pyBEMT: An implementation of the Blade Element Momentum Theory in Python

Giljarhus, Knut Erik Teigen

doi:10.21105/joss.02480

Cited by 5 publications

(2 citation statements)

References 7 publications

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“…A main source of error for this process comes from estimating the propeller's performance. When propeller data are not available, blade element momentum theory [29] (through software such as pyBEMT by Giljarhus [30]) can be used for estimating the performance curves (thrust, torque, power and efficiency) of a known propeller with known geometry such as the radius, number of blades, blade chord, aerofoil section shape and twist distribution. In this work we employed the performance data provided by propellers [31].…”

Section: Battery Depletion Methodsmentioning

confidence: 99%

Experimental evaluation of the drag curves of small fixed wing UAVs

Weishäupl¹,

McLay²,

Sóbester³

2023

Aeronaut. j.

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Tight budgets often limit the scope of test campaigns within the development programmes of small uncrewed air vehicles (UAVs). This paper explores a range of combinations of instrumentation suites and protocols for both wind tunnel and flight evaluation, focusing on the key aspect of drawing up the drag curve of the airframe. Through extensive testing of a 5kg maximum take-off mass, fixed wing, twin motor, richly instrumented test platform, we show that automated glides over a range of airspeeds and the slow down manoeuvre are effective ways of determining power-off drag, while estimating thrust from propeller speed, and voltage and current sensing based methods work well for the power-on case. We also seek the most time-efficient and robust mix of the above manoeuvres to yield a given drag curve accuracy level and we find wind condition impacts the manoeuvre makeup of the optimal strategy.

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Section: Battery Depletion Methodsmentioning

confidence: 99%

Experimental evaluation of the drag curves of small fixed wing UAVs

Weishäupl¹,

McLay²,

Sóbester³

2023

Aeronaut. j.

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“…The above method is implemented in the open source software pyBEMT [21], developed by one of the authors. Equation ( 15) is solved for φ using root-finding functions from the SciPy library [22].…”

Section: Blade Element Momentum Theorymentioning

confidence: 99%

Investigation of Rotor Efficiency with Varying Rotor Pitch Angle for a Coaxial Drone

Giljarhus

Porcarelli

Apeland³

2022

Drones

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Coaxial rotor systems are appealing for multirotor drones, as they increase thrust without increasing the vehicle’s footprint. However, the thrust of a coaxial rotor system is reduced compared to having the rotors in line. It is of interest to increase the efficiency of coaxial systems, both to extend mission time and to enable new mission capabilities. While some parameters of a coaxial system have been explored, such as the rotor-to-rotor distance, the influence of rotor pitch is less understood. This work investigates how adjusting the pitch of the lower rotor relative to that of the upper one impacts the overall efficiency of the system. A methodology based on blade element momentum theory is extended to coaxial rotor systems, and in addition blade-resolved simulations using computational fluid dynamics are performed. A coaxial rotor system for a medium-sized drone with a rotor diameter of 71.12 cm is used for the study. Experiments are performed using a thrust stand to validate the methods. The results show that there exists a peak in total rotor efficiency (thrust-to-power ratio), and that the efficiency can be increased by 2% to 5% by increasing the pitch of the lower rotor. The work contributes to furthering our understanding of coaxial rotor systems, and the results can potentially lead to more efficient drones with increased mission time.

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