Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains

The main motivation of this thesis is the analysis of turbulent flows. Turbulence plays an important role in engineering applications due to the fact that most flows in industrial equipment and surroundings are in turbulent regime. The thesis has a double purpose and is divided in two main parts. Th...

Descripción completa

Detalles Bibliográficos
Autor: Jaramillo Ibarra, Julián Ernesto
Tipo de recurso: tesis doctoral
Estado:Versión publicada
Fecha de publicación:2008
País:España
Institución:CBUC, CESCA
Repositorio:TDR. Tesis Doctorales en Red
OAI Identifier:oai:www.tdx.cat:10803/6696
Acceso en línea:http://www.tdx.cat/TDX-0122110-202710
http://hdl.handle.net/10803/6696
https://dx.doi.org/10.5821/dissertation-2117-94007
Access Level:acceso abierto
Palabra clave:CFD
cortinas de aire
turbulencia
volumenes finitos
621
id ES_8f2cd674ac9461b733145a93eb0aa4e8
oai_identifier_str oai:www.tdx.cat:10803/6696
network_acronym_str ES
network_name_str España
repository_id_str
dc.title.none.fl_str_mv Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
title Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
spellingShingle Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
Jaramillo Ibarra, Julián Ernesto
CFD
cortinas de aire
turbulencia
volumenes finitos
621
title_short Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
title_full Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
title_fullStr Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
title_full_unstemmed Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
title_sort Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtains
dc.creator.none.fl_str_mv Jaramillo Ibarra, Julián Ernesto
author Jaramillo Ibarra, Julián Ernesto
author_facet Jaramillo Ibarra, Julián Ernesto
author_role author
dc.contributor.none.fl_str_mv Pérez Segarra, Carlos David
Oliva, Asensio
Universitat Politècnica de Catalunya. Departament de Màquines i Motors Tèrmics
dc.subject.none.fl_str_mv CFD
cortinas de aire
turbulencia
volumenes finitos
621
topic CFD
cortinas de aire
turbulencia
volumenes finitos
621
description The main motivation of this thesis is the analysis of turbulent flows. Turbulence plays an important role in engineering applications due to the fact that most flows in industrial equipment and surroundings are in turbulent regime. The thesis has a double purpose and is divided in two main parts. The first one is focussed on the basic and fundamental analysis of turbulence models. In the second part the know-how acquired in the first part is applied to the study of air curtains.<br/><br/>Regarding to the first part, the principal difficulty of computing and modelling turbulent flows resides in the dominance of non-linear effects and the continuous and wide spectrum of time and length scales. Therefore, the use of turbulence modelling employing statistical techniques for high Reynolds numbers or complex geometries is still necessary. In general, this modelization is based on time averaging of the Navier-Stokes equations (this approach is known as Reynolds-Averaged Navier-Stokes Simulations, RANS). As consequence of the average new unknowns, so-called Reynolds stresses, arise. Different approaches to evaluate them are: i) Differentially Reynolds Stress Models (DRSM), ii) Explicit Algebraic Reynolds Stress Models (EARSM), and iii) Eddy Viscosity Models (EVM).<br/><br/>Although EVM models assuming a linear relation between the turbulent stresses and the mean rate of strain tensor are extensively used, they present various limitations. In the last few years, with the even-increasing computational capacity, new proposals to overcome many of these deficiencies have started to find their way. Thus, algebraic or non-linear relations are used to determinate the Reynolds stress tensor without introducing any additional differential equation.<br/><br/>Therefore, the first part of this thesis is devoted to the study of several EARSM and EVM models involving linear and higher order terms in the constitutive relation to evaluate turbulent stresses. Accuracy and numerical performance of these models is tested in different flow configurations such as plane channel, backward facing step, and both plane and round impinging jets. Special attention is paid to the verification of the code and numerical solutions, and the validation of the mathematical models used. In the impinging plane configuration, improvements of models using higher order terms in the constitutive relation are limited. Whereas, in the rest of studied cases these non-linear models show a reasonably good behaviour.<br/><br/>Moreover, taken into account models convergence, robustness and predictive realism observed in the analysis of these benchmark flows, some of them are selected for the study of air curtains and their interaction with the environment where they are placed. Air curtains are generally one or a set of vertical or horizontal plane jets used as ambient separator of adjacent areas presenting different conditions. The jet acts as a screen against energy losses/gains, moisture or mass exchanges between the areas.<br/><br/>As was indicated before, the main purpose of the second part of this thesis is to characterize in detail actual air curtains using both experimental and different numerical approaches. Semi-empirical models to design air curtains are presented. Then, an experimental set-up used to study air curtain discharge and jet downstream is explained. Experimental measurements of velocity and temperature are shown. As a result of the experiments carried out, an improved air curtain with a new design of the discharge nozzle is obtained. Furthermore, air curtain experiments are numerically reproduced and predictions validated against the experimental data acquired. Good agreement between numerical and experimental results is observed.<br/><br/>Finally, systematic parametric studies of air curtains in heating and refrigeration applications are done. Global energetic balances are specially considered together with global parameters selected in order to evaluate air curtain performance. It is found that discharge velocity, discharge angle and turbulence intensity of the jet are the most sensitive parameters. Inadequate values for these variables can produce undesirable effects and contribute to increase energy gains/losses.
publishDate 2008
dc.date.none.fl_str_mv 2008
2010
2010
2011
dc.type.none.fl_str_mv info:eu-repo/semantics/doctoralThesis
info:eu-repo/semantics/publishedVersion
format doctoralThesis
status_str publishedVersion
dc.identifier.none.fl_str_mv http://www.tdx.cat/TDX-0122110-202710
http://hdl.handle.net/10803/6696
https://dx.doi.org/10.5821/dissertation-2117-94007
url http://www.tdx.cat/TDX-0122110-202710
http://hdl.handle.net/10803/6696
https://dx.doi.org/10.5821/dissertation-2117-94007
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
application/pdf
dc.publisher.none.fl_str_mv Universitat Politècnica de Catalunya
publisher.none.fl_str_mv Universitat Politècnica de Catalunya
dc.source.none.fl_str_mv TDX (Tesis Doctorals en Xarxa)
reponame:TDR. Tesis Doctorales en Red
instname:CBUC, CESCA
instname_str CBUC, CESCA
reponame_str TDR. Tesis Doctorales en Red
collection TDR. Tesis Doctorales en Red
repository.name.fl_str_mv
repository.mail.fl_str_mv
_version_ 1869413190199148545
spelling Suitability of different RANS models in the description of turbulent forced convection flows: application to air curtainsJaramillo Ibarra, Julián ErnestoCFDcortinas de aireturbulenciavolumenes finitos621The main motivation of this thesis is the analysis of turbulent flows. Turbulence plays an important role in engineering applications due to the fact that most flows in industrial equipment and surroundings are in turbulent regime. The thesis has a double purpose and is divided in two main parts. The first one is focussed on the basic and fundamental analysis of turbulence models. In the second part the know-how acquired in the first part is applied to the study of air curtains.<br/><br/>Regarding to the first part, the principal difficulty of computing and modelling turbulent flows resides in the dominance of non-linear effects and the continuous and wide spectrum of time and length scales. Therefore, the use of turbulence modelling employing statistical techniques for high Reynolds numbers or complex geometries is still necessary. In general, this modelization is based on time averaging of the Navier-Stokes equations (this approach is known as Reynolds-Averaged Navier-Stokes Simulations, RANS). As consequence of the average new unknowns, so-called Reynolds stresses, arise. Different approaches to evaluate them are: i) Differentially Reynolds Stress Models (DRSM), ii) Explicit Algebraic Reynolds Stress Models (EARSM), and iii) Eddy Viscosity Models (EVM).<br/><br/>Although EVM models assuming a linear relation between the turbulent stresses and the mean rate of strain tensor are extensively used, they present various limitations. In the last few years, with the even-increasing computational capacity, new proposals to overcome many of these deficiencies have started to find their way. Thus, algebraic or non-linear relations are used to determinate the Reynolds stress tensor without introducing any additional differential equation.<br/><br/>Therefore, the first part of this thesis is devoted to the study of several EARSM and EVM models involving linear and higher order terms in the constitutive relation to evaluate turbulent stresses. Accuracy and numerical performance of these models is tested in different flow configurations such as plane channel, backward facing step, and both plane and round impinging jets. Special attention is paid to the verification of the code and numerical solutions, and the validation of the mathematical models used. In the impinging plane configuration, improvements of models using higher order terms in the constitutive relation are limited. Whereas, in the rest of studied cases these non-linear models show a reasonably good behaviour.<br/><br/>Moreover, taken into account models convergence, robustness and predictive realism observed in the analysis of these benchmark flows, some of them are selected for the study of air curtains and their interaction with the environment where they are placed. Air curtains are generally one or a set of vertical or horizontal plane jets used as ambient separator of adjacent areas presenting different conditions. The jet acts as a screen against energy losses/gains, moisture or mass exchanges between the areas.<br/><br/>As was indicated before, the main purpose of the second part of this thesis is to characterize in detail actual air curtains using both experimental and different numerical approaches. Semi-empirical models to design air curtains are presented. Then, an experimental set-up used to study air curtain discharge and jet downstream is explained. Experimental measurements of velocity and temperature are shown. As a result of the experiments carried out, an improved air curtain with a new design of the discharge nozzle is obtained. Furthermore, air curtain experiments are numerically reproduced and predictions validated against the experimental data acquired. Good agreement between numerical and experimental results is observed.<br/><br/>Finally, systematic parametric studies of air curtains in heating and refrigeration applications are done. Global energetic balances are specially considered together with global parameters selected in order to evaluate air curtain performance. It is found that discharge velocity, discharge angle and turbulence intensity of the jet are the most sensitive parameters. Inadequate values for these variables can produce undesirable effects and contribute to increase energy gains/losses.DOCTORAT EN ENGINYERIA TÈRMICA (Pla 1998)Universitat Politècnica de CatalunyaPérez Segarra, Carlos DavidOliva, AsensioUniversitat Politècnica de Catalunya. Departament de Màquines i Motors Tèrmics2011201020082010info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersionapplication/pdfapplication/pdfhttp://www.tdx.cat/TDX-0122110-202710http://hdl.handle.net/10803/6696https://dx.doi.org/10.5821/dissertation-2117-94007TDX (Tesis Doctorals en Xarxa)reponame:TDR. Tesis Doctorales en Redinstname:CBUC, CESCAInglésADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs.info:eu-repo/semantics/openAccessoai:www.tdx.cat:10803/66962026-06-14T12:46:07Z
score 15,300724

Similares en LA Referencia