A theoretical analysis of the spatial resolution in terms of modulation transfer function of the Stereo PIV technique with
and without the correction of the misalignment error is performed, and the results show that some wavelengths of the flow
field can be significantly dephased and modulated. A performance assessment has been conducted with both synthetic and real
images and shows a good agreement with the theoretical analysis. The reconstruction of the three-dimensional displacement
field is achieved using both the methods proposed by Soloff et al. (Meas Sci Technol 8:1441–1454, 1997) and by Willert (Meas Sci Technol 8:1465–1479, 1997).
"In this case, two cameras (PCO, 1280 Â 1024 pixels with a 50 mm Nikon objective, f # ¼ 2.8) have been used in order to obtain also the third velocity component of the flow field (i.e. the one orthogonal to the measurement plane). More details about this technique are reported by Giordano and Astarita . The acquired images are interrogated with a high-accuracy image deformation PIV algorithm described by Astarita  . "
[Show abstract][Hide abstract] ABSTRACT: This work deals with an experimental analysis of the flow field downstream of a finite circular cylinder and of the convective heat transfer coefficient over the wall the cylinder is mounted on. The influence of the cylinder aspect ratio AR and of the Reynolds number Re are investigated. Heat transfer measurements are performed by using infrared thermography along with the heated thin foil heat flux sensor, at four values of Re (4,000, 8,000, 16,000 and 32,000) and four values of AR (1, 2, 4 and 8), while flow field measurements are carried out in the cylinder wake at Re = 16,000 by means of PIV and Stereo PIV for AR = 2 and 8. The average flow field and the coherent structures are investigated in order to understand their influence on the heat transfer topology and enhancement. Some correlations for the heat transfer enhancement are also presented.
[Show abstract][Hide abstract] ABSTRACT: The use of the infrared camera as a temperature transducer in wind tunnel applications is convenient and widespread. Nevertheless, the infrared data are available in the form of 2D images while the observed surfaces are often not planar and the reconstruction of temperature maps over them is a critical task. In this work, after recalling the principles of IR thermography, a methodology to rebuild temperature maps on the surfaces of 3D object is proposed. In particular, an optical calibration is applied to the IR camera by means of a novel target plate with control points. The proposed procedure takes also into account the directional emissivity by estimating the viewing angle. All the needed steps are described and analyzed. The advantages given by the proposed method are shown with an experiment in a hypersonic wind tunnel.
Experiments in Fluids 02/2011; 52(2). DOI:10.1007/s00348-011-1225-9 · 1.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: form only given. Stability of radiographic spot has been under intensive study in recent years because of its importance in high-dose flash X-ray radiography. We have investigated a concept of placing a gas cell in front of the target to improve the stability of the spot size. The idea is to use the incoming electron beam to ionize the gas cell to a favorable density (in a time scale of pulse rise time), which causes charge and current neutralization on the electron beam. For an electron beam such as the DARHT beam (2 kA and 20 MeV), which is well below the Alfven current limit, we believe that there is an intermediate gas pressure regime where the stable beam propagation can be achieved. In our study, we first use a simple rate equation to calculate the ionization of the gas cell by the DAHRT beam. The model includes avalanche and recombination of the ionized electrons.
Plasma Science, 2000. ICOPS 2000. IEEE Conference Record - Abstracts. The 27th IEEE International Conference on; 01/2000
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