Determination of Three-Dimensional Body Forms from Given Pressure Distribution Over Their Surfaces

1996 ◽  
Vol 40 (01) ◽  
pp. 22-27
Author(s):  
V. M. Pashin ◽  
V. A. Bushkovsky ◽  
E. L. Amromin
Keyword(s):  
Pressure Distribution ◽  
Three Dimensional ◽  
Bodies Of Revolution ◽  
Design Constraints ◽  
Pressure Distributions ◽  
Axisymmetric Bodies

A method for solving inverse three-dimensional problems in hydromechanics is proposed which makes it possible to fit desired pressure distributions within design constraints immediately in the course of calculations. Examples of the method of application are given for bodies of revolution in flows at nonzero drift angles. These flows are not axisymmetric. Bodies of revolution in them are very handy examples of demonstrations of the method, and these examples have many technical applications.

A Comparison of Theoretical and Experimental Pressure Distributions on Bodies of Revolution

1980 ◽  
Vol 24 (01) ◽  
pp. 60-65
Author(s):  
A. J. Smits ◽  
S. P. Law ◽  
P. N. Joubert
Keyword(s):  
Calculation Method ◽  
The Body ◽  
Viscous Effects ◽  
Bodies Of Revolution ◽  
Pressure Distributions ◽  
Wide Range ◽  
The Right ◽  
Right Order ◽  
Axisymmetric Bodies ◽  
Experimental Pressure

A wide range of experimental pressure distributions along axisymmetric bodies was compared with the results of Landweber's potential flow calculation method. Apart from certain viscous effects, some discrepancies were found, and it is shown that blockage corrections are of the right order to account for these discrepancies. The calculation method was also used to show that the pressure distribution over the nose of the body is largely independent of the tail shape, and vice versa.

A Numerical Elastoplastic Model for Rough Contact

1995 ◽  
Vol 117 (3) ◽  
pp. 422-429 ◽  
Author(s):  
C. Mayeur ◽  
P. Sainsot ◽  
L. Flamand
Keyword(s):  
Yield Criterion ◽  
Kinematic Hardening ◽  
Three Dimensional ◽  
Surface Shape ◽  
Real Surface ◽  
Pressure Distributions ◽  
Surface Displacements ◽  
Elastic Shakedown ◽  
Von Mises

Pressure distributions due to surface roughness in contact induce high stresses just beneath the surface. These stresses can bring on crack initiation and micro-pitting. A purely elastic contact model to account for these effects is restrictive because stress fields often exceed the yield strength of the material. Plastic flow occurs and modifies the surface shape and material properties (work hardening). This paper presents a numerical model for elastoplastic rough contact. It allows the determination of real pressures and permanent surface displacements (flattening of asperities) as well as residual stress and plastic strains useful in fatigue analysis). The material is assumed to obey the Von-Mises yield criterion with linear kinematic hardening. Real surface profiles obtained from a measurement can be considered. In addition, simplified methods have been used to treat cyclic loading. Thus the ability of a rough surface to reach an elastic shakedown state can be investigated, even for a three-dimensional contact found, for instance, in roller bearings.

Report 16: Photoelastic Analysis of Journal Bearings: Preliminary Investigations

1967 ◽  
Vol 182 (7) ◽  
pp. 90-94
Author(s):  
R. W. T. Preater
Keyword(s):  
Pressure Distribution ◽  
Three Dimensional ◽  
Stress Distributions ◽  
Freezing Cycle ◽  
Photoelastic Analysis ◽  
Loading Tests ◽  
Dynamic Loading Conditions ◽  
Time Of Presentation ◽  
The City

Determination of the stress distributions associated with composite shell bearings under static and dynamic loading conditions is discussed briefly. Experimental work recently started at The City University, using the three-dimensional ‘frozen stress’ photoelastic technique, is described. Preliminary static loading tests have been carried out over a range of low temperatures, prior to stress freezing, on a simple bearing and shaft assembly made in Araldite. One successful stress freezing cycle has been completed and the pressure distribution at the point of stress freezing is shown compared with low temperature distributions for a constant duty parameter. It is anticipated that, at the time of presentation of this report, the stress distribution at the lubrication surface, as determined by analysis, may be shown compared with the recorded pressure distribution.

Instability and Transition in a Separation Bubble Under a Three-Dimensional Freestream Pressure Distribution

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
M. I. Yaras
Keyword(s):  
Boundary Layer ◽  
Pressure Distribution ◽  
Pressure Field ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Test Surface ◽  
Two Dimensional ◽  
Transition Processes ◽  
Pressure Distributions ◽  
Separation Bubbles

This paper presents measurements of the instability and transition processes in separation bubbles under a three-dimensional freestream pressure distribution. The measurements are performed on a flat plate on which a pressure distribution is imposed by a contoured surface facing the flat test-surface. The three-dimensional pressure distribution that is established on the test-surface approximates the pressure distributions encountered on swept blades. This type of pressure field produces crossflows in the laminar boundary layer upstream of the separation and within the separation bubble. The effects of these crossflows on the instability of the upstream boundary layer and on the instability, transition onset, and transition rate within the separated shear-layer are examined. The measurements are performed at two flow-Reynolds numbers and relatively low level of freestream turbulence. The results of this experimental study show that the three-dimensional freestream pressure field and the corresponding redistribution of the freestream flow can cause significant spanwise variation in the separation-bubble structure. It is demonstrated that the instability and transition processes in the modified separation bubble develop on the basis of the same fundamentals as in two-dimensional separation bubbles and can be predicted with the same level of accuracy using models that have been developed for two-dimensional separation bubbles.

Instability and Transition in a Separation Bubble Under a Three-Dimensional Freestream Pressure Distribution

2008 ◽  
Author(s):  
M. I. Yaras
Keyword(s):  
Boundary Layer ◽  
Pressure Distribution ◽  
Pressure Field ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Test Surface ◽  
Two Dimensional ◽  
Transition Processes ◽  
Pressure Distributions ◽  
Separation Bubbles

This paper presents measurements of the instability and transition processes in separation bubbles under a three-dimensional freestream pressure distribution. Measurements are performed on a flat plate upon which a pressure distribution is imposed by a contoured surface facing the flat test surface. The three-dimensional pressure distribution that is established on the test surface approximates the pressure distributions encountered on swept blades. This type of pressure field produces crossflows in the laminar boundary layer upstream of separation and within the separation bubble. The effects of these crossflows on the instability of the upstream boundary layer and on the instability, transition onset and transition rate within the separated shear layer are examined. The measurements are performed at two flow Reynolds numbers and relatively low level of freestream turbulence. The results of this experimental study show that the three-dimensional freestream pressure field and the corresponding redistribution of the freestream flow cause significant spanwise variation of the separation-bubble structure. It is demonstrated that the instability and transition processes in the modified separation bubble develop on the basis of the same fundamentals as in two-dimensional separation bubbles, and can be predicted with the same level of accuracy using models that have been developed for two-dimensional separation bubbles.

Stress Analysis of the Multi-Layered System of a Truck Tire

2002 ◽  
Vol 30 (4) ◽  
pp. 240-264 ◽  
Author(s):  
X. Zhang ◽  
S. Rakheja ◽  
R. Ganesan
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Normal Load ◽  
Three Dimensional ◽  
Stress Fields ◽  
Layered System ◽  
Contact Pressure Distribution ◽  
Pressure Distributions ◽  
Truck Tire ◽  
Stress And Deformation

Abstract In this paper, a nonlinear finite element tire model is developed as an effective fast modeling approach to analyze the stress fields within a loaded tire structure, with the contact patch geometry and contact pressure distribution in the tire-road interface as functions of the normal load and the inflation pressure. The model considers the geometry and orientations of the cords in individual layers and the stacking sequence of different layers in the multi-layered system to predict the interply interactions in the belts and carcass layers. The study incorporates nearly incompressible property of the tread rubber block and anisotropic material properties of the layers. The analysis is performed using ANSYS software, and the results are presented to describe the influence of the normal load on the various stress fields and contact pressure distributions. The computed footprint geometry is qualitatively compared with the measured data to examine the validity of the model. It is concluded that the proposed model can provide reliable predictions about the three-dimensional stress and deformation fields in the multi-layered system and the contact pressure distribution in the tire-road interface.

A Surface Panel Method for Design of Hydrofoils

1994 ◽  
Vol 38 (03) ◽  
pp. 175-181
Author(s):  
Chang-Sup Lee ◽  
Young-Gi Kim ◽  
Jung-Chun Suh
Keyword(s):  
Integral Equation ◽  
Boundary Value Problem ◽  
Pressure Distribution ◽  
Three Dimensional ◽  
Panel Method ◽  
Simultaneous Equations ◽  
Surface Panel Method ◽  
Total Potential ◽  
Pressure Distributions

A surface panel method treating a boundary-value problem of the Dirichlet type is presented to design a hydrofoil corresponding to a prescribed pressure distribution. An integral equation is derived from Green's theorem, giving a relation between the total potential of known strength and the unknown local flux. Upon discretization, a system of linear simultaneous equations is formed and solved for an assumed geometry. The pseudo local flux, present due to the incorrect positioning of the assumed geometry, plays a role of the geometry corrector, with which the new geometry is computed for the next iteration. Sample designs for a series of pressure distributions of interest are performed to demonstrate the fast convergence, effectiveness and robustness of the procedure. The method is shown equally applicable to designing two- and three-dimensional hydrofoil geometry.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

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