The Effects of Transverse Inclination on Aeroelastic Cantilever Prisms: Phenomenology, Unsteady Force, and the Base Intensification Phenomenon

TL;DR

This study investigates how transverse inclination affects aeroelastic prism aerodynamics, revealing a base intensification phenomenon that significantly increases unsteady forces and impacts structural safety, especially at low wind speeds.

Contribution

It introduces the concept of Base Intensification caused by transverse inclination, highlighting its effects on wake phenomenology and aerodynamic loads in aeroelastic structures.

Findings

Transverse inclination alters wake phenomenology and breaks symmetry.

Base Intensification increases aerodynamic load by up to 4.3 times.

The phenomenon mainly affects low-speed and VIV regimes.

Abstract

The transverse inclination is a probable scenario when inclined structures experience an inflow of altered attack angles. This work investigates the effects of transverse inclination on an aeroelastic prism through forced-vibration wind tunnel experiments. The aerodynamic characteristics are tri-parametrically evaluated under different wind speeds, inclination angles, and oscillation amplitudes. Results show that transverse inclination fundamentally changes the wake phenomenology by impinging the fix-end horseshoe vortex and breaking the separation symmetry. The aftermath is a bi-polar, once-for-all change in the aerodynamics near the prism base. The suppression of the horseshoe vortex unleashes the Karman vortex, which significantly increases the unsteady crosswind force. After the initial morphology switch, the aerodynamics become independent of inclination angle and oscillation amplitude and depend solely on wind speed. The structure's upper portion does not feel the effect, so this phenomenon is called Base Intensification. The phenomenon only projects notable impacts on the low-speed and VIV regime and is indifferent in the high-speed, quasi-steady Galloping regime. In practice, Base Intensification will disrupt the pedestrian-level wind environment from the unleashed Bernard-Karman vortex shedding, making it erratic and gusty. Moreover, it increases the aerodynamic load at a structure base by as much as 4.3 times. Since fix-end stiffness prevents elastic dissipation, the load translates to massive stress, making detection trickier and failures, if they are to occur, more sudden, extreme, and without any warnings. The 4.3-time amplification also surpasses the safety factor of many standard designs, so transverse inclination deserves engineering attention.