Transonic viscous flow calculations for a turbine cascade with a two equation turbulence model

A numerical method for the study of steady, transonic, turbulent viscous flow through plane turbine cascades is presented. The governing equations are written in Favre-averaged form and closed with a first order model. The turbulent quantities are expressed according to a two-equation kappa-epsilon model where low Reynolds number and compressibility effects are included. The solution is obtained by using a pseudo-unsteady method with improved perturbation propagation properties. The equations are discretized in space by using a finite volume formulation. An explicit multistage dissipative Runge-Kutta algorithm is then used to advance the flow equations in the pseudo-time. First results of calculations compare fairly well with experimental data

Two-dimensional Euler and Navier-Stokes Time accurate simulations of fan rotor flows

Two numerical methods are presented which describe the unsteady flow field in the blade-to-blade plane of an axial fan rotor. These methods solve the compressible, time-dependent, Euler and the compressible, turbulent, time-dependent, Navier-Stokes conservation equations for mass, momentum, and energy. The Navier-Stokes equations are written in Favre-averaged form and are closed with an approximate two-equation turbulence model with low Reynolds number and compressibility effects included. The unsteady aerodynamic component is obtained by superposing inflow or outflow unsteadiness to the steady conditions through time-dependent boundary conditions. The integration in space is performed by using a finite volume scheme, and the integration in time is performed by using k-stage Runge-Kutta schemes, k = 2,5. The numerical integration algorithm allows the reduction of the computational cost of an unsteady simulation involving high frequency disturbances in both CPU time and memory requirements. Less than 200 sec of CPU time are required to advance the Euler equations in a computational grid made up of about 2000 grid during 10,000 time steps on a CRAY Y-MP computer, with a required memory of less than 0.3 megawords

Three-dimensional Euler time accurate simulations of fan rotor-stator interactions

A numerical method useful to describe unsteady 3-D flow fields within turbomachinery stages is presented. The method solves the compressible, time dependent, Euler conservation equations with a finite volume, flux splitting, total variation diminishing, approximately factored, implicit scheme. Multiblock composite gridding is used to partition the flow field into a specified arrangement of blocks with static and dynamic interfaces. The code is optimized to take full advantage of the processing power and speed of the Cray Y/MP supercomputer. The method is applied to the computation of the flow field within a single stage, axial flow fan, thus reproducing the unsteady 3-D rotor-stator interaction

An explicit Runge-Kutta method for turbulent reacting flow calculations

The paper presents a numerical method for the solution of the conservation equations governing steady, reacting, turbulent viscous flow in two-dimensional geometries, in both Cartesian and axisymmetric coordinates. These equations are written in Favre-averaged form and closed with a first order model. A two-equation K-epsilon model, where low Reynolds number and compressibility effects are included, and a modified eddy-break up model are used to simulate fluid mechanics turbulence, chemistry and turbulence-combustion interaction. The solution is obtained by using a pseudo-unsteady method with improved perturbation propagation properties. The equations are discretized in space by using a finite volume formulation. An explicit multi-stage dissipative Runge-Kutta algorithm is then used to advance the flow equations in the pseudo-time. The method is applied to the computation of both diffusion and premixed turbulent reacting flows. The computed temperature distributions compare favorably with experimental data

Il Duomo: Catterdrale

The idea for the ensemble, titled Il Duomo, is inspired by the beauty and detail of cathedrals in Europe. Each piece of the Cattedrale collection utilizes various means of fabric manipulation to emulate the immaculate detail in the cathedral architecture. Il Duomo is inspired by Il Duomo di Milano in Italy

Experimental and Numerical study of a hydrogen fuelled I.C. engine fitted with the hydrogen assisted jet ignition system

The use of hydrogen as an engine fuel poses several challenges as well as opportunities in engine design and control. These challenges are mainly due to hydrogen's high flame temperatures at near stoichiometric mixtures, as well as the reactant volume fraction which can reduce the engine power output significantly. However, the wide flammability limits of hydrogen combustion in air means that a large part of the engine operation regime can be achieved without the use of the engine throttle or exhaust after treatment. This paper presents results of experiments and computations for a research single cylinder pressure boosted hydrogen fuelled internal combustion engine (H2ICE) fitted with the Hydrogen Assisted Jet Ignition system (HAJI) and running extremely lean mixtures

Fractal Graphene Patch Antennas and the THz Communications Revolution

Fractal antennas have and are continuing to receive attention in regard to the futureof wireless communications. This is because of their wide- and multi-band capabilities, theopportunity of fractal geometries to drive multiple resonances, and, the ability to make smallerand lighter antennas with fewer components and radiative elements with higher gains. Smallscale (i.e. on the micro- and nano-scale) and ultra high frequency (in the Terahertz or THz range)fractal antennas composed of Graphene have the potential to enhance wireless communicationsat a data rate that is unprecedented, i.e.∼1012bits per second. A Fractal Graphene antennais a high-frequency tuneable antenna for radio communications in the THz spectrum, enablingunique applications such as wireless nano-networks. This is because (mono-layer) Grapheneis a one-atom-thick two-dimensional allotrope of Carbon with the highest known electricalconductivity that is currently unavailable in any other material, including metals such as Goldand Silver. Thus, combining the properties of Graphene with the self-affine characteristics ofa fractal at the micro- and nano-scale, provides the potential to revolutionise communications,at least in the near field (the order of a few metres) for low power systems. In this paper, weconsider the basic physics and some of the principle mathematical models associated with thedevelopment of this new disruptive technology in order to provide a guide to those engagedin current and future research, a fractal Graphene antenna being an example of an advancedmaterial for demanding applications. This includes some example simulations on the THz fieldpatterns generated by a fractal patch antenna composed of Graphene whose conductivity istaken to scale with the inverse of the frequency according to a ‘Drude’ model. The approachto generating THz sources using Graphene is also explored based on Infrared laser pumping toinduce a THz photo-current

Fractal Graphene Patch Antennas and the THz Communications Revolution

Fractal antennas have and are continuing to receive attention in regard to the futureof wireless communications. This is because of their wide- and multi-band capabilities, theopportunity of fractal geometries to drive multiple resonances, and, the ability to make smallerand lighter antennas with fewer components and radiative elements with higher gains. Smallscale (i.e. on the micro- and nano-scale) and ultra high frequency (in the Terahertz or THz range)fractal antennas composed of Graphene have the potential to enhance wireless communicationsat a data rate that is unprecedented, i.e.∼1012bits per second. A Fractal Graphene antennais a high-frequency tuneable antenna for radio communications in the THz spectrum, enablingunique applications such as wireless nano-networks. This is because (mono-layer) Grapheneis a one-atom-thick two-dimensional allotrope of Carbon with the highest known electricalconductivity that is currently unavailable in any other material, including metals such as Goldand Silver. Thus, combining the properties of Graphene with the self-affine characteristics ofa fractal at the micro- and nano-scale, provides the potential to revolutionise communications,at least in the near field (the order of a few metres) for low power systems. In this paper, weconsider the basic physics and some of the principle mathematical models associated with thedevelopment of this new disruptive technology in order to provide a guide to those engagedin current and future research, a fractal Graphene antenna being an example of an advancedmaterial for demanding applications. This includes some example simulations on the THz fieldpatterns generated by a fractal patch antenna composed of Graphene whose conductivity istaken to scale with the inverse of the frequency according to a ‘Drude’ model. The approachto generating THz sources using Graphene is also explored based on Infrared laser pumping toinduce a THz photo-current

Simulations of Multi Combustion Modes Hydrogen Engines for Heavy Duty Trucks

The paper presents the numerical study of a diesel direct injection heavy duty truck engine converted to hydrogen. The engine has a power turbine connected through a clutch and a continuously variable transmission to the crankshaft. The power turbine may be disconnected and by-passed when it is inefficient or inconvenient to use. The conversion is obtained by replacing the Diesel injector with a hydrogen injector and the glow plug with a jet ignition device. The hydrogen engine operates different modes of combustion depending on the relative phasing of the main injection and the jet ignition. The engine generally operates mostly in Diesel-like mode, with the most part of the main injection following the suitable creation in cylinder conditions by jet ignition. For medium-low loads, better efficienciy is obtained with the gasoline-like mode jet igniting the premixed homogeneous mixture at top dead centre. It’s permitted at higher loads or at very low loads for the excessive peak pressure or the mixture too lean to burn rapidly. The hydrogen engine has better efficiency than Diesel outputs and fuel conversion. Thanks to the larger rate of heat release, it has the opportunity to run closer to stoichiometry and the multi mode capabilities. The critical area for this engine development is found in the design of a hydrogen injector delivering the amount of fuel needed to the large volume cylinder within a Diesel-like injection time

Nanometric resolution magnetic resonance imaging methods for mapping functional activity in neuronal networks

This contribution highlights and compares some recent achievements in the use of k-space and real space imaging (scanning probe and wide-filed microscope techniques), when applied to a luminescent color center in diamond, known as nitrogen vacancy (NV) center. These techniques combined with the optically detected magnetic resonance of NV, provide a unique platform to achieve nanometric magnetic resonance imaging (MRI) resolution of nearby nuclear spins (known as nanoMRI), and nanometric NV real space localization. Atomic size optically detectable spin probe. High magnetic field sensitivity and nanometric resolution. Non-invasive mapping of functional activity in neuronal networks