Mixed grids offer advantages in grid generation,calculation efficiency and numerical accuracy.The p-weighted limiter works effectively on 1D,triangular and tetrahedral grids for the discontinuous Galerkin(DG)method.Wh...Mixed grids offer advantages in grid generation,calculation efficiency and numerical accuracy.The p-weighted limiter works effectively on 1D,triangular and tetrahedral grids for the discontinuous Galerkin(DG)method.Whereas the generalization to unstructured mixed grids for nodal DG methods is not straightforward.On quadrilateral grids,the tensor-product of solution points for nodal DG methods makes it complex and time-consuming to construct bi-linear candidate polynomials and perform weighted summation with the tensor-product polynomials.A simple yet effectiveway is proposed to address this issue.The linear candidate polynomial is constructed by interpolating values on the face and performing a forward difference in the central troubled cell.The truncation strategy on the linear weights is also improved.The weighted summation is carried out dimension-by-dimension on local coordinates as the 1D case.Since the limiting only depends on the central cell type,the final implementation for nodal DG methods on mixed grids is straightforward.A parameter-free shock detector is proposed to identify the troubled cells near shock waves.Several inviscid,laminar and turbulent flows with shocks are employed to showcase the efficiency of the improved p-weighted limiter and shock detector on unstructured mixed grids for nodal DG schemes.展开更多
分流区作为城市道路常见的交通场景,其复杂的交通特性和频繁的车道变换极易引发交通瓶颈和拥堵问题,对其通行能力的提升提出了挑战。为量化分析智能网联环境下干道分流区通行能力的影响因素,提出了一种基于P值检验和熵权法的综合筛选与...分流区作为城市道路常见的交通场景,其复杂的交通特性和频繁的车道变换极易引发交通瓶颈和拥堵问题,对其通行能力的提升提出了挑战。为量化分析智能网联环境下干道分流区通行能力的影响因素,提出了一种基于P值检验和熵权法的综合筛选与量化方法。该方法通过P值检验从潜在影响因素中筛选出显著变量,并结合熵权法对各因素进行权重赋值,从而精准识别关键影响因素。以干道分流区为实例,从道路和交通两个维度,通过P值检验和熵权法筛选出网联渗透率和分流比为关键影响因素。同时,基于SUMO(simulation of urban mobility)仿真平台分析其对分流区通行能力的影响,结果表明:网联渗透率与通行能力呈显著正相关;分流比对通行能力的影响呈现非线性特征,即当分流比低于0.5时,其与通行能力呈正相关,而当分流比超过0.5时,则转为负相关;网联渗透率对通行能力的影响显著高于分流比。此外,通过探讨不同渗透率下网联自动驾驶车辆(connected and automated vehicle,CAV)专用道的实施效果,为智能网联技术的推广和分流区通行能力的优化提供了理论依据和实践指导。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11872383)by the National Numerical Wind Tunnel(NNW)project of China(Grant No.NNW2019-JT01-012).
文摘Mixed grids offer advantages in grid generation,calculation efficiency and numerical accuracy.The p-weighted limiter works effectively on 1D,triangular and tetrahedral grids for the discontinuous Galerkin(DG)method.Whereas the generalization to unstructured mixed grids for nodal DG methods is not straightforward.On quadrilateral grids,the tensor-product of solution points for nodal DG methods makes it complex and time-consuming to construct bi-linear candidate polynomials and perform weighted summation with the tensor-product polynomials.A simple yet effectiveway is proposed to address this issue.The linear candidate polynomial is constructed by interpolating values on the face and performing a forward difference in the central troubled cell.The truncation strategy on the linear weights is also improved.The weighted summation is carried out dimension-by-dimension on local coordinates as the 1D case.Since the limiting only depends on the central cell type,the final implementation for nodal DG methods on mixed grids is straightforward.A parameter-free shock detector is proposed to identify the troubled cells near shock waves.Several inviscid,laminar and turbulent flows with shocks are employed to showcase the efficiency of the improved p-weighted limiter and shock detector on unstructured mixed grids for nodal DG schemes.
文摘分流区作为城市道路常见的交通场景,其复杂的交通特性和频繁的车道变换极易引发交通瓶颈和拥堵问题,对其通行能力的提升提出了挑战。为量化分析智能网联环境下干道分流区通行能力的影响因素,提出了一种基于P值检验和熵权法的综合筛选与量化方法。该方法通过P值检验从潜在影响因素中筛选出显著变量,并结合熵权法对各因素进行权重赋值,从而精准识别关键影响因素。以干道分流区为实例,从道路和交通两个维度,通过P值检验和熵权法筛选出网联渗透率和分流比为关键影响因素。同时,基于SUMO(simulation of urban mobility)仿真平台分析其对分流区通行能力的影响,结果表明:网联渗透率与通行能力呈显著正相关;分流比对通行能力的影响呈现非线性特征,即当分流比低于0.5时,其与通行能力呈正相关,而当分流比超过0.5时,则转为负相关;网联渗透率对通行能力的影响显著高于分流比。此外,通过探讨不同渗透率下网联自动驾驶车辆(connected and automated vehicle,CAV)专用道的实施效果,为智能网联技术的推广和分流区通行能力的优化提供了理论依据和实践指导。
