Learning Forum

[13721489333]

I use fluent to simulate the impact of droplets on the wall. The red is the water phase and the blue is the air phase. When the droplets fall from the air domain and hit the wall, the droplets will spread out. Excuse me, please, how to output the curve of the variation curve of the spread width of the upper droplet with time, and the curve of the variation curve of the droplet drop height with time?

[Amine Ben Hadj Ali]

So you need to get the free surface / contact line (corresponding to volume fraction = 0.5) and use that line to visualize it over time and do some reduction on it get what you want.

[13721489333]

对不起，我不太明白你的观点。我可以理解，等高线是设置为找到两相边界的，但是如何设置它来输出液滴扩散宽度随时间的变化规律呢？

[13721489333]

Sorry, I didn't quite get your point. I can understand that the contour line is set to find the two-phase boundary, but how to set it to output the variation law of the droplet spreading width with time?

[Amine Ben Hadj Ali]

You can create Free Surface and export that as picture every N time steps. So you have a 2D/1D evey N-time Steps which you can overlay on one another and do some more post-processing. Somer other resaerchers calculate h/D or d/D (Maximum Height of impinging Droplet to initial Droplet Diameter D or the diameter of the wetted area to Diameter) verus a dimensionless time. 

 

You need to tell us what do you want to do and perhaps paste an example here.

[13721489333]

As shown in the picture, I want to figure out how the spread diameter of the droplet changes with time. My current method is to export the simulation results for processing through matlab. But I want to know if it is possible to get this data change in the fluent program, in the CFD-post, by setting the monitoring surface and the like？

[13721489333]

Sorry I didn't quite understand your first two posts. I am doing a 2D simulation of a droplet with a diameter of 2mm hitting a wall in fluent (red is water phase. blue is air phase). What I want to ask is, after the calculation is over, in CFD-post, how can we output the variation law of the spreading width of the water phase on the wall with time? I don't have any ideas at the moment, I know how to set the isosurface, and then I don't know how to do it.

[Amine Ben Hadj Ali]

What is the spread factor for you? For me that is what I was describing. Saying that you need to calculate the wetting area by the droplet, from it you estimate a a diameter. With that diameter / Droplet Diameter you can have a time plot.

[13721489333]

sorry，can you tell me your email? specifically, I want to ask you for advice by email, it is too troublesome to communicate like this

[Amine Ben Hadj Ali]

Please keep communicating on this platform. Thanks!

[Amine Ben Hadj Ali]

In CFD-Post you create an Expression to sum all face areas where VOF>0.5 or any limit (so wet by the liquid). With that expression you can calculate a sort of an equivalent circular area diameter. You create a third expression where you divide the second expression by the initial droplet diameter. Now you are finished you go to Chart and create a transient chart you plot the new Expression versus time. Voilà.