Experimental investigations of three-dimensional effects near a crack tip using computer vision

1992 ◽  
Vol 53 (3) ◽  
pp. 201-228
Author(s):  
M. A. Sutton ◽  
J. L. Turner ◽  
Y. J. Chao ◽  
H. A. Bruck ◽  
T. L. Chae
Keyword(s):  
Computer Vision ◽  
Three Dimensional ◽  
Crack Tip ◽  
Experimental Investigations ◽  
Dimensional Effects

Spectral analysis and coherence of aerodynamic lift on rectangular cylinders in turbulent flow

2017 ◽  
Vol 830 ◽  
pp. 408-438 ◽  
Author(s):  
Shaopeng Li ◽  
Mingshui Li
Keyword(s):  
Turbulent Flow ◽  
Closed Form ◽  
Vertical Velocity ◽  
Lift Force ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Velocity Fluctuations ◽  
Dimensional Effects ◽  
Decay Parameters ◽  
Rectangular Cylinders

The goal of the present work is to derive the closed-form expressions of coherence and admittances to describe the spatial distribution of lift on rectangular cylinders in turbulent flow, which can be used to investigate the three-dimensional effects of turbulence. The coherence of the three-dimensional aerodynamic admittance (3D AAF), which takes into full account the spanwise variations in the vertical velocity fluctuations, is introduced to assess the validity of the strip assumption. A theoretical coherence model expressed in a double-exponential form is derived starting from the two-wavenumber spectral tensor of the lift on a thin aerofoil in Fourier space, providing us with explicit insight into the coherence of the lift force. Notably, it is an intrinsic property that the lift force on the structure is more strongly correlated than the oncoming flow and 3D AAF. This coherence model is extended to rectangular cylinders by the introduction of three floating parameters into the decay parameters of the 3D AAF. Based on theoretical and experimental investigations, it is shown that the three-dimensional effects of turbulence grow more prominent as the difference between the decay parameters of the 3D AAF and vertical velocity fluctuations decreases. A generalized approach for rapidly deriving the closed-form expressions of the admittances is proposed to study the unsteady behaviour of the lift force and the distortion of the free stream passing through the rectangular cylinders.

scholarly journals Experimental Investigations of Three-Dimensional Effects on Cavitating Hydrofoils

1961 ◽  
Vol 5 (03) ◽  
pp. 22-43
Author(s):  
R. W. Kermeen
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Experimental Investigations ◽  
Water Tunnel ◽  
Pitching Moment ◽  
Two Dimensional ◽  
Dimensional Effects ◽  
Aspect Ratios

An investigation in the high-speed water tunnel of the hydsrodynamic characteristics of a family of three-dimensional sharp-edged hydrofoils is described. Four rectangular plan-form, 6-deg wedge profiles with aspect ratios of 4.0, 2.0, 1.0 and 0.5 were tested over a range of cavitation numbers from noncavitating to fully cavitating flow. The effects of aspect ratio on the flow and cavity configurations and on the lift, drag and pitching moment are discussed. Where data were available the results have been compared with the two-dimensional case.

Three-Dimensional Effects Near a Crack Tip in a Ductile Three-Point Bend Specimen: Part I—A Numerical Investigation

1990 ◽  
Vol 57 (3) ◽  
pp. 607-617 ◽  
Author(s):  
R. Narasimhan ◽  
A. J. Rosakis
Keyword(s):  
Plane Strain ◽  
Plane Stress ◽  
Crack Front ◽  
Three Dimensional ◽  
Crack Tip ◽  
Upper And Lower Bounds ◽  
Thickness Variation ◽  
Bend Specimen ◽  
Dimensional Effects ◽  
Point Bend

A simultaneous numerical and experimental investigation is undertaken to assess three-dimensional effects and HRR dominance near a crack front in a ductile 3-point bend specimen. In parallel to the three-dimensional calculations, a plane-strain and a plane-stress analysis of the same in-plane specimen geometry is performed to obtain upper and lower bounds for the three-dimensional calculation. The radial, angular, and thickness variation of the stresses and displacements are studied in great detail from contained yielding to fully plastic conditions. The results indicate that the plane-strain HRR field prevails in the interior of the specimen very near the crack front even for moderate extents of yielding. On the other hand, for distances from the crack tip exceeding about half a specimen thickness, plane-stress conditions are approached. The calculations presented here model a series of laboratory experiments involving three independent experimental techniques. Details regarding the experiments and comparisons of the experimental measurements with numerical calculations and theory are emphasized in Part II of this work.

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