Contribution
Numerical Evaluation of the Unsteady Surface Pressure Attenuation due to Finite Sensor Size
* Presenting author
Abstract:
The information of flow-induced unsteady surface pressures is of practical interest. Hydrodynamic pressure fluctuations induce surface vibrations, or when scattered by an edge radiate as noise. Measurements of surface pressure require extra care because a large sensing area will produce signal attenuation, whereas a fine construction such as an ultraminiature pressure transducer under a pinhole requires delicate handling. While the attenuated spectrum of a single-point measurement has already been adequately modelled in previous studies, the effect of sensor size on the two-point spectra is less discussed. In this work, we simulated the turbulent boundary-layer over a flat plate at Reτ= 750 using a wall-modeled large-eddy simulation solver (MGLET) and compared it with measurement results at a roughly equal Reτ of 775, measured using an ultraminiature pressure transducer under a 0.5 mm diameter pinhole. The agreement of simulated and measured one-point autospectra proves to be very good, considering the numerical results has a minimum cell height y+= 8.5 and the measurement has a diameter of d+= 28 in viscous units. In the full paper, the effect of sensor size on coherence, phase angle, the calculation of length scales and convection velocities are analyzed.