JOURNALS

Documents published in Scipedia

• Approximating the Basset force by optimizing the method of van Hinsberg et al.

  G. Casas, A. Ferrer, E. Oñate

  Journal of Computational Physics (2018). Vol. 352, pp. 142-171

  
  

  Abstract

  In this work we put the method proposed by van Hinsberg et al. to the test, highlighting its accuracy and efficiency in a sequence of benchmarks of increasing complexity. Furthermore, we explore the possibility of systematizing the way in which the method's free parameters are determined by generalizing the optimization problem that was considered originally. Finally, we provide a list of worked-out values, ready for implementation in large-scale particle-laden flow simulations.

  Abstract
  In this work we put the method proposed by van Hinsberg et al. to the test, highlighting its accuracy and efficiency in a sequence of benchmarks of increasing complexity. [...]

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• Volumetric constraint models for anisotropic elastic solids

  C. Felippa, E. Oñate

  Journal of Applied Mechanics (2004). Vol. 71 (5), pp. 731-734

  
  

  Abstract

  We study three “incompressibility flavors” of linearly-elastic anisotropic solids that exhibit volumetric constraints: isochoric, hydroisochoric and rigidtropic. An isochoric material deforms without volume change under any stress system. An hydroisochoric material does so under hydrostatic stress. A rigidtropic material undergoes zero deformations under a certain stress pattern. Whereas the three models coalesce for isotropic materials, important differences appear for anisotropic behavior. We find that isochoric and hydroisochoric models under certain conditions may be hampered by unstable physical behavior. Rigidtropic models can represent semistable physical materials of arbitrary anisotropy while including isochoric and hydroisochoric behavior as special cases.

  Abstract
  We study three “incompressibility flavors” of linearly-elastic anisotropic solids that exhibit volumetric constraints: isochoric, hydroisochoric and rigidtropic. [...]

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• Active transonic aerofoil design optimization using robust multiobjective evolutionary algorithms

  D. Lee, J. Periaux, L. González, E. Oñate, N. Qin

  Journal of Aircraft (2011). Vol. 48 (3) pp. 1084-1094

  
  

  Abstract

  The use of adaptive wing/aerofoil designs is being considered, as they are promising techniques in aeronautic/ aerospace since they can reduce aircraft emissions and improve aerodynamic performance of manned or unmanned aircraft. This paper investigates the robust design and optimization for one type of adaptive techniques: active flow control bump at transonic flow conditions on a natural laminar flow aerofoil. The concept of using shock control bump is to control supersonic flow on the suction/pressure side of natural laminar flow aerofoil that leads to delaying shock occurrence (weakening its strength) or boundary-layer separation. Such an active flow control technique reduces total drag at transonic speeds due to reduction of wave drag. The location of boundary-layer transition can influence the position and structure of the supersonic shock on the suction/pressure side of aerofoil. The boundarylayer transition position is considered as an uncertainty design parameter in aerodynamic design due to the many factors, such as surface contamination or surface erosion. This paper studies the shock-control-bump shape design optimization using robust evolutionary algorithms with uncertainty in boundary-layer transition locations. The optimization method is based on a canonical evolution strategy and incorporates the concepts of hierarchical topology, parallel computing, and asynchronous evaluation. Two test cases are conducted: the first test assumes the boundary-layer transition position is at 45% of chord from the leading edge, and the second test considers robust design optimization for the shock control bump at the variability of boundary-layer transition positions. The numerical result shows that the optimization method coupled to uncertainty design techniques produces Pareto optimal shock-control-bump shapes, which have low sensitivity and high aerodynamic performance while having significant total drag reduction.

  Abstract
  The use of adaptive wing/aerofoil designs is being considered, as they are promising techniques in aeronautic/ aerospace since they can reduce aircraft emissions and improve [...]

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• Numerical investigation of wind-tunnel model deformations caused by the twin-sting support system

  F. Flores, E. Ortega, E. Oñate

  Journal of Aircraft (2010). Vol. 47, pp. 708-714

  
  

  Abstract

  The present work is part of a broader investigation aimed at improving the understanding of the aerodynamics of the rear aircraft section. Complex flow phenomena (e.g., the thick fuselage boundary layer at the rear end) present a challenge to the accurate predictions of aerodynamic performance. Significant efficiency gains are expected from improved-fidelity computations and experimental techniques. As part of a joint effort between several research institutions and industrial partners, a series of wind-tunnel test campaigns focusing on accurate rear-end measurements was planned. To obtain accurate tail-force data, a nonstandard live-rear-end test model was adopted. This technique uses a mechanically separate rear-end section attached to the main body through internal balances, allowing direct measurement of the force acting on the tail. This mechanical setup precludes the use of a conventional tail-coneattached sting. Moreover, to minimize aerodynamic interference on the empennage caused by the support system, a wing-attached twinsting mounting was chosen

  Abstract
  The present work is part of a broader investigation aimed at improving the understanding of the aerodynamics of the rear aircraft section. Complex flow phenomena (e.g., [...]

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• Robust design optimization in aeronautics using stochastic analysis and evolutionary algorithms

  J. Pons-Prats, G. Bugeda, F. Zárate, E. Oñate

  Journal of Aerospace Engineering (2011). Vol. 225, (10), pp. 1131-1151

  
  

  Abstract

  Uncertainties are a daily issue to deal with in aerospace engineering and applications. Robust optimization methods commonly use a random generation of the inputs and take advantage of multi-point criteria to look for robust solutions accounting with uncertainty definition. From the computational point of view, the application to coupled problems, like computational fluid dynamics (CFD) or fluid–structure interaction (FSI), can be extremely expensive. This study presents a coupling between stochastic analysis techniques and evolutionary optimization algorithms for the definition of a stochastic robust optimization procedure. At first, a stochastic procedure is proposed to be applied into optimization problems. The proposed method has been applied to both CFD and FSI problems for the reduction of drag and flutter, respectively.

  Abstract
  Uncertainties are a daily issue to deal with in aerospace engineering and applications. Robust optimization methods commonly use a random generation of the inputs and take [...]

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• A monolithic FE formulation for the analysis of membranes in fluids

  R. Rossi, P. Ryzhakov, E. Oñate

  International Journal of Space Structures (2009). Vol. 24 (4), pp. 205-210

  
  

  Abstract

  We propose here an efficient approach for treating the interaction between membranes and fluids. Slight compressibility of the fluid is assumed. Classical total Lagrangian formulation including wrinkling is adopted for the membrane representation, whereas fluid is treated in an updated Lagrangian manner, developed in the current work. Assumption of slight compressibility of the fluid enables one to define the monolithic fluid-membrane system in a natural way. The displacements are the primary variables of both the fluid and the membrane domains. The formulation adopts the Particle Finite Element Method (PFEM) philosophy for free-surface identification and mesh regeneration. Three examples illustrate the functionality of the formulation in application to FSI problems involving motion of membranes in water

  Abstract
  We propose here an efficient approach for treating the interaction between membranes and fluids. Slight compressibility of the fluid is assumed. Classical total Lagrangian [...]

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• Discrete element simulation of rock cutting

  J. Rojek, E. Oñate, C. Labra, H. Kargl

  Int. J. Rock Mechanics and Mining Sciences (2011). Vol. 48 (6), pp. 996-1010

  
  

  Abstract

  This paper presents numerical modelling of rock cutting processes. The model consists of a tool–rock system. The rock is modelled using the discrete element method, which is suitable to study problems of multiple material fracturing such as those involved in rock cutting. Both 2D and 3D models are considered in this work. The paper presents a brief overview of the theoretical formulation and calibration of the discrete element model by a methodology combining the dimensional analysis with simulation of the unconfined compressive strength (UCS) and indirect tension (Brazilian) tests. The rock cutting process with roadheader picks, which is typical for underground excavation, has been simulated. The results of the 2D and 3D analyses have been compared with one another, and numerical results have been compared with the available experimental data.

  Abstract
  This paper presents numerical modelling of rock cutting processes. The model consists of a tool–rock system. The rock is modelled using the discrete element method, [...]

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• Numerical and Experimental Study of Overtopping and Failure of Rockfill Dams

  A. LARESE, R. Rossi, E. Oñate, M. Toledo, R. Morán Moya, H. Campos

  International Journal of Geomechanics (2015). Vol. 15 (4), pp. 04014060-1 (published online)

  
  

  Abstract

  This paper aims to present and validate a numerical technique for the simulation of the overtopping and onset of failure in rockfill dams caused by mass sliding. This goal is achieved by coupling a fluid dynamic model for the simulation of the free surface and through-flow problems together with a numerical technique for the calculation of the rockfill response and deformation. Both the flow within the dam body and in its surroundings are taken into account. An extensive validation of the resulting computational method is performed by solving several failure problems on physical models of rockfill dams for which experimental results have been obtained by the authors.

  Abstract
  This paper aims to present and validate a numerical technique for the simulation of the overtopping and onset of failure in rockfill dams caused by mass sliding. This goal [...]

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• A FIC‐based stabilized mixed finite element method with equal order interpolation for solid–pore fluid interaction problems

  I. de-Pouplana, E. Oñate

  Int. J. Numer. Anal. Meth. Geomech. (2017). Vol. 41 (1), pp. 110-134

  
  

  Abstract

  A new mixed displacement‐pressure element for solving solid–pore fluid interaction problems is presented. In the resulting coupled system of equations, the balance of momentum equation remains unaltered, while the mass balance equation for the pore fluid is stabilized with the inclusion of higher‐order terms multiplied by arbitrary dimensions in space, following the finite calculus (FIC) procedure. The stabilized FIC‐FEM formulation can be applied to any kind of interpolation for the displacements and the pressure, but in this work, we have used linear elements of equal order interpolation for both set of unknowns. Examples in 2D and 3D are presented to illustrate the accuracy of the stabilized formulation for solid–pore fluid interaction problems.

  Abstract
  A new mixed displacement‐pressure element for solving solid–pore fluid interaction problems is presented. In the resulting coupled system of equations, the balance [...]

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• Numerical modelling of landslide‐generated waves with the particle finite element method (PFEM) and a non‐Newtonian flow model

  F. Salazar, J. Irazábal González, A. LARESE, E. Oñate

  Int. J. Numer. Anal. Meth. Geomech. (2016). Vol. 40 (6), pp. 809-826

  
  

  Abstract

  Landslide‐generated impulse waves may have catastrophic consequences. The physical phenomenon is difficult to model because of the uncertainties in the kinematics of the mobilised material and to the intrinsic complexity of the fluid–soil interaction. The particle finite element method (PFEM) is a numerical scheme that has successfully been applied to fluid–structure interaction problems. It uses a Lagrangian description to model the motion of nodes (particles) in both the fluid and the solid domains (the latter including soil/rock and structures). A mesh connecting the particles (nodes) is re‐generated at every time step, where the governing equations are solved. Various constitutive laws are used for the sliding mass, including rigid solid and the Newtonian and non‐Newtonian fluids. Several examples of application are presented, corresponding both to experimental tests and to actual full‐scale case studies. The results show that the PFEM can be a useful tool for analysing the risks associated with landslide phenomena, providing a good estimate to the potential hazards even for full‐scale events.

  Abstract
  Landslide‐generated impulse waves may have catastrophic consequences. The physical phenomenon is difficult to model because of the uncertainties in the kinematics of the [...]

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