The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbu...The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation （DNS） of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the nearwall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Rer can be as low as 1000. The properties of the inner and outer peaks in the spanwise spec- tra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.展开更多
单步分裂迭代方法用于求解大型稀疏线性方程组时,迭代解的精度对迭代过程的收敛和方程组解的精度有很大影响.基于文献(参见[Bai Z Z,Rozlozník M.On the numerical behavior of matrix splitting iteration methods for solving li...单步分裂迭代方法用于求解大型稀疏线性方程组时,迭代解的精度对迭代过程的收敛和方程组解的精度有很大影响.基于文献(参见[Bai Z Z,Rozlozník M.On the numerical behavior of matrix splitting iteration methods for solving linear systems.SIAM J Numer Anal,2015,53(4):1716-1737.])的结果,对给定的精度,给出了一个估计最大外迭代步数的方法.数值实验结果表明,本文所给出的最大外迭代步数的估计与实际计算过程中达到相同精度所需的迭代步数非常接近.展开更多
基金supported by the National Natural Science Foundation of China (Grants 11302238, 11232011, 11572331, and 11490551)the support from the Strategic Priority Research Program (Grant XDB22040104)+1 种基金the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant QYZDJ-SSW-SYS002)the National Basic Research Program of China (973 Program 2013CB834100 : Nonlinear Science)
文摘The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation （DNS） of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the nearwall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number Rer can be as low as 1000. The properties of the inner and outer peaks in the spanwise spec- tra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.
基金supported by the National Natural Science Foundation of China(11571156)
文摘单步分裂迭代方法用于求解大型稀疏线性方程组时,迭代解的精度对迭代过程的收敛和方程组解的精度有很大影响.基于文献(参见[Bai Z Z,Rozlozník M.On the numerical behavior of matrix splitting iteration methods for solving linear systems.SIAM J Numer Anal,2015,53(4):1716-1737.])的结果,对给定的精度,给出了一个估计最大外迭代步数的方法.数值实验结果表明,本文所给出的最大外迭代步数的估计与实际计算过程中达到相同精度所需的迭代步数非常接近.
