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Robust viscous-inviscid interaction scheme for application on unstructured meshes
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0003-1604-4262
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0002-3199-8534
2017 (English)In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 145, p. 37-51Article in journal (Refereed) Published
Abstract [en]

A coupled viscous-inviscid interaction scheme combining the continuity equation for potential flow with the three-dimensional integral boundary layer equations is presented. The inviscid problem is discretized by a finite-element approach whereas an upwind-biased finite-volume scheme is employed for the boundary layer equations. The discretization is applicable to unstructured tetrahedral-triangular meshes and results in a sparse system of non-linear equations which is solved by a Newton-type method. The mathematical reasons for the singularities commonly associated with the integral boundary layer equations in separated flow regions are analyzed and the connection between the mathematical singularities and the numerical ill-conditioning is discussed. It is shown that, by a suitable choice of closure relations, it is possible to obtain a boundary layer model free from numerical ill-conditioning in separated flow regions. The accuracy of the coupled viscous-inviscid model is investigated in a number of test cases including transitional and mildly separated flow over two different natural laminar flow airfoils and three-dimensional flow over a swept wing. It is concluded that the coupled method is able to provide reasonably accurate predictions of viscous and inviscid flow field quantities for the investigated cases.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 145, p. 37-51
Keywords [en]
Integral boundary layer equations, Robustness, Separated flow, Singularities, Unstructured meshes, Viscous-inviscid coupling scheme
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-200874DOI: 10.1016/j.compfluid.2016.12.012ISI: 000393011800004Scopus ID: 2-s2.0-85006341298OAI: oai:DiVA.org:kth-200874DiVA, id: diva2:1071271
Funder
VINNOVA, 2014-00933
Note

QC 20160203

Available from: 2017-02-03 Created: 2017-02-03 Last updated: 2017-11-29Bibliographically approved
In thesis
1. On Aerodynamic and Aeroelastic Modeling for Aircraft Design
Open this publication in new window or tab >>On Aerodynamic and Aeroelastic Modeling for Aircraft Design
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work presented in this thesis was performed with the aim of developing improved prediction methods for aerodynamic and aeroelastic analysis to be used in aircraft design. The first part of the thesis concerns the development of a viscous-inviscid interaction model for steady aerodynamic predictions. Since an inviscid, potential flow, model already is available, the main focus is on the development of a viscous model consisting of a three-dimensional integral boundary layer model. The performance of the viscous-inviscid interaction model is evaluated and it is found that the accuracy of the predictions as well as the computational cost appear to be acceptable for the intended application. The presented work also includes an experimental study aimed at analyzing steady and unsteady aerodynamic characteristics of a laminar flow wing model. An enhanced understanding of these characteristics is presumed to be useful for the development of improved aerodynamic prediction models. A combination of nearly linear as well as clearly nonlinear aerodynamic variations are observed in the steady as well as in the unsteady experimental results and it is discussed how these may relate to boundary layer properties as well as to aeroelastic stability characteristics. Aeroelastic considerations are receiving additional attention in the thesis, as a method for prediction of how flutter characteristics are affected by modeling uncertainties is part of the presented material. The analysis method provides an efficient alternative for obtaining increased information about, as well as enhanced understanding of, aeroelastic stability characteristics.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. p. 27
Series
TRITA-AVE, ISSN 1651-7660 ; 2017:44
Keywords
viscous-inviscid interaction model, laminar flow wing, aerodynamics, aeroelasticity, aircraft design
National Category
Engineering and Technology
Research subject
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-212051 (URN)978-91-7729-480-1 (ISBN)
Public defence
2017-09-22, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20170816

Available from: 2017-08-16 Created: 2017-08-15 Last updated: 2017-08-16Bibliographically approved

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