Computational study of the relationship between the flow resistance and the microscopic structure of polymer monoliths

In this paper, the applicability of a theoretical flow resistance law to sediment-laden flow in pipes is tested. At first, the incomplete self-similarity (ISS) theory is applied to deduce the velocity profile and the corresponding flow resistance law. Then the available database of measurements carried out by clear water and sediment-laden flows with sediments having a quasi-uniform sediment size and three different values of the mean particle diameter Dm (0.88 mm, 0.41 mm and 0.30 mm) are used to calibrate the parameter of the power-velocity profile). The fitting of the measured local velocity to the power distribution demonstrates that (i) for clear flow the exponent δ) can be estimated by the equation of Castaing et al. and (ii) for the sediment-laden flows δ is related to the diameter Dm. A relationship for estimating the parameter Гv obtained by the power-velocity profile) and that Гf of the flow resistance law) is theoretically deduced. The relationship between the parameter Гv, the head loss per unit length and the pipe flow Froude number is also obtained by the available sediment-laden pipe flow data. Finally, the procedure to estimate the Darcy–Weisbach friction factor is tested by the available measurements.

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Overland Flow Resistance Law under Sparse Stem Vegetation Coverage

Water ◽

10.3390/w13121657 ◽

2021 ◽

Vol 13 (12) ◽

pp. 1657

Author(s):

Jingzhou Zhang ◽

Shengtang Zhang ◽

Si Chen ◽

Ming Liu ◽

Xuefeng Xu ◽

...

Keyword(s):

Flow Resistance ◽

Overland Flow ◽

Vegetation Coverage ◽

Dominant Factor ◽

Roughness Coefficient ◽

Hydraulic Parameters ◽

Slope Condition ◽

Manning Roughness ◽

The Relationship ◽

Manning Roughness Coefficient

To explore the characteristics of overland flow resistance under the condition of sparse vegetative stem coverage and improve the basic theoretical research of overland flow, the resistance characteristics of overland flow were systematically investigated under four slope gradients (S), seven flow discharges (Q), and six degrees of vegetation coverage (Cr). The results show that the Manning roughness coefficient (n) changes with the ratio of water depth to vegetation height (h/hv) while the Reynolds number (Re), Froude number (Fr), and slope (S) are closely related to vegetation coverage. Meanwhile, h/hv, Re, and Cr have strong positive correlations with n, while Fr and S have strong negative correlations with n. Through data regression analysis, a power function relationship between n and hydraulic parameters was observed and sensitivity analysis was performed. It was concluded that the relationship between n and h/hv, Re, Cr, Q, and S shows the same law; in particular, for sparse stem vegetation coverage, Cr is the dominant factor affecting overland flow resistance under zero slope condition, while Cr is no longer the first dominant factor affecting overland flow resistance under non-zero slope condition. In the relationship between n and Fr, Cr has the least effect on overland flow resistance. This indicates that when Manning roughness coefficient is correlated with different hydraulic parameters, the same vegetation coverage has different effects on overland flow resistance. Therefore, it is necessary to study overland flow resistance under the condition of sparse stalk vegetation coverage.

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Study on the Relationship between Microscopic Structure and Mechanical Properties of HTPB Propellant

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.152-153.1151 ◽

2010 ◽

Vol 152-153 ◽

pp. 1151-1155 ◽

Cited By ~ 1

Author(s):

Xu Chang Li ◽

Jian Jiao ◽

Jun Yan Yao ◽

Liang Wang

Keyword(s):

Mechanical Properties ◽

Mechanical Property ◽

Cross Section ◽

Structural Integrity ◽

Solid Particles ◽

Microscopic Structure ◽

Structure State ◽

Htpb Propellant ◽

The Relationship ◽

Bond Effect

By means of a tensile instrument and SEM, the mechanical property parameters of HTPB propellant test samples with different formulas were tested, and their microscopic fracture cross section patterns were observed. Take advantage of these testing results, the relationship between microscopic structure and mechanical properties of HTPB propellant was studied. The results show that the mechanical properties of a propellant are closely related to its microscpic structure state. The structural integrity of propellant is mainly influenced by the bond effect of the interface between binder and solid particles, solid particle’s shape, size and its distribution, the content of binder matrix, etc. These factors have important effects on the mechanical properties of propellant.

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Design of nickel donor–acceptor dithiolenes for 2nd order nonlinear optics: an experimental and computational study

New Journal of Chemistry ◽

10.1039/c9nj02976a ◽

2019 ◽

Vol 43 (32) ◽

pp. 12570-12579 ◽

Cited By ~ 1

Author(s):

Salahuddin S. Attar ◽

Luciano Marchiò ◽

Luca Pilia ◽

Maria F. Casula ◽

Davide Espa ◽

...

Keyword(s):

Nonlinear Optics ◽

Energy Absorption ◽

Computational Study ◽

Low Energy ◽

Nlo Properties ◽

Donor Acceptor ◽

The Relationship ◽

Donor Capability

This study, concerning the influence on the NLO properties of a remote functionality in the donor of D–Ni–A dithiolenes 1–4, allows to point out the relationship between NLO properties and the donor capability in modulating the low-energy absorption.

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Influence of Distal Resistance and Proximal Vascular Stiffness on Vascular Impedance and Hemodynamics in Pulmonary Hypertension: A Computational Study With Validation Using an Animal Model

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-204759 ◽

2009 ◽

Author(s):

Zhenbi Su ◽

Kendall Hunter ◽

Wei Tan ◽

Robin Shandas

Keyword(s):

Pulmonary Hypertension ◽

Computational Study ◽

Mean Flow ◽

Vascular Impedance ◽

Vascular Flow ◽

Primary Determinant ◽

Mean Pressure ◽

Pulmonary Arterial ◽

The Relationship ◽

Better Than

Clinically, invasive measurement of pulmonary vascular flow and pressure provides the hemodynamic status of the pulmonary circulation with pulmonary arterial hypertension (PAH). Current diagnostics and therapeutics for PAH revolve around pulmonary vascular resistance (PVR), which is determined by the mean pressure divided by mean flow [1]. Though PVR correlates well with right ventricular (RV) afterload, failure of which is the primary determinant of mortality [2–4], PVR does not provide the complete measure of RV afterload since it neglects dynamic impedance effects [4, 5]. Although we have shown that impedance predicts clinical outcomes better than PVR alone, several key questions remain about the relationship between hemodynamics and impedance changes in pulmonary hypertension.

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Aquatic weed growth and flow resistance: Influence on the relationship between discharge and stage over a 25 year river gauging station record

Hydrological Processes ◽

10.1002/hyp.3360080105 ◽

1994 ◽

Vol 8 (1) ◽

pp. 63-73 ◽

Cited By ~ 33

Author(s):

Angela M. Gurnell ◽

Peter Midgley

Keyword(s):

Flow Resistance ◽

Aquatic Weed ◽

Weed Growth ◽

The Relationship ◽

Station Record ◽

Gauging Station

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Experimental investigation of thermal-hydraulic characteristics of direct-flow honeycomb seal at the injection of cooling air.

Bulletin of Bryansk state technical university ◽

10.12737/23009 ◽

2015 ◽

Vol 2015 (3) ◽

pp. 62-71

Author(s):

Максим Шилин ◽

Maksim Shilin ◽

Виктор Перевезенцев ◽

Viktor Perevezentsev ◽

Игорь Усачев ◽

...

Keyword(s):

Heat Transfer ◽

Flow Resistance ◽

Honeycomb Structure ◽

Geometrical Parameters ◽

Hydraulic Characteristics ◽

Direct Flow ◽

Honeycomb Seal ◽

Honeycomb Seals ◽

Cooling Air ◽

The Relationship

Experimentally studied the influence of operational and geometrical parameters on flow resistance and heat transfer in honeycomb seals. The relationship between the nature of changes in the degree of intensification of hydraulic resistance, heat and vortex structure in the space of the cell. The effect of blowing cooling air through the surface of the honeycomb structure on the thermal hydraulic characteristics of the seal.

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