lecture 11 - Thermal and Fluids Engineering I Lecture 11...

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

View Full Document Right Arrow Icon
Thermal and Fluids Engineering I Lecture 11 Page 1 Lecture 11 – Conservation of Linear Momentum in Open Systems Fluids can exert significant forces as they flow over surfaces. For example: - wind raising a kite - lift on an aircraft - water flowing around the pylons of a bridge To calculate fluid forces, we use conservation of momentum. Momentum is mass times velocity, or m = B V In the x -direction, x x Bm = V
Background image of page 1

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

View Full DocumentRight Arrow Icon
Thermal and Fluids Engineering I Lecture 11 Page 2 () () ,, x xcv i xi Bt B t m =+ V () x e xe Bt t B t t m +∆ = +∆ +∆ V The change of momentum of the closed system in time t is ( ) ( ) , , x x e i Bt t Bt B t t B t m m +∆ − = +∆ −∆ VV ( ) ( ) xx ei x ex i Btt Bt Bt t Bt mm tt t t ∆∆ From Newton's second law, the sum of the forces is equal to the time rate of change of momentum, or ( ) 0 lim x x t B B t dB F dt t ∆→ ⎛⎞ == ⎜⎟ ⎝⎠ B x,cv ( t ) – x-momentum in the control volume at time t B x,cv ( t + t ) – x- momentum in the control volume at time t + t B x ( t ) – x-momentum
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 04/08/2008 for the course ENGR 2250 taught by Professor Borca-tasciuc during the Spring '08 term at Rensselaer Polytechnic Institute.

Page1 / 6

lecture 11 - Thermal and Fluids Engineering I Lecture 11...

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