Method of Tapered Resistive Sheet Loading for Controlling Edge Scattering

The dynamic evolution and the saturated state of a long sheet pinch subject to growth of resistive tearing modes was investigated by numerical solution of the 2D MHD equations. Both the compressible and the incompressible equations were used, and the difference is found to be negligible. The necessity of considering a resistive equilibrium is stressed. The paper concentrates on a static equilibrium maintained by an external electric field and requiring a special distribution of the resistivity η. In addition the dynamics of the resistivity plays an important part. Assuming η to be time independent, the sheet pinch develops a number of soliton-like magnetic islands, which coalesce. The final state consists of a single soliton, while the generation of further sol-itons is inhibited by a strong shear flow allong the current sheet. When allowance is made for parallel diffusion of the resistivity such that η is essentially a flux function, the final state is quite different. Here the longest wavelength dominates, leading to a single, large island and completely destroying the original sheet pinch

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A Fast Circuit Model Description of the Shielding Effectiveness of a Box With Imperfect Gaskets or Apertures Covered by Thin Resistive Sheet Coatings

IEEE Transactions on Electromagnetic Compatibility ◽

10.1109/temc.2006.870703 ◽

2006 ◽

Vol 48 (1) ◽

pp. 134-144 ◽

Cited By ~ 19

Author(s):

T. Konefal ◽

J.F. Dawson ◽

A.C. Marvin ◽

M.P. Robinson ◽

S.J. Porter

Keyword(s):

Circuit Model ◽

Model Description ◽

Shielding Effectiveness ◽

Fast Circuit ◽

Resistive Sheet

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On the noise prediction for serrated leading edges

Journal of Fluid Mechanics ◽

10.1017/jfm.2017.429 ◽

2017 ◽

Vol 826 ◽

pp. 205-234 ◽

Cited By ~ 39

Author(s):

B. Lyu ◽

M. Azarpeyvand

Keyword(s):

Leading Edge ◽

Directivity Pattern ◽

Destructive Interference ◽

Far Field ◽

Low Frequencies ◽

Power Spectral ◽

Edge Scattering ◽

Field Noise ◽

Sound Reduction ◽

Dipolar Pattern

An analytical model is developed for the prediction of noise radiated by an aerofoil with leading-edge serration in a subsonic turbulent stream. The model makes use of Fourier expansion and Schwarzschild techniques in order to solve a set of coupled differential equations iteratively and express the far-field sound power spectral density in terms of the statistics of incoming turbulent upwash velocity. The model has shown that the primary noise-reduction mechanism is due to the destructive interference of the scattered pressure induced by the leading-edge serrations. It has also shown that in order to achieve significant sound reduction, the serration must satisfy two geometrical criteria related to the serration sharpness and hydrodynamic properties of the turbulence. A parametric study has been carried out and it is shown that serrations can reduce the overall sound pressure level at most radiation angles, particularly at small aft angles. The sound directivity results have also shown that the use of leading-edge serration does not significantly change the dipolar pattern of the far-field noise at low frequencies, but it changes the cardioid directivity pattern associated with radiation from straight-edge scattering at high frequencies to a tilted dipolar pattern.

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