Julio Soria - Academia.edu (original) (raw)
Papers by Julio Soria
Experiments in Fluids, 1999
Particle Image Velocimetry (PIV) is now a well established experimental technique to measure two... more Particle Image Velocimetry (PIV) is now a well established experimental technique to measure two components of the velocity in a planar region of a flow field. This paper shows how its proven capabilities can be further extended by using holographic recording to register the particle displacements. Among other unique characteristics, holography enables the acquisition of multiple images on a single plate, and the recording of three dimensional images. These features are used to circumvent some of the limitations of conventional PIV. Some of these possibilities are demonstrated in this study by applying the technique to a high Reynolds number swirling flow using a lens-less off-axis orthogonal recording geometry.
Flow Turbulence and Combustion, 1994
This paper describes a method for identifying and visualising the three-dimensional geometry of f... more This paper describes a method for identifying and visualising the three-dimensional geometry of focal (vortex) structures in complex flows. The method is based primarily on the classification of the local topology as it is identified from the values of the velocity gradient tensor invariants. The identification of the local topology is reference frame invariant. Therefore, focal (vortex) structures can be unambiguously identified in these flows. A novel flow visualisation method is introduced whereby focal structures are rendered using a solid model view of the local topology. This new approach is applied to the identification of focal structures in three-dimensional plane mixing layer and plane wake flows.
Experiments in Fluids, 2005
Proper orthogonal decomposition (POD) was performed on both the fluctuating velocity and vorticit... more Proper orthogonal decomposition (POD) was performed on both the fluctuating velocity and vorticity fields of a backward-facing step (BFS) flow at Reynolds numbers of 580 and 4,660. The data was obtained from particle image velocimetry (PIV) measurements. The vorticity decomposition captured the fluctuating enstrophy more efficiently than the equivalent velocity field decomposition for a given number of modes. Coherent structures in the flow are also more easily identifiable using vorticity-based POD. A common structure of the low-order vorticity POD modes suggests that a large-scale similarity, independent of the Reynolds number, may be present for the BFS flow. The POD modes obtained from a vorticity-based decomposition would help in determining a basis for constructing simplified vortex skeletons and low-order flow descriptions based on the vorticity of turbulent flows.
PIV measurements of a zero-net-mass-flux jet in cross flow
Experiments in Fluids, 2002
Particle image velocimetry (PIV) is used to study a circular zero-net-mass-flux (ZNMF) jet in cro... more Particle image velocimetry (PIV) is used to study a circular zero-net-mass-flux (ZNMF) jet in cross flow (JICF). ZNMF jets are formed by using the working fluid of the environment into which the jet is issuing without net transfer of fluid mass into the environment from the ZNMF jet system during one period of oscillation. Two ZNMF-JICF, which are characterized by Re j=1,240, R=4.6, St=0.016 and Re j=2,960, R=7, St=0.014, are investigated in this study. Phase-averaged in-plane velocity and out-of-plane vorticity vector fields in the jet near field are presented and the time-dependent volume flow is calculated to study the structure of the jets. Ensemble-averaged in-plane velocity data in the jet far field were determined to study the mean jet structure. The ensemble-averaged vector fields are used to determine jet trajectory and the velocity variation along the trajectory. These results are discussed and compared to continuous and pulsed jets in cross flow.
Optics and Laser Technology, 1999
This paper describes a novel approach of acquiring two single-exposed, non-overlapping images usi... more This paper describes a novel approach of acquiring two single-exposed, non-overlapping images using half frame image shift (HFIS) recording on photographic ®lm. This technique permits the recording of two single-exposed, non-overlapping images of seed particles in a¯ow plane on high spatial resolution ®lm with any arbitrary time delay between exposures. A new multigrid CCDPIV (MCCDPIV) analysis method is used to analyse the single-exposed, non-overlapping sequential images resulting in PIV measurements with a larger velocity dynamic range, lower random error and better spatial resolution than standard CCDPIV analysis. HFIS recording followed by MCCDPIV analysis was employed to measure the spatio-temporal evolution of the in-plane velocity vector and the out-of-plane vorticity ®elds of a turbulent starting jet at Reynolds numbers based on the ori®ce diameter and piston velocity of 10,780 and 13,860. #
Particle image velocimetry measurements of a backward-facing step flow
Experiments in Fluids, 2002
Particle image velocimetry (PIV) measurements were carried out on a backward-facing step flow at ... more Particle image velocimetry (PIV) measurements were carried out on a backward-facing step flow at a Reynolds number of Re h =U ∞h/ν=4,660 (based on step height and freestream velocity). In-plane velocity, out-of-plane vorticity, Reynolds stress and turbulent kinetic energy production measurements in the x–y and x–z planes of the flow are presented. Proper orthogonal decomposition was performed on both the fluctuating velocity and vorticity fields of the x–y plane PIV data using the method of snapshots. Low-order representations of the instantaneous velocity fields were reconstructed using the velocity modes. These reconstructions provided insight into the contribution that the various length scales make to the spatial distribution of mean and turbulent flow quantities such as Reynolds stress and turbulent kinetic energy production. Large scales are found to contribute to the Reynolds stresses and turbulent kinetic energy production downstream of reattachment, while small scales contribute to the intense Reynolds stresses in the vicinity of reattachment.
A study of the evolution and characteristics of the invariants of the velocity-gradient tensor in isotropic turbulence
Journal of Fluid Mechanics, 1999
Abstract Since the availability of data from direct numerical simulation (DNS) of turbulence, res... more Abstract Since the availability of data from direct numerical simulation (DNS) of turbulence, researchers have utilized the joint PDFs of invariants of the velocity gradient tensor to study the geometry of small-scale motions of turbulence. However, the joint PDFs only give an ...
Turbulence structures of wall-bounded shear flows found using DNS data
Journal of Fluid Mechanics, 1998
This work extends the study of the structure of wall-bounded flows using the topological properti... more This work extends the study of the structure of wall-bounded flows using the topological properties of eddying motions as developed by Chong et al. (1990), Soria et al. (1992, 1994), and as recently extended by Blackburn et al. (1996) and Chacin et al. (1996). In these works, regions of flow which are focal in nature are identified by being enclosed
Identification and classification of topological structures in free shear flows
Multigrid approach to cross-correlation digital PIV and HPIV analysis
Journal of Fluids and Structures, 1994
Journal of Fluids and Structures, 1994
Experimental Thermal and Fluid Science, 1996
Results are presented on (1) the shear layer vortices developing in the free shear layers located... more Results are presented on (1) the shear layer vortices developing in the free shear layers located between the separation point and the first shed Strouhal vortex of a circular cylinder and (2) the longitudinal vortices developing in the braid region of the Strouhal vortices in the wake.
Experimental Thermal and Fluid Science, 1996
HA cross-correlation particle image velocimetry (PIV) technique has been developed to measure the... more HA cross-correlation particle image velocimetry (PIV) technique has been developed to measure the spatiotemporal in-plane velocity vector field evolution of time-dependent flows. A novel iterative two-stage crosscorrelation scheme of two sequential images of flow tracers has been incorporated in the image analysis. The implementation in hardware and software of this complete recording and analysis system are described. The expected accuracy of the velocity measurements was investigated and is discussed. The technique has been applied to study the near wake behind a circular cylinder at low Reynolds numbers (Red). The measurements presented pertain to cylinders with d = 12.5 and 25 mm (l/d = 19.5 and 9.8, respectively). The respective Reynolds numbers Re d are 875 and 769. Two planes of this flow are considered in this study: (1) plane normal to the cylinder axis (xy plane) and (2) a plane containing the cylinder axis and the stream direction (xz plane). Instantaneous in-plane velocity vector fields and out-of-plane vorticity fields are presented for both planes. The effect of spatial resolution on peak vorticity is discussed using velocity vector field measurements in the near wake of the cylinder that were conducted using different spatial resolutions. The three-dimensional nature of the near wake of circular cylinders at low Re d is demonstrated using quantitative in-plane velocity vector field and out-of-plane vorticity measurements. An upstream influx of relatively high velocity fluid into the stagnant near-wake region in the xy plane and the subsequent deflection of the fluid normal to this plane as it approaches the stagnation region at the cylinder are shown to be responsible for the generation of three-dimensional flow in the near wake of a circular cylinder.
Experiments in Fluids, 1999
Particle Image Velocimetry (PIV) is now a well established experimental technique to measure two... more Particle Image Velocimetry (PIV) is now a well established experimental technique to measure two components of the velocity in a planar region of a flow field. This paper shows how its proven capabilities can be further extended by using holographic recording to register the particle displacements. Among other unique characteristics, holography enables the acquisition of multiple images on a single plate, and the recording of three dimensional images. These features are used to circumvent some of the limitations of conventional PIV. Some of these possibilities are demonstrated in this study by applying the technique to a high Reynolds number swirling flow using a lens-less off-axis orthogonal recording geometry.
Flow Turbulence and Combustion, 1994
This paper describes a method for identifying and visualising the three-dimensional geometry of f... more This paper describes a method for identifying and visualising the three-dimensional geometry of focal (vortex) structures in complex flows. The method is based primarily on the classification of the local topology as it is identified from the values of the velocity gradient tensor invariants. The identification of the local topology is reference frame invariant. Therefore, focal (vortex) structures can be unambiguously identified in these flows. A novel flow visualisation method is introduced whereby focal structures are rendered using a solid model view of the local topology. This new approach is applied to the identification of focal structures in three-dimensional plane mixing layer and plane wake flows.
Experiments in Fluids, 2005
Proper orthogonal decomposition (POD) was performed on both the fluctuating velocity and vorticit... more Proper orthogonal decomposition (POD) was performed on both the fluctuating velocity and vorticity fields of a backward-facing step (BFS) flow at Reynolds numbers of 580 and 4,660. The data was obtained from particle image velocimetry (PIV) measurements. The vorticity decomposition captured the fluctuating enstrophy more efficiently than the equivalent velocity field decomposition for a given number of modes. Coherent structures in the flow are also more easily identifiable using vorticity-based POD. A common structure of the low-order vorticity POD modes suggests that a large-scale similarity, independent of the Reynolds number, may be present for the BFS flow. The POD modes obtained from a vorticity-based decomposition would help in determining a basis for constructing simplified vortex skeletons and low-order flow descriptions based on the vorticity of turbulent flows.
PIV measurements of a zero-net-mass-flux jet in cross flow
Experiments in Fluids, 2002
Particle image velocimetry (PIV) is used to study a circular zero-net-mass-flux (ZNMF) jet in cro... more Particle image velocimetry (PIV) is used to study a circular zero-net-mass-flux (ZNMF) jet in cross flow (JICF). ZNMF jets are formed by using the working fluid of the environment into which the jet is issuing without net transfer of fluid mass into the environment from the ZNMF jet system during one period of oscillation. Two ZNMF-JICF, which are characterized by Re j=1,240, R=4.6, St=0.016 and Re j=2,960, R=7, St=0.014, are investigated in this study. Phase-averaged in-plane velocity and out-of-plane vorticity vector fields in the jet near field are presented and the time-dependent volume flow is calculated to study the structure of the jets. Ensemble-averaged in-plane velocity data in the jet far field were determined to study the mean jet structure. The ensemble-averaged vector fields are used to determine jet trajectory and the velocity variation along the trajectory. These results are discussed and compared to continuous and pulsed jets in cross flow.
Optics and Laser Technology, 1999
This paper describes a novel approach of acquiring two single-exposed, non-overlapping images usi... more This paper describes a novel approach of acquiring two single-exposed, non-overlapping images using half frame image shift (HFIS) recording on photographic ®lm. This technique permits the recording of two single-exposed, non-overlapping images of seed particles in a¯ow plane on high spatial resolution ®lm with any arbitrary time delay between exposures. A new multigrid CCDPIV (MCCDPIV) analysis method is used to analyse the single-exposed, non-overlapping sequential images resulting in PIV measurements with a larger velocity dynamic range, lower random error and better spatial resolution than standard CCDPIV analysis. HFIS recording followed by MCCDPIV analysis was employed to measure the spatio-temporal evolution of the in-plane velocity vector and the out-of-plane vorticity ®elds of a turbulent starting jet at Reynolds numbers based on the ori®ce diameter and piston velocity of 10,780 and 13,860. #
Particle image velocimetry measurements of a backward-facing step flow
Experiments in Fluids, 2002
Particle image velocimetry (PIV) measurements were carried out on a backward-facing step flow at ... more Particle image velocimetry (PIV) measurements were carried out on a backward-facing step flow at a Reynolds number of Re h =U ∞h/ν=4,660 (based on step height and freestream velocity). In-plane velocity, out-of-plane vorticity, Reynolds stress and turbulent kinetic energy production measurements in the x–y and x–z planes of the flow are presented. Proper orthogonal decomposition was performed on both the fluctuating velocity and vorticity fields of the x–y plane PIV data using the method of snapshots. Low-order representations of the instantaneous velocity fields were reconstructed using the velocity modes. These reconstructions provided insight into the contribution that the various length scales make to the spatial distribution of mean and turbulent flow quantities such as Reynolds stress and turbulent kinetic energy production. Large scales are found to contribute to the Reynolds stresses and turbulent kinetic energy production downstream of reattachment, while small scales contribute to the intense Reynolds stresses in the vicinity of reattachment.
A study of the evolution and characteristics of the invariants of the velocity-gradient tensor in isotropic turbulence
Journal of Fluid Mechanics, 1999
Abstract Since the availability of data from direct numerical simulation (DNS) of turbulence, res... more Abstract Since the availability of data from direct numerical simulation (DNS) of turbulence, researchers have utilized the joint PDFs of invariants of the velocity gradient tensor to study the geometry of small-scale motions of turbulence. However, the joint PDFs only give an ...
Turbulence structures of wall-bounded shear flows found using DNS data
Journal of Fluid Mechanics, 1998
This work extends the study of the structure of wall-bounded flows using the topological properti... more This work extends the study of the structure of wall-bounded flows using the topological properties of eddying motions as developed by Chong et al. (1990), Soria et al. (1992, 1994), and as recently extended by Blackburn et al. (1996) and Chacin et al. (1996). In these works, regions of flow which are focal in nature are identified by being enclosed
Identification and classification of topological structures in free shear flows
Multigrid approach to cross-correlation digital PIV and HPIV analysis
Journal of Fluids and Structures, 1994
Journal of Fluids and Structures, 1994
Experimental Thermal and Fluid Science, 1996
Results are presented on (1) the shear layer vortices developing in the free shear layers located... more Results are presented on (1) the shear layer vortices developing in the free shear layers located between the separation point and the first shed Strouhal vortex of a circular cylinder and (2) the longitudinal vortices developing in the braid region of the Strouhal vortices in the wake.
Experimental Thermal and Fluid Science, 1996
HA cross-correlation particle image velocimetry (PIV) technique has been developed to measure the... more HA cross-correlation particle image velocimetry (PIV) technique has been developed to measure the spatiotemporal in-plane velocity vector field evolution of time-dependent flows. A novel iterative two-stage crosscorrelation scheme of two sequential images of flow tracers has been incorporated in the image analysis. The implementation in hardware and software of this complete recording and analysis system are described. The expected accuracy of the velocity measurements was investigated and is discussed. The technique has been applied to study the near wake behind a circular cylinder at low Reynolds numbers (Red). The measurements presented pertain to cylinders with d = 12.5 and 25 mm (l/d = 19.5 and 9.8, respectively). The respective Reynolds numbers Re d are 875 and 769. Two planes of this flow are considered in this study: (1) plane normal to the cylinder axis (xy plane) and (2) a plane containing the cylinder axis and the stream direction (xz plane). Instantaneous in-plane velocity vector fields and out-of-plane vorticity fields are presented for both planes. The effect of spatial resolution on peak vorticity is discussed using velocity vector field measurements in the near wake of the cylinder that were conducted using different spatial resolutions. The three-dimensional nature of the near wake of circular cylinders at low Re d is demonstrated using quantitative in-plane velocity vector field and out-of-plane vorticity measurements. An upstream influx of relatively high velocity fluid into the stagnant near-wake region in the xy plane and the subsequent deflection of the fluid normal to this plane as it approaches the stagnation region at the cylinder are shown to be responsible for the generation of three-dimensional flow in the near wake of a circular cylinder.