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    Limits of the Oberbeck¿Boussinesq approximation in a tall differentially heated cavity filled with water  Open access

     Kizildag, Deniz; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio; Lehmkuhl Barba, Oriol
    International journal of heat and mass transfer
    Date of publication: 2014-01-01
    Journal article

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    The present work assesses the limits of the Oberbeck¿Boussinesq (OB) approximation for the resolution of turbulent fluid flow and heat transfer inside a tall differentially heated cavity of aspect ratio G = 6.67 filled with water (Pr = 3.27, Ra = 2.12e11). The cavity models the integrated solar collector-storage element installed on an advanced façade. The implications of the Oberbeck¿Boussinesq approximation is submitted to investigation by means of direct numerical simulations (DNS) carried out for a wide range of temperature differences. Non-Oberbeck¿Boussinesq (NOB) effects are found to be relevant, especially beyond the temperature difference of 30 °C, in the estimation of heat transfer, stratification, and flow configuration.

    The present work assesses the limits of the Oberbeck–Boussinesq (OB) approximation for the resolution of turbulent fluid flow and heat transfer inside a tall differentially heated cavity of aspect ratio G = 6.67 filled with water (Pr = 3.27, Ra = 2.12e11). The cavity models the integrated solar collector-storage element installed on an advanced façade. The implications of the Oberbeck–Boussinesq approximation is submitted to investigation by means of direct numerical simulations (DNS) carried out for a wide range of temperature differences. Non-Oberbeck–Boussinesq (NOB) effects are found to be relevant, especially beyond the temperature difference of 30 °C, in the estimation of heat transfer, stratification, and flow configuration.

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    Large eddy and direct numerical simulations of a turbulent water-filled differentially heated cavity of aspect ratio 5  Open access

     Kizildag, Deniz; Trias Miquel, Francesc Xavier; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio
    International journal of heat and mass transfer
    Date of publication: 2014-10-01
    Journal article

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    Natural convection in a differentially heated cavity is characterized by different phenomena such as laminar to turbulent flow transition in the boundary layer, turbulent mixing, and thermal stratification in the core of the cavity. In order to predict the thermal and fluid dynamic behavior of the flow in these cavities, the location of transition to turbulence should be accurately determined. In this work, the performance of three subgrid-scale (SGS) models is submitted to investigation in a water-filled cavity of aspect ratio 5 at Rayleigh number Ra=3e11. To do so, the models are compared with the solution obtained by means of direct numerical simulation. The models tested are: (i) the wall-adapting local-eddy viscosity (WALE) model, (ii) the QR model, (iii) the WALE model within a variational multiscale framework (VMS-WALE). It has been shown that the VMS-WALE and WALE models perform better in estimating the location of transition to turbulence, and thus their overall behavior is more accurate than the QR model. The results have also revealed that the use of SGS models is justified in this flow as the transition location and consequently the flow structure cannot be captured properly if no model is used for the tested spatial resolution.

    Natural convection in a differentially heated cavity is characterized by different phenomena such as laminar to turbulent flow transition in the boundary layer, turbulent mixing, and thermal stratification in the core of the cavity. In order to predict the thermal and fluid dynamic behavior of the flow in these cavities, the location of transition to turbulence should be accurately determined. In this work, the performance of three subgrid-scale (SGS) models is submitted to investigation in a water-filled cavity of aspect ratio 5 at Rayleigh number Ra=3e11. To do so, the models are compared with the solution obtained by means of direct numerical simulation. The models tested are: (i) the wall-adapting local-eddy viscosity (WALE) model, (ii) the QR model, (iii) the WALE model within a variational multiscale framework (VMS-WALE). It has been shown that the VMS-WALE and WALE models perform better in estimating the location of transition to turbulence, and thus their overall behavior is more accurate than the QR model. The results have also revealed that the use of SGS models is justified in this flow as the transition location and consequently the flow structure cannot be captured properly if no model is used for the tested spatial resolution.

  • Direct and large-eddy simulation of non-oberbeck-boussinesq effects in a turbulent differentially heated cavity

     Kizildag, Deniz; Trias Miquel, Francesc Xavier; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio
    ERCOFTAC Workshop on Direct and Large-Eddy Simulation
    Presentation's date: 2013-04-04
    Presentation of work at congresses

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  • On the validity of the Oberbeck-Boussinesq approximation in a tall differentially heated cavity with water

     Kizildag, Deniz; Rodriguez Pérez, Ivette Maria; Castro Gonzalez, Jesus
    Progress in computational fluid dynamics
    Date of publication: 2012-07-26
    Journal article

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    On the validity of the Boussinesq approximation in a tall differentially heated cavity with water  Open access

     Kizildag, Deniz; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio
    International Conference on Computational Heat and Mass Transfer
    Presentation's date: 2011-07-19
    Presentation of work at congresses

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    In the present work, the fluid flow and heat transfer inside an integrated solar collector installed on an advanced fac¸ade are investigated. According to Gray and Giorgini [1], the use of the Boussinesq approximation can be considered valid for variations of thermosphysical properties up to 10 % with respect to the mean value. In the configuration under study, there is a variation of about 20 % in the dynamic viscosity and 15 % in the thermal expansion coefficient. Thus, the main objective of this work is to analyse the validity of the Boussinesq approximation for the turbulent natural convection flow of water in a rectangular parallelepiped tank. The significance of the Boussinesq effects is studied comparatively by means of detailed DNS simulations.

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    Development of a multi-functional ventilated façade with an integrated collector-storage: numerical model and experimental facility  Open access

     Kizildag, Deniz; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio
    ISES Solar World Congress
    Presentation's date: 2011-08-29
    Presentation of work at congresses

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    The paper reports on physical modeling and experimental evaluation of glazed systems. A multi-functional ventilated façade with an integrated collector-storage is developed and mounted on a test cell facility under real weather conditions. The component uses solar radiation to produce solar heated water flow, which in turn can provide space heating or fulfill domestic hot water demands. Different operational modes of the ventilation channel are analyzed in order to improve the thermal performance of the buildings with glazed façades. The existing numerical platform for the prediction of the thermal performance of buildings and solar systems is used to implement a numerical model to address the multi-functional ventilated façade with integrated collector-storage element. The model uses the measured outdoor data as boundary conditions to obtain predictions by means of a general energy balance in the test room and the façade component. The model permits different levels of simulation depending on the desired precision in each element, applying a modular methodology. In this study, the convection heat transfer coefficient within the parallelepiped storage tank is obtained from a direct numerical simulation (DNS) of turbulent natural convection flow of water, while the remaining empirical information is obtained from the literature for similar geometries.

    Postprint (author’s final draft)

  • Verification of Multidimensional and Transient CFD Solutions

     Orozco Piñeiro, Cristian; Kizildag, Deniz; Oliva Llena, Asensio; Perez Segarra, Carlos David
    Numerical heat transfer. Part B, fundamentals
    Date of publication: 2010
    Journal article

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  • DESARROLLO NUEVOS ALGORITMOS PARA LA APLICACION DE TECNICAS LES A LA SIMULACION DEL COMPORTAMIENTO TERMICO Y FLUIDO-DINAMICO

     Kizildag, Deniz; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio; Soria Guerrero, Manel
    Participation in a competitive project

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    Non-Oberbeck-Boussinesq natural convection in a tall differentially heated cavity  Open access

     Kizildag, Deniz; Ventosa Molina, Jordi; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio
    European Conference on Computational Fluid Dynamics
    Presentation's date: 2010-06-16
    Presentation of work at congresses

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    Turbulent flow in a water-filled rectangular parallelepiped tank of an integrated solar collector is analyzed by means of a set of two and three dimensional simulations. The geometry and the working conditions of the prototype yield an aspect ratio of Γ = 6:68, Rayleigh number of Ra = 2:2 x 10 11 and a Prandtl number of Pr = 3:42. Diff erent coarse DNS simulations and LES simulations using the dynamic Smagorinsky SGS and WALE model are presented. Validity of the Oberbeck-Boussinesq approximation is questioned. Heat transfer and first and second order statistics are studied.

  • CENTRE TECNOLOGIC TRANSFERENCIA CALOR

     Sadurni Caballol, Alexandre; Mohan Damle, Rashmin; Carmona Muñoz, Angel; Torras Ortiz, Santiago; Lopez Mas, Joan; Rigola Serrano, Joaquim; Kizildag, Deniz; Ablanque Mejia, Nicolas; Lehmkuhl Barba, Oriol; Soria Guerrero, Manel; Gorobets, Andrey; Capdevila Paramio, Roser; Castro Gonzalez, Jesus; Jaramillo Ibarra, Julian Ernesto; Morales Ruiz, Sergio; Trias Miquel, Francesc Xavier; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Perez Segarra, Carlos David; Borrell Pol, Ricard; Oliva Llena, Asensio
    Participation in a competitive project

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  • Numerical simulations of natural convection flow in a rectangular cavity under transient boundary conditions.

     Kizildag, Deniz
    Fifth European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS)
    Presentation's date: 2008-06-30
    Presentation of work at congresses

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  • Numerical simulations of natural convection flow in a rectangular cavity under transient boundary conditions

     Kizildag, Deniz; Perez Segarra, Carlos David; Oliva Llena, Asensio; Rodriguez Pérez, Ivette Maria
    Fifth European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS)
    Presentation of work at congresses

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