HR: 1340h
AN: H23E-1173    [Abstracts]
TI: Stream Discharge Measurement Using A Large-Scale Particle Image Velocimetry Prototype
AU: * Harpold, A A
EM: aharpold@vt.edu
AF: Virginia Tech Biological Systems Engineering Dept., 300 Seitz Hall, Blacksburg, VA 24061 United States
AU: Mostaghimi, S
EM: smostagh@vt.edu
AF: Virginia Tech Biological Systems Engineering Dept., 300 Seitz Hall, Blacksburg, VA 24061 United States
AB: Good water management is founded on accurate open-channel flow measurements. New technology for measuring discharge in streams and rivers has been pursued due to concerns about safety, accuracy, and costs of traditional methods. Large-Scale Particle Image Velocimetry (LSPIV) is an emerging technology for measuring discharge in streams and rivers. LSPIV is a system capable of measuring velocity fields by collecting and analyzing recorded images of the flow field. The LSPIV system tracks the movement of `tracers' through successive images using statistical correspondence. Cross-correlation algorithms divide the image into small interrogation areas; each producing one displacement vector. The surface velocity field can be used to estimate discharge based on the channel bathymetry. Use of LSPIV for flow measurements in low-order streams has several advantages. LSPIV is not as labor intensive and does not present the safety concerns of the conventional methods during high flow events. Another promise for LSPIV is remote monitoring applications, which could also reduce labor and data management costs. The scheme used in this study for the development of LSPIV follows a logical progression: assimilate current knowledge, develop methods and acquire equipment, conduct laboratory and field experiments for `proof-of-concept', and refine the methods to decrease costs and increase usability. A laboratory prototype was developed and tested in a flume, with good results. The experiment evaluated the LSPIV prototype and a Marsh-McBirney flow meter against the flume manometer. Several conclusions were made from the statistical analysis. The Froude number affects the accuracy of the Marsh-McBirney flow meter and the LSPIV prototype. Therefore, future applications may wish to use an adaptive method to determine input parameters based on flow conditions. The LSPIV prototype produced poor flow measurements at camera angles above a 30 degree oblique angle. Therefore, field applications should use camera positions that reduce the oblique angle below 30 degrees. However, a zero degree camera angle may cause out-of-plane losses, which will reduce velocity measurements. The LSPIV discharge measurements were found to be equivalent to the flow meter in the laboratory application. Additionally, the prototype was adapted to field conditions and an operating procedure was developed. An experiment testing the proof-of-concept in the field will be completed during the fall of 2004.
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting