• Dr. Scott Slocum
  • ExxonMobil Upstream Research Company
  • 108 Surge Building
  • 4:00 p.m.
  • Faculty Host: Dr. Rakesh Kapania

Model tests of two different types and two different scales were performed with test cylinders fitted with a freely-rotating riser fairing.  At lower flow speeds, both tests showed the fairings to be effective in suppressing vortex-induced vibration (VIV) of the cylinder and in reducing drag. In both tests, however, large lateral cylinder oscillations developed once the flow exceeded a certain critical speed.  Motion amplitudes in one test significantly exceeded those of a bare pipe undergoing VIV.  A simple two-dimensional model of aircraft wing flutter was used to better understand the cause of the oscillations and to relate the onset of the motion to the fairing's specific design characteristics.  The model predicted the observed threshold speeds with reasonable accuracy, suggesting that riser designers can borrow from existing aerodynamic flutter theory to ensure that riser fairings are designed to remain dynamically stable over the range of current speeds expected in service.