本文对1998年南海季风实验中定点观测的声学多普勒流速剖面仪(Acoustic Doppler Current Profiler,AD-CP)海流数据进行频谱分析,结果表明南海北部地区内波之间的非线性作用的强弱影响着该海域的内波谱特征。在季节性温跃层(水深22m和58m...本文对1998年南海季风实验中定点观测的声学多普勒流速剖面仪(Acoustic Doppler Current Profiler,AD-CP)海流数据进行频谱分析,结果表明南海北部地区内波之间的非线性作用的强弱影响着该海域的内波谱特征。在季节性温跃层(水深22m和58m)中,由于存在着强的非线性作用,内波带的谱斜率趋于σ-1和σ-2之间,而且较高能量的潮谐波频率的峰值随着频率呈现少见的σ-3递减。在季节性温跃层(水深130m)以下,内波非线性相互作用较弱,观测的内波带谱特征与标准Garrett-Munk内波谱相似,均显示了σ-2的谱斜率。展开更多
Most previous studies about chaotic mixing focused on time-periodic or spatialy-periodic flows.In contrary,fewer studies have been done in aperiodic flows.In this paper,the chaotic mixing generated by periodic and ape...Most previous studies about chaotic mixing focused on time-periodic or spatialy-periodic flows.In contrary,fewer studies have been done in aperiodic flows.In this paper,the chaotic mixing generated by periodic and aperiodic flows is investigated through visible experiments and numerical simulations.The distribution of stretching is found to be much more uniform for apeiodic flows and mixing efficiency of aperiodic flows is higher than periodic flows.Among the several aperiodic sequences,the SB sequence is the best one.展开更多
Effect of fluid elasticity and shear-thinning viscosity on the chaotic mixing between two alternately rotating cylinders has been studied. The h-p finite element method is used to obtain high accurate solutions of the...Effect of fluid elasticity and shear-thinning viscosity on the chaotic mixing between two alternately rotating cylinders has been studied. The h-p finite element method is used to obtain high accurate solutions of the steady flow. The unsteady, periodic flow is simulated using the piecewise-steady approximation. Characteristics of the chaotic mixing are analyzed by examining the asymptotic coverage of a passive tracer and the lineal stretching of the fluid elements in the annulus. For the viscoelastic fluids modeled by the upper-convected Maxwell constitutive equation (UCM), our computation predicts little effect of the fluid elasticity on the mixing patterns. On the other hand, the shear-thinning viscosity, modeled by the Carreau equation, has a large impact on the advection of a passive tracer and the distribution of lineal stretching. We find that the zones of the lowest stretching match remarkably well with the regular zones in the tracer-coverage plotting. Our study reveals the vital importance of reducing the discretization errors of the velocity field in the numerical simulation of chaotic flews.展开更多
文摘本文对1998年南海季风实验中定点观测的声学多普勒流速剖面仪(Acoustic Doppler Current Profiler,AD-CP)海流数据进行频谱分析,结果表明南海北部地区内波之间的非线性作用的强弱影响着该海域的内波谱特征。在季节性温跃层(水深22m和58m)中,由于存在着强的非线性作用,内波带的谱斜率趋于σ-1和σ-2之间,而且较高能量的潮谐波频率的峰值随着频率呈现少见的σ-3递减。在季节性温跃层(水深130m)以下,内波非线性相互作用较弱,观测的内波带谱特征与标准Garrett-Munk内波谱相似,均显示了σ-2的谱斜率。
文摘Most previous studies about chaotic mixing focused on time-periodic or spatialy-periodic flows.In contrary,fewer studies have been done in aperiodic flows.In this paper,the chaotic mixing generated by periodic and aperiodic flows is investigated through visible experiments and numerical simulations.The distribution of stretching is found to be much more uniform for apeiodic flows and mixing efficiency of aperiodic flows is higher than periodic flows.Among the several aperiodic sequences,the SB sequence is the best one.
基金Supported by the National Natural Science Foundation of China (No. 29776039), Skloche PRE Laboratory of China and Cao Guangbiao Science Foundation of Zhejiang University.
文摘Effect of fluid elasticity and shear-thinning viscosity on the chaotic mixing between two alternately rotating cylinders has been studied. The h-p finite element method is used to obtain high accurate solutions of the steady flow. The unsteady, periodic flow is simulated using the piecewise-steady approximation. Characteristics of the chaotic mixing are analyzed by examining the asymptotic coverage of a passive tracer and the lineal stretching of the fluid elements in the annulus. For the viscoelastic fluids modeled by the upper-convected Maxwell constitutive equation (UCM), our computation predicts little effect of the fluid elasticity on the mixing patterns. On the other hand, the shear-thinning viscosity, modeled by the Carreau equation, has a large impact on the advection of a passive tracer and the distribution of lineal stretching. We find that the zones of the lowest stretching match remarkably well with the regular zones in the tracer-coverage plotting. Our study reveals the vital importance of reducing the discretization errors of the velocity field in the numerical simulation of chaotic flews.
