Lattice Boltzmann method is adopted to investigate mixed convection in an enclosure filled with porous medium.A heated cylinder (D/L=0.4) is located at center of the enclosure with high temperature.Inlet flow with low temperature is located at lower-left wall of the enclosure and exit is at upper-left wall.Other walls are assumed adiabatic.Influences of Richardson number Ri and Darcy number Da on average Nusselt number Nu around heated cylinder are investigated while Prandtl and Grashof numbers are kept at 0.71 and 1.4×10⁴, respectively.It indicates that Nu decreases with increasing Ri.Influence of Richardson number on Nu is significant as Darcy number is great.At 10^-5≤Da≤10^-2, Nu increases with increasing Darcy number as forced convection dominates flow (Ri≤0.1).As natural convection dominates flow (Ri=10), Nu is not sensitive to Darcy number.

Lattice Boltzmann method is adopted to numerically analyze nonlinear characteristics of double diffusive mixed convection in an enclosure. A heated cylinder is located at center of the enclosure. Fluid flows from an inlet at lower-left wall of enclosure and an outlet is at upper-right,upper-middle and upper-left wall respectively. Simulation results indicate that there are steady stationary solution,periodic and aperiodic oscillatory solutions in double diffusive mixed convection at different parameters. Phase path of velocity of monitoring point finally reaches a point,a closed loop and irregular curves,respectively.

Power coupled equations for a multi-wavelength broadband Raman amplifier (MBRA) are reasonably simplified.A multi-step average power method is used to compute composite Raman gain of multi-signal in a dense wavelength division multiplexed system (DWDM).A conventional simulated annealing algorithm is applied for optimization of MBRA.A simple object function is proposed considering the gain bandwidth,on-off gain,gain flatness and other characteristic parameters.Influences of the number of pump,input power and wavelength distribution on Raman gain are studied.Relations among gain bandwidth,on-off gain,gain flatness and the number of pump of MBRA are revealed.Simulation shows that the optimal signal bandwidth Δλ becomes boarder with the increasing of the number of pump and narrower with the increasing of Raman gain and the improvement of flatness.