共查询到19条相似文献,搜索用时 218 毫秒
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针对柱坐标系下拉氏流体力学的动量方程,提出一种积分梯度格式IGTSP(Integral Gradient Total Symmetry-Preserving),它具备现有积分梯度格式IGA(Integral Gradient Average)和IGT(Integral Gradient Total)的优点,不仅克服了IGT格式不能保持柱坐标系下的一维球对称性的缺点,而且系统的总动量守恒误差为O(h),比IGA格式更好地保持系统的总动量守恒.数值试验进一步显示了该格式理论分析的优点. 相似文献
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广泛应用的二维直角坐标系下的Wilkins有限差分格式在计算一维柱面问题时,通过等角度划分周向网格能够获得严格的对称性,非等角度划分周向网格会产生较严重的不对称性.通过分析Wilkins有限差分格式在处理非等角度划分周向网格的一维柱面问题时破坏对称性的原因,指出周向网格的非等角度划分产生了周向压力分量,从而产生了周向加速度分量和周向运动速度,以此为基础提出一种对该有限差分格式进行修正的方法,将节点处的周向压力分量做算术平均运算,以消除周向压力分量,只剩径向压力分量起作用.因而该修正方法在以任意角度划分周向网格的条件下都能够保持严格的对称性.通过几个典型算例验证该结论,对对称流动,修正方法与原始方法所获得的结果一致,对非对称流动,二者有微小差异. 相似文献
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在移动网格上构造一种反应流的动理学格式.首先利用BGK模型推导含化学反应的流体力学方程组,并利用其积分形式构造移动网格上离散格式,再利用自适应移动网格方法得到网格速度,最后利用时间精确的动理学数值方法构造数值通量,得到移动网格单元上新的物理量.一维与二维的数值实验表明这种格式同时具有高精度、高分辨率的特点. 相似文献
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一维非线性对流占优扩散方程的变网格特征差分方法 总被引:1,自引:0,他引:1
针对一维非线性对流占优扩散方程,提出了一类变网格特征差分格式,该格式能够根据解的梯度变化及时对计算网格进行调整.与均匀网格格式相比,给出的变网格特征差分格式对于对流占优扩散问题有着更好的计算效果. 相似文献
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针对目前激光分束器只能产生小发散角的问题,基于严格的非傍轴近似的衍射积分公式,提出了一种大发散角分束器的设计方法.先对目标光场分布进行坐标和光强修整,再利用改进的GerchbergSaxton迭代算法得到所需分束器的相位分布.分别采用本文设计方法和原有方法设计了发散全角为40°×40°的5×5分束器,仿真和实验结果表明:原有方法设计得到的5×5子光束存在着显著的枕形畸变,并且光强分布不均匀.而本文方法设计得到的子光束呈均匀等间隔排列,并且强度分布更为均匀. 相似文献
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The Lorentz Integral Transform approach allows microscopic calculations of electromagnetic reaction cross-sections without explicit knowledge of final-state wave functions. The necessary inversion of the transform has to be treated with great care, since it constitutes a so-called ill-posed problem. In this work new inversion techniques for the Lorentz Integral Transform are introduced. It is shown that they all contain a regularization scheme, which is necessary to overcome the ill-posed problem. In addition, it is illustrated that the new techniques have a much broader range of application than the present standard inversion method of the Lorentz Integral Transform. 相似文献
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根据对流迎风分裂(AUSM)思想提出一种通量分裂方法,称为K-CUSP格式.它与传统H-CUSP和E-CUSP格式的最大差异在于总能量的分裂:K-CUSP格式将无粘守恒通量中所有的运动学量分裂到对流项,所有的热力学量分裂到压力项,即总能量被分裂成动能和静焓.对于压力项的数值通量,采用一种新的界面构造方法.数值测试表明:①K-CUSP格式继承了FVS格式的简单性和稳健性.在激波后不易出现压力过冲,在膨胀区域没有振荡,优于AUSM和WPS格式;②K-CUSP格式继承了FDS格式的分辨率.激波间断的分辨率和H-CUSP、E-CUSP格式基本相同,接触间断的分辨率高于FVS格式,低于Roe、AUSM和WPS格式.AUSM和WPS格式在计算运动接触间断时,速度存在很大振荡,而新格式不存在振荡. 相似文献
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非定常流动问题计算中常用到含三个时间层的二阶精度时间后差隐式格式,并且希望构成TVD格式,然而理论上的问题多年一直没有解决。本文找到了解决办法,构造了这种类型的隐式TVD格式,证明了其为TVD的充分条件。理论结果为计算所验证,并表明通常未采取本文对时间差分处理方法的格式尚不具备TVD性质。 相似文献
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Numerical Simulation for thermohaline multiple equilibrant system in non—rectangular domains 下载免费PDF全文
In this paper, incompressible, double-diffusive convection is simulated
using finite-difference schemes. The Navier--Stokes equations are
expressed in terms of stream function and vorticity. Because of
the existence of large velocity, temperature and salinity gradients
in boundary layers, a boundary-fitted coordinate system is used
to concentrate the grid points near the wall and fit complex
boundaries. The finite-difference methods used include the high-order
accurate upwind difference scheme. It is
shown that the scheme is a good candidate for direct simulations of
double-diffusive convection flows. The proposed method is first
applied to symmetry breaking and overturning states in
thermohaline-driven flows in trapezoid basins. The basic phenomena
agree well with those by Dijkstra and Molemaker (1997 {\em J. Fluid
Mech.} {\bf 331} 169)
and Quon and Ghil (1992 {\em J. Fluid Mech.} {\bf 245} 449), but symmetry breaking and
overturning states can occur in an asymmetric geometrical region
without perturbations. Then the method is applied to double-diffusive
convections in a cavity with opposing horizontal temperature and
concentration gradients at large thermal ($Rt$), solutal ($Rs$)
Rayleigh numbers and Lewis number. There are three straight sides
and a sine curve side in the cavity. Basically, numerical results
are in agreement with those of Lee and Hyun (1990 {\em Int. J. Heat
Mass Transfer} {\bf 33} 1619) qualitatively, but eddies mixing in the
top left-hand corner near the curved wall affects the layered structure. 相似文献
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Feng-Hua Liu Yong-Ming Li Yi Huang Jian Jing 《International Journal of Theoretical Physics》2009,48(7):1965-1972
Chern-Simons quantum mechanics is studied by using the path integral formulation. We find that the model can be decomposed
into two independent oscillators when a set of new coordinate is chosen. The propagator is constructed in this new set of
coordinate and the spectra is read off directly from it. The spectra will be divergent when the mass of the particle tends
to zero. In order to get a physical result, one must regularize the spectra properly. We afford a new scheme of regularization.
Interestingly, our scheme shows that the regularization we proposed amounts to erase one of the oscillators in the new set
of coordinate. Physical interpretations for the regularization are given and some ambiguities in the literatures are clarified. 相似文献
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磁共振扩散张量成像可以定量无创研究人体内水分子在三维空间中的各向异性扩散规律,进而获取重要的病理及生理信息.为了得到水分子各向异性扩散信息,需要按照一定的方案依次施加不同方向的扩散敏感梯度磁场,测量水分子在这些方向上的扩散系数用以估算扩散张量.扩散张量成像测量结果的准确程度受梯度磁场方向分布方案的影响,本文对扩散敏感梯度磁场方向分布方案进行综述,包括完全随机方案、启发式方案、规则多面体式方案和数值优化方案等,分析这些方案的优势与局限性,并提出需进一步研究的问题. 相似文献