https://etalpykla.vilniustech.lt/handle/123456789/155821 Wed, 08 Apr 2026 23:28:18 GMT 2026-04-08T23:28:18Z https://etalpykla.vilniustech.lt/handle/123456789/156032 Validation of hybrid numerical methods for aeroacoustic simulations in an industrial environment Boenke, Dirk; Ewert, R.; Siebert, J.; Delfs, Jan Airframe noise from deployed slats is considered to be the main contributor to the overall aircraft noise during approach and landing of modern airliners. Since it is generated in the vicinity of edges such as the slat trailing edge, recent slat designs attempt to achieve noise reduction by decreasing the flow velocity in this area through optimized slat positions with special focus to the slat gap. The main challenge for aircraft design is to combine noise reduction methods with aerodynamic performance requirements and therefore accurate but also fast numerical prediction methods are necessary. The goal of the present task is to demonstrate the capability of Computational Aeroacoustics (CAA) to predict slat noise in dependency of angle-of-attack (AoA), position settings, shape deformation and flight velocity in a timeframe compatible to industrial design needs. Therefore experimental data, measured by Pott-Pollenske et al. in the Large Low Speed Facility DNW-LLF of the German-Dutch Wind Tunnel foundation within the EU co-financed project OPENAIR, are compared to simulation data of two hybrid CFD/CAA approaches. Here the acoustic predictions rest on time-averaged steady flow solutions provided by Reynolds Averaged Navier-Stokes (RANS) simulation. In a subsequent acoustic step this steady flow data is translated into synthetic fluctuations of turbulent velocity or vorticity by DLR’s aeroacoustic simulation tools PIANO and DISCO to simulate the broadband turbulent sound field radiated from the high-lift system. […] Wed, 01 Jan 2014 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/156032 2014-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/156031 Parametric study of air curtains for airframe noise reduction Bennett, G.; Kennedy, J.; Ramirez, S. M.; Kun, Z.; Neri, E. The advancement of European society is dependent on safe, efficient, and environmentally-friendly technologies. It is an on-going challenge for European industry to meet customer and legislative requirements, satisfy societal demands and sustain competitiveness in the global arena. Development of novel aircraft concepts requires a complex compromise between contradictory requirements in safety, exhaust emissions, noise, performance and price. Landing gear noise is an example of airframe noise caused by turbulent airflow around aircraft components. Landing gear are very complex and as a result many components such as hydraulic cables, electrical wiring, torque links, front and rear braces etc. are exposed to the airflow. The contribution to the overall level of the generated noise from the various components depends on the specifics of the actual design of the landing gear. Air curtains are a novel concept, currently at a low TRL, which apply an upstream air jet to deflect the flow around a landing gear component, thus reducing the local flow speeds and therefore the aerodynamically generated noise. Small-scale proof-of-concept tests were successfully performed in NLR's Small Anechoic Wind Tunnel using an air curtain to shield a bluff body [1]. Broadband noise reductions of 3–5 dB were obtained using an air curtain with vertical blowing. The noise reductions could be increased by oblique blowing and by applying a small flow deflector directly behind the blowing slot. However, the research found that there is an optimal air curtain flow velocity beyond which the beneficial effects can be lost. This is primarily due to the noise generated by the air curtain itself. [...] Wed, 01 Jan 2014 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/156031 2014-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/156030 Slat noise reduction by means of adaptive leading edge devices Pott-Pollenske, Michael; Wild, J.; Delfs, J.; Herr, M.; Rudenko, A.; Büscher, A. Slat noise is regarded as the major noise source of state of the art high lift systems and contributes to the overall aircraft noise signature in particular during the approach phase [1]. Consequently any attempt to reduce high lift system generated noise should first of all target slat noise reduction. Having furthermore in mind that the slat at the same time is a very important means to achieve the necessary high lift performance any approach to reduce slat noise should address the conservation of the aerodynamic performance as well. In the course of this work two different adaptive systems to reduce slat noise will be presented, namely an “adaptive slat” and the “smart droop nose”. The concept of the adaptive slat was investigated in a joint approach between the DLR internal project SLED (Silent Leading Edge Devices) and the EU co-financed project OPENAIR. In the mainframe of the EU co-financed project SADE [2] and again within SLED studies on the smart droop nose were driven. Both approaches have in common that the conventional slat is replaced by an actuated system. The basic difference is in fact that the adaptive slat addresses a slat gap variation in order to reduce or control slat noise while on the other hand the smart droop nose concept represents a 2-element high lift system without slat aiming at the reduction of the aerodynamic penalty that occurs due to omitting the slat. […] Wed, 01 Jan 2014 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/156030 2014-01-01T00:00:00Z https://etalpykla.vilniustech.lt/handle/123456789/156028 Active control of noise generation in a rod-airfoil configuration Siozos-Rousoulis, Leonidas; Ghorbaniasl, Ghader; Lacor, Chris Flow control and adaptive techniques have been widely investigated as possible noise reduction approaches in modern aviation. Despite extensive studies realized on the aerodynamics of a rotating cylinder (i.e. [1, 2]), its potential as a noise reduction technique has not been investigated in the context of an airframe configuration. In the present paper, the aeroacoustic effects of cylinder rotation are investigated in the rod-airfoil canonical benchmark [3]. A 2D hybrid computational aeroacoustics approach is used for noise prediction. Rotation is introduced to the cylinder at rotational frequencies ranging from 1/32 to 2 times the shedding frequency of the non-rotating case. Overall noise directivities and acoustic spectra are then computed for all cases, using the Ffowcs-Williams and Hawkings equation [4]. Evaluation of all test cases proves that significant noise reduction may be achieved by a cylinder rotating at frequencies higher than the shedding frequency of the non-rotating case. Since suppression of the vortex shedding is expected at high enough rotational velocities [5], additional study of the flow field leads to interconnection of noise reduction with this phenomenon. As is observed by the flow field around the rod and airfoil, the cases that present reduced noise emissions also present gradual suppression of the vortex shedding, which is the main contributor to noise generation. High cylinder rotational frequencies also lead to significant increase of the vortex shedding frequency of the rotating cylinder, while the shift of the vortex shedding frequency additionally leads to a shift of the dominant tones of the acoustic spectra. The present investigation thus proved for the first time the potential of cylinder rotation as an adaptive technique for noise reduction, in airframe configurations. A rotating cylinder offers the capability of reducing the noise levels, while altering the directivity pattern and acoustic spectra, thus finding potential application as part of aircraft or UAV airframe components, landing gear, propulsion devices etc. Future work should include a fully unsteady 3D simulation, focused on the rotating frequencies of interest, in order to account for turbulent and three-dimensional noise generation mechanisms. […] Wed, 01 Jan 2014 00:00:00 GMT https://etalpykla.vilniustech.lt/handle/123456789/156028 2014-01-01T00:00:00Z