Eduardo Alvarez - Academia.edu (original) (raw)

Papers by Eduardo Alvarez

2018 Applied Aerodynamics Conference, 2018

Multirotor configurations introduce complicated aerodynamic and aeroacoustic interactions that mu... more Multirotor configurations introduce complicated aerodynamic and aeroacoustic interactions that must be considered during aircraft design. In this paper we explore two numerical methods to model the acoustic noise caused by aerodynamic rotor-on-rotor interactions of rotors in hover. The first method uses a conventional mesh-based unsteady Reynolds-average Navier-Stokes (URANS) solver, while the second consists of a meshless Lagrangian solver based on the viscous vortex particle method (VPM). Both methods are coupled with an aeroacoustics solver for tonal and broadband noise predictions. Noise predictions are validated for single and multi-rotor configurations, obtaining with the VPM a similar accuracy than URANS while being two orders of magnitude faster. We characterize the interactions of two side-by-side rotors in hover as the tip-to-tip distance and downstream spacing are varied. At an observer located six diameters away, multirotor noise is the strongest above and below the roto...

AIAA AVIATION 2020 FORUM, 2020

Airborne Wind Energy (AWE) technology aspires to provide increased options for wind energy harves... more Airborne Wind Energy (AWE) technology aspires to provide increased options for wind energy harvesting. This includes increased feasibility for temporary and remote installations, as well as the ability to operate at wind speeds both lower and higher than traditional turbines. Additionally, the hope is to be able to produce these extensions of wind energy technology at a lower cost than conventional technologies. As AWE technology is still in its infancy, however, there is very little published information concerning the aerodynamic details of the technology. We have created a set of aerodynamic analysis tools which we apply to wind harvesting aircraft, or windcraft for short, in order to explore some of the basic aerodynamic performance properties of a rigid-wing, on-board generation AWE platform, similar to the Makani M600 prototype. In this work, we perform an introductory exploration of the aerodynamics of a windcraft first in steady, level flight, then following a circular path in crosswind flight. Positive interactions between the upper and lower rotor wakes increase the overall wing lift in the steady, level case by an average of 5.3 percent relative to the wing without rotors present. In addition to the same positive interactions between upper and lower rotors, the crosswind orientation of the circular path leads to the rotor wakes being pushed "up" relative to the wing, leading to an additional increase in force. Specifically, the normal force of the wing with rotors in the circular path is increased by an average of 17.3 percent relative to the wing in the same path without rotors.

AIAA Aviation 2019 Forum, 2019

AIAA Journal, 2020

Electric aircraft technology has enabled the use of multiple rotors in novel concepts for urban a... more Electric aircraft technology has enabled the use of multiple rotors in novel concepts for urban air mobility. However, multirotor configurations introduce strong aerodynamic and aeroacoustic interactions that are not captured through conventional aircraft design tools. In this paper we explore the capability of the viscous vortex particle method (VPM) to model multirotor aerodynamic interactions at a computational cost suitable for conceptual design. A VPM-based rotor model is introduced along with recommendations for numerical stability and computational efficiency. Validation of the individual rotor is presented in both hovering and forward-flight configurations at low, moderate, and high Reynolds numbers. Hovering multirotor predictions are compared to experimental measurements, evidencing the suitability of the proposed model to capture the thrust drop and unsteady loading produced by rotor-onrotor interactions.

2018 Applied Aerodynamics Conference, 2018

Multirotor configurations introduce complicated aerodynamic and aeroacoustic interactions that mu... more Multirotor configurations introduce complicated aerodynamic and aeroacoustic interactions that must be considered during aircraft design. In this paper we explore two numerical methods to model the acoustic noise caused by aerodynamic rotor-on-rotor interactions of rotors in hover. The first method uses a conventional mesh-based unsteady Reynolds-average Navier-Stokes (URANS) solver, while the second consists of a meshless Lagrangian solver based on the viscous vortex particle method (VPM). Both methods are coupled with an aeroacoustics solver for tonal and broadband noise predictions. Noise predictions are validated for single and multi-rotor configurations, obtaining with the VPM a similar accuracy than URANS while being two orders of magnitude faster. We characterize the interactions of two side-by-side rotors in hover as the tip-to-tip distance and downstream spacing are varied. At an observer located six diameters away, multirotor noise is the strongest above and below the roto...

AIAA AVIATION 2020 FORUM, 2020

Airborne Wind Energy (AWE) technology aspires to provide increased options for wind energy harves... more Airborne Wind Energy (AWE) technology aspires to provide increased options for wind energy harvesting. This includes increased feasibility for temporary and remote installations, as well as the ability to operate at wind speeds both lower and higher than traditional turbines. Additionally, the hope is to be able to produce these extensions of wind energy technology at a lower cost than conventional technologies. As AWE technology is still in its infancy, however, there is very little published information concerning the aerodynamic details of the technology. We have created a set of aerodynamic analysis tools which we apply to wind harvesting aircraft, or windcraft for short, in order to explore some of the basic aerodynamic performance properties of a rigid-wing, on-board generation AWE platform, similar to the Makani M600 prototype. In this work, we perform an introductory exploration of the aerodynamics of a windcraft first in steady, level flight, then following a circular path in crosswind flight. Positive interactions between the upper and lower rotor wakes increase the overall wing lift in the steady, level case by an average of 5.3 percent relative to the wing without rotors present. In addition to the same positive interactions between upper and lower rotors, the crosswind orientation of the circular path leads to the rotor wakes being pushed "up" relative to the wing, leading to an additional increase in force. Specifically, the normal force of the wing with rotors in the circular path is increased by an average of 17.3 percent relative to the wing in the same path without rotors.

AIAA Aviation 2019 Forum, 2019

AIAA Journal, 2020

Electric aircraft technology has enabled the use of multiple rotors in novel concepts for urban a... more Electric aircraft technology has enabled the use of multiple rotors in novel concepts for urban air mobility. However, multirotor configurations introduce strong aerodynamic and aeroacoustic interactions that are not captured through conventional aircraft design tools. In this paper we explore the capability of the viscous vortex particle method (VPM) to model multirotor aerodynamic interactions at a computational cost suitable for conceptual design. A VPM-based rotor model is introduced along with recommendations for numerical stability and computational efficiency. Validation of the individual rotor is presented in both hovering and forward-flight configurations at low, moderate, and high Reynolds numbers. Hovering multirotor predictions are compared to experimental measurements, evidencing the suitability of the proposed model to capture the thrust drop and unsteady loading produced by rotor-onrotor interactions.