Large Eddy Simulations of Separated Compressible Flows around Wing Sections
(1999) Abstract
 This thesis concerns numerical calculations of compressible separated flows, with and without shocks, around wing sections using Large Eddy Simulations (LES). The considered geometries are the NACA 0012 wing section and the ONERA AT15A wing section. Compressible separated flows around wing sections are of considerable interest, for engineering and scientific reasons, since they involve transition, nearwall turbulence and separation. At transonic speed the interaction between shock and the viscous boundary layer is of interest. If the shock is strong enough shock induced separation occurs.
Using Reynolds Averaged NavierStokes Simulations (RANS) one has to know in advance where transition to turbulence occurs. The RANS... (More)  This thesis concerns numerical calculations of compressible separated flows, with and without shocks, around wing sections using Large Eddy Simulations (LES). The considered geometries are the NACA 0012 wing section and the ONERA AT15A wing section. Compressible separated flows around wing sections are of considerable interest, for engineering and scientific reasons, since they involve transition, nearwall turbulence and separation. At transonic speed the interaction between shock and the viscous boundary layer is of interest. If the shock is strong enough shock induced separation occurs.
Using Reynolds Averaged NavierStokes Simulations (RANS) one has to know in advance where transition to turbulence occurs. The RANS turbulence models also include a set of model parameters which have to be set a priori. This is not the case for dynamic LESformulation since the model parameters are computed during the simulation utilising the information in the resolved flow field. An explicit filter is used to extract this information.
A filter derived on a mathematical basis is presented as well as a new dynamic model where the divergence of the subgridscale (SGS) terms are modelled rather than the SGSterms themselves. In this way only three model parameters are needed for the momentum equations and still anisotropy effects can be accounted for. A novel idea how to treat filtering close to a shock is presented.
In LES the large scale flow field is resolved both in time and space and the computational time is significant. To obtain results in acceptable time computations using Parallel Virtual Machine (PVM) have been conducted.
The important role of the numerical viscosity as an implicit model in LES is demonstrated. The development of streamwise vortices is shown to be strongly dependent of the spanwise distance of the computational domain. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/40152
 author
 Held, Jörgen ^{LU}
 supervisor
 opponent

 Dr Lindblad, Ingemar, FFA, Bromma
 organization
 publishing date
 1999
 type
 Thesis
 publication status
 published
 subject
 keywords
 turbulence, subgridscale, shockboundary layer interaction, wing section, transonic, subsonic, compressible, separated, Large eddy simulation, LES, PVM, Mechanical engineering, hydraulics, vacuum technology, vibration and acoustic engineering, Maskinteknik, hydraulik, vakuumteknik, vibrationer, akustik
 pages
 152 pages
 publisher
 Department of Heat and Power Engineering, Lund university
 defense location
 Ole Römers väg 1, sal M:B
 defense date
 19991215 10:15:00
 external identifiers

 other:ISRN: LUTMDN/TMVK1018SE
 ISBN
 9178740231
 language
 English
 LU publication?
 yes
 id
 0c9ce2bda67b453fb34897f5f49b6adc (old id 40152)
 date added to LUP
 20160401 15:47:50
 date last changed
 20181121 20:36:25
@phdthesis{0c9ce2bda67b453fb34897f5f49b6adc, abstract = {{This thesis concerns numerical calculations of compressible separated flows, with and without shocks, around wing sections using Large Eddy Simulations (LES). The considered geometries are the NACA 0012 wing section and the ONERA AT15A wing section. Compressible separated flows around wing sections are of considerable interest, for engineering and scientific reasons, since they involve transition, nearwall turbulence and separation. At transonic speed the interaction between shock and the viscous boundary layer is of interest. If the shock is strong enough shock induced separation occurs.<br/><br> <br/><br> Using Reynolds Averaged NavierStokes Simulations (RANS) one has to know in advance where transition to turbulence occurs. The RANS turbulence models also include a set of model parameters which have to be set a priori. This is not the case for dynamic LESformulation since the model parameters are computed during the simulation utilising the information in the resolved flow field. An explicit filter is used to extract this information.<br/><br> <br/><br> A filter derived on a mathematical basis is presented as well as a new dynamic model where the divergence of the subgridscale (SGS) terms are modelled rather than the SGSterms themselves. In this way only three model parameters are needed for the momentum equations and still anisotropy effects can be accounted for. A novel idea how to treat filtering close to a shock is presented.<br/><br> <br/><br> In LES the large scale flow field is resolved both in time and space and the computational time is significant. To obtain results in acceptable time computations using Parallel Virtual Machine (PVM) have been conducted.<br/><br> <br/><br> The important role of the numerical viscosity as an implicit model in LES is demonstrated. The development of streamwise vortices is shown to be strongly dependent of the spanwise distance of the computational domain.}}, author = {{Held, Jörgen}}, isbn = {{9178740231}}, keywords = {{turbulence; subgridscale; shockboundary layer interaction; wing section; transonic; subsonic; compressible; separated; Large eddy simulation; LES; PVM; Mechanical engineering; hydraulics; vacuum technology; vibration and acoustic engineering; Maskinteknik; hydraulik; vakuumteknik; vibrationer; akustik}}, language = {{eng}}, publisher = {{Department of Heat and Power Engineering, Lund university}}, school = {{Lund University}}, title = {{Large Eddy Simulations of Separated Compressible Flows around Wing Sections}}, year = {{1999}}, }