Fabrication and testing of subminiature multi-sensor hot-wire probes

Abstract

A method has been developed for fabrication of subminiature (0.6 mu m diameter, 200 mu m length) hot-wire sensors. Both single horizontal and X-array hot-wire probes have been produced and tested using methods which also may be applied to subminiature three-wire probes, vorticity probes, pulsed wires or temperature probes, and to sensors of larger diameter. Compared with conventional(2-5 mu m diameter) probes, manufacture of the subminiature probes is more complex, requiring special equipment and careful handling. Although fragile and sometimes prone to drift, the subminiature probes obeyed the same calibration laws as hot-wire probes of conventional size. Measurements of mean statistical quantities and spectra in a turbulent boundary layer demonstrate that, because of their improved spatial resolution, subminiature sensors can provide more accurate measurements in boundary layers than conventional-sized probes.