To accomplish the objectives of the contract, using the CNR-INM underwater probe, a Stereo-PIV measurements have been performed to investigate the flow in the wake of the OSHIMA ship scale model. A dedicated experimental program has been carried out in the towing tank n. 1 of CNR-INM, based in ROME. Couples of two-frame images have been collected at the selected position, for 2 model draughts, in 5 appendage configurations - one pre-swirl stator (PSS), 3 Ducts and the basic configuration (no appendages except for the Bilge Fins). A multi-plane calibration procedure has been used so to implement the Soloff technique [1] for a high reconstruction accuracy of the third velocity component. 3C-2D instantaneous velocity fields have been obtained with a standard iterative multi-pass window deformation algorithm applied to both two-frame images acquired. To increase the signal-to-noise ratio, a two-step, image pre-processing procedure has been implemented adopting the subtraction of the average image evaluated on the image collection and the background removal through the subtraction of a sliding Gaussian-weighted kernel. The region of interest has been investigated in a single-window whose dimension was 530 x 280 mm2 with a spatial resolution (i.e. vector grid spacing) as fine as 1.54 mm. Once the instantaneous vector fields have been extracted, an ad hoc algorithm has been designed to evaluate all the quantities of interest. Statistical quantities have been calculated on the collected populations to get a better insight into the involved physical phenomena and for comparison to available CFD data. Large differences, in terms of coherent structures (CS), are evident among the investigated configurations as well as between the two draughts. As expected, the different geometrical configurations of the ESD employed deeply influence the formation of the CS as well as their strength and positioning in the investigated area.
Experimental survey on the wake of the OSHIMA ship model using the SPIV technique Part 1. Wake overview without propeller
2019
Abstract
To accomplish the objectives of the contract, using the CNR-INM underwater probe, a Stereo-PIV measurements have been performed to investigate the flow in the wake of the OSHIMA ship scale model. A dedicated experimental program has been carried out in the towing tank n. 1 of CNR-INM, based in ROME. Couples of two-frame images have been collected at the selected position, for 2 model draughts, in 5 appendage configurations - one pre-swirl stator (PSS), 3 Ducts and the basic configuration (no appendages except for the Bilge Fins). A multi-plane calibration procedure has been used so to implement the Soloff technique [1] for a high reconstruction accuracy of the third velocity component. 3C-2D instantaneous velocity fields have been obtained with a standard iterative multi-pass window deformation algorithm applied to both two-frame images acquired. To increase the signal-to-noise ratio, a two-step, image pre-processing procedure has been implemented adopting the subtraction of the average image evaluated on the image collection and the background removal through the subtraction of a sliding Gaussian-weighted kernel. The region of interest has been investigated in a single-window whose dimension was 530 x 280 mm2 with a spatial resolution (i.e. vector grid spacing) as fine as 1.54 mm. Once the instantaneous vector fields have been extracted, an ad hoc algorithm has been designed to evaluate all the quantities of interest. Statistical quantities have been calculated on the collected populations to get a better insight into the involved physical phenomena and for comparison to available CFD data. Large differences, in terms of coherent structures (CS), are evident among the investigated configurations as well as between the two draughts. As expected, the different geometrical configurations of the ESD employed deeply influence the formation of the CS as well as their strength and positioning in the investigated area.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
