Suppression of auto-resonant stimulated Brillouin scattering in supersonic flowing plasmas by different forms of incident lasers

In supersonic flowing plasmas,the auto-resonant behavior of ion acoustic waves driven by stimulated Brillouin backscattering is self-consistently investigated.A nature of absolute instability appears in the evolution of the stimulated Brillouin backscattering.By adopting certain form of incident lights combined by two perpendicular linear polarization lasers or polarization rotation lasers,the absolute instability is suppressed significantly.The suppression of auto-resonant stimulated Brillouin scattering is verified with the fully kinetic Vlasov code.

Hydrodynamics of a dual-module pontoon-net floating breakwater system:Numerical simulations and prototype tests

Floating breakwaters with a mooring system have been widely applied to protect marine infrastructures(e.g.,artificial beach or island,aquaculture farm or marine vessels in harbors)from being destroyed by severe waves.In this paper,an innovative cylindrical dual pontoon-net floating breakwater was developed to enhance the wave attenuation capacity.This dual-module floating breakwater system was constructed as the prototype for on-site testing.A fully nonlinear time-domain model based on the coupled iterative solutions of the fluid integral equation and the pontoon-net dynamic equations was proposed to simulate the interactions between waves and the floating breakwater system.The flow field around the nets was simulated by introducing a porous-media model with Darcy’s law,while the deformation of the flexible nets was solved by using the lumped mass model.The instantaneous free surface was captured using the mixed Eulerian-Lagrangian(MEL)approach which employs an improved moving-grid technique based on the spring analysis to re-mesh the instantaneous water surface and the body wetted surface.On-site tests were also conducted to evaluate wave transmission performance of the floating breakwater system and to validate the numerical model.The comparisons show that the numerical solutions are in good agreement with the measured data.The effects of incident wave direction,wave period,wave height,net height,net number and net porosity on the hydrodynamic performance of the floating breakwater system were emphatically examined.

Water flooding optimization with adjoint model under control constraints

The oil recovery enhancement is a major technical issue in the development of oil and gas fields. The smart oil field is an effective way to deal with the issue. It can achieve the maximum profits in the oil production at a minimum cost, and represents the future direction of oil fields. This paper discusses the core of the smart field theory, mainly the real-time optimization method of the injection-production rate of water-oil wells in a complex oil-gas filtration system. Computing speed is considered as the primary prerequisite because this research depends very much on reservoir numerical simulations and each simulation may take several hours or even days. An adjoint gradient method of the maximum theory is chosen for the solution of the optimal control variables. Conven-tional solving method of the maximum principle requires two solutions of time series： the forward reservoir simulation and the backward adjoint gradient calculation. In this paper, the two processes are combined together and a fully implicit reservoir simulator is developed. The matrixes of the adjoint equation are directly obtained from the fully implicit reservoir simulation, which accelera-tes the optimization solution and enhances the efficiency of the solving model. Meanwhile, a gradient projection algorithm combined with the maximum theory is used to constrain the parameters in the oil field development, which make it possible for the method to be applied to the water flooding optimization in a real oil field. The above theory is tested in several reservoir cases and it is shown that a better development effect of the oil field can be achieved.

Inertial migration of aerosol particles in three-dimensional microfluidic channels

In recent years,manipulation of particles by inertial microfluidics has attracted significant attention.However,most studies focused on inertial focusing of particles suspended within liquid phase,in which the ratio of the density of the particle to that of the medium is O(1).The investigation on manipulation of aerosol particles in an inertial microfluidics is very limited.In this study,we numerically investigate the aerosol particle's motion in a 3D straight microchannel with rectangular cross section by fully resolved simulation of the particle-air flow.The air flow is modeled by the Navier-Stokes equations.The particle's motions,including translation and rotation,are governed,respectively,by the Newton's second law and the Euler equations without using any approximation models for the lift and drag forces.The coupled mathematical model is numerically solved by combining immersed boundary with lattice Boltzmann method(IB-LBM).We find that the Reynolds number(Re),the particle's initial position,particle's density and diameter are the influential parameters in this process.The equilibrium positions and their stabilities of aerosols are different from those suspended in liquid.