Flow speed has little impact on propulsive characteristics of oscillating foils

Abstract Habitat complexity is recognized to mediate predator–prey relationships by offering refuge or not. We investigated the availability of planktonic microcrustaceans and the diet of a planktivorous fish (Hyphessobrycon eques) at different levels (low, intermediate and high) of aquatic macrophyte biomass. Sampling was carried out in a river with low flow speed, located in a Neotropical floodplain. We collected fish and microcrustaceans in macrophyte stands with variations in biomass. There were no differences in microcrustacean density in the water among the levels of macrophyte biomass, but microcrustacean richness and diet composition of H. eques differed. Microcrustacean richness and trophic niche breadth of the planktivorous fish were higher in high biomass stands. There was high consumption of a small cladoceran species in low macrophyte biomass, which was replaced by larger species, such as copepods, in intermediate and high biomass. Thus, the selection of some species was different among the biomass levels. These results suggest that plant biomass plays an important role in the interaction between fish and microcrustaceans, and prey characteristics such as size, escape ability and energy value make them more or less subject to predation by fish according to habitat structuring.

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A new stability-indicating RP-HPLC method for the determination of dicyclomine hydrochloride and dimethicone combination in tablet dosage forms

Future Journal of Pharmaceutical Sciences ◽

10.1186/s43094-021-00260-0 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

J. Saroja ◽

Anantha Lakshmi P.V. ◽

Y. Rammohan ◽

D. Divya Reddy

Keyword(s):

Liquid Chromatography ◽

Dosage Forms ◽

Flow Speed ◽

Hplc Method ◽

Stability Indicating ◽

Simultaneous Quantification ◽

Rp Hplc ◽

Tablet Formulations ◽

Tablet Dosage

Abstract Background We describe a “stability-indicating liquid chromatography” technique for the estimation of dimethicone (DEC) and dicyclomine hydrochloride (DEH) in the established tablet formulations. Individual quantification of DEH and DEC was reported. But simultaneous quantification of DEH and DEC was lacking. DEH and DEC were analysed on an “XTerra C18 column (250 mm × 4.6 mm, 5 μm)” with the mobile phase solvent run isocratically with 0.1M K2HPO4-acetonitrile (55:45, v/v) on a flow speed of 1.0 mL/min. Results The chromatographic run period for the DEC and DEH assay was 6.0 min with retention times of 2.134 and 2.865 min, respectively. The method was validated for accuracy (99.453 to 100.417% and 99.703 to 100.303% recovery values for DEH and DEC, respectively), precision (RSV value 0.135% for DEC and 0.171% for DEH), linearity (5–15 μg/mL for DEH and 20–60 μg/mL for DEC), selectivity (no hinderance from excipients) and specificity (no hinderance from degradants) recovery. Conclusion The developed stability-indicating liquid chromatography process was well applied to established tablet formulations.

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Spatiotemporal dynamic characteristics of typical temperate glaciers in China

Scientific Reports ◽

10.1038/s41598-020-80418-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Wang Shijin ◽

Che Yanjun ◽

Wei Yanqiang

Keyword(s):

Mass Balance ◽

Dynamic Characteristics ◽

Flow Speed ◽

Hydrothermal Conditions ◽

Humid Climate ◽

Ice Flow ◽

Change Rate ◽

Fast Movement ◽

The 1950S ◽

Yulong Snow Mountain

AbstractChina’s temperate glaciers have a relatively warm and humid climate and hydrothermal conditions at low latitudes. Temperate glaciers, however, have larger ablation, higher ice temperatures, relatively fast movement speeds, and a significant sliding process at the bottom. As a result, these glaciers are more significantly affected by climate change. On the basis of topographic maps, aerial photography, and Landsat OLI images, and combined with existing research results, this paper systematically analyzed the temporal and spatial dynamic characteristics of typical temperate glaciers. The results are as follows: (1) From the 1950s to the 1970s, compared with other types of glaciers, temperate glaciers showed strong retreat and ablation trends in terms of area, length, speed, and mass balance. (2) The reduction rates of glacier areas of Kangri Garpo, Dagu Snow Mountain, Yulong Snow Mountain (YSM), and Meili Snow Mountain (MSM) in China’s temperate glacier areas all exceeded 38%, which was far above the national average of 18% from the 1950s to the 2010s. (3) The recent length retreat rates of Azha Glacier, Kangri Garpo, and Mingyong Glacier, MSM, Hailuogou Glacier (HG), Gongga Snow Mountain (GSM), and Baishui River Glacier No. 1 (BRGN1), YSM were above 22 m/a, which was faster than the retreat rates of other regions. (4) Consistent with glacier retreat, temperate glaciers also had a faster ice flow speed. The ice flow velocities of the BGN1, HG, Parlung River Glaciers No. 4 and 94, and Nyainqêntanglha were, respectively, 6.33–30.78 m/a, 41–205 m/a, 15.1–86.3 m/a, and 7.5–18.4 m/a, which was much faster than the velocity of other types of glaciers. (5) Mass loss of temperate glaciers was most dramatic during the observation period (1959–2015). The annual mass balance from eight typical temperate glaciers fluctuated between − 2.48 and 0.44 m w.e., and the annual average change rate of mass balance (− 0.037 m w.e./a) was much higher than that in China (− 0.015 m w.e./a, p < 0.0001) and globally (− 0.013 m w.e./a, p < 0.0001).

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Two-dimensional leaps in near-critical flow over isolated orography

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2005.1530 ◽

2005 ◽

Vol 461 (2064) ◽

pp. 3747-3763 ◽

Cited By ~ 3

Author(s):

E.R Johnson ◽

G.G Vilenski

Keyword(s):

Unsteady Flow ◽

Equations Of Motion ◽

Fold Increase ◽

Flow Speed ◽

Two Dimensional ◽

Subcritical Flow ◽

One Dimensional ◽

Petviashvili Equation ◽

Lee Wave ◽

Supercritical Flows

This paper describes steady two-dimensional disturbances forced on the interface of a two-layer fluid by flow over an isolated obstacle. The oncoming flow speed is close to the linear longwave speed and the layer densities, layer depths and obstacle height are chosen so that the equations of motion reduce to the forced two-dimensional Korteweg–de Vries equation with cubic nonlinearity, i.e. the forced extended Kadomtsev–Petviashvili equation. The distinctive feature noted here is the appearance in the far lee-wave wake behind obstacles in subcritical flow of a ‘table-top’ wave extending almost one-dimensionally for many obstacles widths across the flow. Numerical integrations show that the most important parameter determining whether this wave appears is the departure from criticality, with the wave appearing in slightly subcritical flows but being destroyed by two-dimensional effects behind even quite long ridges in even moderately subcritical flow. The wave appears after the flow has passed through a transition from subcritical to supercritical over the obstacle and its leading and trailing edges resemble dissipationless leaps standing in supercritical flow. Two-dimensional steady supercritical flows are related to one-dimensional unsteady flows with time in the unsteady flow associated with a slow cross-stream variable in the two-dimensional flows. Thus the wide cross-stream extent of the table-top wave appears to derive from the combination of its occurrence in a supercritical region embedded in the subcritical flow and the propagation without change of form of table-top waves in one-dimensional unsteady flow. The table-top wave here is associated with a resonant steepening of the transition above the obstacle and a consequent twelve-fold increase in drag. Remarkably, the table-top wave is generated equally strongly and extends laterally equally as far behind an axisymmetric obstacle as behind a ridge and so leads to subcritical flows differing significantly from linear predictions.

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Optimization of water flow speed in dams

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1122/1/012031 ◽

2021 ◽

Vol 1122 (1) ◽

pp. 012031

Author(s):

Lusiana Tarihoran ◽

Tulus ◽

Sawalluddin

Keyword(s):

Water Flow ◽

Flow Speed

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

Journal of Marine Science and Engineering ◽

10.3390/jmse9010021 ◽

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.

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