Viscous Dissipation in Laminar Water Flows in Micro-Tubes

2007 ◽  
Author(s):  
In-Hwan Yang ◽  
Mohamed S. El-Genk
Keyword(s):  
Experimental Data ◽  
Viscous Dissipation ◽  
Temperature Rise ◽  
Experimental Results ◽  
Numerical Calculations ◽  
Analytical Expression ◽  
Water Flows ◽  
Good Agreement

Numerical calculations are performed to investigate the effect of viscous dissipation on the temperature rise and friction numbers for laminar water flows in micro-tubes. The calculated values are compared with those determined from reported experimental data for glass and diffused silica micro-tubes (D = 16 – 101 μm and L/D = 625 – 1479). The results confirm a definite slip at the wall with slip lengths of ∼ 0.7 μm and 1.0 μm, which decrease the friction number and the temperature rise in the micro-tubes, but their effect gradually diminishes as either D or L/D increases. The friction number decreases exponentially as D decreases and, to a lesser extent, as L/D increases. The effect of L/D on the friction number is insignificant for micro-tube diameters ≤ 20 μm. For D > 400 μm, the friction number approaches that of Hagen-Posieuille of 64 for macro-tubes when L/D > 1500, but approaches higher values at smaller L/D. The dimensionless analytical expression developed for calculating the friction number and the temperature rise for water flows in micro-tubes is in good agreement with both the numerical and experimental results.

Friction Numbers and Viscous Dissipation Heating for Laminar Flows of Water in Microtubes

2008 ◽  
Vol 130 (8) ◽  
Author(s):  
Mohamed S. El-Genk ◽  
In-Hwan Yang
Keyword(s):  
Experimental Data ◽  
Aspect Ratio ◽  
Viscous Dissipation ◽  
Temperature Rise ◽  
Strong Dependence ◽  
Velocity Slip ◽  
Laminar Flows ◽  
Water Flows ◽  
Aspect Ratios ◽  
Good Agreement

The friction numbers for laminar flows of water in microtubes, determined from the temperature rise due to the viscous dissipation heating assuming a velocity slip, show a strong dependence on the diameter and aspect ratio. The calculated values compare well with those determined from experimental data for water flows in glass and diffused silica microtubes (16–101μm in diameter D and aspect ratios L∕D=499–1479). With a slip, the friction number almost exponentially decreases as D decreases and, to a lesser extent, as L∕D increases. For D>400μm, the friction number approaches the theoretical Hagen–Poiseuille for macrotubes (64) when L∕D>∼1500, but higher values at smaller L∕D. The developed semiempirical analytical expression for calculating the friction number is in good agreement with the numerical and experimental results. The results suggest the presence of a velocity slip in the experiments and the plausible presence of a thin nanolayer at the walls of the microtubes. For D>200μm, this layer, if exists, is estimated to be ∼18.9nm, but increases to ∼21.5nm for D<200μm, when R¯e=800 and L∕D=1479.

scholarly journals Assessing the Instantaneous Stiffness of Cracked Reinforced Concrete Beams Based on a Gradual Change in Strain Distributions

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Chunyu Fu ◽  
Dawei Tong ◽  
Yuyang Wang
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Cross Section ◽  
Concrete Beams ◽  
Internal Force ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Gradual Change ◽  
Concrete Cracking ◽  
Good Agreement

Concrete cracking causes a gradual change in strain distributions along the cross section height of reinforced concrete beams, which will finally affect their instantaneous stiffness. A method for assessing the stiffness is proposed based on the gradual change, which is considered through modeling different strain distributions for key sections in cracked regions. Internal force equilibria are adopted to find a solution to top strains and neutral axes in the models, and then the inertias of the key sections are calculated to assess the beam stiffness. The proposed method has been validated using experimental results obtained from tests on five reinforced concrete beams. The predicted stiffness and displacements are shown to provide a good agreement with experimental data. The instantaneous stiffness is proven to greatly depend on the crack number and depth. This dependence can be exactly reflected by the proposed method through simulating the gradual change in concrete strain distributions.

Buckle Propagation Pressure for Submarine Pipelines

1993 ◽  
Vol 115 (3) ◽  
pp. 162-166 ◽  
Author(s):  
G. D. Hahn ◽  
M. She ◽  
J. F. Carney
Keyword(s):  
Experimental Data ◽  
Design Practice ◽  
Offshore Pipelines ◽  
Analytical Expression ◽  
Geometrical Nonlinearities ◽  
Main Factors ◽  
Buckle Propagation ◽  
Good Agreement

A new analytical expression is proposed for the prediction of the buckle propagation pressure for deepwater offshore pipelines. The expression accounts for the influences of the main factors involved, including the effects of material and geometrical nonlinearities. Predictions of the proposed expression are shown to be in good agreement with available experimental data, and valuable information is developed that can guide applications of the expression in design practice. In addition, a discussion is presented which outlines the derivation of the proposed expression.

Correlation Between Contact Start/Stop and Constant Speed Drag Testing in Magnetic Head-Disk Tribology

1993 ◽  
Vol 115 (3) ◽  
pp. 387-391 ◽  
Author(s):  
S. K. Ganapathi ◽  
F. E. Talke
Keyword(s):  
Experimental Data ◽  
Contact Force ◽  
Experimental Results ◽  
Constant Speed ◽  
Optical Profilometry ◽  
Magnetic Head ◽  
Good Agreement

A model to establish the correlation between wear in constant speed drag testing and contact start/stop testing is developed. The model is based on the Archard wear equation and uses the quasi-steady Kita-Kogure-Mitsuya model for the transition of a slider from sliding to flying to calculate the velocity dependent contact force between the slider and disk during start/stop. Experimental results for the wear of a zirconia overcoated disk are obtained for both start/stop and constant speed drag testing as a function of the number of repeated cycles using optical profilometry. The correlation between predictions and experimental data shows good agreement for up to at least 10,000 cycles of sliding.

Collision–induced absorption in gaseous methane at low temperatures

1986 ◽  
Vol 64 (7) ◽  
pp. 763-767 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
C. G. Joslin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Low Temperatures ◽  
Low Frequency ◽  
Frequency Region ◽  
Experimental Results ◽  
Published Data ◽  
Frequency Range ◽  
Simple Method ◽  
Induced Absorption ◽  
Good Agreement

A recently developed theory for collision-induced absorption in methane is compared with experimental results over a wider spectral range and at lower temperatures than previously reported. The present experimental results covering the frequency range below 400 cm−1 exhibit good agreement with other recently published data. The theory shows excellent agreement with experiment in the low-frequency region below approximately 200 cm−1 but underestimates the experimental data somewhat at higher frequencies. Possible theoretical reasons for this discrepancy are given. The theory represents a simple method of obtaining a good estimate of the collision-induced absorption spectra of methane in this frequency region and for extrapolating to lower temperatures for which experimentation is not feasible. In addition, the moments α1 and γ1are compared with earlier determinations and indicate good agreement with the previously obtained values for the octupole and hexadecapole moments of methane.

A New Slip Theory of Plasticity

1974 ◽  
Vol 41 (3) ◽  
pp. 587-592 ◽  
Author(s):  
T. H. Lin ◽  
Y. M. Ito ◽  
C. L. Yu
Keyword(s):  
Experimental Data ◽  
Equilibrium Condition ◽  
Numerical Calculations ◽  
Thin Wall ◽  
Face Centered Cubic ◽  
Stress Strain ◽  
Elastic Range ◽  
Theory Of Plasticity ◽  
Face Centered ◽  
Good Agreement

A slip theory is presented for the calculation of the incremental stress-strain relations of a face-centered cubic polycrystal such as aluminum and its alloys, from its experimental uniaxial curves. This theory satisfies the conditions of equilibrium, condition of continuity of displacement as well as the slip characteristics of the component crystals. Numerical calculations based on this theory give results which are in good agreement with known experimental data on thin wall cylinders subject to different ratios of incremental axial and torsional loadings after being compressed beyond the elastic range.

The formation of a dip on the surface of a liquid draining from a tank

1967 ◽  
Vol 29 (2) ◽  
pp. 385-390 ◽  
Author(s):  
Barry T. Lubin ◽  
George S. Springer
Keyword(s):  
Experimental Data ◽  
Liquid Surface ◽  
Cylindrical Tank ◽  
Simple Analytical Expression ◽  
Analytical Expression ◽  
Stationary Liquid ◽  
Circular Orifice ◽  
Good Agreement

Experiments were performed studying the formation of a dip on the surface of an initially stationary liquid draining from a cylindrical tank through an axisym-metrically placed circular orifice. Based upon the information obtained from the experiments, a simple analytical expression was derived predicting the height of the liquid surface in the tank at which this dip forms. A comparison was made between the experimental data and the results of the analysis and good agreement was found between theory and data.

scholarly journals Numerical Simulation Using a Modified Solver within OpenFOAM for Compressible Viscous Flows

2020 ◽  
Author(s):  
Valiyollah Ghazanfari ◽  
Ali Akbar Salehi ◽  
Ali Reza Keshtkar ◽  
Mohammad Mahdi Shadman ◽  
Mohammad Hossein Askari
Keyword(s):  
Experimental Data ◽  
Viscous Dissipation ◽  
Energy Equation ◽  
Contact Discontinuity ◽  
Viscous Flows ◽  
Computational Time ◽  
Benchmark Tests ◽  
Compressible Viscous Flows ◽  
Good Agreement

In this work, we attempted to develop an Implicit Coupled Density-Based (ICDB) solver using LU-SGS algorithm based on the AUSM+ up scheme in OpenFOAM. Then sonicFoam solver was modified to include viscous dissipation in order to improve its capability to capture shock wave and aerothermal variables. The details of the ICDB solver as well as key implementation details of the viscous dissipation to energy equation were introduced. Finally, two benchmark tests of hypersonic airflow over a flat plate and a 2-D cylinder were simulated to show the accuracy of ICDB solver. To verify and validate the ICDB solver, the obtained results were compared with other published experimental data. It was revealed that ICDB solver has good agreement with the experimental data. So it can be used as reference in other studies. It was also observed that ICDB solver enjoy advantages such as high resolution for contact discontinuity and low computational time. Moreover, to investigate the performance of modified sonicFoam, a case study of airflow over the prism was considered. Then the results of the modified sonicFoam were compared with the ICDB, rhoCentralFoam and sonicFoam solvers. The results showed that the modified sonicFoam solver possesses higher accuracy and lower computational time in comparison with the sonicFoam and rhoCentralFoam solvers, respectively.

On the swimming of a flexible plate of arbitrary finite thickness

1964 ◽  
Vol 20 (1) ◽  
pp. 1-33 ◽  
Author(s):  
J. P. Uldrick ◽  
J. Siekmann
Keyword(s):  
Experimental Data ◽  
Finite Thickness ◽  
Numerical Calculations ◽  
Flexible Plate ◽  
Two Dimensional ◽  
Present Contribution ◽  
Fish Propulsion ◽  
Special Cases ◽  
Good Agreement

This paper studies the effect of profile thickness on the propulsive forces generated by the swimming of a two-dimensional fish. Comparison of numerical calculations with reported experimental data shows good agreement and demonstrates a decrease of thrust with increasing thickness. Previous two-dimensional linearized theories on fish propulsion dealing with the motion of an infinitesimally thin hydrofoil are included in the present contribution as special cases.

A Theory of Sharp-Edged Orifices

1937 ◽  
Vol 4 (2) ◽  
pp. A53-A54
Author(s):  
W. E. Howland
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Discharge Coefficient ◽  
Reynolds Numbers ◽  
Experimental Results ◽  
Low Reynolds Numbers ◽  
Circular Orifice ◽  
Coefficient Of Discharge ◽  
Theoretical Considerations ◽  
Good Agreement

Abstract The author presents a figure in which the coefficient of discharge Cd, velocity Cv, and contraction Cc determined by several investigators are plotted logarithmically as points against Reynolds’ numbers. Curves for the coefficients drawn by the author, based on theoretical considerations, show good agreement with the experimental data, thus throwing some light upon the basic phenomena of the discharge of sharp-edged orifices. The variation of the coefficient of discharge of a circular orifice as a function of the Reynolds number is explained as a purely viscous phenomenon for low Reynolds numbers, and by means of a momentum analysis for higher speeds. The analysis presented by the author leads to the development of several formulas for the discharge coefficient, which formulas are in fair agreement with experimental results.

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