In order to analyze the hydrodynamic performance of the ducted propeller with high precision, this paper proposes a new method which combines Multi-Block Hybrid Mesh and Reynolds Stress Model (MBHM & RSM). The cal...In order to analyze the hydrodynamic performance of the ducted propeller with high precision, this paper proposes a new method which combines Multi-Block Hybrid Mesh and Reynolds Stress Model (MBHM & RSM). The calculation errors of MBHM & RSM and standard two-equation model (standard k-ε model) on the ducted propeller JD7704 +Ka4-55 are compared. The maximum error of the total thrust coefficient KT, the duct thrust coefficient KTN, the torque coefficient KQ and the open-water efficiency η0 of MBHM & RSM are 2.98%, 4.01%, 1.46%, and 0.89%, respectively, which are lower than those of standard k-ε model. Indeed, the pressure distribution on the propeller surfaces, the pressure and the velocity vector distribution of the flow field are also analyzed, which are consistent with the theory. It is demonstrated that MBHM & RSM on the thruster dynamics analysis are feasible. This paper provides reference in the thruster designing of underwater robot.展开更多
针对数模网格的手工检查及修补过于繁琐的实际问题,基于TCL/TK脚本语言,利用HyperMesh的API(Application Program Interface)接口编写代码,集成了自动划分网格、网格的检查、网格自动清理、重新划网格、网格修补等步骤,并利用跨平台窗...针对数模网格的手工检查及修补过于繁琐的实际问题,基于TCL/TK脚本语言,利用HyperMesh的API(Application Program Interface)接口编写代码,集成了自动划分网格、网格的检查、网格自动清理、重新划网格、网格修补等步骤,并利用跨平台窗体自定义界面直观显示网格修补方式,采用HyperMesh自有功能和自定义功能相结合的方式,集成了分割四边形、分割所有边、合并节点、添加Washer、Smooth、填补孔六种修补方法。并通过汽车后备箱盖实例验证,极大地提高了HyperMesh软件网格划分效率和质量,减小了人工操作出错的概率,为相关工作人员提供了便利工具,为后续企业开发工作积累经验。展开更多
In CAD/CAM,mesh rather than smooth surface is only needed sometimes.A mesh-generating method from permanence principle of Coons patch is developed.A new mesh point is defined through local small subpatch and all mesh ...In CAD/CAM,mesh rather than smooth surface is only needed sometimes.A mesh-generating method from permanence principle of Coons patch is developed.A new mesh point is defined through local small subpatch and all mesh points are computed by a linear system with special symmetric block tridiagonal coefficient matrix.By simplification,the determinant of coefficient matrix is determined by determinants of submatrices.Condition of existence of solution is given.Whether coefficient matrix is singular can be judged by a simple polynomial function with the eigenvalue of submatrix as variable.Numerical examples demonstrate the effects of shape parameters.展开更多
电大尺寸目标高频散射场的仿真一般使用物理光学(physical optics,PO)方法,该方法要求对目标使用尺寸为八分之一倍波长的三角网格进行剖分.然而,随着入射波频率增加,网格数目呈指数增长.本文提出基于一倍波长的二次曲面网格的快速PO(fas...电大尺寸目标高频散射场的仿真一般使用物理光学(physical optics,PO)方法,该方法要求对目标使用尺寸为八分之一倍波长的三角网格进行剖分.然而,随着入射波频率增加,网格数目呈指数增长.本文提出基于一倍波长的二次曲面网格的快速PO(fast PO,FPO)方法,该方法使用线性多项式拟合振幅函数,能够有效降低面片数目.与二次多项式拟合振幅函数的快速物理光学方法相比,本文方法避免了菲涅尔积分的求解,且计算速度快1.22倍.为了进一步降低网格数目,提出了自适应网格技术的快速物理光学(FPO based on the adaptive mesh technique,AFPO)方法,允许使用比标准奈奎斯特采样率更少的网格数目对目标进行离散.通过后验误差估计和数值算例对所提出算法的精度和速度进行了验证,结果表明与采用均匀网格剖分的方法相比,AFPO方法所需的面片数目降低89.58%.展开更多
提出了一种基于三角面元数据生成涂层目标时域有限差分(finite-difference time domain,FDTD)共形网格的方法。通过将原目标中各三角面元的顶点沿曲面在该点处的法线方向内移(内涂层)或外移(外涂层)所需的厚度,得到一组关于涂层的三角...提出了一种基于三角面元数据生成涂层目标时域有限差分(finite-difference time domain,FDTD)共形网格的方法。通过将原目标中各三角面元的顶点沿曲面在该点处的法线方向内移(内涂层)或外移(外涂层)所需的厚度,得到一组关于涂层的三角面元数据。其中曲面上各顶点处的法线方向近似等于包围该顶点的各三角面元的单位法向的矢量和。对于局部涂敷的情况,可根据需要只将涂敷部分所包含的三角面元顶点进行相应的移动,而其余顶点的位置保持不变。利用投影求交法,由原目标的三角面元数据和新生成的涂层三角面元数据即可得到共形FDTD计算所需要的共形网格参数。数值结果验证了方法的正确性和有效性。展开更多
文摘In order to analyze the hydrodynamic performance of the ducted propeller with high precision, this paper proposes a new method which combines Multi-Block Hybrid Mesh and Reynolds Stress Model (MBHM & RSM). The calculation errors of MBHM & RSM and standard two-equation model (standard k-ε model) on the ducted propeller JD7704 +Ka4-55 are compared. The maximum error of the total thrust coefficient KT, the duct thrust coefficient KTN, the torque coefficient KQ and the open-water efficiency η0 of MBHM & RSM are 2.98%, 4.01%, 1.46%, and 0.89%, respectively, which are lower than those of standard k-ε model. Indeed, the pressure distribution on the propeller surfaces, the pressure and the velocity vector distribution of the flow field are also analyzed, which are consistent with the theory. It is demonstrated that MBHM & RSM on the thruster dynamics analysis are feasible. This paper provides reference in the thruster designing of underwater robot.
文摘针对数模网格的手工检查及修补过于繁琐的实际问题,基于TCL/TK脚本语言,利用HyperMesh的API(Application Program Interface)接口编写代码,集成了自动划分网格、网格的检查、网格自动清理、重新划网格、网格修补等步骤,并利用跨平台窗体自定义界面直观显示网格修补方式,采用HyperMesh自有功能和自定义功能相结合的方式,集成了分割四边形、分割所有边、合并节点、添加Washer、Smooth、填补孔六种修补方法。并通过汽车后备箱盖实例验证,极大地提高了HyperMesh软件网格划分效率和质量,减小了人工操作出错的概率,为相关工作人员提供了便利工具,为后续企业开发工作积累经验。
基金Supported by National Natural Science Foundation of China(No.60970097,No.11271376)
文摘In CAD/CAM,mesh rather than smooth surface is only needed sometimes.A mesh-generating method from permanence principle of Coons patch is developed.A new mesh point is defined through local small subpatch and all mesh points are computed by a linear system with special symmetric block tridiagonal coefficient matrix.By simplification,the determinant of coefficient matrix is determined by determinants of submatrices.Condition of existence of solution is given.Whether coefficient matrix is singular can be judged by a simple polynomial function with the eigenvalue of submatrix as variable.Numerical examples demonstrate the effects of shape parameters.
文摘电大尺寸目标高频散射场的仿真一般使用物理光学(physical optics,PO)方法,该方法要求对目标使用尺寸为八分之一倍波长的三角网格进行剖分.然而,随着入射波频率增加,网格数目呈指数增长.本文提出基于一倍波长的二次曲面网格的快速PO(fast PO,FPO)方法,该方法使用线性多项式拟合振幅函数,能够有效降低面片数目.与二次多项式拟合振幅函数的快速物理光学方法相比,本文方法避免了菲涅尔积分的求解,且计算速度快1.22倍.为了进一步降低网格数目,提出了自适应网格技术的快速物理光学(FPO based on the adaptive mesh technique,AFPO)方法,允许使用比标准奈奎斯特采样率更少的网格数目对目标进行离散.通过后验误差估计和数值算例对所提出算法的精度和速度进行了验证,结果表明与采用均匀网格剖分的方法相比,AFPO方法所需的面片数目降低89.58%.
文摘提出了一种基于三角面元数据生成涂层目标时域有限差分(finite-difference time domain,FDTD)共形网格的方法。通过将原目标中各三角面元的顶点沿曲面在该点处的法线方向内移(内涂层)或外移(外涂层)所需的厚度,得到一组关于涂层的三角面元数据。其中曲面上各顶点处的法线方向近似等于包围该顶点的各三角面元的单位法向的矢量和。对于局部涂敷的情况,可根据需要只将涂敷部分所包含的三角面元顶点进行相应的移动,而其余顶点的位置保持不变。利用投影求交法,由原目标的三角面元数据和新生成的涂层三角面元数据即可得到共形FDTD计算所需要的共形网格参数。数值结果验证了方法的正确性和有效性。
