GEC-Alsthom gates (AMIL, AVIS, AVIO, Mixtes)

The Gec-Alsthom gates are also available: AMIL, AVIS, AVIO and Mixte gates.

When you select a type and reference, the default values (as suggested in the Gec-Alsthom documentation) are proposed for the different parameters. You can modify them if you want. But be aware that the correct functioning of these gates depend on the correct selection of these parameters. When you select a new type or reference, or when you change the radius of the gate, the maximum allowed head loss Jmax, the corresponding discharge Q for Jmax, the maximum allowed discharge Qmax, and the corresponding head loss J for Qmax are indicated in order to help you to select the proper reference linked to your local hydraulic conditions.

The abacus recalculated from the equations we programmed are displayed in Annex. We can verify they fit the original ones of Gec-Alsthom.


The "type" corresponds to the range of the selected valves (Amil, Avio High head, Avio Low head, Avis High head, Avis Low head, Mixed without mask max. opening 45°, Mixed without mask max. opening 55°, mixed with mask).


The "reference" corresponds to the manufacturer catalog Gec Alsthom (now Hydrostec). If you want to model a different gate you can select "other." In this case we use some dimensions required for the calculation determined from the radius R indicated by drawing values close to conventional gates:

-* Amil :
-** D=1.6*R
-** E=0.95*R
-** b=0.91*R (Width at bottom)
-* Avis high head:
-** E=0.81*R
-** b=1.19*R
-* Avis low head:
-** E=0.95*R
-** b=1.19*R
-* Avio high head:
-** L=0.5*R
- Avio low head:
-** L=R


The "decrement" is the difference between the minimum and maximum regulated levels. For stability reasons this decrement can not be null. For an AMIL gate the default value suggested by the manufacturer (and the SIC software) is d=0.02*D. For an AVIS gate, the default value is d=0.028*R (low head) and d=0.032*R (high head). For an AVIO gate, the default is d=0.028*R (low head and high head).

Axis elevation

The "axis elevation" is the elevation of the axis of rotation of the gate. It corresponds to the set point for Q=0 for the AVIS, AVIO and the AMIL gates in alternate setting (or for Q=Qmax for an AMIL gate in conventional setting). The default axis elevation proposed by the manufacturer is calculated and proposed by the SIC software.

Sill elevation

The "sill elevation" is the elevation of the bottom of the civil engineering work at the point where the gate stops in full closure.


The "radius" is the radius of the radial gate. It is proposed automatically according to the reference of the chosen gate, but it can be modified. It is an essential parameter for calculating the operation of the gate.

Discharge equations

The equation "GOU 93" corresponds to the equation deduced from a document provided by Goussard, former engineer of Gec-Alsthom, and written in 1993.

The equation "CEM 02" corresponds to an equation developed by Cemagref in 2002.

Maximum opening

The variable "maximum opening" corresponds to the actual blocked opening of the gate if the equation chosen is "CEM 02 (V)" and corresponds to the maximum opening reached for the adjustment related to the decrement of the gate if the equation chosen is "GOU 93". A default value corresponding to the mechanical stop is offered by default depending on the type and reference of the gate. This value can be changed if a different stop limits or maximizes the maximum reachable opening.

For an Amil gate in conventional setting the gate will be at this max opening as soon as the level of the upstream water will be >= the elevation of the axis. For an Amil gate in an alternative setting, the gate will be at this max opening as soon as the level of the upstream water is >= the axis elevation + decrement. For an Amil gate in intermediate setting the gate will be at this max opening as soon as the upstream water level is >= the axis elevation + Z upstream max (see below for the definition of this variable).

For the Avis and Avio gates, the gate will be at this max opening as soon as the level of the downstream water is <= the elevation of the axis - decrement. Changing this value amounts to modifying the stop controlling the maximum opening of the gate and to modify the balancing of the gate.

Minimum Opening

By default, GEC gates in SIC have a minimum closing opening of 0.5% of the gate radius. This makes it possible to mimic the fact that these gates are not perfectly sealed and facilitates the computation in steady state for the AVIS and AVIO gates because a gate completely closed would generate a very important head which will propagate from downstream upstream.

Z upstream max

The variable "Z upstream max" corresponds to the maximum water height in relation to the axis elevation (corresponds to the setting in the case of the AMIL gate): 0 <= Zmax <= d. Zmax = 0 for the standard setting and Zmax = d for the alternate setting. Intermediate settings are possible. For the conventional adjustment, the upstream levels will therefore vary between Z = elevation of the axis - d for Q=0 and Z = axis elevation for Q=Qmax. For the alternative setting, the upstream levels will therefore vary between Z = axis elevation for Q=0 and Z = axis elevation + d for Q=Qmax. This variable is not used for gates other than Amil gates.

Filtrering S1/S2

The variable "Filtering S1/S2" makes it possible to filter the water elevation influencing the displacement of the float of the gate. We do not currently use this variable for Amil gates. One could imagine using it to mimic the damping related to the piston damper installed on these gates. For the Avis and Avio gates, this value mimics the filtering linked to the tank in which the float is located. Theoretically, the coefficient S1/S2 to be entered here corresponds to the ratio between the free surface of the water in the tank around the float divided by the surface of the orifice which causes the tank to communicate with the channel downstream. In practice, however, this coefficient must be increased to take account of the additional head losses associated with the possible piping of this water intake.

Tray offset

The variable "Tray offset" corresponds to the deport of the water intake of the tank towards the downstream reach. In practice, in particular when there are several gates in parallel, the water intake of the tank(s) is connected to a pipe communicating with the downstream reach several meters downstream of the gate in a tranquilized zone. This offset is given in meters (SIC then searches for the water elevation value in the nearest calculation section).