The wind tunnel is a perfectly suitable place to calculate the aerodynamics of a sports car going 0 to 60 mph in 4 seconds. But when designing a “car” to accelerate from 0 to 1,000 mph in a face-melting 40 seconds, embarking on a wind tunnel test is a bit like trying to windsurf in a hurricane.

Calculating how to design for Mach* 1.4 is the charge of engineers behind the UK’s Bloodhound SSC (supersonic car) – a three-year publicly/privately funded engineering endeavor to break the land speed record. Because there’s no wind tunnel in the world to test anything traveling faster than the speed of sound, the Bloodhound’s design is based almost entirely on computational fluid dynamics (CFD), the field of using mathematical models to calculate the impact factors including air pressure, water, and heat – to name just a few - will have on the design of anything from beer cans to Olympic bathing suits.

The Bloodhound is 13-m long and weighs nearly 7 tons, despite a lightweight body structure of carbon fiber and titanium. Its mass is due in large part to its “hybrid” propulsion system, which consists of a Eurojet EJ200 turbojet integrated with a Falcon rocket. The Bloodhound’s mid-section will also carry an 800-hp V12 engine used to start the jet and provide power to a hydraulic pump needed to flush one ton of high test peroxide to fuel the rocket for a 22-second burst to bring the car up to Mach 1.4.

Swansea University is running CFD simulations for the Bloodhound project. The engineering school knows a thing or two about extreme speed, having run the CFD modeling for Thrust SSC, the current land-speed record holder: it reached 763 mph in 1997. For the Bloodhound project, the overall simulation is broken into 65 million computational cells, or mini-simulations of specific surface areas of the craft. Using 60 processors, the comprehensive simulation will take about a day to fully measure how the Bloodhound’s aerodynamics will perform under the pressure of shock waves that accompany breaking the sound barrier.

Here’s a thumbnail of how the process works: The vehicle’s shape is reviewed by design engineers in CAD models for the FLITE system –university-created technology that generates an irregular mesh to represent a craft’s frame. That computational mesh, comprised of millions of cells, is then run through the supercomputer cluster in a CFD simulation, emulating the speed, ground surface, wind force and other conditions. Finally, post processing software coverts it all into a color-coded visualization.

Early CFD testing played a role in the Bloodhound’s design even before the project was announced in October 2008. For instance, preliminary blueprints called for a staggered front wheel configuration to create a narrower, more aerodynamic nose. But the CFD review showed a symmetrical design, which meant a wider nose, would help generate a small amount of downward force during the entire speed range to keep the wheels planted – the critical rule when attempting to break the land-speed record.

*The Mach speed is based on the speed of sound. Mach 1 is 767 mph.