Browsing by Keyword "CFD"
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Item Influence of the contact angle on the wettability of horizontal-tube falling films in the droplet and jet flow modes(2018-06) Fernández de Arroiabe, Peru; Martinez-Urrutia, Asier; Peña, Xabier; Martinez-Agirre, Manex; Bou-Ali, M. Mounir; Tecnalia Research & Innovation; SISTEMAS TÉRMICOS EFICIENTESWettability has a key impact on the performance of LiBr-H2O horizontal-tube falling film absorbers working under typical operating conditions. Therefore, it is necessary to study the influence of the wettability properties on the film hydrodynamics and wetted area. This work analyses the influence of the contact angle (0° – 120°) on the transient film hydrodynamics and the wetted area in the droplet and jet flow modes (7 ≤ Re ≤ 53). The comparison between two-dimensional and three-dimensional models evidences that three-dimensional models are needed for incomplete wetting conditions. The influence of the contact angle on both the film hydrodynamics and wetted area is demonstrated using 3D unsteady CFD model. Furthermore, the results indicate that each Reynolds number has a maximum contact angle to wet the whole tube steadily. When the value of the contact angle is lower than this maximum value, the contact angle has not influence on the wetting ratio. In contrast, at higher values, the wetting ratio decreases as the contact angle increases.Item Performance Assessment of Three Turbulence Models Validated through an Experimental Wave Flume under Different Scenarios of Wave Generation(Multidisciplinary Digital Publishing Institute (MDPI), 2020-11-05) Galera-Calero, Lander; Blanco, Jesús María; Izquierdo, Urko; Esteban, Gustavo AdolfoThis study aimed to adjust the turbulence models to the real behavior of the numerical wave flume (NWF) and the future research that will be carried out on it, according to the turbulence model that best adjusts to each particular case study. The k-", k-! and large-eddy simulation (LES) models, using the volume of fluid (VOF) method, were analyzed and compared respectively. The wavemaker theory was followed to faithfully reproduce the waves, which were measured in an experimental wave flume (EWF) and compared with the theory to validate each turbulence model. Besides, reflection was measured with the Mansard and Funke method, which has shown promising results when studying one of the most critical turbulent behaviors in the wave flume, called the breaking of the waves. The free surface displacement obtained with each turbulence model was compared with the recorded signals located at three points of the experimental wave flume, in the time domain of each run, respectively. Finally, the calculated reflection coefficients and the amplitudes of the reflected waves were compared, aiming to have a better understanding of the wave reflection process at the extinction zone. The research showed good agreement between all the experimental signals and the numerical outcomes for all the turbulence models analyzed.