172
K. S. Vepa et al.
1 Introduction
Unmanned Aircraft Systems (UASs) are widely used in various applications due to
its major advantage of operating without onboard pilot [1, 2]. There are three types
of UASs, i.e., fixed wing, flapping wing, and rotary wing. Rotary wing UASs have
better hovering characteristics as the aerodynamic behavior of rotors have greater
significance in controlling and maneuvering the vehicles. Information exchange at
the interface between the rotor and fluid domains is a challenging task. Computational
fluid dynamic (CFD) analysis helps in addressing this problem. Using CFD analysis,
wake region, formation of vortex, shift of tip vortex to turbulence regimes and multirotor interactions can be studied [3]. Considerable research is available in the field of
CFD [4–6] and multi-rotor dynamics [7, 8]. The forces acting on quadcopter opposite
to the direction of motion affect its performance. The force that opposes the forward
motion is drag and it affects the endurance. The value of drag varies with the angle
of attack and the present study investigates the performance of quadcopter on varied
angles of attack.
Filippone and Michelsen [9] estimated the drag on the structure of a helicopter
for several configurations and respective center of pressure regions are determined.
Also, wind tunnel tests are conducted for various geometries to understand the flow
fields for asymmetric flow conditions. More recently, Yoon et al. [10] studied the
effect of the distance between the rotors and fuselage during hovering condition.
It has been observed that as the distance decreases, the efficiency of the UAS also
decreases. Felismina [11] analyzed the aerodynamic behavior of UAV assembled
with seeder mechanism and drag force is computed using CFD analysis. Lopez
et al. [12] used SA and K-ω models to study the flow field around propeller of a
quadcopter. With the use of Lattice-Boltzmann and LES turbulence methodology,
Thibault et al. [13] simulated the vortex phenomena for a quadcopter. In line with
the existing studies, an off-the-shelf structural model is considered for examining
its aerodynamic behavior. The UAS chosen for this analysis is a quadcopter. The
topology of the frame is optimized to reduce its weight, but the resulting frame is
complex in geometry with intricate flow fields. Hence, we aimed to calculate the
value of drag during the hovering phase and forward motion for various angles of
attack.
2 Design of Quadcopter UAS
The conceptual model of UAS is an off-the-shelf model of a commercially available
quadcopter frame. The model is designed and developed to carry an all-up weight
of 2 kg load. The process of designing the model is carried out in ANSYS Design
Modeler and CFD simulations are carried out using ANSYS CFX. The model considered for the analysis is very complex which involves various spline curves, hence the
model is manufactured using Fused Deposition Modelling (FDM) technology [14].
K. S. Vepa et al.
1 Introduction
Unmanned Aircraft Systems (UASs) are widely used in various applications due to
its major advantage of operating without onboard pilot [1, 2]. There are three types
of UASs, i.e., fixed wing, flapping wing, and rotary wing. Rotary wing UASs have
better hovering characteristics as the aerodynamic behavior of rotors have greater
significance in controlling and maneuvering the vehicles. Information exchange at
the interface between the rotor and fluid domains is a challenging task. Computational
fluid dynamic (CFD) analysis helps in addressing this problem. Using CFD analysis,
wake region, formation of vortex, shift of tip vortex to turbulence regimes and multirotor interactions can be studied [3]. Considerable research is available in the field of
CFD [4–6] and multi-rotor dynamics [7, 8]. The forces acting on quadcopter opposite
to the direction of motion affect its performance. The force that opposes the forward
motion is drag and it affects the endurance. The value of drag varies with the angle
of attack and the present study investigates the performance of quadcopter on varied
angles of attack.
Filippone and Michelsen [9] estimated the drag on the structure of a helicopter
for several configurations and respective center of pressure regions are determined.
Also, wind tunnel tests are conducted for various geometries to understand the flow
fields for asymmetric flow conditions. More recently, Yoon et al. [10] studied the
effect of the distance between the rotors and fuselage during hovering condition.
It has been observed that as the distance decreases, the efficiency of the UAS also
decreases. Felismina [11] analyzed the aerodynamic behavior of UAV assembled
with seeder mechanism and drag force is computed using CFD analysis. Lopez
et al. [12] used SA and K-ω models to study the flow field around propeller of a
quadcopter. With the use of Lattice-Boltzmann and LES turbulence methodology,
Thibault et al. [13] simulated the vortex phenomena for a quadcopter. In line with
the existing studies, an off-the-shelf structural model is considered for examining
its aerodynamic behavior. The UAS chosen for this analysis is a quadcopter. The
topology of the frame is optimized to reduce its weight, but the resulting frame is
complex in geometry with intricate flow fields. Hence, we aimed to calculate the
value of drag during the hovering phase and forward motion for various angles of
attack.
2 Design of Quadcopter UAS
The conceptual model of UAS is an off-the-shelf model of a commercially available
quadcopter frame. The model is designed and developed to carry an all-up weight
of 2 kg load. The process of designing the model is carried out in ANSYS Design
Modeler and CFD simulations are carried out using ANSYS CFX. The model considered for the analysis is very complex which involves various spline curves, hence the
model is manufactured using Fused Deposition Modelling (FDM) technology [14].