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Computation of aeroacoustic sources for a Gulfstream G550 nose landing gear model using adaptive FEM
KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).ORCID iD: 0000-0002-5020-1631
KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).ORCID iD: 0000-0003-4256-0463
2016 (English)In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 124, 136-146 p.Article in journal (Refereed) PublishedText
Abstract [en]

This work presents a direct comparison of unsteady, turbulent flow simulations with measurements performed using a Gulfstream G550 nose landing gear model. The experimental campaign, which was carried out by researchers from the NASA Langley Research Center, provided a series of detailed, well documented wind-tunnel measurements for comparison and validation of computational fluid dynamics (CFD) and computational aeroacoustics (CAA) methodologies. Several computational efforts were collected and presented at the Benchmark for Airframe Noise Computation workshops, BANC-I and II. For our simulations, we used a General Galerkin finite element method (G2), where no explicit subgrid model is used, and where the computational mesh is adaptively refined with respect to a posteriori estimates of the error in a quantity of interest, here the source term in Lighthill's equation. The mesh is fully unstructured and the solution is time-resolved, which are key ingredients for solving problems of industrial relevance in the field of aeroacoustics. Moreover, we choose to model the boundary layers on the landing gear geometry with a free-slip condition for the velocity, which we previously observed to produce good results for external flows at high Reynolds numbers, and which considerably reduces the amount of cells required in the mesh. The comparisons presented here are an attempt to quantify the accuracy of our models, methods and assumptions; to that end, several results containing both time-averaged and unsteady flow quantities, always side by side with corresponding experimental values, are reported. The main finding is that we are able to simulate a complex, unsteady flow problem using a parameter-free methodology developed for high Reynolds numbers, external aerodynamics and aeroacoustics applications.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 124, 136-146 p.
Keyword [en]
Landing gear noise, Computational fluid dynamics, Computational aeroacoustics, Adaptive finite element methods, Turbulence, CAA, CFD, FEM
National Category
Computer Science
Identifiers
URN: urn:nbn:se:kth:diva-180964DOI: 10.1016/j.compfluid.2015.10.017ISI: 000367282700011ScopusID: 2-s2.0-84946867009OAI: oai:DiVA.org:kth-180964DiVA: diva2:898631
Note

Updated from Manuscript to Article.

QC 20160128

Available from: 2016-01-28 Created: 2016-01-26 Last updated: 2016-02-02Bibliographically approved
In thesis
1. High Performance Adaptive Finite Element Methods: With Applications in Aerodynamics
Open this publication in new window or tab >>High Performance Adaptive Finite Element Methods: With Applications in Aerodynamics
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The massive computational cost for resolving all scales in a turbulent flow makes a direct numerical simulation of the underlying Navier-Stokes equations impossible in most engineering applications. Recent advances in adaptive finite element methods offer a new powerful tool in Computational Fluid Dynamics (CFD). The computational cost for simulating turbulent flow can be minimized by adaptively resolution of the mesh, based on a posteriori error estimation. Such adaptive methods have previously been implemented for efficient serial computations, but the extension to an efficient parallel solver is a challenging task. This work concerns the development of an adaptive finite element method that enables efficient computation of time resolved approximations of turbulent flow for complex geometries with a posteriori error control. We present efficient data structures and data decomposition methods for distributed unstructured tetrahedral meshes. Our work also concerns an efficient parallelization of local mesh refinement methods such as recursive longest edge bisection, and the development of an a priori predictive dynamic load balancing method, based on a weighted dual graph. We also address the challenges of emerging supercomputer architectures with the development of new hybrid parallel programming models, combining traditional message passing with lightweight one-sided communication. Our implementation has proven to be both general and efficient, scaling up to more than twelve thousands cores.

Abstract [sv]

Den höga beräkningskostnaden för att lösa upp alla turbulenta skalor för ett realistiskt problem gör en direkt numerisk simulering av Navier-Stokes ekvationer omöjlig. De senaste framstegen inom adaptiva finita element metoder ger ett nytt kraftfullt verktyg inom Computational Fluid Dynamics (CFD). Beräkningskostnaden för en simulering av turbulent flöde kan minimeras genom att beräkningsnätet adaptivt förfinas baserat på en a posteriori feluppskattning. Dessa adaptiva metoder har tidigare implementerats för seriella beräkningar, medan en effektiv parallellisering av metoden inte är trivial. I denna avhandling presenterar vi vår utveckling av en adaptiv finita element lösare, anpassad för att effektivt beräkna tidsupplösta approximationer i komplicerade geometrier med a posteriori felkontroll. Effektiva datastrukturer och metoder för ostrukturerade beräkningsnät av tetrahedrar presenteras. Avhandlingen behandlar även effektiv parallellisering av lokala nätförfiningsmetoder, exempelvis recursive longest edge bisection. Även lastbalanseringsproblematiken behandlas, där problemet lösts genom utvecklandet av en prediktiv dynamisk lastbalanseringsmetod, baserad på en viktad dualgraf av beräkningsnätet. Slutligen avhandlas även problematiken med att effektivt utnyttja nytillkomna superdatorarkitekturer, genom utvecklandet av en hybrid parallelliserings modell som kombinerar traditionell meddelande baserad parallellisering med envägskommunikation. Detta har resulterat i en generell samt effektiv implementation med god skalning upp till fler än tolv tusen processorkärnor.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xii, 50 p.
Series
TRITA-CSC-A, ISSN 1653-5723 ; 2013:07
National Category
Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-125742 (URN)978-91-7501-814-0 (ISBN)
Public defence
2013-09-11, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
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Supervisors
Note

QC 20130816

Available from: 2013-08-16 Created: 2013-08-13 Last updated: 2016-02-02Bibliographically approved

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