Showing papers on "Computational aeroacoustics published in 2012"

Convective effects and the role of quadrupole sources for aerofoil aeroacoustics

Abstract: The present investigation of aerofoil self-noise generation and propagation concerns the effects of mean flow and quadrupole sources on the broadband noise that arises from the interaction of turbulent boundary layers with the aerofoil trailing edge and the tonal noise that arises from vortex shedding generated by laminar boundary layers and trailing-edge bluntness. Compressible large-eddy simulations (LES) are conducted for a NACA0012 aerofoil with rounded trailing edge for four flow configurations with different angles of incidence, boundary layer tripping configurations and free-stream Mach numbers. The Reynolds number based on the aerofoil chord is fixed at . The acoustic predictions are performed by the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation and incorporate convective effects. Surface and volume integrations of dipole and quadrupole source terms appearing in the FWH equation are performed using a three-dimensional wideband multi-level adaptive fast multipole method (FMM) in order to accelerate the calculations of aeroacoustic integrals. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and good agreement is observed in terms of both aerodynamic and aeroacoustic results. For low-Mach-number flows, quadrupole sources can be neglected in the FWH equation and mean flow effects appear only for high frequencies. However, for higher speeds, convection effects are relevant for all frequencies and quadrupole sources have a more pronounced effect for medium and high frequencies. The convective effects are most readily observed in the upstream direction.

Comparison of outflow boundary conditions for subsonic aeroacoustic simulations

Abstract: Aeroacoustics simulations require much more precise boundary conditions than classical aerodynamics. Two classes of non-reflecting boundary conditions for aeroacoustics are compared in the present work: characteristic analysis based methods and Tam and Dong approach. In characteristic methods, waves are identified and manipulated at the boundaries while Tam and Dong use modified linearized Euler equations in a buffer zone near outlets to mimic a non-reflecting boundary. The principles of both approaches are recalled and recent characteristic methods incorporating the treatment of transverse terms are discussed. Three characteristic techniques (the original NSCBC formulation of Poinsot and Lele and two versions of the modified method of Yoo and Im) are compared to the Tam and Dong method for four typical aeroacoustics problems: vortex convection on a uniform flow, vortex convection on a shear flow, acoustic propagation from a monopole and from a dipole. Results demonstrate that the Tam and Dong method generally provides the best results and is a serious alternative solution to characteristic methods even though its implementation might require more care than usual NSCBC approaches.

Simulation of Radial Compressor Aeroacoustics Using CFD

Abstract: This paper focuses on the application of CFD to the prediction of radial compressor aeroacoustics. It concentrates mainly on automotive turbocharger operations in the low mass-flow range where blade leading-edge and tip separation reduce the compressor performance and induce transient flow behaviour. Whereas the blade-passing is tonal and at high frequency, usually beyond the human hearing range, transience in the flow are turbulence-dominated, broad-band in nature, and in magnitude a significant source of aeroacoustics which appears well within the range of peak human hearing (1–5kHz). Other noise sources occur due to distortions in the flow upstream of the compressor face, and rotating stall.The simulation methodology enumerated here pays attention to all the above flow-induced aeroacoustics. Due consideration is given to turbulence modelling, to ensure that both the narrow-band and broad-band sources are directly resolved in the CFD. Appropriate discretisation practices are adopted, so as to capture both turbulent-convection and sound-propagation mechanisms. Pressure-wave non-reflective boundary conditions are applied to the computational boundaries to remove any artificial resonances in the domain.STAR-CCM+, the commercial CFD code used here, was previously benchmarked against experimental data for the same compressor under ideal installation conditions, then the compressor performance assessed under real installation conditions [1]. The main foci of the studies reported here are to exploit possible improvements in modelling of the device performance and efficiency curves using more detailed wall modelling, comparing low-y+ versus high-y+ wall resolution, and to explore the viability for transient CFD calculations to capture the noise sources in the compressor at the challenging low mass flow end of the performance characteristic.© 2012 ASME

Numerical Investigation of 3-D Supersonic Jet Flows using Large Eddy Simulation

Abstract: Supersonic jet flows are studied using 3-D large eddy simulation. The farfield noise generated by the jets is investigated by a computational aeroacoustics methodology that couples the near field unsteady flow field data computed by 3-D LES with a surface integral acoustic method for noise prediction. Since the engines of modern advanced commercial airliners and most military aircraft operate with jets that exhaust at supersonic speed, predicting supersonic jet noise accurately has become one of the keys to designing new low noise emission engines that are suitable for future more restrictive noise regulations. In order to accurately simulate jets at supersonic speeds we employ large eddy simulation and a characteristic filter approach. This approach has low dissipation and is suitable for incorporation into existing solvers based on compact differencing scheme. The results using characteristic filters combined with shock detectors are satisfactory in capturing shocks and resolving turbulent fluctuations. In this study, both perfectly expanded and underexpanded unheated jets are investigated with and without using characteristic filters. Comparisons of the jet mean flow, turbulent statistics, and jet aeroacoustics results with other numerical and experimental data of jets at similar flow conditions were done and reasonable agreement is observed.

Aircraft noise and its nearfield propagation computations

Abstract: Noise generated by civil transport aircraft during take-off and approach-to-land phases of operation is an environmental problem. The aircraft noise problem is firstly reviewed in this article. The review is followed by a description and assessment of a number of sound propagation methods suitable for applications with a background mean flow field pertinent to aircraft noise. Of the three main areas of the noise problem, i.e. generation, propagation, and radiation, propagation provides a vital link between near-field noise generation and far-field radiation. Its accurate assessment ensures the overall validity of a prediction model. Of the various classes of propagation equations, linearised Euler equations are often casted in either time domain or frequency domain. The equations are often solved numerically by computational aeroacoustics techniques, bur are subject to the onset of Kelvin-Helmholtz (K-H) instability modes which may ruin the solutions. Other forms of linearised equations, e.g. acoustic perturbation equations have been proposed, with differing degrees of success.

Validating Large-Eddy Simulation for Jet Aeroacoustics

Abstract: Engineers charged with making jet aircraft quieter have long dreamed of being able to see exactly how turbulent eddies produce sound, and this dream is now coming true with the advent of large-eddy simulation. Two obvious challenges remain: validating the large-eddy-simulation codes at the resolution required to see the fluid–acoustic coupling, and the interpretation of the massive data sets that are produced. This paper addresses the former, the use of advanced experimental techniques such as particle image velocimetry and Raman and Rayleigh scattering, to validate the computer codes and procedures used to create large-eddy-simulation solutions. This paper argues that the issue of accuracy of the experimental measurements be addressed by cross-facility and cross-disciplinary examination of modern data sets along with increased reporting of internal quality checks in particle image velocimetry analysis. Furthermore, it argues that the appropriate validation metrics for aeroacoustic applications are increasingly complicated statistics that have been shown in aeroacoustic theory to be critical to flow-generated sound, such as two-point space-time velocity correlations. A brief review of data sources available is presented along with examples illustrating cross-facility and internal quality checks required of the data before they should be accepted for validation of large-eddy simulation.

Spectral finite elements for computational aeroacoustics using acoustic perturbation equations

Abstract: This paper addresses the application of the spectral finite element (FE) method to problems in the field of computational aeroacoustics (CAA). We apply a mixed finite element approximation to the acoustic perturbation equations, in which the flow induced sound is modeled by assessing the impact of a mean flow field on the acoustic wave propagation. We show the properties of the approximation by numerical benchmarks and an application to the CAA problem of sound generated by an airfoil.

Coupled Discontinuous Galerkin/Finite Difference Solver on Hybrid Meshes for Computational Aeroacoustics

Abstract: T HE field of direct simulation of acoustic waves propagation in the presence of a fluid in motion holds high standards of requirements. This is especially the case when it comes to industrial computational aeroacoustics (CAA), where methods must be able to copewith realistic, complex geometries while involving a high order of accuracy and yet result in affordable solvers in terms of computational resources. In that context, different computational methods have emerged over the years. Resulting from various theoretical backgrounds and approaches, they naturally hold specific characteristics, advantages, and drawbacks. Among them, discontinuous Galerkin (DG)methods [1–4] and finite difference (FD)methods [5– 7] are widely spread. The main characteristics of DG and FD methods are roughly recalled in Table 1. DGmethods arewell adapted to take into account complex geometries as they can deal with unstructured meshes [4,8]. Furthermore, their formulation naturally allows local-order refinement and is well suited for parallel computing. On the other hand, FD methods preferably run on structured meshes and are particularly efficient on Cartesian grids. They are easier to implement and less demanding in terms of CPU resources yet show good numerical dispersion and dissipation properties. Both these methods have been extensively studied, successfully implemented, and applied to that range of problems in industrial configurations. Based on this, a new family of questions have been raised. In particular, the possibility of coupling solvers of different natures in order to locally take advantage of the qualities of each method has already been studied byUtzmann et al. [9–11] in the field of CAA. We will also focus on hybridization techniques of DG/FD schemes based on a computational domain-decomposition approach. A typical motivation behind this is to be able to approximate the solution in the close neighborhood of complex obstacles on an unstructured DG mesh and compute the rest of the field on a Cartesian FD grid in order to alleviate computational time and resources. The purpose of this study is to investigate natural questions raised by such a coupling in order to gather informations on the behavior of the resulting hybrid solver in precision and stability. In this paper, we introduce two two-dimensional (2-D) DG timedomain (DGTD)/FD time-domain (FDTD) hybridization algorithms in the context of the resolution of the linearized Euler equations (LEEs) in two different kinds of geometrical configurations. Our results mainly focus on validation aspects, driven by numerical experiments that were conducted on academic test cases, as theoretical results on the interaction of these two schemes presently seem out of reach in a general case. We also present the behavior of our hybrid solver in the context of an acoustic benchmark problem that consists in the diffraction of an acoustic source by complex-geometries obstacles. The paper is organized as follows. In Sec. II, we present our physical modeling and both the FDTD andDGTD schemes that are used in this study.We also recall their compared properties, advantages, and drawbacks. In Sec. III, after presenting the numerical and theoretical issues raised by the design of a DG/FD coupled solver, we focus on our hybridization strategy and its numerical validation. In Sec. IV, we present an application of our hybrid solver to a complex-geometry acoustic test case, which was proposed at the Fourth CAA Workshop on Benchmark Problems [12].

Rocket Noise Sources Localization Through a Tailored Beam-Forming Technique

Abstract: A source localization technique is applied to analyze wall pressure measurements undertaken on the surface of a space launcher mock-up. The technique is based on the combined use of a standard beam-forming technique and elementary acoustic solutions tailored to the space launcher geometry. Two classes of acoustic elementary solutions are considered: plane waves impinging on the surface of an in nite cylinder computed analytically trough a literature formula, and plane waves impinging on the real space launcher computed numerically through a computational acoustic technique. In both cases, the 3D acoustic eld resulting from the impingement of an arbitrarily oriented plane wave is obtained by a truncated series summation of elementary axial-symmetric solutions. These two classes of basis functions are proven to provide consistent source localization results in the addressed frequency regime. However, although the analytical functional basis enables a faster localization of the noise sources that take place during the rocket ring, the numerical functional basis is expected to enable, at an acceptable computational cost, a more reliable reconstruction of the acoustic loads on the space launcher surface in a higher frequency regime. The proposed CAA-based beam-forming and source reconstruction technique is therefore a useful tool for the vibro-acoustic design of future launch vehicles.

Development and Application of an Efficient, Multiblock 3-D Large Eddy Simulation Tool for Jet Noise

Abstract: The field of jet noise has emerged as one of the most active areas of research due to the recent introduction of stringent aircraft noise regulations. Computational aeroacoustics (CAA) in conjunction with the large eddy simulation (LES) technique shows a tremendous potential in improving our understanding of the noise generation mechanisms and thereby facilitates the development of effective noise reduction devices for jet engines. This potential can be realized on current petascale computing platforms provided that the LES code is capable of handling complex grid topologies with an outstanding scalability to many thousands of cores. The current work aims at developing a scalable, multiblock, structured-grid LES code based on a compact finite difference scheme formulated by a tridiagonal system of equations. The solution of such a system is computed by employing a scalable parallel solver that exhibits good scalability up to 91,125 processor cores. The implementation details of the multiblock topology that simplifies handling complex topologies are discussed. The present multiblock approach does not require overlapping grid points between the neighboring blocks and thus, eliminates routinely-used special treatments at the block boundaries that may compromise the simulation accuracy. The simulation turnaround time using the current LES tool for up to two-billion-grid-point case is compared with our previously developed LES tools to demonstrate the scalability of the code using as many as 91,125 processors. Flow and far-field noise data are reported for an unheated jet at a Reynolds number of 200,000 by utilizing three meshes of different grid resolutions with the finest mesh containing �100 million grid points. The sensitivity of the results to the shear layer thickness is also investigated using the high resolution grids.

Large Eddy Simulations of Supersonic Impinging Jets

Abstract: Supersonic impinging jet flowfields contain self-sustaining acoustic feedback features that create high levels of discrete frequency tonal noise. These types of flowfields are typically found with short takeoff and landing military aircraft as well as jet blast deflector operations on aircraft carrier decks. The US Navy has a goal to reduce the noise generated by these impinging jet configurations and is investing in computational aeroacoustics to aid in the development of noise reduction concepts. In this paper, implicit Large Eddy Simulation (LES) of impinging jet flow-fields are coupled with a far-field acoustic transformation using the Ffowcs Williams and Hawkings (FW-H) equation method. The LES solves the noise generating regions of the flow in the nearfield, and the FW-H transformation is used to predict the far-field noise. The noise prediction methodology is applied to a Mach 1.5 vertically impinging jet at a stand-off distance of five nozzle throat diameters. Both the LES and FW-H acoustic predictions compare favorably with experimental measurements. Time averaged and instantaneous flowfields are shown. A calculation performed previously at a stand-off distance of four nozzle throat diameters is revisited with adjustments to the methodology including a new grid, time integrator, and longer simulation runtime. The calculation exhibited various feedback loops which were not present before and can be attributed to an explicit time marching scheme. In addition, an instability analysis of two heated jets is performed. Tonal frequencies and instability modes are identified for the sample problems.Copyright © 2012 by ASME

Broadband Combustion Noise Simulation of Open Non-Premixed Turbulent Jet Flames:

Abstract: Numerical broadband combustion noise simulations of open non-premixed turbulent jet flames applying the Random Particle-Mesh for Combustion Noise (RPM-CN) approach are presented. The RPM-CN approach is a hybrid Computational Fluid Dynamics/Computational Aeroacoustics (CFD/CAA) method for the numerical simulation of turbulent combustion noise, based on a stochastic source reconstruction in the time domain. The combustion noise sources are modeled on the basis of statistical turbulence quantities, for example achieved by a Reynolds averaged Navier-Stokes (RANS) simulation, using the Random Particle-Mesh (RPM) method. RPM generates a statistically stationary fluctuating sound source that satisfies prescribed one- and two-point statistics which implicitly specify the acoustic spectrum. Subsequently, the propagation of the combustion noise is computed by the numerical solution of the Linearized Euler Equations (LEE). The numerical approach is applied to the DLR-A, the DLR-B and the H3 flames. The open non-prem...

Aerodynamic Noise: An Introduction for Physicists and Engineers

Abstract: Sound as a Wave.- The Case of a Stretched String.- Aerial Waves in Tubes and Closed Rooms.- Relations Between Pressure, Density and Velocity Fluctuations.- Periodic Phenomena.- Probability, Correlations and Spectra.- Monopole, Dipole and Quadrupole Models.- Fluctuating Monopole.- Lighthill's Theory of Aerodynamic Noise.- Lighthill's Equation of Sound.- Subsonic Jet Without Considering Convection.- Dimensional Analysis by Lighthill.- Subsonic Jet Noise (Including Effect of Convection).- Doppler Effect.- Experimental Determination of the Convection Velocity.- Computational Aeroacoustics.- Numerical Non-dissipative Schemes.- Numerical Solution of Acoustiv Propagation of Turbulence.- Further Topics in Aerodynamic Noise.- Supersonic Jet Noise.- Sound at Solid Boundaries.- Combustion Noise.- Sonic Boom.- Measurement Techniques.

A review of state-of-the-art aeroacoustic prediction approaches

Abstract: Review about state-of-the-art of computational aeroacoustics (CAA) approaches: Finite Difference Methods on structured meshes; Discontinuous Galerkin Method; Fast Multipole Method.

Comparison of some optimisation techniques for numerical schemes discretising equations with advection terms

Abstract: We have considered the measures of errors devised by Tam and Webb (1993), Bogey and Bailly (2002) and by Berland et al. (2007) to construct low dispersion, low dissipation and high order numerical schemes in computational aeroacoustics. We modify their measures to obtain three different techniques of optimisation. We investigate the strength and weak points of these three optimisation techniques together with our technique of minimised integrated exponential error for low dispersion and low dissipation (MIEELDLD) (Appadu and Dauhoo, 2009, 2011; Appadu, 2011) when controlling the grade and balance of dispersion and dissipation with reference to some numerical schemes applied to the 1D linear advection equation and the Korteweg-de-Vries Burgers equations. It is observed that the technique of MIEELDLD is more effective than the other three techniques to control the grade and balance of dissipation and dispersion in numerical schemes. Therefore, we use MIEELDLD to optimise parameters in the α-scheme and to obtain a modification to the beam-warming scheme which has improved shock capturing properties. Some numerical experiments are carried out to validate the results by showing that when the optimal parameters are used, better results in terms of shock-capturing properties are obtained.

The Technique of MIEELDLD in Computational Aeroacoustics

Abstract: The numerical simulation of aeroacoustic phenomena requires high-order accurate numerical schemes with low dispersion and low dissipation errors. A technique has recently been devised in a Computational Fluid Dynamics framework which enables optimal parameters to be chosen so as to better control the grade and balance of dispersion and dissipation in numerical schemes (Appadu and Dauhoo, 2011; Appadu, 2012a; Appadu, 2012b; Appadu, 2012c). This technique has been baptised as the Minimized Integrated Exponential Error for Low Dispersion and Low Dissipation (MIEELDLD) and has successfully been applied to numerical schemes discretising the 1-D, 2-D, and 3-D advection equations. In this paper, we extend the technique of MIEELDLD to the field of computational aeroacoustics and have been able to construct high-order methods with Low Dispersion and Low Dissipation properties which approximate the 1-D linear advection equation. Modifications to the spatial discretization schemes designed by Tam and Webb (1993), Lockard et al. (1995), Zingg et al. (1996), Zhuang and Chen (2002), and Bogey and Bailly (2004) have been obtained, and also a modification to the temporal scheme developed by Tam et al. (1993) has been obtained. These novel methods obtained using MIEELDLD have in general better dispersive properties as compared to the existing optimised methods.

Validation of a Hybrid Simulation Method for Flow Noise Prediction

Abstract: In this paper a joint experimental-numerical study which validates a novel hybrid method for computational aeroacoustics (CAA) with experimental results is presented. To this end an experimental investigation of the noise generated by the flow through an air outlet of the HVAC system of the AUDI TT at different flow rates and flap positions was conducted. The generated sound was recorded at thirty different positions in the near field. Of this configuration, a CFD and CAA analysis with a novel method, where a Large-EddySimulation (LES) is coupled with the acoustic-perturbation-equations (APE) in one solver, was conducted. The comparison of the flow variables show a good agreement between the measured and simulated flow fields. The numerically predicted flow noise is compared by means of the total sound pressure levels (SPL) and spectral analysis at each microphone position. The comparison show an excellent agreement between computed and measured signal, the method being able to predict the shape of the spectra, distinct peaks of the spectra, the overal SPL, the directional pattern and the scaling of the generated noise with the flow rates and flap positions correctly. We can show that the acoustic fluctuations in the nozzle can become as large as the hydrodynamic fluctuations and have to be taken into account when comparing simulation results with measured pressure signals. In the employed method a strong emphasis is put on a good computational performance, so that an industrial application of this method is feasible.

Integrating CFD, CAA, and Experiments Towards Benchmark Datasets for Airframe Noise Problems

Abstract: Airframe noise corresponds to the acoustic radiation due to turbulent flow in the vicinity of airframe components such as high-lift devices and landing gears. The combination of geometric complexity, high Reynolds number turbulence, multiple regions of separation, and a strong coupling with adjacent physical components makes the problem of airframe noise highly challenging. Since 2010, the American Institute of Aeronautics and Astronautics has organized an ongoing series of workshops devoted to Benchmark Problems for Airframe Noise Computations (BANC). The BANC workshops are aimed at enabling a systematic progress in the understanding and high-fidelity predictions of airframe noise via collaborative investigations that integrate state of the art computational fluid dynamics, computational aeroacoustics, and in depth, holistic, and multifacility measurements targeting a selected set of canonical yet realistic configurations. This paper provides a brief summary of the BANC effort, including its technical objectives, strategy, and selective outcomes thus far.

Computational aeroacoustic characterization of different orifice geometries under grazing flow conditions

Abstract: This paper deals with the numerical prediction of the aeroacoustic behavior of orifices under grazing flow conditions. A hybrid computational aeroacoustics approach is adopted where the steady, incompressible, mean flow over the orifice is obtained from a RANS simulation. In a next step, the mean flow variables are used to solve the linearized Navier–Stokes equations (LNSE), using a Runge–Kutta Discontinuous Galerkin (RKDG) method. In this way, the linear interaction mechanisms between the aerodynamic and acoustic fluctuations are studied which enables an aeroacoustic characterization of the orifice. A methodology is presented involving a virtual impedance tube and two computations for each geometrical configuration: one with the presence of a mean flow and one for a quiescent medium. This allows to isolate the contribution of the mean flow to the orifice impedance. The method is verified against theoretical models and experimental data from literature, and is used to study the influence of orifice geometry variations, such as the orifice length, the plate thickness and the edge rounding, on the mean flow contribution to the impedance.

Aeroacoustic Study on a Simplified Nose Landing Gear

Abstract: Simulation analysis and experiment research are performed on the aeroacoustic noise of a landing gear component in this paper. Detached Eddy Simulation (DES) is used to produce the flow field of the model. The Ffowcs-Williams/Hawkings (FW-H) equation is used to calculate the acoustic field. The sound field radiated from the model is measured in the acoustic wind tunnel. A comparison shows that the simulation results agree well with the experiment results under the acoustic far field condition. The results show that the noise radiated from the model is broadband noise. The directivity of the noise source is like a type of dipole. The wheel is the largest contributor and the strut is the least contributor to the landing gear noise. The results can provide some reference for low noise landing gear design.

Scale-Resolving Simulation of an Unsteady Turbulent Flow and Acoustic Field of a Screeching Supersonic Jet

Abstract: Unsteady three-dimensional turbulent flow and acoustic field of an imperfectly expanded screeching supersonic cold jet is studied computationally using the general purpose CFD code ANSYS FLUENT. The effects of turbulence are simulated by the Delayed Detached Eddy Simulation (DDES). A quasi-periodic transient solution is calculated using the pressure-based coupled solver formulation with the second-order bounded central-upwind spatial discretization and second-order implicit time marching scheme. The numerical solution recovers the generation of screech tones by the interaction of large scale turbulent structures with jet shock cells. Propagation of flapping and helical mode disturbances along the jet column is reproduced in the simulation. The acoustic near-field is directly resolved by the Computational Aeroacoustics (CAA) to accurately propagate screech tone waves to a permeable Ffowcs Williams and Hawkings (FW-H) acoustics source surface, and to microphone monitors defined on the nozzle lip. Calculated screech tone frequencies and near-field sound pressure levels are compared with experimental data, and favorable nearfield agreement is found. The FW-H model is applied to propagate acoustic waves from the source surface into the far field, and far-field noise directivities are examined.

Acoustic transmission through a 3D rotating fan using Computational AeroAcoustics

Abstract: In the context of the evaluation and reduction of fan noise in modern turbofan engines, the possibility to compute the acoustic transmission through a rotor-stator system, accounting for the rotation of the rotor, is evaluated. The objective is the development of a numerical method to simulate the propagation of acoustic waves in a global fixed region which includes a partial moving zone, with equations solved in a fixed reference frame. In order to insure a high order resolution these CAA developments and computations were performed using Onera’s CAA solver sAbrinA-V0. Firstly, a full or partial 2D moving zone was employed as a reference test case. It was insured that the moving grid acts only as a resolution support and does not affect the propagation of the waves by its rotation. Monopole and planar sources were considered. In order to connect the two (fixed and rotating) zones, spline cubic interpolation functions were employed in the ghost cells rows. Secondly, a cross-shaped rigid obstacle with zero thickness walls was embedded in the moving grid and the interaction between this obstacle and a fixed monopole was computed. Note that, despite the CAA solver can handle any non-homogeneous mean flow, this case was addressed accounting for a medium at rest. The field of application of the method is restricted to non-viscous interactions between boundary layer and acoustics, so the considered mean flows have to respect this condition. Finally, a 3D test case is presented, based on a simplified rotor with four twisted blades with zero thickness in a perfect annular duct. The acoustic interaction of this rotating blades with an helicoidal modal source injected upstream the rotor within a medium at rest was evaluated. Recent developments in sAbrinA-v0 on improved inlet/outlet acoustic boundary conditions and conclusions of gust-fixed airfoil interactions will allow a proper evaluation of CAA simulations of moving surfaces.