非线性优化的保单调差分格式

采用保单调思想，结合非线性优化，构造了六阶精度的保单调差分格式(OMP6). 格式构造过程中采用非线性Forier 分析对格式的色散及耗散误差进行了优化。通过Shu-Osher,双Mach 反射以及RT不稳定性等算例对该格式进行了验证。算例表明，与常用的WENO 等格式相比，该格式(OMP6)具有格式简洁、计算量小、分辨率高等优点

优化的保单调差分格式及激波/湍流边界层干扰的直接数值模拟

基于色散及耗散的非线性优化及保单调技术,构造了6阶精度的优化保单调差分格式(OMP6)。通过Shu-Osher,双Mach反射,R-T不稳定问题对格式进行了测试。算例表明,与目前常用的7阶WENO格式相比,OMP6在激波及小尺度波分辨率上具有一定优势,且计算效率有了明显提高,是进行可压缩复杂流动高分辨率数值模拟的良好候选方法。运用该方法,进行了激波-湍流边界层干扰的直

我国生物地理学研究进展

生物地理学研究是生物学和地理学交叉非常明显的部门自然地理学学科,它具有很强的基础研究特点,同时研究成果也具有很大的应用潜力。近年来,我国生物地理学基础研究在国家自然科学基金委等部门的支持下,在山地植被与地理环境、干旱半干旱区植被与地理环境、植物区系、植物物候、土壤动物与土壤生态功能、土壤生物结皮等方面开展了全面而深入的研究。同时拓展了传统生物地理学的研究方向,在植物地理学与全球变化、植物地理学与生物多样性保护、植物地理学与生态系统管理等方面也开展了大量研究。尤为可贵的是干旱半干旱区土壤生物结皮研究、典型温带荒漠区原生荒漠植被对水分改变的响应与适应研究取得了令国内外关注的高水平研究成果

Optimized sixth-order monotonicity-preserving scheme by nonlinear spectral analysis

In this paper, sixth-order monotonicity-preserving optimized scheme (OMP6) for the numerical solution of conservation laws is developed on the basis of the dispersion and dissipation optimization and monotonicity-preserving technique. The nonlinear spectral analysis method is developed and is used for the purpose of minimizing the dispersion errors and controlling the dissipation errors. The new scheme (OMP6) is simple in expression and is easy for use in CFD codes. The suitability and accuracy of this new scheme have been tested through a set of one-dimensional, two-dimensional, and three-dimensional tests, including the one-dimensional Shu-Osher problem, the two-dimensional double Mach reflection, and the Rayleigh-Taylor instability problem, and the three-dimensional direct numerical simulation of decaying compressible isotropic turbulence. All numerical tests show that the new scheme has robust shock capturing capability and high resolution for the small-scale waves due to fewer numerical dispersion and dissipation errors. Moreover, the new scheme has higher computational efficiency than the well-used WENO schemes

飞行器复杂流动高精度数值方法研究

介绍了作者近期开发的高精度数值方法，包括修正的加权群速度控制格式（WGVC-M），优化的MUSCL 格式(OMUSCL2)以及有限差分-有限体积混合方法。WGVC-M 格式是基于群速度控制、色散优化及加权思想构造的一种高精度差分格式。算例表明，与同阶精度的WENO 格式相比，WGVC-M 格式具有更好的激波及尺度分辨率。OMUSCL2 格式是对传统MUSCL 格式进行优化后得到的一种有限体积重构方法。算例表明OMUSCL2 在不增加重构基架点数及基本不增加计算量的情况下，降低了原MUSCL 格式的耗散及色散误差，并提高了激波分辨率。为了充分利用有限差分及有限体积方法各自的优点，作者构造了基于多块结构网格的有限体积-有限差分混合方法。该方法兼具有限差分的高精度及有限体积可适应复杂网格的优点，可用于复杂几何多尺度流场的数值模拟

Optimization of MUSCL scheme by dispersion and dissipation

A second-order monotonicity-preserving optimized MUSCL scheme (OMUSCL2) isdeveloped based on dispersion and dissipation optimization and monotonicity-preservingtechnique. The new scheme (OMUSCL2) has simple expression and is easy to be used in CFDcodes. Compared with the original second-order or third-order MUSCL scheme, the new schemeshows nearly the same CPU costs and higher resolution to shockwaves and small-scale waves.We test the new scheme through a set of one-dimensional and two-dimensional tests, includingthe Shu-Osher problem, the sod problem, the Lax problem, two dimension double Machreflection and RAE2822 transonic airfoil test. All numerical tests show that, compared withoriginal MUSCL schemes, the new scheme has less dispersion error, less dissipation error andhigher resolution

Experimental and numerical study on gas outburst with soil under gas expansion

The outburst fragmentation of soil caused by the dissociation of the gas hydrate was studied based on experiments and numerical simulation. The dense discrete particle model (DDPM) combined with the kinetic theory of granular flow (KTGF) was presented to reveal the outburst morphology of soil, considering the interphase forces and frictional effect between soil particles. The numerical simulation results in geometric features are consistent with the high-speed photography results. Moreover, the effects of initial gas pressure and thicknesses of the overlying layer on the occurrence of gas outburst were investigated in the experiments. © 2021 by the International Society of Offshore and Polar Engineers (ISOPE)

Optimization of the MUSCL scheme by dispersion and dissipation

A second-order optimized monotonicity-preserving MUSCL scheme (OMUSCL2) is developed based on the dispersion and dissipation optimization and monotonicity-preserving technique. The new scheme (OMUSCL2) is simple in expression and is easy for use in CFD codes. Compared with the original second-order or third-order MUSCL scheme, the new scheme shows nearly the same CPU cost and higher resolution to shockwaves and small-scale waves. This new scheme has been tested through a set of one-dimensional and two-dimensional tests, including the Shu-Osher problem, the Sod problem, the Lax problem, the two-dimensional double Mach reflection and the RAE2822 transonic airfoil test. All numerical tests show that, compared with the original MUSCL schemes, the new scheme causes fewer dispersion and dissipation errors and produces higher resolution. </div

Experimental and Numerical Study of Gas Outburst with Soil Under Gas Expansion

The outburst fragmentation of soil caused by the dissociation of the gas hydrate was studied via experiments and numerical simulation. The dense discrete particle model combined with the kinetic theory of granular flow was presented to reveal the outburst morphology of soil, considering the interphase forces and frictional effect between soil particles. The numerical simulation results in geometric features are consistent with the experimental results. The diameter of the gas outburst with soil can be predicted by the model, and the rule of the particle velocity can be obtained by the simulation. Moreover, the effects of initial gas pressure and thicknesses of the overlying layer on the occurrence of gas outbursts were investigated in the experiments