calculating d vs d full for less than full Q

[ketanco]

in the practice problems for civil engineering pe exam book, question 19-5-d, on the solutions page, 19-9, it calculates q/qfull and then i didnt understand how it calculates d/d full, can someone help, who has the same book? or in general how is it done, it refers to the chart on CERM Appendix 19C, first of all I forgot how to read that graph may be thats why i didnt understand...

also in the next item of the same question it asks what velocity would prevent sediments from settling in the pipe and without any calculation it just gives the answer... any ideas?

 

[John QPE]

What was the answer for the velocity question? 2.5 fps is pretty much industry standard...one of those things I was just always taught. Curious what the book says.

d/D is the ratio of depth to diameter.

I'm forgetting how to use that chart, so I'll leave that for the next guy.

 

[K19]

To use the table start with your calculated value of Q/Qfull and find it on the horizontal/bottom axis, draw a vertical line up until you hit the appropriate discharge (Q) curve,* then draw a horizontal line left to get d/D.

* Unless the problem states otherwise, assume that the Manning "n" is constant (does not vary with depth) and draw to/from the dashed curve.

 

[ketanco]

What was the answer for the velocity question? 2.5 fps is pretty much industry standard...one of those things I was just always taught. Curious what the book says.

d/D is the ratio of depth to diameter.

I'm forgetting how to use that chart, so I'll leave that for the next guy.

yes the book gives it as 2-2.5 fps. so this was just a knowledge question then.. no calculation or anything?

 

[John QPE]

What was the answer for the velocity question? 2.5 fps is pretty much industry standard...one of those things I was just always taught. Curious what the book says.

d/D is the ratio of depth to diameter.

I'm forgetting how to use that chart, so I'll leave that for the next guy.

yes the book gives it as 2-2.5 fps. so this was just a knowledge question then.. no calculation or anything?

Nope...2.5 fps is pretty much industry standard for "cleansing velocity."

This is a requirement you will typicall see in township ordinances as well....something to the fact that storm drains must be designed with minimum velocity of 2.5 fps.