Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Quantitative Visualization (QVix) Hydrodynamic Measurement Technique of Multiphase Unsteady Surfaces
Quantitative Visualization (QVix) Hydrodynamic Measurement Technique of Multiphase Unsteady Surfaces
Pages 927-939
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From page 927... ...
The results being presented include comparisons with finger probe measurements, parametric study of QViz variables and data collected from a surface ship model tests. For measurement verification, comparisons were done between the surface displacements measured using QViz and a conventional fingerprobe method.
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From page 928... ...
The pixel information is transferred to the grid coordinates and then transferred to the model coordinates using the grid positional information. Average Images: The images collected using the laser sheet of the free surface profiles and bow spray envelopes show illuminated regions which are to be quantified spatially using the CCD calibrations mentioned above.
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From page 929... ...
These pixel values are then mapped back to the XYZ coordinates using the calibration grid information acquired at the beginning of each run. This method gave good results for cases with high frequency unsteadiness Figure 3: Average image at Station 7, all= 0.7 for model tests on Carriage 5 at DTMB.
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From page 930... ...
An alternative program interrogates at a fixed location in the image, this allows for investigating time varying flows with a moving free surface boundary. Finger Probe-QViz Comparison using Real Time analysis An experimental, in-situ comparison of a finger probe and QViz system was performed to provide a comparison between an established measurement technique and the light sheet method.
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From page 931... ...
Figure 7b: QViz data for 11 degree viewing angle and laser power set at 2.1 watts. Wave peak to peak amplitude is 0.6 inches.
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From page 932... ...
Figure 7d: QViz data for 11 degree viewing angle and laser power set at 2.1 watts. Wave peak to peak amplitude is 3 inches.
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From page 933... ...
figure 9d: QViz frequency analysis for wave 4 figure lea: finger probe wave setting 1 figure lob: finger probe wave setting 2 7
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From page 934... ...
~ '~ 1 5 -2 5 Figure lib: QViz data for a 36 degree viewing angle, laser power at 1.1 watts. Wave setting 2.
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From page 935... ...
20 25 Figure 12d: QViz data at a 36 degree viewing angle, 2 watts with breakwater for wave setting 4. greater recorded image intensity than for less disturbed free surfaces for the same incident laser sheet power Also, as expected, the images become less sharp for longer exposure settings.
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From page 936... ...
Figure 15a: Averaged image for the spray region illuminated by a laser sheet in the bow region of a planning ship model at station 7, xlI'0.7. Average Cross Section Bow Envelope X (inches)
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From page 937... ...
Analyzing time averaged images using the methods developed provides a realistic measure of the mean boundary defined by the spray in the bow region and wake region of surface ship models. It was found that QViz is not viable for largely dynamic surfaces, where there are a large number of discrete scatterers.
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From page 938... ...
In addition, data from different runs is presented in the figures, yet the authors do not indicate the repeatability of the flows created by the four "wave settings" of the manually controlled paddle type wave maker. If the repeatability of the flows could be demonstrated, it would be easier to study the repeatability of the QViz measurement technique.
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From page 939... ...
In addition, data from different runs is presented in the figures, yet the authors do not indicate the repeatability of the flows created by the four "wave settings" of the manually controlled paddle type wave maker. If the repeatability of the flows could be demonstrated, it would be easier to study the repeatability of the QViz measurement technique.
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