Turbulent Boundary Layers in Adverse Pressure Gradients

Clauser, Francis H.

doi:10.2514/8.2938

Cited by 924 publications

(372 citation statements)

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“…At nozzle inlet, the Clauser method [28] was used to calculate the skin friction coefficient. By multiplying both sides of the standard log-law formula by u τi U δ , the following expression results:…”

Section: Data Processing/derived Quantitiesmentioning

confidence: 99%

Influence of Nozzle Exit Conditions on the Near-Field Development of High Subsonic and Underexpanded Axisymmetric Jets

2018

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Detailed knowledge of jet plume development in the near-field (the first 10-15 nozzle exit diameters for a round jet) is important in aero-engine propulsion system design, e.g., for jet noise and plume infrared (IR) signature assessment. Nozzle exit Mach numbers are often high subsonic but improperly expanded (e.g., shock-containing) plumes also occur; high Reynolds numbers (O (10 6 )) are typical. The near-field is obviously influenced by nozzle exit conditions (velocity/turbulence profiles) so knowledge of exit boundary layer characteristics is desirable. Therefore, an experimental study was carried out to provide detailed data on nozzle inlet and exit conditions and near-field development for convergent round nozzles operated at Nozzle Pressure Ratios (NPRs) corresponding to high subsonic and supersonic (underexpanded) jet plumes. Both pneumatic probe and Laser Doppler Anemometry (LDA) measurements were made. The data revealed that internal nozzle acceleration led to a dramatic reduction in wall boundary layer thickness and a more laminar-like profile shape. The addition of a parallel wall extension to the end of the nozzle allowed the boundary layer to return to a turbulent state, increasing its thickness, and removing vena contracta effects. Differences in nozzle exit boundary layers exerted a noticeable influence but only in the first few diameters of plume development. The addition of the exit extension removed the vena contracta effects of the convergence only design. At underexpanded NPRs, this change to nozzle geometry modified the shock cell pattern and shortened the potential core length of the jet.

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Section: Data Processing/derived Quantitiesmentioning

confidence: 99%

Influence of Nozzle Exit Conditions on the Near-Field Development of High Subsonic and Underexpanded Axisymmetric Jets

2018

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“…[14] First, it is necessary to establish when the enhancement in the wall friction begins. A criterion for the wall shear stress enhancement before turbulent separation under adverse pressure gradient can be found by extending to oscillatory flows the definition of the equilibrium parameter (8) first defined by Clauser [1954] for steady flows:…”

Section: Modeling Of Turbulent Separation Under the Effect Of An Advementioning

confidence: 99%

1DV bottom boundary layer modeling under combined wave and current: Turbulent separation and phase lag effects

2003

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[1] On the basis of the Wilcox [1992] transitional k-w turbulence model, we propose a new k-w turbulence model for one-dimension vertical (1DV) oscillating bottom boundary layer in which a separation condition under a strong, adverse pressure gradient has been introduced and the diffusion and transition constants have been modified. This new turbulence model agrees better than the Wilcox original model with both a direct numerical simulation (DNS) of a pure oscillatory flow over a smooth bottom in the intermittently turbulent regime and with experimental data from Jensen et al. [1989], who attained the fully turbulent regime for pure oscillatory flows. The new turbulence model is also found to agree better than the original one with experimental data of an oscillatory flow with current over a rough bottom by Dohmen-Janssen [1999]. In particular, the proposed model reproduces the secondary humps in the Reynolds stresses during the decelerating part of the wave cycle and the vertical phase lagging of the Reynolds stresses, two shortcomings of all previous modeling attempts. In addition, the model predicts suspension ejection events in the decelerating part of the wave cycle when it is coupled with a sediment concentration equation. Concentration measurements in the sheet flow layer give indication that these suspension ejection events do occur in practice. Citation: Guizien, K., M. Dohmen-Janssen, and G. Vittori, 1DV bottom boundary layer modeling under combined wave and current: Turbulent separation and phase lag effects,

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“…It is to be noted finally that there exist also [9] tables of numerical values of coefficients appearing in the formulas A detailed analysis of the zone of negative values of m (Fig. 2) demonstrates that, over the interval there can exist, for a single value of m, two boundary layers called equilibrated, which is a well known phenomenon discovered experimentally by CLAUSER [4] and reconfirmed by NOVOZILOV [l] in the analogous case but for the Kannan turbulence model.…”

mentioning

confidence: 94%

“…These conditions are derived by replacing (3), (4), and (16) into (5). It is to be noted that for n = 0 and k, = 1, the equation (21) becomes the well known one by Falkner-Skan in the case of the laminar boundary layer.…”

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confidence: 99%

Practical Approximate Turbulent Boundary Layer Calculation into the Divergent Rectangular Channel

Askovic

1996

Z Angew Math Mech

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Both plane and axially symmetrical turbulent boundary layers are analysed in the sense of the well‐known phenomenologic semi‐empiric boundary‐layer theory. The analysis is based on an analogy with the rheologic power‐laws widely used in the study of non‐linear viscous flows. A simple “one layer method” to calculate both plane and axisymmetric turbulent boundary layers is first derived and after that tested on the model of a rectangular channel, used for the hydraulic machines for instance. The model is composed of an annular disc and two perpendicular radial plates in the flow produced by a linear source. Neglecting the interaction between the disc and two plates, both boundary layers are considered separately: the plane boundary layer between two divergent plates and the axially symmetrical boundary layer on the disc (even in the presence of a funnel above the disc to vary the slowing down of the flow).

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Turbulent Boundary Layers in Adverse Pressure Gradients

Cited by 924 publications

References 1 publication

Influence of Nozzle Exit Conditions on the Near-Field Development of High Subsonic and Underexpanded Axisymmetric Jets

Influence of Nozzle Exit Conditions on the Near-Field Development of High Subsonic and Underexpanded Axisymmetric Jets

1DV bottom boundary layer modeling under combined wave and current: Turbulent separation and phase lag effects

Practical Approximate Turbulent Boundary Layer Calculation into the Divergent Rectangular Channel

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