# (Biomedical Engin.) Fluid flow through a semi-porous membrane (COMSOL)

• juvel006
In summary, the conversation discusses a problem involving waste removal from a membrane tube using COMSOL's convection and diffusion modeling. The initial conditions and boundary conditions are described, including the use of a partition coefficient and Brinkman's equations. The individual seeking help also mentions another user with a similar problem but notes that they have not been active for some time.
juvel006
Hi all -

I have a problem that I'm probably going to model in COMSOL and would love to hear some ideas on how to get the proper BCs.

Attached is the picture from Truskey. Essentially, the problem consists of removing waste (water) from the membrane tube at a rate of ~ 1 mL/min with a pressure driven flow ~ 80 mm Hg inlet and ~ 40 mm Hg at the outlet. The radius of the tube should be around ~ 8-10 mm, and length, thickness, and porosity of the membrane to be chosen for optimal and desired waste removal.

I'm using COMSOL's convection and diffusion modeling. The inlet is a known concentration of waste and velocity profile. The outlet BC I use is convective flux resultant from flow out of the pores. The membrane BC is where I'm not sure what to use. Right now, It's a partition coefficient problem with a flux concentration difference (something like K*(C_inside-C_outside)).

I haven't gone into the full problem really, but I was just wanted some feedback on how to set up my BCs properly to capture the waste removal at the membrane of ~ 1ml/min... Another attached picture is the actual modeling domain used. So basically, how can I capture the removal of ~ 1ml/min of waste (water) from the permeate side in COMSOL? Is there a better way to set this problem up using incompressible Navier Stokes in COMSOL to use Brinkman's Equations for the membrane part? If so, how would I go about it given the general problem I've described as far as BC implementation.

Thanks for any feedback.

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juvel006 I am working on a very similar problem and was curious how you went about solving yours in the end? Thanks.

ACulberson said:
juvel006 I am working on a very similar problem and was curious how you went about solving yours in the end? Thanks.
Welcome to the PF.

From the Profile page for @juve006, his last sign-on was in 2010. So he may not answer your question anytime soon. Go ahead and start your own thread with your question, and post as much work as you can so we can see where you are. Thanks.

## 1. What is the purpose of studying fluid flow through a semi-porous membrane in biomedical engineering?

The study of fluid flow through a semi-porous membrane in biomedical engineering is important because it plays a crucial role in many biological processes, such as blood filtration in the kidneys and drug delivery in the body. Understanding this process can help improve medical treatments and devices.

## 2. How is COMSOL used in the study of fluid flow through a semi-porous membrane?

COMSOL is a powerful software tool that allows scientists and engineers to simulate and analyze fluid flow through a semi-porous membrane. It uses finite element analysis to solve complex mathematical models and provides a visual representation of the fluid flow behavior.

## 3. What are some factors that can affect fluid flow through a semi-porous membrane?

There are several factors that can influence the behavior of fluid flow through a semi-porous membrane, including the properties of the membrane material, the size and shape of the pores, the pressure and velocity of the fluid, and the concentration and size of the solute particles in the fluid.

## 4. How does the structure of a semi-porous membrane affect fluid flow?

The structure of a semi-porous membrane, including the size and distribution of its pores, can greatly impact the behavior of fluid flow. A membrane with smaller and more evenly distributed pores will have a higher flow resistance, causing a slower flow rate. On the other hand, a membrane with larger and irregularly shaped pores will have a lower flow resistance and a faster flow rate.

## 5. What are some potential applications of studying fluid flow through a semi-porous membrane?

The study of fluid flow through a semi-porous membrane has many practical applications in biomedical engineering, such as designing more efficient blood filters, improving drug delivery systems, and developing new technologies for water filtration and purification. It can also aid in the understanding of various biological processes and help in the development of new medical treatments.

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