Understanding Laminar-Turbulent Transition Over an Airfoil Used at Low Speed and High Altitude

What is it about?

This study investigates flow behaviour over a DU89-134/14 airfoil at low speeds and high altitudes, conditions typical for the operation of High-Altitude Pseudo-Satellites (HAPS). The research focuses on determining flow separation, transition, and reattachment locations, using oil flow visualization, infrared thermography, and pressure measurements. Two different flow patterns were observed: at lower speeds, the airflow separates and turns turbulent without reattaching, while at higher speeds, it reattaches, forming a laminar separation bubble. The study also compares these experimental results with numerical simulations, showing that the simulations work well at higher speeds but struggle to predict flow patterns at lower speeds. The findings highlight the importance of understanding flow topology for optimizing airfoil performance.

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Photo by Baptiste Buisson on Unsplash

Photo by Baptiste Buisson on Unsplash

Why is it important?

HAPS represent a promising technology that can provide an alternative to conventional satellite systems. They have several key advantages, including lower operational costs, easier deployment, and the ability to provide localized aerial coverage for extended periods, often over a week. However, due to limited power availability and the need for long endurance, HAPS rely on airfoil designs with high aerodynamic efficiency (high lift-to-drag ratios), similar to those used in gliders. Understanding and predicting how air flows over these airfoils at high altitudes and low speeds is crucial for improving their performance. Better designs could lead to longer flight times or the ability to carry heavier payloads, making HAPS more efficient and capable for various applications, such as communication or environmental monitoring.

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