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Large Eddy Simulation of the By-pass Transition Process under Different Inlet Turbulence Conditions

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Journal of Thermal Science 2021年第6期30卷 2112-2121页

作者： BARSI Dario COSTA Carlo LENGANI Davide simoni daniele UBALDI Marina DIME-University of Genova Via Montallegro 11-16145 GenovaItaly

The transition process of the boundary layer developing over a flat plate with elevated inlet Free Stream Turbulence Intensity(FSTI)has been studied by means of Large Eddy Simulation(LES).To this purpose,four cases with different inflow disturbances have been tested varying the magnitude and the length scale of *** has been performed by using the finite-volume ANSYS Fluent *** computational domain,which was constituted by a rectangular domain with a zero thickness plate,was based on an ERCOFTAC test case in order to provide a validation with a well-known set of data by comparing the boundary layer integral parameters and mean and fluctuating streamwise velocity *** four cases were discussed within the paper by looking at classical statistical properties as well as advanced post-processing *** was shown that the decrease in the free stream turbulence level postpones the transition location,whereas the variation of the integral length scale has a very low influence on the distribution of the time-mean flow *** Orthogonal Decomposition(POD)has been applied to the instantaneous LES flow fields in order to provide a statistical representation of the structures responsible for transition and their response to free-stream turbulence intensity and length *** presence of vortical filaments parallel to the wall,typically referred as boundary layer streaks,is clearly identified;their characteristic dimensions and how they change as a function of FSTI properties were analyzed within the paper.

关键词： by-pass transition Large Eddy Simulation(LES) Proper Orthogonal Decomposition(POD) boundary layer streaks

Experimental and Numerical Analysis of Cavity/Mean-Flow Interaction in Low Pressure Axial Flow Turbines

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Journal of Thermal Science 2021年第6期30卷 2178-2185页

作者： BARSI Dario COSTA Carlo LENGANI Davide simoni daniele VENTURINO Giulio ZUNINO Pietro DIME-Universita di Genova Via Montallegro 11-16145 Genova

The increasing performance of modern aeroengines led the research towards the optimization of machine components not deeply analyzed in the *** this context,the mechanisms driving the interaction process between the secondary flows evolving at the hub of low-pressure turbines with the rotor-stator cavity systems have been poorly investigated in the *** this work,an experimental and numerical analysis of the interaction between the endwall near wall flow and the leakage flow of a real cavity system is *** experimental results were carried out in the annular low-pressure axial flow turbine of the University of *** blade loading and pressure distributions into the cavity,as well as the measured total pressure loss coefficient,have been used for a proper validation of CFD *** steady and unsteady calculations were carried out through the commercial solver ***,several numerical approaches have been tested into this work:RANS,Non Linear Harmonic(NLH),and *** most promising CFD techniques have been firstly identified by comparison with experimental results and then systematically employed to extend the analysis of secondary flow-cavity flow interaction to positions and quantities not available from the *** characterizing the mean flow-cavity flow interaction process will be shown to cover a great amount of the overall stage losses and should be properly accounted for the design of future optimized cavity configurations.

关键词： axial flow turbine cavity mean-flow interaction experimental analysis CFD

Experimental Analysis of the Aerodynamic Performance of an Innovative Low Pressure Turbine Rotor

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Journal of Thermal Science 2016年第1期25卷 22-31页

作者： Infantino daniele Satta Francesca simoni daniele Ubaldi Marina Zunino Pietro Bertini Francesco DIME-Universita degli Studi di Genova Via MontaUegro 11-16145 GenovaItaly Avio Aero Viale I Maggio 56I-10040 Rivalta(TO)-Italy

In the present work the aerodynamic performances of an innovative rotor blade row have been experimentally investigated. Measurements have been carried out in a large scale low speed single stage cold flow facility at a Reynolds number typical of aeroengine cruise, under nominal and off-design conditions. The time-mean blade aerodynamic loadings have been measured at three radial positions along the blade height through a pressure transducer installed inside the hollow shaft, by delivering the signal to the stationary frame with a slip ring. The time mean aerodynamic flow fields upstream and downstream of the rotor have been measured by means of a five-hole probe to investigate the losses associated with the rotor. The investigations in the single stage research turbine allow the reproduction of both wake-boundary layer interaction as well as vortex-vortex interaction. The detail of the present results clearly highlights the strong dissipative effects induced by the blade tip vortex and by the momentum defect as well as the turbulence production, which is generated during the migration of the stator wake in the rotor passage. Phase-locked hot-wire investigations have been also performed to analyze the time-varying flow during the wake passing period. In particular the interaction between stator and rotor structures has been investigated also under off-design conditions to further explain the mechanisms contributing to the loss generation for the different conditions.

关键词： Low Pressure Turbine Single Stage Research Turbine Rotor Aerodynamic Loading Hot-wire Anemometry

Combined Experimental and Numerical Investigations on the Roughness Effects on the Aerodynamic Performances of LPT Blades

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Journal of Thermal Science 2016年第1期25卷 32-42页

作者： Marco Berrino Fabio Bigoni daniele simoni Matteo Giovannini Michele Marconcini Roberto Pacciani Francesco Bertini DIME-Universita di Genova Via Montallegro116145GenovaItaly DIEF-Universita di Firenze Via Santa Marta350139FirenzeItaly GE Avio R&D Via I Maggio9910140Rivalta(TO)Italy

The aerodynamic performance of a high-load low-pressure turbine blade cascade has been analyzed for three different distributed surface roughness levels(Ra) for steady and unsteady inflows. Results from CFD simulations and experiments are presented for two different Reynolds numbers(300000 and 70000 representative of take-off and cruise conditions, respectively) in order to evaluate the roughness effects for two typical operating conditions. Computational fluid dynamics has been used to support and interpret experimental results, analyzing in detail the flow field on the blade surface and evaluating the non-dimensional local roughness parameters, further contributing to understand how and where roughness have some influence on the aerodynamic performance of the blade. The total pressure distributions in the wake region have been measured by means of a five-hole miniaturized pressure probe for the different flow conditions, allowing the evaluation of profile losses and of their dependence on the surface finish, as well as a direct comparison with the simulations. Results reported in the paper clearly highlight that only at the highest Reynolds number tested(Re=300000) surface roughness have some influence on the blade performance, both for steady and unsteady incoming flows. In this flow condition profile losses grow as the surface roughness increases, while no appreciable variations have been found at the lowest Reynolds number. The boundary layer evolution and the wake structure have shown that this trend is due to a thickening of the suction side boundary layer associated to an anticipation of transition process. On the other side, no effects have been observed on the pressure side boundary layer.

关键词： low-pressure turbine high-load profile roughness unsteady inflow CFD

Strategic Focus and Business Model Organization： The Mean Field Analysis Approach

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Journal of Modern Accounting and Auditing 2011年第7期7卷 709-718页

作者： Paola Pisano daniele Manini Marco Gribaudo Marco Pironti University of Torino Torino Italy Polytechnic ofMilano Milano Italy University ofTorino Yorino Italy

The objective of this research is to show a new methodology for modeling phenomena present in complex economic systems. The case study we analyzed is the adoption of open organization model among firms operating in a particular industry. A firm with an open system model creates and captures value taking advantage not only from the internal resource but also from external. The organization could approach to open model acquisition using different focus： external focus namely looking out of its boundary, acting and reacting to competitor innovation, costumers＇ changing, demand growth, or internal focus remaining inside its boundary improving its best capabilities ignoring what happened outside （Vagnani, Moran, ＆ simoni, 2010）. The actors involved are firms, customers and suppliers linked together through a business to business model. The methodology is based on an Object-Oriented Analysis Field Model that allows to intuitively describe systems characterized by a large number of objects that interact, as in this case of a system composed by different organizational entities. The system simulation allows to analyze how the actors influence the acquisition and diffusion of the open organization model. This approach permits the generation of different classes of objects to represent all actors involved in the evolution of the system and to define the dynamics that determine their interaction. The solution of the model can be approximated using the Mean-Field analysis technique （Kurtz, 1978）, following the results proposed in Bobbio, Gribaudo, and Yelek （2008）. A qualitative result is illustrated in order to show the applicability of the proposed methodology and to emphasize its relevant features： flexible modeling approach, capacity of solving complex systems and output management facilities. The presented model is comprehensive and its scope is wide; it could be used to study the behavior of enterprises changing model in many different scenarios and situations. In future

关键词： diffusion open organization model internal focus external focus mean field analysis