Search

Reduction of trim loss is essential to raise lift-to-drag ratio and enhance flight control performance for flying wing configuration,so the influence on aerodynamic optimization of transonic flying wing configuration is studied based on discrete adjoint method,and three conditions of 10%,0%,-10%stability margin are considered in the optimization process,respectively.The free-form deformation(FFD)method is used to achieve the parametrization of surface unstructured grid,the control point of FFD is selected to serve as design variable,and the flowfield and adjoint equation is solved to obtain the sensitivity information.The sequential quadratic programming(SQP)algorithm is utilized to obtain the gradient of control points,and the final configuration is obtained by multiple iteration.The results show that the discrete adjoint optimization method can evidently improve the maximum lift-to-drag ratio under the constraint of geometric thickness and moment trim,and the increment is exceeded by 8%at these three conditions.The increment of cruise lift-to-drag ratio appears to reduce with the increase of stability margin while lift coefficient is fixed,the lift-to-drag ratio can increase 5.08%when the stability margin is 10%.

Overmoded relativistic backward wave oscillators (RBWOs) are usually difficult to achieve pure mode ouHowever, until now, radiation equipments for high power microwave (HPM) devices are only matched to a single operating mode. So it is unsuitable to utilize the ready-made HPM antenna to radiate mixed \textTM0{n} modes with high radiation efficiency, and thus practical applications of the overmoded RBWO device becomes limited. For converting these hybrid \textTM0{n} modes into a pure one (e.g., \textTM01 or TEM mode), diagnostics of the overmoded RBWO's output mode is required. In this letter, a practical measurement technique without requiring high precision calibrations of the power distribution and relative phases between the \textTM0{n} modes propagating in overmoded waveguide is described. This method is validated by measuring the output modes of a specially designed \textTM01\!-\!\textTM0{n} mixed modes exciter. [ABSTRACT FROM PUBLISHER]

Plasma is a non-ignorable factor in a high power generator. In this paper, plasma bombardments in the diode region are found in experiment on a Ka-band transit-time oscillator. Microcosmic and energy dispersive analysis has been done first on the plasma spots. Based on the Carbon contents in different areas of the diode, a physical model describing the progress of the plasma from appearance to expansion is built. Subsequently, simulations on the plasma expansion have been done with particle-in-cell code calculation. The result agrees well with the model proposed above. Finally, a special structure is adopted in the improved Ka-band coaxial TTO to suppress or even avoid the plasma Bombardment. The study is of significance to generators for long-pulsed and repetition operation. [ABSTRACT FROM AUTHOR]