scholarly journals Sensitivity analysis of fracture scattering

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. T1-T10 ◽  
Author(s):  
Xinding Fang ◽  
Michael Fehler ◽  
Tianrun Chen ◽  
Daniel Burns ◽  
Zhenya Zhu
Keyword(s):  
Surface Effect ◽  
Scattering Amplitude ◽  
Incident Angle ◽  
Elastic Response ◽  
Single Fracture ◽  
Field Observations ◽  
Slip Boundary ◽  
Explosive Source ◽  
Fracture Height ◽  
2D And 3D

We use 2D and 3D finite-difference modeling to numerically calculate the seismic response of a single finite fracture with a linear-slip boundary in a homogeneous elastic medium. We use a point explosive source and ignore the free surface effect, so the fracture scattered wavefield contains two parts: P-to-P scattering and P-to-S scattering. The elastic response of the fracture is described by the fracture compliance. We vary the incident angle and fracture compliance within a range considered appropriate for field observations and investigate the P-to-P and P-to-S scattering patterns of a single fracture. P-to-P and P-to-S fracture scattering patterns are sensitive to the ratio of normal to tangential fracture compliance and incident angle, whereas the scattering amplitude is proportional to the compliance, which agrees with the Born scattering analysis. We find that, for a vertical fracture, if the source is located at the surface, most of the energy scattered by the fracture propagates downwards. We also study the effect of fracture height on the scattering pattern and scattering amplitude.

Numerical and Experimental Study of Gas Flows in 2D and 3D Microchannels

2007 ◽  
Author(s):  
Xiaohui Guo ◽  
Chihyung Huang ◽  
Alina A. Alexeenko ◽  
John P. Sullivan
Keyword(s):  
Stokes Equations ◽  
Rectangular Cross Section ◽  
Air Flow ◽  
Slip Flow ◽  
Temperature Drop ◽  
Apparent Temperature ◽  
Gas Flows ◽  
Infinite Length ◽  
Slip Boundary ◽  
2D And 3D

In the experiments conducted at Purdue, the air flow in rectangular cross-section microchannels was investigated using the pressure sensitive paints. The high resolution pressure measurements were obtained for inlet-to-outlet pressure ratios from 1.76 to 20 with the outlet Knudsen numbers in the range from 0.002 to 0.06 based on hydraulic diameter of 157.9 micron and the length-to-height ratio of about 50. In the slip flow regime, air flow was simulated by the 2D and 3D Navier-Stokes equations with no-slip and slip boundary conditions. For various pressure ratios, the entrance flow development, compressibility and rarefaction effects were observed in both experiments and numerical simulations. It was found that accurate modeling of gas flows infinite-length channels requires that inlet and outlet reservoirs to be included in computations. Effects of entrance geometry on the friction factor were studied for 3D cases. In both experiments and numerical modelings, significant pressure drop was found starting at the inlet chamber. The numerical modeling also predicted an apparent temperature drop especially at the channel exit.

scholarly journals Scattering amplitude of a single fracture under uniaxial stress

2014 ◽  
Vol 197 (2) ◽  
pp. 875-881 ◽  
Author(s):  
T.E. Blum ◽  
K. van Wijk ◽  
R. Snieder
Keyword(s):  
Scattering Amplitude ◽  
Uniaxial Stress ◽  
Single Fracture

scholarly journals Quantitative comparison of 2D and 3D shock control bumps for drag reduction on transonic wings

2018 ◽  
Vol 233 (7) ◽  
pp. 2344-2359
Author(s):  
Feng Deng ◽  
Ning Qin
Keyword(s):  
Aspect Ratio ◽  
Incident Angle ◽  
Design Parameters ◽  
Comparative Performance ◽  
Cross Sectional ◽  
Shock Control ◽  
Design Variables ◽  
Natural Laminar Flow ◽  
Area Rule ◽  
2D And 3D

In this paper, the design spaces of the 2D and 3D shock control bumps on an infinite unswept natural laminar flow wing are investigated by adopting an optimization enhanced parametric study method. The design space spanned by the design variables are explored through a series of design optimization and their landscapes around the optima are revealed. The effects of the bump spacing, bump length, and Mach number are investigated respectively around the optima. The maximum cross-sectional area, bump incident angle, and aspect ratio are found to be important design parameters. The associated flow physics is discussed in relation to these parameters. The comparative performance of the 2D and 3D bumps are explained in the context of the transonic area rule. Two types of flow separation are identified by varying the bump aspect ratio at off-design conditions. It is concluded that the 2D and 3D shock control bumps can have nearly the same performances at optimal designs with similar cross-sectional areas. Some practical design principles and guidelines are suggested.

Flow and tracer transport in a single fracture: A stochastic model and its relation to some field observations

1988 ◽  
Vol 24 (12) ◽  
pp. 2033-2048 ◽  
Author(s):  
L. Moreno ◽  
Y. W. Tsang ◽  
C. F. Tsang ◽  
F. V. Hale ◽  
I. Neretnieks
Keyword(s):  
Stochastic Model ◽  
Single Fracture ◽  
Field Observations ◽  
Tracer Transport

scholarly journals Prediction of Mean Responses of RC Bridges Considering the Incident Angle of Ground Motions and Displacement Directions

2021 ◽  
Vol 11 (6) ◽  
pp. 2462
Author(s):  
Payam Tehrani ◽  
Denis Mitchell
Keyword(s):  
Incident Angle ◽  
Combination Rules ◽  
Maximum Displacement ◽  
Seismic Demands ◽  
Averaging Methods ◽  
Displacement Direction ◽  
The Mean ◽  
Ground Motion Records ◽  
Directivity Effects ◽  
2D And 3D

Inelastic dynamic analyses were carried out using 3D and 2D models to predict the mean seismic response of four-span reinforced concrete (RC) bridges considering directionality effects. Two averaging methods, including an advanced method considering displacement direction, were used for the prediction of the mean responses to account for different incident angles of ground motion records. A method was developed to predict the variability of the mean displacement predictions due to variability in the incident angles of the records for different averaging methods. When the concepts of averaging in different directions were used, significantly different predictions were obtained for the directionality effects. The accuracy of the results obtained using 2D and 3D analyses with and without the application of the combination rules for the prediction of the mean seismic demands considering the incident angle of the records was investigated. The predictions from different methods to account for the records incident angles were evaluated probabilistically. Recommendations were made for the use of the combination rules to account for the directivity effects of the records and to predict the actual maximum displacement, referred to as the maximum radial displacement.

scholarly journals WAVE FIELD GENERATED BY FINITE-SPAN HYDROFOILS OPERATING BENEATH A FREE SURFACE

Brodogradnja ◽  
2021 ◽  
Vol 72 (1) ◽  
pp. 145-167
Author(s):  
Yavuz Hakan Ozdemir ◽  
◽  
Taner Cosgun ◽  
Baris Barlas ◽  
◽  
...  
Keyword(s):  
Free Surface ◽  
Aspect Ratio ◽  
Wave Field ◽  
Surface Effect ◽  
Hydrodynamic Performance ◽  
Spanwise Direction ◽  
Two Dimensional ◽  
Aspect Ratios ◽  
Wide Range ◽  
2D And 3D

The present paper focuses on the numerical investigation of the flow around the fully submerged 2D and 3D hydrofoils operating close to a free surface. Iterative boundary element method is implemented to predict the flow field. This study aims to investigate the aspect ratio effect on the free surface interactions and hydrodynamic performance of the hydrofoils under a free surface by using potential flow theory. Three different submergence depths and aspect ratios are studied in the wide range of Froude Numbers. In 3D cases, spanwise width of the numerical wave tank model is selected both equal and wider to the foil span, to observe the sidewall effects. Wave field seems to be two dimensional at low Froude numbers. On the other hand, signs of three dimensionalities are observed on the free surface structure for higher Fn, even the predicted wave elevations are very close to 2D calculations in the midsection. Increment in the Fn give a rise to the amplitude of the generated waves first, however a further increase in Fn has a lowering effect with the beginning of waves spill in the spanwise direction in the form of Kelvin waves. Free surface proximity and resultant wave field are also seeming to be linked with the lift force on the hydrofoil. As aspect ratio of the foil increase, 3D lift values are getting closer to those of 2D calculations. However, it is seen that, 3D BEM predictions of a hydrofoil under free surface effect cannot be considered two-dimensional even the aspect ratio is equal to 8.

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