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This paper is devoted to premixed combustion modeling in turbulent flow. First, we briefly remind the main features of the Self-Similar Turbulent Flame model that was more extensively developed in a former paper. Then, we carefully describe some improvements of the model. The determination of the turbulent flame velocity is based on the observed self-similarity of the turbulent flame and uses the local flame brush width as a fundamental parameter, which must be retrieved. With respect to the former version, we now derive more rigorously how the density variation has to be taken into account...
Monitoring the real-time behavior of spatial arrays of single living bacteria cells is only achieved with much experimental difficulty due to the small size and mobility of the cells. To address this problem, we have designed and constructed a simple microfluidic device capable of trapping single bacteria cells in spatially well-defined locations without the use of chemical surface treatments. The device exploits hydrodynamics to slow down and trap cells flowing near a narrow aperture. We have modeled this system numerically by approximating the motion of Escherichia coli cells as rigid 3-D...
The applicability of the commercial CFD-Program STAR-CD for hydraulic problems was evaluated by the pressure distribution downstream of an opening lock valve.Various valve operation speeds were modeled. This gave information about the possibility to simulate the flow around and induced by moving structures. Results of the numerical simulations were compared with results of physical model tests. Differences between measured and computed pressures in the unsteady flow were in a range of 1-2 percent, although the maximum differences in flow rates were about 15 percent.
A time dependence of three-dimensional simulation including water phase change and heat transfer of a PEMFC model has been studied. The overshoot behavior has been observed during a change in the electrical load during operation with fixed flow rates of hydrogen and air. The simulation of 25-cm2 active area with a serpentine flow path shows the interactions of the anode and cathode flow streams, the flow through the gas diffusion media, and the movement of water through the MEA by electroosmotic and back diffusion forces. The simulation used a commercial computational fluid dynamics (CFD)...
Optimization of marine vessels requires that the interaction between hull, propulsion and steering devices, and other appendages is taken into account. In addition, one needs to account for the variable floating position at different operating conditions. Due to the complexity of all interactions, experimental optimization is both costly and time-consuming. Computational methods can help in predicting efficiently the effects of design changes on resistance and other properties of the vessel.The aim of this paper is to present the results of several validation studies which include both...
Optimization of marine vessels requires that the interaction between hull, propulsion and steering devices, and other appendages is taken into account. In addition, one needs to account for the variable floating position at different operating conditions. Due to the complexity of all interactions, experimental optimization is both costly and time-consuming. Computational methods can help in predicting efficiently the effects of design changes on resistance and other properties of the vessel. The aim of this paper is to present the results of several validation studies which include both...
Based on the successful predictions of transient drop sizes in the first part of this research (Maaß et al., Prediction of drop sizes for liquid–liquid systems in stirred slim reactors—part I: single stage impellers. Chem. Eng. J., 162 (2010) 792–801), this part is a straight continuation and extension of the earlier work. The predictive capabilities of the used population balance equation model are increased for single stage impellers and transferred to scale-up procedures of such applications. Therefore different scale-up rules for liquid–liquid systems are tested experimentally and by...
This paper presents recent results obtained as part of the on-going integral validation of an advanced Eulerian-Eulerian two-phase (E2P) computational fluid dynamics based boiling model that allows the detailed analysis of the two-phase flow and heat transfer phenomena in a Boiling Water Reactor (BWR) fuel assembly. The code is being developed as a customized module built on the foundation of the commercial CFD-code STAR-CD which provides general two-phase flow modeling capabilities. Simulations of a prototypic BWR fuel assembly experiment have been completed as an initial assessment of the...
Prediction of bubble size which governs interfacial transfer terms between the two phases is of importance for an accurate prediction of the subcooled boiling flow. In the present work, a mechanistic bubbles size model, S was examined to enhance the prediction capability of subcooled boiling flows for the CFD (computational fluid dynamics) code. In addition to this, advanced subcooled boiling models such as new wall boiling and two-phase logarithmic wall function models were also applied for an improvement of energy partitioning and two-phase turbulence models, respectively. The benchmark...
In order to enhance the prediction capability of subcooled boiling flows, an advanced wall boiling model and mechanistic bubbles size model were examined using a CFD (Computational Fluid Dynamics) code. The advanced wall boiling model consists of a mechanistic bubble departure size model (Klausner et al., 1993), Hibiki et al.’s (2009) active nucleate site density model and Cole’s (1960) bubble departure frequency model. To ensure a wide range applicability of the advanced wall boiling model, each sub-model was evaluated separately over a wide range of flow conditions in pressure, temperature...

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