Proper Orthogonal Decomposition Analysis of Separated and Reattached Pressure Gradient Flows

Shah, Mohammad K.; Tachie, Mark F.

doi:10.2514/1.40095

Cited by 18 publications

(9 citation statements)

References 29 publications

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“…That is, the dominant structures of the flow can be satisfactorily captured within the first few modes. Since its introduction, the POD technique has been applied to investigate coherent structures in boundary layers, [29] separated flows [33] and turbulent offset jets. [10] The snapshot approach proposed by Sirovich [34] was adopted in the present investigation.…”

Section:  Proper Orthogonal Decomposition (Pod)mentioning

confidence: 99%

Flow characteristics of an offset jet over a surface mounted square rib

Nyantekyi-Kwakye

Tachie

Clark

2016

Journal of Turbulence

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A three-dimensional offset jet flow over a surface mounted square rib was investigated using particle image velocimetry at Reynolds number of 7600. The square rib was mounted at three different locations downstream of the nozzle exit. Contour and profile plots in the symmetry plane were used to investigate the effect of the rib on the mean flow distribution and turbulence statistics. Changing the rib location enhanced the mixing and entrainment characteristics of the jet thereby leading to larger wall-normal spread rates. The quadrant analysis revealed a significant contribution of all events towards the Reynolds shear stress. The joint probability density function analysis showed that the structures within the outer shear layer of the jet differed from those of boundary layers. Results from the two-point correlation analysis indicated that the introduction of a surface mounted rib modified the flow structures within the developing region. However, there was no significant structural difference between the flow with mounted rib and the no rib case within the self-similar region. The proper orthogonal decomposition was used to examine how changes in rib location modified the dynamics of the energetic modes towards the turbulent kinetic energy and Reynolds shear stress within the developing and self-similar regions.

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Section:  Proper Orthogonal Decomposition (Pod)mentioning

confidence: 99%

Flow characteristics of an offset jet over a surface mounted square rib

Nyantekyi-Kwakye

Tachie

Clark

2016

Journal of Turbulence

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“…In addition, they observed that the large scales were Reynolds number independent while the small scales were strongly Reynolds number dependent. Shah and Tachie (2009) used POD to analyze the turbulent flow downstream of a transverse square rid in diverging and conversing channels. The reconstructed Reynolds stress profiles showed significant differences at the center of the separated shear layer from those near the reattachment point.…”

Section: Volume Opticmentioning

confidence: 99%

A study of the energetic turbulence structures during stall delay

Lee

Tang

2015

International Journal of Heat and Fluid Flow

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“…Previous experiments on reattaching separated flow have demonstrated that large-scale structures play a key role in flow dynamic (Bhattacharjee et al 1986 ). Actually, the occurrence of coherent structure is one of the most prominent features about turbulent flows (Kline et al 1967 ), the significant turbulence details usually are hidden within coherent structures or vortex characterized by organized motions (Shah and Tachie 2009 ). It is generally accepted that a better cognition of coherent structures is the key to research turbulence (Kostas et al 2005 ).…”

Section: Introductionmentioning

confidence: 99%

“…It is generally accepted that a better cognition of coherent structures is the key to research turbulence (Kostas et al 2005 ). An in-depth understanding of coherent structures would also provide the possibility of elaborating the physical dissipated mechanism of turbulent energy and its control (Shah and Tachie 2009 ). Moreover, it is believed that the Reynolds stress plays a crucial role in the turbulence flow, which can affect turbulent energy transfer over the wall bounded turbulence flow.…”

Section: Introductionmentioning

confidence: 99%

POD analysis of flow over a backward-facing step forced by right-angle-shaped plasma actuator

Wang

2016

SpringerPlus

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PurposeThis study aims to present flow control over the backward-facing step with specially designed right-angle-shaped plasma actuator and analyzed the influence of various scales of flow structures on the Reynolds stress through snapshot proper orthogonal decomposition (POD).Methods2D particle image velocimetry measurements were conducted on region (x/h = 0–2.25) and reattachment zone in the x–y plane over the backward-facing step at a Reynolds number of Reh = 27,766 (based on step height and free stream velocity . The separated shear layer was excited by specially designed right-angle-shaped plasma actuator under the normalized excitation frequency Sth ≈ 0.345 along the 45° direction. The spatial distribution of each Reynolds stress component was reconstructed using an increasing number of POD modes.ResultsThe POD analysis indicated that the flow dynamic downstream of the step was dominated by large-scale flow structures, which contributed to streamwise Reynolds stress and Reynolds shear stress. The intense Reynolds stress localized to a narrow strip within the shear layer was mainly affected by small-scale flow structures, which were responsible for the recovery of the Reynolds stress peak. With plasma excitation, a significant increase was obtained in the vertical Reynolds stress peak.ConclusionsUnder the dimensionless frequencies Sth ≈ 0.345 and which are based on the step height and momentum thickness, the effectiveness of the flow control forced by the plasma actuator along the 45° direction was ordinary. Only the vertical Reynolds stress was significantly affected.

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Proper Orthogonal Decomposition Analysis of Separated and Reattached Pressure Gradient Flows

Cited by 18 publications

References 29 publications

Flow characteristics of an offset jet over a surface mounted square rib

Flow characteristics of an offset jet over a surface mounted square rib

A study of the energetic turbulence structures during stall delay

POD analysis of flow over a backward-facing step forced by right-angle-shaped plasma actuator

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