Resumo em Inglês:

The hydrodynamic interaction between two bodies with rotational motion through an inviscid and incompressible fluid is investigated theoretically. The dynamical behavior of an elliptic cylinder moving around a fixed circular cylinder is described first based on the dynamical equations of motion in the plane of motion. In a relative coordinate system moving with the stream, the kinetic energy of the fluid is expressed as a function of fifteen generalized added masses due to the planar motion of the two cylinders. By means of the generalized added masses, the planar motion of an elliptic cylinder around a fixed circular cylinder can be computed without considering the flow field. The trajectories of an elliptic cylinder around a fixed circular cylinder in planar motion are obtained and the effects of non-circularity, initial position and initial velocity on the interaction between two cylinders are discussed. Similarly, the planar motion of a prolate spheroid around a sphere is investigated. The numerical results show explicitly that the dynamical behaviors of the moving bodies with rotational motion appear nonlinear. Their moving properties exhibit significant difference from those in the particle dynamics.

Resumo em Inglês:

In this paper a weak three-dimensionality of the flow around a slender cylinder is considered and the related model, the so-called Ginzburg-Landau equation, is here obtained as an asymptotic solution of the 3D (discrete) Navier-Stokes equation. The derivation is in line with existing slender bodies theories, as the Lifting Line Theory, for example, where the basic 2D flow, leading to Landau's equation, is influenced now by a "sidewash" that modifies bi-dimensionally the original flow through mass conservation. The theory is asymptotically consistent and rests on an assumption that holds in the vicinity of the Hopf bifurcation (Recr ~ 45); furthermore, it leads to a well-established way to determine numerically both the Landau's coefficient µ and Ginzburg's coefficient gamma . Arguments are given suggesting that this assumption should hold far beyond Hopf bifurcation (Re >> Recr) and, with it, to extend the Ginzburg-Landau equation almost to the border of the transition region Re ~ 105. In this work only the theoretical development is addressed; numerical results will be presented in a forthcoming paper.

Resumo em Inglês:

The purpose of this paper is to explain the attractive applicability of the advanced vortex element methods and their contribution to the beginning of the new generation of CFD, with introduction of epoch-making application of the methods to simulation of unsteady flows around bluff bodies and virtual operation of fluid machinery. The vortex methods have been developed and applied for analysis of complex, unsteady and vortical flows in relation to problems in a wide range of industries, because they consist of simple algorithm based on physics of flow. Nowadays, applicability of the vortex element methods to various engineering problems has been developed and improved dramatically and it has become encouragingly clear that the vortex methods have so much interesting features that they provide easy-to-handle and completely grid-free Lagrangian calculation of unsteady and vortical flows without use of any RANS type turbulent models. In this paper, the mathematical background and numerical procedure of a vortex method developed by the group of the present author are briefly explained, and topics of calculated flows around bluff bodies, an oscillating airfoil, a swimming fish, virtual operation of fluid machinery (pumps and water turbines) are introduced.

Resumo em Inglês:

This paper provides a historical summary of the aerodynamic design of transport aircraft wings during the past 35 years at Empresa Brasileira de Aeronáutica (EMBRAER) and describes, from the application standpoint, the evolution of the theoretical and experimental techniques and tools used. Beginning with the EMB110 Bandeirante and proceeding with the EMB121 Xingu, the EMB120 Brasilia, CBA123 Vector, ERJ145 family and now with the EMBRAER 170 family, there has been a progressive shift from empirical and simplified analytical design techniques to CFD methods of ever increasing capabilities. In the experimental field, more advanced windtunnel test facilities and techniques have also been progressively employed to match the increased complexity of the computational methods.

Resumo em Inglês:

We review some recent advances on the problem of fully developed turbulence within the mathematical and physical points of view. From the mathematical perspective, we discuss a framework which has been developed for the rigorous treatment of the conventional statistical theory of turbulence and address some of the rigorous results which have been obtained concerning the energy cascade, the energy spectrum, the energy dissipation rate and other physical quantities of turbulent flows. Regarding the physical approach, we focus our attention on the relevance of field theoretical methods in the analysis of dimensionally reduced models (Burgers and two-dimensional incompressible turbulence), the problem of randomly advected scalars, and intermittent fluctuations in homogeneous and isotropic turbulent flows.

Resumo em Inglês:

This paper will review several techniques for flow measurements including some of the most recent developments in the field. Discussion of the methods will include basic theory and implementation to research instrumentation. The intent of this review is to provide enough detail to enable a novice user to make an informed decision in selecting the proper equipment to solve a particular flow measurement problem.

Resumo em Inglês:

Railroad wheels fail in two main modes: rolling surface defects like spalling, shelling and wear, and internal defects including cracks propagating after a change takes place in the original stress pattern. Although the effects of the latter are almost always catastrophic, the former is more usual. The onset of rolling surface defects depends on the strength of the surface and the applied loads. The strength is related to surface hardness and can be determined through experimental evaluation under controlled conditions. Evaluating the loads is one of the challenges for contact researchers. This paper presents the evaluation of the stress field inside elastic rolling bodies with an elliptic area of contact. This kind of model can be applied to wheel-rail contact phenomena. Typical high freight transportation loads are used in conjunction with regular recommended wheel and rail sizes. The results have shown that shear stress reaches the maximum magnitude below the surface of contact, and this explains the presence of shelling defects in service. They have also shown that a new model including plasticity is required, because the range of the stresses reached surpasses, by far, the elastic limit

Resumo em Inglês:

The study of algorithms for active vibrations control in flexible structures became an area of enormous interest, mainly due to the countless demands of an optimal performance of mechanical systems as aircraft and aerospace structures. Smart structures, formed by a structure base, coupled with piezoelectric actuators and sensor are capable to guarantee the conditions demanded through the application of several types of controllers. This article shows some steps that should be followed in the design of a smart structure. It is discussed: the optimal placement of actuators, the model reduction and the controller design through techniques involving linear matrix inequalities (LMI). It is considered as constraints in LMI: the decay rate, voltage input limitation in the actuators and bounded output peak (output energy). Two controllers robust to parametric variation are designed: the first one considers the actuator in non-optimal location and the second one the actuator is put in an optimal placement. The performance are compared and discussed. The simulations to illustrate the methodology are made with a cantilever beam with bonded piezoelectric actuators.

Resumo em Inglês:

The present work is inserted into an effort to develop a Chimera flow simulation code capable of handling general launch vehicle configurations. The paper is primarily concerned with presenting results of laminar and turbulent viscous simulations of flows over the first Brazilian satellite launch vehicle, the VLS, during its first-stage flight. The finite difference method is applied to the governing equations written in conservation-law form for general body conforming curvilinear coordinates. The spatial discretization is accomplished with a central difference scheme in which artificial dissipation terms, based on a scalar, non-isotropic model, are added to the numerical scheme to maintain stability. The time march process is accomplished with a 5-stage, 2nd-order accurate, Runge-Kutta scheme. The results here included are indicative of the current status of the Chimera flow simulation capability under development by the authors. The results also highlight interesting features of the flow over the complete VLS and point out the importance of the inclusion of viscous effects for flow simulation over such complex vehicles.