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本文在直角坐标系、柱坐标及球坐标系中研究一维匀速活塞在强引力场中的动力学过程.用特征线法数值求解流体力学方程组,得出符合活塞速度条件及联结条件的解.分析讨论了不同坐标系对压缩区,常流区,稀疏区流场、激波传播速度及活塞面上声速的影响. 相似文献
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采用数值计算方法对亚音速三角翼纵向及带有小侧滑和横侧小扰动情况下的流场结构进行了计算,利用数值计算所得到的大迎角流动流场数据,结合相关的实验研究结果,建立了对大迎角旋涡流场结构进行定量分析的方法.给出了三角翼大迎角情况下相应的气动力、力矩系数,以及机翼前缘分离涡轴线位置和旋涡破裂位置随迎角的变化规律,并对带有小侧滑和横侧小扰动情况下对横侧力矩的影响进行了计算与分析.计算结果表明,在前缘分离涡破裂前的上游旋涡区内,前缘分离涡轴线基本保持为直线,且随着迎角增加,前缘分离涡轴线位置愈靠近翼根,并远离翼面;在前缘分离涡破裂的初始阶段,于旋涡轴线处,压力系数会迅速增加,沿涡轴线方向速度迅速减小,在垂直于流向的截面内,愈靠近涡轴线处,沿涡轴线方向速度愈小,甚至出现负值,说明沿涡轴线方向出现回流.当绕机翼上表面前缘分离涡破裂后,将会导致横侧运动不稳定,如果受到小扰动,将产生横侧力矩发散. 相似文献
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多体系统动力学微分/代数方程组的一类新的数值分析方法 总被引:3,自引:0,他引:3
本文讨论了多体系统动力学微分/代数混合方程组的数值离散问题.首先把参数t并入广义坐标讨论,简化了方程组及其隐含条件的结构,并将其化为指标1的方程组.然后利用方程组的特殊结构,引入一种局部离散技巧并构造了相应的算法.算法结构紧凑,易于编程,具有较高的计算效率和良好的数值性态,且其形式适合于各种数值积分方法的的实施.文末给出了具体算例. 相似文献
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基于有限体积法和有限元法,结合动网格控制技术,建立了横向流体作用下三维弹性直管流致振动计算的数值模型,实现了计算结构动力学与计算流体力学之间的联合仿真.首先,通过对刚性管的静止绕流计算,研究了网格离散方式和不同湍流模型对圆柱类结构静止绕流流场特征的影响和预测能力,得到了适用于双向耦合分析的CFD模型;其次,利用基于双向流固耦合方法的流致振动模型,计算并分析了流体力与结构位移间的相位关系,指出流体力与位移间的相位差是由流体力引起的,同时对双向耦合和单向耦合进行了比较分析;最后通过对直管流致振动的数值计算,联合管表面压力、尾流区时均速度、分离角等时均量,分析了尾流区的流场特征. 相似文献
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同位非结构和结构网格摄动有限体积法(PFV)求解二维Navier-Stokes方程组 总被引:3,自引:0,他引:3
根据NS方程组的一阶迎风和二阶中心有限体积(UFV和CFV)格式,导出NS方程组迎风和中心摄动有限体积(UPFV和CPFV)格式.该格式通过把控制体界面质量通量摄动展开成网格间距的幂级数,并由守恒方程本身求得幂级数系数而获得.迎风和中心摄动有限体积格式使用了与一阶迎风和二阶中心格式相同的基点数和相同的表达形式,宜于计算机编程.顶盖驱动方腔流和驻点流标量输运的数值实验证明,迎风PFV格式比一阶UFV、二阶CFV格式有更高的精度,更高的分辨率.尤其是良好的鲁棒特性.对顶盖驱动方腔流,在Re数从102到104范围内,亚松弛系数可在0.3~0.8任取,收敛性能良好. 相似文献
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本文系统推演了横观各向同性体滑移线场理论.为解决地球动力学与岩土力学问题,考虑到成层地质体横观各向同性与非均匀温度场作用,本文选择了Gol'denblat-Kopnov破坏准则.并使物性参数随温度变化,建立了复杂介质的强度准则.通过关联流动法则,导出了塑性流动基本方程.应用特征线理论,导出了滑移线斜率公式、应力沿滑移线微分公式和速度沿滑移线微分公式.应用本文理论计算了基础承压问题.本文理论将许多着名的经典理论如Mises理论,Hill理论、Coulomb理论概括为特例.这一综合理论可应用于岩土工程、地质构造、石油、采矿等许多领域. 相似文献
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综述了大气运动基本方程组在光滑函数类中的稳定性和Navier-Stokes方程的不稳定性的若干结论.在此基础上,以大气运动方程组的Boussinesq近似为例,阐述了Navier-Stokes方程的不稳定性导致的大气运动基本方程组的某些简化模式的不稳定性,从而得到在简化基本方程过程中应该遵守的一个原则,以保证简化方程的稳定性. 相似文献
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I. G. Brykina V. V. Rusakov V. G. Shcherbak 《Journal of Applied Mathematics and Mechanics》1989,53(6):756-761
The three-dimensional flow of a chemically unstable viscous gas near a plane of symmetry of blunt bodies streamlined at the angle of attack, is considered. The investigation is carried out using a model of a thin, viscous shock layer. To a first approximation of the method of successive approximations for a uniform gas simple formulas are obtained for the distribution of the heat flux over the surface, referred to its value at the stagnation point. It is shown that for a chemically unstable gas the distribution of the heat flux along an ideally catalytic surface depends only slightly on the conditions prevailing within the incident flow, is determined mainly by the geometrical characteristics of the body, and is described quite satisfactorily by the formulas obtained. The accuracy of these formulas is determined by comparison with numerical computations carried out for bodies of various shapes, moving at different angles of attack along a planing trajectory of re-entry into the Earth's atmosphere, and during re-entry into the atmosphere at a constant velocity. 相似文献
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A. Ishak J. H. Merkin R. Nazar I. Pop 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2008,70(3):100-123
The effects of suction/injection on the laminar mixed convection boundary-layer flow on a vertical wall with a prescribed
heat flux are considered. The conditions which allow the equations to be reduced to similarity form are derived and numerical
solutions of the resulting equations are obtained for a range of values of the suction/injection and buoyancy parameters.
Two specific cases, corresponding to a stagnation point flow and uniform wall heat flux, are treated in detail. Results are
presented in terms of the skin friction and wall temperature with a selection of velocity and temperature profiles also being
given. Dual solutions are found to exist for assisting flow, these are an addition to what has been reported previously for
opposing flows. Solutions for some limiting values of the parameters are also derived. 相似文献
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A. Ishak J. H. Merkin R. Nazar I. Pop 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2008,59(1):100-123
The effects of suction/injection on the laminar mixed convection boundary-layer flow on a vertical wall with a prescribed
heat flux are considered. The conditions which allow the equations to be reduced to similarity form are derived and numerical
solutions of the resulting equations are obtained for a range of values of the suction/injection and buoyancy parameters.
Two specific cases, corresponding to a stagnation point flow and uniform wall heat flux, are treated in detail. Results are
presented in terms of the skin friction and wall temperature with a selection of velocity and temperature profiles also being
given. Dual solutions are found to exist for assisting flow, these are an addition to what has been reported previously for
opposing flows. Solutions for some limiting values of the parameters are also derived.
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For flow inside a four-to-one contraction domain, we minimize the vortex that occurs in the corner region by controlling the heat flux along the corner boundary. The problem of matching a desired temperature along the outflow boundary is also considered. The energy equation is coupled with the mass, momentum, and constitutive equations through the assumption that viscosity depends on temperature. The latter three equations are a non-isothermal version of the three-field Stokes–Oldroyd model, formulated to have the same dependent variable set as the equations governing viscoelastic flow. The state and adjoint equations are solved using the finite element method. Previous efforts in optimal control of fluid flows assume a temperature-dependent Newtonian viscosity when describing the model equations, but make the simplifying assumption of a constant Newtonian viscosity when carrying out computations. This assumption is not made in the current work. 相似文献
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The effect of suction or injection on unsteady MHD flow with heat and mass transfer in a micropolar fluid near the forward stagnation point flow with thermophoresis has been investigated. The problem is reduced to a system of non-dimensional partial differential equations, which are solved numerically using the implicit finite-difference scheme. Profiles for velocity, microrotation, temperature and concentration as well as the skin friction, the rate of heat and mass transfer are determined and presented graphically for physical parameters. The results show that the suction increases the skin friction, the rate of heat and mass transfer while opposite trend is observed for the case of injection. It is also found that the effect of thermophoresis is decrease the concentration boundary layer thickness. 相似文献
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Ioan Pop Anuar Ishak Fazlina Aman 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2011,62(5):953-956
This paper considers the effects of radiation on the flow near the two-dimensional stagnation point of a stretching sheet immersed in a viscous and incompressible electrically conducting fluid in the presence of an applied constant magnetic field. The external velocity and the stretching velocity of the sheet are assumed to vary linearly with the distance from the stagnation point. The governing partial differential equations are transformed into a system of ordinary differential equations using a similarity transformation, before being solved numerically by the Keller-box method. The features of the heat transfer characteristics for different values of the governing parameters are analyzed and discussed. The results indicate that the heat transfer rate at the surface decreases in the presence of radiation. 相似文献
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Ioan Pop Anuar Ishak Fazlina Aman 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2011,43(4):953-956
This paper considers the effects of radiation on the flow near the two-dimensional stagnation point of a stretching sheet
immersed in a viscous and incompressible electrically conducting fluid in the presence of an applied constant magnetic field.
The external velocity and the stretching velocity of the sheet are assumed to vary linearly with the distance from the stagnation
point. The governing partial differential equations are transformed into a system of ordinary differential equations using
a similarity transformation, before being solved numerically by the Keller-box method. The features of the heat transfer characteristics
for different values of the governing parameters are analyzed and discussed. The results indicate that the heat transfer rate
at the surface decreases in the presence of radiation. 相似文献
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This paper deals with a numerical method for an airfoil design which was presented in [3, 5]. This method is intended for design of an airfoil from a given velocity distribution along a mean camber line. The method is based on searching for a fixed point of a contractive operator. This operator combines an inexact inverse operator and equations describing the flow. A subsonic flow is assumed, the flow is described by a system of the Euler equations which is solved by an implicit finite volume method. The Newton method is applied to the solution of the nonlinear system. The resulting system of linear algebraic equations is solved by GMRES method, the Jacobian-free version is described. The inexact inverse operator consists of a middle curve function and a thickness function, both depending on the given velocity distribution. In addition to the velocity distribution the velocity in infinity is given. The angle of attack is determined so that the stagnation point is in a specific position. Successful numerical results are presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献