Shock-induced noise plays an important role in “jet screech”, a strong, sharp peak in sound pressure corresponding to high-pitched noise of up to 160 decibels, loud enough to potentially damage aircraft parts that are near the nozzle. Image courtesy of Jan Schulze and Jörn Sesterhenn

Spend some time at the exit nozzle of a supersonic jet engine and you’ll soon notice it’s a rather loud place to play.

Much of the shock-induced noise is caused because the nozzle exit pressure differs from ambient air pressure, which results in a series of shocks, compressions and expansions that interact until the differences in air pressure have been resolved.

Many of the physical processes responsible for this process have not yet been clearly identified, which is why Jan Schulze and Jörn Sesterhenn of UniBW Munich are working to find out more.

Schulze and Sesterhenn used direct numerical simulations to compute a three-dimensional supersonic rectangular jet that had not yet perfectly expanded, simulating jets as they exist at the nozzle exit of aircraft jet engines.

These simulations allowed them to directly compute the sound field that was generated by the supersonic jets.

Schulze said the main challenge was simultaneously resolving the small-scale nonlinear turbulent structures and the large-scale, small amplitude acoustic waves they produce.

This research was conducted using Distributed European Infrastructure for Supercomputing Applications, a consortium of supercomputing centers integrating existing high-performance computing platforms with dedicated networks and innovative system and grid software.