The results are described of the measurement of the mean and fluctuating forces acting on triangular prisms placed vertically on a plane, having isosceles triangular cross-section with 60° or 90° apex angles and aspect ratio ranging from 1.0 to 3.0. The tests are carried out in a wind-tunnel by varying the wind direction theta between 0° and 180°, at a Reynolds number Re ≈ 1.2 x 105. Furthermore, for the model with apex angle of 60° and aspect ratio 3.0, hot-wire measurements and flow visualizations with tufts are performed, in order to characterize the wake morphology and to determine the vortex shedding frequency as a function of the wind direction. The results show that large variations in the mean values of the drag and cross-flow forces occur by varying theta. Moreover, the fluctuations of the cross-flow force, connected with vortex shedding, are found to vary significantly with flow orientation, both in terms of frequency and intensity; in particular, the latter is a function of the streamwise projection of the body surface immersed in the separated wake. Moreover, an increasing vortex shedding frequency is generally found with decreasing aspect ratio.
Experimental evaluation of the mean and fluctuating forces on triangular prisms in cross-flow
IUNGO, GIACOMO VALERIO;BURESTI, GUIDO;LOMBARDI, GIOVANNI
2008-01-01
Abstract
The results are described of the measurement of the mean and fluctuating forces acting on triangular prisms placed vertically on a plane, having isosceles triangular cross-section with 60° or 90° apex angles and aspect ratio ranging from 1.0 to 3.0. The tests are carried out in a wind-tunnel by varying the wind direction theta between 0° and 180°, at a Reynolds number Re ≈ 1.2 x 105. Furthermore, for the model with apex angle of 60° and aspect ratio 3.0, hot-wire measurements and flow visualizations with tufts are performed, in order to characterize the wake morphology and to determine the vortex shedding frequency as a function of the wind direction. The results show that large variations in the mean values of the drag and cross-flow forces occur by varying theta. Moreover, the fluctuations of the cross-flow force, connected with vortex shedding, are found to vary significantly with flow orientation, both in terms of frequency and intensity; in particular, the latter is a function of the streamwise projection of the body surface immersed in the separated wake. Moreover, an increasing vortex shedding frequency is generally found with decreasing aspect ratio.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
