Esteban Ferrer

Universidad Politécnica de Madrid, Matemática Aplicada, Faculty Member

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I hold a Professorship in Applied Mathematics at ETSIAE-UPM (School of Aeronautics in Madrid). My research focusses in developing Discontinuous Galerkin numerical techniques for compressible and incompressible flows and studying flow stability, acoustics, optimisation and flow control .
More information in https://sites.google.com/site/eferrerdg/

I was awarded two Masters Degrees, one in Mechanical Engineering from ETSEIB (Barcelona) and the other in Aeronautical Engineering from ENSICA (Toulouse). As part of my Aeronautical degree I spent six months at Imperial College London, UK.

After graduating, I worked as a CFD researcher studying various aspects of the aerodynamics of wind turbines at CENER (Renewable Energy Centre in Spain) http://www.cener.com.

I obtained my Doctorate (DPhil-PhD) from the University of Oxford in 2012. In 2008, I joined the Low Speed Fluid Mechanics group in the Department of Engineering Science at the University of Oxford http://www.eng.ox.ac.uk/tidal, where I was in receipt of a John Fell OUP Research Fund studentship to support my doctoral work. After completing my doctoral thesis, I moved to Madrid as a post-doctoral researcher, to subsequently become Lecturer and Reader at ETSIAE-UPM.
Phone: +34 674 89 84 04

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Papers by Esteban Ferrer

Sensitivity analysis to unsteady perturbations of complex flows: a discrete approach

International Journal for Numerical Methods in Fluids, 2014

A discrete framework for computing the global stability and sensitivity analysis to external pert... more A discrete framework for computing the global stability and sensitivity analysis to external perturbations for any set of partial differential equations is presented. In particular, a complex-step approximation is used to achieve near analytical accuracy for the evaluation of the Jacobian matrix. Sensitivity maps for the sensitivity to base flow modifications and to a steady force are computed to identify regions of the flow field where an input could have a stabilising effect. Four test cases are presented: (1) an analytical test case to prove the theory of the discrete framework, (2) a lid-driven cavity at low Reynolds case to show the improved accuracy in the calculation of the eigenvalues when using the complex-step approximation, (3) the 2D flow past a circular cylinder at just below the critical Reynolds number used to validate the methodology, and finally, (4) the flow past an open cavity presented to give an example of the discrete method applied to a convectively unstable case. The latter three (2-4) of the aforementioned cases were solved with the 2D compressible Navier-Stokes equations using a Discontinuous Galerkin Spectral Element Method. Good agreement was obtained for the validation test case, (3), with appropriate results in the literature. Furthermore, it is shown that for the calculation of the direct and adjoint eigenmodes and their sensitivity maps to external perturbations, the use of complex variables is paramount for obtaining an accurate prediction.

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Low cost 3D global instability analysis and flow sensitivity based on dynamic mode decomposition and high-order numerical tools

International Journal for Numerical Methods in Fluids, 2014

We explore the recently developed snapshot-based dynamic mode decomposition (DMD) technique, a ma... more We explore the recently developed snapshot-based dynamic mode decomposition (DMD) technique, a matrix-free Arnoldi type method, to predict 3D linear global flow instabilities. We apply the DMD technique to flows confined in an L-shaped cavity and compare the resulting modes to their counterparts issued from classic, matrix forming, linear instability analysis (i.e. BiGlobal approach) and direct numerical simulations. Results show that the DMD technique, which uses snapshots generated by a 3D non-linear incompressible discontinuous Galerkin Navier-Stokes solver, provides very similar results to classical linear instability analysis techniques. In addition, we compare DMD results issued from non-linear and linearised Navier-Stokes solvers, showing that linearisation is not necessary (i.e. base flow not required) to obtain linear modes, as long as the analysis is restricted to the exponential growth regime, that is, flow regime governed by the linearised Navier-Stokes equations, and showing the potential of this type of analysis based on snapshots to general purpose CFD codes, without need of modifications. Finally, this work shows that the DMD technique can provide three-dimensional direct and adjoint modes through snapshots provided by the linearised and adjoint linearised Navier-Stokes equations advanced in time. Subsequently, these modes are used to provide structural sensitivity maps and sensitivity to base flow modification information for 3D flows and complex geometries, at an affordable computational cost. The information provided by the sensitivity study is used to modify the L-shaped geometry and control the most unstable 3D mode.

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Immersed boundary method for high-order flux reconstruction based on volume penalization

Journal of Computational Physics

Simulations of Aerodynamic Separated Flows Using the Lattice Boltzmann Solver XFlow

Energies

We present simulations of turbulent detached flows using the commercial lattice Boltzmann solver ... more We present simulations of turbulent detached flows using the commercial lattice Boltzmann solver XFlow (by Dassault Systemes). XFlow’s lattice Boltzmann formulation together with an efficient octree mesh generator reduce substantially the cost of generating complex meshes for industrial flows. In this work, we challenge these meshes and quantify the accuracy of the solver for detached turbulent flows. The good performance of XFlow when combined with a Large-Eddy Simulation turbulence model is demonstrated for different industrial benchmarks and validated using experimental data or fine numerical simulations. We select five test cases: the Backward-facing step the Goldschmied Body the HLPW-2 (2nd High-Lift Prediction Workshop) full aircraft geometry, a NACA0012 under dynamic stall conditions and a parametric study of leading edge tubercles to improve stall behavior on a 3D wing.

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Insights into the Aeroacoustic Noise Generation for Vertical Axis Turbines in Close Proximity

Energies

We present Large Eddy Simulations and aeroacoustic spectra for three configurations of increasing... more We present Large Eddy Simulations and aeroacoustic spectra for three configurations of increasing flow complexity: an isolated NACA0012 airfoil, an isolated rotating vertical axis wind turbine composed of three rotating airfoils and a farm of four vertical axis turbines (with identical characteristics as the isolated turbine), which are located in close proximity. The aeroacoustic signatures of the simulated airfoil and the isolated turbine are validated using published numerical and experimental data. We provide theoretical estimates to predict tonal frequencies, which are used to identify the main physical mechanisms responsible for the tonal signature and for each configuration and enable the categorisation of the main tonal aeroacoustic sources of vertical axis turbines operating in close proximity. Namely, we identify wake, vortex, blade passing and boundary layer phenomena and provide estimates for the associated tonal frequencies, which are validated with simulations. In the ...

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A discontinuous Galerkin approximation for a wall–bounded consistent three–component Cahn–Hilliard flow model

Computers & Fluids

Sensitivity gradients of surface geometry modifications based on stability analysis of compressible flows

Physical Review Fluids

We derive a discrete framework for the calculation of eigenvalue sensitivity to geometric deforma... more We derive a discrete framework for the calculation of eigenvalue sensitivity to geometric deformations. We apply the technique to the steady compressible Navier-Stokes and Reynolds-averaged Navier-Stokes (RANS) flows. The analysis enables one to control (reduce or increase) the amplification rate or frequency associated to the least stable global mode, which is identified using stability analysis. A methodology using a discrete framework is proposed, allowing one to recover the gradients in compressible and turbulent flows. The potential of the resulting shape gradients is evaluated on the well-known circular cylinder flow problem and on a RANS turbulent flow scenario to control the buffet onset on a NACA0012 airfoil. The predicted deformations show excellent performance on the stabilization or excitation, and frequency control, of the global modes and for the two cases tested.

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Entropy–stable discontinuous Galerkin approximation with summation–by–parts property for the incompressible Navier–Stokes/Cahn–Hilliard system

Journal of Computational Physics

An entropy–stable discontinuous Galerkin approximation for the incompressible Navier–Stokes equations with variable density and artificial compressibility

Journal of Computational Physics

Design of a Smagorinsky spectral Vanishing Viscosity turbulence model for discontinuous Galerkin methods

Computers & Fluids

A Free–Energy Stable Nodal Discontinuous Galerkin Approximation with Summation–By–Parts Property for the Cahn–Hilliard Equation

Journal of Computational Physics

We present a nodal Discontinuous Galerkin (DG) scheme for the Cahn-Hilliard equation that satisfi... more We present a nodal Discontinuous Galerkin (DG) scheme for the Cahn-Hilliard equation that satisfies the summation-by-parts simultaneousapproximation-term (SBP-SAT) property. The latter permits us to show that the discrete free-energy is bounded, and as a result, the scheme is provably stable. The scheme and the stability proof are presented for general curvilinear three-dimensional hexahedral meshes. We use the Bassi-Rebay 1 (BR1) scheme to compute interface fluxes, and an IMplicit-EXplicit (IMEX) scheme to integrate in time. Lastly, we test the theoretical findings numerically and present examples for two and three-dimensional problems.

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Dispersion-Dissipation Analysis for Advection Problems with Nonconstant Coefficients: Applications to Discontinuous Galerkin Formulations

SIAM Journal on Scientific Computing

In this work we study the stability and accuracy of several discontinuous Galerkin (DG) discretiz... more In this work we study the stability and accuracy of several discontinuous Galerkin (DG) discretizations. The Von Neumann stability analysis is a classic tool to analyse numerical methods. Von Neumann analysis estimates dispersion and diffusion errors introduced by a numerical discretisation by tracking the evolution of wave-like initial conditions when introduced in the numerical scheme. However, the traditional analysis (e.g. [1, 2]) relies on the constant speed advection equation, which may mask features which are common to non-linear problems (i.e. aliasing or propagation speed interpolation errors). For that purpose, we present a non-constant speed Von Neumann stability analysis for the advection equation. This analysis is developed such that it suits the investigation of high order Spectral/hp formulations. Analysing non-constant advection speed problems allows to discover behaviours from the numerical method, which are not present in the constant case. For example, methods which are stable under constant speed, become unstable for non-constant advection speeds; e.g. DG with Gauss-Lobatto points and central fluxes. This analysis enables the study of new DG formulations, such as the split forms presented in [3, 4], which guarantee stability in aliased conditions.

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An alternative method to study cross-flow instabilities based on high order dynamic mode decomposition

Physics of Fluids

A transition prediction method for flow over airfoils based on high-order dynamic mode decomposition

Chinese Journal of Aeronautics

Instability onset for submerged cylinders

Physics of Fluids

The Bassi Rebay 1 scheme is a special case of the Symmetric Interior Penalty formulation for discontinuous Galerkin discretisations with Gauss–Lobatto points

Journal of Computational Physics

Identification of flow structures in fully developed canonical and wavy channels by means of modal decomposition techniques

Journal of Physics: Conference Series

A Dynamic Mode Decomposition (DMD) of Direct Numerical Simulations (DNS) of fully developed chann... more A Dynamic Mode Decomposition (DMD) of Direct Numerical Simulations (DNS) of fully developed channel flows is undertaken in order to study the main differences in flow features between a plane-channel flow and a passively "controlled" flow wherein the mean friction was reduced relative to the baseline by modifying the geometry in order to generate a streamwise-periodic spanwise pressure gradient, as is the case for an oblique wavy wall. The present analysis reports POD and DMD modes for the plane channel, jointly with the application of a sparsity-promoting method, as well as a reconstruction of the Reynolds shear stress with the dynamic modes. Additionally, a dynamic link between the streamwise velocity fluctuations and the friction on the wall is sought by means of a composite approach both in the plane and wavy cases. One of the DMD modes associated with the wavy-wall friction exhibits a meandering motion which was hardly identifiable on the instantaneous friction fluctuations.

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Drag reduction via turbulent boundary layer flow control

Science China Technological Sciences

Turbulent Boundary Layer Control (TBLC) for skin-friction drag reduction is a relatively new tech... more Turbulent Boundary Layer Control (TBLC) for skin-friction drag reduction is a relatively new technology made possible through the advances in computational-simulation capabilities, which have improved the understanding of the flow structures of turbulence. Advances in micro-electronic technology have enabled the fabrication of active device systems capable of manipulating these structures. The combination of simulation, understanding and micro-actuation technologies offer new opportunities to significantly decrease drag, and by doing so, increase fuel efficiency of future aircraft. The literature review that follows will show that the application of active control turbulent skin-friction drag reduction is considered of prime importance by industry, even though it is still at a low Technology Readiness Level (TRL). This review presents the state of the art of different technologies oriented to the active and passive control for turbulent skin-friction drag reduction and contributes to the improvement of the actual present status of these technologies. Turbulent boundary layer flow control, drag reduction

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Aerodynamic Shape Optimization Using Geometry Surrogates and Adjoint Method

AIAA Journal

CAD-based Aerodynamic Shape Optimization Using Geometry Surrogate Model And Adjoint Methods

17th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, 2016

Esteban Ferrer

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