July 4, 2023 at 1:34 pmKauê CastroSubscriber
Im a beginner in Ansys, Im trying to get the hang of all it's features.. I need to learn on how to input an sinusoidal excitation to a jet, perhaps someone could help me?
July 4, 2023 at 1:36 pmRobAnsys Employee
Have a look at profiles, expressions and DEFINE_PROFILE UDFs. I'd typically favour the latter, but expressions are possibly a better tool for you to learn.
July 4, 2023 at 1:56 pmKauê CastroSubscriber
Hey Rob, I couldn't find my last post so I tried reposting it (sorry for the complication).
Anyway, I'll have a look at all three of those cited to implement them.
As you've asked on the other post, I want to excite the jet in the range of 10-200 Hz. The Model is really really simple as in the image im uploading below
It consists of a velocity profile coming out generated by an other internal flow simulation.
(Out of the article "Control of a Plane Jet by Fluidic Wall Pulsing" By J. C. Béra, Et al)
I'll post as soon as possible as a reply to this post the contours of velocity & velocity vectors. You've previously asked if I was running transient, and actually I'm initially trying to run steady, and eventually progressing to transient. Also, I'll have a look for fluidic switches as you had said.
July 4, 2023 at 2:46 pmRobAnsys Employee
The vibrations are a little more complicated. You may need to look at moving mesh as you won't have a flow boundary.
July 6, 2023 at 12:14 pmKauê CastroSubscriber
Hey Rob, as you previously asked, the velocity contours map:
As you can see, a recurring problem I'm having is the reversing of the flow on the BC (using outflow), one solution I was thinking of is making the second derivative 0 for the cross-stream directions, however I didn't find where I could change that, in the case it's possible.
July 6, 2023 at 12:21 pmRobAnsys Employee
Don't use outflow, it's a really bad idea generally, and even worse with backflow. You want a pressure outlet.
Now, backflow is also going to happen with that bc, and I'll leave you to explain why (in reality) it's happening.
July 6, 2023 at 2:46 pmKauê CastroSubscriber
Im sorry, I actually don't know haha, is it due to eddies formed curling inwards to the jet?
July 6, 2023 at 3:34 pmRobAnsys Employee
Sort of. You're sending higher speed flow into a confined space. That will entrain additional fluid, and that fluid has to come from somewhere. In this case the fluid comes from outside the domain.
July 6, 2023 at 3:46 pmKauê CastroSubscriber
For me it still doesn’t make sense, intuitively I’d think that the development of the jet would seem something like this:
I tried prolongating the domain and it didn’t change anything, so probably the problem is due to turbulence intensity aaa. Nevertheless, thank you for the help Rob, you’ve been extremely helpful and im very grateful.
July 6, 2023 at 3:54 pmRobAnsys Employee
Not so much turbulence, the same phenomena occurs in laminar jets. Plot vectors on the above model, and look at the flow around the jet. If you block that flow (from the upstream) how will the flow around the jet behave?
There are a couple of modules on Learning that may help explain.
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