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Particle Image Velocimetry and Total Temperature Characterization of Arc-Heated Mach 4.5 Free Jet

AIAA JOURNAL 2024年第5期62卷 1720-1730页

作者： Lee, Gyu Sub Lim, Jie Sakkos, Peter Gessman, Isabella C. Kato, Nozomu Kirchner, Branden Elliott, Greg Lee, Tonghun Univ Illinois Dept Aerosp Engn Urbana IL 61801 USA Univ Illinois Dept Mech Sci & Engn Urbana IL 61801 USA

Particle image velocimetry (PIV) measurements were conducted in the Arc-Heated Combustion Tunnel (ACT-II) on a high-enthalpy Mach 4.5 nozzle flow. The primary motivation for the current work is to establish the feasibility of PIV as a high-quality flow diagnostic technique in hypersonic arc-heated flows and produce a high-resolution hypersonic nozzle flow characterization, including nozzle free jet shear layer velocity profiles. Due to the uncertain nature of the gas composition in the flowfield of interest, PIV measurements of a supersonic wedge flow were used to couple the flow velocities to the oblique shock relations. This enabled a PIV-derived total temperature calculation that does not require a priori assumptions of the exact gas composition. A PIV expansion module was developed for this study, and proper seed sizing and material were selected for the present flow. An analysis of the seed particle response from the PIV measurements provided an initial validation of the seed performance while revealing potential issues with consistent seed sizing. These measurements and derived conditions represent a means of acquiring high-resolution velocimetry and temperature datasets that consider uncertainties in the experimental generation of hypersonic high-enthalpy flows.

关键词： Molecular Tagging Velocimetry Enthalpy flow visualization techniques Oblique Shock Wave Fluid flow Properties Hypersonic Nozzle Hypersonic flows Particle Image Velocimetry Scramjet Hyper Sonic Wind Tunnels

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Tip Vortex Trajectory and Its Application in Small-Rotor/Wing Interaction

Tip Vortex Trajectory and Its Application in Small-Rotor/Win...

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AIAA SciTech Forum

作者： Chen, Mingtai Hua, Jie Shen, Jinwei Hubner, James P. North Carolina State Univ Dept Mech & Aerosp Engn Raleigh NC 27695 USA Embry Riddle Aeronaut Univ Dept Aerosp Engn Daytona Beach FL 32114 USA Univ Alabama Dept Aerosp Engn & Mech Tuscaloosa AL 35487 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

This paper studies the downward tip vortex trajectory of a small rotor in the near proximity of a wing, similar to the geometry of small unmanned-air-vehicles (UAVs) in hover (disk loading < 100 N/m(2) and Reynolds number < 100,000). Rotor height above the wing and rotor wake impingement area on the wing are varied. Empirical equations of the trajectory as a function of rotor height generalized from tip vortex trajectory results in smoke visualization experiments are then employed. Using the rotor wake model based on the tip vortex trajectories, image vortices, and momentum theory, a potential flow solution to predict rotor thrust and download force on the wing is developed and discussed, which links rotor wake, thrust and download force in rotor-wing interaction. The analytical results will be compared to the corresponding experimental force data in terms of magnitude and trend for accuracy assessment.

关键词： Tiltrotor Aircraft Vortex Shedding flow visualization techniques Low Reynolds Number Incompressible flow Transport Aircraft Mass flow Rate Thrust Augmentation CFD simulation Computational Simulation

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Geometric Effects on the Aerodynamic Interactions of a Wing-Propeller Combination in Hover Flight

Geometric Effects on the Aerodynamic Interactions of a Wing-...

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AIAA SciTech Forum

作者： Heidersbach, Ross W. Pisano, Anthony Spens, Alex Murnieks, Victoria A. Seth, Dhuree McCrink, Matthew H. Bons, Jeffrey P. Ohio State Univ Dept Mech & Aerosp Engn Columbus OH 43235 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

The aerodynamic interactions between a propeller, wing, and control surface are investigated at zero freestream velocity to simulate flight conditions associated with hovering operations of a tail-sitter aircraft. Oil flow visualizations and Kiel probe surveys indicated that a thrust-producing propeller operating at zero freestream velocity generates a wake over a wing's surface that is significantly skewed towards the slipstream's downwash component. This testing also showed that a slipstream's velocity profile at a given chord location follows a bimodal distribution with a velocity deficit located behind the propeller hub. After identifying distinctive slipstream characteristics associated with this unique flight condition, additional testing was performed focused on determining the influence of a propeller's rotational direction, distance from a wing's leading edge, radius, and pitch on the resultant lifting force and pitching moment. Test results demonstrated that propeller directionality did not significantly impact the wing's aerodynamic loads. Similarly, the lifting force and pitching moment appeared largely insensitive to changes in propeller standoff distances between 0.5R and 1.5R. The wing's aerodynamic loads increased linearly with the amount of thrust generated by a propeller. For a given control surface deflection, similar thrust-normalized lifting forces and pitching moments were generated regardless of propeller radius and pitch. These thrust-normalized loads increased proportionally with control surface position for small to moderate deflections. Relating the wing's lifting force and pitching moment to propeller thrust provides a succinct method for estimating the aerodynamic loads required to model the flight dynamics of a tail-sitter VTOL aircraft operating at hovering flight conditions.

关键词： Fixed Pitch Propellers Aerodynamic Coefficients flow visualization techniques Rectangular Wing Turboprop Aircraft Velocity Profiles Flight Dynamics Wing Configurations Aerodynamic Performance Control Surfaces

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Application of Schlieren Methods to Flared Cone in Mach-6 Quiet Tunnel

Application of Schlieren Methods to Flared Cone in Mach-6 Qu...

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AIAA SciTech Forum

作者： McDaniel, Zachary A. Jewell, Joseph S. Purdue Univ Sch Aeronaut & Astronaut W Lafayette IN 47907 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

Schlieren processing methods are applied to a flared cone geometry in a Mach 6 quiet tunnel. High speed schlieren videos of laminar and transitional boundary layers over freestream unit Reynolds numbers ranging from 6.4 x 10(6)/m to 10.4 x 10(6)/m are used to analyze the characteristics of second-mode rope waves. The power of PSDs derived from schlieren video generally correlates with PCB RMS measurements at varying Reynolds numbers and axial positions. It is shown that a limited number of schlieren frames can be used to create frequency-based pixel disturbance contours that resemble contours created by schlieren PSDs. Lastly, the performance characteristics of an IC2 MHzPressure (TM) Model EP-1000 sensor is compared to that of a PCB. They are found to detect similar second-mode instability characteristics after a correction is applied.

关键词： Hypersonic Boundary Layer Transition Sensors Pressure Transducers flow visualization techniques Band Pass Filter Image Gradient Boeing Polyether Ether Ketone Data Acquisition System Continuous Wavelets

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A good choice: Why the National Aerospace Laboratory NLR in The Netherlands purchased 18 Task balances in the late 50-ies

A good choice: Why the National Aerospace Laboratory NLR in ...

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AIAA Aviation Forum

作者： Elsenaar, Bram Buruma, Tjeerd Heritage Fdn NLR Anth Fokkenveg 2 NL-1059 CM Amsterdam Netherlands German Dutch Wind Tunnels POB 175 NL-8300 AD Emmeloord Netherlands Royal Netherlands Meteorol Inst KNMI POB 201 NL-3730 AE De Bilt Netherlands

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

In the late 50-ies a transonic and a supersonic wind tunnel was designed and built in The Netherlands. A crucial question was how forces and moments on the wind tunnel model had to be measured. Today no one questions the use of internal strain gauge balances. But there was a time that this was far from obvious. The paper shows the alternative that was considered at that time. And how, at a very late stage, a decision was made for internal balances. Since there was hardly sufficient time left for the 'in house' development of all required balances, the decision was finally made to buy 18 TASK balances. Some of these balances are still in use today, demonstrating that a good choice was made at that time and that the quality of the original design of the TASK balances was excellent. This paper is a contribution to the special session entitled: "65 Years of TASK Wind Tunnel Balances - Past, Present, and Future".

关键词： German Dutch Wind Tunnels Strain Gauge National Aerospace Laboratories Aerodynamic Coefficients Data Acquisition System flow visualization techniques flow Conditions British Aircraft Corporation Control Surfaces Strength of Materials

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Experimental Investigation of an Airfoil with Spanwise Wavy Trailing Edge

Experimental Investigation of an Airfoil with Spanwise Wavy ...

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AIAA Aviation Forum

作者： Ferreira, Paulo Henrique Moura, Rodrigo Costa de Paula, Adson Agrico Inst Tecnol Aeronaut Program Aeronaut & Mech Engn BR-12228900 Sao Jose Dos Campos SP Brazil Inst Tecnol Aeronaut Aeronaut Engn Div BR-12228900 Sao Jose Dos Campos SP Brazil

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

Recently, waviness applied on leading edge of airfoils has been extensively researched. As a biomimetic solution, the also called tubercle has brought up many insights on passive flow control mechanisms and inspired other studies. Therefore, the present study aims to investigate the potential of waviness now applied on the trailing edge of airfoils. For this purpose, experimental tests in wind tunnel is carried out in order to understand the effects of different wavy geometries on the flow. A NACA 0020 airfoil is selected as a baseline profile and three configurations of waviness are tested: A = 0.11c,lambda = 0.40c;A = 0.03c,lambda = 0.40c;and A = 0.03c,lambda = 0.11c. The phenomena are evaluated measuring forces at a single Reynolds numbers of 250,000, and correlating it with a flow topology analysis provided by an oil flow visualization technique. Main results show that the wavy model with parameters A = 0.11c,. = 0.40c presents the best aerodynamic efficiency, with similar lift values compared to the baseline profile, but with reduced drag coefficients, also briefly delaying stall separation. flow visualization shows that this case has larger regions of attached flow.

关键词： Lift to Drag Ratio Cambered Airfoil Aerodynamic Characteristics Aerodynamic Performance flow visualization techniques Wind Tunnel Interference Boundary Layer Separation Airfoil Geometry Two Dimensional flow Post Stall

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Pressure Gradient Effects on Boundary Layer Superstructures

Pressure Gradient Effects on Boundary Layer Superstructures

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AIAA Aviation Forum

作者： Butt, Humza Damani, Shishir Chaware, Shreyas Szoke, Mate Srivastava, Surabhi Lowe, Todd K. Devenport, William Hales, Alistair Colbrook, Matthew Ayton, Lorna J. Virginia Polytech Inst & State Univ Blacksburg VA 24060 USA Univ Cambridge Dept Appl Math & Theoret Phys Cambridge CB3 0WA England

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

Spanwise homogeneous turbulent boundary layers convect groups of flow structures that move with similar momentum, often called coherent structures. These coherent structures remain statistically similar as they get convected downstream. The length scales of such coherent structures vary with the wall-normal distance of the boundary layer. Large-scale motions on the order of 20 delta, often termed superstructures, are conjectured to be present in the outer layer. However, Particle Image Velocimetry (PIV) data acquired at the bottom of the logarithmic layer of the boundary layer provides evidence of the existence of superstructures in the overlap region. Their presence in the close vicinity of the wall makes them a strong candidate to be the prime contributors to the low-wavenumber pressure fluctuations in a smooth wall. A discussion on the fundamental nature of these superstructures in the smooth-wall turbulent boundary layer is presented, followed by the flow field's decomposition into its streamwise wavenumber and frequency components. The experimental data is also analyzed using a novel dynamic mode decomposition technique, ResDMD. This decomposition approach differs from other known techniques due to error control, verification (e.g., of dictionaries) and convergence theorems. This technique was used to uncover the transient behavior within the system and identify turbulence events based on their length scales and convection velocities. The extent of the streamwise flow homogeneity is also discussed. Evidence of high spectral levels at low-wavenumbers confirms the role of superstructures in containing a significant fraction of the turbulence energy. The streamwise wavenumber-frequency spectra of the pressure fluctuations at sub-convective wavenumbers support this.

关键词： Boundary Layer Thickness Pressure Gradient Wavenumber Time Resolved Particle Image Velocimetry Convection Dynamic Mode Decomposition flow visualization techniques Angle of Attack Wall Bounded Turbulent flows Wind Tunnels

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A Novel Deep Learning-Based Approach for Particle Image Velocimetry with Global Motion Aggregation

A Novel Deep Learning-Based Approach for Particle Image Velo...

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AIAA Aviation Forum

作者： Wang, Jincheng Hu, Haiyang He, Ping Hu, Hui Iowa State Univ Dept Aerosp Engn Ames IA 50011 USA

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

Particle Image Velocimetry (PIV) is a widely used flow visualization technique for velocity measurement in experimental fluid mechanics. The classical PIV technique suffers from tremendous parameter tuning by hand. At the same time, the current state-of-the- art machine-learning-based PIV methods are intractable for very large displacement calculations and have difficulties in generalizing across different signal-to- noise ratios (SNR). Transformer is an attention-based method popular for capturing global correlation. In this study, based on the transformer, we proposed a new deep-learning-based PIV method called Global Motion Aggregation-PIV (GMA-PIV), capable of calculating large displacement and generalizing it to raw particle images with a lower SNR ratio. To our knowledge, this is the first practice utilizing a transformer-based deep neural network for particle image velocimetry.

关键词： Convolutional Neural Network Particle Image Velocimetry Transformer Machine Learning Fluid Mechanics flow visualization techniques Backward Facing Step flow Airfoil flow NACA 0012 Aerospace Engineering

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An experimental study of flow past a rotationally oscillating linearly tapered cylinder

An experimental study of flow past a rotationally oscillatin...

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AIAA Aviation Forum and Exposition

作者： Bhattacharyya, Soumarup Vermat, Shivam Kumar, Sanjay Poddar, Kamal Indian Inst Technol Dept Aerosp Engn Kanpur 208016 Uttar Pradesh India

ISBN: (数字)9781624106101

ISBN: (纸本)9781624106101

The wake of a linearly tapered cylinder executing rotational oscillations is studied experimentally at Reynolds number (based on mean diameter D (m)) of 250. The tapered cylinder is forced to perform rotational oscillations at various oscillation amplitudes (45 degrees <=theta <= 180 degrees) and normalized forcing frequencies. Tapered cylinders are characterized by taper ratio defined as the ratio of the length to the difference in diameters at the two ends. Hydrogen bubble technique is used for flow visualization of the wake structure. The cylinder used in the present study has a taper ratio of 70:1 and a mean diameter D (m) of the cylinder is 8mm. Oblique shedding (with oblique angle of 13.5 degrees) is observed for the stationary cylinder which gradually reduces and eventually modifies to parallel shedding with increase of forcing frequency up to a certain forcing frequency which is dependent on the oscillation amplitude. flow visualization provided the forcing parameters for which the flow becomes two dimensional thereby suppressing threedimensionalities and it also provided some insights about the 2S and 2P modes along the span. Cellular structures are found to be formed for some specific forcing parameters. For oscillation amplitude of theta=135 degrees and normalized forcing frequency, FR=2, a new three-dimensional mode is observed at the upper half of the cylinder with the span-wise wavelength of 1.6. PIV used for quantitative study showed that the circulation of spanwise vortices looses its strength as we move from the larger diameter end to the smaller diameter end.

关键词： Vortex Induced Vibrations flow visualization techniques Particle Image Velocimetry Reynolds Number Taper Ratio Immersed Boundary Method Servo Motors Two Dimensional flow Signal Generator Anodizing

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Resonator-Based Pressure Sensor for Wall Pressure 28

Resonator-Based Pressure Sensor for Wall Pressure

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28th AIAA/CEAS Aeroacoustics Conference

作者： Damani, Shishir Braaten, Erik Szoke, Mate Alexander, Nathan Devenport, William J. Balantrapu, N. Agastya Pearce, Benjamin P. Starkey, Timothy A. Hibbins, Alastair P. Sambles, J. Roy Virginia Polytech Inst & State Univ Kevin T Crofton Dept Aerosp & Ocean Engn Blacksburg VA 24061 USA Princeton Univ Dept Mech & Aerosp Engn Princeton NJ 08544 USA Univ Exeter Dept Phys & Astron Exeter EX4 4QL Devon England

ISBN: (数字)9781624106644

ISBN: (纸本)9781624106644

A Kevlar-covered acoustic resonator-based cavity sensor is introduced to measure low-wavenumber pressure fluctuations in a turbulent boundary layer. These sensors have an inherent capability to filter the convective pressure fluctuations based on their physical dimensions, specifically their extent in the streamwise and spanwise directions. This study aims to demonstrate the spatial sensitivity behavior of these sensors and to show their viability towards wall pressure measurements by revealing the lack of effects on the turbulent flow over a sensor using a time-resolved wall parallel flow visualization technique. Additionally, it examines the degree of control that can be achieved on the spatial response of such sensors using sensor shape, and flow interfaces with different materials and porosity distributions. Understanding the sensor operation in this way may enable these sensors to be used more widely.

关键词： Pressure Sensors Sensor Technology Boundary Layer Thickness Turbulent flow flow visualization techniques Dynamic Response Particle Image Velocimetry Resonant Frequencies Kinematic Viscosity Rapid Prototyping

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