Discussion Forum

Hello,

I am working on a transient solute transport model in the Earth Science Module of COMSOL 3.5 a. The purpose of the model is to predict the release of radionuclides from a defective used nuclear fuel container and the subsequent transport through the tunneling system (vault) and through the geosphere. The vault is modeled as a 3D geometry whereas the geosphere is modeled as a 1D pathway.

I want to define the transient flux into the geosphere as the transient flux from the exterior vault boundaries. I have defined the following boundary integration variable on all exterior boundaries of the vault model (3D model):

name: Flux_Ci
Expression: tflux_Ci_esst2
Integration order: 4 (default)
Global destination: selected

With this approach I am having the following problems. First, I want to define a flux boundary condition into the geosphere (1D) as "Flux_Ci" but I am unable to do so. The am not able to define the flux boundary condition into the geosphere using the variable "Flux_Ci". When I try to describe the boundary that way, I get an inconsistent unit error, even when I try to force the proper units. I am also wondering how the program would "know" to use the value calculated for "Flux_Ci" at all the boundaries.

Secondly, when I solve the 3D vault model, and plot Flux_Ci in postprocessing mode, the results are orders of magnitude higher than the results obtained when the expression tflux_Ci_esst2 is entered into the postprocessing expression. These solutions should be identical, any idea why this happens?

Unfortunately, my model file is too large to upload. However, any tips regarding the use of integration coupling variables or any insight into my particular problem would be very appreciated.

Regards,

Yannick