Assessment of the wall shear stress measurement with arrayed micro hot-film sensors in a turbulent channel flow

Arrayed micro hot-film sensors for the measurement of the streamwise and spanwise wall shear stresses were developed and evaluated in a turbulent channel flow. The bandwidth of the sensor is found to be much narrower than previous estimates in the literature. A numerical analysis of the unsteady thermal field around the sensor chip is made in order to obtain a clue to design a hot-film shear stress sensor having higher frequency response. It is found that the phase lag of the thermal boundary layer above the hot-film and the indirect convective heat transfer through the diaphragm are responsible for the deteriorated sensor response.