On the development of a harmonic balance method for aeroelastic analysis

To efficiently simulate time-periodic, non-linear flows in turbomachinery a Harmonic Balance (HB) method has recently been developed within the framework of DLR’s compressible, Unsteady Reynolds Averaged Navier- tokes (URANS) solver TRACE. As a hybrid time- and frequency-domain method, that solves directly for the complex valued solution harmonics of the URANS equations, the approach allows both the integration of highly accurate non-reflecting boundary conditions and the efficient resolution of non-linear flow phenomena. In the current work the HB-solver is extended and applied to investigate the aeroelastic problem of flutter in turbomachinery. Within this context the HB-method is developed, under consideration of the Geometric Conservation Law (GCL), to support deforming meshes. To validate the approach the well documented aeroelastic test case Standard Configuration 10 is simulated and results are compared to those obtained with an inhouse time-linearized solver and reference datafrom the literature

Whole model empirical validation on a full-scale building

This paper describes an empirical validation study undertaken on two identical full‐size buildings within the scope of the IEA ECB Annex 58 project. Details of the experimental configuration and monitoring are included, together with results from measurements and from predictions made by 21 modelling teams using commercial and research simulation programs. The two month side‐by‐side experiment was undertaken on buildings with high levels of thermal mass and in a period with high solar gains. The detailed specification and associated measurement data provide a useful empirical validation dataset for program testing. Results from the modelling demonstrate good agreement between measured data and predictions for a number of programs, both in absolute predictions of temperatures and heat inputs as well as dynamic response. On the other hand, a significant number of user input errors resulted in poor agreement for other programs, especially in the blind validation phase of the modelling methodology

IEA annex 58 : full-scale empirical validation of detailed thermal simulation programs

As simulation programs become more widely used for building performance assessment and building regulations compliance, there is a need to ensure that there are good quality empirical datasets which can be used to assess the predictive accuracy of these programs. This paper summarises a detailed experiment carried out on two identical full-scale buildings located at the Fraunhofer IBP test site at Holzkirchen in Germany and the associated modelling of the buildings. The work was undertaken as part of IEA ECB Annex 58 "Reliable building energy performance characterization based on full scale dynamic measurements". The test sequence, applied to the side-by-side validation experiment conducted on the multi-roomed Twin Houses, consisted of periods of constant internal temperatures, a period of pseudo-random heat injections and a free-float period. All boundary and internal conditions were comprehensively monitored. Modelling teams were given details of the buildings and the boundary conditions, and over 20 teams submitted their predictions of the internal conditions which were subsequently compared with measurements. The paper focuses on a sensitivity study carried out to assess the overall prediction uncertainty resulting from the uncertainties in the input parameters, as well as identifying those inputs which had the most influence on predictions. An assessment of the measurement uncertainty is also included

Knowing without knowing : implicit cognition and the minds of infants and animals

The main aim of this paper is to highlight the need to address the conceptual problem of “implicit knowledge” or “implicit cognition” —a notion especially important in the study of the nonverbal minds of animals and infants. We review some uses of the term ‘implicit’ in psychology and allied disciplines,and conclude that conceptual clarification of this notion is not only lacking, but largely avoided and reduced to a methodological problem. We propose that this elusive notion is central in the study not only of animal and infant minds, but also the human adult mind. Some promising approaches in developmental and evolutionary psychology towards innovative conceptualisation of implicit knowledge remain conceptually underdeveloped and in need of reconsideration and re-elaboration. We conclude by suggesting that the challenge of implicit cognition and nonverbal minds will only be solved through a concerted interdisciplinary approach between psychology and other disciplines.Publisher PDFPeer reviewe

Non-reflecting boundary condtions on unstructured grids

Non-reflecting boundary condition at interfaces for flow simulations in turbomachinery using the method laid out by Giles [1] and Saxer [2] require averages or Fourier decomposition of the flow solution using stations of constant radius at the interface. On structured grids the grid generation process can easily enforce grids having element centers with this property while on unstructured grids this is rarely achievable. We describe an approach which works on an auxiliary mesh with a band structure created from the surface mesh at interfaces and study the influence of the prescribed distribution of the bands on the solution. The effectiveness of the approach is demonstrated by applying it to the simulation of a compressor stage and comparing the results with results obtained by using the existing approach for creating bands and a simulation on a structured grid

Non-reflecting boundary conditions on unstructured grids

Non-reflecting boundary condition at interfaces for flow simulations in turbomachinery using the method laid out by Giles [1] and Saxer [2] require averages or Fourier decomposition of the flow solution using stations of constant radius at the interface. On structured grids the grid generation process can easily enforce grids having element centers with this property while on unstructured grids this is rarely achievable. We describe an approach which works on an auxiliary mesh with a band structure created from the surface mesh at interfaces and study the influence of the prescribed distribution of the bands on the solution. The effectiveness of the approach is demonstrated by applying it to the simulation of a compressor stage and comparing the results with results obtained by using the existing approach for creating bands and a simulation on a structured grid

The dramatic illusion in the theory and later plays of Friedrich Schiller

Statements in Schiller's early essays seem to suggest that he adhered to the view of the dramatic illusion as a temporary escape from reality, an experience in which the spectator is encouraged to forget that he is in the theatre and be caught up in a deceptive and convincing illusion. Analysis of Schiller's dramatic and aesthetic theory and of his correspondence from 1790 onwards, however, shows that the ideas of moral freedom, aesthetic harmony and of the autonomy of art led Schiller to reject the ideal of convincing illusion which was current and popular in his time. In its place he wished to encourage awareness of the illusory nature of the stage action and drama which was obviously different from everyday reality in its subject matter and style. Analysis of Schiller's plays from Wallenstein to Wilhelm Tell shows that Schiller aimed at illusion of this type in his own practice. With reference to the dramatic illusion, Schiller's views actually come close to those of Brecht, in spite of statements to the contrary in Brecht's Kleines Organon für das Theater. The detailed analysis of Schiller's theory and of his later plays is preceded firstly by a chapter on problems associated with the topic of the dramatic illusion. Secondly, a background chapter considers influential developments in drama, dramatic theory and in aesthetics from the origins of western drama in Greek classical tragedy to the theatre of Schiller's time, to establish possible influences on Schiller or similarities between his views and existing traditions, and to suggest Schiller's position with regard to his contemporaries and to the historical development of the dramatic illusion

Capuchin monkeys individuate objects based on spatio-temporal and property/kind information : evidence from looking and reaching measures

This paper is an output of the project ‘Rethinking Mind and Meaning: A case study from a co-disciplinary approach’ (Award Nr.: AH/ L015234/1), funded by the Arts and Humanities Research Council (AHRC), as part of the Science in Culture Theme (http://www.sciculture.ac.uk).A core component of any folk physical understanding of the world is object individuation - the cognitive ability to parse sensory input into discrete objects. Whereas younger human infants use spatio-temporal information to individuate objects, they do not use property and kind information until one year of age. Some researchers propose that object individuation based on property/kind information depends on language acquisition and sortal concepts. However, there is evidence that preverbal infants and nonhuman animals also use both types of information. The present study aimed to further explore the evolutionary origins of object individuation by testing a new-world monkey species, capuchin monkeys (Sapajus spp.), using both manual search (n = 29) and looking time (n = 23) measures. In Spatio-temporal trials, subjects saw one or two objects dropped into a box, but always found (or saw) only one. In Property/kind trials, subjects saw either object A or B being dropped into a box and then always found (or saw) object A. The capuchin monkeys looked longer and searched more on inconsistent trials – with outcome differing in quantity or in kind - which suggested that they had expectations based on both spatio-temporal and property-kind representations. Looking time and search measures gave convergent results at the group but not at the individual level. Our results add to the existing evidence contradicting the linguistic hypothesis of property/kind individuation. However, contrary to recent discussions, we argue that these and related results can be explained without appealing to the notion of sortal concepts or multiple representational systems, and suggest that a full picture of the ontogeny and phylogeny of object individuation requires further empirical and theoretical research.Publisher PDFPeer reviewe

A Log-w Turbulence Model Formulation for Flutter Analysis with Harmonic Balance

When considering flutter problems, unsteady effects in turbulence quantities are often not taken into account when using time-linearized methods. However, several studies have demonstrated that it can be necessary to resolve those effects in certain cases. The harmonic balance method is inherently able to capture the time dependent behaviour of the turbulence model. However, the method can suffer from instabilities due to problems in the turbulence model. As a possible solution, a logarithmic formulation of the w equation of the Wilcox k-w model is applied to the Harmonic Balance method in this paper. The combination is validated using a flutter computation of the NACA 3506 airfoil. One of the operating points exhibits significant oscillations in a shock induced separation. Resolving the unsteady behaviour of the boundary layer proved to be crucial to obtain a converged solution with the harmonic balance method. Both model variants were able to achieve satisfactory results. However, the log(w) model variant was able to provide advantages in accuracy and convergence