Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session B09: Aerodynamics: Rotating Wing |
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Chair: Bo Cheng, Penn State University Room: 213 |
Saturday, November 23, 2019 4:40PM - 4:53PM |
B09.00001: Scaling arguments for the radial vorticity advection and the radial planetary vorticity tilting in the leading-edge vortex of revolving wings Nathaniel Werner, Junshi Wang, Haibo Dong, Bo Cheng Within the leading-edge vortex (LEV) of a revolving wing, planetary vorticity tilting (PVTr) can partly remove the radial vorticity generated by advection, a mechanism that relates the effects of Coriolis acceleration, spanwise flow, and the tilting of the planetary vorticity. It has been shown previously that the non-dimensional PVTr scales independently with Aspect Ratio (AR) while the advection scales inversely with AR, suggesting that separate scalings should be applied to these two terms. This study continues the previous investigation, with the goal of finding the correct scaling of the radial vorticity advection with the AR. The wing AR is changed by increasing the wing span and keeping the wing chord length constant; in this process we either keep the wing tip velocity constant (i.e., keeping the wing-chord-based Reynolds number constant) or keep the wing angular velocity constant constant (i.e., keeping the spanwise local Reynolds number constant). For both cases, we show that the correct length scale for the advection is wing span instead of wing chord (as for the PVTr), while both the advection and the PVTr have the tip velocity and planetary vorticity (or wing angular velocity) as the velocity and vorticity scales. [Preview Abstract] |
Saturday, November 23, 2019 4:53PM - 5:06PM |
B09.00002: Hover Predictions Using a High-Order Discontinuous Galerkin Off-Body Discretization Kursat Kara, Michael Brazell, Andrew Kirby, Earl Duque, Dimitri Mavriplis Hover performance of a four-bladed Sikorsky S-76 is studied using a high-order discontinuous Galerkin (DG) off-body discretization. Time accurate Navier-Stokes calculations are performed using the W$^{\mathrm{2}}$A$^{\mathrm{2}}$KE3D code which combines solution technologies in a multi-mesh, multi-solver paradigm through a dynamic overset framework which employs NSU3D as a near-body solver and dg4est as an off-body solver. The rotor with swept-tapered tip is simulated. The tip Mach number was 0.65, and the Reynolds number based on the reference chord was 1.2 million. A constant coning angle of 3.5\textdegree is applied. Effect of time step size and sub-iterations on the integrated parameters are investigated. Convergence results are presented. The figure of merit is calculated and compared with available data in the literature, and good agreement is found. [Preview Abstract] |
Saturday, November 23, 2019 5:06PM - 5:19PM |
B09.00003: Numerical simulation of a rotating blade using a flat-plate airfoil at low Reynolds numbers for Mars helicopter Daichi Ogasawara, Makoto Sato, Hideaki Sugawara, Yasutada Tanabe, Kotaro Sato To realize a high-performance rotor for a Mars helicopter, the aerodynamic performances and flow characteristics around a rotating blade using a flat-plate airfoil at low Reynolds numbers have been investigated. Numerical simulations have been conducted using a CFD solver of rFlow3D, which has been developed in JAXA for a rotorcraft simulation. The ambient pressures are set to 100 kPa, 50 kPa, 10 kPa, and 5 kPa, corresponding to the Reynolds numbers of 77000, 39000, 7700, and 3900 based on the blade tip velocity and the tip chord length respectively. The thrust and torque coefficients agree well with the previous experimental study for the cases with pitch angles up to 10 deg. The influences of the ambient pressure on the aerodynamic characteristics are not so significant in the cases with low pitch angles. On the other hand, the flow characteristics become highly different between the cases with the ambient pressure of 100 kPa and 5 kPa. For the 5 kPa case, the secondary vortex inside the leading-edge vortex is clearly recognized. In addition, the interaction of the tip vortices with the leading-edge vortices becomes significant, resulting in the reduction of the negative pressure region near the wing tip. [Preview Abstract] |
Saturday, November 23, 2019 5:19PM - 5:32PM |
B09.00004: Scaling effects on aerodynamic interactions of rotorcraft around boundaries Darius Carter, Megan Mazzatenta, Shijie Gao, Carmelo Di Franco, Nicola Bezzo, Daniel Quinn The growth of the Micro Aerial Vehicle (MAV) industry is outpacing our understanding of how MAVs behave in cluttered environments. Search and rescue and product delivery -- two key MAV applications -- occur in tight, confined spaces filled with complex obstacles. Our current understanding of how MAVs interact with boundaries is based primarily on helicopter models, which were designed for high Reynolds-number single-rotor flows. To support better flow models of MAV-boundary interactions, we will measure the lift forces and flow of small quadrotors near a side wall, ground, ceiling, and water surface. To see how our results scaled, we measured differently-sized propellers in these same conditions. Using Particle Image Velocimetry, we quantified the momentum flux of the rotors and evaluated the assumptions made by the existing ground and ceiling models. Better physical models offer a way to predict MAV's reaction to environmental disturbances, which is critical for certifying that MAVs can operate safely near or in cooperation with humans. Better models could offer physics-based situational awareness, which could reduce the need for heavy sensors and cameras and free up payload on small, lightweight MAVs. [Preview Abstract] |
Saturday, November 23, 2019 5:32PM - 5:45PM |
B09.00005: Propellers in Partial Ground Effect Jielong Cai, Sidaard Gunasekaran, Michael OL, Anwar Ahmed The classical result for propellers (or any rotating wing) operating parallel and in close proximity to an unbounded flat-plate, is increase in thrust and decrease in power-required, for a given rotation-rate. We examine “extreme” cases, where the ratio of ground-proximity to propeller-diameter is 0.1 or less. We also reverse the propeller direction, for a “ceiling effect”. The limiting case for small ground separation is halving of power-required. However, this depends strongly on the ratio of propeller pitch to diameter. For large ratios (approaching 1), ground-effect offers almost zero benefit. For small ratios (on the order of 0.5), best results are obtained. We also consider a finite ground-plane as a circular disk. For a ratio of disk diameter to propeller diameter of 0.5, ground-effect is nil, while for a ratio of 1, full ground-effect is restored. Flow visualization gives the explanation: there is a circular time-averaged dividing streamline on the ground-plate, within which the projection of the flow is swirling, but outside of which the flow is radial. For ground-plate-disks of diameter smaller than this dividing streamline, propeller thrust is measured to resemble that in free-air, while for larger disks there is a strong ground-effect. [Preview Abstract] |
Saturday, November 23, 2019 5:45PM - 5:58PM |
B09.00006: Investigating Effects of Cracked Blade under Various Rotor Speed on Aerodynamic Characteristics in 1.5 Stage GE-E3 Gas Turbine Thanh Dam Mai, Myung Gon Choi, Yumin Kim, Jaiyoung Ryu The variation in revolutions per minute (RPM) has significant effects on dynamic behaviors, the flow characteristics, and the heat transfer in gas turbine. Coupled with cracked blade conditions, it can be speculated to have more dramatic effects on the overall performance. This is the first study to address both RPM variation and cracked rotor blade condition in three-dimensional unsteady gas turbine simulation. Reynolds-averaged Navier-Stokes (RANS) equation is used with k- $\omega $ SST $\gamma $ turbulence closure model to solve high-speed, high-pressure compressible flow in GE-E3 gas turbine. Numerical cases are selected with RPMs of 4000, 3600, 3200, and 2800 under same cracked blade conditions. As a result, average temperature and heat flux on the blade surface are found to have inverse relations with RPM. Pressure overshoot occurs at greater RPM changes, but significant drop in average temperature and heat flux is observed at 4000 RPM. Moreover, it is also found that crack condition has significant effects on the aerodynamic behavior of compressed gas in high pressure gas turbine. [Preview Abstract] |
Saturday, November 23, 2019 5:58PM - 6:11PM |
B09.00007: An Experimental Investigation on Drone Propellers Operating Under Icing Conditions Zhe Ning, Yang Liu, Hongwei Ma, Hui Hu An experimental study was conducted to investigate the dynamic ice accretion process over the surfaces of typical drone propeller blades and to characterize the detrimental effects of ice accretion on the performance of the Drone propeller in terms of thrust generation and power consumption. The experimental study was conducted in the Icing Research Tunnel of Iowa State University (i.e., ISU-IRT) with a commonly-used, commercially-available Drone propeller exposed in frozen-cold incoming airflow under various icing conditions usually encountered by Drones in winters (i.e., under both rime and glaze icing conditions). In addition to revealing the transient ice accreting process over the surfaces of the rotating propeller blades by using a ``phase-locked'' imaging technique with a high-resolution imaging system, the dynamic thrust force generated by the Drone propeller was also measured simultaneously along with the required power inputs to drive the Drone propeller during the dynamic ice accreting process. The time-resolved aerodynamic force measurements and power consumption data were correlated with the acquired snapshots of the instantaneous ice accretion images to gain further insight into the underlying icing physics pertinent to Drone icing phenomena. . -/abstract- Zhe Ning, NianHong Han, Hongwei Ma, Hui Hu 1The research work is supported by National Science Foundation under award numbers of OISE1826978, CBET-\textbf{ 1916380~} and CMMI-18248400 and Iowa Energy Center of the Sta [Preview Abstract] |
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