Ground Effects on the Aerodynamic Performance of Microducted Fan Systems
Publication: Journal of Aerospace Engineering
Volume 37, Issue 5
Abstract
Near-ground flight is an important state of microducted fan aircraft. To explore the ground effects on the aerodynamic performance of microducted fan systems in near-ground hovering, a full three-dimensional (3D) numerical simulation methodology, which was validated by current experiments, is established in this paper. First, the hovering performance of ducted fan systems without ground effects was studied. Taking the system without ground effects as the reference, the ground effects due to altitude and slope were calculated and analyzed. The simulation results revealed that compared with the results of the current experiments, the maximum prediction error of 6% is reached when the induced power is 30 W. This indicates that the simulation methodology can work effectively. Moreover, a comparison of the performance of the system without ground effects revealed that ground effects can be ignored when the system altitude is greater than the duct length. In contrast, when the system altitude is within the duct length, the mass flow rate can greatly decrease with decreasing system altitude. This is because the blocking effect from the ground becomes significant. Additionally, the ground slope makes the flow field of the ducted fan system asymmetric. Globally, the system is not as sensitive to ground slopes within 18° because the ground effects for both sides of the ducted system are balanced to a certain extent. A side away from the ground can enhance the aerodynamic performance of the system. However, the other side close to the ground weakens the system performance. The mass flow and thrust performance can increase slightly when the slope is less than 12°, and the system behavior tends to stabilize when the slope is greater than 12°.
Practical Applications
When microducted aircrafts are used to perform tasks, such as taking photos and ground detection, they are usually flown close to the ground, and alternate hovering with and without ground effects is frequently conducted. Thus, problems related to the aerodynamic interference between the terrain and the fuselage and between the fuselage and the rotor can occur. As shown in this study, the aerodynamic performance of ducted fan systems is affected by ground effects when ducted systems operate at an altitude of one times the duct length. In addition, at an altitude of 0.5 times the duct length, the thrust of the duct system increases with increasing slope within 18°. When the slope is greater than 12°, the influence of the slope from the left and right sides at the duct outlet is almost balanced. In general, the system altitude, ground slope and their effects on system performance need to be considered during the design process. The results can provide a design benchmark and optimization directions for designers, thereby reducing environmental constraints on ducted aircrafts and cost and improving the reliability.
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Data Availability Statement
Some or all the data and models that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
The authors also appreciate the technical support from Prof. Gressier and Prof. Barènes in the Propulsion Laboratory of the Department of Aerodynamics, Energetics and Propulsion, Institut Supérieur de l’Aéronautique et de l’Espace.
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Information & Authors
Information
Published In
Journal of Aerospace Engineering
Volume 37 • Issue 5 • September 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Sep 1, 2023
Accepted: Feb 23, 2024
Published online: May 24, 2024
Published in print: Sep 1, 2024
Discussion open until: Oct 24, 2024
ASCE Technical Topics:
- Aerodynamics
- Aerospace engineering
- Aircraft and spacecraft
- Architectural engineering
- Building systems
- Continuum mechanics
- Duct
- Dynamics (solid mechanics)
- Engineering fundamentals
- Engineering mechanics
- Flight
- Geomechanics
- Geotechnical engineering
- HVAC
- Models (by type)
- Numerical models
- Slope stability
- Slopes
- Solid mechanics
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