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55th AIAA Aerospace Sciences Meeting

作者： Fidkowski, Krzysztof J. Department of Aerospace Engineering University of Michigan Ann ArborMI48109 United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

We present a method for estimating spatial and temporal numerical errors in scalar outputs of unsteady fluid dynamics simulations using a continuous-in-time adjoint solution and general time-integration methods. A continuous formulation decouples the primal and adjoint temporal discretizations and allows the use of standard time-integration schemes for the adjoint. For non-variational methods, a scheme-agnostic temporal reconstruction of the primal and adjoint solutions replaces the functional representation in between time nodes. Finally, projection of the adjoint to a semi-refined space yields separate measures of the errors in space and time, which then drive adaptive refinement of the spatial and temporal discretizations. Results for the Euler equations and the compressible Navier-Stokes equations demonstrate accuracy of the error estimates and effectiveness of the adaptation. © 2017 by Krzysztof Fidkowski.

关键词： Navier Stokes Equations Euler Equations Unsteady fluid dynamics Vortices Finite Element Method Free Stream Conservation of Energy NACA 0012 computational fluid dynamics simulation Roe Approximate Riemann Solver

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Deployable Mechanism Design for Span Morphing Wing Aircraft 4th

Deployable Mechanism Design for Span Morphing Wing Aircraft

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4th IFToMM Asian Conference on Mechanism and Machine Science (IFToMM Asian MMS) / International Conference on Mechanism and Machine Science (CCMMS)

作者： Gao, Binbin Kang, Rongjie Chen, Yan Tianjin Univ Minist Educ Key Lab Mech Theory & Equipment Design Tianjin 300072 Peoples R China Tianjin Univ Sch Mech Engn Tianjin 300072 Peoples R China

ISBN: (纸本)9789811028755;9789811028748

Compared with traditional aircrafts, span morphing wing aircrafts can change their span according to different flight conditions and missions to improve flight performances. Also, it has advantages in storage and transportation. In this paper, a single-degree-of-freedom (SDOF) mechanism based on Sarrus linkages is presented and applied to the construction of a span morphing wing aircraft. computational fluid dynamics (CFD) simulation shows that the deployable mechanism generates slight influence on the drag coefficient while having a relatively strong influence on the lift coefficient and lift to drag ratio. Finite Element Model (FEM) methods are used to analyze the mechanical properties of the mechanism during flight. The results indicate that the maximum stress 45.5 Mpa occurs at the link connected to the base link. A series of flight experiments were conducted to prove that the mechanism enables the span change smoothly and improves the flight performances effectively.

关键词： Span morphing wing aircraft Deployable mechanism computational fluid dynamics simulation Finite element model

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Inert state of fuel tank during aircraft ascent 55

Inert state of fuel tank during aircraft ascent

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55th AIAA Aerospace Sciences Meeting

作者： Frank, Michael Drikakis, Dimitris University of Strathclyde GlasgowG1 1XW United Kingdom Faculty of Engineering University of Strathclyde GlasgowG1 1XW United Kingdom

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

Using computational fluid dynamics simulations, we investigate whether the oxygen concentration in the ullage of an aircraft’s fuel tank increases during ascent, subsequently increasing the risk of ignition. The problem was studied for two sets of initial conditions: a non-inert ullage (air with mass fractions 23 wt% oxygen and 77 wt% nitrogen) and an inert ullage (air with mass fractions 14 wt% oxygen and 86 wt% nitrogen). Our results show that as the pressure of the tank decreases with altitude, oxygen and nitrogen initially dissolved in the fuel are released into the fuel tank’s ullage. However, the ratio of oxygen and nitrogen in the released gases is constant throughout the aircraft’s ascent. In turn, only a minor increase in the average oxygen concentration is observed inside the ullage. Despite this small increase in the average concentration, our results show localized oxygen spikes, “hot-spots”, next to the pressure valve of the initially inerted ullage. We attribute this to atmospheric air occasionally flowing into the fuel tank. Since atmospheric air has a higher percentage of oxygen than the air in an inert ullage, it momentarily increases the ullage’s oxygen concentration. However, we believe that this is a result of the fuel bay being modelled in direct contact with the atmosphere and will not occur on a real aircraft. © 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Commercial Aircraft Fuels computational fluid dynamics simulation Henry's Law Federal Aviation Administration Aircraft Altitude Specific Enthalpy Fighter Aircraft

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Tomographic PIV measurement in a bluff body wake utilizing an asymmetric camera configuration and least squares matching 55

Tomographic PIV measurement in a bluff body wake utilizing a...

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55th AIAA Aerospace Sciences Meeting

作者： Fleischhauer, Eric Dahlberg, Jerry L. Bisel, Tucker T. Tkacik, Peter T. Heilman, Samuel University of North Carolina at Charlotte Mechanical Engineering Department CharlotteNC28262 United States University of North Carolina at Charlotte Dantec Dynamics Inc CharlotteNC28262 United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

Tomographic PIV (TomoPIV) measurements are carried out in the wake region of a surface-mounted bluff body utilizing an asymmetric camera configuration. This asymmetric method allows for an unobstructed view and an in-depth assessment of the wake region to more accurately visualize and characterize the flow structures and dynamics. The volumetric flow visualization is accomplished via synchronized multiartifact reduction with tomographic (SMART) reconstruction of voxel spaces from the planar camera inputs and a 3D Least Squares Matching (LSM) algorithm is used to calculate velocity vector fields. The flow in the turbulent wake region behind the bluff body directly effects the loading and pressures, both steady and unsteady, that act on the body. Identifying flow structures in the wake region is key to better understanding the physics of the flow conditions around bluff bodies. The asymmetric TomoPIV configuration provides a complete three dimensional, three component (3D-3C) view of the instantaneous velocity fields downstream of a wall-mounted cube and facilitates a more thorough measurement of flow-structure interactions. © 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Particle Image Velocimetry Free Stream Velocity Reynolds Averaged Navier Stokes Flow Conditions computational fluid dynamics simulation Vortices Matching Algorithm Static Pressure Wind Tunnels

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CFD-based model building of the F-16XL static and dynamic loads using kestrel 55

CFD-based model building of the F-16XL static and dynamic lo...

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55th AIAA Aerospace Sciences Meeting

作者： Morton, Scott A. McDaniel, David R. Eglin AFB FL32542 United States University of Alabama Birmingham United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

This paper documents progress towards a production-quality reduced-order modeling capability in the HPCMP CREATETM-AV Kestrel product. Models of the center-of-gravity aerodynamic loads are generated from the dynamic CFD solution of a training maneuver applied to the F-16XL high-performance aircraft, and used to build an unsteady bounds model of the F16XL. A representative off-design dynamic flight maneuver is simulated, and center-of-gravity aerodynamic loads are compared with those predicted by the reduced-order model. Finally, static center-of-gravity loads are predicted by the system identification models and compared to CFD-generated static loads data. Key conclusions and lessons-learned are discussed. © 2017, American Institute of Aeronautics and Astronautics Inc. All rights reserved.

关键词： Aerodynamic Coefficients System Identification Lift Coefficient Angle of Sideslip Pressure Coefficient Flight Testing High Performance Aircraft computational fluid dynamics simulation fluid Structure Interaction Control Surfaces

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Development and application of an energy balance analysis for combustion 55

Development and application of an energy balance analysis fo...

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55th AIAA Aerospace Sciences Meeting

作者： Pons, Arnau Sardeshmukh, Swanand V. Huang, Cheng Anderson, William E. Purdue University School of Aeronautics and Astronautics Purdue University West LafayetteIN47907 United States

ISBN: (数字)9781624104473

ISBN: (纸本)9781624104473

The energy balance analysis of combustion is essential for assessing the effects and coupling that drive the stability of combustors. This work presents a generalized analysis methodology to enhance the comprehension of combustion processes by means of computing the energy balance and integrating the fluctuating energy in the combustion zone. Three study cases related to practical combustors extensively analyzed at Purdue University are provided to discuss the capabilities of the approach. The methodology provided fundamental understanding of the combustion processes which have proved very useful in the analysis of more complex practical combustors. © 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Combustion Instability Combustors Computing computational fluid dynamics simulation Thermal Conduction Kinetic Energy Combustion Chambers Propulsion and Power Vortex Shedding Heat Transfer

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Investigation of flow characteristics in regions of nasal polypoid change

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COMPUTERS IN BIOLOGY AND MEDICINE 2016年 70卷 148-156页

作者： Chung, Seung-Kyu Jo, Gyehwan Na, Yang Sungkyunkwan Univ Sch Med Samsung Med Ctr Dept Otorhinolaryngol Head & Neck Surg Seoul South Korea Konkuk Univ Dept Mech Engn Seoul 143701 South Korea

We used computational fluid dynamics to study the airflow characteristics in the ostiomeatal complex/middle turbinate of the human upper airway, where clinically relevant nasal polypoid changes occur (designated Regions A1-A4). We assessed six different flow rates representing one full period of respiration, based on realistic human respiration data, in an anatomically correct numerical model of a patient with a history of polypectomy. The simulation results showed that Regions A1-A4 were not correlated with the local stagnation points where a locally high level of wall pressure was achieved. They, however, exhibited a very distinctive feature in that the positive wall-normal pressure gradients evaluated at the epithelial surface were persistent at six different flow rates spanning the whole respiration period in these areas. Therefore, the regions where polypoid changes developed were thought to be subject to mechanical irritation of the epithelium constantly via locally accelerating airflow moving towards the surface from the airway. On the contrary, relatively large or small values for local wall shear stress were not correlated with Regions A1-A4. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Ostiomeatal complex/middle turbinate computational fluid dynamics simulation Wall pressure Pressure gradient Wall shear stress

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Study and optimization of the filtration performance of multi-fiber filter

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ADVANCED POWDER TECHNOLOGY 2016年第2期27卷 638-645页

作者： Li, Wei Shen, Shengnan Li, Hui Wuhan Univ Sch Power & Mech Engn 8 East Lake South Rd Wuhan 430072 Peoples R China

Fibrous media is the most common method of filtration, which is generally characterized by its pressure drop and filtration efficiency. In this work, the computational fluid dynamics (CFD) technology was applied to simulate the filtration performance of multi-fiber filters. The pressure drop and filtration efficiency with different fiber arrangements, fiber diameters, face velocities and particle sizes were studied. It was found that filtration efficiency changed with the face velocity for different particle sizes. The layered structures with the same fiber diameters and total solid volume fraction (SVF) were compared, indicating that the dense-sparse structure had the highest filtration efficiency for all the simulated particle sizes at the cost of high pressure drop. Then the dense-sparse structure was optimized to achieve a better filtration performance by using less tiny fibers in the front-row and removing some fibers in the back-row. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

关键词： Multi-fiber filters Filtration performance Optimization computational fluid dynamics simulation

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Unsteady Reynolds-Averaged Navier-Stokes simulation of Crossflow Rotors, Scaling, and Blockage Effects

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AIAA JOURNAL 2016年第12期54卷 3828-3839页

作者： Lohry, Mark W. Martinelli, Luigi Princeton Univ Dept Mech & Aerosp Engn Princeton NJ 08544 USA

This work presents results and analysis of H-type crossflow rotors using unsteady Reynolds-Averaged Navier-Stokes (URANS) computational fluid dynamics simulations. It is demonstrated that, with an efficient solver, robust high-fidelity time-resolved solutions can be obtained with computational speed and cost that allow the use of high-fidelity computational fluid dynamics in the early stages of a new design. The sensitivity of power prediction on the far-field boundary condition proximity is also shown and an analytical justification is given for this behavior based on blockage effects. The effects of physical scaling over a range of Reynolds numbers between 105 and 108 of four geometrically similar turbines of differing solidity are studied. Significant improvement in power efficiency can be achieved as the Reynolds number increases when turbines are scaled to very large size. Power curves for all test cases, unsteady blade loads for select cases, and effects of three-dimensionality are provided to aid future work.

关键词： Reynolds Averaged Navier Stokes Aerodynamic Force Coefficients computational fluid dynamics simulation Vertical Axis Wind Turbines High Aspect Ratio Two Dimensional Flow Lift Coefficient Electricity Generation Particle Image Velocimetry Wind Tunnel Tests

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The corrosion of X52 steel at an elbow of loop system based on array electrode technology

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MATERIALS CHEMISTRY AND PHYSICS 2016年 181卷 312-320页

作者： Huang, Hualiang Tian, Jing Zhang, Guoan Pan, Zhiquan Wuhan Inst Technol Sch Chem & Environm Engn Hubei Novel Reactor & Green Chem Technol Key Lab Key Lab Green Chem ProcMinist Educ Wuhan 430073 Peoples R China Huazhong Univ Sci & Technol Sch Chem & Chem Engn Hubei Key Lab Mat Chem & Serv Failure Wuhan 430074 Peoples R China

The corrosion behavior and mechanism of X52 steel at an elbow of loop system based on array electrode technology were investigated to determine the correlation between the corrosion behavior and flow velocity, shear stress and the volume fraction of particles by electrochemical techniques, computational fluid dynamics simulation and surface analysis. The results show that the distribution of corrosion rate is in good accordance with the distribution of the volume fraction of CaSO4 particles at the elbow, and the higher corrosion rate corresponds to the bigger volume fraction of CaSO4 particles. The minimum corrosion rate appears at the innermost side of the elbow, the location with the minimum volume fraction of CaSO4 particles. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Steel EIS Polarization computational fluid dynamics simulation

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