Re: [Anuga-user] Anuga infiltration fuction

[Stephen R. <ste...@an...>]

Hi Mike,

We should be able to put together an operator (or a forcing term) to do 
what you want.

We have a rate operator which takes a quantity or a function of x,y,t as 
a rate. See run_rate_spatial_operator.py in the anuga/operators

Should be able to use that as a base for your operator.

By the way, in your formula,

cumulative infiltration Z = k * T^a + f0 * T + c,

what is T, time?

For the rate operator, we will need an instantaneous rate, which I 
assume would be the function

R = ka T^{a-1} + f0

Will have to think about how to deal with c, but maybe we need a 
quantity to store this "crack fill volume" and just remove water until 
this quantity reaches c. We could build this into your operator.

Cheers
Steve

On 5/02/2014 4:52 PM, Mik...@de... wrote:
> Hello all
>
> Quite some time ago I posted a query to the forum on the suitability 
> of anuga for modelling surface irrigation events, with the aim of 
> using anuga to develop better irrigation bay designs.  We've since 
> been successful in attracting funding for this work, and have made 
> good progress with implementing and testing  anuga for the purpose.
>
> In an irrigation context, infiltration is a major flux (in fact its 
> the flux we are most interested in). To date we've been using the 
> Rainfall  forcing term with a negative rate (thanks for the tip, 
> Steve), which effectively provides us with a constant infiltration 
> rate, but we are now at the stage where an approach is required that 
> can represent time varying infiltration rates that start when each 
> cell in the mesh becomes wet.  The thing we are unsure of is how best 
> to implement a function that will have a different start time in each 
> mesh cell.
>
> 1D surface irrigation models in common use implement infiltration with 
> an empirical Kostiakov equation - cumulative infiltration Z = k * T^a 
> + f0 * T + c, where k and a are empirical , f0 is a final infiltration 
> rate and c is an initial crack-fill/rapid adsorption term.  I imagine 
> that the same approach could work in anuga, and that we could use our 
> 1D model calibration routine to provide estimates for the Kostiakov 
> coefficients for input to anuga.
>
> Has anyone attempted developing an infiltration routine for anuga in 
> the 10 months since I last posted?  If not, do you have advice on its 
> development?
>
> Thanks in advance!
>
> Mike
>
> Please note that my working days are Monday, Tuesday, Wednesday.
>
> *Mike Morris | Senior Research Scientist, Irrigation Hydrology | 
> Agriculture Research*
> Department of Environment and Primary Industries | 255 Ferguson Rd, 
> Tatura, VIC 3616
> T:  03 5833 5283 | M: 0419 317 454 | E: mik...@de... 
> <mailto:mik...@de...>| DX: 219130
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