The role of dunes in flow resistance in a large and a small river. The case of the Paraná and Tercero rivers, Argentina

2022 ◽  
pp. 1-19
Author(s):  
Francisco G. Latosinski ◽  
Mario L. Amsler ◽  
Carlos A. Vionnet ◽  
Ana I. Heredia Ligorria ◽  
Ricardo N. Szupiany ◽  
...  
Keyword(s):  
Flow Resistance ◽  
Small River

Hydro-morphodynamic modelling of floodplains: the role of vegetation in suspended sediment transport

2020 ◽  
Author(s):  
Daniel A. S. Conde ◽  
Robert M. Boes ◽  
David F. Vetsch
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Flow Resistance ◽  
Laboratory Data ◽  
Anthropogenic Factors ◽  
Future Research ◽  
Suspended Sediment Transport ◽  
Compound Channels ◽  
Closure Models

<p>Riverine environments are amongst the most complex ecosystems on the planet. As several anthropogenic factors have increasingly disrupted the natural dynamics of rivers, namely through stream regulation, the need for re-establishing the ecological role of these systems has gained relevance.</p><p>Of particular interest are floodplains in compound channels, primarily regarded for safety against floods, but which also comprise an extensive realm for ecological functions and establishment of various species. Floodplain vegetation affects flow resistance and dispersion, playing a fundamental role in erosion and deposition of suspended sediment.</p><p>The present work aims at quantifying the interaction between vegetation and suspended sediment transport on floodplains in compound channels by numerical simulations. The employed numerical tool is BASEMENT v3, a GPU-accelerated hydro-morphodynamic 2D model developed at the Laboratory of Hydraulics, Hydrology and Glaciology of ETH Zurich. In the context of the present study, the model is extended with turbulence and suspended sediment transport capabilities. The implemented closure models for turbulence pertain to three major groups, namely (i) mixing-length, (ii) production-dissipation and (iii) algebraic stress models. For suspended sediment transport, the main classical formulations from fluvial hydraulics were implemented in the numerical model.</p><p>Laboratory data from flume experiments featuring suspended sediment load and vegetation-like proxies are used for model validation. The numerical results are compared with the observed water depths, velocities and sediment concentrations for different sets of experiments with varying properties, such as density and submergence. The implemented closure models for flow resistance, turbulence and suspended sediment are then combined, calibrated and classified in terms of numerical output quality.</p><p>The obtained results from this modelling effort mainly contribute to understanding the applicability of 2D (depth-averaged) models to complex eco-morphodynamics scenarios. The calibration and rating of well-known closure models for turbulence and sediment transport provides relevant guidelines for both future research and practice in fluvial modelling.</p>

Flow Resistance in Tracheotomy Tubes

1973 ◽  
Vol 82 (6) ◽  
pp. 827-830 ◽  
Author(s):  
John Cavo ◽  
Joseph H. Ogura ◽  
Donald G. Sessions ◽  
J. Roger Nelson
Keyword(s):  
Laminar Flow ◽  
Respiratory System ◽  
Flow Resistance ◽  
Airway Resistance ◽  
Upper Airway ◽  
Plastic Tube ◽  
Flow Rates ◽  
Pressure Drops ◽  
Adult Human

The role of the upper airway (the breathing passage above the trachea) in maintaining the normal junction of the respiratory system has been suggested by previous investigators. During a tracheotomy the upper airway is by-passed by a prosthetic metal or plastic tube which is placed into the trachea through the neck. In order to determine which, among the most commonly used tracheotomy tubes, most closely simulate the flow resistance of the adult human upper airway, a series of varying flow rates were passed through different sized tubes. Pressure drops were recorded and resistance values were thereby determined. Our data was compared with previously determined values for flow resistance of the adult human upper airway. Resistance related to turbulent and laminar flow was considered. On the basis of our data we have suggested that large caliber tracheotomy tubes be used in adult patients in whom the prolonged need for a tracheotomy is anticipated.

Role of chemical factors in regulation of flow through kidney, hindlimb, and heart

1965 ◽  
Vol 208 (5) ◽  
pp. 813-824 ◽  
Author(s):  
J. B. Scott ◽  
R. M. Daugherty ◽  
J. M. Dabney ◽  
F. J. Haddy
Keyword(s):  
Blood Flow ◽  
Metabolic Rate ◽  
Flow Resistance ◽  
Reactive Hyperemia ◽  
Venous Outflow ◽  
Chemical Factors ◽  
Study Support ◽  
Dog Blood ◽  
Flow Through

In the anesthetized dog, blood flow or metabolic rate was varied in kidney, hindlimb, or heart (experimental organ) while simultaneously diverting a portion of the venous outflow through forelimb or kidney (bioassay organ). The resistance to blood flow through the experimental organ gradually rose in the first few minutes following a large increase in flow and gradually fell following a large decrease in flow. Resistance to blood flow through an experimental organ (hindlimb) fell following increase in metabolic rate. In each case, bioassay organ resistance changed in the same direction when the assay organ was the forelimb and in the opposite direction when the assay organ was the kidney. These findings suggest that active hyperemia, reactive hyperemia, and autoregulation of blood flow result, at least in part, from alteration in the chemical environment of the blood vessels. Other findings in this study support the possibility that adenosine triphosphate contributes to the change in environment.

The Pollutant Load Factor of Household Wastewater in Japan

1986 ◽  
Vol 18 (7-8) ◽  
pp. 157-167 ◽  
Author(s):  
Masao Ukita ◽  
Hiroshi Nakanishi ◽  
Masahiko Sekine
Keyword(s):  
Mass Balance ◽  
River Basins ◽  
Small River ◽  
Water Bodies ◽  
Load Factor ◽  
Pollutant Load ◽  
Fine Weather ◽  
Household Wastewater ◽  
Load Generation

The objective of this study was to clarify quantitatively the role of household wastewater as one of the causes of the rapid pollution of nearby water-bodies and to consider the importance of countermeasures at the stage of pollutant load generation. Using mass balance techniques, actual samples and measurements, or by referring to the literature, reliable values of the pollutant load factor of household wastewater were obtained for both the residential and occupational population and after every type of treatment system. Then, to verify the reliability of these values, the flow-out rate of the pollutant load from small river basins was investigated in fine weather. The results show that the proposed values of the pollutant load factor were appropriate, and cesspool night soil and miscellaneous household wastewater are the main causes of the pollution of nearby waterbodies. The results of several experiments show that awareness regarding pollutant load at the stage of its generation, e.g. in cooking and dining, can greatly reduce the pollutant load.

Glucocorticoids regulate transendothelial fluid flow resistance and formation of intercellular junctions

1999 ◽  
Vol 277 (2) ◽  
pp. C330-C342 ◽  
Author(s):  
Johnnie L. Underwood ◽  
Collin G. Murphy ◽  
Janet Chen ◽  
Linda Franse-Carman ◽  
Irmgard Wood ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Flow Resistance ◽  
Preferential Flow ◽  
Intercellular Junctions ◽  
Fold Increase ◽  
Cell Junctions ◽  
Biochemical Alterations ◽  
Fold Reduction

The regulation of transendothelial fluid flow by glucocorticoids was studied in vitro with use of human endothelial cells cultured from Schlemm’s canal (SCE) and the trabecular meshwork (TM) in conjunction with computer-linked flowmeters. After 2–7 wk of 500 nM dexamethasone (Dex) treatment, the following physiological, morphometric, and biochemical alterations were observed: a 3- to 5-fold increase in fluid flow resistance, a 2-fold increase in the representation of tight junctions, a 10- to 30-fold reduction in the mean area occupied by interendothelial “gaps” or preferential flow channels, and a 3- to 5-fold increase in the expression of the junction-associated protein ZO-1. The more resistive SCE cells expressed two isoforms of ZO-1; TM cells expressed only one. To investigate the role of ZO-1 in the aforementioned Dex effects, its expression was inhibited using antisense phosphorothioate oligonucleotides, and the response was compared with that observed with the use of sense and nonsense phosphorothioate oligonucleotides. Inhibition of ZO-1 expression abolished the Dex-induced increase in resistance and the accompanying alterations in cell junctions and gaps. These results support the hypothesis that intercellular junctions are necessary for the development and maintenance of transendothelial flow resistance in cultured SCE and TM cells and are likely involved in the mechanism of increased resistance associated with glucocorticoid exposure.

The vulnerable small airway

PEDIATRICS ◽  
1977 ◽  
Vol 59 (5) ◽  
pp. 783-785
Author(s):  
V. Chernick
Keyword(s):  
Flow Resistance ◽  
Gas Flow ◽  
Airway Resistance ◽  
Clear Understanding ◽  
Small Airways ◽  
Peripheral Airways ◽  
Pulmonary Flow ◽  
Peripheral Airway ◽  
First Time

Fundamental physiological work in the late 1960s provided for the first time a clear understanding of (1) the role of the small airways (< 2 mm in diameter) in determining overall airway resistance to gas flow and (2) the relationship between central and peripheral airway resistance and lung growth.1,2 Involvement of the small airways early in the course of cystic fibrosis has been previously commented upon and documented in Pediatrics.3-5 After the age of about 5 years, the flow resistance of peripheral airways constitutes only about 10% to 20% of total pulmonary flow resistance,2 a fraction so small that conventional measurement of total resistance cannot detect small changes in the peripheral component.

scholarly journals Effect of Mixer Type on Particle Coating by Magnesium Stearate for Friction and Adhesion Modification

Pharmaceutics ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1211
Author(s):  
Wei Pin Goh ◽  
Ana Montoya Sanavia ◽  
Mojtaba Ghadiri
Keyword(s):  
Flow Resistance ◽  
Flow Characteristics ◽  
Magnesium Stearate ◽  
Shear Strain Rate ◽  
Mixing Conditions ◽  
Particle Coating ◽  
Powder Characteristics ◽  
Interparticle Friction ◽  
Sharp Corners

Glidants and lubricants are often used to modify interparticle friction and adhesion in order to improve powder characteristics, such as flowability and compactability. Magnesium stearate (MgSt) powder is widely used as a lubricant. Shear straining causes MgSt particles to break, delaminate, and adhere to the surfaces of the host particles. In this work, a comparison is made of the effect of three mixer types on the lubricating role of MgSt particles. The flow behaviour of α-lactose monohydrate, coated with MgSt at different mass percentages of 0.2, 0.5, 1, and 5 is characterised. The mixing and coating process is carried out by dry blending using Turbula, ProCepT, and Mechanofusion. Measures have been taken to operate under equivalent mixing conditions, as reported in the literature. The flow resistance of the coated samples is measured using the FT4 rheometer. The results indicate that the flow characteristics of the processed powders are remarkably similar in the cases of samples treated by Turbula and Mechanofusion, despite extreme conditions of shear strain rate. The least flow resistance of samples is observed in the case of samples treated by the ProCepT mixer. High-velocity collisions of particles round off the sharp corners and edges, making them less resistant to flow. The optimal percentage of magnesium stearate is found to be approximately 1% by weight for all mixer types, as the addition of higher amounts of lubricant does not further improve the flowability of the material.

ROLE OF SLIP VELOCITY IN BLOOD FLOW THROUGH STENOSED ARTERIES: A NON-NEWTONIAN MODEL

2007 ◽  
Vol 07 (03) ◽  
pp. 337-353 ◽  
Author(s):  
J. C. MISRA ◽  
G. C. SHIT
Keyword(s):  
Blood Flow ◽  
Skin Friction ◽  
Flow Rate ◽  
Slip Velocity ◽  
Flow Resistance ◽  
Volumetric Flow Rate ◽  
Flow Through ◽  
Analytical Expressions ◽  
Insight Into

A mathematical model is developed in this paper for studying blood flow through a stenosed arterial segment by taking into account the slip velocity at the wall of the artery. Consideration of the non-Newtonian character of blood is made, where a constitutive relation of blood is described by the Herschel–Bulkley equation. The effect of slip at the arterial wall in the presence of mild, moderate, and severe stenosis growth at the lumen of an artery is investigated. Analytical expressions for skin friction, flow resistance, and the flow rate are derived by using the model. The derived expressions are computed numerically by considering an illustrative example. The study provides an insight into the effects of slip velocity on the volumetric flow rate of blood, flow resistance, and skin friction.

scholarly journals The Arteriolar Glycocalyx Plays a Role in the Regulation of Blood Flow in the Iliac of the Anaesthetised Pig

2018 ◽  
pp. 41-44 ◽  
Author(s):  
T. RUANE-O’HORA ◽  
F. MARKOS
Keyword(s):  
Blood Flow ◽  
Iliac Artery ◽  
Flow Measurement ◽  
Flow Resistance ◽  
Vascular Conductance ◽  
Vascular Bed ◽  
Resistance Vessels ◽  
Flow Pressure

The role of the glycocalyx of arterial resistance vessels in regulating blood flow in vivo is not fully understood. Therefore, the effect of glycocalyx damage using two separate compounds, hyaluronidase and N-Formylmethionyl-leucyl-phenylalanine (fMLP), was evaluated in the iliac artery vascular bed of the anaesthetised pig. Blood flow and pressure were measured in the iliac, an adjustable snare was applied to the iliac above the pressure and flow measurement site to induce step decreases (3 occlusions at 3-4 min intervals were performed for each infusion) in blood flow, and hence iliac pressure, and vascular conductance (flow/pressure) was calculated. Saline, hyaluronidase (14 and 28 µg/ml/min), and fMLP (1 µM/min) were infused separately, downstream of the adjustable snare and their effect on arterial conductance assessed. Hyaluronidase at the higher infusion rate and fMLP both caused a reduction in arterial conductance, and hence an increase in blood flow resistance. In conclusion, the results show that glycocalyx damage causes an increase in resistance to blood flow in the iliac artery vascular bed.

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