# Solving an equasion Implicitly, Hydraulics Question

• Jan 21st 2013, 10:53 AM
CivilEngineer1988
Solving an equasion Implicitly, Hydraulics Question
Ok, so I am trying to solve this equasion for y

0.33392=(1/0.027)*(y+2*y^2)*((y+2*y^2)/(2.236+4.472*y))^(2/3)

I should probably know how to do this myself (I've done a million and one math courses over the past 5 years :P) but I would rather get a refresher from one of you guys/gals

The problem involves trying to find the height of water in an open channel given the rate of flow and channel cross section. y is the height of water in question.

Thanks!
• Jan 21st 2013, 07:21 PM
chiro
Re: Solving an equasion Implicitly, Hydraulics Question
Hey CivilEngineer1988.

Is a numerical approximation OK for your purposes (i.e. to so many decimal places)?
• Jan 21st 2013, 10:54 PM
JJacquelin
Re: Solving an equasion Implicitly, Hydraulics Question
Hi CivilEngineer1988 !
Don't you see that ((y+2*y^2)/(2.236+4.472*y)) = y/2.236 ?
0.33392=(1/0.027)*(y/2.236)^(2/3)
y = 2.236*(0.33392*0.027)^(3/2) = 0.00191417
• Jan 22nd 2013, 12:13 AM
chiro
Re: Solving an equasion Implicitly, Hydraulics Question
Very nice: I'm glad someone is paying attention :)
• Jan 22nd 2013, 01:15 AM
JJacquelin
Re: Solving an equasion Implicitly, Hydraulics Question
Sorry, there is something wrong in my precceding answer, because I consider the equation :
0.33392=(1/0.027)*((y+2*y^2)/(2.236+4.472*y))^(2/3)