The fan noise prediction tool PropNoise (Propulsion Noise) is dedicated to the acoustic assessment of past, modern and future engine concepts. Its aim is to support engineers and researchers during the design of a fan stage and provide them with insight and quantitative results within short time.
Fast and versatile are two central properties of PropNoise. The tool is capable of simulating several configurations over night. A wide range of parameters is covered by the models included in PropNoise in order to find the global optima that lead to the best compromise between aerodynamic performance and noise emission. Moreover, the tool is able to consider various concepts and compare them with each other (e.g. conventional rotor-stator stage, counter-rotating turbofan, open rotors, fan equipped with a variable-area nozzle,etc.).
The models underlying PropNoise are semi-analytical in nature. They are based on the one side on the Acoustic Analogy formulated in the frequency domain for rotating blades. On the other side, the acoustic models are informed by flow quantities (mean velocities, wakes, turbulence spectra, etc.) that are calculated with state-of-the-art semi-empirical correlations. The constants involved in these correlations depend weakly on the fan operating condition and geometry.
PropNoise has a modular structure. Each blade row is modelled separately and can generate noise. The generation, propagation and radiation of noise are considered . The acoustic models require as an input aerodynamic and unsteady flow quantities, which may be calculated either within PropNoise ('stand-alone' mode) or provided by an external flow solver (e.g in-house DLR turbomachinery code TRACE).
The relations established in PropNoise within the frame of the Acoustic Analogy may help to gain insight and infer more general design guidelines. Provided the modular structure of PropNoise, modifications on a blade row may be implemented easily and their impact on noise emissions may be assessed.