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Capizzano F.,Centro Italiano Ricerche Aerospaziali
AIAA Journal | Year: 2011

This paper describes the development of a wall model to extend the applicability of immersed boundary methods to high-Reynolds-number flows. A two-layer approach, based on a decomposition of the near-wall region, is adopted. An outer region is governed by the compressible Reynolds-averaged Navier-Stokes equations, which are solved numerically by using a classical finite volume method. In the proximity of the wall, an inner zone is established and modeled by a simplified version of the thin-boundary-layer equations. The simulation platform is based on Cartesian meshes and an immersed boundary technique. It is able to solve the steady Euler/Reynolds-averaged Navier-Stokes equations in two-and three-dimensional coordinates. The robustness and the accuracy of the methodology are discussed. At present, this work represents the last advance of a research activity for which the final goal is a fast predesign tool for aeronautical/industrial applications. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

Carozza A.,Centro Italiano Ricerche Aerospaziali
Applied Thermal Engineering | Year: 2016

This paper deals with the numerical analysis of the effect a heat exchanger has on the flow field in an oil cooling system for aerospace applications. To this end, an important upgrade of the UZEN in house CIRA Reynolds Averaged Navier-Stokes solver has been carried out to account for the pressure drop and heat rejection that usually are present in a heat exchanger. This upgrade is based on the addition of a source term in the momentum and energy equations of balance, respectively, whose values are updated during the simulation. The correspondent code modification needs a proper validation before any concrete application. At this aim, a two dimensional channel has been firstly studied in order to test the accuracy of the UZEN code. Then a three dimensional circular duct has been studied with a porous insert to validate the porous approach robustness. After this preliminary campaign of assessment, a new generation two engine aircraft has been studied with particular emphasis on its nacelle cooling system. Velocity and pressure are compared using different turbulence models with the well known Fluent ones. The more interesting parameter for such an investigation is the mass flow rate through the cooling ducts as computed by UZEN that show a good agreement with the Fluent one. © 2016 Elsevier Ltd. All rights reserved. Source

Cozzolino D.,University of Naples Federico II | Parrilli S.,Centro Italiano Ricerche Aerospaziali | Scarpa G.,University of Naples Federico II | Poggi G.,University of Naples Federico II | Verdoliva L.,University of Naples Federico II
IEEE Geoscience and Remote Sensing Letters | Year: 2014

Despeckling techniques based on the nonlocal approach provide an excellent performance, but exhibit also a remarkable complexity, unsuited to time-critical applications. In this letter, we propose a fast nonlocal despeckling filter. Starting from the recent SAR-BM3D algorithm, we propose to use a variable-size search area driven by the activity level of each patch, and a probabilistic early termination approach that exploits speckle statistics in order to speed up block matching. Finally, the use of look-up tables helps in further reducing the processing costs. The technique proposed conjugates excellent performance and low complexity, as demonstrated on both simulated and real-world SAR images and on a dedicated SAR despeckling benchmark. © 2013 IEEE. Source

Capizzano F.,Centro Italiano Ricerche Aerospaziali
AIAA Journal | Year: 2016

Immersed boundary methods showed a good compliance for a wide range of complex inviscid and viscous flows. Moreover, the high-Reynolds-number regime still remains an open issue. The paper describes a wall-layer approach to answer the need of a model that goes beyond the actual capability of classical wall functions. A near-wall region is established that gets information from the outer flowfield and returns back the wall stress. The latter is obtained by integrating simplified thin-boundary-layer equations along a normal to the wall subgrid. In the outer zone, the compressible Reynolds-averaged Navier-Stokes equations are solved by means of a finite volume method on two-or three-dimensional Cartesian meshes. The classic validation test dealing with a high-Reynolds-number flow over a flat plate is carried out. A benchmark two-dimensional complex flow is numerically investigated to assess the performance of the wall model in case of a pressure-induced separation. The results are compared with both experiments and body-conforming numerical solutions. © Copyright 2015 by the authors. Source

Viviani A.,The Second University of Naples | Pezzella G.,Centro Italiano Ricerche Aerospaziali | Pezzella G.,Research Engineer
Journal of Spacecraft and Rockets | Year: 2010

This paper deals with aerodynamic and aerothermodynamic studies carried out to design a capsule vehicle suitable for the recovery of crew members from the International Space Station and/or from exploration missions to the moon or Mars. An integrated design tool called ENTRY is used to support vehicle reentry analysis and computational fluid dynamics design activities. A possible low-Earth-orbit reentry scenario, with the associated aeroheating environment, is generated and then analyzed. Several Euler and Navier-Stokes computations are performed to simulate the flowfleld past the vehicle, for both perfect-gas and nonequilibrium reacting-gas models for the air. Numerical results and their comparison with flight data and wind-tunnel data are presented. An analysis of flowflelds, obtained from numerical computations, is provided by means of flight forces and moments coefficients. Experimentally measured surface pressure distributions and aerodynamic coefficients compare rather well with numerical results. Source

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