## Fluids

#### How to create isosurface and rakes to find film thickness over the cylinder

• Prudviraj
Subscriber

Dear sir, I am beginner to the fluent, can someone suggest how to create isosurface and rakes to calculate water film thickness over the cylinder with respect to circumferential angle....I am attaching an image for your reference only....

• Karthik R

Hello,

You could try to create an iso surface of your volume fraction (say 0.5). Since your simulation is 2D, it will give you a curve. If you plot the y-coordinate of this curve, you should get the film thickness (in some form - might require additional manipulations depending on your position of the origin).

Please test this and let us know.

Thank you.

Best,

Karthik

• Prudviraj
Subscriber

Dear sir, I have attached images after creating the isosurface volume fraction of water 0.5...please suggest me the next steps to find film thickness with respect to circumferential angles.......

• Prudviraj
Subscriber

Dear sir, yesterday I read this attached image and how they measured in CFD POST......Can you please elaborate on how to find film thickness over the cylinder at various angles using CFDPOST with the similar approach I have attached...

The corresponding mass flow rate to its velocity inlet is then recorded when a proper film

distribution is achieved in simulation result. The thickness of water sheet film on tube surface

is then measured based on angles of 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, 150°, and

165° as shown in figure 8. These angles have been set as a reference values in accordance with

many previous references. The numerical results have been analyzed in CFD-Post

where 4 mm length of measurement lines were positioned normal to tube surface. These

measurement lines acted as a parameters that measures water film thickness at specified angles

as shown in Fig

The thickness of water film are extracted and plotted in a graph of thickness versus orientation

angles. Each measurement data is measured by taking into account the difference of water

volume fraction length which only 1.

• DrAmine
Ansys Employee
You create rakes or lines over each line you use a user variable with 4*alpha phase 2 * alpha phase 1.
• Prudviraj
Subscriber

Dear sir, please suggest how to create radial rakes for every 30-degree angle over the cylinder...

• DrAmine
Ansys Employee

You do them manually by providing the starting and end point which corresponds to 30° intervals or via script. Either in Fluent or in CFD-Post.

If you have EnSight you can ise "By constant on part sweep" method which you can then easily create a sweep in the Theta direction.

• Prudviraj
Subscriber

Sir, i have created lines by providing starting and endpoint in CFDPOST.....will you please suggest how to measure only water film thickness at these lines. or using these lines....Here attached images are for your understanding.....Your guidance will be highly appreciated in this regard....

• fit78
Subscriber

Alternatively, you can generate a polyline from the water fraction contour. Choose the contour level you see fitting the fluid film.

Once you generated the polyline, generate an XY plot. You will get something like this

Then you can export the XY plot and open it in a spreadsheet.

By using X^2+Y^2=R^2, you can find the R which is the distance of the fluid film from the center axis.

Easily, you may find the thickness by substracting the radius of the cylinder you were working on from the R value.

To find the location of the film thickness, just use trigonometry since you already have the X and Y location.

Hope this helps.

Fit