Turbulence lecture 13

Turbulence lecture 13 - Turbulence Lecture 13 Don't expect...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Turbulence Lecture 13 Don’t expect v τ to be constant in space or time, expect it to be stronger where turbulence is stronger. 2 ij i uu u ρ but 1 0 2 ii ij ii UU SS xx ∂∂ →= + =  clearly not desired extension. People use 2 1 2 3 ki j i j u v S δ =− Plug into mean momentum equation. ( { 2 1 22 3 ji k j P u v S tx x x  += + + +  ±²³²´ ) } i j µ Call this P Mixing Length Models. - Based on laminar flow and Kinetic Theory of Gases. () ( ) 12 ,0,0 Ux U x =   µµ Momentum exchange, thru viscous shear stress
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 ij ij S σ µ = Thus, 1 12 21 2 U x σσ == There is a net momentum transfer across any horizontal surface. On the average from above, bring high momentum and those from below bring lower momentum. On a macroscopic scale there appears to be a force on the upper volume to slow it down. Average (Avg.) rate of change of momentum due to flux. Avg. {momentum of molecules x rate that molecules cross the surface.} 12 1 mu Nu mNu u 2 N – Avg. number of molecules per unit volume.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/07/2011 for the course EGM 6341 taught by Professor Mei during the Spring '09 term at University of Florida.

Page1 / 5

Turbulence lecture 13 - Turbulence Lecture 13 Don't expect...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online