Rolling vortices and chaotic swirling are the most visually compelling aspect of smoke. Standard numerical simulation techniques for the animation of smoke suffer from a loss of these vortex patterns due to numerical damping. The majority of methods in computer animation use techniques such as vorticity confinement [3] to re-capture them. In this work, a Lagrangian method is presented which exp...

This paper presents numerical studies of friction-induced instabilities of brake systems using complex mode analysis. The complex eigenvalue extraction is performed at a deformed configuration; thus, nonlinear effects are taken into account in the modal analysis. An example case is used to illustrate the importance of friction-induced damping and nonlinear effects in brake squeal analysis. It i...

ABSTRACT The important practical and realistic design issues of an electrostatic actuator/positioner with full-gap travel are discussed. Analytic expressions and numerical simulations show that parasitic capacitances, and non-uniform deformation in two and three dimensions influence the range of travel of an electrostatic positioner stabilized by the addition of a series capacitor. The effects ...

A phenomenological theory is proposed to analyze the asymptotic dynamics of perturbed inviscid Kolmogorov shear flows in two dimensions. The phase diagram provided by the theory is in qualitative agreement with numerical observations, which include three phases depending on the aspect ratio of the domain and the size of the perturbation: a steady shear flow, a stationary dipole, and four travel...

In this paper we develop an efficient numerical method for the finite-element model updating of damped gyroscopic systems based on incomplete complex modal measured data. It is assumed that the analytical mass and stiffness matrices are correct and only the damping and gyroscopic matrices need to be updated. By solving a constrained optimization problem, the optimal corrected symmetric damping ...

This paper presents a novel, general method that is aimed at identifying both the harmonic excitations and nonlinear damping of forced nonlinear oscillation systems. An inverse formalism is developed for the identification method, which is shown to be well posed.That is, the inverse formalism has a unique solution and it depends continuously on the data.The unique solution is derived in the clo...

In two recent papers (Adhikari and Woodhouse 2001 Journal of Sound and <ibration 243, 43}61; 63}88), methods were proposed to identify viscous and non-viscous damping models for vibrating systems using measured complex frequencies and mode shapes. In many cases, the identi"ed damping matrix becomes asymmetric, a non-physical result. Methods are presented here to identify damping models which pr...

The relativistic expressions for the anti-hermitian (damping) parts of the dielectric tensor elements can be expressed as a single integral over the parallel momentum variable (see Eq.(1) below). A computer program has been written for the calculation of this single integral [1]. The numerical results are tested for a relativistic Maxwellian distribution and agree with analytical expressions de...

This paper presents a system identification (SI) scheme in time domain using measured acceleration data. The error function is defined as the time integral of the least square errors between the measured acceleration and the calculated acceleration by a mathematical model. Damping parameters as well as stiffness properties of a structure are considered as system parameters. The structural dampi...

We derive the relativistic equations for stellar perturbations, including in a consistent way shear viscosity in the stress-energy tensor, and we numerically integrate our equations in the case of large viscosity. We consider the slow rotation approximation, and we neglect the coupling between polar and axial perturbations. In our approach, the frequency and damping time of the emitted gravitat...