turb+mixing%202007%203MM

# turb+mixing%202007%203MM - FACE8 Turbulence and Mixing...

This preview shows pages 1–10. Sign up to view the full content.

1 FACE8 Turbulence and Mixing FACE8 2007 Turbulence and Mixing 3rd lecture Boundary layers revisitted Free shear flows

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 FACE8 Turbulence and Mixing Laminar/viscous sublayer Turbulence free Buffer layer High dissipation Turbulent boundary layers
3 FACE8 Turbulence and Mixing The layer structure of turbulent boundary layers · Sublayer and buffer layer Shear stress nearly constant Flow governed by τ w , ν , ρ and y We define the friction velocity u * And introduce the Law of the Wall ρ τ w u = * () * * y f y u f u u = = ν

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
4 FACE8 Turbulence and Mixing The layer structure of turbulent boundary layers · Outer (free) layer The deficit law · At interface, the two expressions must have same gradient Differentiate both expressions and set equal to each other Law of the wall Deficit law = δ y g u u U * () κ ν 1 ' ' * * 2 * = = = y g u y f u y u 2 * 1 * * ln 1 ln 1 C y u u U C y u u u + = + = 1 2 0.40 0.41, 4.9. ..5.5 2.5 C C
5 FACE8 Turbulence and Mixing The viscous sublayer profile · For the viscous sublayer u is linear Æ ν y u u u * * =

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
6 FACE8 Turbulence and Mixing Near-wall velocity profiles
7 FACE8 Turbulence and Mixing Single parameter approximations for turbulent boundary layers · The sublayer corresponds to approximately 1% of the boundary layer thickness Æ negligible. .. · Wecanusethelawo f±thewa l ld irect lyas ± approximation · Which is related to the von Kármán equation by n y u C u u 1 * 1 * = ν () 2 * 2 2 / = = = U u U U dx d w w ρ τ θ

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
8 FACE8 Turbulence and Mixing Reynolds number, n and C 1 Power law profiles 12.0 9.6x10 7 10 11.0 3.8x10 7 9 10.1 1.4x10 7 8 9.1 3.3x10 6 7 7.1 5x10 3 6 C 1 Re x n
9

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 25

turb+mixing%202007%203MM - FACE8 Turbulence and Mixing...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online