Properties

[epelde.ane@gmail.com]

Hello all,

I write here several doubts I have inside the properties modules, please if you can give me a hand with this,

First, I see that there is the possibility of selecting the way of discretization of the advection and diffusion. It can be distinguished between explicit and implicit. What is each for? I´ve seen the values you use in a project, but can you explain which criteria I have to follow to decide between them?

Related to this, once this is decided, I have to set the method. Do you always use the upwind order 1? What is the difference between them?

Then, I see the blocks defining the dispersion/long&trans. This aggregates molecular diffusion and mechanical dispersion, right? And would it be like a cte value with which we delay the transport in the flow direction (long) and in perpendicular direction (transversal) right?

I think is enough for now Thanks!!

[Jauch]

Hello Ane
I'll try to answer through our wiki.

1. Explicit and Implicit methods.
http://www.mohid.com/wiki/index.php?tit ... _equations
http://www.mohid.com/wiki/index.php?tit ... Mohid_Land

The criteria to use is the results you have. We usually start using explicit methods, but if the results become too unstable, even making the simulation stopping due to impossibility of convergence, we change to implicit methods.

2. "Order"
http://www.mohid.com/wiki/index.php?tit ... cal_scheme

3. Dispersion
http://www.mohid.com/wiki/index.php?tit ... _Transport
http://www.mohid.com/wiki/index.php?tit ... _Transport
http://www.mohid.com/wiki/index.php?tit ... Mohid_Land

Just one note... Molecular Diffusion is given for each property trough a specific keyword: ADVDIFF_MOLECULAR_DIFF_COEF.

Hope this was enough to you to start

[epelde.ane@gmail.com]

Hi again!

I´ve seen different explanations for the keyword NEW_FORMULATION. They are:

1) NEW_FORMULATION : 1 !1 - do not use moduleadvectiondiffusion (removed advection computation); 0 - old formulation.
2) NEW_FORMULATION : 0 !if 1 then spatial methods will be the same for all properties.

Maybe its my ignorance, but do they mean the same? If not, which is being currently used? And, in case of being the second, we are saying that all spatial methods will be the same, ok, but, which is the keyword being read in that case? (i mean, that if we set new_form:1 and then we set horizontal advection method, for insatnce:1, and vertical advection method: 2.. which is being read?)

thanks!!

[davidbrito]

Hello,

NEW_FORMULATION keyword only exists to speed up computation.
The advection diffusion in MOHID land is the same as MOHID Water. But the original folrmulation from MOHID Water takes a lot of time computing advection coefficients (based on the method the user chooses) for each property. This may be avoided if we declare that we will use to all the properties the same kind of transport method. So the model will not read the property advection methods inside each property block but the one defined once and outside. This speeds up a lot the simulation if ruunning with a lot of properties.

The right one is the second. Where was the first?
And it will read which methods to use inside the file but outside property blocks. It will ignore the same keywords inside each property since it will be used for all.
Since you are running with only one property it will not improve the simulation time using NEW_FORMULATION : 1

Hope it helped,
David

[epelde.ane@gmail.com]

thanks david!

both definitions are in the wiki, in porousmediaproperties (one in the keywords square and the other in sample square).

ok, so you say that in my case it wont improve a lot cause i´m only running with one property, but the case is,l that (and related to the other post of fertilizer application, cause for now I just wanted to run it with the nitrate property) when I set NUTRIENT_FLUXES_WITH_SOIL:1 and FLUXES_TO_SOIL_OUTPUT:1, it starts asking me for properties (I write them below, I have just entered the ones mohid has asked me for). I understand that these are the minimum properties to run mohid with nutrient fluxes?

Drainage network module: nitrate+amonia
PorousMedia prop module: nitrate+PROC+PRON+PLON+amonia+soil dry density
RunOff module: nitrate+amonia

[davidbrito]

If you are only transporting properties that you do not need that but since you want the vegetation fluxes, than to have the organic matter release when plant dies and the uptake you need both dissolved and particulate. and if you run with phosphorus (e,g, phosphorus stresss in vegetation) you will be asked for other properties.

Best regards,
David

[epelde.ane@gmail.com]

Ok, clear now!