Fatigue characteristics of acoustic induced aircraft structure

Important results from the project

After preliminary studies the project has focused on techniques how to model flow induced load, eg cases where the external geometry causes high sound pressure levels. The main difficulties with predicting acoustic fatigue without experimental tests is to predict the spatial and spectral content of the load. To be able to predict the load for e generic design CFD calculations has been used. Important aspects of how the load is modeled has been evaluated in the project, which gives possibilities to further investigate the development of modeling techniques and criterias.

Expected long term effects

Numerical methods (CFD-simulations) used to predict the acoustic load that could cause fatigue problem, have been studied and the knowledge of the problem area has increased. Since the used CFD methods are numerical they can be applied early in the design cycle. Since the methods can be used at an early stage it is possible to change the design without costly tests and improvements can be made before hardware has been manufactured. The increased knowledge of the problem also contributes to a better understanding how to develop design criteria based on numerical methods.

Approach and implementation

After an introductory literature study the focus has been to study the flow phenomena with CFD simulations. To validate the CFD simulations wind tunnel measurements from earlier projects (ACUFAT) where used. This wind tunnel test was performed on a flap. Measurement from wind tunnel tests from University of Cincinnati was also used. In this case a so-called backward-facing step geometry. The latter replacing the planned wind tunnel tests. It was deemed to be more effective to focus on the simulations than spend time on an experiment similar to what was already available.