Roberto Flores Profile : Scipedia

Documents published in Scipedia

Efficient aeroelastic analysis of inflatable structures using enhanced potential flow aerodynamics
E. Ortega, R. Flores, E. Cuartero, E. Oñate

Journal of Fluids and Structures (2019). Vol. 90, pp. 230-245

Abstract
An efficient method for the aeroelastic analysis of wind effects on inflatable structures is presented. The solution scheme is staggered and uses an explicit finite-element structural solver and potential flow aerodynamics. In order to take into account the essential features of the flow around blunt-shaped structures, a physics-based correction of the inviscid solution is proposed. The procedure involves automatic prediction of the detached flow areas (using Stratford’s criterion) and an empirical modification of the calculated pressure field intended to match the real viscous behavior. Several validation benchmarks and a realistic application example are presented. The results show the capability of the model to predict the wind loads on the structure with sufficient accuracy and low computational cost, making it possible to use aeroelastic analysis for routine calculation of inflatable structures.
Abstract
An efficient method for the aeroelastic analysis of wind effects on inflatable structures is presented. The solution scheme is staggered and uses an explicit finite-element [...]
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An edge-based solver for compressible flow
E. Ortega, R. Flores, E. Oñate

(2005). Research Report, Nº PI275

Abstract
An edge-based high-resolution scheme for the solution of the compressible Euler equations on unstructured finite elements grids is presented. The flow solver adopted in the present work is the approximate Riemann solver developed by Roe. A high-order spatial approximation is achieved by means of a piecewise linear reconstruction of the interface variables according to the MUSCL (Monotone Upstream-centered Schemes for Conservation Laws) formulation. Finally, non-linear limiters are introduced in order to prevent the generation of oscillations. The proposed approach corresponds with the methodology presented by Löhner in [1].
Abstract
An edge-based high-resolution scheme for the solution of the compressible Euler equations on unstructured finite elements grids is presented. The flow solver adopted in the [...]
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Shape optimization in aeronautical applications using neural networks
A. Daring, R. López, R. Flores, G. Bugeda, E. Oñate

(2007). Research Report, Nº PI306

Abstract
An optimization methodology based on neural networks was developed for use in 2D optimal shape design problems. Neural networks were used as a parameterization scheme to represent the shape function, and an edge-based high-resolution scheme for the solution of the compressible Euler equations was used to model the flow around the shape. The global system incorporates neural networks and the Euler fluid solver into the C++ Flood optimization framework containing a library of optimization algorithms. The optimization scheme was applied to a minimal drag problem in an unconstrained optimization case and a constrained case in hypersonic flow using evolutionary training algorithms. The results indicate that the minimum drag problem is solved to a high degree of accuracy but at high computational cost. For more complex shapes, parallel computing methods are required to reduce computational time.
Abstract
An optimization methodology based on neural networks was developed for use in 2D optimal shape design problems. Neural networks were used as a parameterization scheme to represent [...]
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PUMI: An explicit ED unstructural finite element solver for the Euler equations
R. Flores, E. Ortega

(2008). Research Report, Nº PI326

Abstract
The PUMI flow solver has been developed at CIMNE in to address the need for fast solutions of the flow field around complex geometries. Nowadays calculations involving a number of cells on the order of ten million are performed routinely. PUMI was created to deal with this kind of large-scale problem using modest hardware, therefore special emphasis was placed on the computational efficiency of the code. Design guidelines where minimum memory requirement, very fast single-threaded performance as well as satisfactory parallel scaling up to a moderate number of threads (as found on current desktop hardware using a small number of multi-core CPUs. In order to speedup the mesh generation activities an unstructured finite element formulation was selected. This papers describes the theoretical basis of the algorithms as well as detail of the implementation that increase the robustness and efficiency of the code.
Abstract
The PUMI flow solver has been developed at CIMNE in to address the need for fast solutions of the flow field around complex geometries. Nowadays calculations involving a number [...]
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A numerical investigation of wind tunnel model deformations caused by the twin-sting support system
R. Flores, E. Ortega, E. Oñate

(2009). Research Report, Nº PI334

Abstract
This work presents a wing deformation analysis of a twin-sting-mounted commercial aircraft model. Twin-sting arrangements minimize flow disturbances around the model fuselage and tail; on the other hand, they cause important changes in the flow field around the wing and also increase aerodynamic interference at the wing and aeroelastic effects on the wing. In some cases, these effects can alter the normal downwash developed behind the wing, modifying the flow pattern at the tail. Consequently, when tail aerodynamics is a major concern, this kind of support interference should be carefully evaluated. The methodology developed in this work employs an unstructured FEM-based flow solver for computing aerodynamic loads. These loads are then transferred to a finite element structural model in order to assess the geometrical deformation of the wing caused by torsional moment exerted by supporting mechanism. The analysis described involves three different twin-sting support configurations taking into account angle of attack variations and Mach numbers spanning from subsonic of high transonic ranges.
Abstract
This work presents a wing deformation analysis of a twin-sting-mounted commercial aircraft model. Twin-sting arrangements minimize flow disturbances around the model fuselage [...]
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A 3D low-order panel method for unsteady aerodynamic problems
E. Ortega, R. Flores, E. Oñate

(2010). Research Report, Nº PI343

Abstract
An unsteady low-order panel method for three-dimensional subsonic analyses is presented. The method, which is based on well-established techniques in computational aerodynamics, is intended to achieve a cost-effective solution of unsteady flows around arbitrary aerodynamic configurations. This work has two main objectives. First, to relax geometry discretization requirements and, second, to simplify the treatment of problems in which the analysis configuration moves along specified flight paths and/or changes its geometry during the simulation. Following this aim, a time-marching solution procedure is adopted in conjunction with a free-wake model which avoids iterative solutions for wake shape and position. The suitability of the present approach for solving typical aerodynamic problems is illustrated by means of several numerical examples.
Abstract
An unsteady low-order panel method for three-dimensional subsonic analyses is presented. The method, which is based on well-established techniques in computational aerodynamics, [...]
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An implicit unsteady hydraulic solver for suspended cuttings transport in managed pressure wells
R. Flores, R. Ortega, A. Ilin, D. Simpkins, E. Oñate

Computational Particle Mechanics (2019). Vol. 6 (2), pp 163–175

Abstract
We present a simulation tool for transient events in complex hydraulic networks. The code includes modelling of the transport of suspended cuttings in near-vertical wells. An unstructured finite volume formulation with implicit time integration has been chosen. The unconditional stability of the integrator makes the method suitable for the simulation of transient events over a wide range of characteristic timescales. It handles both very fast transients (e.g. fluid hammer events) and the long-term evolution of the well (e.g. hole cleaning operations). The software has been developed to address the need of the oil industry for a robust and efficient predictive tool allowing effective well control in managed pressure drilling operations. The physical modelling follows the standard practices accepted by the industry (e.g. mud rheology computations). The mathematical foundation of the algorithm is described followed by validation cases that illustrate its capabilities and accuracy. Finally, a practical industrial application example is provided to demonstrate the real-world performance of the software.
Abstract
We present a simulation tool for transient events in complex hydraulic networks. The code includes modelling of the transport of suspended cuttings in near-vertical wells. [...]
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Comparative accuracy and performance assessment of the finite point method in compressible flow problems
E. Ortega, E. Oñate, S. Idelsohn, R. Flores

Computers and Fluids (2014). Vol. 89, pp. 53-65

Abstract
A comparative assessment of the Finite Point Method (FPM) is presented. Using a wing-fuselage configuration under transonic inviscid flow conditions as reference test case, the performance of the FPM flow solver is compared with an equivalent edge-based Finite Element (FEM) implementation. Efficiency issues have discouraged practical application of meshless methods in the past. Thus, a simplification of the basic FPM technique is proposed in order to reduce the performance gap with respect to classical grid-based algorithms. A comparative evaluation of the accuracy, computational cost and parallel performance of the meshless implementation is carried out with the objective to assess the level of maturity of the technique and identify improvements still required to tackle practical applications. The results obtained show accuracy and performance of the core algorithm comparable to a conventional FEM implementation, thus removing a major obstacle for further developments of the FPM.
Abstract
A comparative assessment of the Finite Point Method (FPM) is presented. Using a wing-fuselage configuration under transonic inviscid flow conditions as reference test case, [...]
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Application of the finite point method to high‐Reynolds number compressible flow problems
R. Ortega, E. Oñate, S. Idelsohn, R. Flores

Int. J. Numer. Meth. Fluids (2014). Vol. 74 (10), pp. 732-748

Abstract
In this work, the finite point method is applied to the solution of high‐Reynolds compressible viscous flows. The aim is to explore this important field of applications focusing on two main aspects: the easiness and automation of the meshless discretization of viscous layers and the construction of a robust numerical approximation in the highly stretched clouds of points resulting in such domain areas. The flow solution scheme adopts an upwind‐biased scheme to solve the averaged Navier–Stokes equations in conjunction with an algebraic turbulence model. The numerical applications presented involve different attached boundary layer flows and are intended to show the performance of the numerical technique. The results obtained are satisfactory and indicative of the possibilities to extend the present meshless technique to more complex flow problems.
Abstract
In this work, the finite point method is applied to the solution of high‐Reynolds compressible viscous flows. The aim is to explore this important field of applications [...]
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A meshless finite point method for three‐dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
R. Ortega, E. Oñate, S. Idelsohn, R. Flores

Int. J. Numer. Meth. Fluids (2013). Vol. 73 (4), pp. 323-343

Abstract
A finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind‐biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual‐time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h‐adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid–structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi‐core performance of the proposed technique is also discussed through the examples provided.
Abstract
A finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind‐biased [...]
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Articles (Documents not available in Scipedia)

Unveiling modal parameters with forced response using SVD and QR during flutter flight testing
Barros, J.; Fernandez, J.M; ; Sanchez, S.; Rodríguez , O.

Proceedings of the institution of mechanical engineers - Part G. Journal of aerospace engineering. DOI: 10.1177/0954410016673393
Simple and efficient numerical tools for the analysis of parachutes
Ortega, E.; Oñate, E.

Engineering computations. 31 - 5, pp. 957 - 985
Application of the finite point method to high- Reynolds number compressible flow problems
Ortega, E.; Oñate, E.; Idelsohn, S.R.

International journal for numerical methods in fluids. 74 - 10, pp. 732 – 748
Comparative accuracy and performance assessment of the finite point method in compressible flow problems
Ortega, E.; Oñate, E.; Idelsohn, S.R.

Computers and fluids. 89, pp. 53 - 65
A meshless finite point method for the three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
Ortega, E.; Oñate, E.; Idelsohn, S.R.

International journal for numerical methods in fluids. 73 - 4, pp. 323 - 343
PUMI: un código explícito no estructurado para resolver las ecuaciones de Euler
Ortega, E.; Oñate, E.

Revista internacional de métodos numéricos para cálculo y diseño en ingeniería. 27 - 2, pp. 129 - 145
Numerical Investigation of Wind-Tunnel Model Deformations Caused by the Twin-Sting Support System
Ortega, E.; Oñate, E.

Journal of aircraft. 47 - 2, pp. 708 - 714
Error estimation and mesh adaptivity in incompressible viscous flows using a residual power approach
E Oñate, J Arteaga, J García, R Flores

Computer Methods in Applied Mechanics and Engineering 195 (4), 339-362, 2006

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Documents published in Scipedia

Efficient aeroelastic analysis of inflatable structures using enhanced potential flow aerodynamics

An edge-based solver for compressible flow

Shape optimization in aeronautical applications using neural networks

PUMI: An explicit ED unstructural finite element solver for the Euler equations

A numerical investigation of wind tunnel model deformations caused by the twin-sting support system

A 3D low-order panel method for unsteady aerodynamic problems

An implicit unsteady hydraulic solver for suspended cuttings transport in managed pressure wells

Comparative accuracy and performance assessment of the finite point method in compressible flow problems

Application of the finite point method to high‐Reynolds number compressible flow problems

A meshless finite point method for three‐dimensional analysis of compressible flow problems involving moving boundaries and adaptivity

Articles (Documents not available in Scipedia)

Unveiling modal parameters with forced response using SVD and QR during flutter flight testing

Simple and efficient numerical tools for the analysis of parachutes

Application of the finite point method to high- Reynolds number compressible flow problems

Comparative accuracy and performance assessment of the finite point method in compressible flow problems

A meshless finite point method for the three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity

PUMI: un código explícito no estructurado para resolver las ecuaciones de Euler

Numerical Investigation of Wind-Tunnel Model Deformations Caused by the Twin-Sting Support System

Error estimation and mesh adaptivity in incompressible viscous flows using a residual power approach

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