Mass transfer UDS between two phases

rarnaunot · March 30, 2017, 10:59

Hello!

I configured a two phase model of bioreactor in CFX, using additional variables to simulate the species of the fluids. These species are transported and transferred from the primary phase to the secondary, in which a sources (defined by an Expression) was actuating over these additional variables.

In CFX the case was “simple” to configure. Additional variables were configured as a fluid dependent and were solved using Transport Equations, having a Kinematic Diffusivity value set in both phases. Then, I could define additional variable pair details, where I indicated the Sherwood number for the variable transferring from the primary phase to the secondary (first image attached). In this example, the additional variable oxygen was “present” in both phases and was transferred from one to another.

Now, I have to implement the same in Fluent. I’m working with UDF and UDS. I have the same additional variables that I had in CFX, as a UDS. I have implemented a UDF to define the sources of the UDS variables. In a determined cell zone of the geometry, I have indicated that is acting this UDF as source (second image attached). This is working fine for one phase bioreactor model.

Then, I have to configure a two phase model (water- non Newtonian fluid) for the bioreactor. I define the same UDS than in one phase model and the UDF (sources) is modified for multiphase model. But at the time to configure the mass transfer between phases (second image attached), I have to configure mass transfer for the UDS… I don’t found where I can do it because I expect to do it similar as I configured it in CFX (in tab Fluid Pair Models). So, the questions is:

- How can I define this transfer for the UDS between two phases in Fluent? I’m thinking to define 2 different UDS for the same species, one for each phase, and then define another UDF which check the volume fraction (VF) of the phases, and when VF <1, equal the UDS value of one phase to the UDS value of the other phase... Then, I will have to implement this UDF as mechanism for transfer in the Mass tab “Phase interaction” (third image attached). Can someone confirm to me if this procedure is correct? If not, can someone help me with this?

image1.png

image2.png

image3.png

zobekenobe · June 25, 2018, 07:22

Hi Rarnaunot,

Did you find the solution to your problem. I have a similar problem.

March 30, 2017, 10:59	Mass transfer UDS between two phases	#1
rarnaunot Member Rosario Arnau Join Date: Feb 2017 Location: Spain Posts: 57 Rep Power: 9	Hello! I configured a two phase model of bioreactor in CFX, using additional variables to simulate the species of the fluids. These species are transported and transferred from the primary phase to the secondary, in which a sources (defined by an Expression) was actuating over these additional variables. In CFX the case was “simple” to configure. Additional variables were configured as a fluid dependent and were solved using Transport Equations, having a Kinematic Diffusivity value set in both phases. Then, I could define additional variable pair details, where I indicated the Sherwood number for the variable transferring from the primary phase to the secondary (first image attached). In this example, the additional variable oxygen was “present” in both phases and was transferred from one to another. Now, I have to implement the same in Fluent. I’m working with UDF and UDS. I have the same additional variables that I had in CFX, as a UDS. I have implemented a UDF to define the sources of the UDS variables. In a determined cell zone of the geometry, I have indicated that is acting this UDF as source (second image attached). This is working fine for one phase bioreactor model. Then, I have to configure a two phase model (water- non Newtonian fluid) for the bioreactor. I define the same UDS than in one phase model and the UDF (sources) is modified for multiphase model. But at the time to configure the mass transfer between phases (second image attached), I have to configure mass transfer for the UDS… I don’t found where I can do it because I expect to do it similar as I configured it in CFX (in tab Fluid Pair Models). So, the questions is: - How can I define this transfer for the UDS between two phases in Fluent? I’m thinking to define 2 different UDS for the same species, one for each phase, and then define another UDF which check the volume fraction (VF) of the phases, and when VF <1, equal the UDS value of one phase to the UDS value of the other phase... Then, I will have to implement this UDF as mechanism for transfer in the Mass tab “Phase interaction” (third image attached). Can someone confirm to me if this procedure is correct? If not, can someone help me with this? image1.png image2.png image3.png zobekenobe likes this.

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June 25, 2018, 07:22		#2
zobekenobe Member zobekenobe Join Date: Mar 2009 Location: Dublin, Ireland Posts: 72 Rep Power: 17	Hi Rarnaunot, Did you find the solution to your problem. I have a similar problem.