TY - JOUR
T1 - The effect of porosity on the drag of cylinders
AU - Steiros, K.
AU - Kokmanian, K.
AU - Bempedelis, N.
AU - Hultmark, M.
N1 - Funding Information:
The authors would like to thank D. Hoffman and M. Fan for their help with the measurements. This work was partially funded by the Andlinger Center for Energy and the Environment, and the National Science Foundation under grant CBET-1652583.
Publisher Copyright:
©
PY - 2020
Y1 - 2020
N2 - It is well known that perforation of a flat plate reduces its drag when exposed to a flow. However, studies have shown an opposite effect in the case of cylinders. Such a counterintuitive result can have significant consequences on the momentum modelling often used for wind turbine performance predictions, where increased porosity is intrinsically linked to lower drag. Here, a study of the drag of various types of porous cylinders, bars and plates under steady laminar inflow is presented. It is shown that, for most cases, the drag decreases with increased porosity. Only special types of perforations can increase the drag on both cylinders and bars, either by enhancing the effect of the rear half of the models or by organizing the wake structures. These rare occurrences are not relevant to wind turbine modelling, which indicates that current momentum models exhibit the qualitatively correct behaviour.
AB - It is well known that perforation of a flat plate reduces its drag when exposed to a flow. However, studies have shown an opposite effect in the case of cylinders. Such a counterintuitive result can have significant consequences on the momentum modelling often used for wind turbine performance predictions, where increased porosity is intrinsically linked to lower drag. Here, a study of the drag of various types of porous cylinders, bars and plates under steady laminar inflow is presented. It is shown that, for most cases, the drag decreases with increased porosity. Only special types of perforations can increase the drag on both cylinders and bars, either by enhancing the effect of the rear half of the models or by organizing the wake structures. These rare occurrences are not relevant to wind turbine modelling, which indicates that current momentum models exhibit the qualitatively correct behaviour.
KW - Wakes
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U2 - 10.1017/jfm.2020.606
DO - 10.1017/jfm.2020.606
M3 - Article
AN - SCOPUS:85092298456
SN - 0022-1120
VL - 901
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
M1 - 606
ER -