Filippo Maria Denaro

Università degli Studi della Campania "Luigi Vanvitelli · Dipartimento di Ingegneria

This note addresses some basic, historical concepts to understand correctly the statistically vs. filtered solutions and their comparison in terms of the ideal solutions. Then, some issues in this approach are highlighted. Any notification of error in the note is welcome.

This note briefly addresses the issues in the discretization of conservative and non-conservative formulations of the Burgers equation in terms of the correct shock velocity. Any notification of error in the note is welcome.

This note briefly addresses the basic reasons of the origin of the adoption of the implicit filtering in the LES equations. Then, some issues in this approach are highlighted. Any notification of error in the note is welcome.

The numerical integration of the Navier-Stokes equations for incompressible flows demands efficient and accurate solution algorithms for pressure-velocity splitting. Such decoupling was traditionally performed by adopting the Fractional Time-Step Method that is based on a formal separation between convective-diffusive momentum terms from the pressu...

This note briefly addresses the differential and integral formulations to the filtered equations used in LES and the deconvolution-based closure modelling. Any notification of error in the note is welcome.

The analysis of the Local Truncation Error (LTE) of a certain Finite Difference (FD) formula shows the theoretical order of accuracy, that is the asymptotic rate at which the LTE vanishes. However, the LTE by alone does not tell us what is the actual error that is introduced by the formula for a certain grid size. What about the error for a given c...

The development of the dynamic procedure as well as the deeper understanding of the link between filtering, modelling and numer-ics, allowed Large Eddy Simulation (LES) to make great progresses during the last years. Among several modelling approaches, the scale-similar-based modelling is based on the observation that the smallest resolved scales a...

Lecture on Large Eddy Simulation at Politecnico di Milano. Content: n.1 File Part I n.1 File Part II n.2 Movies n.1 File Advances in modern LES models

We discuss the design and development of a parallel code for Large Eddy Simulation (LES) by exploiting libraries for sparse matrix computations. We formulate a numerical procedure for the LES of turbulent channel flows, based on an approximate projection method, in terms of linear algebra operators involving sparse matrices and vectors. Then we imp...

I rapporti tecnici dell'ICAR-CNR sono pubblicati dall'Istituto di Calcolo e Reti ad Alte Prestazioni del Consiglio Nazionale delle Ricerche. Tali rapporti, approntati sotto l'esclusiva responsabilità scientifica degli autori, descrivono attività di ricerca del personale e dei collaboratori dell'ICAR, in alcuni casi in un formato preliminare prima d...

The numerical simulation of turbulence is one of the most challenging tasks in the field of the modern computational science. At present, the most advanced approach is the large eddy simulation (LES) technique wherein a formal separation between resolved (large) and unresolved (small) scales of the motion is in effect by means of a filtering operat...

The 20-year old dynamic model is a well-established procedure in large eddy simulation that allowed us achieving several progresses in the field of numerical simulation of turbulence. The key of the procedure is in the derivation of the exact Germano identity, which is a tensor relation. After introducing the eddy viscosity model, in order to achie...

Presentation in PPT

A Finite Volume-based large-eddy simulation method is proposed along with a suitable extension of the dynamic modelling procedure that takes into account for the integral formulation of the governing filtered equations. Discussion about the misleading interpretation of FV in some literature is addressed. Then, the classical Germano identity is cong...

This paper summarizes the activity of the LESinItaly group in a project supported by the CASPUR centre during the year 2010. Commercial, open-source and own-made LES codes were tested by several units in the simulation of the turbulent flow in a plane channel. The codes produced solutions on two different grids, providing also the corresponding no-...

The study illustrated in this paper completes the topics initially investigated in Ref. [42], the aim being here to analyze the role of the integral-based Finite Volume (FV) discretizations in Large Eddy Simulations that exploit the implicit filtering approach. Specifically, a theoretical study on the effective shape and length of three-dimensional...

This paper is focused on the role of integral-based Finite Volume (FV) discretizations in Large Eddy Simulation of turbulence. The integral-based form implicitly induces the top-hat filtering on the balanced variable. This leads us to rewrite also a different decomposition of the fluxes. As a consequence, the development of a new Germano identity c...

Large Eddy Simulation (LES) is based on a separation between large resolved, and small unresolved Sub-Grid Scales (SGS), obtained by applying a low-pass filtering operator on the governing equations. Actually, such filtering operation is often nothing but a formalism while writing the LES equations in continuous form. Indeed, in the so-called impli...

The solution of large and sparse linear systems is one of the main computational kernels in CFD applications and is often a very time-consuming task, thus requiring the use of effective algorithms on high-performance computers. Preconditioned Krylov solvers are the methods of choice for these systems, but the availability of “good” preconditioners...

Filtering in Large Eddy Simulation (LES) is often only a formalism since practically discretization of both the domain and operators is used as implicit grid-filtering to the variables. In the present study, the LES equations are written in the integral form around a Finite Volume (FV) Ώ rather than in the differential form as is more usual in Fini...

A large-eddy simulation method based upon the finite volume approach is developed and evaluated for buoyancy driven turbulence in the absence of rotational effects. The effect of the sub-grid scale motions is modelled by using the dynamic scaling formulation, without introducing any ad hoc assumption for the vertical stratification. This way, the e...

I rapporti tecnici dell'ICAR-CNR sono pubblicati dall'Istituto di Calcolo e Reti ad Alte Prestazioni del Consiglio Nazionale delle Ricerche. Tali rapporti, approntati sotto l'esclusiva responsabilità scientifica degli autori, descrivono attività di ricerca del personale e dei collaboratori dell'ICAR, in alcuni casi in un formato preliminare prima d...

Second‐order accurate projection methods for simulating time‐dependent incompressible flows on cell‐centred grids substantially belong to the class either of exact or approximate projections. In the exact method, the continuity constraint can be satisfied to machine‐accuracy but the divergence and Laplacian operators show a four‐dimension nullspace...

It is well known that exact projection methods (EPM) on non-staggered grids suffer for the presence of non-solenoidal spurious modes. Hence, a formulation for simulating time-dependent incompressible flows while allowing the discrete continuity equation to be satisfied up to machine-accuracy, by using a Finite Volume-based second-order accurate pro...

A source term model to reproduce Micro Vortex Generator effects on the downstream flowfield is developed and tested in the work presented. The advantage of the proposed model is that the MVG can be appropriately reproduced without the need of a detailed (body conforming) meshing around it.

Projection methods are among the most adopted procedures for solving the Navier–Stokes equations system for incompressible flows. In order to simplify the numerical procedures, the pressure–velocity de-coupling is often obtained by adopting a fractional time-step method. In a specific formulation, suitable for the incompressible flows equations, it...

Upwind schemes were judged inappropriate for performing accurate large eddy simulations of turbulent flow owing to the artificial dissipation that is present at high wavenumbers of the energy content. Such a conclusion has been drawn also from some results obtained by adopting Finite Difference schemes. The present paper illustrates the performance...

PREFAZIONE Sapete invece su che poggia tutto?. .. La presunzione che la realtà, quaì e per voi, debba essere e sia ugualmente per tutti gli altri I problemi di reale interesse ingegneristico sono spesso descritti da equazioni che non sono risolvibili in forma analitica. Essenzialmente, fino ad alcuni anni fa, lo studio di tali problemi era prevalen...

This paper is concerned with the development of a new high-order finite volume method for the numerical simulation of highly convective unsteady incompressible flows on non-uniform grids. Specifically, both a high-order fluxes integration and the implicit deconvolution of the volume-averaged field are considered. This way, the numerical solution ef...

This paper is concerned with the development of a new high order Finite Volume method for the numerical simulation of highly convective unsteady incompressible flows on non-uniform grids. Specifically, both a high order fluxes integration and the implicit deconvolution of the volume-averaged field are considered. This way, the numerical solution ef...

The aim of this numerical study is focused on the investigation of the performance of the Large Eddy Simulation (LES) of turbulence in confined flows. An engine intake prototype is the studied flow model. LES methodology is a promising technique that allows capturing the major part of the characteristic flow scales while modeling only the smallest...

This paper is concerned with the analysis of the Helmholtz–Hodge decomposition theorem since it plays a fundamental role in the projection methods that are adopted in the numerical solution of the Navier–Stokes equations for incompressible flows. The paper highlights the role of the orthogonal decomposition of a vector field in a bounded domain whe...

The numerical integration of the Navier–Stokes equations for incompressible flows demands efficient and accurate solution algorithms for pressure–velocity splitting. Such decoupling was traditionally performed by adopting the Fractional Time-Step Method that is based on a formal separation between convective–diffusive momentum terms from the pressu...

Interaction between computational fluid dynamics and clinical researches recently allowed a deeper understanding of the physiology of complex phenomena involving cardio-vascular mechanisms. The aim of this paper is to develop a simplified numerical model based on the Immersed Boundary Method and to perform numerical simulations in order to study th...

A general methodology is presented in order to obtain a hierarchy of high-order filter functions, starting from the standard top-hat filter, naturally linked to control volumes flow simulations. The goal is to have a new filtered variable better represented in its high resolved wavenumber components by using a suitable deconvolution. The proposed f...

This paper is concerned with the development of a fourth order Finite Volume scheme for the numerical solution of the incompressible Navier-Stokes equations on non-uniform grids. In fact, the use of non-uniform computational grids is inevitable in handling non-homogeneous flow computations, while numerical simulation of turbulent flows demand for h...

Noninvasive estimation of diastolic pressure gradients has recently been validated using the space-temporal velocity distribution available from colour Doppler M-mode (CDM). However, the methods currently applied for analysing CDM patterns of left ventricular (LV) filling have limitations, such as lack of automation, subjective variability and limi...

The aim of this study was to analyze the physiological variables regarding the left ventricular filling pattern by means of two numerical models of the diastolic atrial-ventricular flow. Diastolic dysfunction is an important cause of cardiac morbidity and, consequently, there is a need for developing noninvasive techniques to evaluate the diastolic...

The study of the flow over a three-dimensional backward-facing step still provides interesting research when a new numerical method is developed and an investigation of the flow topology is performed. From a numerical point of view, accurate solutions are required, preferably with little computational effort, and the numerical results must lead to...

Studies on the numerical simulation of high-Reynolds-number flows encounter difficulties due to the wide range of characteristic length and time scales existing in the flow field. These are often much smaller than the computational grid size. A new approach based on a model-free local average direct numerical simulation is presented which incorpora...

The structure of 2D solenoidal or non solenoidal incompressible viscous channel flows in presence of obstacles was numerically investigated with special reference to laminar and transition conditions. The results obtained with a ψ,γ model and a Control Volume approach depend upon the supposed inflow-outflow boundary conditions. The numerical soluti...

The experimental flow visualization of mixing phenomena in an array of planar jets has been carried out and compared with the corresponding numerical patterns obtained through flow simulation. To allow a correct evaluation of the results a theoretical analysis relative to Lagrangian as well as Eulerian approaches has been outlined. Qualitative comp...

After a synthesis of existing numerical approaches, a family of single-step time-marching upwind schemes is proposed for the convective-diffusive balance of a scalar in multidimensional incompressible laminar flows. A functional description of the new approach is given too. The schemes are adequate to the simulation of purely or highly convective t...

Grazie al notevole sviluppo delle risorse computazionali, la possibilità di eseguire simulazioni di flussi turbo-lenti di interesse industriale con la metodologia della Large Eddy Simulation (LES) sta divenendo realtà. Questa opportunità è realizzabile con i maggiori codici di calcolo commerciali, diversi codici Open Source oltre che con quelli spe...