Trim Drag Prediction for Blended-Wing-Body UAV Configuration

A rapid method of the trim drag prediction for the blended-wing-body unmanned aerial vehicle(UAV)configuration is proposed.The method consists of four steps.The first step is to parameterizedly model the blended-wing-body UAV configuration;the second is to analyze the aerodynamics of the geometric model;the third is to create aerodynamic surrogate model;and the final step is to predict the trim drag using the surrogate model.Hence,a tool for trim drag prediction is developed by integration of the four steps.The impacts of the allocation of control surfaces,position of gravity center and planform parameters on the trim drag are investigated by using the tool.Results show that using the control surface in outer wing for trim has an advantage of lower trim drag,and the position of gravity center has a primary impact on the trim drag.Moreover,the planform has secondary impacts on the trim drag.

TOPOLOGY OF CONFIGURATION SPACE FOR A THREE-BODY PROBLEM

考虑了限制在球面Ｓ２上运动的三个质点的力学系统，该系统的构型空间是Ｓ２上的一个纤维丛。本文证明了这个丛的第１陈省身示性类等于－２ｃ１（γ），其中γ是复射影空间ＣＰ１＝Ｓ２上的典范线丛。这个结果蕴涵该构型空间是Ｓ２上的非平凡丛。由此又算出了它的上同调群与同伦群。此外还讨论了上述拓扑性质对于诸如平衡位置的数目，周期轨道及约化相空间等涉及系统大范围性状的影响。

Numerical Analysis of Aerodynamic Characteristics of the HALE Diamond Joined-Wing Configuration UAV

The investigation on the aerodynamic characteristics of the high-attitude long-endurance (HALE) Diamond Joined-Wing configuration unmanned aerial vehicle ( UAV) was carried out by the theoretical analysis method and numerical simulation. Research indicates that as the wing of the UAV is composed of the front wing and the after wing, the after wing has the ability to transmit the front wing's boundary layer to the after wing root which can inhibit the front wing's flow separation. Although the front wing was affected by the retardation of the after wing, the aerodynamic performance of the front wing was better than that of alone front wing in most cases. The after wing was also affected by the wake and downwash of the front wing, and its aerodynamic performance was greatly decreased. The characteristic curve of the pitching moment of the UAV had nonlinear characteristics. The flow field structure of the after wing changed by the front wing wake direct sweep and flow separation at the after wing root were the main reasons that non-linear ′rise′phenomenon occurred in two segments ( α = 0° and α = 8° ) of the characteristic curve of pitching moment. Moreover, coupling of the flow separation characteristic of the front wing and the after wing resulted in the pitching moment ′pitchup′ phenomenon. The lateral-directional static stability of the flat layout was weak. The HALE Diamond Joined-Wing configuration UAV ' s aerodynamic performance can be improved and the problems in engineering applications can be effectively alleviated by adjusting the overall layout parameters.

Existence and uniqueness of a class of double pyramidal central configurations in six-body problems

Under the necessary conditions for a double pyramidal central configuration with a diamond base to exist in the real number space, the existence and uniqueness of such configurations were studied by employing combinedly the algebraic method and numerical calculation. It is found that there exists a planar curl triangle region G in a square Q such that any point in G and given by the ratio of the two diagonal lengths of the diamond base and the ratio of one diagonal length of the base to the height of the double pyramid configuration determines a unique double pyramid central configuration, while all points in Q-G have no referance to any central configuration.

Boundedness of Formation Configuration for Nonlinear Three-body Dynamics

The configuration boundedness of the three-body model dynamics is studied for Sun-Earth formation flying missions.The three-body formation flying model is built up with considering the lunar gravitational acceleration and solar radiation pressure.Because traditional linearized dynamics based method has relatively lower accuracy,a modified nonlinear formation configuration analysis method is proposed in this paper.Comparative studies are carried out from three aspects,i.e.,natural formation configuration with arbitrary departure time,initialization time and formation configuration boundedness,and specific initialization time for bounded formation configuration.Simulations demonstrate the differences between the two schemes, and indicate that the nonlinear dynamic method reduces the error caused by the model linearization and disturbance approximation,and thus provides higher accuracy for boundedness analysis,which is of value to initial parameters selection for natural three-body formation flying.

Eight-body central configuration for conjugate-nested regular tetrahedrons

The sufficient and necessary conditions, the existence and uniqueness of a new class of central configuration in R3, for the conjugate-nest consisting of two regular tetrahedrons, are proved. If the configuration is a central configuration, then all masses of outside layer are equivalent, and the masses of inside layer are also equivalent. At the same time ρ (the ratio of the sizes) and mass ratio τ=m/?m must be satisfied by some formulas. For any radius ratios ρ∈(0, 0.152 996 918 2) or (0.715 223 148 7, 1.398 165 037), there is only one central configuration. Otherwise, for any given mass ratio τ , there may exist more than one central configuration.

Existence and uniqueness for a class of nine-bodies central configurations

On some necessary conditions for double pyramidal central configurations with concave heptagon for any given ratio of masses, the existence and uniqueness of a class of double pyramidal central configurations with concave heptagon base for nine-body problems is proved in this paper, and the range of the ratio σ of the circularity radius of the heptagon to the half-height of the double pyramidal central configuration involved in this class configurations is obtained, which is in the interval ( 3 /3,1.099 600 679) , and the configuration involved in the bodies with any σ ∈ ( 3 /3, 1.099 600 679) can form a central configuration which is a uniquely central configuration is proved.

A computational study of the wing-wing and wing-body interactions of a model insect

The aerodynamic interaction between the contralateral wings and between the body and wings of a model insect are studied, by using the method of numerically solving the Navier-Stokes equations over moving overset grids, under typical hovering and forward flight conditions. Both the interaction between the contralateral wings and the interaction between the body and wings are very weak, e.g. at hovering, changes in aerodynamic forces of a wing due to the present of the other wing are less than 3% and changes in aerodynamic forces of the wings due to presence of the body are less than 2%. The reason for this is as following. During each down- or up-stroke, a wing produces a vortex ring, which induces a relatively large jet-like flow inside the ring but very small flow outside the ring. The vortex rings of the left and right wings are on the two sides of the body. Thus one wing is outside vortex ring of the other wing and the body is outside the vortex rings of the left and right wings, resulting in the weak interactions.

The role of climate factors in geographic variation in body mass and wing length in a passerine bird

Background: Geographic variation in body size is assumed to reflect adaptation to local environmental conditions. Although Bergmann's rule is usually sufficient to explain such variation in homeotherms, some exceptions have been documented. The relationship between altitude, latitude and body size, has been well documented for some vertebrate taxa during the past decades. However, relatively little information is available on the effects of climate variables on body size in birds.Methods: We collected the data of 267 adult Eurasian Tree Sparrow(Passer montanus) specimens sampled at 48 localities in China's mainland, and further investigated the relationships between two response variables, body mass and wing length, as well as a suit of explanatory variables, i.e. altitude, latitude, mean annual temperature(MAT), annual precipitation(PRC), annual sunshine hours(SUN), average annual wind speed(WS), air pressure(AP) and relative humidity(RH).Results: Our study showed that(1) although the sexes did not differ significantly in body mass, males had longer wings than females;(2) body mass and wing length were positively correlated with altitude but not with latitude;(3) body mass and wing length were negatively correlated with AP and RH, but not significantly correlated with WS. Body mass was positively correlated with SUN and inversely correlated with MAT. Wing length was not correlated with MAT in either sex, but was positively correlated with SUN and negatively correlated with PRC in male sparrows;(4) variation in body mass could be best explained by AP and SUN, whereas variation in wing length could be explained by RH and AP in both sexes. In addition, variation in male sparrows can be explained by SUN, WS and PRC but not in females.Conclusions: Two different proxies of body size, body mass and wing length, correlated with same geographic factors and different climate factors. These differences may reflect selection for heat conservation in the case of body mass, and for efficient flight in the case of wing length.

Wing/body kinematics measurement and force and moment analyses of the takeoff flight of fruitflies

In the paper, we present a detailed analysis of the takeoff mechanics of fruitflies which perform voluntary takeoff flights. Wing and body kinematics of the insects during takeoff were measured using Based on the measured data, high-speed video techniques. inertia force acting on the insect was computed and aerodynamic force and moment of the wings were calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. The following has been shown. In its voluntary takeoff, a fruitfly jumps during the first wingbeat and becomes airborne at the end of the first wingbeat. When it is in the air, the fly has a relatively large ＂initial＂ pitch-up rotational velocity （more than 5 000~/s） resulting from the jumping, but in about 5 wingbeats, the pitch-up rotation is stopped and the fly goes into a quasi-hovering flight. The fly mainly uses the force of jumping legs to lift itself into the air （the force from the flapping wings during the jumping is only about 5%-10% of the leg force）. The main role played by the flapping wings in the takeoff is to produce a pitch-down moment to nullify the large ＂initial＂ pitch-up rotational velocity （otherwise, the fly would have kept pitching-up and quickly fallen down）.

Existence and Uniqueness of Nested Regular Quadrilateral Central Configurations

Two cases of the nested configurations in R^3 consisting of two regular quadrilaterals are discussed. One case of them do not form central configuration, the other case can be central configuration. In the second case the existence and uniqueness of the central configuration are studied. If the configuration is a central configuration, then all masses of outside layer are equivalent, similar to the masses of inside layer. At the same time the following relation between r(the ratio of the sizes) and mass ratio b = m/m must be satisfied b=24(3的立方根)（3r^2+2r+3）^-3/2-8（1-r）|1-r|^-3-3(6r的立方根)/24(3的立方根)（3+r）（3r^2+2r+3）^-3/2-8r（1-r）|1-r|^-3-3(6r^-2的立方根)in which the masses at outside layer are not less than the masses at inside layer, and the solution of this kind of central configuration is unique for the given ratio (b) of masses.

A New Kind of Conjugate-nested Central Configurations in Consisted of One Regular Tetrahedron and One Regular Octahedron

在 R3 的一种新盒子配置，结合巢由一个常规四面体和一常规八面体组成了是配置是的 discussed.If 一种中央配置，当时，外面的层的所有群众是相等的，里面的群众层也是 equivalent.At 一样的时间在 p 之间的下列关系( r=3/3 是尺寸的半径比率)并且集体比率 r=m/m 一定是满足的r=-m/m=( +3 )( 3+2+2 )为任何妈的 -3/2+(-+3)(3-2+2)-3/2-4.2-3/2-2-4-1-2/2(1+)(3+2+2)-3/2+2(-1)(3-2+2)-3/2-4(22)-3。

EXPERIMENTAL STUDY OF TURBULENT WINGBODY JUNCTION AND WAKE FLOW

The experiments on wing-body junction and wake flow were carried cul in alow-turbulence level wind tunnel. Intensive measurements of various flow parameters,such as the distributions of the pressure on the surfaces of the airfoil and the plate wall,the mean and the fluctuating velocities, as well as the turbulent kinetic energy, u'v' andu'w'etc., were performed. The results indicate that the secondary flow entrains the highvelocity low-turbulence fluid into the boundary layer and the wake vortex dominates thewake flow. Some regions of negative eddy viscosity are also found in the wake flow.

NUMERICAL SIMULATION OF WING-BODY JUNCTION TURBULENCE FLOW

Wing-body junction turbulence flow is simulated by using RANS equation and boundary fitted coordinate technique. Three order differential scheme is used in the computation of convection term and two layers turbulence model are employed in the calculation.

Double Pyramidal Central Configurations with a Concave Quadrilateral Base

As for a doudle pyramidal central configuration in 6-body problems,the case when its bese is a concave polygon is studied.By advancing several assumptions according to the definition of double pyramidal central configuration and deducing two theorems and two corollaries on this subject,the essential and sufficient conditions to form a double pyramidal central configuration with a concave quadriateral base are demonstrated.

Existence and uniqueness for a class of double pyramidal central configurations with a concave pentagonal base

Based on some necessary conditions for double pyramidal central configurations with a concave pentagonal base, for any given ratio of masses, the existence and uniqueness of a class of double pyramidal central configurations with a concave pentagonal base in 7-body problems are proved and the range of the ratio between radius and half-height is obtained, within which the 7 bodies involved form a central configuration or form uniquely a central configuration.

鄂尔多斯盆地大牛地气田二叠系山西组砂体叠置模式及油气开发意义

河流相砂体储层构型对致密砂岩中相对优质储层的分布规律和天然气开发具有重要意义。通过野外地质剖面和钻井岩心观察,结合测井、录井和岩心分析测试资料,对鄂尔多斯盆地大牛地气田大12井区二叠系山西组致密砂岩的砂体构型要素、叠置模式及油气开发意义进行了研究。研究结果表明:(1)鄂尔多斯盆地大牛地气田大12井区二叠系山西组发育六级复合辫流带和五级单一辫流带,其中单一辫流带包括河床(分流河道)和河漫共2个四级构型单元,河道内单个心滩沉积包含有三级增生体和落淤层;(2)辫状河三角洲平原五级单一辫流带中的四级泛滥平原沉积较辫状河河漫沉积更加发育,辫状河心滩沉积中落淤层欠发育;(3)山西组上部山2-2亚段辫状河单一辫流带内砂体呈“河道-心滩”连续沉积,泥质不发育,砂体叠置程度高(多呈复合式叠置)、连通性好,优质储层多;(4)山西组中下部山1段和山2-1亚段三角洲平原沉积中,西部河道连片性好,砂体以复合式和侧拼式叠置样式为主,连通性和生产效果均较好,东部砂体多为孤立式和侧接式,砂体钻遇率低,单井产量差。

高职院校助力职教“一体两翼”高质量发展研究

“一体两翼”是新时代职业教育高质量发展的有效策略,落实职业教育“一体两翼”发展策略具有现实逻辑内涵和重要实践价值。高职院校是职业教育改革发展的重要推动力量,虽然高职院校助力职教“一体两翼”高质量发展取得一系列成效,然而,因受到多种因素的影响和制约,高职院校助力职教“一体两翼”高质量发展仍面临不少挑战。因此,为了增强高职院校助力职教“一体两翼”高质量发展效能,应该立足省域发展,开展针对性专业人才培养;多维度建设市域产教联合体,创设高职教育发展新平台;多方协同发力,全方位推进行业产教融合共同体建设。

创新教育背景下工业设计专业“一体两翼四驱动”教学模式研究

近年来,国家倡导素质教育,提倡在高等院校加大实践能力和创新能力的培养,各高校不断进行教学模式改革和创新,取得了一定成效,但仍没能摆脱传统观念和教学模式的束缚。为适应行业发展趋势和需求,坚持以人为本的教育理念,紧跟时代步伐,引入“一体两翼四驱动”教学模式,开展“一体两翼四驱动”协同育人改革实践,以培养高素质创新复合型人才为主要目的,增强学生实践能力和创新能力,从根本上提升人才培养质量,以满足高速发展的社会需求,为高校人才培养模式变革提供参考依据。

“一体两翼六驱动”发展型资助育人模式探析

党的十九大以来,以习近平同志为核心的党中央高度重视学生资助工作。党的十九大报告明确提出要“健全学生资助制度”。新时代学生资助工作的重点应由单纯的经济保障转变为经济保障与育人发展相结合,使育人功能成为学生资助工作的价值引领。聚焦当前时期学生资助工作,通过“一体两翼六驱动”探索发展型资助育人模式。