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Research Papers: Fundamental Issues and Canonical Flows

# Near Surface Velocity Distributions for Intermittent Separation of Turbulent Boundary Layers

[+] Author and Article Information
V. A. Sandborn

Colorado State University, Fort Collins, CO 80523

J. Fluids Eng 130(4), 041203 (Apr 09, 2008) (4 pages) doi:10.1115/1.2903818 History: Received February 24, 2005; Revised October 11, 2007; Published April 09, 2008

## Abstract

At the location of intermittent turbulent boundary layer separation a finite positive mean surface shear stress still exists. It is demonstrated that viscous coordinates and a mixing length turbulent model may still be used at the location of intermittent separation. The large scale turbulent mixing in the separation region appears to require the universal mixing constant, $K$, increases with Reynolds number. Once true zero-mean-surface-shear-stress separation occurs, the mixing length model for the turbulent flow near the surface is no longer valid and a constant eddy viscosity is indicated.

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## Figures

Figure 1

Velocity distributions upstream and in the separation region. Data of Simpson (4) (uncertainty: U=0.2f∕s, y=0.002in.).

Figure 2

Comparison of intermittent separation profiles with the predictions of Eq. 3. (a) Data of Simpson (4). (b) Data of Simpson (3) and downstream data of Simpson (4).

Figure 3

Velocity near the surface at intermittent separation in the duct. (○) Measured; (◻ and ●) bias corrections, Eq. 5. (a) Rθ=1110. (b) Rθ=1880.

Figure 4

Variation of the non dimensional pressure gradient with Reynolds number

Figure 5

Zero-mean-surface-shear-stress separation velocity profiles. U∕Ue=1+(1−y∕δ)m[mln(1−y∕δ)−1].

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