39 research outputs found
Spatially evolving cascades in wall turbulence with and without interface
Get PDFDirect numerical simulations of channel flow and temporal boundary layer at a Reynolds number Reτ=1500 are used to assess the scale-by-scale mechanisms of wall turbulence. From the peak of turbulence production embedded at the small scales of the near-wall region, spatially ascending reverse cascades are generated that move through self-similar eddies growing in size with the wall distance. These fluxes are followed by spatially ascending forward cascades through detached eddies thus reaching sufficiently small scales where eventually scale energy is dissipated. This phenomenology is shared by both boundary layer and channel flow and is recognized as a robust physical feature characterizing wall turbulence in general. Specific features related to the flow configuration are indeed identified in the outer region. In particular, the central region of channels is characterized by a generalized Richardson energy cascade where large scales are in equilibrium with small scales at different wall distances through a combined forward cascade and spatial flux. On the contrary, the interface region of boundary layers is characterized by an almost two-dimensional physics where spatially ascending reverse cascades sustain long and wide interface structures with a forward cascade that survives only in the wall-normal scales. The overall scenario consists in a variety of scale motions that while protruding from the turbulent core towards the external region, squeeze at the interface thus sustaining vertical shear in a thin layer. The observed multidimensional physics sheds light on the complex interactions between outer entrainment and near-wall self-sustaining mechanisms with possible repercussions for theories.Energy Technolog
Analysis of turbulent Rayleigh-Bénard convection in the compound physical/scale space domain
No full textWe report the results from two distinct direct numerical simulations (DNS) of turbulent Rayleigh-Bénard convection (RBC) for Rayleigh number of 10^5 and Prandtl number of 0.7 in a laterally unbounded domain confined between two horizontal isothermal plates with no-slip and free-slip boundary conditions respectively. The central aim of the present work consists in a simultaneous description of both flows in a compound physical/scale space domain by using a generalized form of the classical Kolmogorov equation for the second-order velocity structure function. It has been found that the dynamics of the coherent structures in RBC, the so-called thermal plumes, are clearly reflected in the multi-scale energy budgets. In particular, the enlargement of thermal plumes following the impingement at the wall entails a transfer of scale-energy from small turbulent scales toward larger ones. This aspect shed light on the role of thermal plumes in turbulent RBC and could have a direct impact on future attempts to model the effects of small-scale motions in thermal convection
Analysis of the Yaglom equation and subgrid modelling approaches for thermally driven turbulence
No full textWe report a Direct Numerical Simulation (DNS) of turbulent Rayleigh-Bénard convection in a laterally unbounded domain confined between two horizontal parallel walls, for Rayleigh number 10^5 and Prandtl number 0.7. The DNS data are used to study the properties of the subgrid-scale flux of the active temperature field in the framework of Large Eddy Simulation (LES). In particular, starting from the generalized Yaglom equation, we analyse how the thermal energy is produced, transferred and dissipated in the augmented space of scales and positions of the flow. The understanding of these processes is then used to propose appropriate formulations for the subgrid-scale flux that will be tested by means of a posteriori analysis of LES simulations performed in the same flow conditions
Does the noise level and number of visitors influence dogs and wolves\u27 behavior?
No full textMaster thesis - University of Veterinary Medicine Vienna - 2022The visitor effect has already been investigated with many different animal species. The goal of these studies is to understand if, and how, visitors influence animals living in captivity. However, to date only few studies have focused on canines, and none have compared equally raised dogs, C. l. familiaris, and wolves, Canis lupus. This direct comparison might give valuable insights on how domestication has changed the perception of humans by dogs and wolves. Here, we observed the animals at the Wolf Science Center (WSC) in their reactions to spontaneously behaving human visitors, and their pet dogs. Following the ‘Hyper-Sociability Hypothesis, we expected dogs to show less negative behavior in reaction to the visitors, compared to wolves. While we found that visitor number itself had no influence on the animals, we could find a significant effect for visitor noise levels, as well as certain visitor behaviors. However, contrary to our hypothesis, we could not find an overall negative visitor effect on neither of the animals, which might be best explained by the extensive socialization of the animals from puppyhood on.Masterarbeit - Veterinärmedizinische Universität Wien - 2022Der Besucher-Effekt wurde bereits anhand vieler verschiedener Tierarten untersucht, um zu verstehen ob und wie Besucher*innen Tiere die in Zoos, und ähnlichen Einrichtungen leben, beeinflussen. Bis heute haben sich jedoch nur wenige Studien mit der Familie der Kaniden befasst, und keine hat identisch aufgezogen Hunde, C. l. familiaris, und Wölfe, Canis lupus, verglichen. Dieser direkte Vergleich kann wertvolle Hinweise geben, wie sich im Laufe der Domestikation die Wahrnehmung bezüglich des Menschen vom Wolf zum Hund verändert hat. In dieser Studie haben wir die Tiere des Wolf Science Center (WSC) in ihren Reaktionen auf sich spontan verhaltene Menschen und ihre privaten Hunde beobachtet. Gemäß der ‘Hyper-Sociability Hypothesis’ erwarteten wir, dass Hunde, im Vergleich zu Wölfen, weniger negatives Verhalten als Reaktion auf die Besucher*innen zeigen würden. Während die Besucher*innen Zahl keinen Einfluss auf die Tiere zu haben scheint, konnten wir einen signifikanten Einfluss des Geräuschpegels, sowie einiger Besucher*innen Verhaltensweisen nachweisen. Entgegen unserer Hypothese konnten wir jedoch einen allgemeinen negativen Besucher*innen Effekt auf die Tiere feststellen, was am wahrscheinlichsten mit der extensiven Sozialisierung der Tiere von klein auf erklärbar ist.Master thesis - University of Veterinary Medicine Vienna - 2022The visitor effect has already been investigated with many different animal species. The goal of these studies is to understand if, and how, visitors influence animals living in captivity. However, to date only few studies have focused on canines, and none have compared equally raised dogs, C. l. familiaris, and wolves, Canis lupus. This direct comparison might give valuable insights on how domestication has changed the perception of humans by dogs and wolves. Here, we observed the animals at the Wolf Science Center (WSC) in their reactions to spontaneously behaving human visitors, and their pet dogs. Following the ‘Hyper-Sociability Hypothesis, we expected dogs to show less negative behavior in reaction to the visitors, compared to wolves. While we found that visitor number itself had no influence on the animals, we could find a significant effect for visitor noise levels, as well as certain visitor behaviors. However, contrary to our hypothesis, we could not find an overall negative visitor effect on neither of the animals, which might be best explained by the extensive socialization of the animals from puppyhood on
Does visitor behaviour in front of enclosures differ between captive dogs and wolves?
No full textMasterarbeit - Veterinärmedizinische Universität Wien - 2022Es wird vermutet, dass unsere Einstellung gegenüber Hunden sich zeitgleich zum Domestizierungsprozess aus der negativen Einstellung gegenüber Wölfen entwickelt hat. Unsere Einstellungen und Verhaltensweisen wurden positiver gegenüber zahmeren Individuen, während wir eine negative Einstellung gegenüber Wölfen beibehielten (Dual-Response Hypothese, DRH). Dies habe eine Feedbackschleife erzeugt, in der die positiveren Einstellungen den Domestikationsprozess weiter förderten. Wenn wir solch differentielle, inherente Einstellungen entwickelt haben, dann sollte unser gegenwärtiges Verhalten negativere Einstellungen gegenüber Wölfen widerspiegeln (d.h. gesteigerte Aufmerksamkeit auf Grund von Angst, mehr störendes und lauteres Verhalten), im Vergleich zu positiveren Einstellungen gegenüber Hunden (d.h. mehr Interaktionsversuche). Um die DRH zu testen haben wir spontanes Besucherverhalten (verschiedene demographische Kategorien berücksichtigend) gegenüber Wölfen und Hunden in einem vergleichbaren Kontext eines Wildparks im Bereich des Wolf Science Centers ausgewertet und dabei die Sichtbarkeit und das Verhalten der Tiere berücksichtigt. In Übereinstimmung mit unseren Vorhersagen traten Interaktionsversuche signifikant häufiger bei den Hunden im Vergleich zu den Wölfen auf und wurden öfter durch jüngere Besucher gezeigt. Im Kontrast zu unseren Vorhersagen waren erwachsene Besucher aufmerksamer gegenüber Hunden, und nicht signifikant störender oder lauter bei den Wolfsgehegen. Darüber hinaus legte die Miteinbeziehung der Sichtbarkeit und des Verhaltens der Kaniden systematische Unterschiede in den Besucherreaktionen gegenüber den beiden Arten offen. Unsere Ergebnisse deuten darauf hin, dass Menschen selbst in einem vergleichbaren Kontext mit indirektem Kontakt dazu neigen mit Hunden zu interagieren und sich vorsichtiger gegenüber Wölfen zu verhalten. Unsere Ergebnisse unterstützen in Teilen die DRH.Master thesis - University of Veterinary Medicine Vienna - 2022It has been proposed that our attitudes towards dogs developed out of our negative attitude towards wolves, simultaneously with the domestication process of dogs from wolves. Our attitudes and behaviours became more positive towards tamer individuals, while we maintained negative attitudes towards wolves (Dual Response Hypothesis, DRH). Supposedly, this created a feedback loop with more positive attitudes further advancing the domestication process. If we developed such differential, inherent attitudes, our contemporary behaviour should reflect more negative attitudes towards wolves (i.e. more attentive because of fear, more disruptive, and noisier), compared to more positive attitudes towards dogs (i.e. more interaction attempts). To test the DRH, we compared spontaneous visitor behaviour (across different demographic categories) in front of captive wolves and dogs in a comparable context at the Wolf Science Center, controlling for the animals’ visibility and behaviour. In line with our predictions, interaction attempts were significantly more prevalent (70%) in front of dogs compared to wolves, and shown more often by younger visitors. Contradicting our predictions, adult visitors were more attentive towards dogs, and not significantly more disruptive, or noisier at wolf enclosures. Further, canids’ visibility and behaviours revealed systematic differences in visitor reactions towards the two species. Our results suggest that even in a comparable, non-direct contact setting, humans are inclined to interact with dogs, and behave more cautiously around wolves. These differences in behaviour found in our study provide partial support to the DRH
Behavioral and epigenetic variations in differentially socialized dogs and a relational approach to aggression in pet dogs
No full textMasterarbeit - Veterinärmedizinische Universität Wien - 2021Abstract nicht vorhandenMaster thesis - University of Veterinary Medicine Vienna - 2021No abstract availabl
Overimitation in Dogs: Is There a Link to the Quality of the Relationship with the Caregiver?
No full textOverimitation, the copying of causally irrelevant or non-functional actions, is well-known from humans but completely absent in other primates. Recent studies from our lab have provided evidence for overimitation in canines. Previously, we found that half of tested pet dogs copied their human caregiver’s irrelevant action, while only few did so when the action was demonstrated by an unfamiliar experimenter. Therefore, we hypothesized that dogs show overimitation as a result of socio-motivational grounds. To test this more specifically, here we investigated how the relationship with the caregiver influenced the eagerness to overimitate. Given the high variability in the tendency to overimitate their caregiver, we hypothesized that not only familiarity but also relationship quality influences whether dogs faithfully copy their caregiver. For this purpose, on the one hand we measured the overimitation tendency (with the same test as in the two studies before) and on the other hand the relationship quality between the dogs and their caregivers. Although we found no significant correlation between the two test results, our data might suggest that, on average, dogs who overimitated seemed to show more referential and affiliative behaviours towards the owner than dogs who showed less or no copying of the irrelevant action. Notably, as a group, those dogs that showed the highest level of copying accuracy of the irrelevant action showed the highest level of gazing and synchronization towards the owner
Free-ranging dogs match a human’s preference in a foraging task
No full textSocial learning is a mechanism used by many species to efficiently gain information about their environment. Although many animals live in an environment where members of other species are present, little is known about interspecific social learning. Domesticated and urbanized species provide the opportunity to investigate whether nonhuman animals can learn from heterospecifics such as humans, who are integral parts of their social landscape. Although domestic dogs Canis familiaris have been intensively researched for their ability to learn from humans, most studies have focused on dogs living as pets. However, free-ranging dogs represent the majority of the world’s dog population, they live alongside humans, scavenge on human refuse, and are subject to natural and sexual selection. Thus, free-ranging dogs with extensive exposure to humans and their artifacts provide the opportunity to investigate interspecific social learning in a naturalistic setting, where learning from humans might be a benefit for them. Here we tested individual free-ranging dogs in a between-subject design: Dogs in the control group could spontaneously choose between two novel and differently patterned food-delivering boxes. In the experimental group, instead, dogs could first observe an unfamiliar human approaching and eating from 1 of the 2 boxes. We provide the first evidence that free-ranging dogs match the choice of an unfamiliar human. These results show that at least simple forms of interspecific social learning might be involved in dogs’ success in living alongside humans in a complex urbanized environment. </p
Dogs understand the role of a human partner in a cooperative task
No full textInternational audienceHumans are exceptionally flexible in cooperation, partly due to our ability to recognize the roles of cooperative partners. While some non-human animals understand the need for a partner in such interactions, it is unclear whether they grasp the consequences of their partner’s actions and adjust accordingly. Previous studies utilizing economic games with non-human animals yielded mixed results. We investigated dogs, known for their close cooperation with humans, in a stag hunt game. Dogs could cooperate for better rewards or defect for lower ones, while their human partners would either cooperate, never cooperate, or act randomly. We control for attraction to food, side bias, and local enhancement. Dogs were more likely to coordinate with their partners when it led to better rewards, suggesting that they understood their partner’s actions. By highlighting this cognitive skill in dogs, we advance our knowledge of the intricate mechanisms driving cooperative behavior in non-human animals
The Other End of the Leash: An Experimental Test to Analyze How Owners Interact with Their Pet Dogs
No full text
