Open AccessBoundary layer state detection using piezoelectric sensors
Author(s) -
Vincent L. Stuber,
Marios Kotsonis,
Sybrand van der Zwaag
Publication year - 2021
Publication title -
smart materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.898
H-Index - 154
eISSN - 1361-665X
pISSN - 0964-1726
DOI - 10.1088/1361-665x/ac3900
Subject(s) - airfoil , boundary layer , laminar flow , flow separation , bimorph , acoustics , naca airfoil , drag , wind tunnel , boundary layer control , boundary layer thickness , particle image velocimetry , reynolds number , boundary layer suction , mechanics , materials science , physics , turbulence , piezoelectricity
Two piezoelectric series bimorph sensors were embedded below the skin of a NACA 0012 symmetrical airfoil to detect the local state of the boundary layer during wind tunnel testing. Small vanes piercing the airfoil skin were glued onto the bimorphs providing a mechanical coupling to the local mechanical force fluctuations imparted by the local unsteady boundary layer flow. The state of the boundary layer at the sensor sites was varied by changing the angle of attack. The objective of this work was to establish the ability of this sensor concept to accurately distinguish among typical boundary layer states such as attached laminar flow, turbulent flow and separated flow. The output of the sensor was compared to concurrent time-resolved particle image velocimetry measurements, which served as a validation technique. Using the developed sensor response envelope, a single data point time series of the piezo electrical signal was proven to be sufficient to accurately detect the boundary layer state on classical airfoils in the low Reynolds number regime. In projected future applications, single or arrays of bimorph sensors can be used to map the boundary layer of more complex or morphing shape airfoils. The fast response of the sensor can in principle be utilised in closed-loop flow control systems, aimed at drag reduction or lift enhancement.