A new method of measuring distance and velocity by optical cross correlation technique is described. The method can be used with stationary detectors, and moving surfaces for applications to liquid level and volume flow rate measurements in open channels. Alternatively it can be used with moving detectors over stationary surfaces with application to aero-space, speed, height, and pitch angle measurements. The information cross correlated is the interaction of irregularities on the moving surface with the incident radiation which are detected by optical transducers. The technique involves viewing the surface patterns by four photodetectors from different positions and angles. Cross correlation technique is used to measure the transit times of these patterns through the fields of view of the photodetectors. Distance and velocity which are related to these transit times are then derived by triangulation calculations. The flow in open channels is derived by measuring the liquid surface velocity and level. Combination of these two measurements enables calculation of volume flow rate. Calibration results of a prototype system using the above technique in a hydraulics laboratory for different flow conditions and optical configurations are described. The results indicate tha~measurement accuracy of + 7% with repeatability of ± 4% are obtained. The effects of optical system and flow condition on the cross correlation function are described and criteria to minimize the error in transit time estimation are presented. A dye marker injection system for use at low flows, where random surface patterns do not naturally exist is described. The design of a rugged and portable instrument for flow measurement in open channels capable of unattended operation is described. The results of field trials with the instrument in underground sewers and open channels are presented. The instrument combines the advantages of optical transducers and cross correlation technique. The study and development of aero-space application of distance and velocity measurement by cross-correlation technique for pitch angle measurement is described. A simple laboratory equipment for demonstrating the applicability of the technique together with pitch angle calibration results are presented.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:461344 |
| Date | January 1979 |
| Creators | Kaghazchi, B. |
| Publisher | University of Bradford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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