Aerodynamics is concerned with the behaviour of gaseous fluids in motion and the forces acting on moving bodies relative to these fluids. Although this branch of science is now fundamental in the study of everything moving in the air, from aeroplanes to rockets, the development of these ideas was initially a challenge due to the inconsistencies of aerodynamic thought. While Leonardo da Vinci is known for his career as an artist, his most famous works including the paintings Mona Lisa and The Last Supper, he was also responsible for significant development in the field of flight. Beforehand it had been a fragmented field of study, but da Vinci created ideas for innovative flying machines using concepts related to fluid flow characteristics. Undoubtedly, da Vinci’s diverse range of interests aided his work in aerodynamics: his military weapon designs, architectural studies, and anatomical sketches, alongside his career in conventional painting, enabled him to culminate status as an engineer and scientist who used diagrams as a visual representation for his ideas.
Aerodynamic concepts date back to the antiquity, led by the “founder of fluid statics” Archimedes. While he dealt with fluids that were at rest, many concepts which focus on fluids in motion can be derived from his theories. He created the first definition of fluid and acknowledged the existence of pressure, albeit in an implicit manner. The period after this was characterised by a brief decline in the development of aerodynamics, followed by the revival of intellectual activity during the Renaissance period. The aerodynamics that da Vinci inherited were therefore incoherent and rooted in old ideas from antiquity. While he was familiar with the ideas of Archimedes, he did not particularly depend on them, as Greek science texts were available only in Latin and da Vinci had no formal education. Nevertheless, he was a genius of his time and persisted, emerging as a prosperous scientist and using his own reasoning to create new ideas regarding fluid motion.
It thus comes as no surprise that aerodynamics emerged in this Renaissance period, led by da Vinci’s brilliant mind. Da Vinci’s dream was “the conquest of the air” and he strongly related the concept of flight with freedom, hence why his aerodynamic concepts proved to be incredibly advanced. As a man with no specific profession, as already stated, bar his time serving several powerful Italian families such as Medici, he was very versatile, eagerly combining art and science to illustrate his flying obsession.
Therefore, he made detailed sketches of ornithopters between 1488 and 1514, in an effort to gain a larger understanding of how wings were used in airlift. The ornithopters were designed to achieve flight by employing flapping wings to provide both thrust and lift. The movements of the machine’s pilot would be translated mechanically into the flapping of wings, which were wooden spars covered by a light fabric. Notably, modern-day helicopters are based on the concept of this flying machine. A balancing mechanism was created for testing the wings of the ornithopter whereby the pilot and wing would be placed on a pan while weights would be placed on the other until the two were balanced. The wing would then be dropped, thus generating lift due to the imbalance of the two pans. Evidently, his initial concept of lift was flawed as he assumed that a lifting surface was formed by a region of air bearing high pressure and density. His ideas later changed to the correct concept that it is the difference in pressure between the top and bottom of the wing which creates lift as the air flows over it. Two important lessons can be gathered from his thoughts on lift: the “wind-tunnel principle” which suggests that the aerodynamic properties of a body remain the same as they move through a medium at a given velocity, and his conclusion that a flying machine could have fixed wings since “the air that moves against motionless wings is the same air that supports the heaviness of the bird through air”. This was the first idea of a fixed-wing aircraft.
Da Vinci also understood the phenomenon of drag. This is the resistance that the body experiences during flight. He stated that lift and drag were proportional to the body’s surface area and the velocity of the fluid over the body, reinforcing the notion that he had some knowledge of fluid mechanics. This is further demonstrated by his sketches of cross-sections of rivers which substantiate this simple relation of AV = constant, where A is the cross-sectional area of the tube and V is the velocity of the fluid. Of course, this is only partly correct since the velocity function is the velocity squared. His understandings of drag were so complex that he even sought out ways to reduce the resistance force against a body. By studying the shape of fish aids, he deduced that a more streamlined body would have a reduced drag. This is now a well-recognised concept; smoother shapes create better airflow than angular ones, hence why the wings of aeroplanes today have an airfoiled shape so that air can flow over easily.
Da Vinci’s later work regarding aerodynamics focused on the study of bird flight. He began to compile a Codex on the Flight of Birds in 1505, in which he outlined the affiliations between the centre of gravity and the centre of lifting pressure on the wing of a bird. This codex gave further explanations of bird flight by examining gliding flight and how flying control could be achieved by shifting one’s body weight, as well as emphasising the importance of constructing lightweight structures which is now a technique utilised in aerospace components. Ultimately, the codex, comprising of around twenty pages of notes and drawings, pioneered early aerodynamic thought in a manner which was striking of the time and these observations now find a place in the timeline of successful aeroplane development.
Unfortunately, da Vinci’s contributions to aerodynamics were not used in the nineteenth and twentieth centuries. George Cayley was the first person to study the flight of aeroplanes in a scientific manner in the 1800s, without reference to da Vinci’s work. This was largely due to da Vinci’s style of notetaking. He wrote in a strangely reverse fashion, from right to left, which made his ideas on flight difficult to interpret by his successors. Whether this was done on purpose, as a way to patent his ideas or leave a personal mark upon the branch of science in the form of chaotic notes and sketches, is unclear. However, had his designs been constructed, perhaps the development of aerodynamics would not have been stifled until three centuries later. It is more fitting to view da Vinci as a theoretical engineer who fuelled his flying obsession by spreading his own wings into the unknown field with sheer enthusiasm.
Written by Kat Jivkova
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Jakab, Peter. “Leonardo da Vinci and Flight.” 2013. Accessed on 18 November 2020. https://airandspace.si.edu/stories/editorial/leonardo-da-vinci-and-flight
Stimson, Richard. “Da Vinci’s Aerodynamics.” Accessed on 18 November 2020. https://wrightstories.com/da-vincis-aerodynamics/