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## Publications

Publications (157)

The present contribution reports the outcome of an experimental and numerical investigation of the behavior of a constant-temperature hot-wire anemometer in the high subsonic flow up to a Mach number of 0.7 of the organic vapor Novec 649 at pressure and temperature levels of typical organic Rankine cycle (ORC) turbine applications. The experiments...

A novel Sparse Bayesian Learning (SBL) framework is introduced for generating stochastic Explicit Algebraic Reynolds Stress (EARSM) closures for the Reynolds-Averaged Navier–Stokes (RANS) equations from high-fidelity data. Building on the recently proposed SpaRTA (Sparse Regression of Turbulent Stress Anisotropy) algorithm of Schmelzer et al. (2020...

In direct and large eddy simulations, very small space steps are used close to the solid walls in order to resolve the boundary-layer structures. Due to the restrictive CFL stability criteria of explicit time-stepping schemes, the maximum allowable time step is also very small, leading to high computational costs, notably for converging flow statis...

****ACCEPTED FOR PUBLICATION IN INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW**** A novel Sparse Bayesian Learning (SBL) framework is introduced for generating stochastic Explicit Algebraic Reynolds Stress (EARSM) closures for the Reynolds-Averaged Navier-Stokes (RANS) equations from high-fidelity data. Building on the recently proposed SpaRTA (Spar...

The simplified model by W. R. Dean, based on a low-curvature assumption, provided an early understanding of the laminar flow in curved ducts. However, most of the following studies relied on computer simulations of the complete curvilinear Navier-Stokes equations controlled by two nondimensional parameters, the curvature ratio and the Reynolds numb...

Transonic flows of a molecularly complex organic fluid through a stator cascade are investigated by means of Large Eddy Simulations (LES). The selected configuration is considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non ideal gas effects.
A heav...

Presentation at the 3rd International Seminar on Non-Ideal Computational Fluid Dynamics (NICFD 2020), organized by TU Delft as a virtual conference (https://live.eventinsight.io/916-nicfd2020/misc/virtualevent/) on October 29 and 30, 2020.

Presentation at the 3rd International Seminar on Non-Ideal Computational Fluid Dynamics (NICFD 2020), organized by TU Delft as a virtual conference (https://live.eventinsight.io/916-nicfd2020/misc/virtualevent/) on October 29 and 30, 2020.

POSITION CLOSED***********
The framework of this research is the ANR-DFG project REGAL-ORC.
The ANR-DFG project REGAL-ORC (REal-GAs effects on Loss mechanisms of ORC turbine flows) will tackle some aspects of this challenging topic thanks to the close collaboration between a theoretical/numerical research group (Paris, France), an experimental gro...

The utility of the wavenumber-frequency spectrum for description and interpretation of wall pressure fluctuations beneath turbulent boundary layers has been amply demonstrated over the past decades. This representation is widely used in modelling the flow-induced noise due to boundary layers developing on vehicle surfaces. A recurring issue concern...

The present article reviews some recent contributions to the study of dense gas effects in turbulent flows by using high-performance computing models, namely, direct and large eddy simulations. Significant deviations from perfect-gas compressible turbulence are observed, driven by the large heat capacity and the peculiar behavior of transport prope...

High-speed turbulent boundary layers of a dense gas (PP11) and a perfect gas (air) over flat plates are investigated by means of Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES). The thermo-dynamic conditions of the incoming flow are chosen to highlight dense gas effects, and laminar-to-turbulent transition is triggered by suctio...

A study of dense-gas effects on the laminar, transitional and turbulent characteristics of boundary layer flows is conducted. The laminar similarity solution shows that temperature variations are small due to the high specific heats of dense gases, leading to velocity profiles close to the incompressible ones. Nevertheless, the complex thermodynami...

Selected data from simulations of periodic hill flow benchmark testcase
(article "Large Eddy Simulation Requirements for the Flow over Periodic Hills" in Flow Turbulence Combust (2019) DOI 10.1007/s10494-018-0005-5)
* 4 files with 2D fields (mean and rms quantities) in Tecplot format for Re=2800, 10595, 19000 and 37000;
* 12 files with profiles of...

High-speed flows of gases with complex thermodynamic behavior (often referred to as “real gases”) have been paid growing interest from the scientific community due to the manifold applications in aerospace and power generation systems. In this work, we focus on so-called dense-gas flows found in several engineering applications, ranging from energy...

The influence of the vortex impingement location on the aerodynamic and acoustic response of a rotating blade during an orthogonal interaction is studied by means of computational fluid dynamics. The objective is to identify and quantify precisely the noise reduction achieved by reducing the blade span. The Batchelor vortex model is primarily consi...

***PUBLISHED ONLINE*** A study of dense-gas effects on the stability of compressible boundary layer flows is conducted. From the laminar similarity solution, the temperature variations are small due to the high specific heat of dense gases, leading to velocity profiles close to the incompressible ones. Concurrently, the complex thermodynamic proper...

We present a minimal model of an incompressible flow in square duct subject to a slight curvature. Using a Poincar\'e-like section we identify stationary, periodic, aperiodic and chaotic regimes, depending on the unique control parameter of the problem: the Dean number (De). Aside from representing a simple, yet rich, dynamical system the present s...

Companion database to the Journal of Fluid Mechanics article:
https://www.researchgate.net/publication/339952798_Dense_gas_effects_on_compressible_boundary_layer_stability/comments
Dense gas effects on compressible boundary layer stability (Gloerfelt, Robinet, Sciacovelli, Cinnella & Grasso, Journal of Fluid Mechanics, 2020, Submitted). Some resu...

A study of dense-gas effects on the laminar, transitional and turbulent characteristics of boundary layer flows is conducted. The laminar similarity solution shows that temperature variations are small due to the high specific heats of dense gases, leading to velocity profiles close to the incompressible ones. Nevertheless, the complex thermodynami...

Hypersonic turbulent boundary layers (HTBL) at Mach number $M{=}6$ of a dense gas (PP11) and a perfect gas (air) are investigated by means of Direct Numerical Simulations (DNS), from the laminar to fully turbulent state.
The operating conditions are chosen in such a way to highlight dense gas effects, which profoundly alter the transition mechanism...

The recent study of Ren et al. ( J. Fluid Mech. , vol. 871, 2019, pp. 831–864) investigated the hydrodynamic linear stability of a compressible boundary layer over an insulated flat plate for a non-ideal gas (supercritical $\text{CO}_{2}$ ). In particular, the authors showed that in the transcritical regime (across the pseudo-critical line) the flo...

A recently developed fourth-order accurate implicit residual smoothing scheme (IRS4) is investigated for the large eddy simulation of turbomachinery flows, characterized by moderate to high Reynolds numbers and subject to severe constraints on the maximum allowable time step if an explicit scheme is used. For structured multi-block meshes, the prop...

REQUIREMENTS: 2nd-year Master student (1st year students as second option) in Aerospace/Mechanical/Energy engineering with background in Numerical Methods, scientific computing and Computational Fluid Dynamic. Knowledge of a compiled language (Fortran or C++) and parallel computing will be appretiated.
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Big Challenges on Joliot-Curie - Before it goes in full production, a series of Grand Challenges – large scale simulations from academic and industry research – were carried out on Joliot-Curie supercomputer, from June to September 2018, to check that the system is functioning properly. These Grand Challenges represent a unique opportunity for sele...

The flow in a transonic turbine cascade using a dense gas (a molecularly complex organic
compound) as the working fluid are investigated by means of large eddy simulations (LES).
The Martin and Hou real gas equation of state and the Chung–Lee–Starling models are used
to describe the thermodynamic behavior and the variations of transport properties...

Oral presentation at the DLES12 Conference (Direct and Large Eddy Simulations XII), Madrid, Spain, 5-7 June 2019

Large eddy simulations are carried out for flows in a channel with streamwise-periodic constrictions, a well-documented benchmark case to study turbulent flow separation from a curved surface. Resolution criteria such as wall units are restricted to attached flows and enhanced criteria, such as energy spectra or two-point correlations, are used to...

Dense gas effects, encountered in many engineering applications, lead to unconventional variations of the thermodynamic and transport properties in the supersonic flow regime, which in turn are responsible for considerable modifications of turbulent flow behavior with respect to perfect gases. The most striking differences for wall-bounded turbulen...

This study investigates the effects of a pressure gradient on the wall pressure beneath equilibrium turbulent boundary layers. Excitation of the walls of a vehicle by turbulent boundary layers indeed constitutes a major source of interior noise and it is necessary to take into account the presence of a pressure gradient to represent the effect of t...

The aeroacoustic response of the orthogonal interaction of a rotating blade with an isolated Batchelor vortex is studied by means of numerical simulation. The relative influence of the vortex tangential and axial velocity on the blade aerodynamics and on the acoustics radiated in the far field is analyzed by comparing the interaction with a Batchel...

In large-eddy simulations (LES), only the dynamics of large scales is computed and the effect of smaller scales is modelled. Scale separation is however difficult to establish since the low-pass filtering arises from a complex combination of implicit filtering by the grid and the discretization schemes. Even when explicit filtering is performed, th...

The generation of a turbulent inflow is a tricky problem. In the framework of aeroacoustics, another important constraint is that the numerical strategy used to reach a turbulent state induces a spurious noise which is lower than the acoustic field of interest. For the study of noise radiated directly by a turbulent boundary layer on a flat plate,...

The influence of dense gas effects on compressible wall-bounded turbulence is investigated by means of direct numerical simulations of supersonic turbulent channel flows. Results are obtained for PP11, a heavy fluorocarbon representative of dense gases, the thermo-physics properties of which are described by using a 5th-order virial equation of sta...

In this study, a new selective filtering technique is proposed for the Lattice Boltzmann Method. This technique is based on an adaptive implementation of the selective filter coefficient σ. The proposed model makes the latter coefficient dependent on the shear stress in order to restrict the use of the spatial filtering technique in sheared stress...

The influence of dense gas effects on compressible turbulence is investigated by means of numerical simulations of the decay of compressible homogeneous isotropic turbulence (CHIT) and of supersonic turbulent flows through a plane channel (TCF). For both configurations, a parametric study on the Mach and Reynolds numbers is carried out. The dense g...

The influence of dense gas effects on compressible turbulence is investigated by means of numerical simulations of the decay of compressible homogeneous isotropic turbulence (CHIT) and of supersonic turbulent flows through a plane channel (TCF). For both configurations, a parametric study on the Mach and Reynolds numbers is carried out. The dense g...

Presentation at the 51st International Conference of Applied Aerodynamics, Strasbourg, France.

In this work we investigate the influence of dense gas effects on compressible wall-bounded turbulence. Direct numerical simulations of supersonic turbulent channel flows are performed both for air and PP11, a heavy fluorocarbon representative of dense gases. Using different thermodynamic models, a parametric study on the bulk Mach and Reynolds num...

The aeroacoustic response of the orthogonal interaction of a rotating blade with an isolated vortex is studied by means of numerical simulation. This study, carried out in a context of noise reduction of propeller and open rotor powered aircrafts, should allow better characterizing the influence blade geometry and vortex properties on the noise rad...

A sensitivity analysis of sound refraction phenomena through a 2D mixing layer subject
to uncertain flow properties and/or source parameters is carried out by means of a Probabilistic Collocation method. Probability distribution functions associated to the uncertain
input parameters are propagated through the system of governing equations to obtain...

The present study aims at getting better insight of the complex flow dynamics in a channel constricted by periodic hills. This is a popular test case ofer used to assess LES and RANS/LES models, which appears as a compendium of flow separation and reattachment from a curved boundary, generation of an unsteady shear layer surrounding the recirculati...

The comprehension of the flow over a vehicle has become a topic of high concern for the
transport industry. The pressure fluctuations beneath a turbulent boundary layer (TBL) are a
source of excitation for the structure which radiates into vehicle and impairs the comfort of the
passengers. The main vortices present in a turbulent boundary layer are...

Excitation of the walls of a vehicle by turbulent boundary layers constitutes a major source of interior noise, and can be dominant for cruising trips. The random character of the pressure distribution induced by the boundary layer has a major effect on the noise transmitted through the fuselage and its cross-spectral density plays a major role in...

Two assumptions commonly made in predictions based on Lighthill's formalism are investigated: A constant density in the quadrupole expression and the evaluation of the source quantity from incompressible simulations. Numerical predictions of the acoustic field are conducted in the case of a subsonic spatially evolving two-dimensional mixing layer a...

Aeroacoustic problems are often multi-scale and a zonal refinement technique is thus desirable to reduce computational effort while preserving low dissipation and low dispersion errors from the numerical scheme. For that purpose, the multi-size-mesh multi-time-step algorithm of Tam and Kurbatskii [AIAA Journal, 2000, 38(8), p. 1331–1339] allows cha...

It is now well established that linear and nonlinear instability waves play a significant role in the noise generation process for a wide variety of shear flows such as jets or mixing layers. In that context, the problem of acoustic radiation generated by spatially growing instability waves of two-dimensional subsonic and supersonic mixing layers a...

The simulation of low-frequency unsteadiness in shock wave/turbulent boundary-layer interactions constitutes a challenging case insofar as very long time integrations are required to describe these broadband motions at frequencies two orders of magnitude lower than those of the turbulent motions. A relatively low-cost numerical strategy is establis...