scholarly journals Change in rheotactic behavior patterns of dinoflagellates in response to different microfluidic environments

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Si-Wei Li ◽  
Po-Hsu Lin ◽  
Tung-Yuan Ho ◽  
Chih-hao Hsieh ◽  
Chen-li Sun
Keyword(s):  
Oscillatory Flow ◽  
Cross Flow ◽  
Decisive Role ◽  
Flow Speed ◽  
Main Channel ◽  
Behavior Patterns ◽  
Flow Conditions ◽  
Karlodinium Veneficum ◽  
Strong Shear ◽  
Hydrodynamic Environment

AbstractPlankton live in dynamic fluid environments. Their ability to change in response to different hydrodynamic cues is critical to their energy allocation and resource uptake. This study used a microfluidic device to evaluate the rheotactic behaviors of a model dinoflagellate species, Karlodinium veneficum, in different flow conditions. Although dinoflagellates experienced forced alignment in strong shear (i.e. “trapping”), fluid straining did not play a decisive role in their rheotactic movements. Moderate hydrodynamic magnitude (20 < |uf| < 40 µm s−1) was found to induce an orientation heading towards an oncoming current (positive rheotaxis), as dinoflagellates switched to cross-flow swimming when flow speed exceeded 50 µm s−1. Near the sidewalls of the main channel, the steric mechanism enabled dinoflagellates to adapt upstream orientation through vertical migration. Under oscillatory flow, however, positive rheotaxis dominated with occasional diversion. The varying flow facilitated upstream exploration with directional controlling, through which dinoflagellates exhibited avoidance of both large-amplitude perturbance and very stagnant zones. In the mixed layer where water is not steady, these rheotactic responses could lead to spatial heterogeneity of dinoflagellates. The outcome of this study helps clarify the interaction between swimming behaviors of dinoflagellates and the hydrodynamic environment they reside in.

Study of Turbulent Models in Jet Impingement at Different Cross-Flow Conditions

2017 ◽  
Vol 17 (17th International Conference) ◽  
pp. 1-21
Author(s):  
Abd Elnaby Kabeel ◽  
Medhat Elkelawy ◽  
Hagar Bastawissi ◽  
Ahmed El-Banna
Keyword(s):  
Cross Flow ◽  
Jet Impingement ◽  
Flow Conditions ◽  
Turbulent Models

Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

2003 ◽  
Vol 3 (1-2) ◽  
pp. 201-207
Author(s):  
H. Nagaoka ◽  
T. Nakano ◽  
D. Akimoto
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Turbulence Model ◽  
Uptake Rate ◽  
Oscillatory Flow ◽  
Substrate Uptake ◽  
Flow Conditions ◽  
Mass Transfer Mechanism ◽  
Substrate Uptake Rate ◽  
Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

scholarly journals Theoretical evaluation of concentration time and storage coefficient with their application to major dam basins in Korea

2018 ◽  
Vol 19 (2) ◽  
pp. 644-652
Author(s):  
Chulsang Yoo ◽  
Jiho Lee ◽  
Eunsaem Cho
Keyword(s):  
Channel Length ◽  
Main Channel ◽  
Flow Conditions ◽  
Empirical Formulas ◽  
Theoretical Evaluation ◽  
Storage Coefficient ◽  
Concentration Time ◽  
Channel Slope ◽  
And Storage ◽  
Laminar Flow Conditions

Abstract This study theoretically evaluated the basin concentration time and storage coefficient with their empirical formulas available worldwide. The evaluation results were also validated in the application to major dam basins in Korea. The findings are summarized as follows. As a result of analytical analysis, the concentration time was found to be proportional to the main channel length under laminar flow conditions and to the square of it under turbulent flow conditions, but inversely proportional to the channel slope. It was also found that the storage coefficient and the concentration time are linearly but loosely related. Most empirical formulas for the concentration time concurred with the basic equation form, but just a few for the storage coefficient. Applications to major dam basins in Korea also showed that the concentration time agrees well with the result of theoretical analysis. However, the behavior of the storage coefficient varied much, basin by basin, indicating that additional factors may be needed to explain it.

Electrochemical Kinetic of a Low Carbon Steel in Seawater at Different Flow Speed

2015 ◽  
Vol 1766 ◽  
pp. 73-80
Author(s):  
A. Carmona ◽  
R. Orozco-Cruz ◽  
E. Mejía-Sánchez ◽  
A. Contreras ◽  
R. Galván-Martínez
Keyword(s):  
Turbulent Flow ◽  
Rotation Speed ◽  
Electrochemical Impedance ◽  
Static Condition ◽  
Flow Speed ◽  
Localized Corrosion ◽  
Low Carbon ◽  
Flow Conditions ◽  
Static Conditions ◽  
Turbulent Flow Conditions

ABSTRACTAn electrochemical impedance spectroscopy (EIS) corrosion study of API X70 steel was carried out in synthetic seawater with different rotation speeds using a rotating cylinder electrode (RCE) to control the hydrodynamic conditions at room temperature, atmospheric pressure and 24 h of exposure time. A superficial analysis through a scanning electron microscope (SEM) was used to analyze the corrosion type. The rotation speed used was 0 rpm (static condition), 1000, 3000 and 5000 rpm (turbulent flow). The results show that the turbulent flow conditions affect directly the corrosion rate (CR) of the steel, because all values of the CR under turbulent flow conditions are higher than the CR values at static conditions. In addition, it is important to point out that at turbulent flow conditions, the CR increased as the rotation speed also increased. The morphology of the corrosion in all experiments was localized corrosion.

Experimental investigation of dryout phenomena under oscillatory flow conditions

Heat Transfer ◽  
2022 ◽  
Author(s):  
Rakesh Kumar ◽  
Dinesh K. Chandraker ◽  
Arnab Dasgupta ◽  
Arun K. Nayak
Keyword(s):  
Experimental Investigation ◽  
Oscillatory Flow ◽  
Flow Conditions

Effect of spark discharge energy scheduling on ignition under quiescent and flow conditions

2020 ◽  
Vol 234 (12) ◽  
pp. 2878-2891
Author(s):  
Zhenyi Yang ◽  
Xiao Yu ◽  
Hua Zhu ◽  
David S-K Ting ◽  
Ming Zheng
Keyword(s):  
Flow Velocity ◽  
High Power ◽  
Cross Flow ◽  
Spark Discharge ◽  
Discharge Process ◽  
Discharge Energy ◽  
Flow Conditions ◽  
Flame Kernel ◽  
Spark Plug ◽  
Spark Energy

The enhancement of the breakdown power during the spark discharge process has been proved to be beneficial for the flame kernel formation process under lean/diluted conditions. Such a strategy is realized by using a conventional transistor coil ignition system with an add-on capacitance in parallel to the spark plug gap in this paper. In practical application, the use of different ceramic material other than aluminum oxide can change the parasitic capacitance of the spark plug, achieving similar effect in terms of rescheduling the discharge energy released during the breakdown phase. Detailed research has been carried out to investigate the effect of the parallel capacitance and the cross flow velocity on the flame kernel formation and propagation process. With the increase in parallel capacitance, more spark energy is delivered during the breakdown phase, while less energy is released during the arc/glow phase. Shadowgraph images of the spark plasma reveal that the high-power spark discharge can generate a larger high-temperature area with enhanced electrically prompted turbulence under quiescent conditions, as compared with that using the conventional transistor coil ignition discharge strategy under the same condition. The breakdown enhanced turbulence of the high-power spark is proved to be beneficial for the flame kernel development, especially with the lean or exhaust gas recirculation diluted combustible mixtures, given that sufficient spark energy is available for the high-power spark strategy to successfully generate the breakdown event. The results of combustion tests under flow conditions reveal that the breakdown enhanced turbulence of the high-power spark tends to be overshadowed by the turbulence generated from the flow field, and both the increase in flow velocity and parallel capacitance contribute to the reduction in discharge duration of the arc/glow phase. Therefore, the benefits brought about by the high-power spark discharge tend to diminish with the intensification of flow velocity.

Jet interaction at supersonic cross flow conditions

Shock Waves ◽  
2003 ◽  
Vol 13 (1) ◽  
pp. 13-23 ◽  
Author(s):  
F. Seiler ◽  
P. Gnemmi ◽  
H. Ende ◽  
M. Schwenzer ◽  
R. Meuer
Keyword(s):  
Cross Flow ◽  
Flow Conditions ◽  
Jet Interaction

The use of turbulence generators to mitigate crystallization fouling under cross flow conditions

Desalination ◽  
2012 ◽  
Vol 288 ◽  
pp. 108-117 ◽  
Author(s):  
Basim O. Hasan ◽  
Graham J. Nathan ◽  
Peter J. Ashman ◽  
Richard A. Craig ◽  
Richard M. Kelso
Keyword(s):  
Cross Flow ◽  
Flow Conditions

scholarly journals Formation of Kinneyia via shear-induced instabilities in microbial mats

2013 ◽  
Vol 371 (2004) ◽  
pp. 20120362 ◽  
Author(s):  
Katherine Thomas ◽  
Stephan Herminghaus ◽  
Hubertus Porada ◽  
Lucas Goehring
Keyword(s):  
Microbial Mats ◽  
Flow Speed ◽  
Glass Beads ◽  
Flowing Water ◽  
Flow Conditions ◽  
Theoretical Predictions ◽  
Laboratory Analogue ◽  
Littoral Habitats ◽  
Over Time ◽  
Ripple Pattern

Kinneyia are a class of microbially mediated sedimentary fossils. Characterized by clearly defined ripple structures, Kinneyia are generally found in areas that were formally littoral habitats and covered by microbial mats. To date, there has been no conclusive explanation of the processes involved in the formation of these fossils. Microbial mats behave like viscoelastic fluids. We propose that the key mechanism involved in the formation of Kinneyia is a Kelvin–Helmholtz-type instability induced in a viscoelastic film under flowing water. A ripple corrugation is spontaneously induced in the film and grows in amplitude over time. Theoretical predictions show that the ripple instability has a wavelength proportional to the thickness of the film. Experiments carried out using viscoelastic films confirm this prediction. The ripple pattern that forms has a wavelength roughly three times the thickness of the film. This behaviour is independent of the viscosity of the film and the flow conditions. Laboratory-analogue Kinneyia were formed via the sedimentation of glass beads, which preferentially deposit in the troughs of the ripples. Well-ordered patterns form, with both honeycomb-like and parallel ridges being observed, depending on the flow speed. These patterns correspond well with those found in Kinneyia, with similar morphologies, wavelengths and amplitudes being observed.

Sign in / Sign up

Export Citation Format

Share Document