Constants definition - turbulent vel. profile

[jkr]

Homework Statement

Hello!

I need some help with a problem:

Problem: Turbulent flow beteween parallel flat plates.

It is defined:

[ tex ] \tau = \mu \frac{d\bar{u}}{dy}-\rho\bar{u'v'} [ \tex ]

The exercise gives that [ tex ] \tau = a y [ \tex ] and [ tex ] \rho\bar{u'v'} = \frac{by}{c+dy^2} [ \tex ], where [ tex ] a,b,c,d[ \tex ] are constants.

I need to know: How can I choose these constants? I'm looking for an approximate solution.

Until now, I used just the no-slip condition at [ tex ] \pm H [ \tex ] and [ tex ] \frac{du(y=0)}{dy}=0 [ \tex ]

Tks for the help!

Homework Equations

[ tex ] \tau = \mu \frac{d\bar{u}}{dy}-\rho\bar{u'v'} [ \tex ]
[ tex ] \tau = a y [ \tex ]
[ tex ] \rho\bar{u'v'} = \frac{by}{c+dy^2} [ \tex ]

The Attempt at a Solution

 

[NascentOxygen]

Hello!

I need some help with a problem:

Problem: Turbulent flow beteween parallel flat plates.

It is defined:

$$\tau = \mu \frac{d\bar{u}}{dy}-\rho\bar{u'v'}$$

The exercise gives that $$\tau = a y$$ and $$\rho\bar{u'v'} = \frac{by}{c+dy^2}$$, where $$a,b,c,d$$ are constants.

I need to know: How can I choose these constants? I'm looking for an approximate solution.

Until now, I used just the no-slip condition at $$\pm H$$ and $$\frac{du(y=0)}{dy}=0$$

Tks for the help!

Homework Equations

$$\tau = \mu \frac{d\bar{u}}{dy}-\rho\bar{u'v'}$$
$$\tau = a y$$
$$\rho\bar{u'v'} = \frac{by}{c+dy^2}$$

Hi jkr! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

I'm astonished that you posted your question with its non-functioning itex formatting instructions. I have fixed them for you. Don't include unnecessary spaces inside the [...] instruction. And its [/tex] NOT [\tex].

I can't help you with a fluidics question, but now maybe someone else can.

 

[jkr]

Tks a lot for this! =D

 

[jkr]

Hi again,

If $$\rho \bar{u'v'} =0$$ at $$y = \pm H$$ then the model $$\rho \bar{u'v'}=\frac{by}{c+dy^2}$$ doesn't work because $$b=0.$$
However, for the case
$$\rho \bar{u'v'} =\frac{by+ey^3}{c+dy^2},$$ How does it work?

[]s