MEASUREMENTS OF FREE-SURFACE PROFILE IN TRANSIENT FLOW WITH A SIMPLE LIGHT-SLICING METHOD

A simple light-slicing technique for the direct measurement of the fre e-surface shape h(x) in one-directional transient liquid flows is stud ied. The method is used to determine h(x) with a precision of the orde r of 10(-2) mm along a line several centimeters long, allowing for hei ght differences of some millimeters. It is useful for transient flows in rectangular channels in which capillarity and liquid adhesion at wa lls perturb lateral observations; the method can also be used for nond iffusive fluids in cases in which it is not advisable to add diffusive particles.