scispace - formally typeset
Search or ask a question
Author

Renzo Arina

Other affiliations: University of Turin
Bio: Renzo Arina is an academic researcher from Polytechnic University of Turin. The author has contributed to research in topics: Aeroacoustics & Euler equations. The author has an hindex of 11, co-authored 59 publications receiving 391 citations. Previous affiliations of Renzo Arina include University of Turin.


Papers
More filters
Journal ArticleDOI

[...]

TL;DR: In this article, a numerical method for the simulation of supercritical fluid flow phenomena, valid for a general real gas equation of state, is presented, where three state equations (van der Waals, Carnahan-Starling-De Santis, Redlich-Kwong) describing the thermodynamic behavior of a gas near its critical point are implemented.
Abstract: Supercritical fluids represent an active field of research, interesting from the theoretical point of view, and for industrial applications. We describe a numerical method for the simulation of supercritical fluid flow phenomena, valid for a general real gas equation of state. Three state equations (van der Waals, Carnahan-Starling-De Santis, Redlich-Kwong), describing the thermodynamic behavior of a gas near its critical point are implemented. Numerical tests in the case of the flow through a nozzle and the shock tube problem, show the reliability of the numerical scheme. The response of a supercritical fluid confined into a slab with closed ends, initially at rest in thermodynamic equilibrium, when one boundary is heated, termed Piston effect, is also investigated.

51 citations

Proceedings ArticleDOI

[...]

22 Jun 2015
TL;DR: This documentation summarizes the results from workshop category 1 (BANC-III-1) which focuses on the prediction of broadband turbulent boundary-layer trailing-edge noise and related source quantities.
Abstract: The Third Workshop on Benchmark Problems for Airframe Noise Computations, BANC-III, was held on 14-15 June 2014 in Atlanta, Georgia, USA. The objective of this workshop was to assess the present computational capability in the area of physics-based prediction of different types of airframe noise problems and to advance the state-of-the-art via a combined effort. This documentation summarizes the results from workshop category 1 (BANC-III-1) which focuses on the prediction of broadband turbulent boundary-layer trailing-edge noise and related source quantities. Since the forerunner BANC-II workshop identified some room for improvements in the achieved prediction quality, BANC-III-1 relies on the same test cases, namely 2D NACA0012 and DU96-W-180 airfoil sections in a uniform flow. Compared to BANC-II particularly the scatter among predictions for the DU96-W- 180 test case could be significantly reduced. However, proposed adaptations of previously applied computational methods did not systematically improve the prediction quality for all requested parameters. The category 1 workshop problem remains a challenging simulation task due to its high requirements on resolving and modeling of turbulent boundary-layer source quantities.

46 citations

Journal ArticleDOI

[...]

TL;DR: In this paper, a numerical model for the exhaust noise radiation problem is presented, in which an incoming wave is propagating through the exhaust nozzle, or the fan duct, and radiating outside.
Abstract: A numerical model for the exhaust noise radiation problem is presented. In the model, it is assumed that an incoming wave is propagating through the exhaust nozzle, or the fan duct, and radiating outside. The near-field propagation is based on the solution of the linearized Euler equations in the frequency domain: for each wave number, a linearized Euler problem is solved using a finite element method on unstructured grids for arbitrarily shaped axisymmetric geometries. The frequency-domain approach enables the suppression of the Kelvin-Helmholtz instability waves. Moreover, each single calculation, limited to a single frequency, is well suited to the exhaust noise radiation problem in which the incoming wave can be treated as a superposition of elementary duct modes. To reduce the memory requirements, a continuous Galerkin formulation with linear triangular and quadrangular elements is employed and the global matrix inversion is performed with a direct solver based on a parallel memory distributed multifrontal algorithm for sparse matrices. The acoustic near field is then radiated in the far field using the formulation of Ffowcs Williams and Hawkings. Numerical calculations for a validation test case, the Munt problem, and two turbomachinery configurations are compared with analytical solutions and experimental data.

41 citations

Journal ArticleDOI

[...]

TL;DR: In this article, a reduced-order model based on the proper orthogonal decomposition applied to a small number of high-fidelity solutions can be used to generate aerodynamic data with good accuracy at a low cost.
Abstract: A surrogate model based on the proper orthogonal decomposition is developed in order to enable fast and reliable evaluations of aerodynamic fields. The proposed method is applied to subsonic turbulent flows and the proper orthogonal decomposition is based on an ensemble of high-fidelity computations. For the construction of the ensemble, fractional and full factorial planes together with central composite design-of-experiment strategies are applied. For the continuous representation of the projection coefficients in the parameter space, response surface methods are employed. Three case studies are presented. In the first case, the boundary shape of the problem is deformed and the flow past a backward facing step with variable step slope is studied. In the second case, a two-dimensional flow past a NACA 0012 airfoil is considered and the surrogate model is constructed in the (Mach, angle of attack) parameter space. In the last case, the aerodynamic optimization of an automotive shape is considered. The results demonstrate how a reduced-order model based on the proper orthogonal decomposition applied to a small number of high-fidelity solutions can be used to generate aerodynamic data with good accuracy at a low cost.

31 citations

Proceedings ArticleDOI

[...]

04 Jun 2012
TL;DR: In this article, the authors investigated the effect of sharp saw-tooth serrations at the trailing edge of a serrated airfoil and showed that the structure of the flow field near the trailing edges is strongly affected by the presence of the serrations.
Abstract: The main objective of the present work is to investigate the mechanism of trailing-edge airfoil noise. The vorticity associated with the unsteady turbulent structures is scattered by the trailing edge and acoustic waves are generated. It has been recognized that trailing-edge noise can be reduced by introducing sharp sawtooth serrations at the trailing-edge. The flow past a serrated airfoil, with free-stream Reynolds number 6.0 × 10 5 and Mach number M = 0 .17 , is studied. A compressible Large Eddy Simulation is used for computing the near field, and the far-field acoustic propagation is obtained applying the integral formulation of Ffowcs Williams and Hawkings. The results of the serrated configurations, and its baseline geometry, are compared with the experimental data obtained by ISVR in the frame of the European Project FLOCON. It is shown that the structure of the flow field near the trailing edge is strongly affected by the presence of the serrations. The integral scale lengths of the flow structures in the wake near the trailing edge, are much smaller than in the baseline case. The OASPL directivities of the acoustic far-field are in good agreement with the experimental data, and the serrated airfoil presents a reduction of acoustic PSD in the low and mid frequency ranges, with a reduction ranging from � 10 dB at low frequencies, to � 5 dB in the mid range. For higher frequencies, the PSD levels of the serrated airfoil become comparable ( f � 4000 Hz) and then are higher with respect to the baseline spectrum.

20 citations


Cited by
More filters
Book ChapterDOI

[...]

01 Jan 1997
TL;DR: The boundary layer equations for plane, incompressible, and steady flow are described in this paper, where the boundary layer equation for plane incompressibility is defined in terms of boundary layers.
Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

2,288 citations

Journal ArticleDOI

[...]

TL;DR: A versatile, high-order accurate immersed boundary method for solving the LPCE in complex domains by combining the ghost-cell approach with a weighted least-squares error method based on a high- order approximating polynomial.
Abstract: A new sharp-interface immersed boundary method based approach for the computation of low-Mach number flow-induced sound around complex geometries is described. The underlying approach is based on a hydrodynamic/acoustic splitting technique where the incompressible flow is first computed using a second-order accurate immersed boundary solver. This is followed by the computation of sound using the linearized perturbed compressible equations (LPCE). The primary contribution of the current work is the development of a versatile, high-order accurate immersed boundary method for solving the LPCE in complex domains. This new method applies the boundary condition on the immersed boundary to a high-order by combining the ghost-cell approach with a weighted least-squares error method based on a high-order approximating polynomial. The method is validated for canonical acoustic wave scattering and flow-induced noise problems. Applications of this technique to relatively complex cases of practical interest are also presented.

142 citations

Journal ArticleDOI

[...]

TL;DR: In this paper, the authors investigated the fully nonlinear regular and focused wave propagation and diffraction around a vertical circular cylinder in a numerical wave tank, where the mixed Eulerian-Lagrangian approach was used to update the moving boundary surfaces in a Lagrangian scheme, in which a higher-order boundary element method was applied to solve the wave field based on an Eulerians description at each time step.
Abstract: The fully nonlinear regular and focused wave propagation and diffraction around a vertical circular cylinder in a numerical wave tank are investigated. The Mixed Eulerian–Lagrangian approach is used to update the moving boundary surfaces in a Lagrangian scheme, in which a higher-order boundary element method is applied to solve the wave field based on an Eulerian description at each time step. In order to increase the efficiency of the calculation, the domain decomposition technique is implemented, with continuity conditions enforced on the interface between adjacent subdomains by an iterative procedure. In this domain decomposition method, the top layers of elements at the interfaces are semi-discontinuous to avoid problems from the singularity. In addition, mesh regridding using the Laplace smoothing technique and interpolation are applied on the free surface to deal with possible numerical instability. Numerical results are obtained for the propagation of nonlinear regular waves and focused wave groups, and for the diffraction of such waves by a vertical cylinder. These results indicate that the present method employing the domain decomposition technique is very efficient, and can provide accurate results when compared with experimental data.

102 citations

Journal ArticleDOI

[...]

TL;DR: This methodology is found to be efficient for cases where the acoustic field does not alter the mean flow field, i.e., when whistling does not occur.
Abstract: Acoustic wave propagation in flow ducts is commonly modeled with time-domain non-linear Navier–Stokes equation methodologies. To reduce computational effort, investigations of a linearized approach in frequency domain are carried out. Calculations of sound wave propagation in a straight duct are presented with an orifice plate and a mean flow present. Results of transmission and reflections at the orifice are presented on a two-port scattering matrix form and are compared to measurements with good agreement. The wave propagation is modeled with a frequency domain linearized Navier–Stokes equation methodology. This methodology is found to be efficient for cases where the acoustic field does not alter the mean flow field, i.e., when whistling does not occur.

84 citations

Proceedings ArticleDOI

[...]

10 Oct 2004
TL;DR: This study study and visualize swirl and tumble flow using three different flow visualization techniques: direct, geometric, and texture-based, and describes the relative strengths and weaknesses of each approach within a specific spatial dimension and across multiple spatial dimensions typical of an engineer's analysis.
Abstract: We investigate two important, common fluid flow patterns from computational fluid dynamics (CFD) simulations, namely, swirl and tumble motion typical of automotive engines. We study and visualize swirl and tumble flow using three different flow visualization techniques: direct, geometric, and texture-based. When illustrating these methods side-by-side, we describe the relative strengths and weaknesses of each approach within a specific spatial dimension and across multiple spatial dimensions typical of an engineer's analysis. Our study is focused on steady-state flow. Based on this investigation we offer perspectives on where and when these techniques are best applied in order to visualize the behavior of swirl and tumble motion.

81 citations