Bulletin of the American Physical Society
73rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 65, Number 13
Sunday–Tuesday, November 22–24, 2020; Virtual, CT (Chicago time)
Session W04: Aerodynamics: Vehicles (10:00am - 10:45am CST)Interactive On Demand
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W04.00001: Analysis of Flow Regime and Pressure Waves in Hyperloop System Kyeongsik Jang, GiangLe ThiThanh, Kwansup Lee, Youngjun Jang, Jaiyoung Ryu Due to drastic technological advancement, the demand for more efficient and economical means of transportation has increased significantly. In 2013, Elon Musk introduced near-vacuum tube-pod system, Hyperloop system, that travels at the speed of near Mach number 1 . This high-speed object in low pressure tube induces pressure waves in tube. For analyzing Hyperloop system, two-dimensional axisymmetric and unsteady simulation with density based solver was performed. As a result, flow regime in Hyperloop system is divide to three type which are similar with converge-diverge nozzle. We also confirmed that pressure waves caused by pod motion greatly affect the aerodynamic characteristics of the pod due to low tube pressure compared with atmosphere. By theoretically analyzing pressure waves, drag acting on the pod was calculated. This theoretical consideration of pressure waves and drag of the pod can contribute further understanding of Hyperloop system. [Preview Abstract] |
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W04.00002: Unsteady Aerodynamics of Turning Maneuvers in Olympic Class Sailboats Sarah Morris, C.H.K Williamson In this work, we use a ``sports-mimetic'' approach to study unsteady sail motion techniques, inspired by bodyweight motions used by Olympic sailors as they maneuver their sailboats when racing. One such technique used to increase a boats propulsion is for sailors to roll the boat about its longitudinal axis. This motion is used especially when turning in light winds, by either ``roll-tacking'' (upwind sailing) or ``roll-gybing'' (downwind sailing). When roll-tacking and roll-gybing, sailors dynamically roll the boat to propel their boats faster than using wind alone; this is in contrast to flat-tacking and flat-gybing, wherein the sailor keeps the boat level (and mast vertical) while turning. These motions are characterized in on-the-water experiments using an Olympic Laser sailboat and a 420 sailboat, equipped with a GPS, IMU, wind sensor and GoPro camera array. We study the underlying vortex dynamics using these characteristic motions, along with full-scale flow visualization. Flow visualization experiments are conducted on Cayuga Lake with an Olympic Laser Sailboat, using an Enola Gaye WP40 smoke grenade to visualize large-scale flow features around the sail. [Preview Abstract] |
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W04.00003: Multirotor Unmanned Aerial Vehicle (UAV) Flight Performances under Shear Flow Turbulence with Different Control Schemes Ningshan Wang, Jean-Eric van der Elst, Amit Sanyal, Mark Glauser In this research, several multi-rotor UAV test flights under shear flow turbulence are carried out. The flight performance of the multi-rotor UAV is evaluated when exposed to such turbulence. The UAV implemented with linear control scheme and nonlinear geometric control scheme are tested with different shear rates and freestream velocities to obtain their performances under a variety of conditions. Characterization of the shear flow field is evaluated by an array of total pressure scanners to measure the shear rate and free stream velocity spatially. Besides, the generated shear flow is simulated by Computational Fluid Dynamics (CFD) tools to compare with the fluid flow data obtained from the pressure scanners. The flight performance data is obtained through the Inertial Measurement Unit (IMU) integrated inside the autopilot hardware of the UAV. [Preview Abstract] |
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W04.00004: Improvement of Bicycle Wheel CFD using Blade Element Momentum Andrew Vigne, George Loubimov, Michael Kinzel The cycling industry has long relied on expensive wind tunnel testing when designing new aerodynamic products. However, with the recent advent of computational fluid dynamics (CFD), the industry now has an economical tool that supplements this iterative design process. While current CFD methods can reliably simulate static bicycle components, the complex aerodynamics of rotating, spoked wheels make them particularly difficult to efficiently simulate as they consume valuable computational time. This research investigates a new CFD method that can accurately model a bicycle wheel at a lower computational cost. A 3D model of a hub, rim, and tire all rotate using overset mesh techniques atop a transversely moving ground plane. Blade Element Momentum (BEM) techniques are then used to model rotating spokes. BEM has never before been used for cycling applications but has a demonstrated history for effectively modeling aerodynamic performances of helicopter and wind turbine blades at a lower computational cost than simulating these 3D geometries directly. Preliminary results suggest that employing BEM on a bicycle wheel has a similar effect, all while accounting for relevant fluid scales and yielding force/moment data comparable to wind tunnel experiments. [Preview Abstract] |
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W04.00005: Feedback control of the bi-modal flow behind a blunt bluff body Dania Ahmed, Aimee S. Morgans The turbulent wake behind a square-back Ahmed body in close proximity to the ground exhibits bi-modal switching. This manifests as the centre of the wake switches between one of two asymmetric positions, either horizontally or vertically. Switches occur over random timescales, with the wake recovering symmetry in the long time-average. Large Eddy Simulations (LES) are employed to investigate feedback control strategies for suppressing wake bi-modality to reduce the drag. The unforced results establish a link between the wake switches and the coherent structures shed from the frontal separation bubble on the body surfaces upstream the wake. A model-based nonlinear controller is synthesized, based upon the nonlinear Langevin equation model. The controller successfully suppresses wake bi-modality, but amplifies higher frequencies, this hindering the drag reduction achieved by wake symmetrisation. A maximum drag reduction of 7.4{\%} is achieved for a semi-symmetrised wake, while a fully symmetrised wake leads to 3{\%} drag reduction. [Preview Abstract] |
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W04.00006: Improving aerodynamic simulation accuracy of a NASCAR body with machine learning augmented turbulence models Kyle Mooney, Colby Mazzuca, Racheet Matai, Anand Pratap Singh, Eric Warren, Karthik Duraisamy Aerodynamic loads on a NASCAR vehicle at race speeds significantly influence its on-track performance. Due in part to complex boundary layer separation and interacting turbulent structures, the accuracy of these loads obtained in CFD simulation environments can be limited by the capabilities of the underlying turbulence model. In this work, we demonstrate how experimental data combined with machine learning (ML) methods can be used to augment a turbulence model and improve simulation accuracy on a NASCAR body. Two similar yet distinct model augmentation methods are shown, both of which use experimental wind tunnel data to drive model augmentation. One method uses flow feature based cell clustering and optimization routines to perform localized calibration of turbulence model parameters. The second method utilizes a combination of adjoint-based field-inversion and machine learning to generate field-based corrections to predicted turbulent quantities. Validation and portability of the model augmentation is demonstrated by applying trained augmentations on unseen vehicle bodies and compared to experimental wind-tunnel measurements. Simulation results show significantly improved agreement with experimentally measured aerodynamic loads compared to baseline k-Omega-BSL results. [Preview Abstract] |
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W04.00007: Collection Device for Dolphin Hormones in Blowhole Jet Flow Field Eric Abele, Kerrick Ray, Jamey Jacob, Richard Gaeta Marine biologist are able to quantify the stress in bottlenose dolphins through analysis of hormones in mucus samples released from the blowhole while breathing. To capture the samples, petri dishes attached to an Unmanned Aerial System (UAS) can fly through the flow field of the dolphin's expelled breath. Analysis of the flow into the dish was performed with Particle Image Velocimetry and flow visualization. The resulting data was used to indicate key areas of flow across the petri dish indicating both clean and separation areas. In preparation for UAS trials, the collection device is connected to the UAS for flight-testing to measure significant changes in control, lift, and drag while the petri dishes open and close. For the UAS trials, the system is flown through the ``breath'' of a simulator to emulate the 20-140 liters per second in a timeframe of 0.26-0.31 seconds of the dolphin breath. The resulting data is used to provide validation of the systems capability for in flight sample collection. [Preview Abstract] |
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W04.00008: Ice Accretion for SUAS Flight Regime on 2D Cylinders. Alyssa Avery, Jamey Jacob While the icing problem has been considered extensively for manned aircraft, the key physical parameters that determine ice accretion are vastly different in the robotic aircraft realm, where sizes and speeds are much smaller. The trajectories of droplets are moving in a significantly lower velocity, the wing is at a smaller scale, and the heat flux properties do not follow the assumptions in established icing models. The need for greater understanding of accretion physics at low speeds and low altitudes is obvious when considering the ways in which icing models for manned aircraft are unsuited for small unmanned aircraft systems (SUAS). In the various experimental and numerical investigations completed, this study has shed significant insight on SUAS icing. Flight tests and an atmospheric model were used to examine the impact of flight conditions. Experimental heat transfer results were used in conjunction with a numerical ice accretion algorithm developed to suit SUAS. The work done with collection efficiency and heat transfer advocate an accurate determination of the amount wet versus dry icing on each simulation. The results of the simulations show that in low velocities a low level of accretion is likely. Wet icing will only form at temperatures close to zero and relatively high liquid water contents. Even when wet icing is present notable horn shapes are unlikely. [Preview Abstract] |
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