Marco Atzori

• PostDoc Position at Johannes Kepler University of Linz

Opposition control (OC) is a reactive flow-control approach that mitigates the near-wall fluctuations by imposing blowing and suction at the wall, being opposite to the off-wall observations. We carried out high-resolution large-eddy simulations to investigate the effects of OC on turbulent boundary layers (TBLs) over a wing at a chord-based Reynol...

This document is a detailed analysis of both the effects of the cylinder height and spacing of two wall-mounted, square cylinder in tandem. We aim to discuss if the definition of "skimming flow", "wake interference" and "Isolated roughness" regimes also applies for two non-identical obstacles in tandem.

We conducted high-resolution large-eddy simulations (LESs) to explore the effects of opposition control (OC) on turbulent boundary layers (TBLs) over a wing at a chord-based Reynolds number (${Re}_c$) of 200,000. Two scenarios were studied: flow over the suction sides of the NACA0012 wing section at a $0^{\circ}$ angle of attack, and the NACA4412 w...

This research focuses on the identification and causality analysis of coherent structures that arise in turbulent flows in square and rectangular ducts. Coherent structures are first identified from direct numerical simulation data via proper orthogonal decomposition (POD), both by using all velocity components, and after separating the streamwise...

This research focuses on the identification and causality analysis of coherent structures that arise in turbulent flows in square and rectangular ducts. Coherent structures are first identified from direct numerical simulation data via proper orthogonal decomposition (POD), both by using all velocity components, and after separating the streamwise...

The present study considers uniform blowing in turbulent boundary layers as active flow control scheme for drag reduction on airfoils. The focus lies on the important question of how to quantify the drag reduction potential of this control scheme correctly. It is demonstrated that mass injection causes the body drag (the drag resulting from the str...

High-fidelity large-eddy simulations of the flow around two rectangular obstacles are carried out at a Reynolds number of 10000 based on the freestream velocity and the obstacle height. The incoming flow is a developed turbulent boundary layer. Mean-velocity components, turbulence fluctuations, and the terms of the turbulent-kinetic-energy budget a...

The present study considers uniform blowing in turbulent boundary layers as active flow control scheme for drag reduction on airfoils. The focus lies on the important question of how to quantify the drag reduction potential of this control scheme correctly. It is demonstrated that mass injection causes the body drag (the drag resulting from the str...

We examine the effects of three basic but effective control strategies, namely uniform blowing, uniform suction, and body-force damping, on the intense Reynolds-stress events in the turbulent boundary layer (TBL) developing on the suction side of a NACA4412 airfoil. This flow is subjected to a non-uniform adverse pressure gradient (APG), which subs...

In this work, time-resolved three-dimensional numerical simulations supported by laboratory experiments aim to provide complementary information of the spray drying process, revealing pivotal details about the flow and particles dynamics. A drying model was implemented in the OpenFOAM open-source code and large-eddy simulations (LES) of the flow we...

In the present paper, we evaluate the performances of three stochastic models for particle dispersion in the case of a three-dimensional turbulent flow. We consider the flow in a channel with a cubic wall-mounted obstacle, and perform large-eddy simulations (LESs) including passive particles injected behind the obstacle, for cases of low and strong...

In-situ visualization on high-performance computing (HPC) systems allows us to analyze simulation results that would otherwise be impossible , given the size of the simulation data sets and offline post-processing execution time. We develop an in-situ adaptor for Paraview Catalyst and Nek5000, a massively parallel Fortran and C code for computation...

Received xx; revised xx; accepted xx) 9 The application of drag-control strategies on canonical wall-bounded turbulence, such as 10 periodic channel and zero-or adverse-pressure-gradient boundary layers, raises the equation 11 on how to distinguish consistently the origin of control effects under different reference 12 conditions. We employ the RD...

A detailed analysis of the effects of uniform blowing, uniform suction and body-force damping on the turbulent boundary layer developing around a NACA4412 airfoil at moderate Reynolds number is presented. The flow over the suction and the pressure sides of the airfoil is subjected to a non-uniform adverse pressure gradient and a moderate favourable...

We present a comprehensive parametric study on the flow-control scheme denoted as wall-normal uniform blowing and suction in turbulent boundary layers around airfoils. The focus is primarily put on the influence of the drag caused by the power consumption of the support system. We also assess the theoretical background of the momentum budget includ...

Fundamental fluid--mechanics studies and many engineering developments are based on tripped cases. Therefore, it is essential for CFD simulations to replicate the same forced transition in spite of the availability of advanced transition modelling. In the last decade, both direct and large--eddy simulations (DNS and LES) include tripping methods in...

The application of drag-control strategies on canonical wall-bounded turbulence, such as periodic channel and zero-or adverse-pressure-gradient boundary layers, raises the question of how to describe control effects consistently for different reference cases. We employ the RD identity (Renard & Deck, J. Fluid Mech., 790, 2016, pp. 339-367) to decom...

An extensive parametric study of turbulent boundary-layer control on airfoils via uniform blowing or suction is presented. The control is applied on either the suction or pressure side of several four-digit NACA-series airfoils. The considered parameter variations include angle of attack, Reynolds number, control intensity, airfoil camber, and airf...

The aim of the present work is to investigate the role of intense Reynolds shear-stress events in the generation of the secondary flow in turbulent ducts. We consider the connected regions of flow where the product of the instantaneous fluctuations of two velocity components is higher than a threshold based on the long-time turbulence statistics, i...

In the present study, we exploit the Renard-Deck identity ["A theoretical decomposition of mean skin friction generation into physical phenomena across the boundary layer", J. Fluid Mech. 790, 339-367 (2016)] to decompose the mean friction drag in adverse-pressure-gradient turbulent boundary layers (APG-TBLs) into three components , associated with...

We carried out high-fidelity large-eddy simulations (LES) to investigate the effects of uniform blowing and uniform suction on the aerodynamic efficiency of a NACA4412 airfoil at the moderate Reynolds number based on chord length and incoming velocity of Re c = 200, 000. We found that uniform blowing applied at the suction side reduces the aerodyna...

Developing efficient flow control techniques remain a challenging task due to the complexity of turbulent flows in industrial applications, a relevant example of which are turbulent boundary layers (TBL) subjected to pressure gradients. In the present study, we employ high-fidelity numerical simulations to assess the impact of different control str...

This preliminary study is concerned with the identification of three-dimensional coherent structures, defined as intense Reynolds-stress events, in the turbulent boundary layer developing over the suction side of a NACA4412 airfoil at a Reynolds number based on the chord lenght and the incoming velocity of Rec = 200, 000. The scientific interest fo...

Direct and Large-Eddy Simulation (DLES) 12 Proceedings

The aim of the present work is to investigate the role of coherent structures in the generation of the secondary flow in a turbulent square duct. The coherent structures are defined as connected regions of flow where the product of the instantaneous fluctuations of two velocity components is higher than a threshold based on the long-time turbulence...

The aim of the present work is to investigate the role of coherent structures in the generation of the secondary flow in a turbulent square duct. The coherent structures are defined as connected regions of flow where the product of the instantaneous fluctuations of two velocity components is higher than a threshold based on the long-time turbulence...

The present work is aimed at evaluating the contribution to the secondary flow in duct flow with square and rectangular cross section from three-dimensional coherent structures, defined as intense Reynolds-stress events. The contribution to a certain mean quantity is defined as the ensemble average over the detected coherent structures, weighted wi...

Reynolds-number effects in the adverse-pressure-gradient (APG) turbulent boundary layer (TBL) developing on the suction side of a NACA4412 wing section are assessed in the present work. To this end, we analyze four cases at Reynolds numbers based on freestream velocity and chord length ranging from Rec = 100, 000 to 1,000,000, all of them with 5 de...

Technical Report. TRITA-SCI-RAP 2018:010, 2018

The scope of the present project is to quantify the effects of uniform blowing and body-force damping on turbulent boundary layers subjected to a non-uniform adverse-pressure-gradient distribution. To this end, well-resolved large-eddy simulations are employed to describe the flow around the NACA4412 airfoil at moderate Reynolds number 200, 000 bas...

Four well-resolved LESs of the turbulent boundary layers around a NACA4412 wing section, with Rec ranging from 100,000 to 1,000,000, were performed at 5 degree angle of attack. By comparing the turbulence statistics with those in ZPG TBLs at approximately matching Re_tau, we find that the effect of the adverse pressure gradient (APG) is more intens...

The scope of the present project is to quantify the effects of uniform blowing and body-force damping on turbulent boundary layers subjected to a non-uniform adverse-pressure-gradient distribution. To this end, well-resolved large-eddy simulations are employed to describe the flow around the NACA4412 airfoil at moderate Reynolds number 200, 000 bas...

Four well-resolved LESs of the turbulent boundary layers around a NACA4412 wing section, with Re c ranging from 100, 000 to 1, 000, 000, were performed at 5 • angle of attack. By comparing the turbulence statistics with those in ZPG TBLs at approximately matching Re τ , we find that the effect of the adverse pressure gradient (APG) is more intense...

Reynolds-number effects in the adverse-pressure-gradient (APG) turbulent boundary layer (TBL) developing on the suction side of a NACA4412 wing section are assessed in the present work. To this end, we analyze four cases at Reynolds numbers based on freestream velocity and chord length ranging from Rec = 100,000 to 1,000,000, all of them with 5 deg...

This work is aimed at a first characterization of coherent structures in turbulent square duct flows. Coherent structures are defined as connected components in the domain identified as places where a quantity of interest (such as Reynolds stress or vorticity) is larger than a prescribed non-uniform threshold. Firstly, we qualitatively discuss how...