Directional sensitivity of wall mounted hot-film gauges

Abstract

The directional sensitivity of a constant temperature, thin, wall mounted hot-film gauge with respect to variations in yaw angle is investigated. Results obtained for the response of a hot-film gauge in a boundary layer flow fit the correlation between the effective cooling velocity for a hot-wire gauge and the yaw angle suggested by other workers. The yaw factor used in this correlation is typically less than 1.0. Results presented for the hot-film gauge in a boundary layer indicate that the yaw factor depends on both the distance into the boundary layer and the magnitude of the free stream velocity. At some velocity, close to zero, the results predict a yaw factor greater than unity. Computer simulations using the turbulence model are presented which verify this prediction. Yaw factors greater than one result because diffusion from the edges of the gauge becomes significant at low velocities with respect to the total heat transferred.

FEM-Analysis of 2D Micromachined Flow Transduers based on aGe-Thermistor Arrays and a Double Bridge Readout

“…Numerous unique flow transducer implementations have been published in the past [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31] but reports on comprehensive exploration of the design space of a given technological approach are not available yet. We have investigated a total of twelve basic flow transducer designs, some of them including subsets, but all simulation models adhere to the aGe microthermistor technology.…”

“…However, the complex interaction of these two thermal subsystems have to be considered for a satisfying result. Consequently, numerous attempts have been made to establish appropriate 2D flow transducers [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29], which are often referred to as wind sensors. The vast diversity of investigated transducer implementations and related requirements on signal conditioning strategies can be perceived from the summary [25].…”