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基于计算流体动力学的两栖车辆水动力特性数值计算 总被引:8,自引:1,他引:7
应用计算流体动力学(Computational fluid dynamics,CFD)理论,建立某型两栖车模型带自由表面粘性绕流场的数学模型,阐述求解的数值计算方法.采用RNG κ-ε湍流模型、流体体积法(volume of fluid,VOF)和压力隐式算子分割(Pressure implicit with splitting ofoperators,PISO)算法,运用FLUENT软件对车体绕流场进行三维瞬态数值计算,得到绕流场的速度与压力分布、阻力和兴波特性,并结合相关试验数据验证了数值方法的正确性,解决了以往由于忽略兴波特性导致数值计算结果随航速提高误差不断增大的问题.在此基础上,对该两栖车外形提出了优化方案,计算分析车体首、尾端切角及车轮不同收、放状态对绕流场的影响.计算结果表明,两栖车改进后的水动力性能有了较大改善,航速10 km/h时,减阻效果可达原车总阻力的51.2%,为减阻提速的研究提供了一定的参考. 相似文献
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应用计算流体力学软件Fluent ,采用分块网格划分,选择层流模型和不可压缩的N -S方程,对低雷诺数下不同流速的球柱模型黏性绕流场进行仿真计算。结果表明:圆柱杆与来流方向的绝对倾角越大,对圆球绕流场的影响越大,圆球表面的受力越不对称。建立了模型圆球表面所受作用力与来流速度、流向间的关系曲线,说明来流速度越大,圆球表面所受阻力越大;带有较细的圆柱杆的模型使其圆球表面受力发生了微小变化;圆柱杆的摆放位置对圆球表面受力影响不大。圆柱杆在 XZ平面内与X轴正向夹角θ越小,圆球表面受到的阻力就越小,更接近单个圆球绕流场。 相似文献
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应用计算流体力学软件Fluent,采用分块网格划分,选择层流模型和不可压缩的N-S方程,对低雷诺数下不同流速的球柱模型黏性绕流场进行仿真计算。结果表明:圆柱杆与来流方向的绝对倾角越大,对圆球绕流场的影响越大,圆球表面的受力越不对称。建立了模型圆球表面所受作用力与来流速度、流向间的关系曲线,说明来流速度越大,圆球表面所受阻力越大;带有较细的圆柱杆的模型使其圆球表面受力发生了微小变化;圆柱杆的摆放位置对圆球表面受力影响不大。圆柱杆在XZ平面内与X轴正向夹角θ越小,圆球表面受到的阻力就越小,更接近单个圆球绕流场。 相似文献
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利用计算流体力学软件,对粘性不可压缩流体的平板翼型绕流进行了三维数值模拟,采用有限体积法计算程式,求解不可压缩Navier-Stokes方程,模拟平板翼型在尾缘有无吹气时的流动情况,得到了平板翼型尾迹的传播特性。并使用四种常用湍流模型在相同的网格条件下进行数值模拟,模拟结果与相应的试验数据对比,分析各种湍流模型对带尾缘吹气的三维模型数值模拟结果的影响,得出了不同湍流模型对带尾缘吹气的模型的适用性以及精度的评估性结论。数值模拟的结果表明SST湍流模拟对模拟尾迹区流动具有很好的适应性,预测得到的轴向速度分布、尾迹特征长度变化以及流动相似性和试验结果进行了对比,和试验结果吻合较好。 相似文献
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为有效回收车辆悬挂振动能量,对馈能影响因素及相互间的关系进行分析。建立复合式电磁悬挂系统(composite electrical-magnetic suspension system,简称CESS)动力学及馈能电路模型,采用功率流的方法分析悬挂系统的能量输入、输出及耗散关系。在考虑传递效率的条件下,分析电阻比、激励频率及振幅对馈能效率与馈能功率的影响。讨论了减振指标及馈能性能之间的关系,通过台架试验分析了外接电阻与悬挂相对运动速度对馈能性能的影响。结果表明:采用功率流的方法可有效分析悬挂能量流动关系,馈能效率和馈能功率受电阻比、激励频率及振幅等因素影响;悬挂系统不能同时满足最大馈能效率和最大馈能功率,悬挂系统减振及馈能性能存在一定的相互制约关系。 相似文献
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Dolfred Vijay Fernandes Sangmo Kang Yong Kweon Suh 《Journal of Mechanical Science and Technology》2010,24(12):2467-2477
This paper investigates the ion transport and electroosmotically induced flow around the cylindrical electrodes under both
direct current (DC) and alternating current (AC) fields. The Poisson-Nernst-Plank (PNP) equations governing the ion transport
around the ideally polarizable electrodes are solved numerically by neglecting the Stern layer effect. The fractional-step
(FS) based decoupled solver is used in time integration of the ion-transport equations. A new immersed boundary (IB) methodology
is described for imposing no-flux boundary conditions of ion concentration on the electrodes. A fully implicit coupled solver
is also developed for calculating the ion transport around a pair of rectangular electrodes. The validity of the decoupled
solver is verified by comparing its results with those obtained from the coupled solver. For further confirmation of the validity,
the results are also compared with those obtained from the Poisson-Boltzmann model and both results are found to be in excellent
agreement. The electroosmotically induced flow field is studied by numerically solving the Stokes equations. The system attains
a steady state under DC, where the conduction term of ion transport is balanced by the diffusion term. Until the system attains
a steady state for a few ms for the case of DC, fluid flow is induced. The electroosmotic flow under AC is more interesting,
in that instantaneous flow oscillates with the frequency double of the applied field and a nonzero steady velocity field persists. 相似文献
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YANG Wugang ZHANG Yuwen YANG Jie ZUO Liankai 《机械工程学报(英文版)》2008,21(1):61-65
For some vehicles travelling through water, it is advantageous to cover the vehicle in a supercavity for the sake of reducing the drag acting on it. The method of artificial ventilation is most effective for generating and dominating the supercavity. This paper focuses on the numerical simulation of flow field around three dimensional body. The method is based on the multiphase computational fluid dynamics (CFD) model combined with the turbulence model and the full cavity model. The flow field of cavity is simulated by solving the compressible Navier-Stokes equations. The fundamental similarity parameters of ventilated supercavitaty flows that include cavitation number, Froude number, ventilation rate and drag coefficient are all investigated numerically in the case of steady flow and gravity field. We discuss the following simulations results in section 3: The variations of the cavitation number and the supercavity's relative diameter with ventilation rate (subtopic 3.1); The drag coefficient versus the cavitation number (subtopic 3.2); Deformation of supercavity axis caused by gravitational effect for three different fixed Froude numbers-2.8, 3.4, 4.2 (subtopic 3.3). In subtopic 3.2, we give the comparison results of the drag reduction ratio among numerical simulation and experiment conducted in hydrodynamic tunnel and towing tank respectively. In subtopic 3.3, we summarize our discussion of gravitational effect on the axis deformation of supercavity as follows: In the case of smaller Froude number, the inclination of the cavity axis increases monotonously with increasing horizontal length, and reaches its maximal value at the end of supercavity; This deformation can be almost completely negligible when the Froude number Fr〉7. The comparisons with the experimental data in the hydrodynamic tunnel and the towing tank indicate that the present method is effective for predicting the flows around ventilated supercavity; that the numerical results is in good agreement with the experimental one 相似文献
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主要针对汽车的动力特性进行研究。在结合具体车型参数的基础上,应用Origin的数据分析和绘图功能,分析汽车的驱动力与行驶阻力平衡关系、功率平衡和动力因数,并绘制相关曲线图。依据所绘制的特性图,分析汽车的综合动力性,为汽车的动力性计算方法与特性图形绘制提供了一个实例。 相似文献
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LIU Yue PAN Yuxue School of Mechanical Electrical Engineering Changchun University of Science Technology Changchun China LIU Chunbao College of Mechanical Science Engineering Jilin University Changchun China 《机械工程学报(英文版)》2007,20(2):94-96
Three-dimensional flow field of turbine in torque converter is simulated by numerical calculation in order to improve the performance of torque converter. Calculation model of a torque converter is presented based on the mixing-plane technology. In the calculation of flow field,the 3D N-S equations are separated by finite-volume method and solved by semi-implicit method for pressure-linked equations(SIMPLE). Based on flow field calculation,the flow field of turbine is simulated. The velocity and pressure in the flow field of turbine are analyzed. The external performance of the torque converter is also calculated. Results of flow simulation show that there are secondary flow,off flow and velocity gradient in turbine passage. The validity of numerical simulation is verified by comparing the results of numerical simulation with experiment data. 相似文献
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W. R. D. Wilson 《International Journal of Mechanical Sciences》1977,19(2):103-112
An upper-bound method for axisymmetric metal-forming problems is developed. The method uses regions of constant axial velocity and radial velocity inversely proportional to radius to build up a kinematically admissable velocity field. A technique for constructing the velocity field and calculating the associated power dissipation is described. Applications to various forming problems are discussed. 相似文献
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Y. Tomita 《International Journal of Mechanical Sciences》1982,24(12):711-716
In order to predict the influence of change in parameters in the constitutive equation upon deformation behaviour, a rigid plastic finite element perturbation method is developed. The change of such field variables as velocity, pressure, forming force and so on are expressed in terms of a power series of the perturbation of the parameters. The coefficients of the series are determined by solving the rigid plastic finite element perturbation equations. Several examples are presented to illustrate the advantages of using the proposed method to solve specific problems in preference to the conventional rigid plastic finite element method. 相似文献
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《Measurement》2016
In strap-down gyro-compass in-motion alignment, the alignment accuracy depends not only on the quality of the gyroscopes and accelerometers, but also on the accuracy of the velocity provided by the aiding sensors such as odometers. To improve the accuracy of the in-motion alignment, real-time accurate odometer velocity estimation is required. In this paper, the effect of the noise of the odometer velocity on strap-down gyro-compass in-motion alignment accuracy is presented, based on the strap-down gyro-compass algorithm. A velocity tracking model is designed as the state model, to describe the relationship between and among the vehicle’s velocity, acceleration and jerk in the vehicle frame. Based on the velocity equation applied to strap-down navigation system mechanizations, the vehicle’s acceleration in the vehicle frame can be obtained from the specific forces measured by accelerometers. With the observations including the vehicle’s acceleration in the vehicle frame and the vehicle’s velocity in the vehicle frame obtained from the odometer using the first order difference algorithm, real-time velocity estimates are produced by a Kalman filter. The field test results show that the proposed method can successfully improve the accuracy of the odometer velocity. The comparison with the traditional method highlights the superior performance of the proposed method. 相似文献