Search

When there exists overturning wave crest on the sea surface, the sophisticated coupling effect between the overturning wave crest and sea surface may give rise to sea spikes. As sea spikes will cause the increase of radar false probability, the investigation of electromagnetic (EM) scattering characteristics of threedimensional (3-D) local sea surface with time-varying overturning wave crest is meaningful for the remote sensing. In this paper, the influence of wind speed and time factor is taken into consideration when constructing the overturning wave crest, which is ignored in the traditional Longtank model. In addition, the Integral Equation Method (IEM) is adopted to calculate the EM scattering from a 3-D local sea surface with time-varying overturning wave crest for different incident angles and wind speeds. The simulation results are meaningful for analyzing the physical mechanism of sea spikes. [ABSTRACT FROM AUTHOR]

Vehicles flying at high velocity within the atmosphere become enveloped in a time-varying plasma sheath. This paper adopts a more efficient and stable modified advection upstream splitting method by introducing the pressure-based weight functions (AUSMPW+) to solve the Navier-Stokes equations, calculating aircraft periphery flow field based on Dunn-Kang 11 -component air chemical model and obtaining the flow field parameter of different flight speeds. According to the simulation flow field parameter, it applies physical optics method to calculate electromagnetic scattering section of blunt-nosed cone aircraft. Moreover, according to plasma critical frequency of different wave bands, it puts forward a blackout prediction model. The calculation result indicates that when the aircraft has a high-speed flight, with the rising speed of the aircraft, electron density of plasma sheath will increase continuously. Influenced by it, aircraft radar cross section shows a decreasing trend. When electron density inside plasma sheath around aircraft exceeds critical plasma densities of the corresponding communication frequency, it will result in "blackout." This model pre-dicts the blackout of S, C, and X wave bands of spacecraft reentry. The result perfectly cor-responds to the experimental data. The results obtained in this paper are significant to the guidance technology and communication technique for hypersonic vehicle. [ABSTRACT FROM AUTHOR]

An efficient geometric modeling method has been proposed for investigation on the properties of the electromagnetic (EM) scattering from two-dimensional (2D) rough surface. In this approach, the plane surface related to the rough surface is firstly modeled by the non-uniform rational B-spline (NURBS) surface through the computer aided geometric design (CAGD). Then the rough surface is reconstructed with the parameters of the plane surface and its height function. The method of moments (MOM) is adopted to solve the electric field integral equation (EFIE) with the rooftop basis function and line matching technique. Moreover, based on the message passing interface (MPI) platform, the parallel MOM algorithm is presented to reduce the simulation time of a single-processor. The conjugate gradient method (CGM) is developed to solve the matrix equation and parallelized with the impedance matrix divided to different processors by lines according to the property of MPI. The validity of this approach is shown by comparing to the flat triangular patch. Some numerical simulations are also exhibited and analyzed. [ABSTRACT FROM AUTHOR]