scholarly journals Optimization of Conical Hydrostatic Bearing for Minimum Friction

1972 ◽  
Vol 94 (2) ◽  
pp. 136-142 ◽  
Author(s):  
L. J. Nypan ◽  
B. J. Hamrock ◽  
H. W. Scibbe ◽  
W. J. Anderson
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Rate ◽  
Load Capacity ◽  
Friction Torque ◽  
Radius Ratio ◽  
Hydrostatic Bearing ◽  
Laminar And Turbulent Flow

Equations for the flow rate, load capacity, and friction torque for a conical hydrostatic bearing were developed. These equations were solved by a digital computer program to determine bearing configurations for minimum friction torque. Design curves are presented that show optimal bearing dimensions for minimum friction torque as a function of dimensionless flow rate for a range of dimensionless load capacity. Results are shown for both laminar and turbulent flow conditions. The results indicate the hydrostatic pocket friction is a significant portion of the total friction torque. However, the bearing dimensions for a minimum friction design are affected very little by inclusion of pocket friction in the analysis. For laminar flow the values of the outerland radius ratio X3 and outer bearing radius ratio X4 did not change significantly with increasing friction factor. For turbulent flow, the outer bearing radius ratio X4 did not change with increasing friction factor; therefore, the value determined for X4 in the laminar flow case is valid for all turbulent flows.

scholarly journals Unravelling turbulence near walls

2009 ◽  
Vol 630 ◽  
pp. 1-4 ◽  
Author(s):  
IVAN MARUSIC
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Turbulent Flows ◽  
Direct Numerical Simulations ◽  
Aircraft Wing ◽  
Physical Mechanisms ◽  
Drag And Lift

Turbulent flows near walls have been the focus of intense study since their first description by Ludwig Prandtl over 100 years ago. They are critical in determining the drag and lift of an aircraft wing for example. Key challenges are to understand the physical mechanisms causing the transition from smooth, laminar flow to turbulent flow and how the turbulence is then maintained. Recent direct numerical simulations have contributed significantly towards this understanding.

Heat transfer from a rotating disk

1956 ◽  
Vol 236 (1206) ◽  
pp. 343-351 ◽  
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Outer Part ◽  
Rotating Disk ◽  
Friction Torque ◽  
Practical Applications ◽  
A Value ◽  
Flow Heat

The flow due to a disk rotating in its own plane has been investigated theoretically by von Kármán, Goldstein, and others, but little has been published on the heat transfer. For laminar conditions theoretical solutions have been given by Millsaps & Pohlhausen and by Wagner, but for conditions when the flow is turbulent over the outer part of the disk there is no previous information. The present paper describes an experimental investigation of the heat transfer for a range of conditions from entirely laminar flow to conditions when the outer 80% of the disk area is under turbulence. For laminar flow the heat transfer agrees with Wagner’s results, but Millsap’s theory is found to give too low values and an explanation is given. For the turbulent case, which occurs in most practical applications, values are given for the heat transfer which is found to approach the expression N = 0∙015 R 0∙8 for all-turbulent flow. An attempt is made to deduce the turbulent flow heat transfer theoretically by assuming a 1/7 power law of temperature distribution, but this gives too low a value. Some measurements of the velocity and temperature profiles both for laminar and for turbulent conditions are given. For laminar flow these show fair agreement with the theoretical values. For turbulent flow the temperature ratios are higher than those of velocity, which explains the low heat transfer values calculated assuming a 1/7 power temperature distribution. The relation between heat transfer and friction torque is also discussed.

scholarly journals Effect of nanofluid properties and mass-flow rate on heat transfer of parabolic-trough concentrating solar system

2019 ◽  
Vol 16 (1) ◽  
pp. 33-44 ◽  
Author(s):  
M.K. Islam ◽  
Md. Hasanuzzaman ◽  
N.A. Rahim ◽  
A. Nahar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Parabolic Trough ◽  
Concentrated Solar Energy

Sustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector’s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow.

Rate of advancement of reactions in turbulent flows

1964 ◽  
Vol 17 (8) ◽  
pp. 821 ◽  
Author(s):  
RCL Bosworth ◽  
CM Groden
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Residence Times ◽  
Cylindrical Reactor ◽  
The Times ◽  
Very High

When a reacting substance or mixture is caused to flow in a cylindrical reactor, all portions of the stream will not flow at the same rate and will exhibit different residence times and, accordingly, are subject to different extents of degrees of reaction. The average degrees of reaction following the residence time distribution proper to laminar flow are given in the earlier publication1 and this paper extends the treatment to that of turbulent flow. In the earlier treatment of laminar flow the ratio of average extent of reaction with non-interacting streams to that of complete intermingling, or the C/Cm, is plotted against the ratio of the times of flow with those of reaction (S). The C/Cm versus S curves are all above unity and increase with increasing S, with the exception of very high orders of chemical reaction for which values of C/Cm are all unity. In the case of turbulent flow the values of C/Cm are more nearly unity at all values of S.

Performance Analysis of High Speed Floating Ring Hybrid Bearing in the Laminar and Turbulent Regimes

2011 ◽  
Vol 197-198 ◽  
pp. 1776-1780 ◽  
Author(s):  
Hong Guo ◽  
Bo Qian Xia ◽  
Shao Qi Cen
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Load Capacity ◽  
Flow Equation ◽  
The Finite Element Method ◽  
Static And Dynamic Characteristics ◽  
Hybrid Bearing

This paper presents a theoretical study concerning the static and dynamic characteristics of high speed journal floating ring hybrid bearing compensated by interior restrictor under laminar flow and turbulent flow respectively. The turbulent flow fluid film control equations and the pressure boundary conditions of this floating ring bearing together with the restrictor flow equation are solved by using the Finite Element Method. The variation regularity of static and dynamic characteristics such as load capacity, friction power loss, stiffness, damping etc. is analyzed. By comparing the laminar flow results and turbulent flow results, it is found that the characteristics coefficients are adjacent under small Reynolds number (laminar flow is dominant). But the characteristics coefficients are discrepant under big Reynolds number (turbulent flow is dominant). So turbulence lubrication theory is more accurate to high speed floating ring bearing.

scholarly journals The influence of shear stress on the adhesion capacity of Legionella pneumophila

2017 ◽  
Vol 68 (2) ◽  
pp. 109-115 ◽  
Author(s):  
Martina Oder ◽  
Rok Fink ◽  
Klemen Bohinc ◽  
Karmen Godič Torkar
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
Bacterial Growth ◽  
Legionella Pneumophila ◽  
Bacterial Adhesion ◽  
Flow Chamber ◽  
Bacterial Cells ◽  
Flow Conditions ◽  
Laminar And Turbulent Flow ◽  
Hydrodynamic Effects

Abstract Bacterial adhesion is a complex process influenced by many factors, including hydrodynamic conditions. They affect the transfer of oxygen, nutrients, and bacterial cells in a water supply and cooling systems. The aim of this study was to identify hydrodynamic effects on bacterial adhesion to and detachment from stainless steel surfaces. For this purpose we observed the behaviour of bacterium L. pneumophila in no-flow and laminar and turbulent flow conditions simulated in a fluid flow chamber. The bacterial growth in no-flow and laminar flow conditions was almost identical in the first 24 h, while at 48 and 72 h of incubation, the laminar flow stimulated bacterial growth. In the second part of this study we found that laminar flow accelerated bacterial adhesion in the first 48 h, but after 72 h the amount of bacterial cells exposed to the flow dropped, probably due to detachment. In the third part we found that the turbulent flow detached more bacterial cells than the laminar, which indicates that the strength of shear forces determines the rate of bacterial removal.

Investigations in Hydrostatic Planar Bearings Compensated by Tapered-Spool Restrictors I: Flow Rate

2015 ◽  
Vol 32 (1) ◽  
pp. 63-69
Author(s):  
Y. Kang ◽  
H.-C. Cheng ◽  
C.-W. Lee ◽  
S.-Y. Hu
Keyword(s):  
Flow Rate ◽  
Analytical Method ◽  
Pressure Difference ◽  
Load Capacity ◽  
Design Parameters ◽  
Static Characteristics ◽  
Static Stiffness ◽  
Flow Rates ◽  
Single Action ◽  
Hydrostatic Bearing

ABSTRACTThis paper is former part of serial studies to investigate the influence of design parameters of tapered-spool type restrictors on static characteristics of hydrostatic bearing. The flow rates passing restrictors can determine the static characteristics of hydrostatic bearings. In this part an analytical method which includes formulas and solving is utilized to simulate dimensionless flow rate in both single-action and double-action tapered-spool restrictors. The numerical results illustrate the variations of flow rates with respect to the change of pressure and pressure difference, respectively. The findings give that the design parameters of tapered-spool restrictors and the useful range of recess pressure. The following part will depend on this paper results to study load capacity and static stiffness of hydrostatic bearing compensated by tapered-spool restrictor.

The Steady-State and Dynamic Characteristics of a Full Circular Bearing and a Partial Arc Bearing in the Laminar and Turbulent Flow Regimes

1967 ◽  
Vol 89 (2) ◽  
pp. 143-153 ◽  
Author(s):  
F. K. Orcutt ◽  
E. B. Arwas
Keyword(s):  
Steady State ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Flow Regime ◽  
Dynamic Characteristics ◽  
Reynolds Numbers ◽  
Operating Parameters ◽  
Design Data ◽  
Design Charts ◽  
Laminar And Turbulent Flow

The steady-state and dynamic characteristics of a full circular bearing and a centrally loaded, 100 deg, arc bearing are calculated for a range of eccentricity ratios to 0.95 and of mean Reynolds numbers to 13,300, and presented in design charts. These are compared with the measured performance of these bearings over the same ranges of the operating parameters. There is good correlation between the theoretical and test data, leading to the conclusion that the present turbulent lubrication analysis may be used to obtain general design data for self-acting bearings, operating in the superlaminar flow regime, to supplement that presently existing for laminar flow bearings.

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