User Forum of Software BASEMENT

clemenza

User

Registered: 2016-02-08

Posts: 3

Bed forms - Skin friction correction

Hello,

in the reference manual v2.5.3, page 2.1-3 the formula for the skin friction correction is described.

So my question:
for the calculation of the Strickler grain roughness kstr' in formula RI-1.25, on page 1.1-7, per default you use d90 or 3*d90 in the denominator?

I would be very glad for an answer!

Best regards,
Clemens

clemenza

User

Registered: 2016-02-08

Posts: 3

Re: Bed forms - Skin friction correction

Hello,

another question:

the formula for the Strickler grain roughness kstr' (formula RI-1.25) used in Basement is written as: kst = 21.1/ks^(1/6), with ks = d90.
Where does the formula come from? Do you have a reference?
The value of 21.1 in the numerator is from Strickler (1923), however in combination with ks=d50.

I know, the question seems a little bit pedantic but we want to compare different models, so we want to get sure about the different approaches.

Best regards,
Clemens

sajjad

User

Registered: 2014-10-01

Posts: 101

Re: Bed forms - Skin friction correction

The formula is quoted by Chaudhry in his book Open-Channel Flow (2nd edition), chapter 4 'Uniform Flow'.

clemenza

User

Registered: 2016-02-08

Posts: 3

Re: Bed forms - Skin friction correction

Hello,

thank you very much!

Clemens