Entropy generation for thermally developing forced convection in a porous medium bounded by two isothermal parallel plates is investigated analytically on the basis of the Darcy flow model where the viscous dissipatio...Entropy generation for thermally developing forced convection in a porous medium bounded by two isothermal parallel plates is investigated analytically on the basis of the Darcy flow model where the viscous dissipation effects had also been taken into account. A parametric study showed that decreasing the group parameter and the Peclet number increases the entropy generation while for the Brinkman number the converse is true. Heatline visualization technique is applied with an emphasis on the Br 〈 0 case where there is somewhere that heat transfer changes direction at some streamwise location to the wall instead of its original direction, i.e., from the wall.展开更多
A dominant role played by energy dispersion in the explosive development of extratropical marine cyclones over the Northwest Pacific has been revealed based on both the eddy energy equations and the energy flux vector...A dominant role played by energy dispersion in the explosive development of extratropical marine cyclones over the Northwest Pacific has been revealed based on both the eddy energy equations and the energy flux vectors of nonlinear wave packet.At the initial and explosive time. the eddy energy from neighboring upstream systems beyond the radius of Rossby deformation is dispersed into the eddy energy center associated with the cyclone via ageostrophic geopotential fluxes,and results in the rapid increase of eddy kinetic energy and the occurrence of explosive cyclogenesis.When the cyclone begins to decay,its corresponding eddy energy is exported downstream and hence triggers the growth of new perturbation downstream.Through generalizing the energy flux vectors of quasigeostrophic wave packets to the nonlinear forms and making use of the relationship between the energy flux vectors and the total eddy energy,the approximation expressions of the total group velocity and relative group velocity are derived,and then they are used to compute an explosive case.The normalized ageostrophic geopotential fluxes by dividing the volume integral of ageostrophic geopotential fluxes by the integral of the total eddy energy determine the relative group velocity at which the eddy energy is spreading out,and they can be used to evaluate the position of next new disturbance.The nonlinear advective fluxes influence primarily the phase speed and translation of the cyclones.The results in this paper facilitate to expanding the mechanism research on explosive cyclones and have great significance for predicting the explosive intensification and downstream disturbance growth.展开更多
文摘Entropy generation for thermally developing forced convection in a porous medium bounded by two isothermal parallel plates is investigated analytically on the basis of the Darcy flow model where the viscous dissipation effects had also been taken into account. A parametric study showed that decreasing the group parameter and the Peclet number increases the entropy generation while for the Brinkman number the converse is true. Heatline visualization technique is applied with an emphasis on the Br 〈 0 case where there is somewhere that heat transfer changes direction at some streamwise location to the wall instead of its original direction, i.e., from the wall.
文摘A dominant role played by energy dispersion in the explosive development of extratropical marine cyclones over the Northwest Pacific has been revealed based on both the eddy energy equations and the energy flux vectors of nonlinear wave packet.At the initial and explosive time. the eddy energy from neighboring upstream systems beyond the radius of Rossby deformation is dispersed into the eddy energy center associated with the cyclone via ageostrophic geopotential fluxes,and results in the rapid increase of eddy kinetic energy and the occurrence of explosive cyclogenesis.When the cyclone begins to decay,its corresponding eddy energy is exported downstream and hence triggers the growth of new perturbation downstream.Through generalizing the energy flux vectors of quasigeostrophic wave packets to the nonlinear forms and making use of the relationship between the energy flux vectors and the total eddy energy,the approximation expressions of the total group velocity and relative group velocity are derived,and then they are used to compute an explosive case.The normalized ageostrophic geopotential fluxes by dividing the volume integral of ageostrophic geopotential fluxes by the integral of the total eddy energy determine the relative group velocity at which the eddy energy is spreading out,and they can be used to evaluate the position of next new disturbance.The nonlinear advective fluxes influence primarily the phase speed and translation of the cyclones.The results in this paper facilitate to expanding the mechanism research on explosive cyclones and have great significance for predicting the explosive intensification and downstream disturbance growth.
