AN EXPERIMENTAL APPROACH TO THE CALIBRATION AND USE OF TRIPLE HOT-WIRE PROBES

A method of calibrating and extracting velocities from arbitrary geome try triple hot-wire probes has been developed and tested. The three-st ep procedure involves experimental determination of an accurate coolin g law for each wire in the array, use of these models to develop a set of tables relating anemometer output to flow velocity input, and a ta ble look-up procedure to extract the velocities. The functional form f or the cooling law can be arbitrarily chosen and these equations are n ever directly inverted. Solutions are tabulated making use of special variable transformations that separate the dependence on flow angle an d velocity magnitude. Errors in the table look-up procedure are commen surate with those in exact inversion techniques. Most of the error ari ses from accurate determination of the cooling laws. An application to turbulent boundary layer measurements is presented as an example of t he use of the method.