scholarly journals Evaporation and deposition of inclined colloidal droplets

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jin Young Kim ◽  
Marta Gonçalves ◽  
Narina Jung ◽  
Hyoungsoo Kim ◽  
Byung Mook Weon
Keyword(s):  
Particle Size ◽  
Relative Humidity ◽  
Colloidal Particle ◽  
Flow Speed ◽  
Speed Ratio ◽  
Particle Movement ◽  
Capillary Flows ◽  
Solid Substrates ◽  
Speed Dependence ◽  
Evaporation Dynamics

AbstractColloidal droplets on flat solid substrates commonly leave symmetric ring-like deposits due to coffee-ring flows during evaporation. On inclined substrates, droplet shapes may become asymmetric by gravity. On this basis, it is not clear how their evaporation dynamics and final deposits are changed depending on inclination. Here we explore evaporation and deposition dynamics of colloidal droplets on inclined substrates, mainly by controlling colloidal particle size, substrate inclination, and relative humidity, which are crucial to gravitational intervention and evaporation dynamics. We experimentally investigate two different flows with opposite directions: downward sedimentation flows by gravity ($$v_s$$ v s ) and upward capillary flows by evaporation ($$v_c$$ v c ). We find that the competition of two flows determines the formation of final deposits with a flow speed ratio of $$\alpha = v_s/v_c$$ α = v s / v c . Notably, for $$\alpha$$ α $$\ll$$ ≪ 1, evaporation-driven upward flows overwhelm sedimentation-driven downward flows, resulting in accentuated particle movement towards the top ring, which seems to defy gravitational intervention. We suggest a possible explanation for the flow speed dependence of final deposits in evaporating colloidal droplets. This study offers a framework to understand the intervention of inclination to the formation of final deposits and how to overcome the deposit pattern radial asymmetry, achieving symmetric deposit widths from inclined colloidal droplets.

scholarly journals A Model for Performance Estimation of Flapping Foil Operating as Biomimetic Stream Energy Device

2020 ◽  
Vol 9 (1) ◽  
pp. 21
Author(s):  
Iro E. Malefaki ◽  
Kostas A. Belibassakis
Keyword(s):  
Vertical Axis ◽  
Flow Speed ◽  
Performance Estimation ◽  
Speed Ratio ◽  
Power Extraction ◽  
Flapping Foil ◽  
Flow Energy ◽  
Novel Concept ◽  
Angular Oscillations ◽  
Energy Converters

During the recent period intensive research has focused on the advancement of engineering and technology aspects concerning the development and optimization of wave and current energy converters driven by the need to increase the percentage of marine renewable sources in the energy-production mix, particularly from offshore installations. Most stream energy-harvesting devices are based on hydro-turbines, and their performance is dependent on the ratio of the blade-tip speed to incident-flow speed. As the oncoming speed of natural-occurring currents varies randomly, there is a penalty for the latter device’s performance when operating at non-constant tip-speed ratio away from the design value. Unlike conventional turbines that are characterized by a single degree of freedom rotating around an axis, a novel concept is examined concerning hydrokinetic energy converters based on oscillating hydrofoils. The biomimetic device includes a rotating, vertically mounted, biomimetic wing, supported by an arm linked at a pivot point on the mid-chord. Activated by a controllable self-pitching motion the system performs angular oscillations around the vertical axis in incoming flow. In this work, the performance of the above flapping-foil, biomimetic flow energy harvester is investigated by application of a semi-3D model based on unsteady hydrofoil theory and the results are verified by comparison to experimental data and a 3D boundary element method based on vortex rings. By systematical application of the model the power extraction and efficiency of the system is presented for various cases including different geometric, mechanical, and kinematic parameters, and the optimal performance of the system is determined.

scholarly journals Observational aspects of IMF draping-related magnetosheath accelerations for northward IMF

2013 ◽  
Vol 31 (10) ◽  
pp. 1779-1789 ◽  
Author(s):  
B. Harris ◽  
C. J. Farrugia ◽  
N. V. Erkaev ◽  
R. B. Torbert
Keyword(s):  
Magnetic Field ◽  
Statistical Study ◽  
Flow Speed ◽  
Event Studies ◽  
Speed Ratio ◽  
Recent Theory ◽  
Interplanetary Coronal Mass Ejections ◽  
Low Latitudes ◽  
Flow Speeds ◽  
Rule Out

Abstract. Acceleration of magnetosheath plasma resulting from the draping of the interplanetary magnetic field (IMF) around the magnetosphere can give rise to flow speeds that exceed that of the solar wind (VSW) by up to ~60%. Three case event studies out of 34 identified events are described. We then present a statistical study of draping-related accelerations in the magnetosheath. Further, we compare the results with the recent theory of Erkaev et al. (2011, 2012). We present a methodology to help distinguish draping-related accelerations from those caused by magnetic reconnection. To rule out magnetopause reconnection at low latitudes, we focus mainly on the positive Bz phase during the passage of interplanetary coronal mass ejections (ICMEs), as tabulated in Richardson and Cane (2010) for 1997–2009, and adding other events from 2010. To avoid effects of high-latitude reconnection poleward of the cusp, we also consider spacecraft observations made at low magnetic latitudes. We study the effect of upstream Alfvén Mach number (MA) and magnetic local time (MLT) on the speed ratio V/VSW. The comparison with theory is good. Namely, (i) flow speed ratios above unity occur behind the dawn–dusk terminator, (ii) those below unity occur on the dayside magnetosheath, and (iii) there is a good general agreement in the dependence of the V ratio on MA.

Concentration of respirable dust and bioaerosols and identification of certain microbial types in a hog-growing facility

1991 ◽  
Vol 71 (2) ◽  
pp. 271-277 ◽  
Author(s):  
M. Butera ◽  
J. H. Smith ◽  
W. D. Morrison ◽  
R. R. Hacker ◽  
F. A. Kains ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Particle Size ◽  
Light Scattering ◽  
Relative Humidity ◽  
Ventilation Rate ◽  
Potato Dextrose Agar ◽  
Respirable Dust ◽  
Bacterial Isolates ◽  
Gram Positive Bacteria ◽  
Andersen Sampler

In order to assess the effects of ventilation rate, temperature, relative humidity and source of air on bioaerosol levels and dust with particle size < 10 μm, a total of 120 pigs housed in 12 pens in two separate rooms were used. Pigs averaged 30 kg initially and the trials were discontinued when 20% of the pigs were marketed. A six-stage Andersen sampler and a light scattering particle counter were used to determine bioaerosols and respirable dust (0.1–10 μm), respectively. Total bioaerosols were assessed using Trypticase Soy Agar. Potato Dextrose Agar was used for fungal aeorsols and Baird-Parker Agar used for isolation of Staphylococcus aureus. Moulds amounted to less than 1% of total microorganisms. Gram positive bacteria made up 72% of the bacterial isolates. Respirable dust was not correlated with respirable bioaerosols. Ventilation rate (2, 5 or 8 changes h−1) did not affect bioaerosol level or respirable dust. Total bioaerosols were significantly reduced (P < 0.05) in higher temperatures only. Relative humidity did not influence total bioaerosols but in one series respirable bioaerosols were significantly (R = 0.53) (P < 0.05) correlated with RH. Total bioaerosols were not different in outside air or attic air. Key words: Dust, bioaerosols, pigs, ventilation

scholarly journals Developing a Relative Humidity Correction for Low-Cost Sensors Measuring Ambient Particulate Matter

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2790 ◽  
Author(s):  
Andrea Di Antonio ◽  
Olalekan Popoola ◽  
Bin Ouyang ◽  
John Saffell ◽  
Roderic Jones
Keyword(s):  
Particle Size ◽  
Particulate Matter ◽  
Relative Humidity ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Low Cost ◽  
Monitoring Networks ◽  
Ambient Particulate Matter ◽  
Correction Algorithm ◽  
Ambient Conditions

There is increasing concern about the health impacts of ambient Particulate Matter (PM) exposure. Traditional monitoring networks, because of their sparseness, cannot provide sufficient spatial-temporal measurements characteristic of ambient PM. Recent studies have shown portable low-cost devices (e.g., optical particle counters, OPCs) can help address this issue; however, their application under ambient conditions can be affected by high relative humidity (RH) conditions. Here, we show how, by exploiting the measured particle size distribution information rather than PM as has been suggested elsewhere, a correction can be derived which not only significantly improves sensor performance but which also retains fundamental information on particle composition. A particle size distribution–based correction algorithm, founded on κ -Köhler theory, was developed to account for the influence of RH on sensor measurements. The application of the correction algorithm, which assumed physically reasonable κ values, resulted in a significant improvement, with the overestimation of PM measurements reduced from a factor of ~5 before correction to 1.05 after correction. We conclude that a correction based on particle size distribution, rather than PM mass, is required to properly account for RH effects and enable low cost optical PM sensors to provide reliable ambient PM measurements.

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