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Nicosia, Cyprus

Spiliotis K.G.,University of Cyprus | Radhakrishnan H.,EXA | Georgiou G.C.,University of Cyprus
AIP Conference Proceedings | Year: 2012

The interpallidal network of the two areas, the Globus Pallidus External (GPE) and the Subthalamic nucleus, (STN) plays an important role for controlling the movement. Changes in the dynamics of this network are closed related with the Parkinson Disease (PD) symptoms. In this paper we show how the connectivity between these two areas affects the dynamics of a biophysical-based neuronal-model. By changing the kind of interconnection from local (or lattice) to random structure between the two areas, the system switches the dynamics from correlated and clustered firing state (associated with PD) to a relatively quietness and less correlate state. In addition, the synchronization of the GPE and STN with respect to the connectivity distribution is examined by using the phase synchronization index. © 2012 American Institute of Physics. Source

Perot F.,EXA | Kim M.-S.,EXA | Le Goff V.,EUROXA | Carniel X.,CETIM | And 2 more authors.
Noise Control Engineering Journal | Year: 2013

This paper focuses on a passive noise control device based on a flow obstruction of a certain shape which can reduce a fan's Blade Passing Frequency tonal noise. The obstruction is located upstream of a centrifugal fan with a heat exchanger placed in between. Measurements performed at various operating conditions show that for an optimal position and orientation of the obstruction, the blade passing frequency noise is reduced by 10-13 dB. This paper uses a CFD/CAA approach for modeling this problem and numerically determining the optimized position of the obstruction. Simulations results are also used to provide a better understanding of the physical mechanisms involved in the noise reduction. © 2013 Institute of Noise Control Engineering. Source

Choudhari,NASA | Lockard,NASA | Jenkins,NASA | Neuhart,NASA | And 37 more authors.
21st AIAA/CEAS Aeroacoustics Conference | Year: 2015

This paper presents a summary of the computational predictions and measurement data contributed to Category 7 of the 3rd AIAA Workshop on Benchmark Problems for Airframe Noise Computations (BANC-III), which was held in Atlanta, GA, on June 14-15, 2014. Category 7 represents the first slat-noise configuration to be investigated under the BANC series of workshops, namely, the 30P30N two-dimensional high-lift model (with a slat contour that was slightly modified to enable unsteady pressure measurements) at an angle of attack that is relevant to approach conditions. Originally developed for a CFD challenge workshop to assess computational fluid dynamics techniques for steady high-lift predictions, the 30P30N configurations has provided a valuable opportunity for the airframe noise community to collectively assess and advance the computational and experimental techniques for slat noise. The contributed solutions are compared with each other as well as with the initial measurements that became available just prior to the BANC-III Workshop. Specific features of a number of computational solutions on the finer grids compare reasonably well with the initial measurements from FSU and JAXA facilities and/or with each other. However, no single solution (or a subset of solutions) could be identified as clearly superior to the remaining solutions. Grid sensitivity studies presented by multiple BANC-III participants demonstrated a relatively consistent trend of reduced surface pressure fluctuations, higher levels of turbulent kinetic energy in the flow, and lower levels of both narrow band peaks and the broadband component of unsteady pressure spectra in the nearfield and farfield. The lessons learned from the BANC-III contributions have been used to identify improvements to the problem statement for future Category-7 investigations. © 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved. Source

Yakhot V.,Boston University | Bartlett C.,Boston University | Chen H.,EXA | Shock R.,EXA | And 2 more authors.
Notes on Numerical Fluid Mechanics and Multidisciplinary Design | Year: 2015

Renormalization or coarse-graining applied to basic equations governing multi -scale phenomena, leading to effective equations for large-scale properties is often called model-building. Unlike fluids in thermodynamic equilibrium, in case of high-Reynolds number turbulent flows the procedure leads to generation of an infinite number relevant high-order nonlinearities which are hard to deal with. In this paper, based on the recently discovered universality of transition to strongly non- Gaussian (anomalous) statistics of velocity derivatives, we show that in the infrared limit k → 2π/L, where L is the integral scale corresponding to the top of inertial range, the lowest-order contributions to the renormalized perturbation expansion give asymptotically exact equations for the large-scale features of the flow. The quality of the derived models is demonstrated on a few examples of complex flows. At the small scales Δ < L, an infinite number of O(1) non-linear terms, generated by the procedure invalidate low-order models widely used for Large-Eddy-Simulations (LES) of turbulent flows. © Springer International Publishing Switzerland 2015. Source

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