钝体绕流非定常解

本文结合目前流场显示的研究课题,对方块物体和山形物体的钝体绕流在起动阶段的运动情况,进行相应的数值模拟.并用有限差分方法求解二维不可压缩流体运动的N-S方程的非定常解.对差分格式中的显式,隐式和交替方向隐式几种格式进行了讨论.最后用显式和交替方向隐式方法计算了山形物体和方块物体在起动阶段的运动情况.     

高寒草甸地区陆面过程观测及耦合模式研究

对海北高寒草甸地区水热传输过程进行了系统观测,特别考虑了叶片气孔为非饱和水汽条件下的交换情况,结合修正的根系吸水公式,发展了一个多层陆气耦合模式．利用该模式对中国科学院海北高寒草甸生态试验站地区矮嵩草草甸陆气水热交换进行了数值模拟,分析了湍流交换的物理过程,给出了沿高度分布的各物理量．模拟结果与实测值吻合较好．     

A coupling model for terrestrial processes in arid areas and its application

IntroductionItiswell-knownthatland-atmosphereinteractionexertsgreatinfluencesonglobalandregionalenvironment(Woodfool,Yih1994).Inordertodeterminethefluxesandtheparameterizationschemeattheland-atmosphereinterface,itisnecessaryforustoinvestigateterrestrialprocessesontypicalunderlyingsurface.Aridarea(includingextremelyarid,aridandsend-aridareas)ofsabillionklnZ,occupiesalmostonethirdofthelandsurface,mainlyinNorthAfrica,CentralAsia,AustraliaandNorthAInerica.Amongthemdesertcoversnearly6millionkl…     

植物固沙区土壤水热运移耦合模型研究

根据Ｐｈｉｌｉｐ与Ｖｒｉｅｓ提出的土壤中水热交换的耦合理论，建立了植物固沙区土壤水热运移的耦合模型，考虑了液态水和汽态水运移对温度的变化，分析了植物根系吸水对土壤水热交换的影响，给出了植物蒸腾量、土壤蒸发量、根系汲水率及土壤表面热通量等有关变量的计算公式．利用本模式并采用具有二阶精度的Ｃｒａｎｋ－Ｎｉｃｏｌｓｏｎ格式对非线性扩散方程进行离散，对沙坡头植物固沙区土壤水热交换过程进行了数值模拟，模拟结果和实测值进行了比较，总体上符合较好，证明本模型具有实用价值，可为改造沙漠提供科学依据     

Computation of unsteady flow past blunt bodies

In accordance with the recent experimental research for flow visualization,theunsteady behavior of the starting period is investigated numerically for flow past bluntbodies.Finite difference methods are employed to solve the unsteady two-dimensionalincompressible Navier-Stokes equations.A short discussion is presented of explicit,implicit and ADI methods.Finally,the explicit and ADI schemes are used to study the flowfield in the starting period for flow past mountain-shaped and rectangular bodies.     

干旱地区陆面过程耦合模式及应用

本文主要论述干旱地区陆面过程在改善人类生存环境与研究区域经济中的重要地位与研究现状,强调了采用耦合模式的必要性,详细描述了该模式的特点,并将它应用于我国西北腾格里沙漠南缘植物固沙区的水热循环研究,揭示干旱区陆面过程的主要特征,并同现场测试进行了比较。     

圆盘形和圆环形压膜轴承的气动力分析

本文按照气体动力学理论,对圆盘形和圆环形压膜轴承的气动力作了详细的分析;给出了这两种轴承的压力分布的解析表达式,并用该方法修正了圆盘形压膜轴承的部分计算公式;还给出了这两种轴承的压力分布和承载能力的计算结果,可供设计者参考.     

New insights on low energy πN scattering amplitudes:comprehensive analyses at ■(p~3) level

A production representation of partial-wave S matrix is utilized to construct low-energy elastic pion-nucleon scattering amplitudes from cuts and poles on complex Riemann sheets. Among them, the contribution of left-hand cuts is estimated using the ■(p~3) results obtained in covariant baryon chiral perturbation theory within the extendedon-nass-shell scheme. By fitting to data on partial-wave phase shifts, it is indicated that the existences of hidden poles in S11 and P11 channels, as conjectured in our previous paper [Eur. Phys. J. C, 78(7): 543(2018)], are firmly established. Specifically, the pole mass of the S11 hidden resonance is determined to be(895±81)-(164±23)i MeV,whereas,the virtual pole in the P11 channel locates at(966±18) MeV. It is found that analyses at the■ (p~3) level improves significantly the fit quality, comparing with the previous■ (p~2) one. Quantitative studies with cautious physical discussions are also conducted for the other S-and P-wave channels.