Frequency response of hot wires used for atmospheric turbulence measurements in the marine environment

Abstract

We have examined the frequency response of hot wire anemometers using 4.5‐μ tungsten wires with laboratory‐produced salt layers. The salt layers are produced by exposure of the heated wire to a NaCl–water aerosol and are intended to simulate salt layers produced on wires used in the marine environment. The frequency dependence was determined by measuring the response of the wires to a sinusoidal velocity field generated in a sound chamber. The relaxation frequency (or rolloff frequency) was found to vary as t⁻², where t is the thickness of the salt layer, in agreement with the theory presented in this paper. In addition, the dc calibration parameters for thick coatings were investigated and compared with theory.