Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session R38: Vortex Dynamics and Vortex Flows: Aerodynamics |
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Chair: Roberto Verzicco, University of Roma Tor Vergata Room: 355 D |
Monday, November 25, 2024 1:50PM - 2:03PM |
R38.00001: Using synthetic jets to emulate rectangular tab-style vortex generators Frank Anthony Tricouros, Valerie Moore, Tyler Van Buren Vortex generators are a predominant flow control strategy for aircraft due to reliability and efficient function. However, there are instances where you do not necessarily need the vortex structure (e.g., an aircraft in cruise) and thus it becomes parasitic. We explore a common active flow control actuator, the synthetic jet, as being capable of directly replacing a vortex generator. We compare the vortex structure and resultant vorticity fields produced by synthetic jets and rectangular tab-style vortex generators. These vortex generators produce a strong, coherent wall-bounded vortex core that develops downstream. Synthetic jet parameters such as orifice orientation, orifice size, and blowing ratio are tuned to best mimic the vortex structure. The resulting flow fields will be analysed for potential performance benefits. Dimensional analysis will be performed to create a predictive model for vortex size and strength for both the synthetic jets and for the vortex generators. Ultimately, our aim is to provide guidance on the best configuration of a synthetic jet for completely replacing a single tab-style vortex generator. |
Monday, November 25, 2024 2:03PM - 2:16PM |
R38.00002: Characterization of Unsteady Flow Scales on a Pitching NACA 0012 Across a Range of Reynolds Numbers. Vanessa G Awate, Phillip J Ansell Dynamic stall is a well-known phenomenon in rotary wing flows, leading initially to an overshoot in lift performance followed by a rapid loss in such performance. During the dynamic stall process, the flow over a lifting surface becomes unsteady and evolves into a flow dominated by large-scale vortex structures. The emergence and evolution of these vortex flow structures contribute to large variations in loading, thus affecting both the aerodynamic performance and the structural integrity of aircraft. |
Monday, November 25, 2024 2:16PM - 2:29PM |
R38.00003: Connection between vortex structures and the center of pressure in unsteady separated flow over pitching swept wings DIPAN DEB, Yuanhang Zhu, Kenneth S Breuer We analyze the stability characteristics of elastically mounted rigid swept wings using previously acquired measurements (Zhu et al. JFM, 2023). The NACA0012 wings featured sweep angles of 0°, 10°, and 20°, and experienced large amplitude sinusoidal pitching instabilities below a critical torsional spring stiffness. The time-varying location of the center of pressure (CP) is calculated from the measured forces and moments. Although there is little change in the CP in the cross-chord direction, the spanwise position shows considerable movement, and its trajectory varies with sweep angle due to the changing strength and evolution of the leading edge and tip vortices. The Force Moment Partitioning Method (FMPM) is applied to time-resolved stereo PIV measurements, and used to disentangle contributions due to wing kinematics, vortex and viscous phenomena as well as the different roles of the leading edge and tip vortices. |
Monday, November 25, 2024 2:29PM - 2:42PM |
R38.00004: Fluid-Structure-Surface Interactions of a Plunging Plate Near a Free Surface Hadi Samsam-Khayani, Banafsheh Seyed-Aghazadeh This experimental study investigated fluid-structure-surface interactions of a flexibly mounted rigid flat plate oscillating in the plunging direction in axial flow. Using water tunnel experiments and time-resolved particle image velocimetry (PIV), the effects of proximity to the free surface on the plate's flow-induced vibration response were analyzed. Various Reynolds numbers and angles of attack were tested across different submerged heights. Results show that at deeper submergence, increasing the angle of attack intensifies fluid-plate interaction, leading to distinct leading-edge and trailing-edge vortex shedding (LEV and TEV). However, this interaction does not induce oscillations. Near the free surface, distinct flow regimes characterized by vortex shedding and the Coanda effect emerged, varying with angles of attack and flow velocities. Notably, limit-cycle oscillations (LCO) occurred within specific ranges of angles of attack and flow velocity due to the rebounded LEV from the free surface, causing surface deformation and interaction with the plate. The generated jet-like flow and immediate vortex coupling between LEV and free surface vortices result in a momentum surplus in the wake of the oscillating plate. |
Monday, November 25, 2024 2:42PM - 2:55PM |
R38.00005: Impingement of a Vortex Pair on Static and Dynamic Perturbed Walls David J Nelson, Sarah E Morris Counter-rotating vortex pair wakes (CRVP) are an unavoidable by-product of aircraft lift generation. Aircraft encountering these wakes can be subjected to unexpected hazardous rolling moments, which can prove fatal. This is especially true in terminal flight phases where there is insufficient altitude to recover. In contrast to terrestrial landings, Naval aircraft in terminal flight phases must also contend with approaches above a highly dynamic oceanic free surface. Understanding the behavior of these wakes near the ground is therefore of peak importance for aircraft operations and safety. This investigation uses a towed delta wing to generate a spatially-evolving CRVP that descends towards the ground plane under its own self-induced velocity. A static perturbed wall is placed at the ground, representative of a perturbed oceanic surface. Laser-induced fluorescence and particle-image velocimetry (PIV) measurements are taken to assess the vortex-wall interaction and quantify the rate of CRVP decay. The spatially-evolving CRVP comprises of both axial and circumferential flows, and approaches the ground plane at an angle. The inclined vortex pair produces three-dimensional secondary vortex structures at the wall, increasing the decay rate of the primary CRVP. Preliminary results show that the interaction of the vortex pair with the dynamic perturbed wall yields highly time-dependent secondary vortex structures. |
Monday, November 25, 2024 2:55PM - 3:08PM |
R38.00006: Turbulent wake vortices at equilibrium and their interaction with the ground at ReΓ = 2 x 105 Gregoire Winckelmans, Matthieu Duponcheel, Laurent Bricteux, Ivan De Visscher, Olivier Thiry A turbulent two-vortex system at equilibrium, that is typical of aircraft wakes in the far field, is first obtained using large eddy simulation and is characterized: circulation distributon of the vortices; energy of the mean and fluctuating fields; energy dissipation rate associated with the turbument equilibrium. A wall-resolved simulation of that system further interacting with a smooth ground is then performed at ReΓ = 2 x 105 , which allows to capture the high Reynolds number behaviour. The high release height of the system also ensures a physically correct approach to the ground. For comparison, we also simulate the case of a system with non-turbulent vortices interacting with the same ground at the same Reynolds number. The flow topologies are discussed, and significant differences are highlighted regarding the separation of the boundary layer generated at the ground, and the way this secondary vorticity interacts with the primary vortices and makes them decay. The vortex trajectories are also measured, together with their circulation distribution and global circulation evolution, and the differences are discussed. |
Monday, November 25, 2024 3:08PM - 3:21PM |
R38.00007: Effect of 3D Surface Contour on the Flow Field over a Delta Wing Sean Patrick Devey, Morteza Gharib The flow field over delta-wing aircraft is predominantly influenced by a pair of counter-rotating leading-edge vortices (LEVs). The trajectory of these LEVs can be manipulated by the three-dimensional contour of the wing’s leeward surface. However, the mechanisms behind these vortex trajectories and their consequent effects have not been comprehensively studied. Specifically, the impact of non-uniform surface thickness on the leeside flow field, vortex bursting locations, and secondary vorticity concentrations remains unclear. These factors are critical as they can substantially affect the performance and stability of delta-wing aircraft. |
Monday, November 25, 2024 3:21PM - 3:34PM |
R38.00008: Extreme vortex-gust encounters by a finite wing HIROTO ODAKA, Luke Smith, Kunihiko Taira This study examines the influence of wing tip vortices on the evolution of a strong gust-wing interaction. We consider flows around a NACA0015 wing impacted by an extremely strong, spanwise-oriented vortex gust at a chord-based Reynolds number of Re = 600. An extreme gust encounter is defined as a case in which the characteristic gust velocity is larger than the free stream velocity. |
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