Vol. 17, No 3-4, 2013 < Volumes
(ISSN 1428-6394)

Contents:

  • Emmanuel A. Anagnostakis On Negative Differential Mobility in Nanophotonic Device Functionality   abstract | full text
  • Georgios E. Zardas and Emmanuel A. Anagnostakis InP:Fe Nanodiode Conductivity Current Persistent Photoenhamcement Decay   abstract | full text
  • Sławomir Dykas, Włodzimierz Wróblewski and Sebastian Rulik Application of Hybrid CFD//CAA Technique for Modeling Pressure Fluctuations in Transonic Flows   abstract | full text
  • Leonardo Pasini and Sandro Feliziani Vehicular Flow Simulators Based on Complex Queuing Systems   abstract | full text
  • Jos\é Fernando Cuenca Jim\énez Particle agglomeration in flow modelled with Molecular Dynamics coupled to a thermal lattice Boltzmann code   abstract | full text
  • Sofiya Tvardovska Influence of External Electric Field on Parameters of Mechanical Waves in Saturated Porous Medium   abstract | full text
  • Krzysztof Tesch On Invariants of Fluid Mechanics Tensors   abstract | full text

Abstracts:

hEmmanuel A. Anagnostakis On Negative Differential Mobility in Nanophotonic Device Functionality

The negative differential mobility (NDM) of two-dimensional carrier-gas against some proper external regulator allowing gradual controlled modification of the nanointerfacial environment tends to occur as interwoven with the nanophotonic device functionality. In this work, several instances from our two-decade principal research of both experimental observation and conceptual prediction concerning nanophotonics NDM are reconsidered towards outlining a global potential for the appearance of the effect.

 

hGeorgios E. Zardas and Emmanuel A. Anagnostakis InP:Fe Nanodiode Conductivity Current Persistent Photoenhamcement Decay

The temporal decay of the persistent photoenhancement of the conductivity current flowing through the active channel of two samples of a typical nanodevice comprising a low resistivity n-type InP:Fe epitaxial layer and a semi-insulating InP:Fe substrate is experimentally investigated at room temperature and interpreted via consideration of the functionality of the diodic interface potential barrier. A mean decay mechanism and its distinct regimes are singled out.

 

hSławomir Dykas, Włodzimierz Wróblewski and Sebastian Rulik Application of Hybrid CFD//CAA Technique for Modeling Pressure Fluctuations in Transonic Flows

Solving AeroAcoustics (CAA) problems by means of the Direct Numerical Simulation (DNS) or even the Large Eddy Simulation (LES) for a large computational domain is very time consuming and cannot be applied widely for engineering purposes. In this paper in-house CFD and CAA codes are presented. The in-house CFD code is based on the LES approach whereas the CAA code is an acoustic postprocessor solving non-linearized Euler equations for fluctuating (acoustic) variables. These codes are used to solve the pressure waves generated aerodynamically by a flow over a rectangular cavity and by the vortex street behind a turbine blade. The obtained results are discussed with respect to the application of the presented numerical techniques to pressure waves modeling in steam turbine stages.

 

hLeonardo Pasini and Sandro Feliziani Vehicular Flow Simulators Based on Complex Queuing Systems

The crux of this paper is to demonstrate how it is possible to model systems of vehicular trafic by means of complex queuing network models. The objects comprising the library that we define in this work all follow the approach whereby they are composed of one or more queuing networks of service systems that are traversed by customers (vehicles).

 

hJos\é Fernando Cuenca Jim\énez Particle agglomeration in flow modelled with Molecular Dynamics coupled to a thermal lattice Boltzmann code

Particle agglomeration can arise naturally (e.g. dust, salt) or as a result of industrial activities andór combustion processes (e.g. spray drying, particle flame synthesis). The process itself and its mechanisms are important for many applications since the physical properties of the final structures are mainly determined by the composition, number, diameter and geometric arrangement of their constituent primary particles. Thus, knowing and controlling the extent of agglomeration meets a growing interest in environmental and industrial concerns. The objective of the paper is to develop a simulation model of particles suspended in a flowing fluid using MD simulations coupled to a Lattice Boltzmann (LB) solver. These simulations allowed determining the agglomerate transport and deposition rates depending on the flow conditions and agglomerate structure and understanding the relationship between agglomerate characteristics (i.e. growth kinetics and morphology) and their behavior in a flow field. Two systems of 2000 and 1000 particles were simulated at 300 K and 600 K both of them in a known fluid. Simulations using a Langevin thermostat were also performed to compare with the LB thermostat. This allowed quantifying the influence of the fluid flow on the agglomeration process and agglomerate properties. In further applications, this will help to a priori tailor the flow conditions to achieve a desired aggregate morphology. As a result, reasonable aggregate morphologies were achieved. One of the main conclusions is that taking into account the fluid flow (LB solver) the agglomeration process of the particles is notably accelerated in comparison to the Langevin simulations. One of the main implications of this work could be the possibility of using a known fluid to accelerate an agglomeration process given a suitable fluid and to find a desirable configuration of agglomerates. Another conclusion is that the agglomeration process is sensitive to the temperature variation and that the number of particles in the system influences the final configuration of agglomerates in LB simulations.

 

hSofiya Tvardovska Influence of External Electric Field on Parameters of Mechanical Waves in Saturated Porous Medium

A dispersive equation for plane longitudinal mechanoelectromagnetic waves in a porous medium, saturated by an electrolytic solution and placed in an external electrical field was obtained and investigated. The main attention was paid to the effect of the electric field on the parameters of waves. It was established that the external field could determine the value and sign of the decay coefficient of the waves of the first kind. This allows influencing the mechanoelectromagnetic wave parameters by suitable choosing of the external electric field intensity, which can be useful for seismoelectric investigations of the Earth's crust.

 

hKrzysztof Tesch On Invariants of Fluid Mechanics Tensors

This paper presents physical interpretations of the first and second invariants of tensors of fluid mechanics. Some examples of elementary applications and meanings are also given.

 

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