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It is well-known that chaotic dynamic systems, e.g., three-body system and turbulent flow, have sensitive dependence on the initial conditions (SDIC). Unfortunately, numerical noises, i.e., truncation error and round-off error, always exist in practice. Thus, due to the SDIC, the long-term accurate prediction of chaotic dynamic systems is practically impossible. In this paper, a new strategy for chaotic dynamic systems, i.e., the clean numerical simulation (CNS), is briefly described, and applied to a few Hamiltonian chaotic systems. With negligible numerical noises, the CNS can provide convergent (reliable) chaotic trajectories in a long enough interval of time. This is very important for Hamiltonian systems, and thus should have many applications in various fields. It is found that the traditional numerical methods in double precision cannot give not only reliable trajectories but also reliable Fourier power spectra and autocorrelation functions (ACFs). In addition, even the statistic properties of chaotic systems cannot be correctly obtained by means of traditional numerical algorithms in double precision, as long as these statistics are time-dependent. The CNS results strongly suggest that one had better to be very careful on the direct numerical simulation (DNS) results of statistically unsteady turbulent flows, although DNS results often agree well with experimental data when the turbulent flow is in a statistical stationary state. [ABSTRACT FROM AUTHOR]

The ultra-sonic gas atomization (USGA) nozzle is an important apparatus in the metal liquid air-blast atomization process. It can generate oscillating supersonic gas efflux, which is proved to be effective to enforce the atomization and produce narrow-band particle distributions. A double-actuator ultra-sonic gas nozzle is proposed in the present paper by joining up two active signals at the ends of the resonance tubes. Numerical simulations are adopted to study the effects of the flow development on the acoustic resonant properties inside the Hartmann resonance cavity with/without actuators. Comparisons show that the strength and the onset process of oscillation are enhanced remarkably with the actuators. The multiple oscillating amplitude peaks are found on the response curves, and two kinds of typical behaviors, i.e., the Hartmann mode and the global mode, are discussed for the corresponding frequencies. The results for two driving actuators are also investigated. When the amplitudes, the frequencies, or the phase difference of the input signals of the actuators are changed, the oscillating amplitudes of gas efflux can be altered effectively. [ABSTRACT FROM AUTHOR]

This paper presents the numerical simulations of two Richtmyer-Meshkov (RM) instability experiments using the conservative front-tracking method developed in (Mao, D. Towards front-tracking based on conservation in two space dimensions II, tracking discontinuities in capturing fashion. J. Comput. Phys., 226, 1550-1588 (2007)). The numerical results are compared with those obtained in (Holmes, R. L., Grove, J. W., and Sharp, D. H. Numerical investigation of Richtmyer-Meshkov instability using front-tracking. J. Fluid Mech., 301, 51-64 (1995)). The present simulations are generally in good agreement with those obtained by Holmes et al., and also capture the nonlinear and compessive phenomenon, i.e., the self-interactions of the transmitted and reflected wave edges, which was pointed out by Holmes et al. as the cause of the deceleration of the interfaces. However, the perturbation amplitudes and the amplitude growth rates of the interfaces obtained with the present conservative front-tracking method are a bit larger than those obtained by Holmes et al. [ABSTRACT FROM AUTHOR]

In the paper, a numerical study on symmetrical and asymmetrical laminar jet-forced flows is carried out by using a lattice Boltzmann method (LBM) with a special boundary treatment. The simulation results are in very good agreement with the available numerical prediction. It is shown that the LBM is a competitive method for the laminar jet-forced flow in terms of computational efficiency and stability. [ABSTRACT FROM AUTHOR]

This paper introduces a new spontaneous potential log model for the case in which formation resistivity is not piecewise constant. The spontaneous potential satisfies an elliptic boundary value problem with jump conditions on the interfaces. It has been shown that the elliptic interface problem has a unique weak solution. Furthermore, a jump condition capturing finite difference scheme is proposed and applied to solve such elliptic problems. Numerical results show validity and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The application of the wavelet method to vortex motion prediction is investigated. First, the wavelet method is used to solve two initial boundary problems so as to verify its abilities of controlling numerical errors and capturing local structures. Then, the adaptive wavelet method is used to simulate the vortex emerging process. The results show that the wavelet method can control numerical errors easily, can capture local structures adaptively, and can predict the vortex fluctuation evolution. Therefore, the application of the wavelet method to turbulence is suggested. [ABSTRACT FROM AUTHOR]

A formulation of the skin-friction drag related to the Reynolds shear stress in a turbulent channel flow is derived. A direct numerical simulation (DNS) of the turbulent control is performed by imposing the spatially oscillating spanwise Lorentz force. Under the action of the Lorentz force with several proper control parameters, only the periodically well-organized streamwise vortices are finally observed in the near-wall region. The Reynolds shear stress decreases dramatically, especially in the near-wall area, resulting in a drag reduction. [ABSTRACT FROM AUTHOR]

For the system of multilayer dynamics of fluids in porous media, the second order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward. Some techniques, such as calculus of variations, energy method, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates are adopted. Optimal order estimates are derived to determine the error in the second order approximate solution. These methods have already been applied to the numerical simulation of migration-accumulation of oil resources. [ABSTRACT FROM AUTHOR]

The method for controlling chaotic transition system was investigated using sampled-data. The output of chaotic transition system was sampled at a given sampling rate, then the sampled output was used by a feedbacks subsystem to construct a control signal for controlling chaotic transition system to the origin. Numerical simulations are presented to show the effectiveness and feasibility of the developed controller. [ABSTRACT FROM AUTHOR]

The orientation distribution function of cylindrical particle suspensions was deduced and numerically simulated, and an application was taken in a wedge-shaped flow field. The relationship between the orientation distribution function and particle orientation angles was obtained. The results show that comparing with the most probable angle distribution which comes to being in short time, the distribution of the steady state doesn't vary much in range; the main difference is the anti-clockwise rotation in the right and upper field, that is, particles rotate more at the points where the velocity gradients are larger. The most probable orientations are close to the direction of local streamlines. In the direction of streamlines, with poleradius decreasing, the most probable angles increase, but the angles between their orientations and the local streamlines decrease. [ABSTRACT FROM AUTHOR]

A numerical analysis of Newtonian and non-Newtonian flow in an axi-symmetric tube with a local constriction simulating a stenosed artery under steady and pulsatile flow conditions was carried out. Based on these results, the concentration fields of LDL (low-density lipoprotein) and Albumin were discussed. According to the results, in great details the macromolecule transport influences of wall shear stress, non-Newtonian fluid character and the scale of the molecule etc are given. The results of Newtonian fluid flow and non-Newtonian fluid flow, steady flow and pulsatile flow are compared. These investigations can provide much valuable information about the correlation between the flow properties, the macromolecule transport and the development of atherosclerosis. [ABSTRACT FROM AUTHOR]