Fort.20: Non-periodic Normal Flow Boundary Condition File

The fort.20 file contains non-periodic, normal flow boundary conditions for “specified non-zero normal flow” boundary nodes. This file is only read when a “specified non-zero normal flow” boundary condition has been specified in the Grid and Boundary Information File (IBTYPE=2, 12, or 22) and NFFR=0 in the Model Parameter and Periodic Boundary Condition File.

File Structure

The basic file structure is shown below. Each line of input data is represented by a line containing the input variable name(s). Loops indicate multiple lines of input.

FTIMINC
for k=1 to NFLBN
   QNIN(k)
end k loop

Repeat the block above for each time step until the end of the simulation.

Notes

  • The first set of normal flow values is provided at TIME=STATIM (as specified in fort.15). Additional sets of normal flow values are provided every FTIMINC.

  • Enough sets of normal flow values must be provided to extend for the entire model run, otherwise the run will crash!

  • The node order in this file must match the order specified in the normal flow boundary condition part of the Grid and Boundary Information File.

  • A positive flow/unit width is into the domain and a negative flow/unit width is out of the domain.

Example

The following is a simple example of a fort.20 file with two normal flow boundary nodes:

3600.0
10.5
-5.2
12.0
-6.3
15.0
-8.1

This example shows:

  • A time increment (FTIMINC) of 3600.0 seconds (1 hour)

  • Two normal flow boundary nodes (NFLBN=2)

  • Three time steps of data, with:

    • Node 1: Flow into the domain (positive values) increasing over time

    • Node 2: Flow out of the domain (negative values) increasing in magnitude over time