There are in Germany. I send you one document where the existing guidelines are discussed. Unfortunately it is in German, if it is not urgent I can translate the main parts and send them later to you.

Thank you dear Rafael. the attached file was so good and seems to be the one I was Looking for, but I Should find the English version . Anyway thanks

You may find some valuable information USBR documents e.g. Design of small canal structures.

www.usbr.gov/tsc/.../SmallCanals.pdf

www.usbr.gov/.../designstandards3...

Amin you will not find an english version of it. If you tell me with a little more detail what you need and what you are doing I  can translate the most important parts of the document for you.

Dear Mohammad,

I Searched them but Closet Type of Structure I Found Was Inverted siphon!

Unfortunately there was no information about drop manholes.

Thank you so much anyway.

Dear Rafael,

I Attached a ُScheme of my problem Generally.

I Wanna to Calculate Head loss of  water.

Please look at it.

thanks alot

Ok, so you basically need the loss coefficients. You can use the two tables on page 10.

First you have to check what type of manhole you are trying to calculate and choose one of the two tables accordingly. Now the loss coefficients depend on the flow conditions (partially full, full, impounded) and how much the flow will change direction inside the manholes.

The first and second column refer to the same, that is the flow conditions and it translates like this:

Ablusssituation = Flow Conditions

- Teilfühlung = partially full

- Scheitelfühlung = full flow

-Einstau = impounded flow

Now I guess from your drawing that you are not expecting direction changes in your flow within the manholes, so you would get your coefficients from the third column on these tables. In case you wonder Umlenkung means something like redirection (direction change). Hope it helps.

Finally and just as a note there is the last row of both tables, this is something special. If you place a perforated plate inside the manholes where the "roof" of the pipes would be, you can reduce the losses. I know about two studies regarding this issue, one was carried out at my laboratory. You can get an idea of its effect by looking at the "turbulence intensity"  with and without perforated plate, for which I have attached two images.

Dear Rafael,

thanks a million For your Kindness. the last appendix  and translation was really practical and helpful.

the pictures that you attached, help me to find a good concept.

I'll hope to be able to do something for you in the future.

i agree with Rafael Anleu