On the Comparison Between Lubrication Theory, Including Turbulence and Inertia Forces, and Some Existing Experimental Data

1975 ◽  
Vol 97 (3) ◽  
pp. 439-448 ◽  
Author(s):  
V. N. Constantinescu ◽  
S. Galetuse ◽  
F. Kennedy
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Reynolds Numbers ◽  
Lubrication Theory ◽  
Incoming Flow ◽  
Flow Conditions ◽  
Film Rupture ◽  
Inertia Forces ◽  
Proper Consideration ◽  
Good Agreement

The results obtained by using lubrication theory, including inertia forces, are checked against experimental data concerning flows in relatively thin films at moderate and large Reynolds numbers. It is shown that a reasonably good agreement is obtained provided that the peculiar features of the experimental flow are properly taken into account; namely, proper consideration of the type of flow (laminar, transition, turbulent), proper evaluation of the region where lubrication flow prevails, entrance flow conditions (relating the flow into the film to the incoming flow), conditions for film rupture, cavitation or separation.

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

Simulation and prediction of optical characterization of casting (Adamantan-Fulgide) thin films using (CTANNs) approach

2019 ◽  
Vol 33 (11) ◽  
pp. 1950093 ◽  
Author(s):  
A. M. A. EL-Barry ◽  
D. M. Habashy
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Back Propagation ◽  
Optical Characterization ◽  
Experimental Information ◽  
Training Algorithm ◽  
Energy Gaps ◽  
Resilient Back Propagation ◽  
Good Agreement

For reinforcement, the photochromic field and the cooperation between the theoretical and experimental branches of physics, the computational, theoretical artificial neural networks (CTANNs) and the resilient back propagation (R[Formula: see text]) training algorithm were used to model optical characterizations of casting (Admantan-Fulgide) thin films with different concentrations. The simulated values of ANN are in good agreement with the experimental data. The model was also used to predict values, which were not included in the training. The high precision of the model has been constructed. Moreover, the concentration dependence of both the energy gaps and Urbach’s tail were, also tested. The capability of the technique to simulate the experimental information with best accuracy and the foretelling of some concentrations which is not involved in the experimental data recommends it to dominate the modeling technique in casting (Admantan-Fulgide) thin films.

scholarly journals A Method of Predicting the Energy Losses in Vaneless Diffusers of Centrifugal Compressors

1989 ◽  
Author(s):  
Huashu Dou
Keyword(s):  
Experimental Data ◽  
Energy Loss ◽  
Total Energy ◽  
Wall Friction ◽  
Energy Losses ◽  
Flow Conditions ◽  
Centrifugal Compressors ◽  
Flow Losses ◽  
Vaneless Diffusers ◽  
Good Agreement

The flow losses in the veneless diffusers of centrifugal compressors is investigated. It is found that the total energy loss in vaneless diffusers is a function of Bsin2 α0 when inlet flow conditions and radius ratio between inlet and outlet are given. A wall friction coefficient equation is derived and a method of predicting the total energy loss excepting mixing loss is presented. A comparison is made between results obtained from this method and experimental data generated by the author as well as data from the literature. Good agreement is obtained.

scholarly journals Weak Localization Effect in Superconductors

1998 ◽  
Vol 12 (19) ◽  
pp. 763-773 ◽  
Author(s):  
Yong-Jihn Kim ◽  
K. J. Chang
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Sheet Resistance ◽  
Three Dimensional ◽  
Weak Localization ◽  
Transition Temperatures ◽  
Universal Behavior ◽  
Localization Effect ◽  
Disordered Superconductors ◽  
Good Agreement

We investigate the effect of weak localization on the transition temperatures of superconductors using Anderson's time-reversed scattered-state pairs, and show that disorder weakens electron–phonon interactions. With solving the BCS T c -equation, the calculated values for T c are in good agreement with experimental data for various two- and three-dimensional disordered superconductors. We find that the critical sheet resistance for the suppression of superconductivity in thin films does not satisfy the universal behavior but depends on sample, in good agreement with experiments.

scholarly journals Influence of fin thickness on heat transfer and flow performance of a parallel flow evaporator

2019 ◽  
Vol 23 (4) ◽  
pp. 2413-2419 ◽  
Author(s):  
Haijun Li ◽  
Enhai Liu ◽  
Guanghui Zhou ◽  
Fengye Yang ◽  
Zhiyong Su ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Comprehensive Evaluation ◽  
Reynolds Numbers ◽  
Parallel Flow ◽  
Heat Transfer Factor ◽  
Heat Transfer Capacity ◽  
Fin Thickness ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

This paper studies numerically the influence of the louver?s fin thickness on heat transfer and flow performance of a parallel flow evaporator, a comprehensive evaluation and analysis of the five structures at different Reynolds numbers are systematically carried out. Comparison of the numerical results with the experimental data shows good agreement with maximal errors of 12.16% and 5.29% for the heat transfer factor and the resistance factor, respectively. The results show that the heat transfer coefficient and the pressure drop increase with the increase of the thickness of the louver fins when the Reynolds number is a constant. The analysis of the comprehensive evaluation factor shows that the A-type fin is the best, and it can effectively strengthen the heat exchange on the air side and improve the heat transfer capacity of the system. The research results can provide reference for the structural optimization of the louver fins.

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.

scholarly journals Measurements of Squeeze Film Bearing Forces to Demonstrate the Effect of Fluid Inertia

1984 ◽  
Author(s):  
John A. Tichy
Keyword(s):  
Dynamic Systems ◽  
High Speed ◽  
Hydrodynamic Lubrication ◽  
Reynolds Numbers ◽  
Lubrication Theory ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Viscous Forces ◽  
Rotor Dynamic ◽  
Inertia Forces

Squeeze film dampers are commonly applied to high speed rotating machinery, such as aircraft engines, to reduce vibration problems. The theory of hydrodynamic lubrication has been used for the design and modeling of dampers in rotor dynamic systems despite typical modified Reynolds numbers in applications between ten and fifty. Lubrication theory is strictly valid for Reynolds numbers much less than one, which means that fluid viscous forces are much greater than inertia forces. Theoretical papers which account for fluid inertia in squeeze films have predicted large discrepancies from lubrication theory, but these results have not found wide acceptance by workers in the gas turbine industry. Recently, experimental results on the behavior of rotor dynamic systems have been reported which strongly support the existence of large fluid inertia forces. In the present paper direct measurements of damper forces are presented for the first time. Reynolds numbers up to ten are obtained at eccentricity ratios 0.2 and 0.5. Lubrication theory underpredicts the measured forces by up to a factor of two (100% error). Qualitative agreement is found with predictions of earlier improved theories which include fluid inertia forces.

The decay of a turbulent swirl in a pipe

1965 ◽  
Vol 22 (2) ◽  
pp. 257-271 ◽  
Author(s):  
Frank Kreith ◽  
O. K. Sonju
Keyword(s):  
Experimental Data ◽  
Eddy Diffusivity ◽  
Reynolds Numbers ◽  
Experimental Measurements ◽  
Number Range ◽  
Swirl Velocity ◽  
Linearized Theory ◽  
Flow Through ◽  
Initial Intensity ◽  
Good Agreement

This paper presents a linearized theory for the average decay of a tape-induced fully developed turbulent swirl in flow through a pipe. In the Reynolds number range between 104 and 105 the theoretical analysis was found to be in good agreement with experimental data obtained with water in a 1 in. pipe, provided the eddy diffusivity was chosen appropriately.It was observed that a turbulent swirl decays to about 10–20% of its initial intensity in a distance of about 50 pipe diameters, the decay being more rapid at smaller than at larger Reynolds numbers. The theoretical swirl velocity distribution agreed qualitatively with experimental measurements at distances less than 20 diameters downstream from the outlet of the swirl inducer, but deviated from the experimental results further downstream.

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