单圆盘转子非线性振动模型及机理

根据转子非线性振动的力学性质及大变形假设,结合工程实际构建了转子非线性振动具有Duffing方程形式的力学模型,推导了非线性系统的等效频率和频响方程,研究了刚度元件、阻尼元件与非线性元件对系统振动的影响.通过单圆盘转子非线性振动实验,验证了非线性振动模型结构与Duffing方程求解及频响方程的合理性与有效性,揭示了共振、突变、滞后等非线性现象的机理,为转子振动特性分析提供了一种新的研究方法.      

节流通风的航空发动机轴承腔腔压计算方法

为解决节流通风的航空发动机轴承腔的腔压难以计算的问题,考虑节流孔处通风介质可压缩性,结合某典型节流通风轴承腔的实例,分析了节流通风的发动机轴承腔通风气体流动的特点,提出了其腔压计算方法.通过实例计算,结果表明:计算值与试验值的绝对误差较小,结果满足滑油系统与空气系统联合计算的工程需要.该计算方法可为节流通风的航空发动机轴承腔腔压计算提供参考.      

Experiment of heat transfer in oscillating turbulent flow in a pipe with constant heat flux

Heat transfer characteristics of oscillating turbulent air flow in a pipe heated with constant heat flux were experimentally investigated.The experiments were performed over a range of 245.7 to 902 of the kinetic Reynolds number and 25 to 175 of the dimensionless oscillation amplitude.The effects of these two dimensionless parameters were analyzed.The results show that the cycle-averaged local Nusselt number increases with both the kinetic Reynolds number and the dimensionless oscillation amplitude.The space-cycle averaged Nusselt number also effectively increases with the kinetic Reynolds number and the dimensionless oscillation amplitude.Based on the experimental data,a correlation equation of the space-cycle averaged Nusselt number for air in terms of these two dimensionless parameters has been obtained.      

含裂纹固体推进剂装药的内流场数值模拟

利用“N－S方程＋粒子仿真”方法来计算含裂纹翼柱型装药内流场。计算结果表明：环形裂纹内的流动对主流的影响大于纵向裂纹，环形裂纹向上游位置流动对主流的影响较下游位置的大，并可保持到喷管喉部，翼槽附近环形裂纹内的流动对主流的影响相对较弱。     

飞机尾涡系Rayleigh-Ludwieg不稳定性实验研究

以飞机起降过程中主翼和尾翼产生反向涡系存在相互作用的事实为背景,设计了一套反向双漩涡发生装置。通过改变两涡的位置关系与初始涡强度比值,采用流动显示与粒子成像测速(PIV)技术,对涡系相交不稳定性的作用特性进行了研究。结果表明:小涡的引入改变了主涡原有运动轨迹,合理地引入小涡的位置与小涡的强度,对主涡能量的衰减有明显的促进作用,但它们之间不呈现明显的线性关系;涡空间运动轨迹的分析,对未来完善机场起降控制模型有一定借鉴意义;实验结果也为飞机整体设计提供了一定参考依据,在满足飞行力学的设计基础上,优化整体气动布局对降低飞机尾流强度有显著的影响。     

高超声速内收缩进气道分步优化设计方法

提出了基准流场与唇口平面形状分步优化的高超声速内收缩进气道设计方法。基准流场以反射激波不均匀性最小和总压恢复最大进行多目标优化设计,使用结合Tayler-Maccoll方程的有旋特征线方法(MOC)进行流场计算,获得双拐点母线内收缩锥基准流场。进气道唇口形状以沿流线积分(Streamline Integral Method, SIM)获得的进气道无黏阻力最小为目标进行优化设计,获得类椭圆形唇口平面形状。针对优化设计结果进行数值模拟,与传统直母线基准流场相比,双拐点母线基准流场反射激波后流动不均匀性下降40%左右,总压损失减少35%左右,总体性能提升明显。类椭圆唇口进气道在设计点的单位质量流量无黏阻力相较于圆形唇口降低6%,具有良好的压缩特性和气动效率,能够减弱进气系统对飞行器气动性能的不利影响。研究结果表明该方法是一种高效且实用的高超声速内收缩进气道设计方法。     

Evolution and History in a new “Mathematical SETI” model

In a recent paper (Maccone, 2011 [15]) and in a recent book (Maccone, 2012 [17]), this author proposed a new mathematical model capable of merging SETI and Darwinian Evolution into a single mathematical scheme. This model is based on exponentials and lognormal probability distributions, called “b-lognormals” if they start at any positive time b (“birth”) larger than zero. Indeed:

• 1.Darwinian evolution theory may be regarded as a part of SETI theory in that the factor f_l in the Drake equation represents the fraction of planets suitable for life on which life actually arose, as it happened on Earth.
• 2.In 2008 (Maccone, 2008 [9]) this author firstly provided a statistical generalization of the Drake equation where the number N of communicating ET civilizations in the Galaxy was shown to follow the lognormal probability distribution. This fact is a consequence of the Central Limit Theorem (CLT) of Statistics, stating that the product of a number of independent random variables whose probability densities are unknown and independent of each other approached the lognormal distribution if the number of factors is increased at will, i.e. it approaches infinity.
• 3.Also, in Maccone (2011 [15]), it was shown that the exponential growth of the number of species typical of Darwinian Evolution may be regarded as the geometric locus of the peaks of a one-parameter family of b-lognormal distributions constrained between the time axis and the exponential growth curve. This was a brand-new result. And one more new and far-reaching idea was to define Darwinian Evolution as a particular realization of a stochastic process called Geometric Brownian Motion (GBM) having the above exponential as its own mean value curve.
• 4.The b-lognormals may be also be interpreted as the lifespan of any living being, let it be a cell, or an animal, a plant, a human, or even the historic lifetime of any civilization. In Maccone, (2012 [17, Chapters 6, 7, 8 and 11]), as well as in the present paper, we give important exact equations yielding the b-lognormal when its birth time, senility-time (descending inflexion point) and death time (where the tangent at senility intercepts the time axis) are known. These also are brand-new results. In particular, the σ=1 b-lognormals are shown to be related to the golden ratio, so famous in the arts and in architecture, and these special b-lognormals we call “golden b-lognormals”.
• 5.Applying this new mathematical apparatus to Human History leads to the discovery of the exponential trend of progress between Ancient Greece and the current USA Empire as the envelope of the b-lognormals of all Western Civilizations over a period of 2500 years.
• 6.We then invoke Shannon's Information Theory. The entropy of the obtained b-lognormals turns out to be the index of “development level” reached by each historic civilization. As a consequence, we get a numerical estimate of the entropy difference (i.e. the difference in the evolution levels) between any two civilizations. In particular, this was the case when Spaniards first met with Aztecs in 1519, and we find the relevant entropy difference between Spaniards an Aztecs to be 3.84 bits/individual over a period of about 50 centuries of technological difference. In a similar calculation, the entropy difference between the first living organism on Earth (RNA?) and Humans turns out to equal 25.57 bits/individual over a period of 3.5 billion years of Darwinian Evolution.
• 7.Finally, we extrapolate our exponentials into the future, which is of course arbitrary, but is the best Humans can do before they get in touch with any alien civilization. The results are appalling: the entropy difference between aliens 1 million years more advanced than Humans is of the order of 1000 bits/individual, while 10,000 bits/individual would be requested to any Civilization wishing to colonize the whole Galaxy (Fermi Paradox).
• 8.In conclusion, we have derived a mathematical model capable of estimating how much more advanced than humans an alien civilization will be when SETI succeeds.

     

双层壁冷却结构中多排射流冲击冷却的换热和流阻特性

采用稳态热敏液晶技术对双层壁冷却结构中的多排（包括顺排和叉排）射流冲击冷却结构进行了风洞实验,同时结合数值模拟的方法,对两种射流冲击冷却结构的传热和流阻特性的差异进行了研究。实验结果表明:流量系数和冲击靶板上的努塞尔数均随着雷诺数的增大而增大,而冲击孔的排布方式对面平均努塞尔数的影响较小,但是叉排结构的流量系数高于顺排结构,且冲击靶板上换热更加均匀。数值结果显示冲击靶板中心区域的流量分配和换热均随着冲击距离的增大而增大;而在下游区域内恰好与之相反。      

剪切气流中无黏液体横向射流破碎机理

航空发动机燃烧室中,液体燃料的雾化过程、特别是初始雾化过程非常复杂,至今无法建立准确的初始雾化模型。忽略液体射流黏性,采用线性不稳定性分析法对无黏液体（工质为水）在二维剪切横向气流中的破碎机理进行研究。通过建立射流的色散方程,根据其表面波的增长率及波数的发展情况对射流破碎进行预测。当气体韦伯数或液体韦伯数增大时,射流表面波增长率显著增加,最佳波长明显减小。液气动量比大于临界值时,Kelvin-Helmholtz （K-H）不稳定性占主导作用;反之,Rayleigh-Taylor （R-T）不稳定性占主导作用。二维剪切气流在射流方向上具有速度梯度,只改变横向气动力对射流表面波的作用。气体韦伯数与液体韦伯数对射流破碎的作用与均匀气流相似;保持气流流量相同时,负梯度剪切气流可以加速射流的破碎。     

奇异积分方程方法在接触压力分析中的应用

总结回顾了奇异积分方程的数值解法,对于第二类奇异积分方程使用分段连续函数法进行了求解;对于两个弹性体接触问题,通过接触体之间的滑移函数和间隙函数,建立求解接触压力的奇异积分方程.分别针对圆柱体与弹性半空间体、抛物线型压头与弹性半空间体、榫头与榫槽3类接触问题,确立奇异积分方程的具体表达式,而后使用分段连续函数方法进行求解,获得接触面上的接触压力.最后将计算所得的接触压力分别与理论解和有限元解进行了对比.对于圆柱体与弹性半空间体接触问题,奇异积分方程法的最大接触压力与理论解和有限元解的相对误差分别为0.3%和0.5%;对于榫头与榫槽接触问题,奇异积分方程方法计算所得的最大接触压力与有限元解的相对误差为1.8%,验证了奇异积分方程方法的有效性.