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De Oliveira Andrade, G.L. (author), Balbino Dos Santos Pereira, R. (author), Timmer, W.A. (author), van Rooij, R.P.J.O.M. (author)
The accuracy of airfoil polar predictions is limited by the usage of imperfect turbulence models. Can machine-learning improve this situation? Will airfoil polars teach the effect of turbulence on skin-friction? We try to answer these questions by refining turbulence treatment in the Rfoil code: boundary layer closure relations are learned...
journal article 2018
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Pires, O (author), Munduate, X (author), Boorsma, K (author), Ceyhan Yilmaz, O. (author), Aa Madsen, H. (author), Timmer, W.A. (author)
Aerodynamic experiments have been executed in the wind tunnel and on a wind turbine blade to measure the impact of roughness on the airfoil characteristics and the associated effect on rotor performance and to establish the transition location on a rotating blade. The wind tunnel tests have been performed in the low-speed, low-turbulence wind...
journal article 2018
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Baldacchino, D. (author), Simao Ferreira, C. (author), de Tavernier, D.A.M. (author), Timmer, W.A. (author), van Bussel, G.J.W. (author)
Passive vane-type vortex generators (VGs) are commonly used on wind turbine blades to mitigate the effects of flow separation. However, significant uncertainty surrounds VG design guidelines. Understanding the influence of VG parameters on airfoil performance requires a systematic approach targeting wind energy-specific airfoils. Thus, the 30...
journal article 2018
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Balbino Dos Santos Pereira, R. (author), De Oliveira Andrade, G.L. (author), Timmer, W.A. (author), Quaeghebeur, E.R.G. (author)
We describe a probabilistic approach to design airfoils for wind energy applications. An analytical expression is derived for the probability of perturbations to the operational blade-section angle of attack. It includes the combined influence of wind shear, yaw-misalignment, and turbulence intensity. The theoretical fluctuations in angle of...
journal article 2018
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Haidari, A.H. (author), Blankert, Bastiaan (author), Timmer, H. (author), Heijman, Sebastiaan (author), van der Meer, W.G.J. (author)
Depletion of fresh groundwater sources as the result of overdraft, salinization and pollution becomes a major problem in parts of the world. Desalination of brackish groundwater by membrane technology, e.g. reverse osmosis (RO), seems to be a promising solution to water scarcity problems. However, energy consumption and concentrate disposal...
journal article 2017
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De Oliveira Andrade, G.L. (author), Timmer, W.A. (author), van Oudheusden, B.W. (author)
We explore integral boundary layer approximations for shear layer flows with vortex generators. The flow field is decomposed to highlight two phenomena: shear over the wall and vortex-driven mixing of the shear layer. The Navier-Stokes Equations are normalized to identify a new adimensional parameter: the vortex strength number (Vg). Usual...
conference paper 2017
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Ubbens, H.H. (author), Dwight, R.P. (author), Sciacchitano, A. (author), Timmer, W.A. (author)
Bobsleighs races nowadays are decided upon hundredths of a second. As the margins are that small the aerodynamics of a bobsleigh can play a significant role in a race outcome. This paper investigates the influence of the gap between the nose and the rear cowling of a two-man bobsleigh. The paper especially focusses on the misalignment between...
journal article 2016
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Baldacchino, D. (author), Manolesos, M. (author), Simao Ferreira, C. (author), Gonz?alez Salcedo, A (author), Aparicio, M. (author), Chaviaropoulos, T. (author), Diakakis, K. (author), Florentie, L. (author), Garci??a, M. (author), Papadakis, G (author), So?rensen, N.N. (author), Timmer, W.A. (author), Troldborg, N. (author), Voutsinas, S. (author), van Zuijlen, A.H. (author)
Experimental results and complimentary computations for airfoils with vortex generators are compared in this paper, as part of an e_ort within the AVATAR project to develop tools for wind turbine blade control devices. Measurements from two airfoils equipped with passive vortex generators, a 30% thick DU97W300 and an 18% thick NTUA T18 have been...
journal article 2016
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De Oliveira Andrade, G.L. (author), Balbino Dos Santos Pereira, R. (author), Timmer, W.A. (author), Ragni, D. (author), Lau, F. (author), van Bussel, G.J.W. (author)
There are many ways to learn from data. Our first experiment consisted in reproducing the way aerodynamicists work [2] with a genetic optimizer. The data pool was too narrow and asymptotic tendencies were unreliable. Our 2nd Experiment, a simple version of [4], had a virtually unlimited data pool and used neural networks. Results were better,...
poster 2016
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Pereira, R. (author), Van Bussel, G.J.W. (author), Timmer, W.A. (author)
The increasing size of Horizontal Axis Wind Turbines and the trend to install wind farms further offshore demand more robust design options. If the pitch system could be eliminated, the availability of Horizontal Axis Wind Turbines should increase. This research investigates the use of active stall control to regulate power production in...
journal article 2014
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Alpern, S. (author), Fokkink, R. (author), Gal, S. (author), Timmer, M. (author)
We present a stochastic game that models ambush/search in a finite region Q which has area but no other structure. The searcher can search a unit area of Q in unit time or adopt an "ambush" mode for a certain period. The searcher "captures" the hider when the searched region contains the hider's location or if the hider moves while the searcher...
journal article 2013
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Saunders-Smits, G.N. (author), Roling, P. (author), Brügemann, V. (author), Timmer, N. (author), Melkert, J. (author)
Over the past four years the Faculty of Aerospace Engineering at Delft University of Technology in the Netherlands has redeveloped its BSc curriculum to mimic an engineering design cycle. Each semester represents a step in the design cycle: exploration; system design; sub-system design; test, analysis & simulation; verification & validation.
conference paper 2012
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Timmer, W.A. (author)
Airfoil characteristics at deep stall angles were investigated. It appeared that the maximum drag coefficient as a function of the airfoil upwind y/c ordinate at x/c=0.0125 can be approximated by a straight line. The lift-drag ratios in deep stall of a number of airfoils with moderate lower surface thickness coincide. It was found that the lift...
conference paper 2010
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Timmer, W.A. (author)
This paper investigates the NACA 63 and 64 6-digit series of airfoils tested in the NACA LTPT in view to verify the RFOIL calculated airfoil characteristics for high Reynolds numbers. Some anomalies in the zero-lift angles of 15% and 18% thick airfoils from these series are identified, both in the airfoil clean case and in case of wrap-around...
conference paper 2009
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Timmer, W.A. (author)
journal article 2008
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Timmer, D.F. (author), De Looff, A.P. (author), Holtrop, A. (author), Van Driel, G.B. (author)
Op 15 januari 1996 is de Wet op de waterkering in werking getreden. DezeWet schrijft voor dat de waterkeringbeheerder iedere vijf jaar aan GedeputeerdeStaten dient te rapporteren over de algemene waterstaatkundige toestand vande primaire waterkeringen in zijn beheersgebied. Gedeputeerde Statenrapporteert vervolgens aan de Minister van Verkeer en...
report 2002
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Bruining, A. (author), Timmer, W.A. (author)
journal article 1992
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Van Benschop, M. (author), Groen, D. (author), Timmer, M. (author)
Document uit de collectie Chemische Procestechnologie
report 1985
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