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Publication# Experimental investigation on the aerodynamic loads and wake flow features of low aspect-ratio triangular prisms at different wind directions

Abstract

The results are described of measurements of the mean and fluctuating forces acting on low aspect-ratio triangular prisms placed vertically on a plane, having isosceles triangular cross-section with 60∘ or 90∘ apex angles and aspect ratios ranging from 1.0 to 3.0. The tests are carried out in a wind-tunnel by varying the wind direction, θ, between 0∘ and 180∘, at a Reynolds number Re ≃1.2×105. Furthermore, for the model with apex angle of 60∘ and aspect ratio 3.0, flow visualizations with tufts and hot-wire measurements are performed, which permit to characterize the wake morphology as a function of wind direction and to assess that an alternate vortex shedding always exists, with a frequency that is roughly inversely proportional to the wake width. The force measurements show that large variations in the mean values of the drag and cross-flow forces occur by varying θ, in strict correspondence with changes in wake flow features. The intensity of the fluctuating cross-flow forces, directly connected with vortex shedding, is found to vary significantly with flow orientation and aspect ratio, and to be approximately proportional to the streamwise projection of the body surface immersed in the separated wake. Finally, an increase in vortex shedding frequency is generally found with decreasing aspect ratio.

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Right triangle

A right triangle (American English) or right-angled triangle (British), or more formally an orthogonal triangle, formerly called a rectangled triangle (ὀρθόσγωνία), is a triangle in which one angle is a right angle (that is, a 90-degree angle), i.e., in which two sides are perpendicular. The relation between the sides and other angles of the right triangle is the basis for trigonometry. The side opposite to the right angle is called the hypotenuse (side c in the figure).

Golden ratio

In mathematics, two quantities are in the golden ratio if their ratio is the same as the ratio of their sum to the larger of the two quantities. Expressed algebraically, for quantities and with , where the Greek letter phi ( or ) denotes the golden ratio. The constant satisfies the quadratic equation and is an irrational number with a value of The golden ratio was called the extreme and mean ratio by Euclid, and the divine proportion by Luca Pacioli, and also goes by several other names.

Display aspect ratio

The display aspect ratio (or DAR) is the of a display device and so the proportional relationship between the physical width and the height of the display. It is expressed as two numbers separated by a colon (x:y), where x corresponds to the width and y to the height. Common aspect ratios for displays, past and present, include 5:4, 4:3, 16:10, and 16:9. To distinguish: The display aspect ratio (DAR) is calculated from the physical width and height of a display, measured each in inch or cm (Display size).

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