Near-wall measurements in a three-dimensional turbulent boundary layer

Compton, Debora A.; Eaton, John K.

doi:10.1017/s0022112097007106

Cited by 18 publications

(4 citation statements)

References 16 publications

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“…This trend has been reported in other studies (e.g. Flack & Johnston 1994;Compton & Eaton 1997). At subsequent downstream locations the effects of the crossflow on the primary Reynolds stress diffuse out into the boundary layer.…”

Section: Ensemble-averaged Velocity Field Statisticssupporting

confidence: 86%

“…A variety of pressure-driven studies of 3DTBLs have been performed over the past decade or so and can be separated by how the spanwise pressure gradient was generated. Wedge flows were examined by Anderson & Eaton (1987, 1989 and Compton & Eaton (1997). 3TDBLs generated by bends in ducts were investigated by Schwarz & Bradshaw (1993, 1994 and Flack & Johnston (1993, 1994.…”

Section: Introduction and Objectivesmentioning

confidence: 99%

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Near-wall physics of a shear-driven three-dimensional turbulent boundary layer with varying crossflow

Kiesow

Plesniak

2003

J. Fluid Mech.

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The near-wall physics and turbulence structure of a planar shear-driven three-dimensional turbulent boundary layer (3DTBL) with varying strengths of crossflow are examined in a specialized facility. Spanwise shear modifies the near-wall turbulence structure. Flow visualization reveals a reduction of mean streak length by as much as 50%, while streak spanwise spacing remains constant. Power spectra of velocity confirm this shift towards higher temporal frequencies, corresponding to decreased streamwise length scales. Particle image velocimetry (PIV) measurements indicate that the spanwise shear increases the number and strength of flow structures that interact in the inner region of the boundary layer. This leads to increased momentum transfer between low- and high-speed fluids, resulting in a thickening of the inner region of the boundary layer. In addition, the organized two-dimensional boundary layer spanwise vorticity layer along the wall surface is disrupted and forms strong vortical structures that are lifted off the wall surface and diffuse into the boundary layer with streamwise distance. The transverse vorticity experiences a similar alteration. Streamwise velocity profiles exhibit an increasing velocity deficit with increased crossflow, consistent with the thickening of the inner region of the boundary layer. Increases in the normal Reynolds stresses are associated with interaction of the secondary flow structures and modifications to vortical structures with increasing three-dimensionality and higher relative wall speed. Significant increases are observed for the most highly sheared cases with translating wall velocities 2.0 and 2.75 times the free-stream velocity. This increase in the normal stresses leads to an increase in the turbulent kinetic energy over the belt surface, which diffuses into the inner region of the boundary layer with streamwise distance. The Reynolds shear stresses also exhibit a significant increase in magnitude over the belt surface owing to enhanced turbulence production over the translating wall section. In general, three-dimensional effects are confined to the area close to the wall and the crossflow increases the interaction of secondary flow structures leading to modifications of the vorticity in the inner region of the boundary layer. These flow distortions disrupt the near-wall streak structure and result in increased levels of turbulent kinetic energy and Reynolds stresses, particularly over the translating wall section.

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Section: Ensemble-averaged Velocity Field Statisticssupporting

confidence: 86%

Section: Introduction and Objectivesmentioning

confidence: 99%

Near-wall physics of a shear-driven three-dimensional turbulent boundary layer with varying crossflow

Kiesow

Plesniak

2003

J. Fluid Mech.

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“…Over the past decades, a variety of additional experimental studies on 3DTBL have been performed, each characterised by the different mechanism utilised to induce threedimensionality in the flow. Among them, we can highlight 3DTBL over wedges (Anderson & Eaton 1987, 1989Compton & Eaton 1997), rotating cylinders (Furuya & Fujita 1966;Bissonnette & Mellor 1974;Lohmann 1976;Driver & Hebbar 1987, 1989, 1991, rotating disks (Littell & Eaton 1994), flow within the bend of ducts (Schwarz & Bradshawt 1993;Schwarz & Bradshaw 1994;Flack 1993;Flack & Johnston 1994), swept steps and bumps (Flack 1993;Webster et al 1996), and wing-body junctions (Ölçmen & Simpson 1992(Ölçmen & Simpson , 1995. More recently, Kiesow & Plesniak (2002 used particle-image velocimetry (PIV) to acquire detailed information of the flow structure at varying degrees of crossflow generated by moving belts.…”

Section: Introductionmentioning

confidence: 99%

Non-equilibrium three-dimensional boundary layers at moderate Reynolds numbers

et al. 2019

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Non-equilibrium wall turbulence with mean-flow three-dimensionality is ubiquitous in geophysical and engineering flows. Under these conditions, turbulence may experience a counter-intuitive depletion of the turbulent stresses, which has important implications for modelling and control. Yet, current turbulence theories have been established mainly for statistically two-dimensional equilibrium flows and are unable to predict the reduction in the Reynolds stress magnitude. In the present work, we propose a multiscale model which explains the response of non-equilibrium wall-bounded turbulence under the imposition of three-dimensional strain. The analysis is performed via direct numerical simulation of transient three-dimensional turbulent channels subjected to a sudden lateral pressure gradient at friction Reynolds numbers up to 1,000. We show that the flow regimes and scaling properties of the Reynolds stress are consistent with a model comprising momentum-carrying eddies with sizes and time scales proportional to their distance to the wall. We further demonstrate that the reduction in Reynolds stress follows a spatially and temporally self-similar evolution caused by the relative horizontal displacement between the core of the momentum-carrying eddies and the flow layer underneath. Inspection of the flow energetics reveals that this mechanism is associated with lower levels of pressurestrain correlation which ultimately inhibits the generation of Reynolds stress. Finally, we assess the ability of the state-of-the-art wall-modelled large-eddy simulation to predict non-equilibrium, three-dimensional flows.

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“…In an early study by Compton and Eaton [14], detailed near-wall measurements of velocity and Reynolds stress profiles were made in a three-dimensional turbulent boundary layer. Throughout most of the boundary layer, the eddy viscosity is anisotropic.…”

Section: Anisotropic Eddy Viscosity Validation In a Three-dimensional Boundary Layer Flowmentioning

confidence: 99%

Near-Field Simulations of Film Cooling with a Modified DES Model

Yavuzkurt

2020

Inventions

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Modeling the heat transfer characteristics of highly turbulent flow in gas turbine film cooling is important for providing better insights and engineering solutions to the film cooling problem. This study proposes a modified detached eddy simulation (DES) model for better film cooling simulations. First, spatially varying anisotropic eddy viscosity is found from the results of the large eddy simulation (LES) of film cooling. Then the correlation for eddy viscosity anisotropy ratio has been established based on the LES results and is proposed as the modification approach for the DES model. The modified DES model has been tested for the near-field film cooling simulations under different blowing ratios. Detailed comparisons of the centerline and 2D film cooling effectiveness indicate that the modified DES model enhances the spanwise spreading of the temperature field. The DES model leads to deviations of 62.4%, 39.8%, and 33.5% from the experimental centerline effectiveness under blowing ratios of 0.5, 1.0, and 1.5, respectively, while the modified DES reduces the deviations to 51.5%, 26.7%, and 28.9%. The modified DES model provides a promising approach for film cooling numerical simulations. It embraces the advantage of LES in resolving detailed vortical structure dynamics with a moderate computational cost. It also significantly improves the original DES model on the spanwise counter rotating vortex pair (CRVP) spreading, mixing, and effectiveness prediction.

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Near-wall measurements in a three-dimensional turbulent boundary layer

Cited by 18 publications

References 16 publications

Near-wall physics of a shear-driven three-dimensional turbulent boundary layer with varying crossflow

Near-wall physics of a shear-driven three-dimensional turbulent boundary layer with varying crossflow

Non-equilibrium three-dimensional boundary layers at moderate Reynolds numbers

Near-Field Simulations of Film Cooling with a Modified DES Model

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