Bayesian uncertainty analysis of SA turbulence model for supersonic jet interaction simulations

The Reynolds Averaged Navier-Stokes(RANS) models are still the workhorse in current engineering applications due to its high efficiency and robustness. However, the closure coefficients of RANS turbulence models are determined by model builders according to some simple fundamental flows, and the suggested values may not be applicable to complex flows, especially supersonic jet interaction flow. In this work, the Bayesian method is employed to recalibrate the closure coefficients of Spalart-Allma...     

An internal power angle control strategy for high-speed sensorless brushless DC motors

High-speed Brushless DC Motors (BLDCMs) usually adopt a sensorless control strategy and operate in three-phase six-state drive mode. However, the sampling errors of the rotor position and the driving method increase the Internal Power Angle (IPA), resulting in a decrease in the efficiency of the system. Conventional IPA reduction strategies are either sensitive to motor parameters, or ignore diode freewheeling during the commutation process, or require additional current sensors. In this paper, a new strategy to reduce the IPA is proposed. Firstly, a Zero-Crossing Point (ZCP) detection method for the back-EMF without filter is proposed to reduce the sampling errors of the rotor position. Secondly, the relationship between the non-energized terminal voltage and the ZCP of the corresponding back-EMF is analyzed. The non-energized terminal voltage that has completed the diode freewheeling is divided into two triangles by half of the bus voltage. When the IPA is suppressed, the areas of the two triangles are equal. Thirdly, an advanced angle for reducing the IPA is obtained through a PI regulator which can eliminate the deviation between the two areas. Finally, both a simulation model and an experimental circuit are built to verify the proposed control strategy.     

无强波构型理论发展现状研究

本文引入了一种由Busemann超声速双翼理论发展而来的无强激波构型,该构型可明显消弱超声速飞行时带来的波阻和声爆。文中分析了无强波构型的机理和气动特性,介绍了该构型理论研究和应用研究进展,并探讨了该构型在超声速飞行器设计应用中的关键性问题。该理论为未来低声爆超声速飞机的设计提供了一个全新的思路,是未来超声速/高超声速飞行器发展必要的技术基础。     

Adaptive cubature Kalman filter with the estimation of correlation between multiplicative noise and additive measurement noise

Mobile robots are often subject to multiplicative noise in the target tracking tasks, where the multiplicative measurement noise is correlated with additive measurement noise. In this paper,first, a correlation multiplicative measurement noise model is established. It is able to more accurately represent the measurement error caused by the distance sensor dependence state. Then, the estimated performance mismatch problem of Cubature Kalman Filter(CKF) under multiplicative noise is analyzed. An i...     

Adjoint-based robust optimization design of laminar flow wing under flight condition uncertainties

It is an inherent uncertainty problem that the application of laminar flow technology to the wing of large passenger aircraft is affected by flight conditions. In order to seek a more robust natural laminar flow control effect, it is necessary to develop an effective optimization design method. Meanwhile, attention must be given to the impact of crossflow(CF) instability brought on by the sweep angle. This paper constructs a robust optimization design framework based on discrete adjoint methods ...     

军用飞机维修大纲修订流程研究

本文首先论述了维修大纲修订的必要性和实际状况,接着介绍了B777、Y8和某型军机的维修大纲修订情况,以及波音的维修大纲修订实施程序,最后重点阐述了如何从实际情况出发,并借鉴波音的经验,建立一套适用于我国军用飞机维修大纲修订工作的实施流程,以有效地指导该项工作,提高军用飞机的可用度,降低维修成本。