Setting New Windsurfing Record Speeds Above 100 KPH With Fidelity CFD

Picture Courtesy: Peter Davis Photography

In high-speed sports like windsurfing, performance optimization is everything. A fraction of a second, a marginal gain in efficiency, can be the difference between a personal best and a world record. Reaching extreme water speeds, where velocities exceed 28-29m/s (100kph or 54 knots), introduces complex hydrodynamic challenges, including nonlinear free-surface interactions and localized cavitation on high-load fin sections.

For decades, hydrodynamic design relied on empirical theories, which provide a foundational understanding but lack the precision to model these extreme conditions. This is where computational fluid dynamics (CFD) offers an advantage, enabling engineers to simulate and analyze these complex interactions with accuracy. The Zephir Project, a high-performance research program led in collaboration with ALTEN, was initiated to explore this very edge, aiming to push the absolute limits of sailing speed using Fidelity CFD Software.

ALTEN and the Zephir Project

ALTEN, a global leader in engineering and technology consulting, conducts advanced applied research focusing on performance optimization in elite sports using numerical simulation and multiphysics modeling. The Zephir Project, co-founded in 2020 by Marc Amerigo (engineer) and Antoine Albeau (sailing athlete), is a prime example of this mission, based on strong partnerships. Led (in collaboration with ALTEN) by Antony Costes, an engineer and high-level triathlete, the initiative brings together CFD specialists, equipment designers, and elite athletes to analyze the hydrodynamics and aerodynamics of high-speed sailing.

The Zephir project directly supports windsurfing legend Antoine Albeau, a 27-time world champion. Through this collaboration, the team set windsurfing instantaneous speeds above 100 kph (54 knots). This achievement demonstrates a new level of engineering rigor applied to sports equipment design, where the board and fin act as a highly optimized hydrodynamic system, and this has been possible using CFD simulation.

Picture Courtesy: Peter Davis Photography

An Absolute Necessity: Shift from Empirical Theory to CFD Simulation

Historically, the hydrodynamic design of planing craft has been guided by Savitsky’s planing plate theory. Developed in the 1960s, the formulation idealizes the hull as a flat, rigid plate and has proven remarkably effective for conventional boats operating at moderate speeds. However, when pushed into the extreme velocity envelope of modern windsurfing, the foundational assumptions of this model begin to fail.

Savitsky’s approach is built on several simplifying assumptions:

• A flat, rigid planing surface
• Uniform or spatially averaged pressure distributions
• Steady-state hydrodynamic behavior
• No explicit treatment of the air–water interface

At world-record windsurfing speeds, these assumptions are no longer valid.

The Reality of Record-Setting Windsurfing Hydrodynamics

In high-speed windsurfing, the physical regime is fundamentally different from classical planing:

• Only a small, wetted area remains in contact with water
• The free surface is highly deformed
• The fin operates near cavitation inception, where small pressure errors are critical

In this regime, Savitsky’s theory provides qualitative trends but cannot predict the local pressure field governing fin loading, cavitation onset, and stability/control.

The Zephir team recognized that pushing beyond existing speed records required a fundamental shift in methodology. Rather than abandoning Savitsky’s legacy, they extended it. High-fidelity, cavitation-aware CFD was introduced to capture the nonlinear, multiphase physics that classical theory cannot represent.

Enabling Record-Setting Windsurfing with Fidelity CFD

To move beyond the constraints of classical planing theory, the Zephir project leverages Fidelity Fine Marine to perform high-fidelity multiphase CFD simulations of the windsurf board under true planing conditions.

Fidelity Marine Solver makes it possible to:

• Explicitly resolve the air–water interface
• Accurately compute transient and localized pressure fields beneath the board
• Capture trim, immersion, and free-surface coupling effects
• Generate realistic boundary conditions for downstream fin analysis

CFD Workflow for Fin Design and Validation

In the project, Fidelity CFD plays a central role by establishing a physically consistent link between board hydrodynamics and fin optimization, enabling higher sustainable speeds with improved control and safety. The CFD workflow for the design is listed as follows:

1. Multiphase CFD simulation of the board using Fidelity Marine Solver
2. Extraction of boundary conditions representing real sailing conditions
3. Use of these boundary conditions as inputs for fin optimization and cavitation-aware CFD analysis

Mass fraction and pressure field/contour around the windsurf

This workflow allows engineers to move beyond empirical safety margins by directly resolving the physics that limit performance. It enables precise identification of local pressure minima responsible for vapor formation, assessment of sensitivity to trim and angle-of-attack variations, and the design of fins that operate just below cavitation inception. As a result, operational margins can be quantified with confidence rather than inferred solely from experience.

From Proven Physics to Future Performance

Savitsky’s planing theory remains a foundational pillar of marine hydrodynamics, but record-breaking performance in modern watersports demands far deeper physical insight. At the extreme limits of speed, advanced CFD is no longer an academic luxury; it is a competitive necessity. The Zephir project clearly illustrates how high-fidelity simulation shifts design from approximation to precision by resolving the physics that truly govern performance.

The collaboration between ALTEN and Cadence has set a new benchmark for CFD-driven sports engineering. As this workflow continues to evolve, the partnership is well-positioned to keep pushing hydrodynamic limits and redefining what is possible in marine sports.

If you would like to try Fidelity Fine Marine for your next high-speed sailing project, request a demo today!