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Time step size adaptation for unsteady aerodynamic flow simulations: Application to gust encounter simulations

Lenz, Christian (2018) Time step size adaptation for unsteady aerodynamic flow simulations: Application to gust encounter simulations. Dissertation. DLR-Forschungsbericht. 2018-25, 144 S.

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Abstract

This thesis investigates suitable time integration, error estimation and step size control algorithms for the temporal discretization and approximate solution of the unsteady Euler, Navier-Stokes, and Reynolds-Averaged-Navier-Stokes (RANS) equations. The focus lies on applications with an induced unsteadiness such as gust encounter simulations. Embedded Runge-Kutta methods are used to get an estimate of the temporal discretization error. Based on this error, different adaptation algorithms are used to adjust the time step size. The effect of the time step size adaptation is demonstrated for the gust encounter simulations resulting in small time step sizes during the actual encounter with larger time steps before and afterwards. A new time step size limiter is introduced which uses the information from a rejected step to avoid subsequent rejections. Diagonally implicit Runge-Kutta methods with constant and adaptive time step sizes are investigated and compared to backward difference formulae. To solve the linear systems several iterative solution methods are compared together with a discussion on different stage value predictors which yield suitable initial values for the iterative methods.

Item URL in elib:https://elib.dlr.de/122101/
Document Type:Monograph (DLR-Forschungsbericht, Dissertation)
Title:Time step size adaptation for unsteady aerodynamic flow simulations: Application to gust encounter simulations
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Lenz, ChristianChristian.Lenz (at) dlr.deUNSPECIFIED
Date:2018
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Number of Pages:144
ISSN:1434-8454
Status:Published
Keywords:RANS equations, time step adaptation, unsteady flow simulations, gust encounter
Institution:Institut für Aerodynamik und Strömungstechnik
Department:C²A²S²E
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Simulation and Validation
Location: Braunschweig
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > CASE, BS
Deposited By: Seyfried, Beate
Deposited On:09 Oct 2018 12:50
Last Modified:09 Oct 2018 12:50

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