Presence of different terms with various values can alter the thermal behavior of the nanofluids flow over porous surfaces.The aim of this research is to study the influence of nanoparticles volume fraction,nanopartic...Presence of different terms with various values can alter the thermal behavior of the nanofluids flow over porous surfaces.The aim of this research is to study the influence of nanoparticles volume fraction,nanoparticles type,suction or injection,the heat generation or absorption,the Eckert number,thermal and velocity slip parameters,and radiation on the velocity and temperature fields on the flow and heat transfer over a porous flat plate.Four different types of nanoparticles including metal nanoparticles (Cu),metal oxide nanoparticles (Al2O3) and carbon-based nanomaterials (MWCNTs and SWCNTs) which were dispersed in the water (as based fluid) are studied.The governing equations are converted into the ordinary differential equations using similarity solution and solved numerically by the RKF45 algorithm.The results of the simulations showed a contradiction with the results of other researchers who expressed that using nanoparticles with higher thermal conductivity and volume fraction led to increasing heat transfer rate in nanofluids;this study proves that,in some cases,boosting the volume fraction of nanoparticles has a potential to decrease the heat transfer rate due to significant changes in values of some parameters including radiation,heat generation,and viscous dissipation.展开更多
A slip critical connection has various values to adopt the proper slip coefficient in various conditions of faying surfaces in AISC, AIJ and Eurocode3. The Korean Building Code regulates the unique slip coefficient, f...A slip critical connection has various values to adopt the proper slip coefficient in various conditions of faying surfaces in AISC, AIJ and Eurocode3. The Korean Building Code regulates the unique slip coefficient, from 0.45 to 0.5 without consideration of the diverse faying conditions in 2009. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The slip coefficient of specimens over zinc primer thickness of 128 lam exhibit was 0.42. The clean mill treated surface had prominently lower values as slip coefficient, 0.27. For red lead painted treatment, it is suggested to setup a minimum slip coefficient, 0,21, below a coating thickness of 65 μam. The slip coefficient of one faced lap connection was higher 1.4 times than the slip coefficient of two faced lap connection.展开更多
A theoretical model extended from the Frenkel-Eyring molecular kinetic theory(MKT)was applied to describe the boundary slip on textured surfaces.The concept of the equivalent depth of potential well was adopted to cha...A theoretical model extended from the Frenkel-Eyring molecular kinetic theory(MKT)was applied to describe the boundary slip on textured surfaces.The concept of the equivalent depth of potential well was adopted to characterize the solid-liquid interactions on the textured surfaces.The slip behaviors on both chemically and topographically textured surfaces were investigated using molecular dynamics(MD)simulations.The extended MKT slip model is validated by our MD simulations under various situations,by constructing different complex surfaces and varying the surface wettability as well as the shear stress exerted on the liquid.This slip model can provide more comprehensive understanding of the liquid flow on atomic scale by considering the influence of the solid-liquid interactions and the applied shear stress on the nano-flow.Moreover,the slip velocity shear-rate dependence can be predicted using this slip model,since the nonlinear increase of the slip velocity under high shear stress can be approximated by a hyperbolic sine function.展开更多
文摘Presence of different terms with various values can alter the thermal behavior of the nanofluids flow over porous surfaces.The aim of this research is to study the influence of nanoparticles volume fraction,nanoparticles type,suction or injection,the heat generation or absorption,the Eckert number,thermal and velocity slip parameters,and radiation on the velocity and temperature fields on the flow and heat transfer over a porous flat plate.Four different types of nanoparticles including metal nanoparticles (Cu),metal oxide nanoparticles (Al2O3) and carbon-based nanomaterials (MWCNTs and SWCNTs) which were dispersed in the water (as based fluid) are studied.The governing equations are converted into the ordinary differential equations using similarity solution and solved numerically by the RKF45 algorithm.The results of the simulations showed a contradiction with the results of other researchers who expressed that using nanoparticles with higher thermal conductivity and volume fraction led to increasing heat transfer rate in nanofluids;this study proves that,in some cases,boosting the volume fraction of nanoparticles has a potential to decrease the heat transfer rate due to significant changes in values of some parameters including radiation,heat generation,and viscous dissipation.
文摘A slip critical connection has various values to adopt the proper slip coefficient in various conditions of faying surfaces in AISC, AIJ and Eurocode3. The Korean Building Code regulates the unique slip coefficient, from 0.45 to 0.5 without consideration of the diverse faying conditions in 2009. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The slip coefficient of specimens over zinc primer thickness of 128 lam exhibit was 0.42. The clean mill treated surface had prominently lower values as slip coefficient, 0.27. For red lead painted treatment, it is suggested to setup a minimum slip coefficient, 0,21, below a coating thickness of 65 μam. The slip coefficient of one faced lap connection was higher 1.4 times than the slip coefficient of two faced lap connection.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1262103,11302218 and 11172289)Anhui Provincial Natural Science Foundation(Grant Nos.1308085QA10 and 1408085J08)the Fundamental Research Funds for the Central Universities of China
文摘A theoretical model extended from the Frenkel-Eyring molecular kinetic theory(MKT)was applied to describe the boundary slip on textured surfaces.The concept of the equivalent depth of potential well was adopted to characterize the solid-liquid interactions on the textured surfaces.The slip behaviors on both chemically and topographically textured surfaces were investigated using molecular dynamics(MD)simulations.The extended MKT slip model is validated by our MD simulations under various situations,by constructing different complex surfaces and varying the surface wettability as well as the shear stress exerted on the liquid.This slip model can provide more comprehensive understanding of the liquid flow on atomic scale by considering the influence of the solid-liquid interactions and the applied shear stress on the nano-flow.Moreover,the slip velocity shear-rate dependence can be predicted using this slip model,since the nonlinear increase of the slip velocity under high shear stress can be approximated by a hyperbolic sine function.
