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Active flow Control in Compressor Cascades with Steady and Pulsed Jets

JOURNAL OF PROPULSION AND POWER 2023年第4期39卷 501-510页

作者： Chen, Shaowen Yang, Pengcheng Shi, Yuchen Meng, Qinghe Harbin Inst Technol Sch Energy Sci & Engn Harbin 150001 Peoples R China

This paper describes a detailed experimental investigation into the impact of steady and pulsed blowing on endwall secondary structures and losses in a compressor cascade. Owing to their high configuration flexibility, injection holes are integrated in the cascade sidewalls to manage the secondary flows. Loss reductions of 3.2 and 5.72% relative to the uncontrolled case are achieved by steady blowing with straight and optimized inclined holes, respectively. Superior loss reduction of 7.85% is obtained by pulsed blowing through inclined holes. To identify the secondary flow structures near the endwall and suction surfaces, a self-developed oil visualization method and spatial-spectral analysis are performed. Experimental results show that two concentrated shedding vortices exist in the cascade corner region. Loss reduction is achieved as the blowing suppresses the dominant vortex. Pulsed blowing intensifies the acceleration effect on the boundary layer, resulting in better performance with the same injection velocity. The impact of the pulse frequency on loss generation is investigated, and it is found that the optimal frequency is close to the shedding frequency of the dominant vortex in the cascade corner region.

关键词： Active flow Control Horseshoe Vortex flow visualization techniques Oil visualizations Spatial-Spectral Analysis Compressor Cascade Steady and Pulsed Blowing Low-Speed Wind Tunnel

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flow Topology of a Slanted Cylinder with Rounded-Edges Under Compressible Conditions

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AIAA JOURNAL 2023年第12期61卷 5446-5460页

作者： Huss, Rhylan A. Zigunov, Fernando Alvi, Farrukh Florida A&M Univ Coll Engn Florida Ctr Adv Aeroprop Dept Mech Engn 2003 Levy Ave Tallahassee FL 32310 USA Florida A&M Univ Coll Engn Los Alamos Natl Lab Florida Ctr Adv AeropropDept Mech Engn Tallahassee FL 32310 USA Florida State Univ Coll Engn Florida Ctr Adv Aeroprop Dept Mech Engn 2003 Levy Ave Tallahassee FL 32310 USA Florida State Univ Coll Engn Los Alamos Natl Lab Florida Ctr Adv AeropropDept Mech Engn Tallahassee FL 32310 USA

In this study, the slanted afterbody was modified to more closely represent cargo aircraft afterbodies through the addition of a basal edge fillet. Two slant angles (& phi;=32 deg and & phi;=45 deg) were explored over two Mach numbers (M & INFIN;=0.3 and M & INFIN;=0.6) and two Reynolds numbers (ReD=0.832E6 and ReD=1.47E6) using oil flow visualization and pressure-sensitive paint to identify surface flow phenomena, while the spanwise shadowgraph enabled the observation of mean wake phenomena. The & phi;=45 deg rounded-edge afterbody surface measurements displayed a centerline-separated vortex state with flow features and regions of suction qualitatively similar to those of the baseline sharp-edge case, with some notable differences. For example, a separation bubble at the slant leading edge is nearly twice the size of the baseline sharp-edge model. This is accompanied by the presence of a "source point," indicated by a region of high pressure where the flow reattaches, and a tighter counter-rotating vortex pair in comparison to the baseline. The rounded-edge prevented the previously seen compressible transition to a fully separated wake state within the Mach number range studied while showing an increase in separation bubble size with increasing Mach number. Also noteworthy was the existence of a new vortex state for the & phi;=32 deg model, where the flow remains attached at the model centerline. This is in contrast to the previously observed flow topology of the centerline-separated vortex state in the sharp-edge model, which formed a separation bubble at the model centerline. The transition between the new centerline-attached vortex state and the traditional centerline-separated vortex state was shown to be dependent on both Mach number and Reynolds number, revealing the importance of boundary-layer development on the rounded afterbody flowfield. Overall, these observations indicate that the rounded afterbody produces flowfields with distinct features that vary f

关键词： Afterbody flowfield Strouhal Number Low Reynolds Number Boundary Layer Separation flow visualization techniques Separated flows

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Swept-Wing Active flow Control with a Streamwise Row of Vortex Generating Jets

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AIAA JOURNAL 2023年第3期61卷 1142-1150页

作者： McFadden, Evan J. Brandt, Patrick J. Bons, Jeffrey P. Ohio State Univ Dept Mech & Aerosp Engn Columbus OH 43235 USA

A novel swept-wing active flow control (AFC) technique was developed and tested on a NACA 64(3)-618 wing with 30 degrees leading-edge sweep. A streamwise row of 20 vortex generating jets (VGJs), pitched 30 degrees from the wing surface and skewed 60 degrees toward the wing root, was applied at three different spanwise locations. Performance was assessed using load-cell measurements and surface oil flow visualizations at a Reynolds number of 100,000. More inboard placement of the AFC produced higher values of C-L max, but further outboard placement resulted in a higher stall angle. With a momentum coefficient of only 2%, lift was enhanced up to 15% and stall was delayed up to 12 degrees, depending on the AFC location. The number of jets used in the row was reduced, resulting in nearly the same performance benefits with half of the momentum coefficient required for the full row of jets. The performance enhancements of this active flow control technique are comparable to a passive boundary-layer fence without the 25% increase in drag caused by the fence. The mass flow cost of the streamwise row of VGJs is 75% lower than the mass flow required for a previously studied swept-wing active flow control technique involving a streamwise slot.

关键词： Aerodynamic Coefficients Aircraft Wing Design Vortex Dynamics flow visualization techniques Turbulent Boundary Layer Active flow Control Swept Wing flow visualization Vortex Generators flow Control (Fluid)

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Experimental Investigation of the Effect of Wavefront Aberration on the flow Generated by Laser-Induced Breakdown

Experimental Investigation of the Effect of Wavefront Aberra...

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AIAA SciTech Forum

作者： Noel, Zareb A. Gordeyev, Stanislav Rennie, R. Mark Univ Notre Dame Dept Aerosp & Mech Engn Hessert Lab Aerosp Res Notre Dame IN 46556 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

Phase aberrations and their effect on the development of flowfields caused by laser-induced breakdown is investigated. The phase aberrations are imparted onto a high-energy laser pulse at a wavelength of 1064nm using a deformable mirror. An experimental setup was devised to capture the motion of the flowfields resulting from laser-induced breakdown with phase aberration which focuses on capturing both the transverse profile, as well as the coaxial profile of the flowfield. It is shown that the laser pulse energy (181mJ) absorbed by the spark decreases significantly due to the presence of non-planar phase, which is due to spreading in the focal plane where breakdown typically occurs. Of the data collected, a single instance of Zernike ***, Zernike Y-Coma, and Zernike Spherical aberrations are investigated. The well-known Horn-Schunck optical flow method is used to analyze the shadowgraph images, producing dense optical flowfield representations of the motion. It is shown that each aberration investigated creates a unique flowfield, showing potential for hyper-specific local flow specification and the implications are further discussed.

关键词： Toroidal Vortex Laser Energy Velocity Profiles flow visualization techniques Lagrange Multipliers Axisymmetric flow Polarization Internal Combustion Engines Drag Reduction Finite Difference Formulation

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Design and flow Characterization of Noise Reduction System for a SupersonicWind Tunnel

Design and Flow Characterization of Noise Reduction System f...

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AIAA SciTech Forum

作者： Magnani, Jacopo Baird, Sarah Farr, Steven Singh, Surabhi Embry Riddle Aeronaut Univ Dept Aerosp Engn Daytona Beach FL 32114 USA

ISBN: (数字)9781624107115

ISBN: (纸本)9781624107115

Open-return supersonic wind tunnels are significantly loud and require a noise baffling system in place for continued and safe operation. To this end, a noise reduction system is designed and fabricated for an instructional supersonic tunnel for the undergraduate experimental aerodynamics laboratory at Embry-Riddle Aeronautical University. The flow through the baffle was simulated which revealed the velocity and pressure contours inside the baffle. The baffle was then integrated into the tunnel and the extent of noise reduction was measured at different locations around the tunnel using a decibel meter.

关键词： Hypersonic Wind Tunnels Sound Pressure Level Experimental Aerodynamics Boundary Layer Transition Incompressible flow flow visualization techniques Absorption Coefficient Static Pressure Nozzle Walls Kinetic Energy

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Supersonic Cavity flow Control Using a Spanwise Array of Leading-Edge Tabs

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JOURNAL OF AIRCRAFT 2022年第3期59卷 788-798页

作者： Singh, Surabhi Ukeiley, Lawrence Zhang, Yang Cattafesta, Louis Taira, Kunihiko Univ Florida Dept Mech & Aerosp Engn Gainesville FL 32611 USA Florida State Univ Florida Ctr Adv Aeropropuls Dept Mech Engn Tallahassee FL 32310 USA Univ Calif Los Angeles Dept Mech & Aerosp Engn Los Angeles CA 90095 USA

Motivated by the successful application of active control using segmented spanwise blowing, this work investigates passive flow control for a rectangular cavity in supersonic flow using a spanwise array of leading-edge tabs to reduce unsteady pressure loads on the cavity surface. The cavity studied here has a length-to-depth ratio of 6 and width-to-depth ratio of 6 with a turbulent boundary layer at the leading edge and a freestream Mach number of 1.4. Fluctuating surface pressure measurements within the cavity show that the leading-edge tabs have similar effectiveness as leading-edge blowing of the same spanwise wavelength in reducing pressure fluctuations on the cavity surfaces. Streamwise-aligned particle image velocimetry (PIV) measurements show evidence of deflection of the shear layer at the cavity opening and modification of recirculation characteristics associated with the controlled flow. Furthermore, cross-stream stereoscopic PIV measurements reveal counter-rotating streamwise vortices, which persist throughout the cavity length. Proper orthogonal decomposition modes of cross-stream-aligned PIV measurements show that leading-edge tabs are successful in breaking up the flow into smaller-scale modes. Surface flow visualization of the cavity floor and aft wall show differences in the recirculation patterns for the baseline and controlled flows. The present analysis provides insights on how the passive tabs effectively control high-speed cavity flow and demonstrates that the control mechanisms are analogous to steady leading-edge blowing strategies.

关键词： Leading Edges Turbulent Boundary Layer Particle Image Velocimetry Freestream Mach Number Horseshoe Vortex flow Conditions flow visualization techniques Passive Control Supersonic Wind Tunnels Power Spectral Density

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Experimental Study of an Air-to-Ground Store Release from a Jet-Fighter Weapons Bay in Transonic flow Conditions

Experimental Study of an Air-to-Ground Store Release from a ...

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AIAA Aviation Forum

作者： Ben-Gida, Hadar Israeli Air Force Aeronaut Engn Branch Aeronaut Engn IL-6473428 Tel Aviv Israel

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

In this study, wind tunnel experiments are conducted to study the release of an air-to-ground store (AGS) model from a rectangular weapons bay (WB) that is part of a generic jet-fighter configuration in transonic flow conditions. A total of three WB configurations are investigated here: i) a 'clean' baseline rectangular WB, ii) a rectangular WB with two doors installed on the two side edges of the bay, and iii) a rectangular WB with one door installed on the outboard side edge of the bay. The pressure field and acoustic spectra within the bay are evaluated for each WB configuration, without and with an AGS placed within, in a range of angles of attack and sideslip angles of the aircraft. The release of an AGS model from the various WB configurations is investigated by measuring its aerodynamic forces and moments using two methods: i) placing the AGS at three different elevations from the ceiling of the bay (captive tests), and ii) performing grid Z-sweeps of the AGS out from the bay along a normal path. Results show that the flight conditions (alpha, beta) are the primary factor to affect the WB flow field, and, thus, the initial aerodynamic and acoustic conditions for the AGS release. Both door configurations reveal a distinct effect on the acoustic spectra within the WB, resulting in a significant augmentation of the second mode. Moreover, adding doors to the bay relaxes the dependency of the captive loads in flight conditions while increasing the maximum loads exerted on the AGS throughout its release. The insights provided here can improve our understanding of the various phenomena affecting store separation from bays and may serve as a basis to improve future designs of jet-fighters' WBs.

关键词： Two Dimensional flow Angle of Attack Sideslip Angle Aerodynamic Coefficients Wind Tunnel Tests Sound Pressure Level flow Separation flow visualization techniques Pressure Transducers Acoustic Resonance

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Fluid-Structure Interactions of a Hemispherically Rounded Blunt Fin over a Compliant Panel in Mach 2 flow

Fluid-Structure Interactions of a Hemispherically Rounded Bl...

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AIAA Aviation Forum

作者： Mills, John G. Dutton, J. Craig Ehrhardt, David A. Elliott, Gregory S. Univ Illinois Aerosp Engn 104 S Wright St Champaign IL 61801 USA Univ Illinois Aerosp Engn Champaign IL 61801 USA Univ Illinois Appl Res Inst Champaign IL 61801 USA

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

The fluid-structure interactions of a blunt fin mounted over a compliant panel in Mach 2 flow were investigated. The test geometry consisted of a thin, flexible panel fixed on all edges with a blunt fin with a hemispherically rounded leading edge mounted in a manner that the leading edge of the fin overhung the panel. The blunt fin was also pivoted to several angles of attack to the oncoming flow. This allowed for the study of the dynamic system created by the interactions between the flexible panel and the blunt fin geometries. Both rigid and compliant panel models were also used in order to provide a comparison between the flow with and without the dynamics of the compliant panel. High-speed schlieren and oil flow visualizations showed that the time-averaged flow remained almost entirely unchanged between the rigid and compliant panels. The instantaneous flow fields, however, showed a highly dynamic system where the compliant panel induced oscillatory shock waves that were both stationary and freely moving. Simultaneous high-speed schlieren visualization and stereo digital-image correlation showed a strong linkage between the motion of the shock waves and the deformation of the panel. This was demonstrated through frequency analysis and modal decomposition of the panel deformation and shock motions.

关键词： Fluid Structure Interaction Angle of Attack Shock Waves Leading Edges flow visualization techniques Dynamic Mode Decomposition Linkages Wind Tunnel Tests Power Spectral Density Separated flows

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Electrothermal Ice Protection Systems De-Icing: An Experimentally Validated Idealized Ice Shedding Model

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AIAA JOURNAL 2023年第6期61卷 2526-2551页

作者： Enache, Adriana Bernay, Bruno Glabeke, Gertjan Planquart, Philippe van Beeck, Jeroen Hendrick, Patrick Free Univ Brussels Brussels Belgium Von Karman Inst Fluid Dynam B-1640 Rhode St Genese Belgium Sonaca Grp B-6041 Gosselies Belgium Free Univ Brussels B-1050 Brussels Belgium Free Univ Brussels Aerothermo Mech Dept & Environm Brussels Belgium Free Univ Brussels Appl Fluid Dynam Dept Brussels Belgium Von Karman Inst Fluid Dynam Environm & Appl Fluid Dynam Dept B-1640 Rhode St Genese Belgium

The increased use of electrothermal ice protection systems (ETIPSs) in various industries (manned and unmanned aviation, energy production) requires improvements to de-icing efficiency, ice shedding predictability, and energy consumption. To achieve these, a coupled numerical and experimental investigation of ETIPS's ice removal (ice shedding) mechanism is presented in this paper. Idealized ETIPS de-icing experiments performed in the icing wind tunnel of the von Karman Institute show several ice shedding mechanisms. A one-dimensional phase change solver developed for ice melting simulations highlights the water layer thickness influence over the ice shedding process. Coupled numerical-experimental results are employed to develop an idealized ice shedding model. The model is validated in realistic de-icing experiments in a second experimental campaign in the icing wind tunnel of the LeClerc Icing Research Laboratory.

关键词： Ice Protection System Aviation Energy Consumption Aerodynamic Force flow visualization techniques Convective Boundary Condition Icing Wind Tunnel De-Icing Phase Transition

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Experimental Investigation of flow Interaction Dynamics in Supersonic Retropropulsion

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JOURNAL OF SPACECRAFT AND ROCKETS 2022年第5期59卷 1753-1762页

作者： Mejia, N. A. Schmidt, B. E. Case Western Reserve Univ Mech & Aerosp Engn 2123 Martin Luther King Jr Dr Cleveland OH 44106 USA

Supersonic retropropulsion experiments were performed using a 12.7-cm-diameter 70 deg sphere-cone body with a single jet in the center of the model with a 4:1-area-ratio Laval nozzle directed into a Mach 4 freestream. Data were acquired using high-speed schlieren imaging and direct axial force measurements. Spectral analyses of the total axial force, jet total pressure, and bow shock standoff distance were performed, resulting in the observation of three characteristic modes. For all tests, a dominant frequency in the axial force, independent of the jet and tunnel flow, of 1.9 kHz was observed, which was determined to be a structural vibration mode. A mode at 4.2 kHz in the axial force is observed to correspond to the motion of flow structures, suggesting a coupling between the jet flow and the freestream. A dependency on the presence of the jet and the selection of jet gas is shown for a 13.7 kHz mode, indicating it is acoustic in nature. Proper orthogonal decomposition on the schlieren image data is used to show that the flowfield structures in which dominant modes manifest are dependent on the thrust coefficient.

关键词： Supersonic Retropropulsion Bow Shock Aerodynamic Force Coefficients flow Conditions Blowdown Wind Tunnels Nozzle Thrust Coefficients Resonant Frequencies Shear Layers flow visualization techniques Power Spectral Density

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