APSIM is a Ffowcs-Williams & Hawkins Code for post-processing aerodynamic data to compute the acoustic noise at remote microphone locations. In contrast to computational aero-acoustics (CAA), the noise sources have to be provided by the user in the form of pressure surfaces, e.g. the pressure distributions on body surfaces. The transportation of the acoustic signals to the microphones far away is then done with APSIM. The input data is not just limited to CFD based data, but may be from panel codes (e.g. DLR UPM) or wind tunnel experiments. A modification of the Farassat 1a formulation allows for not only evaluating pressure distributions on body surfaces but also using any surface in the room that envelops a body to compute the emitted sound. An example results is shown in fig. 1 for the HART II model rotor.
Example of HART II Modellrotor
Fig. 1: Noise carpet of HARTII experiment (left) and flow simulation with FLOWer and acoustics post processing with APSIM (right).
APSIM is currently mostly used to efficiently predict the noise of helicopter rotor blades. The main contributions are thickness and loading noise and therefore the negligence of broadband noise is acceptable. APSIM is employed within the aero-elastically coupled computational chain for helicopter rotor blades (fig. 2). APSIM is used to analyze the noise emission of innovative helicopters, such as the RACER compound helicopter or propellers of eVTOLs (air cabs), as well as for the acoustic optimisation of quiet rotor blades. In the calculation process, the data for APSIM are provided by UPM or FLOWer-HOST coupled calculations.
Aeroelastic coupling process
Fig. 2: Aeroelastic coupling process of helicopter rotors including the acoustic prediction with APSIM.
Access to these software products can only be granted if the organization you are representing holds a valid license or your organization is interested in signing such a license. If either of the aforementioned two points are fulfilled please get in touch with us providing additional information. Afterwards, we will support you in getting access to our software products. Please note, that we are, in general, not signing license agreements with private individuals.
