Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

Abstract

A summary is provided for the Second AIAA Sonic Boom Workshop held 8-9 January 2017 in conjunction with AIAA SciTech 2017. The workshop used three required models of increasing complexity: an axisymmetric body, a wing body, and a complete configuration with flow-through nacelle. An optional complete configuration with propulsion boundary conditions is also provided. These models are designed with similar nearfield signatures to isolate geometry and shock/expansion interaction effects. Eleven international participant groups submitted nearfield signatures with forces, pitching moment, and iterative convergence norms. Statistics and grid convergence of these nearfield signatures are presented. These submissions are propagated to the ground, and noise levels are computed. This allows the grid convergence and the statistical distribution of a noise level to be computed. While progress is documented since the first workshop, improvement to the analysis methods for a possible subsequent workshop are provided. The complete configuration with flow-through nacelle showed the most dramatic improvement between the two workshops. The current workshop cases are more relevant to vehicles with lower loudness and have the potential for lower annoyance than the first workshop cases. The models for this workshop with quieter ground noise levels than the first workshop exposed weaknesses in analysis, particularly in convective discretization. * Research Scientist, Computational AeroSciences Branch, Mike.Park@NASA.gov, AIAA Senior Member. † Aerospace Engineer, Computational Aerosciences Branch, Marian.Nemec@NASA.gov, AIAA Senior Member.

Geometry Modeling for Unstructured Mesh Adaptation

“…Derlaga, Park, and Rallabhandi [67] provide details on how the inlet shock is reflected from the upper wing surface and lower horizontal tail surface to impact the nearfield and propagated ground signatures. This observation appears to be supported by the relatively large discretization error estimates reported in this region by Park and Nemec [26].…”

“…10. The fixed meshes provided by the SBPW-2 committee lacked adequate resolution to capture this interaction on coarser members of a uniformly-refined mesh family [26,67].…”

“…The combination of BREP evaluation (with intended and unintended artifacts), discrete mesh to BREP association persistence, and interpolation error control allow for CFD solutions to be generated from MCAD models without tedious geometry preparation and manual mesh sizing specification. Examples are provided from two AIAA prediction workshops: The NASA Concept 25D with Flow-Through Nacelle (C25F) used in the Second AIAA Sonic Boom Prediction Workshop (SBPW-2) [26] and the Japan Aerospace Exploration Agency Standard Model (JSM) with nacelle used as Case 2d of the Third AIAA High Lift Prediction Workshop (HiLiftPW-3) [27].…”

Cart3D Simulations for the Second AIAA Sonic Boom Prediction Workshop

“…2008: Nasa Fundamental Aeronautics Program Sonic Boom Prediction Workshop 1 2014: Aiaa Sonic Boom Prediction Workshop 1 (sbpw1) 2 2017: Aiaa Sonic Boom Prediction Workshop 2 (sbpw2) 3 The purpose of these workshops is both to document the evolving state of the art in boom prediction methods and provide focus for future investment and research e↵orts.…”

Introduction to the Special Section on Second AIAA Sonic Boom Prediction Workshop

“…In this special section, seven articles related to SBPW2 were published in Volume 56, Issue 3 of the Journal of Aircraft. Summaries and statistical analysis of the nearfield CFD [2] and atmospheric propagation [3] submission are provided. Detailed methods and submission descriptions are included for participants that used Cart3D [4], DLR-TAU [5], USM3D [6], Wolf [7], and Linearized Error Transport Equations [8].…”