Scanning tomographic particle image velocimetry applied to a turbulent jet

Casey, Tiernan; Sakakibara, Jun; Thoroddsen, Sigurður T.

doi:10.1063/1.4790640

Cited by 32 publications

(32 citation statements)

References 48 publications

(77 reference statements)

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“…The solutions are first resampled using linear interpolation on epipolar planes with a regularly spaced grid (x, z) for arbitrary y and then resampled again to provide reconstructions on a regularly spaced Cartesian grid (x, y, z). This combines the multiple view problem discussed by Casey et al (2013) and Ponitz et al (2012) with the multiple sheet problem described by Brücker et al (2013). In addition, this method is not restricted to the use of a simple camera pinhole model.…”

Section: Scanning Piv Reconstructionmentioning

confidence: 95%

“…However, the advantages the technique provides in terms of seeding density may justify its use in cases where the flow can be quite slow moving and small-scale information is important. For example, scanning methods have already been applied to the far field of a turbulent jet (Hori and Sakakibara 2004;Diez et al 2011;Casey et al 2013), to study unsteady separation around a flapping wing (David et al 2012) and the unsteady flow field in a model IC engine (Brücker 1997). The present work specifically addresses the issue of how fast one needs to scan.…”

mentioning

confidence: 97%

“…To get around the limitations of conventional tomographic PIV, a number of authors have turned to laser scanning methods (Casey et al 2013;Ponitz et al 2012;Brücker et al 2013). The approach is to perform tomographic reconstructions of the 3D particle field as the first step, then use 3D reconstructions (discretised into cubic voxels) to perform a velocimetry.…”

mentioning

confidence: 99%

“…Brücker et al (2013) solve a tomographic reconstruction problem (although it is not expressed in such terms) for just one camera with many images taken at different laser sheet positions. Ponitz et al (2012) and Casey et al (2013) combine multiple-camera tomographic reconstructions independently calculated for each position of the (thin) laser sheet. Both techniques reduce the incidence of ghost particles and permit high seeding densities to be used.…”

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confidence: 99%

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A scanning PIV method for fine-scale turbulence measurements

Lawson

Dawson

2014

Exp Fluids

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mechanics. It is a desirable aim, as the fine scales are responsible for (amongst other things) the dissipation of kinetic energy and chemical mixing (Tsinober 2009) and have an important role in phenomena such as cloud formation (Bodenschatz et al. 2010) and flame extinction (Sreenivasan 2004). The challenge stems from the fact that as the Reynolds number increases, the smallest length-and timescales become smaller and faster, requiring significant measurement or computational capability to capture even low Reynolds number flows.For laboratory investigations of turbulence, it would be valuable to have an accurate, three-dimensional, three-component (3D-3C) velocimetry technique with good space and time resolution. Of particular importance is access to the full velocity gradient tensor (VGT), as it embodies the fine scales of turbulence and provides direct access to the turbulent kinetic energy dissipation rate (Wallace 2009). Because of the wide range of lengthscales involved, a large spatial dynamic range (SDR, the ratio of the smallest measureable lengthscale to the largest) is also valuable.Hot wire probes with nine, twelve or even twenty wires (Wallace 2009) offer access to the full VGT with good temporal resolution, but are invasive, complicated to calibrate and only offer pointwise measurements. Dual plane PIV can offer a 3D-3C measurement with good accuracy, time and spatial resolution (Mullin and Dahm 2006), but the setup is complex: it requires four cameras and some means of differentiating between planes, usually chromatically by using two different wavelength laser sources. Furthermore, the depth of the measurement volume is very limited (i.e. between two planes), and the full VGT is only available in one plane. Cinematographic stereo PIV can be used to yield snapshots of 3D-3C velocity fields (Ganapathisubramani et al. 2007), but is only applicable to convective flows as it relies upon Taylor's frozen turbulence hypothesis.Abstract A hybrid technique is presented that combines scanning PIV with tomographic reconstruction to make spatially and temporally resolved measurements of the fine-scale motions in turbulent flows. The technique uses one or two high-speed cameras to record particle images as a laser sheet is rapidly traversed across a measurement volume. This is combined with a fast method for tomographic reconstruction of the particle field for use in conjunction with PIV cross-correlation. The method was tested numerically using DNS data and with experiments in a large mixing tank that produces axisymmetric homogeneous turbulence at R ≃ 219. A parametric investigation identifies the important parameters for a scanning PIV setup and provides guidance to the interested experimentalist in achieving the best accuracy. Optimal sheet spacings and thicknesses are reported, and it was found that accurate results could be obtained at quite low scanning speeds. The two-camera method is the most robust to noise, permitting accurate measurements of the velocity gradients and direct determination of the di...

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Section: Scanning Piv Reconstructionmentioning

confidence: 95%

mentioning

confidence: 97%

mentioning

confidence: 99%

mentioning

confidence: 99%

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A scanning PIV method for fine-scale turbulence measurements

Lawson

Dawson

2014

Exp Fluids

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“…5, −∂u/∂x and (∂v/∂y + ∂w/∂z) is a commonly used technique to assess the measurement quality (Tsinober et al 1992;Casey et al 2013;Ganapathisubramani et al 2007;amongst others). For the present tomographic PIV result, this cross-correlation coefficient equals 0.88 (Jodai and Elsinga 2016) and for the VIC+ result it is 0.9994.…”

Section: Velocity Statisticsmentioning

confidence: 99%

Resolving vorticity and dissipation in a turbulent boundary layer by tomographic PTV and VIC+

2017

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dissipation rate is heavily underestimated by tomographic PIV with approximately 50% damping, whereas the VIC+ analysis yields a dissipation rate to within approximately 5% for y + > 25. The fact that dissipation can be directly measured by a volumetric experiment is novel. It differs from existing approaches that involve 2d measurements combined with isotropic turbulence assumptions or apply corrections based on sub-grid scale turbulence modelling. Finally, the study quantifies the spatial response of VIC+ with a sine-wave lattice analysis. The results indicate a twofold increase of spatial resolution with respect to cross-correlation interrogation.

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Long-range μPIV to resolve the small scales in a jet at high Reynolds number

2014

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The investigation of flows at high Reynolds number is of great interest for the theory of turbulence, in that the large and the small scales of turbulence show a clear separation. But, as the Reynolds number of the flow increases, the size of the Kolmogorov length scale (g) drops almost proportionally. Aiming at achieving the adequate spatial resolution in the central region of a selfsimilar round jet at high Reynolds numbers (Re k % 350), a long-range lPIV system was applied. A vector spacing of 1:5g was achieved, where the Kolmogorov length scale was estimated to be 55 lm. The resulting velocity fields were used to characterize the small-scale flow structures in this jet. The autocorrelation maps of vorticity and k ci (the imaginary part of the eigenvalue of the reduced velocity gradient tensor) reveal that the structures of intense vorticity have a characteristic diameter of approximately 10g. From the autocorrelation map of the reduced (2D) rate of dissipation, it is inferred that the regions of intense dissipation tend to organize in the form of sheets with a characteristic thickness of approximately 10g. The regions of intense dissipation have the tendency to appear in the vicinity of intense vortices. Furthermore, the joint pdf of the two invariants of the reduced velocity gradient tensor exhibits the characteristic teapot-shape. These results, based on a statistical analysis of the data, are in agreement with previous numerical and experimental studies at lower Reynolds number, which validates the suitability of longrange lPIV for characterizing turbulent flow structures at high Reynolds number.

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Scanning tomographic particle image velocimetry applied to a turbulent jet

Cited by 32 publications

References 48 publications

A scanning PIV method for fine-scale turbulence measurements

A scanning PIV method for fine-scale turbulence measurements

Resolving vorticity and dissipation in a turbulent boundary layer by tomographic PTV and VIC+

Long-range μPIV to resolve the small scales in a jet at high Reynolds number

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