-SiC 4°-Off (0001) p-n Diodes Terminated with a Floating-Field Ring

2015 ◽  
Vol 821-823 ◽  
pp. 640-643 ◽  
Author(s):  
Kazuhiro Mochizuki ◽  
Hiroyuki Okino ◽  
Hiroyuki Matsushima ◽  
Yoshiaki Toyota
Keyword(s):  
Opposite Direction ◽  
Impact Ionization ◽  
Two Dimensional ◽  
Ionization Coefficient ◽  
Dry Oxidation ◽  
Aluminum Implantation ◽  
Dimensional Simulation ◽  
The Impact

4H-SiC (0001) p-n diodes terminated with a floating-field ring were found to emit light at breakdown in the opposite direction to that of substrate misorientation when the diodes were fabricated by aluminum implantation and dry-oxidation passivation. Two-dimensional simulation revealed that such non-uniform breakdown was mainly attributable to the asymmetric lateral straggling of implanted aluminum acceptors, rather than the anisotropic nature of the impact ionization coefficient.

TWO-DIMENSIONAL SIMULATION OF STEAM-AIR JET CONDENSED INTO SUBCOOLED WATER

2018 ◽  
Author(s):  
Haibo Li ◽  
Maocheng Tian ◽  
Xiaohang Qu ◽  
Min Wei
Keyword(s):  
Two Dimensional ◽  
Subcooled Water ◽  
Air Jet ◽  
Dimensional Simulation
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