Symmetric Radial Laminar Channel Flow With Particular Reference to Aerostatic Bearings

1992 ◽  
Vol 114 (3) ◽  
pp. 630-636 ◽  
Author(s):  
F. Al-Bender ◽  
H. Van Brussel
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Channel Flow ◽  
Flow Model ◽  
Separation Of Variables ◽  
Wide Range ◽  
Laminar Channel Flow ◽  
Aerostatic Bearings ◽  
Laminar Flow Model

After a short survey of the different methods and formulas used to determine the pressure distribution in radial (converging or diverging) flow between nominally parallel discs, the method of “separation of variables,” established in reference [1], is applied to the problem, especially the case pertaining to centrally fed circular aerostatic bearings. The results are compared extensively with experimental data from various sources and the agreement is found to be remarkably good, suggesting that a laminar flow model is sufficient in characterizing the flow over a wide range of Reynolds number values.

Development-Length Requirements for Fully Developed Laminar Flow in Concentric Annuli

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
R. J. Poole
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Channel Flow ◽  
Characteristic Length ◽  
Radius Ratio ◽  
Length Scale ◽  
Development Length ◽  
Characteristic Length Scale ◽  
Annular Gap ◽  
Wide Range

In this technical brief we report the results of a systematic numerical investigation of developing laminar flow in axisymmetric concentric annuli over a wide range of radius ratio (0.01<Ri/Ro<0.8) and Reynolds number (0.001<Re<1000). When the annular gap is used as the characteristic length scale we find that for radius ratios greater than 0.5 the development length collapses to the channel-flow correlation. For lower values of radius ratio the wall curvature plays an increasingly important role and the development length remains a function of both radius ratio and Reynolds number. Finally we show that the use of an empirical modified length scale to normalize both the development length and the characteristic length scale in the Reynolds number collapses all of the data onto the channel-flow correlation regardless of the radius ratio.

Comparison of Numerical Modeling to Experimental Data in a Small, Low Power Data Center Test Cell

2009 ◽  
Author(s):  
Ethan Cruz ◽  
Yogendra Joshi ◽  
Madhusudan Iyengar ◽  
Roger Schmidt
Keyword(s):  
Experimental Data ◽  
Laminar Flow ◽  
Data Center ◽  
Flow Model ◽  
Turbulence Models ◽  
Computational Effort ◽  
Test Cell ◽  
Air Cooling ◽  
Measured Temperature ◽  
Laminar Flow Model

As the performance of Information Technology (IT) equipment continues to rise, so do the power dissipated and overall power density. Air cooling this increasing power has proved a significant challenge even at the data center level. In order to combat this challenge, Computational Fluid Dynamics and Heat Transfer (CFD/HT) models have been employed as the dominant technique for the design and optimization of both new and existing data centers. This study is a continuation of earlier comparisons of CFD/HT models to experimentally measured temperature and flow fields in a small data center test cell. It compares previously unpublished experimentally collected data for the 11 kW dissipation cases using three different layouts of perforated tiles to a CFD/HT model using eight turbulence models and a laminar flow model. Insight into the location of the deviation between the different turbulence models and experimental data are discussed, along with the computational effort involved in running the CFD/HT models. It was found that the laminar flow model and the Spalart-Allamaras turbulence model produced the smallest deviations from experimental data, but the former required only one twentieth of the computational effort of the latter.

scholarly journals A Semi-Analytical Method for the Solution of Entrance Flow Effects in Inherently Restricted Aerostatic Bearings

2008 ◽  
Author(s):  
Tobias Waumans ◽  
Farid Al-Bender ◽  
Dominiek Reynaerts
Keyword(s):  
Separation Of Variables ◽  
Pressure Profile ◽  
Empirical Formulas ◽  
Experimental Conditions ◽  
Boundary Layer Equations ◽  
Wide Range ◽  
Laminar Channel Flow ◽  
Aerostatic Bearings ◽  
Flow Effects ◽  
Entrance Flow

The behaviour of aerostatic bearings is strongly influenced by the entrance flow effects nearby feeding sources. A basic understanding of these flow phenomena and accurate prediction of their relevant parameters are therefore essential in the design and optimisation process of any aerostatic bearing application. The subject matter of this paper has for long been the topic of extensive research. An overview of the different approaches found in literature shows mostly methods based on empirical formulas with a validity limited to the experimental conditions that produced them. The proposed solution method uses the technique of separation of variables to convert the boundary-layer equations describing the laminar channel flow into an initial value problem. This allows the exact calculation of the pressure profile from gap entrance up to the attainment of viscous flow. Knowledge of the pressure distribution near the gap entrance together with the mass flow rate leads to the determination of an expedient coefficient of discharge, allowing a more practical lumped parameter formulation. The results are compared with experimental data from various sources and the agreement is found to be remarkably good, indicating that a laminar flow model is adequate in characterising the entrance flow over a wide range of working parameters.

A Study of Flow of Plastics Through Pipes

1946 ◽  
Vol 13 (2) ◽  
pp. A101-A105
Author(s):  
R. C. Binder ◽  
J. E. Busher
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Friction Coefficient ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Dynamic Viscosity ◽  
Apparent Viscosity ◽  
Turbulent Viscosity ◽  
Yield Value

Abstract The pipe friction coefficient for true fluids is usually expressed as a function of Reynolds number. This method of organizing data has been extended to tests on the flow of different suspensions which behaved as ideal plastics in the laminar-flow range and as true fluids in the turbulent-flow range. In the laminar-flow range, Reynolds number below about 2100, the denominator in Reynolds number is taken as the apparent viscosity. The apparent viscosity can be determined from the yield value and the coefficient of rigidity. In the turbulent-flow range, the denominator in Reynolds number is an equivalent or turbulent viscosity equal to the dynamic viscosity of a true fluid having the same friction coefficient, velocity, diameter, and density as that of the plastic. The various experimental data on plastics correlate well with this extension of the method for true fluids.

Effect of Size and Slip Coefficient of a Porous Manifold on Thermal Stratification in Storage Tanks

2009 ◽  
Author(s):  
N. M. Brown ◽  
F. C. Lai
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Numerical Simulations ◽  
Storage Tank ◽  
Richardson Number ◽  
Thermal Stratification ◽  
Temperature Fields ◽  
Storage Tanks ◽  
Slip Coefficient ◽  
Wide Range

Numerical simulations have been performed to study the effects of size and slip coefficient of a porous manifold on the thermal stratification in a storage tank. The model is used to predict the development of flow and temperature fields during a charging process. Computations have covered a wide range of the Grashof number (1.8 × 105 &lt; Gr &lt; 1.8 × 108) and Reynolds number (10 ≤ Re ≤ 104), or in terms of the Richardson number, 10−2 &lt; Ri &lt; 105. The results obtained compare favorably well with the experimental data. In addition, the present results have confirmed the effectiveness of porous manifold in the promotion of thermal stratification and provide useful information for the design of such system.

Laminar Flow Model in Ducts of Circular Section With Arbitrary Axial Variation

2010 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Juan S. Stockle ◽  
Andy Huilcan
Keyword(s):  
Laminar Flow ◽  
Flow Model ◽  
Pressure Field ◽  
Axial Direction ◽  
Working Fluid ◽  
Circular Section ◽  
Circular Duct ◽  
Variable Section ◽  
Axial Variation ◽  
Laminar Flow Model

Laminar flow inside a circular duct of variable section in the axial direction is modeled, assuming that the working fluid is Newtonian, incompressible, with laminar flow, a permanent state, and constant properties. The results describe the behavior of the stream function, the velocity field, and the pressure field, and graphic results are presented for each of those functions. The method used to solve the problem makes use of regular perturbations around the shape factor ε parameter. This research can be used for the design of new technological devices important to industry, optimizing processes in which fluids are transported, energy is transferred, etc.

Improved Correlations for Counting the Effect of Natural Convection on Laminar Flow of Nanofluids

2013 ◽  
Author(s):  
Si-pu Guo ◽  
Zhao-zan Feng ◽  
Ze-cong Fang ◽  
Wei Li ◽  
Jin-liang Xu ◽  
...  
Keyword(s):  
Experimental Data ◽  
Natural Convection ◽  
Laminar Flow ◽  
Prandtl Number ◽  
Single Phase ◽  
Colloidal Suspensions ◽  
Horizontal Tube ◽  
Laminar Mixed Convection ◽  
Wide Range ◽  
Phase Fluid

Nanofluids are colloidal suspensions of nano-scale particles in water, or other base fluids. In this paper, the effect of natural convection on laminar flow of nanofluids in a horizontal tube has been addressed. The obtained experimental data could not be reconciled with existing correlations over a wide range of Prandtl number under laminar mixed convection. Three improved correlations have been derived by using single-phase fluid approach. These correlations fit our data to within ± 10 % and also agree with the data in literature quite well. Such results verify that nanofluids can be treated as a homogeneous mixture with effective thermophysical properties. Utimately, the new correlations have grasped the essence of natural convection and can reduce to both normal forced convection and pure natural convection equations at limiting cases.

Calculation of Pressure Gradients from MR Velocity Data in a Laminar Flow Model

1991 ◽  
Vol 15 (3) ◽  
pp. 483-488 ◽  
Author(s):  
Ronald S. Adler ◽  
Thomas L. Chenevert ◽  
J. Brian Fowlkes ◽  
James Pipe ◽  
Jonathan M. Rubin
Keyword(s):  
Laminar Flow ◽  
Flow Model ◽  
Pressure Gradients ◽  
Velocity Data ◽  
Laminar Flow Model
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