ISSN:0044-2267    

DOI:10.1002/zamm.19970770102

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractFor internal flow the influence of vortices on heat transfer is studied mainly numerically. Laminar channel flows with two types of periodic vortex generators (VGs), transverse ribs and rectangular winglets, are considered. The transverse ribs generate transverse vortices (TVs), and the rectangular winglets at 45° angle of attack generate longitudinal vortices (LVs). Velocity and temperature fields, local and global friction, flow losses, and heat transfer are computed from the full unsteady, three‐dimensional conservation equations. Point comparisons with experimental results are given. For steady flow the TVG configuration strongly influences heat transfer locally, but not globally. The stationary TVs don't provide an additional mechanism for convective thermal energy transport, but cause additional flow losses for their generation. The LVG configuration enhances local and global heat transfer for both steady and unsteady flow. For steady flow the LVs generate swirl which is an additional mode of convective thermal energy transport. When the flow reaches a critical Re‐number, which is more than an order of magnitude lower than the normal transition Re‐number, self‐sustained oscillations set in. They provide an additional heat transfer mode due to “Reynolds” averaged transport which further increases the heat transfer. For the same heat transfer increase the LVG configuration causes only half the flow losses of the TVG configuration. For practical applications, where high heat transfer and low flow losses are important, LVG configurations are better suited than TVG co

ISSN:0044-2267    

DOI:10.1002/zamm.19970770103

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe nonlinear analysis of the Rayleigh‐Taylor stability of two superposed magnetic fluids with interfacial transfer of mass and heat is presented for two layers each of finite thickness. The system is subjected to a tangential magnetic field. The method of multiple scale expansion is employed for the analysis. It is shown that the evolution of the amplitude is governed by a nonlinear Ginzburg‐Landau equation. There is also obtained a nonlinear diffusion equation describing the evolution of wave packets near the marginal state. Further, the nonlinear Schrödinger equation is obtained when the influence of mass and heat transfer is neglected. The various stability criteria are discussed both analytically and numerically and the stability diagrams are obtained. It is found that, in the linear theory, the stability criterion is independent of mass and heat transfer coefficient. While in the nonlinear theory it is found that, when this coefficient is large enough, the system which would be unstable classically, can be stabilized for finite amplitude disturba

ISSN:0044-2267    

DOI:10.1002/zamm.19970770104

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0044-2267    

DOI:10.1002/zamm.19970770105

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractEs wird ein Anfangs‐Randwertproblem aus der Theorie der linearen Thermoviskoelastizität betrachtet. Nach Formulierung des zugeordneten Variationsproblems werden Existenz und Eindeutigkeit seiner Lösung in einem geeigneten funktionalanalytischen Rahmen studi

ISSN:0044-2267    

DOI:10.1002/zamm.19970770106

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0044-2267    

DOI:10.1002/zamm.19970770107

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe present paper concerns the hemivariational inequality approach to the laminated plate theory under abstract subdifferential conditions. The mechanical problem is formulated as a nonlinear eigenvalue problem for hemivariational inequalities and a corresponding bifurcation theory is given.

ISSN:0044-2267    

DOI:10.1002/zamm.19970770108

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0044-2267    

DOI:10.1002/zamm.19970770109

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA single‐freedom multi‐body system with determinate structure having friction‐affected sliders and hinges is considered. For the determination of the solutions of initial value problems the governing equations are put in the form of a system of linear algebraic equations having the absolute values of the friction forces as unknowns. The coefficients of these equations contain the signs of the unknown normal reactions, and the unknown friction torques are included in the right‐hand‐sides of these equations. With all possible sets of assumptions for the signs of the normal reactions and approaches of the friction torques these equations are solved, and the solutions, which are approaches of the friction forces, are selected. With these approaches of the friction forces new approaches of the friction torques can be established, which can be used for repeating the calculations, until the desired accuracy is reached. The determination of the accelerations and reaction forces of a five‐body system with three sliders and four hinges with this method evidenced advantages in comparison with pure iterat

ISSN:0044-2267    

DOI:10.1002/zamm.19970770110

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractWe construct discrete approximations for a class of singularly perturbed boundary value problems, such as the Dirichlet problem for a parabolic differential equation, for which the coefficient multiplying the highest derivatives can take an arbitrarily small value from the interval (0, 1]. Discretisation errors for classical discrete methods depend on the value of this parameter and can be of a size comparable with the solution of the original problem. We describe how to construct special discrete methods for which the accuracy of the discrete solution does not depend on the value of the parameter, but only on the number of mesh points used. Moreover, using defect correction techniques, we construct a discrete method that yields a high order of accuracy with respect to the time variable. The approximation, obtained by this special method, converges in the discretel∞‐norm to the true solution, independent of the small parameter. For a model problem we show results for our scheme and we compare them with results obtained by the classical met

ISSN:0044-2267    

DOI:10.1002/zamm.19970770111

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY