Drop & supercritical manhole hydraulics

I am interested in technical references that might allude to investigations of hydraulics at manhole junctions where flows from opposed laterals meet, with the added complication that one or both of the opposed lateral flows involve a significant drop (greater than 0.75 m) relative to the manhole base or outgoing pipe invert.

I am aware of G.C. Christodoulou's work on drop manholes in supercritical lines for straight through and 90 degree bends but have not come across any experimental investigations involving supercritical drop manholes where a main and a lateral or opposed laterals meet. I am also familiar with the work carried out by J. Marsalek on various manhole configurations but note that no drop type configurations (that I am aware of) were investigated.

Further to this issue I am wondering if anyone might have experience with trying to credibly represent supercritical drop junctions within an EXTRAN or other hydraulic simulation. Issues including quntification of energy losses, location and stability of hydraulic jumps, air flow requirements, venting designs and surge conditions are also of interest.

Any documentation or personal experience with these issues would be greatly appreciated.

Thanks
Frank Frigo
ffrigo@agraee.com

It might not be exactly what you are looking for, but check out the article "Observations on Flow in Vertical Dropshafts in Urban Drainage Systems" by N. Rajaratnam et al., ASCE Jour. of Environmental Engineering, Vol. 123, No. 5, May 1997 (486-491).

Try these:

Gayer, J.A., "On the Hydraulic Role of Manholes in the Urban Drainage System" Third INternational Conference Urban Storm water, 1984, Sweden. Deals with a drop at one lateral and develops drop coefficient chart based on exp. data.

Hager, Willi, discusson of the Christodoulou paper, J-ASCE Hyd Div, date unknown.

Townsend, Ron D and Jan R. Prins, "Performance of MOdel Storm Sewer Junctions" Tech NOte, ASCE Hyd Div Jnl 1/78. Considers a jct with a partially elevated lateral.

Also, the FHA Hydrain Manual includes a formula for head loss with a plunging flow correction; however they do not document the source or the data.

Good luck, Ron K

Correction on last note. The FHA equation for plunging flow is documented in the following: FHWA-RD-94-080," Energy Losses Through Junction Manholes, Volume I: Research Report and Design Guide" 1994.

Available from NTIS PB95-164950. FHA staff told me there never was a volume II. Ron K.

Let me suggest looking at Section 7.1.6 of the FHWA's Urban Drainage Design Manual - Hydraulic Engineering Circular 22. (NTIS PB97-134308) There's a good discussion of energy losses in manholes including a piece on plunging flows. This document will cost about $70.

Roger W. Lehman, P.E.
Lehmanr@mail.rfweston.com