The Complete Beginner Guide to CFD Tunnel

July 2026

This guide walks you through everything you need to start using CFD Tunnel, even if you have never run a simulation before. By the end you will know how to set up a test, read your results, and pick the plan that fits you. You do not need to install anything or know any special software to follow along.

What CFD Tunnel does

CFD Tunnel is a virtual wind tunnel that runs in your browser. You give it a 3D shape and a wind speed, and it shows you how the air flows around that shape and how much drag it makes. It is built for anyone who wants to test aerodynamics without buying expensive software or owning a powerful computer. Students, hobbyists, and small teams are exactly who it is for.

Running your first simulation

The fastest way to learn the tool is to solve one of the built-in shapes. Here is the whole process from start to finish.

Open the app and look at the sidebar on the left. This is where every setting lives.
Under Input Geometry, pick a Reference Geometry from the dropdown. The Simple Car is a good first choice.
Under Wind Tunnel Conditions, set the Freestream Velocity, which is how fast the air moves. Twenty to forty meters per second is a normal starting point.
Press the Compute 3D Flow Field button in the middle of the sidebar.
Wait a few seconds, then look at the viewer. You will see streamlines flowing around the shape and a summary of the numbers on the right.

That is a full simulation. Everything else in this guide is about doing this with more control and more accuracy.

Choosing a solver

CFD Tunnel has two solvers, and picking the right one matters. You choose between them at the top of the sidebar under Solver Engine.

Heuristic (Fast) runs right in your browser and finishes in seconds. It is great for a quick look and for learning the tool, but it is an approximation, not a full simulation.
OpenFOAM (High Fidelity) runs a real simulation on our servers. It takes longer, usually a couple of minutes, but the numbers actually come from solving the physics. This is the one to use when you care about the answer.

The fast solver is available on every plan. OpenFOAM is a Premium feature, since it does the heavy work on our hardware.

Using your own CAD model

The built-in shapes are good for practice, but the real point is testing your own designs. On a Premium plan you can upload your own model.

Supported formats are .stl and .obj, which almost every CAD program can export.
Under Input Geometry, use the Upload CAD file button and pick your file.
Keep your model reasonably clean and closed. A watertight mesh solves much better than one full of holes.

If you are on the Free plan you use the built-in shapes instead, and you can upgrade any time to unlock uploads.

Setting up your test

A few settings control the conditions your model sees. Getting these right is what makes your result mean something.

Freestream Velocity is the wind speed. Higher speeds mean more drag and a higher Reynolds number.
Model scale sets the real size of your object. A small RC car and a full size car of the same shape actually behave differently, so this matters.
Wind Vector Normal is the direction the wind comes from.
Vehicle mass does not change the airflow, but it lets the tool tell you how your downforce compares to the weight of the car.

Ground plane and rolling road

If you are testing something that drives on a road, turn on the Ground plane option under the OpenFOAM settings. This puts a floor under your model so the air cannot flow underneath it the way it would in open sky. For the most realistic result, also turn on the Rolling road option. A real road moves relative to the car, and a still floor grows a layer of slow air that a real road does not have. The rolling road fixes that, which is exactly how a professional automotive wind tunnel works.

Reading your results

When a solve finishes, the numbers appear in a panel on the right side of the viewer. Here is what the main ones mean.

Drag Coefficient (Cd) tells you how slippery your shape is. Lower is better. It barely depends on size or speed, so it is the fairest way to compare two designs.
Drag Force is the actual push of the air against your model, in newtons. This one does grow with size and speed.
Downforce or Lift is the up or down push. Downforce presses a car into the road, which is what you want for grip.
Centre of Pressure tells you where along the body that force acts. It is the number aero balance is tuned around.
Reynolds Number describes the flow conditions, and it comes from your size and speed together.
Max Local Velocity and Stagnation Pressure show where the air speeds up and where it piles up against the front.

You can also double click anywhere in the flow to probe the exact speed and pressure at that point.

Visualization and exports

The Visualization section of the sidebar controls how the flow looks. You can color the flow by speed or pressure, change the colormap, show or hide streamlines, add a slice plane through the model, and turn on a smoke trail. None of this changes the result, it just changes how you see it.

When you are happy with a result, you have a few ways to keep it.

Download a viewer image or the metrics as a CSV file.
Download a full PDF study report, which is a Premium feature and includes your setup, your results, and a picture of the flow.
Share a link to your result, which anyone can open to see the 3D flow without an account.

History, reports, and sweeps

Premium members get a saved history of every run under the account menu in the top right. You can reopen any past run at no cost, or download its PDF report again later. Premium Pro adds automated sweeps, which run the same model across a range of angles or speeds and chart how the drag changes, along with high fidelity solves and a choice of turbulence models for more advanced work.

Plans and pricing

There are three plans. You can start free and upgrade whenever you want, and paid plans can be billed monthly or yearly, where paying yearly saves you about two months.

Free Beta, $0 a month

Good for learning the tool and exploring the built-in shapes.

5 simulations a month
Built-in reference shapes
The fast in-browser solver
Interactive 3D streamlines and slices

Premium Lite, $8 a month or $80 a year

For hobbyists, makers, and RC enthusiasts who simulate regularly.

20 simulations a month
Upload your own CAD in .stl or .obj
The real OpenFOAM solver
Drag, lift, and aero balance numbers
Rolling road for ground vehicles
Saved run history
A PDF study report for every run

Premium Pro, $19 a month or $190 a year

Built for consultants and advanced prototyping work.

Everything in Lite
50 simulations a month
High fidelity solves with a denser mesh
A choice of turbulence models
Automated angle and speed sweeps

Every plan gives you a set number of simulations each month, and the counter resets on the first of the month. You can manage or cancel a paid plan any time from the billing portal.

Where to go next

The best way to really learn CFD Tunnel is to run a few solves and change one thing at a time. Try the same car at two different speeds, or two different shapes at the same speed, and watch how the numbers move. Once you are comfortable, upload your own design and see how it does. The shapes and settings are all reversible, so you cannot break anything by experimenting.