In order to quantitatively evaluate water blocking damage of tight reservoirs in flowback period, based on the relationship between capillary pressure and relative permeability with water saturation, Darcy's formula was used to characterize gas-water two-phase flow equations in invaded areas, and a quantitative evaluation model of water blocking damage of fracturing fluid in tight reservoir was established. The water saturation, relative permeability and permeability damage degree of invaded areas in flowback period were solved by the Taylor's nonlinear solution method, and the effect of fracturing fluid invasion depth, fracturing fluid viscosity, flowback and production differential pressure and pressure sensitivity were analyzed. The results show that, water blocking damage starts to gradually be relieved once the pressure differential of flowback and production exceeds the capillary force. The higher the differential pressure between flowback and production, the more effectively water blockage can be relieved and the less damage water blockage can cause. It is challenging to release the water blockage at the flowback period when the invasion depth, viscosity, and stress sensitivity coefficient of the fracturing fluid are high. The higher the damage degree of the water blockage, the lower the recovery of gas will finally be.

A fast numerical algorithm for nonlinear finite sound beams is studied.Multiple couplings in nonlinear finite sound beams are found,including full coupling between the harmonics,recursive coupling between field points along the axial direction,and local coupling along the radial direction.Calculation efficiency is improved by a spatial-domain decomposition of acoustic field along radial direction.The method is achieved through a multi-threading parallel computation.Calculation results for nonlinear focused Gaussian beams show that as problem size and the number of threads are reasonablly matched,this algorithm can significantly improve calculation speed while ensuring accuracy.Calculation results are compared with theoretical analysis.

Based on the theoretical study of spatial coherence of laboratory x-ray lasers, a principle setup is proposed for x-ray laser holography, and corresponding theoretical simulation is performed for the recording and reconstruction of the lenseless Fourier transform hologram.

The efficiency of laser light energy absorbed by the coronal plasma of target is crucial to laser fusion. Using prepulse to irradiate target for increasing absorption efficiency of high intensity incident laser beam is considered and some theoretical simulations have been done. 1-D non-LTE radiative hydrodynamic code is used to simulate the interactions of laser beam with matter. The basic equations of this code are consisted of:the 1-D equations of radiative hydrodynamics, the average-atom population rate equations, the multigroup flux-limited diffusion equations for radiation transport, and the equations for deposition of laser light energy in plasma. The following physical processes are considered:the bremsstrahlung effect, radiative ionizations and recombinations, collisional ionizations by electrons and three-boby recombinations, collisional excitations and de-excitations by electrons, radiative line transitions and Compton scattering.A gaussian laser prepulse of wavelength 1.06μm, FWHM 600ps and peak intensity 1.5×10¹²W/cm² was used to irradiate thickness 20μm Au plate target, after 3ns a main gaussian pulsewith wavelength 1.06μm, FWHM 600ps and peak intensity 3.0×10¹⁴W/cm² irradiated the expanding Au plasma. The responces of laser-produced plasma conditions are shown. By comparison with without prepulsing, under the condition of same main incident laser pulse, the absorption efficiency is increased from 0.36 to 0.60 and the laser-x-ray conversion efficiency is increased from 0.16 to 0.25. The electron temperature of hot plasma is also higher than without prepulsing, and the x-ray spectrum which is emitted from laser-produced hot plasma is harder and more intense than without prepulsing. The responces of laser-produced plasma for Fe target with prepulsing are shown as well. The conclusion is that using prepulsing is useful way for getting high absorption laser beam.

The 1-D non-LTE radiative hydrodynamic laser irradiated code JB-19 is used to calculate the laser-produced plasma conditions of high z gold disk. Following physical processes are considered:bremsstrahlung effect, radiative ionization and recombination, collisional ionization by electrons and three-boby recombination, collisional excitation and de-excitation by electrons, radiative line emission and absorption and Compton scattering. A gaussian laser pulse with wavelength 1. 06μm, FWHM 600ps and peak intensity 3×10¹⁴W/cm² is used to irradiate thickness 20μm gold disk. The computational results for laser-produced plasma conditions and the absorption efficiency and laser-x-rays conversion efficiency for gold disk are shown.

In this paper we used one-dimentional non-LTE laser irradiated code to simulate the laser-produced plasmas conditions of thin middle Z targets with high intensities (about 10¹³W/cm²)irradiation.Following physical processes are considered; bremsstrahlung,radiative ionization,collisional ionization by electrons and their inverse processes, Compton scatterion. Fokker-Planck approximtaion is used in Compton scattering; The thermal flux limits are taken for electrons and ions in the calculating and the multigroup flux-limited diffusion approximation is taken for the radiative transport equations.Using average-atom model to calculate the population probabilities of atoms. Laser absorption via inverse bresstr-ahlung is considered to be the most important in our simulation.Using, laser beams with intensities 5×10¹³W/cm² and 1×10¹⁴ W/cm², λ_L=0.53μm, τ=450ps to irradiate thin Se target from single-side and double-sides separately, the computational results for laser-produced plasmas conditions are good agree with experimental results.

In this paper, the rate equetions of average atom model and hydrogen-like ions are discussed. At very high ionization they are equivalent. The emphasis is put on the investigation of using average atom model to calculate population inversions. Stripping the inner electrons with X-ray and recombining them to outer shell by three-body recombination, we can obtain the population inversions. Some conditions and results are given.