We present analysis from planar time-resolved particle image velocimetry fields in the streamwise surface-normal plane of turbulent flow surrounding NACA 0012 and NACA 65-410 airfoils at Rec approximate to 7 x 10(4) f...
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We present analysis from planar time-resolved particle image velocimetry fields in the streamwise surface-normal plane of turbulent flow surrounding NACA 0012 and NACA 65-410 airfoils at Rec approximate to 7 x 10(4) focusing on stall phenomena at intermediate to high angles of attack a. Dominant flow frequencies, identified from the lift spectra obtained from a load cell mounted to the foils, highlight the presence of bluff-body shedding [f(a)(star) = f(c)/U-infinity ) sin alpha of O(10(-1)), where f is the frequency, c the airfoil chord, andU(infinity) the freestream velocity] for all cases and prominent low frequencies [f(a)(star) of O(10(-2))] for cases in transient stall (TS). A data-driven modeling framework via the proper orthogonal decomposition (POD) reveals that the low frequencies are associated to flow separation and reattachment driven by underlying expansion and contraction normal to the suction surface. Further, the ability to predict the low-order features from (pseudo) pressure probes at the leading, midchord, and trailing edges for both TS and deep stall (DS) cases is quantified using linear stochastic estimation (LSE). The framework pinpoints the centroid of the region of reverse flow with error on the order of 5 and20% for DS and TS regimes, respectively. Notably, it is found that LSE coefficients governing the low-order POD correlations do not strongly depend on the airfoil geometry. This is demonstrated by the comparative performance of training the LSE using the probes of the NACA 0012 cases to predict the NACA 65-410 velocity fields and vice versa. This work demonstrates the insight afforded by the POD on the low-order features of turbulent stalled airfoils as well as the similarity of such features across geometries toward predicting flow features for potentially any airfoil geometry without the need to retrain an LSE library.
The flow within the inlet of an engine nacelle model in the absence of a fan and the presence of crosswind is investigated in wind-tunnel experiments, with specific emphasis on the effects of separation over the inlet...
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The flow within the inlet of an engine nacelle model in the absence of a fan and the presence of crosswind is investigated in wind-tunnel experiments, with specific emphasis on the effects of separation over the inlet's inner windward surface on the flow distortion and pressure recovery. The inlet's entrance plane is tilted forward, and its cross section is asymmetric about the horizontal centerline. The flow topology within the inlet is characterized over a range of Mach numbers and crosswind speeds up to M = 0.72 and U-o = 18 m/s, respectively. It is shown that in the presence of sufficiently high crosswind to the inlet speed ratio, a three-dimensional horseshoe-like separation domain is formed over the inlet's inner windward surface. Owing to the cross-sectional asymmetry of the entrance plane, the separation domain migrates azimuthally downward and expands azimuthally with increased crosswind to the inlet speed ratio. The present investigations demonstrate the utility of flowcontrol for mitigating the adverse effects of the separation. The actuation is based on controllable distributed aerodynamic air bleed that is driven by the pressure differences across the nacelle's inner and outer surfaces and reattaches the separated base flow up to crosswind speeds of 15.4 m/s, resulting in a gain of up to 38% in total pressure recovery and a decrease of up to 55% in total pressure distortion. The efficacy of the bleed actuation can be further improved by tailoring the bleed distribution to the topology of the separated flow domain.
Companion volumes, Dynamics of Explosions and Dynamics of Reactive Systems, present revised and edited versions papers given at the Tenth International Colloquium on the Dynamics of Explosions and Reactive System...
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ISBN:
(数字)9781600865800
ISBN:
(纸本)9780930403157
Companion volumes, Dynamics of Explosions and Dynamics of Reactive Systems, present revised and edited versions papers given at the Tenth International Colloquium on the Dynamics of Explosions and Reactive Systems held in Berkeley, CA in August 1985. Dynamics of Explosions primarily concerns the interrelationship between the rate processes of energy deposition in a compressible medium and the concurrent nonsteady flow as it typically occurs in explosion phenomena. Dynamics of Reactive Systems (Volume 105: Parts I and II) spans a broader area, encompassing the processes coupling the dynamics of fluid flow and molecular transformations in reactive media, and occurring in any combustion *** this volume, Dynamics of Explosions, papers have been arranged into chapters on flame acceleration and transition to detonation; initiation and transmission of detonations; detonation structure and limit propagation; detonation kinetics, structure, and boundary effects; explosions, reflections, and blast waves; heterogeneous detonations and explosions; and condensed phase shocks and detonations.
The four companion volumes on Dynamic Aspects of Detonations and Explosion Phenomena and Dynamics of Gaseous and Heterogeneous Combustion and Reactive Systems present 111 of the 230 papers given at the Thirteenth...
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ISBN:
(数字)9781600866272
ISBN:
(纸本)9781563470592
The four companion volumes on Dynamic Aspects of Detonations and Explosion Phenomena and Dynamics of Gaseous and Heterogeneous Combustion and Reactive Systems present 111 of the 230 papers given at the Thirteenth International Colloquium on the Dynamics of Explosions and Reactive Systems held in Nagoya, Japan. These books embrace the topics of explosions, detonations, shock phenomena, and reactive flow, as well as the gasdynamic aspects of nonsteady flow in combustion systems, the fluid mechanics aspects of combustion, and diagnostic techniques. Two of the volumes, Dynamics of Gaseous Combustion (Vol. 151) and Dynamics of Heterogeneous Combustion and Reacting Systems (Vol. 152), focus on the processes of coupling the exothermic energy release with the fluid mechanics occurring in various combination processes. The other two volumes, Dynamic Aspects of Detonations (Vol. 153) and Dynamic Aspects of Explosion Phenomena (Vol. 154), address the rate processes of energy deposition in a compressible medium and the concurrent nonsteady flow as it typically occurs in explosion phenomena.
This volume undoubtedly contains one of the largest and most interesting collections of recent papers on metal and hybrid combustion. Most were presented at the AIAA Heterogeneous Combustion Conference in December 196...
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ISBN:
(数字)9781600864896
ISBN:
(纸本)9781563478642
This volume undoubtedly contains one of the largest and most interesting collections of recent papers on metal and hybrid combustion. Most were presented at the AIAA Heterogeneous Combustion Conference in December 1963. In the initial section of the book are some of the first published works on the analytical determination of metal burning rates, the various flame mechanisms of aluminum and magnesium, the combustion of aluminum in carbon dioxide atmospheres, and the ignition temperature of beryllium. Papers deal with the oxidation and flame studies with diborane and its alkyl derivatives and reaction studies between boron and nitrogen compounds. Papers in the third section deal with some aspects of the over-all hybrid combustion process.
This volume is a compilation of papers presented at a conference on hypersonics held at the Massachusetts Institute of Technology in August 1961 and sponsored jointly by the Air Force Office of Scientific Research and...
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ISBN:
(数字)9781600864810
ISBN:
(纸本)9781563478567
This volume is a compilation of papers presented at a conference on hypersonics held at the Massachusetts Institute of Technology in August 1961 and sponsored jointly by the Air Force Office of Scientific Research and the American Rocket Society. The topics that are covered are low Reynolds number effects, chemical kinetics effects, in viscid flow calculations, and a survey of current experimental techniques, as they relate to the problems of acquiring an understanding of hypersonic flow. Others, such as the structure and composition of hypersonic wakes with attendant complex chemical kinetic effects, are treated only briefly.
By combining into one volume a number of papers carefully chosen to illuminate important areas of technical development, it is possible to get this broader view of the whole field, its state of the art, and its patter...
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ISBN:
(数字)9781600864827
ISBN:
(纸本)9781563478574
By combining into one volume a number of papers carefully chosen to illuminate important areas of technical development, it is possible to get this broader view of the whole field, its state of the art, and its pattern of development. This is the purpose of the present volume. The editors have grouped the the papers broadly into space guidance and path control, terrestrial guidance concepts and components, and other control topics. The first of these comprises three major mission phases: ascent from Earth to an orbit or space trajectory operations in space requiring navigation or guidance, and descent to the surface of Earth or the moon. The second group includes the system aspects of inertial navigation, gyroscopes as basic components of inertial navigation, and topics in optical navigation. The third group is less homogeneous. Its major divisions are adaptive control, a subject currently in the forefront of modern control theory developments, and attitude control, the major control phase in a space environment.
This and a companion volume include revised and edited version of papers presented at the Ninth International Colloquium on the Dynamics of Explosions and Reactive Systems held in Poitiers, France, in July 1983. ...
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ISBN:
(数字)9781600865701
ISBN:
(纸本)9780915928927
This and a companion volume include revised and edited version of papers presented at the Ninth International Colloquium on the Dynamics of Explosions and Reactive Systems held in Poitiers, France, in July 1983. The contributions have been assembled into two volumes: Dynamics of Shock Waves, Explosions, and Detonations and Dynamics of Flames and Reactive Systems. The dynamics of explosions, which the former addresses, is concerned principally with the interrelationship between the rate processes of energy deposition in a compressible medium and the concurrent nonsteady flow as it occurs typically in explosion phenomena. The dynamics of reactive systems, which is the focus of the latter volume, is a broader area encompassing the processes of coupling between the dynamics of fluid flow and molecular transformations in reactive media occurring in any combustion system. In this volume, Dynamics of Flames and Reactive Systems, the papers have been arranged into chapters on premixed flames, diffusion flames, turbulent combustion, constant volume combustion, spray combustion, nonequilibrium flows, and combustion diagnostics.
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