Dynamics of capillary-driven liquid–liquid displacement in open microchannels

2014 ◽  
Vol 16 (44) ◽  
pp. 24473-24478 ◽  
Author(s):  
D. Yang ◽  
M. Krasowska ◽  
C. Priest ◽  
J. Ralston
Keyword(s):  
Flow Velocity ◽  
Channel Width ◽  
Liquid Front ◽  
Liquid Displacement

For capillary-driven liquid–liquid displacement in rectangular open microchannels, the square of the position of the liquid–liquid front increases linearly with time, whereas the flow velocity decreases with increasing channel width.

Theoretical Analysis of Flame Propagation in Meso and Microscale Channels

2003 ◽  
Author(s):  
Yiguang Ju
Keyword(s):  
Flow Velocity ◽  
Heat Loss ◽  
Flame Propagation ◽  
Critical Value ◽  
Flow Speed ◽  
External Heat ◽  
Channel Width ◽  
Recent Experimental Data ◽  
Quenching Distance ◽  
Large Flow

Extinction and flame propagation in a meso and microscale channels are investigated analytically. Emphasis was paid to the coupling of wall heat loss, wall preheating, external heat loss and chemical reaction. The results showed that, wall thermal properties, channel width and flow velocity have dramatic effects on the flame propagation and lead to multiple flame regimes and extinction limits. With the decrease of channel width, flame reaches its first quenching limit, the so called critical quenching distance. However, with a further decrease of channel width, the results show that there exists a slow burning flame. With the increase of wall heat loss the speed of the slow burning flame slightly decreases and eventually reaches its second burning limit. With the change of the flow velocity, the results show that sub-limit flame can only exist at flow velocity larger than a critical value. At moderate flow velocity, flame speed increases with the increase of flow speed. At very large flow velocity, flame will be blown off. The above results are confirmed from the recent experimental data.

scholarly journals Empirical Assessment Tool for Bathymetry, Flow Velocity and Salinity in Estuaries Based on Tidal Amplitude and Remotely-Sensed Imagery

2018 ◽  
Vol 10 (12) ◽  
pp. 1915 ◽  
Author(s):  
Jasper Leuven ◽  
Steye Verhoeve ◽  
Wout van Dijk ◽  
Sanja Selaković ◽  
Maarten Kleinhans
Keyword(s):  
Flow Velocity ◽  
Assessment Tool ◽  
Numerical Models ◽  
High Water ◽  
Remotely Sensed ◽  
Channel Width ◽  
Tidal Amplitude ◽  
Intertidal Area ◽  
Cross Sectional ◽  
Remotely Sensed Imagery

Hydromorphological data for many estuaries worldwide is scarce and usually limited to offshore tidal amplitude and remotely-sensed imagery. In many projects, information about morphology and intertidal area is needed to assess the effects of human interventions and rising sea-level on the natural depth distribution and on changing habitats. Habitat area depends on the spatial pattern of intertidal area, inundation time, peak flow velocities and salinity. While numerical models can reproduce these spatial patterns fairly well, their data need and computational costs are high and for each case a new model must be developed. Here, we present a Python tool that includes a comprehensive set of relations that predicts the hydrodynamics, bed elevation and the patterns of channels and bars in mere seconds. Predictions are based on a combination of empirical relations derived from natural estuaries, including a novel predictor for cross-sectional depth distributions, which is dependent on the along-channel width profile. Flow velocity, an important habitat characteristic, is calculated with a new correlation between depth below high water level and peak tidal flow velocity, which was based on spatial numerical modelling. Salinity is calculated from estuarine geometry and flow conditions. The tool only requires an along-channel width profile and tidal amplitude, making it useful for quick assessments, for example of potential habitat in ecology, when only remotely-sensed imagery is available.

Channel widening quantification under laboratory conditions

2020 ◽  
Author(s):  
Chao Qin ◽  
Fenli Zheng ◽  
Robert Wells
Keyword(s):  
Flow Velocity ◽  
Sediment Supply ◽  
Channel Width ◽  
Sediment Discharge ◽  
Inflow Rate ◽  
Sediment Delivery ◽  
Negative Power ◽  
Manual Sampling ◽  
Channel Widening ◽  
Bed Slope

<p>Channel widening constitutes about 80% of total soil loss, especially in the presence of a plow pan which manifests a less or nonerodible soil layer. Channel bank erosion quantification is prerequisite to couple effectively the bank sediment supply system with fluvial sediment transport fluxes. The objectives of this study were to: 1) describe and evaluate methods for monitoring and data post-analysis of channel widening and 2) investigate how inflow rate, slope gradient and initial channel width affect channel widening processes in the presence of a non-erodible layer. Technology was developed to capture 5-cm spaced cross-sections along a soil flume at 3-s time intervals. Two off-the-shelf digital cameras were positioned 3-m above the soil bed and controlled by a program to trigger simultaneously and download images to the computer. Methods utilizing color differences in images and elevation differences in DEMs were applied to detect discontinuities between channel walls and the soil bed. Channel widths were calculated by differentiating the coordinates of these surface discontinuities. A volumetric method was used to calculate flow velocity with measurements of flow depths obtained from ultrasonic depth sensors. Sediment concentration was determined by manual sampling.</p><p>The results showed that different channel width calculation methods exhibited comparable outcomes and achieved satisfactory accuracy. Sediment discharge showed a significant positive linear correlation with channel widening rate, while exhibiting a 5 to 25-s time lag compared to the peak of channel widening rate. Total sediment discharge calculated by photogrammetry was 3.1% lower than that calculated by manual sampling. Flow velocity decreased with time and showed a significant negative power correlation with channel width. Sediment delivery and channel width increased with the increase of inflow rate, bed slope and the decrease of initial channel width. Exponential equations were used to predict the channel width time series. Toe scour, crack development, sidewall failure and block detachment and transport, in sequence, were the four main processes of channel widening. Basal scour arc length, tension crack length and width decreased with initial channel width and increased with time, flow discharge and bed slope. Basal scour arcs were divided into three patterns according to different shapes in comparison to the failure arcs. Sediment delivery equations based on the disaggregation of concentrated flow entrainment and mass failure were also fitted. Advantages of the described methodology include automated high spatial and temporal monitoring resolution, semi-automated data post-processing, and the potential to be generalized to large scale river/reservoir bank failure monitoring. This study provides new insight on improving channel widening measurements and prediction technology.</p>

scholarly journals Influence of outlet channel width to the flow velocity and pressure of a flow focusing microfluidic device

2016 ◽  
Vol 160 ◽  
pp. 012086
Author(s):  
Chin Fhong Soon ◽  
Yap Hiung Yin ◽  
Kian Sek Tee ◽  
Mohd Khairul Ahmad ◽  
Mohd Zainizan Sahdan ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Microfluidic Device ◽  
Channel Width ◽  
Flow Focusing ◽  
Outlet Channel

Flow Properties of Fluids Confined in Parallel-Plate Nanochannels

2012 ◽  
Vol 229-231 ◽  
pp. 22-25
Author(s):  
Zhong Qiang Zhang ◽  
Guang Gui Cheng ◽  
Jian Ning Ding ◽  
Zhi Yong Ling
Keyword(s):  
Pressure Gradient ◽  
Flow Velocity ◽  
Parallel Plate ◽  
Stokes Equations ◽  
Channel Width ◽  
Mean Flow ◽  
The Mean ◽  
Dynamics Simulations ◽  
Mean Flow Velocity ◽  
Pressure Driven

Molecular dynamics simulations are carried out to explore the fluid flows in parallel-plate nanochannels. A “channel moving” pressure-driven model is utilized to study the planar Poiseuille flows. Considering the slip boundary conditions, relationships among the pressure gradient, mean flow velocity and the channel width are investigated to couple the atomistic regime to continuum. The results show that the mean flow velocity almost linearly increases with the increase of the pressure gradient. The slope of the linear relationship between the pressure gradient and the mean flow velocity is nonlinearly decreased with increasing the channel width. The results indicate that the approximate accuracy is reduced with decreasing the channel width while the pressure-driven flows confined in nanochannels are approximately described by the Navier-Stokes equations.

scholarly journals Nannochloropsis oceanica Cultivation in Pilot-Scale Raceway Ponds—From Design to Cultivation

2020 ◽  
Vol 10 (5) ◽  
pp. 1725 ◽  
Author(s):  
Pedro Cunha ◽  
Hugo Pereira ◽  
Margarida Costa ◽  
João Pereira ◽  
Joana T. Silva ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Water Depth ◽  
Production Systems ◽  
Biomass Productivity ◽  
Pilot Scale ◽  
Channel Width ◽  
Nannochloropsis Oceanica ◽  
Efficient System ◽  
Standard Configuration ◽  
Raceway Ponds

Raceways ponds are the microalgal production systems most commonly used at industrial scale. In this work, two different raceway configurations were tested under the same processing conditions to compare their performance on the production of Nannochloropsis oceanica. Biomass productivity, biochemical composition of the produced biomass, and power requirements to operate those reactors were evaluated. Water depths of 0.20 and 0.13 m, and culture circulation velocities of 0.30 and 0.15 m s−1 were tested. A standard configuration, which had a full channel width paddlewheel, proved to be the most energy efficient, consuming less than half of the energy required by a modified configuration (had a half channel width paddlewheel). The later showed to have slightly higher productivity, not enough to offset the large difference in energetic consumption. Higher flow velocity (0.30 m s−1) led to a 1.7 g m−2 d−1 improvement of biomass productivity of the system, but it increased the energy consumption twice as compared to the 0.15 m s−1 flow velocity. The latter velocity showed to be the most productive in lipids. A water depth of 0.20 m was the most suitable option tested to cultivate microalgae, since it allowed a 54% energy saving. Therefore, a standard raceway pond using a flow velocity of 0.3 m s−1 with a 0.20 m water depth was the most efficient system for microalgal cultivation. Conversely, a flow velocity of 0.15 m s−1 was the most suitable to produce lipids.

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