scholarly journals Passive Flow Through an Unstalked Intertidal Ascidian: Orientation and Morphology Enhance Suspension Feeding in Pyura stolonifera

2004 ◽  
Vol 207 (3) ◽  
pp. 217-224 ◽  
Author(s):  
N. A. Knott ◽  
A. R. Davis ◽  
W. A. Buttemer
Keyword(s):  
Suspension Feeding ◽  
Passive Flow ◽  
Flow Through

Enhanced vortex stability in trapped vortex combustor

2010 ◽  
Vol 114 (1155) ◽  
pp. 333-337 ◽  
Author(s):  
S. Vengadesan ◽  
C. Sony
Keyword(s):  
Numerical Simulation ◽  
Vortex Flow ◽  
Cavity Size ◽  
Vortex Stability ◽  
Cold Flow ◽  
Air Jets ◽  
Passive Flow ◽  
Flow Through ◽  
Trapped Vortex ◽  
Driver Air

Abstract The Trapped Vortex Combustor (TVC) is a new design concept in which cavities are designed to trap a vortex flow structure established through the use of driver air jets located along the cavity walls. TVC offers many advantages when compared to conventional swirl-stabilised combustors. In the present work, numerical investigation of cold flow (non-reacting) through the two-cavity trapped vortex combustor is performed. The numerical simulation involves passive flow through the two-cavity TVC to obtain an optimum cavity size to trap stable vortices inside the second cavity and to observe the characteristics of the two cavity TVC. From the flow attributes, it is inferred that vortex stability is achieved by circulation and the vortex is trapped inside when a second afterbody is added.

Fluid transmission and filtration efficiency of the labral fans of black fly larvae (Diptera: Simuliidae): hydrodynamic, morphological, and behavioural aspects

1993 ◽  
Vol 71 (1) ◽  
pp. 148-162 ◽  
Author(s):  
Jean O. Lacoursière ◽  
Douglas A. Craig
Keyword(s):  
Filtration Efficiency ◽  
Suspension Feeding ◽  
Optimal Filtering ◽  
Feedback Process ◽  
Simulium Vittatum ◽  
Active Feedback ◽  
Flow Through ◽  
Feeding Process ◽  
Behavioural Aspects ◽  
Feeding Behaviours

Body stance and water flow through the labral fans of suspension-feeding Simulium vittatum Zetterstedt larvae were examined using dead and live larvae. Transmission of flowing water through the fans was determined by means of dye injections. Feeding stance is the outcome of an active feedback process between flow forces and behavioural reactions that maintains the fans in an optimal filtering position. Fans responded to velocity increases through structural reconfiguration, which resulted in an increase in aperture size. As the velocity decreased, an increased fraction of the water directly approaching the fan aperture flowed around its perimeter, with no flow through the fans below 2.5 cm∙s−1. Fluid transmission never exceeded 30–35%, even at velocities up to 50 cm∙s−1. Calculations of suspension-feeding efficiency are reformulated to reflect labral fan transmission and behavioural components of the feeding process. Simulium vittatum larvae are consequently shown to be 4–26 times more efficient in filter feeding than has been previously assessed. The effect of flow on labral fan transmission is discussed in relation to known habitat choices and feeding behaviours of simuliid larvae.

scholarly journals A Critical Comparison between Flow-through and Lateral Flow Immunoassay Formats for Visual and Smartphone-Based Multiplex Allergen Detection

Biosensors ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 143 ◽  
Author(s):  
Georgina M. S. Ross ◽  
Gert IJ. Salentijn ◽  
Michel W. F. Nielen
Keyword(s):  
Test Line ◽  
Color Space ◽  
Lateral Flow ◽  
Critical Comparison ◽  
Passive Flow ◽  
Allergen Detection ◽  
Assay Time ◽  
Flow Through ◽  
Allergen Labeling ◽  
Active Flow

(1) Background: The lack of globally standardized allergen labeling legislation necessitates consumer-focused multiplexed testing devices. These should be easy to operate, fast, sensitive and robust. (2) Methods: Herein, we describe the development of three different formats for multiplexed food allergen detection, namely active and passive flow-through assays, and lateral flow immunoassays with different test line configurations. (3) Results: The fastest assay time was 1 min, whereas even the slowest assay was within 10 min. With the passive flow approach, the limits of detection (LOD) of 0.1 and 0.5 ppm for total hazelnut protein (THP) and total peanut protein (TPP) in spiked buffer were reached, or 1 and 5 ppm of THP and TPP spiked into matrix. In comparison, the active flow approach reached LODs of 0.05 ppm for both analytes in buffer and 0.5 and 1 ppm of THP and TPP spiked into matrix. The optimized LFIA configuration reached LODs of 0.1 and 0.5 ppm of THP and TPP spiked into buffer or 0.5 ppm for both analytes spiked into matrix. The optimized LFIA was validated by testing in 20 different blank and spiked matrices. Using device-independent color space for smartphone analysis, two different smartphone models were used for the analysis of optimized assays.

Functional significance of regular archaeocyathan central cavity diameter: a biomechanical and paleoecological test

Paleobiology ◽  
1995 ◽  
Vol 21 (3) ◽  
pp. 356-378 ◽  
Author(s):  
Michael Savarese
Keyword(s):  
Flow Direction ◽  
South Australia ◽  
Outer Wall ◽  
Flow Speed ◽  
Central Cavity ◽  
Ambient Flow ◽  
Passive Flow ◽  
Pore Area ◽  
Flow Through ◽  
Fluorescein Dye

Theoretical and experimental biomechanical approaches are used to test the effect regular archaeocyathan central cavity diameter has on the generation of passive flow through the skeleton. These results are then used to predict a correspondence between gross morphology and paleoenvironmental occurrence. Previous work has demonstrated that regular archaeocyathan morphology generates passive flow, via Bernoulli and viscous entrainment effects, through its porous walls for suspension feeding, a phenomenon that occurs in modern sponges. Efficacy of entrainment depends upon the area of the excurrent pore (i.e., central cavity) over which the ambient flow is moving. Consequently, archaeocyaths should have maximized their central cavity diameters.Five-centimeter-long, conical and cylindrical acrylic pipes with varying end diameters were tested in a flume to document the relative effects of Bernoulli and viscous entrainment. Each pipe was oriented perpendicular to the flow direction in a uniform flow field, and fluorescein dye was injected at the pipe's mid-length for flow visualization. Models with different-sized apertures consistently exhibit dye movement to the larger opening and greater dye entrainment speeds than models with identically sized apertures, thereby suggesting that viscous entrainment effects are significant and operating in concert with Bernoulli effects. To test for similar effects in archaeocyaths, four brass models were constructed with varying central cavity diameters. Both volume flux and excurrent flow speed of the exiting water increased as the central cavity diameter increased. An analysis of the morphologies that occur in nature confirm these results. Regular archaeocyaths most commonly have central cavity diameters close to their outer wall diameter, thereby maximizing the excurrent pore area.These results have implications for archaeocyathan paleoecology. Environments with low-magnitude currents should support individuals with larger central cavity diameters than higher energy settings. Data on the occurrence of morphotypes within bioherms of varying flow energies from South Australia support this prediction.

Cold flow analysis of trapped vortex combustor using two equation turbulence models

2008 ◽  
Vol 112 (1136) ◽  
pp. 569-580 ◽  
Author(s):  
P. Selvaganesh ◽  
S. Vengadesan
Keyword(s):  
Flow Analysis ◽  
Turbulence Models ◽  
The Other ◽  
Cavity Size ◽  
Reattachment Length ◽  
Cold Flow ◽  
Passive Flow ◽  
Non Linear ◽  
Flow Through ◽  
Trapped Vortex

Abstract A new combustor concept referred as the trapped vortex combustor (TVC) employs a vortex that is trapped inside a cavity to stabilise the flame. The cavity is formed between two axisymmetric disks mounted in tandem. TVC offers many advantages when compared to conventional swirl stabilisers. In the present work, numerical investigation of cold flow (non-reacting) through trapped vortex combustor is performed. The numerical simulation involves passive flow through TVC to obtain an optimum cavity size to trap stable vortices inside the cavity and to observe the important characteristics of TVC. One of the main objectives is to evaluate various two equation turbulence models for the aerodynamic predictions of TVC. Commercial CFD software Fluent is used for the present study. In addition to many models available, Non-linear k-ω and modified k-ω models are incorporated through user defined functions. Results obtained include streamlines, residence time and entrainments for all models. The reattachment length obtained by non-linear k-ω model closely matches with that obtained by DNS in the case of forebody-spindle alone. Non-linear k-ω model alone captures the corner vortices while all the other models failed to capture. From the entrainment characteristics study, it is inferred that the primary air needs to be injected for accommodating the decrease in oxidizer inside the cavity to obtain better performance from the TVC.

WHEN DOES MOTION RELATIVE TO NEIGHBORING SURFACES ALTER THE FLOW THROUGH ARRAYS OF HAIRS?

1994 ◽  
Vol 193 (1) ◽  
pp. 233-254 ◽  
Author(s):  
C Loudon ◽  
B Best ◽  
M Koehl
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Gas Exchange ◽  
Flow Fields ◽  
Physical Models ◽  
Suspension Feeding ◽  
Flow Through ◽  
Unbounded Fluid ◽  
Hair Diameter

Many animals from different phyla use structures bearing arrays of hairs to perform a variety of important functions, such as olfaction, gas exchange, suspension feeding and locomotion. The performance of all these functions depends on the motion of water or air around and through these arrays of hairs. Because organisms often move such hair-bearing appendages with respect to their bodies or the substratum, we assessed the effects of such motion relative to walls on the fluid flow between neighboring hairs. We compared flow fields near dynamically scaled physical models of hairs moving near walls with those calculated for such hairs in an unbounded fluid. Our results suggest that the methods an organism can use to change the flow through a hair-bearing appendage differ with Reynolds number (based on hair diameter). When Re is 10(-2) or below, changing speed does not alter the proportion of the fluid that moves through rather than around the array, whereas moving relative to a wall increases it. In contrast, when Re is between 10(-2) and 1, changes in speed have a big effect on the proportion of fluid moving through the array, while moving near walls makes little difference.

scholarly journals A new model of respiration in blastoid (Echinodermata) hydrospires based on computational fluid dynamic simulations of virtual 3D models

2017 ◽  
Vol 91 (4) ◽  
pp. 662-671 ◽  
Author(s):  
Johnny A. Waters ◽  
Lyndsie E. White ◽  
Colin D. Sumrall ◽  
Bonnie K. Nguyen
Keyword(s):  
Water Flow ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
3D Models ◽  
Dynamic Simulations ◽  
Vertical Orientation ◽  
Feeding Mode ◽  
Passive Flow ◽  
Internal Structures ◽  
Flow Through

AbstractHydrospires are internal structures in blastoids that primarily served a respiratory function. Historically, hydrospires have been modeled as passive-flow respiratory structures with a vertical orientation. This project constructed virtual 3D models of blastoids from legacy acetate peel collections at the Naturalis Museum in the Netherlands. Computational fluid dynamic (CFD) simulations of the blastoid models reconstructed in living position indicated that hydrospires likely were oriented horizontally when the blastoid was in feeding mode in current velocities>0.5 cm/s to 10 cm/s. In this range of current velocities, passive water flow through the hydrospires did not produce conditions optimized for efficient gas exchange. However, optimal water flow through the hydrospires could be achieved if the excurrent velocity of water exiting the hydrospire through the spiracle was approximately one-half the velocity of ambient environmental currents. Maintaining such a ratio in the dynamic current systems in which blastoids lived suggests that cilia-driven active water flow through the hydrospires is a better model for optimizing respiratory effectiveness.

Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water

1983 ◽  
Vol 41 ◽  
pp. 462-463
Author(s):  
Richard L. Leino ◽  
Jon G. Anderson ◽  
J. Howard McCormick
Keyword(s):  
Confidence Interval ◽  
Chronic Exposure ◽  
Lake Superior ◽  
Pimephales Promelas ◽  
Chloride Cells ◽  
Fathead Minnows ◽  
Secondary Lamellae ◽  
Untreated Water ◽  
Water Ph ◽  
Flow Through

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.

Sign in / Sign up

Export Citation Format

Share Document