An
outfall
is a pollutant point source. The outfall is small if we compare it with the size
of the area in which we are simulating (point source). If you click this button,
the next dialog box is shown:

Depending on the used model, some data of the dialog box can be modified:
Buoyant jet model or Stratified model (see calculation models).

Buoyant jet model:
The necessary data in the Buoyant jet model is:

Effluent velocity u_{a }(m/s):The average velocity of the pollutant
effluent. It can be around 1 m/s.

Pollutant concentration (g/m^{3}):
The discharge concentration of the material of interest (pollutant or tracer) is
defined as the excess concentration above any ambient concentration of that same
material. 1g/m^{3}=1ppm in water.

Water depth at discharge location (m):The actual water depth at the sumerged
discharge location. For surface discharges it is the water depth at the channel
entry location.

Discharge flow rate (m^{3}/s):The discharge flow rate and the discharge
velocity are related through the port cross-sectional area. (Flow rate)=(area)x(discharge
velocity).

Discharge density (kg/m^{3}):
It is the density of the pollutant discharge.

Discharge conditions:There are three options: Vertical discharge,
Horizontal discharge (A-type) and Horizontal discharge (B-type). In the vertical
discharge, the discharge flow is perpendicular to the water surface. In the
horizontal discharges (A and B), the discharge flow is parallel to the water
surface. In the horizontal discharge case, we assume that the discharge vector
is always perpendicular to current vector. That is to simplify the calculations.
In the A-type, the flow vector points the South and the current vector points
the East. In the B-type, the flow vector points the North and the current vector
points the East.

Stratified model:
The necessary data in the Stratified model is:

Pipe angle (0 to 360):
It is the horizontal angle of discharge measured clockwise from the North (at
the window top).

Diffusor length (m):The diffuser length is the distance from the
first to the last port or nozzle.

1/T90 (1/horas):
This coefficient considers the half life of the pollutant if this disappears by
means of chemical reactions (non-conservative pollutant). This is the T90 for
E.Coli. For towns with less than 10.000 inhabitants we can take a T90=2 hours
(1/T90=0,5 hours^{-1}) in the Mediterranean and T90=3 hours (1/T90=0,33
hours^{-1}) in the Atlantic.

Important
note for DESCAR 3.2 (or lower versions):

In the
approved model, T90 is un hours (this is used by the program).
However, and in equation F_{0}(t)=10^{-t/T90 } of
the approved model(1), time must be in seconds . Following criteria of
mathematical coherence and results T90 must be expressed in seconds
(multiply by 3600 seconds in one hour). At this point, the user can
work following two different ways: using the approved model as is or
rectify in the T90 input data. For example, for a T90=2
hours value, the user can introduce as input data:

(a) Following the approved model:

1/T90=0.5 hours^{-1} as input data. Then, write 0.5 in the
window textbox for a T90=2 hours value .

(b) Following criteria of
mathematical coherence and results:

1/T90=1/(2 x 3600)=0,000278 as input data. Then, write 0,000278 in the
window textbox for a T90=2 hours value.

(1)
Orden del 13 de Julio de 1993 del Ministerio de Obras Públicas y
Transportes del Reino de ESPAÑA, B.O.E. Martes 27 de Julio de 1993,
página 22861.

Number of openings:DESCAR allows for different types of
discharge geometries. There are three options: Single port, Multiport diffuser
and Separated ports. We have a multiport diffuser when the separation among the
ports is less than 3% of the depth. We have Separated ports when the separation
among the ports is bigger than 20% of the water depth.