Renormalization group theory applied to turbulence will be reviewed in this article.Techniques associated are used for analyzing thermally-induced turbulence.Transport properties such as effective viscosity and therma...Renormalization group theory applied to turbulence will be reviewed in this article.Techniques associated are used for analyzing thermally-induced turbulence.Transport properties such as effective viscosity and thermal diffusivity are derived.展开更多
Strongly swirl flow simulation are still under deve1oping. In this paper, ε equation based on the Renormalization. Group theory is used into algebraic stress model. Standard κ-ε model, algebraic stress model by Jia...Strongly swirl flow simulation are still under deve1oping. In this paper, ε equation based on the Renormalization. Group theory is used into algebraic stress model. Standard κ-ε model, algebraic stress model by Jiang Zhang[5]. and present model (RNG-ASM) are applied simultaneously to simulating the confined strongly swirling flow. The Simulating results by RNG-ASM model are compared to the results by other two model, it is shown that the predictions by this model display reasonable agreement with experimental data, and lead to gnater improvement than Zhang’s ASM turbulence model[5].展开更多
In this paper,the dynamic characteristics of building clusters are simulated by large eddy simulation at high Reynolds number for both homogeneous and heterogeneous building clusters.To save the computational cost a c...In this paper,the dynamic characteristics of building clusters are simulated by large eddy simulation at high Reynolds number for both homogeneous and heterogeneous building clusters.To save the computational cost a channel-like flow model is applied to the urban canopy with free slip condition at the upper boundary.The results show that the domain height is an important parameter for correct evaluation of the dynamic characteristics.The domain height must be greater than 8h(h is the average building height)in order to obtain correct roughness height while displacement height and roughness sublayer are less sensitive to the domain height.The Reynolds number effects on the dynamic characteristics and flow patterns are investigated.The turbulence intensity is stronger inside building cluster at high Reynolds number while turbulence intensity is almost unchanged with Reynolds number above the building cluster.Roughness height increases monotonously with Reynolds number by 20%from Re*=103 to Re*=105 but displacement height is almost unchanged.Within the canopy layer of heterogeneous building clusters,flow structures vary between buildings and turbulence is more active at high Reynolds number.展开更多
A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures. The fluid phase is calculated by large eddy simulation and particles are tracked using L...A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures. The fluid phase is calculated by large eddy simulation and particles are tracked using Lagrangian trajectory method. The flow Reynolds number is 180 based on the friction velocity and half-width of the channel. The particle is lycopodium with St=0.93 which may well follow the fluid phase. The mean and fluctuating velocities of both two phases are obtained, which are in good agreement with previous data. The strongest accumulations of particles in low-speed streak structures are observed at y~=l 1.3. Moreover, once particles are captured in low-speed streaks, most of them will reside there for a long period. Particles clustered in low-speed streaks obtain smaller instantaneous wall-normal and spanwise velocities than those out of there, which induce a larger particle flux into low-speed streaks than that out of there. The study is important for understanding particle dispersion mechanisms in gas-particle turbulent channel flows.展开更多
文摘Renormalization group theory applied to turbulence will be reviewed in this article.Techniques associated are used for analyzing thermally-induced turbulence.Transport properties such as effective viscosity and thermal diffusivity are derived.
文摘Strongly swirl flow simulation are still under deve1oping. In this paper, ε equation based on the Renormalization. Group theory is used into algebraic stress model. Standard κ-ε model, algebraic stress model by Jiang Zhang[5]. and present model (RNG-ASM) are applied simultaneously to simulating the confined strongly swirling flow. The Simulating results by RNG-ASM model are compared to the results by other two model, it is shown that the predictions by this model display reasonable agreement with experimental data, and lead to gnater improvement than Zhang’s ASM turbulence model[5].
基金supported by the University of Macao(Grant No.MYRG157(Y3-L2)-FST11-WZS)the National Natural Science Foundation of China(Grant No.11132005),+1 种基金MOST-2011BAK07B01-03,LIAMA Project TIPEthe National Laboratory for Information Science and Technology
文摘In this paper,the dynamic characteristics of building clusters are simulated by large eddy simulation at high Reynolds number for both homogeneous and heterogeneous building clusters.To save the computational cost a channel-like flow model is applied to the urban canopy with free slip condition at the upper boundary.The results show that the domain height is an important parameter for correct evaluation of the dynamic characteristics.The domain height must be greater than 8h(h is the average building height)in order to obtain correct roughness height while displacement height and roughness sublayer are less sensitive to the domain height.The Reynolds number effects on the dynamic characteristics and flow patterns are investigated.The turbulence intensity is stronger inside building cluster at high Reynolds number while turbulence intensity is almost unchanged with Reynolds number above the building cluster.Roughness height increases monotonously with Reynolds number by 20%from Re*=103 to Re*=105 but displacement height is almost unchanged.Within the canopy layer of heterogeneous building clusters,flow structures vary between buildings and turbulence is more active at high Reynolds number.
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.11132005)the National Natural Science Foundation of China(Grant No.50876053)Opening Fund of State of Key Laboratory of Nonlinear Mechanics
文摘A particle-laden turbulent channel flow is investigated to study particle clusters in large-scale turbulent coherent structures. The fluid phase is calculated by large eddy simulation and particles are tracked using Lagrangian trajectory method. The flow Reynolds number is 180 based on the friction velocity and half-width of the channel. The particle is lycopodium with St=0.93 which may well follow the fluid phase. The mean and fluctuating velocities of both two phases are obtained, which are in good agreement with previous data. The strongest accumulations of particles in low-speed streak structures are observed at y~=l 1.3. Moreover, once particles are captured in low-speed streaks, most of them will reside there for a long period. Particles clustered in low-speed streaks obtain smaller instantaneous wall-normal and spanwise velocities than those out of there, which induce a larger particle flux into low-speed streaks than that out of there. The study is important for understanding particle dispersion mechanisms in gas-particle turbulent channel flows.
