- #1
how to determine the value to start with ? the Re and relative roughness is not given ?Chestermiller said:
Like I said, start with the friction factor f for Re = 100000. As far as roughness is concerned, you would have to know that for the particular pipe from its specs or just assume a worst-case value.foo9008 said:
when Re = 100000 , we have to choose the friction factor based on the relative roughness , right ? how to know the relative roughness?Chestermiller said:
As I said, the pipe may come with that kind of information when it is purchased. Or, you could choose what you would consider a worst case value. Or, if it a homework problem, they will typically tell you what roughness to use.foo9008 said:
yes , this is a homework -like problem , the roughness , e is given , but we don't know the D , how to get the relative roughness(e / D) so that we can choose the friction factor ?Chestermiller said:
Once you know D, you will have e/D for the next iteration. So just assume smooth for the first iteration.foo9008 said:
But, we do not know D, how to assume the value of D?Chestermiller said:
1. Guess value of Dfoo9008 said:
so , we need to assume the value of D first ?Chestermiller said:
That's what I would do. Choose values for D that give you the exact values of e/D on your Moody chart.foo9008 said:
is there any tips to assume the value of D ?Chestermiller said:
The formula for finding the diameter of a pipe is d = 2r, where d is the diameter and r is the radius. Alternatively, you can also use the formula d = 4A/π, where A is the cross-sectional area of the pipe and π is the mathematical constant pi (approximately 3.14).
You can measure the diameter of a pipe using a ruler, caliper, or tape measure. Place the measuring tool perpendicular to the pipe and measure the distance across the widest point of the pipe to get an accurate diameter measurement.
Yes, you can find the diameter of a pipe if you know its circumference by using the formula d = c/π, where d is the diameter, c is the circumference, and π is the mathematical constant pi.
The unit of measurement typically used for pipe diameter is inches (in) or millimeters (mm). However, in some cases, it may also be measured in feet (ft) or centimeters (cm).
The precision of your measurements depends on the accuracy required for your specific application. In most cases, a measurement accuracy of 1/16 inch or 1 millimeter is sufficient for determining the diameter of a pipe.
