View source for HY8:Outlet Control Computations

== Outlet Control Flow Types ==

Outlet control means that the amount of water the culvert barrel can carry is limited by the barrel and/or tailwater conditions downstream.  As a result, the flow in the barrel is subcritical, and the energy equation may be used to find the upstream headwater depth.  Several flow profiles are possible as are shown below and as described in HDS-5.  HY-8 flow types 2, 3, 4, 6, and 7 are all outlet control flow types and are shown in the figure below.  The various flow type properties may be found in HY-8 by selecting the '''Flow Types''' button from the ''Culvert Summary Table'' and are shown [[#HY-8_Flow_Types|below]].

[[Image:OutletControlFlowTypes.png|450px]]

== Outlet Control Computations ==

The logic for determining flow type due to outlet control is shown in the figure below: {{only in print|(Zoom in or click on this image to see it more clearly)}}

{{hide in print|[[Image:OutletControlFlowchart.png|650px]]}}
{{only in print|[[Image:OutletControlFlowchart.png|x800px|center]]}}

This flowchart uses the following terms:

'''HJ''' = Check for [[HY8:Hydraulic Jump Calculations|Hydraulic Jumps]]

'''Full flow''' = Check if the culvert is flowing full

'''TWH''' = Depth of the tailwater from the invert of the tailwater channel at the culvert outlet

'''twOutletDepth''' = Depth of the tailwater from the invert of the culvert at the culvert outlet.  If the culvert is buried, this value is taken from the top of the embedment material.

'''IH''' = Inlet control headwater depth measured at the inlet invert of the culvert

'''OH''' = Outlet control headwater depth measured at the inlet invert of the culvert

'''RISE''' = Height of the culvert.  If the culvert is buried, this value is taken from the top of the embedment material.

'''Inlet Depth''' = The depth computed at the entrance to the culvert using the direct step profile computation method

'''Critical''' = The critical depth in the culvert

'''Normal''' = The normal depth in the culvert

{{WMS:HY-8 Flow Types}}


[[Category:HY-8 Analysis|O]]