TY - JOUR
T1 - PIV measurements of anisotropy and inhomogeneity in decaying fractal generated turbulence
AU - Discetti, Stefano
AU - Ziskin, Isaac B.
AU - Astarita, Tommaso
AU - Adrian, Ronald
AU - Prestridge, Kathy P.
PY - 2013/12/1
Y1 - 2013/12/1
N2 - 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 ∝ Re λ (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 = Cε k3/2 /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 C ε is not at all constant for this flow, varying by more than a factor of 4 over the observed decay range.
AB - 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 ∝ Re λ (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 = Cε k3/2 /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 C ε is not at all constant for this flow, varying by more than a factor of 4 over the observed decay range.
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U2 - 10.1088/0169-5983/45/6/061401
DO - 10.1088/0169-5983/45/6/061401
M3 - Article
AN - SCOPUS:84885157347
SN - 0169-5983
VL - 45
JO - Fluid Dynamics Research
JF - Fluid Dynamics Research
IS - 6
M1 - 061401
ER -