A Transition-Turbulent Lubrication Theory Using Mixing Length Concept

1993 ◽  
Vol 115 (4) ◽  
pp. 591-596
Author(s):  
P. B. Kosasih ◽  
A. K. Tieu
Keyword(s):  
Reynolds Stress ◽  
Stress Gradient ◽  
Three Dimensional ◽  
Turbulent Regime ◽  
Transition Regime ◽  
Mixing Length ◽  
Parallel Plates ◽  
Pressure Distributions ◽  
Load Carrying ◽  
Local Shear

This paper applies the recently introduced Reynolds stress expression (Tieu and Kosasih, 1992) in the transition-turbulent lubrication analysis. The Reynolds stress is modeled using the mixing length expression which is able to account for the effect of local shear stress gradient, and it can be extended to apply in the transition regime. This theory is then used to determine three-dimensional velocity distributions between parallel plates. From the results, a set of coefficients covering transition-turbulent regime used in conjunction with the modified Reynolds equation is presented. It is shown that the resulting coefficients agree well with results of Elrod and Ng (1967) in the fully turbulent regime while differences are shown in the transition regime. Pressure distributions and load carrying capacity of superlaminar journal bearing are compared with available experimental data.

scholarly journals Mean dynamics of transitional channel flow

2011 ◽  
Vol 678 ◽  
pp. 451-481 ◽  
Author(s):  
J. ELSNAB ◽  
J. KLEWICKI ◽  
D. MAYNES ◽  
T. AMEEL
Keyword(s):  
Reynolds Number ◽  
Reynolds Stress ◽  
Channel Flow ◽  
Inflection Point ◽  
Stress Gradient ◽  
Development Stage ◽  
Stress Profile ◽  
Turbulent Regime ◽  
Nonlinear Development ◽  
The Mean

The redistribution of mean momentum and vorticity, along with the mechanisms underlying these redistribution processes, is explored for post-laminar flow in fully developed, pressure driven, channel flow. These flows, generically referred to as transitional, include an instability stage and a nonlinear development stage. The central focus is on the nonlinear development stage. The present analyses use existing direct numerical simulation data sets, as well as recently reported high-resolution molecular tagging velocimetry measurements. Primary considerations stem from the emergence of the effects of turbulent inertia as represented by the Reynolds stress gradient in the mean differential statement of dynamics. The results describe the flow evolution following the formation of a non-zero Reynolds stress peak that is known to first arise near the critical layer of the most unstable disturbance. The positive and negative peaks in the Reynolds stress gradient profile are observed to undergo a relative movement toward both the wall and centreline for subsequent increases in Reynolds number. The Reynolds stress profiles are shown to almost immediately exhibit the same sequence of curvatures that exists in the fully turbulent regime. In the transitional regime, the outer inflection point in this profile physically indicates a localized zone within which the mean dynamics are dominated by inertia. These observations connect to recent theoretical findings for the fully turbulent regime, e.g. as described by Fife, Klewicki & Wei (J. Discrete Continuous Dyn. Syst., vol. 24, 2009, p. 781) and Klewicki, Fife & Wei (J. Fluid Mech., vol. 638, 2009, p. 73). In accord with momentum equation analyses at higher Reynolds number, the present observations provide evidence that a logarithmic mean velocity profile is most rapidly approximated on a sub-domain located between the zero in the Reynolds stress gradient (maximum in the Reynolds stress) and the outer region location of the maximal Reynolds stress gradient (inflection point in the Reynolds stress profile). Overall, the present findings provide evidence that the dynamical processes during the post-laminar regime and those operative in the high Reynolds number regime are connected and describable within a single theoretical framework.

Buoyancy Driven Flow Between Vertical Parallel Plates of Finite Width

2007 ◽  
Author(s):  
Carl-Olof Olsson
Keyword(s):  
Three Dimensional ◽  
Thermal Boundary Condition ◽  
Uniform Heat Flux ◽  
Finite Width ◽  
Turbulent Regime ◽  
Parallel Plates ◽  
Plate Spacing ◽  
3D Effects ◽  
Pressure Regime ◽  
Plate Width

In the present investigation, three-dimensional (3D) simulations have been carried out in order to study the influence of Rayleigh number (Ra″, 0.1 to 1000) and the geometric proportions H/S (5 and 10) and W/S (2.5 to 20), where H is the duct height, S is the plate spacing, and W is the plate width. The Prandtl number is 0.72, and the thermal boundary condition is uniform heat flux. The results are compared to the corresponding two-dimensional (2D) situation that is approached when W/S is very large. The investigation is restricted to laminar flow. For H/S = 5, the 3D effects increase the Nusslet number (Nu3D) at low Ra″ as compared to the 2D situation. For increasing Ra″, Nu3D approaches the 2D correlation, however, for the largest Ra″, Nu3D is slightly larger than Nu2D and there is a local minimum in Nu3D/Nu2D in the range 1 < Ra″ < 100. The minimum occurs at smaller Ra″ for increasing W/S. In general, it seems as the buoyancy driven flow between parallel plates of finite width can be characterized by four regimes: conduction regime, pressure regime, boundary layer regime, and turbulent regime.

A Length-Scale Model For Developing Turbulent Flow in a Rectangular Duct

1977 ◽  
Vol 99 (2) ◽  
pp. 347-356 ◽  
Author(s):  
F. B. Gessner ◽  
A. F. Emery
Keyword(s):  
Reynolds Stress ◽  
Three Dimensional ◽  
Scale Model ◽  
Length Scale ◽  
Pressure Gradients ◽  
Mixing Length ◽  
Two Dimensional ◽  
Rectangular Duct ◽  
Corner Flows ◽  
Theory And Experiment

A three-dimensional mixing length model is proposed for modeling local Reynolds stress behavior in rectangular ducts of arbitrary aspect ratio. The model is applicable to both developing and fully-developed flows, and can be applied to other 90-degree corner flows with mild streamwise pressure gradients. Comparisons between theory and experiment show that all components of the Reynolds stress tensor are modeled reasonably well, both in the vicinity of a corner and in two-dimensional regions away from the corner.

Analysis of Thrust Bearings Operating in Turbulent Regime

1988 ◽  
Vol 110 (3) ◽  
pp. 555-560 ◽  
Author(s):  
M. Harada ◽  
H. Aoki
Keyword(s):  
Steady State ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Cross Coupling ◽  
Fluid Film ◽  
Turbulent Regime ◽  
Pressure Gradients ◽  
Mixing Length ◽  
Thrust Bearings ◽  
Mixing Length Theory

This paper relates to the turbulent motion in the lubricant fluid film with centrifugal effects and the lubrication theory for thrust bearings operating in turbulent regime. Using Prandtl’s mixing-length theory, three-dimensional turbulent velocity distributions, including pressure gradients and centrifugal effects, are calculated, and the cross-coupling of nonplanar flow of the lubricant fluid film is discussed. From these results, turbulent lubrication equations with centrifugal effects are derived. Applying these lubrication equations to a sectorial inclined thrust bearing, the steady-state characteristics and the dynamic ones are calculated.

Analysis of Misaligned Journal Bearings Operating in Turbulent Regime

1989 ◽  
Vol 111 (2) ◽  
pp. 215-219 ◽  
Author(s):  
Z. S. Safar ◽  
M. M. Elkotb ◽  
D. M. Mokhtar
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Turbulent Regime ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Local Shear ◽  
Bearing Behavior ◽  
Journal Misalignment ◽  
Local Shear Stress

This paper presents an analysis of the performance characteristics for a misaligned full journal bearing operating in turbulent regime. The modified Reynolds equation for turbulent flow is solved taking into consideration that the distribution of the effective viscosity is dependent on local shear stress. It is found that journal misalignment influences bearing behavior especially at lower eccentricity ratios. Also, it is concluded that for the same load carrying capacity misaligned journal bearing consumes more power than an aligned one.

Analysis of Bearings Operating in Turbulent Regime

1962 ◽  
Vol 84 (1) ◽  
pp. 139-151 ◽  
Author(s):  
V. N. Constantinescu
Keyword(s):  
Three Dimensional ◽  
Lubricant Layer ◽  
Turbulent Regime ◽  
Mixing Length ◽  
Thrust Bearings ◽  
Mixing Length Theory

Proceeding from the results obtained previously [5] this paper analyzes theoretically the three-dimensional motion in the lubricant layer by using Prandtl’s mixing length theory. Formulas and diagram are presented for calculating journal and thrust bearings subjected to turbulent lubrication.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

A Liquid Metal Flow Between Two Coaxial Cylinders System

2019 ◽  
Vol 11 (1) ◽  
pp. 79-86
Author(s):  
Abdelkrim Merah ◽  
Ridha Kelaiaia ◽  
Faiza Mokhtari
Keyword(s):  
Couette Flow ◽  
Metal Flow ◽  
Three Dimensional ◽  
Liquid Sodium ◽  
Taylor Vortex ◽  
Turbulent Regime ◽  
Coaxial Cylinders ◽  
Concentric Cylinders ◽  
Ideal Tool ◽  
The Stability

Abstract The Taylor-Couette flow between two rotating coaxial cylinders remains an ideal tool for understanding the mechanism of the transition from laminar to turbulent regime in rotating flow for the scientific community. We present for different Taylor numbers a set of three-dimensional numerical investigations of the stability and transition from Couette flow to Taylor vortex regime of a viscous incompressible fluid (liquid sodium) between two concentric cylinders with the inner one rotating and the outer one at rest. We seek the onset of the first instability and we compare the obtained results for different velocity rates. We calculate the corresponding Taylor number in order to show its effect on flow patterns and pressure field.

EXPERIMENTAL INVESTIGATION OF FLOW RESPONSE TO STATIONARY DISTURBANCE IN ROTATING-DISK FLOW

2019 ◽  
Vol XVI (2) ◽  
pp. 13-22
Author(s):  
Muhammad Ehtisham Siddiqui
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Careful Analysis ◽  
Laboratory Frame ◽  
Transition To Turbulence ◽  
Turbulent Regime ◽  
Mean Velocity ◽  
Layer Flow

Three-dimensional boundary-layer flow is well known for its abrupt and sharp transition from laminar to turbulent regime. The presented study is a first attempt to achieve the target of delaying the natural transition to turbulence. The behaviour of two different shaped and sized stationary disturbances (in the laboratory frame) on the rotating-disk boundary layer flow is investigated. These disturbances are placed at dimensionless radial location (Rf = 340) which lies within the convectively unstable zone over a rotating-disk. Mean velocity profiles were measured using constant-temperature hot-wire anemometry. By careful analysis of experimental data, the instability of these disturbance wakes and its estimated orientation within the boundary-layer were investigated.

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

Sign in / Sign up

Export Citation Format

Share Document