# Continuity equation

1. Apr 8, 2005

### kinglk

i do not understand how the continuity equation works?

2. Apr 8, 2005

### dextercioby

What continuity equation do you refer to?I can think of 2 or maybe more,but u need to be more specific.

Daniel.

3. Apr 8, 2005

### kinglk

that is the problem that i have ran into. on my assignment it does not say. it just ask us to use coninuity equation to explain how jet engines provide a forward thrust for an airplane? i have tried to research it but i am still lost.

part 2 of the question ask us to use Bernoulli's equation and explain hoe it relates to continuity equation?

4. Apr 8, 2005

### dextercioby

This equation

$$\frac{\partial\rho\left(\vec{r},t\right)}{\partial t}+\nabla\cdot\left[\rho\left(\vec{r},t\right)\vec{v}\left(\vec{r},t\right)\right]= 0$$

Daniel.

5. Jul 29, 2011

### Loneliheart

Hello, am study Continuity Equation right now for my problem Solving Class at ITT Tech
The Continuity Equation was give in the book. A1V1=A2V2 where A1 is the cross-sectional area at point 1, V1 is the velocity of the fluid at point 1, A2 is the cross-sectional area at point 2, and then V2 is the velocity of the fluid at point 2. Like you I stuck on Skill Level Problem II about using the equation to explain how jet engines provide forward trust for an airplane.

The Bernoulli's Equation and I still search for the equation but I think I end up using the one from Engineering Tool Box. The link is http://www.engineeringtoolbox.com/bernouilli-equation-d_183.html. I hope this helps but if you already finish maybe you can send help on the jet engine problem.

Last edited by a moderator: Jul 31, 2011
6. Jul 29, 2011

### rock.freak667

The equation of continuity in fluid dynamics is used when a fluid flows through an area which is then changed. The total flow remains constant i.e. volume per unit time is constant.

In equation form this is

A1v1=A2v2

How would A2 have to be with respect to A1 for there to be an increase in velocity?

Loneliheart posted a link that should prove to be helpful.

7. Jul 31, 2011

### Redbelly98

Staff Emeritus
This ol' thread is locked. (And by "old", I mean that literally.)