Turbulence Sensor Demo at UGA

Direct Measurement of Turbulence Over Hydrofoil with Embedded Turbulence Sensors

NanoSonic demonstrated the use of embedded turbulence sensors to directly measure turbulence on a hydrofoil in a high-speed water tunnel (HSWT) operated by the University of Georgia (UGA). Two flexible turbulence sensors were embedded in a NACA 0018 hydrofoil and placed at the leading edge (x/c = 0.3) and trailing edge (x/c = 0.7) of the chord length. Using the UGA water tunnel, the performance of the NM sensors was evaluated at different flow velocities and angles of attack to characterize various turbulent conditions: attached flow, partially detached flow, and fully detached flow. In each ramp test, the angle of attack (AoA) was kept constant, and the water tunnel velocity was increased stepwise (up to 3.5 m/s in steps of 0.5 m/s) to reach each test point.

 

Leading and trailing edge sensor installation (left) and PIV based visualization of NACA 0018 hydrofoil mounted in the tunnel with NanoSonic sensors embedded into the leading/ trailing edge 

To evaluate the frequency response of the pressure signals over time, a short-time Fourier transform was used. This allowed the frequency content to be analyzed as the velocity changed, specifically in the ramp velocity cases. Spectrograms with a 5° angle of attack on the ramp velocity signal from the leading-edge and trailing-edge sensors are shown. The spectrogram illustrates key behaviors (ladder structure, harmonic frequencies) consistent with tonal noise, emphasizing the sensor's acoustic sensing capability. The static results highlighted the sensors' ability to identify flow disturbances, while taking advantage of upstream and downstream locations. The frequency-domain response showed the sensors' detection of acoustic events and turbulence over the hydrofoil. The static and dynamic responses of NanoSonic’s sensor products highlight a unique advantage of turbulence/pressure sensor technology and emphasize the potential for use in a variety of subsea applications.

 

Spectrogram of pressure signals from a) the leading-edge sensor and b) the trailing edge sensor at AoA = 5° with a filtered pressure signal superimposed and the velocity noted.

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