Cohesive Incipient Motion
Camera analysis is being performed to examine the incipient motion of sand particles at the base of a circular wave flume in Gregg Hall at the University of New Hampshire in Durham, New Hampshire. Images of particle motion are being captured with Point Grey’s high-resolution CCD camera, the Grasshopper 2. Once the images are collected, they are analyzed in a Matlab program, MatPIV, which determines their velocity vectors and velocity, knowing the times the images were captured. The objective of this yearlong project is to learn proper technique for sediment transport analysis. This technique could be used in imperative situations, such as oil spills, where it needs to be determined whether oil particles are moving or not in order to initiate the most effective cleanup protocol. To validate this camera analysis technique before the main objective is accomplished, a dry run of the experiment using the same camera analysis procedure will be performed. A sand-bed will be constructed and pulled using a pulley system across a table surface. The Grasshopper 2 will capture the particle images to be analyzed in MatPIV. The velocities obtained in the Matlab program will be compared to experimentally collected velocities found using kinematic equations. Distance and timing of the sand-bed in motion will be collected to use in the kinematic equations. If the MatPIV program provides the same velocities as the experimentally derived velocities via the kinematic equations, it can be concluded that this MatPIV camera analysis technique is valid. Before measurements are taken in the circular wave flume in Gregg Hall, a specific position in the tank must be chosen based off of velocity measurements. A site with uniform flow is desired. Velocity measurements will be taken with Nortek’s 3D velocimetry sensor, the Vector. Once a position has been chosen, data for a 3D flow map will be collected. Based on the collected velocity measurements, a sediment size will be chosen to enable incipient motion of sediment at the base of the flume to be captured using the camera. Once captured, the particles images will be analyzed in MatPIV.
Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant
- Cohesive incipient motion (2012). Ben Anibal, Laura Baldinger and Dustin Metayer. Advisor: Diane Foster.