Presentation on theme: "Measuring Two-Dimensional Surface Velocity Distribution"— Presentation transcript:
1 Measuring Two-Dimensional Surface Velocity Distribution using Two RiverSondesRalph T ChengCODAR OS and U. S. Geological SurveyJon R. Burau and James DeRoseU. S. Geological SurveyDonald E. Barrick, Calvin C. Teagueand Peter M. LilleboeCODAR Ocean Sensors
2 Outline Radar Technology for Surface Velocity RiverSonde System Multi-Dimensional Channel FlowsTwo-RiverSonde for Two-DimensionalSurface Velocity DistributionProof-of-the-Concept ExperimentsThreemile SloughSacramento River at Georgiana Slough, CADiscussion of Results
3 The widely used approach to estimating total roughness for hydraulic studies is to first estimate a base value for the bed material, and then to add components to this base value for various extraneous flow-retarding elements. These components include:surface irregularitiesvariations in shape and size of the channelobstructionsvegetationThe composited value is then multiplied by a correction factor for meandering of the channel.
4 RiverSonde System UHF radar: 0.7-m radar wavelength (435 MHz) 3-yagi antenna system on bankBragg scatter from 0.35-m wavelength water wavesDoppler shift gives radial velocity, water phase velocity known from their wavelengthTime delay (time-gating) gives distanceMUSIC direction finding gives directionEstimate along-channel flow from radial velocityStraight channel: assume flow parallel to banksComplex geometry: calculate total vectors using 2 RiverSondes
8 Sacramento River near Walnut Grove, CA Delta Cross-Channel, Georgiana Slough
9 Concept of Two RiverSondes for Two-Dimensional Surface Velocity DistributionRadar line of sightRiverSonde AOABOA = Radial Velocity AOB = Radial Velocity BOC = Total VelocityRiver BankCRiverSonde B
10 Continuing Development of RiverSonde at Three Mile Slough San Francisco Bay-Delta(Cooperation with California District)
11 Threemile Slough, California Straight channel between Sacramento andSan Joaquin Rivers in California DeltaTidally-dominated flowIn operation for several years with a singleRiverSondeOne day proof-of-the-concept experiment(21 February 2007) with 2 RiverSondesAntenna interference?Antenna patterns measured in field
17 BASIC FINDINGS:Two-RiverSonde operating in close proximity does not have interference issuesTotal vectors are generated with same software used in SeaSonde for ocean currents5- or 10-m grid spacingManual masking of river banksObserved complex flow pattern during tidal reversal
18 Proof-of-the-Concept II: April 23-25, 2007 Sacramento River at Georgiana Slough, CA Tidally-influenced flowFlow patterns affect fish migration2 RiverSondes1.5 days with units on same bank0.5 day with units on opposite banksAntenna patterns measured with a transponder on a boatUSGS measurementsBoat-mounted ADCP transects every 30 min for 12 hoursFour Flow Stations in the region
19 Proof-of-the-concept at Georgiana Slough Two-RiverSonde Experiment for 2D Velocity Mapping
20 View From Levee SiteGeorgiana SloughSacramento RiverDWRGLVEG
30 Preliminary Conclusion 2-RiverSonde operation works wellBoth units on same bank or on opposite bankTotal vectors generated with same software used with SeaSonde for ocean currentsUnfortunately ADCP transects did not overlap with the complex flow patterns observed by 2-RiverSondeMistakes in the current experiment lead to a better design of the next experimentFurther experiment and Comparisons with in-situ data and numerical model underway
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