What CFD Simulation Teaches Us About the Aerodynamics of a Javelin Throw

As engineers inspired by the recent Paris 2024 Olympic Games, we couldn’t help but wonder about the physics behind the sports equipment used by world-class athletes. To satisfy our curiosity, we ran a CFD simulation of one of the oldest Olympic events—the javelin throw—a battle of strength and precision where athletes aim to hurl a spear as far as possible.

The history of the javelin

The javelin throw made its debut in the modern Olympic Games in 1908 in London, but its roots go all the way back to Ancient Greece in 708 BC. Part of the pentathlon (which also included running, discus, long jump, and wrestling), ancient athletes hurled wooden javelins using a leather loop that helped extend the thrower's arm and made the javelin rotate around its axis (pretty ingenious, right?).

Today’s javelins are a high-tech marvel, crafted from materials like carbon fiber and fiberglass, designed for perfect weight distribution and flexibility. They’re aerodynamically optimized to slice through the air with minimal drag and maximum stability.

Why run CFD simulations in sports?

CFD simulation is becoming a go-to tool in the world of competitive sports, where the margin between victory and defeat is often measured in milliseconds or millimeters. Top sports manufacturers like Trek Bicycles and Cobra Golf use Luminary Cloud to optimize their designs and help customers gain that winning edge.

For javelin design, CFD lets engineers tweak and fine-tune without the need for endless prototypes or expensive physical tests. Here’s a glimpse of how it works:

• Flow Analysis: CFD shows how air moves around the javelin mid-flight, revealing how even tiny changes in shape or texture can affect drag, lift, and stability.

• Optimization: ​​Virtually test countless designs, fine-tuning the javelin’s shape to balance regulatory constraints with peak performance. It’s like having a javelin design lab on your laptop.

• Safety Considerations: No one wants a javelin to land flat. CFD helps ensure compliance with IAAF rules for a forward center of gravity, so the javelin noses down for a safe, accurate landing.

How we simulated the javelin throw in Luminary Cloud

Step 1: Modeling the javelin. We started by creating a digital 3D model of the javelin using official dimensions, ensuring that our virtual replica matched reality as closely as possible.

Step 2: Meshing the Geometry. We used Lumi Mesh Adaptation (LMA)—a game changer in the simulation world. LMA automatically generates the ideal mesh for each point in a Design of Experiments (DoE), eliminating the need for tedious manual iterations and ensuring grid independence. For example, as the angle of attack changes, the wake region of the javelin may not fully capture the physics with the initial mesh. LMA adapts the mesh to each geometry and flow physics, maximizing accuracy with zero extra effort for the user.

In our study, we explored angles of attack from 0° to 40°, mirroring a real javelin throw trajectory. And LMA made sure that each design point had an individually adapted mesh. The best part? We completed the entire end-to-end cycle—from geometry upload to mesh generation, running a RANS simulation through 10 design points, generating a 50M cell mesh, and post-processing—in under 50 minutes. That’s fast enough to fit between coffee breaks!

Step 3: Simulating the throw. With key parameters like release angle and velocity defined, Luminary Cloud’s powerful CFD solver got to work, calculating the airflow and painting a precise picture of the forces at play.

Step 4: Analyzing the Flow Wake. The real magic happens behind the javelin in the turbulent wake. By visualizing this region, we pinpoint areas of high drag, tweak the design, and reduce resistance—all aimed at boosting the javelin’s distance and flight stability.

Step 5: Optimizing the Design. Armed with insights from the wake analysis, we can fine-tune the javelin’s design. A sleeker nose or rougher texture could significantly enhance its performance. Luminary Cloud lets us instantly test these adjustments and see real-time feedback, speeding up the optimization cycle.

CFD’s role in sports

We believe the role of CFD in sports is poised to take off dramatically. Whether you’re a sports equipment manufacturer, aerodynamics engineer, coach, or athlete, the insights from simulation can help unlock new levels of peak performance. Just like Olympic athletes striving for gold, Luminary Cloud is pushing the boundaries of what’s possible in physics simulation. Analyzing the aerodynamics of the javelin throw is just one example of how we’re exploring the endless opportunities CFD offers. Curious to learn more about how we’re changing the game? Want to dive deeper into Lumi Mesh Adaptation? Reach out to us on our website, and let’s talk about how we can help you unlock your next breakthrough.