Measurement of velocity in water flow model

A method for the measurement of the velocity of a flow in a water flow model, characterized by the steps of conducting compressed aerated water into a model water tank through an orifice having at least one hole not more than 3 mm in diameter pierced therethrough, thereby allowing a phenomenon of deareation resulting from a local pressure drop of said water during the passage thereof through the orifice to induce release of a large volume of fine, uniform air bubbles into said flow and causing the portions of said flow containing a dense concentration of said fine, uniform air bubbles to give rise to a field of flow within said water tank;

• projecting a slit of light on said field of flow and thereby making said flow visible in a given cross section by virtue of the irregular reflection of light on said air bubbles;
• photographing said irregularly reflected beams of light with a television camera and displaying said photographed beams of light on the screen of a monitor television set;
• measuring changes of said displayed, irregularly reflected beams of light at two close points with two photosensors on said screen;
• determining a time interval in the changes of irregularly reflected beams of light at said two close points on the basis of mutual, interrelated functions;
• and finding the velocity of said flow with said time interval taken as defining the duration required for the pictured aggregate of air bubbles to move from one to the other of said two photosensors.