As improving the performance of turbofan designs becomes increasingly difficult, manufacturers are looking to new technologies for the next generation of jet engines. An 'open rotor' replaces the fan of the turbofan with a set of external rotors. This has the potential to offer a significant improvement in propulsive efficiency, but the design for low noise is a key challenge. Hence, high fidelity noise prediction methods are needed to accurately predict and compare the noise of different designs. This thesis focuses on one set of methods based on the Ffowcs Williams-Hawkings (\fwh) equation. This equation is considered to be the most realistic description of aeroacoustic noise generation, as it is a direct rearrangement of the Navier-Stokes equations. The \fwh\ equation is difficult to solve for realistic test cases such as an open rotor, and is susceptible to several types of error. This thesis categorises these errors as ``input'', ``neglection'' and ``discretisation'' errors. Discretisation errors arise from the need to integrate a discretised source field for the total noise, neglection errors result from needing to ignore part of the source field for practical reasons, and input errors relate to any errors caused by inaccurate input to the solver. The fundamental motivation of this thesis is to advance the understanding of neglection and discretisation errors and how they can be mitigated, in order to develop best practice solvers and methodologies for application to open rotors. Dimensional analysis is combined with analytical flow solutions to develop a process for isolating and quantifying discretisation errors. This process is used to study a wide range of solver methodologies and select a best practice solver methodology for open rotor noise prediction. This first-of-a-kind study produces a solver methodology that reduces discretisation errors by an order of magnitude compared to an industry standard solver. Previous research into neglection errors has shown that avoiding density perturbations in acoustic source terms can be beneficial. This thesis uses a generic aeroacoustic analogy to provide a new, physically intuitive method of incorporating a surface discontinuity that enables density perturbations to be avoided in a far more elegant manner than previous research. The above method improvements are investigated using a modern open rotor rig test case. The results demonstrate that discretisation and neglection errors can be severe in realistic cases and the potential of the method improvements to significantly mitigate them.

Uma nova ferramenta de aeroacústica computacional baseada em simulações RANS (Reynolds Averaged Navier-Stokes) foi desenvolvida para a predição do ruído gerado pelo escoamento tri-dimensional de jatos complexos. O método é denominado de LRT o qual surgiu da combinação da analogia acústica de Lighthill com o método de acústica geométrica Ray-Tracing. A grande vantagem da utilização do método LRT para predições de ruído é que este determina não apenas as fontes sonoras presentes no escoamento, mas também modela os efeitos da interação fluidoacústica e, sua influência no ruído em um campo distante. Esta característica tornou-se extremamente importante para a indústria de motores aeronáuticos já que investigações em bocais assimétricos estão atualmente em andamento devido à necessidade de redução de ruído. O método LRT é uma ferramenta relativamente rápida de predição de ruído de jatos baseado na Analogia Acústica de Lighthill e que usa como dados de entrada os resultados obtidos à partir de uma simulação RANS do escoamento. A interação fluidoacústica é calculada através da utilização da Teoria de Traçamento de Raios. O método LRT foi formulado como um método tri-dimensional e, portanto, não possui limitações de aplicabilidade para a predição sonora em relação ao tipo de escoamento ou à geometria do bocal. Diversas simulações numéricas foram conduzidas com sucesso para uma grande variedade de escoamento de jatos (jatos simples, coaxiais e assimétricos) utilizando o LRT como uma ferramenta de engenharia. O resultado deste trabalho é uma ferramenta numérica que permite a realização de predições de ruído para casos de escoamento de jatos complexos, assim como possibilita sua aplicação para a investigação de efeitos de interação do escoamento do jato com superfícies hiper-sustentadoras no campo acústico. Adicionalmente, o método LRT pode ser aplicado para complementar análises experimentais possibilitando, portanto, um melhor entendimento sobre os mecanismos fluidodinâmicos e acústicos presentes em escoamentos de jatos complexos. / A novel computational aeroacoustics tool based on RANS (Reynolds Averaged Navier-Stokes method) is developed for predicting the noise generated by complex three-dimensional jet flows. The new method is called LRT which arises from the combination of Lighthills acoustic analogy with Ray-Tracing acoustics. The powerful advantage of applying the LRT method for noise predictions is that it calculates not only the noise sources but it also models and takes into account sound-flow interaction effects without any geometric simplification, such as flow symmetries of the problem. This is now a strong requirement from aero-engines manufactures since investigations on asymmetric nozzles, as a means of noise reductions are in progress. The LRT method is a relatively fast jet noise prediction tool based on Lighthills Acoustic Analogy and it uses a Reynolds-Average Navier-Stokes (RANS) computational fluid dynamics (CFD) simulation as input information. The sound-flow interaction is computed by solving the propagation using Ray-Tracing equations. The LRT method has been formulated as a general three-dimensional method and it has no restrictions on the type of the flow field or nozzle geometry for noise prediction. Successful numerical noise predictions have been carried out for a variety of jet flows (single, coaxial and asymmetric jets) using the LRT as an engineering tool. The outcome from this thesis is a numerical tool that allows noise predictions of complex exhaust systems and the variations in sound field due to modifications of the flow field generated by the interaction of the jet flow with high-lift surfaces. In addition, the LRT method can be applied to complement experimental analysis providing a better understanding about the flow and acoustics mechanisms for complex jets.

No description available.

When sound waves propagate in a duct in the presence of turbulent flow, turbulent mixing can cause attenuation of the sound waves extra to that caused by the viscothermal effects. Experiments show that compared to the viscothermal effects, this turbulent absorption becomes the dominant contribution to the sound attenuation at sufficiently low frequencies. The mechanism of this turbulent absorption is attributed to the turbulent stress and the turbulent heat transfer acting on the coherent perturbations (including the sound waves) near the duct wall, i.e. sound-turbulence interaction. The purpose of the current investigation is to understand the mechanism of the sound-turbulence interaction in low-Mach-number internal flows by theoretical modeling and numerical simulations. The turbulence absorption can be modeled through perturbation turbulent Reynolds stresses and perturbation turbulent heat flux in the linearized perturbation equations. In this thesis, the linearized perturbation equations are reviewed, and different models for the turbulent absorption of the sound waves are investigated. A new non–equilibrium model for the perturbation turbulent Reynolds stress is also proposed. The proposed model is validated by comparing with experimental data from the literature, and with the data from Direct Numerical Simulations (DNS) of pulsating turbulent channel flow. Good agreement is observed. / <p>QC 20150526</p>

The evaluation of the noise produced by flows has reached a high level of importance in the past years. The physics surrounding flow-induced noise is quite complex and sensitive to various flow conditions like temperature, shape. Empirical models were built in the past for some special geometries but they cannot be used in a general case for a shape optimization for instance. Experimental aeroacoustic facilities represent the main tool for acoustic analyses of flow fields, but are quite expensive because extreme care must be exercised not to introduce acoustic perturbations in the flow (silent facilities). These tools allow a good analysis of the physical phenomena responsible for noise generation in the flow by a comparison of the noise sources and the flow characteristics (pressure, turbulence,...). Nevertheless, the identification and location of noise sources to compare with flow structures requires quite complex methods. The numerical approach complements the experimental one in the sense that the flow characteristics are deeply analyzed where experiments suggest noise production. For the numerical approach, the turbulence modeling is quite important. In the past, some models were appreciated for their good prediction of some aerodynamic parameters as lift and drag for instance. The challenge is now to tune these models for a correct prediction of the noise sources. In the low subsonic range, the flow field is completely decoupled from acoustics, and noise sources can be computed from a purely hydrodynamic simulation before this information is transferred to an acoustical solver which will compute the acoustic field at the listener position. This post processing of the aerodynamic results is not obvious since it can introduce non-physical noise into the solution. This project considers the aspect of noise generation in turbulent jets and especially the noise generated by vortex pairing, as it occurs for instance in jet flows. The axisymmetric version of the flow solver SFELES has been part of this PhD research, and numerical results obtained on the jet are similar to the experimental values. Analyses performed on the numerical results are interesting to go to complete turbulence modeling for aeroacoustics since vortex pairing is one of the basic acoustical processes in vortex dynamics. Currently, a standard static Smagorinski model is used for turbulence modeling. However, this model has well known limitations, and its influence on the noise sources extracted from the flow field is not very clear. For this reason, it is planned to adopt a dynamic procedure in which the subgrid scale model automatically adapts to the flow. We planned also to perform simulations with the variational multiscale approach to better simulate the different interactions between large and unresolved scales. The commercial software ACTRAN distributed by Free Field Technologies is used for the computation of sound propagation inside the acoustic domain.

L'objectif de cette thèse est d'étudier numériquement l'aéroacoustique à faibles nombres de Mach(M inf 0.3) pour un écoulement de couche limite turbulente épaisse affleurant une cavité, sur la base de simulations numériques à grandes échelles (LES). Un profil de vitesse en loi puissance et pour une couche limite d'équilibre ont servi comme conditions en entrée du domaine de calcul. La couche limite d'équilibre, sans et avec gradient de pression adverse, a été résolue par une approche asymptotique basée sur une formulation déficitaire avec un nouveau modèle de longueur de mélange. Ce dernier a été validé pour améliorer les comparaisons avec les expériences et les simulations numériques directes. Des simulations LES ont permis de regarder l'influence de l'épaisseur de la couche limite turbulente amont sur le mode d'oscillation d'une cavité L/D=4. Un accord satisfaisant avec les expériences d'Haigermoser et l'émergence du mode de cisaillement a été obtenu pour la vitesse amont de 5.8m/s. Le mode était de type sillage pour les deux autres cas tests (20et40m/s). Finalement, une simulation 3D a montré que le mode de sillage est un artefact du calcul 2D. En utilisant l'analogie de Lighthill-Curle et les champs de pression in stationnaire issus de la simulation, nous avons déterminé les niveaux de pression sonore dans le champ proche et lointain. Conformément aux expériences d'Haigermoser, une faible directivité vers l'amont est trouvée. Le mode de sillage influence très fortement les niveaux de pression acoustique. / The objective of this thesis is to study numerically the aeroacoustics of low Mach number (M inf 0.3) fow with thick turbulent boundary layer past a cavity based on Large Eddy Simulation (LES). Velocity profiles from power law and equilibrium turbulent boundary layer were imposed as inlet conditions on the computational domain. The equilibrium turbulent boundary layer profles (zero and adverse pressure gradient) have been generated using a symptotic approach with an improved mixing length model. A good agreement is observed between the computed boundary layer profiles and the profiles obtained from experiments and direct numerical simulations. LES results present the infuence of the thickness of the incoming turbulent boundary layers on the mode of oscillation in the shallow cavity of L/D=4. An agreement with the experiments of Haigermoser and the shear mode have been found for the upstream velocity 5.8m/s. Wake mode was observed for the other two test cases at 20 and 40m/s. A 3D cavity simulation is performed to show that the wake mode observed in the 2D calculations is an artifact. The hydrodynamic pressure feld obtained from the 2D simulation is used as an input to the acoustic analogy (Lighthill-Curle's analogy), to compute the acoustic pressure feld at the near and far feld of the cavities. Conforming the experiments of Haigermoser, a weak directivity of sound propagation was observed. Shear mode infuences the sound pressure levels strongly.

Cette thèse propose différentes méthodologies de calcul du bruit à large bande générée par l’interaction rotor-stator d’une soufflante de turboréacteur et ce de la génération des sources acoustiques jusqu’au rayonnement en champ lointain. En premier lieu, le mécanisme d’interaction rotor-stator est étudié à travers une turbulence de grille homogène et isotrope (THI) impactant un profil isolé. Le cas de l’interaction rotor-stator en milieu guidé est ensuite traité et appliqué à une maquette de compresseur axial. Enfin, la dernière partie traite de la simulation du rayonnement aval en sortie de conduit. Dans chacune de ces parties, des approches analytiques et numériques sont proposées. Les méthodes analytiques permettentune prévision rapide du problème simplifié, et les méthodes numériques permettent de leverles hypothèses au prix d’un temps de calcul plus long.Le modèle d’Amiet est mis en œuvre pour simuler le bruit d’interaction THI-profil àtravers une expérience en soufflerie anéchoïque. Ce modèle simplifiant le profil en une plaque plane non portante, une approche numérique est également mise en place. La convection de perturbations de vitesse incidentes synthétisant une THI et impactant un profil isolé est simulée à l’aide d’un code CAA (Computational AeroAcoustics) résolvant les équations d’Euler en deux dimensions. Les différences de rayonnement entre une plaque plane et un profil cambré épais observées expérimentalement sont en partie retrouvées. Une simulation plus avancée d’un calcul LES (Large Eddy Simulation) 3D est également abordée.Dans la deuxième partie du mémoire, le modèle d’Amiet est étendu au problème de l’interaction rotor-stator en conduit. Différentes formulations sont proposées et discutées. Elles sont appliquées au cas d’un banc d’essai du DLR (centre de recherche aérospatiale allemand) avec des données d’entrée provenant d’un calcul RANS (Reynolds Averaged Navier-Stockes) ou bien directement de mesures. Les prévisions acoustiques ainsi obtenues sont satisfaisantes (+/-2 dB avec des données d’entrée expérimentales) compte tenu de la relative simplicité des modèles. Un calcul LES est exploité pour fournir directement les sources de bruit (fluctuations de pression pariétale). Les spectres obtenus montrent des tendances similaires à ceux issus du modèle d’Amiet malgré certains phénomènes non-physiques encore présents au niveau du calcul LES.Pour terminer, le rayonnement en champ libre est traité. Une manière simple et rapidede résoudre ce problème consiste à utiliser une intégrale de Kirchhoff, en supposant unécoulement moyen uniforme. Une comparaison avec une solution analytique (technique deWiener-Hopf) exacte pour les mêmes conditions montre que le rayonnement du bruit largebande est bien prévu par la méthode de Kirchhoff pour des angles de rayonnement inférieursà 90°. Cependant, pour prendre en compte la géométrie d’éjection de la nacelle et l’effet d’un écoulement hétérogène (cisaillement) sur le rayonnement en champ libre, une approche numérique est mise en place. Une technique permettant de simuler le caractère aléatoire des sources turbulentes ainsi que de satisfaire l’hypothèse de modes acoustiques incohérents est développée. Cette méthodologie est appliquée au cas simple du conduit semi-infini, puis à une tuyère réaliste. Les calculs sont validés à l’aide de solutions analytiques sur les configurations simplifiées. Une analyse critique des instabilités créées dans la couche de cisaillement et de leur influence sur les formulations intégrales couplées au calcul Euler pour obtenir le bruit en champ lointain complète ce dernier chapitre. / This report presents several methodologies aiming to predict broadband noise generatedby the interaction between the rotor and the stator of a turbofan. The main objective is toobtain a complete prediction procedure from the acoustic sources generation to the far fieldnoise radiation. As a first step, the rotor-stator mechanism is studied as the interaction betweena homogeneous and isotropic turbulence (HIT) and an isolated airfoil. Then, the ductedrotor/stator interaction case is treated. Finally, the last part is devoted to the aft radiationthrough the bypass duct. In each part, analytical and numerical approaches are investigated.On the one hand, analytical models allow a fast prediction but on a simplified problem, onthe other hand numerical methods remove many assumptions with a longer computationaltime.The Amiet theory is applied to simulate the airfoil-HIT interaction and comparisons withexperimental results obtained in an anechoic wind tunnel are discussed. Since this modelsimplifies the airfoil to a non-lifting flat plate, a numerical approach has also been investigatedusing a CAA (Computational AeroAcoustics) code solving the Euler equations in twodimensions. The incoming HIT is synthesized by a sum of convected harmonic velocity perturbationsinjected through the inlet boundary. The acoustic radiation discrepancies betweena flat plate and a lifting airfoil observed between experimental results and the Amiet theoryare partly verified. Finally, the possibility to use a 3D LES (Large Eddy Simulation) is alsodiscussed.In the second part, the Amiet model for an isolated airfoil is extended in order to solvethe turbofan interaction noise problem. Several formulations are proposed and are validatedby comparisons with measurements obtained from an axial compressor test bed. Input dataare provided either by a CFD (Computational Fluid Dynamics) or experiment. Acoustic resultsshown to be quite reasonable (�}2 dB in the later case) considering the simplicity of themodel. A LES computation is also studied in order to directly obtain the acoustic sources(vane surface pressure fluctuations). The resulting acoustic spectra shape are in relativelygood agreement with the Amiet model even if some non-physical phenomena are observed inthe LES data.The acoustic radiation in the free field is studied in the last part. A simple way to solvethe problem is to use a Kirchhoff integral along the outlet duct section assuming an uniformmean flow. A comparison with an exact(under uniform mean flow assumption) analytical modelinvolving a Wiener-Hopf technique demonstrates that good results can be obtained withthe Kirchhoff method up to 90°of radiation angle. However, in order to take in considerationthe effect of nacelle geometry and heterogeneous flow (shear) on the acoustic radiation, anumerical approach is set up. This method allows to simulate the non-deterministic and thenon-coherent mode behavior of a fan broadband noise. Simplified configurations are used topartly validate these numerical simulations by comparison with analytical solutions. This approachis finally applied to a realistic nozzle case. The instability waves created in the shearlayer and their effects on the integral formulations used to obtain the far field radiation arecarefully analyzed.

O desenvolvimento de uma ferramenta de Dinâmica de Fluidos Computacional que utiliza Método de Elementos Finitos baseada na discretização de Galerkin descontínuo é apresentado neste trabalho com objetivo de resolver a equação de Euler linearizada para escoamento compressível em duas dimensões usando malhas estruturadas e não estruturadas. Procuramos utilizar esta ferramenta como um propagador de ondas sonoras para estudar fenômenos aeroacústicos. O problema de Riemann presente no fluxo convectivo da equação de Euler é tratado com um método upwind HLL e para o avanço da solução no tempo é usado o método de Runge-Kutta explícito de 4 estágios com segunda ordem de precisão. A eficiência computacional, a convergência do método e a precisão são testadas através de simulações de escoamentos já apresentadas na literatura. A taxa de convergência para altas ordens de aproximação é assintótica que é um resultado compatível com a formulação Galerkin descontínuo. / The development of a Computation Fluid Dynamic Tool based on the Finite Element Method with discontinuous Galerkin discretization is presented in this work. The aim of this study is to solve the compressible linearized Euler\'s equation in two dimensions on structured and non structured meshes. This tool has been used as a means to study aeroacoustics phenomena. The Riemann\'s problem presented on a convective flow in Euler\'s equation is tackled by a HLL\'s method and the time integration being used is the four-stage Runge-Kutta explicit method with second order of accuracy. The computational efficiency, the convergence of the method and the accuracy are tested by comparing our results for flow simulations with those that are available in the literature. The convergence rate to high approximation order is asymptotic and it shows a result which is compatible with a discontinuous Galerkin formulation.

Et une quantification de la distorsion due à l’effet potentiel des OGVs et de celle due à l’asymétrie de l’entrée d’air sont proposées. Les effets de la distorsion sur l’aérodynamique sont mis en évidence avec notamment une modification importante des sillages des pales de la soufflante, des chocs et de la charge instationnaire exercée sur les différentes pales et aubes. Des prévisions Les objectifs en termes de réduction de la consommation et du bruit émis par les moteurs d’avions ont progressivement mené aux architectures à très grand taux de dilution (UHBR). Leur géométrie est caractérisée par une entrée d’air courte et par une réduction de l’espace entre la soufflante et les aubes du redresseur du flux secondaire (OGVs), entraînant alors une augmentation de l’inhomogénéité azimutale de l’écoulement au niveau de la soufflante. Cette inhomogénéité, appelée distorsion, pourrait impacter le bruit tonal généré par le module de la soufflante. Ce bruit est généralement supposé être dominé par le mécanisme d’interaction des sillages des pales de la soufflante avec les OGVs. En régime transsonique, le bruit de choc et le bruit de charge stationnaire deviennent également prépondérants. L’augmentation de la distorsion pourrait être à l’origine de nouvelles sources de bruit en interagissant avec les pales de la soufflante et l’objectif de cette thèse est d’évaluer leur contribution. Les effets de la distorsion sur les mécanismes de bruit déjà existants sont également analysés. Cette étude est réalisée à l’aide de simulations numériques des équations instationnaires de Navier-Stokes moyennées (URANS). Un module complet de fan est considéré sur 360 degrés et se compose d’un conduit d’entrée d’air, de la soufflante et des redresseurs des flux primaire et secondaire (IGVs/OGVs). Le redresseur du flux secondaire est typique des moteurs actuels avec un pylône intégré et deux entrées d’air différentes sont étudiées de manière à isoler les effets de la distorsion d’entrée d’air. La première est axisymétrique et ne produit donc pas de distorsion alors que la deuxième ne l’est pas et produit un niveau de distorsion typique de ceux attendus dans les moteurs UHBR. Une description acoustiques basées sur les approches directe et hybride sont réalisées et soulignent la contribution importante des sources localisées sur les pales de la soufflante sur le bruit amont. Le bruit aval reste dominé par les sources sur les OGVs mais est tout de même impacté par la distorsion d’entrée d’air via la modification des sillages. / Fuel consumption and noise reduction trigger the evolution of aircraft engines towards Ultra High Bypass Ratio (UHBR) architectures. Their short air inlet design and the reduction of their interstage length lead to an increased circumferential inhomogeneity of the flow close to the fan. This inhomogeneity, called distortion, may have an impact on the tonal noise radiated from the fan module. Usually, such a noise source is supposed to be dominated by the interaction of fan-blade wakes with Outlet Guide Vanes (OGVs). At transonic tip speeds, the noise generated by the shocks and the steady loading on the blades also appears to be significant. The increased distortion may be responsible for new acoustic sources while interacting with the fan blades and the present work aims at evaluating their contribution. The effects of distortion on the other noise mechanisms are also investigated. The work is based on full-annulus simulations of the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. A whole fan module including the inlet duct, the fan and the Inlet and Outlet Guide Vanes (IGVs/OGVs) is studied. The OGV row is typical of current engine architecture with an integrated pylon and two different air inlet ducts are compared in order to isolate the effects of inlet distortion. The first one is axisymmetric and does not produce any distortion while the other one is asymmetric and produces a level of distortion typical of the ones expected in UHBR engines. A description and a quantification of the distortion that is caused by both the potential effect of the OGVs and the inlet asymmetry are proposed. The effects of the distortion on aerodynamics are highlighted with significant modifications of the fanblade wakes, the shocks and the unsteady loading on the blades and on the vanes. Both direct and hybrid acoustic predictions are provided and highlight the contribution of the fan-blade sources to the upstream noise. The downstream noise is still dominated by the OGV sources but it is shown to be significantly impacted by the inlet distortion via the modification of the impinging wakes.

Desde a última década, as autoridades aeronáuticas dos países membros da ICAO vem, gradativamente, aumentando as restrições nos níveis de ruído externo de aeronaves, principalmente nas proximidades dos aeroportos. Por isso os novos motores aeronáuticos precisam ter projetos mais silenciosos, tornando as técnicas de predição de ruído de motores cada vez mais importantes. Diferente das técnicas semi-analíticas, que vêm evoluindo nas últimas décadas, as técnicas semiempíricas possuem suas bases lastreadas em técnicas e dados que remontam à década de 70, como as desenvolvidas no projeto ANOPP. Uma bancada de estudos aeroacústicos para um conjunto rotor/estator foi construída no departamento de Engenharia Aeronáutica da Escola de Engenharia de São Carlos, permitindo desenvolver uma metodologia capaz de gerar uma técnica semi-empírica utilizando métodos e dados novos. Tal bancada é capaz de variar a rotação, o espaçamento rotor/estator e controlar a vazão mássica, resultando em 71 configurações avaliadas. Para isso, uma antena de parede com 14 microfones foi usada. O espectro do ruído de banda larga é modelado como um ruído rosa e o ruído tonal é modelado por um comportamento exponencial, resultando em 5 parâmetros: nível do ruído, decaimento linear e fator de forma da banda larga, nível do primeiro tonal e o decaimento exponencial de seus harmônicos. Uma regressão superficial Kriging é utilizada para aproximar os 5 parâmetros utilizando as variáveis do experimento e o estudo mostrou que Mach Tip e RSS são as principais variáveis que definem o ruído, assim como utilizado pelo projeto ANOPP. Assim, um modelo de previsão é definido para o conjunto rotor/estator estudado na bancada, o que permite prever o espectro em condições não ensaiadas. A análise do modelo resultou em uma ferramenta de interpretação dos resultados. Ao modelo são aplicadas 3 técnicas de validação cruzada: leave one out, monte carlo e repeated k-folds e mostrou que o modelo desenvolvido possui um erro médio, do nível do ruído total do espectro, de 2.35 dBs e desvio padrão de 0.91. / Since the last decade, the countries members of ICAO, via its aeronautical authorities, has been gradually increasing the restrictions on external aircraft noise levels, especially in the vicinity of airports. Because that, the new aero-engines need quieter designs, so noise prediction techniques for aero-engines are getting even more important. Semi-analytical techniques have undergone a major evolution since the 70th until nowadays, but semi-empirical techniques still have their bases pegged in techniques and data defined on the 70th, developed in the ANOPP project. An Aeroacoustics Fan Rig to investigate a Rotor/Stator assembly was developed at Aeronautical Engineering Department of São Carlos School of Engineering, allowing the development of a methodology capable of defining a semi-empirical technique based on new data and methods. Such rig is able to vary the rotation, the rotor/stator spacing and mass flow rate, resulting in a set of 71 configurations tested. To measure the noise, a microphone wall antenna with 14 sensors were used. The broadband noise was modeled by a pink noise and the tonal with exponential behavior, resulting in 5 parameters: broadband noise level, decay and form factor and the level and decay of tonal noise. A superficial kriging regression were used to approach the parameters using the experimental variables and the investigation has shown that Mach Tip and RSS are the most important variables that defines the noise, as well on ANOPP. A prediction model for the rotor/stator noise are defined with the 5 approximation of the parameters, that allow to predict the spectra at operations points not measured. The model analyses of the model resulted on a tool for results interpretation. Tree different cross validation techniques are applied to model: leave ou out, Monte Carlo and repeated k-folds. That analysis shows that the model developed has average error of 2.35 dBs and standard deviation of 0.91 for the spectrum level predicted.