Effects of floating ice on the flow drag of a circular cylinder with finite length

Abstract

In present paper, free surface is covered with artificial ice of uniform size. Effects of characteristic sizes of ice, i.e. DL/D = 0.28, 0.56 and 1.08 (DL is diameter of equivalent circle of ice block section and D cylinder diameter), local coverage ratio n and cylinder draught H on drag of ice-water flows around finite length circular cylinder are investigated experimentally. Two hydrodynamic states when Froude number Fr=0.50 in subcritical and Fr=0.99 in supercritical are selected, where Fr=V/gD, V is towing speed and g gravitational acceleration. When Fr=0.99, wave-making increases drag coefficient by 0.1–0.2. For DL/D = 0.56 and 1.08, cross-correlation coefficient between n and drag coefficient exceeds 0.85. Higher n results in greater drag. With H/D increasing from 0.4 to 2.0, momentum transferred from water pushed by cylinder to ice increases, making relative velocity between ice and cylinder decrease and collision contribution to total drag be reduced. While DL/D = 0.28, ice blocks follow water flow closely due to small inertia, making collision between cylinder and ice blocks weak and drag caused by collision insignificant. Also ice-water mixture is more like single phase flow of higher viscosity than water, with drag coefficient almost not affected by draught.