The near-wall domain decomposition method(NDD)has proved to be very efficient for modeling near-wall fully turbulent flows.In this paper the NDD is extended to non-equilibrium regimeswith laminar-turbulent transition(...The near-wall domain decomposition method(NDD)has proved to be very efficient for modeling near-wall fully turbulent flows.In this paper the NDD is extended to non-equilibrium regimeswith laminar-turbulent transition(LTT)for the first time.The LTT is identified with the use of the e^(N)-method which is applied to both incompressible and compressible flows.TheNDD ismodified to take into account LTT in an efficientway.In addition,implementation of the intermittency expands the capabilities of NDD to model non-equilibrium turbulent flows with transition.Performance of the modified NDD approach is demonstrated on various test problems of subsonic and supersonic flows past a flat plate,a supersonic flow over a compression corner and a planar shock wave impinging on a turbulent boundary layer.The results of modeling with and without decomposition are compared in terms of wall friction and show good agreement with each other while NDD significantly reducing computational resources needed.It turns out that the NDD can reduce the computational time as much as three times while retaining practically the same accuracy of prediction.展开更多
In this paper we analyze a long standing problem of the appearance of spurious,non-physical solutions arising in the application of the effective mass theory to low dimensional nanostructures.The theory results in a s...In this paper we analyze a long standing problem of the appearance of spurious,non-physical solutions arising in the application of the effective mass theory to low dimensional nanostructures.The theory results in a system of coupled eigenvalue PDEs that is usually supplemented by interface boundary conditions that can be derived from a variational formulation of the problem.We analyze such a system for the envelope functions and show that a failure to restrict their Fourier expansion coeffi-cients to small k components would lead to the appearance of non-physical solutions.We survey the existing methodologies to eliminate this difficulty and propose a simple and effective solution.This solution is demonstrated on an example of a two-band model for both bulk materials and low-dimensional nanostructures.Finally,based on the above requirement of small k,we derive a model for nanostructures with cylindrical symmetry and apply the developed model to the analysis of quantum dots using an eight-band model.展开更多
文摘The near-wall domain decomposition method(NDD)has proved to be very efficient for modeling near-wall fully turbulent flows.In this paper the NDD is extended to non-equilibrium regimeswith laminar-turbulent transition(LTT)for the first time.The LTT is identified with the use of the e^(N)-method which is applied to both incompressible and compressible flows.TheNDD ismodified to take into account LTT in an efficientway.In addition,implementation of the intermittency expands the capabilities of NDD to model non-equilibrium turbulent flows with transition.Performance of the modified NDD approach is demonstrated on various test problems of subsonic and supersonic flows past a flat plate,a supersonic flow over a compression corner and a planar shock wave impinging on a turbulent boundary layer.The results of modeling with and without decomposition are compared in terms of wall friction and show good agreement with each other while NDD significantly reducing computational resources needed.It turns out that the NDD can reduce the computational time as much as three times while retaining practically the same accuracy of prediction.
文摘In this paper we analyze a long standing problem of the appearance of spurious,non-physical solutions arising in the application of the effective mass theory to low dimensional nanostructures.The theory results in a system of coupled eigenvalue PDEs that is usually supplemented by interface boundary conditions that can be derived from a variational formulation of the problem.We analyze such a system for the envelope functions and show that a failure to restrict their Fourier expansion coeffi-cients to small k components would lead to the appearance of non-physical solutions.We survey the existing methodologies to eliminate this difficulty and propose a simple and effective solution.This solution is demonstrated on an example of a two-band model for both bulk materials and low-dimensional nanostructures.Finally,based on the above requirement of small k,we derive a model for nanostructures with cylindrical symmetry and apply the developed model to the analysis of quantum dots using an eight-band model.
