## Fluids

#### CFD analysis of a viscoelastic material

• grv
Subscriber

Hi all

I am into the stress analysis of a visocelastic fluid which having a vertical downwards inlet velocity, hits the moving flat surface and then deforms freely (free surface). I tried to model it using FEM (ALE, moving mesh, COMSOL) but the solution did not converge. One possible reason, could be the topological change due to free surface. but I am not quite sure. If that is the case then two phase fluid flow, considering one as visocelastic (OLDROYD B) and other as air could be a better choice considering the topological changes. COMSOL document says it can handle two phase flow of non Newtonian fluid but it can't handle it by phase field or level set method if one of the fluid is viscoelastic.

I have not used ANSYS-Fluent in past. I get some information about Polyflow which seems attractive at the moment. Can any one knows if it can handle two phase viscoelastic modelling involving free surfaces?

Thankyou.

• ydai
Ansys Employee
Hello Gaurav Does your flow look like a slot or curtain coater flow, i.e., the fluid exits a slot channel and flows down towards a moving plate in a given direction, the most convenient case is in a constant translational speed, it is like a flow in coating fluid on a paper belt, which can be done in polyflow. Polyflow has viscoelastic fluid model in modeling the viscoelastic fluid flow. It uses the similar ALE for modeling the flow with free surface. In terms of modeling viscoelastic fluid flow, simulation can still be challenging in high viscoelasticity of the flow measured with Weissenberg number We = Lambda * Gamma
where Lambda = relaxation time of the viscoelastic material, in second
Gamma = typical shear rate of the flow, in 1/s
In terms of viscoelastic material model, Polyflow does have Oldroyd-B model, and also has Phan Thien - Tanner (PTT) and Giesekus models.
Ployflow has a curtain coater example 22, though using Newtonian fluid properties in the example, but may be used as the starting point for the further study with other fluid models. You can download the polyflow example package from ansys help site: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/prod_page.html?pn=Polyflow&pid=Polyflow&lang=en

Hope this helps
Yi

• grv
Subscriber
Hi Yi

Thankyou for the comment. But I am unable to download the example. I am using the university licence for running the software. I don't see any personnel Account Number(Customer Number) for me.
How to get that?

Best wishes Gaurav

• ydai
Ansys Employee
Hello Gaurav I asked our forum moderator who let me pass you an instruction below. Please check if it works on your side.
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Our student users aren't provided access to the ANSYS Customer Portal, but we do provide students with access to the ANSYS Online help from within the ANSYS Student products. This access bypasses the need to login into the Customer Portal when using the online Help from within the Student Product, but that path isn't taken when you click on a link in a post here. The workaround is as follows:
1. From ANSYS Workbench, use the menu Help > ANSYS Workbench Help.A browser window will open.
2. In the post that has a link to the ANSYS Online Help,Right Mouse Buttonon the link and selectCopy Link Address 3. Go to the browser window that opened in step 1 andPastein the address bar and you get to the required page.
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Thanks
Yi
• ydai
Ansys Employee
Hello Gaurav is it true that you are able to access the online help site and could view the document, but you are not able to download file from the site?
Thanks
Yi
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