# Reynolds

> Reynolds is agentic CFD: an open-source agent with a hosted Linux workspace, OpenFOAM v2512 on it, and no script telling it how to work. It writes the case, meshes it, launches the solver, reads the residuals while they come in, and hands back the figures and the files that made them. Every page of tryreynolds.com is mirrored here as plain Markdown; a study page carries the whole session transcript, every command the agent ran and everything that came back.

Reynolds is built by InviscidAI, backed by Y Combinator, Winter 2026 batch, and
funded with more than $2.4 million raised. The agent is open source under the MIT
licence, the most permissive of the common licences: commercial use, modification,
self-hosting and redistribution inside your own product, with no copyleft. Reynolds
is deployed and in live use today on real engineering work. Pro ships with SOC 2
Type II, an MSA and a DPA.

Using it requires no OpenFOAM knowledge. You state the engineering problem and
upload the geometry you actually have, including a dirty CAD export with open edges,
duplicate facets or mixed units, and the agent inspects and measures the surface,
meshes it with whichever of gmsh, blockMesh, snappyHexMesh and cfMesh fits the shape,
sizes the boundary layers, solves, renders and reports. A study runs free-form, or as a guided, resumable pipeline: geometry,
preview, mesh, checkMesh, probe, solve, reconstruct, render, animate, report.

Each page twin below ends with a "Notes for agents" section carrying context that is
not on the rendered page.

## Studies

- [A cylinder let go in its own wake, and the audit that took 13% off the answer](https://tryreynolds.com/studies/vortex-induced-vibration.md): Graded in two stages on purpose: the mesh has to reproduce the shedding frequency of a cylinder bolted still before the cylinder is allowed to move at all.
- [Eight percent below the correlation, and five explanations ruled out one at a time](https://tryreynolds.com/studies/staggered-tube-bundle.md): This one misses. Heat transfer across a staggered tube bank came out 8% below the floor of the published correlation band and would not move, so it was taken apart with five controlled experiments, each designed to kill a specific explanation. Five died.
- [A sizing question with no right answer, and an agent that said so four different ways](https://tryreynolds.com/studies/data-centre-aisle.md): Not every question has a benchmark. This one is a room: two rows of racks, a raised floor, and a customer who wants to know whether hot air comes back over the top.
- [It hit the benchmark, then told the customer the question was slightly wrong](https://tryreynolds.com/studies/backward-facing-step.md): The reattachment length behind a backward-facing step is a standard benchmark.
- [3.677 against a textbook 3.657, and an agent that said which digit not to trust](https://tryreynolds.com/studies/laminar-heated-pipe.md): Heat transfer into laminar pipe flow has an exact asymptote that every heat-transfer textbook prints on the same page.
- [A mesh that slides, checked against an answer that cannot be argued with](https://tryreynolds.com/studies/couette-sliding-interface.md): Before a rotor blade goes inside a spinning zone, the spinning zone itself has to be trusted.
- [A hull set afloat](https://tryreynolds.com/studies/wigley-free-surface.md): The towing-tank test every hull method answers to: release the model in heave and pitch, tow it through its own wave system, and measure where it settles.
- [A hull, a friction line, and a form factor](https://tryreynolds.com/studies/wigley-hull.md): Given an STL and a towing speed, Reynolds noticed the file was not the shape the request described, corrected the reference area, and produced a viscous and form drag breakdown in under three minutes.
- [The lambda-shock, at one seventh the mesh](https://tryreynolds.com/studies/onera-m6-transonic.md): The standard transonic validation case since 1979 asks for a shape, not a number: two shocks inboard that merge into one toward the tip.
- [Where the wind speeds up around a tower](https://tryreynolds.com/studies/pedestrian-wind-comfort.md): Pedestrian wind comfort is a question about one horizontal plane two metres off the ground. Reynolds built the atmospheric boundary layer properly, refined where the answer lives, and solved it in fifteen seconds.
- [A submarine hull, measured off its own geometry](https://tryreynolds.com/studies/suboff-submarine-hull.md): The reference area in a drag coefficient is not a detail, it is a third of the answer. Reynolds measured the wetted surface directly from the supplied hull before it computed anything, then landed just outside a published band.
- [Static thrust from a drone propeller, and a boundary condition it had to reason about](https://tryreynolds.com/studies/propeller-static-thrust.md): Hover is the hardest condition to set up, because the standard far-field boundary condition divides by a freestream speed that is exactly zero. Reynolds hit the divide, diagnosed it, and replaced it with the right one.
- [A heat sink, and an energy balance closed to 99.7%](https://tryreynolds.com/studies/finned-heat-sink.md): Aluminium conducting into air, solved as one coupled problem on 8,320 cells. The agent audited the run against the first law of thermodynamics and kept solving until the books balanced.
- [The solver said it had converged. The agent checked.](https://tryreynolds.com/studies/converging-diverging-nozzle.md): A nozzle with a shock standing inside it, found where theory says it should be. The reason to read this one is what happened first: a solver reported success, and the agent tested the claim against physics before believing it.
- [A benchmark hit to a quarter of a percent, then checked against itself](https://tryreynolds.com/studies/natural-convection-cavity.md): The oldest benchmark in the book, run on 1,600 cells and one core. The number landed within 0.24% of the published value, and then the agent proved it twice.
- [Four numbers, four published bands, one animation](https://tryreynolds.com/studies/vortex-shedding-cylinder.md): The cylinder wake at Re = 100 is the most measured flow in fluid dynamics, which makes it the least forgiving thing to run. Reynolds hit every quantity it was asked for, inside the published range, and drew the wake while it did.

## Product

- [Reynolds: an AI agent that runs CFD simulations for you](https://tryreynolds.com/index.md): Reynolds is a CFD agent with a hosted OpenFOAM workspace. Describe the flow in plain English; it writes the case, meshes it, runs the solver, and hands back figures, numbers and the files that made them.
- [How Reynolds works: the method, the checks and the workspace](https://tryreynolds.com/how-it-works.md): The agent writes the OpenFOAM case, asks the cheap questions first, looks at the mesh before paying for the solve, runs detached jobs, reads residuals as they arrive, and returns figures with the files that made them.
- [Pricing: hosted, Pro and Enterprise](https://tryreynolds.com/pricing.md): Reynolds is free with a work email, no credit card. The agent is open source and free to run yourself. Reynolds Pro is the stronger model and harness for teams, in limited batches. Enterprise is self-hosted in your network.
- [Apply for Reynolds Pro](https://tryreynolds.com/pro.md): Request a place in the next Reynolds Pro batch: a model tuned for CFD, a deeper-checking harness, priority machines and a direct line to the team. Four short questions.
- [Why did we call it Reynolds?](https://tryreynolds.com/why-reynolds.md): Osborne Reynolds put dye in a pipe in 1883 and found the number that decides how every fluid behaves. We named an agent after him because of how he worked, not just what he found.

## Reference

- [Studies: CFD cases, every number with its evidence](https://tryreynolds.com/studies/index.md): Complete CFD studies run by the Reynolds agent: a sliding-mesh interface against an exact solution, a cylinder set free to vibrate in its own wake, vortex shedding, natural convection, a choked nozzle, a heat sink, a heated pipe, a backward-facing step, a propeller, a staggered tube bank, a data-centre row, the SUBOFF hull, pedestrian wind, the ONERA M6 wing and the Wigley hull in calm water and with a free surface, each with its numbers, cross-checks and caveats.
- [Reynolds documentation: the agent, the workspace, and how to run one](https://tryreynolds.com/docs/index.md): How Reynolds works and how to run it: install and first study, the tool-use loop and its tools, the three modes, choosing and changing a model, what lives on the workspace instance, the commands, and what to do when a run goes wrong.
- [Quickstart: from nothing to a finished CFD case](https://tryreynolds.com/docs/quickstart.md): Make an account, connect a model, and ask Reynolds for a simulation. Covers both the browser app and the openreynolds command line, what the first study costs, and how to read the result it gives back.
- [How Reynolds works: the loop, the tools, and the one rule](https://tryreynolds.com/docs/how-it-works.md): Reynolds is a tool-use loop with eight tools pointed at a Linux workspace running OpenFOAM v2512. What the harness does, what it is forbidden from doing, the one exception you can choose, how long solves are watched, and why the working method is the model's own.
- [Modes: full auto, ask before compute, structured](https://tryreynolds.com/docs/modes.md): A Reynolds session runs in one of three modes. Full auto holds nothing, ask before compute puts every background job and mesh-desk build to you first, and structured has you approve a plan and each stage. What each one holds, how to answer, and how to switch.
- [Models and cost: Reynolds' own model, or a key of your own](https://tryreynolds.com/docs/models.md): Run Reynolds on its own metered Claude model with no key of your own, or bring a key from Anthropic, OpenAI, Z.ai, DeepSeek, Moonshot, MiniMax, OpenRouter or a local Ollama. Reasoning effort, what drives the bill, and how to spend less.
- [Changing the model or effort mid-study](https://tryreynolds.com/docs/switching-models.md): Switch model, provider or reasoning effort in the middle of a Reynolds study without leaving the session: what is checked before a switch is accepted, when it takes effect, what happens to the thread, and what it costs.
- [The workspace: the instance, the jobs, and what survives](https://tryreynolds.com/docs/workspace.md): Every study gets an isolated Linux instance with OpenFOAM v2512 on it. What lives there, how jobs outlive the calls that start them, how files mirror home, where renders go, and what is kept when a session ends.
- [Moving mesh: sliding interfaces, prescribed motion, and bodies the flow moves](https://tryreynolds.com/docs/moving-mesh.md): What Reynolds does with a mesh that moves: a cyclicAMI sliding interface, solid-body prescribed motion, and a rigid body moved by the forces on it. The two repeatable benchmarks, what the grader reads, the measured numbers, and where the record is thinner.
- [The mesh editor: picking faces, drawing a domain, handing it back](https://tryreynolds.com/docs/mesh-editor.md): The browser app's mesh tab: pick faces, or the edges of a 2D domain, and name them inlet, outlet, wall or anything you like; set the flow through an inlet; draw a domain in metres and mesh it with gmsh; move and scale; undo; and hand the mesh back to the agent with what you meant by it.
- [Running more than one study at once](https://tryreynolds.com/docs/running-several-studies.md): One account may have three studies running at the same time, and the platform keeps five live workspaces for an account that has paid and two for one that has not. What happens at each limit, what two studies share, and how the terminal behaves.
- [Command reference: every openreynolds subcommand and flag](https://tryreynolds.com/docs/cli.md): The full openreynolds command line: session flags, login, config, doctor, studies, files, pull, push, stop, renders and video, plus the environment variables and where the settings file lives.
- [Driving Reynolds from a program](https://tryreynolds.com/docs/from-a-program.md): Run a study non-interactively with -p, read the whole session as one JSON object per line with --output-format stream-json, answer it on stdin, bound the waiting with --max-wait, and tell the endings apart by the exit code.
- [Commands, help and completion in a session](https://tryreynolds.com/docs/session-commands.md): What you can type while a Reynolds study runs, in the terminal and in the app: every command and alias, /help and its topics, answering a question, and how completion and suggestions work.
- [When something goes wrong: solves, meshes, jobs and keys](https://tryreynolds.com/docs/troubleshooting.md): A solve that will not converge, a mesh that fails checkMesh, a job killed under you, a model that refuses, and the errors worth reading closely. What each one usually means and what to do about it.

## Other

- [Privacy Policy](https://tryreynolds.com/privacy.md): How Inviscid AI Co. collects, uses and protects information in Reynolds, including exactly what we receive when you sign in with Google and what we never do with it.