Hi,
I need to check a design we have inherited from another consultant. The design relies on a Venturi flume to reduce flow downstream modelled as a culvert and the storage area upstream is represented using three channel sections and a bunch of interpolates.
The flume itself is modelled as culvert laid flat with the following attributes
Solution Criteria – highest U.S. EG
Shape Box
Chart #12 – non offset flared wingwalls, 3/4 inch chamfered inlet
Scale # 2 – Wingwalls flared 18.4 deg(3:1) inlet not skewed [design is 2:1 over approx 5m]
Distance to upstream XS – 5
Culvert Length – 4.8 [throat length]
Entrance Loss Coef – 0.3
Exit Loss Coef – 0.3
Manning’s n for Top – 0.01
Manning’s n for Bottom – 0.025
Depth to use Bottom n – 0.1
Depth Blocked 0
Is this an appropriate way to model a flume? I am not really familiar with HECRAS so not entirely sure about all the attributes.
I presume that water passing through the flume will not get to critical depth as the head and tailwater levels are similar and large (3-4m). If the flume does operate in this way will the schematisation accurately reproduce the flumes behaviour?
How would you model a flume and attenuation basin?
Thanks
Alex