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Study of transitions in the atmospheric boundary layer using explicit algebraic turbulence models.
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Turbulens.
Stockholm University, Department of Meteorology.
Météo-France, CNRM-GAME.
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Turbulens.ORCID-id: 0000-0002-9819-2906
Visa övriga samt affilieringar
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Nationell ämneskategori
Strömningsmekanik och akustik Meteorologi och atmosfärforskning
Identifikatorer
URN: urn:nbn:se:kth:diva-166803OAI: oai:DiVA.org:kth-166803DiVA, id: diva2:812366
Anmärkning

QS 2015

Tillgänglig från: 2015-05-18 Skapad: 2015-05-18 Senast uppdaterad: 2015-05-22Bibliografiskt granskad
Ingår i avhandling
1. Turbulence modelling applied to the atmospheric boundary layer
Öppna denna publikation i ny flik eller fönster >>Turbulence modelling applied to the atmospheric boundary layer
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Turbulent flows affected by buoyancy lie at the basis of many applications, both within engineering and the atmospheric sciences. A prominent example of such an application is the atmospheric boundary layer, the lowest layer of the atmosphere, in which many physical processes are heavily influenced by both stably stratified and convective turbulent transport. Modelling these turbulent flows correctly, especially in the presence of stable stratification, has proven to be a great challenge and forms an important problem in the context of climate models. In this thesis, we address this issue considering an advanced class of turbulence models, the so-called explicit algebraic models.In the presence of buoyancy forces, a mutual coupling between the Reynolds stresses and the turbulent heat flux exists, which makes it difficult to derive a fully explicit turbulence model. A method to overcome this problem is presented based on earlier studies for cases without buoyancy. Fully explicit and robust models are derived for turbulence in two-dimensional mean flows with buoyancy and shown to give good predictions compared with various data from direct numerical simulations (DNS), most notably in the case of stably stratified turbulent channel flow. Special attention is given to the problem of determining the production-to-dissipation ratio of turbulent kinetic energy, for which the exact equation cannot be solved analytically. A robust approximative method is presented to calculate this quantity, which is important for obtaining a consistent formulation of the model.The turbulence model derived in this way is applied to the atmospheric boundary layer in the form of two idealized test cases. First, we consider a purely stably stratified boundary layer in the context of the well-known GABLS1 study. The model is shown to give good predictions in this case compared to data from large-eddy simulation (LES). The second test case represents a full diurnal cycle containing both stable stratification and convective motions. In this case, the current model yields interesting dynamical features that cannot be captured by simpler models. These results are meant as a first step towards a more thorough investigation of the pros and cons of explicit algebraic models in the context of the atmospheric boundary layer, for which additional LES data are required. 

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2015. s. xvi, 64
Serie
TRITA-MEK, ISSN 0348-467X ; 2015.05
Nyckelord
turbulence; RANS models; explicit algebraic Reynolds-stress models; buoyancy; stable stratification; thermal convection; atmospheric boundary layer
Nationell ämneskategori
Strömningsmekanik och akustik Meteorologi och atmosfärforskning
Identifikatorer
urn:nbn:se:kth:diva-166806 (URN)978-91-7595-603-9 (ISBN)
Disputation
2015-06-12, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:15 (Engelska)
Opponent
Handledare
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QC 20150522

Tillgänglig från: 2015-05-22 Skapad: 2015-05-18 Senast uppdaterad: 2015-05-22Bibliografiskt granskad

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Brethouwer, GeertWallin, StefanJohansson, Arne

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Lazeroms, WernerBrethouwer, GeertWallin, StefanJohansson, Arne
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Turbulens
Strömningsmekanik och akustikMeteorologi och atmosfärforskning

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