Carlos Pimentel's blog

Around two years ago, I launched this blog with the initial goal of demystifying my doctoral research, translating complex concepts and terminology into simple language accessible to a general audience. While many early articles focused on straightforward explanations (mostly in Spanish), the content naturally evolved to address deeper technical inquiries from engaged readers. This entire process has been a valuable exercise for organizing my thoughts and sharpening my scientific communication skills. Since beginning this project, I have successfully authored and published one paper in a Q1 journal [1] and co-authored a second paper available on ArXiv [2] as a preprint. Furthermore, I utilized this knowledge to successfully prepare and file by myself the corresponding patent application [3], saving hundred of dollars in an attorney. My research is fundamentally open. I offer my findings for review and use by the community, having moved past the need to convince any particular audience....

 This is a second version of the original article:  Can a brick 'fly' (glide)? This time, Google's AI Gemini (Flash v2.5) enhanced (or not...) this article by simply adding "Improve this:" to each original paragraph. This was done as an exercise to provide an alternative explanation and formatting while maintaining the original ideas. No major changes have been made to the AI-generated text, and the additional explanations (marked with asterisks in the original article) have been removed. Redefining Aerodynamics: Beyond the Smooth Surface Yes, it can—but perhaps not in the way most people understand. The common perception of "aerodynamics" often fixates on curvatures, rounded leading edges, smooth surfaces, and sharp trailing edges . These features, while visually appealing and often associated with modern design, are largely just cosmetic embellishments when we consider the fundamental meaning of the term. Etymologically, "aerodynamics" si...

Go to the first part:  On innovation and other hoaxes: a true story at university (Part 1) Most real aerodynamicists, even computationalists, know the typical pressure coefficient (cp) distribution for an airfoil (with positive AoA) in the pre-stall region,  cp tends to increase from the suction side (top) towards the leading edge (LE), typically with a negative peak value. On the other hand, at the frontal stagnation point, such a value must be equal to 1 (for the incompressible case), which no longer coincides with the geometric frontal point of the airfoil, since it is naturally shifted backwards due to its inclination. Obviously, a zero value of cp must be located in such a curved region, i.e. close to the geometric frontal point (see Fig. 1). But what happens if instead of an airfoil we use an "infinitely thin" flat plate? Yes, in the limit of thickness equal to zero, cp must be equal to the difference between the upper and lower side cp's , which have a different...

Go to the first part:  On innovation and other hoaxes: a true story at university (Part 1) After numerically understanding the effects of adding lateral wakes to flat plates, especially for low aspect ratio (LAR) configurations, a more complex steady-state scheme was proposed by my advisor. It consists of including internal detached wakes to account for flow separation, similar to Gersten's vortex model (see Fig. 1, up). Therefore, I first explored a simpler model, the lifting line method (based on the Lifting Line Theory or LLT), by including detached horseshoe vortices instead of bounded vortex rings as in the VLM. Such a scheme is not new, in fact some authors have proposed similar approaches in the past to account for flow separation in the context of Potential Flow Theory (PFT), improving the obtained results by far. Furthermore, I found that in the 90s, Prof. D.A. Durston of NASA published a similar vortex model ( LinAir code) to account for flow separation by including trai...

Go to the first part:  On innovation and other hoaxes: a true story at university (Part 1) After the development, verification, and validation (v&v) of the last code for massive flow separation, the time has come to explore a three-dimensional low-order panel method. The vortex lattice method (VLM) was chosen because of its simplicity in implementation compared to more complex potential-based schemes, such as the doublet lattice method (DLM). In addition, the VLM has historically provided good agreement with the expected results at the lowest computational cost, although it only allows calculations for zero-thickness bodies or plates, similar to a fabric (e.g., a parachute canopy). Originally, the standard (or single wake) VLM provides a linear solution (for the lift coefficient), since it allows flow separation only along the trailing edge. Historically, such a method has been applied from medium-high (AR>4) to high aspect ratio configurations, such as wings or airplanes, ...

This is a true story told in the first person. Real names are omitted because my goal is not to demonize anyone; fight ideas, not people. However, this situation may soon change as all of those mentioned continue to affect my interests. It was 2017 when I crossed the Atlantic Ocean for the third time to attend a conference series about computational fluid dynamics (CFD) software that we distribute in my country. The last two times it was to take summer courses at Moscow and Kharkiv/Kharkov aviation institutes, in 2011 (MAI) and 2014 (KhAI), during my bachelor and master programs, respectively. This last time, I took the opportunity to meet my future PhD advisor and co-advisor, whose I contacted some months ago via e-mail to ask for a chance to develop a project related to parachute aerodynamics, a field in which I have some experience, designing, manufacturing and testing small-scale ones for different applications ( www.chuteshiut.com ). Everything goes fine, as I presented some C...