Include Page | ||||
---|---|---|---|---|
|
Include Page | ||||
---|---|---|---|---|
|
Exercises
Simulating a Non-Newtonian Fluid Using the Casson Model
A user defined function (UDF) can be used to implement the Casson fluid model. The Casson fluid model is given below:
Latex |
---|
{\large
\begin{align*}
&\mu = \frac{\mu_{\infty}^2}{\dot{\gamma}}+\frac{2\mu_{\infty} N_{\infty}}{\sqrt{\dot{\gamma}}}+N_{\infty}^2\\
&N_{\infty}=\sqrt{\mu_p (1-Hct)^{-0.25}}\\
&\mu_{\infty}=\sqrt{(0.625Hct)}\\
&\text{For blood:}\mu_p=0.00145 [Pa\cdot s];\>Hct=0.4
\end{align*}
} |
Latex |
---|
Note that $\tau_y=\mu_{\infty}^2$, also know as the yield stress. $k_c=N_{\infty}$, also known as the consistency index. |
A UDF incorporating the equations above is included in the file that you can download here. This file also contains the UDF for defining the time variation of the inlet velocity. You need to use this file for the Casson model and not the one provided in the tutorial. This is necessary because all UDF's need to be in one .c file. You could also use this .c file for all your cases whether you are using the Casson model or not.
In order to implement this file in FLUENT, in the top menu bar, under "Define" -> "User Defined" -> "Functions", choose "Interpreted". Find the .c file in the directory, and choose "Interpret". Then under materials, double click on the fluid you defined, and for viscosity, choose "User Defined". Then choose "casson_viscosity". You assign the inlet velocity as in the tutorial.
Info |
---|
The following videos go through the steps for modifying the bifurcating artery geometry in ANSYS SpaceClaim. For instructions on modifying the geometry using SolidWorks, |
Info |
This page goes through the geometry steps for the 3D Bifurcating Artery - Exercises in the SpaceClaim geometry engine included with ANSYS Workbench. For instructions on creating the geometry using SolidWorks see the page 3D Bifurcating Artery - Exercises (Legacy). |
...
Create a new sketch, move to one end of the obstruction
Use Spline to mimic the artery boundary (just click on the edge of the artery that is visible and follow the dots that show up)
Use Offset Curve to create two more curves: one inside and one outside the artery
Return to 3D mode
Hide the artery
Delete the inner portions of the resulting surfaces leaving only the outer ring
Unhide the artery
Do the same on the other end of the obstruction
Hide the artery
Use Blend and then control + click the two faces that remain
Unhide the artery
Ctrl + Click the missing ellipse and fillet and click Fill if you haven’t already
Use Combine as before to create three solids
Delete or suppress all entities except the artery
Use pull to smooth any sharp edges as desired
Simulating the Non-Newtonian Fluid Using Casson Fluid Model
A user defined function (UDF) can be used to implement the Casson fluid model. The Casson fluid model is given below:
Latex |
---|
{\large
\begin{align*}
&\mu = \frac{\mu_{\infty}^2}{\dot{\gamma}}+\frac{2\mu_{\infty} N_{\infty}}{\sqrt{\dot{\gamma}}}+N_{\infty}^2\\
&N_{\infty}=\sqrt{\mu_p (1-Hct)^{-0.25}}\\
&\mu_{\infty}=\sqrt{(0.625Hct)}\\
&\text{For blood:}\mu_p=0.00145 [Pa\cdot s];\>Hct=0.4
\end{align*}
} |
Latex |
---|
Note that $\tau_y=\mu_{\infty}^2$, also know as the yield stress. $k_c=N_{\infty}$, also known as the consistency index. |
A UDF incorporating the equations above is included in the file that you can download here. This file also contains the UDF for defining the time variation of the inlet velocity. You need to use this file for the Casson model and not the one provided in the tutorial. This is necessary because all UDF's need to be in one .c file. You could also use this .c file for all your cases whether you are using the Casson model or not.
...
Go to Comments
Go to all FLUENT Learning Modules
...