Drones, otherwise known as unmanned aerial vehicles (UAVs) have become indispensable tools in several industries. Stable and efficient flight is essential for the safe operation of drones in various environments, and the key to this is advancements in engineering since drones were first developed.
Image Credit: Gorodenkoff/Shutterstock.com
How Do Drones Fly?
Drones operate either via a human controller or using sensors to provide autonomous or semi-autonomous navigation capabilities. Several different designs are used in drones, with two of the most common being either propellor or jet engine-driven (like an airplane) or a quadrotor design similar to a helicopter.
In a rotor design (commonly referred to as a quadcopter), thrust is provided by four brushless motors connected to propellers located on rotor shafts. These rotors rotate at extremely high speeds to provide lift or hovering capabilities. If the thrust is higher than the gravitational force exerted on the drone, it ascends, and vice versa.
In a quadcopter drone, pitch and roll can be controlled by varying the speed of individual propellers, allowing the drone to fly in various directions and change altitude quickly. Another key element of a rotor-based drone design’s operation is that each pair of diametrically opposite propellers rotates in different directions, one clockwise and one counter-clockwise.
There are different scenarios wherein drone motion in a quadcopter design can be controlled by the human operator or autonomously via sensors. These are:
- When all rotors are rotating at high speed together, the drone ascends and vice versa.
- When the rear propellers rotate faster than the front ones, the nose of the drone pitches down and forward thrust is generated.
- When the front propellers rotate faster, the drone moves backwards.
- When the right side propellers rotate faster, roll control is enabled via generated thrust and the drone moves to the left and vice versa.
- Yaw force is generated by the diagonal propellers spinning faster, allowing the drone to rotate in different directions.
Airplane-like drones operate the same way as their piloted counterparts, with rear or front propellers or jet engines providing motion and various control elements located on the wings, allowing the drone to move vertically or horizontally. Larger designs incorporate distinct fuselages and tails for stability.
Multirotor drone designs have been developed in recent years. These incorporate six or more rotors and are used for applications where larger UAVs are the best design and they prioritize redundancy.
Principles of Drone Aerodynamics
Multiple fundamental principles govern how aerodynamic a drone is and inform its rational design, making stable and efficient drone flight possible. These are lift, thrust, drag, weight, stability, control, and the effects of wind.
Lift is generated by the drone’s rotors or wings, with thrust provided by propellers or engines. Drag and weight significantly impact a drone’s aerodynamics; therefore, the weight of the drone must be minimized, and streamlined surfaces must reduce drag. Control and stability systems are fundamental for controlling drone motion and stability.
Finally, wind effects like headwinds, crosswinds, and shear forces significantly impact flight performance. For this reason, wind conditions must be considered by experienced drone operators or accounted for by onboard control systems in autonomous and semi-autonomous designs.
Case Study: Optimizing an Offshore SAR Drone’s Aerodynamics
Research published in 2020 on IOP Science explored the aerodynamic optimization of drones for offshore search and rescue (SAR) purposes. Using drones for this application is essential as it can save lives in the event of accidents where workers are washed overboard or off of oil rigs by significantly reducing the time and resources needed.
One of the critical considerations during the design of these types of drones is their power consumption, especially in inclement weather conditions. Therefore, optimizing the aerodynamic design of quadrotor SAR drones can extend their battery life, flight time, and operational capabilities.
One of the key approaches highlighted in the research is improving the design of the propellers to increase their overall thrust. Simulations and experiments with computer models of the optimized propeller design can inform the rational development of SAR drones with enhanced aerodynamic capabilities. Additionally, one of the research goals was to determine designs with optimal lift-to-drag ratio.
The optimal design selected in the paper incorporates a hexa-drone frame due to power output potential and price. 9.0 x 4.5 inch propellers were found to provide optimal aerodynamics for offshore SAR applications.
The drone proposed by the author is faster than its counterparts and possesses greater flight time capabilities, making it a highly efficient and aerodynamic offshore search and rescue tool.
Optimizing Drone Aerodynamics Through Design and Computer Modeling
Computer modeling is used by multiple companies and government agencies, such as NASA, to optimize the aerodynamic performance of drones. Optimizing the shape of drones is crucial to ensure the best performance possible, especially in inclement weather conditions and extreme environments, as well as in everyday operations.
Before a drone is even built, numerical simulations can be employed to assess how it performs using a range of environmental conditions and flow velocities. However, a drawback of using them is their complexity and cost in numerical terms. Each time a design is tweaked, the simulation must be re-run, making it an extremely expensive and time-consuming process.
One company that provides computer modeling capabilities for the drone industry is Neural Concept. The company’s AirShaper platform gives engineers and designers the option to upload a 3D model of the drone design to the cloud and have its aerodynamics analyzed and optimized.
The entire process takes place on the cloud, leveraging improved computational space and is automated from start to finish. Neural Concept Shape (NCS), which uses convolutional neural networks, can be integrated into Neural Concept’s technology to further enhance its capabilities, giving engineers a powerful tool for optimizing drone aerodynamics.
In Conclusion
To improve the safe, stable, and efficient operation of drones in multiple industries and environments, optimizing their aerodynamics is key. Several engineering techniques have been developed over the years, with computer modeling a cornerstone of rational aerodynamic design.
The different types of drones available on the market today come with their own engineering challenges, making this emerging engineering space highly dynamic, with cutting-edge technologies employed daily by engineers and designers.
References and Further Reading
Kumar, A (2020) A Technical Overview of Drones and their Autonomous Applications [online] Control Automation. Available at: https://control.com/technical-articles/a-technical-overview-of-drones-and-their-autonomous-applications/
Neural Concept (website) Drone Aerodynamics — Design Optimization by SenseFly & Neural Concept [online] neuralconcept.com. Available at: https://www.neuralconcept.com/post/sensefly-airshaper-and-neural-concept-designing-the-ultimate-drone
Dol, S.S (2020) Aerodynamic optimization of unmanned aerial vehicle for offshore search and rescue (SAR) operation IOP Conf. Ser: Mater. Sci. Eng. 716 012015 [online] iopscience. Available at: https://iopscience.iop.org/article/10.1088/1757-899X/715/1/012015/pdf
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.