A Kinematic Velocity Decomposition of Stratified Flow

Yokota, Jeffrey W.

doi:10.1080/10618569808940846

“…Complex-lamellar decompositions have been used by Panton [31] for studying turbulent flows, since this decomposition can be used to separate the flow into an irrotational component and a rotational component. Yokota [32], has used this decomposition for studying stratified flow. Finnigan [33] used complex-lamellar decomposition in defining a streamwise coordinate system for studying turbulence.…”

Section: Examples Where Complex-lamellar Decompositions Have Been Usedmentioning

confidence: 99%

A Complex-Lamellar Description Of Boundary Layer Transition

Kolla¹

2021

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0

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Flow transition is important, in both practical and phenomenological terms. However, there is currently no method for identifying the spatial locations associated with transition, such as the start and end of intermittency. The concept of flow stability and experimental correlations have been used, however, flow stability only identifies the location where disturbances begin to grow in the laminar flow and experimental correlations can only give approximations as measuring the start and end of intermittency is diffcult. Therefore, the focus of this work is to construct a method to identify the start and end of intermittency, for a natural boundary layer transition and a separated flow transition. We obtain these locations by deriving a complex-lamellar description of the velocity field that exists between a fully laminar and fully turbulent boundary condition. Mathematically, this complex-lamellar decomposition, which is constructed from the classical Darwin-Lighthill-Hawthorne drift function and the transport of enstrophy, describes the flow that exists between the fully laminar Pohlhausen equations and Prandtl's fully turbulent one seventh power law. We approximate the difference in enstrophy density between the boundary conditions using a power series. The slope of the power series is scaled by using the shape of the universal intermittency distribution within the intermittency region. We solve the complex-lamellar decomposition of the velocity field along with the slope of the difference in enstrophy density function to determine the location of the laminar and turbulent boundary conditions. Then from the difference in enstrophy density function we calculate the start and end of intermittency. We perform this calculation on a natural boundary layer transition over a flat plate for zero pressure gradient flow and for separated shear flow over a separation bubble. We compare these results to existing experimental results and verify the accuracy of our transition model.

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“…Complex-lamellar decompositions have been used by Panton [31] for studying turbulent flows, since this decomposition can be used to separate the flow into an irrotational component and a rotational component. Yokota [32], has used this decomposition for studying stratified flow. Finnigan [33] used complex-lamellar decomposition in defining a streamwise coordinate system for studying turbulence.…”

Section: Examples Where Complex-lamellar Decompositions Have Been Usedmentioning

confidence: 99%

A Complex-Lamellar Description Of Boundary Layer Transition

Kolla¹

2021

Preprint

1

0

View full text Add to dashboard Cite

Flow transition is important, in both practical and phenomenological terms. However, there is currently no method for identifying the spatial locations associated with transition, such as the start and end of intermittency. The concept of flow stability and experimental correlations have been used, however, flow stability only identifies the location where disturbances begin to grow in the laminar flow and experimental correlations can only give approximations as measuring the start and end of intermittency is diffcult. Therefore, the focus of this work is to construct a method to identify the start and end of intermittency, for a natural boundary layer transition and a separated flow transition. We obtain these locations by deriving a complex-lamellar description of the velocity field that exists between a fully laminar and fully turbulent boundary condition. Mathematically, this complex-lamellar decomposition, which is constructed from the classical Darwin-Lighthill-Hawthorne drift function and the transport of enstrophy, describes the flow that exists between the fully laminar Pohlhausen equations and Prandtl's fully turbulent one seventh power law. We approximate the difference in enstrophy density between the boundary conditions using a power series. The slope of the power series is scaled by using the shape of the universal intermittency distribution within the intermittency region. We solve the complex-lamellar decomposition of the velocity field along with the slope of the difference in enstrophy density function to determine the location of the laminar and turbulent boundary conditions. Then from the difference in enstrophy density function we calculate the start and end of intermittency. We perform this calculation on a natural boundary layer transition over a flat plate for zero pressure gradient flow and for separated shear flow over a separation bubble. We compare these results to existing experimental results and verify the accuracy of our transition model.

show abstract