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941.
The variation of main turbulent quantities in an isotropic turbulent flow, such as the decay of turbulent energy and the variation
of Taylor microscale of turbulence with time are obtained, by employing a hot-wire anemometer and a nearly isotropic turbulent
flow which is produced by a gridscreen located at the entrance of the test section in a low-level turbulence and low-speed
wind tunnel in Peking University. The experimental results of the decay of turbulent energy and the variation of Taylor microscale
of turbulence with time at the whole period from initial to final stage, normalized in an non-dimensional form, are consistent
quite well with the computational results by the theory of the statistical vorticity structure[1]. The experimental results presented in this paper also agree with Townsend's results obtained in earlier years[2] as well as with Bennett's in the seventy's[3]. 相似文献
942.
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944.
介质参数反演的广义射线近似方法 总被引:2,自引:0,他引:2
在对无粘性介质参数反演问题进行的研究中,引入一种全波场广义射线近似形式,提出一种新的反演参数的方法,文中,首先对由弹性波动方程演变成的声波方程进行分析,引入背景场量和扰动量,并结合Green函数理论,得到了介质参数的积分方程;然后结合前人对非均匀介质中波函数局部理论的定性分析,引入一种全波场广度射线近似形式,把问题归结为一个第一类Fredholm积分方程;最后对半空间问题层状介质模型进行了反演,算 相似文献
945.
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947.
Niu Xiang-jun 《应用数学和力学(英文版)》1981,2(5):549-565
This paper suggests a new solid variational principle of discrete form. Basing on the true case of the discrete analysis by the finite element method and considering the variable boundaries of the elements and the unknown functions of piecewise approximation, the unknown functions have various discontinuities at the interfaces between successive element.Thus, we have used mathematical technique of variable boundary with discontinuity of the unknown functions, based on the conditions that the first variation vanishes immediately, to establish the solid variation principles of discrete form. It generalizes the classical and non-classical variational principles. Successive equations that have to be satisfied by the unknown functions are the convergency necessary conditions for the finite elements method (including conforming and non-conforming). They expand that convergency necessary conditions of the compatibility conditions in the internal interfaces. 相似文献
948.
方沸石大单晶及多晶粉饼力学性能的实验研究 总被引:2,自引:0,他引:2
报道了采用纳米压痕硬度计和Instron仪器分别对方沸石ANA大单晶和方沸石ANA多晶粉饼进行的力学性能测试工作。在纳米压痕实验中可实时测得连续载荷和随载荷连续变化而变化的位移,得到载荷-位移曲线图。根据W.C.O live算法,利用接触刚度连续测量(CSM)技术,实现了ANA沸石的硬度、弹性模量随压痕深度变化的连续测量,得到了ANA沸石单晶的硬度、弹性模量分别为0.25GPa和4GPa。用Instron仪器测得ANA多晶粉饼的弹性模量值为125MPa。对ANA沸石大单晶和ANA沸石多晶粉饼的力学性能进行了比较。 相似文献
949.
NON-LINEAR DYNAMIC MODEL RETRIEVAL OF SUBTROPICAL HIGH BASED ON EMPIRICAL ORTHOGONAL FUNCTION AND GENETIC ALGORITHM 总被引:1,自引:0,他引:1
Aiming at the difficulty of accurately constructing the dynamic model of subtropical high, based on the potential height field time series over 500 hPa layer of T106 numerical forecast products, by using EOF(empirical orthogonal function) temporal-spatial separation technique, the disassembled EOF time coefficients series were regarded as dynamical model variables, and dynamic system retrieval idea as well as genetic algorithm were introduced to make dynamical model parameters optimization search, then, a reasonable non-linear dynamic model of EOF time-coefficients was established. By dynamic model integral and EOF temporal-spatial components assembly, a mid-/long-term forecast of subtropical high was carried out. The experimental results show that the forecast results of dynamic model are superior to that of general numerical model forecast results. A new modeling idea and forecast technique is presented for diagnosing and forecasting such complicated weathers as subtropical high. 相似文献
950.
IntroductionAsanimportantnumericalmethod ,BoundaryElementMethod (BEM)hasbeenappliedinmanyareas[1].However,theBEMhasthedifficultiesofcalculatingsingularintegralsatnodesonboundaryoratinteriorpointsveryclosetotheboundary .TheaccuracyoftheBEMdependsontheprecisionofthecalculatedvaluesofthesingularintegrals,toagreatdegree.Manyresearchersdevotethemselvestothetreatmentofthesingularintegrals[2~3],whicharereviewedindetailbyRef.[4] .Ageneralregularizationalgorithmofevaluatingthephysicalquantitiesa… 相似文献