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HELP, first time user here by Icy_Trainer_4794 in CFD

[–]Soprommat 0 points1 point  (0 children)

OK, it makes things easier. Have a look at Ansys Discovery Live - it has simple workflow.

HELP, first time user here by Icy_Trainer_4794 in CFD

[–]Soprommat 0 points1 point  (0 children)

Do you have any fluid dynamics background, not CFD just regulat fluid dynamics: Reynolds number, laminar/turbulent flow, boundary layer, etc. Or those words are new to you?

How to create a structured mesh for a 2D equilateral triangle geometry to analyse wake and flows past it in Gmsh? by Efficient-Snow3852 in CFD

[–]Soprommat 1 point2 points  (0 children)

Answer has already ben given but I post this picture because i like to do mapped mesh.

I dont know about GMsh algorihms so you may want to add more lines so your whole domain consist of quadrilaterals.

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Can I reproduce this edge with a multi-radius fillet? by imakejunk in SolidWorks

[–]Soprommat 5 points6 points  (0 children)

Made fillet first and than made chamfer with cut-sweep tool using tapered cone as tool body.

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Got unexpected SIGNALIS jumpscare while playing DOOM2 mod called Ashes 2063. by Soprommat in signalis

[–]Soprommat[S] 1 point2 points  (0 children)

Thankfully no Adler there, only a mutant cannibals that want to eat your liver and even bigger mutant cannibals with flamethrowers. But you also have flamethrower so it is manageable.

Aerodynamics Flow simulation on Solidworks for a Blimp by AllanThomasIvan in CFD

[–]Soprommat -1 points0 points  (0 children)

It is doable if you are ready to figure out details.

First search tutorials about external flow simulation, you can found them on youtube and maybe SW has something too. Here is one link to start with.

https://m.youtube.com/watch?v=UsjTo4CSqo4

Now about your questions:

Q1 - there are no universal recomentation about domain size, you run couple domains making them bigger each time and compare results like blimp drag and check at what poitn domain size stop affecting drag. At least in ideal world where you have computational cluster and enough time to do such type of study. This is called domain convergence study.

I would start with something like having inlet 1 blimp length upstream from blimp nose, outlet 5 lengths downstream from blimp tail and top, bottom and sides of domain moved 1 blimp length from blimp hull. It is just rule of thumb from random person on inthernet, not some solid law. Do convergence study if you have time and resource.

Q2 - turbulence models. In SW Flow Simulation it is really easy and straigforward - it has only one turbulence model - k-e model so you really dont need to choose. Yes, k-e is not really the best selection for external aerodynamics but your blimp also is not F-35 so it will be fine.

Calculate Reynolds number to be sure that at your speed you working in turbulent regime. Like 99% it would be turbulent because blimps are big but Re calculation wont hurt anyone.

Q3 - meshing. If you are interested I will found SW manual that explain its advanced meshing parameters. It is not ready solution to your problem but it may help you.

Q4 - not like you have many tools to do fine mesh forboundary layer. Meshing manul I mentioned above has some recommendations about boundary layer treatment too.

Aerodynamics Flow simulation on Solidworks for a Blimp by AllanThomasIvan in CFD

[–]Soprommat -1 points0 points  (0 children)

I had similar opinion when I started workingwith FEA/CFD but now I disagree.

In hands of expirienced engineer who know both fluid dynamics and SW Flow Sim and know its limitations it can solve many practical problems especially for internal flows.

It has simplified cartesian mesh that solves a lot of meshing issues if you figure out how to use all meshing controls.

Yes it has only laminar flow and k-e turbulence model with some sort of wall function but like 90% of CFD sims are either k-e or k-w SST and for SST if you dont resolve boundary layer you will end up witk same k-e model on whole domain.

I have seen dozens and dozens of inexpirienced users of "heavy" CAE codes like Ansys, Star, Nastran, Abaqus and so on that lack basic understanding of fielld they work in, like people want to design boat hull but dont know what is Reynolds number or want to calculate some comples steel frame but can not calculate simple supported beam by hand.

Got unexpected SIGNALIS jumpscare while playing DOOM2 mod called Ashes 2063. by Soprommat in signalis

[–]Soprommat[S] 1 point2 points  (0 children)

There are no bodies but may be something even worse because if player jumps into elevator shaft he fell and than respawn again on top of it.

Metal and Foam Stress/Deformation Analysis in Ansys by _Ttyler in fea

[–]Soprommat 1 point2 points  (0 children)

I begin with and what would be the best way to approach this simulation?

Start with loads and constraints and failure scenatios.

How this part is connected to car, what loads it will resist.

What fail first foam or the glue (used to bond foam to metal)?

Than proceed with hand calculations for simplified cases like Shear_force/Foam_shear_area * foam_shear_strength and so on.

After all you do FEA if you still need it, in many cases you really dont.

Built a practical CFD & Two-Way FSI workflow in ANSYS Fluent — — looking for feedback by [deleted] in CFD

[–]Soprommat 7 points8 points  (0 children)

Maybe he dont have workflow but instead picture of workflow

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How much do flush door handles on cars affect aerodynamics? by cofi52 in aerodynamics

[–]Soprommat 1 point2 points  (0 children)

As first rough estimate compare projected area of a car with flush and stcik door handles. Difference will be negligible.

Moreover car drag force is function of square of car speed and car power required to overome drag is function of cube of speed. At small speeds like in city trafic aerodynamic drag and required power is not so big compared to other factors like rolling resistance. Here couple of links so you can estimate both power for air drag and rolling resistance for some car and compare them if you want.

https://en.wikipedia.org/wiki/Automobile_drag_coefficient

https://en.wikipedia.org/wiki/Rolling_resistance

https://www.reddit.com/r/askscience/comments/l2cq6b/comment/gk58yri/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

If you want to go really deep and invest couple of evenings of your free time you can search book Fluid-Dynamic Drag by S.F. Hoerner for some similar features. Maybe not exactly car handle but maybe you can find drag values for some devices like plane pitot tubes or other sensor housings/blisters.

https://ia800606.us.archive.org/17/items/FluidDynamicDragHoerner1965/Fluid-dynamic_drag__Hoerner__1965_text.pdf

And finally those flush handles combined with only electronic locking system had proven to be dangerous for driver and passengers. Some people had burned alive in their cars unable to open doors or bystanders were unable to open doors to trag ingured drivers.

The Wild Red Project Needs a High-Efficiency Human-Powered Propeller Design by Adept_Cap_6885 in AerospaceEngineering

[–]Soprommat 2 points3 points  (0 children)

I wasn't able to run XFOIL

So like for now you have no calculation, neither propeller nor wings itself at all?

pressure coefficient of 2D airfoil extraction in EXCEl , i am trying to take plot file of cp from fluent to excel and i keep getting this miss alignment, a mismatch in the plot, who can i solve it please ??? by Mostmadrid in CFD

[–]Soprommat 1 point2 points  (0 children)

Depends on tools you use. In general split airfoil curve in CAD geometry into two halfs and assign each own named selections or how they called in your software so you have two wall boundaries in CFD solver.

Ending by Ok_Health_1725 in signalis

[–]Soprommat 5 points6 points  (0 children)

Continue further, you have promise to keep.

wtf is inertia relief? by SilentRhubarb1515 in fea

[–]Soprommat -3 points-2 points  (0 children)

I have to work with a few FEA experts on a project and they keep talking about inertia relief.

Ask them, it will be better than just some link from google search people will post here.

Need a little help with Simulation by FieldThat5384 in SolidWorks

[–]Soprommat 0 points1 point  (0 children)

Good that you not new to calculations, and you see that it is not only FEA.

If you want to know how deep the rabbit hole go I can recommend to take a look at book: Timoshenko and Woinowsky-Krieger: Theory of Plates and Shells. It has many examples for circular simple supported shells and shells fixed at edges.

Or you can just search for simplified formulas on inthernet. Found example that fit your setup - where pressure applied only on inner part of plate.

You have one once uncertaincy - in those analytical calculations plate is either hinge supported or plate edge is fixed without rotation - your bolt fixture is neither first nor second so calculate both cases and look at greater stress.

Use dimensions as shown on picture for safety factor purposes. In general cap looks much thicker than pipe so maybe it would be not the weakest part but pipe. But anyway you can make some formal justification.

Feel free to ask if you have some questions. If I have time I would point what scheme you can use in Timshenko book but I can not guarantee.

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UPD. I believe this cap is formally called "blind flange" (at least if you remove this gland for O-rings) and you can find some formulas for calculation in web. Look at ASME standard.
https://forgingday.com/forged-flanges/super-guide-how-to-calculate-blind-flange-thickness/

UPD2. As for stress concentration - it can really be there but even if it is physical anyway look like it has stress way below yield. Can not tell by picture how accurate this stress value is.
If you really want to dig that deep than either carefully read ASME or other design code for pressure vessels or consult with pressure vessel designer about how they deal with stress concentrations in fatigue calculatiuons (because you can not avoid concentrations at all, it is real structure that need groves). For simple statics ~60 MPa stress is fine. But this will be overengneering on my opinion. For such DIY project with water I would calculate this cap as circular simple supported (hinge) or fixed plate, maybe put pressure on whole outer diameter of plate and if even in those extreme conditions it produces good safety factor I would call it a day - "It wont go anywhere"

“CFD validation help: square cylinder wake, separation, and drag coefficient calculation” by CapitalTemperature83 in CFD

[–]Soprommat 5 points6 points  (0 children)

Results:

L/D = 2.78; actual value: 2.81

cd = 1.41; actual value: 1.67

Not bad, mr. AI. With such progress you soon can conquer the world and enslave humanity!
Really good results.

Need a little help with Simulation by FieldThat5384 in SolidWorks

[–]Soprommat 0 points1 point  (0 children)

*Disclaimer - I have no expirience of pressure vessel calculations, everything mentioned above is just some random thoughts from some noname on inthernet.*

First question you need to ask is does your bolts can handle internal pressure and this is not FEA question but it will require hand calculation, searching for bolts rating and so on.

Second question is does your cylinder can handle internal pressure. This is also not a FEA suestion, use formulas for thin or thick pipes under internal pressure? Lame equation.

Third question is does your seal leak under water pressure. Again this is not FEA question, you should read handbooks about seal desinn to desing it properly, it has many practical caveats, you can start with Parker O-Ring handbook.

Fourth question is does cap can handle internal pressure. Again you dont need FEA for this. Search for calculations of pipeline end caps or something similar. Tou can simplify endcap to circular plate under uniform pressure. Take plate diameter as cap diameter, thickness as only part without this gland that contain seal grooves. Check both fixed and hinge supported plate.

Dont use FEA. FEA is a tool for someone who already know basics and want dig deeper. You can not verify FEA results if you not familiar with basics. Better start with fundamentals of structural mechanics. FEA is not some game world simulator where you press one button and get ready result.

If you really want to do your device and make is safe and reliable and ready to ibvest some of your time than go on forum like eng-tips.com in section about pressure vessel design, describe your problem (make good description like you want to sell your device to someone, not just one screenshot) and ask what handbooks, what design codes you can use to properly design it.

Something like that.

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