A staggered scheme for nonconvex hyperbolic systems of conservation laws

Electrical Engineering, Mathematics and Computer Scienc

Full wave analysis of the influence of the jet engine air intake on the radar signature of modern fighter aircraft

Radar cross section prediction techniques are used to determine the radar signature of a military platform when the radar signature can not be determined experimentally, because the platform is not available or for reasons of time and cost. For classic jet aircraft the radar cross section for forward observation angles is dominated by the contribution of the open ended cavity formed by the jet engine air intake and compressor fan. This cavity is characterized by its large depth (L/d>3), curved centerline and nonuniform cross section, for which the scattering characteristics can not by analyzed by approximate high frequency methods. Jin et al. have published a numerical method based on a higher order finite element discretisation of the Maxwell equations, where the resulting linear system is solved by means of a frontal solution method. The method takes full advantage of the topology of the cavity scattering problem and has been successfully applied for the analysis of cavities of intermediate size. In this paper an adaptation of their algorithm is discussed that can efficiently compute the electric field scattered by very large cavities, in particular the jet engine air intake cavity for X-band radar frequencies

Segregated solution methods for compressible flow

Electrical Engineering, Mathematics and Computer Scienc

Evaluation of the interface-capturing algorithm of OpenFoam for the simulation of incompressible immiscible two-phase flow

The Mass-Conserving Level-Set method combines the efficiency of a Level-Set algorithm with the mass conserving properties of the Volume Of Fluid method. It avoids the work intensive interface construction of the former method and imposes a mass-conserving correction to the distance function of the latter. The interface capturing algorithm implemented in OpenFOAM uses a compressive convection scheme for the evolution of the VOF colour function, as opposed to an interface reconstruction algorithm. Therefore, it can be assumed to match the efficiency of the MCLS method. Further analysis of the accuracy of the algorithm is required to make a fair comparison. In this report the accuracy will be evaluated for the simulation of incompressible, immiscible two-phase flow in two and three spatial dimensions. Three representative test cases are considered: The advection of a spherical bubble for an imposed, constant velocity field (2D), a rising (buoyant) bubble in a quiescent fluid (2D and 3D) and a stationary bubble in a stationary fluid (2D and 3D). The computed results are compared with results obtained with the Mass-Conserving Level-Set method of [8], benchmark results of [5] and other references. The compressive scheme accurately conserves mass, but shows large spurious currents for the test cases with surface tension. Additionally, the error in the predicted rise velocity of the gas bubble is large in comparison with that of the MCLS method.Electrical Engineering, Mathematics and Computer Scienc