Nominal Wake Fluctuation due to Waves

－Volume Mean and Distribution Based on CFD －

Abstract

The KVLCC2 tanker in fully-loaded condition free to heave and pitch at Froude number 0.142 in three head wave-ship length ratios (0.6, 1.1 and 1.6) is simulated by CFDSHIP-IOWA V4.5. The detailed phenomena of nominal wake behaving in waves are studied by analyzing the velocity and vorticity distribution, and vector field on the propeller plane. The periodic change with phase lag for the volume average axial velocity and circulation are observed. The axial velocity distribution is also decomposed by Fourier analysis. Two vortex systems appear: bilge vortex shedding from the hull body and secondary vortex shedding around the shaft. Based on the results, the propulsion design with higher efficiency, more proper engine margin and lower gas emission are expected.