Instantaneous time-constant adjustment of cold-wires acting as resistance thermometers when using multi-wire anemometer probes

A technique is described for unsteady flow measurements which permits automatic time-constant adjustment of a cold-wire resistance thermometer by placing it parallel to one of the inclined wires of a multi-wire hot-wire anemometer array. It is shown that this is possible because the cold-wire's time constant is a function of its effective cooling velocity which in turn is simply related to the voltage squared of a constant temperature hot-wire anemometer if the two wires are parallel. Separation of the hot-wire anemometer's effective cooling velocity into various velocity components prior to compensation is, therefore, not required thus making the technique highly efficient for digital data processing.