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An appropriate choice of physical resolution for the Scale-Resolved Simulations (SRS) method is crucial for the accurate prediction of flow dynamics. The present study deals with numerical simulations of the flow past a circular cylinder using the Partially-Averaged Navier-Stokes bridging method. A subcritical Reynolds number 3900 is investigated at various physical resolution (the ratio of unresolved to total resolved turbulent kinetic energy f k) involving two approaches to estimate the ratio of unresolved to total resolved eddy dissipation rate fε, in particular a low Reynolds number fε = f k and a high Reynolds number fε = 1 approaches. Good agreement with experimental and DNS results was achieved for a higher physical resolution f k ≤ 0.5, fε = 1. The low Re approach led to the earlier transition of the separated boundary layer which resulted in a short recirculation region. Additionally, predicted results from simulations with the low Re approach were not influenced by a refinement of the computational grid.

This paper describes investigation of the influence of the protective layer thickness on the calibration sensitivity of PVDF films sensors for the cavitation impacts measurements. The PVDF film sensor is casted into an aluminium block. The drop ball method is used for the measurement of the relation between impact force and the voltage detected on the PVDF film sensor. The calibration constants are measured for three different protective layers thicknesses. Five different ball weights for 400 mm drop height are used to reach the required impact force range. The ball positions for the evaluation of the impact force are measured with a high speed camera. The voltage signal detected on the PVDF film clamps was measured with a high speed digitizer. The measured signals are analysed in LabVIEW Signal Express.

Piezoelectric PVDF sensors offer a unique option for the measurement of cavitation aggressiveness represented by the magnitude of impacts due to cavitation bubble collapses near walls. The aggressiveness measurement requires specific sensor shape and area, whereas commercial PVDF sensors are fabricated in limited geometry and size ranges. The photolithography method offers a possibility of production of home-made PVDF sensors of arbitrary shape and size. The methodology of a unique application of the standard photolithography method, which is commonly used for the production of printed circuit boards, is described in this paper. It enables mass production of high quality sensors contrary to laboratory techniques. This paper deals with the fabrication and the calibration of a photolithographically home-made PVDF sensor for the cavitation impact load measurement. The calibration of sensors was carried out by the ball drop method. Sensors of different sizes were fabricated by the photolithography method from a multi-purpose, both side metallized PVDF sheet. Commercial PVDF sensors of the same size were calibrated, and the calibration results were compared with the home-made sensors. The effect of size and the effect of one added protective layer of Kapton tape on a sensor sensitivity were investigated. The theoretical and numerical analysis was conducted to explain some issues during the ball impact.

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