Castilla, R.; Gamez-Montero, P.J.; Raush, G.; Codina-Macia, Esteban Journal of fluids engineering. Transactions of ASME Vol. 139, num. 11, p. 1-9 DOI: 10.1115/1.4037060 Data de publicació: 2017-07-21 Article en revista
A new approach based on the open source tool OpenFOAM is presented for the numerical simulation of a mini gerotor pump working at low pressure. The work is principally focused on the estimation of leakage flow in the clearance disk between pump case and gears. Two main contributions are presented for the performance of the numerical simulation. On one hand, a contact point viscosity model is used for the simulation of solid–solid contact between gears in order to avoid the teeth tip leakage. On the other hand, a new boundary condition has been implemented for the gear mesh points motion in order to keep the mesh quality while moving gears with relative velocity. Arbitrary coupled mesh interface (ACMI) has been used both in the interface between clearance disk in inlet/outlet ports and between clearance disk and interteeth fluid domain. Although the main goal of the work is the development of the numerical method rather than the study of the physical analysis of the pump, results have been compared with experimental measurement and a good agreement in volumetric efficiency and pressure fluctuations has been found. Finally, the leakage flow in the clearance disk has been analyzed.
Liu, X.; Zhou, L.; Wang, Z.; Escaler, X.; Luo, Y.; Torre, O. Journal of fluids engineering. Transactions of ASME Vol. 139, num. 4, p. 1-8 DOI: 10.1115/1.4035113 Data de publicació: 2017-01-20 Article en revista
A fluid-structure interaction system has been solved using the coupled acoustic structural finite element method to simplify the cavitating flow conditions around a hydrofoil. The modes of vibration and the added mass effects have been numerically simulated for various flow conditions including leading edge attached partial cavitation on a 2D NACA0009 hydrofoil. The hydrofoil has been first simulated surrounded by only air and by only water. Then, partial cavities with different lengths have been modeled as pure vapor fluid domains surrounded by the corresponding water and solid domains. The obtained numerical added mass coefficients and mode shapes are in good agreement with the experimental data available for the same conditions. The study confirms that the fluid added mass effect decreases with the cavitation surface ratio and with the thickness of the cavitation sheet. Moreover, the simulations also predict slight mode shape variations due to cavitation that have also been detected in the experiments. Finally, the effects of changes in cavity location have been evaluated with the previously validated model.
Coussirat, M.; Moll, F.; Cappa, E. Franco; Fontanals, A. Journal of fluids engineering. Transactions of ASME Vol. 138, num. 9, p. 091304-1-091304-13 DOI: 10.1115/1.4033372 Data de publicació: 2016-09 Article en revista
Cavitating flow in nozzles is a complex flow which implies a highly turbulent two-phase
one. An accurate simulation which improves some numerical results found in the literature was achieved by means of an extensive analysis of the capabilities of several numerical models for turbulence and cavitation. The analysis performed involves calibration/
optimization tasks based on the physics of this kind of flow. This work aims to provide a quantitative criterion for the judgment of internal flow state, because it was demonstrated that the numerical results obtained with noncalibrated models could be enhanced by means of a careful calibration and thus saving computational costs.
Castilla, R.; Gamez-Montero, P.J.; Del Campo, D.; Raush, G.; M. Garcia-Vilchez; Codina-Macia, Esteban Journal of fluids engineering. Transactions of ASME Vol. 137, num. 4, p. 041105-1-041105-10 DOI: 10.1115/1.4029223 Data de publicació: 2015-04-01 Article en revista
Recently several works have been published on numerical simulation of an external gear pump (EGP). Such kinds of pumps are simple and relatively inexpensive, and are frequently used in fluid power applications, such as fluid power in aeronautical, mechanical, and civil engineering. Nevertheless, considerable effort is being undertaken to improve efficiency and reduce noise and vibration produced by the flow and pressure pulsations. Numerical simulation of an EGP is not straightforward principally for two main reasons. First, the gearing mechanism between gears makes it difficult to handle a dynamic mesh without a considerable deterioration of mesh quality. Second, the dynamic metal-metal contact simulation is important when high pressure outflow has to be reproduced. The numerical studies published so far are based on a two-dimensional (2D) approximation. The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster. The 3D flow is simulated in a LINUX cluster with a solver developed with the OPENFOAM Toolbox. The hexahedral mesh quality is maintained by periodically replacing the mesh and interpolating the physical magnitudes fields. The meshing contact point is simulated with the viscous wall approach, using a viscosity model based on wall proximity. The results for the flow rate ripples show a similar behavior to that obtained with 2D simulations. However, the flow presents important differences inside the suction and the discharge chambers, principally in the regions of the pipes' connection. Moreover, the decompression slot below the gearing zone, which can not be simulated with a 2D approximation, enables a more realistic simulation of a contact ratio greater than 1. The results are compared with experimental measurements recently published.
A full-scale Francis turbine has been experimentally investigated over its full range of operation to detect draft tube swirling flows and cavitation. The unit is of interest due to the presence of severe pressure fluctuations at part load and of advanced blade suction-side cavitation erosion. Moreover, the turbine has a particular combination of guide vanes (20) to runner blades (15) that makes it prone to significant rotor-stator interaction (RSI). For that, a complete measurement system of dynamic pressures, temperatures, vibrations, and acoustic emissions has been setup with the corresponding transducers mounted at selected sensitive locations. The experiments have comprised an efficiency measurement, a signal transmissibility evaluation, and the recording of the raw signals at high sampling rates. Signal processing methods for demodulation, peak power estimation, and cross correlation have also been applied. As a result, draft tube pressure fluctuations have been detected around the Rheingans frequency for low loads and at 4% of the rotating frequency for high loads. Moreover, maximum turbine guide bearing acoustic emissions have been measured at full load with amplitude modulations at both the guide vane passing frequency and the draft tube surge frequency.
Del Campo, D.; Castilla, R.; Raush, G.; Gamez-Montero, P.J.; Codina-Macia, Esteban Journal of fluids engineering. Transactions of ASME Vol. 134, num. 8 DOI: 10.1115/1.4007106 Data de publicació: 2012-08 Article en revista
Coussirat, M.; van Beeck, J.; Mestres, M.; Egusquiza, E.; Buchlin, J.-M; Escaler, X. Journal of fluids engineering. Transactions of ASME Vol. 127, num. 4, p. 691-703 DOI: 10.1115/1.1949634 Data de publicació: 2005-07-15 Article en revista
Computational fluid dynamics plays an important role in engineering design. To gain insight into solving problems involving complex industrial flows, such as impinging gas-jet systems (IJS), an evaluation of several eddy viscosity models, applied to these IJS has been made. Good agreement with experimental mean values for the field velocities and Nusselt number was obtained, but velocity fluctuations and local values of Nusselt number along the wall disagree with the experiments in some cases. Experiments show a clear relation between the nozzle-to-plate distance and the Nusselt number at the stagnation point. Those trends were only reproduced by some of the numerical experiments. The conclusions of this study are useful in the field of heat transfer predictions in industrial IJS devices, and therefore for its design.
Coussirat, M.; van Beeck, J.; Mestres, M.; Egusquiza, E.; Buchlin, J.-M; Valero, M. Journal of fluids engineering. Transactions of ASME Vol. 127, num. 4, p. 704-713 DOI: 10.1115/1.1949635 Data de publicació: 2005-07-15 Article en revista
A numerical analysis of the flow behavior in industrial cooling systems based on arrays of impinging jets has been performed, using several eddy viscosity models to determine their modeling capabilities. For the cooling system studied, and in terms of mean Nusselt number values, the best agreement between experimental results and numerical predictions was obtained with the realizable k-e model. On the other hand, numerical predictions of the local Nusselt number and its spatial variations along the wall are better adjusted to the experiments when using either the standard k-e or the standard k-¿ models. The results obtained also show that the predicted thermal field depends strongly on the combination of near-wall treatment and selected turbulence model.