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
The present paper proposes a new scheme for identifying free surface particles in an improved SPH (Smoothed Particle Hydrodynamics). With the development of the SPH, free surface identification becomes a key challenge...The present paper proposes a new scheme for identifying free surface particles in an improved SPH (Smoothed Particle Hydrodynamics). With the development of the SPH, free surface identification becomes a key challenge in free surface flow simulations, especially for violent breaking water waves. According to numerical tests, existing free surface identified schemes are not reliable for weakly compressible SPH when violent waves are modeled. The new free surface identification scheme suggested here considers changes in density ratio and three auxiliary functions. Although this new scheme originates from a scheme for another meshfree method (MLPG_R method), it includes several improvements, especially developed for the improved SPH. The limited numerical tests have indicated that the scheme does not significantly increase CPU time required, but it considerably improves the identification of free surface particles.展开更多
Recently, cavity optomechanics has become a rapidly developing research field exploring the coupling between the optical field and mechanical oscillation. Cavity optomechanical systems were predicted to exhibit rich a...Recently, cavity optomechanics has become a rapidly developing research field exploring the coupling between the optical field and mechanical oscillation. Cavity optomechanical systems were predicted to exhibit rich and nontrivial effects due to the nonlinear optomechanical interaction. However, most progress during the past years have focused on the linearization of the optomechanical interaction, which ignored the intrinsic nonlinear nature of the optomechanical coupling. Exploring nonlinear optomechanical interaction is of growing interest in both classical and quantum mechanisms, and nonlinear optomechanical interaction has emerged as an important new frontier in cavity optomechanics. It enables many applications ranging from single-photon sources to generation of nonclassical states. Here, we give a brief review of these developments and discuss some of the current challenges in this field.展开更多
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.
基金supported by the National Natural Science Foundation of China (Grant No. 51009034)Foundational Research Funds for the Central Universities (Grant No. HEUCF100102)111 Program (Grant No.B07019)
文摘The present paper proposes a new scheme for identifying free surface particles in an improved SPH (Smoothed Particle Hydrodynamics). With the development of the SPH, free surface identification becomes a key challenge in free surface flow simulations, especially for violent breaking water waves. According to numerical tests, existing free surface identified schemes are not reliable for weakly compressible SPH when violent waves are modeled. The new free surface identification scheme suggested here considers changes in density ratio and three auxiliary functions. Although this new scheme originates from a scheme for another meshfree method (MLPG_R method), it includes several improvements, especially developed for the improved SPH. The limited numerical tests have indicated that the scheme does not significantly increase CPU time required, but it considerably improves the identification of free surface particles.
基金supported by the National Natural Fundamental Research Program of China(Grant No.2012CB922103)the National Science Foundation of China(Grant Nos.11375067,11275074,11374116,11204096 and 11405061)the Fundamental Research Funds for the Central Universities HUST(Grant No.2014QN193)
文摘Recently, cavity optomechanics has become a rapidly developing research field exploring the coupling between the optical field and mechanical oscillation. Cavity optomechanical systems were predicted to exhibit rich and nontrivial effects due to the nonlinear optomechanical interaction. However, most progress during the past years have focused on the linearization of the optomechanical interaction, which ignored the intrinsic nonlinear nature of the optomechanical coupling. Exploring nonlinear optomechanical interaction is of growing interest in both classical and quantum mechanisms, and nonlinear optomechanical interaction has emerged as an important new frontier in cavity optomechanics. It enables many applications ranging from single-photon sources to generation of nonclassical states. Here, we give a brief review of these developments and discuss some of the current challenges in this field.