Multiple-Scattering Resonances Between Parallel Conducting Cylinders

1973 ◽  
Vol 51 (23) ◽  
pp. 2415-2427 ◽  
Author(s):  
B. A. Howarth
Keyword(s):  
Multiple Scattering ◽  
Cross Section ◽  
Near Field ◽  
Experimental Results ◽  
Resonance Phenomenon ◽  
Circular Cylinders ◽  
Exact Formulation ◽  
Null Pair ◽  
Conducting Cylinders ◽  
Characteristic Maximum

The results of numerical computations on the scattering of TM waves by two and three parallel conducting cylinders are described. Measurements of the diffracted field behind two 1.0λ, diameter conducting circular cylinders are compared with the predictions of approximate and exact formulations of the multiple scattering equations obtained through the multipole induction formalism. A feature of the experimental results is the occurrence of a null pair in the near field behind the array. These field singularities are also predicted by the exact formulation and are apparently a manifestation of multiple-scattering resonance. Polar diagrams of the currents induced on the surfaces of the cylindrical scatterers are presented for several sets of parameters. These diagrams show the occurrence of a resonant multiple-scattering phenomenon at critical values of cylinder separation under broadside illumination of the array. Calculations also indicate that with this illumination the forward scattering cross section of a two-cylinder array should display a characteristic maximum at a multiple-scattering resonance. Analogous resonant phenomena for the case of end-on illumination were not obtained and an explanation for this is proposed. A suggestion for the application of this resonance phenomenon is incidentally advanced, and it is also shown that the multipole induction formalism may be extended to scattering by noncircular boundaries.

The influence of the nuclear and atomic form factors on the muon bremsstrahlung cross section

1968 ◽  
Vol 46 (10) ◽  
pp. S377-S380 ◽  
Author(s):  
A. A. Petrukhin ◽  
V. V. Shestakov
Keyword(s):  
Form Factor ◽  
Cross Section ◽  
Born Approximation ◽  
Form Factors ◽  
Experimental Results ◽  
Simple Analytical Expression ◽  
Nuclear Form Factor ◽  
The Cross ◽  
Atomic Electrons ◽  
Bremsstrahlung Process

The cross section for the muon bremsstrahlung process is calculated as a function of the nuclear form factor in the Born approximation following the Bethe and Heitler theory. The influence of the nuclear form factor is greater than that taken by Christy and Kusaka. The simple analytical expression for the effect of the screening of the atomic electrons is found. The influence of a decrease in the cross section upon the interpretation of some experimental results is estimated.

scholarly journals Buoyancy Effect on the Flow Pattern and the Thermal Performance of an Array of Circular Cylinders

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Francesco Fornarelli ◽  
Antonio Lippolis ◽  
Paolo Oresta
Keyword(s):  
Nusselt Number ◽  
Flow Pattern ◽  
Richardson Number ◽  
Near Field ◽  
Circular Cylinders ◽  
Momentum Exchange ◽  
Force Coefficients ◽  
The Earth ◽  
Spacing Ratio ◽  
Oscillatory Character

In this paper, we found, by means of numerical simulations, a transition in the oscillatory character of the flow field for a particular combination of buoyancy and spacing in an array of six circular cylinders at a Reynolds number of 100 and Prandtl number of 0.7. The cylinders are isothermal and they are aligned with the earth acceleration (g). According to the array orientation, an aiding or an opposing buoyancy is considered. The effect of natural convection with respect to the forced convection is modulated with the Richardson number, Ri, ranging between −1 and 1. Two values of center-to-center spacing (s = 3.6d–4d) are considered. The effects of buoyancy and spacing on the flow pattern in the near and far field are described. Several transitions in the flow patterns are found, and a parametric analysis of the dependence of the force coefficients and Nusselt number with respect to the Richardson number is reported. For Ri=−1, the change of spacing ratio from 3.6 to 4 induces a transition in the standard deviation of the force coefficients and heat flux. In fact, the transition occurs due to rearrangement of the near-field flow in a more ordered wake pattern. Therefore, attention is focused on the influence of geometrical and buoyancy parameters on the heat and momentum exchange and their fluctuations. The available heat exchange models for cylinders array provide a not accurate prediction of the Nusselt number in the cases here studied.

Discussion on Venkat & Spaulding: “Numerical Simulation of Nonlinear Free-Surface Flows Generated by a Heaving Body of Arbitrary Cross Section”

1991 ◽  
Vol 35 (03) ◽  
pp. 250-253
Author(s):  
Apostolos Papanikolaou
Keyword(s):  
Free Surface ◽  
Cross Section ◽  
Euler Method ◽  
Free Surface Flows ◽  
Arbitrary Cross Section ◽  
Circular Cylinders ◽  
Published Data ◽  
The Time Domain ◽  
Heave Motion ◽  
Nonlinear Free Surface

A method has been presented recently by Venkat and Spaulding to solve the nonlinear boundary-value problem of oscillating two-dimensional cylinders of arbitrary cross section on the free surface of a fluid. The method relies on a second-order finite-difference technique with a modified Euler method for the time domain and a successive over-relaxation procedure for the spatial domain. The authors compare their numerical results with those of other authors (theoretical and experimental), as they have published data for specialized forms like a wedge, circular cylinders, and ship-like sections in forced heave motion (references [4] to [7] and [22], [23] of the paper).

Near-field mean flow dynamics of a cylindrical canopy patch suspended in deep water

2018 ◽  
Vol 858 ◽  
pp. 634-655 ◽  
Author(s):  
Jian Zhou ◽  
Subhas K. Venayagamoorthy
Keyword(s):  
Deep Water ◽  
Near Field ◽  
Flow Dynamics ◽  
Flow Diversion ◽  
Circular Cylinders ◽  
Published Data ◽  
Global Flow ◽  
Mean Flow ◽  
Near Wake ◽  
Local Flow

The time-averaged flow dynamics of a suspended cylindrical canopy patch with a bulk diameter of $D$ is investigated using large-eddy simulations (LES). The patch consists of $N_{c}$ constituent solid circular cylinders of height $h$ and diameter $d$, mimicking patchy vegetation suspended in deep water ($H/h\gg 1$, where $H$ is the total flow depth). After validation against published data, LES of a uniform incident flow impinging on the canopy patch was conducted to study the effects of canopy density ($0.16\leqslant \unicode[STIX]{x1D719}=N_{c}(d/D)^{2}\leqslant 1$, by varying $N_{c}$) and bulk aspect ratio ($0.25\leqslant AR=h/D\leqslant 1$, by varying $h$) on the near-wake structure and adjustment of flow pathways. The relationships between patch geometry, local flow bleeding (three-dimensional redistribution of flow entering the patch) and global flow diversion (streamwise redistribution of upstream undisturbed flow) are identified. An increase in either $\unicode[STIX]{x1D719}$ or $AR$ decreases/increases/increases bleeding velocities through the patch surface area along the streamwise/lateral/vertical directions, respectively. However, a volumetric flux budget shows that a larger $AR$ causes a smaller proportion of the flow rate entering the patch to bleed out vertically. The global flow diversion is found to be determined by both the patch geometrical dimensions and the local bleeding which modifies the sizes of the patch-scale near wake. While loss of flow penetrating the patch increases monotonically with increasing $\unicode[STIX]{x1D719}$, its partition into flow diversion around and beneath the patch shows a non-monotonic dependence. The spatial extents of the wake, the flow-diversion dynamics and the bulk drag coefficients of the patch jointly reveal the fundamental differences of flow responses between suspended porous patches and their solid counterparts.

A Near-Field to Far-Field RCS Measurement Method for Multiple-Scattering Target

2019 ◽  
Vol 68 (10) ◽  
pp. 3733-3739 ◽  
Author(s):  
Chufeng Hu ◽  
Nanjing Li ◽  
Weijun Chen ◽  
Shuxia Guo
Keyword(s):  
Multiple Scattering ◽  
Measurement Method ◽  
Near Field ◽  
Far Field

Analytical extraction of via near-field coupling using a multiple scattering approach

2013 ◽  
Author(s):  
Sebastian Muller ◽  
Andreas Hardock ◽  
Renato Rimolo-Donadio ◽  
Heinz-D. Bruns ◽  
Christian Schuster
Keyword(s):  
Multiple Scattering ◽  
Near Field ◽  
Field Coupling

The Use of Strain Energy and Fracture Correlation to Determine Life Expectancy for Notched Components

2009 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross ◽  
M.-H. Herman Shen
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Cross Section ◽  
Strain Energy ◽  
Notch Root ◽  
Stress Gradient ◽  
Strain Curve ◽  
Experimental Results ◽  
Cyclic Process ◽  
Notched Components

An energy-based method for predicting fatigue life of half-circle notched specimens, based on the nominal applied stress amplitude, has been developed. This developed method is based on the understanding that the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where the density of each can be determined by measuring the area underneath the monotonic true stress-strain curve and measuring the sum of the area within each Hysteresis loop in the cyclic process, respectively. Using this understanding, the criterion for determining fatigue life prediction of half-circle notched components is constructed by incorporating the stress gradient effect through the notch root cross-section. Though fatigue at a notch root is a local phenomenon, evaluation of the stress gradient through the notch root cross-section is essential for incorporating this method into finite element analysis minimum potential energy process. The validation of this method was carried out by comparison with both notched and unnnotched experimental fatigue life of Aluminum 6061-T6 (Al 6061-T6) specimens under tension/compression loading at the theoretical notch fatigue stress concentration factor of 1.75. The comparison initially showed a slight deviation between prediction and experimental results. This led to the analysis of strain energy density per cycle up to failure, and an improved Hysteresis representation for the energy-based prediction analysis. With the newly developed Hysteresis representation, the energy-based prediction comparison shows encouraging agreement with unnotched experimental results and a theoretical notch stress concentration value.

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