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1.
基于动网格技术的柔性后缘自适应机翼气动特性分析 总被引:3,自引:0,他引:3
研究了带柔性后缘的可变弯度自适应机翼在自适应变弯度过程中的气动特性.自适应变弯度过程中的气动力计算采用了基于弹簧理论的非结构动网格技术,求解NS方程时采用有限体积的二阶迎风格式离散,时间推进为隐格式双时间推进方法.通过计算柔性后缘机翼的升力特性、阻力特性及升阻比特性,并与带刚性后缘机翼的气动特性进行比较,发现柔性后缘机翼在后缘偏转时,其最大升阻比对应的迎角随着偏转角增大而降低.在中等迎角及接近失速迎角情况下,柔性后缘机翼升力系数明显优于刚性后缘机翼,并且其升力线变化较为平缓,有效迎角范围更大. 相似文献
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The problem of unsteady heat and mass transfer for a single bubble containing an evaporating liquefied-gas drop is considered within the spherically symmetric formulation. The numerical solution and the quasi-steady analog of the problem are obtained. The existence of two stages of the process, namely, the dynamic and thermal stages, is shown. The quasi-steady solution is a good approximation for the thermal stage. 相似文献
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In this paper, the Spectral-Element Dynamic Model (SEDM), suited for Large-Eddy Simulation (LES) using Discontinuous Finite Element Methods (DFEM), is assessed using unstructured meshes. Five test cases of increasing complexity are considered, namely, the Taylor-Green vortex at Re =?5000, the turbulent channel flow at Reτ =?587, the circular cylinder in cross-flow at ReD =?3900, the square cylinder in cross-flow at ReD =?22400 and the channel with periodic constrictions at Reh =?10595. Various discretization parameters such as the grid spacing, polynomial degree and numerical flux are assessed and very accurate results are reported in all cases. This consistency in the results demonstrates the versatility of the SEDM approach and its ability to gage the actual resolution and quality of the mesh and, accordingly, to introduce an amount of sub-grid dissipation which is adapted to the spatial discretization considered. 相似文献
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本文讨论了具有内外阻尼的高速充液转子的动力稳定性。首先通过对旋转流体的平面流场的求解,导出充液转子作简谐运动时流体对转子的动压力,由此导出转子的运动方程;讨论了充液转子的动力稳定性,给出了稳定性解析判据和稳定性边界。结果表明,存在转速门槛值,低于该转速时,充液转子可存在稳定区;当高于该转速时,系统永远失稳,这一结论复盖了已有文献的结果。 相似文献
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G.J. McShane S.M. Pingle V.S. Deshpande N.A. Fleck 《International Journal of Solids and Structures》2012,49(19-20):2830-2838
The dynamic compressive response of a sandwich plate with a metallic corrugated core is predicted. The back face of the sandwich plate is held fixed whereas the front face is subjected to a uniform velocity, thereby compressing the core. Finite element analysis is performed to investigate the role of material inertia, strain hardening and strain rate hardening upon the dynamic collapse of the corrugated core. Three classes of collapse mode are identified as a function of impact velocity: (i) a three-hinge plastic buckling mode of wavelength equal to the strut length, similar to the quasi-static mode, (ii) a ‘buckle-wave’ regime involving inertia-mediated plastic buckling of wavelength less than that of the strut length, and (iii) a ‘stubbing’ regime, with shortening of the struts by local fattening at the front face. The presence of strain hardening reduces the regime of dominance of the stubbing mode. The influence of material strain rate sensitivity is evaluated by introducing strain rate dependent material properties representative of type 304 stainless steel. For this choice of material, strain rate sensitivity has a more minor influence than strain hardening, and consequently the dynamic collapse strength of a corrugated core is almost independent of structural dimension. 相似文献
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Yu. B. Sedov 《Fluid Dynamics》1976,11(6):857-862
The turbulent flow of an ideal fluid is represented by a discrete model, in which the turbulence is concentrated at individual points and the cloud of these point eddies determines the turbulent flow. In the given mathematical model of turbulence (in contrast to other models of finite dimensions), the accurate hydrodynamic equation is not replaced by a finite system of coupled ordinary differential equations, and singular initial data are used. Advantages of such an approach are that the interactions between the point eddies are obvious, and their dynamics can be described by comparatively simple equations. The present work is a numerical investigation of the interactions between 100 identical point eddies which are initially distributed uniformly over a circle. This model is used to trace the tendency to directional energy transfer from small scale to large scale in two-dimensional turbulence. This phenomenon, which has been shown to be possible in several theoretical works and numerical investigations [1–3], may be attributed to the static irreversibility of turbulence [4]. A similar effect can be observed directly in the earth's atmosphere, in that the general circulation of the atmosphere is fed by cyclonic energy; this is referred to as negative viscosity [5]. A spectral analysis is carried out for such a system of point eddies, using a new procedure based on the formula obtained in [6]. In the evolution of the spectrum, sections close to the –5/3 law and the –3 law are obtained. Secondary instability of the eddy system is noted. At the end of the numerical experiment, a quasisteady state is established in the system.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 43–48, November–December, 1976.In conclusion, we thank E. A. Novikov for formulating the problem and for his constant interest in the work. 相似文献
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李庆明 《应用数学和力学(英文版)》1990,11(1):63-68
The conception of buckling relative initial imperfection is presented in this paper. According to Boulli-Euler beam equation, the dynamic buckling mode of an elastic bar under the homogeneous boundary conditions can be derived by applying the preferred mode analytical method. As an example, the dynamic buckling mode of an elastic bar clamped at both ends is discussed. 相似文献
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A. V. Krivochenko A. N. Sporykhin 《Journal of Applied Mechanics and Technical Physics》2009,50(5):872-877
The stress-strain state of a hollow sphere under time-dependent loading is studied using the constitutive relations for a
hardening compressible elastoviscoplastic sold. Analytical solutions are obtained for displacement fields in the elastic and
plastic regions. Time dependences of the reciprocal of the radius of the elastoplastic boundary are constructed, and the effect
of the physicomechanical parameters on the radius of the elastoplastic boundary is determined. 相似文献
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The influence of the pendulum parameters and the follower force on the evolution of equilibrium states is analyzed using a
generalized mathematical model of inverted pendulum. Equilibrium curves are plotted using the parameter continuation method.
It is shown that the pendulum with certain values of the angular eccentricity has one or three nonvertical equilibrium positions
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Translated from Prikladnaya Mekhanika, Vol. 43, No. 3, pp. 122–131, March 2007. 相似文献
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It has been shown that pressure waves can have a large effect on the burning rate of flames. In this paper, the evolution
of convection-driven fast flame, which is acoustically linked to a shock wave via an induction zone, is examined in detail.
It is found that there is positive feedback mechanism and the asymptotic model breaks down as blow up occurs. Comparison
is made between the case of a piston driving a shock wave into a combustible atmosphere with these studies of a shock wave
passing through an existing premixed flame.
Received 4 August 1995 / Accepted 20 March 1996 相似文献
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针对球-盘滑动试验,在磨合过程中获得超低摩擦的液体润滑状态,建立耦合流体润滑、粗糙接触力学、Archard磨损方程和相关物理参数(液体黏度、表面粗糙度和磨损系数)时变函数的混合模型,研究磨合过程中液体润滑的摩擦系数演化.通过数值模拟结果可知:在磨合过程中,润滑介质等效黏度增大,形成流体动压润滑薄膜,有效隔开粗糙表面;其次在磨合过程中,新生成的表面粗糙度降低,减少粗糙峰承载比,实现超低摩擦润滑状态;最后在适当的液体黏度和提高表界面效应减少边界摩擦系数,可进一步实现液体超低摩擦润滑状态.为磨合过程宏观液体润滑性能演化所建立的混合数值模型对提高液体润滑超低摩擦设计效率具有重要价值意义. 相似文献
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A fundamental solution for an infinite elastic medium containing a penny-shaped crack subjected to dynamic torsional surface tractions is attempted. A double Laplace–Hankel integral transform with respect to time and space is applied both to motion equation and boundary conditions yielding dual integral equations. The solution of the derived dual integral equations is based on an analytic procedure using theorems of Bessel functions and ordinary differential equations. The dynamic displacements’ field is obtained by inversion of the corresponding Laplace–Hankel transformed variable. Results of a representative example for a crack subjected to pulse surface tractions are obtained and discussed. 相似文献
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The principal objective of this study is to present a new numerical scheme based on a combination of q-homotopy analysis approach and Laplace transform approach to examine the Fitzhugh–Nagumo (F–N) equation of fractional order. The F–N equation describes the transmission of nerve impulses. In order to handle the nonlinear terms, the homotopy polynomials are employed. To validate the results derived by employing the used scheme, we study the F–N equation of arbitrary order by using the fractional reduced differential transform scheme. The error analysis of the proposed approach is also discussed. The outcomes are shown through the graphs and tables that elucidate that the used schemes are very fantastic and accurate. 相似文献
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Institute of Mechanics, Academia Sinica of China. Published in Prikladnaya Mekhanika, Vol. 27, No. 7, pp. 88–95, July, 1991. 相似文献