Paola Cinnella

Sorbonne Université | UPMC · Institut Jean Le Rond d'Alembert (IJLRA) - UMR 7190

The robust optimization (RDO) of complex flow configurations by means of advanced CFD models often relies on surrogate models to approximate the response of the cost function and to reduce the computational cost. The construction of accurate surrogates is a difficult task, namely for highly dimensional design and event spaces. In this paper we desc...

A hypersonic turbulent boundary layer over a flat plate is numerically investigated. The large Mach number and temperature values in the freestream (M e = 12.48 and T e = 594.3 K, respectively) lead to a high-enthalpy regime and to the occurrence of thermochemical non-equilibrium effects. Vibrational relaxation phenomena are shown to be predominant...

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...

Surrogate models are necessary to optimize meaningful quantities in physical dy-1 namics as their recursive numerical resolutions are often prohibitively expensive. It 2 is mainly the case for fluid dynamics and the resolution of Navier-Stokes equations. 3 However, despite the fast-growing field of data-driven models for physical systems, 4 referen...

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...

A high-order shock-capturing finite-difference scheme for scale-resolving numerical simulations of hypersonic high-enthalpy flows, involving thermal non-equilibrium effects, is presented. The suitability of the numerical strategy for such challenging configurations is assessed in terms of accuracy and robustness, with special focus on shock-capturi...

****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...

Presentation of the Sparse Bayesian Learning and spatial model aggregation (x-MA) algorithms for turbulence model data-driven augmentation and uncertainty quantification, and application to the collaborative testing challenge at 2022 Symposium on Turbulence Modeling: Roadblocks, and the Potential for Machine Learning, in honour of 60th birthday of...

Keynote Lecture

A hypersonic, spatially-evolving turbulent boundary layer at Mach 12.48 with a cooled wall is analyzed by means of direct numerical simulations. At the selected conditions, massive kinetic-to-internal energy conversion triggers thermal and chemical nonequilibrium phenomena. Air is assumed to behave as a five species reacting mixture, and a two-temp...

A CFD-driven deterministic symbolic identification algorithm for learning explicit algebraic Reynolds-stress models (EARSM) from high-fidelity data is developed building on the frozen-training SpaRTA algorithm of [1]. Corrections for the Reynolds stress tensor and the production of transported turbulent quantities of a baseline linear eddy viscosit...

******ACCEPTED FOR PUBLICATION IN THE JOURNAL OF COMPUTATIONAL PHYSICS************** A CFD-driven deterministic symbolic identification algorithm for learning explicit algebraic Reynolds-stress models (EARSM) from high-fidelity data is developed building on the CFD-free SpaRTA algorithm of [1]. Corrections for the Reynolds stress tensor and the pro...

The ORC technology is subject to manifold sources of uncertainty that can have a severe impact on the thermodynamic and economic efficiency of plant components, particularly when the system is operated at off-design conditions. In this contribution we focus on the development of ORC turbines with stable performance under uncertainty: a novel multi-...

###ACCEPTED#### Robust predictions of turbulent turbomachinery flows, namely, flows through the NACA65 V103 compressor cascade at various operating conditions, are obtained by accounting for uncertainties associated with the turbulence models. First, an efficient strategy is introduced for calibrating turbulence model coefficients from high fidelit...

High-speed turbulent flows are encountered in most space-related applications (including exploration, tourism and defense fields) and represent a subject of growing interest in the last decades. A major challenge in performing high-fidelity simulations of such flows resides in the stringent requirements for the numerical schemes to be used. These m...

Presentation at Symposium on "Model-Consistent Data-driven Turbulence Modeling", Organized by U. Michigan, June 22-24, 2021 (ZOOM).

Presentation for Stanford University Fluid Mechanics Seminar Series. ENGR298. Spring Session 2020-2021.

The influence of high-enthalpy effects on hypersonic turbulent boundary layers is investigated by means of direct numerical simulations (DNS). A quasi-adiabatic flat-plate air flow at free-stream Mach number equal to 10 is simulated up to fully-developed turbulent conditions using a five-species, chemically-reacting model. A companion DNS based on...

The influence of high-enthalpy effects in hypersonic, spatially developing boundary layers is investigated by means of direct numerical simulations. The flow of a reacting mixture of nitrogen and oxygen over a flat plate at Mach 10, previously investigated in the literature using linear stability theory (LST), is simulated using a computational dom...

A CFD-driven approach for building data-augmented explicit algebraic Reynolds-stress models (EARSM) with improved performance with respect to a baseline linear eddy viscosity model for a given class of flows is presented. The proposed methodology is used to learn a model improving the predictions of the k-ω SST model for 2D turbulent separated flow...

This paper presents the application of high-order vorticity confinement (VC) to the simulation of two cases: the decay of compressible homogeneous isotropic turbulence (HIT) in an implicit LES approach and a flat plate with zero pressure gradient in a hybrid RANS/LES simulation. For the HIT case, VC has been found to reduce the numerical dissipatio...

********PUBLISHED IN COMPUTERS AND FLUIDS, AUGUST 2021*****************************High-speed turbulent flows are encountered in most space-related applications (including exploration, tourism and defense fields) and represent a subject of growing interest in the last decades. A major challenge in performing high-fidelity simulations of such flows...

******PUBLISHED IN PHYSICAL REVIEWS FLUIDS********* The influence of high-enthalpy effects on hypersonic turbulent boundary layers is investigated by means of direct numerical simulations (DNS). A quasi-adiabatic flat-plate air flow at free-stream Mach number equal to 10 is simulated up to fully-developed turbulent conditions using a five-species,...

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 online Seminar "Saisir le mouvement" (initially scheduled at Institut Henri Poincaré, Paris) (https://seminaire.phimeca.com/) organized by Institut pour la maitrise des risques and AMIES (Agence pour les Mathématiques en Interaction avec l'Entreprise).

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...

FINAL VERSION AVAILABLE ONLINE: https://www.mdpi.com/1999-4893/13/10/248/pdf Efficient Robust Design Optimization (RDO) strategies coupling a parsimonious uncertainty quantification (UQ) method with a surrogate-based multi-objective genetic algorithm (SMOGA) are investigated for a test problem in Computational Fluid Dynamics (CFD), namely, the inv...

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 robust design optimization (RDO) methodology for Organic Rankine Cycles (ORC) is presented, allowing to ensure an improved, stable performance over a large range of operating conditions. In contrast with classical ORC design methods, whereby all modeling hypotheses and operating conditions are considered as perfectly known, i.e. deterministic, th...

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...

***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...

The Reynolds-Averaged Navier-Stokes (RANS) equations represent the computational workhorse for engineering design, despite their numerous flaws. Improving and quantifying the uncertainties associated with RANS models is particularly critical in view of the analysis and optimization of complex turbomachinery flows. In this work, we use Bayesian infe...

Computational Fluid Dynamics (CFD) models have become a fundamental tool for preliminary and advanced aerodynamic design and optimization. So-called high-fidelity CFD models like DNS (Direct Numerical Simulation) or LES (Large Eddy Simulation) remain very costly for complex high-Reynolds flows, and lower fidelity methods, relying on the Reynolds-Av...

A novel deterministic symbolic regression method SpaRTA (Sparse Regression of Turbulent Stress Anisotropy) is introduced to infer algebraic stress models for the closure of RANS equations directly from high-fidelity LES or DNS data. The models are written as tensor polynomials and are built from a library of candidate functions. The machine-learnin...

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...

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. ************* ********************************...

A high level of know-how has been reached about Organic Rankine Cycles (ORCs). However, improving and optimizing their design is still a fundamental issue. Traditionally, thermodynamic and techno-economic ORC optimization have been performed only at the point identified by plant nominal working conditions. Just recently, some optimizations have sta...

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...

After the extraordinary diffusion that we have observed over the last ten years, Organic Rankine Cycles (ORCs) are nowadays widely recognized as “the unrivalled technical solution for generating electricity from low-medium temperature heat sources of limited capacity” [1]. Despite the high level of confidence and know-how reached about ORCs, they s...

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...

https://arxiv.org/abs/1905.07510#### A novel deterministic symbolic regression method SpaRTA (Sparse Regression of Turbulent Stress Anisotropy) is introduced to infer algebraic stress models for the closure of RANS equations directly from high-fidelity LES or DNS data. The models are written as tensor polynomials and are built from a library of c...

***AVAILABLE FROM ArXiv: https://arxiv.org/abs/1905.07510**** A novel deterministic symbolic regression method SpaRTA is introduced to infer algebraic stress models for the closure of RANS equations directly from high-fidelity LES or DNS data. The models are written as tensor polynomials and are built from a library of candidate functions. The mac...

A novel deterministic symbolic regression method SpaRTA (Sparse Regression of Turbulent Stress Anisotropy) is introduced to infer algebraic stress models for the closure of RANS equations directly from high-fidelity LES or DNS data. The models are written as tensor polynomials and are built from a library of candidate functions. The machine-learnin...

****PUBLISHED ONLINE in PROGRESS IN AEROSPACE SCIENCES https://doi.org/10.1016/j.paerosci.2018.10.001**** In computational fluid dynamics simulations of industrial flows, models based on the Reynolds-averaged Navier--Stokes (RANS) equations are expected to play an important role in decades to come. However, model uncertainties are still a major obs...

In computational fluid dynamics simulations of industrial flows, models based on the Reynolds-averaged Navier–Stokes (RANS) equations are expected to play an important role in decades to come. However, model uncertainties are still a major obstacle for the predictive capability of RANS simulations. This review examines both the parametric and struc...

A Bayesian approach is developed to quantify uncertainties associated with the thermodynamic models used for the simulation of dense gas flows, i.e. flows of gases characterized by complex molecules of moderate to high molecular weight, in thermodynamic conditions of the general order of magnitude of the liquid/vapor critical point. The thermodynam...