35 research outputs found
Multigrid Preconditioning for a Space-Time Spectral-Element Discontinuous-Galerkin Solver
In this work we examine a multigrid preconditioning approach in the context of a high- order tensor-product discontinuous-Galerkin spectral-element solver. We couple multigrid ideas together with memory lean and efficient tensor-product preconditioned matrix-free smoothers. Block ILU(0)-preconditioned GMRES smoothers are employed on the coarsest spaces. The performance is evaluated on nonlinear problems arising from unsteady scale- resolving solutions of the Navier-Stokes equations: separated low-Mach unsteady ow over an airfoil from laminar to turbulent ow. A reduction in the number of ne space iterations is observed, which proves the efficiency of the approach in terms of preconditioning the linear systems, however this gain was not reflected in the CPU time. Finally, the preconditioner is successfully applied to problems characterized by stiff source terms such as the set of RANS equations, where the simple tensor product preconditioner fails. Theoretical justification about the findings is reported and future work is outlined
Adaptive design of experiments for efficient and accurate estimation of aerodynamic loads
Aerodynamic design, which aims at developing the outer shape of the aircraft while meeting several contrasting requirements, demands an accurate and reliable aerodynamic database. Computing forces and moments with the highest level of ?fidelity is a prerequisite, but practically limited by wall clock time and available computing resources. An e?fficient and robust approach is therefore sought after. This study investigates two design of experiments algorithms in combination with surrogate modelling. In traditional design of experiments, the samples are selected a priori before running the numerical explorative campaign. It is well-?known that this may result in either poor prediction capabilities or high computational costs. The second strategy employs an adaptive design of experiments algorithm. As opposed to the former, this is a self?-learning technique that iteratively: i) identi?fies the regions of the design space that are characterised by stronger non?linearities; and ii) select the new samples in order to maximise the information contentassociated with the simulations to be performed during the next iteration. In this work, the Reynolds?-averaged Navier-?Stokes equations are solved around a complete aircraft confi?guration. A representative ?flight envelope is created taking the angle of attack and Mach number as design parameters. The adaptive strategy is found to perform better than the traditional counterpart. This is quantifi?ed in terms of the sum of the squared error between the surrogate model predictions and CFD results. For the pitch moment coe?fficient, which shows strong non?linearities, the error metric using the adaptive strategy is reduced by about one order of magnitude compared to the traditional approach. Furthermore, the proposed adaptive methodology, which is employed on a high performance computing facility, requires no extra costs or complications than a traditional methodolog
Extension of analytical indicial aerodynamics to generic trapezoidal wings in subsonic flow
Analytical indicial aerodynamic functions are calculated for several trapezoidal wings in subsonic flow, with a Mach number 0.3≤ Ma≤ 0.7. The formulation herein proposed extends well-known aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to generic trapezoidal wing planforms. Firstly, a thorough study is executed to assess the accuracy and limitation of analytical predictions, using unsteady results from two state-of-the-art computational fluid dynamics solvers as cross-validated benchmarks. Indicial functions are calculated for a step change in the angle of attack and for a sharp-edge gust, each for four wing configurations and three Mach numbers. Then, analytical and computational indicial responses are used to predict dynamic derivatives and the maximum lift coefficient following an encounter with a one-minus-cosine gust. It is found that the analytical results are in excellent agreement with the computational results for all test cases. In particular, the deviation of the analytical results from the computational results is within the scatter or uncertainty in the data arising from using two computational fluid dynamics solvers. This indicates the usefulness of the developed analytical theories
An algorithm for the regression of the UNIQUAC interaction parameters in liquid-liquid equilibrium for single- and multi-temperature experimental data
This paper describes an algorithm for the computation of the UNIQUAC interaction parameters from liquid-liquid experimental data. The algorithm comprises two separate levels. The inner level is devoted to the calculation of the interaction parameters, minimizing an objective function which is function of the activities. The outer level uses the parameters by the inner level and aims to minimize the error between experimental and calculated molar fractions through an adjustment of the experimental molar fractions, provided that the condition of common tangent to the change of the Gibbs free energy of mixing is matched.
The algorithm is applied to seven binary systems for the evaluation of single temperature parameters and to the tetrahydrofuran/water system for the evaluation of the temperature dependent parameters. In both cases, the calculated parameters provide results with lower error than the previously published parameters. In all cases thermodynamically consistent and precise results are obtained in terms of common tangent of the Gibbs free energy of mixing and molar faction errors
Probing the inflationary particle content: extra spin-2 field
We study how inflationary observables associated with primordial tensor modes
are affected by coupling the minimal field content with an extra spin-2
particle during inflation. We work with a model that is ghost-free at the fully
non-linear level and show how the new degrees of freedom modify standard
consistency relations for the tensor bispectrum. The extra interacting spin-2
field is necessarily massive and unitarity dictates its mass be in the range. Despite the fact that this bound selects a decaying solution
for the corresponding tensor mode, cosmological correlators still carry the
imprints of such "fossil" fields. Remarkably, fossil(s) of spin
generate distinctive anisotropies in observables such as the tensor power
spectrum. We show how this plays out in our set-up.Comment: 25 pages, 3 figure
Cosmology with the Laser Interferometer Space Antenna
254 pags:, 44 figs.The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological applications of gravitational-wave observations extends well beyond these two objectives. This publication presents a summary of the state of the art in LISA cosmology, theory and methods, and identifies new opportunities to use gravitational-wave observations by LISA to probe the universe.This work is partly supported by: A.G. Leventis Foundation; Academy of Finland
Grants 328958 and 345070; Alexander S. Onassis Foundation, Scholarship ID: FZO 059-1/2018-2019;
Amaldi Research Center funded by the MIUR program “Dipartimento di Eccellenza” (CUP:
B81I18001170001); ASI Grants No. 2016-24-H.0 and No. 2016-24-H.1-2018; Atracción de Talento
Grant 2019-T1/TIC-15784; Atracción de Talento contract no. 2019-T1/TIC-13177 granted by the
Comunidad de Madrid; Ayuda ‘Beatriz Galindo Senior’ by the Spanish ‘Ministerio de Universidades’,
Grant BG20/00228; Basque Government Grant (IT-979-16); Belgian Francqui Foundation; Centre national
d’Etudes spatiales; Ben Gurion University Kreitman Fellowship, and the Israel Academy of Sciences and
Humanities (IASH) & Council for Higher Education (CHE) Excellence Fellowship Program for
International Postdoctoral Researchers; Centro de Excelencia Severo Ochoa Program SEV-2016-0597;
CERCA program of the Generalitat de Catalunya; Cluster of Excellence “Precision Physics, Fundamental
Interactions, and Structure of Matter” (PRISMA? EXC 2118/1); Comunidad de Madrid, Contrato de
Atracción de Talento 2017-T1/TIC-5520; Czech Science Foundation GAČR, Grant No. 21-16583M; Delta
ITP consortium; Department of Energy under Grant No. DE-SC0008541, DE-SC0009919 and DESC0019195; Deutsche Forschungsgemeinschaft (DFG), Project ID 438947057; Deutsche Forschungsgemeinschaft under Germany’s Excellence Strategy - EXC 2121 Quantum Universe - 390833306; European
Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports (Project
CoGraDS - CZ.02.1.01/0.0/0.0/15 003/0000437); European Union’s H2020 ERC Consolidator Grant
“GRavity from Astrophysical to Microscopic Scales” (Grant No. GRAMS-815673); European Union’s
H2020 ERC, Starting Grant Agreement No. DarkGRA-757480; European Union’s Horizon 2020
programme under the Marie Sklodowska-Curie Grant Agreement 860881 (ITN HIDDeN); European
Union’s Horizon 2020 Research and Innovation Programme Grant No. 796961, “AxiBAU” (K.S.);
European Union’s Horizon 2020 Research Council grant 724659 MassiveCosmo ERC-2016-COG; FCT
through national funds (PTDC/FIS-PAR/31938/2017) and through project “BEYLA – BEYond LAmbda”
with Ref. Number PTDC/FIS-AST/0054/2021; FEDER-Fundo Europeu de Desenvolvimento Regional
through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI-01-0145-
FEDER-031938) and research Grants UIDB/04434/2020 and UIDP/04434/2020; Fondation CFM pour la
Recherche in France; Foundation for Education and European Culture in Greece; French ANR project
MMUniverse (ANR-19-CE31-0020); FRIA Grant No.1.E.070.19F of the Belgian Fund for Research, F.R.
S.-FNRS Fundação para a Ciência e a Tecnologia (FCT) through Contract No. DL 57/2016/CP1364/
CT0001; Fundação para a Ciência e a Tecnologia (FCT) through Grants UIDB/04434/2020, UIDP/04434/
2020, PTDC/FIS-OUT/29048/2017, CERN/FIS-PAR/0037/2019 and “CosmoTests – Cosmological tests of
gravity theories beyond General Relativity” CEECIND/00017/2018; Generalitat Valenciana Grant
PROMETEO/2021/083; Grant No. 758792, project GEODESI; Government of Canada through the
Department of Innovation, Science and Economic Development and Province of Ontario through the
Ministry of Colleges and Universities; Grants-in-Aid for JSPS Overseas Research Fellow (No.
201960698); I?D Grant PID2020-118159GB-C41 of the Spanish Ministry of Science and Innovation;
INFN iniziativa specifica TEONGRAV; Israel Science Foundation (Grant No. 2562/20); Japan Society for
the Promotion of Science (JSPS) KAKENHI Grant Nos. 20H01899 and 20H05853; IFT Centro de
Excelencia Severo Ochoa Grant SEV-2; Kavli Foundation and its founder Fred Kavli; Minerva
Foundation; Ministerio de Ciencia e Innovacion Grant PID2020-113644GB-I00; NASA Grant
80NSSC19K0318; NASA Hubble Fellowship grants No. HST-HF2-51452.001-A awarded by the Space
Telescope Science Institute with NASA contract NAS5-26555; Netherlands Organisation for Science and
Research (NWO) Grant Number 680-91-119; new faculty seed start-up grant of the Indian Institute of
Science, Bangalore, the Core Research Grant CRG/2018/002200 of the Science and Engineering; NSF
Grants PHY-1820675, PHY-2006645 and PHY-2011997; Polish National Science Center Grant 2018/31/D/
ST2/02048; Polish National Agency for Academic Exchange within the Polish Returns Programme under
Agreement PPN/PPO/2020/1/00013/U/00001; Pró-Reitoria de Pesquisa of Universidade Federal de Minas
Gerais (UFMG) under Grant No. 28359; Ramón y Cajal Fellowship contract RYC-2017-23493; Research
Project PGC2018-094773-B-C32 [MINECO-FEDER]; Research Project PGC2018-094773-B-C32
[MINECO-FEDER]; ROMFORSK Grant Project. No. 302640; Royal Society Grant URF/R1/180009
and ERC StG 949572: SHADE; Shota Rustaveli National Science Foundation (SRNSF) of Georgia (Grant
FR/18-1462); Simons Foundation/SFARI 560536; SNSF Ambizione grant; SNSF professorship Grant
(No. 170547); Spanish MINECO’s “Centro de Excelencia Severo Ochoa” Programme Grants SEV-2016-
0597 and PID2019-110058GB-C22; Spanish Ministry MCIU/AEI/FEDER Grant (PGC2018-094626-BC21); Spanish Ministry of Science and Innovation (PID2020-115845GB-I00/AEI/10.13039/
501100011033); Spanish Proyectos de I?D via Grant PGC2018-096646-A-I00; STFC Consolidated
Grant ST/T000732/1; STFC Consolidated Grants ST/P000762/1 and ST/T000791/1; STFC Grant ST/
S000550/1; STFC Grant ST/T000813/1; STFC Grants ST/P000762/1 and ST/T000791/1; STFC under the
research Grant ST/P000258/1; Swiss National Science Foundation (SNSF), project The Non-Gaussian
Universe and Cosmological Symmetries, Project Number: 200020-178787; Swiss National Science
Foundation Professorship Grants No. 170547 and No. 191957; SwissMap National Center for Competence
in Research; “The Dark Universe: A Synergic Multi-messenger Approach” Number 2017X7X85K under
the MIUR program PRIN 2017; UK Space Agency; UKSA Flagship Project, Euclid.Peer reviewe