Surrogate-Based Low-Boom Low-Drag Nose Design for the JAXA S4 Supersonic Airliner

Robust low-boom low-drag design methods were developed within a trilateral collaboration between JAXA, ONERA and DLR on the en-route noise of supersonic civil aircraft. In this paper the nose of the JAXA S4.134 supersonic low-boom airliner is optimized using a surrogate-based optimization method. The optimization process includes near-field Euler simulations with the DLR TAU code and a propagation algorithm developed at ONERA based on the TRAPS code. The maximum level of perceived loudness for different off-track angles as well as the drag coefficient are used as objective functions for a multi-objective optimization. A reduction of the off-track noise by 2 dB PL as well as a small drag reduction can be achieved by the nose optimization. The impact on the pitching moment is analyzed

DLR TAU Simulations for the Third AIAA Sonic Boom Prediction Workshop

The presentation summarizes the DLR contribution to the 3rd AIAA Sonic Boom Prediction Workshop. A grid generation approach using CENTAUR is presented. Near-field simulation results for the jet-plume interaction case and the C608 low boom geometry were presented. Results for both, workshop-provided and CENTAUR-generated grids are compared. A good grid convergence is achieved for fine grids

Validation of the Flow Topology Around Several Airdrop Cargo Configurations at Static Conditions

A numerical study was carried out to assess the interference effects between the wake of a transport aircraft and several generic cargo bodies during the early stage of an airdrop scenario. Based on experimental data and preceding numerical simulations distinct positions of the trajectory being subject to strong interference effects were stati- cally reproduced. The flow field around the bodies was experimentally investigated using stereoscopic Particle Image Velocimetry and compared to steady and unsteady Reynolds- averaged Navier-Stokes (RANS) computations. The latter were carried out using the unstructured DLR TAU code. The primary focus is to assess the suitability, accuracy and the limitations of RANS methods in such challenging flow conditions. Therefore, the influence of several turbulence models was investigated and compared to experimental field velocity data. Although deviations in the wake of the bodies were observed, the qualitative agreement between the steady simulations and experiment was very good. Quantitatively, however, the steady approach leaves room for further improvements. The gap to the experimental data could partially be reduced in applying unsteady RANS methods

DLR TAU Near-Field Simulations for the Third AIAA Sonic Boom Prediction Workshop

The accurate prediction of the sonic boom is essential for the development of a future low-boom supersonic aircraft. In this paper, the best practice for predicting near-field pressure signatures with the DLR TAU code is applied for geometries and grids provided by the third AIAA Sonic Boom Prediction Workshop. The near-field part of the workshop provided two cases, the biconvex case and the NASA C608 case. Both geometries were analyzed by DLR. The biconvex case is used to study shock–plume interactions and the NASA C608 case is used to assess the status of near-field simulations for a realistic low- boom flight demonstrator. Results for the DLR TAU simulations on the workshop-provided grids are presented for different grid refinement levels using Reynolds-averaged Navier–Stokes simulations. In addition to the provided grids, a setup for mixed-element grids with varying setups is described. The predicted near-field signatures agree very well with other workshop participants’ results and wind-tunnel data

DLR TAU Simulations for the Third AIAA Sonic Boom Prediction Workshop Near-Field Cases

The accurate prediction of the sonic boom is essential for the development of a future low boom supersonic aircraft. In this paper the best practice for predicting near-field pressure signatures with the DLR TAU code is applied for geometries and grids provided by the third AIAA Sonic Boom Prediction Workshop. The near-field part of the workshop provided two cases, the Biconvex case and the NASA C608. Both geometries were analyzed by DLR. The Biconvex case is utilized to study shock-plume interactions and the NASA C608 case is used to assess the status of near-field simulations for a realistic low boom flight demonstrator. Results for the DLR TAU simulations on the workshop-provided grids are presented for different grid refinement levels using RANS simulations. In addition to the provided grids, a setup for mixed-element grids with varying setups is described. The predicted near-field signatures agree very well with other workshop participants' results and wind tunnel data

Überblick über das DLR-Projekt ELTON_SST

The DLR-project ELTON_SST (Estimation of Landing and Take-Off Noise of SuperSonic Transport) was established in 2020 to support EASA and the German BMVI with numerical data in order to assess the noise performance of potential supersonic aircraft. Five departments of the DLR Institute of Aerodynamics and Flow Technology and Institute of Propulsion Technology are involved. The project is split into two phases. The first phase covers the landing and take-off (LTO) noise estimation based on analytical and empirical models and the verification of the models with published data. A one-dimensional engine design is performed based on data published by NASA for the 55t STCA configuration. The fidelity of the simulations will be increased in the second phase. RANS simulations are performed to increase the accuracy of the aerodynamic performance analysis and acoustic BEM simulations are performed to verify acoustic assumptions made in the first phase, for example the reduction of fan noise due to structural shielding. A three-dimensional engine geometry and high-lift devices will be designed in this second project phase

Numerische Strömungssimulation von Schlitzvariationen bei tangentialem Ausblasen über dem Ruder an einem gepfeilten Seitenleitwerk unendlicher Streckung

In dieser Arbeit erfolgt die numerische Simulation von Schlitzvariationen bei tangentialem Ausblasen über dem ausgeschlagenen Ruder einer 2,5D-Seitenleitwerksgeometrie. Ziel ist die Steigerung des maximal erreichbaren Seitenkraftbeiwertes bei einem möglichst geringen Ausblasekoeff�zienten. Es erfolgt die Variation der Schlitzbreite und Schlitzanzahl auf einer gewählten Spannweite und die Generierung hybrider Netze mit strukturierten Bereichen. Ohne Strömungskontrollmaßnahmen ist die Strömung auf dem Ruder fast vollständig abgelöst. Anhand stationärer RANS-Simulationen mit dem DLR TAU-Code wird gezeigt, dass die Ablösung der Strömung vom Ruder durch kontinuierliches Ausblasen verhindert werden kann. Für jede Schlitzvariation werden drei unterschiedliche Strahlgeschwindigkeiten untersucht und mit einem durchgehenden Schlitz verglichen. Bei der Simulation diskreter Schlitze entsteht an jedem Schlitz ein gegensinnig rotierendes Wirbelpaar. Damit es sich vollständig ausbildet, dürfen die Schlitze nicht zu nah zueinander stehen. Wird der Abstand jedoch zu groß, so decken die Wirbel nicht die gesamte Spannweite ab. Beide Effekte vermindern die Effizienz der Ausblasung. Verglichen mit dem durchgehenden Schlitz kann bei diskreten Schlitzen der zur Steigerung des Seitenkraftbeiwertes um etwa 57% benötigte Ausblasekoeffi�zient auf die Hälfte und der benötigte Massenstrom auf fast ein Drittel reduziert werden. Bei einem gleichen Ausblasekoe�ffizienten liefert immer die Konfiguration die höchste Effizienz, die kleine Schlitze mit einer hohen Strahlgeschwindigkeit kombiniert. Zusätzlich werden numerische Einflüsse etwa durch die periodische Randbedingung, unterschiedliche Aktuatorrandbedingungen und die Netzfeinheit untersucht

Grid Setups and Numerical Simulations of a Low Boom Concept at Off Design Flight Conditions

The accurate prediction of the sonic boom along all parts of the mission trajectory is essential for the development and certification of a future low boom supersonic commercial aircraft. In this paper, the C25D low-boom concept geometry from the Second AIAA Sonic Boom Prediction Workshop is used to conduct numerical simulations at off-design flight conditions with the DLR TAU code. The flight altitude and flight Mach number are varied to simulate a mission trajectory while the lift is kept constant. The focus of this paper is the evaluation of a core grid setup with a non-circular cross section and the assessment of the applicability of the grid deformation and the Chimera technique for the variation of angle of attack while the farfield grid remains aligned to the Mach cone. It is shown that both techniques are viable and that differences in the pressure signatures between both techniques are negligible. Using the grid deformation technique resulted in lower grid node numbers and thus lower computational cost. In addition, the sensitivities of varying flight conditions on the pressure fields are evaluated. It is shown that the pressure signatures are strongly affected by varying flight conditions. While the shape of the front part of the pressure signatures stays constant for all flight conditions and only the magnitude changes, the impact on the aft part of the signature is large. The shocks and expansions are adversely interacting if only Mach number or the altitude are changed. Especially, the magnitudes of the main expansions are increasing. The lowest peak interactions for the on-track pressure signature can be found for accelerating while climbing

Numerical Near-Field Simulations of Low Boom Aircraft Concepts

This paper presents the setup of the DLR TAU code for sonic boom near-field simulations and results obtained for the low-boom geometries developed within the EC project RUMBLE. A process for surrogate-based low-boom low-drag fuselage design based on a near-field target pressure signature is described. The focus of the paper is the robust parameterization of the fuselage geometry to prevent the generation of irregular shapes as well as the modular grid generation approach that significantly reduces the time to generate the grids. The numerical results of four RUMBLE milestone shape evolutions with flow through nacelles are presented and geometrical influences on the near-field pressure signatures are analyzed. It is shown that the pressure signatures for shape derivatives with powered engine boundary conditions or with modifications for wind tunnel measurements are very similar to the signatures of the original shapes