Osteons are cylindrical structures of bone created by matrix resorbing osteoclasts, followed by osteoblasts that deposit new bone. Osteons align with the principal loading direction and it is thought that the osteoclasts are directed by osteocytes, the mechanosensitive cells that reside inside the bone matrix. These osteocytes are presumably controlled by interstitial fluid flow, induced by the physiological loading of bones. Here I consider the stimulation of osteocytes while the osteon is closed by osteoblasts. In a conceptual finite (...) element model, bone is considered a poro‐elastic material and subjected to locomotion‐induced loading conditions. It appears that the magnitude of flow is constant along the closing cone, while shear strain rate in the bone matrix diminishes linearly with the deposition of bone. This suggests that shear strain rate, rather than fluid flow, is the physical cue that controls osteocytes and bone deposition in newly formed osteons. (shrink)

The 3D Prandtl fluid flow through a bidirectional extending surface is analytically investigated. Cattaneo–Christov fluid model is employed to govern the heat and mass flux during fluid motion. The Prandtl fluid motion is mathematically modeled using the law of conservations of mass, momentum, and energy. The set of coupled nonlinear PDEs is converted to ODEs by employing appropriate similarity relations. The system of coupled ODEs is analytically solved using the well-established mathematical technique of HAM. The (...) impacts of various physical parameters over the fluid state variables are investigated by displaying their corresponding plots. The augmenting Prandtl parameter enhances the fluid velocity and reduces the temperature and concentration of the fluid. The momentum boundary layer boosts while the thermal boundary layer mitigates with the rising elastic parameter strength. Furthermore, the enhancing thermal relaxation parameter ) reduces the temperature distribution, whereas the augmenting concentration parameter drops the strength of the concentration profile. The increasing Prandtl parameter declines the fluid temperature while the augmenting Schmidt number drops the fluid concentration. The comparison of the HAM technique with the numerical solution shows an excellent agreement and hence ascertains the accuracy of the applied analytical technique. This work finds applications in numerous fields involving the flow of non-Newtonian fluids. (shrink)

The human body has been a potent and persistent metaphor for social and political relations throughout human history. For example, different parts of the body have traditionally represented different social functions. We refer to the ‘head of state’ without really recognizing the metaphor, and the heart has been a rich source of ideas about life, imagination and emotions. The heart is the house of the soul and the book of life, and the ‘tables of the heart’ provided an insight into (...) the whole of Nature. The hand also plays an important role in conventional imagination regarding things that are beautiful (handsome) or damaged and incomplete (handicap). We can generalize from these diverse examples to argue that the fluids flowing from the inside of the body to the outside are regarded as socially dangerous and contaminating, because these fluids on the outside of the body directly challenge our sense of order and orderliness. This inside/outside division of the body combines with a wet/dry dichotomy to delineate these risky borders. Although leaking bodies have been a source of ancient metaphors of disorder, the modern world, that sociologists increasingly characterize by its liquidity, is peculiarly fascinated by flow as an image of global flexibility. The more our world is economically and militarily interconnected, the more we fear social fluidity. In political terms, asylum seekers and terrorists are thought not to respect our bodies or our borders; we are especially sensitive to their capacity to disrupt the solidity of sovereignty. In short, metaphors of the human body, even in an age of high technology, continue to shape the social and political imagination, but they are challenged by emerging metaphors of liquidity, that is by liquid modernity. (shrink)

The Western school classroom can no longer remain a secluded and impermeable space in a world that is increasingly hyperconnected through dynamic flows of capital, technologies, populations, media images and ideas. Books brought to the school by diverse students, narratives from far-away countries and YouTube tunes from different cultures can become powerful teaching and learning tools in this frame. Such tools enable multiple metaphors and connections between various life spheres, diverse cultural and socio-economic milieus, and different times and places, as (...) manifested in the thought-provoking ethnographic observation on ‘The book and the author’s reading’ by Elise v. Bernstorff and Carla J. Maier. (shrink)

Rationality - as opposed to 'ad-hoc' - and asymptotics - to emphasize the fact that perturbative methods are at the core of the theory - are the two main concepts associated with the Rational Asymptotic Modeling (RAM) approach in fluid dynamics when the goal is to specifically provide useful models accessible to numerical simulation via high-speed computing. This approach has contributed to a fresh understanding of Newtonian fluid flow problems and has opened up new avenues for tackling (...) real fluid flow phenomena, which are known to lead to very difficult mathematical and numerical problems irrespective of turbulence. With the present scientific autobiography the author guides the reader through his somewhat non-traditional career; first discovering fluid mechanics, and then devoting more than fifty years to intense work in the field. Using both personal and general historical contexts, this account will be of benefit to anyone interested in the early and contemporary developments of an important branch of theoretical and computational fluid mechanics. (shrink)

We live in a liquid new world driven by incessant change. Our reality is constantly shaped by new forms of non-linear individualism, which is expressed in countless factions, networks, tribes and alliances. Social systems do not maintain their shape for very long, because they decompose and melt faster than the time it takes to cast them, according to the sociologist Zygmunt Bauman. Religious institutions that do not come to terms with these rapid rates of change soon find themselves trapped in (...) a so-called parallel universe, with hardly any influence on society. In order to embrace our fluid new reality with its numerous open systems and ever-increasing levels of complexity, ekerk understands herself as a movement of Jesus followers whose tribal identity is shaped around his teachings on the Kingdom of God, and which is reflected in the values of relationality and generosity. We have ‘tribal habitats’ in various digital and physical spaces. Under the radar of institutionalised church and academia, but also as their ally in a somewhat subversive manner, ekerk facilitates the spreading of the good news of Jesus in decentralised but very real ways. ekerkalso runs a large generosity ministry, as well as various seminars, meetings and growth programmes such as DieGang/TheGang to invest in young Christian leaders. (shrink)

The debate around ethical consumption is often characterised by discussion of its numerous failures arising from complexity in perceived trade-offs. In response, this paper advances a pragmatist understanding of the role and nature of trade-offs in ethical consumption. In doing so, it draws on the central roles of values and value in consumption and pragmatist philosophical thought, and proposes a critique of the ethical consumer as rational maximiser and the cognitive and utilitarian discourse of individual trade-offs to understand how sustainable (...) consumption practices are established and maintained. An in-depth qualitative study is conducted employing phenomenological interviews and hermeneutic analysis to explore the consumption stories of a group of ethically minded consumers. The research uncovers the location of value within a fluid, yet habitual, plurality of patterns, preferences, morals, identities and relationships. Its contribution is to propose that consumer perception of value in moral judgements is represented by an overall form of aggregate personal advantage, which lacks conscious reflection and delivers a phenomenological form of value rooted in habits, reflecting a pragmatist representation of value unified as a ‘consummatory experience’. (shrink)

The first of its kind, this book is an in-depth history of hydrodynamics from its eighteenth-century foundations to its first major successes in twentieth-century hydraulics and aeronautics. It documents the foundational role of fluid mechanics in developing a new mathematical physics. It gives full and clear accounts of the conceptual breakthroughs of physicists and engineers who tried to meet challenges in the practical worlds of hydraulics, navigation, blood circulation, meteorology, and aeronautics, and it shows how hydrodynamics at last began (...) to fulfill its early promise to unify the different worlds of flow. Richly illustrated, technically thorough, and sensitive to cross-cultural effects, this history should attract a broad range of historians, scientists, engineers, and philosophers and be a standard reference for anyone interested in fluid mechanics. (shrink)

The following article treats the 'applicational turn' of modern fluid dynamics as it set in at the beginning of the 20th century with Ludwig Prandtl's concept of the boundary layer. It seeks to show that there is much more to applying a theory in a highly mathematical field like fluid dynamics than deriving a special case from a general explanatory theory under particular antecedent conditions. In Prandtl's case, the decisive move was to introduce a model that provided a (...) physical/causal conception of viscous flow at high Reynolds numbers. It facilitated an approximate solution to the Navier-Stokes equations, which in turn gave rise to many special applications. After a detailed account of Prandtl's achievement, the article discusses the role of the physical model and its experimental and mathematical significance. It is shown that the mathematical simplification provided by the physical model greatly expanded the explanatory capacity of the theory which the Navier-Stokes equations alone could not provide. (shrink)

This contribution to the Common Knowledge symposium “Fuzzy Studies” argues that the inclusion of space in form brings varying degrees of fuzziness and fluidity to all natural identities. Such inclusion is vital to evolutionary creativity, from subatomic to cosmic scales of natural energy flow. Examples abound throughout the natural world of indeterminate forms and processes unclassifiable under any of the discrete categories that are preferred and imposed by definitive theoretical models. Here, the much-neglected kingdom of the fungi is used (...) to illustrate the workings of a logic of fluid boundaries. (shrink)

BackgroundConventionally, transcranial direct current stimulation (tDCS) aims to focalize the current reaching the target region-of-interest (ROI). The focality can be quantified by the dose-target-determination-index (DTDI). Despite having a uniform tDCS setup, some individuals receive focal stimulation (high DTDI) while others show reduced focality (“non-focal”). The volume of cerebrospinal fluid (CSF), gray matter (GM), and white matter (WM) underlying each ROI govern the tDCS current distribution inside the brain, thereby regulating focality.AimTo determine the regional volume parameters that differentiate the focal (...) and non-focal groups.MethodsT1-weighted images of the brain from 300 age-sex matched adults were divided into three equal groups- (a) Young (20 ≤ × < 40 years), (b) Middle (40 ≤ × < 60 years), and (c) Older (60 ≤ × < 80 years). For each group, inter and intra-hemispheric montages with electrodes at (1) F3 and right supraorbital region (F3-RSO), and (2) CP5 and Cz (CP5-Cz) were simulated, targeting the left- Dorsolateral Prefrontal Cortex (DLPFC) and -Inferior Parietal Lobule (IPL), respectively. Both montages were simulated for two current doses (1 and 2 mA). For each individual head simulated for a tDCS configuration (montage and dose), the current density at each region-of-interest (ROI) and their DTDI were calculated. The individuals were categorized into two groups- (1) Focal (DTDI ≥ 0.75), and (2) Non-focal (DTDI < 0.75). The regional volume of CSF, GM, and WM of all the ROIs was determined. For each tDCS configuration and ROI, three 3-way analysis of variance was performed considering- (i) GM, (ii) WM, and (iii) CSF as the dependent variable (DV). The age group, sex, and focality group were the between-subject factors. For a given ROI, if any of the 3 DV’s showed a significant main effect or interaction involving the focality group, then that ROI was classified as a “focal ROI.”ResultsRegional CSF was the principal determinant of focality. For interhemispheric F3-RSO montage, interaction effect (p < 0.05) of age and focality was observed at Left Caudate Nucleus, with the focal group exhibiting higher CSF volume. The CSF volume of focal ROI correlated positively (r ∼ 0.16, p < 0.05) with the current density at the target ROI (DLPFC). For intrahemispheric CP5-Cz montage, a significant (p < 0.05) main effect was observed at the left pre- and post-central gyrus, with the focal group showing lower CSF volume. The CSF volume correlated negatively (r ∼ –0.16, p < 0.05) with current density at left IPL. The results were consistent for both current doses.ConclusionThe CSF channels the flow of tDCS current between electrodes with focal ROIs acting like reservoirs of current. The position of focal ROI in the channel determines the stimulation intensity at the target ROI. For focal stimulation in interhemispheric F3-RSO, the proximity of focal ROI reserves the current density at the target ROI (DLPFC). In contrast, for intrahemispheric montage (CP5-Cz), the far-end location of focal ROI reduces the current density at the target (IPL). (shrink)

Though some influentially critical objections have been raised during the ‘classical’ pre-computational simulation philosophy of science tradition, suggesting a more nuanced methodological category for experiments, it safe to say such critical objections have greatly proliferated in philosophical studies dedicated to the role played by computational simulations in science. For instance, Eric Winsberg suggests that computer simulations are methodologically unique in the development of a theory’s models suggesting new epistemic notions of application. This is also echoed in Jeffrey Ramsey’s notions of (...) “transformation reduction,”—i.e., a notion of reduction of a more highly constructive variety. Computer simulations create a broadly continuous arena spanned by normative and descriptive aspects of theory-articulation, as entailed by the notion of transformation reductions occupying a continuous region demarcated by Ernest Nagel’s logical-explanatory “domain-combining reduction” on the one hand, and Thomas Nickels’ heuristic “domain-preserving reduction,” on the other. I extend Winsberg’s and Ramsey’s points here, by arguing that in the field of computational fluid dynamics as well as in other branches of applied physics, the computer plays a constitutively experimental role—supplanting in many cases the more traditional experimental methods such as flow-visualization, etc. In this case, however CFD algorithms act as substitutes, not supplements when it comes to experimental practices. I bring up the constructive example involving the Clifford-Algebraic algorithms for modeling singular phenomena in CFD by Gerik Scheuermann and Steven Mann & Alyn Rockwood who demonstrate that their algorithms offer greater descriptive and explanatory scope than the standard Navier-Stokes approaches. The mathematical distinction between Navier-Stokes-based and Clifford-Algebraic based CFD has essentially to do with the regularization features exhibited to a far greater extent by the latter, than the former. Hence, CACFD indicate that the utilization of computational techniques can be based on principled reasons, as opposed to merely practical. CACFD hence exhibit a new generative role in the field of fluid mechanics, by offering categories of experimental evidence that are optimally descriptive and explanatory—i.e., pace Batterman can be both ontologically and epistemically fundamental. (shrink)

Lattice-gas cellular automaton (LGCA) and lattice Boltzmann (LB) models are promising models for studying emergent behaviour of transport and interaction processes in biological systems. In this chapter, we will emphasise the use of LGCA/LB models and the derivation and analysis of LGCA models ranging from the classical example dynamics of fluid flow to clotting phenomena in cerebral aneurysms and the invasion of tumour cells.

Whereas recent framings of planetary urbanization stress the planet-scaled impacts of contemporary urban processes, we might also conceive of cities as being constitutively ‘planetary’ from their very outset. This article looks at two ways in which the earliest urban centres or ‘civilizations’ on the floodplains of the Fertile Crescent harnessed the deep, geological forces of the Earth. The first is the tapping and channelling of sedimentary processes, central to what Wittfogel referred to as hydraulic civilizations (1963). The second is the (...) use of high-heat technologies to smelt and forge metals, which can be construed as a capture of igneous processes. What both sets of practices have in common is that they involve skilled intervention in fluid-solid phase transitions between solid rock and flowing particulate matter. Viewing cities as constitutively geological or planetary in this way can help us reimagine the challenges posed to urban spaces by looming transformations in Earth systems. (shrink)

The increasing global demand for energy necessitates devoted attention to the formulation and exploration of mechanisms of thermal heat exchangers to explore and save heat energy. Thus, innovative thermal transport fluids require to boost thermal conductivity and heat flow features to upsurge convection heat rate, and nanofluids have been effectively employed as standard heat transfer fluids. With such intention, herein, we formulated and developed the constitutive flow laws by utilizing the Rossland diffusion approximation and Stephen’s law along with (...) the MHD effect. The mathematical formulation is based on boundary layer theory pioneered by Prandtl. Governing nonlinear partial differential flow equations are changed to ODEs via the implementation of the similarity variables. A well-known computational algorithm BVPh2 has been utilized for the solution of the nonlinear system of ODEs. The consequence of innumerable physical parameters on flow field, thermal distribution, and solutal field, such as magnetic field, Lewis number, velocity parameter, Prandtl number, drag force, Nusselt number, and Sherwood number, is plotted via graphs. Finally, numerical consequences are compared with the homotopic solution as a limiting case, and an exceptional agreement is found. (shrink)

Analysis of three kinds of flow of viscous, incompressible, electrically conducting fluids in high-aspect-ration rectangular channels subjected to transverse magnetic fields: turbulent flow in the presence of a d-c magnetic field, and both laminar and turbulent induction-driven flows.

Both society and plasma (ionized gas) fluid are composed of active, interactive, and free, individuals. These individuals are responded to any internal and external effects (fields for plasma), and exhibit collective behaviour. According to this structure, there are a wide range of similarities between the plasma fluid and the society. The nature of fluidity of plasma arises from the interaction of its free interactive charges, so the society may behave as a fluid owing to the free interactive (...) individuals. This fluid model may explain many social phenomena like social instability, diffusion, flow, viscosity...So the society behaves as a sort of intellectual fluid. (shrink)

Both society and plasma (ionized gas) fluid are composed of active, interactive, and free, in-dividuals. These individuals response to any internal and external effects (fields for plasma), and exhibit collective behaviour. According to this structure, there are a wide range of similar-ities between the plasma fluid and the society. The nature of fluidity of plasma arises from the interaction of its free interactive charges, so the society may behave as a fluid owing to the free interactive individuals (...) (persons). This fluid model may explain many social phenomena like social instability, diffusion, flow, viscosity...So the society behaves as a sort of intellectu-al fluid. It may be possible to suggest a modification of plasma computation simulation tech-nique to study the social phenomena. (shrink)

In the energy–momentum density expressions for a relativistic perfect fluid with a bulk motion, one comes across a couple of pressure-dependent terms, which though well known, are to an extent, lacking in their conceptual basis and the ensuing physical interpretation. In the expression for the energy density, the rest mass density along with the kinetic energy density of the fluid constituents due to their random motion, which contributes to the pressure as well, are already included. However, in a (...) fluid with a bulk motion, there are, in addition, a couple of explicit, pressure-dependent terms in the energy–momentum density, whose presence to an extent, is shrouded in mystery, especially from a physical perspective. We show here that one such pressure-dependent term appearing in the energy density, represents the work done by the fluid pressure against the Lorentz contraction during transition from the rest frame of the fluid to another frame in which the fluid has a bulk motion. This applies equally to the electromagnetic energy density of electrically charged systems in motion and explains in a natural manner an apparently paradoxical result that the field energy of a charged capacitor system decreases with an increase in the system velocity. The momentum density includes another pressure-dependent term, that represents an energy flow across the system, due to the opposite signs of work being done by pressure on two opposite sides of the moving fluid. From Maxwell’s stress tensor we demonstrate that in the expression for electromagnetic momentum of an electric charged particle, it is the presence of a similar pressure term, arising from electrical self-repulsion forces in the charged sphere, that yields a natural solution for the notorious, more than a century old but thought by many as still unresolved, 4/3 problem in the electromagnetic mass. (shrink)

The evolution of the equation of mass conservation in fluid mechanics is studied. Following early hydraulic approximations, and progress by Daniel and Johann Bernoulli, its first expression as a partial differential equation was achieved by d’Alembert, and soon given definitive form by Euler. Later reworkings by Lagrange, Laplace, Poisson and others advanced the subject, but all based their derivations on the conserved mass of a moving fluid particle. Later, Duhamel and Thomson gave a simpler derivation, by considering mass (...) flow into and out of a fixed portion of space. The later propagation of these derivations in nineteenth-century British textbooks and treatises is also examined, including Maxwell’s on the kinetic theory of gases. (shrink)

At the turn of the nineteenth and twentieth centuries a concerted effort was made in the discipline of fluid mechanics to make hidden and fleeting processes visible and to capture the results photographically. I examine two important cases. One concerns the photographs taken by H. S. Hele-Shaw in the 1890s showing the flow of a “perfect”, frictionless fluid. The other case deals with the photographs of boundary layer separation taken by Ludwig Prandtl. These were presented to the (...) Third International Congress of Mathematicians in Heidelberg in 1904. My concern in both cases will be with the relation of the photographs to the reality actually or putatively portrayed in the photograph. Superficially the two cases are very different. “Perfect” fluids were accepted as mere mathematical abstractions to which nothing real could correspond while the reality of the boundary layer has been accepted as a discovery of enormous physical and technical importance. A detailed examination, however, suggests some inner connections of a kind that challenges the understanding of certain “common sense” distinctions between the two cases.Keywords: Sichtbarmachung; Fluid mechanics; Perfect fluids; Boundary layer; Social construction; Prandtl; Hele-Shaw. (shrink)

The present study addresses the fluid transport behaviour of the flow of gold -copper /biomagnetic blood hybrid nanofluid in an inclined irregular stenosis artery as a consequence of varying viscosity and Lorentz force. The nonlinear flow equations are transformed into dimensionless form by using nonsimilar variables. The finite-difference technique is involved in computing the nonlinear transport dimensionless equations. The significant parameters like angle parameter, the Hartmann number, changing viscosity, constant heat source, the Reynolds number, and nanoparticle volume (...) fraction on the flow field are exhibited through figures. Present results disclose that the Lorentz force strongly lessens the hybrid nanofluid velocity. Elevating the Grashof number values enhances the rate of blood flow. Growing values of the angle parameter cause to reduce the resistance impedance on the wall. Hybrid nanoparticles have a superior wall shear stress than copper nanoparticles. The heat transfer rate is amplifying at the axial direction with the growing values of nanoparticles concentration. The applied Lorentz force significantly reduces the hybrid and unitary nanofluid flow rate in the axial direction. The hybrid nanoparticles expose a supreme rate of heat transfer than the copper nanoparticles in a blood base fluid. Compared to hybrid and copper nanofluid, the blood base fluid has a lower temperature. (shrink)

Fibre suspension has garnered considerable attention in turbulent flows that are used in many industries. Solid particles, such as dust particles, notably affect the turbulent flow field in a rotational frame. In assessing their impacts, the dusty turbulent flow for fibre suspensions needs to be studied in a frame of rotation that can be substantially applied in many industries. This study, therefore, aims to build a theoretical model for the energy motion of dusty turbulent flow of fibre (...) suspensions in a rotational frame. The turbulence momentum equation was considered to formulate the model in presence of dusty fluid rotating flow of fibre suspensions. The newly derived equation was derived in second-order correlation tensors Fi,j, Wi,j, Gi,j, Si,j, Xi,j, Yi,j, Qi,j, and Ri,j at any two points in the flow domain, where the tensors were expressed as space, time, and distance functions. The developed model is a considerable improvement because it takes into account all of the potential influential parameters that could affect the motion of turbulent energy, such as dust particles, suspending particles, and rotating frame. However, the impact of these parameters on turbulence energy motion must be evaluated in order to assess the performance of turbulence systems utilized in a variety of industries, such as paper manufacturing. The present theoretical development will contribute to open up experimental and numerical research opportunities for the advancement of the industry, science, and technology. (shrink)

In this article, ethylene glycol + waterbased Maxwell nanofluid with radiation and Soret effects within two parallel plates has been investigated. The problem is formulated in the form of partial differential equations. The dimensionless governing equations for concentration, energy, and momentum are generalized by the fractional molecular diffusion, thermal flux, and shear stress defined by the Caputo–Fabrizio time fractional derivatives. The solutions of the problems are obtained via Laplace inversion numerical algorithm, namely, Stehfest’s. Nanoparticles of silver are suspended in a (...) mixture of EG + water to have a nanofluid. It is observed that the thermal conductivity of fluid is enhanced by increasing the values of time and volume fraction. The temperature and velocity of water-silver nanofluid are higher than those of ethylene glycol + water -silver nanofluid. The results are discussed at 2% of volume fraction. The results justified the thermo-physical characteristics of base fluids and nanoparticles shown in the tables. The effects of major physical parameters are illustrated graphically and discussed in detail. (shrink)

Unlike basic sciences, scientific research in advanced technologies aims to explain, predict, and (mathematically) describe not phenomena in nature, but phenomena in technological artefacts, thereby producing knowledge that is utilized in technological design. This article first explains why the covering-law view of applying science is inadequate for characterizing this research practice. Instead, the covering-law approach and causal explanation are integrated in this practice. Ludwig Prandtl's approach to concrete fluid flows is used as an example of scientific research in the (...) engineering sciences. A methodology of distinguishing between regions in space and/or phases in time that show distinct physical behaviours is specific to this research practice. Accordingly, two types of models specific to the engineering sciences are introduced. The diagrammatic model represents the causal explanation of physical behaviour in distinct spatial regions or time phases; the nomo-mathematical model represents the phenomenon in terms of a set of mathematically formulated laws. (shrink)

The distinction between the discrete and the continuous lies at the heart of mathematics. Discrete mathematics (arithmetic, algebra, combinatorics, graph theory, cryptography, logic) has a set of concepts, techniques, and application areas largely distinct from continuous mathematics (traditional geometry, calculus, most of functional analysis, differential equations, topology). The interaction between the two – for example in computer models of continuous systems such as fluid flow – is a central issue in the applicable mathematics of the last hundred years. (...) This article explains the distinction and why it has proved to be one of the great organizing themes of mathematics. (shrink)

What is special about all our living exchanges with our surroundings is that they occur within the ceaseless, intertwined flow of many unfolding strands of spontaneously responsive, living activity. This requires us to adopt a kind of fluid, process thinking, a shift from thinking of events as occurring between things and beings existing as separate entities prior to their inter-action, to events occurring within a continuously unfolding, holistic but stranded flow of events, with no clear, already existing (...) boundaries to be found anywhere (Mol & Law, 1994)—a flow of events within which we ourselves are also immersed. We thus become involved in activities within which we find things happening to us, as much as we make things happen in our surroundings—in other words, our surroundings are also agentive in that they can exert “calls” upon us to respond within them in appropriate ways. Consequently, what we can learn in such encounters is not just new facts or bits of information, but new ways of relating or orienting ourselves bodily to the others and othernesses in the world around us—although much can “stand in the way” of our doing this. My concern below is to explore events happening on the (inter)-subjective side of the Cartesian subject/object divide which “shape” our spontaneous ways of acting in, and reflecting on, the “worlds” within which we live out our lives. (shrink)

Experimental engineering models have been used both to model general phenomena, such as the onset of turbulence in fluid flow, and to predict the performance of machines of particular size and configuration in particular contexts. Various sorts of knowledge are involved in the method - logical consistency, general scientific principles, laws of specific sciences, and experience. I critically examine three different accounts of the foundations of the method of experimental engineering models (scale models), and examine how theory, practice, (...) and experience are involved in employing the method to obtain practical results. Models of machines and mechanisms can be (and generally are) involved in establishing criteria for similar phenomena, which provide guidance in using events to model other events. Conversely, models of phenomena such as events that model other events can be (and generally are) involved in experimentation on models of machines. I conclude that often it is not more detailed models or the more precise equations they engender that leads to better understanding, but rather an insightful use of knowledge at hand to determine which similarity principles are appropriate in allowing us to infer what we do not know from what we are able to observe. (shrink)

For two hundred years materialist philosophers have argued that man is some sort of machine. The claim began with French materialists of the Enlightenment such as Pierre Cabanis, Julien La Mettrie, and Baron d’Holbach (La Mettrie even wrote a book titled Man the Machine). Likewise contemporary materialists like Marvin Minsky, Daniel Dennett, and Patricia Churchland claim that the motions and modifications of matter are sufficient to account for all human experiences, even our interior and cognitive ones. Whereas the Enlightenment philosophes (...) might have thought of humans in terms of gear mechanisms and fluid flows, contemporary materialists think of humans in terms of neurological systems and computational devices. The idiom has been updated, but the underlying impulse to reduce mind to matter remains unchanged. (shrink)

In order to study drag reduction mechanism in mud parts’ operation of surface machine tools for paddy field, this paper takes floating plate, the main working part of laminating mechanism, as the research object and systematically analyzes the mechanism of action of elevation angle, curved angle, penetrating angle, and local microstructure of floating plate on working resistance and local fluid flow characteristics of the laminating structure based on VOF model in Fluent. Using ship mechanics theory and fluid (...) lubrication theory, the drag reduction mechanism under different structural parameters of the floating plate is analyzed. The results show that, compared with the ordinary floating plate, the pressure difference resistance can be reduced by increasing the elevation angle by 60°, curved angle by 20°, and mud separation angle by 20°. The increase of the concave nonsmooth bottom surface structure can reduce viscous frictional resistance, and the total working resistance after structural optimization is comparatively reduced by 48.3%, with lowered hilling height in the forward direction and improved lubrication condition of the bottom surface, forming liquid lubrication effect. This study can provide theoretical references for the optimization design of muddy soil mud parts, mud-machine interaction research, and the development of paddy field laminating mechanism. (shrink)

This paper illustrates how an experimental discovery can prompt the search for a theoretical explanation and also how obtaining such an explanation can provide heuristic benefits for further experimental discoveries. The case considered begins with the discovery of Poiseuille’s law for steady fluid flow through pipes. The law was originally supported by careful experiments, and was only later explained through a derivation from the more basic Navier–Stokes equations. However, this derivation employed a controversial boundary condition and also relied (...) on a contentious approach to viscosity. By comparing two editions of Lamb’s famous Hydrodynamics textbook, I argue that explanatory considerations were central to Lamb’s claims about this sort of fluid flow. In addition, I argue that this treatment of Poiseuille’s law played a heuristic role in Reynolds’ treatment of turbulent flows, where Poiseuille’s law fails to apply. (shrink)

In this paper, I review a collection of recently published papers that have provided significant new information about the biogenesis and functions of motile cilia. In vertebrates, the activity of motile cilia has been associated with a fascinating diversity of developmental and physiological processes. Despite the importance, much remains to be learned about the genetic control and cellular events that are involved in the differentiation of motile cilia. We also need to better understand the mechanisms by which cilia‐driven fluid (...) flow is able to influence such a variety of developmental and physiological processes. The Foxj1 family of proteins has now been definitively established as master regulators of motile ciliogenesis.1,2 Identification of the Kintoun/PF13 protein has shed light on the assembly of dynein arms,3 whereas live imaging of ciliary motility has led to the discovery of an intriguing new role for motile cilia in otolith formation in the ear.4. (shrink)

Professor Michael Edgeworth McIntyre is an eminent scientist who has also had a part-time career as a musician. From a lifetime's thinking, he offers this extraordinary synthesis exposing the deepest connections between science, music, and mathematics, while avoiding equations and technical jargon. He begins with perception psychology and the dichotomization instinct and then takes us through biological evolution, human language, and acausality illusions all the way to the climate crisis and the weaponization of the social media, and beyond that into (...) the deepest parts of theoretical physics - demonstrating our unconscious mathematical abilities. He also has an important message of hope for the future. Contrary to popular belief, biological evolution has given us not only the nastiest, but also the most compassionate and cooperative parts of human nature. This insight comes from recognizing that biological evolution is more than a simple competition between selfish genes. Rather, he suggests, in some ways it is more like turbulent fluid flow, a complex process spanning a vast range of timescales. Professor McIntyre is a Fellow of the Royal Society of London (FRS) and has worked on problems as diverse as the Sun's magnetic interior, the Antarctic ozone hole, jet streams in the atmosphere, and the psychophysics of violin sound. He has long been interested in how different branches of science can better communicate with each other and with the public, harnessing aspects of neuroscience and psychology that point toward the deep 'lucidity principles' that underlie skilful communication. (shrink)

Darcy's law is a phenomenological relationship for fluid flow rate that finds one of its principle applications in hydrology. Theoretical hydrologists rely upon a multiplicity of conceptual models to carry out approximate derivations of Darcy's law. These derivations provide structural explanations of the law; they require the application of fundamental principles, such as conservation of momentum, to idealized models of the porous media within which the flow occurs. In practice, recognition of the idealized conditions incorporated into models (...) facilitates the empirical clarification of the domain within which the law remains accurate. Structural explanations also contribute to the physical interpretation of phenomenological parameters. (shrink)

This concluding section applies the results of the previous part to some important thermodynamical systems. Even if time reversibility is allowed, it is shown that the flow vectors used to derive Onsager reciprocity from time translational invariance is of questionable validity. The fundamental fluctuation dissipation theorem of Callen, Welton, Green and Kubo which underpin descriptions of irreversibility, insofar as they are derived from time translational invariance, is also questioned; from Part I, they cannot be derived properly from time reversal (...) symmetry. The common view of entropy as some type of caloric fluid flow is critiqued as not conforming to the Kelvin Clausius Planck definition. An example of developing reciprocal relations to any order in the coupling indices based on the peculiar physical and defining characteristics of conductive heat is given for the steady state whenever a temperature gradient is present, free from time reversible and translation assumptions. A major challenge in the theory is to extend it to isothermal states. It is concluded that other more deterministic views mediated by authentic work anamnesis may be needed for long term coherence. (shrink)

In this Very Short Introduction, John H. Holland, one of the leading figures in the field, introduces the key elements and conceptual framework of complexity. From complex physical systems such as fluid flow and the difficulties of predicting weather, to complex adaptive systems such as the diverse and interdependent ecosystems of rainforests, he uses simple examples to illustrate the approach and insights provided by complexity theory.

In this Very Short Introduction, John H. Holland, one of the leading figures in the field, introduces the key elements and conceptual framework of complexity. From complex physical systems such as fluid flow and the difficulties of predicting weather, to complex adaptive systems such as the diverse and interdependent ecosystems of rainforests, he uses simple examples to illustrate the approach and insights provided by complexity theory.

The external surfaces of the human body, as well as its internal organs, constantly experience different kinds of mechanical stimulations. For example, tubular epithelial cells of the kidney are continuously exposed to a variety of mechanical forces, such as fluid flow shear stress within the lumen of th nephron. The majority of epithelial cells along the nephron, except intercalated cells, possess a primary cilium, an organelle projecting from the cell's apical surface into the luminal space. Despite its discovery (...) over 100 years ago, the primary cilium's function continued to elude researchers for many decades. However, recent studies indicate that renal cilia have a sensory function. Studies on polycystic kidney disease (PKD) have identified many of the molecular players, which should help solve the mystery of how the renal cilium senses fluid flow. In this review, we will summarize the recent breakthroughs in PKD research and discuss the role(s) of th polycystin signaling complex in mediating mechanosensory function by the primary cilium of renal epithelium as well as of the embryonic node. BioEssays 26:844–856, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Unlike basic sciences, scientific research in advanced technologies aims to explain, predict, and describe not phenomena in nature, but phenomena in technological artefacts, thereby producing knowledge that is utilized in technological design. This article first explains why the covering‐law view of applying science is inadequate for characterizing this research practice. Instead, the covering‐law approach and causal explanation are integrated in this practice. Ludwig Prandtl’s approach to concrete fluid flows is used as an example of scientific research in the engineering (...) sciences. A methodology of distinguishing between regions in space and/or phases in time that show distinct physical behaviours is specific to this research practice. Accordingly, two types of models specific to the engineering sciences are introduced. The diagrammatic model represents the causal explanation of physical behaviour in distinct spatial regions or time phases; the nomo‐mathematical model represents the phenomenon in terms of a set of mathematically formulated laws. (shrink)

Mental representation has long been central to standard accounts of action and cognition generally, and in the context of sport. We argue for an enactive and embodied account that rejects the idea that representation is necessary for cognition, and posit instead that cognition arises, or is enacted, in certain types of interactions between organisms and their environment. More specifically, we argue that enactive theories explain some kinds of high-level cognition, those that underlie some of the best performances in sport and (...) similar practices (dance, martial arts), better than representational accounts. Flow and mushin (mindfully fluid awareness) are explained enactively to this end. This results in a mutually beneficial analysis where enactivism offers theoretical and practical advantages as an explanation of high performance in sports, while the latter validates enactivism. (shrink)

We revisit the analogy suggested by Madelung between a non-relativistic time-dependent quantum particle, to a fluid system which is pseudo-barotropic, irrotational and inviscid. We first discuss the hydrodynamical properties of the Madelung description in general, and extract a pressure like term from the Bohm potential. We show that the existence of a pressure gradient force in the fluid description, does not violate Ehrenfest’s theorem since its expectation value is zero. We also point out that incompressibility of the (...) class='Hi'>fluid implies conservation of density along a fluid parcel trajectory and in 1D this immediately results in the non-spreading property of wave packets, as the sum of Bohm potential and an exterior potential must be either constant or linear in space. Next we relate to the hydrodynamic description a thermodynamic counterpart, taking the classical behavior of an adiabatic barotopric flow as a reference. We show that while the Bohm potential is not a positive definite quantity, as is expected from internal energy, its expectation value is proportional to the Fisher information whose integrand is positive definite. Moreover, this integrand is exactly equal to half of the square of the imaginary part of the momentum, as the integrand of the kinetic energy is equal to half of the square of the real part of the momentum. This suggests a relation between the Fisher information and the thermodynamic like internal energy of the Madelung fluid. Furthermore, it provides a physical linkage between the inverse of the Fisher information and the measure of disorder in quantum systems—in spontaneous adiabatic gas expansion the amount of disorder increases while the internal energy decreases. (shrink)

Hartmut Rosa advances an account of the temporal structure of society from the perspective of critical theory. He identifies three categories of change in the tempo of modern social life: technological acceleration, evident in transportation, communication, and production; the acceleration of social change, reflected in cultural knowledge, social institutions, and personal relationships; and acceleration in the pace of life, which happens despite the expectation that technological change should increase an individual's free time. According to Rosa, both the structural and cultural (...) aspects of our institutions and practices are marked by the "shrinking of the present," a decreasing time period during which expectations based on past experience reliably match the future. When this phenomenon combines with technological acceleration and the increasing pace of life, time seems to flow ever faster, making our relationships to each other and the world fluid and problematic. It is as if we are standing on "slipping slopes," a steep social terrain that is itself in motion and in turn demands faster lives and technology. As Rosa deftly shows, this self-reinforcing feedback loop fundamentally determines the character of modern life. (shrink)

Considered by many to be Abraham Robinson's magnum opus, this book offers an explanation of the development and applications of non-standard analysis by the mathematician who founded the subject. Non-standard analysis grew out of Robinson's attempt to resolve the contradictions posed by infinitesimals within calculus. He introduced this new subject in a seminar at Princeton in 1960, and it remains as controversial today as it was then. This paperback reprint of the 1974 revised edition is indispensable reading for anyone interested (...) in non-standard analysis. It treats in rich detail many areas of application, including topology, functions of a real variable, functions of a complex variable, and normed linear spaces, together with problems of boundary layer flow of viscous fluids and rederivations of Saint-Venant's hypothesis concerning the distribution of stresses in an elastic body. (shrink)

A long-standing tradition presents economic activity in terms of the flow of fluids. This metaphor lies behind a small but influential practice of hydraulic modelling in economics. Yet turning the metaphor into a three-dimensional hydraulic model of the economic system entails making numerous and detailed commitments about the analogy between hydraulics and the economy. The most famous 3-D model in economics is probably the Phillips machine, the central object of this paper.

In this article the author argues that we need not just to ‘decolonize’ the Anthropocene but also to ‘desecularize’ it – to be aware that in the new age of the Earth we may be coeval with gods and spirits. Drawing particularly on the work of Gilles Deleuze, Félix Guattari and Georges Bataille, and using concepts from both thermodynamics and fluid dynamics, the author starts to develop an interdisciplinary theory of planetary spirit and use this to speak of both (...) the ‘laminar’ high gods of time that are being invoked to summon the story of Earth’s ongoing transformation into a canonical mythos, and the turbulent lower spirits of place which manifest particular, situated dynamics on an Earth crossed by interlocking gradients and flows of energy, value, power and entropy. He suggests that what might once have been distinct territorialized ‘cultures’ or ‘natures’ in which humans engaged in particular situated patterns of interaction with animals, spirits and other beings are increasingly being convened into a global multinatural system. (shrink)