Design and analysis of a ducted fan UAV

The ducted fan unmanned aerial vehicle (UAV) can operate in vertical flight and horizontal flight. A new tilt-body ducted fan UAV with wings, which is capable of high-speed forward flight in wing-borne mode, is designed. Two fixed wings can provide sufficient lift of the ducted fan UAV in the high-speed wing-borne flight. The fixed geometry duct design reflects a compromise between low and high speed performance requirements of it. Computational fluid dynamics (CFD) and wind tunnel testing are used to study its aerodynamic characteristics in various modes. Momentum source items are utilized to replace two counter-rotating propellers in the numerical simulation. The results illustrate that the ducted fan MAV designed can hover, take off and land vertically. Furthermore, it has the ability to fly slowly in helicopter mode and fly rapidly in wing-borne mode and has excellent aerodynamic characteristics throughout the whole flight envelope

Computational study on aerodynamic characteristics of a flying wing MAV

In this paper an effective method is developed to study aerodynamic characteristics of a flying wing micro air vehicle (MAV). The method is based on momentum source method (MSM), low Mach number preconditioning and lower-upper symmetric Gauss-Seidel (LU-SGS) implicit dual time-stepping algorithm on hybrid dynamic meshes. The S-A turbulence model is also applied to capture flow separation. Momentum source items are utilized to replace the propeller in the numerical simulation by simplifying the unsteady flow into a steady one. Compared with wind tunnel experimental results, the computed results indicate that the method developed is capable of dealing with steady and unsteady aerodynamic characteristics of flying wing MAV

Aerodynamic characteristics of multiple flapping wing configurations

Natural flyers and man-made MAVs generally use multiple flapping wing configurations. To understand the aerodynamic performance, three different flapping configurations: single wing, tandem wings, and biplane wings are numerically simulated by a URANS solver coupled with an overset grid method. Moreover, effect of kinematics including oscillating frequency, angle of attack and wing to tail distance are detailed investigated. Results show that the wing-tail interaction significantly benefits the thrust generation when the wings are tandem arranged. Additionally, the tandem arrangement is the most efficiency configuration when applied with high frequencies. Biplane wings model has the most inefficiency propulsive performance, nevertheless it can provide an extensive aerodynamic force. With the increasing AOA, biplane has the largest critical angle from thrust to drag. Wing-tail interaction becomes weaker when the tail is mounted further from the flapping wings. The present of the tail in tandem model bring more benefits compared with the tail in biplane model. The tail in biplane model is only functional for flight control when applied with a non-zero angle of attack

A stream processing framework based on linked data for information collaborating of regional energy networks

© 2005-2012 IEEE. Coordinating of energy networks to form a city-level multidimensional integrated energy system becomes a new trend in Energy Internet (EI). The collaborating in the information layer is a core issue to achieve smart integration. However, the heterogeneity of multiagent data, the volatility of components, and the real-time analysis requirement in EI bring significant challenges. To solve these problems, in this article we propose a stream processing framework based on linked data for information collaboration among multiple energy networks. The framework provides a universal data representation based on linked data and semantic relation discovery approach to model and semantically fuse heterogeneous data. Semantics-based information transmission contracts and channels are automatically generated to adapt to structural changes in EI. A multimodel-based dynamic adjusting stream processing is implemented using data semantics. A real-world case study is implemented to demonstrate the adaptability, feasibility, and flexibility of the proposed framework

Large Variation of Mercury Isotope Composition During a Single Precipitation Event at Lhasa City, Tibetan Plateau, China

AbstractThis study examined for the first time the Hg isotope composition in rain samples from a single precipitation event at Lhasa City (China) on the Tibetan Plateau, the “world's third pole”. Large variations of both mass-dependent fractionation (MDF, δ202Hg from -0.80‰ to -0.42‰) and mass-independent fractionation (MIF, Δ199Hg from 0.38‰ to 0.76‰) were observed, with the latter increasing with time. Our results demonstrated that the large variation of Hg isotope ratios likely resulted from mixing of locally emitted Hg and long-term transported Hg, which were characterized by different Hg isotope signatures and mainly leached by below-cloud scavenging and in-cloud scavenging processes, respectively. Our findings demonstrated that Hg isotopes are a powerful tool for investigating the dynamics of precipitation events and emphasized the importance of systematic monitoring studies of the chemical and isotope variability of Hg and other elements during rainfall events