CFD helps firms lap rivals

Aerotech Engineering, a consultancy in computational fluid dynamics, is helping motor sport manufacturers design vehicles that outperform those of their rivals, without the need for as many costly experiments on the physical product. The five-strong firm, based in Hull, uses computer-based simulation technologies to investigate racing car body and component designs, and suggests ways in […]

Aerotech Engineering, a consultancy in computational fluid dynamics, is helping motor sport manufacturers design vehicles that outperform those of their rivals, without the need for as many costly experiments on the physical product.

The five-strong firm, based in Hull, uses computer-based simulation technologies to investigate racing car body and component designs, and suggests ways in which the designs can be improved.

A few years ago, some of these complex engineering problems would have taken months to simulate – far too long for the racing car industry. Now, with better and faster software and hardware, they take hours or days.

But computational fluid dynamics (CFD), which is used to analyse the aerodynamic performance of products, remains mostly the preserve of experts within big companies, such as aircraft or automotive manufacturers, or small specialist firms serving multiple clients.

`CFD is expensive; you have to use it every day for it to be cost-effective,’ says Julian Hasinski, co-founder of Aerotech, a spin-off from British Aerospace. `You also need expert analysts to use CFD.’

Aerotech has invested in 3D CAD for design and CFD for analysis. It uses Matra Datavision’s Euclid Styler to create accurate 3D surface models and, whenever possible, an associated program, Euclid Analyst, to create a mesh on the model prior to analysis. Otherwise the model has to be transferred to the CFD program for meshing.

Mesh creation, says Hasinski, used to be a laborious process but advances in meshing software, such as Analyst, have made the process easier and faster. `Four years ago, it might have taken up to six months to successfully mesh a typical three-element rear wing section,’ he says. `I would have had to build, in 3D, a grid around a model of that wing. Now I would expect to do the job in an afternoon.’

For fluid flow analysis, Aerotech uses Flotran from Ansys as its main program. Recently it has purchased a newer CFD package, Linflow from Anker-Zemer Engineering in Sweden, which solves fluid flow problems much faster – in some cases, in minutes rather than the days taken with traditional technologies. Linflow is also one of few programs that allows fluid-structure interactions to be studied, which Hasinski sees as a big growth area.

He claims it will soon be feasible, using the fluid-structure interaction program, for Aerotech to simulate vehicle behaviour throughout a complete race circuit lap, taking into account transient conditions such as acceleration, cornering and bumps in the road.

`This will be a major step forward,’ he says. `Until now, virtually all analysis of vehicle aerodynamic performance has been carried out under steady-state conditions.’

Aerotech is also using CFD to solve complex problems in the simulation of engine air induction systems. `This is the last area of engine design that has not been fully examined,’ says Hasinski.

Typically the induction system is designed last, which means air has to go through a circuitous route before reaching its destination at the inlet manifold. By designing the induction system first, a much smoother air flow can be accommodated. The system can also be designed to recover most of the pressure that is lost and to distribute the air evenly between the cylinders.

`Many thousands of pounds are spent getting the balance of racing car engines correct only to feed it with imbalanced air,’ says Hasinski.

With the induction systems designed and analysed by Aerotech – for example, for a Judd racing engine for Engine Developments – the firm claims to have overcome many of these problems. `In terms of pressure recovery, we can improve performance of the induction system by two to three orders of magnitude,’ says Hasinski.

More information is available from: www.aerotecheng.com