Reduction of base drag

Tanner, M.

doi:10.1016/0376-0421(75)90003-2

Cited by 91 publications

(35 citation statements)

References 17 publications

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“…Tanner [31] showed the same results as Roshko, where the greatest reduction in base drag occurred when the base flow lacked strong vortex shedding. Thus, it is possible that increased fore-body drag may somehow affect the vortex shedding at the base thereby lowering drag.…”

Section: Introductionmentioning

confidence: 60%

“…It is believed that the absence of vortex shedding may have been caused by the model surface downstream of the base area, which, as discussed previously, is known to impede vortex dynamics (see Roshko [21] and Tanner [31]). However, this observation may also be due to high levels of fore-body drag present here.…”

Section: Wake Measurementsmentioning

confidence: 97%

“…While all of these studies are relevant to base drag and its reduction, this literature review focuses on splitter plates and boundary layer effects. For a more detailed review base drag reduction methods, see Tanner [31].…”

Section: Literature Reviewmentioning

confidence: 99%

“…Tanner [31] reviewed his own work with several wedges, with and without splitter plates, under nominally two-dimensional test conditions. From these tests, it was concluded that a splitter plate of sufficient length (typically four or five times the body thickness) wholly suppressed the periodic vortex shedding from the body and the base flow could be considered "steady" (it should be noted that "steady" base flow is usually highly turbulent).…”

Section: Splitter Platesmentioning

confidence: 99%

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Viscous Drag Measurement and Its Application to Base Drag Reduction

Decker¹

2002

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Public reporting burden for th ls collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining f e. data needed, and completing and reviewing the collection of information. 2D LT DECKER ROBERT K FUNDING NUMBERS PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)UNIVERSITY OF WYOMING PERFORMING ORGANIZATION REPORT NUMBERCI02-75 In this study two important topics have been investigated. First, a new automation procedure has been developed to detect fringe patterns in oil-film interferograms. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)The procedure combines a windowed Fourier transform and a cross correlation technique to determine regions where fringes are likely to reside. The cross correlation of a single cycle cosine function and the original intensity produce a filtered result that isolates the information being sought. The automation procedure is able to capture approximately 75% of the fringes in an image but additional refining of the technique could increase this percentage. Second, the effect of viscous fore-body drag on base drag has been investigated on a 2-D ramp model. Measurements made during the study include oil-film interferometry and hot-wire anemometry for viscous fore-body drag, and pressure measurements on the fore-body and base for fore-body and base drag. The results of this investigation show that an increase in viscous fore-body drag has very little effect on base drag, which contrasts previous studies where increases in viscous fore-body drag tended to decrease base drag. This means that a simple jet pumping mechanism is not the sole effect responsible for base drag reduction in this type of geometry. Hot-wire measurements in the wake of the model show that the flow in the base region is devoid of a dominant shedding frequency. It may be possible that the boundary layer somehow affects the vortex shedding mechanism but further investigations would be necessary to demonstrate that this is true.

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Section: Introductionmentioning

confidence: 60%

Section: Wake Measurementsmentioning

confidence: 97%

Section: Literature Reviewmentioning

confidence: 99%

Section: Splitter Platesmentioning

confidence: 99%

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Viscous Drag Measurement and Its Application to Base Drag Reduction

Decker¹

2002

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“…This can be achieved by either breaking up the coherent structures using serrated trailing edges, by hampering the von Kármán instability with splitter plates or by means of cavities at the trailing edge that shift the shedding vortices away from the airfoil base. An overview of these modifications can be found in Tanner (1975) and Van Dam et al (2008).…”

Section: Improvement Of the Aerodynamic Efficiency In The Blade Root mentioning

confidence: 99%

Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine

et al. 2018

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Abstract. The present study investigates flow dynamics in the hub region of a wind turbine focusing on the influence of nacelle geometry on the root aerodynamics by means of Reynolds averaged Navier-Stokes simulations with the code FLOWer. The turbine considered is a generic version of the Enercon E44 converter incorporating blades with flat-back-profiled root sections. First, a comparison is drawn between an isolated rotor assumption and a setup including the baseline nacelle geometry in order to elaborate the basic flow features of the blade root. It was found that the nacelle reduces the trailed circulation of the root vortices and improves aerodynamic efficiency for the inner portion of the rotor; on the other hand, it induces a complex vortex system at the juncture to the blade that causes flow separation. The origin of these effects is analyzed in detail. In a second step, the effects of basic geometric parameters describing the nacelle have been analyzed with the purpose of increasing the aerodynamic efficiency in the root region. Therefore, three modification categories have been addressed: the first alters the nacelle diameter, the second varies the blade position relative to the nacelle and the third comprises modifications in the vicinity of the blade-nacelle junction. The impact of the geometrical modifications on the local flow physics are discussed and assessed with respect to aerodynamic performance in the blade root region. It was found that increasing the nacelle diameter deteriorates the root aerodynamics, since the flow separation becomes more pronounced. Possible solutions identified to reduce the flow separation are a shift of the blade in the direction of the rotation or the installation of a fairing fillet in the junction between the blade and the nacelle.

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