Spatial resolution of the Stereo PIV technique

Experiments in Fluids (Impact Factor: 1.57). 04/2009; 46(4):643-658. DOI: 10.1007/s00348-008-0589-y

ABSTRACT 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).

  • [Show abstract] [Hide abstract]
    ABSTRACT: An experimental investigation of the turbulence generated by low-blockage-ratio space-filling square fractal grids is performed by means of particle image velocimetry (PIV) in an open-circuit wind tunnel. Careful corrections are performed to account for and eliminate sources of noise and error that become significant in very-low-turbulence-intensity flows such as highly decayed grid turbulence. The signal-to-noise ratio varies between 20 and 70, but despite noise and some spatial filtering, it is possible to accurately measure the turbulent viscous dissipation within ±10%. The results confirm that the proportionality relation Lu /λ ∝ Reλ (where Lu is the integral length scale, λ is the Taylor microscale and Reλ is the Reynolds number based on the Taylor microscale), stemming from the scaling of the turbulent dissipation ε = Cεk3/2 /Lu (where k is the turbulent kinetic energy), does not apply to the turbulence generated by square fractal grids. More importantly, the semi-empirical constant Cε is not at all constant for this flow, varying by more than a factor of 4 over the observed decay range.
    Fluid Dynamics Research 08/2013; 45(6):061401. · 0.76 Impact Factor
  • Proc. SPIE 8511, Infrared Remote Sensing and Instrumentation XX, San Diego, California, USA; 08/2012
  • [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