scholarly journals Pumping Rate and Size of Demosponges—Towards an Understanding Using Modeling

2021 ◽  
Vol 9 (11) ◽  
pp. 1308
Author(s):  
Poul S. Larsen ◽  
Hans Ulrik Riisgård
Keyword(s):  
Benthic Communities ◽  
Grazing Impact ◽  
Cross Sectional ◽  
Length Scales ◽  
Pumping Rate ◽  
Pressure Losses ◽  
Matter Transport ◽  
Standard Pressure ◽  
Geometric Length ◽  
Aquiferous System

Filter-feeding sponges pump large amounts of water and contribute significantly to grazing impact, matter transport and nutrient cycling in many marine benthic communities. For ecological studies it is therefore of interest to be able to estimate the pumping rate of different species from their volume size or osculum cross-sectional area by means of experimentally determined allometric correlations. To help understand allometric data correlations and observed large variations of volume-specific pumping rate among species we developed a model that determines the pumping rate as a function of the size (volume) of a tubular-type demosponge described by 4 geometric length scales. The model relies on a choanocyte-pump model and standard pressure loss relations for flow through the aquiferous system, and density and pumping rate per choanocyte is assumed to be constant. By selecting different possibilities for increase of the length scales, which may also simulate different growth forms, we demonstrate that the model can imitate the experimental allometric correlations. It is concluded that the observed dependence of pumping rate on size is primarily governed by the hydraulics of pump performance and pressure losses of the aquiferous system rather than, e.g., decreasing density of choanocytes with increasing sponge size.

scholarly journals Microcrystal alignment in drawn fiber over sub-meter to kilometer length scales

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Laurel Tauzer ◽  
Ann Mescher
Keyword(s):  
Aspect Ratio ◽  
Composite Fiber ◽  
Polymer Surfaces ◽  
Crystal Length ◽  
Cross Sectional ◽  
Length Scales ◽  
Grapeseed Oil ◽  
The Mean ◽  
Width Reduction ◽  
Uniform Reduction

AbstractThis paper describes a method for aligning stiff, high-aspect-ratio microcrystals over macro-length scales using a polymer fiber drawing process. A composite preform was constructed with an interfacial, liquid shell layer of grapeseed oil suspending ytterbium-doped potassium lutetium fluoride microcrystals (30% Yb:K2LuF5, KLF) between adjacent cylindrical surfaces of acrylic (polymethyl methacrylate, PMMA). The mean length of synthesized KLF microcrystals was 67 microns, and the mean aspect ratio, equivalent to crystal length divided by diameter, was eight. The acrylic-host preform was drawn into fiber, resulting in uniform reduction of all cross-sectional dimensions by a factor of approximately 20 in the final fiber. A corresponding width reduction of the interstitial liquid-filled gap, containing microcrystals between the polymer surfaces, constrains the microcrystals and causes alignment of the crystal long axes parallel to the axis of the drawn composite fiber. Alignment was best for clearly separated microcrystals and improved even further with the longest lengths, or highest aspect-ratio microcrystals.

Correlations between flow resistance and geometry in a model of the human nose

1993 ◽  
Vol 75 (4) ◽  
pp. 1767-1775 ◽  
Author(s):  
S. Schreck ◽  
K. J. Sullivan ◽  
C. M. Ho ◽  
H. K. Chang
Keyword(s):  
Nasal Congestion ◽  
Magnetic Resonance Images ◽  
Healthy Male Subject ◽  
Scale Model ◽  
Good Correspondence ◽  
Cross Sectional ◽  
Circular Duct ◽  
Pressure Losses ◽  
Dimensionless Analysis

The relationship between the pressure losses within the nasal airways and nasal geometry were studied in a 3:1 scale model. The geometry of the model was based on magnetic resonance images of the skull of a healthy male subject. Pressure measurements, flow visualization, and hot-wire anemometry studies were performed at flow rates that, in vivo, corresponded to flows of between 0.05 and 1.50 l/s. The influence of nasal congestion and the collapse of the external nares were examined by using modeling clay to simulate local constrictions in the cross section. A dimensionless analysis of the pressure losses within three sections of the airway revealed the influence of various anatomic dimensions on nasal resistance. The region of the exterior nose behaves as a contraction-expansion nozzle in which the pressure losses are a function of the smallest cross-sectional area. Losses in the interior nose resemble those associated with channel flow. The nasopharynx is modeled as a sharp bend in a circular duct. Good correspondence was found between the predicted and actual pressure losses in the model under conditions that stimulated local obstructions and congestion.

scholarly journals The Influence of Flow Rate on the Wake in a Centrifugal Impeller

1982 ◽  
Author(s):  
M. W. Johnson ◽  
J. Moore
Keyword(s):  
Flow Rate ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Stagnation Pressure ◽  
Centrifugal Impeller ◽  
Suction Surface ◽  
Cross Sectional ◽  
Flow Rates ◽  
Pressure Losses ◽  
Compressor Impeller

Three-dimensional flows and their influence on the stagnation pressure losses in a centrifugal compressor impeller have been studied. All 3 mutally perpendicular components of relative velocity and stagnation pressure on 5 cross-sectional planes, between the inlet and outlet of a 1 m dia shrouded impeller running at 500 rpm were measured. Comparisons were made between results for a flow rate corresponding to nearly zero incidence angle and two other flows, with increased and reduced flow rates. These detailed measurements show how the position of separation of the shroud boundary layer moved downstream and the wake’s size decreased, as the flow rate was increased. The wake’s location, at the outlet of the impeller, was also observed to move from the suction surface at the lowest flow rate, to the shroud at higher flow rates.

Mechanism of reduced maximum expiratory flow in methacholine-induced bronchoconstriction in dogs

1983 ◽  
Vol 55 (3) ◽  
pp. 897-912 ◽  
Author(s):  
S. N. Mink
Keyword(s):  
Wave Speed ◽  
Cross Sectional ◽  
Pressure Losses ◽  
Lung Capacity ◽  
Group I ◽  
Maximum Expiratory Flow ◽  
Pressure Area ◽  
Expiratory Flow ◽  
Group Ii ◽  
Viscous Pressure

Airway sites of flow limitation [“choke points” (CP)] were identified during forced deflation in open-chest dogs before (C) and after (B) bronchoconstriction was produced by nebulizing a solution of methacholine chloride into their airways. CP were identified in two respective groups. In group I (n = 8) a retrograde catheter was used to locate CP and in the other a Pitot static tube (group II, n = 5), CP were identified at multiple lung volumes (VL) over the lower one-half of total lung capacity. Both groups showed similar findings at each condition. At B, corresponding values of maximum expiratory flow (Vmax) at each VL decreased to about 10% of those at C. Movement of CP relative to their original location varied at each VL and, especially at the lower VL, showed little peripheral movement. In group I, equal pressure points were also measured and were found to move peripherally at all the measured VL. In group II, cross-sectional area (A*) and airway compliance (K) at CP were estimated. During bronchoconstriction, A* decreased at the respective VL, and airways became less compliant. The reduction in Vmax could be explained in terms of changes in A* and K as described by wave-speed theory, and Vmax decreased because A* decreased. The decrease in A* was related in part to an increase in viscous pressure losses that reduced total pressure at CP and also in part to a change in the pressure-area behavior of bronchi at CP. Their relative effects on reducing A* and Vmax were examined.

Scaling Analysis and Its Implication for Asphaltene Deposition in a Wellbore

SPE Journal ◽  
2017 ◽  
Vol 23 (02) ◽  
pp. 274-285 ◽  
Author(s):  
Davud Davudov ◽  
Rouzbeh Ghanbarnezhad Moghanloo ◽  
Jonathan Flom
Keyword(s):  
Reynolds Numbers ◽  
Stream Velocity ◽  
Scaling Analysis ◽  
Cross Sectional ◽  
Pressure Losses ◽  
Flow Capacity ◽  
Dimensionless Groups ◽  
Asphaltene Deposition ◽  
The Many ◽  
Hydrodynamic Effects

Summary The study presented here uses order-of-one—or o(1)—scaling analysis to identify dimensionless groups specific to asphaltene deposition along production tubing. The precipitation and subsequent deposition of asphaltene can lead to significant complications related to oilfield production. Aside from the many complications within a reservoir as well as surface equipment, the reduction in cross-sectional area caused by its deposition leads to increased pressure losses, reductions in volumetric flow capacity, and possible flow perturbations within a wellbore. Attempts to mitigate these adverse effects have focused on both hindering the precipitation of asphaltene and preventing its deposition after precipitated. The study used here attempts to quantify various hydrodynamic controls specific to asphaltene deposition. With o(1) scaling analysis, four independent dimensionless groups were generated from momentum and mass-balance equations relating hydrodynamic effects to the rate of asphaltene deposition. The dimensionless group π4 was of particular interest because of its inherent relationship to the rate of deposition. This group was compared with both data and existing correlations taken from literature, and noticeable trends in the deposition rate with respect to average stream velocity were observed. One of the most important trends discerned by these comparisons was a clear distinction whereby the rate of asphaltene deposition, related through π4, decreases with increasing Reynolds numbers (Re) in lower ranges, but actually increases in higher ranges. Although the data did not cover the specific region of transition, various correlations suggest a clear cutoff between what was deemed a favorable regime, or Regime I, and a nonfavorable regime, or Regime II.

The Flow and Pressure Losses in Smooth Pipe Bends of Constant Cross Section

1963 ◽  
Vol 67 (631) ◽  
pp. 437-447 ◽  
Author(s):  
A. J. Ward Smith
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Experimental Information ◽  
Bend Angle ◽  
Geometrical Parameters ◽  
Constant Cross Section ◽  
Cross Sectional ◽  
Pressure Losses ◽  
Smooth Pipe ◽  
Sectional Shape

SummaryIncompressible turbulent flow in smooth pipe bends of circular-arc curvature and constant cross section is discussed. The effects of bend angle, radius ratio, duct cross-sectional shape and Reynolds number are considered. Particular attention is paid to the influence of the tangents on the flow and losses in a bend. In addition consideration is given to the definition and measurement of the bend loss.A correlation of experimental pressure loss data is made. It is shown that large variations in experimental results, which cannot be ascribed to the effects of geometrical parameters or Reynolds number, are accounted for by the effects of the downstream tangent and position at which the pressure measurements were made. The inadequacy of existing experimental information is an obstacle to the presentation of comprehensive data on the effect of geometrical parameters on bend losses.

Hydrodynamics of particles embedded in a flat surfactant layer overlying a subphase of finite depth

1998 ◽  
Vol 369 ◽  
pp. 151-173 ◽  
Author(s):  
HOWARD A. STONE ◽  
ARMAND AJDARI
Keyword(s):  
Friction Coefficient ◽  
Surface Film ◽  
Finite Depth ◽  
Surface Velocity ◽  
Length Scale ◽  
Dual Integral Equations ◽  
Length Scales ◽  
Sublayer Thickness ◽  
Membrane Bound ◽  
Geometric Length

The motion of membrane-bound objects is important in many aspects of biology and physical chemistry. A hydrodynamic model for this Fconfiguration was proposed by Saffman & Delbrück (1975) and here it is extended to study the translation of a disk-shaped object in a viscous surface film overlying a fluid of finite depth H. A solution to the flow problem is obtained in the form of a system of dual integral equations that are solved numerically. Results for the friction coefficient of the object are given for a complete range of the two dimensionless parameters that describe the system: the ratio of the sublayer (η) to membrane (ηm) viscosities, Λ=ηR/ηmh (where R and h are the object radius and thickness of the surface film, respectively), and the sublayer thickness ratio, H/R. Scaling arguments are presented that predict the variation of the friction coefficient based upon a comparison of the different length scales that appear in the problem: the geometric length scales H and R, the naturally occurring length scale [lscr ]m=ηmh/η, and an intermediate length scale [lscr ]H= (ηmhH/η)1/2. Eight distinct asymptotic regimes are identified based upon the different possible orderings of these length scales for each of the two limits Λ[Lt ]1 and Λ[Gt ]1. Moreover, the domains of validity of available approximations are established. Finally, some representative surface velocity fields are given and the implication of these results for the characterization of hydrodynamic interactions among membrane-bound proteins adjacent to a finite-depth sublayer is discussed briefly.

On the Preliminary Design and Noncavitating Performance Prediction of Tapered Axial Inducers

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Luca d’Agostino ◽  
Lucio Torre ◽  
Angelo Pasini ◽  
Angelo Cervone
Keyword(s):  
Performance Prediction ◽  
Axisymmetric Flow ◽  
Momentum Conservation ◽  
Design Flow ◽  
Flow Coefficient ◽  
Test Facility ◽  
Preliminary Design ◽  
Cross Sectional ◽  
Pressure Losses ◽  
Flow Deviation

A reduced order model for preliminary design and noncavitating performance prediction of tapered axial inducers is illustrated. In the incompressible, inviscid, irrotational flow approximation, the model expresses the 3D flow field in the blade channels by superposing a 2D cross-sectional vorticity correction to a fully guided axisymmetric flow with radially uniform axial velocity. Suitable redefinition of the diffusion factor for bladings with non-negligible radial flow allows for the control of the blade loading and the estimate of the boundary layer blockage at the specified design flow coefficient, providing a simple criterion for matching the hub profile to the axial variation of the blade pitch angle. Carter’s rule is employed to account for flow deviation at the inducer trailing edge. Mass continuity, angular momentum conservation, and Euler’s equation are used to derive a simple second order boundary value problem, whose numerical solution describes the far-field axisymmetric flow at the inducer discharge. A closed form approximate solution is also provided, which proved to yield equivalently accurate results in the prediction of the inducer performance. Finally, the noncavitating pumping characteristic is obtained by introducing suitably adapted correlations of pressure losses and flow deviation effects. The model has been verified to closely approximate the geometry and noncavitating performance of two space inducers tested in Alta’s Cavitating Pump Rotordynamic Test Facility, as well as the measured pumping characteristics of a number of tapered-hub inducers documented in the literature.

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