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In the present work, a numerical study is conducted in order to investigate the unsteady aerodynamics of finite-span flapping rigid wings. The non-dimensional incompressible Navier-Stokes equations are solved in their velocity-pressure formulation using a second-order accurate in space and time finite-difference scheme. To tackle the problem of moving boundaries, the governing equations are solved on overlapping structured grids. The main goal is to investigate the wake topology and aerodynamic performance of low aspect-ratio flapping wings and their dependence on the flapping parameters (such as flapping frequency, flapping amplitude and Reynolds number). Specifically, the root-flapping motion characteristic of flying animals is studied. The numerical simulations are performed at a Reynolds number of Re = 1000 (a Reynolds number value often found in nature) and at different values of Strouhal number St.
In the present work, we have studied the root-flapping motion characteristic of flying animals, a subject virtually unexplored. It was found that, indeed, root-flapping motion produces wake structures similar to those of heaving or coupled heaving-and-pitching motions, but with the difference that the latter motions generate larger vortices and forces than root-flapping motion, presumably because the average velocity is higher across the span; aside from this, similar wake regimes occurs at similar St. In general, it was found that for values less than St < 0.25 we are in the drag production regime, for values approximately equal to St = 0.25 we produce little or no drag (or thrust), whereas for values higher that St > 0.25 we are in the thrust production regime.
The simulations also show that the wake of thrust producing, rigid finite-span wings is formed by vortex loops close to the wing surface, that slowly convert into vortex rings as they are convected downstream. It was also observed that the vortex rings are themselves inclined with respect to the free-stream; the angle of inclination of the vortex rings is found to be in the direction of their travel and in the streamwise direction for thrust producing configurations, whereas for drag producing configurations the angle of inclination is opposite to the direction of travel.
Additionally, the effect of aspec- ratio AR on the aerodynamic forces of finite-span wings was also assessed. It was observed that as we increase the wing AR, the aerodynamic forces also increase and this is chiefly attributed to the large area of high aspect ratio wings and to the decrease of three-dimensional effects in long wings. This observation leads us to think that the assumption of two-dimensionality has some validity for birds and insects, where the wings of many species tend to have relatively large aspect ratio.
All the qualitative and quantitative results found during this research support the hypothesis that: “flying and swimming animals cruise at a Strouhal number tuned for high power efficiency”
Most scanners for small animal are based on cone-beam geometry with flat detector orbiting on a circular path. The reconstruction of these systems is usually done with a method based on the algorithm proposed by Feldkamp, Davis and Kress (FDK). The speed increase in the reconstruction for X-ray tomography (CT) is a prerequisite for the expansion of its clinical application. This paper presents an efficient implementation of a reconstruction algorithm FDK-based, modular, which uses the possibilities of parallel computing and efficient interpolation provided in CUDA using texture memory offered by the graphics-processing unit (GPU). The algorithm, tested on a micro-high-resolution CT, has improved the execution speed of a rear-projection stage 40x factor over a sequential implementation of reference written in C, remaining at all times the quality of the reconstruction.
This paper presents a solution to the problem of accelerated reconstruction for FDK. It provides a modular implementation of the stages of filtering and back projection, which improves time on a 25x and 162X respectively. Although it is difficult to make direct comparisons between different implementations due mainly to differences between the hardware, we can say that the proposed implementation is an improvement over recently published a 4x.The main disadvantage of making filtered back projection with different modules is the inability to exploit synergies between the different stages, leading to a significant increase in transfers between CPU and GPU. However, the modularity allows efficient replacement algorithms implemented, facilitating the adaptability of the proposed solution to new architectures and devices.
The chosen strategy is to store the entire volume loaded in main memory and on the projections. This technique significantly reduces processing time and increase the locality of data stored in memory.
The need to interpolate the values of the projection makes the projections are ideal candidates to be stored in texture memory. In this way you get two benefits. On the one hand, the cost of collection is roughly equivalent to a simple reading, saving, the calculation of the interpolation. On the other hand, the cache memory access speeds texture continued access to data physically close.
The objective was to calculate the first few energy levels of fac-Ir(ppy)3 in the gas-phase by means of ab-initio calculations. The main goal was to find a propper description of the orbital space (frozn, active, virtual) in terms of a CAS-SCF calculation, furtheron to calculate a perturbational correction for correlation effects to at least second order and finally to calculate spin-orbit coupling effects on the basis of the configuration space from the CAS calculations.
The main goal, to find a propper active space was achieved. A whole series of frontier orbital combinations was tested in terms of compuational feasibility and physical relevance in time consuming calculations. Based on MP2 and CC2 diagnostics and visual inspections of the frontier orbitals the active was pre-selected. The convergence behaviour in the CAS calculations and the energy convergence with respect to a further enlargement of the active space (which was non significant) could prove the validity of the found CAS space. First results on perturbational energy corrections were achieved. However the usage of different programms resultred in differing values. The reason for that has to be investigated to finish this part and to carry out highly-accurate calcuations as intended. Due to these unforseen problems no attempts to calculate in the last step spin-orbit effects by ab-initio methods could be made, yet.