Selected papers and research contributions associated with this student’s work.
Citation: 4. Cai, Jielong, Sidaard Gunasekaran, Michael OL, and Anwar Ahmed. "Propeller Ground and Ceiling Effect Parametric Data." Journal of Aircraft (2020): 1-4. https://doi.org/10.2514/1.C035839
Short abstract: Click on the DOI link to access this article at the publishers website (may not be free).
Citation: 8. Cai, Jielong, Sidaard Gunasekaran, and Michael Ol. "Effect of Partial Ground and Partial Ceiling on Propeller Performance." Journal of Aircraft (2022): 1-14. https://doi.org/10.2514/1.C036974
Short abstract: Finite extent flat obstacles behind a propeller (“partial ground”) and ahead of the propeller (“partial ceiling”) were examined experimentally for a small-scale fixed-pitch propeller in hover. Cases included circular and annular plates, which can be summed up or superimposed.
Citation: 9. Cai, Jielong, and Sidaard Gunasekaran. "Propeller Ground Effect in Forward Flight." AIAA Journal 61, no. 10 (2023): 4378-4390. https://doi.org/10.2514/1.J062984
Short abstract: The study of the fixed-pitch small-scale propeller in-ground effect is extended to forward flight conditions at different incidence angles of the propeller. Force-based experiments, smoke flow visualization, surface flow visualization, and phase-locked particle image velocimetry (PIV) indicate the presence of three distinct performance zones as a function of the advance ratio and ground distance, where the ground effect changes drastically.
Citation: 11. Cai, Jielong, and Sidaard Gunasekaran. "Frequency Response of RC Propellers to Streamwise Gusts in Forward Flight." Wind 3, no. 2 (2023): 253-272. https://doi.org/10.3390/wind3020015
Short abstract: The RC propeller performance under steady and sinusoidally time-varying freestream (stream-wise or longitudinal gust) was investigated in the University of Dayton Low-Speed Wind Tunnel (UD-LSWT) in the open-jet configuration. The propellers were tested at varying incidence angles and reduced frequencies.
Citation: 13. Cai, Jielong, and Sidaard Gunasekaran. "Propeller Ceiling Effect in Forward Flight." Journal of Aircraft (2024): 1-17. https://doi.org/10.2514/1.C037779
Short abstract: The study extends the investigation of the fixed-pitch small-scale propeller in the ceiling effect to forward flight conditions at different propeller incidence angles. Force-based experiments, phase-locked particle image velocimetry (PIV), and surface oil flow visualization were conducted on two APC propellers at the University of Dayton Low Speed Wind Tunnel.
Citation: 19. Cai, Jielong, Sidaard Gunasekaran, Anwar Ahmed, and Michael V. Ol. "Changes In Propeller Performance Due to Ground Proximity." In AIAA Scitech 2019 Forum, p. 1097. 2019. https://doi.org/10.2514/6.2019-1097
Short abstract: Click on the DOI link to access this article at the publishers website (may not be free).
Citation: 27. Cai, Jielong, Sidaard Gunasekaran, Anwar Ahmed, and Michael V. Ol. "Propeller Partial Ground Effect." In AIAA Scitech 2020 Forum, p. 1028. 2020. https://doi.org/10.2514/6.2020-1028
Short abstract: We extend our recent electric propeller ground-effect study to consider a circular ground-plate, instead of planar-surface of assumed infinite extent. Parameter studies include propeller to plate diameter ratio, propeller diameter to ground-offset ratio, and propeller pitch to diameter ratio.
Citation: 29. Culpepper, Grace G., Jielong Cai, and Sidaard Gunasekaran. "Propeller and Propeller-in-Wing Thrust Vectoring." In AIAA Scitech 2021 Forum, p. 0615. 2021. https://doi.org/10.2514/6.2021-0615
Short abstract: We investigate the efficiency of a thrust vectoring system utilizing a set of vanes designed to create forward force at a minimum loss in net thrust, placed in both a stand-alone propeller configuration and a propeller-in-wing configuration. Both static and wind-on force-based experiments were conducted at the University of Dayton Low Speed Wind Tunnel (UD-LSWT) with off-the-shelf R/C propellers.
Citation: 30. Cai, Jielong, Sidaard Gunasekaran, and Michael V. Ol. "Propeller Partial Ground and Ceiling Effect Prediction." In AIAA Scitech 2021 Forum, p. 0614. 2021. https://doi.org/10.2514/6.2021-0614
Short abstract: Our propeller partial ground-effect study was extended to annulus ground-plates. Correlations between force data and flow visualization indicate that onset of strong outward radial flow on the ground plate, as normalized ground-separation distance decreases, appears together with thrust-augmentation and power-reduction in ground effect.
Citation: 36. Cai, Jielong, Sidaard Gunasekaran, and Michael V. Ol. "Sinusoidal Gust Response of RC Propellers at Different Incidence Angles." In AIAA SCITECH 2022 Forum, p. 1536. 2022. https://doi.org/10.2514/6.2022-1536
Short abstract: We investigate propeller performance under steady and sinusoidally time-varying freestream velocity in an open-jet wind tunnel. Changes in thrust, power, pitching moment, and rolling moment observed with increase in propeller incidence angle under steady freestream was then used to predict response under sinusoidal time-varying freestream.
Citation: 38. Culpepper, Grace G., Jielong Cai, and Sidaard Gunasekaran. "Effect of Forward Propeller Tilt and Inlet Shape in Propeller-in-Wing Thrust Vectoring." In AIAA SCITECH 2022 Forum, p. 1539. 2022. https://doi.org/10.2514/6.2022-1539
Short abstract: We continue to investigate the efficacy of a propeller-in-wing thrust vectoring system utilizing a set of vanes placed in the wake of the propeller with two additional variables: the global forward tilt of the propeller with respect to the freestream and the inlet shape. All experiments were conducted at the University of Dayton Low-Speed Wind Tunnel (UD-LSWT) with off-the-shelf R/C electric propellers.
Citation: 39. Hung, Lucas K., Jielong Cai, Neal Novotny, and Sidaard Gunasekaran. "Development of a Multi-Purpose Flap and Spoiler Mechanism for High Endurance Unmanned Aerial Vehicles." In AIAA SCITECH 2022 Forum, p. 1027. 2022. https://doi.org/10.2514/6.2022-1027
Short abstract: High endurance aircraft can provide benefits to many operations. However, sub-optimal flap mechanisms hinder takeoff and landings, especially on small unmanned aerial vehicles (UAVs).
Citation: 43. Cai, Jielong., Sidaard Gunasekaran, “Propeller Ground and Ceiling Effect in Forward Flight”, Vertical Flight Society, Forum 78, Dallas, TX, USA, 2022. SKU # 78-2022-0072-Cai 44. Killian, Andrew, Sidaard Gunasekaran, Michael P. Mongin, and Albert Medina. "Periodic Vortical Gust Encounter and Mitigation Using Closed Loop Control." In AIAA SCITECH 2023 Forum, p. 2477. 2023. https://doi.org/10.2514/6.2023-717042477
Short abstract: A wing’s response to periodic vortical gusts of different frequencies and magnitudes was investigated and controlled using a PID based closed loop control system. All experiments were conducted in the University of Dayton Water Tunnel (UD-WaT).
Citation: 48. Cai, Jielong, Sidaard Gunasekaran, and Michael V. Ol. "Vertically Offset Overlapping Propellers in Tandem Configuration." In AIAA SCITECH 2023 Forum, p. 2464. 2023. https://doi.org/10.2514/6.2023-717042464
Short abstract: Modern VTOL configurations often seek minimal footprint simultaneously with minimal disk loading (often competing constraints), the latter to improve propulsive efficiency at low speeds. One approach is to stagger neighboring propellers in partial overlap.
Citation: 49. Gogidze, George J., Sidaard Gunasekaran, and Jielong Cai. "Effect of Propeller Incidence Angle on Wing Embedded Propeller Configuration in Forward Flight." In AIAA SCITECH 2023 Forum, p. 2284. 2023. https://doi.org/10.2514/6.2023-717042284
Short abstract: We continue our study on the effect of a propeller embedded in the wing under various propeller incidence angles. The current study focuses on the performance of the wing and the wing-embedded propulsion as one system.
Citation: 51. Cai, Jielong, and Sidaard Gunasekaran. "Sinusoidal Gust Response of RC Propellers in Tandem Configuration" In VFS Forum 79, https://doi.org/10.4050/F-0079-2023-17981
Short abstract: The study of the fixed-pitch small-scale propeller under sinusoidally time-varying freestream is extended to a tandem propeller configuration. The changes in thrust and pitching moment of both the front and back propeller were characterized when encountering the sinusoidal gust in edgewise flight conditions.
Citation: 52. Pabon, Julian A., Xinyu Gao, Jielong Cai, and Sidaard Gunasekaran. "Experimental Investigation of a Novel Morphing Wing Design." In AIAA 2023 Region III Student Conference, Dayton, OH https://doi.org/10.2514/6.2023-71704
Short abstract: Short summary unavailable from DOI metadata. This work focuses on experimental investigation of a novel morphing wing design.
Citation: 53. Duncan, Lucas, Jielong Cai, and Sidaard Gunasekaran. "Powered Wing's Response to Streamwise Gust Encounters." In AIAA 2023 Region III Student Conference, Dayton, OH https://doi.org/10.2514/6.2023-7170471287
Short abstract: Propeller-wing interactions have been studied in great detail over several decades. However, almost all of them were conducted in steady initial conditions where the freestream remained constant.
Citation: 56. Cai, Jielong, Sidaard Gunasekaran, and Michael Ol. "Investigation of Positively Staggered Vertically Offset Propellers in Tandem." In AIAA SCITECH 2024 Forum, p. 1510. 2024. https://doi.org/10.2514/6.2024-1510
Short abstract: We continue our study on the aerodynamic investigation of two propellers mounted partially overlapping and in tandem configurations. In the previous study, the rear propeller was placed above the plane of the front propeller (negative stagger).
Citation: 59. Kulig, Jacob, Jielong Cai, Sidaard Gunasekaran, and Carson L. Running. "Back-Imaging of Pressure-Sensitive Paint to Determine Close Proximity Ground Effects of Propellers." In AIAA SCITECH 2024 Forum, p. 0878. 2024. https://doi.org/10.2514/6.2024-0878
Short abstract: The ground effects of propellers have been extensively studied in the literature both theoretically and experimentally via a variety of methods; however, there are limitations with regards to global analyses of the mean and unsteady flow along the surface of the ground plate. This study provides a proof of concept that back-imaged pressure-sensitive paint (PSP) can successfully analyze the mean and unsteady surface pressure distributions along such a ground plate.
Citation: 60. Pabon, Julian A., Xinyu Gao, Jielong Cai, and Sidaard Gunasekaran. "Experimental Investigation of a Novel Morphing Wing Design." In AIAA SCITECH 2024 Forum, p. 1349. 2024. https://doi.org/10.2514/6.2024-1349
Short abstract: The aerodynamic performance of a novel Fishbone Skin-Actuated-Camber (SAC) morphing wing design, which actuates its skin to change its effective camber, was studied both experimentally and numerically. Force-based experiments were conducted at the University of Dayton Low Speed Wind Tunnel (UD-LSWT) to compare the performance of four morphing wing designs with different hinge locations, two ideal trailing edge flap wings, and one conventional trailing edge flap wing.
Citation: 61. Duncan, Lucas, Jielong Cai, and Sidaard Gunasekaran. "Powered Wing's Response to Streamwise Gust Encounters." In AIAA SCITECH 2024 Forum, p. 0077. 2024. https://doi.org/10.2514/6.2024-0077
Short abstract: We continue our study of a powered wing’s response to streamwise gusts and investigate its performance. A full span aspect ratio 2.67 wing model with different propeller installation locations was subjected to streamwise gusts of varying reduced frequencies in the University of Dayton Low Speed Wind Tunnel (UD-LSWT).
Citation: 63. Cai, Jielong, Caiden Guzman, Emma Schutter, and Sidaard Gunasekaran. "On the Linear Superposition of Wing and Propeller Performance in a Wing Embedded Propeller System." In AIAA SCITECH 2024 Forum, p. 1511. 2024. https://doi.org/10.2514/6.2024-1511
Short abstract: We continue our study on the aerodynamic performance of a Wing-Embedded Propeller (WEP) system by considering the effect of propeller installation location along the span and its overall size on the entire system. Six semi-span AR 2 wings with different spanwise opening locations and opening diameter-to-wing-chord ratios were investigated numerically using FlightStream® and experimentally in the University of Dayton Low-Speed Wind Tunnel without the installation of the propeller.
Citation: 66. Cai, Jielong, and Sidaard Gunasekaran. "Prediction of the Tandem Propeller Performance Using Linear Superposition Method." In AIAA SCITECH 2025 Forum, p. 1268. 2025. https://doi.org/10.2514/6.2025-1268
Short abstract: We continue our study on the aerodynamic investigation of two propellers mounted partially overlapping and in tandem configurations. In the previous study, the force-based experiment was conducted in both positive and negative staggered configurations.
Citation: 67. Foster, Michael, Jessica DeMoor, Sidaard Gunasekaran, and Jielong Cai. "Flight Test Validation of Tandem Propeller Performance With Vertical Offset." In AIAA SCITECH 2025 Forum, p. 1445. 2025. https://doi.org/10.2514/6.2025-1445
Short abstract: Strategic placement of the rotors in a non-planar configuration in a multirotor vehicle can improve power efficiency. We extend our wind tunnel study on the investigation of the negatively staggered tandem propeller performance, aiming to validate the results through flight tests.
Citation: 71. Parlett, Samuel L., Jielong Cai, Sidaard Gunasekaran, and Michael Ol. "Experimental Investigation of a Variable Pitch Propeller at Various Incidence Angles in Foward Flight." In AIAA SCITECH 2025 Forum, p. 1267. 2025. https://doi.org/10.2514/6.2025-1267
Short abstract: We extend our experiments on fixed-pitch propellers in forward flight at various incidence angles with respect to the freestream, to a propeller with variable collective pitch. Different combinations of blade pitch, incidence angle, and flight speed were tested at the University of Dayton Low-Speed Wind Tunnel in an open-jet test section.
Citation: 72. Schreyer, Grace A., Sidaard Gunasekaran, Julian A. Pabon, and Jielong Cai. "Variations in the Wake Structure of Non-Elliptical Lift Distributions Near Wingtip." In AIAA SCITECH 2025 Forum, p. 0253. 2025. https://doi.org/10.2514/6.2025-0253
Short abstract: Non-elliptical lift distributions, particularly bell-shaped distributions with extended spans, have shown potential to disrupt conventional tip vortex roll-up, even eliminating trailing vortices in the near wake. This study investigates the aerodynamic performance and near-wake characteristics of four wing configurations: a baseline untwisted wing, an elliptically loaded wing, and two nonelliptical lift distributions.
Citation: 78. Parlett, Samuel L., Jielong Cai, Michael V. OL, and Sidaard Gunasekaran. "Experimental Investigation of a Variable Collective Pitch Propeller in Near Edgewise Flight." In AIAA SCITECH 2026 Forum, p. 0026. 2026. https://doi.org/10.2514/6.2026-0026
Short abstract: We extend our experiments on fixed and variable collective pitch propellers in forward flight, to near-edgewise flight conditions. Different combinations of blade pitch, incidence angle, and flight speed were tested in an open-jet test section wind tunnel, at incidence angles of 75 to 100 degrees.