Generalization of the PIV loss-of-correlation formula introduced by Keane and Adrian

Scharnowski, Sven; Grayson, Kristian; Silva, Charitha de; Hutchins, Nicholas; Marušić, Ivan; Kähler, Christian J.

doi:10.1007/s00348-017-2431-x

Cited by 18 publications

(6 citation statements)

References 22 publications

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“…typically 0.8m/s, if U e ≈ 500m/s. Finally the influence of the presence of fluctuations in the third direction w′ was estimated from the work of Scharnowski et al (2017) . The thickness of the light sheet is about 1mm.…”

Section: Introductionmentioning

confidence: 99%

Compressible mixing layer in shock-induced separation

2019

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Unsteadiness in separated shock–boundary layer interactions have been previously analysed in order to propose a scenario of entrainment–discharge as the origin of unsteadiness. It was assumed that the fluid in the separated zone is entrained by the free shear layer formed at its edge, and that this layer follows the properties of the canonical mixing layer. This last point is addressed by reanalysing the velocity measurements in an oblique shock reflection at a nominal Mach number of 2.3 and for two cases of flow deviation ($8^{\circ }$ and $9.5^{\circ }$). The rate of spatial growth of this layer is evaluated from the spatial growth of the turbulent stress profiles. Moreover, the entrainment velocity at the edge of the layer is determined from the mean velocity profiles. It is shown that the values of turbulent shear stress, spreading rate and entrainment velocity are consistent, and that they follow the classical laws for turbulent transport in compressible shear layers. Moreover, the measurements suggest that the vertical normal stress is sensitive to compressibility, so that the anisotropy of turbulence is affected by high Mach numbers. Dimensional considerations proposed by Brown & Roshko (J. Fluid Mech., vol. 64, 1974, 775–781) are reformulated to explain this observed trend.

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Section: Introductionmentioning

confidence: 99%

Compressible mixing layer in shock-induced separation

2019

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“…This shift allows precise flowfield measurements without strong bias errors due to curved streamlines [33]. For the spanwise plane, where the main flow direction is the out-of-plane direction, the time separation was reduced to 0.75 μs to ensure a sufficiently small amount of loss of pairs for reliable velocity estimation, according to [34,35]. For the data evaluation, iterative window correlation including image deformation and Gaussian window weighting was applied.…”

Section: Methodsmentioning

confidence: 99%

Passive Flow Control for the Load Reduction of Transonic Launcher Afterbodies

et al. 2019

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“…Therefore, the selection of the particle size should also consider its effects on particle reconstruction accuracy. (ii) Interrogation volume size: To alleviate the loss-of-pair effect [21,36], which leads to a drastic decrease in the VDP, the upper limit of the ratio of the local particle displacement to the interrogation volume size should be determined. Although the 3D cross-correlation calculation is regarded as an extension of the 2D cross-correlation, whether the 'onequarter rule' can be extended to the third direction (i.e., depth) remains to be verified according to the achievable VDP.…”

Section: Introductionmentioning

confidence: 99%

Approach to select optimal cross-correlation parameters for light field particle image velocimetry

Zhu

Hossain

et al. 2022

Physics of Fluids

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The light field particle image velocimetry (LF-PIV) has shown a great potential for three-dimensional (3D) flow measurement in space-constrained applications. Usually, the parameters of the cross-correlation calculation in the LF-PIV are chosen based on empirical analysis or introduced from conventional planar PIV, which lowers the accuracy of 3D velocity field measurement. This study presents an approach to selecting optimal parameters of the cross-correlation calculation and thereby offers systematic guidelines for experiments. The selection criterion of the interrogation volume size is studied based on the analysis of the valid detection probability of the correlation peak. The optimal seeding concentration and the size of tracer particles are then explored through synthetic Gaussian vortex field reconstruction. The optimized parameters are employed in a cylinder wake flow measurement in a confined channel. A comparative study is conducted between the LF-PIV and a planar PIV system. Results indicate that the LF-PIV along with the optimized parameters can measure the 3D flow velocity of the cylinder wakes accurately. It has been observed that the mean and max errors of velocity decrease by 32.6% and 18.8%, respectively compared to the related LF-PIV techniques without consideration of optimal parameters. Therefore, it is suggested that the optimized cross-correlation parameters in the LF-PIV can improve the accuracy of 3D flow measurement.

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Generalization of the PIV loss-of-correlation formula introduced by Keane and Adrian

Cited by 18 publications

References 22 publications

Compressible mixing layer in shock-induced separation

Compressible mixing layer in shock-induced separation

Passive Flow Control for the Load Reduction of Transonic Launcher Afterbodies

Approach to select optimal cross-correlation parameters for light field particle image velocimetry

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