Parameter values for Aw

Alles zu DELPHIN, dem Programm zur hygrothermischen Bauteilsimulation.

Moderatoren: ghorwin, fechner, ruisinger

Antworten
Gregor2019
Beiträge: 7
Registriert: Do 28. Nov 2019, 13:32

Parameter values for Aw

Beitrag von Gregor2019 » Do 13. Feb 2020, 07:52

Dear Delphin Team,
I am going to analyse heat and water transport in a soil environment in which power cables are bedded. The water uptake coefficient Aw plays a crucial role in correctly calculating the water transport within the soil body, correct? Concerning this parameter, I would like to know whether the Aw values that are assigned to the soil types that are integrated in the material bank of Delphin were determined in the laboratory by you or if those values are referenced to any literature.

As I am not able to find any literature regarding Aw values of different soil types myself, I am wondering where those Aw values given in the data bank come from and how realistic they are.

If they were determined by you in a laboratory, I could just use those values for my study. In case they are based on a literature research I would be tremendously grateful for the information to which literature these values refer to.

I am greatly thankful for any help and wish a good day,
Markus.

ghorwin
Beiträge: 12
Registriert: Mo 3. Dez 2018, 12:49

Re: Parameter values for Aw

Beitrag von ghorwin » Do 13. Feb 2020, 09:48

Dear Markus,

moisture transport in soil is a bit more complicated than in regular porous building materials. The composition of the soil (compaction degree) and stratification may be an important factor in your application.

With respect to the Aw-value: while it is possible to measure this for certain soils, the calibration of the transport functions requires more data than just that. The data in our material database is based on lab measurements with several different tests, and on literature data, for example based on Mualem model approximations. This is indicated in the "source" property of the individual material.

Greetings,
Andreas

Gregor2019
Beiträge: 7
Registriert: Do 28. Nov 2019, 13:32

Re: Parameter values for Aw

Beitrag von Gregor2019 » Do 13. Feb 2020, 11:01

Dear Andreas,
thank you very much for your quick response!

I am well aware that for the calculation of water transport in a medium I also need the water retention curve and the water conductivity. However, before I used Delphin for the first time, I had never heard of a water uptake coefficient Aw. Due to the model´s complexity, it seems to be an important parameter that has an effect onto the water balance. But as far as I am informed, the Aw parameter is not related to the Mualem/van Genuchten models (cannot be determined by them), which is why I still do not fully understand why the respective Aw values were assigned to the soils in the data bank.

I am sorry for being so precise, but I am going to use my simulations for my doctoral degree. Consequently, every parameter I use has to be reasonable and linkable to a source.

Alternatively I would exclude this parameter from my simulations by assigning values of 0 to the Aw parameter.

Thank you very much again,
Markus.

ghorwin
Beiträge: 12
Registriert: Mo 3. Dez 2018, 12:49

Re: Parameter values for Aw

Beitrag von ghorwin » Fr 14. Feb 2020, 13:59

Hi,

ok, now I understand the confusion. Indeed, the Aw-value is reported in the material data sets primarily for comparision and evaluation of the materials. It is, however, not used in the actual calculation. The liquid conductivity function must be given in the material and Aw is just an additional parameter (that may assist during calibration of the liquid conductivity).

-Andreas

Gregor2019
Beiträge: 7
Registriert: Do 28. Nov 2019, 13:32

Re: Parameter values for Aw

Beitrag von Gregor2019 » Mo 17. Feb 2020, 06:49

Hi,
perfect. Thank you very much!

Markus.

Antworten