The Edge Singularity of an Actuator Disc with a Constant Normal Load

2003 ◽  
Author(s):  
Gijs van Kuik
Keyword(s):  
Normal Load ◽  
Edge Singularity ◽  
Actuator Disc ◽  
Constant Normal Load

The Edge Singularity of an Actuator Disc With a Constant Normal Load

2003 ◽  
Author(s):  
Gijs A. M. van Kuik
Keyword(s):  
Normal Load ◽  
Leading Edge ◽  
Radial Component ◽  
Pressure Jump ◽  
Axial Component ◽  
Field Calculation ◽  
Edge Singularity ◽  
Momentum Theory ◽  
Actuator Disc ◽  
Constant Normal Load

All rotor and propeller design methods using momentum theory are based on the concept of the actuator disc, formulated by Froude. In this concept, the rotor load is represented by a uniform pressure jump. This pressure jump generates infinite pressure gradients at the edge of the disc, leading to a velocity singularity. The subject of this paper is the characterization of this velocity singularity assuming inviscid flow. The edge singularity is also the singular leading edge of the vortex sheet emanating from the edge. The singularity is determined as a simple bound vortex of order O(1), carrying an edge force Fedge = −ρ Vedge × Γ. The order of Fedge equals the order of Vedge. This order is determined by a radial momentum analysis. The classical momentum theory for actuators with a constant, normal load Δp appears to be inconsistent: the axial balance provides a value for the velocity at the actuator, with which the radial balance cannot be satisfied. The only way to obtain consistency is to allow the radial component of Fedge to enter the radial balance. The analysis does not resolve on the axial component of Fedge. A quantitative analysis by a full flow field calculation has to assess the value of Fedge for the various actuator disc flow states. Two other solutions for the edge singularity have been published. It is shown that both solutions do not comply with the governing boundary conditions.

On the Edge Singularity of an Actuator Disk with Large Constant Normal Load

1977 ◽  
Vol 21 (02) ◽  
pp. 125-131
Author(s):  
G. H. Schmidt ◽  
J. A. Sparenberg
Keyword(s):  
Potential Theory ◽  
Normal Load ◽  
Curved Surface ◽  
Singular Behavior ◽  
Nonlinear Potential Theory ◽  
Edge Singularity ◽  
Actuator Disk ◽  
Nonlinear Potential ◽  
Constant Normal Load ◽  
Special Case

In this paper some aspects of the nonlinear potential theory of actuator disks are considered. A rather general formulation of the problem for a prescribed load on a curved surface is given. For the special case of constant normal load and no incoming velocity the singular behavior of the flow at the edge of the disk is discussed.

Frictional complete contacts subject to shear and bulk tension

2008 ◽  
Vol 222 (12) ◽  
pp. 2301-2309 ◽  
Author(s):  
N Banerjee ◽  
D Dini ◽  
D A Hills
Keyword(s):  
Normal Load ◽  
Cyclic Shear ◽  
Edge Angle ◽  
Subsequent Application ◽  
Constant Normal Load

This paper provides a set of ‘maps’ showing the response of three example frictional complete contacts (with edge angle of 60°, 90°, and 120°) subject to a constant normal load and the subsequent application of cyclic shear and bulk tension, the latter present in only one body. The maps define the region of full adhesion, the nature of violations, and conditions under which they arise.

Rock joint modeling using a visco-plastic multilaminate model at constant normal load condition

2006 ◽  
Vol 24 (5) ◽  
pp. 1449-1468 ◽  
Author(s):  
Reza Mahin Roosta ◽  
Mohammad Hossein Sadaghiani ◽  
Ali Pak ◽  
Yaser Saleh
Keyword(s):  
Normal Load ◽  
Rock Joint ◽  
Load Condition ◽  
Joint Modeling ◽  
Constant Normal Load ◽  
Constant Normal Load Condition

Friction Characteristics and Adhesion Force Under Low Normal Load

1995 ◽  
Vol 117 (4) ◽  
pp. 569-574 ◽  
Author(s):  
Yasuhisa Ando ◽  
Yuichi Ishikawa ◽  
Tokio Kitahara
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Adhesion Force ◽  
Normal Load ◽  
Adhesion Forces ◽  
Test Pieces ◽  
Before And After ◽  
Constant Normal Load ◽  
The Mean ◽  
Steel Balls

The friction coefficient and adhesion force between steel balls and flat test pieces were measured during friction under low normal load in order to examine the tribological characteristics. First, the friction coefficients were measured under a constant normal load of 0.8 to 2350 μN, and the adhesion forces were measured before and after each friction. The result showed that the friction coefficient was highest at low normal loads, while the friction force divided by the sum of the normal load and the mean adhesion force was almost constant over the whole range of loads. Second, when the normal load was reduced gradually during friction, friction still acted when the normal load became negative and a pulling off force was applied to the surface. Thus an adhesion force acts during friction and this adhesion force affects the friction force in the same way as the normal load.

Fretting Fatigue Design of Subsea Connectors: A Generalised Approach to Testing

2020 ◽  
Author(s):  
H. Andresen ◽  
D. A. Hills ◽  
Anders Wormsen ◽  
K. A. Macdonald
Keyword(s):  
Crack Nucleation ◽  
Normal Load ◽  
Asymptotic Methods ◽  
Fretting Fatigue ◽  
Test Design ◽  
Frictional Contacts ◽  
Fatigue Design ◽  
Geometrical Features ◽  
Fatigue Data ◽  
Constant Normal Load

Abstract In this paper fretting fatigue is addressed as a potential design consideration for wellhead connectors. The study of near-edge relative motion for frictional contacts under constant normal load is described using analytical, numerical and asymptotic methods. Based on published fretting fatigue experimental data an argument is drawn for a generalised fretting fatigue test design. We do this by reducing the parameters responsible for crack nucleation to the smallest number possible and thereby revealing the fretting fatigue strength as a material property independent of geometrical features. Easy to apply recipes are described and thoughts on a potential apparatus are shared with the reader. Commercial potential lies in the wide-ranging applicability of experimental results across many prototypes and loadings once an appropriate amount of fretting fatigue data has been generated for the material in question.

Effect of a-CNx Coating on Tribological Properties of SiC Ceramic in Water

2005 ◽  
Vol 475-479 ◽  
pp. 2899-2904 ◽  
Author(s):  
Fei Zhou ◽  
Koji Kato ◽  
Koshi Adachi
Keyword(s):  
Room Temperature ◽  
Normal Load ◽  
Film Surface ◽  
Mean Value ◽  
Low Velocity ◽  
Sliding Speed ◽  
Wear Rates ◽  
Sic Ceramic ◽  
Constant Normal Load ◽  
The Mean

The tribological behaviors of a-CNx/SiC tribo-pairs in water at low velocity were investigated and compared with SiC/SiC at room temperature. The results showed that the mean value µ of friction coefficients at steady state for a-CNx/SiC tribo-pairs (µ=0.075~0.12) was lower than that of SiC/SiC systems (µ=0.24~0.27). At a constant sliding speed, µ for two kinds of tribo-couples decreased with an increase in normal load, but at a constant normal load, µ for SiC/SiC system was nearly independence of sliding speed, whereas that of a-CNx/SiC tribo-pair decreased with sliding speed. The specific wear rates (ws) of ball and disk for a-CNx/SiC tribo-couples were considerably reduced by a factor up to 10 in the comparison to those of SiC/SiC systems. The observations of wear scars showed that the wear mechanism of CNx coating was micro-fracture of irregularities on the film surface for build-up of tribolayer, while that of SiC/SiC system was dominated by mechanical wear.

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