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941.
A generalized treatment for the wall boundary conditions relating to turbulent flows is developed that blends the integration to a solid wall with wall functions. The blending function ensures a smooth transition between the viscous and turbulent regions. An improved low Reynolds number k?ε model is coupled with the proposed compound wall treatment to determine the turbulence field. The eddy viscosity formulation maintains the positivity of normal Reynolds stresses and Schwarz' inequality for turbulent shear stresses. The model coefficients/functions preserve the anisotropic characteristics of turbulence. Computations with fine and coarse meshes of a few flow cases yield appreciably good agreement with the direct numerical simulation and experimental data. The method is recommended for computing the complex flows where computational grids cannot satisfy a priori the prerequisites of viscous/turbulence regions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
942.
We prove that generalized exponential splitting methods making explicit use of commutators of the vector fields are limited to order four when only real coefficients are admitted. This generalizes the restriction to order two for classical splitting methods with only positive coefficients. 相似文献
943.
944.
Eric Feulvarch Jean-Christophe Roux Jean-Michel Bergheau 《Comptes Rendus Mecanique》2011,339(10):649-654
An implicit enriched finite element algorithm is proposed to simulate heat transfer involving isothermal phase changes. This technique is based on a mixed variational formulation discretized by means of an enriched finite element approximation of the enthalpy in space. The interface is implicitly described without coupling with an interface-capturing technique. The time integration is carried out with an implicit (backward) Euler algorithm in time. Two examples in 1D and 2D clearly evidence the efficiency of the method developed. 相似文献
945.
946.
基于修正积分模型的油量表重新标定与储油罐变位识别的研究 总被引:1,自引:0,他引:1
针对储油罐在使用一定时间后会发生变位即纵向倾斜和横向偏转导致罐容表度量不准确的问题,利用修正的积分方法分别建立椭圆油罐变位后储油量与油位高度模型和两头为球冠体储油罐变位后储油量与油位高度模型及变位参数确定模型,针对上述模型通过Matlab软件求解,得到了重新标定的椭圆储油罐和两头为球冠体储油罐的油量表,确定了储油罐的纵... 相似文献
947.
948.
949.
A family of structural finite elements using a modern absolute nodal coordinate formulation (ANCF) is discussed in the paper with many applications. This approach has been initiated in 1996 by A. Shabana. It introduces large displacements of 2D/3D finite elements relative to the global reference frame without using any local frame. The elements employ finite slopes as nodal variables and can be considered as generalizations of ordinary finite elements that use infinitesimal slopes. In contrast to other large deformation formulations, the equations of motion contain constant mass matrices and generalized gravity forces as well as zero centrifugal and Coriolis inertia forces. The only nonlinear term is a vector of elastic forces. This approach allows applying known abstractions of real elastic bodies: Euler–Bernoulli beams, Timoshenko beams and more general models as well as Kirchhoff and Mindlin plate theories. 相似文献
950.
We consider a nonholonomic system describing the rolling of a dynamically nonsymmetric sphere over a fixed sphere without
slipping. The system generalizes the classical nonholonomic Chaplygin sphere problem and it is shown to be integrable for
one special ratio of radii of the spheres. After a time reparameterization the system becomes a Hamiltonian one and admits
a separation of variables and reduction to Abel-Jacobi quadratures. The separating variables that we found appear to be a
non-trivial generalization of ellipsoidal (spheroconic) coordinates on the Poisson sphere, which can be useful in other integrable
problems. Using the quadratures we also perform an explicit integration of the problem in theta-functions of the new time.
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