Adrian Bejan's Blog, page 3
June 15, 2025
Adrian Bejan | Perspective Drawing, from Design in Nature
In this lecture, Adrian Bejan connects the invisible reality of flow, such as heat transfer through solids, with the visible logic of drawing. He begins with the flow of heat in electronics, driven by temperature differences, and illustrates how these unseen structures are represented through drawing. Bejan uses sketches not simply for visualization but as a way of teaching design, blending geometry with the logic of flow architecture. Drawing becomes a way to express how flow moves through systems, and how it should be shaped for efficiency. He shows how visual techniques, if misused, distort physical understanding, and how correct drawing reveals the true nature of flow.
He warns against the mistake of using parallel lines in drawings, explaining that they mislead the viewer by making the object appear to grow wider with distance.
He explains that the correct way is to use tapered lines that intersect at a point far away, called the horizon. This approach is known as perspective, which is the key to making a drawing look realistic.
Bejan notes that even software users often fall into the trap of parallelism, forgetting that lines must appear to converge to represent three-dimensional form correctly.
He refers to paintings before the Renaissance, which lacked perspective and therefore appeared unnatural. These are contrasted with Renaissance breakthroughs.
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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com
June 13, 2025
Theme Issue in Philosophical Transactions of the Royal Society A
We are pleased to announce that selected papers from the Constructal Law Conference 2025 will be published in a Theme Issue of Philosophical Transactions of the Royal Society A. Continuing its long history of influential scientific publishing, Philosophical Transactions of the Royal Society A publishes high-quality theme issues on topics of current importance and general interest within the physical, mathematical and engineering sciences. This theme issue covers design, evolution, and the emerging science of form and focuses on Constructal Law and its applications.
CONSTRUCTAL LAW CONFERENCE 2025🗓️ 5-7 November 2025 Florida International University, Miami FL, USA
Deadlines for Constructal Law Conference 2025Abstract Submission: July 15, 2025
Abstract Acceptance: July 31, 2025
Extended Abstract Submission: September 15, 2025
Extended Abstract Acceptance: September 30, 2025
More details on the Constructal Law Conference 2025
June 7, 2025
Adrian Bejan | Birth of Constructal Law, from Design in Nature
“For a finite size flow system (not infinitesimal) to persist in time (to live) it must evolve with freedom such that it provides easier and greater access to what flows.” - Adrian Bejan
May 29, 2025
Adrian Bejan | Minimal length designs, from Design in Nature
In this lecture, Adrian Bejan explores designs with minimal length in fluid flow and how they are reflected in nature and human-made designs. He discusses the principles behind efficient flow paths, such as bifurcation angles in corridors, and the relationship between shape and flow efficiency in environments, drawing parallels between natural and engineering systems.
Bejan emphasizes creating efficient fluid flow paths in natural and engineering systems. He points out that angles of bifurcation, like those found in animal travel paths and modern airport designs, can enhance flow efficiency, contrasting this with less optimal 90-degree turns.
Bejan highlights the historical development of key fluid mechanics principles, including the contributions of different scientists. He references important figures like Hess and Murray, explaining how their work on pressure drop and flow resistance laid foundational concepts that continue to influence modern fluid dynamics.
Bejan introduces the concept of minimal length designs, proposing that the best designs minimize distance and friction in flow pathways. He demonstrates this through geometric examples, showing how variations in area shape can drastically alter travel efficiency from one point to another.
The discussion includes practical applications of the theoretical concepts presented. Bejan illustrates how the principles of minimal length design can be applied in various contexts, specifically in soil and water flow architectures, suggesting ways to optimize these designs using mathematical formulations.
The lecture concludes with a reflection on how natural systems offer insights into efficient design. Bejan points out that observing natural flows can guide the creation of better architectural and fluid systems, noting that complex structures often originate from simple principles.
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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com
May 25, 2025
Adrian Bejan | Entrance length channels, from Design in Nature
In this lecture, Adrian Bejan discusses the significance of the entrance region in fluid dynamics and heat transfer. The entrance region is crucial for understanding heat transfer characteristics, particularly fluid flow through channels. Bejan explains concepts such as boundary layers, temperature distributions, and fluid flow behavior as it transitions from entrance regions to fully developed flow. The discussion highlights equations related to heat flux and the implications of channel design in natural systems, emphasizing that the entrance area is often overlooked in traditional heat transfer studies.
The entrance region of channels significantly affects fluid dynamics, impacting how fluids interact with solid boundaries. Fluid slows down due to friction with the channel wall, leading to the formation of a boundary layer whose characteristics differ from those of a fully developed flow.
As fluid enters a channel, it experiences a temperature distribution where the center remains hot and the temperature decreases towards the wall. The heat flux is prominent at the entrance, which is central for heat exchange processes.
The thickness of the boundary layer is crucial for understanding how temperature and flow transfer occur. Equations related to Reynolds numbers provide insight into the flow characteristics and how they change across different regions in the channel.
Bejan emphasizes that the design of heat transfer systems should prioritize the entrance region for efficiency, challenging traditional views that often focus solely on the fully developed flow.
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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com
May 21, 2025
Adrian Bejan | Know how, models, applications, from Design in Nature
Adrian Bejan discusses fluid flow architecture, focusing on simplifying models to enhance real-world applications. He explains the importance of moving from basic to more complex models to better understand heat flow and fluid dynamics. He emphasizes recognizing entrance regions in ducts to capitalize on flow dynamics.
Bejan explains the transition from simple fluid flow models to more realistic ones. This progression is driven by the need for better applications, particularly in understanding heat flow. As models become more intricate, they more accurately represent real-world scenarios, thus facilitating broader applications.
He introduces the concept of entrance regions in ducts. The entrance region, which shows distinct flow characteristics, highlights how flow dynamics can change based on the duct's length and shape.
Bejan discusses the example of transitioning from T-shaped to Y-shaped flows, illustrating how introducing additional degrees of freedom can enhance flow models. This example signifies the importance of adapting fluid flow models to inspire real-world applications and innovations.
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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com
May 15, 2025
Adrian Bejan | Size of duct, from Design in Nature
In this video, Adrian Bejan explores the principle of determining the optimal size of ducts and pipes in moving systems, focusing on how diameter affects efficiency, energy consumption, and structural design in biological and engineering systems.
The mathematical analysis illustrates how the pressure loss in a pipe (delta P) varies with the diameter to the fourth power, while weight-related factors vary quadratically. This leads to a total resistance that shows an intersection point, enabling the calculation of an optimal diameter.
Bejan shares an anecdote about the empirical observation of blood vessel sizes and mass flow rates in biology, reinforcing the predictability of duct sizes based on fundamental principles he discussed. His predictions align well with biological evidence, showcasing the application of theoretical models in real-world scenarios.
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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com
May 8, 2025
Adrian Bejan | More realism, from Design in Nature
Adrian Bejan discusses fluid dynamics, particularly the differences between laminar and turbulent flow in ducts. He emphasizes the significance of understanding these flows for practical applications in engineering and design, elaborating on parameters such as entrance length, pressure drop, and flow profiles. Bejan also explores the effects of duct shape and size on flow characteristics, advocating for a more realistic approach to design inspired by nature.
Bejan explains the fundamental differences between laminar and turbulent flow. While laminar flow has a uniform profile, turbulent flow exhibits complexity with fluctuations in velocity. Understanding these distinctions is crucial for effectively applying fluid dynamics in engineering contexts.
Bejan discusses how flow changes from laminar to turbulent as it travels through ducts. The concept of entrance length is crucial, as it describes the distance over which the flow develops.
Bejan urges considering factors such as duct shapes and minimizing flow resistance. He suggests a greater realism in design inspired by nature’s complexity.
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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com
May 2, 2025
The Birth of the Constructal Newsletter
Just as all things change, so too do publishing platforms. I created the Constructal Newsletter to bring ideas and innovations to a broader audience through posts, publications, and announcements.
The platform I previously created, constructal@googlegroups.com, had around 200 members, most of whom know each other personally. Then I realized that this platform was confining us to a relatively small group. For this reason, I designed a more inclusive platform. The Constructal Newsletter quickly reached over 440 subscribers.
The primary content source is the Constructal YouTube Channel. It currently has over 1000 subscribers and an impressive archive of over YouTube videos. We are also organizing the Constructal Law Conference (CLC) series, which we hold annually in different countries around the globe.
This year, the 15th Constructal Law Conference will be held from November 5 to 7 at Florida International University in Miami. We publish the conference outcomes in reputable journals such as Biosystems, International Communications in Heat and Mass Transfer, and Philosophical Transactions of the Royal Society A.
The constructal society has taken form naturally. It is now home for many activities, such as publishing newsletter items, YouTube videos, conference presentations, and articles in special journal issues. You can access the newsletter archive.
Contact: info@constructal.org
What is Constructal Law?The constructal law, stated by Duke’s Adrian Bejan in 1996, is the law of physics that accounts for the phenomenon of evolution (change, configuration, form, design) throughout nature, inanimate flow systems, and animate systems together.
For a finite size flow system (not infinitesimal) to persist in time (to live) it must evolve with freedom such that it provides easier and greater access to what flows.
The law places the concepts of life, evolution, freedom, form, configuration, directionality, and objective in physics, which is in the broadest scientific arena.
It is the law of physics of life and evolution everywhere, animate, inanimate, human made, and not human made.
It is the arrow of time, the direction of the evolution of flow organization.
Who is Umit Gunes?I love science, technology, high-quality academic work, data science, visualization, and networking, which is why I enjoy being part of the constructal society. My brief resume is below; more is available on my webpage.
In 2007, I enrolled in Yıldız Technical University’s Department of Naval Architecture and Marine Engineering, from which I graduated in 2011. During my undergraduate studies, I was a visiting student in the Department of Mechanical Engineering at the University of Applied Sciences Düsseldorf and the Department of Mechanical Engineering at Kiel University of Applied Sciences. I earned my master’s degree at Yıldız Technical University in 2013.
In August 2019, I completed my doctoral dissertation, titled “Performance and Size in Moving Systems: Constructal Law”. Between January 2017 and April 2018, I was a visiting researcher in the Department of Mechanical Engineering and Materials Science at Duke University.
I started as a research assistant in the Department of Naval Architecture and Marine Engineering at Yildiz Technical University, where I also served as an assistant professor from June 2020 to November 2023. From August 2021 to August 2022, I was a visiting professor at Duke University. I am an associate professor at Yıldız Technical University since November 2023.
May 1, 2025
Adrian Bejan | Can I do better?, from Design in Nature
In this video, Adrian Bejan discusses the transition from basic flow systems to complex dendritic structures, emphasizing their relevance in natural and human-made environments. He explores how scientific knowledge relates to practical applications in engineering and design, including the aesthetic aspects of engineering that contribute to functionality and value.
Bejan highlights the shift from basic flow connecting two points to complex flows that connect a point to a large area or volume. He illustrates this with examples from natural systems that exhibit tree-like, branched structures, demonstrating the evolution of these concepts in various industries.
Knowledge encompasses understanding and applying that information effectively ('know-how'), which is critical for creating designs and innovations that enhance quality of life.
He discusses how engineering is a vital science that involves creating and configuring useful phenomena. Beauty and aesthetics in engineering are essential, as they contribute to effective communication of value and functionality in design.
Bejan offers insights into the principles of creating designs, emphasizing the importance of understanding variables, constraints, and their interplay. The aspect ratios in designs reflect the quest for efficiency and perfection in flow.
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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com
