We like to regard as useless what we do not know; it is a kind of revenge; and since mathematics and physics are rather generally unknown, they rather generally pass for useless. The source of their misfortune is plain; they are prickly, wild, and hard to reach …. Such is the destiny of sciences handled …
Author Archives: saemiller
Aeroacoustic and Aerodynamic Interaction Effects Between eVTOL Rotors
My student presented his MS thesis on the aerodynamics and aeroacoustics of rotors. Abstract: Electric vertical take-off and landing (eVTOL) aircraft are characterized by their unconventional wing and electric rotor configurations, which involve both side-by-side and tandem rotor configurations. These configurations create unique aerodynamic and aeroacoustic flow-fields. We numerically investigate the interaction effects between rotor …
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On Infinity by Euler
We may here deduce from it a few consequences that are extremely curious, and worthy of attention. The fraction $\frac{1}{\infty}$ represents the quotient resulting from the division of the dividend 1 by the divisor $\infty$. Now, we know, that if we divide the dividend 1 by the quotient $\frac{1}{\infty}$, which is equal to nothing, we …
Teller on Uncertainty
… we have a radioactive substance that emits, on the average, a particle, an alpha particle, once every second on the average. Now, here I have a counter, and I close that counter, so it won’t count, except that I open it for half a second. If, in that half a second, a particle arrives, …
On Large Language Models (AI) and Aerospace Education
Artificial intelligence (AI) is changing all aspects of our lives, much like the internet did when it became widely available to consumers in the mid-1990s. There are many discussions about how the AI revolution has affected different areas, including the workplace, art, culture, writing, and academics. Recently, the “ChatGPT: Optimizing Language Models for Dialogue” has …
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Codex Arundel
While reading Leonardo da Vinci’s Codex Arundel last evening, I noticed that the Codex had less scholars examining it relative to others. The fluid dynamics of da Vinci have been extensively studied, with entire dissertations dedicated to the subject. I came across a curious drawing that exhibited turbulent flow. The text is written backward in …
Additional Thoughts on Pressure
I am obsessed with pressure, particularly the internal pressure of fluids. Unlike viscosity, it is absent of frictional forces, and it is a key driving force in both human behavior and aerospace flows. Pressure is an essential component of a perfect fluid and appears on the right-hand side of the Navier-Stokes equations. Without pressure, fluid …
A simplified semi-empirical model for long-range low-frequency noise propagation in the turbulent atmosphere
My student, Dr. Tianshu Zhang, and myself recently published a modified long range acoustic propagation model that handles turbulence in the atmosphere. The abstract is We present a semi-empirical long-range low-frequency acoustic propagation model, which accounts for atmospheric turbulence. Ostashev and Wilson’s scattering model is combined with a ray-theory based refraction model to account for …
NASA Langley Feb. 2023
Caverns of the Wind
Silent are the caverns of the wind, But within them, a secret lies pinned Like Pandora’s box, locked up tight Holding within, a glimmer of light For in these tunnels, dreams did reside And hope for the future, they did provide But like Pandora’s box, they were lost Their secrets stolen, at a great cost …