Computational Turbulence Dynamics

The Computational Turbulence Dynamics (CTD) Group engages in experiments on and simulation of turbulence. A turbulent flow is a flow that loses its coherence and becomes chaotic. Turbulence is everywhere. The slipstream behind a car is turbulent, but a fluid flowing through a tube also becomes turbulent at higher speeds. In this case, the turbulence causes a sharp increase in the resistance that the fluid encounters in the tube. We now know that adding small particles to the fluid partly cancels out the turbulence. For instance, the water that American fire-fighters use to extinguish fires contains minuscule polymer particles. These ensure that the water can be pumped more easily through the hose. But why this technique works so effectively is not known. That is one of the subjects the group is working on.

Turbulent flows can also cause noise. Think of the jet engine of an aeroplane, which produces an ear-deafening roar. Or the slipstream of a high-speed train. The CTD Group carries out simulations to determine how the turbulence – and hence the noise – can be reduced. The results could provide valuable input for improving the design of jet engines or trains.

Calculating turbulence is highly complex because it occurs on all scales. So to make an accurate calculation, both the small and large scales must be taken on board. This is beyond the capability of an ordinary PC. The group therefore does most of its calculations on a cluster of supercomputers.

To ensure the calculation work produces meaningful outcomes, half of the work carried out in the group is of an experimental nature. Several large thirty-metre-long pipe flows have been built for this purpose. Two wind tunnels and one water tunnel are also present. These are used to measure the speed of fluids and gases with advanced photographic techniques.

Contact:

Link: http://www.ahd.tudelft.nl/