Particle image velocimetry for predictions of acceleration fields and force within fluid flows

Jakobsen, Michael Linde; Dewhirst, T.; Greated, Clive

doi:10.1088/0957-0233/8/12/013

Cited by 51 publications

(30 citation statements)

References 6 publications

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“…Christensen and Adrian (2002) found that for their advecting turbulence experiment, the material acceleration was about one order of magnitude smaller than the time change of the velocity at one point, which would also promote the use of a Lagrangian approach. On the other hand, Jakobsen et al (1997) found that for waves impinging on a vertical wall, their Lagrangian approach had limitations and showed bias effects, resulting in a worse performance than their Eulerian approach. These contradictory results show the need of a direct comparison of the two approaches.…”

Section: Introductionmentioning

confidence: 99%

Instantaneous planar pressure determination from PIV in turbulent flow

2011

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This paper deals with the determination of instantaneous planar pressure fields from velocity data obtained by particle image velocimetry (PIV) in turbulent flow. The operating principles of pressure determination using a Eulerian or a Lagrangian approach are described together with theoretical considerations on its expected performance. These considerations are verified by a performance assessment on a synthetic flow field. Based on these results, guidelines regarding the temporal and spatial resolution required are proposed. The interrogation window size needs to be 5 times smaller than the flow structures and the acquisition frequency needs to be 10 times higher than the corresponding flow frequency (e.g. Eulerian time scales for the Eulerian approach). To further assess the experimental viability of the pressure evaluation methods, stereoscopic PIV and tomographic PIV experiments on a square cylinder flow (Re D = 9,500) were performed, employing surface pressure data for validation. The experimental results were found to support the proposed guidelines.

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Section: Introductionmentioning

confidence: 99%

Instantaneous planar pressure determination from PIV in turbulent flow

2011

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“…Unal et al (1998) used a momentum-based approach to determine the instantaneous force on a circular cylinder. Two methods based on the Lagrangian and the Eulerian specifications are compared by Jakobsen et al (1997) using a four-CCD-camera system to predict the acceleration field from velocity measurements in wave phenomena. In the Eulerian description of fluid motion all variables are taken to be functions of time and local position, rather than initial position as in the case of Lagrangian description.…”

Section: Introductionmentioning

confidence: 99%

Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV

Kurtuluş

Scarano

Lee³

2006

Exp Fluids

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The unsteady aerodynamic forces acting on a square cross-sectional cylinder are investigated by means of time-resolved particle image velocimetry (TR-PIV) at Reynolds number 4,900. The objective of the investigation is to prove the feasibility of nonintrusive force measurements around two-dimensional bodies. The PIV measurements performed at a rate of 1 kHz enable a time resolved (TR) description of the vortex shedding phenomenon occurring at 10 Hz and to follow the time evolution of vortex dominated wake. The instantaneous aerodynamic force coefficients are obtained from the integration of the force equations within a control volume enclosing the object. The required instantaneous pressure distribution is inferred making use of two physical models: Bernoulli relation is adopted in the potential slowly-evolving flow region; in the turbulent wake, the Navier-Stokes equations are invoked to determine the pressure gradient spatial distribution, which integrated in space yields the pressure distribution. The spatial acceleration field is directly obtained from the temporal difference of the time-filtered velocity field. For a choice of the control volume approximately one model height away from the surface the contributions to the aerodynamic forces coming from the different terms of the force equation are individually examined. The convective term dominates the unsteady lift forces whereas the pressure term prevails for the drag. The temporal evolution of C L returns a clear periodic pattern in phase with the vortex shedding at a frequency of 10.1 Hz (Strouhal number St = 0.128) with oscillation amplitude of 0.9, whereas C D barely shows periodicity. The measurement uncertainties associated to the evaluation of all the terms in the force equation and especially in relation to TR-PIV measurements are discussed.

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“…Assuming that the temporal velocity gradient is approximately constant or linear in time within the time interval between the two snapshots, dt, and for all spatial locations (Jakobsen et al, 1997), the acceleration at time t (eq. 3), as well as the pressure gradient (eq.…”

Section: Eulerian Approach (Eu)mentioning

confidence: 99%

“…However, the acceleration can also be determined using a Lagrangian approach and the comparison of the two methods has also been the focus of several recent works. Using PIV on surface waves to predict flow accelerations and forces, Jakobsen et al (1997) compared Eulerian and Lagrangian approaches and the results indicated that the former approach matched closely the analytical calculations. The Lagrangian approach exhibited a small bias, which led to a systematic error in the estimation of flow acceleration and seemed to be limited due to poor tracking or deformation of fluid volume.…”

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confidence: 94%

Full-field pressure from snapshot and time-resolved volumetric PIV

2016

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This paper deals with pressure estimation from snapshot and time-resolved three component (3C) volumetric PIV data using Taylor's hypothesis, an Eulerian and a pseudo-Lagrangian approach. The Taylor's hypothesis approach has been shown to provide accurate results for pressure in the case of 3C planar PIV data with an appropriate choice of convection velocity (de Kat and Ganapathisubramani, 2013) and here we extend its use on 3C volumetric velocity snapshots. Application of the techniques to synthetic data shows that the Taylor's hypothesis approach performs best using the streamwise mean as the convection velocity and is affected the least by noise, while the Eulerian approach suffers the most. In terms of resolution, the pseudoLagrangian approach is the most sensitive. Its accuracy can be improved by increasing the frame time-separation when computing the material derivative, at the expense of volume loss from fluid parcels leaving the FOV. Comparison of the techniques on turbulent boundary layer data with DNS supports these observations and shows that the Taylor's hypothesis approach is the only way we can get pressure when time information is not present.

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Particle image velocimetry for predictions of acceleration fields and force within fluid flows

Cited by 51 publications

References 6 publications

Instantaneous planar pressure determination from PIV in turbulent flow

Instantaneous planar pressure determination from PIV in turbulent flow

Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV

Full-field pressure from snapshot and time-resolved volumetric PIV

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