Unrestrained Cylinders Rolling in Steady Uniform Flows
Abstract
Ordnance remediation projects for underwater sites have suggested that understanding the motion of cylinders (the approximate shape of ordnance) in flows would help to predict regions of ordnance mobility, prioritize remediation efforts, and improve the design of engineering works trap ordnance. Therefore, to develop a better understanding of the motion of cylinders, the characteristics of motion of smooth, unrestrained cylinders in contact with a smooth horizontal bed were investigated in a flume with steady, uniform flows. Inviscid flow theory was used to estimate maximum cylinder velocities and numerical simulations were used to understand the hydrodynamic forces on the cylinders. Eight cylinders were used in the laboratory experiments having varying specific gravities and diameters. At low velocities, experiments showed that the cylinders follow trends similar to those noted in sediment particle studies. Incipient motion velocities were highest for the heavier cylinders. At high flows, the terminal velocity of the cylinders was limited to between 60-80 percent of the free stream flow. The cylinders accelerated to their maximum velocities within about one second. Inviscid-flow theory derivations implied that the maximum velocity of the cylinder would be 71 percent of the free stream flow which was consistent with the experiments. Use of potential flow theory was assumed valid (as an estimator) because experiments verified that flow over the rolling cylinder did not separate from the cylinder surface and that they were reasonably two-dimensional. The numerical results showed that separation from the cylinder would be eliminated by the moving surface of the cylinder. In fact, suppression of separation occurred even when the cylinder was rolling at only 60 percent of the free-stream flow velocity.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2000
- Accession Number
- ADA377851
Entities
People
- Jack E. Davis