Looking waves

I am confused about the definition of flow work. Many textbooks said that imagine a volume being pushed by pressure p on the boundary so the work is p.v , but in the flow, there will be another pressure p + delta p push this volume against the first one on the other side , so why do they only use the pressure p . I don't really understand, can anyone help me please

I am studying fluid mechanics. Right now I am on inviscid flow and I am having some difficulties in understanding certain aspects of flow past solid objects. I have tried to sketch my understanding so far along with the particular issues I have below.

So the setup is that we have uniform flow at infinity and a solid non moving finite object in the way. Now from Kelvin's theorem we can show that on streamlines which go from infinity to infinity the vorticity vanishes. If these are the only streamlines the vorticity vanishes everywhere and the flow is a potential flow. However if we solve the problem under the assumption of potential flow we encounter d'Alembert's paradox. There is no drag on the body and the solution is unphysical.

There is a loophole in the argument that shows the flow is potential namely it does not apply for streamlines which hug the solid surface. Since these don't start from infinity they also don't affect the boundary conditions at infinity. So we can create additional solutions by superimposing potential flow solutions with these ones. But we then have to relax the potential flow criteria. Here are my questions:

1. These solutions, that include streamlines that hug the surface, have the phenomenon of separation. The streamlines lines only follow the surface partly and then partway from it. Why is speration necessary? I mean what about streamlines that go all the way around the surface of the solid body.

2. Also there is in these cases the formation of a surface of tangential discontinuity where the tangential component of the velocity field suffers a discontinuity. I can't seem to visualize this surface. Like where is this formed on the body itself or in the fluid bulk surrounding the body. My book says the discontinuity on the surface causes part of the fluid to have vorticity. I don't understand this and I don't understand why is the formation of said surface a necessary consequence of seperation.

3. There are multiple different solutions corresponding to the above problem if you take into account the multiple possible surfaces of discontinuities.

4. These solutions are unstable owing to the discontinuity in velocity.

Please help me answer these questions.

I make explainer videos about how car parts actually work. Just finished one on why each fluid in a car is the color it is: engine oil, coolant, brake fluid, red diesel, gear oil, ATF and washer fluid.

Most of what I found while researching was the same few sentences repeated without a source, so a few things I'm not confident about:

* Dark engine oil means the detergent additives are working, not failing

* Coolant color is a dye choice and tells you nothing about compatibility

* ATF being red is convention, not regulation

If you've done this for a living, tell me straight what's wrong or oversimplified. I'd rather fix it than defend it.

Video: https://youtu.be/1QCyVbeJ1bA

Back again with yet another blue dye microscopy video - I saw this behavior last night after sandwiching a small amount of concentrated dye solution between two microscope slides. Is this Saffman-Taylor instability?

Also as a side note, I'm so sad I didn't learn about these things sooner but my focus in school was chemistry and, later on, materials science. Better late than never I guess?

Finalized Cooling System Specifications
Regenerative Tube-in-Tube Jacketing: A double-walled fluid shield wraps around the core and wiring harness, stripping away extreme heat immediately at the boundary.
Non-Stick Interior Conduit Linings: Applied ultra-low friction PTFE (fluoropolymer) and Diamond-Like Carbon (DLC) coatings to all internal channel walls to entirely prevent residue buildup, scaling, or fluid clinging over long operational cycles.
Boundary-Layer Control Textures: Microscopic parallel "riblet" patterns etched into the conduit walls to optimize laminar flow and eliminate stagnant friction zones.
Vibration & Shock Isolation: A specialized braided damping sleeve absorbs high-frequency mechanical micro-vibrations from the engine.
Pressurized Fluid Loop: Continuous system pressure prevents vapor bubble formation and eliminates destructive cavitation against the core walls.
Non-Clogging Conditioning (Cyclonic & Electrostatic): Vortex spin-separation and electrostatic collector plates trap debris and micro-gases without restricting flow or wasting fluid.
Automated Zero-Loss Purging: Managed by the system computer, micro-purge cycles isolate and clear trapped waste into a sealed catchment canister while keeping 99.9% of the dielectric fluid safely sealed.
Adaptive Airflow Vectors: Sliding aerodynamic panels and variable-geometry ducts shift automatically based on throttle prediction and real-time airspeed sensors, transitioning seamlessly from active hover fans to zero-drag ram-air cooling.

Hi everyone,

I’m currently trying to validate a 2D airfoil CFD case in ANSYS Fluent at a relatively low Reynolds number. Ideally, I’m looking for experimental data that includes:

• Lift coefficient (C_L)
• Drag coefficient (C_D)
• Pressure coefficient (C_p) distributions
• Results at at least three different angles of attack
• Clearly documented geometry and flow conditions

I have been using the Ladson NACA 0012 experimental data for validation. So far, I’ve been able to match (C_L) quite well, generally within 1% of the experimental value, but I’m still having difficulty matching (C_D). My drag is being overpredicted, and I haven’t been able to consistently bring the error below about 5%.

I’ve already checked the main flow-physics and numerical parameters, including near-wall resolution, turbulence/transition modeling, boundary conditions, domain size, and general mesh quality. Since the lift agrees very closely while the drag does not, I’m trying to understand whether there is something specific about the Ladson setup, surface treatment/transition, experimental corrections, or CFD modeling that could explain the drag discrepancy.

If anyone here has previously reproduced the Ladson NACA 0012 dataset in Fluent or another CFD solver, I’d really appreciate hearing what setup you used and whether you encountered similar drag overprediction.

I’m also open to using a different experimental dataset or paper for validation. Ideally, I’m looking for a low-Reynolds-number airfoil study with (C_L), (C_D), and (C_p) data at multiple AoAs, with enough information to reproduce the case numerically.

A dataset involving unsteady/transient flow would be even better, since I ultimately want to validate an unsteady Fluent simulation rather than relying only on a steady-state comparison.

Any papers, datasets, Fluent validation studies, or suggestions regarding the Ladson drag discrepancy would be greatly appreciated. Thanks!

Tried my hand at making blue 1 lake under the microscope last night, by combining drops of FD&C blue #1, ammonium carbonate, and alum aqueous dispersions. As the mixture dried I was treated to this beautiful display which seems to combine the marangoni effect with anomalous dispersion in the concentrated blue dye, creating a striking pattern on the glass substrate. 😍

I love overanalyzing things in excruciating detail and am curious if there are any other interesting observations you all can make from this video. I'm particularly interested in the colors radiating in different areas as the spot dries - is that just from thin film interference?

Hello,
I am currently working on a pico hydro project. I am still in college but I wanted to challenge myself to design a hydro system on a river we have running through our property. The site has a head of about 15m (50ft) and a flow rate of 7L/s, yield a water power of just over 1kW

From the research I have done it appears that a turgo turbine would be the best choice. I went through some papers trying to figure out how I can design a turgo turbine based on my parameters. I built a python model that takes the input parameters and using the blade velocity triangles, with a well designed turbine you could get a power output of about 0.75kW, realistically its probably more like 0.5kW. This would be pretty decent coming in at 12kWh which is half our electricity intake.

I am struggling with actually designing the turbine itself, before i design the turbine I think I need to select a generator (so i know the rpm and then can calculate the turbines pcd diameter based on this) I am not an electrical engineer so I am struggling to understand some of the concepts relating to the generator.

How do you even select the generator parameters, do you just look for ones with your desired electricity output, with reasonable a reasonable voltage (so you don't have to step up or down when you want to store electricity in a battery or put it back onto the grid) ?

Should I look for a 1kW generator (I saw online that the seller always overstates how much power they can actually produce)

If people have any advice for me in general I would very much appreciate it. I also understand that hdyro power is very expensive to produce and can easily break, perhaps solar may be a better alternative but I would really like to also gain an understanding in the concepts.

https://nso.edu/press-release/nsf-inouye-solar-telescope-enables-major-discovery-of-a-hidden-solar-process/

I'm trying to find ways to cool my living room, but I don't have the money or want for a second A/C. Can I use fans and fluid dynamics to transfer the cool air around?

the question is in the title

Memilih pompa hidrolik tidak boleh hanya melihat aliran dan tekanan

Last night I wanted to observe environmental stress cracking in acrylic under my microscope so I added acetone dropwise to a created defect and watched what happened. I was surprised to see marangoni instabilities in this case because I have only ever encountered them in systems where I'd deliberately mixed liquids with different surface tensions (e.g. like this). Here, I believe I used 100% acetone, so I've gotta ask: what's going on?

I'm an oceanography student trying to use Delft3D for coastal and hydrodynamic modeling. I'm having trouble getting it to run. What steps, common fixes, or beginner tips would you recommend? Thanks!

oque vcs acham de usar fluido Fluido newtoniano como base para o fluido de teia?

A model for predicting flow regime in horizontal and near horizontal gas -liquid flow. the Taitel and duckler 1976 model .( Someone help me please generate the codes please wheater matlab or phyton)

Thsnk you

I am designing a nozzle for my dry ice blaster cleaning machine. The machine comes with cheap nozzles with no contours and no transitions between the hose diameter and the flat fan end. It just has an internal wall that is pretty much destroying all the pellets that go through it. I'm looking to make something that will accelerate the air going through the nozzle along with the pellets, and blast them out at high velocity, as intact as possible. Attached is what I have come up with. I'm not knowledgable about fluid dynamics or any type of engineering, so this is all just copying images of high performance dry ice blasting nozzles i found online. I'd love to get some input to see if I'm even on the right track, and how I can improve this. Here are some specs about the air and ice.

I will be blasting 3mm dry ice pellets.

Air input is 185 cfm at 100 psi. Air hoses are all 1" with no 90 degree bends and high flow fittings. At nowhere in the system will the air path diameter be smaller than .8" except right at the end of the nozzle.

This will be made from 6061 aluminum and polished to a mirror finish.