Mixing in convective thermal fluxes in unsteady nonhomogeneous flows generating complex three dimensional vorticity patterns

Diffusion and scaling of the velocity and vorticity in a thermoelectric driven heating and cooling experimental device is presented in order to map the different patterns and transitions between two and three dimensional convection in an enclosure with complex driven flows. The size of the water tank is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks can be regulated both in power and sign [1-3]. The thermal convective driven flows are generated by means of Peltier effects in 4 wall extended positions of 0.05 x 0.05 cm each. The parameter range of convective cell array varies strongly with the Topology of the boundary conditions. Side heat and momentum fluxes are a function of Rayleigh, Peclet and Nusselt numbers, [4-6] Visualizations are performed by PIV, Particle tracking and shadowgraph. The structure of the flow is shown by setting up a convective flow generated by buoyant heat fluxes. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form a density interface and low Prandtl number mixing with temperature gradients. The evolution of the mixing fronts are compared and the topological characteristics of the merging of the convective structures are examined for different configurations. Based on two dimensional Vorticity spectral analysis, new techniques can be very useful to determine the evolution of scales considering the multi-fractal structure of the convective flows.Peer ReviewedPostprint (published version

An overview on armor research for the laser fusion project HiPER

During the current preparatory phase of the European laser fusion project HiPER, an intensive effort has being placed to identify an armour material able to protect the internal walls of the chamber against the high thermal loads and high fluxes of x-rays and ions produced during the fusion explosions. This poster addresses the different threats and limitations of a poly-crystalline Tungsten armour. The analysis is carried out under the conditions of an experimental chamber hypothetically constructed to demonstrate laser fusion in a repetitive mode, subjected to a few thousand 48MJ shock ignition shots during its entire lifetime. If compared to the literature, an extrapolation of the thermomechanical and atomistic effects obtained from the simulations of the experimental chamber to the conditions of a Demo reactor (working 24/7 at hundreds of MW) or a future power plant (producing GW) suggests that “standard” tungsten will not be a suitable armour. Thus, new materials based on nano-structured W and C are being investigated as possible candidates. The research programme launched by the HiPER material team is introduced

An Explicit Nodal Space-Time Discontinuous Galerkin Method for Maxwell’s Equations

A novel implicit nodal Space-Time Discontinuous Galerkin (STDG) method is proposed in this paper. An eigenvalue analysis is performed and compared with that for a DG scheme solved with a 4th-Order Runge-Kutta time integrator. We show that STDG offers a significant improvement of dissipative and dispersive properties and allows larger time steps, regardless of the spatial hp-refinement. A domain-decomposition technique is used to introduce an explicit formulation of the method in order to render it computationally efficient.This work is partially funded by the National Projects TEC2010-20841- C04-04, TEC2013-48414-C3-01, CSD2008-00068, P09-TIC-5327, P12-TIC- 1442, and from the GENIL excellence network

Convective thermal fluxes in unsteady non-homogeneous flows

In this paper we describe a novel experimental apparatus consisting of a thermoelectric driven heating and cooling device that could be used in didactic laboratories and research. Is possible to model common environmental flows by means of convective cooling and/or heating. We describe here a four cell device, in a 3D enclosure, but furthermore, it is possible to generate a convective flow of complex profiles using an array of thermoelectric devices (Peltier/Seebeck cells) controlled by a thermal proportional-integral-derivative controller generating a multisource buoyant flux. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. The experiments made by our thermoelectric driven device could be used to analyze complex mixing, in either low or high Prandtl numbers, using scalar or heat transport in different liquids. From the varied experiments carried out with our device, we can compute and visualize the fields of velocity, vorticity, density and their gradients, here just a few configurations and the corresponding flows will be shown.This work was partially supported by the company BEROTZA S.L. under Grant No. UPC-BEROTZA-2014-0880 We would also like to thank FLUMEN-UPC and ERCOFTAC and the PELNoHT for travel support for J.T.. Technology Transfer Centre of Technical University of Catalonia (CTT-UPC) grant supported the implementation and analyses of the experiments. Sincere gratitude is extended to Dr. H. Takeda and Masao Kuramitsu from Hokaido Univ.Peer ReviewedPostprint (author's final draft

Impact of Computer Experience on the Viability and Repeatablity of the Moorfields Motion Displacement Test in a Developing and Underserved African Setting

Background: The current study was designed to explore the effect of computer experience on the viability and testretest repeatability of the Moorfields Motion Displacement Test (MMDT), a novel computer-driven glaucoma screening device, in an African community setting. Methods: 164 healthy subjects were recruited from a semi-rural Mozambican environment, and stratified according to computer experience (computer naïve: n=85, computer familiar: n=79). A suprathreshold screening test algorithm was employed, and the global probability of true damage (GPTD), testing time (TT) and false positive (FP) response rate were recorded. The visual field test was conducted twice on the same eye, and results compared to determine intra-sessional repeatability. Results: No inter-group differences in GPTD or TT (p\u3e0.05) were observed between computer subgroups, although FP response rate was significantly higher among computer naïve subjects (p=0.00 for both tests). No inter-sessional differences were observed for GPTD, TT and FP (p\u3e0.05 for all) for either subgroup. A statistically significant positive correlation was found between repeat GPTD, TT and FP measures for all subgroups (

The Role of the Spatial and Temporal Radiation Deposition in Inertial Fusion Chambers: The case of HiPER

The first wall armour for the reactor chamber of HiPER will have to face short energy pulses of 5 to 20 MJ mostly in the form of x-rays and charged particles at a repetition rate of 5–10 Hz. Armour material and chamber dimensions have to be chosen to avoid/minimize damage to the chamber, ensuring the proper functioning of the facility during its planned lifetime. The maximum energy fluence that the armour can withstand without risk of failure, is determined by temporal and spatial deposition of the radiation energy inside the material. In this paper, simulations on the thermal effect of the radiation–armour interaction are carried out with an increasing definition of the temporal and spatial deposition of energy to prove their influence on the final results. These calculations will lead us to present the first values of the thermo-mechanical behaviour of the tungsten armour designed for the HiPER project under a shock ignition target of 48 MJ. The results will show that only the crossing of the plasticity limit in the first few micrometres might be a threat after thousands of shots for the survivability of the armour

TechnoFusion: new Spanish singular scientific-technical facility for fusion research

Technofusion is the scientific&technical installation for fusion research in Spain, based on three pillars: • It is an open facility to European users. • It is a facility with instrumentation not accesible to small research groups. • It is designed to be closely coordiated with the European Fusion Program. With a budget of 80-100 M€ over five years, several top laboratories will be constructe

Temperature Evolution and Light Species Diffusion in Armor and Structural Material for Inertial Fusion Reactor Chambers: a Case for HiPER 4a

One of the most advance designs for HiPER fusion reactor is a spherical chamber 10 m in diameter based on dry wall concept. In this system, the first wall will have to withstand short energy pulses of 5 to 20 MJ at a repetition rate of 0.5-10 Hz mostly in form of X-rays and charged particles. To avoid melting of the inner surface, the first wall consists on a thin armor attached to the structural material. Thickness (th) and material of each layer have to be chosen to assure the proper functioning of the facility during its planned lifetime