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Rapid Transonic Flutter Analysis for Aircraft Conceptual Design Applications

AIAA JOURNAL 2018年第6期56卷 2389-2402页

作者： Mallik, Wrik Schetz, Joseph A. Kapania, Rakesh K. Virginia Polytech Inst & State Univ Dept Aerosp & Ocean Engn Blacksburg VA 24061 USA Technion Israel Inst Technol Dept Aerosp Engn IL-3200003 Haifa Israel

This study presents a new approach for the rapid transonic flutter analysis of large-aspect-ratio wings via a combination of time-linearized two-dimensional unsteady indicial functions and a database of steady two-dimensional Reynolds-averaged Navier-Stokes simulations. The approach is limited to large-aspect-ratio wings that can be discretized into multiple, streamwise, independent strips;and the well-documented "strip theory" with sweep corrections is applicable. This formulation allows the extension of Leishman's indicial functions ("Validation of Approximate Indicial Aerodynamic Functions for Two-Dimensional Subsonic Flow," Journal of Aircraft, Vol.25, No.10, 1988, pp.914-922) to three-dimensional wings but also restricts the present method to attached flows. However, when supported with two-dimensional steady Reynolds-averaged Navier-Stokes simulations, the present method predicts flutter speeds that are within 10% of that predicted by two-dimensional time-accurate Reynolds-averaged Navier-Stokes simulations. Application of the proposed method for a large-aspect-ratio wing is validated by comparing the predicted flutter boundary against wind-tunnel experiments. More importantly, the current method predicts the transonic dip phenomena observed in the experiments but not predicted by NASTRAN analysis. This is achieved at several orders-of-magnitude lower computation time than high-fidelity time-accurate computational fluid dynamics simulations. The level of accuracy obtained at such an extremely low computation time makes the present approach very suitable for applications in conceptual design studies of large-aspect-ratio transonic vehicles.

关键词： Flutter Analysis Aircraft Conceptual Design Reynolds Averaged Navier Stokes computational fluid dynamics simulation High Aspect Ratio Incompressible Flow Wind Tunnel Models Nastran Prandtl Glauert Transformation Lift Coefficient

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Numerical Investigation on Radiative Heat Loads in Liquid Rocket Thrust Chambers

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JOURNAL OF PROPULSION AND POWER 2019年第5期35卷 930-943页

作者： Leccese, Giuseppe Bianchi, Daniele Nasuti, Francesco Univ Roma La Sapienza Dipartimento Ingn Meccan & Aerosp Via Eudossiana 18 I-00184 Rome Italy Italian Space Agcy Sci Res Unit Via Politecn Snc I-00133 Rome Italy

In liquid rocket engines, wall heat transfer analyses are of primary importance for the thrust chamber design. Numerical investigations usually derive the convective heat flux from computational fluid dynamics simulations, whereas the radiative counterpart is often neglected. The goal of the present paper is a systematic numerical investigation on the role of radiative heat transfer on the overall thermal loads occurring in the thrust chamber of liquid rocket engines. To this purpose, a numerical code for thermal radiation computations is coupled to a computational fluid dynamics solver. The results of the numerical setup are discussed and compared to the available literature's numerical data. Then, the radiative contribution to the overall heat flux in the thrust chamber of oxygen/hydrogen and oxygen/methane liquid rocket engines is investigated through a wide parametric analysis. The results show that, in typical operating conditions, the radiative heat load is proportionally greater in methane-fueled engines than in hydrogen-fueled engines, and that the radiative contribution to the overall wall heat flux becomes increasingly relevant for large-scale low-chamber-pressure engines. A methodology for a quick preliminary evaluation of the radiative wall heat flux in liquid rocket thrust chambers is finally presented and verified against coupled simulations.

关键词： Roe Approximate Riemann Solver Rocket Thrust Chamber Radiative Heating Heat Flux Chamber Pressure computational fluid dynamics simulation Convective Heat Transfer Coefficient Thermal Radiation Model Hydrogen Fuels Liquid Rocket Engine

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Experimental Research on Electrochemical Machining of an Arc-Shaped Slot Array

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INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE 2018年第10期13卷 9466-9480页

作者： Wang, Feng Zhao, Jianshe Liu, Dingming Fan, Yantao Tian, Zongjun Nanjing Univ Aeronaut & Astronaut Coll Mech & Elect Engn Nanjing 210016 Jiangsu Peoples R China

Slot array structure is widely used in the aerospace industry, precision molds, instrumentation and other fields. Electrochemical machining has a unique advantage in the fabrication of slot arrays. However, there are still problems for electrochemical machining slot arrays with complex shapes, such as poor stability, low forming accuracy and difficult processing. To improve the processing ability of arc-shaped slot arrays, the influence of electrolyte flow pattern and pressure on flow field stability in a closed channel was studied with a computational fluid dynamics simulation, and the flow pattern and pressure parameters were optimized. Moreover, comparative experiments of continuous-feed electrochemical machining mode and low-frequency oscillation assisted electrochemical machining mode were carried out based on a self-developed oscillation apparatus. The influence of auxiliary oscillation motion on the processing stability frequency, average slot width, and slot slope was analyzed, and an arc-shaped slot array with a slot width of 0.244 +/- 0.01 mm and high accuracy in shape and dimension was fabricated on a rotary workpiece.

关键词： Arc-shaped slot array Electrochemical machining Low-frequency oscillation Reverse flow computational fluid dynamics simulation

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Calculation of Reaction Force For the Gas-Blast Type Circuit breaker 2

Calculation of Reaction Force For the Gas-Blast Type Circuit...

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2nd IEEE Conference on Energy Internet and Energy System Integration (EI2)

作者： Wang, Zhijun Zhang, Hao Liu, Yapei Zhang, Bo Hao, Xiangyu State Grid Corp China Pinggao Grp Co Ltd Pingdingshan City Peoples R China

ISBN: (纸本)9781538685495

In order to explore the calculation method of the arc chamber gas reaction force and provide support for the design of the high-voltage circuit breaker mechanical transmission system, four calculation formulas of the reaction force micro-element under the four gas-solid interface conditions were derived, a test calculation case was designed and the effectiveness of the calculation method was verified. The no-arc simulation calculation model of the 252kV SF6 arc chamber was established, and the pressure distribution and the gas reaction force were obtained, the simulation results showed that: with the piston moving, the pressure inside the compression chamber increased first and then decreased, the max pressure of 1.86 MPa occurred at 0.029s;similarly, the reaction force changed with the same trend, the max reaction force of 1.95x104N occurred at 0.03s, which showed that under no-arc condition, the pressure load of the compressor chamber dominates the reaction force for arc chamber.

关键词： computational fluid dynamics simulation Reaction Force High Voltage Circuit Breaker Arc Chamber

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A Test of Possibility on Relative Humidity Function in Minor Operation Theatre

A Test of Possibility on Relative Humidity Function in Minor...

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International Conference on Advanced Manufacturing and Industry Applications (ICAMIA)

作者： Rahman, M. N. Y. Razlan, Z. M. Izham, M. Omar, M. I. Zambri, N. A. A. Shahriman, A. B. Zunaidi, I. Wan, W. K. Univ Malaysia Perlis Sch Mechatron Engn Pauh Putra Campus Arau 02600 Perlis Malaysia

High humidity air flow in Minor Operation Theatre (MOT) is undesired as it will cause discomfort to the occupant. Acceptable humidity air flow is important as it will affect the pureness of the indoor environment as well. The objective of this research work is to construct a realistic computational fluid dynamics (CFD) model of MOT for investigation. The MOT which is occupied with one unit of Air Conditioner has been selected for this study. The RH of air is analysed. The experimental data is collected by applying a digital air flow anemometer with USB interface and the channels digital handheld temperature thermometer meter data loggers for validation purpose. CFD simulation is conducted by applying ANSYS Fluent software. The experimental result and simulation is compared and validated. Based on the simulation and experiment findings, it reveals that ANSYS Fluent can be used for RH in MOT.

关键词： computational fluid dynamics simulation Minor Operation Theater Relative Humidity

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Influence of Blade Deformations on Open-Rotor Low-Speed and High-Speed Aerodynamics and Aeroacoustics 23

Influence of Blade Deformations on Open-Rotor Low-Speed and ...

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23rd AIAA/CEAS Aeroacoustics Conference

作者： Falissard, F. Boisard, R. Gaveriaux, R. Delattre, G. Gardarein, P. Chelius, A. Canard-Caruana, S. Mauffrey, Y. ONERA French Aerosp Lab Aerodynam Aerolast & Acoust Dept F-92190 Meudon France ONERA French Aerosp Lab Aerodynam Aerolast & Acoust Dept F-92322 Chatillon France

ISBN: (数字)9781624105043

ISBN: (纸本)9781624105043

This paper investigates by means of computational fluid dynamics (CFD) and acoustic analogy the influence of blade deformations on open-rotor aerodynamics and aeroacoustics for three key operating points: cruise, takeoff, and approach conditions. For each operating point, simulation results obtained with unrunning blade shapes and running blade shapes are compared with wind tunnel test measurements. Experiments show that blade deformations affect mostly the front rotor, with twist deviations at tip varying within a range of +/- 2 deg and of opposite sign between cruise and takeoff conditions. Although blade deformations are low for the rear rotor, aerodynamic performance exhibits significant variations due to the modifications of the front rotor wash. Numerical results show that accounting for blade deformations increases or decreases the thrust or power depending on the operating point and leads to a much better prediction of the open-rotor aerodynamic performance. The same comments apply for the noise prediction although differences on self-noise and interaction noise directivities are rather low.

关键词： Blade Passing Frequency Overall Sound Pressure Level Power Coefficient computational fluid dynamics simulation Transonic Wind Tunnel Reynolds Averaged Navier Stokes Airbus Fixed Wing Aircraft Flow Separation Power Spectral Density

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computational fluid dynamics simulation of formaldehyde emission characteristics and its experimental validation in environment chamber

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Journal of Chongqing University 2010年第3期9卷 124-132页

作者：刘志坚 School of Environmental and Municipal Engineering Xi'an University of Architecture and Technology

We investigated the effect of supply air rate and temperature on formaldehyde emission characteristics in an environment chamber.A three-dimensional computational fluid dynamics(CFD) chamber model for simulating formaldehyde emission in twelve different cases was developed for obtaining formaldehyde concentration by the area-weighted average *** experiments were conducted in an environment chamber to validate the simulation results of twelve different cases and the formaldehyde concentration was measured by continuous *** results show that there was good agreement between the model prediction and the experimental values within 4.3 difference for each *** CFD simulation results varied in the range from 0.21 mg/m3 to 0.94 mg/m3,and the measuring results in the range from 0.17 mg/m3 to 0.87 mg/*** variation trend of formaldehyde concentration with supply air rate and temperature variation for CFD simulation and experiment measuring was *** the existence of steady formaldehyde emission sources,formaldehyde concentration generally increased with the increase of temperature,and it decreased with the increase of air supply *** also provided some reasonable suggestions to reduce formaldehyde concentration and to improve indoor air quality for newly decorated rooms.

关键词： formaldehyde concentration environment chamber computational fluid dynamics simulation supply air rate temperature

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Ballistic Wave from Projectiles and Vehicles of Simple Geometry

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AIAA JOURNAL 2018年第7期56卷 2725-2742页

作者： Varnier, Jean Le Pape, Marie-Claire Sourgen, Frederic Off Natl Etud & Rech Aerosp Dept DAAC Aeroacoust F-92320 Chatillon France Off Natl Etud & Rech Aerosp Dept DMFN Fluid Mech F-92320 Chatillon France Off Natl Etud & Rech Aerosp Dept DMAE Aerothermodynam F-31400 Toulouse France

The ballistic wave is a shock wave generated by a solid body moving at supersonic speed in the atmosphere. It sounds like the crack of a whip for small projectiles and like a detonation (sonic boom) for large-sized objects. Their common signature is a N-shaped pressure profile, the formalism of which is well known but presents a practical difficulty, namely, the calculation of the shape factor, which characterizes the aerodynamic behavior of the object flying at supersonic speed. In the present Paper, we present that calculation for simple geometric shapes defined by their algebraic equations, by using both numerical and analytical approaches. The results do not seem realistic in some cases of round-tipped shapes, which leads us to adopt, in general, a simplified form for the shape factor, different from what is sometimes used in the literature. On the other hand, such an approach suggests to us to take into account separately the ogival length and the overall length of the body. To compare classic and improved models, examples of ballistic-wave calculation are given for some bullets and small-caliber shells of which the shape is roughly defined. Finally, it appears interesting to test these models on a larger scale by simulating the sonic boom of the Apollo Command Module during its atmospheric reentry and the sonic boom of the F-104 Starfighter in horizontal flight. The results obtained seem to justify the improvements proposed for the theoretical model of ballistic wave and sonic boom arising from flying objects of simple geometry.

关键词： Projectiles Shock Front Hypersonic Speed Detonation Aerodynamics Supersonic Aircraft computational fluid dynamics simulation Lift Coefficient Rockets Stagnation Point

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Investigation of Mixed Convection Heat Transfer Through Metal Foams Partially Filled in a Vertical Channel by Using computational fluid dynamics

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JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME 2018年第11期140卷 112501-112501页

作者： Kotresha, Banjara Gnanasekaran, N. Natl Inst Technol Karnataka Dept Mech Engn Surathkal 575025 India

Two-dimensional computational fluid dynamics simulations of mixed convection heat transfer through aluminum metal foams partially filled in a vertical channel are carried out numerically. The objective of the present study is to quantify the effect of metal foam thickness on the fluid flow characteristics and the thermal performance in a partially filled vertical channel with metal foams for a fluid velocity range of 0.05-3 m/s. The numerical computations are performed for metal foam filled with 40%, 70%, and 100% by volume in the vertical channel for four different pores per inch (PPIs) of 10, 20, 30, and 45 with porosity values varying from 0.90 to 0.95. To envisage the characteristics of fluid flow and heat transfer, two different models, namely, Darcy Extended Forchheirmer (DEF) and Local thermal non-equilibrium, have been incorporated for the metal foam region. The numerical results are compared with experimental and analytical results available in the literature for the purpose of validation. The results of the parametric studies on vertical channel show that the Nusselt number increases with the increase of partial filling of metal foams. The thermal performance of the metal foams is reported in terms of Colburn j and performance factors.

关键词： computational fluid dynamics simulation metal foams partial filled mixed convection LTNE

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Air assist atomization characterization of palm biodiesel through experimental investigation and CFD simulation

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BIOFUELS-UK 2017年第5期8卷 571-577页

作者： Tan, Ee Sann Anwar, M. Kumaran, P. Indra, T. M. Yoshikawa, Kunio Univ Tenaga Nas Dept Mech Engn Jalan Ikram Uniten Kajang 43000 Selangor Malaysia Tokyo Inst Technol Frontier Res Ctr Tokyo Japan

The depletion of fossil fuel and environmental concerns have elevated biodiesel to emerge as a suitable alternative fuel to substitute diesel fuel. The study of spray formation is essential to improve the combustion systems of internal combustion engines and gas turbines. This paper aims to study the atomization characteristics of biodiesel derived from palm biodiesel through experimental test and simulation. The chemical fuel properties of biodiesel such as viscosity and density, will adversely affect the spray characteristics such as spray pattern, spray length, spray angle and Sauter Mean Diameter. The biodiesel fuels are blended with diesel in various ratios before being tested in an atomization test rig. Modelling of the atomizer are presented using computational fluid dynamics whereby comparisons are made with respect to the experimental results carried out in the atomizer test rig. There is no large discrepancy with the simulation results. The results showed that the higher content of biodiesel gives a larger droplet size and longer spray length. However, it produces smaller spray angle and spray width but with clearer vortex shape of spray pattern.

关键词： Biodiesel spray pattern spray angle spray Sauter Mean Diameter computational fluid dynamics simulation

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