Practical flow examples

Over the last five or six years several practical applications of SHV for high sensitivity analysis of local motion have been explored. Usually these have been associated with measurement of stress / strain relationships in yarns & ropes. In such testing the local motions involved can be very small indeed and yet it is imperative that the measurement technique avoids any contact with the material being tested. Equally it is important that any ‘markers’ attached to such materials shall not significantly affect the behaviour of the material - hence it is imperative that such markers are physically very small. Yet again, it proves to be very difficult to guarantee ‘simple’ lighting of the subject matter.

To the right is shown a typical yarn sample as viewed for strain measurements. It will be seen that the measurement / analysis equipment must cope with both specular glare from the (rather shiny) yarn surface and a considerable gradation of background brightness across the field of view.