Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session MX: Industrial Applications I |
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Chair: Andrey Filippov, Corning Inc. Room: Hyatt Regency Long Beach Regency D |
Tuesday, November 23, 2010 8:00AM - 8:13AM |
MX.00001: Aerodynamic stability of blunted-cone heat shields for atmospheric entry vehicles John Sader, Eleanor Button, Daniel Ladiges, Charles Lilley, Nicholas Mackenzie, Edward Ross Spacecraft entry into the atmosphere of a planet requires protection against the extreme temperatures that result from aerodynamic heating. This is normally achieved through use of a heat shield, which also provides the necessary aerodynamic braking and stability. The shape of the heat shield used varies considerably between spacecraft, and spherical and blunted-cone geometries are often employed. The ``blunted-cone'' heat shield has been developed through experimental design and computational simulation. Here, we demonstrate that this generic shape can be derived mathematically and yields the \textit{maximum stabilizing aerodynamic torque} of all possible shapes. The derived single shape is universal, depending only on the center-of-mass, and provides invariance in static stability due to minor heat shield damage. Importantly, the design of practical heat shields involves numerous competing factors, which include the expected heat load and the craft volumetric efficiency, in addition to aerodynamic stability. We thus emphasize that the presented results focus on only one component of this multi-objective problem. Nonetheless, the derived shape shows good agreement with the heat shields of previous entry vehicles, a comparison of which shall be given. [Preview Abstract] |
Tuesday, November 23, 2010 8:13AM - 8:26AM |
MX.00002: An Experimental Investigation of Compressible Dynamic Stall on a 2-D Airfoil Subjected to Non-Harmonic Pitching Motion Dustin Coleman, Flint Thomas, Thomas Corke, Patrick Bowles, Katie Thorne An experimental study of dynamic stall was conducted on a 2-D airfoil operating at Reynolds number up to 2x10$^6$ and over a Mach number range of 0.2 - 0.4. The primary pitching frequency was 6.58 Hz producing reduced frequencies ranging from 0.035 - 0.075. The facility was constructed to allow a second pitching frequency to be mechanically added to the primary mode of the airfoil providing both harmonic and non-harmonic disturbances to the pitch motion in order to simulate aerodynamic conditions where stall flutter may occur. Static pressure data was acquired using 30 surface mounted dynamic pressure transducers simultaneously sampled at a rate of 5 kHz. Instantaneous pressure time series and resultant forces were analyzed to elucidate the consequent fluid interactions. Preliminary results indicate that the higher frequency input provides a mechanism for increased aerodynamic stability throughout the dynamic stall cycle. [Preview Abstract] |
Tuesday, November 23, 2010 8:26AM - 8:39AM |
MX.00003: Compressibility effects on dynamic stall attributes Patrick Bowles, Thomas Corke, Flint Thomas, Katie Thorne, Dustin Coleman An experimental study of the compressibility effects on the load, stability, and separation characteristics of a modern rotor-blade geometry is presented under dynamic stall conditions. The airfoil was oscillated in pitch about the quarter chord at free-stream Mach numbers from 0.2 to 0.55, reduced frequencies from 0.025 to 0.10, and Reynolds numbers up to 3.5 million - all values relevant to a helicopter retreating or advancing blade. Thirty high frequency absolute pressure transducers measured the airfoil's static pressure distribution. Emphasis was placed on the development of the leading edge vortex. Increased free stream Mach numbers resulted in a reduced ability of the near leading edge flow to overcome the adverse pressure gradient on the airfoil's suction side, limiting dynamic load overshoot as well as negative damping. Indeed, light dynamic stall conditions showed a greater aptitude to toward unstable motion. At free-stream Mach numbers greater than 0.4, airfoil local Mach numbers consistently neared 1.6 prior to an abrupt flow separation, considered to be the result of shock induced boundary layer interactions. [Preview Abstract] |
Tuesday, November 23, 2010 8:39AM - 8:52AM |
MX.00004: Linear Stability Analysis on Multiple Solutions of Steady Transonic Small Disturbance Equation Ya Liu, Feng Liu, Shijun Luo Multiple solutions of the steady Transonic Small Disturbance (TSD) potential equation occur within a narrow range of freestream Mach number. Three numerical solutions for the NACA $0012$ airfoil at freestream Mach number $0.85$ and zero angle of attack are computed using the conservative Murman-Cole scheme. One solution is symmetric and the other two are asymmetric and mirror-images of each other. The linear stability of the numerical solutions are analyzed by an eigenvalue technique. The Jacobi matrix is constructed from the discrete steady TSD equation and evaluated with the converged numerical solution. The maximum real part of the eigenvalues for the symmetric solution is positive ($0.7 \times 10^{-2}$) and that for the asymmetric solution is negative ($-0.8 \times 10^{-2}$) indicating that the symmetric solution is unstable and the two asymmetric solutions are stable under small perturbations. These stability conclusions are verified by numerical computations. [Preview Abstract] |
Tuesday, November 23, 2010 8:52AM - 9:05AM |
MX.00005: Numerical flow simulation of a reusable sounding rocket during nose-up rotation Kazuto Kuzuu, Keiichi Kitamura, Keiichiro Fujimoto, Eiji Shima Flow around a reusable sounding rocket during nose-up rotation is simulated using unstructured compressible CFD code. While a reusable sounding rocket is expected to reduce the cost of the flight management, it is demanded that this rocket has good performance for wide range of flight conditions from vertical take-off to vertical landing. A rotating body, which corresponds to a vehicle's motion just before vertical landing, is one of flight environments that largely affect its aerodynamic design. Unlike landing of the space shuttle, this vehicle must rotate from gliding position to vertical landing position in nose-up direction. During this rotation, the vehicle generates massive separations in the wake. As a result, induced flow becomes unsteady and could have influence on aerodynamic characteristics of the vehicle. In this study, we focus on the analysis of such dynamic characteristics of the rotating vehicle. An employed numerical code is based on a cell-centered finite volume compressible flow solver applied to a moving grid system. The moving grid is introduced for the analysis of rotating motion. Furthermore, in order to estimate an unsteady turbulence, we employed DDES method as a turbulence model. In this simulation, flight velocity is subsonic. Through this simulation, we discuss the effect on aerodynamic characteristics of a vehicle's shape and motion. [Preview Abstract] |
Tuesday, November 23, 2010 9:05AM - 9:18AM |
MX.00006: Qualitative CFD for Rapid Learning in Industrial and Academic Applications Evan Variano We present a set of tools that allow CFD to be used at an early stage in the design process. Users can rapidly explore the qualitative aspects of fluid flow using real-time simulations that react immediately to design changes. This can guide the design process by fostering an intuitive understanding of fluid dynamics at the prototyping stage. We use an extremely stable Navier-Stokes solver that is available commercially (and free to academic users) plus a custom user interface. The code is designed for the animation and gaming industry, and we exploit the powerful graphical display capabilities to develop a unique human-machine interface. This interface allows the user to efficiently explore the flow in 3D + real time, fostering an intuitive understanding of steady and unsteady flow patterns. There are obvious extensions to use in an academic setting. The trade-offs between accuracy and speed will be discussed in the context of CFD's role in design and education. [Preview Abstract] |
Tuesday, November 23, 2010 9:18AM - 9:31AM |
MX.00007: Characterization of Synthetic GTL Jet Fuel for use in Gas Turbine Engines Reza Sadr, Kumaran Kannaiyan Stringent emission regulations have instigated the search for alternative-clean source of energy. Recently, Gas-to-Liquid (GTL) fuel has grabbed the global attention by its clean combustion characteristics owing to the absence of aromatics and Sulphur. However, this will introduce potential risks and benefits. Last fall Qatar airways has proven the feasibility of using GTL as a potential alternative clean fuel by a 3200 mile flight using a fuel blend of 50{\%} JetA + 50{\%} GTL. Researchers from Texas A {\&} M University at Qatar (TAMUQ) in collaboration with their counterparts in Rolls-Royce (RR), UK, and German Aerospace Laboratory (DLR) are in a joint effort to establish an in-depth characterization of the combustion performance of GTL fuel in gas turbine engines. In TAMUQ, the research focus is to investigate the spray characteristics of GTL fuels. The results will be compared with that of standard fuel and correlate with combustion results to gain insights on GTL performance. This will help designers to optimize the nozzle geometry to improve the combustor performance. The objective of this talk is to introduce this ongoing effort and to discuss the experimental facility and preliminary results. [Preview Abstract] |
Tuesday, November 23, 2010 9:31AM - 9:44AM |
MX.00008: Coaxial twin-fluid atomization with pattern air gas streams Chin Hei Ng, Alberto Aliseda Coaxial twin-fluid atomization has numerous industrial applications, most notably fuel injection and spray coating. In the coating process of pharmaceutical tablets, the coaxial atomizing air stream is accompanied by two diametrically opposed side jets that impinge on the liquid/gas coaxial jets at an angle to produce an elliptical shape of the spray's cross section. Our study focuses on the influence of these side jets on the break up process and on the droplet velocity and diameter distribution along the cross section. The ultimate goal is to predict the size distribution and volume flux per unit area in the spray. With this predictive model, an optimal atomizing air/pattern air ratio can be found to achieve the desired coating result. This model is also crucial in scaling up the laboratory setup to production level. We have performed experiments with different atomized liquids, such as water and glycerine-water mixtures, that allow us to establish the effect of liquid viscosity, through the Ohnesorge number, in the spray characteristics. The gas Reynolds number of our experiments ranges from 9000 to 18000 and the Weber number ranges from 400 to 1600. We will present the effect of pattern air in terms of the resulting droplets size, droplet number density and velocity at various distances downstream of the nozzle where the effect of pattern air is significant. [Preview Abstract] |
Tuesday, November 23, 2010 9:44AM - 9:57AM |
MX.00009: Large eddy simulation on a pulverized coal combustion furnace with a complex swirl burner Hiroaki Watanabe, Kenji Tanno, Ryoichi Kurose, Satoru Komori Large-eddy simulation (LES) is applied to a pulverized coal combustion field in a combustion test furnace with a complex swirl burner called the advanced low NOx burner CI-alpha, and its validity is investigated by comparing with the experiment. The motion of coal particles is calculated by the Lagrangian method with a parcel model. In the coal combustion modeling, three chemical processes are considered, namely devolatilization, char combustion and gaseous reactions. The direct closure SSFRRM (scale similarity filtered reaction rate model) is employed as a turbulent combustion model. The results shows that a swirling recirculation flow is formed in a central region close to the burner and its size and strength dynamically change with time. The predicted distributions of time-averaged and variance of particle velocity and time-averaged gaseous temperature, oxygen and NO concentrations are in general agreement with the experiment. [Preview Abstract] |
Tuesday, November 23, 2010 9:57AM - 10:10AM |
MX.00010: Hydrophobic coating study for anti-icing aircraft Katsuaki Morita, Akihito Aoki, Akihisa Konno, Hirotaka Sakaue Anti-icing or deicing of an aircraft is necessary for a safe flight operation. Mechanical processes, such as heating and deicer boot, are widely used. Deicing fluids, such as ethylene glycol type, are used to coat the aircraft. However, these should be coated every time before the take-off, since the fluids come off from the aircraft while cruising. We study a hydrophobic coating as a anti-icing for an aircraft. It is designed to coat the aircraft without removal. Since a hydrophobic coating prevents water by reducing the surface energy, it would be another way to prevent ice on the aircraft. We provide a temperature-controlled room, which can control its temperature at an icing condition (-10 to 0 degrees C). The contact angle is tested for various hydrophobic coatings. A water jet impingement on a hydrophobic-coated plate is included. The jet freezes under the icing condition. Qualitative comparison among various hydrophobic coatings as anti-icing is discussed. [Preview Abstract] |
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