The intricacies of the “steady-state” regime in methanol-to-hydrocarbons experimentation over H-ZSM-5

The various reaction regimes in methanol to hydrocarbons conversion, i.e. initiation, transition, steady-state and deactivation, have been experimentally assessed over a H-ZSM-5 zeolite with considerable acidity (Si/Al=40). Aiming at directly...

New single vortex generation method for flame/vortex interaction using flow behind a rotating cylinder

This paper investigates a new experimental method to generate a single two-dimensional translated vortex for flame/vortex interaction studies. A rotating cylinder is immersed in a uniform flow and, its rotating speed is impulsively reduced. This sudden action triggers the generation of a single vortex when both the initial and the final rotation speeds are in the range of a steady-state regime. Flow visualization allows confirming the applicability of this method, while a complementary two-dimensional numerical simulation is conducted to understand the vortex formation process. A vorticity layer is detached from the cylinder, initiating a feeding process and gradual growth of a single leading vortex. The feeding process is saturated at a specific distance from the cylinder and, vortex separation from the vorticity layer is observed. At the final stage of the formation process, the generated vortex is advected away and, a steady-state regime is again established behind the cylinder. The vortex characteristics appear to be related to the normalized reduction in the rotation rate ∆α, defined as the initial and final rotation rates difference normalized by the initial rotation rate. Several combinations of initial and final rotation rates corresponding to different normalized reductions are investigated experimentally and numerically. The results allow understanding the effect of this parameter; a higher normalized reduction generates a stronger, more rapidly growing vortex. However, its trajectory is related to the wake deviation corresponding to the final rotation rate.

Simulation of a two-dimensional binary gas mixture outflow into vacuum through a thin slit on the basis of direct solution of the Boltzmann kinetic equation

Two-dimensional binary gas mixture outflow from a vessel into vacuum through a thin slit is studied on the basis of direct solution of the Boltzmann kinetic equation. For evaluation of collision integrals in the Boltzmann equation a conservative projection method is used. Numerical simulation of a two-dimensional argon-neon gas mixture outflow from a vessel into vacuum was performed. Graphs of mixture components flow rate dependence on time during the flow formation, as well as fields of molecular density and temperature for steady-state regime, were obtained.

Numerical Analysis of the Performance of an Innovative Daylighting System Named Modified Double Light Pipe

This paper focuses on the performance of an innovative daylighting system named Modified Double Light Pipe (MDLP). It consists of a device integrating a Double Light Pipe (DLP) with a light shelf. The DLP has been created by the authors to enter daylight into two levels underground buildings. It involves an excessive bulk and the risk of glare in the passage environment. The MDLP is an attempt to solve these problems by coupling the DLP and the light shelf technologies. The authors used a numerical approach modeling the MDLP by the software Rhinoceros and simulating its performance by Grasshopper plugins Ladybug and Honeybee. After calibrating the software by the comparison between numerical and experimental data on the DLP, they carried out a numerical analysis on the MDLP in steady-state and dynamic conditions. In steady-state regime, the MDLP performs better than the DLP, giving quite a uniform illuminance distribution on the horizontal work plane. This is confirmed by the results of the dynamic analysis, carried out evaluating the metric Spatial Daylight Autonomy (sDA). Moreover, the risk of glare is avoided by the MDLP, thanks to the presence of the light shelf that prevents the observer from seeing the device directly.

On the Control of the 2D Navier–Stokes Equations with Kolmogorov Forcing

This paper is devoted to the control problem of a nonlinear dynamical system obtained by a truncation of the two-dimensional (2D) Navier–Stokes (N-S) equations with periodic boundary conditions and with a sinusoidal external force along the x-direction. This special case of the 2D N-S equations is known as the 2D Kolmogorov flow. Firstly, the dynamics of the 2D Kolmogorov flow which is represented by a nonlinear dynamical system of seven ordinary differential equations (ODEs) of a laminar steady state flow regime and a periodic flow regime are analyzed; numerical simulations are given to illustrate the analysis. Secondly, an adaptive controller is designed for the system of seven ODEs representing the approximation of the dynamics of the 2D Kolmogorov flow to control its dynamics either to a steady-state regime or to a periodic regime; the value of the Reynolds number is determined using an update law. Then, a static sliding mode controller and a dynamic sliding mode controller are designed for the system of seven ODEs representing the approximation of the dynamics of the 2D Kolmogorov flow to control its dynamics either to a steady-state regime or to a periodic regime. Numerical simulations are presented to show the effectiveness of the proposed three control schemes. The simulation results clearly show that the proposed controllers work well.

Dissipative and Generative Fractional Electric Elements in Modeling RC and RL Circuits

Generalized capacitor (inductor) is constitutively modeled by expressing charge (magnetic flux) in terms of voltage (current) memory as a sum of instantaneous and power type hereditary contributions and it is proved to be a dissipative electric element by thermodynamic analysis. On the contrary, generalized capacitor (inductor) as a generative electric element is modeled using the same form of the constitutive equation, but by expressing voltage (current) in terms of charge (magnetic flux) memory. These constitutive models are used in transient and steady state regime analysis of the series RC and RL circuits subject to electromotive force, as well as in the study of circuits' frequency characteristics including asymptotic behavior.