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Electrogenic vortex wave refer to the wave that carry orbital angular momentum (OAM) in the radio frequency (RF) domain. The OAM mode is expected to be initially explored and applied as a full novel spatial dimension resource. However, the radiation energy distribution pattern of electromagnetic vortex wave exhibits a central hollow. The energy hollow phenomenon has become one of the major drawbacks limiting the popularization of electromagnetic vortex wave. In this article, a generation scheme of convergent vortex wave is proposed and research generated by uniform circular array (UCA). Orthogonal waveforms are introduced into the antenna to change the phase relationship between the original signals so that the energy remains in the wave center region. The numerical results validate the effectiveness of the proposed scheme. The circular intensity disappears, while the spiral phase wavefront features can still be maintained.

The effects of chevrons on the performance of a supersonic vacuum ejector-diffuser system are investigated numerically and evaluated theoretically in this work. A three-dimensional geometrical domain is numerically solved using a fully implicit finite volume scheme based on the unsteady Reynolds stress model. A one-dimensional mathematical model provides a useful tool to reveal the steady flow physics inside the vacuum ejector-diffuser system. The effects of the chevron nozzle on the generation of recirculation regions and Reynolds stress behaviors are studied and compared with those of a conventional convergent nozzle. The present performance parameters obtained from the simulated results and the mathematical results are validated with existing experimental data and show good agreement. Primary results show that the duration of the transient period and the secondary chamber pressure at a dynamic equilibrium state depend strongly on the primary jet conditions, such as inlet pressure and primary nozzle shape. Complicated oscillatory flow, generated by the unsteady movement of recirculation, finally settles into a dynamic equilibrium state. As a vortex generator, the chevron demonstrated its strong entrainment capacity to accelerate the starting transient flows to a certain extent and reduce the dynamic equilibrium pressure of the secondary chamber significantly.

Computational Fluid Dynamics (CFD) simulations were completed for a series of convergent nozzles in participation of the American Institute of Aeronautics and Astronautics (AIAA) 1st Propulsion Aerodynamics Workshop. The simulations were performed using the Wind-US flow solver. Discharge and thrust coefficients were computed for four axisymmetric nozzles with nozzle pressure ratios (NPR) ranging from 1.4 to 7.0. The computed discharge coefficients showed excellent agreement with available experimental data; the computed thrust coefficients captured trends observed in the experimental data, but over-predicted the thrust coefficient by 0.25 to 1.0 percent. Sonic lines were computed for cases with NPR >= 2.0 and agreed well with experimental data for NPR >= 2.5. Simulations were also performed for a 25 deg. conic nozzle bifurcated by a flat plate at NPR = 4.0. The jet plume shock structure was compared with and without the splitter plate to the experimental data. The Wind-US simulations predicted the shock structure well, though lack of grid resolution in the plume reduced the sharpness of the shock waves. Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations and Detached Eddy Simulations (DES) were performed at NPR = 1.6 for the 25 deg conic nozzle with splitter plate. The simulations predicted vortex shedding from the trailing edge of the splitter plate. However, the vortices of URANS and DES solutions appeared to dissipate earlier than observed experimentally. It is believed that a lack of grid resolution in the region of the vortex shedding may have caused the vortices to break down too soon

Experiments by Phan & Stollery (In Proc. 14th International Symposium on Shock Tubes and Waves, pp. 519-526 (1983)) indicated the presence of a supersonic vortex ring with an embedded rearward-facing shock in the unsteady flow that follows the emergence of a normal shock from a circular tube. The vortex flow is supersonic in the sense that the on-axis flow is supersonic in the frame of reference of the vortex ring. In the present work this flow phenomenon is studied by using differential interferometry and a detailed description of the flow-starting process is given. A simplified quasi-steady calculation is performed and a comparison is made with previously measured pressures in the flow field. These results are in agreement with the physical description of the flow development.