Rotational Galloping of Square and Bundle Cylinders in Cross-flow at Low Reynolds Numbers

摘要

The occurrence of rotational or torsional galloping for a square cylinderand a generic bundle is assessed through two-dimensional flow andfluid-structure interaction simulations. A finite element formulationspecifically designed for fluid-structure interactions simulations hasbeen used. Stiffness, damping and added moment of inertia coefficientsare obtained from simulations results. A quasi-steady criterion aimed atpredicting rotational galloping is also evaluated based on cross-flowsimulations around fixed cylinders for various angles of attack. Addedmoment of inertia and torsional fluid damping coefficients arecalculated based on the results of forced rotational oscillationsimulations. Finally, the free angular response of rigid cylindersmounted on torsional springs in cross-flow are obtained from fullycoupled fluid-structure simulations. Results show that fixed and forcedrotations of the cylinders are able to predict quite well the staticdeflection angles and instability ranges respectively.