Assessment on critical technologies for conceptual design of blended-wing-body civil aircraft

Civil aviation faces great challenges because of its robust projected future growth and potential adverse environmental effects. The classical Tube-And-Wing(TAW) configuration following the Cayley’s design principles has been optimized to the architecture’s limit, which can hardly satisfy the further requirements on green aviation. By past decades’ investigations the BlendedWing-Body(BWB) concept has emerged as a potential solution, which can simultaneously fulfill metrics of noise, emission and fuel burn. The purpose of the present work is to analyze the developments of critical technologies for BWB conceptual design from a historical perspective of technology progress. It was found that the high aerodynamic efficiency of BWB aircraft can be well scaled by the mean aerodynamic chord and wetted aspect ratio, and should be realized with the trade-offs among stability and control and low-speed performance. The structure concepts of non-cylinder pressurized cabin are of high risks on weight prediction and weight penalty. A static stability criterion is recommended and further clear and adequate criteria are required by the evaluations of flying and handling qualities. The difficulties of propulsion and airframe integration are analyzed. The energy to revenue work ratios of well-developed BWB configurations are compared,which are 31.5% and 40% better than that of TAW, using state-of-art engine technology and future engine technology, respectively. Finally, further study aspects are advocated.

Square cavity flow driven by two mutually facing sliding walls

We investigate the flow inside a 2D square cavity driven by the motion of two mutually facing walls independently sliding at different speeds.The exploration,which employs the lattice Boltzmann method(LBM),extends on previous studies that had the two lids moving with the exact same speed in opposite directions.Unlike there,here the flow is governed by two Reynolds numbers(Re_(T),Re_(B))associated to the velocities of the two moving walls.For convenience,we define a bulk Reynolds number Re and quantify the driving velocity asymmetry by a parameterα.Parameterαhas been defined in the rangeα∈[-π4,0]and a systematic sweep in Reynolds numbers has been undertaken to unfold the transitional dynamics path of the two-sided wall-driven cavity flow.In particular,the critical Reynolds numbers for Hopf and NeimarkSacker bifurcations have been determined as a function ofα.The eventual advent of chaotic dynamics and the symmetry properties of the intervening solutions are also analyzed and discussed.The study unfolds for the first time the full bifurcation scenario as a function of the two Reynolds numbers,and reveals the different flow topologies found along the transitional path.