“Constructal Theory: From Engineering to Physics, and How Flow Systems Develop Shape and Structure”

Constructal theory and its applications to various fields ranging from engineering to natural living and inanimate systems, and to social organization and economics, are reviewed in this paper. The constructal law states that if a system has freedom to morph it develops in time the flow architecture that provides easier access to the currents that flow through it. It is shown how constructal theory provides a unifying picture for the development of flow architectures in systems with internal flows (e.g., mass, heat, electricity, goods, and people). Early and recent works on constructal theory by various authors covering the fields of heat and mass transfer in engineered systems, inanimate flow structures (river basins, global circulations) living structures, social organization, and economics are reviewed. The relation between the constructal law and the thermodynamic optimization method of entropy generation minimization is outlined. The constructal law is a self-standing principle, which is distinct from the Second Law of Thermodynamics. The place of the constructal law among other fundamental principles, such as the Second Law, the principle of least action and the principles of symmetry and invariance is also presented. The review ends with the epistemological and philosophical implications of the constructal law

Constructal theory of global circulation and climate

The constructal law states that every flow system evolves in time so that it develops the flow architecture that maximizes flow access under the constraints posed to the flow. Earlier applications of the constructal law recommended it as a self-standing law that is distinct from the second law of thermodynamics. In this paper, we develop a model of heat transport on the earth surface that accounts for the solar and terrestrial radiation as the heat source and heat sink and with natural convection loops as the transport mechanism. In the first part of the paper, the constructal law is invoked to optimize the latitude of the boundary between the Hadley and the Ferrel cells, and the boundary between the Ferrel and the Polar cells. The average temperature of the earth surface, the convective conductance in the horizontal direction as well as other parameters defining the latitudinal circulation also match the observed values. In the second part of the paper, the constructal law is invoked in the analysis of atmospheric circulation at the diurnal scale. Here the heat transport is optimized against the Ekman number. Even though this second optimization is based on very different variables than in the first part of the paper, it produces practically the same results for the earth surface temperature and the other variables. The earth averaged temperature difference between day and night was found to be approximately 7 K, which matches the observed value. The accumulation of coincidences between theoretical predictions and natural flow configuration adds weight to the claim that the constructal law is a law of nature

Climate change, in the framework of the Constructal Law

Here we present a simple and transparent alternative to the complex models of earth’s thermal behaviour under time-changing conditions. We show the one-to-one relationship between changes in atmospheric properties and time-dependent changes in temperature and its distribution on earth. The model accounts for convection and radiation, thermal inertia and changes in albedo (ρ) and greenhouse factor (γ). The constructal law is used as the principle that governs the evolution of fl ow confi guration on earth. The model showed that for two time-dependent scenarios, (δρ = 0.002; δγ = 0.011) and (δρ = 0.002; δγ = 0.005) the predicted equatorial and polar temperature increases and the time scales are (ΔTH = 1.16 K; ΔTL = 1.11 K; 104 years) and (0.41 K;0.41 K; 57 years), respectively. A continuous model of temperature variation was used to predict the thermal response of the Earth’s surface to changes bounded by δρ = δγ and δρ = −δγ. The poleward heat current reaches its maximum in the vicinity of 35° latitude,accounting for the position of the Ferrel cell between the Hadley and Polar Cells

Biophilic urban developments following dynamic flows of tree-shaped architectures

Latest theories and practices in Biophilic designs of the urban space regard the urban fabric as being composed of several interrelated layers of energetic structure influencing each other in a non-linear manner primarily. The interaction between two or more interfaces of the urban space layers evolves into new and non-predictable properties. Evolution and creation of new boundaries/interfaces follows laws related to fractal growth; most of the times this particular evolution is defined by laws of physics, such as Thermodynamics and Constructal Law. Designs that do not follow these laws may produce anti-natural and hostile environments, which do not fit into human beings’ evolution, and thus, fail to enhance life by all means. The author of this paper should like to illustrate how new developments of urbanism worldwide currently work upon conceptual and town planning models based not only upon cutting-edge technology, but also upon natural laws and patterns of life and human behaviours strictly related to flaws and movement dictated by natural phenomena. When abrupt interruption of the urban structure has occurred, a consequent design solution does not even guarantee flowing and freedom to morph. It is impossible to create harmonic designs which naturally “unite the animate with the inanimate”, as Adrian Bejan and Sylvie Lorente affirm, whenever urban sprawl fails to encompass Biophilic solutions related to tree-shaped architectures. The author argues that Constructal invasion into the urban space “as fundamental problems of access to flow: volume to point, area to point, line to point, and the respective reverse flow directions” can only guarantee high standard quality of life in either contemporary or future cities developments

Thermodynamic optimization of global circulation and climate

The constructal law of generation of flow structure is used to predict the main features of global circulation and climate. The flow structure is the atmospheric and oceanic circulation. This feature is modelled as convection loops, and added to the earth model as a heat engine heated by the Sun and cooled by the background. It is shown that the dissipation of the power produced by the earth engine can be maximized by selecting the proper balance between the hot and cold zones of the Earth, and by optimizing the thermal conductance of the circulation loops. The optimized features agree with the main characteristics of global circulation and climate. The robustness of these predictions, and the place of the constructal law as a selfstanding principle in thermodynamics, are discussed

Natural flow patterns and structured people dynamics: a constructal view

Constructal theory that has been successfully applied to planetary circulations and climate and to river basin morphology is shown to provide a useful framework for describing flows of people. We showed here, with simple examples, that intuitive rules of traffic organization can be anticipated based on principle, i.e., based on the Constructal Law. In addition, and similarly to the case of flows of inanimate matter, in the case of flows of people, flow patterns emerge as a necessary consequence of reduction of global flow resistances. These flow patterns point to decreasing resistivity to flows of people and commodities. Pathway length varies inversely with resistivity while pathway number increases with resistivity

Constructal view of the scaling laws of street networks — the dynamics behind geometry

The distributions of street lengths and nodes follow inverse-power distribution laws. That means that the smaller the network components, the more numerous they have to be. In addition, street networks show geometrical self-similarities over a range of scales. Based on these features many authors claim that street networks are fractal in nature. What we show here is that both the scaling laws and self-similarity emerge from the underlying dynamics, together with the purpose of optimizing flows of people and goods in time, as predicted by the Constructal Law. The results seem to corroborate the prediction that cities’ fractal dimension approaches 2 as they develop and become more complex

A new paradigm for deep sustainability: biourbanism

Biourbanism introduces new conceptual and planning models for a new kind of city, valuing social and economical regeneration of the built environment through developing and healthy communities. Thus, it combines technical aspects, such as zero-emission, energy efficiency, information technology, etc. and the promotion of social sustainability and human well being. In effect, this new paradigm endorses principles of geometrical coherence, Biophilic design, BioArchitecture, Biomimesis, etc. in practices of design and also new urban policies and, especially Biopolitics to promote urban revitalization by ensuring that man-made changes do not have harmful effects to humans. Green city standards start inside the designs of each building and continue either in unbuilt spaces surrounding buildings or inside complex infrastructural networks, connecting buildings and people. The proposed presentation should illustrate how new exciting developments recently, such as fractals, complexity theory, evolutionary biology and artificial intelligence are interrelated and constantly stimulate interaction between human beings and the surrounding environment. New Biophilic solutions in designs of buildings have been proved as attractive opportunities for new markets of housing. Thus, some new infrastructural projects start embracing Biophilic advanced solutions which finally aim at energy efficiency and optimal performance. As parallel activity we can now see emerging new innovative monitoring systems of building health not only in small scale, but also in large scale buildings, such as rail stations, for example, and commercial centres or even sometimes entire educational complexes integrated to new infrastructural projects. Some important case studies are going to be presented; they have been analysed and evaluated by Biourbanism and Biophilia principles and applied methods of design

The city of future: biourbanism and constructural law

Nowadays dynamic elements in urban fabric are often concealed by the insertion of stylish new architecture; real patterns of social life (‘bios’), have been replaced by rigid geometric grids and compact building blocks. New Urbanism and Biourbanism affirm that cities are now risking to be unstable and deprived of healthy social interactions. As an expansion of older historical urban fabric patterns, harmonious architecture can have a positive impact on the fitness of both human body and mind. Not only Biourbanism attempts to reinstate balance and lost values in the urban fabric, but also reinforces human-oriented design emergences in micro and macro scales. As a multifaceted discipline, it embraces laws of physics, such as Constructal Law and acknowledges its noticeable and unremitting influence to urban human behaviours. Urban life and behaviours are based upon systems of human communication formed by dynamic patterns; we are now talking about negotiating boundaries between human activities, changes in geographic mapping and mainly about sustainable systems to support uninterrupted growth of communities worldwide. Therefore, as a vital shift in architectural education, not only Biourbanism offers the opportunity to explore patterns and linguistics deeply imbedded into the built environment, but also enables scholars and communities to come together and participate actively into fast and innovative urban interventions. Projects developed during educational and professional training aim at reinstating memorable and preferential paths of communication, favouring everyday life rituals of the body and mind. Hence, by following everlasting laws of physics and formulas inherited from nature, architectural forms can be considered as the real innovation in urban design and planning of the City of the Future.Conference presentation funded by Department of Engineering