Modelling Questions

What type of problems is ANUGA good for?

General 2D waterflows in complex geometries such as dam breaks, flows among structures, coastal inundation etc.

What type of problems are beyond the scope of ANUGA?

See the chapter on "Restrictions and Limitations" in the ​User Manual.

Can I start the simulation at an arbitrary time?

Yes, using domain.set_time() you can specify an arbitrary starting time. This is for example useful in conjunction with a file_boundary, which may start hours before anything hits the model boundary. By assigning a later time for the model to start, computational resources aren't wasted.

Can I change values for any quantity during the simulation?

Yes, by using domain.set_quantity() inside the domain.evolve loop you can change values of any quantity. This is for example useful if you wish to let the system settle for a while before assigning an initial condition. Another example would be changing the values for elevation to model e.g. erosion.

Can I change boundary conditions during the simulation?

Yes, see the example in the section "Changing boundary conditions on the fly" in the ​User Manual.

How do I access model time during the simulation?

The variable t in the evolve for loop is the model time. For example to change the boundary at a particular time (instead of basing this on the state of the system as in the "Changing boundary conditions on the fly" section of the manual) one would write something like

for t in domain.evolve(yieldstep = 0.2, duration = 40.0):
    if Numeric.allclose(t, 15):
        print 'Changing boundary to outflow'
        domain.set_boundary({'right': Bo})

The model time can also be accessed through the public interface domain.get_time(), or changed (at your own peril) through domain.set_time().

Why does a file_function return a list of numbers when evaluated?

Currently, file_function works by returning values for the conserved quantities stage, xmomentum and ymomentum at a given point in time and space as a triplet. To access, or example, stage one must specify element 0 of the triplet returned by file_function, to access xmomentum one must specify element 1 of the triplet, etc.

How do I use a DEM in my simulation?

You use dem2pts to convert your DEM to the required .pts format. This .pts file is then called when setting the elevation data to the mesh in domain.set_quantity.

What sort of DEM resolution should I use?

Try and work with the best you have available. Onshore DEMs are typically available in 25m, 100m and 250m grids. Note, offshore data is often sparse, or non-existent.

Note that onshore DEMS can be much finer as the underlying datasets from which they are created often contain several datapoints per squate metre. It may be necessary to thin out the data so that it can be imported without exceeding available memory. One tool available on the net is called 'decimate'. (Need reference?).