共查询到19条相似文献,搜索用时 125 毫秒
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本文开发了一套基于非结构网格的间断有限元方法(DG)程序,并对与单元形状无关的斜率限制器进行了研究。此程序支持多种网格类型,能够方便应用于具有混合单元的非结构网格,具有处理复杂几何结构的能力,为研究叶轮机械内部复杂流动现象提供了有效的研究工具。本文利用该程序对若干典型无黏和黏性问题进行数值模拟,结果表明,该程序具有较高的可信度,能够处理具有混合单元的非结构网格,并给出良好的数值模拟结果。 相似文献
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利用通量限制思想改进紧致格式 总被引:2,自引:0,他引:2
利用通量限制思想改进紧致格式计算有间断流场的性能,并设计出一种限制器,该限制器被运用在一系列3至8阶的紧致格式上.数值实验表明,通量限制型紧致格式不仅具有较高的精度和分辨率,而且还能有效地抑制非物理振荡,适用于各种高低Mach数的流动,捕捉到的流场间断所占网格点数少. 相似文献
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二维结构自适应多重网格的Euler方程解 总被引:2,自引:0,他引:2
将原来的结构网格中的提出了AUSM^ (Advection Upstream Splitting Method)格式,推广应用于二维非结构网格中。利用格林-高期分工对控制体内的变量进行线性重构,获得空间二阶精度,并采用Barth型限制器以抑制数值解的振荡。为提高计算效率,采用了自适应多重网格法。在生成非结构网格时,采用了一种新颖的数据结构-数组链接表。最后给出了NACA0012翼型和带10%鼓包的管道流动的几个Euler方程的算例,并进了分析比较。 相似文献
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为消除传统单元中心型Godunov方法在求解稀疏波问题时的非物理过热现象,发展一种适用于等熵流动的交错拉氏Godunov方法.主要的特征是采用速度与热力学变量交错分布的形式,避免在单元内进行速度平均,从而消除由于动量平均过程导致的动能耗散.与传统的von Neumann型交错网格方法相比,网格的边界通量由节点处的多维黎曼求解器提供,克服了多维人工粘性选取带来的困难.为减少多维黎曼求解器在求解稀疏波问题时的非物理熵增,给出稀疏波出现的合理判据,从而保证了热力学关系式的满足.数值实验表明:该方法能很好地消除稀疏波的过热现象,同时在求解激波问题时又能保持与传统单元中心型拉氏方法相同的激波捕捉能力. 相似文献
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1前言非结构化网格流场数值模拟是近十几年来计算流体力学发展的重要标志之一。非结构网格与结构网格相比,在网格划分的灵活性上远远超出,这正好是复杂区域划分所必需的。非结构网格可在某一局部加密,修改而不影响其余部分,用于自适应网格时其方便处也是结构网格所无法比拟的。非结构网格划分的灵活性和加密、修改的方便,使它得以在复杂几何结构流动的计算中得以充分应用,十几年来成为计算流体力学界的潮流,得到了大发展[‘-‘]本文在三角划分的计算域上,进行了二维无粘流场数值计算。采用Roe格式离散二维Euler方程组,三步Run… 相似文献
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随着计算能力的飞速发展,在非结构网格上进行大涡模拟是研究叶轮机械真实几何结构下复杂流动问题的有效途径。本文针对非结构网格上数值格式人工黏性过大的缺点,利用湍流中动能级联特性,发展了适用于大涡模拟的低耗散数值格式,并结合亚格子模型,考察了其在基础湍流算例中的有效性。通过与传统迎风格式的对比,说明本文发展的低耗散格式可以显著提高非结构网格上大涡模拟的精度和可靠性。 相似文献
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随着计算能力的飞速发展,在非结构网格上进行大涡模拟是研究叶轮机械真实几何结构下复杂流动问题的有效途径。本文针对非结构网格上数值格式人工黏性过大的缺点,利用湍流中动能级联特性,发展了适用于大涡模拟的低耗散数值格式,并结合亚格子模型,考察了其在基础湍流算例中的有效性。通过与传统迎风格式的对比,说明本文发展的低耗散格式可以显著提高非结构网格上大涡模拟的精度和可靠性。 相似文献
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二维非结构自适应多重网格的Euler方程解 总被引:1,自引:0,他引:1
将原来在结构网格中提出的AUSM+(Advection Upstream Splitting Method)格式,推广应用于二维非结构网格中。利用格林-高斯公式对控制体内的变量进行线性重构,获得空间二阶精度,并采用Barth型限制器以抑制数值解的振荡。为提高计算效率,采用了自适应多重网格法。在生成非结构网格时,采用了一种新颖的数据结构——数组链接表。最后给出了NACA0012翼型和带10%鼓包的管道流动的几个Euler方程的算例,并进行了分析比较。 相似文献
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An enhanced Multi-dimensional Limiting Process (e-MLP) is developed for the accurate and efficient computation of multi-dimensional flows based on the Multi-dimensional Limiting Process (MLP). The new limiting process includes a distinguishing step and an enhanced multi-dimensional limiting process. First, the distinguishing step, which is independent of high order interpolation and flux evaluation, is newly introduced. It performs a multi-dimensional search of a discontinuity. The entire computational domain is then divided into continuous, linear discontinuous and nonlinear discontinuous regions. Second, limiting functions are appropriately switched according to the type of each region; in a continuous region, there are no limiting processes and only higher order accurate interpolation is performed. In linear discontinuous and nonlinear discontinuous regions, TVD criterion and MLP limiter are respectively used to remove oscillation. Hence, e-MLP has a number of advantages, as it incorporates useful features of MLP limiter such as multi-dimensional monotonicity and straightforward extensionality to higher order interpolation. It is applicable to local extrema and prevents excessive damping in a linear discontinuous region through application of appropriate limiting criteria. It is efficient because a limiting function is applied only to a discontinuous region. In addition, it is robust against shock instability due to the strict distinction of the computational domain and the use of regional information in a flux scheme as well as a high order interpolation scheme. This new limiting process was applied to numerous test cases including one-dimensional shock/sine wave interaction problem, oblique stationary contact discontinuity, isentropic vortex flow, high speed flow in a blunt body, planar shock/density bubble interaction, shock wave/vortex interaction and, particularly, magnetohydrodynamic (MHD) cloud-shock interaction problems. Through these tests, it was verified that e-MLP substantially enhances the accuracy and efficiency with both continuous and discontinuous multi-dimensional flows. 相似文献
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High performance limiters are described in this paper for applications in high frequency ultrasound imaging systems. Limiters protect the ultrasound receiver from the high voltage (HV) spikes produced by the transmitter. We present a new bipolar power transistor (BPT) configuration and compare its design and performance to a diode limiter used in traditional ultrasound research and one commercially available limiter. Limiter performance depends greatly on the insertion loss (IL), total harmonic distortion (THD) and response time (RT), each of which will be evaluated in all the limiters. The results indicated that, compared with commercial limiter, BPT-based limiter had less IL (−7.7 dB), THD (−74.6 dB) and lower RT (43 ns) at 100 MHz. To evaluate the capability of these limiters, they were connected to a 100 MHz single element transducer and a two-way pulse-echo test was performed. It was found that the −6 dB bandwidth and sensitivity of the transducer using BPT-based limiter were better than those of the commercial limiter by 22% and 140%, respectively. Compared to the commercial limiter, BPT-based limiter is shown to be capable of minimizing signal attenuation, RT and THD at high frequencies and is thus suited for high frequency ultrasound applications. 相似文献
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为研究液态锂在电磁驱动限制器表面的铺展特性,设计了与EAST限制器接口相同的限制器测试平台.该平台运行时真空环境可达10?4Pa,对被测限制器可加热至350℃.在限制器锂回路管道上,利用外部2T水平磁场以及竖直方向施加的最大为200A的直流电流,形成电磁驱动力驱动下的锂液循环回路.测试平台设有顶部和正面两个观察窗,能够... 相似文献
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针对磁流体动力学方程, 通过分析数据重建所需的条件, 构造一种基于MUSCL(Monotone Upstream-Centred Scheme for Conservation Laws)型重建方法的斜率限制器, 获得了一种求解理想磁流体动力学方程的高分辨率熵相容格式。该格式在解的光滑区域具有高精度; 在解的间断区域可以合理地控制耗散, 可有效避免非物理现象的产生。采用熵稳定格式、熵相容格式和新的高分辨率熵相容格式对一维、二维理想磁流体动力学方程进行数值模拟。结果表明: 新格式能准确地捕捉解的结构, 且具有无振荡、高分辨、鲁棒等特性。 相似文献
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介绍了L波段低温限幅器的设计和分析,并给出了测试结果.该限幅器具有插入损耗小、驻波低、限幅电平低及体积小等特点.在12K,限幅器插入损耗小于0.2dB,端口驻波比小于1.25,限幅性能较好. 相似文献
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Accuracy preserving limiter for the high-order accurate solution of the Euler equations 总被引:1,自引:0,他引:1
Higher-order finite-volume methods have been shown to be more efficient than second-order methods. However, no consensus has been reached on how to eliminate the oscillations caused by solution discontinuities. Essentially non-oscillatory (ENO) schemes provide a solution but are computationally expensive to implement and may not converge well for steady-state problems. This work studies the extension of limiters used for second-order methods to the higher-order case. Requirements for accuracy and efficient convergence are discussed. A new limiting procedure is proposed. Ringleb’s flow problem is used to demonstrate that nearly nominal orders of accuracy for schemes up to fourth-order can be achieved in smooth regions using the new limiter. Results for the fourth-order accurate solution of transonic flow demonstrates good convergence properties and significant qualitative improvement of the solution relative the second-order method. The new limiter can also be successfully applied to reduce the dissipation of second-order schemes with minimal sacrifices in convergence properties relative to existing approaches. 相似文献
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The hierarchical reconstruction (HR) [Y.-J. Liu, C.-W. Shu, E. Tadmor, M.-P. Zhang, Central discontinuous Galerkin methods on overlapping cells with a non-oscillatory hierarchical reconstruction, SIAM J. Numer. Anal. 45 (2007) 2442-2467] is applied to the piecewise quadratic discontinuous Galerkin method on two-dimensional unstructured triangular grids. A variety of limiter functions have been explored in the construction of piecewise linear polynomials in every hierarchical reconstruction stage. We show that on triangular grids, the use of center biased limiter functions is essential in order to recover the desired order of accuracy. Several new techniques have been developed in the paper: (a) we develop a WENO-type linear reconstruction in each hierarchical level, which solves the accuracy degeneracy problem of previous limiter functions and is essentially independent of the local mesh structure; (b) we find that HR using partial neighboring cells significantly reduces over/under-shoots, and further improves the resolution of the numerical solutions. The method is compact and therefore easy to implement. Numerical computations for scalar and systems of nonlinear hyperbolic equations are performed. We demonstrate that the procedure can generate essentially non-oscillatory solutions while keeping the resolution and desired order of accuracy for smooth solutions. 相似文献