Publications (6)0 Total impact
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Chapter: CICLoPE – A Large Pipe Facility for Detailed Turbulence Measurements at High Reynolds Number
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ABSTRACT: High Reynolds number turbulence is ubiquitous in a number of flow of practical interest and crucial to draw conclusions regarding the physics of turbulence. Although recent laboratory experiments, measurements in planetary boundary layer and direct numerical simulations provide a huge amount of information, none of these data sets provide high Reynolds number, high spatial resolution and well converged statistics at the same time. As a response to this problem, an international collaboration between a group of universities and research centers started some years ago to build large scale infrastructures for high Reynolds number experiments. The Center for International Cooperation in Long Pipe Experiments, CICLOPE (www.ciclope.unibo.it) at the University of Bologna, was created for this purpose and will be open to international scientists through different collaboration programs. The laboratory is currently under construction and the first facility, which will be installed there is a large pipe flow experiment that will allow fully resolved turbulence measurements even at high Reynolds number.12/2008: pages 73-77; -
Article: A mechanistic model of separation bubble
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ABSTRACT: This work uncovers the low-dimensional nature the complex dynamics of actuated separated flows. Namely, motivated by the problem of model-based predictive control of separated flows, we identify the requirements on a model-based observer and the key variables and propose a prototype model in the case of thick airfoils as motivated by practical applications. The approach in this paper differs fundamentally from the logic behind known models, which are either linear or based on POD-truncations and are unable to reflect even the crucial bifurcation and hysteresis inherent in separation phenomena. This new look at the problem naturally leads to several important implications, such as, firstly, uncovering the physical mechanisms for hysteresis, secondly, predicting a finite amplitude instability of the bubble, and thirdly to new issues to be studied theoretically and tested experimentally. More importantly, by employing systematic reasoning, the low-dimensional nature of these complex phenomena at the coarse level is revealed.11/2007; -
Article: Longitudinal vortices inducted in a stagnation region by wakes: Their incipient formation and effects on heat transfer from cylinders
06/1975; -
Article: A low-dimensional model of separation bubbles
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ABSTRACT: In this work, motivated by the problem of model-based predictive control of separated flows, we identify the key variables and the requirements on a model-based observer and construct a prototype low-dimensional model to be embedded in control applications.Namely, using a phenomenological physics-based approach and dynamical systems and singularity theories, we uncover the low-dimensional nature of the complex dynamics of actuated separated flows and capture the crucial bifurcation and hysteresis inherent in separation phenomena. This new look at the problem naturally leads to several important implications, such as, firstly, uncovering the physical mechanisms for hysteresis, secondly, predicting a finite amplitude instability of the bubble, and, thirdly, to new issues to be studied theoretically and tested experimentally.Physica D: Nonlinear Phenomena. -
Article: A low-dimensional model of separation bubbles
[show abstract] [hide abstract]
ABSTRACT: In this work, motivated by the problem of model-based predictive control of separated flows, we identify the key variables and the requirements on a model-based observer and construct a prototype low-dimensional model to be embedded in control applications. Namely, using a phenomenological physics-based approach and dynamical systems and singularity theories, we uncover the low-dimensional nature of the complex dynamics of actuated separated flows and capture the crucial bifurcation and hysteresis inherent in separation phenomena. This new look at the problem naturally leads to several important implications, such as, firstly, uncovering the physical mechanisms for hysteresis, secondly, predicting a finite amplitude instability of the bubble, and, thirdly, to new issues to be studied theoretically and tested experimentally. -
Article: Wall-bounded turbulent flows at high Reynolds numbers: Recent advances and key issues
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ABSTRACT: Wall-bounded turbulent flows at high Reynolds numbers have become an increasingly active area of research in recent years. Many challenges remain in theory, scaling, physical understanding, experimental techniques, and numerical simulations. In this paper we distill the salient advances of recent origin, particularly those that challenge textbook orthodoxy. Some of the outstanding questions, such as the extent of the logarithmic overlap layer, the universality or otherwise of the principal model parameters such as the von Kármán “constant,” the parametrization of roughness effects, and the scaling of mean flow and Reynolds stresses, are highlighted. Research avenues that may provide answers to these questions, notably the improvement of measuring techniques and the construction of new facilities, are identified. We also highlight aspects where differences of opinion persist, with the expectation that this discussion might mark the beginning of their resolution.
