# Homework Help: Constants definition - turbulent vel. profile

1. May 13, 2012

### jkr

1. The problem statement, all variables and given/known data

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 aproximate 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!

2. Relevant 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 ]

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. May 14, 2012

### Staff: Mentor

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

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.

Last edited by a moderator: May 6, 2017
3. May 14, 2012

### jkr

Tks a lot for this! =D

4. May 14, 2012

### 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