Permanent magnet tubular linear motors(TLMs) arranged in multiple rows and multiple columns used for a radiotherapy machine were studied. Due to severe volumetric and thermal constraints, the TLMs were at high risk of...Permanent magnet tubular linear motors(TLMs) arranged in multiple rows and multiple columns used for a radiotherapy machine were studied. Due to severe volumetric and thermal constraints, the TLMs were at high risk of overheating. To predict the performance of the TLMs accurately, a multi-physics analysis approach was proposed. Specifically, it considered the coupling effects amongst the electromagnetic and the thermal models of the TLMs, as well as the fluid model of the surrounding air. To reduce computation cost, both the electromagnetic and the thermal models were based on lumped-parameter methods. Only a minimum set of numerical computation(computational fluid dynamics, CFD) was performed to model the complex fluid behavior. With the proposed approach, both steady state and transient state temperature distributions, thermal rating and permissible load can be predicted. The validity of this approach is verified through the experiment.展开更多
A 3D numerical investigation has been carried out to examine periodic laminar flow and heat transfer characteristics in a circular tube with 45°V-baffles with isothermal wall.The computations are based on the fin...A 3D numerical investigation has been carried out to examine periodic laminar flow and heat transfer characteristics in a circular tube with 45°V-baffles with isothermal wall.The computations are based on the finite volume method(FVM),and the SIMPLE algorithm has been implemented.The fluid flow and heat transfer characteristics are presented for Reynolds numbers ranging from 100 to 2000.To generate main longitudinal vortex flows through the tested section,V-baffles with an attack angle of 45°are mounted in tandem and in-line arrangement on the opposite positions of the circular tube.Effects of tube blockage ratio,flow direction on heat transfer and pressure drop in the tube are studied.It is apparent that a pair of longitudinal twisted vortices(P-vortex)created by a V-baffle can induce impingement on a wall of the inter-baffle cavity and lead a drastic increase in heat transfer rate at tube wall.In addition,the larger blockage ratio results in the higher Nusselt number and friction factor values.The computational results show that the optimum thermal enhancement factor is around 3.20 at baffle height of B=0.20 and B=0.25 times of the tube diameter for the V-upstream and V-downstream,respectively.展开更多
An unstructured Reynolds-averaged Navier-Stokes flow solver using the finite volume method is studied. The spatial discretisation is based on the Osher approximate Riemann solvers. A two-equation turbulence model (k-...An unstructured Reynolds-averaged Navier-Stokes flow solver using the finite volume method is studied. The spatial discretisation is based on the Osher approximate Riemann solvers. A two-equation turbulence model (k-ω model) is also developed for hybrid grids to compute the turbulence flow. The turbulence flow past NACA0012 airfoil and the double ellipsolids are computed, and the numerical results show that the above methods are very efficient.展开更多
Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR1...Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR108 and KCS in 120 degree regular oblique wave conditions. WISDAM has the capability of handling 6DOF （six degrees of freedom） in ship motions. Finite volume method with structured and overlapping grid system is employed. The flow variables are described in staggered manner, i.e., velocity components arc defined at the face center while pressure is at the cell center. Computational results agree favorably well with existing towing tank results especially for ship motions. Computational results also show that ship with bulbous bow experience higher hydrodynamic loads on bow section.展开更多
The governing equations are derived by circumferentially averaging the three-dimensional （3D） Navier-Stokes equations, which are solved using a time marching finite volume approach. Both Euler throughflow model and ...The governing equations are derived by circumferentially averaging the three-dimensional （3D） Navier-Stokes equations, which are solved using a time marching finite volume approach. Both Euler throughflow model and Navier-Stokes （N-S） throughflow model are employed to investigate the performance and flow fields of a highly loaded transonic single-stage fan ATS-2 and a four-stage fan. The results are compared with the experimental and three-dimensional computational results. It shows that the throughflow models can provide reasonable perform- ance characteristics and N-S throughflow model gives better predictions in endwall regions. A throughflow com- putation in which all the non-axisymmetric terms are included has been performed at off-design condition and the radial distributions of the flow field can be well described.展开更多
基金Project(2015BAI03B00)supported by the National Key Technology R&D Program of ChinaProject(Z141100000514015)supported by Science and Technology Planning Program of Beijing,ChinaProject(SKLT12A03)supported by Tribology Science Fund of State Key Laboratory of Tribology,China
文摘Permanent magnet tubular linear motors(TLMs) arranged in multiple rows and multiple columns used for a radiotherapy machine were studied. Due to severe volumetric and thermal constraints, the TLMs were at high risk of overheating. To predict the performance of the TLMs accurately, a multi-physics analysis approach was proposed. Specifically, it considered the coupling effects amongst the electromagnetic and the thermal models of the TLMs, as well as the fluid model of the surrounding air. To reduce computation cost, both the electromagnetic and the thermal models were based on lumped-parameter methods. Only a minimum set of numerical computation(computational fluid dynamics, CFD) was performed to model the complex fluid behavior. With the proposed approach, both steady state and transient state temperature distributions, thermal rating and permissible load can be predicted. The validity of this approach is verified through the experiment.
基金Supported by the King Mongkut's Institute of Technology Ladkrabang research fund,Thailand(KREF015611)
文摘A 3D numerical investigation has been carried out to examine periodic laminar flow and heat transfer characteristics in a circular tube with 45°V-baffles with isothermal wall.The computations are based on the finite volume method(FVM),and the SIMPLE algorithm has been implemented.The fluid flow and heat transfer characteristics are presented for Reynolds numbers ranging from 100 to 2000.To generate main longitudinal vortex flows through the tested section,V-baffles with an attack angle of 45°are mounted in tandem and in-line arrangement on the opposite positions of the circular tube.Effects of tube blockage ratio,flow direction on heat transfer and pressure drop in the tube are studied.It is apparent that a pair of longitudinal twisted vortices(P-vortex)created by a V-baffle can induce impingement on a wall of the inter-baffle cavity and lead a drastic increase in heat transfer rate at tube wall.In addition,the larger blockage ratio results in the higher Nusselt number and friction factor values.The computational results show that the optimum thermal enhancement factor is around 3.20 at baffle height of B=0.20 and B=0.25 times of the tube diameter for the V-upstream and V-downstream,respectively.
文摘An unstructured Reynolds-averaged Navier-Stokes flow solver using the finite volume method is studied. The spatial discretisation is based on the Osher approximate Riemann solvers. A two-equation turbulence model (k-ω model) is also developed for hybrid grids to compute the turbulence flow. The turbulence flow past NACA0012 airfoil and the double ellipsolids are computed, and the numerical results show that the above methods are very efficient.
文摘Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR108 and KCS in 120 degree regular oblique wave conditions. WISDAM has the capability of handling 6DOF （six degrees of freedom） in ship motions. Finite volume method with structured and overlapping grid system is employed. The flow variables are described in staggered manner, i.e., velocity components arc defined at the face center while pressure is at the cell center. Computational results agree favorably well with existing towing tank results especially for ship motions. Computational results also show that ship with bulbous bow experience higher hydrodynamic loads on bow section.
基金supported by National Natural Science Foundation of China (50736007, 51006005)
文摘The governing equations are derived by circumferentially averaging the three-dimensional （3D） Navier-Stokes equations, which are solved using a time marching finite volume approach. Both Euler throughflow model and Navier-Stokes （N-S） throughflow model are employed to investigate the performance and flow fields of a highly loaded transonic single-stage fan ATS-2 and a four-stage fan. The results are compared with the experimental and three-dimensional computational results. It shows that the throughflow models can provide reasonable perform- ance characteristics and N-S throughflow model gives better predictions in endwall regions. A throughflow com- putation in which all the non-axisymmetric terms are included has been performed at off-design condition and the radial distributions of the flow field can be well described.
