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An investigation in actuator disc CFD solution applicabillity for aeroacoustic analysis of propellers and rotors

Verweij, A.P. (2010) An investigation in actuator disc CFD solution applicabillity for aeroacoustic analysis of propellers and rotors.

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Abstract:Summary of content The report covers an investigation into the feasibility of the use of the actuator disk approach in aeroacoustic analysis of a propeller/rotor. In the actuator disk approach, a propeller or rotor is represented as an infinitesimally thin disk where flow field quantities are added to the flow in a discontinuous jump. This approximation results in a dramatic reduction of computational workload. The approach has been validated on aerodynamical grounds for a steady computation in earlier investigations. Recent developments at CIRA extend the use of the actuator disk approach to unsteady flow calculation. However, little investigation has been done in the past on the effects of using the approach in this way and therefore in the first part of the project, the effect of using the actuator approach in unsteady computation is investigated. Also the way to properly model a specific propeller/rotor as an unsteady actuator disk boundary condition has not been formulated before, and so a distribution is constructed and validated. In the second part of the report, the output of the unsteady CFD computations are used as input data for an in-house aero-acoustic code that is based on the permeable Ffowcs Williams-Hawkings analogy. This can be done by formulating a surface around the actuator disk. In order to investigate the result of using this approach, a comparison is made between computations that use this ZEN input data and regular input data containing a moving body. The report is structured in the following way. In chapter 2, an overview of ZEN is given, which is the used CFD code. This chapter starts with a small introduction into the features of ZEN and the theory behind the actuator disk approach. Then, a short description of the unsteady form of ZEN (UZEN) is given, together with an explanation in the way an unsteady boundary condition is formulated. The last paragraph of the chapter contains a description of possible phenomena that can emerge with the use of UZEN in comparison to ZEN. Chapter 3 contains an investigation into ZEN and UZEN using a simple test case. First, a steady simulation is done to generate reference data and investigate the effects of mesh density. Then, the unsteady boundary condition is constructed and ran through a series of tests. The chapter ends with observations and conclusions on the effects of using the actuator disk approach in UZEN for propellers/rotors. Then in chapter 4 an attempt is made in generating an actuator disk boundary condition from the output data of a potential flow solver for number of propellers and rotors. The code used for this is RAMSYS. The reason for this is that RAMSYS output can be used reference data for the aero-acoustic analysis. The chapter contains a description on how to convert the output data of RAMSYS to an actuator disk boundary condition. Then, the result is investigated for 3 different geometries and a geometry is chosen on which the aero-acoustic investigation will be performed. Chapter 5 covers the investigation of aero-acoustics. As with the other chapters, this section starts with an introduction into the method used. The first paragraph contains information about the theory of the FW-H analogy and the description of the test setup. Then, a number of tests are conducted comparing the results of a variety of aero-acoustic simulations with UZEN input data to a simulation done with RAMSYS input data.
Item Type:Internship Report (Master)
Italian Aerospace Research Center, Capua, Italy
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
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