Digital Simulation Data Research Articles

Digitalized turbulent behaviors of air and rice husk flow in a vertical suspension furnace from computational fluid dynamics simulation

AbstractThe knowledge of fluid–particle flow behavior is necessary. Unfortunately, computational fluid dynamics (CFD) studies are mostly focused on developing numerical methods in detail. Instead, the CFD studies should also subtly shift to become a tool for digitalizing fluid science to guide the practical industrial aspects. Therefore, this simulation study intends to reveal the air and rice husk flow behaviors in a vertical suspension furnace, complete with presenting digital simulation data, aiming to alleviate the escape particle amount. According to this study, the escaped particle amount was suppressed under more sphere particle, smaller particle size, and feed inlet pipe that sunk into the burner. The properties change from rice husk to ash, along with temperature escalation (as in combustion phenomena), enlarging the escaped particle amount, so the cyclone should be installed to handle it. In addition, the results of digital turbulent data from CFD simulation have succeeded in intriguing and revealing the fluid–particle flow behavior in the vertical suspension furnace. The data show a close match to the real phenomena occurring inside this furnace which reflects the standard k–ε model can conclusively predict fluid–particle flow behavior without conflicting Newton's second law of particle motion.

Finite element simulation of cracks formation in parabolic flume above fixed service live

In the article, digital simulation data on influence of defect different characteristics on cracks formation in a parabolic flume are presented. The finite element method is based on general hypotheses of the theory of elasticity. The studies showed that the values of absolute movements satisfy the standards of design. The results of the digital simulation of stresses and strains for cracks formation in concrete parabolic flumes after long-term service above the fixed service life are described. Stressed and strained state of reinforced concrete bearing elements under different load combinations is considered. Intensive threshold of danger to form longitudinal cracks in reinforced concrete elements is determined.

Real-Time Attitude Simulation of Aerocraft Using dSPACE Emulator and Three-Axis Turn Table

To solve the problem of ground simulation of aerocraft attitude in hardware-in-the-loop simulation (HILS), recurrence of aerocraft attitude is realized using dSPACE emulator and three-axis turn table. The hardware configuration and key technologies of control system are introduced. Construction and downloading of the dynamic model is done in dSPACE monitor computer, the model is calculated in dSPACE emulator. The communication between dSPACE and turn table is settled with serial-port of DS4201s card. The rotate motion of the inner middle and outer axis correspond to the three-channel motion of the aerocraft body. Simulation results indicate that dSPACE finish calculating complicated dynamic model, sending and receiving velocity data through serial-port is proper, bandwidth of turn table satisfies the need of simulation. Real rotating velocity of turn table is displayed using Controldesk tools, and fits well with the digital simulation data in pitching yawing and rolling directions, and the need for real-time attitude simulation in HILS is satisfied.

Analytical expression for transient chronoamperometric current at ultramicroband electrode

Analytical solution of non-steady state chronoamperometric current at ultramicroband electrode is derived. The analytical expression for current (Pade approximant), valid for entire time domain is compared with the analytical and digital simulation data. A satisfactory agreement with the available limiting cases of analytical expressions and digital simulation data is noted.

Digital Simulation of Full Scale Static Test of Aircraft

Full scale aircraft static test is a very important process of aircraft design, it is costly and time consuming. The testing accuracy and validity mainly depend on the rationality of the test scheme design. When the aircraft is being tested, the specimen's safety mainly depends on monitoring and understanding the testing data by way of evaluating the coherence with the digital simulation data synchyononsly. The test digital simulation can aid realizing above requirements and improving the test efficiency significantly during test scheme design stage or testing stage respectively. The key technologies and the solving methods of test digital simulation are presented and the application example is given.

Stochastic response of linear and non-linear systems to α-stable Lévy white noises

The stochastic response of linear and non-linear systems to external α-stable Lévy white noises is investigated. In the literature, a differential equation in the characteristic function (CF) of the response has been recently derived for scalar systems only, within the theory of the so-called fractional Einstein–Smoluchowsky equations (FESEs). Herein, it is shown that the same equation may be built by rules of stochastic differential calculus, previously applied by one of the authors to systems driven by arbitrary delta-correlated processes. In this context, a straightforward formulation for multi-degree-of-freedom (MDOF) systems is also developed. Approximate CF solutions to the derived equation are sought for polynomial non-linearities, in stationary conditions. To this aim a wavelet representation is used, in conjunction with a weighted residual method. Numerical results prove in excellent agreement with exact solutions, when available, and digital simulation data.

Reductive electrocatalytic dehalogenation of nitrobenzyl halides: nitrophilic or halophilic attack?

Electrochemical reduction of Cp2TiCl2 in the presence of benzylic halides results in their catalytic dehalogenation to form toluene derivatives. Possible schemes for the process were proposed on the basis of the results of electrochemical studies and digital simulation data. The catalytic scheme including the halophilic attack of the TiIII complex to organic halide as a key step occurs for unsubstituted benzylic halides. In the case of nitro-substituted substrates, the reaction is strongly accelerated. In this case, an electron transfer from the reduced form of the catalyst to the NO2 group of organic halide is possibly accompanied by the intramolecular charge transfer to the C-Hal bond, thus facilitating its cleavage. Thus, the nitro group in the starting benzylic halide acts as a “redox antenna,” transferring an electron to the C-Hal bond. The proposed scheme is supported by semiempirical calculations of the geometry of molecular complexes with the Ti-Hal or Ti-NO2 coordination.

Response Power Spectrum of Multi-Degree-of-Freedom Nonlinear Systems by a Galerkin Technique

This paper deals with the estimation of spectral properties of randomly excited multi-degree-of-freedom (MDOF) nonlinear vibrating systems. Each component of the vector of the stationary system response is expanded into a trigonometric Fourier series over an adequately long interval T. The unknown Fourier coefficients of individual samples of the response process are treated by harmonic balance, which leads to a set of nonlinear equations that are solved by Newton’s method. For polynomial nonlinearities of cubic order, exact solutions are developed to compute the Fourier coefficients of the nonlinear terms, including those involved in the Jacobian matrix associated with the implementation of Newton’s method. The proposed technique is also applicable for arbitrary nonlinearities via a cubicization procedure over the interval T. Upon determining the Fourier coefficients, estimates of the response power spectral density matrix are constructed by averaging their squared moduli over the samples ensemble. Examples of application prove the reliability of the technique by comparison with digital simulation data.

Diffusion at Ultramicro Disk Electrodes: Chronoamperometric Current for Steady-State Ec‘ Reaction Using Scattering Analogue Techniques

An accurate polynomial expression for the steady-state current in the case of first-order EC‘ reaction is reported using scattering analogue techniques for ultramicro disk electrodes. When the reaction rate is small, seven terms of diffusion-limited current are reported, and when it is large, five terms of the same are reported. A two-point Padé approximant is derived for all values of reaction rates. By a proper transcription of variables, the methodology is extended to derive chronoamperometric current for diffusion-controlled processes, and excellent agreement with digital simulation data is noticed.

A two-point Padé approximation for the non-steady-state chronoamperometric current at ultramicrodisc electrodes

The mixed boundary value problem for the two dimensional diffusion equation pertaining to ultramicrodisc electrodes, is analysed and a two-point Padé approximation result is derived for the non steady-state chronoamperometric current. A satisfactory agreement with the available digital simulation data is noted.

Noise perturbations of a non-linear system with multiple steady states

We examine the effects of small white Gaussian noise perturbations on a harmonically forced Duffing oscillator. For specific values of the parameters, the noise-free system admits two coexisting steady-state attractors. The presence of noise induces transitions from one attractor to the other, however small the noise intensity may be. As a first step, the equation of motion is transformed into a system of stochastic differential equations for the slowly varying van der Pol variables, by assuming that the predominant frequency of response is that of the forcing term. The condition for bistability, the stable fixed points and the separatrix defining the domains of attraction are then examined. In the second step, the effects of noise perturbations on the system are analyzed by determining the steady-state probability density of the fluctuations of the response, as well as the probabilities of escape from one attractor to the other. The latter are found by determination of the expected times of first-passage to the separatrix starting from a point in the domain of attraction of each stable state. This analysis is done in the limit of small damping and small noise intensity by use of an averaging scheme which reduces the dimensionality of the problem from two to one; this yields valuable information about the relative stability of the stable states. The obtained theoretical results are supported by digital simulation data. The analytical theory gives good agreement even for large noise.

Inversion of source parameters and attenuation of the Tangshan aftershocks

Source parameters and characteristics of regional attenuation of Tangshan aftershocks are studied by using digital records of Tangshan aftershocks. An inversion method of P wave spectra to reduce influence on the ambiguity in the estimates of parameters by the usual spectrum analysis method is developed. By testing with digital simulation data and applying to actual data, it is confirmed that the method is usable.

Analysis of granular simple shear flows with a rate-dependent model

The theory of the thermodynamically consistent rate-dependent model for flow of granular materials is reviewed. The material coefficients are evaluated by matching the model with the kinetic theory of Lun et al. in the limit of nearly elastic spherical particles. The special case of simple shear flow of granular materials in the grain inertia regime is studied in detail. The predicted stresses are compared with a previously derived rate-dependent model and the existing digital simulation data for a range of solid volume fraction. It is shown that the use of the new material coefficients improves the agreement between the model predictions and the simulation and experimental data.

A rate-dependent thermodynamical model for rapid granular flows

The averaged equations of balance and the Clausius-Duhem inequality for the rapid granular flows are considered and the thermodynamics of the mean motion is studied. On the basis of the averaged entropy inequality, constitutive equations including a rate-dependent one for the stress tensor are formulated. For spherical nearly elastic particles, the material coefficients are evaluated. The special case of a simple shear flow is analyzed in detail. The predicted stresses are compared with the available digital simulation data for a range of solid volume fractions and reasonable agreement is observed. It is shown that the rate-dependent model properly predicts the observed normal stress effects for rapid granular flows in simple shear.

Barrier Crossing Due to Transient Excitation

The first‐passage time problem for the response amplitude of a linear lightly damped single‐degree‐of‐freedom oscillator under evolutionary random excitation is considered. A Markovian approximation of the amplitude allows the use of a Fokker‐Planck equation for the formulation of the problem. This equation is solved exactly for the special case of a step function‐modulated stationary excitation. These results are used in determining a solution for the general excitation case via a Galerkin technique. Pertinent digital simulation data demonstrate the reliability and extreme efficiency of the developed solution method.