湍流中的相干结构

30年来,对湍流的研究出现了不少新的研究手段,如大涡模拟、混沌、分叉及相干结构等。但是,目前在湍流机理上最有希望突破的是大尺度相干结构的研究和把大型计算机作为湍流研究工具。本文综述了近年来相干结构研究发展概况,讨论了在相千结构的理论研究方面应该开展的工作

高超声速升力体气动力气动热数值计算

升力体气动布局，由于其良好的高超声速气动特性、有效的内部空间和有益的防热特性，越来越受到气动工作者的重视，该文应用张涵信院士的NND格式思想，用数值模拟的方法对类似于美国X-33的升力体外形进行了气动力、气动热研究。特别是在粘性项的离散和表面热流率的计算中应用了散度和梯度的积分定义，避免了数值计算的奇异性，保证了通量守恒，提高了计算效率。结果表明气动热计算结果与美国同类飞行器结果接近，驻点热流率与经典理论结果一致

Aerodynamic characteristics research on wide-speed range waverider configuration

Waverider generated from a given flow field has a high lift-to-drag ratio because of attached bow shock on leading edge. However, leading edge blunt and off-design condition can make bow shock off leading edge and have unfavorable influence on aerodynamic characteristics. So these two problems have always been concerned as important engineering science issues by aeronautical engineering scientists. In this paper, through respectively using low speed and high speed waverider design principles, a wide-speed rang vehicle is designed, which can level takeoff and accelerate to hypersonic speed for cruise. In addition, sharp leading edge is blunted to alleviated aeroheating. Theoretical study and wind tunnel test show that this vehicle has good aerodynamic performance in wide-speed range of subsonic, transonic, supersonic and hypersonic speeds

Unsteady Aerodynamic Modeling Based on POD-ARX

The lack of stability is a problem encountered when applying the classical POD-Galerkin method to problems of unsteady compressible flows around a moving structure. To solve this problem, a hybrid reduced-order model named POD-ARX is constructed in this paper. The construction of this model involves two steps, including first extracting the fluid modes with the POD technique and then identifying the modal coefficients with the ARX model. The POD modes with the block of all modified primitive variables are extracted from the system response to the training signal. Once the POD modes are obtained, the snapshots are projected on these modes to determine the time history of modal coefficients and the resulting modal coefficients are used to identify the parameters of ARX model. Then, the ARX model is used to predict the modal coefficients of the system response to the validation signal. Sample two-dimensional aerodynamic force calculations are conducted to demonstrate this method. Results show that this method can produce a stable and accurate prediction to the aerodynamic response with significant improvement of computational efficiency for linear and even some nonlinear aerodynamic problems. In addition, this method also shows good wide-band characteristics by using the &quot;3211&quot; multistep signal as the training signal.</p

Triple-region structure for turbulent-flow in a square duct - a finite-element approach

The Reynolds-averaged Navier-Stokes equations for describing the turbulent flow in a straight square duct are formulated with two different turbulence models. The governing equations are then expanded as a multi-deck structure in a plane perpendicular to the streamwise direction, with each deck characterized by its dominant physical forces as commonly carried out in analytical work using triple-deck expansion. The resulting equations are numerically integrated using higher polynomial (H-P) finite element technique for each cross-sectional plane to be followed by finite difference representation in the streamwise direction until a fully developed state is reached. The computed results using the two different turbulence models show fair agreement with each other, and concur with the vast body of available experimental data. There is also general agreement between our results and the recent numerical works anisotropic k-epsilon turbulence model

Research Progresses on Appearance Quality of Rice Grain and Strategies for its Molecular Improvement

Corresponding auther, [email protected] j.cn[中文文摘]本文综述了稻米外观品质 (长、宽、长宽比和垩白 )的经典遗传及分子遗传研究状况 ,归纳列举了已定位的外观品质性状的QTLs,提出了稻米外观品质改良的分子策略[英文文摘]This paper has review ed the classical and molecular genetic research progresses of rice appearance quality,which including traits of grain length, grain width, length- width ratio and chalkiness, and compared the QTLs conferring these traits which was detected by deferent labs using deferent kind populat ions.The authors have put forward the molecular strategy for appearance quality improvement.国家863项目(2002AA211091)及(2001AA211091)资

Research Progresses on Nutrient Quality of Rice Grain and Molecular Breeding Approach

Corresponding author, zjhym@ public xm f j cn[中文文摘]本文综述了稻米营养品质 (蛋白质、赖氨酸和微量营养素 )的经典遗传学和分子遗传学、分子育种的研究现状 ,并对利用分子标记辅助育种方法提高稻米营养品质作了展望。[英文文摘]This paper reviewed the classical and molecular genetic research progresses on nutrient qulity (including protein, lysine and micronutrient) of rice grain and its molecular breeding, furthermore, the molecular markerassisted breeding strategy for nut rient quality improvement was put forward

高超声速乘波飞行器气动特性研究(英文)

用计算流体力学和风洞试验的方法对以锥导乘波体为基础生成的高超声速乘波飞行器的气动性能进行了研究。结果表明,以马赫数6,攻角4度为设计状态的乘波体,在马赫数5~7,攻角4~6度的范围内,都具有良好的气动特性,升阻比接近4。最后,提出了一个简单的以参考温度方法为基础的粘性阻力分析方法。该方法配合使用风洞试验和计算流体的结果,可以用来验证计算流体中难以计算准确的粘性阻力,也可以用来分析在风洞试验难以直接得到的粘性阻力。对于工程上的粘性阻力分析是一个有用的办法

Waverider configuration design and forebody compressibility analysis

提出了用相交楔锥流场构造乘波构型飞行器前体的方法。该方法利用无粘相交楔锥流场生成具有两个压缩面的乘波前体，不仅兼具楔型流场和锥型流场构造乘波体的优点，而且充分发挥了高超声速飞行器前体的预压缩作用，为进气道的正常工作提供了条件。同时用数值模拟的方法研究了不同前体压缩角度组合的预压缩效果，并在压缩角优化的基础上进行了前体／进气道的一体化设计

Parametric waveriders design method study

开展变楔角参数化乘波器的研究。研究中考虑了粘性效应，分析了不同设计参数对乘波器气动性能的影响。对比MAXWARP乘波器设计结果和数值求解NS方程的结果，验证了变楔角参数化乘波器设计方法的正确性。分析了不同的设计参数对乘波器气动性能的影响，为研究复杂的乘波器设计和优化规律提供了一个途径。参数化乘波器设计可方便的控制乘波器的外形尺寸，使乘波器的应用性大大提高