727 research outputs found
Augmented Prediction of Turbulent Flows via Sequential Estimators Sensitivity of State Estimation to Density of Time Sampling for Available Observation
No full textInternational audienceA sensitivity analysis of new methodological approaches for state estimation (Meldi and Poux J. Comput. Phys. 347, 207-234, 2017) is proposed in this manuscript. The performance of the estimator is tested via the analysis of a number of aspects that play a major role in the augmented prediction process, such as the density in time sampling of available observation, the placement of sensors and the interaction with boundary conditions. The work is developed for the turbulent spatially evolving mixing layer test case, using high precision DNS samples as observation and Smagorinsky LES as underlying model. A number of estimators combining LES with DNS data integrated via sensors are performed, varying the frequency of time sampling of observation f T = 1// T , where T is the period between successive assimilation phases. It is concluded that if T ≤≈ 0.5t A , where t A is the characteristic average advection time, the prediction via estimator shows minimal differences i.e. the process of state estimation has reached convergence. This relation can be interpreted as a threshold for converged state estimation. However, the results show as well that a linear converge towards pure model performance is not obtained for every physical quantity with progressive decrease of f T , while eventually pure model results are obtained for f T → 0. In addition, the effect of upstream boundary conditions over the state estimation are investigated and strategies for optimized positions of sensors are derived
La Vestale 'incesta'
No full textMarcello Salvadore: La Vestale incesta.
Dionysius of Halicarnassus, Pliny the Younger and Plutarch are the sources
of a detailed account of Vestalis incesta’s punishment: they say that she was
sentenced to death. Dionysius adds that there was no after death ritual.
Modern scholars generally accept what the three authors assert. In this article
the author surmises that the Vestalis incesta, together with the parricida, was
not condemned to death: both of them were sentenced to a particular kind
of banishment from the Society
De Lope a Celano: la adaptación italiana de "Los tres diamantes"
No full textAbstract
This paper explores an Italian adaptation of Lope de Vega’s play Los tres diamantes, written in the
second part of the seventeenth century. Its author, Carlo Celano, was a famous writer of opere regie,
i.e., adaptations of Spanish comedies of situation. The analysis focuses on the way in which the
adaptation of the Aristotelian units of space and time leads to a reduction of the characters and a
simplification of the situation, although this is compensated by enriching its ludic component. This
last trait can be also observed in a previous re-elaboration of Lope’s comedy, the scenario of the
Commedia dell’arte titled Il cavaliere dai tre gigli d’oro
Error response surfaces in large eddy simulation of a spatially evolving mixing layer
No full textInternational audienceno abstrac
Due note critiche
No full textMarcello Garzaniti
Answers to Criticism
The author answers to the critics of M. Capaldo and A.Giambelluca Kossova with the aim to bring the different proposed questions back into the sphere of scientifi c dialogue
Multigrid sequential data assimilation for the Large Eddy Simulation of a massively separated bluff-body flow
No full textInternational audienceThe potential of sequential Data Assimilation (DA) techniques to improve the numerical accuracy of Large Eddy Simulation (LES) performed on coarse grid is assessed. Specifically, this paper evaluates the performance of the Multigrid Ensemble Kalman Filter (MGEnKF) method, recently introduced by Moldovan, Lehnasch, Cordier and Meldi (Journal of Computational Physics, 2021). The international benchmark referred to as BARC (Benchmark of the Aerodynamics of a Rectangular 5:1 Cylinder) is chosen as test configuration, as it includes several complex flow dynamics encountered in turbulence studies. The results for the statistical moments of the velocity and pressure flow field show that the data-driven techniques employed are able to significantly improve the predictive features of the solver for reduced grid resolution. In addition, it was observed that, despite the sparse and asymmetric distribution of observation in the data-driven process, the DA augmented LES exhibits symmetric statistics and a significantly improved accuracy also far from the observation zone
Simulations of the flow around a circular cylinder by a continuous universal hybrid model
No full textA new hybrid RANS/LES approach is presented.
The key feature of this approach is a blending between
two eddy-viscosities, one given by the k-\epsilon RANS
model and the other by the Smagorinsky VMS-LES
(variational multiscale LES) closure. The blending
is set by a parameter theta: VMS-LES mode is active when theta=0,
RANS mode if theta=1, a hybrid mode for 0<theta<1.
The hybrid model is applied to the simulation of the flow
around a circular cylinder at Re=140000, testing the sensitivity of the model to blending parameter variations, to grid refinements and to preconditioning changes.
The results are also compared with those obtained using the detached eddy simulation (DES) approach and with experimental data avaible in the literature
Quantification of epistemic uncertainties and parameter calibration in RANS turbulence models
No full textThanks to its limited computational requirements, the RANS approach has extensively been used and is still used to predict the low-order statistics of high Reynolds number turbulent flows. The main drawback is that an universal setup of the closure turbulence models has proved to be elusive. The free parameters present in turbulence models are usually derived from estimated deterministic values of some properties of benchmark turbulent flows, as e.g. the energy power law exponent for decaying homogeneous isotropic turbulence or the value of the Von Karman constant. The free parameters present in different well-known turbulence models are obtained herein by considering the underlying properties as random variables over a bounded range. This range has been recovered from the results reported in literature for the relevant properties, so that the considered epistemic uncertainty is realistic. The sensitivity to this uncertainty of the results of turbulent channel flow RANS simulations is then investigated for different Reynolds numbers and for two popular RANS models, viz. the K-epsilon Launder-Sharma and the Menter K-omega SST. The RANS solution is reconstructed over the continuous multi-dimensional uncertainty space of the considered random variables through the application of a surrogate model (response surface) obtained by means of generalized Polynomial Chaos. The model coefficients of the two considered RANS models are then calibrated and compared to literature standard values
The Pragmatics of Literature
No full textThis translation of the work of one of the founding fathers of literary structuralism and semiotics in Italy is a timely introduction to the theoretical study of literary communication. Marcello Pagnini is a leading figure in the post-structuralist endeavor to return the text to something resembling its social matrix. He explores not only the dynamics of the author/reader rapport but also the connections between the literary text and its sociocultural and historical contexts
Sulla presenza di Cipriano nel “De aleatoribus”
No full textIn ps.cyprianic De aleatoribus the whole way of composing shows
a deep assimilation of Cyprian’s model by the anonymous author.
The similarities attract attention for their evidence: the main subjects in common, the reference to single words and expressions, the similar structure of several sentences, the same expressions for introducing biblical quotations, the quotation of the same biblical texts too. Everything induces to admit that the anonymous author depends directly on Cyprian
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