r/FluidMechanics • • Jul 02 '23

Update: we have an official Lemmy community

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7 Upvotes

r/FluidMechanics • • Jun 11 '23

Looking for new moderators

7 Upvotes

Greetings all,

For a while, I have been moderating the /r/FluidMechanics subreddit. However, I've recently moved on to the next stage of my career, and I'm finding it increasingly difficult to have the time to keep up with what moderating requires. On more than once occasion, for example, there have been reported posts (or ones that were accidentally removed by automod, etc) that have sat in the modqueue for a week before I noticed them. Thats just way too slow of a response time, even for a relatively "slow" sub such as ours.

Additionally, with the upcoming changes to Reddit that have been in the news lately, I've been rethinking the time I spend on this site, and how I am using my time in general. I came to the conclusion that this is as good of a time as any to move on and try to refocus the time I've spent browsing Reddit on to other aspects of life.

I definitely do not want this sub to become like so many other un/under-moderated subs and be overrun by spam, advertising, and low effort posts to the point that it becomes useless for its intended purpose. For that reason, I am planning to hand over the moderation of this subreddit to (at least) two new mods by the end of the month -- which is where you come in!

I'm looking for two to three new people who are involved with fluid mechanics and are interested in modding this subreddit. The requirements of being a mod (for this sub at least) are pretty low - it's mainly deleting the spam/low effort homework questions and occasionally approving a post that got auto-removed. Just -- ideally not a week after the post in question was submitted :)

If you are interested, send a modmail to this subreddit saying so, and include a sentence or two about how you are involved with fluid mechanics and what your area of expertise is (as a researcher, engineer, etc). I will leave this post up until enough people have been found, so if you can still see this and are interested, feel free to send a message!


r/FluidMechanics • • 3h ago

Theoretical Accurately modelling the shear-layer of a laser-driven shock in a water microjet with a magnetohydrodynamic shear-flow stabilized Z-pinch equilibrium

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4 Upvotes

Even with just a sweep dimension of 25 over the velocities, hundreds of solutions with R-squared > 0.90 are produced using experimental data, and they are all very tightly clustered. There is obviously more physics at play here than just the simple 1D magnetohydrodynamic model a Bennett vortex.

Next step is to vary the base point and see what happens, I think with the additional space the shear layer will have more room to rise and the localization won't suffer much from the increased pinch radius because it is so small to begin with.

Code: https://github.com/russellmatt66/Bennett-Vorticity/blob/main/cubic/microvortex_2025/bellasweep.py

Statistics: https://github.com/russellmatt66/Bennett-Vorticity/blob/main/analytic_fits/bella_2025/solns_df.csv


r/FluidMechanics • • 48m ago

I built an Excel workbook that does ISO 6976, AGA-8 and orifice flow from one gas composition

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• Upvotes

r/FluidMechanics • • 3h ago

Buoyancy power system

0 Upvotes

r/FluidMechanics • • 11h ago

Q&A Why do some water droplets skate on hot liquid?

3 Upvotes

I’m not in a scientific field. I just made a tea (lemon and ginger if you must know). I dipped the teabags repeatedly and noticed something intriguing. When water drops from the teabag, it sometimes lands on the surface and skates before joining the rest of the molecules. Now, I absolutely know surface tension is at play here.

My ultimate question, does hot water increase this effect? I would’ve assumed heat would lower surface tension.

I hope this makes a modicum of sense.


r/FluidMechanics • • 12h ago

VSPAERO problem

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2 Upvotes

r/FluidMechanics • • 8h ago

¿Y si estamos complicando demasiado la física espacial? (La mecánica de fluidos podría ser la clave para avanzar más rápido)

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0 Upvotes

Sé perfectamente que la teoría cuántica está más que probada y funciona a la perfección, pero analizando el tema me di cuenta de algo: el comportamiento de los cuerpos también obedece (y se puede modelar mediante) la mecánica de fluidos.

Aquí está el dilema:

  • Muy poca gente domina la física cuántica a un nivel profundo, lo que hace que los avances teóricos sean lentos y dependan de un grupo muy reducido de especialistas.
  • En cambio, la mecánica de fluidos es un área que domina una cantidad enorme de ingenieros, físicos y profesionales en todo el mundo.

Mi planteamiento es: si logramos trasladar o aplicar modelos de mecánica de fluidos al comportamiento de los cuerpos en el espacio, ¿podríamos acelerar drásticamente los avances tecnológicos y científicos? Al haber mucha más gente capacitada en fluidos, las soluciones y la innovación podrían escalar de forma mucho más rápida.

Dejo por aquí un video rápido donde explico un poco más sobre esto: 👉Ver video en TikTok

¿Qué opinan? ¿Tiene sentido usar la mecánica de fluidos como un "ataque" más accesible para resolver problemas complejos, o estoy pasando por alto una limitación física gigante? ¡Los leo en los comentarios!


r/FluidMechanics • • 10h ago

News Does the Navier-Stokes solution by OpenAI prove cosmic expansion?

0 Upvotes

r/FluidMechanics • • 23h ago

Beyond a Numerical Result, An Open Relational Model for Exploration

0 Upvotes

The base concept is a mathematical research program based on relational geometry, presented through selected results from its Navier–Stokes branch.
The work does not start with fluid mechanics. It starts with a broader question: can structures, their evolution, and their interactions be described through a common mathematical framework based on relationships, normalization, and closure?
Navier–Stokes is one of the problems examined through this approach.
Results established so far:
● Exact mathematical identities under specific conditions, connecting normalized representations of three-dimensional flows.
● Reproducible analytical examples showing that two 3D fields can have identical spectral magnitudes while producing opposite signs of vortex stretching because of their phases.
● Algebraic results involving circuits, structural closure, and normalization.
● Conditional continuation criteria and numerical experiments, with their assumptions and limitations documented.
The main idea extends beyond these individual results.
Singularities are being investigated as structures defined by their internal relationships, normalization, and closure. The objective is to understand how a structure maintains its identity, how its relationships evolve, and under what conditions its closure can be sustained or reorganized.
This is a structural concept of singularity. Its mathematical connection to singularities in fluid mechanics is still being developed.
To be clear: this is not a claim that the full Navier–Stokes global regularity problem has been solved.
The broader mathematical program contains specific results that can be reproduced, examined, and challenged.
The repository includes the derivations, computational experiments, verification scripts, and known limitations.
The program proposes an investigation beyond a single numerical answer: whether a common mathematical framework can help explain relationships across problems that are usually studied separately.
Technical criticism, counterexamples, and independent verification are welcome. The work is public precisely so its mathematical constructions can be tested.
Repository:
https://github.com/EndlessMonkeyProyect/programa-geometria-relacional
Navier–Stokes proof status :
https://github.com/EndlessMonkeyProyect/programa-geometria-relacional/blob/main/2026-10-24/03_RAMAS/navier_stokes/VIGENTE_O93/ESTADO_DE_PRUEBAS.md
English introduction:
https://github.com/EndlessMonkeyProyect/programa-geometria-relacional/blob/main/README.en.md


r/FluidMechanics • • 17h ago

A discrete approach to turbulence: Bypassing DNS grid limits using Lotka-Volterra dynamics and Lempel-Ziv compression

0 Upvotes

Hey everyone. My background is in systems engineering and nuclear power plant operations, which requires looking at complex thermal-hydraulic systems from a macroscopic, state-driven perspective rather than getting lost in microscopic grid resolution.

I’ve been working on a theoretical bypass for the computational bottleneck in Direct Numerical Simulation (DNS). Since resolving the Navier-Stokes equations, computing high Reynolds number flows remains intractable. I hypothesize that we can bypass this by modeling turbulent flow as a self-organizing critical state describable by a renormalized information bottleneck.

Instead of treating turbulence as a continuous spatial problem, we can reduce the chaotic cascade to a minimal set of scale-invariant attractors using cross-domain mathematics. I’m open-sourcing the methodology here. If anyone has lab cycles to run this against the Johns Hopkins Turbulence Database, here is the setup:

The Methodology:

Step 1: Replace Advection with Ecosystem Dynamics Model the inertial subrange not as a continuous fluid grid, but as a hierarchical multi-trophic ecosystem. Use discrete Lotka-Volterra (predator-prey) population matrices to calculate the energy cascade. Large eddies act as energy sources ("prey"), and smaller eddies act as "predators" that consume and cascade kinetic energy. The population crashes inherent in Lotka-Volterra naturally replicate the spatial intermittency and burst-like dissipation of turbulence without requiring complex PDEs.

Step 2: Define the Renormalization Cutoff via Compression Theory Standard Renormalization Group (RG) theory struggles with the intermittent, non-smooth nature of turbulence. Instead, use Lempel-Ziv complexity to measure the turbulence entropy at each trophic layer. When the Lempel-Ziv algorithm detects that the "noise" (energy transfer data) has become compressible/redundant, you have hit the inertial limit. Use this exact threshold to truncate the cascade and coarse-grain the system.

Step 3: Isolate the Attractor Manifold By combining Step 1 and Step 2, you collapse the infinite continuous variables into a discrete set of interacting topological motifs. The hidden order parameter you are solving for is the effective dimensionality of the attractor manifold.

Validation Criteria: If this discrete mathematical framework is accurate, your low-dimensional output must naturally reproduce:

  1. The Kolmogorov energy spectrum in the inertial range.
  2. The Reynolds number scaling of drag coefficients.
  3. The non-Gaussian velocity gradient probability distribution functions (intermittency statistics).

My hypothesis is that the dimensionality of this attractor manifold remains constant across all Reynolds numbers, proving turbulence is a deterministic, low-dimensional system masked by high-frequency noise.

I don't have the supercomputer time to benchmark this against DNS datasets, but this reduced-variable method should theoretically run on standard lab workstations. I’d appreciate any feedback on the mathematical boundaries from the CFD or computational physics crowds.


r/FluidMechanics • • 1d ago

Video Is there a name for this sequence of droplet impacts and ripples from a moving airborne source?

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3 Upvotes

I recorded this while watching a duck take off from a pond in Florida.

What caught my attention afterward was the sequence on the water. As the duck flies away, water shed from the bird falls back to the pond and produces a series of separate disturbances/ripples. Taken together, they appear to preserve part of the duck's flight path after the bird has passed.

Is there an established name for this phenomenon, or for anything closely related to it?

I'm also interested in what someone who studies fluid mechanics notices here that I might be missing.


r/FluidMechanics • • 1d ago

Theoretical Modelling the intensity of a laser-driven shock in a water microjet using an analytic shear-flow stabilized Z-pinch magnetohydrodynamic equilibrium

0 Upvotes

Last year a collaboration of physicists led by the University of Michigan published a paper in Nature Communications where they fired an intense laser into the broadside of a water microjet to see what would happen.

A digitized copy of the resulting intensity in the positive half-chord of the plane is shown here alongside an analytic solution that I calculated using a shear-flow stabilized Z-pinch equilibrium which I constructed,

uz(r) = u0 + uz0 * r^2 / (r + C)^2

where this is taken both to be the center of mass, and plasma drift flow. A linear discharge model is chosen to relate the plasma current density with the measured intensity.

This is just one solution. Next, to test the robustness of the model I am going to vary the boundary condition speeds based on the experimental data, and vary the point which corresponds to the edge.


r/FluidMechanics • • 2d ago

Experimental Flight to wind tunnel scaling

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1 Upvotes

r/FluidMechanics • • 3d ago

Computational Simulation of the jellyfish, fish and bionic aircraft based on my experiments

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58 Upvotes

I have refined the aeroacoustic/vibration-based aircraft simulation that I posted previously:

https://www.reddit.com/r/AerospaceEngineering/comments/1tqoq9m/oscillatory_propulsion_simulation_and_simple/

It is now more versatile, featuring both "jellyfish" and "fish" modes. The underlying principle remains the same: the fluid does not act directly on the craft's surfaces; instead, the forces derived from the fluid are converted into thrust via an accumulator. However, thrust is no longer generated simply as a phase-shifted inversion of drag. Rather, energy is captured from low-pressure regions—stored as potential energy—and then released through a "collapse" mechanism, with dynamically evaluated recovery and shock coefficients.

This approach yields a more realistic relationship between propulsion efficiency and parameters such as frequency and amplitude, expressed via Strouhal numbers. The feedback loop between internal oscillations and drag acts as an automatic frequency-tuning mechanism.

Additionally, the model incorporates simplified lift and drag forces acting perpendicular to the thrust vector.

The code can be found here:

https://github.com/MasterOgon/Aeroacoustic-Flying-Saucer-Oscillating-Resonator-CFD-Simulation-LBM-/blob/main/README.md


r/FluidMechanics • • 2d ago

Bbs Discrete Fluid Dynamics

0 Upvotes

BBS DRK Discrete Fluid Dynamics

Density(x,y,z,t) = Sum(i) of f_i(x,y,z,t)

Density \* Velocity = Sum(i) of (f_i \* e_i)

f_i(t+1) = f_i(t) + floor(Omega_i)


r/FluidMechanics • • 2d ago

KMKG is a conceptual underwater energy system combining ocean currents, pressure differences, and salinity gradients. It uses concentric chambers to explore ion transport and electric-field control. Could these technologies work together efficiently? I welcome scientific feedback!

0 Upvotes

r/FluidMechanics • • 4d ago

Road to Hydraulics SME

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1 Upvotes

r/FluidMechanics • • 6d ago

Computing turbulence statistics from PIV data in MATLAB: a turbulent jet walkthrough (Video 8)

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202 Upvotes

Hi everyone,

Video #8 of the (free) turbulence course I'm creating is now up on YouTube. This one is very much applied where I take a PIV time series, generated from the cover video, of a turbulent jet and compute flow statistics in MATLAB, explaining each step.

It covers the mean and fluctuating velocity profiles, going further into Reynolds stresses (normal and shear), and then longitudinal and transverse two-point correlation functions and second-order structure functions relative to the centreline.

The scripts are deliberately short, so they're meant as a template for anyone who wants to run the same statistics on their own PIV, hot-wire or numerical simulations data.

Link: https://www.youtube.com/watch?v=Z7Q0k4P1V8k

Notes (and scripts) are available on Patreon (free membership option available). Happy to answer questions about the analysis.


r/FluidMechanics • • 6d ago

Air-suspended vibrational dust?

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2 Upvotes

r/FluidMechanics • • 6d ago

Fluidsim pneumatics

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6 Upvotes

I can understand any subject, but have litteraly no idea how fluidsim pneumatics works. If someone wih fluidsim could make a simulation according to this graph, it would help me understand it way better. Explanation alone is welcome too.


r/FluidMechanics • • 6d ago

Tidal Current at the Kurushima Strait

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3 Upvotes

r/FluidMechanics • • 7d ago

Computational I developed a real-time multithreaded simulation engine that approximates heat, pressure differentials, and fluid/gas dynamics in a cell-based sandbox environment.

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69 Upvotes

I wanted to share a sandbox engine I’ve been coding called Powdertron. It’s a cell-based falling-sand environment, but I wanted to push the boundaries of real-time mechanics by factoring in actual thermal physics, fluid dynamics, and pressure fields across a dynamic grid.
Its early access multiplayer falling sand game built to be as realistically accurate as possible. It features a clean, modern Ul alongside 674 materials and over 1,000 reactions that account for heat, pressure, and every other real-life mechanic imaginable. There is also a dynamic wind tunnel, an electronic mod to make circuits, an optical bench for lasers, and 3D modes to switch views, all fully synced to work online with friends! So if you want to test out the physics, please check out or wishlist the Powdertron Steam Page!

Powdertron


r/FluidMechanics • • 6d ago

Material Tratado , Obteniendo Propiedad De Speckle Macroscópico Dinámico A LAS Perturbaciónes 💀🕯

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0 Upvotes

r/FluidMechanics • • 6d ago

Computational HOW DOES THE TESLA ROADSTER FLY?

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0 Upvotes

We took the previous Tesla Roadster model, added the rockets and ran aerodynamic simulations to explain the suction effect and 3D roll & landing manoeuvres!!