1,720,995 research outputs found
Diffuser shape optimization for GEM, a tethered system based on two horizontal axis hydro turbines
No full textThis paper concerns the numerical shape optimization of the diffuser of a horizontal axis hydro turbine. The turbine is part of the tethered system GEM developed for harnessing ocean current energy. The applied methodology consists of two phases. Firstly, a diffuser optimization with axis-symmetric 2D CFD simulations has been performed, in which the turbine is modeled with a pressure drop across the actuator disk. Secondly, several 3D CFD computations for the original and optimized configuration have been performed and compared with experiments on the reference diffuser configuration. Results from both 2D CFD axis-symmetric model and experimental data show an increase for the power coefficient, while the 3D CFD model not fully confirms this advantage, even though computations are in good agreement with the reference GEM experimental tests
Improvements in performance estimation of wind turbine blade at low Reynolds number
No full textIn this paper we propose a comparison between two Reynolds–Averaged–Navier–Stokes (RANS) turbulence models as Spalart–Allmaras (S–A) and the more recent transitional k–w SST in
descibing low Reynolds number laminar bubble bursting stall for three different airfoils: a NACA 0012 used as reference airfoil with a well known behaviour and a NACA 0018, widely used on many vertical–axis–wind–turbine (VAWT), of which TU Delft recent experimental data al low Reynolds number are available.
Finally an extension to higher Reynold number is proposed
with an analysis on S809 airfoil. Emphasys is posed on different turbulence models desciption of experimental physical condition such as turbulence intensity and flow field description of laminar
separation inside bubble
CFD sensitivity analysis on bumped airfoil characteristics for inflatable winglet
No full textThe new aerospace technological milestone is
aimed to reducing direct operating costs and pol-
lution. In order to obtain pollution reductions via
high aerodynamic efficiency, a performance anal-
ysis for bumped airfoil based winglet has been pro-
posed. Most conventional aircrafts are equipped
with fixed winglets to decrease the induced drag;
thus, saving more fuel. New projects point to-
wards advanced smart materials and telescopic
wing tip devices to obtain an adaptive morphing
shape that gives, through performance improve-
ment, a fuel consumption reduction resulting in
less pollutants. The focus of this paper is to evalu-
ate the aerodynamic performance, in terms of lift,
drag and moment coefficient for a bumped airfoil
in climb/descent flight condition at 5000 meters
altitude. The performance analysis has been con-
ducted via a numerical investigation of the effects
of bumps number, height and width for inflatable
winglet airfoil, a system that would guarantee a
more comfortable arrangement of extraction sys-
tem and just minor surplus of weight compared to
classical winglet solutions, with all the subsequent
advantages
DES study of airfoil lift coefficient sensitivity to flow turbulence
No full textThe aerodynamic behavior of wind turbines is strongly influenced by the
turbulence level. However, the design of the rotor blades is usually based on experimental results of airfoils operating under laminar conditions. This leads to great uncertainties in the design process, which in turn make wind turbines less reliable and cost-effective. In this work a DES numerical study of the flow around a Wortmann FX 79-W-151A airfoil is performed for different turbulence intensities. Special attention is paid to the resulting loads. The simulations are then compared and validated with already available load measurements. The aim of this work is on one hand to gain a better understanding of the aerodynamics of an airfoil working in a turbulent flow. On the other hand, it is also of great interest to see up to which degree the numerical simulations are able to predict the force coefficients
Hierarchical Multi-follower Decision Making Models with Genetic Algorithms and Applications
No full textConceptual adaptive wing-tip design for pollution reductions
No full textMost of the commercial long-range aircraft are equipped with winglet to decrease the induced drag thus saving more fuel; this feature can also be found on birds, but in conventional aircraft, the winglet device is fixed. Recent projects point toward advanced smart materials and telescopic wing-tip devices to obtain an adaptive morphing shape that gives, through performances improvement, a fuel consumption and so a pollutant reduction. In order to obtain pollution reductions via high aerodynamic efficiency, the design of a telescopic inflatable variable height wing-tip device has been addressed. The span variation is pursued toward a telescopic device that is linked to an inflatable system distributed in chord and along the base of tip, ready to be extruded according to flight conditions. The performance analysis has been conducted especially to evaluate range performance, which mainly provides the relation to fuel consumption. The hinged telescopic device gives the chance of obtaining variation in winglet span according to flight condition requirements in terms of stability and aerodynamic efficiency. The solution of the inflatable system would guarantee a more comfortable arrangement of deployment system and just minor surplus of weight compared to classical winglet solutions, with all the subsequent advantages
Adaptive wing-tip design for pollution reduction
No full textMost of the commercial long-range aircraft are equipped with winglet to decrease the induced drag thus saving more
fuel; this feature can also be found on birds, but in conventional aircraft, the winglet device is fixed. Recent projects point
toward advanced smart materials and telescopic wing-tip devices to obtain an adaptive morphing shape that gives, through performances improvement, a fuel consumption and so a pollutant reduction. In order to obtain pollution reductions via high aerodynamic efficiency, the design of a telescopic inflatable variable height wing-tip device has been addressed. The span variation is pursued toward a telescopic device that is linked to an inflatable system distributed in chord and along the base of tip, ready to be extruded according to flight conditions. The performance analysis has been conducted especially to evaluate range performance, which mainly provides the relation to fuel consumption. The hinged telescopic device gives the chance of obtaining variation in winglet span according to flight condition requirements in terms of stability and aerodynamic efficiency. The solution of the inflatable system would guarantee a more comfortable arrangement of deployment system and just minor surplus of weight compared to classical winglet solutions, with all the subsequent advantages
A Multiple Leader Stackelberg-Nash Model with Genetic Algorithm
No full textWe present a computational methodology to reach a Stackelberg - Nash solution for a hierarchical 2+n person game via genetic algorithm (GA). There are two players acting as leaders in a two level leader-follower model, the rest of players play a noncooperative game and react to the optimal decision taken by the two leaders who also play a noncooperative game between themselves. The idea of the Stackelberg-Nash GA is to bring together genetic algorithms and the leader-follower strategy in order to process a genetic algorithm to build the solution. The follower players, as well as the leader players, make their decisions simultaneously at each step of the evolutionary process, solving a Nash equilibrium problem. In this model the uniqueness of the Nash equilibrium of the follower players has been supposed. Applications to global emission games, together with some test cases, will be illustrated
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