Powers, Sheryll Goecke; Huffman, Jarrett K.; Fox, Charles H., Jr.
1986-01-01
The effectiveness of a trailing disk, or trapped vortex concept, in reducing the base drag of a large body of revolution was studied from measurements made both in flight and in a wind tunnel. Pressure data obtained for the flight experiment, and both pressure and force balance data were obtained for the wind tunnel experiment. The flight test also included data obtained from a hemispherical base. The experiment demonstrated the significant base drag reduction capability of the trailing disk to Mach 0.93 and to Reynolds numbers up to 80 times greater than for earlier studies. For the trailing disk data from the flight experiment, the maximum decrease in base drag ranged form 0.08 to 0.07 as Mach number increased from 0.70 to 0.93. Aircraft angles of attack ranged from 3.9 to 6.6 deg for the flight data. For the trailing disk data from the wind tunnel experiment, the maximum decrease in base and total drag ranged from 0.08 to 0.05 for the approximately 0 deg angle of attack data as Mach number increased from 0.30 to 0.82.
Mizukaki, Toshiharu; Borg, Stephen E.; Danehy, Paul M.; Murman, Scott M.
2014-01-01
This paper presents the results of visualization of separated flow around a generic entry capsule that resembles the Apollo Command Module (CM) and the Orion Multi-Purpose Crew Vehicle (MPCV). The model was tested at flow speeds up to Mach 0.4 at a single angle of attack of 28 degrees. For manned spacecraft using capsule-shaped vehicles, certain flight operations such as emergency abort maneuvers soon after launch and flight just prior to parachute deployment during the final stages of entry, the command module may fly at low Mach number. Under these flow conditions, the separated flow generated from the heat-shield surface on both windward and leeward sides of the capsule dominates the wake flow downstream of the capsule. In this paper, flow visualization of the separated flow was conducted using the background-oriented schlieren (BOS) method, which has the capability of visualizing significantly separated wake flows without the particle seeding required by other techniques. Experimental results herein show that BOS has detection capability of density changes on the order of 10(sup-5).
Quasiperpendicular high Mach number Shocks
Sulaiman, A H; Dougherty, M K; Burgess, D; Fujimoto, M; Hospodarsky, G B
2015-01-01
Shock waves exist throughout the universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasi-perpendicular shocks across two orders of magnitude in Alfven Mach number (MA) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted timescale of ~0.3 {\\tau}c, where {\\tau}c is the ion gyroperio...
Resolving high Reynolds numbers in SPH simulations of subsonic turbulence
Price, Daniel J
2011-01-01
Accounting for the Reynolds number is critical in numerical simulations of turbulence, particularly for subsonic flow. For Smoothed Particle Hydrodynamics (SPH) with constant artificial viscosity coefficient alpha, it is shown that the effective Reynolds number in the absence of explicit physical viscosity terms scales linearly with the Mach number - compared to mesh schemes, where the effective Reynolds number is largely independent of the flow velocity. As a result, SPH simulations with alpha=1 will have low Reynolds numbers in the subsonic regime compared to mesh codes, which may be insufficient to resolve turbulent flow. This explains the failure of Bauer and Springel (2011, arXiv:1109.4413v1) to find agreement between the moving-mesh code AREPO and the GADGET SPH code on simulations of driven, subsonic (v ~ 0.3 c_s) turbulence appropriate to the intergalactic/intracluster medium, where it was alleged that SPH is somehow fundamentally incapable of producing a Kolmogorov-like turbulent cascade. We show tha...
Quasiperpendicular High Mach Number Shocks
Sulaiman, A. H.; Masters, A.; Dougherty, M. K.; Burgess, D.; Fujimoto, M.; Hospodarsky, G. B.
2015-09-01
Shock waves exist throughout the Universe and are fundamental to understanding the nature of collisionless plasmas. Reformation is a process, driven by microphysics, which typically occurs at high Mach number supercritical shocks. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. In this Letter we present a study of very high Mach number shocks in a parameter space that has been poorly explored and we identify reformation using in situ magnetic field observations from the Cassini spacecraft at 10 AU. This has given us an insight into quasiperpendicular shocks across 2 orders of magnitude in Alfvén Mach number (MA ) which could potentially bridge the gap between modest terrestrial shocks and more exotic astrophysical shocks. For the first time, we show evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted time scale of ˜0.3 τc , where τc is the ion gyroperiod. In addition, we experimentally reveal the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA , a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming.
Chaotic behaviour of high Mach number flows
Varvoglis, H.; Ghosh, S.
1985-01-01
The stability of the super-Alfvenic flow of a two-fluid plasma model with respect to the Mach number and the angle between the flow direction and the magnetic field is investigated. It is found that, in general, a large scale chaotic region develops around the initial equilibrium of the laminar flow when the Mach number exceeds a certain threshold value. After reaching a maximum the size of this region begins shrinking and goes to zero as the Mach number tends to infinity. As a result high Mach number flows in time independent astrophysical plasmas may lead to the formation of 'quasi-shocks' in the presence of little or no dissipation.
National transonic facility Mach number system
Kern, F. A.; Knight, C. W.; Zasimowich, R. F.
1985-01-01
The Mach number system for the Langley Research Center's National Transonic Facility was designed to measure pressures to determine Mach number to within + or - 0.002. Nine calibration laboratory type fused quartz gages, four different range gages for the total pressure measurement, and five different range gages for the static pressure measurement were used to satisfy the accuracy requirement over the 103,000-890,000 Pa total pressure range of the tunnel. The system which has been in operation for over 1 year is controlled by a programmable data process controller to select, through the operation of solenoid valves, the proper range fused quartz gage to maximize the measurement accuracy. The pressure gage's analog outputs are digitized by the process controller and transmitted to the main computer for Mach number computation. An automatic two-point on-line calibration of the nine quartz gages is provided using a high accuracy mercury manometer.
Low Mach Number Fluctuating Hydrodynamics for Electrolytes
Péraud, Jean-Philippe; Chaudhri, Anuj; Bell, John B; Donev, Aleksandar; Garcia, Alejandro L
2016-01-01
We formulate and study computationally the low Mach number fluctuating hydrodynamic equations for electrolyte solutions. We are interested in studying transport in mixtures of charged species at the mesoscale, down to scales below the Debye length, where thermal fluctuations have a significant impact on the dynamics. Continuing our previous work on fluctuating hydrodynamics of multicomponent mixtures of incompressible isothermal miscible liquids (A. Donev, et al., Physics of Fluids, 27, 3, 2015), we now include the effect of charged species using a quasielectrostatic approximation. Localized charges create an electric field, which in turn provides additional forcing in the mass and momentum equations. Our low Mach number formulation eliminates sound waves from the fully compressible formulation and leads to a more computationally efficient quasi-incompressible formulation. We demonstrate our ability to model saltwater (NaCl) solutions in both equilibrium and nonequilibrium settings. We show that our algorithm...
Subsonic Aerodynamic Research Laboratory (SARL)
Federal Laboratory Consortium — Description: The SARL is a unique high contraction, open circuit subsonic wind tunnel providing a test velocity up to 436 mph (0.5 Mach number) and a high quality,...
Low Mach number fluctuating hydrodynamics for electrolytes
Péraud, Jean-Philippe; Nonaka, Andy; Chaudhri, Anuj; Bell, John B.; Donev, Aleksandar; Garcia, Alejandro L.
2016-11-01
We formulate and study computationally the low Mach number fluctuating hydrodynamic equations for electrolyte solutions. We are interested in studying transport in mixtures of charged species at the mesoscale, down to scales below the Debye length, where thermal fluctuations have a significant impact on the dynamics. Continuing our previous work on fluctuating hydrodynamics of multicomponent mixtures of incompressible isothermal miscible liquids [A. Donev et al., Phys. Fluids 27, 037103 (2015), 10.1063/1.4913571], we now include the effect of charged species using a quasielectrostatic approximation. Localized charges create an electric field, which in turn provides additional forcing in the mass and momentum equations. Our low Mach number formulation eliminates sound waves from the fully compressible formulation and leads to a more computationally efficient quasi-incompressible formulation. We demonstrate our ability to model saltwater (NaCl) solutions in both equilibrium and nonequilibrium settings. We show that our algorithm is second order in the deterministic setting and for length scales much greater than the Debye length gives results consistent with an electroneutral approximation. In the stochastic setting, our model captures the predicted dynamics of equilibrium and nonequilibrium fluctuations. We also identify and model an instability that appears when diffusive mixing occurs in the presence of an applied electric field.
The small-scale dynamo: Breaking universality at high Mach numbers
Schleicher, Dominik R G; Federrath, Christoph; Bovino, Stefano; Schmidt, Wolfram
2013-01-01
(Abridged) The small-scale dynamo may play a substantial role in magnetizing the Universe under a large range of conditions, including subsonic turbulence at low Mach numbers, highly supersonic turbulence at high Mach numbers and a large range of magnetic Prandtl numbers Pm, i.e. the ratio of kinetic viscosity to magnetic resistivity. Low Mach numbers may in particular lead to the well-known, incompressible Kolmogorov turbulence, while for high Mach numbers, we are in the highly compressible regime, thus close to Burgers turbulence. In this study, we explore whether in this large range of conditions, a universal behavior can be expected. Our starting point are previous investigations in the kinematic regime. Here, analytic studies based on the Kazantsev model have shown that the behavior of the dynamo depends significantly on Pm and the type of turbulence, and numerical simulations indicate a strong dependence of the growth rate on the Mach number of the flow. Once the magnetic field saturates on the current ...
Increased Mach Number Capability for the NASA Glenn 10x10 Supersonic Wind Tunnel
Slater, J. W.; Saunders, J. D.
2015-01-01
Computational simulations and wind tunnel testing were conducted to explore the operation of the Abe Silverstein Supersonic Wind Tunnel at the NASA Glenn Research Center at test section Mach numbers above the current limit of Mach 3.5. An increased Mach number would enhance the capability for testing of supersonic and hypersonic propulsion systems. The focus of the explorations was on understanding the flow within the second throat of the tunnel, which is downstream of the test section and is where the supersonic flow decelerates to subsonic flow. Methods of computational fluid dynamics (CFD) were applied to provide details of the shock boundary layer structure and to estimate losses in total pressure. The CFD simulations indicated that the tunnel could be operated up to Mach 4.0 if the minimum width of the second throat was made smaller than that used for previous operation of the tunnel. Wind tunnel testing was able to confirm such operation of the tunnel at Mach 3.6 and 3.7 before a hydraulic failure caused a stop to the testing. CFD simulations performed after the wind tunnel testing showed good agreement with test data consisting of static pressures along the ceiling of the second throat. The CFD analyses showed increased shockwave boundary layer interactions, which was also observed as increased unsteadiness of dynamic pressures collected in the wind tunnel testing.
Design of a continuously variable Mach-number nozzle
Institute of Scientific and Technical Information of China (English)
郭善广; 王振国; 赵玉新
2015-01-01
A design method was developed to specify the profile of the continuously variable Mach-number nozzle for the supersonic wind tunnel. The controllable contour design technique was applied to obtaining the original nozzle profile, while other Mach- numbers were derived from the transformation of the original profile. A design scheme, covering a Mach-number range of 3.0
Federrath, Christoph; Schober, Jennifer; Banerjee, Robi; Klessen, Ralf S; Schleicher, Dominik R G; 10.1103/PhysRevLett.107.114504
2011-01-01
We study the growth rate and saturation level of the turbulent dynamo in magnetohydrodynamical simulations of turbulence, driven with solenoidal (divergence-free) or compressive (curl-free) forcing. For models with Mach numbers ranging from 0.02 to 20, we find significantly different magnetic field geometries, amplification rates, and saturation levels, decreasing strongly at the transition from subsonic to supersonic flows, due to the development of shocks. Both extreme types of turbulent forcing drive the dynamo, but solenoidal forcing is more efficient, because it produces more vorticity.
Mach number study of supersonic turbulence: The properties of the density field
Konstandin, Lukas; Girichidis, Philipp; Peters, Thomas; Shetty, Rahul; Klessen, Ralf S
2015-01-01
We model driven, compressible, isothermal, turbulence with Mach numbers ranging from the subsonic ($\\mathcal{M} \\approx 0.65$) to the highly supersonic regime ($\\mathcal{M}\\approx 16 $). The forcing scheme consists both solenoidal (transverse) and compressive (longitudinal) modes in equal parts. We find a relation $\\sigma_{s}^2 = \\mathrm{b}\\log{(1+\\mathrm{b}^2\\mathcal{M}^2)}$ between the Mach number and the standard deviation of the logarithmic density with $\\mathrm{b} = 0.457 \\pm 0.007$. The density spectra follow $\\mathcal{D}(k,\\,\\mathcal{M}) \\propto k^{\\zeta(\\mathcal{M})}$ with scaling exponents depending on the Mach number. We find $\\zeta(\\mathcal{M}) = \\alpha \\mathcal{M}^{\\beta}$ with a coefficient $\\alpha$ that varies slightly with resolution, whereas $\\beta$ changes systematically. We extrapolate to the limit of infinite resolution and find $\\alpha = -1.91 \\pm 0.01,\\, \\beta =-0.30\\pm 0.03$. The dependence of the scaling exponent on the Mach number implies a fractal dimension $D=2+0.96 \\mathcal{M}^{-0.3...
A new numerical solver for flows at various Mach numbers
Miczek, F; Edelmann, P V F
2014-01-01
Many problems in stellar astrophysics feature low Mach number flows. However, conventional compressible hydrodynamics schemes frequently used in the field have been developed for the transonic regime and exhibit excessive numerical dissipation for these flows. While schemes were proposed that solve hydrodynamics strictly in the low Mach regime and thus restrict their applicability, we aim at developing a scheme that correctly operates in a wide range of Mach numbers. Based on an analysis of the asymptotic behavior of the Euler equations in the low Mach limit we propose a novel scheme that is able to maintain a low Mach number flow setup while retaining all effects of compressibility. This is achieved by a suitable modification of the well-known Roe solver. Numerical tests demonstrate the capability of this new scheme to reproduce slow flow structures even in moderate numerical resolution. Our scheme provides a promising approach to a consistent multidimensional hydrodynamical treatment of astrophysical low Ma...
Low Mach Number Fluctuating Hydrodynamics of Diffusively Mixing Fluids
Donev, A; Sun, Y; Fai, T; Garcia, A L; Bell, J B
2012-01-01
We formulate low Mach number fluctuating hydrodynamic equations appropriate for modeling diffusive mixing in isothermal mixtures of fluids with different density and transport coefficients. These equations eliminate the fast isentropic fluctuations in pressure associated with the propagation of sound waves by replacing the equation of state with a local thermodynamic constraint. We demonstrate that the low Mach number model preserves the spatio-temporal spectrum of the slower diffusive fluctuations. We develop a strictly conservative finite-volume spatial discretization of the low Mach number fluctuating equations in both two and three dimensions. We construct several explicit Runge-Kutta temporal integrators that strictly maintain the equation of state constraint. The resulting spatio-temporal discretization is second-order accurate deterministically and maintains fluctuation-dissipation balance in the linearized stochastic equations. We apply our algorithms to model the development of giant concentration fl...
Mathematical and numerical aspects of low mach number flows
Energy Technology Data Exchange (ETDEWEB)
Schochet, St.; Bresch, D.; Grenier, E.; Alazard, T.; Gordner, A.; Sankaran, V.; Massot, M.; Sery, R.; Pebay, P.; Lunch, O.; Mazhorova, O.; Turkel, O.E.; Faille, I.; Danchin, R.; Allain, O.; Birken, P.; Lafitte, O.; Kloczko, T.; Frick, W.; Bui, T.; Dellacherie, S.; Klein, R.; Roe, Ph.; Accary, G.; Braack, M.; Picano, F.; Cadiou, A.; Dinescu, C.; Lesage, A.C.; Wesseling, P.; Heuveline, V.; Jobelin, M.; Weisman, C.; Merkle, C.
2004-07-01
Low Mach number flows represent a significant part of the various flows encountered in geophysics, industry or every day life. Paradoxically, the mathematical analysis of the equations governing these flows is difficult and on the practical side, the research of numerical algorithms valid for all flow speeds is continuing to be a challenge. However, in the last decade, both from the theoretical and the numerical sides, significant progresses were made in the understanding and analysis of the equations governing these flows. This conference intends to provide an up-to-date inventory of recent mathematical and numerical results in the analysis of these flows by bringing together both mathematicians and numericists active in this area. In the framework of the conference, a numerical workshop is organized which proposes to compute several challenging low Mach number flows: liquid flow around non-cavitating and cavitating NACA0015 hydrofoil, natural convection with large temperature differences, free convection, free surface flow, vessel pressurization. This document brings together the descriptions of the test cases of the numerical workshop and the abstracts of the conference papers: A 3D high order finite volume method for the prediction of near-critical fluid flows (G. ACCARY, I. RASPO, P. BONTOUX, B. ZAPPOLI); low Mach number limit of the non-isentropic Navier-Stokes equations (T. ALAZARD); simulation of cavitation rolls past a forward step with a bubble model (O. ALLAIN, N. BLASKA, C. LECA); flux preconditioning methods and fire events (P. BIRKEN, A. MEISTER); an adaptive finite element solver for compressible flows: application to heat-driven cavity benchmarks in 2D and 3D (M. BRAACK); comparison of various implicit, explicit, centered and upwind schemes for the simulation of compressed flows on moving mesh (A. CADIOU, M. BUFFAT, L. Le PENVEN, C. Le RIBAULT); low Mach number limit for viscous compressible flows (R. DANCHIN); some Properties of the low Mach number
Mathematical and numerical aspects of low mach number flows
Energy Technology Data Exchange (ETDEWEB)
Schochet, St.; Bresch, D.; Grenier, E.; Alazard, T.; Gordner, A.; Sankaran, V.; Massot, M.; Sery, R.; Pebay, P.; Lunch, O.; Mazhorova, O.; Turkel, O.E.; Faille, I.; Danchin, R.; Allain, O.; Birken, P.; Lafitte, O.; Kloczko, T.; Frick, W.; Bui, T.; Dellacherie, S.; Klein, R.; Roe, Ph.; Accary, G.; Braack, M.; Picano, F.; Cadiou, A.; Dinescu, C.; Lesage, A.C.; Wesseling, P.; Heuveline, V.; Jobelin, M.; Weisman, C.; Merkle, C.
2004-07-01
Low Mach number flows represent a significant part of the various flows encountered in geophysics, industry or every day life. Paradoxically, the mathematical analysis of the equations governing these flows is difficult and on the practical side, the research of numerical algorithms valid for all flow speeds is continuing to be a challenge. However, in the last decade, both from the theoretical and the numerical sides, significant progresses were made in the understanding and analysis of the equations governing these flows. This conference intends to provide an up-to-date inventory of recent mathematical and numerical results in the analysis of these flows by bringing together both mathematicians and numericists active in this area. In the framework of the conference, a numerical workshop is organized which proposes to compute several challenging low Mach number flows: liquid flow around non-cavitating and cavitating NACA0015 hydrofoil, natural convection with large temperature differences, free convection, free surface flow, vessel pressurization. This document brings together the descriptions of the test cases of the numerical workshop and the abstracts of the conference papers: A 3D high order finite volume method for the prediction of near-critical fluid flows (G. ACCARY, I. RASPO, P. BONTOUX, B. ZAPPOLI); low Mach number limit of the non-isentropic Navier-Stokes equations (T. ALAZARD); simulation of cavitation rolls past a forward step with a bubble model (O. ALLAIN, N. BLASKA, C. LECA); flux preconditioning methods and fire events (P. BIRKEN, A. MEISTER); an adaptive finite element solver for compressible flows: application to heat-driven cavity benchmarks in 2D and 3D (M. BRAACK); comparison of various implicit, explicit, centered and upwind schemes for the simulation of compressed flows on moving mesh (A. CADIOU, M. BUFFAT, L. Le PENVEN, C. Le RIBAULT); low Mach number limit for viscous compressible flows (R. DANCHIN); some Properties of the low Mach number
Low Mach Number Fluctuating Hydrodynamics of Multispecies Liquid Mixtures
Donev, A; Bhattacharjee, A K; Garcia, A L; Bell, J B
2014-01-01
We develop a low Mach number formulation of the hydrodynamic equations describing transport of mass and momentum in a multispecies mixture of incompressible miscible liquids at specified temperature and pressure that generalizes our prior work on ideal mixtures of ideal gases and binary liquid mixtures. In this formulation we combine and extend a number of existing descriptions of multispecies transport available in the literature. The formulation applies to non-ideal mixtures of arbitrary number of species, without the need to single out a 'solvent' species, and includes contributions to the diffusive mass flux due to gradients of composition, temperature and pressure. Momentum transport and advective mass transport are handled using a low Mach number approach that eliminates fast sound waves (pressure fluctuations) from the full compressible system of equations and leads to a quasi-incompressible formulation. Thermal fluctuations are included in our fluctuating hydrodynamics description following the princi...
Statistical error in particle simulations of low mach number flows
Energy Technology Data Exchange (ETDEWEB)
Hadjiconstantinou, N G; Garcia, A L
2000-11-13
We present predictions for the statistical error due to finite sampling in the presence of thermal fluctuations in molecular simulation algorithms. The expressions are derived using equilibrium statistical mechanics. The results show that the number of samples needed to adequately resolve the flowfield scales as the inverse square of the Mach number. Agreement of the theory with direct Monte Carlo simulations shows that the use of equilibrium theory is justified.
Low Mach Number Fluctuating Hydrodynamics of Binary Liquid Mixtures
Nonaka, A J; Bell, J B; Donev, A
2014-01-01
Continuing on our previous work [ArXiv:1212.2644], we develop semi-implicit numerical methods for solving low Mach number fluctuating hydrodynamic equations appropriate for modeling diffusive mixing in isothermal mixtures of fluids with different densities and transport coefficients. We treat viscous dissipation implicitly using a recently-developed variable-coefficient Stokes solver [ArXiv:1308.4605]. This allows us to increase the time step size significantly compared to the earlier explicit temporal integrator. For viscous-dominated flows, such as flows at small scales, we develop a scheme for integrating the overdamped limit of the low Mach equations, in which inertia vanishes and the fluid motion can be described by a steady Stokes equation. We also describe how to incorporate advanced higher-order Godunov advection schemes in the numerical method, allowing for the treatment of fluids with high Schmidt number including the vanishing mass diffusion coefficient limit. We incorporate thermal fluctuations in...
Henneberry, Hugh M.; Snyder, Christopher A.
1993-01-01
An analysis of gas turbine engines using water and oxygen injection to enhance performance by increasing Mach number capability and by increasing thrust is described. The liquids are injected, either separately or together, into the subsonic diffuser ahead of the engine compressor. A turbojet engine and a mixed-flow turbofan engine (MFTF) are examined, and in pursuit of maximum thrust, both engines are fitted with afterburners. The results indicate that water injection alone can extend the performance envelope of both engine types by one and one-half Mach numbers at which point water-air ratios reach 17 or 18 percent and liquid specific impulse is reduced to some 390 to 470 seconds, a level about equal to the impulse of a high energy rocket engine. The envelope can be further extended, but only with increasing sacrifices in liquid specific impulse. Oxygen-airflow ratios as high as 15 percent were investigated for increasing thrust. Using 15 percent oxygen in combination with water injection at high supersonic Mach numbers resulted in thrust augmentation as high as 76 percent without any significant decrease in liquid specific impulse. The stoichiometric afterburner exit temperature increased with increasing oxygen flow, reaching 4822 deg R in the turbojet engine at a Mach number of 3.5. At the transonic Mach number of 0.95 where no water injection is needed, an oxygen-air ratio of 15 percent increased thrust by some 55 percent in both engines, along with a decrease in liquid specific impulse of 62 percent. Afterburner temperature was approximately 4700 deg R at this high thrust condition. Water and/or oxygen injection are simple and straightforward strategies to improve engine performance and they will add little to engine weight. However, if large Mach number and thrust increases are required, liquid flows become significant, so that operation at these conditions will necessarily be of short duration.
Courant Number and Mach Number Insensitive CE/SE Euler Solvers
Chang, Sin-Chung
2005-01-01
It has been known that the space-time CE/SE method can be used to obtain ID, 2D, and 3D steady and unsteady flow solutions with Mach numbers ranging from 0.0028 to 10. However, it is also known that a CE/SE solution may become overly dissipative when the Mach number is very small. As an initial attempt to remedy this weakness, new 1D Courant number and Mach number insensitive CE/SE Euler solvers are developed using several key concepts underlying the recent successful development of Courant number insensitive CE/SE schemes. Numerical results indicate that the new solvers are capable of resolving crisply a contact discontinuity embedded in a flow with the maximum Mach number = 0.01.
Hysteresis phenomenon of hypersonic inlet at high Mach number
Jiao, Xiaoliang; Chang, Juntao; Wang, Zhongqi; Yu, Daren
2016-11-01
When the hypersonic inlet works at a Mach number higher than the design value, the hypersonic inlet is started with a regular reflection of the external compression shock at the cowl, whereas a Mach reflection will result in the shock propagating forwards to cause a shock detachment at the cowl lip, which is called "local unstart of inlet". As there are two operation modes of hypersonic inlet at high Mach number, the mode transition may occur with the operation condition of hypersonic inlet changing. A cowl-angle-variation-induced hysteresis and a downstream-pressure-variation-induced hysteresis in the hypersonic inlet start↔local unstart transition are obtained by viscous numerical simulations in this paper. The interaction of the external compression shock and boundary layer on the cowl plays a key role in the hysteresis phenomenon. Affected by the transition of external compression shock reflection at the cowl and the transition between separated and attached flow on the cowl, a hysteresis exists in the hypersonic inlet start↔local unstart transition. The hysteresis makes the operation of a hypersonic inlet very difficult to control. In order to avoid hysteresis phenomenon and keep the hypersonic inlet operating in a started mode, the control route should never pass through the local unstarted boundary.
Low Mach number fluctuating hydrodynamics of multispecies liquid mixtures
Energy Technology Data Exchange (ETDEWEB)
Donev, Aleksandar, E-mail: donev@courant.nyu.edu; Bhattacharjee, Amit Kumar [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Nonaka, Andy; Bell, John B. [Center for Computational Science and Engineering, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Garcia, Alejandro L. [Department of Physics and Astronomy, San Jose State University, San Jose, California 95192 (United States)
2015-03-15
We develop a low Mach number formulation of the hydrodynamic equations describing transport of mass and momentum in a multispecies mixture of incompressible miscible liquids at specified temperature and pressure, which generalizes our prior work on ideal mixtures of ideal gases [Balakrishnan et al., “Fluctuating hydrodynamics of multispecies nonreactive mixtures,” Phys. Rev. E 89 013017 (2014)] and binary liquid mixtures [Donev et al., “Low mach number fluctuating hydrodynamics of diffusively mixing fluids,” Commun. Appl. Math. Comput. Sci. 9(1), 47-105 (2014)]. In this formulation, we combine and extend a number of existing descriptions of multispecies transport available in the literature. The formulation applies to non-ideal mixtures of arbitrary number of species, without the need to single out a “solvent” species, and includes contributions to the diffusive mass flux due to gradients of composition, temperature, and pressure. Momentum transport and advective mass transport are handled using a low Mach number approach that eliminates fast sound waves (pressure fluctuations) from the full compressible system of equations and leads to a quasi-incompressible formulation. Thermal fluctuations are included in our fluctuating hydrodynamics description following the principles of nonequilibrium thermodynamics. We extend the semi-implicit staggered-grid finite-volume numerical method developed in our prior work on binary liquid mixtures [Nonaka et al., “Low mach number fluctuating hydrodynamics of binary liquid mixtures,” http://arxiv.org/abs/1410.2300 (2015)] and use it to study the development of giant nonequilibrium concentration fluctuations in a ternary mixture subjected to a steady concentration gradient. We also numerically study the development of diffusion-driven gravitational instabilities in a ternary mixture and compare our numerical results to recent experimental measurements [Carballido-Landeira et al., “Mixed-mode instability of a
DSMC Simulation of High Mach Number Taylor-Couette Flow
Pradhan, Sahadev, , Dr.
2017-01-01
The main focus of this work is to characterise the Taylor-Couette flow of an ideal gas between two coaxial cylinders at Mach number Ma = (U_w /√{ kbT_w / m }) in the range 0.01 Boltzmann constant. The cylindrical surfaces are specified as being diffusely reflecting with the thermal accommodation coefficient equal to one. In the present analysis of high Mach number compressible Taylor-Couette flow using DSMC method, wall slip in the temperature and the velocities are found to be significant. Slip occurs because the temperature/velocity of the molecules incident on the wall could be very different from that of the wall, even though the temperature/velocity of the reflected molecules is equal to that of the wall. Due to the high surface speed of the inner cylinder, significant heating of the gas is taking place. The gas temperature increases until the heat transfer to the surface equals the work done in moving the surface. The highest temperature is obtained near the moving surface of the inner cylinder at a radius of about (1.26 r_1).
Subsonic loads on wings having sharp leading edges and tips
Kandil, O. A.; Mook, D. T.; Nayfeh, A. H.
1976-01-01
A vortex-lattice method for predicting the aerodynamics of wings having separation at the sharp edges in incompressible flows is extended to compressible subsonic flows using a modified Prandtl-Glauert transformation. Numerical results showing the effect of freestream Mach number on the aerodynamic coefficients are compared with available experimental data for several planforms. It is shown that the proposed method is suitable for predicting the aerodynamic loads on low-aspect wings at moderate angles of attack for high subsonic freestream Mach number. The method is limited to angles of attack up to 12 deg for high subsonic freestream Mach number and to angles of attack up to 20 deg for Mach number not exceeding 0.5.
The Variation of Slat Noise with Mach and Reynolds Numbers
Lockhard, David P.; Choudhari, Meelan M.
2011-01-01
The slat noise from the 30P30N high-lift system has been computed using a computational fluid dynamics code in conjunction with a Ffowcs Williams-Hawkings solver. By varying the Mach number from 0.13 to 0.25, the noise was found to vary roughly with the 5th power of the speed. Slight changes in the behavior with directivity angle could easily account for the different speed dependencies reported in the literature. Varying the Reynolds number from 1.4 to 2.4 million resulted in almost no differences, and primarily served to demonstrate the repeatability of the results. However, changing the underlying hybrid Reynolds-averaged-Navier-Stokes/Large-Eddy-Simulation turbulence model significantly altered the mean flow because of changes in the flap separation. However, the general trends observed in both the acoustics and near-field fluctuations were similar for both models.
Low Mach number theory of freely cooling granular gases
Meerson, Baruch; Vilenkin, Arkady
2007-01-01
We use hydrodynamic equations to investigate the dynamics of a freely cooling dilute granular gas with nearly elastic particle collisions. We assume a narrow channel geometry and focus on the regime where the sound travel time through the system is much shorter than the typical cooling time of the gas. As a result, the pressure rapidly becomes almost homogeneous, while the Mach number is small. Eliminating the sound waves and employing Lagrangian coordinates, we reduce the full hydrodynamics to a single nonlinear/nonlocal equation of a reaction-diffusion type. This equation describes a broad class of flows and, in particular, can follow the development of strongly nonlinear states during clustering instability. Without heat diffusion, the reduced equation is exactly soluble and develops a finite-time density blowup with the same local features as those exhibited by the recently found family of exact solutions of the full set of ideal hydrodynamic equations (Fouxon et al. 2007). The heat diffusion, however, ar...
Turbomachinery for Low-to-High Mach Number Flight
Tan, Choon S.; Shah, Parthiv N.
2004-01-01
The thrust capability of turbojet cycles is reduced at high flight Mach number (3+) by the increase in inlet stagnation temperature. The 'hot section' temperature limit imposed by materials technology sets the maximum heat addition and, hence, sets the maximum flight Mach number of the operating envelope. Compressor pre-cooling, either via a heat exchanger or mass-injection, has been suggested as a means to reduce compressor inlet temperature and increase mass flow capability, thereby increasing thrust. To date, however, no research has looked at compressor cooling (i.e., using a compressor both to perform work on the gas path air and extract heat from it simultaneously). We wish to assess the feasibility of this novel concept for use in low-to-high Mach number flight. The results to-date show that an axial compressor with cooling: (1) relieves choking in rear stages (hence opening up operability), (2) yields higher-pressure ratio and (3) yields higher efficiency for a given corrected speed and mass flow. The performance benefit is driven: (i) at the blade passage level, by a decrease in the total pressure reduction coefficient and an increase in the flow turning; and (ii) by the reduction in temperature that results in less work required for a given pressure ratio. The latter is a thermodynamic effect. As an example, calculations were performed for an eight-stage compressor with an adiabatic design pressure ratio of 5. By defining non-dimensional cooling as the percentage of compressor inlet stagnation enthalpy removed by a heat sink, the model shows that a non-dimensional cooling of percent in each blade row of the first two stages can increase the compressor pressure ratio by as much as 10-20 percent. Maximum corrected mass flow at a given corrected speed may increase by as much as 5 percent. In addition, efficiency may increase by as much as 5 points. A framework for characterizing and generating the performance map for a cooled compressor has been developed
Rescaling of the Roe scheme in low Mach-number flow regions
Boniface, Jean-Christophe
2017-01-01
A rescaled matrix-valued dissipation is reformulated for the Roe scheme in low Mach-number flow regions from a well known family of local low-speed preconditioners popularized by Turkel. The rescaling is obtained explicitly by suppressing the pre-multiplication of the preconditioner with the time derivative and by deriving the full set of eigenspaces of the Roe-Turkel matrix dissipation. This formulation preserves the time consistency and does not require to reformulate the boundary conditions based on the characteristic theory. The dissipation matrix achieves by construction the proper scaling in low-speed flow regions and returns the original Roe scheme at the sonic line. We find that all eigenvalues are nonnegative in the subsonic regime. However, it becomes necessary to formulate a stringent stability condition to the explicit scheme in the low-speed flow regions based on the spectral radius of the rescaled matrix dissipation. With the large disparity of the eigenvalues in the dissipation matrix, this formulation raises a two-timescale problem for the acoustic waves, which is circumvented for a steady-state iterative procedure by the development of a robust implicit characteristic matrix time-stepping scheme. The behaviour of the modified eigenvalues in the incompressible limit and at the sonic line also suggests applying the entropy correction carefully, especially for complex non-linear flows.
Edge, cavity and aperture tones at very low Mach numbers
Howe, M. S.
1997-01-01
This paper discusses self-sustaining oscillations of high-Reynolds-number shear layers and jets incident on edges and corners at infinitesimal Mach number. These oscillations are frequently sources of narrow-band sound, and are usually attributed to the formation of discrete vortices whose interactions with the edge or corner produce impulsive pressures that lead to the formation of new vorticity and complete a feedback cycle of operation. Linearized analyses of these interactions are presented in which free shear layers are modelled by vortex sheets. Detailed results are given for shear flows over rectangular wall apertures and shallow cavities, and for the classical jet edge interaction. The operating stages of self-sustained oscillations are identified with poles in the upper half of the complex frequency plane of a certain impulse response function. It is argued that the real parts of these poles determine the Strouhal numbers of the operating stages observed experimentally for the real, nonlinear system. The response function coincides with the Rayleigh conductivity of the ‘window’ spanned by the shear flow for wall apertures and jet edge interactions, and to a frequency dependent drag coefficient for shallow wall cavities. When the interaction occurs in the neighbourhood of an acoustic resonator, exemplified by the flue organ pipe, the poles are augmented by a sequence of poles whose real parts are close to the resonance frequencies of the resonator, and the resonator can ‘speak’ at one of these frequencies (by extracting energy from the mean flow) provided the corresponding pole has positive imaginary part.
DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number
Pradhan, Sahadev, , Dr.
2017-01-01
The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf /√{kBTinf / m }) in the range Boltzmann constant. The variation of streamwise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the streamwise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the streamwise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the streamwise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain.
Variation with Mach Number of Static and Total Pressures Through Various Screens
Adler, Alfred A
1946-01-01
Tests were conducted in the Langley 24-inch highspeed tunnel to ascertain the static-pressure and total-pressure losses through screens ranging in mesh from 3 to 12 wires per inch and in wire diameter from 0.023 to 0.041 inch. Data were obtained from a Mach number of approximately 0.20 up to the maximum (choking) Mach number obtainable for each screen. The results of this investigation indicate that the pressure losses increase with increasing Mach number until the choking Mach number, which can be computed, is reached. Since choking imposes a restriction on the mass rate of flow and maximum losses are incurred at this condition, great care must be taken in selecting the screen mesh and wire dimmeter for an installation so that the choking Mach number is
A Device for Measuring Sonic Velocity and Compressor Mach Number
1948-07-01
resonator (the only 4 NACA TN No. 1664 accurate measurement required) is measured, as shomn in figure 1, by means of a mercury manometer . The compressor Mach...tube vs not connected to the ccmpressor inlet until after calibration. The pressure in the device was measured by means of the mercury manometer . Fram
Numerical Simulation of Low Mach Number Fluid - Phenomena.
Reitsma, Scott H.
A method for the numerical simulation of low Mach number (M) fluid-acoustic phenomena is developed. This computational fluid-acoustic (CFA) methodology is based upon a set of conservation equations, termed finite-compressible, derived from the unsteady Navier-Stokes equations. The finite-compressible and more familiar pseudo-compressible equations are compared. The impact of derivation assumptions are examined theoretically and through numerical experimentation. The error associated with these simplifications is shown to be of O(M) and proportional to the amplitude of unsteady phenomena. A computer code for the solution of the finite -compressible equations is developed from an existing pseudo -compressible code. Spatial and temporal discretization issues relevant in the context of near field fluid-acoustic simulations are discussed. The finite volume code employs a MUSCL based third order upwind biased flux difference splitting algorithm for the convective terms. An explicit, three stage, second order Runge-Kutta temporal integration is employed for time accurate simulations while an implicit, approximately factored time quadrature is available for steady state convergence acceleration. The CFA methodology is tested in a series of problems which examine the appropriateness of the governing equations, the exacerbation of spatial truncation errors and the degree of temporal accuracy. Characteristic based boundary conditions employing a spatial formulation are developed. An original non-reflective boundary condition based upon the generalization and extension of existing methods is derived and tested in a series of multi-dimensional problems including those involving viscous shear flows and propagating waves. The final numerical experiment is the simulation of boundary layer receptivity to acoustic disturbances. This represents the first simulation of receptivity at a surface inhomogeneity in which the acoustic phenomena is modeled using physically appropriate
Effect of Riblets upon Flow Separation in a Subsonic Diffuser
1988-12-01
Technology Air University In Partial Fulfillment of the Requirements for the Degree of Master of Science in Aeronautical Engineering Nathan W. Martens...afterburner where the flow leaving the turbine must be 4 slowed from a high subsonic Mach number to a Mach number of about 0.2" (8:305). Physicall ., a...Riblets," Proceedings of the AIAA 20th Aerospace Sciences Meeting. Paper No. 82-0169. New York: American Institute of Aeronautics and Astronautics
Multiobjective Design Optimization of Supersonic Jet Engine in Different Cruise Mach Numbers
Ogawa, Masamichi; Sato, Tetsuya; Kobayashi, Hiroaki; Taguchi, Hideyuki
The aim of this paper is to apply a multi-objective optimization generic algorithm (MOGA) to the conceptual design of the hypersonic/supersonic vehicles with different cruise Mach number. The pre-cooled turbojet engine is employed as a propulsion system and some engine parameters such as the precooler size, compressor size, compression ratio and fuel type are varied in the analysis. The result shows that the optimum cruise Mach number is about 4 if hydrogen fuel is used. Methane fuel instead of hydrogen reduces the vehicle gross weight by 33% in case of the Mach 2 vehicle.
Turbulent mixing of a slightly supercritical Van der Waals fluid at Low-Mach number
Battista, Francesco; Casciola, Carlo Massimo
2014-01-01
Supercritical fluids near the critical point are characterized by liquid-like densities and gas-like transport properties. These features are purposely exploited in different contexts ranging from natural products extraction/fractionation to aerospace propulsion. Large part of studies concerns this last context, focusing on the dynamics of supercritical fluids at high Mach number where compressibility and thermodynamics strictly interact. Despite the widespread use also at low Mach number, the turbulent mixing properties of slightly supercritical fluids have still not investigated in detail in this regime. This topic is addressed here by dealing with Direct Numerical Simulations (DNS) of a coaxial jet of a slightly supercritical Van der Waals fluid. Since acoustic effects are irrelevant in the Low Mach number conditions found in many industrial applications, the numerical model is based on a suitable low-Mach number expansion of the governing equation. According to experimental observations, the weakly superc...
Le, G.; Russell, C. T.; Gosling, J. T.
1994-12-01
We use International Sun-Earth Explorer (ISEE) magnetic field and plasma data to examine dayside magnetopause crossing under conditions of low Mach number and strongly northward interplanetary magnetic field (IMF). When the solar wind Mach number is low, the IMF stregth and magnetoseath field stregth are large, and we expect the effects of magnetic reconection to be the strongest. When the IMF is strongly northward, we find that the location of the magnetopause boundary layer is very stationary in the space, and we observe many features that are common for both typical and low Mach numbers. However, under low Mach number conditions, we have observed some features that would be expected for cusp reconnection. The boundary layer near the subsolar region contains heated magnetosheath plasma with little hot magnetospheric component that has clearly entered the magnetosphere elsewhere. At least some of the structures present in the boundary layer are impulsive. Inside the boundary layer there is also clear evidence of acceleratedflow from the cusp region for strongly northward IMF at low Mach number. Reconnection beyond the cusp can explain the observed field, plasma, and flow signatures. Therefore at low Mach number, reconection is important in the formation of the boundary layer for northward IMF.
Note: A high Mach number arc-driven shock tube for turbulence studies.
Titus, J B; Alexander, A B; Johnson, J A
2013-04-01
A high Mach arc-driven shock tube has been built at the Center for Plasma Science and Technology of Florida A&M University to study shock waves. A larger apparatus with higher voltage was built to study more stable shock waves and subsequent plasmas. Initial measurements of the apparatus conclude that the desired Mach numbers can be reached using only two-thirds the maximum possible energy that the circuit can provide.
Effect of Mach number on the efficiency of microwave energy deposition in supersonic flow
Lashkov, V. A.; Karpenko, A. G.; Khoronzhuk, R. S.; Mashek, I. Ch.
2016-05-01
The article is devoted to experimental and numerical studies of the efficiency of microwave energy deposition into a supersonic flow around the blunt cylinder at different Mach numbers. Identical conditions for energy deposition have been kept in the experiments, thus allowing to evaluate the pure effect of varying Mach number on the pressure drop. Euler equations are solved numerically to model the corresponding unsteady flow compressed gas. The results of numerical simulations are compared to the data obtained from the physical experiments. It is shown that the momentum, which the body receives during interaction of the gas domain modified by microwave discharge with a shock layer before the body, increases almost linearly with rising of Mach number and the efficiency of energy deposition also rises.
Energy Technology Data Exchange (ETDEWEB)
Dellacherie, St
2004-07-01
This work deals with the derivation of a diphasic low Mach number model obtained through a Mach number asymptotic expansion applied to the compressible diphasic Navier Stokes system, expansion which filters out the acoustic waves. This approach is inspired from the work of Andrew Majda giving the equations of low Mach number combustion for thin flame and for perfect gases. When the equations of state verify some thermodynamic hypothesis, we show that the low Mach number diphasic system predicts in a good way the dilatation or the compression of a bubble and has equilibrium convergence properties. Then, we propose an entropic and convergent Lagrangian scheme in mono-dimensional geometry when the fluids are perfect gases and we propose a first approach in Eulerian variables where the interface between the two fluids is captured with a level set technique. (author)
Sundkvist, David; Krasnoselskikh, V; Bale, S D; Schwartz, S J; Soucek, J; Mozer, F
2012-01-13
Whistler wave trains are observed in the foot region of high Mach number quasiperpendicular shocks. The waves are oblique with respect to the ambient magnetic field as well as the shock normal. The Poynting flux of the waves is directed upstream in the shock normal frame starting from the ramp of the shock. This suggests that the waves are an integral part of the shock structure with the dispersive shock as the source of the waves. These observations lead to the conclusion that the shock ramp structure of supercritical high Mach number shocks is formed as a balance of dispersion and nonlinearity.
Moore, P.D.
2009-01-01
Jet noise is an extensively studied phenomenon since the deployment of the first civil jet aircraft more than 50 years ago. Jet noise makes up a considerable portion of the total noise of jet aircraft, and the expansion of the numbers of airplanes and airports has only been possible by keeping the
Tanaka, Kento; Watanabe, Tomoaki; Nagata, Koji; Sasoh, Akihiro; Sakai, Yasuhiko; Hayase, Toshiyuki; Nagoya Univ Collaboration
2016-11-01
The interaction between homogeneous isotropic turbulence and normal shock wave is investigated by direct numerical simulations (DNSs). In the DNSs, a normal shock wave with a shock Mach number 1.1 passes through homogeneous isotropic turbulence with a low turbulent Mach number and a moderate turbulent Reynolds number. The statistics are calculated conditioned on the distance from the shock wave. The results showed that the shock wave makes length scales related to turbulence small. This effect is significant for the Taylor microscale defined with the velocity derivative orthogonal to the shock wave. The decrease in the Kolmogorov scale is also found. Statistics of velocity derivative are found to be changed by the shock wave propagation. The shock wave causes enstrophy amplification due to the dilatation/vorticity interaction. By this interaction, the vorticity components parallel to the shock wave is more amplified than the normal component. The strain rate is also amplified by the shock wave.
Mach number scaling of helicopter rotor blade/vortex interaction noise
Leighton, Kenneth P.; Harris, Wesley L.
1985-01-01
A parametric study of model helicopter rotor blade slap due to blade vortex interaction (BVI) was conducted in a 5 by 7.5-foot anechoic wind tunnel using model helicopter rotors with two, three, and four blades. The results were compared with a previously developed Mach number scaling theory. Three- and four-bladed rotor configurations were found to show very good agreement with the Mach number to the sixth power law for all conditions tested. A reduction of conditions for which BVI blade slap is detected was observed for three-bladed rotors when compared to the two-bladed baseline. The advance ratio boundaries of the four-bladed rotor exhibited an angular dependence not present for the two-bladed configuration. The upper limits for the advance ratio boundaries of the four-bladed rotors increased with increasing rotational speed.
Two-dimensional lattice Boltzmann model for compressible flows with high Mach number
Gan, Yanbiao; Xu, Aiguo; Zhang, Guangcai; Yu, Xijun; Li, Yingjun
2008-03-01
In this paper we present an improved lattice Boltzmann model for compressible Navier-Stokes system with high Mach number. The model is composed of three components: (i) the discrete-velocity-model by M. Watari and M. Tsutahara [Phys. Rev. E 67 (2003) 036306], (ii) a modified Lax-Wendroff finite difference scheme where reasonable dissipation and dispersion are naturally included, (iii) artificial viscosity. The improved model is convenient to compromise the high accuracy and stability. The included dispersion term can effectively reduce the numerical oscillation at discontinuity. The added artificial viscosity helps the scheme to satisfy the von Neumann stability condition. Shock tubes and shock reflections are used to validate the new scheme. In our numerical tests the Mach numbers are successfully increased up to 20 or higher. The flexibility of the new model makes it suitable for tracking shock waves with high accuracy and for investigating nonlinear nonequilibrium complex systems.
Flow-induced cylinder noise formulated as a diffraction problem for low Mach numbers
Gloerfelt, X.; Pérot, F.; Bailly, C.; Juvé, D.
2005-10-01
The role of surfaces in the mechanism of sound generation by low Mach number flows interacting with solid nonvibrating surfaces is well established by the classical aeroacoustic papers by Powell, Doak, Ffowcs Williams, Crighton, or Howe. It can be formulated as a problem of diffraction of the flow sources by the rigid body. The present study illustrates this statement in the case of flow-induced cylinder noise. Curle's formulation is analytically and numerically compared to a formulation based on an exact Green's function tailored to a cylindrical geometry. The surface integral of Curle's formulation represents exactly the diffraction effects by the rigid body. The direct and scattered parts of the sound field are studied. In this low Mach number configuration, the cylinder is compact, and the scattered (dipole) field dominates the direct (quadrupole) field. The classical properties of the scattering by a cylinder are retrieved by considering a point quadripole source near the cylinder surface.
Extension of the pressure correction method to zero-Mach number compressible flows
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
In the present paper,the classical pressure correction method was extended into low Mach number compressible flow regime by integrating equation of state into SIMPLE algorithm.The self-developed code based on this algorithm was applied to predicting the lid-driven cavity flow and shock tube prob-lems,and the results showed good agreement with benchmark solutions and the Mach number can reach the magnitude of as low as 10-5.The attenuation of sound waves in viscous medium was then simulated.The results agree well with the analytical solutions given by theoretical acoustics.This demonstrated that the present method could also be implemented in acoustics field simulation,which is crucial for thermoacoustic simulation.
The Density Variance--Mach Number Relation in Supersonic Turbulence: I. Isothermal, magnetised gas
Molina, F Z; Federrath, C; Klessen, R S
2012-01-01
It is widely accepted that supersonic, magnetised turbulence plays a fundamental role for star formation in molecular clouds. It produces the initial dense gas seeds out of which new stars can form. However, the exact relation between gas compression, turbulent Mach number, and magnetic field strength is still poorly understood. Here, we introduce and test an analytical prediction for the relation between the density variance and the root-mean-square Mach number in supersonic, isothermal, magnetised turbulent flows. We approximate the density and velocity structure of the interstellar medium as a superposition of shock waves. We obtain the density contrast considering the momentum continuity equation for a single magnetised shock and extrapolate this result to the entire cloud. Depending on the field geometry, we then make three different assumptions based on observational and theoretical constraints: B independent of density, B proportional to the root square of the density and B proportional to the density....
Extension of the pressure correction method to zero-Mach number compressible flows
Institute of Scientific and Technical Information of China (English)
HE YaLing; HUANG Jing; TAO YuBing; TAO WenQuan
2009-01-01
In the present paper, the classical pressure correction method was extended into low Mach number compressible flow regime by integrating equation of state into SIMPLE algorithm. The self-developed code based on this algorithm was applied to predicting the lid-driven cavity flow and shock tube prob-lems, and the results showed good agreement with benchmark solutions and the Mach number can reach the magnitude of as low as 10-5. The attenuation of sound waves in viscous medium was then simulated. The results agree well with the analytical solutions given by theoretical acoustics. This demonstrated that the present method could also be implemented in acoustics field simulation, which is crucial for thermoacoustic simulation.
Axisymmetric vortex method for low-Mach number, diffusion-controlled combustion
Lakkis, I
2003-01-01
A grid-free, Lagrangian method for the accurate simulation of low-Mach number, variable-density, diffusion-controlled reacting flow is presented. A fast-chemistry model in which the conversion rate of reactants to products is limited by the local mixing rate is assumed in order to reduce the combustion problem to the solution of a convection-diffusion-generation equation with volumetric expansion and vorticity generation at the reaction fronts. The solutions of the continuity and vorticity equations, and the equations governing the transport of species and energy, are obtained using a formulation in which particles transport conserved quantities by convection and diffusion. The dynamic impact of exothermic combustion is captured through accurate integration of source terms in the vorticity transport equations at the location of the particles, and the extra velocity field associated with volumetric expansion at low Mach number computed to enforced mass conservation. The formulation is obtained for an axisymmet...
Low Mach and Peclet number limit for a model of stellar tachocline and upper radiative zones
Directory of Open Access Journals (Sweden)
Donatella Donatelli
2016-09-01
Full Text Available We study a hydrodynamical model describing the motion of internal stellar layers based on compressible Navier-Stokes-Fourier-Poisson system. We suppose that the medium is electrically charged, we include energy exchanges through radiative transfer and we assume that the system is rotating. We analyze the singular limit of this system when the Mach number, the Alfven number, the Peclet number and the Froude number approache zero in a certain way and prove convergence to a 3D incompressible MHD system with a stationary linear transport equation for transport of radiation intensity. Finally, we show that the energy equation reduces to a steady equation for the temperature corrector.
Nearfield Unsteady Pressures at Cruise Mach Numbers for a Model Scale Counter-Rotation Open Rotor
Stephens, David B.
2012-01-01
An open rotor experiment was conducted at cruise Mach numbers and the unsteady pressure in the nearfield was measured. The system included extensive performance measurements, which can help provide insight into the noise generating mechanisms in the absence of flow measurements. A set of data acquired at a constant blade pitch angle but various rotor speeds was examined. The tone levels generated by the front and rear rotor were found to be nearly equal when the thrust was evenly balanced between rotors.
Bispen, Georgij; Lukáčová-Medvid'ová, Mária; Yelash, Leonid
2017-04-01
In this paper we will present and analyze a new class of the IMEX finite volume schemes for the Euler equations with a gravity source term. We will in particular concentrate on a singular limit of weakly compressible flows when the Mach number M ≪ 1. In order to efficiently resolve slow dynamics we split the whole nonlinear system in a stiff linear part governing the acoustic and gravity waves and a non-stiff nonlinear part that models nonlinear advection effects. For time discretization we use a special class of the so-called globally stiffly accurate IMEX schemes and approximate the stiff linear operator implicitly and the non-stiff nonlinear operator explicitly. For spatial discretization the finite volume approximation is used with the central and Rusanov/Lax-Friedrichs numerical fluxes for the linear and nonlinear subsystem, respectively. In the case of a constant background potential temperature we prove theoretically that the method is asymptotically consistent and asymptotically stable uniformly with respect to small Mach number. We also analyze experimentally convergence rates in the singular limit when the Mach number tends to zero.
Particle-in-cell simulations of particle energization from low Mach number fast mode shocks
Park, Jaehong; Blackman, Eric G; Ren, Chuang; Siller, Robert
2012-01-01
Astrophysical shocks are often studied in the high Mach number limit but weakly compressive fast shocks can occur in magnetic reconnection outflows and are considered to be a site of particle energization in solar flares. Here we study the microphysics of such perpendicular, low Mach number collisionless shocks using two-dimensional particle-in-cell (PIC) simulations with a reduced ion/electron mass ratio and employ a moving wall boundary method for initial generation of the shock. This moving wall method allows for more control of the shock speed, smaller simulation box sizes, and longer simulation times than the commonly used fixed wall, reflection method of shock formation. Our results, which are independent of the shock formation method, reveal the prevalence shock drift acceleration (SDA) of both electron and ions in a purely perpendicular shock with Alfv\\'en Mach number $M_A=6.8$ and ratio of thermal to magnetic pressure $\\beta=8$. We determine the respective minimum energies required for electrons and ...
A half-explicit, non-split projection method for low Mach number flows.
Energy Technology Data Exchange (ETDEWEB)
Pousin, Jerome G. (National Institute for Applied Sciences, France); Najm, Habib N.; Pebay, Philippe Pierre
2004-02-01
In the context of the direct numerical simulation of low MACH number reacting flows, the aim of this article is to propose a new approach based on the integration of the original differential algebraic (DAE) system of governing equations, without further differentiation. In order to do so, while preserving a possibility of easy parallelization, it is proposed to use a one-step index 2 DAE time-integrator, the Half Explicit Method (HEM). In this context, we recall why the low MACH number approximation belongs to the class of index 2 DAEs and discuss why the pressure can be associated with the constraint. We then focus on a fourth-order HEM scheme, and provide a formulation that makes its implementation more convenient. Practical details about the consistency of initial conditions are discussed, prior to focusing on the implicit solve involved in the method. The method is then evaluated using the Modified KAPS Problem, since it has some of the features of the low MACH number approximation. Numerical results are presented, confirming the above expectations. A brief summary of ongoing efforts is finally provided.
The Dynamics of Very High Alfvén Mach Number Shocks in Space Plasmas
Sundberg, Torbjörn; Burgess, David; Scholer, Manfred; Masters, Adam; Sulaiman, Ali H.
2017-02-01
Astrophysical shocks, such as planetary bow shocks or supernova remnant shocks, are often in the high or very-high Mach number regime, and the structure of such shocks is crucial for understanding particle acceleration and plasma heating, as well inherently interesting. Recent magnetic field observations at Saturn’s bow shock, for Alfvén Mach numbers greater than about 25, have provided evidence for periodic non-stationarity, although the details of the ion- and electron-scale processes remain unclear due to limited plasma data. High-resolution, multi-spacecraft data are available for the terrestrial bow shock, but here the very high Mach number regime is only attained on extremely rare occasions. Here we present magnetic field and particle data from three such quasi-perpendicular shock crossings observed by the four-spacecraft Cluster mission. Although both ion reflection and the shock profile are modulated at the upstream ion gyroperiod timescale, the dominant wave growth in the foot takes place at sub-proton length scales and is consistent with being driven by the ion Weibel instability. The observed large-scale behavior depends strongly on cross-scale coupling between ion and electron processes, with ion reflection never fully suppressed, and this suggests a model of the shock dynamics that is in conflict with previous models of non-stationarity. Thus, the observations offer insight into the conditions prevalent in many inaccessible astrophysical environments, and provide important constraints for acceleration processes at such shocks.
Agarwal, Shankar
2013-01-01
We calculate the cosmic Mach number M - the ratio of the bulk flow of the velocity field on scale R to the velocity dispersion within regions of scale R. M is effectively a measure of the ratio of large-scale to small-scale power and can be a useful tool to constrain the cosmological parameter space. Using a compilation of existing peculiar velocity surveys, we calculate M and compare it to that estimated from mock catalogues extracted from the LasDamas (a LCDM cosmology) numerical simulations. We find agreement with expectations for the LasDamas cosmology at ~ 1.5 sigma CL. We also show that our Mach estimates for the mocks are not biased by selection function effects. To achieve this, we extract dense and nearly-isotropic distributions using Gaussian selection functions with the same width as the characteristic depth of the real surveys, and show that the Mach numbers estimated from the mocks are very similar to the values based on Gaussian profiles of the corresponding widths. We discuss the importance of ...
Dixon, G. V.; Barringer, S. R.; Gray, C. E.; Leatherman, A. D.
1975-01-01
Computer programs and resulting tabulations are presented of pipeline length-to-diameter ratios as a function of Mach number and pressure ratios for compressible flow. The tabulations are applicable to air, nitrogen, oxygen, and hydrogen for compressible isothermal flow with friction and compressible adiabatic flow with friction. Also included are equations for the determination of weight flow. The tabulations presented cover a wider range of Mach numbers for choked, adiabatic flow than available from commonly used engineering literature. Additional information presented, but which is not available from this literature, is unchoked, adiabatic flow over a wide range of Mach numbers, and choked and unchoked, isothermal flow for a wide range of Mach numbers.
The Experimental Measurement of Aerodynamic Heating About Complex Shapes at Supersonic Mach Numbers
Neumann, Richard D.; Freeman, Delma C.
2011-01-01
In 2008 a wind tunnel test program was implemented to update the experimental data available for predicting protuberance heating at supersonic Mach numbers. For this test the Langley Unitary Wind Tunnel was also used. The significant differences for this current test were the advances in the state-of-the-art in model design, fabrication techniques, instrumentation and data acquisition capabilities. This current paper provides a focused discussion of the results of an in depth analysis of unique measurements of recovery temperature obtained during the test.
Convective heat transport in stratified atmospheres at low and high Mach number
Anders, Evan H
2016-01-01
Convection in astrophysical systems is stratified and often occurs at high Rayleigh number (Ra) and low Mach number (Ma). Here we study stratified convection in the context of plane-parallel, polytropically stratified atmospheres. We hold the density stratification ($n_{\\rho}$) and Prandtl number (Pr) constant while varying Ma and Ra to determine the behavior of the Nusselt number (Nu), which quantifies the efficiency of convective heat transport. As Ra increases and $\\text{Ma} \\rightarrow 1$, a scaling of Nu $\\propto$ Ra$^{0.45}$ is observed. As Ra increases to a regime where Ma $\\geq 1$, this scaling gives way to a weaker Nu $\\propto$ Ra$^{0.19}$. In the regime of Ma $\\ll 1$, a consistent Nu $\\propto$ Ra$^{0.31}$ is retrieved, reminiscent of the Nu $\\propto$ Ra$^{2/7}$ seen in Rayleigh-B\\'{e}nard convection.
Effects of nonuniform Mach-number entrance on scramjet nozzle flowfield and performance
Zhang, Pu; Xu, Jinglei; Quan, Zhibin; Mo, Jianwei
2016-12-01
Considering the non-uniformities of nozzle entrance influenced by the upstream, the effects of nonuniform Mach-number coupled with shock and expansion-wave on the flowfield and performances of single expansion ramp nozzle (SERN) are numerically studied using Reynolds-Averaged Navier-Stokes equations. The adopted Reynolds-averaged Navier-Stokes methodology is validated by comparing the numerical results with the cold experimental data, and the average method used in this paper is discussed. Uniform and nonuniform facility nozzles are designed to generate different Mach-number profile for the inlet of SERN, which is direct-connected with different facility nozzle, and the whole flowfield is simulated. Because of the coupling of shock and expansion-wave, flow direction of nonuniform SERN entrance is distorted. Compared with Mach contour of uniform case, the line is more curved for coupling shock-wave entrance (SWE) case, and flatter for the coupling expansion-wave entrance (EWE) case. Wall pressure distribution of SWE case appears rising region, whereas decreases like stairs of EWE case. The numerical results reveal that the coupled shock and expansion-wave play significant roles on nozzle performances. Compared with the SERN performances of uniform entrance case at the same work conditions, the thrust of nonuniform entrance cases reduces by 3-6%, pitch moment decreases by 2.5-7%. The negative lift presents an incremental trend with EWE while the situation is the opposite with SWE. These results confirm that considering the entrance flow parameter nonuniformities of a scramjet nozzle coupled with shock or expansion-wave from the upstream is necessary.
Specularly reflected He sup 2+ at high Mach number quasi-parallel shocks
Energy Technology Data Exchange (ETDEWEB)
Fuselier, S.A.; Lennartsson, O.W. (Lockheed Palo Alto Research Lab., CA (United States)); Thomsen, M.F. (Los Alamos National Lab., NM (United States)); Russell, C.T. (Univ. of California, Los Angeles (United States))
1990-04-01
Upstream from the Earth's quasi-parallel bow shock, the Lockheed Plasma Composition Experiment on ISEE 1 often observes two types of suprathermal He{sup 2+} distributions. Always present to some degree is an energetic (several keV/eto 17.4 keV/e, the maximum energy of the detector) diffuse He{sup 2+} distribution. Sometimes, apparently when the Alfven Mach number, M{sub A}, is high enough and the spacecraft is near the shock (within a few minutes of a crossing), a second type of suprathermal He{sup 2+} distribution is also observed. This nongyrotropic, gyrating He{sup 2+} distribution has velocity components parallel and perpendicular to the magnetic field that are consistent with near-specular reflection of a portion of the incident solar wind He{sup 2+} distribution off the shock. Specularly reflected and diffuse proton distributions are associated with these gyrating He{sup 2+} distributions. The presence of these gyrating He{sup 2+} distributions suggests that specular reflection is controlled primarily by magnetic forces in high Mach number quasi-parallel shocks and that these distributions may be a seed population for more energetic diffuse He{sup 2+} distributions.
The influence of incident shock Mach number on radial incident shock wave focusing
Directory of Open Access Journals (Sweden)
Xin Chen
2016-04-01
Full Text Available Experiments and numerical simulations were carried out to investigate radial incident shock focusing on a test section where the planar incident shock wave was divided into two identical ones. A conventional shock tube was used to generate the planar shock. Incident shock Mach number of 1.51, 1.84 and 2.18 were tested. CCD camera was used to obtain the schlieren photos of the flow field. Third-order, three step strong-stability-preserving (SSP Runge-Kutta method, third-order weighed essential non-oscillation (WENO scheme and adaptive mesh refinement (AMR algorithm were adopted to simulate the complicated flow fields characterized by shock wave interaction. Good agreement between experimental and numerical results was observed. Complex shock wave configurations and interactions (such as shock reflection, shock-vortex interaction and shock focusing were observed in both the experiments and numerical results. Some new features were observed and discussed. The differences of structure of flow field and the variation trends of pressure were compared and analyzed under the condition of different Mach numbers while shock wave focusing.
The density variance - Mach number relation in isothermal and non-isothermal adiabatic turbulence
Nolan, Chris A; Sutherland, Ralph S
2015-01-01
The density variance - Mach number relation of the turbulent interstellar medium is relevant for theoretical models of the star formation rate, efficiency, and the initial mass function of stars. Here we use high-resolution hydrodynamical simulations with grid resolutions of up to 1024^3 cells to model compressible turbulence in a regime similar to the observed interstellar medium. We use Fyris Alpha, a shock-capturing code employing a high-order Godunov scheme to track large density variations induced by shocks. We investigate the robustness of the standard relation between the logarithmic density variance (sigma_s^2) and the sonic Mach number (M) of isothermal interstellar turbulence, in the non-isothermal regime. Specifically, we test ideal gases with diatomic molecular (gamma = 7/5) and monatomic (gamma = 5/3) adiabatic indices. A periodic cube of gas is stirred with purely solenoidal forcing at low wavenumbers, leading to a fully-developed turbulent medium. We find that as the gas heats in adiabatic comp...
A NOVEL SLIGHTLY COMPRESSIBLE MODEL FOR LOW MACH NUMBER PERFECT GAS FLOW CALCULATION
Institute of Scientific and Technical Information of China (English)
邓小刚; 庄逢甘
2002-01-01
By analyzing the characteristics of low Mach number perfect gas flows, a novel Slightly Compressible Model (SCM) for low Mach number perfect gas flows is derived. In view of numerical calculations, this model is proved very efficient,for it is kept within the p-v frame but does not have to satisfy the time consuming divergence-free condition in order to get the incompressible Navier-Stokes equation solutions. Writing the equations in the form of conservation laws, we have derived the characteristic systems which are necessary for numerical calculations. A cellcentered finite-volume method with flux difference upwind-biased schemes is used for the equation solutions and a new Exact Newton Relaxation (ENR) implicit method is developed. Various computed results are presented to validate the present model.Laminar flow solutions over a circular cylinder with wake developing and vortex shedding are presented. Results for inviscid flow over a sphere are compared in excellent agreement with the exact analytic incompressible solution. Three-dimensional viscous flow solutions over sphere and prolate spheroid are also calculated and compared well with experiments and other incompressible solutions. Finally, good convergent performaces are shown for sphere viscous flows.
Airfoil Aeroelastic Flutter Analysis Based on Modified Leishman-Beddoes Model at Low Mach Number
Institute of Scientific and Technical Information of China (English)
SHAO Song; ZHU Qinghua; ZHANG Chenglin; NI Xianping
2011-01-01
Based on modified Leishman-Beddoes(L-B)state space model at low Mach number(lower than 0.3),the airfoil aeroelastic system is presented in this paper.The main modifications for L-B model include a new dynamic stall criterion and revisions of normal force and pitching moment coefficient.The bifurcation diagrams,the limit cycle oscillation (LCO)phase plane plots and the time domain response figures are applied to investigating the stall flutter bifurcation behavior of airfoil aeroelastic systems with symmetry or asymmetry.It is shown that the symmetric periodical oscillation happens after subcritical bifurcation caused by dynamic stall,and the asymmetric periodical oscillation,which is caused by the interaction of dynamic stall and static divergence,only happens in the airfoil aeroelastic system with asymmetry.Validations of the modified L-B model and the airfoil aeroelastic system are presented with the experimental airload data of NACA0012 and OA207 and experimental stall flutter data of NACA0012 respectively.Results demonstrate that the airfoil aeroelastic system presented in this paper is effective and accurate,which can be applied to the investigation of airfoil stall flutter at low Mach number.
Opacity Broadening of $^{13}$CO Linewidths and its Effect on the Variance-Sonic Mach Number Relation
Correia, Caio; Lazarian, Alex; Ossenkopf, Volker; Stutzki, Jürgen; Kainulainen, Jouni; Kowal, Grzegorz; de Medeiros, José Renan
2014-01-01
We study how the estimation of the sonic Mach number ($M_s$) from $^{13}$CO linewidths relates to the actual 3D sonic Mach number. For this purpose we analyze MHD simulations which include post-processing to take radiative transfer effects into account. As expected, we find very good agreement between the linewidth estimated sonic Mach number and the actual sonic Mach number of the simulations for optically thin tracers. However, we find that opacity broadening causes $M_s$ to be overestimated by a factor of ~ 1.16 - 1.3 when calculated from optically thick $^{13}$CO lines. We also find that there is a dependency on the magnetic field: super-Alfv\\'enic turbulence shows increased line broadening as compared with sub-Alfv\\'enic turbulence for all values of optical depth for supersonic turbulence. Our results have implications for the observationally derived sonic Mach number--density standard deviation ($\\sigma_{\\rho/}$) relationship, $\\sigma^2_{\\rho/}=b^2M_s^2$, and the related column density standard deviatio...
Parametric investigation of single-expansion-ramp nozzles at Mach numbers from 0.60 to 1.20
Capone, Francis J.; Re, Richard J.; Bare, E. Ann
1992-01-01
An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of varying six nozzle geometric parameters on the internal and aeropropulsive performance characteristics of single-expansion-ramp nozzles. This investigation was conducted at Mach numbers from 0.60 to 1.20, nozzle pressure ratios from 1.5 to 12, and angles of attack of 0 deg +/- 6 deg. Maximum aeropropulsive performance at a particular Mach number was highly dependent on the operating nozzle pressure ratio. For example, as the nozzle upper ramp length or angle increased, some nozzles had higher performance at a Mach number of 0.90 because of the nozzle design pressure was the same as the operating pressure ratio. Thus, selection of the various nozzle geometric parameters should be based on the mission requirements of the aircraft. A combination of large upper ramp and large lower flap boattail angles produced greater nozzle drag coefficients at Mach number greater than 0.80, primarily from shock-induced separation on the lower flap of the nozzle. A static conditions, the convergent nozzle had high and nearly constant values of resultant thrust ratio over the entire range of nozzle pressure ratios tested. However, these nozzles had much lower aeropropulsive performance than the convergent-divergent nozzle at Mach number greater than 0.60.
Tests of Full-Scale Helicopter Rotors at High Advancing Tip Mach Numbers and Advance Ratios
Biggers, James C.; McCloud, John L., III; Stroub, Robert H.
2015-01-01
As a continuation of the studies of reference 1, three full-scale helicopter rotors have been tested in the Ames Research Center 40- by SO-foot wind tunnel. All three of them were two-bladed, teetering rotors. One of the rotors incorporated the NACA 0012 airfoil section over the entire length of the blade. This rotor was tested at advance ratios up to 1.05. Both of the other rotors were tapered in thickness and incorporated leading-edge camber over the outer 20 percent of the blade radius. The larger of these rotors was tested at advancing tip Mach numbers up to 1.02. Data were obtained for a wide range of lift and propulsive force, and are presented without discussion.
On the proper Mach number and ratio of specific heats for modeling the Venus bow shock
Tatrallyay, M.; Russell, C. T.; Luhmann, J. G.; Barnes, A.; Mihalov, J. D.
1984-01-01
Observational data from the Pioneer Venus Orbiter are used to investigate the physical characteristics of the Venus bow shock, and to explore some general issues in the numerical simulation of collisionless shocks. It is found that since equations from gas-dynamic (GD) models of the Venus shock cannot in general replace MHD equations, it is not immediately obvious what the optimum way is to describe the desired MHD situation with a GD code. Test case analysis shows that for quasi-perpendicular shocks it is safest to use the magnetospheric Mach number as an input to the GD code. It is also shown that when comparing GD predicted temperatures with MHD predicted temperatures total energy should be compared since the magnetic energy density provides a significant fraction of the internal energy of the MHD fluid for typical solar wind parameters. Some conclusions are also offered on the properties of the terrestrial shock.
Relativistic Electron Shock Drift Acceleration in Low Mach Number Galaxy Cluster Shocks
Matsukiyo, Shuichi; Yamazaki, Ryo; Umeda, Takayuki
2011-01-01
An extreme case of electron shock drift acceleration in low Mach number collisionless shocks is investigated as a plausible mechanism of initial acceleration of relativistic electrons in large-scale shocks in galaxy clusters where upstream plasma temperature is of the order of 10 keV and a degree of magnetization is not too small. One-dimensional electromagnetic full particle simulations reveal that, even though a shock is rather moderate, a part of thermal incoming electrons are accelerated and reflected through relativistic shock drift acceleration and form a local nonthermal population just upstream of the shock. The accelerated electrons can self-generate local coherent waves and further be back-scattered toward the shock by those waves. This may be a scenario for the first stage of the electron shock acceleration occurring at the large-scale shocks in galaxy clusters such as CIZA J2242.8+5301 which has well defined radio relics.
Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients
Gaensler, Bryan M; Burkhart, Blakesley; Newton-McGee, Katherine J; Ekers, Ronald D; Lazarian, Alex; McClure-Griffiths, Naomi M; Robishaw, Timothy; Dickey, John M; Green, Anne J; 10.1038/nature10446
2011-01-01
The interstellar medium of the Milky Way is multi-phase, magnetized and turbulent. Turbulence in the interstellar medium produces a global cascade of random gas motions, spanning scales ranging from 100 parsecs to 1000 kilometres. Fundamental parameters of interstellar turbulence such as the sonic Mach number (the speed of sound) have been difficult to determine because observations have lacked the sensitivity and resolution to directly image the small-scale structure associated with turbulent motion. Observations of linear polarization and Faraday rotation in radio emission from the Milky Way have identified unusual polarized structures that often have no counterparts in the total radiation intensity or at other wavelengths, and whose physical significance has been unclear. Here we report that the gradient of the Stokes vector (Q,U), where Q and U are parameters describing the polarization state of radiation, provides an image of magnetized turbulence in diffuse ionized gas, manifested as a complex filamenta...
Varsakelis, Christos; Papalexandris, Miltiadis V.
2017-01-01
A conundrum in non-equilibrium thermodynamics of heterogeneous mixtures with microstructure concerns the selection of thermodynamic currents and forces in the entropy production rate from the multitude of available options. The objective of this article is to demonstrate that the low-Mach-number approximation can narrow down this ambiguity. More specifically, by postulating that the post-constitutive equations are well behaved with respect to this perturbation analysis we assert that thermal non-equilibrium should be chosen as an independent force even if this requires the explicit manipulation of the entropy inequality. According to our analysis, alternative choices result in post-constitutive equations; the incompressible limit of which gives rise to questionable predictions.
Electron acceleration in a nonrelativistic shock with very high Alfv\\'en Mach number
Matsumoto, Y; Hoshino, M
2013-01-01
Electron acceleration associated with various plasma kinetic instabilities in a nonrelativistic, very-high-Alfv\\'en Mach-number ($M_A \\sim 45$) shock is revealed by means of a two-dimensional fully kinetic PIC simulation. Electromagnetic (ion Weibel) and electrostatic (ion-acoustic and Buneman) instabilities are strongly activated at the same time in different regions of the two-dimensional shock structure. Relativistic electrons are quickly produced predominantly by the shock surfing mechanism with the Buneman instability at the leading edge of the foot. The energy spectrum has a high-energy tail exceeding the upstream ion kinetic energy accompanying the main thermal population. This gives a favorable condition for the ion acoustic instability at the shock front, which in turn results in additional energization. The large-amplitude ion Weibel instability generates current sheets in the foot, implying another dissipation mechanism via magnetic reconnection in a three-dimensional shock structure in the very-hi...
Peng, Naifu; Yang, Yue
2016-11-01
We investigate the evolution of vortex-surface fields (VSFs) in viscous compressible Taylor-Green flows. The VSF is applied to the direct numerical simulation of the Taylor-Green flows at a range of Mach numbers from Ma = 0 . 6 to Ma = 2 . 2 for characterizing the Mach-number effects on evolving vortical structures. We find that the dilatation and baroclinic force strongly influence the geometry of vortex surfaces and the energy dissipation rate in the transitional stage. The vortex tubes in compressible flows are less curved than those in incompressible flows, and the maximum dissipation rate occurs earlier in high-Mach-number flows perhaps owing to the conversion of kinetic energy into heat. Moreover, the relations between the evolutionary geometry of vortical structures and flow statistics are discussed. This work has been supported in part by the National Natural Science Foundation of China (Grant Nos. 11522215 and 11521091), and the Thousand Young Talents Program of China.
Schaeffer, D. B.; Fox, W.; Haberberger, D.; Fiksel, G.; Bhattacharjee, A.; Barnak, D. H.; Hu, S. X.; Germaschewski, K.
2017-07-01
We present the first laboratory generation of high-Mach-number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient plasma. Time-resolved, two-dimensional imaging of plasma density and magnetic fields shows the formation and evolution of a supercritical shock propagating at magnetosonic Mach number Mms≈12 . Particle-in-cell simulations constrained by experimental data further detail the shock formation and separate dynamics of the multi-ion-species ambient plasma. The results show that the shocks form on time scales as fast as one gyroperiod, aided by the efficient coupling of energy, and the generation of a magnetic barrier between the piston and ambient ions. The development of this experimental platform complements present remote sensing and spacecraft observations, and opens the way for controlled laboratory investigations of high-Mach number collisionless shocks, including the mechanisms and efficiency of particle acceleration.
Background-oriented schlieren imaging of flow around a circular cylinder at low Mach numbers
Stadler, Hannes; Bauknecht, André; Siegrist, Silvan; Flesch, Robert; Wolf, C. Christian; van Hinsberg, Nils; Jacobs, Markus
2017-09-01
The background-oriented schlieren (BOS) imaging method has, for the first time, been applied in the investigation of the flow around a circular cylinder at low Mach numbers (Mnumbers of 0.1× 10^6 ≤ Re ≤ 6.0× 10^6. Even at ambient pressure and the lowest Reynolds number investigated, density gradients associated with the flow around the cylinder were recorded. The signal-to-noise ratio of the evaluated gradient field improved with increasing stagnation pressure. The separation point could easily be identified with this non-intrusive measurement technique and corresponds well to simultaneous surface pressure measurements. The resulting displacement field is in principle of qualitative nature as the observation angle was parallel to the cylinder axis only in a single point of the recorded images. However, it has been possible to integrate the density field along the surface of the cylinder by successive imaging at incremental angular positions around the cylinder. This density distribution has been found to agree well with the pressure measurements and with potential theory where appropriate.
Aerodynamic Characteristics of a Revised Target Drone Vehicle at Mach Numbers from 1.60 to 2.86
Blair, A. B., Jr.; Babb, C. Donald
1968-01-01
An investigation has been conducted in the Langley Unitary Plan wind tunnel to determine the aerodynamic characteristics of a revised target drone vehicle through a Mach number range from 1.60 to 2.86. The vehicle had canard surfaces and a swept clipped-delta wing with twin tip-mounted vertical tails.
Slot, H.J.; Moore, P.; Delfos, R.; Boersma, B.J.
2009-01-01
In this paper we present the experimental results of a detailed investigation of the flow and acoustic properties of a turbulent jet with Mach number 0·75 and Reynolds number 3·5 103. We describe the methods and experimental procedures followed during the measurements, and subsequently present the f
Anomalous flow deflection at planetary bow shocks in the low Alfven Mach number regime
Nishino, Masaki N.; Fujimoto, Masaki; Tai, Phan-Duc; Mukai, Toshifumi; Saito, Yoshifumi; Kuznetsova, Masha M.; Rastaetter, Lutz
A planetary magnetosphere is an obstacle to the super-sonic solar wind and the bow shock is formed in the front-side of it. In ordinary hydro-dynamics, the flow decelerated at the shock is diverted around the obstacle symmetrically about the planet-Sun line, which is indeed observed in the magnetosheath most of the time. Here we show a case under a very low density solar wind in which duskward flow was observed in the dawnside magnetosheath of the Earth's magnetosphere. A Rankine-Hugoniot test across the bow shock shows that the magnetic effect is crucial for this "wrong flow" to appear. A full three-dimensional Magneto- Hydro-Dynamics (MHD) simulation of the situation in this previously unexplored parameter regime is also performed. It is illustrated that in addition to the "wrong flow" feature, various peculiar characteristics appear in the global picture of the MHD flow interaction with the obstacle. The magnetic effect at the bow shock should become more conspicuously around the Mercury's magnetosphere, because stronger interplanetary magnetic field and slower solar wind around the Mercury let the Alfven Mach number low. Resultant strong deformation of the magnetosphere induced by the "wrong flow" will cause more complex interaction between the solar wind and the Mercury.
Pendergraft, O. C., Jr.; Schmeer, J. W.
1972-01-01
Twin-jet afterbody models were investigated by using two balances to measure the thrust-minus-total drag and the afterbody drag, separately, at static conditions and at Mach numbers up to 2.2 for an angle of attack of 0 deg. Hinged-flap convergent-divergent nozzles were tested at subsonic-cruise- and maximum-afterburning-power settings with a high-pressure air system used to provide jet-total-pressure ratios up to 20. Two nozzle lateral spacings were studied, using afterbodies with similar interfairing shapes but with different longitudinal cross-sectional area distributions. Alternate, blunter, interfairings with different shapes for the two spacings, which produced afterbodies having identical cross-sectional area progressions corresponding to an axisymmetric minimum wave-drag configuration, were also tested. The results indicate that the wide-spaced configurations improved the flow field around the nozzles, thereby reducing drag on the cruise nozzles; however, the increased surface and projected cross-sectional areas caused an increase in afterbody drag. Except for a slight advantage with cruise nozzles at subsonic speeds, the wide-spaced configurations had the higher total drag at all other test conditions.
Pedrosa, A. C. F.; Nagamatsu, H. T.; Hinckel, J. A.
1984-01-01
Heat transfer measurements were determined for a flat plate with and without pressure gradient for various free stream temperatures, wall temperature ratios, and Reynolds numbers for an inlet flow Mach number of 0.45, which is a representative inlet Mach number for gas turbine rotor blades. A shock tube generated the high temperature and pressure air flow, and a variable geometry test section was used to produce inlet flow Mach number of 0.45 and accelerate the flow over the plate to sonic velocity. Thin-film platinum heat gages recorded the local heat flux for laminar, transition, and turbulent boundary layers. The free stream temperatures varied from 611 R (339 K) to 3840 R (2133 K) for a T(w)/T(r,g) temperature ratio of 0.87 to 0.14. The Reynolds number over the heat gages varied from 3000 to 690,000. The experimental heat transfer data were correlated with laminar and turbulent boundary layer theories for the range of temperatures and Reynolds numbers and the transition phenomenon was examined.
Seiff, Alvin; Wilkins, Max E.
1961-01-01
The aerodynamic characteristics of a hypersonic glider configuration, consisting of a slender ogive cylinder with three highly swept wings, spaced 120 apart, with the wing chord equal to the body length, were investigated experimentally at a Mach number of 6 and at Reynolds numbers from 6 to 16 million. The objectives were to evaluate the theoretical procedures which had been used to estimate the performance of the glider, and also to evaluate the characteristics of the glider itself. A principal question concerned the viscous drag at full-scale Reynolds number, there being a large difference between the total drags for laminar and turbulent boundary layers. It was found that the procedures which had been applied for estimating minimum drag, drag due to lift, lift curve slope, and center of pressure were generally accurate within 10 percent. An important exception was the non-linear contribution to the lift coefficient which had been represented by a Newtonian term. Experimentally, the lift curve was nearly linear within the angle-of-attack range up to 10 deg. This error affected the estimated lift-drag ratio. The minimum drag measurements indicated that substantial amounts of turbulent boundary layer were present on all models tested, over a range of surface roughness from 5 microinches maximum to 200 microinches maximum. In fact, the minimum drag coefficients were nearly independent of the surface smoothness and fell between the estimated values for turbulent and laminar boundary layers, but closer to the turbulent value. At the highest test Reynolds numbers and at large angles of attack, there was some indication that the skin friction of the rough models was being increased by the surface roughness. At full-scale Reynolds number, the maximum lift-drag ratio with a leading edge of practical diameter (from the standpoint of leading-edge heating) was 4.0. The configuration was statically and dynamically stable in pitch and yaw, and the center of pressure was less
A comparative study of scramjet injection strategies for high Mach numbers flows
Riggins, D. W.; Mcclinton, C. R.; Rogers, R. C.; Bittner, R. D.
1992-01-01
A simple method for predicting the axial distribution of supersonic combustor thrust potential is described. A complementary technique for illustrating the spatial evolution and distribution of thrust potential and loss mechanisms in reacting flows is developed. Wall jet cases and swept ramp injector cases for Mach 17 and Mach 13.5 flight enthalpy inflow conditions are numerically modeled and analyzed using these techniques. The visualization of thrust potential in the combustor for the various cases examined provides a unique tool for increasing understanding of supersonic combustor performance potential.
Schaeffer, Derek; Haberberger, Dan; Fiksel, Gennady; Bhattacharjee, Amitava; Barnak, Daniel; Hu, Suxing; Germaschewski, Kai
2016-01-01
Shocks act to convert incoming supersonic flows to heat, and in collisionless plasmas the shock layer forms on kinetic plasma scales through collective electromagnetic effects. These collisionless shocks have been observed in many space and astrophysical systems [Smith 1975, Smith 1980, Burlaga 2008, Sulaiman 2015], and are believed to accelerate particles, including cosmic rays, to extremely high energies [Kazanas 1986, Loeb 2000, Bamba 2003, Masters 2013, Ackermann 2013]. Of particular importance are the class of high-Mach number, supercritical shocks [Balogh 2013] ($M_A\\gtrsim4$), which must reflect significant numbers of particles back into the upstream to accommodate entropy production, and in doing so seed proposed particle acceleration mechanisms [Blandford 1978, McClements 2001, Caprioli 2014, Matsumoto 2015]. Here we present the first laboratory generation of high-Mach number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient ...
Nagata, T.; Nonomura, T.; Takahashi, S.; Mizuno, Y.; Fukuda, K.
2016-05-01
In this study, analysis of flow properties around a sphere and its aerodynamic coefficients in the high-Mach-and-low-Reynolds-numbers conditions is carried out by direct numerical simulations solving the three-dimensional compressible Navier-Stokes equations. The calculation is performed on a boundary-fitted coordinate system with a high-order scheme of sufficient accuracy. The analysis is conducted by assuming a rigid sphere with a Reynolds number of between 50 and 300, based on the diameter of the sphere and the freestream velocity and a freestream Mach number of between 0.3 and 2.0, together with the adiabatic wall boundary condition. The calculation shows the following yields: (1) unsteady fluctuation of hydrodynamic forces become smaller as the Mach number increases under the same Reynolds number condition, (2) the drag coefficient increases with the Mach number due to an increase in the pressure drag by the shock wave, and (3) an accurate prediction of the drag coefficient in the supersonic regime using traditional models might be difficult.
Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh
2014-10-01
Electron acceleration to non-thermal energies in low Mach number (Ms Diffusive shock acceleration, also known as first-order Fermi acceleration, cannot be directly invoked to explain the acceleration of electrons. Rather, an additional mechanism is required to pre-accelerate the electrons from thermal to supra-thermal energies, so they can then participate in the Fermi process. In this work, we use two- and three-dimensional particle-in-cell plasma simulations to study electron acceleration in low Mach number shocks. We focus on the particle energy spectra and the acceleration mechanism in a reference run with Ms = 3 and a quasi-perpendicular pre-shock magnetic field. We find that about 15% of the electrons can be efficiently accelerated, forming a non-thermal power-law tail in the energy spectrum with a slope of p ~= 2.4. Initially, thermal electrons are energized at the shock front via shock drift acceleration (SDA). The accelerated electrons are then reflected back upstream where their interaction with the incoming flow generates magnetic waves. In turn, the waves scatter the electrons propagating upstream back toward the shock for further energization via SDA. In summary, the self-generated waves allow for repeated cycles of SDA, similarly to a sustained Fermi-like process. This mechanism offers a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.
Meerson, Baruch; Fouxon, Itzhak; Vilenkin, Arkady
2008-02-01
We employ hydrodynamic equations to investigate nonstationary channel flows of freely cooling dilute gases of hard and smooth spheres with nearly elastic particle collisions. This work focuses on the regime where the sound travel time through the channel is much shorter than the characteristic cooling time of the gas. As a result, the gas pressure rapidly becomes almost homogeneous, while the typical Mach number of the flow drops well below unity. Eliminating the acoustic modes and employing Lagrangian coordinates, we reduce the hydrodynamic equations to a single nonlinear and nonlocal equation of a reaction-diffusion type. This equation describes a broad class of channel flows and, in particular, can follow the development of the clustering instability from a weakly perturbed homogeneous cooling state to strongly nonlinear states. If the heat diffusion is neglected, the reduced equation becomes exactly soluble, and the solution develops a finite-time density blowup. The blowup has the same local features at singularity as those exhibited by the recently found family of exact solutions of the full set of ideal hydrodynamic equations [I. Fouxon, Phys. Rev. E 75, 050301(R) (2007); I. Fouxon,Phys. Fluids 19, 093303 (2007)]. The heat diffusion, however, always becomes important near the attempted singularity. It arrests the density blowup and brings about previously unknown inhomogeneous cooling states (ICSs) of the gas, where the pressure continues to decay with time, while the density profile becomes time-independent. The ICSs represent exact solutions of the full set of granular hydrodynamic equations. Both the density profile of an ICS and the characteristic relaxation time toward it are determined by a single dimensionless parameter L that describes the relative role of the inelastic energy loss and heat diffusion. At L>1 the intermediate cooling dynamics proceeds as a competition between "holes": low-density regions of the gas. This competition resembles Ostwald
Measurement and Analysis of the Noise Radiated by Low Mach Number Centrifugal Blowers.
Yeager, David Marvin
An investigation was performed of the broad band, aerodynamically generated noise in low tip-speed Mach number, centrifugal air moving devices. An interdisciplinary experimental approach was taken which involved investigation of the aerodynamic and acoustic fields, and their mutual relationship. The noise generation process was studied using two experimental vehicles: (1) a scale model of a homologous family of centrifugal blowers typical of those used to cool computer and business equipment, and (2) a single blade from a centrifugal blower impeller placed in a known, controllable flow field. The radiation characteristics of the model blower were investigated by measuring the acoustic intensity distribution near the blower inlet and comparing it with the intensity near the inlet to an axial flow fan. Results showed that the centrifugal blower is a distributed, random noise source, unlike an axial fan which exhibited the effects of a coherent, interacting source distribution. Aerodynamic studies of the flow field in the inlet and at the discharge to the rotating impeller were used to assess the mean flow distribution through the impeller blade channels and to identify regions of excessive turbulence near the rotating blade row. Both circumferential and spanwise mean flow nonuniformities were identified along with a region of increased turbulence just downstream of the scroll cutoff. The fluid incidence angle, normally taken as an indicator of blower performance, was estimated from mean flow data as deviating considerably from an ideal impeller design. An investigation of the noise radiated from the single, isolated airfoil was performed using modern correlation and spectral analysis techniques. Radiation from the single blade in flow was characterized using newly developed expressions for the correlation area and the dipole source strength per unit area, and from the relationship between the blade surface pressure and the incident turbulent flow field. Results
Carlson, J. R.; Compton, W. B., III
1984-01-01
A wind tunnel investigation was conducted to determine the aerodynamic interference associated with the installation of a long duct, flow-through nacelle on a straight unswept untapered supercritical wing. Experimental data was obtained for the verification of computational prediction techniques. The model was tested in the 16-Foot Transonic Tunnel at Mach numbers from 0.20 to 0.875 and at angles of attack from about 0 deg to 5 deg. The results of the investigation show that strong viscous and compressibility effects are present at the transonic Mach numbers. Numerical comparisons show that linear theory is adequate for subsonic Mach number flow prediction, but is inadequate for prediction of the extreme flow conditions that exist at the transonic Mach numbers.
Drake, Hubert M; Mclaughlin, Milton D; Goodman, Harold R
1948-01-01
Results are presented of tests up to a Mach number of 0.92 at altitudes around 30,000 feet. The data obtained show that the airplane can be flown to this Mach number above 30,000 feet. Longitudinal trim changes have been experienced but the forces involved have been small. The elevator effectiveness decreased about one-half with increase of Mach number from 0.70 to 0.87. Buffeting has been experienced in level flight but it has been mild and the associated tail loads have been small. No aileron buzz or other flutter phenomena have been noted.
Shaw, C. S.; Margason, R. J.
1973-01-01
The induced static pressures due to a highly underexpanded sonic jet ejecting normally from a flat plate into a subsonic crosswind have been investigated. These pressure data have been recorded on the flat plate for a range of nominal jet-to-free-stream dynamic-pressure ratios from 0 to 1000 at free-stream Mach numbers of 0.1, 0.2, 0.4, and 0.6. The static pressure data measured on the flat plate are presented and correlated based upon the Riemann shock geometry in the jet plume. This data correlation improves with increasing free-stream Mach number.
Spreading of Exhaust Jet from 16 Inch Ream Jet at Mach Number 2.0 / Fred Wilcox, Donald Pennington
Wilcox, Fred; Pennington, Donald
1952-01-01
An investigation of the jet-spreading characteristics of a 16 inch ram-jet engine was conducted in the 8 by 6 foot supersonic tunnel at a Mach number of 2.0; both a converging nozzle having a contraction ratio of 0.71 and a cylindrical extension to the combustion chamber were used. The jet boundaries determined by means of pitot pressure surveys were compared with boundaries calculated from one-dimensional continuity and momentum relations. For the cylindrical nozzle, the jet reaches its maximum diameter, 4 percent greater than calculated, about 0.6 nozzle-exit diameter downstream of the nozzle exit. The maximum diameter for the converging nozzle was 7 percent greater than calculated from one dimensional relations and occurred from 1 to 1.5 nozzle-exit diameters downstream of the exit. Non dimensional maximum jet diameters agreed closely with results of an investigation by Rousso and Baughman; these data were obtained with low-temperature jets exhausting into a stream at a Mach number of 1.91 from nozzles having exit diameters of 0.75 inch.
Guo, Xinyi; Narayan, Ramesh
2014-01-01
Electron acceleration to non-thermal energies in low Mach number (M<5) shocks is revealed by radio and X-ray observations of galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Diffusive shock acceleration, also known as first-order Fermi acceleration, cannot be directly invoked to explain the acceleration of electrons. Rather, an additional mechanism is required to pre-accelerate the electrons from thermal to supra-thermal energies, so they can then participate in the Fermi process. In this work, we use two- and three-dimensional particle-in-cell plasma simulations to study electron acceleration in low Mach number shocks. We focus on the particle energy spectra and the acceleration mechanism in a reference run with M=3. We find that about 15 percent of the electrons can be efficiently accelerated, forming a non-thermal power-law tail in the energy spectrum with a slope of p~2.4. Initially, thermal electrons are energized at the shock front via shock drift a...
Performance characteristics of two multiaxis thrust-vectoring nozzles at Mach numbers up to 1.28
Wing, David J.; Capone, Francis J.
1993-01-01
The thrust-vectoring axisymmetric (VA) nozzle and a spherical convergent flap (SCF) thrust-vectoring nozzle were tested along with a baseline nonvectoring axisymmetric (NVA) nozzle in the Langley 16-Foot Transonic Tunnel at Mach numbers from 0 to 1.28 and nozzle pressure ratios from 1 to 8. Test parameters included geometric yaw vector angle and unvectored divergent flap length. No pitch vectoring was studied. Nozzle drag, thrust minus drag, yaw thrust vector angle, discharge coefficient, and static thrust performance were measured and analyzed, as well as external static pressure distributions. The NVA nozzle and the VA nozzle displayed higher static thrust performance than the SCF nozzle throughout the nozzle pressure ratio (NPR) range tested. The NVA nozzle had higher overall thrust minus drag than the other nozzles throughout the NPR and Mach number ranges tested. The SCF nozzle had the lowest jet-on nozzle drag of the three nozzles throughout the test conditions. The SCF nozzle provided yaw thrust angles that were equal to the geometric angle and constant with NPR. The VA nozzle achieved yaw thrust vector angles that were significantly higher than the geometric angle but not constant with NPR. Nozzle drag generally increased with increases in thrust vectoring for all the nozzles tested.
Syvertson, Clarence A; Gloria, Hermilo R; Sarabia, Michael F
1958-01-01
A study is made of aerodynamic performance and static stability and control at hypersonic speeds. In a first part of the study, the effect of interference lift is investigated by tests of asymmetric models having conical fuselages and arrow plan-form wings. The fuselage of the asymmetric model is located entirely beneath the wing and has a semicircular cross section. The fuselage of the symmetric model was centrally located and has a circular cross section. Results are obtained for Mach numbers from 3 to 12 in part by application of the hypersonic similarity rule. These results show a maximum effect of interference on lift-drag ratio occurring at Mach number of 5, the Mach number at which the asymmetric model was designed to exploit favorable lift interference. At this Mach number, the asymmetric model is indicated to have a lift-drag ratio 11 percent higher than the symmetric model and 15 percent higher than the asymmetric model when inverted. These differences decrease to a few percent at a Mach number of 12. In the course of this part of the study, the accuracy to the hypersonic similarity rule applied to wing-body combinations is demonstrated with experimental results. These results indicate that the rule may prove useful for determining the aerodynamic characteristics of slender configurations at Mach numbers higher than those for which test equipment is really available. In a second part of the study, the aerodynamic performance and static stability and control characteristics of a hypersonic glider are investigated in somewhat greater detail. Results for Mach numbers from 3 to 18 for performance and 0.6 to 12 for stability and control are obtained by standard text techniques, by application of the hypersonic stability rule, and/or by use of helium as a test medium. Lift-drag ratios of about 5 for Mach numbers up to 18 are shown to be obtainable. The glider studied is shown to have acceptable longitudinal and directional stability characteristics through the
Rikanati, A; Oron, D; Sadot, O; Shvarts, D
2003-02-01
Effects of high-Mach numbers and high initial amplitudes on the evolution of the single-mode Richtmyer-Meshkov shock-wave induced hydrodynamic instability are studied using theoretical models, experiments, and numerical simulations. Two regimes in which there is a significant deviation from the linear dependence of the initial velocity on the initial perturbation amplitude are defined and characterized. In one, the observed reduction of the initial velocity is primarily due to large initial amplitudes. This effect is accurately modeled by a vorticity deposition model, quantifying both the effect of the initial perturbation amplitude and the exact shape of the interface. In the other, the reduction is dominated by the proximity of the shock wave to the interface. This effect is modeled by a modified incompressible model where the shock wave is mimicked by a moving bounding wall. These results are supplemented with high initial amplitude Mach 1.2 shock-tube experiments, enabling separation of the two effects. It is shown that in most of the previous experiments, the observed reduction is predominantly due to the effect of high initial amplitudes.
A Reynolds Number Study of Wing Leading-Edge Effects on a Supersonic Transport Model at Mach 0.3
Williams, M. Susan; Owens, Lewis R., Jr.; Chu, Julio
1999-01-01
A representative supersonic transport design was tested in the National Transonic Facility (NTF) in its original configuration with small-radius leading-edge flaps and also with modified large-radius inboard leading-edge flaps. Aerodynamic data were obtained over a range of Reynolds numbers at a Mach number of 0.3 and angles of attack up to 16 deg. Increasing the radius of the inboard leading-edge flap delayed nose-up pitching moment to a higher lift coefficient. Deflecting the large-radius leading-edge flap produced an overall decrease in lift coefficient and delayed nose-up pitching moment to even higher angles of attack as compared with the undeflected large- radius leading-edge flap. At angles of attack corresponding to the maximum untrimmed lift-to-drag ratio, lift and drag coefficients decreased while lift-to-drag ratio increased with increasing Reynolds number. At an angle of attack of 13.5 deg., the pitching-moment coefficient was nearly constant with increasing Reynolds number for both the small-radius leading-edge flap and the deflected large-radius leading-edge flap. However, the pitching moment coefficient increased with increasing Reynolds number for the undeflected large-radius leading-edge flap above a chord Reynolds number of about 35 x 10 (exp 6).
Winters, Andrew R.; Derigs, Dominik; Gassner, Gregor J.; Walch, Stefanie
2017-03-01
We describe a unique averaging procedure to design an entropy stable dissipation operator for the ideal magnetohydrodynamic (MHD) and compressible Euler equations. Often in the derivation of an entropy conservative numerical flux function much care is taken in the design and averaging of the entropy conservative numerical flux. We demonstrate in this work that if the discrete dissipation operator is not carefully chosen as well it can have deleterious effects on the numerical approximation. This is particularly true for very strong shocks or high Mach number flows present, for example, in astrophysical simulations. We present the underlying technique of how to construct a unique averaging technique for the discrete dissipation operator. We also demonstrate numerically the increased robustness of the approximation.
Directory of Open Access Journals (Sweden)
Krishna Pandey
2016-01-01
Full Text Available A numerical analysis of the inlet-combustor interaction and flow structure through a scramjet engine at a flight Mach number M = 6 with parallel injection (Strut with circular inlet is presented in the present research article. Three different angles of attack (α=-4°, α=0°, α=4° have been studied for parallel injection. The scramjet configuration used here is a modified version of DLR scramjet model. Fuel is injected at supersonic speed (M=2 through a parallel strut injector. For parallel injection, the shape of the strut is chosen in a way to produce strong stream wise vorticity and thus to enhance the hydrogen/air mixing inside the combustor. These numerical simulations are aimed to study the flow structure, supersonic mixing, and combustion phenomena for the three different types of geometries along with circular shaped strut configuration.
The influence of the Mach number of shock waves on turbulent mixing growth at an interface of gases
Nevmerzhitsky, N. V.; Sotskov, E. A.; Sen'kovsky, E. D.; Razin, A. N.; Ustinenko, V. A.; Krivonos, O. L.; Tochilina, L. V.
2010-12-01
The results of our experimental investigation of the turbulent mixing occurring at a Richtmayer-Meshkov instability driven by a shock wave (SW) in gases at different Mach numbers (M) ranging from ≈1.4 to ≈9 are presented in this paper. The experiments were performed by using an air shock tube with a channel section of 40×40 mm2. The SW passed from 'light' to 'heavy' gases. Air (helium) was used as a 'light' gas and Xe, CO2 and Ar were used as 'heavy' gases. The gases were initially separated by a thin (≈1 μm) polymer film, which was failed after the passing of the SW. A film of the flow was made using a high-speed camera by the Schlieren method.
Wolf, Stephen W. D.; Laub, James A.; King, Lyndell S.; Reda, Daniel C.
1992-01-01
A unique, low-disturbance supersonic wind tunnel is being developed at NASA-Ames to support supersonic laminar flow control research at cruise Mach numbers of the High Speed Civil Transport (HSCT). The distinctive design features of this new quiet tunnel are a low-disturbance settling chamber, laminar boundary layers along the nozzle/test section walls, and steady supersonic diffuser flow. This paper discusses these important aspects of our quiet tunnel design and the studies necessary to support this design. Experimental results from an 1/8th-scale pilot supersonic wind tunnel are presented and discussed in association with theoretical predictions. Natural laminar flow on the test section walls is demonstrated and both settling chamber and supersonic diffuser performance is examined. The full-scale wind tunnel should be commissioned by the end of 1993.
Rao, Pooja; She, Dan; Lim, Hyunkyung; Glimm, James
2015-11-01
The qualitative and quantitative effect of initial conditions (linear and non-linear) and high Mach number (1.3 and 1.45) is studied on the turbulent mixing induced by the Richtmyer-Meshkov instability in idealized ICF conditions. The Richtmyer-Meshkov instability seeds Rayleigh-taylor instabilities in ICF experiments and is one of the factors that contributes to reduced performance of ICF experiments. Its also found in collapsing cores of stars and supersonic combustion. We use the Stony Brook University code, FronTier, which is verified via a code comparison study against the AMR multiphysics code FLASH, and validated against vertical shock tube experiments done by the LANL Extreme Fluids Team. These simulations are designed as a step towards simulating more realistic ICF conditions and quantifying the detrimental effects of mixing on the yield.
Schneider, T.; Botta, N.; Geratz, K. J.; Klein, R.
1999-11-01
When attempting to compute unsteady, variable density flows at very small or zero Mach number using a standard finite volume compressible flow solver one faces at least the following difficulties: (i) Spatial pressure variations vanish as the Mach number M→0, but they do affect the velocity field at leading order; (ii) the resulting spatial homogeneity of the leading order pressure implies an elliptic divergence constraint for the energy flux; (iii) violations of this constraint crucially affect the transport of mass, preventing a code to properly advect even a constant density distribution. We overcome these difficulties through a new algorithm for constructing numerical fluxes in the context of multi-dimensional finite volume methods in conservation form. The construction of numerical fluxes involves: (1) An explicit upwind step yielding predictions for the nonlinear convective flux components. (2) A first correction step that introduces pressure gradients which guarantee compliance of the convective fluxes with a divergence constraint. This step requires the solution of a first Poisson-type equation. (3) A second projection step which provides the yet unknown (non-convective) pressure contribution to the total flux of momentum. This second projection requires the solution of another Poisson-type equation and yields the cell centered velocity field at the new time. This velocity field exactly satisfies a divergence constraint consistent with the asymptotic limit. Step (1) can be done by any standard finite volume compressible flow solver. The input to steps (2) and (3) involves solely the fluxes from step (1) and is independent of how these were obtained. Thus, our approach allows any such solver to be extended to compute variable density incompressible flows.
Marchionna, N. R.; Diehl, L. A.; Trout, A. M.
1973-01-01
Tests were conducted to determine the effect of inlet air humidity on the formation of oxides of nitrogen (NOx) from a gas turbine combustor. Combustor inlet air temperature ranged from 506 K (450 F) to 838 K (1050 F). The tests were primarily run at a constant pressure of 6 atmospheres and reference Mach number of 0.065. The NOx emission index was found to decrease with increasing inlet air humidity at a constant exponential rate: NOx = NOx0e-19H (where H is the humidity and the subscript 0 denotes the value at zero humidity). the emission index increased exponentially with increasing normalized inlet air temperature to the 1.14 power. Additional tests made to determine the effect of pressure and reference Mach number on NOx showed that the NOx emission index varies directly with pressure to the 0.5 power and inversely with reference Mach number.
Coumar, Sandra; Lago, Viviana
2017-06-01
This paper presents an experimental investigation, carried out at the Icare Laboratory by the FAST team, focusing on plasma flow control in supersonic and rarefied regime. The study analyzes how the Mach number as well as the ambient pressure modify the repercussions of the plasma actuator on the shock wave. It follows previous experiments performed in the MARHy (ex-SR3) wind tunnel with a Mach 2 flow interacting with a sharp flat plate, where modifications induced by a plasma actuator were observed. The flat plate was equipped with a plasma actuator composed of two aluminum electrodes. The upstream one was biased with a negative DC potential and thus, created a glow discharge type plasma. Experimental measurements showed that the boundary layer thickness and the shock wave angle increased when the discharge was ignited. The current work was performed with two nozzles generating Mach 4 flows but at two different static pressures: 8 and 71 Pa. These nozzles were chosen to study independently the impact of the Mach number and the impact of the pressure on the flow behavior. In the range of the discharge current considered in this experimental work, it was observed that the shock wave angle increased with the discharge current of +15% for the Mach 2 flow but the increase rate doubled to +28% for the Mach 4 flow at the same static pressure, showing that the discharge effect is even more significant when boosting the flow speed. When studying the effect of the discharge on the Mach 4 flow at higher static pressure, it was observed that the topology of the plasma changed drastically and the increase in the shock wave angle with the discharge current of +21 %.
Pendergraft, Odis C., Jr.; Burley, James R., II; Bare, E. Ann
1986-01-01
An investigation has been conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of upper and lower external nozzle flap geometry on the external afterbody/nozzle drag of nonaxisymmetric two-dimensional convergent-divergent exhaust nozzles having parallel external sidewalls installed on a generic twin-engine, fighter-aircraft model. Tests were conducted over a Mach number range from 0.60 to 1.20 and over an angle-of-attack range from -5 to 9 deg. Nozzle pressure ratio was varied from jet off (1.0) to approximately 10.0, depending on Mach number.
Al-Maaitah, Ayman A.; Nayfeh, Ali H.; Ragab, Saad A.
1990-01-01
The effect of wall cooling on the two-dimensional linear stability of subsonic flows over two-dimensional surface imperfections is investigated. Results are presented for flows over smooth humps and backward-facing steps with Mach numbers up to 0.8. The results show that, whereas cooling decreases the viscous instability, it increases the shear-layer instability and hence it increases the growth rates in the separation region. The coexistence of more than one instability mechanism makes a certain degree of wall cooling most effective. For the Mach numbers 0.5 and 0.8, the optimum wall temperatures are about 80 pct and 60 pct of the adiabatic wall temperature, respectively. Increasing the Mach number decreases the effectiveness of cooling slightly and reduces the optimum wall temperature.
Practical computational aeroacoustics for compact surfaces in low mach number flows
DEFF Research Database (Denmark)
Pradera-Mallabiabarrena, Ainara; Keith, Graeme; Jacobsen, Finn
2011-01-01
compared to the wavelength of interest. This makes it possible to focus on the surface source term of the Ffowcs Williams-Hawkings equation. In this paper, in order to illustrate the basic method for storing and utilizing data from the CFD analysis, the flow past a circular cylinder at a Reynolds number...
Mack, R. J.
1974-01-01
Wing models were tested in the high-speed section of the Langley Unitary Plan wind tunnel to study the effects of the leading-edge sweep angle and the design lift coefficient on aerodynamic performance and efficiency. The models had leading-edge sweep angles of 69.44 deg, 72.65 deg, and 75.96 deg which correspond to values of the design Mach-number-sweep-angle parameter (beta cotangent A) sub DES of 0.6, 0.75, and 0.9, respectively. For each sweep angle, camber surfaces having design lift coefficients of 0,0.08, and 0.12 at a design Mach number of 2.6 were generated. The wind-tunnel tests were conducted at Mach numbers of 2.3, 2.6, and 2.96 with a stagnation temperature of 338.7 K (150 F) and a Reynolds number per meter of 9.843 times 10 to the 6th power. The results of the tests showed that only a moderate sweeping of the wing leading edge aft of the Mach line along with a small-to-moderate amount of camber and twist was needed to significantly improve the zero-lift (flat camber surface) wing performance and efficiency.
Mahto, Navin Kumar; Choubey, Gautam; Suneetha, Lakka; Pandey, K. M.
2016-11-01
The two equation standard k-ɛ turbulence model and the two-dimensional compressible Reynolds-Averaged Navier-Stokes (RANS) equations have been used to computationally simulate the double cavity scramjet combustor. Here all the simulations are performed by using ANSYS 14-FLUENT code. At the same time, the validation of the present numerical simulation for double cavity has been performed by comparing its result with the available experimental data which is in accordance with the literature. The results are in good agreement with the schlieren image and the pressure distribution curve obtained experimentally. However, the pressure distribution curve obtained numerically is under-predicted in 5 locations by numerical calculation. Further, investigations on the variations of the effects of the length-to-depth ratio of cavity and Mach number on the combustion characteristics has been carried out. The present results show that there is an optimal length-to-depth ratio for the cavity for which the performance of combustor significantly improves and also efficient combustion takes place within the combustor region. Also, the shifting of the location of incident oblique shock took place in the downstream of the H2 inlet when the Mach number value increases. But after achieving a critical Mach number range of 2-2.5, the further increase in Mach number results in lower combustion efficiency which may deteriorate the performance of combustor.
MacArt, Jonathan F.; Mueller, Michael E.
2016-12-01
Two formally second-order accurate, semi-implicit, iterative methods for the solution of scalar transport-reaction equations are developed for Direct Numerical Simulation (DNS) of low Mach number turbulent reacting flows. The first is a monolithic scheme based on a linearly implicit midpoint method utilizing an approximately factorized exact Jacobian of the transport and reaction operators. The second is an operator splitting scheme based on the Strang splitting approach. The accuracy properties of these schemes, as well as their stability, cost, and the effect of chemical mechanism size on relative performance, are assessed in two one-dimensional test configurations comprising an unsteady premixed flame and an unsteady nonpremixed ignition, which have substantially different Damköhler numbers and relative stiffness of transport to chemistry. All schemes demonstrate their formal order of accuracy in the fully-coupled convergence tests. Compared to a (non-)factorized scheme with a diagonal approximation to the chemical Jacobian, the monolithic, factorized scheme using the exact chemical Jacobian is shown to be both more stable and more economical. This is due to an improved convergence rate of the iterative procedure, and the difference between the two schemes in convergence rate grows as the time step increases. The stability properties of the Strang splitting scheme are demonstrated to outpace those of Lie splitting and monolithic schemes in simulations at high Damköhler number; however, in this regime, the monolithic scheme using the approximately factorized exact Jacobian is found to be the most economical at practical CFL numbers. The performance of the schemes is further evaluated in a simulation of a three-dimensional, spatially evolving, turbulent nonpremixed planar jet flame.
Kubiak, M A; Bzowski, M; Sokol, J M; Fuselier, S A; Galli, A; Heirtzler, D; Kucharek, H; Leonard, T W; Moebius, D J McComas E; Park, J; Schwadron, N A; Wurz, P
2016-01-01
With the velocity vector and temperature of the pristine interstellar neutral (ISN) He recently obtained with high precision from a coordinated analysis summarized by McComas et al.2015b, we analyzed the IBEX observations of neutral He left out from this analysis. These observations were collected during the ISN observation seasons 2010---2014 and cover the region in the Earth's orbit where the Warm Breeze persists. We used the same simulation model and a very similar parameter fitting method to that used for the analysis of ISN He. We approximated the parent population of the Warm Breeze in front of the heliosphere with a homogeneous Maxwell-Boltzmann distribution function and found a temperature of $\\sim 9\\,500$ K, an inflow speed of 11.3 km s$^{-1}$, and an inflow longitude and latitude in the J2000 ecliptic coordinates $251.6^\\circ$, $12.0^\\circ$. The abundance of the Warm Breeze relative to the interstellar neutral He is 5.7\\% and the Mach number is 1.97. The newly found inflow direction of the Warm Bree...
Myllys, M. E.; Kilpua, E.; Lavraud, B.
2015-12-01
We have investigated the effect of key solar wind driving parameters on the solar wind-magnetosphere coupling efficiency and saturation of the cross polar cap potential (CPCP) during sheath and magnetic cloud driven storms. The particular focus of the study was on the coupling efficiency dependence with Alfven Mach number (MA).Since we are studying the instantaneous coupling efficiency instead of the average efficiency over the whole solar wind structure, we needed to take into account the communication time between the solar wind and the magnetosphere. We present the results of the time delay analysis between geomagnetic indices (PCN, AE and SYM-H) and the interplanetary electric field y-component (EY, GSM coordinate system) and Newell and Borovsky functions. The study shows that the MA has a clear effect to the saturation of the PCN index, which can be used as a proxy of the polar cap potential. The higher the MA the higher the limit EY value after which the saturation starts to occur. Thus, the coupling efficiency increases as a function of MA. Also, the AE index saturates during high solar wind driving but the saturation is not MA depended. However, the results also suggest that the MA it is not the primary cause for the PCN saturation.
Sovardi, Carlo; Jaensch, Stefan; Polifke, Wolfgang
2016-09-01
A numerical method to concurrently characterize both aeroacoustic scattering and noise sources at a duct singularity is presented. This approach combines Large Eddy Simulation (LES) with techniques of System Identification (SI): In a first step, a highly resolved LES with external broadband acoustic excitation is carried out. Subsequently, time series data extracted from the LES are post-processed by means of SI to model both acoustic propagation and noise generation. The present work studies the aero-acoustic characteristics of an orifice placed in a duct at low flow Mach numbers with the "LES-SI" method. Parametric SI based on the Box-Jenkins mathematical structure is employed, with a prediction error approach that utilizes correlation analysis of the output residuals to avoid overfitting. Uncertainties of model parameters due to the finite length of times series are quantified in terms of confidence intervals. Numerical results for acoustic scattering matrices and power spectral densities of broad-band noise are validated against experimental measurements over a wide range of frequencies below the cut-off frequency of the duct.
Johnson, F. T.; Samant, S. S.; Bieterman, M. B.; Melvin, R. G.; Young, D. P.; Bussoletti, J. E.; Hilmes, C. L.
1992-01-01
The TranAir computer program calculates transonic flow about arbitrary configurations at subsonic, transonic, and supersonic freestream Mach numbers. TranAir solves the nonlinear full potential equations subject to a variety of boundary conditions modeling wakes, inlets, exhausts, porous walls, and impermeable surfaces. Regions with different total temperature and pressure can be represented. The user's manual describes how to run the TranAir program and its graphical support programs.
CFD-Based Design Optimization Tool Developed for Subsonic Inlet
1995-01-01
The traditional approach to the design of engine inlets for commercial transport aircraft is a tedious process that ends with a less-than-optimum design. With the advent of high-speed computers and the availability of more accurate and reliable computational fluid dynamics (CFD) solvers, numerical optimization processes can effectively be used to design an aerodynamic inlet lip that enhances engine performance. The designers' experience at Boeing Corporation showed that for a peak Mach number on the inlet surface beyond some upper limit, the performance of the engine degrades excessively. Thus, our objective was to optimize efficiency (minimize the peak Mach number) at maximum cruise without compromising performance at other operating conditions. Using a CFD code NPARC, the NASA Lewis Research Center, in collaboration with Boeing, developed an integrated procedure at Lewis to find the optimum shape of a subsonic inlet lip and a numerical optimization code, ADS. We used a GRAPE-based three-dimensional grid generator to help automate the optimization procedure. The inlet lip shape at the crown and the keel was described as a superellipse, and the superellipse exponents and radii ratios were considered as design variables. Three operating conditions: cruise, takeoff, and rolling takeoff, were considered in this study. Three-dimensional Euler computations were carried out to obtain the flow field. At the initial design, the peak Mach numbers for maximum cruise, takeoff, and rolling takeoff conditions were 0.88, 1.772, and 1.61, respectively. The acceptable upper limits on the takeoff and rolling takeoff Mach numbers were 1.55 and 1.45. Since the initial design provided by Boeing was found to be optimum with respect to the maximum cruise condition, the sum of the peak Mach numbers at takeoff and rolling takeoff were minimized in the current study while the maximum cruise Mach number was constrained to be close to that at the existing design. With this objective, the
Moes, Timothy R.; Whitmore, Stephen A.; Jordan, Frank L., Jr.
1993-01-01
A nonintrusive airdata-sensing system was calibrated in flight and wind-tunnel experiments to an angle of attack of 70 deg and to angles of sideslip of +/- 15 deg. Flight-calibration data have also been obtained to Mach 1.2. The sensor, known as the flush airdata sensor, was installed on the nosecap of an F-18 aircraft for flight tests and on a full-scale F-18 forebody for wind-tunnel tests. Flight tests occurred at the NASA Dryden Flight Research Facility, Edwards, California, using the F-18 High Alpha Research Vehicle. Wind-tunnel tests were conducted in the 30- by 60-ft wind tunnel at the NASA LaRC, Hampton, Virginia. The sensor consisted of 23 flush-mounted pressure ports arranged in concentric circles and located within 1.75 in. of the tip of the nosecap. An overdetermined mathematical model was used to relate the pressure measurements to the local airdata quantities. The mathematical model was based on potential flow over a sphere and was empirically adjusted based on flight and wind-tunnel data. For quasi-steady maneuvering, the mathematical model worked well throughout the subsonic, transonic, and low supersonic flight regimes. The model also worked well throughout the angles-of-attack and -sideslip regions studied.
Kuhlman, John M.; Liaw, Paul; Cerney, Michael J.
1988-01-01
A numerical design study was conducted to assess the drag reduction potential of winglets installed on a series of low aspect ratio wings at a design point of M=0.8, C sub L=0.3. Wing-winglet and wing-alone design geometries were obtained for wings of aspect ratios between 1.75 and 2.67, having leading edge sweep angles between 45 and 60 deg. Winglet length was fixed at 15% of wing semispan. To assess the relative performance between wing-winglet and wing-alone configurations, the PPW nonlinear extended small disturbance potential flow code was utilized. This model has proven to yield plausible transonic flow field simulations for the series of low aspect ratio configurations selected. Predicted decreases in pressure drag coefficient for the wing-winglet configurations relative to the corresponding wing-alone planform are about 15% at the design point. Predicted decreases in wing-winglet total drag coefficient are about 12%, relative to the corresponding wing-alone design. Longer winglets (25% of the wing semispan) yielded decreases in the pressure drag of up to 22% and total drag of up to 16.4%. These predicted drag coefficient reductions are comparable to reductions already demonstrated by actual winglet designs installed on higher aspect ratio transport type aircraft.
Eaves, R. H.; Buchanan, T. D.; Warmbrod, J. D.; Johnson, C. B.
1972-01-01
Heat transfer tests for two delta wing configurations were conducted in the hypervelocity wind tunnel. The 24-inch long models were tested at a Mach number of approximately 10.5 and at angles of attack of 20, 40, and 60 degrees over a length Reynolds number range from 5 million to 23 million on 4 May to 4 June 1971. Heat transfer results were obtained from model surface heat gage measurements and thermographic phosphor paint.
Contribution from the Earth's Bow Shock to Region 1 Current under Low Alfvén Mach Numbers
Institute of Scientific and Technical Information of China (English)
PENG Zhong; HU You-Qiu
2009-01-01
@@ Using global MHD simulations of the solar wind-magnetosphere--ionosphere system, we investigate the depen-dence of the contribution from the Earth's bow shock (I1bs) to ionospheric region I field aligned current (FAC) (I1). It is found that I1bs increases with increasing southward interplanetary magnetic field (IMF) strength Bs, if the Alfven Mach number MA of the solar wind exceeds 2, a similar result as obtained by previous authors. However, if MA becomes close to or falls below 2, I1bs will decrease with B8 in both magnitude and percentage (i.e., I1bs/I1) because of the resultant reduction of the bow shock strength. Both the surface current density Jbs at the nose of the bow shock and the total bow shock current lb, share nearly the same relationship with MA, and vary non-monotonically with MA or Bs. The maximum point is found to be located at MA = 2.7. Three conclusions are then made as follows: (1) The surface current density at the nose, which is much easier to be evaluated, may be used to largely describe the behaviour of the bow shock instead of the total bow shock current. (2) The peak of the total bow shock current is reached at about MA = 2.7 when only Bs is adjusted. (3) The non-monotonic variation of the bow shock current with MA causes a similar variation of its contribution to region 1 FAC. The turning point for such contribution is found to be nearly MA= 2. The implication of these conclusions to the saturation of the ionospheric transpolar potential is briefly discussed.
Yu, Rixin; Yu, Jiangfei; Bai, Xue-Song
2012-06-01
We present an improved numerical scheme for numerical simulations of low Mach number turbulent reacting flows with detailed chemistry and transport. The method is based on a semi-implicit operator-splitting scheme with a stiff solver for integration of the chemical kinetic rates, developed by Knio et al. [O.M. Knio, H.N. Najm, P.S. Wyckoff, A semi-implicit numerical scheme for reacting flow II. Stiff, operator-split formulation, Journal of Computational Physics 154 (2) (1999) 428-467]. Using the material derivative form of continuity equation, we enhance the scheme to allow for large density ratio in the flow field. The scheme is developed for direct numerical simulation of turbulent reacting flow by employing high-order discretization for the spatial terms. The accuracy of the scheme in space and time is verified by examining the grid/time-step dependency on one-dimensional benchmark cases: a freely propagating premixed flame in an open environment and in an enclosure related to spark-ignition engines. The scheme is then examined in simulations of a two-dimensional laminar flame/vortex-pair interaction. Furthermore, we apply the scheme to direct numerical simulation of a homogeneous charge compression ignition (HCCI) process in an enclosure studied previously in the literature. Satisfactory agreement is found in terms of the overall ignition behavior, local reaction zone structures and statistical quantities. Finally, the scheme is used to study the development of intrinsic flame instabilities in a lean H2/air premixed flame, where it is shown that the spatial and temporary accuracies of numerical schemes can have great impact on the prediction of the sensitive nonlinear evolution process of flame instability.
Park, Jaehong; Workman, Jared C; Blackman, Eric G
2012-01-01
Low Mach number, high beta fast mode shocks can occur in the magnetic reconnection outflows of solar flares. These shocks, which occur above flare loop tops, may provide the electron energization responsible for some of the observed hard X-rays and contemporaneous radio emission. Here we present new 2D particle-in-cell simulations of low Mach number/high beta quasi-perpendicular shocks. The simulations show that electrons above a certain energy threshold experience shock-drift-acceleration. The transition energy between the thermal and non-thermal spectrum and the spectral index from the simulations are consistent with some of the X-ray spectra from RHESSI in the energy regime, $E\\lesssim 40\\sim 100$ keV. Plasma instabilities associated with the shock structure such as the modified-two-stream and the electron whistler/mirror instabilities are examined and compared with the numerical solutions of the kinetic dispersion relations.
Allan Brian G.; Owens, Lewis, R.
2006-01-01
This paper will investigate the validation of a NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as the baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a freestream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the length of the fan-face diameter. The numerical simulations with and without wind tunnel walls are performed, quantifying effects of the tunnel walls on the BLI inlet flow measurements. The wind tunnel test evaluated several different combinations of jet locations and mass flow rates as well as a vortex generator (VG) vane case. The numerical simulations will be performed on a single jet configuration for varying actuator mass flow rates at a fix inlet mass flow condition. Validation of the numerical simulations for the VG vane case will also be performed for varying inlet mass flow rates. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCPavg, very well for comparisons made within the designed operating range of the BLI inlet. However the CFD simulations did predict a total pressure recovery that was 0.01 lower than the experiment. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe
Phillips, W. P.
1981-01-01
Subsonic longitudinal andd laternal directional characteristics were obtained for several modified configurations of the 140 A/B orbiter (0.010 scale). These modifications, designed to extend longitudinal trim capability forward of the 65 percent fuselage length station, consisted of modified wing planform fillet and a canard. Tests were performed in the Langley Low Turbulence Pressure Tunnel at Reynolds numbers from about 4.2 million to 14.3 million based on the fuselage reference length.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
On super-sonic or trans-sonic planar cascade wind tunnel of free jet intermittent type, wind blowing experiments were performed on the typical sections of stator and rotor blades in the last stage of ultra-ultra-critical steam turbine with extra-long blade of 1200mm. The influences of attack angle and Mach number on the aerodynamic performances of these sections of the blade profiles were verified, and their operating ranges were also specified.
Keenan, James A.; Kuhlman, John M.
1991-01-01
A computational study was conducted on two wings, of aspect ratios 1.244 and 1.865, each having 65 degree leading edge sweep angles, to determine the effects of nonplanar winglets at supersonic Mach numbers. A Mach number of 1.62 was selected as the design value. The winglets studied were parametrically varied in alignment, length, sweep, camber, thickness, and dihedral angle to determine which geometry had the best predicted performance. For the computational analysis, an available Euler marching technique was used. The results indicated that the possibility existed for wing-winglet geometries to equal the performance of wing-alone bodies in supersonic flows with both bodies having the same semispan. The first wing with winglet used NACA 1402 airfoils for the base wing and was shown to have lift-to-pressure drag ratios within 0.136 percent to 0.360 percent of the NACA 1402 wing-alone. The other base wing was a natural flow wing which was previously designed specifically for a Mach number of 1.62. The results obtained showed that the natural wing-alone had a slightly higher lift-to-pressure drag than the natural wing with winglets.
Energy Technology Data Exchange (ETDEWEB)
Li, Pak Shing; Klein, Richard I. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Martin, Daniel F. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); McKee, Christopher F., E-mail: psli@astron.berkeley.edu, E-mail: klein@astron.berkeley.edu, E-mail: DFMartin@lbl.gov, E-mail: cmckee@astro.berkeley.edu [Physics Department and Astronomy Department, University of California, Berkeley, CA 94720 (United States)
2012-02-01
Performing a stable, long-duration simulation of driven MHD turbulence with a high thermal Mach number and a strong initial magnetic field is a challenge to high-order Godunov ideal MHD schemes because of the difficulty in guaranteeing positivity of the density and pressure. We have implemented a robust combination of reconstruction schemes, Riemann solvers, limiters, and constrained transport electromotive force averaging schemes that can meet this challenge, and using this strategy, we have developed a new adaptive mesh refinement (AMR) MHD module of the ORION2 code. We investigate the effects of AMR on several statistical properties of a turbulent ideal MHD system with a thermal Mach number of 10 and a plasma {beta}{sub 0} of 0.1 as initial conditions; our code is shown to be stable for simulations with higher Mach numbers (M{sub rms}= 17.3) and smaller plasma beta ({beta}{sub 0} = 0.0067) as well. Our results show that the quality of the turbulence simulation is generally related to the volume-averaged refinement. Our AMR simulations show that the turbulent dissipation coefficient for supersonic MHD turbulence is about 0.5, in agreement with unigrid simulations.
Li, Pak Shing; Klein, Richard I; McKee, Christopher F
2011-01-01
Performing a stable, long duration simulation of driven MHD turbulence with a high thermal Mach number and a strong initial magnetic field is a challenge to high-order Godunov ideal MHD schemes because of the difficulty in guaranteeing positivity of the density and pressure. We have implemented a robust combination of reconstruction schemes, Riemann solvers, limiters, and Constrained Transport EMF averaging schemes that can meet this challenge, and using this strategy, we have developed a new Adaptive Mesh Refinement (AMR) MHD module of the ORION2 code. We investigate the effects of AMR on several statistical properties of a turbulent ideal MHD system with a thermal Mach number of 10 and a plasma $\\beta_0$ of 0.1 as initial conditions; our code is shown to be stable for simulations with higher Mach numbers ($M_rms = 17.3$) and smaller plasma beta ($\\beta_0 = 0.0067$) as well. Our results show that the quality of the turbulence simulation is generally related to the volume-averaged refinement. Our AMR simulati...
Energy Technology Data Exchange (ETDEWEB)
Kubiak, Marzena A.; Swaczyna, P.; Bzowski, M.; Sokół, J. M. [Space Research Centre of the Polish Academy of Sciences (CBK PAN), 00-716 Warsaw (Poland); Fuselier, S. A.; McComas, D. J. [Southwest Research Institute, San Antonio, TX (United States); Galli, A.; Wurz, P. [Physikalisches Institut, Universität Bern, Bern (Switzerland); Heirtzler, D.; Kucharek, H.; Leonard, T. W.; Möbius, E.; Park, J.; Schwadron, N. A., E-mail: mkubiak@cbk.waw.pl [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH (United States)
2016-04-15
Following the high-precision determination of the velocity vector and temperature of the pristine interstellar neutral (ISN) He via a coordinated analysis summarized by McComas et al., we analyzed the Interstellar Boundary Explorer (IBEX) observations of neutral He left out from this analysis. These observations were collected during the ISN observation seasons 2010–2014 and cover the region in the Earth's orbit where the Warm Breeze (WB) persists. We used the same simulation model and a parameter fitting method very similar to that used for the analysis of ISN He. We approximated the parent population of the WB in front of the heliosphere with a homogeneous Maxwell–Boltzmann distribution function and found a temperature of ∼9500 K, an inflow speed of 11.3 km s{sup −1}, and an inflow longitude and latitude in the J2000 ecliptic coordinates 251.°6, 12.°0. The abundance of the WB relative to ISN He is 5.7% and the Mach number is 1.97. The newly determined inflow direction of the WB, the inflow directions of ISN H and ISN He, and the direction to the center of the IBEX Ribbon are almost perfectly co-planar, and this plane coincides within relatively narrow statistical uncertainties with the plane fitted only to the inflow directions of ISN He, ISN H, and the WB. This co-planarity lends support to the hypothesis that the WB is the secondary population of ISN He and that the center of the Ribbon coincides with the direction of the local interstellar magnetic field (ISMF). The common plane for the direction of the inflow of ISN gas, ISN H, the WB, and the local ISMF is given by the normal direction: ecliptic longitude 349.°7 ± 0.°6 and latitude 35.°7 ± 0.6 in the J2000 coordinates, with a correlation coefficient of 0.85.
Sawyer, J. W.
1972-01-01
A wind-tunnel investigation was conducted at free-stream Mach numbers from 0.20 to 1.00 and corresponding Reynolds numbers, based on maximum afterbody diameter, from 2.25 x one million to 6.90 x one million on a solid model of an attached inflatable decelerator (AID) connected to the base of an ogive-cylinder. Tests were conducted to obtain ram-air and surface pressure distributions about the AID. AID shapes derived for subsonic deployment are dependent on the pressure distributions used in their derivation, and the different shapes obtained are dependent on the Mach number for which the design is made. The resulting pressure distributions were used in a design program to obtain new shapes which were compared with the original pressure-distribution shape.
Shrout, B. L.; Corlett, W. A.; Collins, I. K.
1979-01-01
The tabulated results of surface pressure tests conducted on the wing and fuselage of an airplane model in the Langley Unitary Plan wind tunnel are presented without analysis. The model tested was that of a supersonic-cruise airplane with a highly swept arrow-wing planform, two engine nacelles mounted beneath the wing, and outboard vertical tails. Data were obtained at Mach numbers of 2.30, 2.96, and 3.30 for angles of attack from -4 deg to 12 deg. The Reynolds number for these tests was 6,560,000 per meter.
Holland, Scott D.; Murphy, Kelly J.
1993-01-01
Since mission profiles for airbreathing hypersonic vehicles such as the National Aero-Space Plane include single-stage-to-orbit requirements, real gas effects may become important with respect to engine performance. The effects of the decrease in the ratio of specific heats have been investigated in generic three-dimensional sidewall compression scramjet inlets with leading-edge sweep angles of 30 and 70 degrees. The effects of a decrease in ratio of specific heats were seen by comparing data from two facilities in two test gases: in the Langley Mach 6 CF4 Tunnel in tetrafluoromethane (where gamma=1.22) and in the Langley 15-Inch Mach 6 Air Tunnel in perfect gas air (where gamma=1.4). In addition to the simulated real gas effects, the parametric effects of cowl position, contraction ratio, leading-edge sweep, and Reynolds number were investigated in the 15-Inch Mach 6 Air Tunnel. The models were instrumented with a total of 45 static pressure orifices distributed on the sidewalls and baseplate. Surface streamline patterns were examined via oil flow, and schlieren videos were made of the external flow field. The results of these tests have significant implications to ground based testing of inlets in facilities which do not operate at flight enthalpies.
Shrewsbury, George D.; Vadyak, Joseph; Schuster, David M.; Smith, Marilyn J.
1989-01-01
A computer analysis was developed for calculating steady (or unsteady) three-dimensional aircraft component flow fields. This algorithm, called ENS3D, can compute the flow field for the following configurations: diffuser duct/thrust nozzle, isolated wing, isolated fuselage, wing/fuselage with or without integrated inlet and exhaust, nacelle/inlet, nacelle (fuselage) afterbody/exhaust jet, complete transport engine installation, and multicomponent configurations using zonal grid generation technique. Solutions can be obtained for subsonic, transonic, or hypersonic freestream speeds. The algorithm can solve either the Euler equations for inviscid flow, the thin shear layer Navier-Stokes equations for viscous flow, or the full Navier-Stokes equations for viscous flow. The flow field solution is determined on a body-fitted computational grid. A fully-implicit alternating direction implicit method is employed for the solution of the finite difference equations. For viscous computations, either a two layer eddy-viscosity turbulence model or the k-epsilon two equation transport model can be used to achieve mathematical closure.
Capone, F. J.
1982-01-01
An investigation to determine the aeropropulsive characteristics of nonaxisymmetric nozzles on an F-18 jet effects model was conducted in the Langley 16-foot transonic tunnel and the AEDC 16-foot supersonic wind tunnel. The performance of a two dimensional convergent-divergent nozzle, a single expansion ramp nozzle, and a wedge nozzle was compared with that of the baseline axisymmetric nozzle. Test data were obtained at static conditions and at Mach numbers from 0.60 to 2.20 at an angle of attack of 0 deg. Nozzle pressure ratio was varied from jet-off to about 20.
Calleja, John; Tamagno, Jose
1993-01-01
A series of air calibration tests were performed in GASL's HYPULSE facility in order to more accurately determine test section flow conditions for flows simulating total enthalpies in the Mach 13 to 17 range. Present calibration data supplements previous data and includes direct measurement of test section pitot and static pressure, acceleration tube wall pressure and heat transfer, and primary and secondary incident shock velocities. Useful test core diameters along with the corresponding free-stream conditions and usable testing times were determined. For the M13.5 condition, in-stream static pressure surveys showed the temporal and spacial uniformity of this quantity across the useful test core. In addition, finite fringe interferograms taken of the free-stream flow at the test section did not indicate the presence of any 'strong' wave system for any of the conditions investigated.
de Gasperin, F; van Weeren, R J; Dawson, W A; Golovich, N; Wittman, D; Bonafede, A; Bruggen, M
2015-01-01
Diffuse radio emission in the form of radio halos and relics has been found in a number of merging galaxy clusters. These structures indicate that shock and turbulence associated with the merger accelerate electrons to relativistic energies. We report the discovery of a radio relic + radio halo system in PSZ1 G108.18-11.53 (z=0.335). This cluster hosts the second most powerful double radio relic system ever discovered. We observed PSZ1 G108.18-11.53 with the Giant Meterwave Radio Telescope (GMRT) and the Westerbork Synthesis Radio Telescope (WSRT). We obtained radio maps at 147, 323, 607 and 1380 MHz. We also observed the cluster with the Keck telescope, obtaining the spectroscopic redshift for 42 cluster members. From the injection index we obtained the Mach number of the shocks generating the two radio relics. For the southern shock we found M = 2.33^{+0.19}_{-0.26}, while the northern shock Mach number goes from M = 2.20^{+0.07}_{-0.14} in the north part down to M = 2.00^{+0.03}_{-0.08} in the southern reg...
Directory of Open Access Journals (Sweden)
Moritz Schulze
2016-10-01
Full Text Available The interaction of a plane acoustic wave and a sheared flow is numerically investigated for simple orifice and perforated plate configurations in an isolated, non-resonant environment for Mach numbers up to choked conditions in the holes. Analytical derivations found in the literature are not valid in this regime due to restrictions to low Mach numbers and incompressible conditions. To allow for a systematic and detailed parameter study, a low-cost hybrid Computational Fluid Dynamic/Computational Aeroacoustic (CFD/CAA methodology is used. For the CFD simulations, a standard k–ϵ Reynolds-Averaged Navier–Stokes (RANS model is employed, while the CAA simulations are based on frequency space transformed linearized Euler equations (LEE, which are discretized in a stabilized Finite Element method. Simulation times in the order of seconds per frequency allow for a detailed parameter study. From the application of the Multi Microphone Method together with the two-source location procedure, acoustic scattering matrices are calculated and compared to experimental findings showing very good agreement. The scattering properties are presented in the form of scattering matrices for a frequency range of 500–1500 Hz.
Kainulainen, Jouni
2012-01-01
Measuring the mass distribution of infrared dark clouds (IRDCs) over the wide dynamic range of their column densities is a fundamental obstacle in determining the initial conditions of high-mass star formation and star cluster formation. We present a new technique to derive high-dynamic-range, arcsecond-scale resolution column density data for IRDCs and demonstrate the potential of such data in measuring the density variance - sonic Mach number relation in molecular clouds. We combine near-infrared data from the UKIDSS/Galactic Plane Survey with mid-infrared data from the Spitzer/GLIMPSE survey to derive dust extinction maps for a sample of ten IRDCs. We then examine the linewidths of the IRDCs using 13CO line emission data from the FCRAO/Galactic Ring Survey and derive a column density - sonic Mach number relation for them. For comparison, we also examine the relation in a sample of nearby molecular clouds. The presented column density mapping technique provides a very capable, temperature independent tool f...
Supersonic and subsonic measurements of mesospheric ionization.
Hale, L. C.; Nickell, L. C.; Kennedy, B.; Powell, T. A.
1972-01-01
An Arcas rocket-parachute system was used at night to compare supersonic and subsonic ionization measurements below 75 km. A hemispherical nose-tip probe was used on ascent and a parachute-borne blunt probe on descent to measure polar conductivities, which were due entirely to positive and negative ions. The velocity of the supersonic probe was Mach 2.5 at 50 km and 1.75 at 70 km; the blunt probe was subsonic below 71 km. Between 65 and 75 km the ratio of negative to positive conductivities (and thus of mobilities) determined by the blunt probe was about 1.2, and it approached 1 below this altitude range. The ratio obtained by the nose-tip probe varied from 1.5 at 75 km to .6 at 65 km, thus indicating a rapid variation of the effects of the shock wave on the sampled ions. The absolute values of positive conductivity measured subsonically and supersonically were essentially identical from 60 to 75 km, indicating that the sampled ions were unchanged by the shock. However, below 60 km the shock apparently 'broke up' the positive ions, as indicated by higher measured conductivities.
Energy Technology Data Exchange (ETDEWEB)
Core, X.
2002-02-01
The isobar approximation for the system of the balance equations of mass, momentum, energy and chemical species is a suitable approximation to represent low Mach number reactive flows. In this approximation, which neglects acoustics phenomena, the mixture is hydrodynamically incompressible and the thermodynamic effects lead to an uniform compression of the system. We present a novel numerical scheme for this approximation. An incremental projection method, which uses the original form of mass balance equation, discretizes in time the Navier-Stokes equations. Spatial discretization is achieved through a finite volume approach on MAC-type staggered mesh. A higher order de-centered scheme is used to compute the convective fluxes. We associate to this discretization a local mesh refinement method, based on Flux Interface Correction technique. A first application concerns a forced flow with variable density which mimics a combustion problem. The second application is natural convection with first small temperature variations and then beyond the limit of validity of the Boussinesq approximation. Finally, we treat a third application which is a laminar diffusion flame. For each of these test problems, we demonstrate the robustness of the proposed numerical scheme, notably for the density spatial variations. We analyze the gain in accuracy obtained with the local mesh refinement method. (author)
Devade, Kiran D.; Pise, Ashok T.
2017-01-01
Ranque Hilsch vortex tube is a device that can produce cold and hot air streams simultaneously from pressurized air. Performance of vortex tube is influenced by a number of geometrical and operational parameters. In this study parametric analysis of vortex tube is carried out. Air is used as the working fluid and geometrical parameters like length to diameter ratio (15, 16, 17, 18), exit valve angles (30°-90°), orifice diameters (5, 6 and 7 mm), 2 entry nozzles and tube divergence angle 4° is used for experimentation. Operational parameters like pressure (200-600 kPa), cold mass fraction (0-1) is varied and effect of Mach number at the inlet of the tube is investigated. The vortex tube is tested at sub sonic (0 tube is observed for CMF up to 0.5. Experimental correlations are proposed for optimum COP. Parametric correlation is developed for geometrical and operational parameters.
Lanfranco, M. J.; Sparks, V. W.; Kavanaugh, A. T.
1973-01-01
An experimental investigation was conducted in a 9- by 7-foot supersonic wind tunnel to determine the effect of plume-induced flow separation and aspiration effects due to operation of both the orbiter and the solid rocket motors on a 0.019-scale model of the launch configuration of the space shuttle vehicle. Longitudinal and lateral-directional stability data were obtained at Mach numbers of 1.6, 2.0, and 2.2 with and without the engines operating. The plumes exiting from the engines were simulated by a cold gas jet supplied by an auxiliary 200 atmosphere air supply system, and by solid body plume simulators. Comparisons of the aerodynamic effects produced by these two simulation procedures are presented. The data indicate that the parameters most significantly affected by the jet plumes are the pitching moment, the elevon control effectiveness, the axial force, and the orbiter wing loads.
Miser, James W; Stewart, Warner L
1957-01-01
A blade design study is presented for a two-stage air-cooled turbine suitable for flight at a Mach number of 2.5 for which velocity diagrams have been previously obtained. The detailed procedure used in the design of the blades is given. In addition, the design blade shapes, surface velocity distributions, inner and outer wall contours, and other design data are presented. Of all the blade rows, the first-stage rotor has the highest solidity, with a value of 2.289 at the mean section. The second-stage stator also had a high mean-section solidity of 1.927, mainly because of its high inlet whirl. The second-stage rotor has the highest value of the suction-surface diffusion parameter, with a value of 0.151. All other blade rows have values for this parameter under 0.100.
Voit, Charles H; Guentert, Donald C; Dugan, James F
1950-01-01
A complete stage of an axial-flow compressor was designed and built to investigate the possibility of obtaining a high pressure ratio with an acceptable efficiency through the use of the optimum combination of high blade loading and high relative inlet Mach number. Over-all stage performance was investigated over a range of flows at equivalent tip speeds of 418 to 836 feet per second. At design speed (836 ft/sec), a peak total-pressure ration of 1.445 was obtained with an adiabatic efficiency of 0.89. For design angle of attack at the mean radius, a total-pressure ratio of 1.392 was obtained.
基于预处理HLLEW格式的全速域数值算法%Preconditioning HLLEW Scheme for Flows at All Mach Numbers
Institute of Scientific and Technical Information of China (English)
刘中玉; 张明锋; 郑冠男; 杨国伟
2016-01-01
Based on HLLEW ( Harten⁃Lax⁃Van Leer⁃Einfeldt⁃Wada) scheme, low speed preconditioning technology is introduced to develop a three⁃dimensional Navier⁃Stokes solver for flows at all Mach numbers. Low speed preconditioning techniques is introduced to reconstruct dissipative term in HLLEW scheme and preconditioning HLLEW scheme is proposed. Implicit time⁃marching method is constructed based on preconditioning Jacobian Matrix. Results of NACA 4412 incompressible flow and RAE 2822 transonic flow with preconditioning HLLEW scheme are compared with results by original method and experimental data. It shows that preconditioning HLLEW method improves accuracy and convergence rate for low speed flow. It can be applied for flows at all Mach numbers.%基于HLLEW（ Harten⁃Lax⁃Van Leer⁃Einfeldt⁃Wada）格式引入预处理技术发展适合求解全速域流场的三维Navier⁃Stokes求解器。引入低速预处理技术，重新构造HLLEW格式的耗散项，给出预处理后的HLLEW格式，并根据预处理后的雅克比矩阵构造相应的隐式时间推进方程。利用预处理方法求解 NACA 4412低速不可压流动与RAE 2822跨声速可压缩流动，并与实验结果及原有方法的计算结果对比。结果表明：预处理HLLEW格式不仅提高低速不可压缩流动的计算效率和精度，也保持了对可压缩流动的处理能力，是一种适用于全速域流场数值模拟的有效方法。
On the Importance of Very-light Internally-subsonic AGN Jets in Radio-mode AGN Feedback
Guo, Fulai
2016-01-01
Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kpc-scale interaction of AGN jets with the hot halo gas, where jet properties may play an important role. Large-scale jet simulations often initiate light internally-supersonic jets with density contrast $0.01<\\eta<1$. Here we argue for the importance of very-light ($\\eta<0.01$) internally-subsonic jets in AGN feedback. We investigated the shapes of young X-ray cavities produced by AGN jets in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally-subsonic jets, while internally-supersonic jets produce cylindrical, center-wide, or top-wide cavities. We found examples of real cavities inflated by internally-subsonic and internally-supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resul...
Subsonic Indicial Aerodynamics for Aerofoil's Unsteady Loads via Numerical and Analytical Methods
Berci, Marco
2016-01-01
This study deals with generating aerodynamic indicial-admittance functions for predicting the unsteady lift of two-dimensional aerofoils in subsonic flow, using approximate numerical and analytical formulations. Both a step-change in the angle of attack and a sharp-edge gust are suitably considered as small perturbations. Novel contributions concern both a systematic analysis of the computational simulations process and an effective theoretical synthesis of its outcome, providing with sound cross-validation. Good practice for generating the indicial-admittance functions via computational fluid dynamics is first investigated for several Mach numbers, angles of attack and aerofoil profiles. Convenient analytical approximations of such indicial functions are then obtained by generalising those available for incompressible flow, taking advantage of acoustic wave theory for the non-circulatory airload and Prandtl-Glauert's scalability rule for the circulatory airload. An explicit parametric formula is newly propos...
Jackson, Charles M., Jr.; Harris, Roy V., Jr.
1960-01-01
An investigation has been made in the Langley 4- by 4-foot supersonic pressure tunnel at a Mach number of 1.99 to determine the longitudinal stability and control characteristics of a reentry model consisting of a lenticular-shaped body with two fin configurations (horizontal fins with end plates). Effects of deflecting the larger size fins as pitch-control surfaces were also investigated. The results indicate that the body alone was unstable from an angle of attack of 0 deg to about 55 deg where it became stable and remained so to 90 deg. The addition of fins provided positive longitudinal stability throughout the angle-of-attack range and increased the lift-drag ratio of the configuration. Reducing the horizontal-fin area at the inboard trailing edge of the fin had only a small effect on the aerodynamic characteristics of the vehicle for the condition of no fin deflection. Deflecting the fins, appeared to be an effective means of pitch control and had only a small effect on lift-drag ratio.
Sayadi, Taraneh; Hamman, Curtis; Moin, Parviz
2011-11-01
Transition to turbulence via spatially evolving secondary instabilities in compressible, zero-pressure-gradient flat plate boundary layers is numerically simulated for both the Klebanoff K-type and Herbert H-type disturbances. The objective of this work is to evaluate the universality of the breakdown process between different routes through transition in wall-bounded shear flows. Each localized linear disturbance is amplified through weak non-linear instability that grows into lambda-vortices and then hairpin-shaped eddies with harmonic wavelength, which become less organized in the late-transitional regime once a fully populated spanwise turbulent energy spectrum is established. For the H-type transition, the computational domain extends from Rex =105 , where laminar blowing and suction excites the most unstable fundamental and a pair of oblique waves, to fully turbulent stage at Rex = 10 . 6 ×105 . The computational domain for the K-type transition extends to Rex = 9 . 6 ×105 . The computational algorithm employs fourth-order central differences with non-reflective numerical sponges along the external boundaries. For each case, the Mach number is 0.2. Supported by the PSAAP program of DoE, ANL and LLNL.
Directory of Open Access Journals (Sweden)
Matthias Bauer
2016-10-01
Full Text Available This paper discusses wind tunnel test results aimed at advancing active flow control technology to increase the aerodynamic efficiency of an aircraft during take-off. A model of the outer section of a representative civil airliner wing was equipped with two-stage fluidic actuators between the slat edge and wing tip, where mechanical high-lift devices fail to integrate. The experiments were conducted at a nominal take-off Mach number of M = 0.2. At this incidence velocity, separation on the wing section, accompanied by increased drag, is triggered by the strong slat edge vortex at high angles of attack. On the basis of global force measurements and local static pressure data, the effect of pulsed blowing on the complex flow is evaluated, considering various momentum coefficients and spanwise distributions of the actuation effort. It is shown that through local intensification of forcing, a momentum coefficient of less than c μ = 0.6 % suffices to offset the stall by 2.4°, increase the maximum lift by more than 10% and reduce the drag by 37% compared to the uncontrolled flow.
Seo, Jung Hee; Mittal, Rajat
2011-02-20
A new sharp-interface immersed boundary method based approach for the computation of low-Mach number flow-induced sound around complex geometries is described. The underlying approach is based on a hydrodynamic/acoustic splitting technique where the incompressible flow is first computed using a second-order accurate immersed boundary solver. This is followed by the computation of sound using the linearized perturbed compressible equations (LPCE). The primary contribution of the current work is the development of a versatile, high-order accurate immersed boundary method for solving the LPCE in complex domains. This new method applies the boundary condition on the immersed boundary to a high-order by combining the ghost-cell approach with a weighted least-squares error method based on a high-order approximating polynomial. The method is validated for canonical acoustic wave scattering and flow-induced noise problems. Applications of this technique to relatively complex cases of practical interest are also presented.
Bzowski, M; Kubiak, M A; Sokol, J M; Fuselier, S A; Galli, A; Heirtzler, D; Kucharek, H; Leonard, T W; McComas, D J; Moebius, E; Schwadron, N A; Wurz, P
2015-01-01
We analyzed observations of interstellar neutral helium (ISN~He) obtained from the Interstellar Boundary Explorer (IBEX) satellite during its first six years of operation. We used a refined version of the ISN~He simulation model, presented in the companion paper by Sokol_et al. 2015, and a sophisticated data correlation and uncertainty system and parameter fitting method, described in the companion paper by Swaczyna et al 2015. We analyzed the entire data set together and the yearly subsets, and found the temperature and velocity vector of ISN~He in front of the heliosphere. As seen in the previous studies, the allowable parameters are highly correlated and form a four-dimensional tube in the parameter space. The inflow longitudes obtained from the yearly data subsets show a spread of ~6 degree, with the other parameters varying accordingly along the parameter tube, and the minimum chi-square value is larger than expected. We found, however, that the Mach number of the ISN~He flow shows very little scatter an...
Subsonic tests of an all-flush-pressure-orifice air data system
Larson, T. J.; Siemers, P. M., III
1981-01-01
The use of an all-flush-pressure-orifice array as a subsonic air data system was evaluated in flight and wind tunnel tests. Two orifice configurations were investigated. Both used orifices arranged in a cruciform pattern on the airplane nose. One configuration also used orifices on the sides of the fuselage for a source of static pressure. The all-nose-orifice configuration was similar to the shuttle entry air data system (SEADS). The flight data were obtained with a KC-135A airplane. The wind tunnel data were acquired with a 0.035-scale model of the KC-135A airplane. With proper calibration, several orifices on the vertical centerline of the vehicle's nose were found to be satisfactory for the determination of total pressure and angle of attack. Angle of sideslip could be accurately determined from pressure measurements made on the horizontal centerline of the aircraft. Orifice pairs were also found that provided pressure ratio relationships suitable for the determination of Mach number. The accuracy that can be expected for the air data determined with SEADS during subsonic orbiter flight is indicated.
Effect of Initial Condition on Subsonic Jet Noise from Two Rectangular Nozzles
Zaman, K. B. M. Q.
2012-01-01
Differences in jet noise data from two small 8:1 aspect ratio nozzles are investigated experimentally. The interiors of the two nozzles are identical but one has a thin-lip at the exit while the has a perpendicular face at the exit (thick-lip). It is found that the thin-lip nozzle is substantially noisier throughout the subsonic Mach number range. As much as 5dB difference in OASPL is noticed around Mj =0.96. Hot-wire measurements are carried out for the characteristics of the exit boundary layer and, overall, the noise difference can be ascribed to differences in the boundary layer state. The boundary layer of the quieter (thick-lip) nozzle goes through transition around M(sub j) =0.25 and at higher M(sub j) it remains "nominally turbulent". In comparison, the boundary layer of the thin-lip nozzle is found to remain "nominally laminar". at high subsonic conditions. The nominally laminar state involves significantly larger turbulence intensities commensurate with the higher radiated noise.
Lewis, B. W.
1961-01-01
A limited investigation of the deterioration characteristics of 22 refractory materials was conducted by exposing them to a stagnation temperature of 3,800 F in a Mach number 2 ceramic-heated jet at the Langley Research Center. The materials tested were six materials whose major constituent was silicon carbide, five cermets whose major constituent was titanium carbide, six materials whose major constituents were metal borides, four cermets containing alumina, and one silicon nitride model. Tests consisted of obtaining weight change and appearance changes for 1/2-inch-diameter hemispherical-nose cylindrical models exposed to the air jet for 30 seconds at a time for a total of four runs or 2 minutes exposure. Curves of weight changes plotted against the number of 30-second tests in the jet were obtained. Estimates of average surface temperature near the stagnation point of the model were obtained by use of a special temperature-measuring camera. The models were examined before and after the completion of the tests for possible changes in microstructure; no significant changes were found. The data obtained were analyzed with the view that the oxidation characteristics of the materials were the main factor in deterioration of the materials under the conditions of the tests. It was concluded that only those materials which changed in weight the least could be recommended for further extensive application-oriented evaluations. The following materials fell in this category: silicon carbide - silicon, chromium - 28-percent alumina cermet, titanium boride - 5-percent boron carbide. The remainder of the materials tested had oxidation characteristics which appeared to be too severely limiting of their general applications to flight vehicles.
Directory of Open Access Journals (Sweden)
Corneliu STOICA
2009-09-01
Full Text Available The INCAS Subsonic Wind Tunnel is a closed circuit, continuous, atmospheric pressure facility with a maximum speed of 110 m/s. The test section is octagonal ,of 2.5 m wide, 2.0 m high and 4 m long. The tunnel is powered by a 1200 kW, air cooled variable speed DC motor which drives a 12 blade, 3.5 m diameter fan and is equipped with a six component pyramidal type external mechanical balance with a 700 Kgf maximum lift capacity.The angle of attack range is between -45º and +45º while the yaw angle range is between -140º and +216º .The data acquisition system has been modified recently to allow the recording of all test data on a PC - type computer using LABVIEW and a PXI – type chassis containing specialized data acquisition modules.The tunnel is equipped with a variable frequency electrical supply system for powered models and a 10 bar compressed air supply for pneumatic flow control applications.In the recent years the subsonic wind tunnel has been intensively used for tests within several European projects (AVERT, CESAR and others.
Gapcynski, John P; Carlson, Harry W
1955-01-01
The changes in the aerodynamic characteristics of a body of revolution with a fineness ratio of 8 have been determined at Mach numbers of 1.41 and 2.01, a Reynolds number, based on body length, of 4.54 x 10 to the 6th power, and angles of incidence of 0 degrees and plus or minus 3 degrees as the position of the body is varied with respect to a reflection plane. The data are compared with theoretical results.
Littoral Subsonic Seismoacoustic Phenomena Ultrasonic Modeling
2016-06-07
Littoral Subsonic Seismoacoustic Phenomena Ultrasonic Modeling Jacques R. Chamuel Sonoquest Advanced Ultrasonics Research P.O. Box 81153 Wellesley... variable water/air content, and benthic shelled animals leading to accurate acoustic modeling of littoral surficial layer and geophysical inversion...UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Sonoquest Advanced Ultrasonics Research ,P.O. Box 81153,Wellesley Hills,MA,02481-0001 8
Institute of Scientific and Technical Information of China (English)
王键灵; 徐让书; 侯亚军; 王娟娟
2014-01-01
To predict the characteristics of subsonic flow field in front of aircraft inlet-engine combination in the free jet test of engine altitude simulation and to optimize the aerodynimic configuration of the test cell, the CFD method has been used to simulate the external flow of a fighter inlet in subsonic free-jet and in the real flight environment in the atmosphere. The relation of compression effect of the inlet to the inflow air and flight Mach number is analyzed. Optimized installation location of inlet has been found in three Mach num-ber of subsonic free-jet. And we compared the Mach number distribution of the forward and entrance of inlet between the condition that in free-jet and in real atmospheric environment. As a result,it can obtain the flow field of similar Mach number that the simulating of real atmospheric flight environment with subsonic free-jet.%为了预测航空发动机高空模拟自由射流试验中飞机进气道-发动机组合体前方的亚声速流场特性，优化试验舱的气动设计，采用 CFD 方法在亚声速自由射流和真实大气飞行条件下对某战斗机进气道的外流场进行数值模拟。分析了进气道对前方气流压缩作用与飞行马赫数关系，对比和分析了分别在自由射流与真实大气中进气道前和进气道入口处的马赫数分布，确定了3种马赫数下进气道在自由射流中的最佳安装位置。比较发现，亚声速自由射流对真实高空大气飞行进行模拟，可以得到马赫数相似的流场。
3D CFD modeling of subsonic and transonic flowing-gas DPALs with different pumping geometries
Yacoby, Eyal; Sadot, Oren; Barmashenko, Boris D.; Rosenwaks, Salman
2015-10-01
Three-dimensional computational fluid dynamics (3D CFD) modeling of subsonic (Mach number M ~ 0.2) and transonic (M ~ 0.9) diode pumped alkali lasers (DPALs), taking into account fluid dynamics and kinetic processes in the lasing medium is reported. The performance of these lasers is compared with that of supersonic (M ~ 2.7 for Cs and M ~ 2.4 for K) DPALs. The motivation for this study stems from the fact that subsonic and transonic DPALs require much simpler hardware than supersonic ones where supersonic nozzle, diffuser and high power mechanical pump (due to a drop in the gas total pressure in the nozzle) are required for continuous closed cycle operation. For Cs DPALs with 5 x 5 cm2 flow cross section pumped by large cross section (5 x 2 cm2) beam the maximum achievable power of supersonic devices is higher than that of the transonic and subsonic devices by only ~ 3% and ~ 10%, respectively. Thus in this case the supersonic operation mode has no substantial advantage over the transonic one. The main processes limiting the power of Cs supersonic DPALs are saturation of the D2 transition and large ~ 60% losses of alkali atoms due to ionization, whereas the influence of gas heating is negligible. For K transonic DPALs both the gas heating and ionization effects are shown to be unimportant. The maximum values of the power are higher than those in Cs transonic laser by ~ 11%. The power achieved in the supersonic and transonic K DPAL is higher than for the subsonic version, with the same resonator and K density at the inlet, by ~ 84% and ~ 27%, respectively, showing a considerable advantaged of the supersonic device over the transonic one. For pumping by rectangular beams of the same (5 x 2 cm2) cross section, comparison between end-pumping - where the laser beam and pump beam both propagate at along the same axis, and transverse-pumping - where they propagate perpendicularly to each other, shows that the output power and optical-to-optical efficiency are not
Wallskog, Harvey A.
1954-01-01
A 1/5-scale, rocket-propelled model of the Convair F-102 configuration was tested in free flight to determine zero-lift drag at Mach numbers up to 1.34 and at Reynolds numbers comparable to those of the full-scale airplane. This large-scale model corresponded to the prototype airplane and had air flow through the duct. Additional zero-lift drag tests involved a series of small equivalent bodies of revolution which were launched by means of a helium gun. The several small-scale models tested corresponded to: the basic configuration, the 1/5-scale rocket-propelled model configuration, a 2-foot (full-scale) fuselage-extension configuration, and a 7-foot (full-scale) fuselage-extension configuration. Models designed to correspond to the area distribution at a Mach number of 1.0 were flown for each of these 'shapes and, in addition, models designed to correspond to the area distribution at a Mach number of 1.2 were flown for the 1/5-scale rocket-propelled model and the 7-foot-fuselage-extension configuration. The value of external pressure drag coefficient (including base drag) obtained from the large-scale rocket model was 0.0190 at a Mach number of 1..05 and the corresponding values from the equivalent-body tests varied from 0.0183 for the rocket-propelled model shape to 0.0137 for the 7-foot-fuselage-extension configuration. From the results of tests of equivalent bodies designed to correspond to the area distribution at a Mach number of 1.0, it is evident that the small changes in shape incorporated in the basic and 2-foot-fuselage-extension configurations from that of the rocket-propelled model configuration will provide no significant change in pressure drag. On the other hand, the data from the 7-foot-fuselage-extension model indicate a substantial reduction in pressure drag at transonic speeds.
Applin, Zachary T.; Jones, Kenneth M.; Gile, Brenda E.; Quinto, P. Frank
1994-01-01
A test was conducted in the Langley 14 by 22 Foot Subsonic Tunnel to determine the effect of the reverse-thrust flow field of a wing-mounted advanced ducted propeller on the aerodynamic characteristics of a semispan subsonic high-lift transport model. The advanced ducted propeller (ADP) model was mounted separately in position alongside the wing so that only the aerodynamic interference of the propeller and nacelle affected the aerodynamic performance of the transport model. Mach numbers ranged from 0.14 to 0.26; corresponding Reynolds numbers ranged from 2.2 to 3.9 x 10(exp 6). The reverse-thrust flow field of the ADP shielded a portion of the wing from the free-stream airflow and reduced both lift and drag. The reduction in lift and drag was a function of ADP rotational speed and free-stream velocity. Test results included ground effects data for the transport model and ADP configuration. The ground plane caused a beneficial increase in drag and an undesirable slight increase in lift. The ADP and transport model performance in ground effect was similar to performance trends observed for out of ground effect. The test results form a comprehensive data set that supports the application of the ADP engine and airplane concept on the next generation of advanced subsonic transports. Before this investigation, the engine application was predicted to have detrimental ground effect characteristics. Ground effect test measurements indicated no critical problems and were the first step in proving the viability of this engine and airplane configuration.
Mitchell, Glenn A; Campbell, Robert C
1957-01-01
Provided sufficient throat bleed was employed, maximum pressure recoveries of 0.87 to 0.88 at Mach number 2.0 were obtained for a fuselage-mounted 14 degrees ramp inlet regardless of the amount of fuselage boundary layer ingested. The addition of inlet side fairings yielded further increases in pressure recovery to 0.90 to 0.91, decreased critical drag coefficients, and increased critical mass-flow ratios. With throat bleed, peak pressure recoveries and calculated thrust-minus-drag values were comparable at two axial positions of the scoop and were highest with the greatest amount of fuselage boundary layer ingested.
Experimental study of subsonic microjet escaping from a rectangular nozzle
Aniskin, V. M.; Maslov, A. A.; Mukhin, K. A.
2016-10-01
The first experiments on the subsonic laminar microjets escaping from the nozzles of rectangular shape are carried out. The nozzle size is 83.3x3823 microns. Reynolds number calculated by the nozzle height and the average flow velocity at the nozzle exit ranged from 58 to 154. The working gas was air at room temperature. The velocity decay and velocity fluctuations along the center line of the jet are determined. The fundamental difference between the laminar microjets characteristics and subsonic turbulent jets of macro size is shown. Based on measurements of velocity fluctuations it is shown the presence of laminar-turbulent transition in microjets and its location is determined.
Erickson, Gary E.
2017-01-01
A wind tunnel experiment was conducted in the NASA Langley Research Center 7- by 10-Foot High Speed Tunnel to determine the effects of passive surface porosity on the subsonic vortex flow interactions about a general research fighter configuration. Flow-through porosity was applied to the leading-edge extension, or LEX, and leading-edge flaps mounted to a 65deg cropped delta wing model as a potential vortex flow control technique at high angles of attack. All combinations of porous and nonporous LEX and flaps were investigated. Wing upper surface static pressure distributions and six-component forces and moments were obtained at a free-stream Mach number of 0.20 corresponding to a Reynolds number of 1.35(106) per foot, angles of attack up to 45deg, angles of sideslip of 0deg and +/-5deg, and leading-edge flap deflections of 0deg and 30deg.
Ernst Mach a deeper look : documents and new perspectives
1992-01-01
Ernst Mach -- A Deeper Look has been written to reveal to English-speaking readers the recent revival of interest in Ernst Mach in Europe and Japan. The book is a storehouse of new information on Mach as a philosopher, historian, scientist and person, containing a number of biographical and philosophical manuscripts publihsed for the first time, along with correspondence and other matters published for the first time in English. The book also provides English translations of Mach's controversies with leading physicists and psychologists, such as Max Planck and Carl Stumpf, and offers basic evidence for resolving Mach's position on atomism and Einstein's theory of relativity. Mach's scientific, philosophical and personal influence in a number of countries -- Austria, Germany, Bohemia and Yugoslavia among them -- has been carefully explored and many aspects detailed for the first time. All of the articles are eminently readable, especially those written by Mach's sister. They are deeply researched, new interpre...
Aljabri, Abdullah S.
1988-01-01
High speed subsonic transports powered by advanced propellers provide significant fuel savings compared to turbofan powered transports. Unfortunately, however, propfans must operate in aircraft-induced nonuniform flow fields which can lead to high blade cyclic stresses, vibration and noise. To optimize the design and installation of these advanced propellers, therefore, detailed knowledge of the complex flow field is required. As part of the NASA Propfan Test Assessment (PTA) program, a 1/9 scale semispan model of the Gulfstream II propfan test-bed aircraft was tested in the NASA-Lewis 8 x 6 supersonic wind tunnel to obtain propeller flow field data. Detailed radial and azimuthal surveys were made to obtain the total pressure in the flow and the three components of velocity. Data was acquired for Mach numbers ranging from 0.6 to 0.85. Analytical predictions were also made using a subsonic panel method, QUADPAN. Comparison of wind-tunnel measurements and analytical predictions show good agreement throughout the Mach range.
Institute of Scientific and Technical Information of China (English)
翟永玺; 张堃元; 王磊; 李永洲; 张林
2014-01-01
A parametric research on the curved compression surface with controllable Mach number distri-bution was commenced to find the effect regularity of design parameters on the performance parameters of curved compression surface. On this basis,a polynomial response surface proxy model was built to make a multi-objec-tive optimization,and a hypersonic curved shock two-dimensional inlet was designed based on the optimization result, the performance was compared with the three-ramp compression inlet which was designed under the same constraints. Results indicate among the design parameters, the initial compress angle θ and the factor C and factor md1 affect most. The flow coefficient of the innovative inlet is up to 0.769 at Mach 4,when Mach num-ber ranges from 4 to 7,the two inlets have equally the same mass capture ratio,while the innovative inlet has high total pressure recovery of throat and outlet section. Compared with the relative three-ramp inlet , the total pressure recovery of throat section of the innovative inlet increased by 6.5%at Mach 4, 8.4%at Mach 6, and 10.7%at Mach 7.%针对一种马赫数分布可控的二元高超弯曲压缩面进行参数化研究，获得其设计参数对压缩面性能的影响规律，在此基础上建立多项式响应面代理模型并进行多目标优化，基于优化结果设计了二元弯曲激波进气道，并与同等约束条件下的三楔进气道进行比较。结果表明：压缩面初始压缩角θ与马赫数梯度函数中的设计参数md1，C对压缩面性能影响最为显著；Ma∞=4.0时弯曲激波进气道流量系数达0.769，与三楔进气道相比，在Ma∞=4～7工作范围内的流量捕获能力相当，但其喉道、出口截面的总压恢复系数均高于三楔进气道，在Ma∞=4，6，7工况下，喉道截面总压恢复分别有6.5%，8.4%和10.7%的提高。
Hunt, L. Roane; Notestine, Kristopher K.
1990-06-01
Surface and gap pressures and heating-rate distributions were obtained for simulated Thermal Protection System (TPS) tile arrays on the curved surface test apparatus of the Langley 8-Foot High Temperature Tunnel at Mach 6.6. The results indicated that the chine gap pressures varied inversely with gap width because larger gap widths allowed greater venting from the gap to the lower model side pressures. Lower gap pressures caused greater flow ingress from the surface and increased gap heating. Generally, gap heating was greater in the longitudinal gaps than in the circumferential gaps. Gap heating decreased with increasing gap depth. Circumferential gap heating at the mid-depth was generally less than about 10 percent of the external surface value. Gap heating was most severe at local T-gap junctions and tile-to-tile forward-facing steps that caused the greatest heating from flow impingement. The use of flow stoppers at discrete locations reduced heating from flow impingement. The use of flow stoppers at discrete locations reduced heating in most gaps but increased heating in others. Limited use of flow stoppers or gap filler in longitudinal gaps could reduce gap heating in open circumferential gaps in regions of high surface pressure gradients.
Energy Technology Data Exchange (ETDEWEB)
Ansanay-Alex, G.
2009-06-17
The development of simulation codes aimed at a precise simulation of fires requires a precise approach of flame front phenomena by using very fine grids. The need to take different spatial scale into consideration leads to a local grid refinement and to a discretization with homogeneous grid for computing time and memory purposes. The author reports the approximation of the non-linear convection term, the scalar advection-diffusion in finite volumes, numerical simulations of a flow in a bent tube, of a three-dimensional laminar flame and of a low Mach number an-isotherm flow. Non conformal finite elements are also presented (Rannacher-Turek and Crouzeix-Raviart elements)
Capone, F. J.
1972-01-01
An exploratory investigation was conducted in the Langley 16-foot transonic tunnel at Mach numbers from 0.20 to 1.30 to determine the induced lift characteristics of a body and swept-wing configuration having a partial-span two-dimensional propulsive nozzle with exhaust exit in the notch of the swept-wing trailing edge. The Reynolds number per meter varied from 4,900,000 to 14,030,000. The effects on wing-body characteristics of deflecting the propulsive jet in the flap mode at nominal exhaust-nozzle deflection angles of 0 deg and 30 deg were studied for two nozzle designs with different geometry and wing spans.
Stimpert, D. L.; Clemons, A.
1977-01-01
Sound data which were obtained during tests of a 50.8 cm diameter, subsonic tip speed, low pressure ratio fan were analyzed. The test matrix was divided into two major investigations: (1) source noise reduction techniques; and (2) aft duct noise reduction with acoustic treatment. Source noise reduction techniques were investigated which include minimizing second harmonic noise by varying vane/blade ratio, variation in spacing, and lowering the Mach number through the vane row to lower fan broadband noise. Treatment in the aft duct which includes flow noise effects, faceplate porosity, rotor OGV treatment, slant cell treatment, and splitter simulation with variable depth on the outer wall and constant thickness treatment on the inner wall was investigated. Variable boundary conditions such as variation in treatment panel thickness and orientation, and mixed porosity combined with variable thickness were examined. Significant results are reported.
Alford, William J; King, Thomas, Jr
1957-01-01
An investigation was made at high subsonic speeds in the Langley high-speed 7- by 10-foot tunnel to determine the static aerodynamic forces and moments on a missile model during simulated launching from the midsemispan location of a 45 degree sweptback wing-fuselage-pylon combination. The results indicated significant variations in all the aerodynamic components with changes in chordwise location of the missile. Increasing the angle of attack caused increases in the induced effects on the missile model because of the wing-fuselage-pylon combination. Increasing the Mach number had little effect on the variations of the missile aerodynamic characteristics with angle of attack except that nonlinearities were incurred at smaller angles of attack for the higher Mach numbers. The effects of finite wing thickness on the missile characteristics, at zero angle of attack, increase with increasing Mach number. The effects of the pylon on the missile characteristics were to causeincreases in the rolling-moment variation with angle of attack and a negative displacement of the pitching-moment curves at zero angle of attack. The effects of skewing the missile in the lateral direction relative to and sideslipping the missile with the wing-fuselage-pylon combination were to cause additional increments in side force at zero angle of attack. For the missile yawing moments the effects of changes in skew or sideslip angles were qualitatively as would be expected from consideration of the isolated missile characteristics, although there existed differences in theyawing-moment magnitudes.
Tavelli, Maurizio; Dumbser, Michael
2017-07-01
We propose a new arbitrary high order accurate semi-implicit space-time discontinuous Galerkin (DG) method for the solution of the two and three dimensional compressible Euler and Navier-Stokes equations on staggered unstructured curved meshes. The method is pressure-based and semi-implicit and is able to deal with all Mach number flows. The new DG scheme extends the seminal ideas outlined in [1], where a second order semi-implicit finite volume method for the solution of the compressible Navier-Stokes equations with a general equation of state was introduced on staggered Cartesian grids. Regarding the high order extension we follow [2], where a staggered space-time DG scheme for the incompressible Navier-Stokes equations was presented. In our scheme, the discrete pressure is defined on the primal grid, while the discrete velocity field and the density are defined on a face-based staggered dual grid. Then, the mass conservation equation, as well as the nonlinear convective terms in the momentum equation and the transport of kinetic energy in the energy equation are discretized explicitly, while the pressure terms appearing in the momentum and energy equation are discretized implicitly. Formal substitution of the discrete momentum equation into the total energy conservation equation yields a linear system for only one unknown, namely the scalar pressure. Here the equation of state is assumed linear with respect to the pressure. The enthalpy and the kinetic energy are taken explicitly and are then updated using a simple Picard procedure. Thanks to the use of a staggered grid, the final pressure system is a very sparse block five-point system for three dimensional problems and it is a block four-point system in the two dimensional case. Furthermore, for high order in space and piecewise constant polynomials in time, the system is observed to be symmetric and positive definite. This allows to use fast linear solvers such as the conjugate gradient (CG) method. In
Phillips, W. P.
1984-01-01
Aerodynamic characteristics at M=5.97 for the 140 A/B Space Shuttle Orbiter configuration and for the configuration modified by geometric changes in the wing planform fillet region and the fuselage forebody are presented. The modifications, designed to extend the orbiter's longitudinal trim capability to more forward center of gravity locations, include reshaping the baseline wing fillet, changing the fuselage forebody camber, and adding canards. The Langley 20 inch Mach 6 Tunnel at a Reynolds number of approximately 6 million based on fuselage reference length was used. The angle of attack range of the investigation varied from about 15 deg to 35 deg at 0 deg and -5 deg sideslip angles. Data are obtained with the elevators and body flap deflected at appropriate negative and positive conditions to assess the trim limits.
Study on Mach stems induced by interaction of planar shock waves on two intersecting wedges
Institute of Scientific and Technical Information of China (English)
Gaoxiang Xiang; Chun Wang; Honghui Teng; Yang Yang; Zonglin Jiang
2016-01-01
The properties of Mach stems in hypersonic corner flow induced by Mach interaction over 3D inter-secting wedges were studied theoretically and numerically. A new method called “spatial dimension reduction” was used to analyze theoretically the location and Mach num-ber behind Mach stems. By using this approach, the problem of 3D steady shock/shock interaction over 3D intersecting wedges was transformed into a 2D moving one on cross sec-tions, which can be solved by shock-polar theory and shock dynamics theory. The properties of Mach interaction over 3D intersecting wedges can be analyzed with the new method, including pressure, temperature, density in the vicinity of triple points, location, and Mach number behind Mach stems. Theoretical results were compared with numerical results, and good agreement was obtained. Also, the influence of Mach number and wedge angle on the properties of a 3D Mach stem was studied.
Ng, Lian Lai
1990-01-01
When a jet is perturbed by a periodic excitation of suitable frequency, a large-scale coherent structure develops and grows in amplitude as it propagates downstream. The structure eventually rolls up into vortices at some downstream location. The wavy flow associated with the roll-up of a coherent structure is approximated by a parallel mean flow and a small, spatially periodic, axisymmetric wave whose phase velocity and mode shape are given by classical (primary) stability theory. The periodic wave acts as a parametric excitation in the differential equations governing the secondary instability of a subharmonic disturbance. The (resonant) conditions for which the periodic flow can strongly destabilize a subharmonic disturbance are derived. When the resonant conditions are met, the periodic wave plays a catalytic role to enhance the growth rate of the subharmonic. The stability characteristics of the subharmonic disturbance, as a function of jet Mach number, jet heating, mode number and the amplitude of the periodic wave, are studied via a secondary instability analysis using two independent but complementary methods: (1) method of multiple scales, and (2) normal mode analysis. It is found that the growth rates of the subharmonic waves with azimuthal numbers beta = 0 and beta = 1 are enhanced strongly, but comparably, when the amplitude of the periodic wave is increased. Furthermore, compressibility at subsonic Mach numbers has a moderate stabilizing influence on the subharmonic instability modes. Heating suppresses moderately the subharmonic growth rate of an axisymmetric mode, and it reduces more significantly the corresponding growth rate for the first spinning mode. Calculations also indicate that while the presence of a finite-amplitude periodic wave enhances the growth rates of subharmonic instability modes, it minimally distorts the mode shapes of the subharmonic waves.
Pfyl, Frank A.; Presley, Leroy L.
1961-01-01
The local recovery factor was determined experimentally along the surface of a thin-walled 20 deg included angle cone for Mach numbers near 6.0 at stagnation temperatures between 1200 deg R and 2600 deg R. In addition, a similar cone configuration was tested at Mach numbers near 4.5 at stagnation temperatures of approximately 612 deg R. The local Reynolds number based on flow properties at the edge of the boundary layer ranged between 0.1 x 10(exp 4) and 3.5 x 10(exp 4) for tests at temperatures above 1200 deg R and between 6 x 10(exp 4) and 25 x 10(exp 4) for tests at temperatures near 612 deg R. The results indicated, generally, that the recovery factor can be predicted satisfactorily using the square root of the Prandtl number. No conclusion could be made as to the necessity of evaluating the Prandtl number at a reference temperature given by an empirical equation, as opposed to evaluating the Prandtl number at the wall temperature or static temperature of the gas at the cone surface. For the tests at temperatures above 1200 deg R (indicated herein as the tests conducted in the slip-flow region), two definite trends in the recovery data were observed - one of increasing recovery factor with decreasing stagnation pressure, which was associated with slip-flow effects and one of decreasing recovery factor with increasing temperature. The true cause of the latter trend could not be ascertained, but it was shown that this trend was not appreciably altered by the sources of error of the magnitude considered herein. The real-gas equations of state were used to determine accurately the local stream properties at the outer edge of the boundary layer of the cone. Included in the report, therefore, is a general solution for the conical flow of a real gas using the Beattie-Bridgeman equation of state. The largest effect of temperature was seen to be in the terms which were dependent upon the internal energy of the gas. The pressure and hence the pressure drag terms were
McMIllin, S. Naomi; Byrd, James E.; Parmar, Devendra S.; Bezos-O'Connor, Gaudy M.; Forrest, Dana K.; Bowen, Susan
1996-01-01
An experimental investigation of the effect of leading-edge radius, camber, Reynolds number, and boundary-layer state on the incipient separation of a delta wing at supersonic speeds was conducted at the Langley Unitary Plan Wind Tunnel at Mach number of 1.60 over a free-stream Reynolds number range of 1 x 106 to 5 x 106 ft-1. The three delta wing models examined had a 65 deg swept leading edge and varied in cross-sectional shape: a sharp wedge, a 20:1 ellipse, and a 20:1 ellipse with a -9.750 circular camber imposed across the span. The wings were tested with and without transition grit applied. Surface-pressure coefficient data and flow-visualization data are electronically stored on the CD-ROM. The data indicated that by rounding the wing leading edge or cambering the wing in the spanwise direction, the onset of leading-edge separation on a delta wing can be raised to a higher angle of attack than that observed on a sharp-edged delta wing. The data also showed that the onset of leading-edge separation can be raised to a higher angle of attack by forcing boundary-layer transition to occur closer to the wing leading edge by the application of grit or the increase in free-stream Reynolds number.
Directory of Open Access Journals (Sweden)
L. A. Benderskiy
2015-01-01
Full Text Available Effect of Mach number and temperature on subsonic jets flow with a combined highresolution RANS/ILES method (Reynolds Averaged Navier-Stokes - RANS, Implicit Large Eddy Simulation - ILES was investigated. Cold Mj=0.985 T0=300К and hot Mj=0.548 T0=858.6К jets were considered (Mj – Mach number at the nozzle exit and T0 – total temperature at the nozzle inlet. Conical and two chevron nozzles with angle of chevrons to the nozzle axis α=5° and α=18.2° were investigated. The jet flow calculations were carried out together with flow calculation in nozzles. Computation grids were Meshes for simulations (2.8-3.2×106 cells. Investigated cases were compared by average velocity and velocity fluctuations at the jet axis and at the mixing layer. The magnitude of velocity fluctuations at the jet axis and at the mixing layer for hot jets is higher than for cold jets. It leads to increasing expansion angle of the mixing layer inward the jet axis. This is why the initial part length of hot jets becomes shorter than in cold jets. Comparison of simulations with the experimental data of other authors showed a good agreement by flow and turbulences characteristics.
Brown, C. A., Jr.; Campbell, J. F.; Tudor, D. H.
1971-01-01
An investigation was conducted to obtain flow properties in the wake of the Viking '75 entry vehicle at Mach numbers from 1.60 to 3.95 and at angles of attack of 0 deg and 5 deg. The wake flow properties were calculated from total and static pressures measured with a pressure rake at longitudinal stations varying from 1.0 to 8.39 body diameters and lateral stations varying from -0.42 to 3.0 body diameters. These measurements showed a a consistent trend throughout the range of Mach numbers and longitudinal distances and an increase in dynamic pressure with increasing downstream position.
Reynolds, Robert M; Samonds, Robert I; Walker, John H
1957-01-01
An investigation has been made to determine the aerodynamic characteristics of the NACA 4-(5)(05)-041 four-blade, single-relation propeller and the NACA 4-(5)(05)-037 six- and eight-blade, dual-rotation propellers in combination with various spinners and NACA d-type spinner-cowling combinations at Mach numbers up to 0.84. Propeller force characteristics, local velocity distributions in the propeller planes, inlet pressure recoveries, and static-pressure distributions on the cowling surfaces were measured for a wide range of blade angles, advance ratios, and inlet-velocity ratios. Included are data showing: (a) the effect of extended cylindrical spinners on the characteristics of the single-rotation propeller, (b) the effect of variation of the difference in blade angle setting between the front and rear components of the dual-rotation propellers, (c) the negative- and static-thrust characteristics of the propellers with 1 series spinners, and (d) the effects of ideal- and platform-type propeller-spinner junctures on the pressure-recovery characteristics of the single-rotation propeller-spinner-cowling combination.
Aeroacoustic computation of low mach number flow
Energy Technology Data Exchange (ETDEWEB)
Skriver Dahl, K. [Risoe National Laboratory, Roskilde (Denmark)
1997-12-31
The possibilities of applying a recently developed numerical technique to predict aerodynamically generated sound from wind turbines is explored. The technique is a perturbation technique that has the advantage that the underlying flow field and the sound field are computed separately. Solution of the incompressible, time dependent flow field yields a hydrodynamic density correction to the incompressible constant density. The sound field is calculated from a set of equations governing the inviscid perturbations about the corrected flow field. Here, the emphasis is placed on the computation of the sound field. The nonlinear partial differential equations governing the sound fields are solved numerically using an explicit MacCormack scheme. Two types of non-reflecting boundary conditions are applied; one based on the asymptotic solution of the governing equations and the other based on a characteristic analysis of the governing equations. The former condition is easy to use and it performs slightly better than the charcteristic based condition. The technique is applied to the problems of the sound generation of a co-rotating vortex pair, which is a quadrupole, and the viscous flow over a circular cylinder, which is a dipole. Numerical results agree very well with the analytical solution for the problem of the co-rotating vortex pair. Numerical results for the viscous flow over a cylinder are presented and evaluated qualitatively. (au)
Meyer, Robert R., Jr.; Covell, Peter F.
1986-01-01
The effect of sideslip on winglet loads and selected wing loads was investigated at high and low subsonic Mach numbers. The investigation was conducted in two separate wind tunnel facilities, using two slightly different 0.035-scale full-span models. Results are presented which indicate that, in general, winglet loads as a result of sideslip are analogous to wing loads caused by angle of attack. The center-of-pressure locations on the winglets are somewhat different than might be expected for an analogous wing. The spanwise center of pressure for a winglet tends to be more inboard than for a wing. The most notable chordwise location is a forward center-of-pressure location on the winglet at high sideslip angles. The noted differences between a winglet and an analogous wing are the result of the influence of the wing on the winglet.
Subsonic Ultra Green Aircraft Research
Bradley, Marty K.; Droney, Christopher K.
2011-01-01
This Final Report summarizes the work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team in Phase 1, which includes the time period of October 2008 through March 2010. The team consisted of Boeing Research and Technology, Boeing Commercial Airplanes, General Electric, and Georgia Tech. The team completed the development of a comprehensive future scenario for world-wide commercial aviation, selected baseline and advanced configurations for detailed study, generated technology suites for each configuration, conducted detailed performance analysis, calculated noise and emissions, assessed technology risks, and developed technology roadmaps. Five concepts were evaluated in detail: 2008 baseline, N+3 reference, N+3 high span strut braced wing, N+3 gas turbine battery electric concept, and N+3 hybrid wing body. A wide portfolio of technologies was identified to address the NASA N+3 goals. Significant improvements in air traffic management, aerodynamics, materials and structures, aircraft systems, propulsion, and acoustics are needed. Recommendations for Phase 2 concept and technology projects have been identified.
Institute of Scientific and Technical Information of China (English)
金志伟; 杨兴锐; 苏北辰
2016-01-01
It is hard to use precise mechanism to describe system dynamic feature of 2.4 m transonic wind tunnel. Put forwards wind tunnel Mach number predictive control strategy based on neural network. Combine the advanteges of model predictive control and nueral network modeling, it is good at processing control parameter unkown, unlinear system and time varing system. Use dynamic response of nueral network based on radial basis function and nonlinear neural network to capture system dynamic feature, apply nerual nwork model in MPC structure. The simulation results show that the control strtegy has a good control effect and trace performance.%针对2.4 m跨声速风洞很难用精确的机理模型表示系统的动态特性的问题,提出了基于神经网络模型的风洞马赫数预测控制策略.综合了模型预测控制和神经网络建模的优点,对于控制参数未知、非线性和时变系统具有很好的处理效果.利用基于径向基函数的神经网络模型预测系统的动态响应、非线性神经网络模型可以在训练过程中捕获系统的动态特性等措施,实现了将神经网络模型应用到MPC结构中.仿真结果表明,该控制策略具有很好的跟踪性能和控制效果.
Phillips, W. P.; Fournier, R. H.
1985-01-01
Wind-tunnel tests were conducted at Mach 1.5 to 2.5 to determine the effect of modifications designed to extend the forward center-of-gravity trim capability on the static longitudal and lateral directional characteristics of a Space shuttle 140 A/B orbiter model (0.01 scale). The modifications consisted of a forward-extended wing fillet, a flat plate canard, and a blended canard. The investigation was conducted in the low Mach number test section of the Langley unitary plan wind tunnel at a Reynolds number of approximately 2.15 million based on the fuselage reference length. The test angle of attack range was -1 deg to 32 deg and the sideslip angles were 0 deg and 5 deg.
Jacobs, P. F.
1978-01-01
The effects of winglets on the static aerodynamic stability characteristics of a KC-135A jet transport model at high subsonic speeds are presented. The investigation was conducted in the Langley 8 foot transonic pressure tunnel using 0.035-scale wing panels mounted on a generalized research fuselage. Data were taken over a Mach number range from 0.50 to 0.95 at angles of attack ranging from -12 deg to 20 deg and sideslip angles of 0 deg, 5 deg, and -5 deg. The model was tested at two Reynolds number ranges to achieve a wide angle of attack range and to determine the effect of Reynolds number on stability. Results indicate that adding the winglets to the basic wing configuration produces small increases in both lateral and longitudinal aerodynamic stability and that the model stability increases slightly with Reynolds number. The winglets do increase the wing bending moments slightly, but the buffet onset characteristics of the model are not affected by the winglets.
Simulation of Atmospheric-Entry Capsules in the Subsonic Regime
Murman, Scott M.; Childs, Robert E.; Garcia, Joseph A.
2015-01-01
The accuracy of Computational Fluid Dynamics predictions of subsonic capsule aerodynamics is examined by comparison against recent NASA wind-tunnel data at high-Reynolds-number flight conditions. Several aspects of numerical and physical modeling are considered, including inviscid numerical scheme, mesh adaptation, rough-wall modeling, rotation and curvature corrections for eddy-viscosity models, and Detached-Eddy Simulations of the unsteady wake. All of these are considered in isolation against relevant data where possible. The results indicate that an improved predictive capability is developed by considering physics-based approaches and validating the results against flight-relevant experimental data.
Miller, Rolf W.; Argrow, Brian M.; Center, Kenneth B.; Brauckmann, Gregory J.; Rhode, Matthew N.
1998-01-01
The NASA Langley Research Center Unitary Plan Wind Tunnel and the 20-Inch Mach 6 Tunnel were used to test two osculating cones waverider models. The Mach-4 and Mach-6 shapes were generated using the interactive design tool WIPAR. WIPAR performance predictions are compared to the experimental results. Vapor screen results for the Mach-4 model at the on- design Mach number provide visual verification that the shock is attached along the entire leading edge, within the limits of observation. WIPAR predictions of pressure distributions and aerodynamic coefficients show general agreement with the corresponding experimental values.
Brown, C. A., Jr.; Campbell, J. F.
1973-01-01
An investigation was conducted to obtain flow properties in the wake of a preliminary configuration of the Viking '75 Entry Vehicle at Mach numbers from 0.20 to 1.20 and at angles of attack of 0 deg, 5 deg, and 10 deg. The wake flow properties were calculated from total and static pressures measured with a pressure rake at longitudinal stations varying from 1.50 to 11.00 body diameters, and are presented in tabulated and plotted form. The wake properties were essentially symmetrical about the X-axis at alpha = 0 deg and the profiles were shifted away from the X-axis at angles of attack. An unexpected reduction in wake property ratios occurred as the Mach number increased from 0.60 to 1.00; these ratios then increased as the Mach number increased to 1.20. The reduction was present for all the longitudinal stations of the tests and decreased with increased longitudinal distance.
Schrenk, Markus
2011-01-01
In his Contributions to the Analysis of the Sensations (Mach 1885) the phenomenalist philosopher Ernst Mach confronts us with a difficulty: “If we regard the Ego as a real unity, we become involved in the following dilemma: either we must set over against the Ego a world of unknowable entities […] or we must regard the whole world, the Egos of other people included, as comprised in our own Ego.” (Mach 1885: 21) In other words, if we start from a phenomenalist viewpoint, i.e., if we believ...
Energy Technology Data Exchange (ETDEWEB)
Fortin, T
2006-05-15
This work deals with the discretization of Navier-Stokes equations using different finite element methods adapted to the problem of two-phase flows. These methods must be of high order to limit the presence of spurious flows (which contradict the establishment of a physical equilibrium) and to verify energy conservation properties. Several solutions are proposed which seem to fulfill these expectations. A reformulation of the six-equation system adapted to low Mach two-phase flows has been also proposed. These methods have been implemented into the Trio-U code of CEA Grenoble, but have been tested only on simple 'academic' configurations. (J.S.)
Fourier time spectral method for subsonic and transonic flows
Institute of Scientific and Technical Information of China (English)
Lei Zhan; Feng Liu; Dimitri Papamoschou
2016-01-01
The time accuracy of the exponentially accu-rate Fourier time spectral method (TSM) is examined and compared with a conventional 2nd-order backward differ-ence formula (BDF) method for periodic unsteady flows. In particular, detailed error analysis based on numerical com-putations is performed on the accuracy of resolving the local pressure coefficient and global integrated force coefficients for smooth subsonic and non-smooth transonic flows with moving shock waves on a pitching airfoil. For smooth sub-sonic flows, the Fourier TSM method offers a significant accuracy advantage over the BDF method for the predic-tion of both the local pressure coefficient and integrated force coefficients. For transonic flows where the motion of the discontinuous shock wave contributes significant higher-order harmonic contents to the local pressure fluctuations, a sufficient number of modes must be included before the Fourier TSM provides an advantage over the BDF method. The Fourier TSM, however, still offers better accuracy than the BDF method for integrated force coefficients even for transonic flows. A problem of non-symmetric solutions for symmetric periodic flows due to the use of odd numbers of intervals is uncovered and analyzed. A frequency-searching method is proposed for problems where the frequency is not known a priori. The method is tested on the vortex shedding problem of the flow over a circular cylinder.
Jernell, Lloyd S.
1961-01-01
An investigation w a s made i n the Langley Unitary Plan wind tunnel o determine the effects of fin area and the effects of antennas and w iring tunnels on the static longitudinal and lateral stability of a 0 .10- scale model of a three- stage configuration of the Scout vehicle. The tests were performed at Mach numbers of 2.29, 2.96, 3.96, and 4. 65 6 and at Reynolds numbers of about 3.5 X 10 per foot.
Slow light Mach-Zehnder fiber interferometer
Institute of Scientific and Technical Information of China (English)
Yundong Zhang; Jinfang Wang; Xuenan Zhang; Hao Wu; Yuanxue Cai; Jing Zhang; Ping Yuan
2012-01-01
A slow light structure Mach-Zehnder fiber interferometer is theoretically demonstrated.The sensitivity of the interferometer is significantly enhanced by the dispersion of the slow light structure.The numerical results show that the sensitivity enhancement factor varies with the coupling coefficient and reaches its maximum under critical coupling conditions.Interferometers have been investigated in relation to their applications in fields such as metrology[1],optical sensing[2],optical communication[3,4],quantum information processing[5],and biomedical engineering[6].A number of schemes have been proposed to improve the performance of interferometers[7],such as using photonic crystal structures to minimize the size of on-chip devices[8],utilizing the dispersive property of semiconductor to enhance the spectral sensitivity of interferometers[9,10],utilizing slow light medium to enhance the resolution of Fourier transform interferometer[11],exploiting fast light medium or slow light structure to increase the rotation sensitivity of a Sagnac interferometer[12,13],enhancing the transmittance of the Mach-Zehnder interferometer (MZI) in the slow light region by gratings[14],and using liquid crystal light valve to derive high sensitivity interferometers[15].%A slow light structure Mach-Zehnder fiber interferometer is theoretically demonstrated. The sensitivity of the interferometer is significantly enhanced by the dispersion of the slow light structure. The numerical results show that the sensitivity enhancement factor varies with the coupling coefficient and reaches its maximum under critical coupling conditions.
Energy Technology Data Exchange (ETDEWEB)
Kegalj, Martin
2013-11-01
In axial turbines tip leakage forms a large portion of the overall losses. Applying a shroud is very aerodynamically useful, but the higher mechanical loads of the revolving rotor blading exposed to a high thermal load and the higher costs suggest a shroudless configuration is better. The main parameter in the tip leakage loss is the tip gap height, which cannot be reduced arbitrarily as a running gap is necessary due to thermal expansion and vibration of the jet engine. The pressure ratio between pressure and suction of the rotor blade forces the fluid over the blade tip and leads to the formation of the tip leakage vortex. Reduced turning and losses caused by vortices and subsequent mixing are responsible for the reduced efficiency. Using a squealer cavity on the flat blade tip is a feasible way to reduce the aerodynamic losses. A portion of the kinetic energy of the tip leakage flow is dissipated while entering the cavity; the flow exiting the cavity enters the passage with reduced momentum and reduced tip gap mass flow. A 1(1)/(2) stage low mach number turbine was used to investigate the influence of tip geometry. Aerodynamic measurements, performed with five-hole probes, two-component hot-wire anemometer, unsteady wall pressure sensors, stereo and borescopic particle-image-velocimetry setups and oil and dye flow visualization, found small differences in the flow velocities and angles between the flat and squealer tip configuration in the measurement planes downstream of the rotor. The measurement uncertainty proves the difficulty of determining the influence of the squealer cavity on the blade row outflow with global measurement data. To gather information on the flow close to the casing inside the rotor passage is only possible with non-intrusive laser measurement techniques. Comparison of the different tip geometries is still difficult due to the small differences in the absolute flow data. The use of the {lambda}{sub 2} vortex criterion enables an objective
Subsonic Analysis of 0.04-Scale F-16XL Models Using an Unstructured Euler Code
Lessard, Wendy B.
1996-01-01
The subsonic flow field about an F-16XL airplane model configuration was investigated with an inviscid unstructured grid technique. The computed surface pressures were compared to wind-tunnel test results at Mach 0.148 for a range of angles of attack from 0 deg to 20 deg. To evaluate the effect of grid dependency on the solution, a grid study was performed in which fine, medium, and coarse grid meshes were generated. The off-surface vortical flow field was locally adapted and showed improved correlation to the wind-tunnel data when compared to the nonadapted flow field. Computational results are also compared to experimental five-hole pressure probe data. A detailed analysis of the off-body computed pressure contours, velocity vectors, and particle traces are presented and discussed.
Ball, J. W.; Lindahl, R. H.
1976-01-01
The purpose of the test was to investigate the nature of the Orbiter boundary layer characteristics at angles of attack from -4 to 32 degrees at a Mach number of 4.6. The effect of large grit, employed as transition strips, on both the nature of the boundary layer and the force and moment characteristics were investigated along with the effects of large negative elevon deflection on lee side separation. In addition, laminar and turbulent boundary layer separation phenomena which could cause asymmetric flow separation were investigated.
Subsonic and Supersonic Jet Noise Calculations Using PSE and DNS
Balakumar, P.; Owis, Farouk
1999-01-01
Noise radiated from a supersonic jet is computed using the Parabolized Stability Equations (PSE) method. The evolution of the instability waves inside the jet is computed using the PSE method and the noise radiated to the far field from these waves is calculated by solving the wave equation using the Fourier transform method. We performed the computations for a cold supersonic jet of Mach number 2.1 which is excited by disturbances with Strouhal numbers St=.2 and .4 and the azimuthal wavenumber m=l. Good agreement in the sound pressure level are observed between the computed and the measured (Troutt and McLaughlin 1980) results.
Subsonic Mechanical Alignment of Irregular Grains
Lazarian, Alex
2007-01-01
We show that grains can be efficiently aligned by interacting with a subsonic gaseous flow. The alignment arises from grains having irregularities that scatter atoms with different efficiency in the right and left directions. The grains tend to align with long axes perpendicular to magnetic field, which corresponds to Davis-Greenstein predictions, but does not involve magnetic field. For rather conservative factors characterizing the grain helicity and scattering efficiency of impinging atoms, the alignment of helical grains is much more efficient than the Gold-type alignment processes.
The prediction of noise and installation effects of high-subsonic dual-stream jets in flight
Saxena, Swati
Both military and civil aircraft in service generate high levels of noise. One of the major contributors to this noise generated from the aircraft is the jet engine exhaust. This makes the study of jet noise and methods to reduce jet noise an active research area with the aim of designing quieter military and commercial aircraft. The current stringent aircraft noise regulations imposed by the Federal Aviation Administration (FAA) and other international agencies, have further raised the need to perform accurate jet noise calculations for more reliable estimation of the jet noise sources. The main aim of the present research is to perform jet noise simulations of single and dual-stream jets with engineering accuracy and assess forward flight effects on the jet noise. Installation effects such as caused by the pylon are also studied using a simplified pylon nozzle configuration. Due to advances in computational power, it has become possible to perform turbulent flow simulations of high speed jets, which leads to more accurate noise predictions. In the present research, a hybrid unsteady RANS-LES parallel multi-block structured grid solver called EAGLEJet is written to perform the nozzle flow calculations. The far-field noise calculation is performed using solutions to the Ffowcs Williams and Hawkings equation. The present calculations use meshes with 5 to 11 million grid points and require about three weeks of computing time with about 100 processors. A baseline single stream convergent nozzle and a dual-stream coaxial convergent nozzle are used for the flow and noise analysis. Calculations for the convergent nozzle are performed at a high subsonic jet Mach number of Mj = 0.9, which is similar to the operating conditions for commercial aircraft engines. A parallel flow gives the flight effect, which is simulated with a co-flow Mach number, Mcf varying from 0.0 to 0.28. The grid resolution effects, statistical properties of the turbulence and the heated jet effects
Phillips, W. P.; Fournier, R. H.
1979-01-01
Supersonic aerodynamic characteristics are presented for the 140A/B space shuttle orbiter configuration (0.010 scale) and for the configuration modified to incorporate geometry changes in the wing planform fillet region. The modifications designed to extend the orbiter's longitudinal trim capability to more forward center-of-gravity locations, included reshaping of the baseline wing planform fillet and adding canards. The investigation was made in the high Mach number test section of the Langley Unitary Plan Wind Tunnel at a Reynolds number of approximately 2.2 million based on fuselage reference length. The angle-of-attack range for the investigation extended from -1 deg to 31 deg. Data were obtained with the elevators and body flap deflected at appropriate negative and positive conditions to assess the trim limits.
Stability of separating subsonic boundary layers
Masad, Jamal A.; Nayfeh, Ali H.
1994-01-01
The primary and subharmonic instabilities of separating compressible subsonic two-dimensional boundary layers in the presence of a two-dimensional roughness element on a flat plate are investigated. The roughness elements considered are humps and forward- and backward-facing steps. The use of cooling and suction to control these instabilities is studied. The similarities and differences between the instability characteristics of separating boundary layers and those of the boundary layer over a flat plate with a zero pressure gradient are pointed out and discussed. The theoretical results agree qualitatively and quantitatively with the experimental data of Dovgal and Kozlov. Cooling and suction decrease the growth rates of primary and subharmonic waves in the attached-flow regions but increase them in the separated-flow regions.
Mach-like capillary-gravity wakes.
Moisy, Frédéric; Rabaud, Marc
2014-08-01
We determine experimentally the angle α of maximum wave amplitude in the far-field wake behind a vertical surface-piercing cylinder translated at constant velocity U for Bond numbers Bo(D)=D/λ(c) ranging between 0.1 and 4.2, where D is the cylinder diameter and λ(c) the capillary length. In all cases the wake angle is found to follow a Mach-like law at large velocity, α∼U(-1), but with different prefactors depending on the value of Bo(D). For small Bo(D) (large capillary effects), the wake angle approximately follows the law α≃c(g,min)/U, where c(g,min) is the minimum group velocity of capillary-gravity waves. For larger Bo(D) (weak capillary effects), we recover a law α∼√[gD]/U similar to that found for ship wakes at large velocity [Rabaud and Moisy, Phys. Rev. Lett. 110, 214503 (2013)]. Using the general property of dispersive waves that the characteristic wavelength of the wave packet emitted by a disturbance is of order of the disturbance size, we propose a simple model that describes the transition between these two Mach-like regimes as the Bond number is varied. We show that the new capillary law α≃c(g,min)/U originates from the presence of a capillary cusp angle (distinct from the usual gravity cusp angle), along which the energy radiated by the disturbance accumulates for Bond numbers of order of unity. This model, complemented by numerical simulations of the surface elevation induced by a moving Gaussian pressure disturbance, is in qualitative agreement with experimental measurements.
Chan, David T.; Brauckmann, Gregory J.
2011-01-01
A 6%-scale unpowered model of the Orion Launch Abort Vehicle (LAV) ALAS-11-rev3c configuration was tested in the NASA Langley National Transonic Facility to obtain static aerodynamic data at flight Reynolds numbers. Subsonic and transonic data were obtained for Mach numbers between 0.3 and 0.95 for angles of attack from -4 to +22 degrees and angles of sideslip from -10 to +10 degrees. Data were also obtained at various intermediate Reynolds numbers between 2.5 million and 45 million depending on Mach number in order to examine the effects of Reynolds number on the vehicle. Force and moment data were obtained using a 6-component strain gauge balance that operated both at warm temperatures (+120 . F) and cryogenic temperatures (-250 . F). Surface pressure data were obtained with electronically scanned pressure units housed in heated enclosures designed to survive cryogenic temperatures. Data obtained during the 3-week test entry were used to support development of the LAV aerodynamic database and to support computational fluid dynamics code validation. Furthermore, one of the outcomes of the test was the reduction of database uncertainty on axial force coefficient for the static unpowered LAV. This was accomplished as a result of good data repeatability throughout the test and because of decreased uncertainty on scaling wind tunnel data to flight.
Supersonic—Subsonic Transition in Relatively Narrow Channels
Institute of Scientific and Technical Information of China (English)
RudlfDvorak
2000-01-01
The flow structure in relatively narrow channels has a strong three-dimensional character with complex flow phenomena.Including regions of localized spearation.various vortical structures.etc.,all of which have to be considered when dealing with the problem of supersonic-subsonic transition.In this paper only the following three problems are considered:1.the effect of channel width on transition form supersonic to subsonic velocities.2.transition from supersonic to subsonic velocities in a system of shock waves-pseudoshock wave.3.transition from subsonic to supersonic velocities in a critical cross section at the end of a duct with fully developed turbulent channel flow.Problems connectewd with vortical structures and flow separation were discussed by the same author elsewhere (see References).
Stability and Existence of Multidimensional Subsonic Phase Transitions
Institute of Scientific and Technical Information of China (English)
Ya-Guang Wang; Zhouping Xin
2003-01-01
The purpose of this paper is to prove the uniform stability of multidimensional subsonic phase transitions satisfying the viscosity-capillarity criterion in a van der Waals fluid, and further to establish the local existence of phase transition solutions.
Erickson, Gary E.; Gonzalez, Hugo A.
2006-01-01
A pressure-sensitive paint (PSP) technique was applied in a wind tunnel experiment in the NASA Langley Research Center 8-Foot Transonic Pressure Tunnel to study the effect of wing fillets on the global vortex induced surface static pressure field about a sharp leading-edge 76 deg./40 deg. double delta wing, or strake-wing, model at subsonic and transonic speeds. Global calibrations of the PSP were obtained at M(sub infinity) = 0.50, 0.70, 0.85, 0.95, and 1.20, a Reynolds number per unit length of 2.0 million, and angles of attack from 10 degrees to 20 degrees using an insitu method featuring the simultaneous acquisition of electronically scanned pressures (ESP) at discrete locations on the model. The mean error in the PSP measurements relative to the ESP data was approximately 2 percent or less at M(sub infinity) = 0.50 to 0.85 but increased to several percent at M(sub infinity) =0.95 and 1.20. The PSP pressure distributions and pseudo-colored, planform-view pressure maps clearly revealed the vortex-induced pressure signatures at all Mach numbers and angles of attack. Small fillets having parabolic or diamond planforms situated at the strake-wing intersection were respectively designed to manipulate the vortical flows by removing the leading-edge discontinuity or introducing additional discontinuities. The fillets caused global changes in the vortex-dominated surface pressure field that were effectively captured in the PSP measurements. The vortex surface pressure signatures were compared to available off-surface vortex cross-flow structures obtained using a laser vapor screen (LVS) flow visualization technique. The fillet effects on the PSP pressure distributions and the observed leading-edge vortex flow characteristics were consistent with the trends in the measured lift, drag, and pitching moment coefficients.
Heat transfer from cylinders in subsonic slip flows
Nagabushana, K. A.; Stainback, P. C.
1992-01-01
The heat transfer in heated wires was measured using a constant temperature anemometer over a Mach number range from 0.05 to 0.4 and pressures from 0.5 to 8.0 atmospheres. The total temperature ranged from 80 to 120 F and the wire diameters were 0.00015, 0.00032, and 0.00050 inch. The heat transfer data is presented in the form of a corrected Nusselt number. Based on suggested criteria, much of the data was obtained in the slip flow regime. Therefore, the data is compared with data having comparable flow conditions. The possible application of the heat transfer data to hot wire anemometry is discussed. To this end, the sensitivity of the wires to velocity, density, and total temperature is computed and compared using two different types of correlations.
Nonlinear evolution of subsonic and supersonic disturbances on a compressible free shear layer
Leib, S. J.
1991-01-01
The effects of a nonlinear-nonequilibrium-viscous critical layer on the spatial evolution of subsonic and supersonic instability modes on a compressible free shear layer is considered. It is shown that the instability wave amplitude is governed by an integrodifferential equation with cubic-type nonlinearity. Numerical and asymptotic solutions to this equation show that the amplitude either ends in a singularity at a finite downstream distance or reaches an equilibrium value, depending on the Prandtl number, viscosity law, viscous parameter and a real parameter which is determined by the linear inviscid stability theory. A necessary condition for the existence of the equilibrium solution is derived, and whether or not this condition is met is determined numerically for a wide range of physical parameters including both subsonic and supersonic disturbances. it is found that no equilibrium solution exists for the subsonic modes unless the temperature ratio of the low-to-high-speed streams exceeds a critical value, while equilibrium solutions for the most rapidly growing supersonic mode exist over most of the parameter range examined.
Optimal Design of a Subsonic Submerged Inlet
Taskinoglu, Ezgi; Jovanovic, Vasilije; Elliott, Gregory; Knight, Doyle
2003-11-01
A multi-objective optimization study based on an epsilon-constraint method is conducted for the design optimization of a subsonic submerged air vehicle inlet. The multi-objective optimization problem is reformulated by minimizing one of the objectives and restricting the other objectives within user specified values. The figures of merits are the engine-face distortion and swirl that determines the inlet/engine compatibility. The distortion index is minimized while the feasible design space is determined by the swirl index. The design variables are the geometrical parameters defining the surface alteration. The design algorithm is driven by a gradient-based optimizer, and is constructed by integrating the optimizer with a solid modeller (Pro/Engineer), a mesh generator (Grid/Pro) and a flow solver (GASPex). The optimizer is CFSQP (C code for Feasible Sequential Quadratic Programming). Integration of the software packages is achieved by a Perl script. In order to verify the numerical results, an experimental setup for the same inlet geometry is prepared to run at the same flow conditions. The presentation will describe the numerical approach and summarize the results.
MACH: Fast Randomized Tensor Decompositions
Tsourakakis, Charalampos E
2009-01-01
Tensors naturally model many real world processes which generate multi-aspect data. Such processes appear in many different research disciplines, e.g, chemometrics, computer vision, psychometrics and neuroimaging analysis. Tensor decompositions such as the Tucker decomposition are used to analyze multi-aspect data and extract latent factors, which capture the multilinear data structure. Such decompositions are powerful mining tools, for extracting patterns from large data volumes. However, most frequently used algorithms for such decompositions involve the computationally expensive Singular Value Decomposition. In this paper we propose MACH, a new sampling algorithm to compute such decompositions. Our method is of significant practical value for tensor streams, such as environmental monitoring systems, IP traffic matrices over time, where large amounts of data are accumulated and the analysis is computationally intensive but also in "post-mortem" data analysis cases where the tensor does not fit in the availa...
Landrum, E. J.; Babb, C. D.
1979-01-01
Flow visualization and force data for a series of six bodies of revolution are presented without analysis. The data were obtained in the Langley Unitary Plan wind tunnel for angles of attack from -4 deg to 60 deg. The Reynolds number used for these tests was 6,600,000 per meter.
Dynamical Friction in a Gas: The Subsonic Case
Lee, Aaron T
2011-01-01
We study the force of dynamical friction acting on a gravitating point mass that travels through an extended, isothermal gas. This force is well established in the hypersonic limit, but remains less understood in the subsonic regime. Using perturbation theory, we analyze the changes in gas velocity and density far from the mass. We show analytically that the steady-state friction force is Mdot*V, where Mdot is the mass accretion rate onto an object moving at speed V. It follows that the speed of an object experiencing no other forces declines as the inverse square of its mass. Using a modified version of the classic Bondi-Hoyle interpolation formula for Mdot as a function of V, we derive an analytic expression for the friction force. This expression also holds when mass accretion is thwarted, e.g. by a wind, as long as the wind-cloud interaction is sufficiently confined spatially. Our result should find application in a number of astrophysical settings, such as the motion of galaxies through intracluster gas.
Mach stem formation in reflection and focusing of weak shock acoustic pulses.
Karzova, Maria M; Khokhlova, Vera A; Salze, Edouard; Ollivier, Sébastien; Blanc-Benon, Philippe
2015-06-01
The aim of this study is to show the evidence of Mach stem formation for very weak shock waves with acoustic Mach numbers on the order of 10(-3) to 10(-2). Two representative cases are considered: reflection of shock pulses from a rigid surface and focusing of nonlinear acoustic beams. Reflection experiments are performed in air using spark-generated shock pulses. Shock fronts are visualized using a schlieren system. Both regular and irregular types of reflection are observed. Numerical simulations are performed to demonstrate the Mach stem formation in the focal region of periodic and pulsed nonlinear beams in water.
Energy Technology Data Exchange (ETDEWEB)
Abbett, M. J.; Fort, R.
1968-09-01
The three-dimensional ideal gas flow in the shock layer of a blunted supersonic cone at an angle of attack is calculated using two asymptotic solutions. The first solution calculates the steady state flow in the subsonic nose region by obtaining a time-dependent solution of the hyperbolic equations using numerical techniques. Internal, nonboundary points are calculated using a Lax-Wendroff numerical type technique. Boundary points, shock and body surface, are computed using a time-dependent method of characteristics. When a steady state solution is reached the flow properties on a surface of constant {theta}, (where the Mach number is everywhere > 1) are used for initial data for the afterbody solution. The afterbody solution, using polar coordinates (r, {theta}, {phi}) assumes at r{sub 0} an arbitrary set of initial conditions provided by the nose region solution and computes the downstream flow as a function of {theta}, {phi}, and r until an asymptotic state independent of r develops. The interior mesh points are again calculated using a Lax- Wendroff type technique and the boundary points by a method of characteristics. This report covers the coupling of the time-dependent and radius (r) dependent solutions. Instructions are given for the operation of the resulting Fortran code. The type of input data required is detailed and sample output is provided. Output data is given in two sets of coordinates. One is wind orientated; the other set is given in body orientated coordinates; The analytical transformation from one coordinate system to the other is given.
Aeroelasticity Benchmark Assessment: Subsonic Fixed Wing Program
Florance, Jennifer P.; Chwalowski, Pawel; Wieseman, Carol D.
2010-01-01
Aeroelasticity Branch will examine other experimental efforts within the Subsonic Fixed Wing (SFW) program (such as testing of the NASA Common Research Model (CRM)) and other NASA programs and assess aeroelasticity issues and research topics.
Peterson, Victor L.; Menees, Gene P.
1961-01-01
Tabulated results of a wind-tunnel investigation of the aerodynamic loads on a canard airplane model with twin vertical tails are presented for Mach numbers from 0.70 to 2.22. The Reynolds number for the measurements was 2.9 x 10(exp 6) based on the wing mean aerodynamic chord. The results include local static-pressure coefficients measured on the wing, body, and one of the vertical tails for angles of attack from -4 degrees to 16 degree angles of sideslip of 0 degrees and 5.3 degrees, and nominal canard deflections of O degrees and 10 degrees. Also included are section force and moment coefficients obtained from integrations of the local pressures and model-component force and moment coefficients obtained from integrations of the section coefficients. Geometric details of the model are shown and the locations of the pressure orifices are shown. An index to the data contained herein is presented and definitions of nomenclature are given. Detailed descriptions of the model and experiments and a brief discussion of some of the results are given. Tabulated results of measurements of the aerodynamic loads on the same canard model but having a single vertical tail instead of twin vertical tails are presented.
Peterson, Victor L.; Menees, Gene P.
1961-01-01
Tabulated results of a wind-tunnel investigation of the aerodynamic loads on a canard airplane model with a single vertical tail are presented for Mach numbers from 0.70 to 2.22. The Reynolds number for the measurements was 2.9 x 10(exp 6) based on the wing mean aerodynamic chord. The results include local static pressure coefficients measured on the wing, body, and vertical tail for angles of attack from -4 deg to + 16 deg, angles of sideslip of 0 deg and 5.3 deg, vertical-tail settings of 0 deg and 5 deg, and nominal canard deflections of 0 deg and 10 deg. Also included are section force and moment coefficients obtained from integrations of the local pressures and model-component force and moment coefficients obtained from integrations of the section coefficients. Geometric details of the model and the locations of the pressure orifices are shown. An index to the data contained herein is presented and definitions of nomenclature are given.
Subsonic potential aerodynamics for complex configurations - A general theory
Morino, L.; Kuo, C.-C.
1974-01-01
A general theory of subsonic potential aerodynamic flow around a lifting body having arbitrary shape and motion is presented. By using the Green function method, an integral representation for the velocity potential is obtained for both supersonic and subsonic flow. Under the small perturbation assumption, the potential at any point in the field depends only upon the values of the potential and its normal derivative on the surface of the body. On the surface of the body, this representation reduces to an integro-differential equation relating the potential and its normal derivative (which is known from the boundary conditions) on the surface. The theory is applied to finite-thickness wings in subsonic steady and oscillatory flows.
Bradley, Marty K.; Allen, Timothy J.; Droney, Christopher
2014-01-01
This Test Report summarizes the Truss Braced Wing (TBW) Aeroelastic Test (Task 3.1) work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team, which includes the time period of February 2012 through June 2014. The team consisted of Boeing Research and Technology, Boeing Commercial Airplanes, Virginia Tech, and NextGen Aeronautics. The model was fabricated by NextGen Aeronautics and designed to meet dynamically scaled requirements from the sized full scale TBW FEM. The test of the dynamically scaled SUGAR TBW half model was broken up into open loop testing in December 2013 and closed loop testing from January 2014 to April 2014. Results showed the flutter mechanism to primarily be a coalescence of 2nd bending mode and 1st torsion mode around 10 Hz, as predicted by analysis. Results also showed significant change in flutter speed as angle of attack was varied. This nonlinear behavior can be explained by including preload and large displacement changes to the structural stiffness and mass matrices in the flutter analysis. Control laws derived from both test system ID and FEM19 state space models were successful in suppressing flutter. The control laws were robust and suppressed flutter for a variety of Mach, dynamic pressures, and angle of attacks investigated.
Interplay between Mach cone and radial expansion in jet events
Tachibana, Y.; Hirano, T.
2016-12-01
We study the hydrodynamic response to jet propagation in the expanding QGP and investigate how the particle spectra after the hydrodynamic evolution of the QGP reflect it. We perform simulations of the space-time evolution of the QGP in gamma-jet events by solving (3+1)-dimensional ideal hydrodynamic equations with source terms. Mach cone is induced by the jet energy deposition and pushes back the radial flow of the expanding background. Especially in the case when the jet passage is off-central one, the number of particles emitted in the direction of the push back decreases. This is the signal including the information about the formation of the Mach cone and the jet passage in the QGP fluid.
Overview of the Langley subsonic research effort on SCR configuration
Coe, P. L., Jr.; Thomas, J. D.; Huffman, J. K.; Weston, R. P.; Schoonover, W. E., Jr.; Gentry, C. L., Jr.
1980-01-01
Recent advances achieved in the subsonic aerodynamics of low aspect ratio, highly swept wing designs are summarized. The most significant of these advances was the development of leading edge deflection concepts which effectively reduce leading edge flow separation. The improved flow attachment results in substantial improvements in low speed performance, significant delay of longitudinal pitch up, increased trailing edge flap effectiveness, and increased lateral control capability. Various additional theoretical and/or experimental studies are considered which, in conjunction with the leading edge deflection studies, form the basis for future subsonic research effort.
Mach, the Universe, and Foundations of Mechanics
Mashhoon, B
2011-01-01
Barbour's response to our recent paper on "Mach's principle and higher-dimensional dynamics" describes an approach to Mach's principle in which the universe as a whole is involved in the definition of inertial frames of reference. Moreover, Barbour's theoretical procedure is in agreement with general relativity for a finite universe that is spatially closed. However, we prefer an operational approach that relies ultimately on observational data.
Emergent gravity of fractons: Mach's principle revisited
Pretko, Michael
2017-07-01
Recent work has established the existence of stable quantum phases of matter described by symmetric tensor gauge fields, which naturally couple to particles of restricted mobility, such as fractons. We focus on a minimal toy model of a rank 2 tensor gauge field, consisting of fractons coupled to an emergent graviton (massless spin-2 excitation). We show how to reconcile the immobility of fractons with the expected gravitational behavior of the model. First, we reformulate the fracton phenomenon in terms of an emergent center of mass quantum number, and we show how an effective attraction arises from the principles of locality and conservation of center of mass. This interaction between fractons is always attractive and can be recast in geometric language, with a geodesiclike formulation, thereby satisfying the expected properties of a gravitational force. This force will generically be short-ranged, but we discuss how the power-law behavior of Newtonian gravity can arise under certain conditions. We then show that, while an isolated fracton is immobile, fractons are endowed with finite inertia by the presence of a large-scale distribution of other fractons, in a concrete manifestation of Mach's principle. Our formalism provides suggestive hints that matter plays a fundamental role, not only in perturbing, but in creating the background space in which it propagates.
Fenomenologia e fenomenismo em Husserl e Mach
Directory of Open Access Journals (Sweden)
Denis Fisette
2009-12-01
Full Text Available Como conciliar as repetidas críticas ao fenomenismo de Mach, um pouco por toda a obra de Husserl, com o papel proeminente que Husserl parece nele reconhecer em seus últimos trabalhos, quanto à gênese de sua própria fenomenologia? Para responder a essa questão, examinaremos, primeiramente, a relação estreita que Husserl estabelece entre o método fenomenológico e o descritivismo de Mach à luz do debate que opõe nativismo e empirismo sobre a origem da percepção do espaço. Em seguida, examinaremos dois aspectos da crítica que Husserl faz ao positivismo de Mach: o primeiro se refere ao fenomenismo e sua doutrina dos elementos, enquanto o segundo, ao princípio de economia de pensamento, que Husserl associa a uma forma de psicologismo em Prolegômenos. A hipótese que nos guiará nesse estudo é que as opiniões aparentemente contraditórias de Husserl sobre o positivismo de Mach se explicam em parte pelo estatuto duplo que a fenomenologia recebe em seus últimos trabalhos: enquanto programa filosófico, ela se opõe explicitamente ao positivismo; enquanto método, ela se aparenta ao descritivismo de Mach. Concluiremos com a ideia de que esses dois filósofos de origem checa perseguiam o objetivo comum de apreender o sentido originário de positividade.How to conciliate the recurrent criticisms to Mach's phenomenism, a bit in all Husserl's work, with the outstanding role Husserl seems to recognise in phenomenism in his last works, as to the genesis of his own phenomenology? In order to answer this question, we examine, first, the close relationship stablished by Husserl between the phenomenological method and Mach's descriptivism in light of the debate that opposes nativism and empiricism regarding the origin of the perception of space. Next, we examine two features of Husserl's criticism to Mach's positivism: the first refers to phenomenism ans its doctrine of elements, and the second, to the principle of economy of thought, which
Numerical Simulation of Shock Bubble Interaction with Different Mach Numbers
Yang, Jie; Wan, Zhen-Hua; Wang, Bo-Fu; Sun, De-Jun
2015-03-01
Not Available Supported by the National Natural Science Foundation of China under Grant Nos 11232011 and 11402262, the 111 Project under Grant No B07033, and the China Postdoctoral Science Foundation Funded Project under Grant No 2014M561833.
Experimental Studies of Very-High Mach Number Hydrodynamics
1994-02-14
intensity of the from Rotman (1991. symbol R) shock amplification of the density fluctuations as a parameter, together with a turbulent kinetic energy...overlapsubgrid scale model while predicting an increase in the model where an algebraic identity provides a procedure for overall grid spectral energy... Rotman , and W. P. improvement in the dissipative near-wal region. Dannevik during the course of this work. Figure 8. indicates that for even steeper
Plasma flow at a high Mach-number
Energy Technology Data Exchange (ETDEWEB)
Yu, Bing; Hameiri, Eliezer [Courant Institute of Mathematical Sciences, New York University New York, New York 10012 (United States)
2013-09-15
Unlike the case of static magnetohydrodynamic (MHD) equilibria, where an expansion in large aspect ratio of toroidal devices is common, cases of MHD equilibria with flow are rarely treated this way, and when this is done the expansion tends to be only partial. The main reason for the difference seems to be the difficulty of expanding the larger system of equilibrium equations with flow. Here, we use a recent expansion technique which employs a variational principle to simplify the process [E. Hameiri, Phys. Plasmas 20, 024504 (2013)]. We treat four cases of MHD equilibria with flow, developing their asymptotic expansions in full, and for an application consider the effect of the flow on the Shafranov shift.
Hydrocarbon-Fueled Scramjet Research at Hypersonic Mach Numbers
2005-03-31
hypersonic flow. Laser-induced fluorescence has the threefold advantages for combustion studies of being non- intrusive , species-specific and highly sensitive...Propulsion Conference and Exhibit, Seattle, WA. Griffiths, A. (2004), Development and Demonstration of a Diode Laser Based Temperature and Water Vapour
SPHYNX: SPH hydrocode for subsonic hydrodynamical instabilities and strong shocks
Cabezon, Ruben M.; Garcia-Senz, Domingo
2017-09-01
SPHYNX addresses subsonic hydrodynamical instabilities and strong shocks; it is Newtonian, grounded on the Euler-Lagrange formulation of the smoothed-particle hydrodynamics technique, and density based. SPHYNX uses an integral approach for estimating gradients, a flexible family of interpolators to suppress pairing instability, and incorporates volume elements to provides better partition of the unity.
The structure of subsonic air wakes behind a flat plate
Energy Technology Data Exchange (ETDEWEB)
Barreras, F.; Dopazo, C. [Centro Politecnico Superior de Ingenieros Area de Mecanica de Fluidos, Zaragoza (Spain); Lozano, A.; Yates, A.J. [LITEC/CSIC, Maria de Luna 3 E-50015-Zaragoza (Spain)
1999-04-01
Acetone vapor planar laser-induced fluorescence has been used to visualize the structure of a subsonic air wake behind a flat plate. Longitudinal and transversal wavelengths have been directly measured from the acquired images. The ratio between them has been calculated to be 2/5. (orig.) With 3 figs., 1 tab., 10 refs.
Numerical Investigation of Subsonic Flow through an Aggressive Flat Bottom Diffuser
Mati, Nicholas Alexander
Airflow through an aggressive, constant pressure gradient, flat-bottomed 2D diffuser is simulated with the compressible version of the stabilized, implicit finite element code PHASTA. The freestream Mach number of fluid entering the diffuser is held at a value of M=0.7 with a PI feedback loop. For a quasi 1D flow, the expansion ratio of AAIP / AInlet = 2.33 produces a Mach number of 0.25 by the end of the diffuser or Aerodynamics Interface Plane (AIP). However, the compact geometry and high targeted pressure gradient of dp/dx=162 kPa/m result in massive asymmetric separation off of the curved ceiling. Wall suction is applied to the ceiling, floor, and corners of the duct as a flow control surrogate while the geometry is iterated to better achieve the targeted pressure gradient. The separation dynamics are then studied in greater detail with both URANS and DDES simulations.
Afsar, M. Z.; Leib, S. J.; Bozak, R. F.
2017-01-01
In this paper we extend the Rapid-distortion theory (RDT)-based model derived by Goldstein, Afsar & Leib (J. Fluid Mech., vol. 736, pp. 532-569, 2013) for the sound generated by the interaction of a large-aspect-ratio rectangular jet with the trailing edge of a flat plate to include a more realistic upstream turbulence spectrum that possess a de-correlation (i.e. negative dip) in its space-time structure and use results from three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions to determine the mean flow, turbulent kinetic energy and turbulence length & time scales. Since the interaction noise dominates the low-frequency portion of the spectrum, we use an appropriate asymptotic approximation for the Rayleigh equation Green's function, which enters the analysis, based on a two-dimensional mean flow representation for the jet. We use the model to predict jet-surface interaction noise for a range of subsonic acoustic Mach number jets, nozzle aspect ratios, streamwise and transverse trailing-edge locations and compare them with experimental data. The RANS meanflow computations are also compared with flow data for selected cases to assess their validity. We find that finite de-correlation in the turbulence spectrum increases the low-frequency algebraic decay (the low-frequency "roll-off") of the acoustic spectrum with angular frequency to give a model that has a pure dipole frequency scaling. This gives better agreement with noise data compared to Goldstein et al. (2013) for Strouhal numbers less than the peak jet-surface interaction noise. For example, through sensitivity analysis we find that there is a difference of 10 dB at the lowest frequency for which data exists (relative to a model without de-correlation effects included) for the highest acoustic Mach number case. Secondly, our results for the planar flow theory provide a first estimate of the low-frequency amplification due to the jet-surface interaction for moderate aspect ratio nozzles when RANS
Dag, Yusuf
Forced convection over traditional surfaces such as flat plate, cylinder and sphere have been well researched and documented. Data on forced convection over airfoil surfaces, however, remain very scanty in literature. High altitude vehicles that employ airfoils as lifting surfaces often suffer leading edge ice accretions which have tremendous negative consequences on the lifting capabilities and stability of the vehicle. One of the ways of mitigating the effect of ice accretion involves judicious leading edge convective cooling technique which in turn depends on the accuracy of convective heat transfer coefficient used in the analysis. In this study empirical investigation of convective heat transfer measurements on asymmetric airfoil is presented at different angle of attacks ranging from 0° to 20° under subsonic flow regime. The top and bottom surface temperatures are measured at given points using Senflex hot film sensors (Tao System Inc.) and used to determine heat transfer characteristics of the airfoils. The model surfaces are subjected to constant heat fluxes using KP Kapton flexible heating pads. The monitored temperature data are then utilized to determine the heat convection coefficients modelled empirically as the Nusselt Number on the surface of the airfoil. The experimental work is conducted in an open circuit-Eiffel type wind tunnel, powered by a 37 kW electrical motor that is able to generate subsonic air velocities up to around 41 m/s in the 24 square-inch test section. The heat transfer experiments have been carried out under constant heat flux supply to the asymmetric airfoil. The convective heat transfer coefficients are determined from measured surface temperature and free stream temperature and investigated in the form of Nusselt number. The variation of Nusselt number is shown with Reynolds number at various angles of attacks. It is concluded that Nusselt number increases with increasing Reynolds number and increase in angle of attack from 0
On fluttering modes for aircraft wing model in subsonic air flow
Shubov, Marianna A.
2014-01-01
The paper deals with unstable aeroelastic modes for aircraft wing model in subsonic, incompressible, inviscid air flow. In recent author’s papers asymptotic, spectral and stability analysis of the model has been carried out. The model is governed by a system of two coupled integrodifferential equations and a two-parameter family of boundary conditions modelling action of self-straining actuators. The Laplace transform of the solution is given in terms of the ‘generalized resolvent operator’, which is a meromorphic operator-valued function of the spectral parameter λ, whose poles are called the aeroelastic modes. The residues at these poles are constructed from the corresponding mode shapes. The spectral characteristics of the model are asymptotically close to the ones of a simpler system, which is called the reduced model. For the reduced model, the following result is shown: for each value of subsonic speed, there exists a radius such that all aeroelastic modes located outside the circle of this radius centred at zero are stable. Unstable modes, whose number is always finite, can occur only inside this ‘circle of instability’. Explicit estimate of the ‘instability radius’ in terms of model parameters is given. PMID:25484610
Subsonic Aerodynamics of Spinning and Non-Spinning Type 200 Lightcraft: Progress Report
Kenoyer, David A.; Myrabo, Leik N.
2010-05-01
A combined experimental and numerical investigation of subsonic aerodynamics for Type 200 laser lightcraft is underway for both spinning and non-spinning cases. A 12.2 cm diameter aluminum model with a "closed" annular airbreathing inlet was fitted to a sting balance in RPI's 61 cm by 61 cm subsonic wind tunnel. Aerodynamic forces and moments were measured first for the non-spinning case vs. angle of attack, at several freestream flow velocities (e.g., 30, 45, and 60 m/s) to assess Reynolds number effects. The CFD analysis was performed for 0-180° angles of attack for a fixed coordinate system (i.e., non-spinning Type 200 model), and predictions compared favorably with the experimental data. In the near future, for the spinning case, a brushless electric motor has been installed to rotate the wind tunnel model at 3000 to 13,000 RPM; Magnus force effects upon the coefficients (Cd, Cl, and Cm) are expected to reveal interesting departures from the non-spinning database in forthcoming experiments.
Mach bands change asymmetrically during solar eclipses.
Ross, John; Diamond, Mark R; Badcock, David R
2003-01-01
Observations made during two partial eclipses of the Sun show that the Mach bands on shadows cast by the Sun disappear and reappear asymmetrically as an eclipse progresses. These changes can be explained as due to changes in the shape of the penumbras of shadows as the visible portion of the Sun forms crescents of different orientation.
Edge and divertor plasma measurements with ion sensitive and Mach probes in LHD
Energy Technology Data Exchange (ETDEWEB)
Hayashi, Y., E-mail: shihaya_uki884@yahoo.co.jp [Nagano National College of Technology, 716 Tokuma, Nagano 381-8550 (Japan); Ezumi, N. [Nagano National College of Technology, 716 Tokuma, Nagano 381-8550 (Japan); Masuzaki, S.; Tanaka, H.; Kobayashi, M. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Sawada, K. [Shinshu University, Wakasato, Nagano 380-8553 (Japan); Ohno, N. [Nagoya University, Furo-cho Chikusa-ku, Nagoya 464-8603 (Japan)
2013-07-15
Spatial profiles of plasma flow and Mach number in the stochastic magnetic boundary layer as well as ion temperature (T{sub i}) and electron temperature (T{sub e}) in the divertor region in Large Helical Device (LHD) have been studied by a movable multiple functions probe, which consists of Mach probes and an ion sensitive probe. The results of ion saturation current measurements indicated plasma flow direction is alternated in the stochastic magnetic boundary. Mach number profiles for different plasma densities have been evaluated experimentally which compared with 3-D transport code. T{sub i} and T{sub e} in the divertor region measured by the ion sensitive probe decreased with increasing line-averaged density. Although T{sub i} was higher than T{sub e} in the low density plasma, both temperatures became almost the same at higher density.
National Aeronautics and Space Administration — This proposal defines innovative aerodynamic concepts and technology goals aimed at vehicle efficiency for future subsonic aircraft in the 2020 ? 2030 timeframe....
Mach-Zehnder interferometer for movement monitoring
Vasinek, Vladimir; Cubik, Jakub; Kepak, Stanislav; Doricak, Jan; Latal, Jan; Koudelka, Petr
2012-06-01
Fiber optical interferometers belong to highly sensitive equipments that are able to measure slight changes like distortion of shape, temperature and electric field variation and etc. Their great advantage is that they are insensitive on ageing component, from which they are composed of. It is in virtue of herewith, that there are evaluated no changes in optical signal intensity but number interference fringes. To monitor the movement of persons, eventually to analyze the changes in state of motion we developed method based on analysis the dynamic changes in interferometric pattern. We have used Mach- Zehnder interferometer with conventional SM fibers excited with the DFB laser at wavelength of 1550 nm. It was terminated with optical receiver containing InGaAs PIN photodiode. Its output was brought into measuring card module that performs on FFT of the received interferometer signal. The signal rises with the composition of two waves passing through single interferometer arm. The optical fiber SMF 28e in one arm is referential; the second one is positioned on measuring slab at dimensions of 1x2m. A movement of persons around the slab was monitored, signal processed with FFT and frequency spectra were evaluated. They rose owing to dynamic changes of interferometric pattern. The results reflect that the individual subjects passing through slab embody characteristic frequency spectra, which are individual for particular persons. The scope of measuring frequencies proceeded from zero to 10 kHz. It was also displayed in experiments that the experimental subjects, who walked around the slab and at the same time they have had changed their state of motion (knee joint fixation), embodied characteristic changes in their frequency spectra. At experiments the stability of interferometric patterns was evaluated as from time aspects, so from the view of repeated identical experiments. Two kinds of balls (tennis and ping-pong) were used to plot the repeatability measurements and
On Mach's critique of Newton and Copernicus
Hartman, H I; Hartman, Herbert I.; Nissim-Sabat, Charles
2003-01-01
Maintaining the relativity of all motion, especially rotational motion, Mach denied the existence of absolute motion and absolute space. He maintained the equivalence of the Ptolemaic and the Copernican systems and the equivalence of a fixed bucket in a rotating universe with the converse. An analysis of the Foucault pendulum shows that there cannot be a fixed bucket in a rotating universe. Also, Mach's views violate the physics he espoused: non-inertial experiments, e.g. stellar aberration and electromagnetic effects, distinguish between a rotating bucket in a fixed universe and the converse, between the Copernican and the Ptolemaic systems, and establish that one cannot ascribe all observations solely to relative motion between a system and the universe.
Dynamics of compressional Mach cones in a strongly coupled complex plasma
Bandyopadhyay, P; Kadyan, Sangeeta; Sen, Abhijit
2016-01-01
Using a Generalised-Hydrodynamic (GH) fluid model we study the influence of strong coupling induced modification of the fluid compressibility on the dynamics of compressional Mach cones in a dusty plasma medium. A significant structural change of lateral wakes for a given Mach number and Epstein drag force is found in the strongly coupled regime. With the increase of fluid compressibility, the peak amplitude of the normalised perturbed dust density first increases and then decreases monotonically after reaching its maximum value. It is also noticed that the opening angle of the cone structure decreases with the increase of the compressibility of the medium and the arm of the Mach cone breaks up into small structures in the velocity vector profile when the coupling between the dust particles increases.
Institute of Scientific and Technical Information of China (English)
履之
1994-01-01
Most engines compress air, add fuel and burn it, and then allow theheated gas to expand, creating power or thrust. A radical aircraft enginedevised by ONERA, France’s equivalent of NASA, does the opposite.The Priam inverse-cycle" engine is designed for hypersonic speedsabove Mach 4 (2, 650 mph). Conventional jets do not work at suchspeeds, because the air becomes so hot when it is rammed into the
Dynamic transition from Mach to regular reflection of shock waves in a steady flow
CSIR Research Space (South Africa)
Naidoo, K
2014-07-01
Full Text Available decreased with increased rotation speed. The sensitivity of the transition angle to changing the rotation point from the trailing edge to the experimental model pivot point was investigated briefly at a free-stream Mach number of M=2.98 with M(subE)=-0...
Mach's Principle and Higher-Dimensional Dynamics
Mashhoon, B
2011-01-01
We briefly discuss the current status of Mach's principle in general relativity and point out that its last vestige, namely, the gravitomagnetic field associated with rotation, has recently been measured for the earth in the GP-B experiment. Furthermore, in his analysis of the foundations of Newtonian mechanics, Mach provided an operational definition for inertial mass and pointed out that time and space are conceptually distinct from their operational definitions by means of masses. Mach recognized that this circumstance is due to the lack of any a priori connection between the inertial mass of a body and its Newtonian state in space and time. One possible way to improve upon this situation in classical physics is to associate mass with an extra dimension. Indeed, Einstein's theory of gravitation can be locally embedded in a Ricci-flat 5D manifold such that the 4D energy-momentum tensor appears to originate from the existence of the extra dimension. An outline of such a 5D Machian extension of Einstein's gen...
Carlson, H. W.; Walkley, K. B.
1982-01-01
Numerical methods incorporated into a computer program to provide estimates of the subsonic aerodynamic performance of twisted and cambered wings of arbitrary planform with attainable thrust and vortex lift considerations are described. The computational system is based on a linearized theory lifting surface solution which provides a spanwise distribution of theoretical leading edge thrust in addition to the surface distribution of perturbation velocities. The approach used relies on a solution by iteration. The method also features a superposition of independent solutions for a cambered and twisted wing and a flat wing of the same planform to provide, at little additional expense, results for a large number of angles of attack or lift coefficients. A previously developed method is employed to assess the portion of the theoretical thrust actually attainable and the portion that is felt as a vortex normal force.
Numerical Calculation of Interaction Between Plane Jet and Subsonic Flow
Directory of Open Access Journals (Sweden)
V. O. Moskalenko
2016-01-01
Full Text Available The paper makes numerical calculation of interaction between plane jet and subsonic flow. Its aim is to determine the jet trajectory, velocity profiles, distribution of pressure coefficient on the plate surface at different jet angles, namely ωj=45°; 90°; 105° and at low blowing strengths ( ≤1.5 as well as a to make comparison with the experimental data of other authors.To simulate a two-dimensional jet in the subsonic flow the software package “CAD SolidWorks Flow Simulation” has been used. Initially, the test task was solved with its calculation results compared with experimental ones [6.8] in order to improve the convergence; the size of the computational domain and a computational grid within the k-ε turbulence model were selected. As a result of the calculation, were identified and analysed the pressure values, jet trajectories, and velocity profiles. In the graphs the solid lines show calculation results, and dots represent experimental data.From the calculation results it is seen that, with increasing intensity of the reduced mass flow ¯q in the above range, the change of the jet pressure coefficient p¯ distribution behind a slotted nozzle is almost linear and significant. Before the nozzle, with increasing ¯q the pressure coefficient increases slightly.Analysis of results has shown that blowing of jets with ωj>90ω, provides a greater perturbation of the subsonic flow. Thus, the jet penetrates into the flow deeper, forms a dead region of the greater length, and more significantly redistributes the pressure coefficient on the surface of the plate.The calculation results are in good compliance with the experimental data both for the jet axis and for the pressure coefficient distribution on the plate surface. The research results can be used in the designing the jet control of aircrafts.
A Study On Recent Trends In High Subsonic Flow Over Delta Wings .
Directory of Open Access Journals (Sweden)
Vishnu G Nair,
2014-01-01
Full Text Available An understanding of the vortical structures and vortex breakdown is essential for the development of highly maneuverable and high angle of attack flight. This is primarily due to the physical limits these phenomena impose on aircraft and missiles at extreme flight conditions. In today’s competitive world, demands for more maneuverable and stealthy air vehicles have encouraged the development of new control concepts for separated flows and vortex flow.An overview is given about investigations on a 65◦ delta wing using the Pressure Sensitive Paint (PSP and Particle Image Velocimetry (PIV techniques, carried out in the framework of Vortex flow experiment. For the delta wing with rounded leading edges and subsonic flow, the occurrence of a flat vortical structure as well as the onset of the primary vortex and the development of a vortex system consisting of an inner and outer vortex is described in dependency of the angle of attack and the Reynolds number. The Q - criterion is applied to the measured velocity data to estimate the circulation strength of individual vortices allowing for a quantitative description of the vortex developments and interactions. Furthermore, a case at transonic flow speeds (M = 0.8 is described, showing a sudden occurrence of vortex breakdown above the delta wing, most probably induced by a shock wave.Vortex Flow Experiment provided a variety of experimental data for a 65◦ swept delta wing sharp and blunt leading edges. Flow details including forces and moments, surface pressures,Pressure Sensitive Paint measurements, and off-surface flow variables from Particle Image Velocimetry were made available for comparisons with computational simulations. This paper concentrates on some typical problems of delta wings with rounded leading edges at subsonic speed: the prediction of the main leading edge separation, the generation of the second inner vortex, the effect of transition, and Reynolds number effects.
Finite element analysis of inviscid subsonic boattail flow
Chima, R. V.; Gerhart, P. M.
1981-01-01
A finite element code for analysis of inviscid subsonic flows over arbitrary nonlifting planar or axisymmetric bodies is described. The code solves a novel primitive variable formulation of the coupled irrotationality and compressible continuity equations. Results for flow over a cylinder, a sphere, and a NACA 0012 airfoil verify the code. Computed subcritical flows over an axisymmetric boattailed afterbody compare well with finite difference results and experimental data. Interative coupling with an integral turbulent boundary layer code shows strong viscous effects on the inviscid flow. Improvements in code efficiency and extensions to transonic flows are discussed.
NASA Subsonic Rotary Wing Project - Structures and Materials Discipline
Halbig, Michael C.; Johnson, Susan M.
2008-01-01
The Structures & Materials Discipline within the NASA Subsonic Rotary Wing Project is focused on developing rotorcraft technologies. The technologies being developed are within the task areas of: 5.1.1 Life Prediction Methods for Engine Structures & Components 5.1.2 Erosion Resistant Coatings for Improved Turbine Blade Life 5.2.1 Crashworthiness 5.2.2 Methods for Prediction of Fatigue Damage & Self Healing 5.3.1 Propulsion High Temperature Materials 5.3.2 Lightweight Structures and Noise Integration The presentation will discuss rotorcraft specific technical challenges and needs as well as details of the work being conducted in the six task areas.
Experimental and CFD analysis of nozzle position of subsonic ejector
Institute of Scientific and Technical Information of China (English)
Xilai ZHANG; Shiping JIN; Suyi HUANG; Guoqing TIAN
2009-01-01
The influence of nozzle position on the performance of an ejector was analyzed qualitatively with free jet flow model. Experimental investigations and computational fluid dynamics (CFD) analysis of the nozzle position of the subsonic ejector were also conducted. The results show that there is an optimum nozzle position for the ejector. The ejecting coefficient reaches its maximum when the nozzle is positioned at the optimum and decreases when deviating. Moreover, the nozzle position of an ejector is not a fixed value, but is influenced greatly by the flow parameters. Considering the complexity of the ejector, CFD is reckoned as a useful tool in the design of ejectors.
Institute of Scientific and Technical Information of China (English)
T. Irie; T. Yasunobu; H. Kashimura; T. Setoguchi
2003-01-01
When the high-pressure gas is exhausted to the vacuum chamber from the nozzle, the underexpanded supersonic jet contained with the Mach disk is generally formed. The eventual purpose of this study is to clarify the unsteady phenomenon of the underexpanded free jet when the back pressure continuously changes with time. The characteristic of the Mach disk has been clarified in consideration of the diameter and position of it by the numerical analysis in this paper. The sonic jet of the exit Mach number Me=1 is assumed and the axisymmetric conservational equation is solved by the TVD method in the numerical calculation.The diameter and position of the Mach disk differs with the results of a steady jet and the influence on the continuously changing of the back pressure is evidenced from the comparison with the case of steady supersonic jet.
Combustion-Powered Actuation for Dynamic Stall Suppression - Simulations and Low-Mach Experiments
Matalanis, Claude G.; Min, Byung-Young; Bowles, Patrick O.; Jee, Solkeun; Wake, Brian E.; Crittenden, Tom; Woo, George; Glezer, Ari
2014-01-01
An investigation on dynamic-stall suppression capabilities of combustion-powered actuation (COMPACT) applied to a tabbed VR-12 airfoil is presented. In the first section, results from computational fluid dynamics (CFD) simulations carried out at Mach numbers from 0.3 to 0.5 are presented. Several geometric parameters are varied including the slot chordwise location and angle. Actuation pulse amplitude, frequency, and timing are also varied. The simulations suggest that cycle-averaged lift increases of approximately 4% and 8% with respect to the baseline airfoil are possible at Mach numbers of 0.4 and 0.3 for deep and near-deep dynamic-stall conditions. In the second section, static-stall results from low-speed wind-tunnel experiments are presented. Low-speed experiments and high-speed CFD suggest that slots oriented tangential to the airfoil surface produce stronger benefits than slots oriented normal to the chordline. Low-speed experiments confirm that chordwise slot locations suitable for Mach 0.3-0.4 stall suppression (based on CFD) will also be effective at lower Mach numbers.
Numerical simulation of Mach reflection of cellular detonations
Li, J.; Lee, J. H. S.
2016-09-01
The Mach reflection of cellular detonation waves on a wedge is investigated numerically in an attempt to elucidate the effect of cellular instabilities on Mach reflection, the dependence of self-similarity on the thickness of a detonation wave, and the initial development of the Mach stem near the wedge apex. A two-step chain-branching reaction model is used to give a thermally neutral induction zone followed by a chemical reaction zone for the detonation wave. A sufficiently large distance of travel of the Mach stem is computed to observe the asymptotic behavior in the far field. Depending on the scale at which the Mach reflection process occurs, it is found that the Mach reflection of a cellular detonation behaves essentially in the same way as a planar ZND detonation wave. The cellular instabilities, however, cause the triple-point trajectory to fluctuate. The fluctuations are due to interactions of the triple point of the Mach stem with the transverse waves of cellular instabilities. In the vicinity of the wedge apex, the Mach reflection is found to be self-similar and corresponds to that of a shock wave of the same strength, since the Mach stem is highly overdriven initially. In the far field, the triple-point trajectory approaches a straight line, indicating that the Mach reflection becomes self-similar asymptotically. The distance of the approach to self-similarity is found to decrease rapidly with decreasing thickness of the detonation front.
Modelling of subsonic COIL with an arbitrary magnetic modulation
Beránek, Jaroslav; Rohlena, Karel
2007-05-01
The concept of 1D subsonic COIL model with a mixing length was generalized to include the influence of a variable magnetic field on the stimulated emission cross-section. Equations describing the chemical kinetics were solved taking into account together with the gas temperature also a simplified mixing model of oxygen and iodine molecules. With the external time variable magnetic field the model is no longer stationary. A transformation in the system moving with the mixture reduces partial differential equations to ordinary equations in time with initial conditions given either by the stationary flow at the moment when the magnetic field is switched on combined with the boundary conditions at the injector. Advantage of this procedure is a possibility to consider an arbitrary temporal dependence of the imposed magnetic field and to calculate directly the response of the laser output. The method was applied to model the experimental data measured with the subsonic version of the COIL device in the Institute of Physics, Prague, where the applied magnetic field had a saw-tooth dependence. We found that various values characterizing the laser performance, such as the power density distribution over the active zone cross-section, may have a fairly complicated structure given by combined effects of the delayed reaction to the magnetic switching and the flow velocity. This is necessarily translated in a time dependent spatial inhomogeneity of output beam intensity profile.
Vorticity, Shocks and Magnetic Fields in Subsonic, ICM-like Turbulence
Porter, David H; Ryu, Dongsu
2015-01-01
We analyze high resolution simulations of compressible, MHD turbulence with properties resembling conditions in galaxy clusters. The flow is driven to turbulence Mach number $\\mathcal{M}_t \\sim 1/2$ in an isothermal medium with an initially very weak, uniform seed magnetic field ($\\beta = P_g/P_B = 10^6$). Since cluster turbulence is likely to result from a mix of sheared (solenoidal) and compressive forcing processes, we examine the distinct turbulence properties for both cases. In one set of simulations velocity forcing is entirely solenoidal ($\
Parametric study of single expansion ramp nozzles at subsonic/transonic speeds
Capone, F. J.; Re, R. J.; Bare, E. A.; Maclean, M. K.
1987-01-01
The Langley Research Center has conducted a parametric investigation to determine the aeropropulsive characteristics of single expansion ramp nozzles (SERN). The SERN is a nonaxisymmetric, variable-area, internal/external expansion exhaust nozzle. Internal nozzle parameters that were varied included upper ramp length, ramp chordal angle, lower flap length, flap angle and the axial and vertical locations of nozzle throat. Convergent-divergent and convergent nozzles were included in this investigation which was conducted in the Langley 16-Foot Transonic Tunnel at Mach numbers from 0.6 to 1.2 and at nozzle pressure ratios up to 12.0.
On Mach's principle: Inertia as gravitation
Martín, J; Tiemblo, A; Ranada, Antonio F.
2007-01-01
In order to test the validity of Mach's principle, we calculate the action of the entire universe on a test mass in its rest frame, which is an acceleration ${\\bf g}^*$. We show the dependence of the inertia principle on the lapse and the shift. Using the formalism of linearized gravitation, we obtain the non-relativistic limit of ${\\bf g}^*$ in terms of two integrals. We follow then two approaches. In the first one, these integrals are calculated in the actual time section $t=t_0$ up to the distance $R_U=ct_0$. In the more exact and satisfactory second approach, they are calculated over the past light cone using the formalism of the retarded potentials. The aim is to find whether the acceleration $\\dot{\\bf v}$ in the LHS of Newton's second law can be interpreted as a reactive acceleration, in other words, as minus the acceleration of gravity ${\\bf g}^*$ in the rest frame of the accelerated particle ({\\it i. e.} to know whether or not ${\\bf g}^*=-\\dot{\\bf v}$). The results strongly support Mach's idea since t...
Sub-sonic thermal explosions investigated by radiography
Energy Technology Data Exchange (ETDEWEB)
Smilowitz, Laura B [Los Alamos National Laboratory; Henson, Bryan F [Los Alamos National Laboratory; Romero, Jerry J [Los Alamos National Laboratory; Asay, Blaine W [Los Alamos National Laboratory
2010-01-01
This paper reviews the past 5 years of experiments utilizing radiographic techniques to study defiagration in thermal explosions in HMX based formulations. Details of triggering and timing synchronization are given. Radiographic images collected using both protons and x-rays are presented. Comparisons of experiments with varying size, case confinement, binder, and synchronization are presented. Techniques for quantifying the data in the images are presented and a mechanism for post-ignition burn propagation in a thermal explosion is discussed. From these experiments, we have observed a mechanism for sub-sonic defiagration with both gas phase convective and solid phase conductive burning. The convective front velocity is directly measured from the radiographic images and consumes only a small fraction of the HE. It lights the HE as it passes beginning the slower solid state conductive burn process. This mechanism is used to create a model to simulate the radiographic results and a comparison will be shown.
Propagation of Weak Pressure Waves against Two Parallel Subsonic Streams
Institute of Scientific and Technical Information of China (English)
Makiko YONAMINE; Takanori USHIJIMA; Yoshiaki MIYAZATO; Mitsuharu MASUDA; Hiroshi KATANODA; Kazuyasu MATSUO
2006-01-01
In this paper, the characteristics of a pressure wave propagating against two parallel subsonic streams in a constant-area straight duct are investigated by one-dimensional analysis, two-dimensional numerical simulation,and experiments. Computations have been carried out by the two-dimensional Euler Equations using the Chakravarthy-Osher-type TVD scheme. Optical observations by the schlieren method as well as wall pressure measurements have been performed to clarify both the structure and the propagation velocity of pressure waves.The results show that the pressure wave propagating against the streams changes into a bifurcated pressure wave and the bifurcation occurs in the low speed streams. It is also found that the propagation velocity of the pressure wave obtained by the analysis and computation agrees well with the present experimental data.
Study on the subsonic speed flame spraying coating of hydroxyapatite
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
A new method of preparation of biomaterial composite coating by the technique of subsonic thermal sprayingwas discussed in this paper. Ti6A14V and pure Ti were chosen as substrate and sublayer material respectively and the work-ing layer was sprayed with biomaterial hydroxyapatite (HAP), forming the composite coating. The experiments of heatshock and tensile strength showed that the bonding strength between coating and substrate is almost as same as that of spe-cimen in which Ni/Al powder was adopted as sublayer. The phases of TiN, TiO2, and Ti2O3 were formed in the sublayer,which are free of toxic and have no side effects. The powder of working layer HAP was decomposed partly during spraying,but it can be solved by later treatment.
Evaluation of the Advanced Subsonic Technology Program Noise Reduction Benefits
Golub, Robert A.; Rawls, John W., Jr.; Russell, James W.
2005-01-01
This report presents a detailed evaluation of the aircraft noise reduction technology concepts developed during the course of the NASA/FAA Advanced Subsonic Technology (AST) Noise Reduction Program. In 1992, NASA and the FAA initiated a cosponsored, multi-year program with the U.S. aircraft industry focused on achieving significant advances in aircraft noise reduction. The program achieved success through a systematic development and validation of noise reduction technology. Using the NASA Aircraft Noise Prediction Program, the noise reduction benefit of the technologies that reached a NASA technology readiness level of 5 or 6 were applied to each of four classes of aircraft which included a large four engine aircraft, a large twin engine aircraft, a small twin engine aircraft and a business jet. Total aircraft noise reductions resulting from the implementation of the appropriate technologies for each class of aircraft are presented and compared to the AST program goals.
An Investigation of Transonic Resonance in a Mach 2.2 Round Convergent-Divergent Nozzle
Dippold, Vance F., III; Zaman, Khairul B. M. Q.
2015-01-01
Hot-wire and acoustic measurements were taken for a round convergent nozzle and a round convergent-divergent (C-D) nozzle at a jet Mach number of 0.61. The C-D nozzle had a design Mach number of 2.2. Compared to the convergent nozzle jet flow, the Mach 2.2 nozzle jet flow produced excess broadband noise (EBBN). It also produced a transonic resonance tone at 1200 Herz. Computational simulations were performed for both nozzle flows. A steady Reynolds-Averaged Navier-Stokes simulation was performed for the convergent nozzle jet flow. For the Mach 2.2 nozzle flow, a steady RANS simulation, an unsteady RANS (URANS) simulation, and an unsteady Detached Eddy Simulation (DES) were performed. The RANS simulation of the convergent nozzle showed good agreement with the hot-wire velocity and turbulence measurements, though the decay of the potential core was over-predicted. The RANS simulation of the Mach 2.2 nozzle showed poor agreement with the experimental data, and more closely resembled an ideally-expanded jet. The URANS simulation also showed qualitative agreement with the hot-wire data, but predicted a transonic resonance at 1145 Herz. The DES showed good agreement with the hot-wire velocity and turbulence data. The DES also produced a transonic tone at 1135 Herz. The DES solution showed that the destabilization of the shock-induced separation region inside the nozzle produced increased levels of turbulence intensity. This is likely the source of the EBBN.
Nonlinear interaction of instability waves and vortex-pairing noise in axisymmetric subsonic jets
Yang, Hai-Hua; Zhou, Lin; Zhang, Xing-Chen; Wan, Zhen-Hua; Sun, De-Jun
2016-10-01
A direct simulation with selected inflow forcing is performed for an accurate description of the jet flow field and far-field noise. The effects of the Mach number and heating on the acoustic field are studied in detail. The beam patterns and acoustic intensities are both varied as the change of the Mach number and temperature. The decomposition of the source terms of the Lilley-Goldstein (L-G) equation shows that the momentum and thermodynamic components lead to distinctly different beam patterns. Significant cancellation is found between the momentum and thermodynamic components at low polar angles for the isothermal jet and large polar angles for the hot jet. The cancellation leads to the minimum values of the far-field sound. Based on linear parabolized stability equation solutions, the nonlinear interaction model for sound prediction is built in combination with the L-G equation. The dominant beam patterns and their original locations predicted by the nonlinear model are in good agreement with the direct simulation results, and the predictions of sound pressure level (SPL) by the nonlinear model are relatively reasonable.
Mach 5 to 7 RBCC Propulsion System Testing at NASA-LeRC HTF
Perkins, H. Douglas; Thomas, Scott R.; Pack, William D.
1996-01-01
A series of Mach 5 to 7 freejet tests of a Rocket Based Combined Cycle (RBCC) engine were cnducted at the NASA Lewis Research Center (LERC) Hypersonic Tunnel Facility (HTF). This paper describes the configuration and operation of the HTF and the RBCC engine during these tests. A number of facility support systems are described which were added or modified to enhance the HTF test capability for conducting this experiment. The unfueled aerodynamic perfor- mance of the RBCC engine flowpath is also presented and compared to sub-scale test results previously obtained in the NASA LERC I x I Supersonic Wind Tunnel (SWT) and to Computational Fluid Dynamic (CFD) analysis results. This test program demonstrated a successful configuration of the HTF for facility starting and operation with a generic RBCC type engine and an increased range of facility operating conditions. The ability of sub-scale testing and CFD analysis to predict flowpath performance was also shown. The HTF is a freejet, blowdown propulsion test facility that can simulate up to Mach 7 flight conditions with true air composition. Mach 5, 6, and 7 facility nozzles are available, each with an exit diameter of 42 in. This combination of clean air, large scale, and Mach 7 capabilities is unique to the HTF. This RBCC engine study is the first engine test program conducted at the HTF since 1974.
Runyan, Harry L; Watkins, Charles E
1953-01-01
This report treats the effect of wind-tunnel walls on the oscillating two-dimensional air forces in a compressible medium. The walls are simulated by the usual method of placing images at appropriate distances above and below the wing. An important result shown is that, for certain conditions of wing frequency, tunnel height, and Mach number, the tunnel and wing may form a resonant system so that the forces on the wing are greatly changed from the condition of no tunnel walls. It is pointed out that similar conditions exist for three-dimensional flow in circular and rectangular tunnels and apparently, within certain Mach number ranges, in tunnels of nonuniform cross section or even in open tunnels or jets.
Ernst Mach and the episode of the monocular depth sensations.
Banks, E C
2001-01-01
Although Ernst Mach is widely recognized in psychology for his discovery of the effects of lateral inhibition in the retina ("Mach Bands"), his contributions to the theory of depth perception are not as well known. Mach proposed that steady luminance gradients triggered sensations of depth. He also expanded on Ewald Hering's hypothesis of "monocular depth sensations," arguing that they were subject to the same principle of lateral inhibition as light sensations were. Even after Hermann von Helmholtz's attack on Hering in 1866, Mach continued to develop theories involving the monocular depth sensations, proposing an explanation of perspective drawings in which the mutually inhibiting depth sensations scaled to a mean depth. Mach also contemplated a theory of stereopsis in which monocular depth perception played the primary role. Copyright 2001 John Wiley & Sons, Inc.
Flechner, S. G.; Jacobs, P. F.; Whitcomb, R. T.
1976-01-01
The effects of winglets on the aerodynamic forces and moments, loads, and crossflow velocities behind the wing tip are discussed. The results of the investigation indicate that winglets significantly reduce the drag coefficient at lifting conditions. The experiments were conducted in an 8-foot transonic pressure tunnel at Mach numbers from 0.70 to 0.83 and over a lift coefficient range up to 0.65. A semispan model was used.
Theoretical prediction of interference loading on aircraft stores: Part I - Subsonic speeds
Fox, C. H., Jr.; Fernandes, F.
1973-01-01
Computer program is developed for theoretically predicting loading on pylon-mounted stores in subsonic compressible flow. Linear theory predicts flow field produced by aircraft wing, nose, inlet, and pylons. Program was written in FORTRAN IV for CDC 6000 computer.
Distributed optical fiber perturbation sensing system based on Mach-Zehnder interferometer
Institute of Scientific and Technical Information of China (English)
Wengang WANG; Deming LIU; Hairong LIU; Qizhen SUN; Zhifeng SUN; Xu ZHANG; Ziheng XU
2009-01-01
A novel distributed optical fiber vibration-sensing system based on Mach-Zehnder interferometer has been designed and experimentally demonstrated. Firstly, the principle of Mach-Zehnder optical path interferometer technique is clarified. The output of the Mach-Zehnder interferometer is proportional to the phase shift induced by the perturbation. Secondly, the system consists of the laser diode (LD) as the light source, fiber, Mach-Zehnder optical interferometers as the sensing units, a 1×N star fiber-optic coupler, an N×1 fiber-optic coupler, a photodiode (PD) detector, and a computer used in signal processing. The entire monitoring region of this system is divided into several small zones, and each small monitoring zone is independent from each other. All of the small monitoring zones have their own sensing unit, which is defined by Mach-Zehnder optical interferometer. A series of sensing units are connected by the star fiber-optic couplers to form a whole sensing net. Thirdly, signal-processing techniques are subsequently used to calculate the phase shift to estimate whether intruders appear. The sensing system is able to locate the vibration signal simultaneously, includ-ing multiple vibrations at different positions, by employing the time-division multiplexed (TDM) technique. Finally, the operation performance of the proposed system is tested in the experiment lab with the conditions as follows: the number of the sensing units is 3, the length of the sensing fiber is 50 m, and the wavelength of the light diode is 1550nm. Based on these investigations, the fiber surrounding alert system is achieved. We have experimen-tally demonstrated that the sensing system can measure both the frequency and position of the vibration in real time, with a spatial positional resolution better than 50 m in an area of 1 km2.
Progress in the development of a Mach 5 quiet tunnel
Beckwith, I. E.; Andere, J. B.; Stainback, P. C.; Harvey, W. D.; Srokowski, A. J.
1977-01-01
Various techniques to control and reduce radiated noise and the application of these techniques to a 1/2-water Mach 5 quiet tunnel are reviewed. Measurements in a small scale nozzle have shown that the upstream part of the supersonic wall boundary layer could be maintained laminar up to Reynolds numbers of nearly 4 x 1 million based on the test region length upstream of the nozzle exit. Turbulent noise levels in this test region were then reduced by an order of magnitude. To maintain low noise levels at higher Reynolds numbers, laminar flow noise shields are required. Data are presented for shields that consist of small diameter rods alined nearly parallel to the entrance flow with small gaps between the rods for boundary layer suction. Analysis and data presented on the noise shielding and reflection characteristics of flat plates and a rod-wall test panel indicate that freestream turbulent noise can be reduced by 70 to 90 deg at high Reynolds numbers. Performance estimates for the 1/2-meter tunnel are based on these results.
A Direct-Fire Trajectory Model for Supersonic, Transonic, and Subsonic Projectile Flight
2014-07-01
motions of the projectile about the trajectory due to the angular motion of the projectile . For a stable projectile , these motions are typically small...A Direct-Fire Trajectory Model for Supersonic, Transonic, and Subsonic Projectile Flight by Paul Weinacht ARL-TR-6998 July 2014...Direct-Fire Trajectory Model for Supersonic, Transonic, and Subsonic Projectile Flight Paul Weinacht Weapons and Materials Research Directorate, ARL
Interference-free measurements of the subsonic aerodynamics of slanted-base ogive cylinders
Britcher, Colin P.; Alcorn, Charles W.
1991-01-01
Drag, lift, pitching moment, and base-pressure measurements have been made, free of support interference, on a range of slanted-base ogive cylinders, using the NASA Langley Research Center 13-in magnetic suspension and balance system. Test Mach numbers were in the range 0.04-0.2. Two types of wake flow were observed, a quasi-symmetric turbulent closure or a longitudinal vortex flow. Aerodynamic characteristics differ dramatically between the two wake types. Drag measurements are shown to be in agreement with previous tests. A hysteretic behavior of the wake with varying Reynold's number has been discovered for the 45-deg base. An interaction between forebody boundary-layer state and wake flow and base pressures has been detected for higher slant angles.
The role of coherent structures in the generation of noise for subsonic jets
Morrison, G. L.; Whitaker, K. W.
1982-01-01
Acoustic measurements were made in the 'near' (r/D 60, x/D 60) field for high Reynolds number (184,000 to 262,000) axisymmetric cold air jets exhausting at atmospheric pressure. These measurements were in conjunction with an investigation which characterized the large scale coherent structure in the flow field of Mach number 0.6 to 0.8 jets. Natural jets as well as artificially excited jets were studied. Directivity plots were made for both natural jets and jets excited at various frequencies. Overall noise radiated by the jets reached a maximum value around 30 deg from the jet axis. However, individual frequencies emitted maximum sound pressure level at different angles from the jet axis. As the angle from the jet axis increased, the spectra of the noise shifted to higher frequencies.
Mode interactions of a high-subsonic deep cavity
Chen, Zhenli; Adams, Nikolaus A.
2017-05-01
To understand the interactions of the acoustic modes associated with the tunnel walls and the cavity oscillations in the experiment, flows over a deep cavity having a length-to-depth ratio L/D = 0.42 at high subsonic speeds with and without an upper tunnel wall were investigated by using an implicit large-eddy simulation with an adaptive local deconvolution method. The results of the simulations with the upper tunnel wall converge well to the experimental results as the resolution increases. However, in the simulations without the upper tunnel wall the flow converges to a different mean state. The mode interactions were analyzed by using a Dynamic Mode Decomposition (DMD) method based on a memory-efficient snapshot algorithm. It was found that nearly trapped global modes, which have almost zero upstream and downstream radiation, can occur. The interactions of the trapped modes, the acoustic resonant modes in the cavity, and the shear-layer modes can be observed in the DMD modes of the flow with the upper tunnel wall, which results in the enhancement of harmonic modes and the existence of higher-order modes. In the flow without the upper tunnel wall, the pressure waves can transmit freely away from the cavity, but the interactions of the acoustic resonant modes and the shear-layer modes can also be observed when the frequencies of both kinds of modes coincide. The effects of the ratio of the cavity depth to the tunnel height (D/H) on the formation of trapped modes were also investigated. As the ratio D/H decreases, the frequency window of the trapped modes shrinks and finally closes, which is consistent with a theoretical model. It can be concluded that the effects of the upper tunnel wall on the dynamics of the cavity flow are strong and are promoted by the interactions of different kinds of modes. The appearance and enhancement of high order harmonic modes in the high-subsonic deep cavity are due to the effects of the trapped modes, but are not due to the directly
Mach band type lateral inhibition in different sense organs.
von Békésy, G
1967-01-01
Experiments were done on the skin with shearing forces, vibrations, and heat stimuli and on the tongue with taste stimuli to show that the well known Mach bands are not exclusively a visual phenomenon. On the contrary, it is not difficult to produce areas of a decreased sensation magnitude corresponding to the dark Mach bands in vision. It is shown on a geometrical model of nervous interaction that the appearance of Mach bands for certain patterns of stimulus distribution is correlated with nervous inhibition surrounding the area of sensation. This corroborates the earlier finding that surrounding every area transmitting sensation there is an area simultaneously transmitting inhibition.
The Influence of Ernst Mach in the Teaching of Mechanics
Assis, Andre K. T.; Zylbersztajn, Arden
We present Newton's main ideas for the formulation of classical mechanics as given in the Principia. Then we discuss Ernst Mach's criticisms of Newtonian mechanics as contained in his book The Science of Mechanics. We analyze the influence of Mach's ideas in the teaching of classical mechanics considering five representative textbooks: those of Kittel, Knight and Ruderman; Marion and Thornton; Symon; Feynman, Leighton and Sands; and Goldstein. We conclude that the influence of Mach's ideas has been very great, being incorporated in the textbooks, although not always with the deserved acknowledgment.
Experimental investigation on a high subsonic compressor cascade flow
Directory of Open Access Journals (Sweden)
Zhang Haideng
2015-08-01
Full Text Available With the aim of deepening the understanding of high-speed compressor cascade flow, this paper reports an experimental study on NACA-65 K48 compressor cascade with high subsonic inlet flow. With the increase of passage pressurizing ability, endwall boundary layer behavior is deteriorated, and the transition zone is extended from suction surface to the endwall as the adverse pressure gradient increases. Cross flow from endwall to midspan, mixing of corner boundary layer and the main stream, and reversal flow on the suction surface are caused by corner separation vortex structures. Passage vortex is the main corner separation vortex. During its movement downstream, the size grows bigger while the rotating direction changes, forming a limiting circle. With higher incidence, corner separation is further deteriorated, leading to higher flow loss. Meanwhile, corner separation structure, flow mixing characteristics and flow loss distribution vary a lot with the change of incidence. Compared with low aspect-ratio model, corner separation of high aspect-ratio model moves away from the endwall and is more sufficiently developed downstream the cascade. Results obtained present details of high-speed compressor cascade flow, which is rare in the relating research fields and is beneficial to mechanism analysis, aerodynamic optimization and flow control design.
Chaos control for the plates subjected to subsonic flow
Norouzi, Hamed; Younesian, Davood
2016-07-01
The suppression of chaotic motion in viscoelastic plates driven by external subsonic air flow is studied. Nonlinear oscillation of the plate is modeled by the von-Kármán plate theory. The fluid-solid interaction is taken into account. Galerkin's approach is employed to transform the partial differential equations of the system into the time domain. The corresponding homoclinic orbits of the unperturbed Hamiltonian system are obtained. In order to study the chaotic behavior of the plate, Melnikov's integral is analytically applied and the threshold of the excitation amplitude and frequency for the occurrence of chaos is presented. It is found that adding a parametric perturbation to the system in terms of an excitation with the same frequency of the external force can lead to eliminate chaos. Variations of the Lyapunov exponent and bifurcation diagrams are provided to analyze the chaotic and periodic responses. Two perturbation-based control strategies are proposed. In the first scenario, the amplitude of control forces reads a constant value that should be precisely determined. In the second strategy, this amplitude can be proportional to the deflection of the plate. The performance of each controller is investigated and it is found that the second scenario would be more efficient.
Mach-Zehnder Phasing Sensor for Elts
Dohlen, Kjetil; Montoya-Martinez, Luzma
Segmented mirror technology has been successfully applied to 10m class telescopes (Keck HET GTC) and its application to future extremely large telescopes (20m NG-CFHT 30m CELT 50m EURO50 100m OWL) is required. Extensive use of adaptive optics in these telescopes puts stringent specifications on wavefront error allowing typically of the order of lambda/20 to segmentation errors. Several phasing metrology schemes adaptable to these giant telescopes are under development. We investigate a novel technique based on the Mach-Zehnder interferometer with a spatial filter in one arm. Atmospheric turbulence is tolerated in this setup if the spatial filter has the size similar to that of the seeing disk. The resulting interference pattern only contains the high-frequency spatial information including information about the piston step height. We describe the theoretical analysis of this system and show simulated and experimatal results. Different error sources are analyzed in order to provide a preliminary idea of the merits of this technique compared with other phasing techniques.
Mach 6 flowfield survey at the engine inlet of a research airplane
Johnson, C. B.; Lawing, P. L.
1977-01-01
A flowfield survey was conducted to better define the nature of vehicle forebody flowfield at the inlet location of an airframe-integrated scramjet engine mounted on the lower surface of a high-speed research airplane to be air launched from a B-52 and rocket boosted to Mach 6. The tests were conducted on a 1/30-scale brass model in a Mach-6 20-in. wind tunnel at Reynolds number of 11,200,000 based on distance to engine inlet. Boundary layer profiles at five spanwise locations indicate that the boundary layer in the area of the forebody centerline is more than twice as thick as the boundary layer at three outboard stations. It is shown that the cold streak found in heating contours on the centerline of the forebody is caused by a thickening of the boundary layer on the centerline, and that this thickening decreases with angle of attack.
A fast spatial scanning combination emissive and mach probe for edge plasma diagnosis
Energy Technology Data Exchange (ETDEWEB)
Lehmer, R.D.; LaBombard, B.; Conn, R.W.
1989-04-01
A fast spatially scanning emissive and mach probe has been developed for the measurement of plasma profiles in the PISCES facility at UCLA. A pneumatic cylinder is used to drive a multiple tip probe along a 15cm stroke in less than 400msec, giving single shot profiles while limiting power deposition to the probe. A differentially pumped sliding O-ring seal allows the probe to be moved between shots to infer two and three dimensional profiles. The probe system has been used to investigate the plasma potential, density, and parallel mach number profiles of the presheath induced by a wall surface and scrape-off-layer profile modifications in biased limiter simulation experiments. Details of the hardware, data acquisition electronics, and tests of probe reliability are discussed. 30 refs., 24 figs.
Krypton tagging velocimetry in a turbulent Mach 2.7 boundary layer
Zahradka, D.; Parziale, N. J.; Smith, M. S.; Marineau, E. C.
2016-05-01
The krypton tagging velocimetry (KTV) technique is applied to the turbulent boundary layer on the wall of the "Mach 3 Calibration Tunnel" at Arnold Engineering Development Complex (AEDC) White Oak. Profiles of velocity were measured with KTV and Pitot-pressure probes in the Mach 2.7 turbulent boundary layer comprised of 99 % {N}2/1 % Kr at momentum-thickness Reynolds numbers of {Re}_{\\varTheta }= 800, 1400, and 2400. Agreement between the KTV- and Pitot-derived velocity profiles is excellent. The KTV and Pitot velocity data follow the law of the wall in the logarithmic region with application of the Van Driest I transformation. The velocity data are analyzed in the outer region of the boundary layer with the law of the wake and a velocity-defect law. KTV-derived streamwise velocity fluctuation measurements are reported and are consistent with data from the literature. To enable near-wall measurement with KTV (y/δ ≈ 0.1-0.2), an 800-nm longpass filter was used to block the 760.2-nm read-laser pulse. With the longpass filter, the 819.0-nm emission from the re-excited Kr can be imaged to track the displacement of the metastable tracer without imaging the reflection and scatter from the read-laser off of solid surfaces. To operate the Mach 3 AEDC Calibration Tunnel at several discrete unit Reynolds numbers, a modification was required and is described herein.
Improvement of Flow Quality in NAL Chofu Mach 10 Nozzle
Lacey, John; Inoue, Yasutoshi; Higashida, Akio; Inoue, Manabu; Ishizaka, Kouichi; Korte, John J.
2002-01-01
As a result of CFD analysis and remachining of the nozzle, the flow quality of the Mach 10 Hypersonic Wind Tunnel at NAL Chofu, Japan was improved. The subsequent test results validated the CFD analytical predictions by NASA and MHL.
Mach's Principle selects 4 space-time dimensions
Altshuler, Boris L
2012-01-01
Bi-tensor kernel in integral form of Einstein equations realizing Mach's idea of non-existence of empty space-times is taken as an inverse of differential operator ("Mach operator") defined conventionally as a second variation of Einstein's gravity Action over contravariant components of metric tensor. The choice of transverse gauge condition used in this definition does not influence results of the paper since only transverse and traceless tensor modes written on different background space-times are studied. Presence of ghosts among modes of Mach operator invalidates the integral formulation of Einstein equations. And the demand of absence of these ghosts proves to be a selection rule for dimensionality of the background space-time. In particular Mach operator written on De Sitter background or on the background of so called "Einstein Universe" does not possess tensor ghosts only in 4-dimensions. The similar demand gives non-trivial formula for dimensionalities of subspaces of the Freund-Rubin background.
Mach-Zehnder Fiber-Optic Links for ICF Diagnostics
Energy Technology Data Exchange (ETDEWEB)
Miller, E. K., Hermann, H. W.
2012-11-01
This article describes the operation and evolution of Mach-Zehnder links for single-point detectors in inertial confinement fusion experimental facilities, based on the Gamma Reaction History (GRH) diagnostic at the National Ignition Facility.
Improvement of Flow Quality in NAL Chofu Mach 10 Nozzle
Lacey, John; Inoue, Yasutoshi; Higashida, Akio; Inoue, Manabu; Ishizaka, Kouichi; Korte, John J.
2002-01-01
As a result of CFD analysis and remachining of the nozzle, the flow quality of the Mach 10 Hypersonic Wind Tunnel at NAL Chofu, Japan was improved. The subsequent test results validated the CFD analytical predictions by NASA and MHL.
Wu, Chung-Hua
1993-01-01
This report represents a general theory applicable to axial, radial, and mixed flow turbomachines operating at subsonic and supersonic speeds with a finite number of blades of finite thickness. References reflect the evolution of computational methods used, from the inception of the theory in the 50's to the high-speed computer era of the 90's. Two kinds of relative stream surfaces, S(sub 1) and S(sub 2), are introduced for the purpose of obtaining a three-dimensional flow solution through the combination of two-dimensional flow solutions. Nonorthogonal curvilinear coordinates are used for the governing equations. Methods of computing transonic flow along S(sub 1) and S(sub 2) stream surfaces are given for special cases as well as for fully three-dimensional transonic flows. Procedures pertaining to the direct solutions and inverse solutions are presented. Information on shock wave locations and shapes needed for computations are discussed. Experimental data from a Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt e.V. (DFVLR) rotor and from a Chinese Academy of Sciences (CAS) transonic compressor rotor are compared with the computed flow properties.
Modeling flue pipes: Subsonic flow, lattice Boltzmann, and parallel distributed computers
Skordos, Panayotis A.
1995-01-01
The problem of simulating the hydrodynamics and the acoustic waves inside wind musical instruments such as the recorder the organ, and the flute is considered. The problem is attacked by developing suitable local-interaction algorithms and a parallel simulation system on a cluster of non-dedicated workstations. Physical measurements of the acoustic signal of various flue pipes show good agreement with the simulations. Previous attempts at this problem have been frustrated because the modeling of acoustic waves requires small integration time steps which make the simulation very compute-intensive. In addition, the simulation of subsonic viscous compressible flow at high Reynolds numbers is susceptible to slow-growing numerical instabilities which are triggered by high-frequency acoustic modes. The numerical instabilities are mitigated by employing suitable explicit algorithms: lattice Boltzmann method, compressible finite differences, and fourth-order artificial-viscosity filter. Further, a technique for accurate initial and boundary conditions for the lattice Boltzmann method is developed, and the second-order accuracy of the lattice Boltzmann method is demonstrated. The compute-intensive requirements are handled by developing a parallel simulation system on a cluster of non-dedicated workstations. The system achieves 80 percent parallel efficiency (speedup/processors) using 20 HP-Apollo workstations. The system is built on UNIX and TCP/IP communication routines, and includes automatic process migration from busy hosts to free hosts.
Energy Technology Data Exchange (ETDEWEB)
Itasse, Maxime, E-mail: Maxime.Itasse@onera.fr; Brazier, Jean-Philippe, E-mail: Jean-Philippe.Brazier@onera.fr; Léon, Olivier, E-mail: Olivier.Leon@onera.fr; Casalis, Grégoire, E-mail: Gregoire.Casalis@onera.fr [Onera - The French Aerospace Lab, F-31055 Toulouse (France)
2015-08-15
Nonlinear evolution of disturbances in an axisymmetric, high subsonic, high Reynolds number hot jet with forced eigenmodes is studied using the Parabolized Stability Equations (PSE) approach to understand how modes interact with one another. Both frequency and azimuthal harmonic interactions are analyzed by setting up one or two modes at higher initial amplitudes and various phases. While single mode excitation leads to harmonic growth and jet noise amplification, controlling the evolution of a specific mode has been made possible by forcing two modes (m{sub 1}, n{sub 1}), (m{sub 2}, n{sub 2}), such that the difference in azimuth and in frequency matches the desired “target” mode (m{sub 1} − m{sub 2}, n{sub 1} − n{sub 2}). A careful setup of the initial amplitudes and phases of the forced modes, defined as the “killer” modes, has allowed the minimizing of the initially dominant instability in the near pressure field, as well as its estimated radiated noise with a 15 dB loss. Although an increase of the overall sound pressure has been found in the range of azimuth and frequency analyzed, the present paper reveals the possibility to make the initially dominant instability ineffective acoustically using nonlinear interactions with forced eigenmodes.
Rotating Stall and Stall-Controlled Performance of a Single Stage Subsonic Axial Compressor
Institute of Scientific and Technical Information of China (English)
Eisuke OUTA
2006-01-01
Activities by various authors on aerodynamics and control dynamics of rotating stall in axial compressor are first traced. Then, a process of stall cell evolution in a subsonic stage is discussed based on a 2-D CFD. A few numbers of vortices grow ahead of the rotor accumulating vorticity ejected from lightly stalled blades, and eventually organize a cell of circumferentially aligned huge vortices, which merge and recess repeatedly during the rotation. Such stall disturbance is intensified on trailing side of a circumferential inlet distortion and decays on the leading side. Considering these features, a new algorithm for stall warning is developed based on a correlation between pressure waveforms at each passing of a fixed blade. A remarkable change in the correlation level at near-stall provides a warning signal prior to the stall onset with sufficiently large time margin. This scheme is applied to achieve rotating stall prevention by actuating flaps installed on the hub. The last issue is on characteristics of forward swept blade which has much increased throttle margin with decreased tip loss. A 3-D computation shows that a secondary vortex generated in suction surface mid span interacts to reduce the tip leakage vortex that initiates the stall.
Hryniewicki, M. K.; Gottlieb, J. J.; Groth, C. P. T.
2017-07-01
The transition boundary separating the region of regular reflection from the regions of single-, transitional-, and double-Mach reflections for a planar shock wave moving in air and interacting with an inclined wedge in a shock tube is studied by both analytical methods and computational-fluid-dynamic simulations. The analytical solution for regular reflection and the corresponding solutions from the extreme-angle (detachment), sonic, and mechanical-equilibrium transition criteria by von Neumann (Oblique reflection of shocks, Explosive Research Report No. 12, Navy Department, Bureau of Ordnance, U.S. Dept. Comm. Tech. Serv. No. PB37079 (1943). Also, John von Neumann, Collected Works, Pergamon Press 6, 238-299, 1963) are first revisited and revised. The boundary between regular and Mach reflection is then determined numerically using an advanced computational-fluid-dynamics algorithm to solve Euler's inviscid equations for unsteady motion in two spatial dimensions. This numerical transition boundary is determined by post-processing many closely stationed flow-field simulations, to determine the transition point when the Mach stem of the Mach-reflection pattern just disappears and this pattern then transcends into that of regular reflection. The new numerical transition boundary is shown to agree well with von Neumann's closely spaced sonic and extreme-angle boundaries for weak incident shock Mach numbers from 1.0 to 1.6, but this new boundary trends upward and above von Neumann's sonic and extreme-angle boundaries by a couple of degrees at larger shock Mach numbers from 1.6 to 4.0. Furthermore, the new numerically determined transition boundary is shown to agree well with very few available experimental data obtained from previous experiments designed to reflect two symmetrical moving oblique shock waves along a plane without a shear or boundary layer.
Hryniewicki, M. K.; Gottlieb, J. J.; Groth, C. P. T.
2016-12-01
The transition boundary separating the region of regular reflection from the regions of single-, transitional-, and double-Mach reflections for a planar shock wave moving in air and interacting with an inclined wedge in a shock tube is studied by both analytical methods and computational-fluid-dynamic simulations. The analytical solution for regular reflection and the corresponding solutions from the extreme-angle (detachment), sonic, and mechanical-equilibrium transition criteria by von Neumann (Oblique reflection of shocks, Explosive Research Report No. 12, Navy Department, Bureau of Ordnance, U.S. Dept. Comm. Tech. Serv. No. PB37079 (1943). Also, John von Neumann, Collected Works, Pergamon Press 6, 238-299, 1963) are first revisited and revised. The boundary between regular and Mach reflection is then determined numerically using an advanced computational-fluid-dynamics algorithm to solve Euler's inviscid equations for unsteady motion in two spatial dimensions. This numerical transition boundary is determined by post-processing many closely stationed flow-field simulations, to determine the transition point when the Mach stem of the Mach-reflection pattern just disappears and this pattern then transcends into that of regular reflection. The new numerical transition boundary is shown to agree well with von Neumann's closely spaced sonic and extreme-angle boundaries for weak incident shock Mach numbers from 1.0 to 1.6, but this new boundary trends upward and above von Neumann's sonic and extreme-angle boundaries by a couple of degrees at larger shock Mach numbers from 1.6 to 4.0. Furthermore, the new numerically determined transition boundary is shown to agree well with very few available experimental data obtained from previous experiments designed to reflect two symmetrical moving oblique shock waves along a plane without a shear or boundary layer.
Foster, Lancert E.; Saunders, John D., Jr.; Sanders, Bobby W.; Weir, Lois J.
2012-01-01
NASA is focused on technologies for combined cycle, air-breathing propulsion systems to enable reusable launch systems for access to space. Turbine Based Combined Cycle (TBCC) propulsion systems offer specific impulse (Isp) improvements over rocket-based propulsion systems in the subsonic takeoff and return mission segments along with improved safety. Among the most critical TBCC enabling technologies are: 1) mode transition from the low speed propulsion system to the high speed propulsion system, 2) high Mach turbine engine development and 3) innovative turbine based combined cycle integration. To address these challenges, NASA initiated an experimental mode transition task including analytical methods to assess the state-of-the-art of propulsion system performance and design codes. One effort has been the Combined-Cycle Engine Large Scale Inlet Mode Transition Experiment (CCE-LIMX) which is a fully integrated TBCC propulsion system with flowpath sizing consistent with previous NASA and DoD proposed Hypersonic experimental flight test plans. This experiment was tested in the NASA GRC 10 by 10-Foot Supersonic Wind Tunnel (SWT) Facility. The goal of this activity is to address key hypersonic combined-cycle engine issues including: (1) dual integrated inlet operability and performance issues-unstart constraints, distortion constraints, bleed requirements, and controls, (2) mode-transition sequence elements caused by switching between the turbine and the ramjet/scramjet flowpaths (imposed variable geometry requirements), and (3) turbine engine transients (and associated time scales) during transition. Testing of the initial inlet and dynamic characterization phases were completed and smooth mode transition was demonstrated. A database focused on a Mach 4 transition speed with limited off-design elements was developed and will serve to guide future TBCC system studies and to validate higher level analyses.
Numerical simulations of Mach stem formation via intersecting bow shocks
Hansen, E. C.; Frank, A.; Hartigan, P.; Yirak, K.
2015-12-01
Hubble Space Telescope observations show bright knots of Hα emission within outflowing young stellar jets. Velocity variations in the flow create secondary bow shocks that may intersect and lead to enhanced emission. When the bow shocks intersect at or above a certain critical angle, a planar shock called a Mach stem is formed. These shocks could produce brighter Hα emission since the incoming flow to the Mach stem is parallel to the shock normal. In this paper we report first results of a study using 2-D numerical simulations designed to explore Mach stem formation at the intersection of bow shocks formed by hypersonic "bullets" or "clumps". Our 2-D simulations show how the bow shock shapes and intersection angles change as the adiabatic index γ changes. We show that the formation or lack of a Mach stem in our simulations is consistent with the steady-state Mach stem formation theory. Our ultimate goal, which is part of an ongoing research effort, is to characterize the physical and observational consequences of bow shock intersections including the formation of Mach stems.
3D shock-bubble interactions at Mach 3
Hejazialhosseini, Babak; Koumoutsakos, Petros
2012-01-01
We present a simulation for the interactions of shockwaves with light spherical density inhomogeneities. Euler equations for two-phase compressible flows are solved in a 3D uniform resolution finite volume based solver using 5th order WENO reconstructions of the primitive quantities, HLL-type numerical fluxes and 3rd order TVD time stepping scheme. In this study, a normal Mach 3 shockwave in air is directed at a helium bubble with an interface Atwood number of -0.76. We employ 4 billion cells on a supercomputing cluster and demonstrate the development of this flow until relatively late times. Shock passage compresses the bubble and deposits baroclinic vorticity on the interface. Initial distribution of the vorticity and compressions lead to the formation of an air jet, interface roll-ups and the formation of a long lasting vortical core, the white core. Compressed upstream of the bubble turns into a mixing zone and as the vortex ring distances from this mixing zone, a plume-shaped region is formed and sustain...
Integrated Mach-Zehnder interferometer for Bose-Einstein condensates.
Berrada, T; van Frank, S; Bücker, R; Schumm, T; Schaff, J-F; Schmiedmayer, J
2013-01-01
Particle-wave duality enables the construction of interferometers for matter waves, which complement optical interferometers in precision measurement devices. This requires the development of atom-optics analogues to beam splitters, phase shifters and recombiners. Integrating these elements into a single device has been a long-standing goal. Here we demonstrate a full Mach-Zehnder sequence with trapped Bose-Einstein condensates confined on an atom chip. Particle interactions in our Bose-Einstein condensate matter waves lead to a nonlinearity, absent in photon optics. We exploit it to generate a non-classical state having reduced number fluctuations inside the interferometer. Making use of spatially separated wave packets, a controlled phase shift is applied and read out by a non-adiabatic matter-wave recombiner. We demonstrate coherence times a factor of three beyond what is expected for coherent states, highlighting the potential of entanglement as a resource for metrology. Our results pave the way for integrated quantum-enhanced matter-wave sensors.
A multiobjective shape optimization study for a subsonic submerged inlet
Taskinoglu, Ezgi S.
The purpose of the present work is to summarize the findings of a multiobjective shape optimization study conducted for a subsonic submerged air vehicle inlet. The objective functions of the optimization problem are distortion and swirl indices defined by the distribution of flow parameters over the exit cross-section of the inlet. The geometry alteration is performed by placing a protrusion in the shape of a fin on the baseline inlet surface. Thus, the design variables of the optimization problem are chosen to be the geometrical parameters defining the fin protrusion; namely fin height, length and incidence angle. The Trade Off (also known as epsilon-constraint) method is employed for finding the Pareto optimal set formed by the nondominated solutions of the feasible design space. Since the flow domain solution is required for every step along the line search, an automated optimization loop is constructed by integrating the optimizer with a surface modeler, a mesh generator and a flow solver through which the flow parameters over the compressor face are computed. In addition, the trade study for fin protrusion, the analyses and the comparison of the baseline and Pareto optimal solutions are presented and observations concerning grid resolution and convergence behaviour are discussed. The results display an irregular and discontinuous Pareto optimal set. Optimum inlet designs are scattered in two regions from which one representative inlet design is chosen and analyzed. As a result, it is concluded that an inlet designer has two options within the framework of this optimization study: an inlet design with high swirl but low distortion or an inlet design with low swirl but higher distortion.
Hot-wire calibration in subsonic/transonic flow regimes
Nagabushana, K. A.; Ash, Robert L.
1995-01-01
A different approach for calibrating hot-wires, which simplifies the calibration procedure and reduces the tunnel run-time by an order of magnitude was sought. In general, it is accepted that the directly measurable quantities in any flow are velocity, density, and total temperature. Very few facilities have the capability of varying the total temperature over an adequate range. However, if the overheat temperature parameter, a(sub w), is used to calibrate the hot-wire then the directly measurable quantity, voltage, will be a function of the flow variables and the overheat parameter i.e., E = f(u,p,a(sub w), T(sub w)) where a(sub w) will contain the needed total temperature information. In this report, various methods of evaluating sensitivities with different dependent and independent variables to calibrate a 3-Wire hot-wire probe using a constant temperature anemometer (CTA) in subsonic/transonic flow regimes is presented. The advantage of using a(sub w) as the independent variable instead of total temperature, t(sub o), or overheat temperature parameter, tau, is that while running a calibration test it is not necessary to know the recovery factor, the coefficients in a wire resistance to temperature relationship for a given probe. It was deduced that the method employing the relationship E = f (u,p,a(sub w)) should result in the most accurate calibration of hot wire probes. Any other method would require additional measurements. Also this method will allow calibration and determination of accurate temperature fluctuation information even in atmospheric wind tunnels where there is no ability to obtain any temperature sensitivity information at present. This technique greatly simplifies the calibration process for hot-wires, provides the required calibration information needed in obtaining temperature fluctuations, and reduces both the tunnel run-time and the test matrix required to calibrate hotwires. Some of the results using the above techniques are presented
Li, Fei; Choudhari, Meelan M.; Carpenter, Mark H.; Malik, Mujeeb R.; Eppink, Jenna; Chang, Chau-Lyan; Streett, Craig L.
2010-01-01
A high fidelity transition prediction methodology has been applied to a swept airfoil design at a Mach number of 0.75 and chord Reynolds number of approximately 17 million, with the dual goal of an assessment of the design for the implementation and testing of roughness based crossflow transition control and continued maturation of such methodology in the context of realistic aerodynamic configurations. Roughness based transition control involves controlled seeding of suitable, subdominant crossflow modes in order to weaken the growth of naturally occurring, linearly more unstable instability modes via a nonlinear modification of the mean boundary layer profiles. Therefore, a synthesis of receptivity, linear and nonlinear growth of crossflow disturbances, and high-frequency secondary instabilities becomes desirable to model this form of control. Because experimental data is currently unavailable for passive crossflow transition control for such high Reynolds number configurations, a holistic computational approach is used to assess the feasibility of roughness based control methodology. Potential challenges inherent to this control application as well as associated difficulties in modeling this form of control in a computational setting are highlighted. At high Reynolds numbers, a broad spectrum of stationary crossflow disturbances amplify and, while it may be possible to control a specific target mode using Discrete Roughness Elements (DREs), nonlinear interaction between the control and target modes may yield strong amplification of the difference mode that could have an adverse impact on the transition delay using spanwise periodic roughness elements.
Timmerman, B. H.; Skeen, A. J.; Bryanston-Cross, P. J.; Graves, M. J.
2009-07-01
The development of a highly configurable triple digital particle image velocimetry (DPIV) system is described, which is capable of acquiring both continuous, statistically independent measurements at up to 14 Hz and time-resolved PIV data at MHz rates. The system was used at QinetiQ's Noise Test Facility (NTF) as part of the EU-funded CoJeN programme to obtain measurements from high subsonic (Mach <= 0.9), hot (~500 °C), large (1/10th) scale coaxial jet flows at a standoff distance of ~1 m. High-resolution time-averaged velocity and turbulence data were obtained for complete coaxial engine exhaust plumes down to 4 m (20 jet diameters) from the nozzle exit in less than 1 h. In addition, the system allowed volumetric data to be obtained, enabling fast assessment of spatial alignment of nozzle configurations. Furthermore, novel six-frame time-series data-capture is demonstrated up to 330 kHz, used to calculate time-space correlations within the exhaust, allowing for study of spatio-temporal developments in the jet, associated with jet-noise production. The highly automated system provides synchronization triggers for simultaneous acquisition from different measurement systems (e.g. LDA) and is shown to be versatile, rugged, reliable and portable, operating remotely in a hostile environment. Data are presented for three operating conditions and two nozzle geometries, providing a database to be used to validate CFD models of coaxial jet flow.
Numerical Simulations of Mach Stem Formation via Intersecting Bow Shocks
Hansen, Edward C; Hartigan, Patrick
2014-01-01
Hubble Space Telescope observations show bright knots of H$\\alpha$ emission within outflowing young stellar jets. Velocity variations in the flow create secondary bow shocks that may intersect and lead to enhanced emission. When the bow shocks intersect at or above a certain critical angle, a planar shock called a Mach stem is formed. These shocks could produce brighter H$\\alpha$ emission since the incoming flow to the Mach stem is parallel to the shock normal. In this paper we report first results of a study using 2-D numerical simulations designed to explore Mach stem formation at the intersection of bow shocks formed by hypersonic "bullets" or "clumps". Our 2-D simulations show how the bow shock shapes and intersection angles change as the adiabatic index $\\gamma$ changes. We show that the formation or lack of a Mach stem in our simulations is consistent with the steady-state Mach stem formation theory. Our ultimate goal, which is part of an ongoing research effort, is to characterize the physical and obse...
Energy Technology Data Exchange (ETDEWEB)
Persiantseva, N.V.; Popovitcheva, O.B.; Rakhimova, T.V. [Moscow State Univ. (Russian Federation)
1997-12-31
Heterogeneous chemistry of HCl, as a main reservoir of chlorine content gases, has been considered after plume cooling and ice particle formation. The HCl, HNO{sub 3}, N{sub 2}O{sub 5} uptake efficiencies by frozen water were obtained in a Knudsen-cell flow reactor at the subsonic cruise conditions. The formation of ice particles in the plume of subsonic aircraft is simulated to describe the kinetics of gaseous HCl loss due to heterogeneous processes. It is shown that the HCl uptake by frozen water particles may play an important role in the gaseous HCl depletion in the aircraft plume. (author) 14 refs.
Al-Maaitah, Ayman A.; Nayfeh, Ali H.; Ragab, Saad A.
1989-01-01
The effect of suction on the stability of compressible flows over backward-facing steps is investigated. Mach numbers up to 0.8 are considered. The results show that continuous suction stabilizes the flow outside the separation bubble, but it destabilizes the flow inside it. Nevertheless, the overall N factor decreases as the suction level increases due to the considerable reduction of the separation bubble. For the same suction flow rate, properly distributed suction strips stabilize the flow more than continuous suction. The size of the separation bubble, and hence its effect on the instability can be considerably reduced by placing strips with high suction velocities in the separation region.
Sandford, M. C.; Ricketts, R. H.; Watson, J. J.
1981-01-01
A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static orifices and 164 in situ dynamic pressure gases for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Data from the present test (this is the second in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60 and 0.78 and are presented in tabular form.
Mach-Zehnder recording systems for pulsed power diagnostics
Energy Technology Data Exchange (ETDEWEB)
Miller, E. K.; Abbott, R. Q.; McKenna, I.; Macrum, G.; Baker, D.; Tran, V.; Rodriguez, E.; Kaufman, M. I.; Tibbits, A.; Silbernagel, C. T.; Waltman, T. B. [National Security Technologies, LLC, Santa Barbara and Livermore, California 93111 (United States); National Security Technologies, LLC, Los Alamos, New Mexico 87544 (United States); and National Security Technologies, LLC, North Las Vegas, Nevada 89193 (United States); Herrmann, H. W.; Kim, Y. H.; Mack, J. M.; Young, C. S.; Caldwell, S. E.; Evans, S. C.; Sedillo, T. J. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Stoeffl, W.; Grafil, E. [Lawrence Livermore National Laboratory, Livermore, California (United States); and others
2012-10-15
Fiber-optic transmission and recording systems, based on Mach-Zehnder modulators, have been developed and installed at the National Ignition Facility (NIF), and are being developed for other pulsed-power facilities such as the Z accelerator at Sandia, with different requirements. We present the design and performance characteristics for the mature analog links, based on the system developed for the Gamma Reaction History diagnostic at the OMEGA laser and at NIF. For a single detector channel, two Mach-Zehnders are used to provide high dynamic range at the full recording bandwidth with no gaps in the coverage. We present laboratory and shot data to estimate upper limits on the radiation effects as they impact recorded data quality. Finally, we will assess the technology readiness level for mature and developing implementations of Mach-Zehnder links for these environments.
Mach-Zehnder recording systems for pulsed power diagnostics.
Miller, E K; Abbott, R Q; McKenna, I; Macrum, G; Baker, D; Tran, V; Rodriguez, E; Kaufman, M I; Tibbits, A; Silbernagel, C T; Waltman, T B; Herrmann, H W; Kim, Y H; Mack, J M; Young, C S; Caldwell, S E; Evans, S C; Sedillo, T J; Stoeffl, W; Grafil, E; Liebman, J; Beeman, B; Watts, P; Carpenter, A; Horsfied, C J; Rubery, M S; Chandler, G A; Torres, J A; Smelser, R M
2012-10-01
Fiber-optic transmission and recording systems, based on Mach-Zehnder modulators, have been developed and installed at the National Ignition Facility (NIF), and are being developed for other pulsed-power facilities such as the Z accelerator at Sandia, with different requirements. We present the design and performance characteristics for the mature analog links, based on the system developed for the Gamma Reaction History diagnostic at the OMEGA laser and at NIF. For a single detector channel, two Mach-Zehnders are used to provide high dynamic range at the full recording bandwidth with no gaps in the coverage. We present laboratory and shot data to estimate upper limits on the radiation effects as they impact recorded data quality. Finally, we will assess the technology readiness level for mature and developing implementations of Mach-Zehnder links for these environments.
Mach-Zehnder Recording Systems for Pulsed Power Diagnostics
Energy Technology Data Exchange (ETDEWEB)
Miller, E K; McKenna, I; Macrum, G; Baker, D; Tran, V; Rodriguez, E; Kaufman, M I; Tibbits, A; Silbernagel, C T; Waltman, T B; Herrmann, H W; Kim, Y H; Mack, J M; Young, C S; Caldwell, S E; Evans, S C; Sedillo, T J; Stoeffl, W; Grafil, E; Liebman, J; Beeman, B; Watts, P; Carpenter, A; Horsfied, C J; Rubery, M S; Chandler, G A; Torres, J A
2012-10-01
Fiber-optic transmission and recording systems, based on Mach-Zehnder modulators, have been developed and installed at the National Ignition Facility (NIF), and are being developed for other pulsed-power facilities such as Z-R at Sandia, with different requirements. We present the design and performance characteristics for the mature analog links, based on the system developed for the Gamma Reaction History (GRH) diagnostic at OMEGA and NIF. For a single detector channel, two Mach-Zehnders are used to provide high dynamic range at the full recording bandwidth with no gaps in the coverage. We present laboratory and shot data to estimate upper limits on the radiation effects as they impact recorded data quality. Finally, we will assess the technology readiness level for mature and developing implementations of Mach-Zehnder links for these environments.
Quantum heat engines based on electronic Mach-Zehnder interferometers
Hofer, Patrick P.; Sothmann, Björn
2015-05-01
We theoretically investigate the thermoelectric properties of heat engines based on Mach-Zehnder interferometers. The energy dependence of the transmission amplitudes in such setups arises from a difference in the interferometer arm lengths. Any thermoelectric response is thus of purely quantum-mechanical origin. In addition to an experimentally established three-terminal setup, we also consider a two-terminal geometry as well as a four-terminal setup consisting of two interferometers. We find that Mach-Zehnder interferometers can be used as powerful and efficient heat engines which perform well under realistic conditions.
Transition to Double Mach Stem for Nuclear Explosion at 104 ft Height of Burst.
1981-11-17
intersecting the ground. The initialization provides a strong shock with Mach number MI = 12. This speed and the need for restart capability led to the choice...a HOB of 104 ft (31.7m). A strong spherical shock is created in the surrounding air, and’ reflects from the grcund. 9 The outward-traveling airbiast...AIR FCIPCF SYST T’M CCvfvtANC NORTON" A!7, CA 9?40Pg (MIIJ’r’-MAN) QICY ATTN "INNYH "D IALAN5S<Y 0O1C Y ATTNJ MMN)) eHM kF-LVECCHir OICY ATTN fuNN w
Study of Rayleigh scattering for visualization of helium-air mixing at Mach 6
Shirinzadeh, B.; Balla, R. J.; Hillard, M. E.; Anders, J. B.; Exton, R. J.; Waitz, I. A.
1991-01-01
Using an ArF excimer laser, planar Rayleigh scattering measurements were performed to investigate helium mixing into air at supersonic speeds. These experiments were conducted in the Mach 6, high-Reynolds-number facility at NASA Langley Research Center. The capability of the Rayleigh scattering technique for flow visualization of a turbulent environment was demonstrated. The qualitative agreement between the averaged Rayleigh results and the reduced mean-mass-densities obtained from probe measurements substantiate that careful application of the technique, even in the presence of clusters, can give very useful results. It was also demonstrated that planar, quantitative measurements can be made in the absence of clusters.
Data Reduction Functions for the Langley 14- by 22-Foot Subsonic Tunnel
Boney, Andy D.
2014-01-01
The Langley 14- by 22-Foot Subsonic Tunnel's data reduction software utilizes six major functions to compute the acquired data. These functions calculate engineering units, tunnel parameters, flowmeters, jet exhaust measurements, balance loads/model attitudes, and model /wall pressures. The input (required) variables, the output (computed) variables, and the equations and/or subfunction(s) associated with each major function are discussed.
Subsonic Euler Flows with Large Vorticity Through an Infinitely Long Axisymmetric Nozzle
Du, Lili; Duan, Ben
2016-09-01
This paper is a sequel to the earlier work Du and Duan (J Diff Equ 250:813-847, 2011) on well-posedness of steady subsonic Euler flows through infinitely long three-dimensional axisymmetric nozzles. In Du and Duan (J Diff Equ 250:813-847, 2011), the authors showed the existence and uniqueness of the global subsonic Euler flows through an infinitely long axisymmetric nozzle, when the variation of Bernoulli's function in the upstream is sufficiently small and the mass flux of the incoming flow is less than some critical value. The smallness of the variation of Bernoulli's function in the upstream prevents the attendance of the possible singularity in the nozzles, however, at the same time it also leads that the vorticity of the ideal flow is sufficiently small in the whole nozzle and the flows are indeed adjacent to axisymmetric potential flows. The purpose of this paper is to investigate the effects of the vorticity for the smooth subsonic ideal flows in infinitely long axisymmetric nozzles. We modify the formulation of the problem in the previous work Du and Duan (J Diff Equ 250:813-847, 2011) and the existence and uniqueness results on the smooth subsonic ideal polytropic flows in infinitely long axisymmetric nozzles without the restriction on the smallness of the vorticity are shown in this paper.
Two Dimensional Subsonic Euler Flows Past a Wall or a Symmetric Body
Chen, Chao; Du, Lili; Xie, Chunjing; Xin, Zhouping
2016-08-01
The existence and uniqueness of two dimensional steady compressible Euler flows past a wall or a symmetric body are established. More precisely, given positive convex horizontal velocity in the upstream, there exists a critical value {ρ_cr} such that if the incoming density in the upstream is larger than {ρ_cr}, then there exists a subsonic flow past a wall. Furthermore, {ρ_cr} is critical in the sense that there is no such subsonic flow if the density of the incoming flow is less than {ρ_cr}. The subsonic flows possess large vorticity and positive horizontal velocity above the wall except at the corner points on the boundary. Moreover, the existence and uniqueness of a two dimensional subsonic Euler flow past a symmetric body are also obtained when the incoming velocity field is a general small perturbation of a constant velocity field and the density of the incoming flow is larger than a critical value. The asymptotic behavior of the flows is obtained with the aid of some integral estimates for the difference between the velocity field and its far field states.
Wing-Alone Aerodynamic Characteristics to High Angles of Attack at Subsonic and Transonic Speeds.
1982-11-01
indicators of symmetry since the wings were unbanked within the limits of tolerances and flow angularity. Longitudinal, spanwise, and vertical... unbanked wings at subsonic and transonic speeds from low to high angles of attack. The wing planforms varied in aspect ratio and taper ratio with
FINITE DIFFERENCE METHOD FOR CALCULATING OF THE GAS FLOW IN A SUBSONIC GAS EJECTOR
Directory of Open Access Journals (Sweden)
Kostjantin Kapitanchuk
2015-12-01
Full Text Available Describe analysis of eddy viscosity actual mathematical models for numerical simulation a reversal gas flow in subsonic gas ejector. Considered advantages and disadvantages each of it. Proposed use method of finite elements for provides viscous gas flow calculation of gas ejectors.
Concept Development of a Mach 1.6 High-Speed Civil Transport
Shields, Elwood W.; Fenbert, James W.; Ozoroski, Lori P.; Geiselhart, Karl A.
1999-01-01
A high-speed civil transport configuration with a Mach number of 1.6 was developed as part of the NASA High-Speed Research Program to serve as a baseline for assessing advanced technologies required for an aircraft with a service entry date of 2005. This configuration offered more favorable solutions to environmental concerns than configurations with higher Mach numbers. The Mach 1.6 configuration was designed for a 6500 n.mi. mission with a 250-passenger payload. The baseline configuration has a wing area of 8732 square feet a takeoff gross weight of 591570 lb, and four 41000-lb advanced turbine bypass engines defined by NASA. These engines have axisymmetric mixer-ejector nozzles that are assumed to yield 20 dB of noise suppression during takeoff, which is assumed to satisfy, the FAR Stage III noise requirements. Any substantial reduction in this assumed level of suppression would require oversizing the engines to meet community noise regulations and would severly impact the gross weight of the aircraft at takeoff. These engines yield a ratio of takeoff thrust to weight of 0.277 and a takeoff wing loading of 67.8 lb/square feet that results in a rotation speed of 169 knots. The approach velocity of the sized configuration at the end of the mission is 131 knots. The baseline configuration was resized with an engine having a projected life of 9000 hr for hot rotating parts and 18000 hr for the rest of the engine, as required for commercial use on an aircraft with a service entry date of 2005. Results show an increase in vehicle takeoff gross weight of approximately 58700 lb. This report presents the details of the configuration development, mass properties, aerodynamic design, propulsion system and integration, mission performance, and sizing.
Tunable multiwavelength erbium-doped fiber laser based on an in-line Mach Zehnder interferometer
Energy Technology Data Exchange (ETDEWEB)
Han, Young-Geun [Hanyang University, Seoul (Korea, Republic of)
2010-12-15
A tunable multiwavelength erbium-doped fiber laser based on an in-line Mach Zehnder interferometer is proposed and experimentally demonstrated. The in-line Mach Zehnder interferometer is realized by using cascaded long-period fiber gratings. The long-period fiber gratings can couple the guided core mode to several cladding modes. If two identical long-period fiber gratings are concatenated, an interference pattern can be generated, which results from an interaction of the core and the cladding modes in the second long-period fiber grating. Therefore, a simple multichannel filter based on an in-line Mach Zehnder interferometer can be realized. The wavelength spacing of the proposed multichannel filter is controlled by the number of long-period fiber gratings. We apply the proposed multichannel fiber to the generation of a multiwavelength erbium-doped fiber laser with a tunability on the order of the wavelength spacing. An erbium-doped fiber amplifier is implemented as a gain medium. The gain competition of erbium ions is suppressed by soaking the erbium-doped fiber in liquid nitrogen. The power fluctuation of the proposed multiwavelength fiber laser is measured to be less than 0.5 dB. A high-quality multiwavelength output with a high extinction ratio of more than 40 dB is achieved. The wavelength spacing of the proposed multiwavelength fiber laser is controlled by increasing the number of long-period fiber gratings. The wavelength spacing is changed from 0.8 nm to 1.6 nm discretely.
Jeništa, J.; Takana, H.; Nishiyama, H.; Bartlová, M.; Aubrecht, V.; Křenek, P.; Hrabovský, M.; Kavka, T.; Sember, V.; Mašláni, A.
2011-11-01
This paper presents a numerical investigation of characteristics and processes in the worldwide unique type of thermal plasma generator with combined stabilization of arc by argon flow and water vortex, the so-called hybrid-stabilized arc. The arc has been used for spraying of ceramic or metallic particles and for pyrolysis of biomass. The net emission coefficients as well as the partial characteristics methods for radiation losses from the argon-water arc are employed. Calculations for 300-600 A with 22.5-40 standard litres per minute (slm) of argon reveal transition from a transonic plasma flow for 400 A to a supersonic one for 600 A with a maximum Mach number of 1.6 near the exit nozzle of the plasma torch. A comparison with available experimental data near the exit nozzle shows very good agreement for the radial temperature profiles. Radial velocity profiles calculated 2 mm downstream of the nozzle exit show good agreement with the profiles determined from the combination of calculation and experiment (the so-called integrated approach). A recent evaluation of the Mach number from the experimental data for 500 and 600 A confirmed the existence of the supersonic flow regime.
Weinstein, I.
1973-01-01
Heat-transfer and pressure distributions were measured over the surfaces of three hemisphere-cylinder models tested at a nominal Mach number of 7 in the Langley 8-foot high-temperature structures tunnel which uses methane-air products of combustion as a test medium. The results showed that the heat-transfer and pressure distributions over the surface of the models were in good agreement with experimental data obtained in air and also with theoretical predictions.
Jacobs, P. F.; Flechner, S. G.; Montoya, L. C.
1977-01-01
The effects of winglets and a simple wing-tip extension on the aerodynamic forces and moments and the flow-field cross flow velocity vectors behind the wing tip of a first generation jet transport wing were investigated in the Langley 8-foot transonic pressure tunnel using a semi-span model. The test was conducted at Mach numbers of 0.30, 0.70, 0.75, 0.78, and 0.80. At a Mach number of 0.30, the configurations were tested with combinations of leading- and trailing-edge flaps.
Wing Configuration Impact on Design Optimums for a Subsonic Passenger Transport
Wells, Douglas P.
2014-01-01
This study sought to compare four aircraft wing configurations at a conceptual level using a multi-disciplinary optimization (MDO) process. The MDO framework used was created by Georgia Institute of Technology and Virginia Polytechnic Institute and State University. They created a multi-disciplinary design and optimization environment that could capture the unique features of the truss-braced wing (TBW) configuration. The four wing configurations selected for the study were a low wing cantilever installation, a high wing cantilever, a strut-braced wing, and a single jury TBW. The mission that was used for this study was a 160 passenger transport aircraft with a design range of 2,875 nautical miles at the design payload, flown at a cruise Mach number of 0.78. This paper includes discussion and optimization results for multiple design objectives. Five design objectives were chosen to illustrate the impact of selected objective on the optimization result: minimum takeoff gross weight (TOGW), minimum operating empty weight, minimum block fuel weight, maximum start of cruise lift-to-drag ratio, and minimum start of cruise drag coefficient. The results show that the design objective selected will impact the characteristics of the optimized aircraft. Although minimum life cycle cost was not one of the objectives, TOGW is often used as a proxy for life cycle cost. The low wing cantilever had the lowest TOGW followed by the strut-braced wing.
Bell, James H.; Heineck, James T.; Zilliac, Gregory; Mehta, Rabindra D.; Long, Kurtis R.
2016-01-01
An important goal for modern fluid mechanics experiments is to provide datasets which present a challenge for Computational Fluid Dynamics simulations to reproduce. Such "CFD validation experiments" should be well-characterized and well-documented, and should investigate flows which are difficult for CFD to calculate. It is also often convenient for the experiment to be challenging for CFD in some aspects while simple in others. This report is part of the continuing documentation of a series of experiments conducted to characterize the flow around an axisymmetric, modified-cosine-shaped, wall-mounted hill named "FAITH" (Fundamental Aero Investigates The Hill). Computation of this flow is easy in some ways - subsonic flow over a simple shape - while being complex in others - separated flow and boundary layer interactions. The primary set of experiments were performed on a 15.2 cm high, 45.7 cm base diameter machined aluminum model that was tested at mean speeds of 50 m/s (Reynolds Number based on height = 500,000). The ratio of model height to boundary later height was approximately 3. The flow was characterized using surface oil flow visualization, Cobra probe to determine point-wise steady and unsteady 3D velocities, Particle Image Velocimetry (PIV) to determine 3D velocities and turbulence statistics along specified planes, Pressure Sensitive Paint (PSP) to determine mean surface pressures, and Fringe Imaging Skin Friction (FISF) to determine surface skin friction magnitude and direction. A set of pathfinder experiments were also performed in a water channel on a smaller scale (5.1 cm high, 15.2 cm base diameter) sintered nylon model. The water channel test was conducted at a mean test section speed of 3 cm/s (Reynolds Number of 1500), but at the same ratio of model height to boundary layer thickness. Dye injection from both the model and an upstream rake was used to visualize the flow. This report summarizes the experimental set-up, techniques used, and data
Effects of wind-tunnel noise on swept-cylinder transition at Mach 3.5
Creel, T. R., Jr.; Beckwith, I. E.; Chen, F.-J.
1986-01-01
Transition data are reported for circular cylinders at swept angles of 45 and 60 degrees in the Mach 3.5 pilot-low-disturbance tunnel where free-stream noise levels are varied from approximately .05-0.5 percent in terms of the rms fluctuating pressure normalized by the mean static pressure. Results indicate that end plate or boundary layer trip disturbances at the upstream end of the cylinders cause turbulent flow along the entire test Reynolds number range of 10-170 thousand per inch. With all end plate and trip disturbances removed, transition at the attachment lines occurred at free-stream Reynolds numbers based on diameters of about 70-80 thousand, independent of stream noise levels. The installation of small trips on the attachement lines caused transition at lower Reynolds numbers, depending on both the roughness height and the wind tunnel noise level.
3 TUNNELS IN THE ENGINE RESEARCH BUILDING ERB - IN CELL CE-26 VARIABLE REYNOLDS NUMBER SUPERSONIC NO
1956-01-01
3 TUNNELS IN THE ENGINE RESEARCH BUILDING ERB - IN CELL CE-26 VARIABLE REYNOLDS NUMBER SUPERSONIC NOZZLE - CELL CE-4 6X6 INCH MACH NUMBER 2.96 SUPERSONIC AIRPLANE - CELL 1-NW 1X1 FOOT MACH 3.12 SUPERSONIC TUNNEL
Heineck, James T.; Ross, James C.; Yamauchi, Gloria K.
2015-01-01
The subsonic regime of Crew Capsule reentry has a very turbulent waker through which the Drogue Chutes must deploy. This presentation describes the particle image velocimetry measurement campaign used to help retire the risk.
Mach-Zehnder fiber interferometer for people monitoring
Vasinek, Vladimir; Latal, Jan; Koudelka, Petr; Siska, Petr; Vitasek, Jan; Skapa, Jan
2010-10-01
Fiber optical interferometers belong to highly sensitive equipments that are able to measure slight changes like distortion of shape, temperature and electric field variation and etc. Their great advantage is that they are insensitive on ageing component, from which they are composed of. It is in virtue of herewith, that there are evaluated no changes in optical signal intensity but number interference fringes. To monitor the movement of persons, eventually to analyze the changes in state of motion we developed method based on analysis the dynamic changes in interferometric pattern. We have used Mach- Zehnder interferometer with conventional SM fibers excited with the DFB laser at wavelength of 1550 nm. It was terminated with optical receiver containing InGaAs PIN photodiode. Its output was brought into measuring card module that performs on FFT of the received interferometer signal. The signal rises with the composition of two waves passing through single interferometer arm. The optical fiber SMF 28e in one arm is referential; the second one is positioned on measuring slab at dimensions of 1x2m. A movement of persons over the slab was monitored, signal processed with FFT and frequency spectra were evaluated. They rose owing to dynamic changes of interferometric pattern. The results reflect that the individual subjects passing through slab embody characteristic frequency spectra, which are individual for particular persons. The scope of measuring frequencies proceeded from zero to 10 KHz. It was also displayed in experiments that the experimental subjects, who walked around the slab and at the same time they have had changed their state of motion (knee joint fixation), embodied characteristic changes in their frequency spectra. At experiments the stability of interferometric patterns was evaluated as from time aspects, so from the view of repeated identical experiments. Two kinds of balls (tennis and ping-pong) were used to plot the repeatability measurements and
Alignment of dust particles by ion drag forces in subsonic flows
Energy Technology Data Exchange (ETDEWEB)
Piel, Alexander [IEAP, Christian-Albrechts-University, D-24098 Kiel (Germany)
2011-07-15
The role of ion drag forces for the alignment of dust particles is studied for subsonic flows. While alignment by wake-field attraction is a well known mechanism for supersonic flows, it is argued here that ion-scattering forces become more important in subsonic ion flows. A model of non-overlapping collisions is introduced and numerical results are discussed. For typical conditions of dusty plasma experiments, alignment by drag forces is found strong enough to overcome the destabilizing force from Coulomb repulsion between dust particles. It turns out that the major contribution to the horizontal restoring force originates from the transverse momentum transfer, which is usually neglected in ion drag force calculations because of an assumed rotational symmetry of the flow.
Fluctuation diagrams for hot-wire anemometry in subsonic compressible flows
Stainback, P. C.; Nagabushana, K. A.
1991-01-01
The concept of using 'fluctuation diagrams' for describing basic fluctuations in compressible flows was reported by Kovasznay in the 1950's. The application of this technique, for the most part, was restricted to supersonic flows. Recently, Zinovev and Lebiga published reports where they considered the fluctuation diagrams in subsonic compressible flows. For the above studies, the velocity and density sensitivities of the heated wires were equal. However, there are considerable data, much taken in the 1950's, which indicate that under some conditions the velocity and density sensitivities are not equal in subsonic compressible flows. Therefore, possible fluctuation diagrams are described for the cases where the velocity and density sensitivities are equal and the more general cases where they are unequal.
Far-Field Turbulent Vortex-Wake/Exhaust Plume Interaction for Subsonic and HSCT Airplanes
Kandil, Osama A.; Adam, Ihab; Wong, Tin-Chee
1996-01-01
Computational study of the far-field turbulent vortex-wake/exhaust plume interaction for subsonic and high speed civil transport (HSCT) airplanes is carried out. The Reynolds-averaged Navier-Stokes (NS) equations are solved using the implicit, upwind, Roe-flux-differencing, finite-volume scheme. The two-equation shear stress transport model of Menter is implemented with the NS solver for turbulent-flow calculation. For the far-field study, the computations of vortex-wake interaction with the exhaust plume of a single engine of a Boeing 727 wing in a holding condition and two engines of an HSCT in a cruise condition are carried out using overlapping zonal method for several miles downstream. These results are obtained using the computer code FTNS3D. The results of the subsonic flow of this code are compared with those of a parabolized NS solver known as the UNIWAKE code.
Valdarnini, R
2016-01-01
In this paper we present results from a series of hydrodynamical tests aimed at validating the performance of a smoothed particle hydrodynamics (SPH) formulation in which gradients are derived from an integral approach. We specifically investigate the code behavior with subsonic flows, where it is well known that zeroth-order inconsistencies present in standard SPH make it particularly problematic to correctly model the fluid dynamics. In particular we consider the Gresho-Chan vortex problem, the growth of Kelvin-Helmholtz instabilities, the statistics of driven subsonic turbulence and the cold Keplerian disc problem. We compare simulation results for the different tests with those obtained, for the same initial conditions, using standard SPH. We also compare the results with the corresponding ones obtained previously with other numerical methods, such as codes based on a moving-mesh scheme or Godunov-type Lagrangian meshless methods. We quantify code performances by introducing error norms and spectral prope...
Hurst, Janet
2011-01-01
A brief overview is presented of the current materials and structures research geared toward propulsion applications for NASA s Subsonic Fixed Wing Project one of four projects within the Fundamental Aeronautics Program of the NASA Aeronautics Research Mission Directorate. The Subsonic Fixed Wing (SFW) Project has selected challenging goals which anticipate an increasing emphasis on aviation s impact upon the global issue of environmental responsibility. These goals are greatly reduced noise, reduced emissions and reduced fuel consumption and address 25 to 30 years of technology development. Successful implementation of these demanding goals will require development of new materials and structural approaches within gas turbine propulsion technology. The Materials and Structures discipline, within the SFW project, comprise cross-cutting technologies ranging from basic investigations to component validation in laboratory environments. Material advances are teamed with innovative designs in a multidisciplinary approach with the resulting technology advances directed to promote the goals of reduced noise and emissions along with improved performance.
INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Subsonic radiation waves in neon
Loseva, T. V.; Nemchinov, I. V.
1989-02-01
Numerical methods are used to investigate the propagation of plane subsonic radiation waves in neon from an obstacle in the direction opposite to the incident radiation of Nd and CO2 lasers. An analysis is made of the influence of the power density of the incident radiation (in the range 10-100 MW/cm2) and of the initial density of neon (beginning from the normal valuep ρ0 up to 10ρ0) on the various characteristics of subsonic radiation waves. It is shown that waves traveling in neon can provide an effective source of radiation with a continuous spectrum and an efficiency of ~ 12-27% in the ultraviolet range (with a characteristic photon energy ~ 5-10 eV).
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo; Woodiga, Sudesh
2012-01-01
This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.
Global versus Local -- Mach's Principle versus the Equivalence Principle
Singleton, Douglas
2016-01-01
The equivalence principle is the conceptual basis for general relativity. In contrast Mach's principle, although said to have been influential on Einstein in his formulation of general relativity, has not been shown to be central to the structure of general relativity. In this essay we suggest that the quantum effects of Hawking and Unruh radiation are a manifestation of a {\\it thermal} Mach's principle, where the local thermodynamic properties of the system are determined by the non-local structure of the quantum fields which determine the vacuum of a given spacetime. By comparing Hawking and Unruh temperatures for the same local acceleration we find a violation of the Einstein elevator version of the equivalence principle, which vanishes in the limit that the horizon is approached.
A Solar System Test of Mach's Principle with Gravimetric Data
Unzicker, A; Fabian, Karl; Unzicker, Alexander
2006-01-01
We present a new test for a possible Mach-Sciama dependence of the Gravitational constant G. According to Ernst Mach (1838-1916), the gravitational interaction depends on the distribution of masses in the universe. A corresponding hypothesis of Sciama (1953) on the gravitational constant, $c^2/G = \\sum m_i/r_i$, can be tested since the elliptic earth orbit should then cause minute annual variations in G. The test is performed by analyzing the gravity signals of a network of superconducting gravimeters (SG) which reach a precision of $10^{-10} m/s^2$. After reducing the signal by modelling tidal, meteorologic and geophysical effects, no significant evidence for the above dependence is found.
Quantum interference in an asymmetric Mach-Zehnder interferometer
Trenti, A.; Borghi, M.; Mancinelli, M.; Price, H. M.; Fontana, G.; Pavesi, L.
2016-08-01
A re-visitation of the well known free space Mach-Zehnder interferometer is reported here. The coexistence between one-photon and two-photons interference from collinear color entangled photon pairs is investigated. Thisarises from an arbitrarily small unbalance in the arm transmittance. The tuning of such asymmetry is reflected in dramatic changes in the coincidence detection, revealing beatings between one particle and two particle interference patterns. In particular, the role of the losses and of the intrinsic phase imperfectness of the lossy beamsplitter are explored in a single-port excited Mach-Zehnder interferometer. This configuration is especially useful for quantum optics on a chip, where the guiding geometry forces photons to travel in the same spatial mode.
Spatial heterodyne spectrometer based on the Mach-Zehnder interferometer
Cai, Qisheng; Xiangli, Bin; Du, Shusong
2015-11-01
Spatial heterodyne spectroscopy (SHS) is a new kind of Fourier-transform spectroscopic technique capable of very high spectral resolution. In this paper, a spatial heterodyne spectrometer based on the Mach-Zehnder interferometer (MZ-SHS) is proposed. It is modified by replacing one mirror in the Mach-Zehnder interferometer with a diffraction grating. This technique retains many of the advantages of traditional SHS. Moreover, the spatial frequency of the interferogram is strictly linear with wavenumber. We describe the concept of the new MZ-SHS and elaborate the exact expression of the interferogram. Also, a design example and two kinds of imitated interferograms are presented in this paper. One is simulated in MATLAB and the other is generated in ZEMAX using ray tracing method. The retrieved spectra from these two interferograms show a good agreement with the theoretical results.
Automatic computation of Euler-marching and subsonic grids for wing-fuselage configurations
Barger, Raymond L.; Adams, Mary S.; Krishnan, Ramki R.
1994-01-01
Algebraic procedures are described for the automatic generation of structured, single-block flow computation grids for relatively simple configurations (wing, fuselage, and fin). For supersonic flows, a quasi two-dimensional grid for Euler-marching codes is developed, and some sample results in graphical form are included. A type of grid for subsonic flow calculation is also described. The techniques are algebraic and are based on a generalization of the method of transfinite interpolation.
Directory of Open Access Journals (Sweden)
Ioan STEFANESCU
2012-03-01
Full Text Available The use of subsonic single control aircraft and especially of double–control ones, instead of supersonic combat aircraft in the military pilot training programs in the operational units, has be-come a necessity due to the economic and financial world-wide crisis which began during the 70’s-80’s, with the advent of the oil crisis, affecting many countries, which have their own Military Air Forces.
Analysis of boundary conditions for SSME subsonic internal viscous flow analysis
Baker, A. J.
1986-01-01
A study was completed of mathematically proper boundary conditions for unique numerical solution of internal, viscous, subsonic flows in the space shuttle main engine. The study has concentrated on well posed considerations, with emphasis on computational efficiency and numerically stable boundary condition statements. The method of implementing the established boundary conditions is applicable to a wide variety of finite difference and finite element codes, as demonstrated.
Meyer, R. R., Jr.
1978-01-01
The static longitudinal and lateral directional characteristics of a 0.035 scale model of a first generation jet transport were obtained with and without upper winglets. The data were obtained for take off and landing configurations at a free stream Mach number of 0.30. The results generally indicated that upper winglets had favorable effects on the stability characteristics of the aircraft.
Emergent physics on Mach's principle and the rotating vacuum
Jannes, G
2015-01-01
Mach's principle applied to rotation can be correct if one takes into account the rotation of the quantum vacuum together with the Universe. Whether one can detect the rotation of the vacuum or not depends on its properties. If the vacuum is fully relativistic at all scales, Mach's principle should work and one cannot distinguish the rotation: in the rotating Universe+vacuum, the co-rotating bucket will have a flat surface (not concave). However, if there are "quantum gravity" effects which violate Lorentz invariance at high energy, then the rotation will become observable. This is demonstrated by analogy in condensed-matter systems, which consist of two subsystems: superfluid background (analog of vacuum) and "relativistic" excitations (analog of matter). For the low-energy (long-wavelength) observer the rotation of the vacuum is not observable. In the rotating frame, the "relativistic" quasiparticles feel the background as a Minkowski vacuum, i.e. they do not feel the rotation. Mach's idea of the relativity...
A Detailed Investigation of Staged Normal Injection into a Mach 2 Flow
Eklund, Dean R.; Northam, G. Burton; Hartfield, Roy J., Jr.
1990-01-01
A study of the staged injection of two jets of air behind a rearward facing step into a Mach 2 flow was performed using the SPARK 3-D Navier-Stokes code. Calculated mole fraction distributions were compared with an extensive set of planar mole fraction measurements made with a laser induced iodine fluorescence technique. A statistical measure, the standard deviation, was used to help assess agreement between calculation and experiment. Overall, good agreement was found between calculated and measured values. Generally, agreement was better in the far field of the injectors. The effect of grid resolution was investigated by calculating solutions on grids of 60,000, 200,000, and 450,000 points. Differences in the solutions on the two finer grids were small. However, the mole fraction distributions were distinguishable. The effect of turbulence modeling was investigated by employing three different algebraic models for the jet turbulence: the Baldwin-Lomax model, the Prandtl mixing length model, and the Eggers mixing length model. Overall, the Eggers mixing length model was found to be superior for this case. Finally, the effect of the jet exit conditions was examined. A recently proposed Mach number distribution at the jet exit was found to slightly improve agreement between measurement and calculation.
Hypersonic characteristics of an advanced aerospace plane at Mach 20.3
Mccandless, R. S.
1985-01-01
Wind-tunnel studies have been performed in the Langley Hypersonic Helium Tunnel Facility to obtain static longitudinal and lateral-directional aerodynamic characteristics of an advanced aerospace plane concept. The nominal test conditions are a Mach number of 20.3 and a Reynolds number of 6.8 x 10 to the 6th power per foot at angles of attack from 0 to 25 deg and angles of sideslip of -3 and 0 deg. Stability and control characteristics are obtained for several deflections of the elevators, elevons, and rudder. In addition, a modified canopy is examined. The results indicate that this vehicle is longitudinally stable at angles of attack near the maximum lift-drag ratio. Also, the vehicle is shown to be directionally unstable with positive dihedral effect.
CONDUCTION IN LOW MACH NUMBER FLOWS. I. LINEAR AND WEAKLY NONLINEAR REGIMES
Energy Technology Data Exchange (ETDEWEB)
Lecoanet, Daniel [Department of Astronomy and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States); Brown, Benjamin P.; Zweibel, Ellen G.; Burns, Keaton J.; Oishi, Jeffrey S. [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Vasil, Geoffrey M., E-mail: dlecoanet@berkeley.edu [School of Mathematics and Statistics, University of Sydney, NSW 2006 (Australia)
2014-12-20
Thermal conduction is an important energy transfer and damping mechanism in astrophysical flows. Fourier's law, in which the heat flux is proportional to the negative temperature gradient, leading to temperature diffusion, is a well-known empirical model of thermal conduction. However, entropy diffusion has emerged as an alternative thermal conduction model, despite not ensuring the monotonicity of entropy. This paper investigates the differences between temperature and entropy diffusion for both linear internal gravity waves and weakly nonlinear convection. In addition to simulating the two thermal conduction models with the fully compressible Navier-Stokes equations, we also study their effects in the reduced ''soundproof'' anelastic and pseudoincompressible (PI) equations. We find that in the linear and weakly nonlinear regime, temperature and entropy diffusion give quantitatively similar results, although there are some larger errors in the PI equations with temperature diffusion due to inaccuracies in the equation of state. Extrapolating our weakly nonlinear results, we speculate that differences between temperature and entropy diffusion might become more important for strongly turbulent convection.
Calibration and Performance of the AEDC/VKF Tunnel C, Mach Number 4, Aerothermal Wind Tunnel
1982-06-01
Beattie - Bridgeman equation of state for air is shown in the figures included in this appendix. Real-Gas Enthalpy General Forms The following... Beattie - Bridgeman equation of state for air. 106 AEDC-TR-82-6 P(Rea1 Gas) R(P/PT)(P/PT)Idea1 8 PT1. 02 Sym 0 Computed Real-Gas Values Curve Fit TT, oR ~600...chamber properties; then the results were adjusted to include the real-gas effects. The real-gas properties are based on the Beattie - Bridgeman equation
Performance Limiting Flow Processes in High-State Loading High-Mach Number Compressors
2008-03-13
stage matching, and thus the performance of such machines. As such, the understanding, empiricism , and guidelines which apply well to machines of lower...discrete vortex with opposite circulation to the previous one is shed. A vortex street which is " locked " to the rotor passing is thus formed downstream of...255-6802 x231 (email: [)ouglas.Rabc,(wpatb.af.rnil) Dr. John Adamczyk, retired scientist from NASA GRC, has also contributed much to the research 18. 0
Numerical prediction of flow induced noise in free jets of high Mach numbers
Schönrock, Olaf
2009-01-01
A direct aeroacoustic simulation methodology is developed on the basis of the numerical schemes implemented in the commercial tool ANSYS CFX. The focus lies upon the efficient and direct numerical prediction of the flow-induced noise generated by natural gas and pneumatic applications. The respective compressed gas related components are characterized by tiny supersonic gas jets, strong noise emissions, poor accessibility by measurement techniques and excessive simulation costs in particular...
Numerical Simulations of Flow in a 3-D Supersonic Intake at High Mach Numbers
Directory of Open Access Journals (Sweden)
R. Sivakumar
2006-10-01
Full Text Available Numerical simulations of the compressible, 3-D non reacting flow in the engine inlet sectionof a concept hypersonic air-breathing vehicle are presented. These simulations have been carriedout using FLUENT. For all the results reported, the mesh has been refined to achieve areaaveragedwall y+ about 105. Mass flow rate through the intake and stagnation pressure recoveryare used to compare the performance at various angles of attack. The calculations are able topredict the mode of air-intake operation (critical and subcritical for different angles of attack.Flow distortion at the intake for various angles of attack is also calculated and discussed. Thenumerical results are validated by simulating the flow through a 2-D mixed compression hypersonicintake model and comparing with the experimental data.
High Mach-number collisionless shock driven by a laser with an external magnetic field
Directory of Open Access Journals (Sweden)
Morita T.
2013-11-01
Full Text Available Collisionless shocks are produced in counter-streaming plasmas with an external magnetic field. The shocks are generated due to an electrostatic field generated in counter-streaming laser-irradiated plasmas, as reported previously in a series of experiments without an external magnetic field [T. Morita et al., Phys. Plasmas, 17, 122702 (2010, Kuramitsu et al., Phys. Rev. Lett., 106, 175002 (2011] via laser-irradiation of a double-CH-foil target. A magnetic field is applied to the region between two foils by putting an electro-magnet (∼10 T perpendicular to the direction of plasma expansion. The generated shocks show different characteristics later in time (t > 20ns.
Boundary Layer Trip Performance Test on a 7-deg Cone Model at Mach Number 8
1983-10-01
b r a t i o n Re ldenha in Rotary Encoder ROD700 Resolut lo=:O, O000 des Dvora l l Accuracy: 0-001 des P a n a x e t r i c a MG-IOI Mois...LAYER STABILITY TEST PUN NUHuER 1028 PAGE 1 / - % DATE COMPUTED I1-0Cm~83 DATE R~CORDEO 2-~1 TI~E RECORDED 71~56~0 TIHK COMPUTED 09130 PROJECT... kiln NJOm;~Vle Jo~k LRETA 1.053E*03 1.821E+O$ 2.192E*03 2.553E*03 3.104E+03 4.54bE+03 6 .352E*03 80101E*03 10068E*04 1.250E*04 1.52~Et04
DEFF Research Database (Denmark)
Pradera-Mallabiabarrena, Ainara; Jacobsen, Finn; Svendsen, Christian
2013-01-01
-compact surfaces are involved. Here the generation of noise is dominated by the interaction of the flow with a surface whose maximum dimension is shorter than the wavelength of interest. The analysis is based on the surface-source term of the Ffowcs Williams-Hawkings equation. The acoustic source data of the flow...
Comparison of Experiment and Analysis for a High Primary Mach Number Ejector
1977-05-01
ure the secondary total pressure, also recorded on the HP plotter. A 30" (76.2cm) mercury manometer was used to measure directly the secondary total...supply pressure were readjusted to give the required total secondary pressure reading on the mercury manometer . Heat was added to keep the air streams at
Influence of Mach Number and Dynamic Pressure on Cavity Tones and Freedrop Trajectories
2014-03-27
1 0 ) ; 157 A. p12= p o l y f i t ( x ’ ,A. fcon , 1 2 ) ; 158 A. p14= p o l y f i t ( x ’ ,A. fcon , 1 4 ) ; 159 A. p16 = p o l y f i t ( x ’ ,A...x ) ; 164 A. f i t 1 2 = p o l y v a l (A. p12 , x ) ; 165 A. f i t 1 4 = p o l y v a l (A. p14 , x ) ; 166 A. f i t 1 6 = p o l y v a l (A. p16
Asymptotic Steady State Solution to a Bow Shock with an Infinite Mach Number
Yalinewich, Almog
2015-01-01
The problem of a cold gas flowing past a stationary object is considered. It is shown that at large distances from the obstacle the shock front forms a parabolic solid of revolution. The interior of the shock front is obtained by solution of the hydrodynamic equations in parabolic coordinates. The results are verified with a hydrodynamic simulation. The drag force and expected spectra are calculated for such shock, both in case of an optically thin and thick media. Finally, relations to astrophysical bow shocks and other analytic works on oblique shocks are discussed.
High-Speed Noninvasive Multi-Parameter Laser Diagnostics for High-Mach-Number Flows Project
National Aeronautics and Space Administration — Numerous ground test and wind tunnel facilities are used extensively to generate forces and moments as well as surface measurements of test articles required to...
Growth of a gas bubble in a supersaturated and slightly compressible liquid at low Mach number
Mohammadein, S. A.; Mohamed, K. G.
2011-12-01
In this paper, the growth of a gas bubble in a supersaturated and slightly compressible liquid is discussed. The mathematical model is solved analytically by using the modified Plesset and Zwick method. The growth process is affected by: sonic speed in the liquid, polytropic exponent, diffusion coefficient, initial concentration difference, surface tension, viscosity, adjustment factor and void fraction. The famous formula of Plesset and Zwick is produced as a special case of the result at some values of the adjustment factor. Moreover, the resultant formula is implemented to the case of the growth of underwater gas bubble.
Guilloud, G.; Schram, C.; Golliard, J.
2009-01-01
Despite the aeroacoustic expertise reached nowadays in air and ground transportation, energy sector or domestic appliances, reaching a decibel accuracy of an acoustic prediction for industrial cases is still challenging. Strong investments are made nowadays by oil and gas companies to determine and
Directory of Open Access Journals (Sweden)
K. S. Egorov
2015-01-01
Full Text Available The presented paper regards the influence of one of similarity criteria – the Prandtl number of gas (Pr - on the efficiency of the machine-less energetic separation device (Leontiev pipe, using numerical modeling in ANSYS software. This device, equally as Rank-Hilsch and Hartman-Schprenger pipes, is designed to separate one gas flow into two flows with different temperatures. One flow (supersonic streams out of the pipe with a temperature higher than initial and the other (subsonic flows out with a temperature lower than initial. This direction of energetic separation is true if the Prandtl number is less than 1 that corresponds to gases.The Prandtl number affects the efficiency of running Leontiev pipe indirectly both through a temperature difference on which a temperature recovery factor has an impact and through a thermal conductivity coefficient that shows the impact of heat transfer intensity between gas and solid wall.The Prandtl number range in the course of research was from 0.1 to 0.7. The Prandtl number value equal to 0.7 corresponds to the air or pure gases (for example, inert argon gas. The Prandtl number equal to 0.2 corresponds to the mixtures of inert gases such as helium-xenon.The numerical modeling completed for the supersonic flow with Mach number 2.0 shows that efficiency of the machine-less energetic separation device has been increased approximately 2 times with the Prandtl number decreasing from 0.7 to 0.2. Moreover, for the counter-flow scheme this effect is a little higher due to its larger heat efficiency in comparison with the straight-flow one.Also, the research shows that the main problem for the further increase of the Leontiev pipe efficiency is a small value of thermal conductivity coefficient, which requires an intensification of the heat exchange, especially in the supersonic flow. It can be obtained, for example, by using a system of oblique shock waves in the supersonic channel.
Visualization of conventional and combusting subsonic jet instabilities
Kozlov, Victor; Litvinenko, Yury
2016-01-01
Based on new information obtained on free microjets, this book explains the latest phenomena in flame evolution in the presence of a transverse acoustic field with round and plane propane microjet combustion. It gives an overview of recent experimental results on instability and dynamics of jets at low Reynolds numbers and provides the reader, step by step, with the milestones and recent advances in jet flow stability and combustion. Readers will also discover a clarification of the differences between top-hat and parabolic round and plane jet instability. Chapters demonstrate features of the interaction between jet and crossflow, and how experimental data testify to similarities of the perturbed flow patterns of laminar and turbulent round jets. A similar response of the jets to external acoustic oscillations is shown, as well as the peculiarities of the effect of a transverse acoustic field on downstream evolution of round and plane macro- and microjets. Basic features of round and plane, macro and micro je...
Impinging Jet Resonant Modes at Mach 1.5
Davis, Timothy
2013-01-01
High speed impinging jets have been the focus of several studies owing to their practical application and resonance dominated flow-field. The current study focuses on the identification and visualization of the resonant modes at certain critical impingement heights for a Mach 1.5 normally impinging jet. These modes are associated with high amplitude, discrete peaks in the power spectra and can be identified as having either axisymmetric or azimuthal modes. Their visualization is accomplished through phase-locked Schlieren imaging and fast-response pressure sensitive paint (PC-PSP) applied to the ground plane.
Temperature sensitivity of waveguide Mach-Zehnder interferometer
Sokolov, Viktor
2013-01-01
This thesis is part of a project that aims to develop a sensor for the detection of methane in the air and in water based on a waveguide Mach-Zehnder interferometer. The main application of this sensor is monitoring the environment and the ability to detect a leakage of methane. The development of a sensor includes analysis of operational conditions. In this project one of the greatest concerns is temperature. The temperature difference can reach several tens of degrees in the air, and severa...
Quantum logic processor: Implementation with electronic Mach-Zehnder interferometer
Sarkar, Angik; Bhattacharyya, T. K.; Patwardhan, Ajay
2006-05-01
An approach for implementation of quantum logic in electronic Mach-Zehnder interferometer (MZI) has been described in this letter. All single qubit gates can be achieved by electron spin manipulation using Rashba spin-orbit coupling. Double qubit gates can also be implemented using the orbital degree of freedom of the electron. The MZI can be realized with intertwined ballistic nanowires. Spin injection and detection in the system can be done by a mesoscopic Stern-Gerlach apparatus. The system can be coupled in an array to form the quantum logic processor.
On Mach's Principle and the "Special" Theory of Relativity
Ashura, Uzumaki
2016-01-01
First, we present a history of the school of thought that the Cosmic Microwave Background Radiation acts as an ether in language familiar to high school students in English-speaking countries. Then we illustrate the properties of this ether and of a hypothetical "test mass" using a brand new thought experiment. Finally, we recount some post-Einstein efforts at a mathematical formulation of Mach's principle and raise some questions about what implications it has for the locality of rotation and for quantum gravity. This paper does not prove Einstein wrong.
Calibration of the 7—Equation Transition Model for High Reynolds Flows at Low Mach
Colonia, S.; Leble, V.; Steijl, R.; Barakos, G.
2016-09-01
The numerical simulation of flows over large-scale wind turbine blades without considering the transition from laminar to fully turbulent flow may result in incorrect estimates of the blade loads and performance. Thanks to its relative simplicity and promising results, the Local-Correlation based Transition Modelling concept represents a valid way to include transitional effects into practical CFD simulations. However, the model involves coefficients that need tuning. In this paper, the γ—equation transition model is assessed and calibrated, for a wide range of Reynolds numbers at low Mach, as needed for wind turbine applications. An aerofoil is used to evaluate the original model and calibrate it; while a large scale wind turbine blade is employed to show that the calibrated model can lead to reliable solutions for complex three-dimensional flows. The calibrated model shows promising results for both two-dimensional and three-dimensional flows, even if cross-flow instabilities are neglected.
Breakup characteristics of a liquid jet in subsonic crossflow
Gopala, Yogish
This thesis describes an experimental investigation of the breakup processes involved in the formation of a spray created by a liquid jet injected into a gaseous crossflow. This work is motivated by the utilization of this method to inject fuel in combustors and afterburners of airplane engines. This study aims to develop a better understanding of the spray breakup processes and to provide better experimental inputs to improve the fidelity of numerical models. A review of the literature in this field identified the fundamental physical processes involved in the breakup of the spray and the dependence of spray properties on operating conditions. The time taken for the liquid column to break up into ligaments and droplets, the primary breakup time and the effect of injector geometry on the spray formation processes and spray properties as the key research areas in which research done so far has been inadequate. Determination of the location where the liquid column broke up was made difficult by the presence of a large number of droplets surrounding it. This study utilizes the liquid jet light guiding technique that enables accurate measurements of this location for a wide range of operating conditions. Prior to this study, the primary breakup time was thought to be a function the density ratio of the liquid and the gas, the diameter of the orifice and the air velocity. This study found that the time to breakup of the liquid column depends on the Reynolds number of the liquid jet. This suggests that the breakup of a turbulent liquid jet is influenced by both the aerodynamic breakup processes and the turbulent breakup processes. Observations of the phenomenon of the liquid jet splitting up into two or more jets were made at some operating conditions with the aid of the new visualization technique. Finally, this thesis investigates the effect of injector geometry on spray characteristics. One injector was a round edged orifice with a length to diameter ratio of 1 and a
Ball, J. W.; Lindahl, R. H.
1976-01-01
An investigation was conducted in the NASA/LaRC Low-Turbulence Pressure Tunnel on a 0.03614-scale orbiter model of a 089B configuration with a 139B configuration nose forward of F.S. 500. The tailcone was the TC sub 4 design and was instrumented with eighty-nine pressure orifices. Control surfaces were deflected and three wind tunnel mounting techniques were investigated over an angle-of-attack range from -2 deg to a maximum of 18 deg. In order to determine the sensitivity of the tailcone to changes in Reynolds number, most of the test was made at a Mach number of 0.20 over a Reynolds number range of 2.0 to 10 million per foot. A few runs were made at a Mach number of 0.30 at Reynolds numbers of 4.0, 6.0, and 8 million per foot.
Dittmar, James H.; Hall, David G.; Moore, Royce D.
1993-01-01
The tone noise levels of a supersonic throughflow fan were measured at subsonic and supersonic axial duct Mach numbers. The noise in the inlet plenum showed no blade passing and harmonic tones at subsonic or supersonic axial flow conditions. At subsonic axial flow conditions, the supersonic throughflow fan showed no inlet plenum tones at fan operating conditions where tone noise had been previously measured for a subsonic fan design. This lower inlet-quadrant noise level for the supersonic throughflow fan was the result of high subsonic inlet velocities acting to reduce the noise propagating out the inlet. The fan noise, which was prevented from propagating upstream by the high subsonic inlet velocities, appeared to increase the noise in the exhaust duct at subsonic throughflow conditions. The exhaust duct noise decreased at supersonic axial throughflow Mach numbers, with the lowest blade passing and harmonic tones levels being observed at the design axial Mach number of 2.0. Multiple pure tone noise was observed in the inlet duct at subsonic axial flow Mach numbers but was seen only in the exhaust duct at supersonic axial flow conditions.
Valdarnini, R.
2016-11-01
In this paper, we present results from a series of hydrodynamical tests aimed at validating the performance of a smoothed particle hydrodynamics (SPH) formulation in which gradients are derived from an integral approach. We specifically investigate the code behavior with subsonic flows, where it is well known that zeroth-order inconsistencies present in standard SPH make it particularly problematic to correctly model the fluid dynamics. In particular, we consider the Gresho-Chan vortex problem, the growth of Kelvin-Helmholtz instabilities, the statistics of driven subsonic turbulence and the cold Keplerian disk problem. We compare simulation results for the different tests with those obtained, for the same initial conditions, using standard SPH. We also compare the results with the corresponding ones obtained previously with other numerical methods, such as codes based on a moving-mesh scheme or Godunov-type Lagrangian meshless methods. We quantify code performances by introducing error norms and spectral properties of the particle distribution, in a way similar to what was done in other works. We find that the new SPH formulation exhibits strongly reduced gradient errors and outperforms standard SPH in all of the tests considered. In fact, in terms of accuracy, we find good agreement between the simulation results of the new scheme and those produced using other recently proposed numerical schemes. These findings suggest that the proposed method can be successfully applied for many astrophysical problems in which the presence of subsonic flows previously limited the use of SPH, with the new scheme now being competitive in these regimes with other numerical methods.
Energy Technology Data Exchange (ETDEWEB)
Moellhoff, M.; Hendricks, J.; Lippert, E.; Petry, H. [Koeln Univ. (Germany). Inst. fuer Geophysik und Meteorologie; Sausen, R. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere
1997-12-31
A box model and two different one-dimensional models are used to investigate the chemical conversion of exhaust species in the dispersing plume of a subsonic aircraft flying at cruise altitude. The effect of varying daytime of release as well as the impact of changing dispersion time is studied with special respect to the aircraft induced O{sub 3} production. Effective emission amounts for consideration in mesoscale and global models are calculated. Simulations with modified photolysis rates are performed to show the sensitivity of the photochemistry to the occurrence of cirrus clouds. (author) 8 refs.
2016-09-01
Introduction 1 2. Solution Technique 3 2.1 Steady-State Simulation 3 2.2 Quasi-Steady Sweep Simulation 4 3. Geometry 5 3.1 Model Geometry 5 3.2...Location of the projectile at various stages of the sweep procedure ..... 5 Fig. 2 Subsonic geometries : BF (top) and body–fin–canard configuration...scheme using a Harten–Lax–van Leer-Contact (commonly, HLLC) Riemann solver and Metacomp’s multidimensional Total-Variation-Diminishing (commonly
Tadghighi, H.; Holz, R.; Farassat, F.; Lee, Yung-Jang
1991-01-01
A previously defined airfoil subsonic shock-noise prediction formula whose result depends on a mapping of the time-dependent shock surface to a time-independent computational domain is presently coded and incorporated in the NASA-Langley rotor-noise prediction code, WOPWOP. The structure and algorithms used in the shock-noise prediction code are presented; special care has been taken to reduce computation time while maintaining accuracy. Numerical examples of shock-noise prediction are presented for hover and forward flight. It is confirmed that shock noise is an important component of the quadrupole source.
Unsteady flow in a supersonic cascade with subsonic leading-edge locus
Adamczyk, J. J.; Goldstein, M. E.
1978-01-01
Linearized theory is used to predict the unsteady flow in a supersonic cascade with subsonic axial flow velocity. A closed-form analytical solution is obtained by using a double application of the Wiener-Hopf technique. Although numerical and semianalytical solutions of this problem have already appeared in the literature, this paper contains the first completely analytical solution. It has been stated in the literature that the blade source should vanish at the infinite duct resonance condition. The present analysis shows that this does not occur. This apparent discrepancy is explained in the paper.
Subsonic flow past an oscillating cascade with steady blade loading - Basic formulation
Verdon, J. M.; Caspar, J. R.; Adamczyk, J. J.
1975-01-01
A nonlinear boundary value problem governing the subsonic flow in a single, extended, blade passage region of a high-deflection, two dimensional, oscillating cascade is derived. The blades are assumed to be undergoing identical harmonic motions of small amplitude with constant phase angle between the motion of adjacent blades. An asymptotic perturbation approach is used to determine the velocity potential. This formulation can be used in the numerical determination of unsteady potential and thus the unsteady aerodynamic force and moment under various combinations of cascade and flow parameters.
Guidelines for Computing Longitudinal Dynamic Stability Characteristics of a Subsonic Transport
Thompson, Joseph R.; Frank, Neal T.; Murphy, Patrick C.
2010-01-01
A systematic study is presented to guide the selection of a numerical solution strategy for URANS computation of a subsonic transport configuration undergoing simulated forced oscillation about its pitch axis. Forced oscillation is central to the prevalent wind tunnel methodology for quantifying aircraft dynamic stability derivatives from force and moment coefficients, which is the ultimate goal for the computational simulations. Extensive computations are performed that lead in key insights of the critical numerical parameters affecting solution convergence. A preliminary linear harmonic analysis is included to demonstrate the potential of extracting dynamic stability derivatives from computational solutions.
Stanford, Bret K.; Jutte, Christine V.
2014-01-01
Several minimum-mass aeroelastic optimization problems are solved to evaluate the effectiveness of a variety of novel tailoring schemes for subsonic transport wings. Aeroelastic strength and panel buckling constraints are imposed across a variety of trimmed maneuver loads. Tailoring with metallic thickness variations, functionally graded materials, composite laminates, tow steering, and distributed trailing edge control effectors are all found to provide reductions in structural wing mass with varying degrees of success. The question as to whether this wing mass reduction will offset the increased manufacturing cost is left unresolved for each case.
Stainback, P. C.; Johnson, C. B.; Basnett, C. B.
1983-01-01
The heat transfer characteristics of a three-wire hot-wire probe operated with a constant temperature anemometer were investigated in the subsonic compressible flow regime. The sensitivity coefficients, with respect to velocity, density and total temperature, were measured and the results were used to calculate the velocity, density, and total temperature fluctuations in the test section of the Langley 0.3-m Transonic Cryogenic Tunnel (TCT). These results were extended to give estimates for fluctuations due to vorticity, sound, and entropy. In addition, attempts were made to determine the major source of disturbances in the 0.3-m TCT.
Self-similar solution of the subsonic radiative heat equations using a binary equation of state
Heizler, Shay I.; Shussman, Tomer; Malka, Elad
2016-01-01
Radiative subsonic heat waves, and their radiation driven shock waves, are important hydro-radiative phenomena. The high pressure, causes hot matter in the rear part of the heat wave to ablate backwards. At the front of the heat wave, this ablation pressure generates a shock wave which propagates ahead of the heat front. Although no self-similar solution of both the ablation and shock regions exists, a solution for the full problem was found in a previous work. Here, we use this model in orde...
Burning of a spherical fuel droplet in a uniform subsonic flowfield
Energy Technology Data Exchange (ETDEWEB)
Madooglu, K.; Karagozian, A.R.
1989-01-01
An analytical/numerical model is described for the evaporation and burning of a spherical fuel droplet in a subsonic crossflow. The external gaseous flowfield is represented using an approximate compressible potential solution, while the internal flowfield of the droplet is represented by the classical Hill's spherical vortex. This allows numerical solution for the external boundary layer and diffusion flame characteristics to be made, from which the droplet's effective drag coefficient, rate of mass loss, size, and flame shape are determined. Comparison with experimental data indicate good agreement, and thus the potential for such simplified models in performing parametric studies.
Burning of a spherical fuel droplet in a uniform subsonic flowfield
Energy Technology Data Exchange (ETDEWEB)
Madooglu, K.; Karagozian, A.R.
1989-12-31
An analytical/numerical model is described for the evaporation and burning of a spherical fuel droplet in a subsonic crossflow. The external gaseous flowfield is represented using an approximate compressible potential solution, while the internal flowfield of the droplet is represented by the classical Hill`s spherical vortex. This allows numerical solution for the external boundary layer and diffusion flame characteristics to be made, from which the droplet`s effective drag coefficient, rate of mass loss, size, and flame shape are determined. Comparison with experimental data indicate good agreement, and thus the potential for such simplified models in performing parametric studies.
Cosmological constant implementing Mach principle in general relativity
Namavarian, Nadereh; Farhoudi, Mehrdad
2016-10-01
We consider the fact that noticing on the operational meaning of the physical concepts played an impetus role in the appearance of general relativity (GR). Thus, we have paid more attention to the operational definition of the gravitational coupling constant in this theory as a dimensional constant which is gained through an experiment. However, as all available experiments just provide the value of this constant locally, this coupling constant can operationally be meaningful only in a local area. Regarding this point, to obtain an extension of GR for the large scale, we replace it by a conformal invariant model and then, reduce this model to a theory for the cosmological scale via breaking down the conformal symmetry through singling out a specific conformal frame which is characterized by the large scale characteristics of the universe. Finally, we come to the same field equations that historically were proposed by Einstein for the cosmological scale (GR plus the cosmological constant) as the result of his endeavor for making GR consistent with the Mach principle. However, we declare that the obtained field equations in this alternative approach do not carry the problem of the field equations proposed by Einstein for being consistent with Mach's principle (i.e., the existence of de Sitter solution), and can also be considered compatible with this principle in the Sciama view.
Establishing Consensus Turbulence Statistics for Hot Subsonic Jets
Bridges, James; Werner, Mark P.
2010-01-01
Many tasks in fluids engineering require knowledge of the turbulence in jets. There is a strong, although fragmented, literature base for low order statistics, such as jet spread and other meanvelocity field characteristics. Some sources, particularly for low speed cold jets, also provide turbulence intensities that are required for validating Reynolds-averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) codes. There are far fewer sources for jet spectra and for space-time correlations of turbulent velocity required for aeroacoustics applications, although there have been many singular publications with various unique statistics, such as Proper Orthogonal Decomposition, designed to uncover an underlying low-order dynamical description of turbulent jet flow. As the complexity of the statistic increases, the number of flows for which the data has been categorized and assembled decreases, making it difficult to systematically validate prediction codes that require high-level statistics over a broad range of jet flow conditions. For several years, researchers at NASA have worked on developing and validating jet noise prediction codes. One such class of codes, loosely called CFD-based or statistical methods, uses RANS CFD to predict jet mean and turbulent intensities in velocity and temperature. These flow quantities serve as the input to the acoustic source models and flow-sound interaction calculations that yield predictions of far-field jet noise. To develop this capability, a catalog of turbulent jet flows has been created with statistics ranging from mean velocity to space-time correlations of Reynolds stresses. The present document aims to document this catalog and to assess the accuracies of the data, e.g. establish uncertainties for the data. This paper covers the following five tasks: Document acquisition and processing procedures used to create the particle image velocimetry (PIV) datasets. Compare PIV data with hotwire and laser Doppler
Generation of sub-Poissonian photon number distribution
DEFF Research Database (Denmark)
Grønbech-Jensen, N.; Ramanujam, P. S.
1990-01-01
An optimization of a nonlinear Mach-Zehnder interferometer to produce sub-Poissonian photon number distribution is proposed. We treat the system quantum mechanically and estimate the mirror parameters, the nonlinearity of the medium in the interferometer, and the input power to obtain minimal...... output uncertainty in the photon number. The power efficiency of the system is shown to be high....
On the transfer of energy to an unstable liquid jet in a coflowing compressible airstream
Li, Hsi-Shang; Kelly, Robert E.
1993-01-01
The transfer of energy from a compressible airstream to a coflowing unstable liquid jet via the pressure perturbation at the interface is studied as the Mach number varies continuously from subsonic to supersonic values. The 'lift' component of the pressure perturbation has been demonstrated to predominate up to slightly supersonic free-stream Mach numbers, after which the 'drag' component predominates.
Multi-Mission Earth Vehicle Subsonic Dynamic Stability Testing and Analyses
Glaab, Louis J.; Fremaux, C. Michael
2013-01-01
Multi-Mission Earth Entry Vehicles (MMEEVs) are blunt-body vehicles designed with the purpose of transporting payloads from outer space to the surface of the Earth. To achieve high-reliability and minimum weight, MMEEVs avoid use of limited-reliability systems, such as parachutes, retro-rockets, and reaction control systems and rely on the natural aerodynamic stability of the vehicle throughout the Entry, Descent, and Landing (EDL) phase of flight. The Multi-Mission Systems Analysis for Planetary Entry (M-SAPE) parametric design tool is used to facilitate the design of MMEEVs for an array of missions and develop and visualize the trade space. Testing in NASA Langley?s Vertical Spin Tunnel (VST) was conducted to significantly improve M-SAPE?s subsonic aerodynamic models. Vehicle size and shape can be driven by entry flight path angle and speed, thermal protection system performance, terminal velocity limitations, payload mass and density, among other design parameters. The objectives of the VST testing were to define usable subsonic center of gravity limits, and aerodynamic parameters for 6-degree-of-freedom (6-DOF) simulations, for a range of MMEEV designs. The range of MMEEVs tested was from 1.8m down to 1.2m diameter. A backshell extender provided the ability to test a design with a much larger payload for the 1.2m MMEEV.
Sandford, M. C.; Ricketts, R. H.
1983-01-01
A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static pressure orifices and 164 in situ dynamic pressure gages for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Results from the present test (the third in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60, 0.78, and 0.86 and are presented in tabular form.
3-D Wizardry: Design in Papier-Mache, Plaster, and Foam.
Wolfe, George
Papier-mache, plaster, and foam are inexpensive and versatile media for 3-dimensional classroom and studio art experiences. They can be used equally well by elementary, high school, or college students. Each medium has its own characteristic. Papier-mache is pliable but dries into a hard, firm surface that can be waterproofed. Plaster can be…
3-D Wizardry: Design in Papier-Mache, Plaster, and Foam.
Wolfe, George
Papier-mache, plaster, and foam are inexpensive and versatile media for 3-dimensional classroom and studio art experiences. They can be used equally well by elementary, high school, or college students. Each medium has its own characteristic. Papier-mache is pliable but dries into a hard, firm surface that can be waterproofed. Plaster can be…
Fundamental and analytical studies of optical emission from the Mach disk extracted from an ICP
Energy Technology Data Exchange (ETDEWEB)
Luan, S.; Pang, H.; Houk, R.S. [Iowa State Univ., Ames, IA (United States)
1994-12-31
An inductively coupled plasma is extracted into a small quartz vacuum chamber (approximately 1 torr) through a sampling orifice in a copper disk. Optical emission from the Mach disk region is measured with a new type of echelle spectrometer with two segmented-array charge-coupled device detectors (SCD), the Optima 3000 from Perkin-Elmer. This detector provides excellent quantum efficiency throughout the UV-visible region, as well as low dark current and readout noises. The spectral background emitted by the Mach disk is very low. If analyte line intensities from the Mach disk can be enhanced, the combined ICP-Mach disk-Optima instrument should provide excellent detection limits for simultaneous multielement analysis. Axial profiles of the optical emission of various atom and ion lines are measured. Intensities of various lines are maximized at the Mach disk location. The relationship between the location of the Mach disk and the vacuum operating pressure is studied, using a cathetometer to measure small changes in the location of the Mach disk. The effects of aerosol gas flow rate on the intensities of various lines are also investigated. Finally, several schemes for boosting the intensity from the Mach disk will be presented.
Density Measurement of Compact Toroid with Mach-Zehnder Interferometer
Laufman-Wollitzer, Lauren; Endrizzi, Doug; Brookhart, Matt; Flanagan, Ken; Forest, Cary
2016-10-01
Utilizing a magnetized coaxial plasma gun (MCPG) built by Tri Alpha Energy, a dense compact toroid (CT) is created and injected at high speed into the Wisconsin Plasma Astrophysics Laboratory (WiPAL) vessel. A modified Mach-Zehnder interferometer from the Line-Tied Reconnection Experiment (LTRX) provides an absolute measurement of electron density. The interferometer is located such that the beam intersects the plasma across the diameter of the MCPG drift region before the CT enters the vessel. This placement ensures that the measurement is taken before the CT expand. Results presented will be used to further analyze characteristics of the CT. Funding provided by DoE, NSF, and WISE Summer Research.
Structure optimization of polymeric Mach-Zehnder rib waveguide
Institute of Scientific and Technical Information of China (English)
LU Rong-guo; LiU Yong-zhi; LIAO Jin-kun; LIAO Yi-tao; HAN Wen-jie
2007-01-01
A systematic analysis of the polymeric Mach-Zehnder rib waveguide is presented based on the calculation and optimization. The simulation is carried out with the Effective Index Method (EIM) and two-dimensional (2-D)Finite Difference Beam Propagation Method (FD-BPM). The large refractive index step between the consecutive polymer layers is reduced by using EIM and thus the precision of the calculation is ensured. The important parameters of the waveguide such as Y-junction angle and the separation gap are discussed and their relationships with the optical power propagation and the loss characteristics are investigated in this paper. The total loss of the optimized structure is 0.258 dB.
Vibration induced phase noise in Mach-Zehnder atom interferometers
Miffre, A; Büchner, M; Trénec, G; Vigué, J; Miffre, Alain; Jacquey, Marion; B\\"{u}chner, Matthias; Vigu\\'{e}, Jacques
2006-01-01
The high inertial sensitivity of atom interferometers has been used to build accelerometers and gyrometers but this sensitivity makes these interferometers very sensitive to the laboratory seismic noise. This seismic noise induces a phase noise which is large enough to reduce the fringe visibility in many cases. We develop here a model calculation of this phase noise in the case of Mach-Zehnder atom interferometers and we apply this model to our thermal lithium interferometer. We are thus able to explain the observed dependence of the fringe visibility with the diffraction order. The dynamical model developed in the present paper should be very useful to further reduce this phase noise in atom interferometers and this reduction should open the way to improved interferometers.
Unification of Gravity and Electromagnetism I: Mach's Principle and Cosmology
Ghose, Partha
2014-01-01
The phenomenological consequences of unification of Einstein gravity and electromagnetism in an early phase of a Machian universe with a very small and uniform electrical charge density $\\rho_q$ are explored. A form of the Strong Equivalence Principle for unified electrogravity is first formulated, and it immediately leads to (i) the empirical Schuster-Blackett law relating the magnetic moments and angular momenta of neutral astronomical bodies, (ii) an analogous relation between the linear acceleration of neutral massive bodies and associated electric fields, (iii) gravitational lensing in excess of Einstein gravity, and, with the additional assumption of scaling, to (iv) the Wesson relation between the angular momentum and the square of the mass of astronomical bodies. Incorporation of Sciama's version of Mach's principle leads to a new post-Newtonian dynamics (in the weak field limit of gravity alone without electromagnetism) that predicts flat rotation curves of galaxies without the need of dark matter ha...
Mach-Zehnder Interferometer Based on Coupled Dielectric Pillars
Institute of Scientific and Technical Information of China (English)
GAO Ding-Shan; HAO Ran; ZHOU Zhi-Ping
2007-01-01
We propose a Mach-Zehnder interferometer (MZI) based on coupled dielectric pillars. It is composed of single-row pillar coupled waveguide modulating arms and three-row pillar waveguide 3 dB couplers. The slow light property and transmission loss of the single-row pillar modulating arm are optimized by the plane wave expansion method. A short 3dB coupler is designed based on the modes transformation in three-row pillar waveguide. Finite difference time domain simulations prove the validity of this MZI and show that it has low insertion loss of＜1.1 dB and high extinction ratio of＞12 dB.
A new magnetic sensor with Mach-Zehnder/Sagnac optical fiber interferometer
Institute of Scientific and Technical Information of China (English)
Shuguang LI; Xinwan LI; Xin WANG; Jianping CHEN
2009-01-01
This paper presents a new structure for magnetic sensor with Mach-Zehnder/Sagnac optical fiber interferometer. The magnetostrictive optical fiber sensor is placed in one of the two arms of the Mach-Zehnder interferometer, which can detect the optic phase shift by testing the length difference of the arm caused by environmental magnetic field. Because of forward and backward transmission in the arms, the Mach-Zehnder/ Sagnac optical fiber interferometer can deduce twice exactly of the phase shift proportional to the length difference as Mach-Zehnder interferometer. Theoretically, description of the Mach-Zehnder/Sagnac interferometer is given, and some main issues in the magnetic field sensor with optical fiber interferometer are demonstrated with experiments. The magnetic sensors are implemented using the proposed methods.
[Thought Experiments of Economic Surplus: Science and Economy in Ernst Mach's Epistemology].
Wulz, Monika
2015-03-01
Thought Experiments of Economic Surplus: Science and Economy in Ernst Mach's Epistemology. Thought experiments are an important element in Ernst Mach's epistemology: They facilitate amplifying our knowledge by experimenting with thoughts; they thus exceed the empirical experience and suspend the quest for immediate utility. In an economical perspective, Mach suggested that thought experiments depended on the production of an economic surplus based on the division of labor relieving the struggle for survival of the individual. Thus, as frequently emphasized, in Mach's epistemology, not only the 'economy of thought' is an important feature; instead, also the socioeconomic conditions of science play a decisive role. The paper discusses the mental and social economic aspects of experimental thinking in Mach's epistemology and examines those within the contemporary evolutionary, physiological, and economic contexts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Matula, Thomas John
Electromagnetic acoustic wave transducers (EMATs) are described for generating low-frequency tone bursts on metalized membranes in air and elastic plates in water. Bursts on the membrane have phase velocities much less than the speed of sound in the surrounding air and are accompanied by plane evanescent waves. The frequency and time-domain responses of the EMAT and the dependence on gap spacing between the coupling coil and the membrane were studied. Wave -number selective optical and capacitive probes were used to measure the wave properties. Versions of these transducers are insensitive to long wavelength motion of the membrane. Diffraction of the burst by a sharp edge in air was observed as a function of the gap between the membrane and a razor edge. The scattered pressure decreases exponentially with increasing gap as expected from an approximate analysis of edge diffraction of evanescent waves. In related work an EMAT is used to generate 28 kHz tone bursts of bending waves on an aluminum plate. The bursts propagate down into water where the surrounding wavefield is probed. Observations described indicate that there occurs a branching of energy as the wave crosses the air-water interface. Radiation from subsonic flexural plate waves due to the discontinuity in fluid -loading is observed. It is partially analogous to the transition radiation of fast charged particles crossing a dielectric interface. The angular radiation pattern resembles that of a line quadrupole. Near the interface there exists an interference between the two energy branches in water that produces a series of pressure nulls. The pressure nulls are associated with a pi phase change in the wavefield and are indicators of wavefront dislocations. A computation of the wavefield in an unbounded fluid due to a line-moment excitation of a plate is comparable with the null pattern observed but differs in certain details.
An Aerodynamic Analysis of Deformed Wings in Subsonic and Supersonic Flow.
1981-04-01
primary interest include wing twist, cam - bered airfoils, and arbitrary chordwise and spanwise deformations. For the case of w. ig twist, at any given...2.0100 MACH NO. = 2.0100 CR = 2.74,75 CR = 2.7475 CT = 0.0000 C CT - 0.0000 Y/(B/2) = 0.1000 Y /(B/2 = 0.14000 o 0L. C- L -- ( D C 0 CD CAD -c oD...No. Format Variable List 1 18A4 WING 2 7F10.0 SPAN,CR,CT,LAMDA,SAREA,CBAR,MACH 3 F10.0,15 ALPHA,KSTOP 4 1015 NC,NS, NX ,NY,NCF,NSF,NXF,NYF,NSPAN, NCORD
Indian Academy of Sciences (India)
Balla Venukumar; K P J Reddy
2007-02-01
Substantial aerodynamic drag, while ﬂying at hypersonic Mach number, due to the presence of strong standing shock wave ahead of a large-angle bluntcone conﬁguration, is a matter of great design concern. Preliminary experimental results for the drag reduction by a forward-facing supersonic air jet for a 60° apex-angle blunt cone at a ﬂow Mach number of 8 are presented in this paper. The measurements are carried out using an accelerometer-based balance system in the hypersonic shock tunnel HST2 of the Indian Institute of Science, Bangalore. About 29% reduction in the drag coefﬁcient has been observed with the injection of a supersonic gas jet.
Boundary-layer transition on blunt slender cones at Mach 10
Bell, R. L.
1984-08-01
Investigations of the effects of nose blunting on the location of boundary-layer transition on slender cones at supersonic or hypersonic speeds so back 25 years. For some time it was thought that the movement of the transition point was simply due to the reduction in local Reynolds number associated with the loss in total pressure through the bow shock. More recently, it has been shown that variations in the local transition Reynolds number also occur on a blunt cone and that both these effects must be taken into account in explaining the observed movement in transition along the cone frustum. The present investigation was carried out as a demonstration test for the development of a new capability in Hypervelocity Tunnel 9 at the Naval Surface Weapon Center. The objective of this development effort was to raise the Reynolds number at mach 10 from about 5 x 1000000 per foot to 20 x 1000000 per foot. This was done so that naturally turbulent boundary layers (i.e., without tripping) could be obtained on R/V models. Thus an investigation of boundary layer transition was an appropriate choice for the demonstration test.
Mateer, G. G.
1972-01-01
Tests were conducted on 5 deg and 15 deg half-angle sharp cones at wall-to-total-temperature ratios of 0.08 to 0.4, and angles of attack from 0 deg to 20 deg. The results indicate that (1) transition Reynolds numbers decrease with decreasing temperature ratio, (2) local transition Reynolds numbers decrease from the windward to the leeward side of the model, and (3) transition data on the windward ray of cones can be correlated in terms of the crossflow velocity gradient, momentum thickness Reynolds number, local Mach number, and cone half-angle.
Capone, Francis J.; Bare, E. Ann
1987-01-01
The aeropropulsive characteristics of an advanced twin-engine fighter aircraft designed for supersonic cruise have been studied in the Langley 16-Foot Tansonic Tunnel and the Lewis 10- by 10-Foot Supersonic Tunnel. The objective was to determine multiaxis control-power characteristics from thrust vectoring. A two-dimensional convergent-divergent nozzle was designed to provide yaw vector angles of 0, -10, and -20 deg combined with geometric pitch vector angles of 0 and 15 deg. Yaw thrust vectoring was provided by yaw flaps located in the nozzle sidewalls. Roll control was obtained from differential pitch vectoring. This investigation was conducted at Mach numbers from 0.20 to 2.47. Angle of attack was varied from 0 to about 19 deg, and nozzle pressure ratio was varied from about 1 (jet off) to 28, depending on Mach number. Increments in force or moment coefficient that result from pitch or yaw thrust vectoring remain essentially constant over the entire angle-of-attack range of all Mach numbers tested. There was no effect of pitch vectoring on the lateral aerodynamic forces and moments and only very small effects of yaw vectoring on the longitudinal aerodynamic forces and moments. This result indicates little cross-coupling of control forces and moments for combined pitch-yaw vectoring.
Schairer, Edward T.; Heineck, James T.; Walker, Louise Ann; Kushner, Laura Kathryn; Zilliac, Gregory
2010-01-01
This paper describes simultaneous, synchronized, high-frequency measurements of both unsteady flow in the wake of a tension-cone decelerator in subsonic flow (by PIV) and the unsteady shape of the decelerator (by photogrammetry). The purpose of these measurements was to develop the test techniques necessary to validate numerical methods for computing fluid-structure interactions of flexible decelerators. A critical need for this effort is to map fabric surfaces that have buckled or wrinkled so that code developers can accurately represent them. This paper describes a new photogrammetric technique that performs this measurement. The work was done in support of the Entry, Descent, and Landing discipline within the Supersonics Project of NASA s Fundamental Aeronautics Program.
Nickol, Craig L.; Frederic, Peter
2013-01-01
A conceptual design and cost estimate for a subsonic flight research vehicle designed to support NASA's Environmentally Responsible Aviation (ERA) project goals is presented. To investigate the technical and economic feasibility of modifying an existing aircraft, a highly modified Boeing 717 was developed for maturation of technologies supporting the three ERA project goals of reduced fuel burn, noise, and emissions. This modified 717 utilizes midfuselage mounted modern high bypass ratio engines in conjunction with engine exhaust shielding structures to provide a low noise testbed. The testbed also integrates a natural laminar flow wing section and active flow control for the vertical tail. An eight year program plan was created to incrementally modify and test the vehicle, enabling the suite of technology benefits to be isolated and quantified. Based on the conceptual design and programmatic plan for this testbed vehicle, a full cost estimate of $526M was developed, representing then-year dollars at a 50% confidence level.
Onset of cavity deformation upon subsonic motion of a projectile in a fluid complex plasma.
Zhukhovitskii, D I; Ivlev, A V; Fortov, V E; Morfill, G E
2013-06-01
We study the deformation of a cavity around a large projectile moving with subsonic velocity in the cloud of small dust particles. To solve this problem, we employ the Navier-Stokes equation for a compressible fluid with due regard for friction between dust particles and atoms of neutral gas. The solution shows that due to friction, the pressure of a dust cloud at the surface of a cavity around the projectile can become negative, which entails the emergence of a considerable asymmetry of the cavity, i.e., the cavity deformation. Corresponding threshold velocity is calculated, which is found to decrease with increasing cavity size. Measurement of such velocity makes it possible to estimate the static pressure inside the dust cloud.
Onset of cavity deformation upon subsonic motion of a projectile in a fluid complex plasma
Zhukhovitskii, D I; Fortov, V E; Morfill, G E
2013-01-01
We study deformation of a cavity around a large projectile moving with subsonic velocity in the cloud of small dust particles. To solve this problem, we employ the Navier-Stokes equation for a compressible fluid with due regard for friction between dust particles and atoms of neutral gas. The solutions shows that due to friction, the pressure of dust cloud at the boundary of the cavity behind the projectile can become negative, which entails formation of a microscopic void free from dust particles -- the cavity deformation. The corresponding threshold velocity is calculated, which is found to decrease with increasing cavity size. Measurement of such velocity makes it possible to estimate the static pressure inside the dist cloud.
Hussein, A. M. H.; Majid, D. L. Abdul; Abdullah, E. J.
2016-10-01
Shape memory alloy (SMA) is one of the smart materials that have unique properties and used recently in several aerospace applications. SMAs are metallic alloys that can recover permanent strains when they are heated above a certain temperature. In this study, the effects of SMA actuation on the composite plate under subsonic aeroelastic conditions are examined. The wind tunnel test is carried out for two configurations of a cantilever shape memory alloy composite plate with a single SMA wire fixed eccentrically. Strain gage data for both bending and torsional strain are recorded and demonstrated during the aeroelastic test for active and non-active SMA wire in two locations. The cyclic actuation of the SMA wire embedded inside the composite plate is also investigated during the aeroelastic test. The results show reduction in both bending and torsional strain of the composite plate after activation of the SMA wire during the wind tunnel test.
Validating a Monotonically-Integrated Large Eddy Simulation Code for Subsonic Jet Acoustics
Ingraham, Daniel; Bridges, James
2017-01-01
The results of subsonic jet validation cases for the Naval Research Lab's Jet Engine Noise REduction (JENRE) code are reported. Two set points from the Tanna matrix, set point 3 (Ma = 0.5, unheated) and set point 7 (Ma = 0.9, unheated) are attempted on three different meshes. After a brief discussion of the JENRE code and the meshes constructed for this work, the turbulent statistics for the axial velocity are presented and compared to experimental data, with favorable results. Preliminary simulations for set point 23 (Ma = 0.5, Tj=T1 = 1.764) on one of the meshes are also described. Finally, the proposed configuration for the farfield noise prediction with JENRE's Ffowcs-Williams Hawking solver are detailed.
The model evaluation of subsonic aircraft effect on the ozone and radiative forcing
Energy Technology Data Exchange (ETDEWEB)
Rozanov, E.; Zubov, V.; Egorova, T.; Ozolin, Y. [Main Geophysical Observatory, St.Petersburg (Russian Federation)
1997-12-31
Two dimensional transient zonally averaged model was used for the evaluation of the effect of subsonic aircraft exhausts upon the ozone, trace gases and radiation in the troposphere and lower stratosphere. The mesoscale transformation of gas composition was included on the base of the box model simulations. It has been found that the transformation of the exhausted gases in sub-grid scale is able to influence the results of the modelling. The radiative forcing caused by gas, sulfate aerosol, soot and contrails changes was estimated as big as 0.12-0.15 W/m{sup 2} (0.08 W/m{sup 2} globally and annually averaged). (author) 10 refs.
A Laplace transform/potential-theoretic method for acoustic propagation in subsonic flows
Hariharan, S I
2003-01-01
This paper introduces a competitive computational approach for determining time-dependent far-field sound generated by subsonic flows around lifting airfoils. The procedure assumes the linearity of the sound field away from a bounded region surrounding the airfoil. It is assumed that the sound pressure on the boundary of this enclosed region (referred to as the Kirchhoff surface) is specified, possibly by another procedure such as solving the full Euler equations. Away from the Kirchhoff surface, the Euler equations are linearized about a uniform mean flow. It is well known that linearized Euler equations can be uncoupled into a scalar convective wave equation. However, due to the anisotropy present in the convective wave equation, it is difficult to compute solutions. In this context, direct numerical simulation of the convective wave equation requires proper numerical descriptions of far-field boundary conditions which is a non-trivial task. Moreover, if accurate far-field conditions can be formulated, the ...
Gérard, Anthony; Berry, Alain; Masson, Patrice; Gervais, Yves
2009-03-01
This paper presents the acoustic performance of a novel approach for the passive adaptive control of tonal noise radiated from subsonic fans. Tonal noise originates from non-uniform flow that causes circumferentially varying blade forces and gives rise to a considerably larger radiated dipolar sound at the blade passage frequency (BPF) and its harmonics compared to the tonal noise generated by a uniform flow. The approach presented in this paper uses obstructions in the flow to destructively interfere with the primary tonal noise arising from various flow conditions. The acoustic radiation of the obstructions is first demonstrated experimentally. Indirect on-axis acoustic measurements are used to validate the analytical prediction of the circumferential spectrum of the blade unsteady lift and related indicators generated by the trapezoidal and sinusoidal obstructions presented in Ref. [A. Gérard, A. Berry, P. Masson, Y. Gervais, Modelling of tonal noise control from subsonic axial fans using flow control obstructions, Journal of Sound and Vibration (2008), this issue, doi: 10.1016/j.jsv.2008.09.027.] and also by cylindrical obstructions used in the literature. The directivity and sound power attenuation are then given in free field for the control of the BPF tone generated by rotor/outlet guide vane (OGV) interaction and the control of an amplified BPF tone generated by the rotor/OGV interaction with an added triangular obstruction between two outlet guide vanes to enhance the primary non-uniform flow. Global control was demonstrated in free field, attenuation up to 8.4 dB of the acoustic power at BPF has been measured. Finally, the aerodynamic performances of the automotive fan used in this study are almost not affected by the presence of the control obstruction.
Wornom, Dewey E.
1960-01-01
Force tests of a model of a proposed six-engine hull-type seaplane were performed in the Langley 8-foot transonic pressure tunnel. The results of these tests have indicated that the model had a subsonic zero-lift drag coefficient of 0.0240 with the highest zero-lift drag coefficient slightly greater than twice the subsonic drag level. Pitchup tendencies were noted for subsonic Mach numbers at relatively high lift coefficients. Wing leading-edge droop increased the maximum lift-drag ratio approximately 8 percent at a Mach number of 0.80 but this effect was negligible at a Mach number of 0.90 and above. The configuration exhibited stable lateral characteristics over the test Mach number range.
Receptivity of Boundary Layer over a Blunt Wedge due to Freestream Pulse Disturbances at Mach 6
Directory of Open Access Journals (Sweden)
Jianqiang Shi
2016-01-01
Full Text Available Direct numerical simulation (DNS of a hypersonic compressible flow over a blunt wedge with fast acoustic disturbances in freestream is performed. The receptivity characteristics of boundary layer to freestream pulse acoustic disturbances are numerically investigated at Mach 6, and the frequency effects of freestream pulse wave on boundary layer receptivity are discussed. Results show that there are several main disturbance mode clusters in boundary layer under acoustic pulse wave, and the number of main disturbance clusters decreases along the streamwise. As disturbance wave propagates from upstream to downstream direction, the component of the modes below fundamental frequency decreases, and the component of the modes above second harmonic components increases quickly in general. There are competition and disturbance energy transfer between different boundary layer modes. The nose boundary layer is dominated by the nearby mode of fundamental frequency. The number of the main disturbance mode clusters decreases as the freestream disturbance frequency increases. The frequency range with larger growth narrows along the streamwise. In general, the amplitudes of both fundamental mode and harmonics become larger with the decreasing of freestream disturbance frequency. High frequency freestream disturbance accelerates the decay of disturbance wave in downstream boundary layer.
Highly stable polarization independent Mach-Zehnder interferometer
Energy Technology Data Exchange (ETDEWEB)
Mičuda, Michal, E-mail: micuda@optics.upol.cz; Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav, E-mail: jezek@optics.upol.cz [Department of Optics, Faculty of Science, Palacký University, 17. listopadu 1192/12, 77146 Olomouc (Czech Republic)
2014-08-15
We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27×40 cm offers individually accessible paths and shows phase deviation less than 0.4° during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3° or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually.
Ultra-Abrupt Tapered Fiber Mach-Zehnder Interferometer Sensors
Directory of Open Access Journals (Sweden)
Lanying Zhou
2011-05-01
Full Text Available A fiber inline Mach-Zehnder interferometer (MZI consisting of ultra-abrupt fiber tapers was fabricated through a new fusion-splicing method. By fusion-splicing, the taper diameter-length ratio is around 1:1, which is much greater than those (1:10 made by stretching. The proposed fabrication method is very low cost, 1/20–1/50 of those of LPFG pair MZI sensors. The fabricated MZIs are applied to measure refractive index, temperature and rotation angle changes. The temperature sensitivity of the MZI at a length of 30 mm is 0.061 nm/°C from 30–350 °C. The proposed MZI is also used to measure rotation angles ranging from 0° to 0.55°; the sensitivity is 54.98 nm/°. The refractive index sensitivity is improved by 3–5 fold by fabricating an inline micro–trench on the fiber cladding using a femtosecond laser. Acetone vapor of 50 ppm in N2 is tested by the MZI sensor coated with MFI–type zeolite thin film. The proposed MZI sensors are capable of in situ detection in many areas of interest such as environmental management, industrial process control, and public health.
Ultra-abrupt tapered fiber Mach-Zehnder interferometer sensors.
Li, Benye; Jiang, Lan; Wang, Sumei; Zhou, Lanying; Xiao, Hai; Tsai, Hai-Lung
2011-01-01
A fiber inline Mach-Zehnder interferometer (MZI) consisting of ultra-abrupt fiber tapers was fabricated through a new fusion-splicing method. By fusion-splicing, the taper diameter-length ratio is around 1:1, which is much greater than those (1:10) made by stretching. The proposed fabrication method is very low cost, 1/20-1/50 of those of LPFG pair MZI sensors. The fabricated MZIs are applied to measure refractive index, temperature and rotation angle changes. The temperature sensitivity of the MZI at a length of 30 mm is 0.061 nm/°C from 30-350 °C. The proposed MZI is also used to measure rotation angles ranging from 0° to 0.55°; the sensitivity is 54.98 nm/°. The refractive index sensitivity is improved by 3-5 fold by fabricating an inline micro-trench on the fiber cladding using a femtosecond laser. Acetone vapor of 50 ppm in N(2) is tested by the MZI sensor coated with MFI-type zeolite thin film. The proposed MZI sensors are capable of in situ detection in many areas of interest such as environmental management, industrial process control, and public health.
Batterton, P. G.; Arpasi, D. J.; Baumbick, R. J.
1974-01-01
A digitally implemented integrated inlet-engine control system was designed and tested on a mixed-compression, axisymmetric, Mach 2.5, supersonic inlet with 45 percent internal supersonic area contraction and a TF30-P-3 augmented turbofan engine. The control matched engine airflow to available inlet airflow. By monitoring inlet terminal shock position and over-board bypass door command, the control adjusted engine speed so that in steady state, the shock would be at the desired location and the overboard bypass doors would be closed. During engine-induced transients, such as augmentor light-off and cutoff, the inlet operating point was momentarily changed to a more supercritical point to minimize unstarts. The digital control also provided automatic inlet restart. A variable inlet throat bleed control, based on throat Mach number, provided additional inlet stability margin.
Xie, Bin; Deng, Xi; Sun, Ziyao; Xiao, Feng
2017-04-01
We propose a novel Mach-uniform numerical model for 2D Euler equations on unstructured grids by using multi-moment finite volume method. The model integrates two key components newly developed to solve compressible flows on unstructured grids with improved accuracy and robustness. A new variant of AUSM scheme, so-called AUSM+-pcp (AUSM+ with pressure-correction projection), has been devised including a pressure-correction projection to the AUSM+ flux splitting, which maintains the exact numerical conservativeness and works well for all Mach numbers. A novel 3th-order, non-oscillatory and less-dissipative reconstruction has been proposed by introducing a multi-dimensional limiting and a BVD (boundary variation diminishing) treatment to the VPM (volume integrated average (VIA) and point value (PV) based multi-moment) reconstruction. The resulting reconstruction scheme, the limited VPM-BVD formulation, is able to resolve both smooth and non-smooth solutions with high fidelity. Benchmark tests have been used to verify the present model. The numerical results substantiate the present model as an accurate and robust unstructured-grid formulation for flows of all Mach numbers.
Wavelength conversion based on cross-phase modulation in a semiconductor Mach-Zehnder modulator
DEFF Research Database (Denmark)
Liu, Fenghai; Zheng, Xueyan; Oxenløwe, Leif Katsuo
2001-01-01
Wavelength conversion based on cross-phase modulation in a reversely biased semiconductor Mach-Zehnder modulator is proposed and successfully demonstrated in a commercial device. The converted signals exhibit extinction ratio >13 dB and penalty......Wavelength conversion based on cross-phase modulation in a reversely biased semiconductor Mach-Zehnder modulator is proposed and successfully demonstrated in a commercial device. The converted signals exhibit extinction ratio >13 dB and penalty...
Structural design and analysis of a Mach zero to five turbo-ramjet system
Spoth, Kevin A.; Moses, Paul L.
1993-01-01
The paper discusses the structural design and analysis of a Mach zero to five turbo-ramjet propulsion system for a Mach five waverider-derived cruise vehicle. The level of analysis detail necessary for a credible conceptual design is shown. The results of a finite-element failure mode sizing analysis for the engine primary structure is presented. The importance of engine/airframe integration is also discussed.
[Investigation of Empiricism. On Ernst Mach's Conception of the Thought Experiment].
Krauthausen, Karin
2015-03-01
Investigation of Empiricism. On Ernst Mach's Conception of the Thought Experiment. The paper argues that Ernst Mach's conception of the thought experiment from 1897/1905 holds a singular position in the lively discussions and repeated theorizations that have continued up to the present in relation to this procedure. Mach derives the thought experiment from scientific practice, and does not oppose it to the physical experiment, but, on the contrary, endows it with a robust relation to the facts. For Mach, the thought experiment is a reliable means of determining empiricism, and at the same time a real, because open and unbiased, experimenting. To shed light on this approach, the paper carries out a close reading of the relevant texts in Mach's body of writings (in their different stages of revision) and proceeds in three steps: first, Mach's processual understanding of science will be presented, which also characterizes his research and publication practice (I. 'Aperçu' and 'Sketch'. Science as Process and Projection); then in a second step the physiological and biological justification and valorization of memory and association will be examined with which Mach limits the relevance of categories such as consciousness and will (II. The Biology of Consciousness. Or The Polyp Colony); against this background, thirdly, the specific empiricism can be revealed that Mach inscribes into the thought experiment by on the one hand founding it in the memory and association, and on the other by tracing it back to geometry, which he deploys as an experimenting oriented to experience (III. Thinking and Experience. The Thought Experiment). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Mach Cutoff Analysis and Results from NASA's Farfield Investigation of No-Boom Thresholds
Cliatt, Larry J., II; Hill, Michael A.; Haering, Edward A., Jr.
2016-01-01
In support of the ongoing effort by the National Aeronautics and Space Administration (NASA) to bring supersonic commercial travel to the public, the NASA Armstrong Flight Research Center and the NASA Langley Research Center, in partnership with other industry organizations and academia, conducted a flight research experiment to analyze acoustic propagation in the Mach cutoff shadow zone. The effort was conducted in the fall of 2012 and named the Farfield Investigation of No-boom Thresholds (FaINT). The test helped to build a dataset that will go toward further understanding of the unique acoustic propagation characteristics below Mach cutoff altitude. FaINT was able to correlate sonic boom noise levels measured below cutoff altitude with precise airplane flight conditions, potentially increasing the accuracy over previous studies. A NASA F-18B airplane made supersonic passes such that its Mach cutoff caustic would be at varying distances above a linear 60-microphone, 7375-ft (2247.9 m) long array. A TG-14 motor glider equipped with a microphone on its wing-tip also attempted to capture the same sonic boom waves above ground, but below the Mach cutoff altitude. This paper identified an appropriate metric for sonic boom waveforms in the Mach cutoff shadow zone called Perceived Sound Exposure Level; derived an empirical relationship between Mach cutoff flight conditions and noise levels in the shadow zone; validated a safe cutoff altitude theory presented by previous studies; analyzed the sensitivity of flight below Mach cutoff to unsteady atmospheric conditions and realistic aircraft perturbations; and demonstrated the ability to record sonic boom measurements over 5000 ft (1524.0 m) above ground level, but below Mach cutoff altitude.
An experimental investigation of a Mach 3.0 high-speed civil transport at supersonic speeds
Hernandez, Gloria; Covell, Peter F.; Mcgraw, Marvin E., Jr.
1993-01-01
An experimental study was conducted to determine the aerodynamic characteristics of a proposed high speed civil transport. This configuration was designed to cruise at Mach 3.0 and sized to carry 250 passengers for 6500 n.mi. The configuration consists of a highly blended wing body and features a blunt parabolic nose planform, a highly swept inboard wing panel, a moderately swept outboard wing panel, and a curved wingtip. Wind tunnel tests were conducted in the Langley Unitary Plan Wind Tunnel on a 0.0098-scale model. Force, moment, and pressure data were obtained for Mach numbers ranging from 1.6 to 3.6 and at angles of attack ranging from -4 to 10 deg. Extensive flow visualization studies (vapor screen and oil flow) were obtained in the experimental program. Both linear and advanced computational fluid dynamics (CFD) theoretical comparisons are shown to assess the ability to predict forces, moments, and pressures on configurations of this type. In addition, an extrapolation of the wind tunnel data, based on empirical principles, to full-scale conditions is compared with the theoretical aerodynamic predictions.
Gerberding, Oliver; Mehmet, Moritz; Danzmann, Karsten; Heinzel, Gerhard
2016-01-01
Low frequency high precision laser interferometry is subject to excess laser frequency noise coupling via arm-length differences which is commonly mitigated by locking the frequency to a stable reference system. This is crucial to achieve picometer level sensitivities in the 0.1 mHz to 1 Hz regime, where laser frequency noise is usually high and couples into the measurement phase via arm-length mismatches in the interferometers. Here we describe the results achieved by frequency stabilising an external cavity diode laser to a quasi-monolithic unequal arm-length Mach-Zehnder interferometer read out at mid-fringe via balanced detection. This stabilisation scheme has been found to be an elegant solution combining a minimal number of optical components, no additional laser modulations and relatively low frequency noise levels. The Mach-Zehnder interferometer has been designed and constructed to minimise the influence of thermal couplings and to reduce undesired stray light using the optical simulation tool IfoCAD...
Revisiting Einstein's Happiest Thought: On Ernst Mach and the Early History of Relativity
Staley, Richard
2016-03-01
This paper argues we should distinguish three phases in the formation of relativity. The first involved relational approaches to perception, and physiological and geometrical space and time in the 1860s and 70s. The second concerned electrodynamics and mechanics (special relativity). The third concerned mechanics, gravitation, and physical and geometrical space and time. Mach's early work on the Doppler effect, together with studies of visual and motor perception linked physiology, physics and psychology, and offered new approaches to physiological space and time. These informed the critical conceptual attacks on Newtonian absolutes that Mach famously outlined in The Science of Mechanics. Subsequently Mach identified a growing group of ``relativists,'' and his critiques helped form a foundation for later work in electrodynamics (in which he did not participate). Revisiting Mach's early work will suggest he was still more important to the development of new approaches to inertia and gravitation than has been commonly appreciated. In addition to what Einstein later called ``Mach's principle,'' I will argue that a thought experiment on falling bodies in Mach's Science of Mechanics also provided a point of inspiration for the happy thought that led Einstein to the equivalence principle.
Rumsey, Christopher L.; Wahls, Richard A.
2008-01-01
Several recent workshops and studies are used to make an assessment of the current status of CFD for subsonic fixed wing aerodynamics. Uncertainty quantification plays a significant role in the assessment, so terms associated with verification and validation are given and some methodology and research areas are highlighted. For high-subsonic-speed cruise through buffet onset, the series of drag prediction workshops and NASA/Boeing buffet onset studies are described. For low-speed flow control for high lift, a circulation control workshop and a synthetic jet flow control workshop are described. Along with a few specific recommendations, gaps and needs identified through the workshops and studies are used to develop a list of broad recommendations to improve CFD capabilities and processes for this discipline in the future.
Design of all-optical multi-level regenerators based on Mach-Zehnder interferometer
Kong, Xiangjian; Wu, Baojian; Zhou, Xingyu; Wan, Qingyao; Jiang, Shanglong; Wen, Feng; Qiu, Kun
2016-12-01
We propose a design method for all-optical multi-level regenerators by mimicking the normalized power transfer function (PTF) in the first-order approximation to the ideal step-like PTF, in which a key step is to appropriately select the amplitude and phase conditions of Mach-Zehnder-interferometer (MZI)-based regenerators. As an example, we describe the design process of the self-phase-modulation (SPM)-based MZI regenerator constructed by a section of nonlinear fiber and an optical phase shifter (OPS). It is shown that the parameter of reference power level (RPL) can be regarded as the upper limit of input power, which is useful for the measure of the multi-level regeneration performance. The number of regenerative power levels increases with the RPL parameter. For 4-level pulse amplitude modulated (4PAM) optical signals degraded by the Gaussian noises with the standard deviation of 0.02, the SPM-based MZI regenerator has an average noise reduction ratio (NRR) of 6.5 dB, better than that of 1st-order regenerator by about 5 dB.
Unsteadiness of a shock train in Mach 2.0 flow
Hunt, Robin; Driscoll, James; Gamba, Mirko
2016-11-01
Experimental observations of the progression of flow unsteadiness within a shock train are presented. A downstream control valve is used to generate a shock train in the constant area test section of a wind tunnel with a freestream Mach number of 2.0. Even with nominally constant boundary conditions the shock train exhibits inherent unsteady motion about the time average position. At the conditions presented the shocks can be displaced by up to 0.35 duct heights. Better knowledge of the shock train's dynamics may allow us to introduce control algorithms to reduce the system's unsteadiness and thus minimize the associated mechanical and thermal loads. An edge detection algorithm is applied to the instantaneous frames of high speed Schlieren movies to track the location of morphological features within the shock system. Simultaneously, high speed pressure transducers record the pressure fluctuations along the bottom wall of the duct. The results indicate a complex frequency dependent dynamical system. A strong component of the dynamics involves a disturbance traveling upstream through the boundary layer. Once the disturbance reaches the leading shock foot the shocks respond in order with the most upstream shock moving first.
Effects of Fin Leading Edge Sweep on Shock-Shock Interaction at Mach 6
Berry, Scott A.; Nowak, Robert J.
1996-01-01
The effects of fin leading edge sweep on peak heating rates due to shock-shock interaction have been experimentally examined in the Langley 20-Inch Mach 6 Tunnel. The shock interaction was produced by the intersection of a planar incident shock (16.8 deg shock angle relative to the freestream, generated by a 9 deg wedge) with the bow shock formed around a O.5-inch diameter cylindrical leading edge fin. Heating distributions along the leading edge stagnation line have been obtained using densely spaced thin film resistive-type sensors. Schlieren images were obtained to illustrate the very complex shock-shock interactions. The fin leading edge sweep angle was varied from 15-degrees swept back to 45-degrees swept forward for a freestream unit Reynolds number of 2 x 10(exp 6)/ft. Two models were utilized during the study, one with 0.025-inch spacing between gage centers, and the other 0.015-inch spacing. Gage spatial resolution on the order of 0.015-in appeared to accurately capture the narrow spike in heating. Peak heating due to shock interaction was maximized when the fin was swept forward 15 deg and 25 deg, both promoting augmentations about 7 times the baseline value. The schlieren images for these cases revealed Type 4 and Type 3 interactions, respectively.
Paryz, Roman W.
2014-01-01
Several upgrade projects have been completed at the NASA Langley Research Center National Transonic Facility over the last 1.5 years in an effort defined as STARBUKS - Subsonic Transonic Applied Refinements By Using Key Strategies. This multi-year effort was undertaken to improve NTF's overall capabilities by addressing Accuracy and Validation, Productivity, and Reliability areas at the NTF. This presentation will give a brief synopsis of each of these efforts.
Maria Bersani, Alberto; Della Corte, Alessandro; Piccardo, Giuseppe; Rizzi, Nicola Luigi
2016-08-01
The authors investigate the linear vibrations induced in an elastic string by a loading point-like mass constrained to moving on it with constant horizontal velocity. Exact solutions are shown in the case of subsonic regime. The displacement is explicitly provided in terms of a power series determined by iteration, which is shown to converge to the solution of the problem. The presence of a discontinuity in the right extremum of the considered space interval is also shown both analytically and numerically.
Anderson, B. H.; Bowditch, D. N.
1958-01-01
Investigation of the control parameters of an external-internal compression inlet indicates that the cowl-lip shock provides a signal to position the spike and to start the inlet over a Mach number range from 2.1 to 3.0. Use of a single fixed probe position to control the spike over the range of conditions resulted in a 3.7-count loss in total-pressure recovery at Mach 3.0 and 0 deg angle of attack. Three separate shock-sensing-probe positions were required to set the spike for peak recovery from Mach 2.1 to 3.0 and angles of attack from 0 deg to 6 deg. When the inlet was unstarted, an erroneous signal was obtained from the normal-shock control through most of the starting cycle that prevented the inlet from starting. Therefore, it was necessary to over-ride the normal-shock control signal and not allow the control to position the terminal shock until the spike was positioned.
Drozda, Tomasz G.; Cabell, Karen F.; Passe, Bradley J.; Baurle, Robert A.
2017-01-01
Computational fluid dynamics analyses and experimental data are presented for the Mach 6 facility nozzle used in the Arc-Heated Scramjet Test Facility for the Enhanced Injection and Mixing Project (EIMP). This project, conducted at the NASA Langley Research Center, aims to investigate supersonic combustion ramjet (scramjet) fuel injection and mixing physics relevant to flight Mach numbers greater than 8. The EIMP experiments use a two-dimensional Mach 6 facility nozzle to provide the high-speed air simulating the combustor entrance flow of a scramjet engine. Of interest are the physical extent and the thermodynamic properties of the core flow at the nozzle exit plane. The detailed characterization of this flow is obtained from three-dimensional, viscous, Reynolds-averaged simulations. Thermodynamic nonequilibrium effects are also investigated. The simulations are compared with the available experimental data, which includes wall static pressures as well as in-stream static pressure, pitot pressure and total temperature obtained via in-stream probes positioned just downstream of the nozzle exit plane.
Mendonça, J. Ricardo G.
2012-01-01
We define a new class of numbers based on the first occurrence of certain patterns of zeros and ones in the expansion of irracional numbers in a given basis and call them Sagan numbers, since they were first mentioned, in a special case, by the North-american astronomer Carl E. Sagan in his science-fiction novel "Contact." Sagan numbers hold connections with a wealth of mathematical ideas. We describe some properties of the newly defined numbers and indicate directions for further amusement.
Vorob'ev, Nikolai Nikolaevich
2011-01-01
Fibonacci numbers date back to an 800-year-old problem concerning the number of offspring born in a single year to a pair of rabbits. This book offers the solution and explores the occurrence of Fibonacci numbers in number theory, continued fractions, and geometry. A discussion of the ""golden section"" rectangle, in which the lengths of the sides can be expressed as a ration of two successive Fibonacci numbers, draws upon attempts by ancient and medieval thinkers to base aesthetic and philosophical principles on the beauty of these figures. Recreational readers as well as students and teacher
Number names and number understanding
DEFF Research Database (Denmark)
Ejersbo, Lisser Rye; Misfeldt, Morten
2014-01-01
through using mathematical names for the numbers such as one-ten-one for 11 and five-ten-six for 56. The project combines the renaming of numbers with supporting the teaching with the new number names. Our hypothesis is that Danish children have more difficulties learning and working with numbers, because...... the Danish number names are more complicated than in other languages. Keywords: A research project in grade 0 and 1th in a Danish school, Base-10 system, two-digit number names, semiotic, cognitive perspectives....
Directory of Open Access Journals (Sweden)
Marianna A. Shubov
2010-01-01
Full Text Available In this paper, the numerical results on two problems originated in aircraft wing modeling have been presented. The first problem is concerned with the approximation to the set of the aeroelastic modes, which are the eigenvalues of a certain boundary-value problem. The affirmative answer is given to the following question: can the leading asymptotical terms in the analytical formulas be used as reasonably accurate description of the aeroelastic modes? The positive answer means that these leading terms can be used by engineers for practical calculations. The second problem is concerned with the flutter phenomena in aircraft wings in a subsonic, incompressible, inviscid air flow. It has been shown numerically that there exists a pair of the aeroelastic modes whose behavior depends on a speed of an air flow. Namely, when the speed increases, the distance between the modes tends to zero, and at some speed that can be treated as the flutter speed these two modes merge into one double mode.
Subsonic Ultra Green Aircraft Research. Phase II - Volume I; Truss Braced Wing Design Exploration
Bradley, Marty K.; Droney, Christopher K.; Allen, Timothy J.
2015-01-01
This report summarizes the Truss Braced Wing (TBW) work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team, consisting of Boeing Research and Technology, Boeing Commercial Airplanes, General Electric, Georgia Tech, Virginia Tech, NextGen Aeronautics, and Microcraft. A multi-disciplinary optimization (MDO) environment defined the geometry that was further refined for the updated SUGAR High TBW configuration. Airfoil shapes were tested in the NASA TCT facility, and an aeroelastic model was tested in the NASA TDT facility. Flutter suppression was successfully demonstrated using control laws derived from test system ID data and analysis models. Aeroelastic impacts for the TBW design are manageable and smaller than assumed in Phase I. Flutter analysis of TBW designs need to include pre-load and large displacement non-linear effects to obtain a reasonable match to test data. With the updated performance and sizing, fuel burn and energy use is reduced by 54% compared to the SUGAR Free current technology Baseline (Goal 60%). Use of the unducted fan version of the engine reduces fuel burn and energy by 56% compared to the Baseline. Technology development roadmaps were updated, and an airport compatibility analysis established feasibility of a folding wing aircraft at existing airports.
Energy Technology Data Exchange (ETDEWEB)
Lorteau, Mathieu, E-mail: mathieu.lorteau@onera.fr; Cléro, Franck, E-mail: franck.clero@onera.fr; Vuillot, François, E-mail: francois.vuillot@onera.fr [Onera–The French Aerospace Lab, F-92322 Châtillon (France)
2015-07-15
In the framework of jet noise computation, a numerical simulation of a subsonic turbulent hot jet is performed using large-eddy simulation. A geometrical tripping is used in order to trigger the turbulence at the nozzle exit. In a first part, the validity of the simulation is assessed by comparison with experimental measurements. The mean and rms velocity fields show good agreement, so do the azimuthal composition of the near pressure field and the far field spectra. Discrepancies remain close to the nozzle exit which lead to a limited overestimation of the pressure levels in both near and far fields, especially near the 90{sup ∘} angular sector. Two point correlation analyses are then applied to the data obtained from the simulation. These enable to link the downstream acoustic radiation, which is the main direction of radiation, to pressure waves developing in the shear layer and propagating toward the potential core end. The intermittency of the downstream acoustic radiation is evidenced and related to the coherent structures developing in the shear layer.
Subsonic Ultra Green Aircraft Research: Phase 2. Volume 2; Hybrid Electric Design Exploration
Bradley, Marty K.; Droney, Christopher K.
2015-01-01
This report summarizes the hybrid electric concept design, analysis, and modeling work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team, consisting of Boeing Research and Technology, Boeing Commercial Airplanes, General Electric, and Georgia Tech.Performance and sizing tasks were conducted for hybrid electric versions of a conventional tube-and-wing aircraft and a hybrid wing body. The high wing Truss Braced Wing (TBW) SUGAR Volt was updated based on results from the TBW work (documented separately) and new engine performance models. Energy cost and acoustic analyses were conducted and technology roadmaps were updated for hybrid electric and battery technology. NOx emissions were calculated for landing and takeoff (LTO) and cruise. NPSS models were developed for hybrid electric components and tested using an integrated analysis of superconducting and non-superconducting hybrid electric engines. The hybrid electric SUGAR Volt was shown to produce significant emissions and fuel burn reductions beyond those achieved by the conventionally powered SUGAR High and was able to meet the NASA goals for fuel burn. Total energy utilization was not decreased but reduced energy cost can be achieved for some scenarios. The team was not able to identify a technology development path to meet NASA's noise goals
Study of different biocomposite coatings on Ti alloy by a subsonic thermal spraying technique
Energy Technology Data Exchange (ETDEWEB)
Li Muqin [Provincial Key Laboratory of Biomaterials, Jiamusi University, Heilongjiang Province, 154007 (China); Zhang Rui [College of Stomatology, Jiamusi University, Heilongjiang Province, 154003 (China); Wang Jianping [College of Stomatology, Jiamusi University, Heilongjiang Province, 154003 (China); Yang Shiqin [State Key Laboratory Advanced Welding Production Technology, Harbin Institute of Technology, 150001 (China)
2007-03-01
A subsonic thermal spraying technique (STS) was used to make different biocomposite coatings on titanium alloys for preparing three kinds of implants: 8Ti2G, HA and 8H2B, respectively. The implants were embedded in a region of jaw of dogs whose teeth were pulled out three months previously. The dogs, in two groups, were killed 30 days and 90 days, respectively, after they were operated on. Osteointegration between the implants and host bone was investigated by x-ray, histology and the SEM technique. The results showed that the three kinds of coatings all exhibited good biocompatibility and synostosis, but their osteointegration capability showed a difference and decreased in the sequence of 8H2B, HA and 8Ti2G. The activity of coating, which promoted the reactions between implants and bone tissue, was further increased by the addition of bioglass in the 8H2B coating. Subsequently, chemical bonding was formed, and the osteointegration strength was increased. The study provided a new approach to prepare biocomposite coatings. The 8H2B implants, which formed an integral functional biocomposite coating on Ti alloys, showed a better osteointegration capability with bioactivity and pore gradient variation. A theoretical base was provided for the biocomposite coating application.
Kuhlman, J. M.
1979-01-01
The aerodynamic design of a wind-tunnel model of a wing representative of that of a subsonic jet transport aircraft, fitted with winglets, was performed using two recently developed optimal wing-design computer programs. Both potential flow codes use a vortex lattice representation of the near-field of the aerodynamic surfaces for determination of the required mean camber surfaces for minimum induced drag, and both codes use far-field induced drag minimization procedures to obtain the required spanloads. One code uses a discrete vortex wake model for this far-field drag computation, while the second uses a 2-D advanced panel wake model. Wing camber shapes for the two codes are very similar, but the resulting winglet camber shapes differ widely. Design techniques and considerations for these two wind-tunnel models are detailed, including a description of the necessary modifications of the design geometry to format it for use by a numerically controlled machine for the actual model construction.
The dense ring in the Coalsack: the merging of two subsonic flows
Rathborne, J M; Walsh, W; Saul, M; Butner, H M
2008-01-01
A recent high angular resolution extinction map toward the most opaque molecular globule, Globule 2, in the Coalsack Nebula revealed that it contains a strong central ring of dust column density. This ring represents a region of high density and pressure that is likely a transient and possibly turbulent structure. Dynamical models suggest that the ring has formed as a result of a sudden increase in external pressure which is driving a compression wave into the Globule. Here we combine the extinction measurements with a detailed study of the C18O (1-0) molecular line profiles toward Globule 2 in order to investigate the overall kinematics and, in doing so, test this dynamical model. We find that the ring corresponds to an enhancement in the C18O non-thermal velocity dispersion and non-thermal pressure. We observe a velocity gradient across the Globule that appears to trace two distinct systematic subsonic velocity flows that happen to converge within the ring. We suggest, therefore, that the ring has formed as...
Mixing characteristics of pulsed air-assist liquid jet into an internal subsonic cross-flow
Lee, Inchul; Kang, Youngsu; Koo, Jaye
2010-04-01
Penetration depth, spray dispersion angle, droplet sizes in breakup processes and atomization processes are very important parameters in combustor of air-breathing engine. These processes will enhance air/fuel mixing inside the combustor. Experimental results from the pulsed air-assist liquid jet injected into a cross-flow are investigated. And experiments were conducted to a range of cross-flow velocities from 42˜136 m/s. Air is injected with 0˜300kPa, with air-assist pulsation frequency of 0˜20Hz. Pulsation frequency was modulated by solenoid valve. Phase Doppler Particle Analyzer(PDPA) was utilized to quantitatively measuring droplet characteristics. High-speed CCD camera was used to obtain injected spray structure. Pulsed air-assist liquid jet will offer rapid mixing and good liquid jet penetration. Air-assist makes a very fine droplet which generated mist-like spray. Pulsed air-assist liquid jet will introduce additional supplementary turbulent mixing and control of penetration depth into a cross-flow field. The results show that pulsation frequency has an effect on penetration, transverse velocities and droplet sizes. The experimental data generated in these studies are used for a development of active control strategies to optimize the liquid jet penetration in subsonic cross-flow conditions and predict combustion low frequency instability.
Application of the aeroacoustic analogy to a shrouded, subsonic, radial fan
Buccieri, Bryan M.; Richards, Christopher M.
2016-12-01
A study was conducted to investigate the predictive capability of computational aeroacoustics with respect to a shrouded, subsonic, radial fan. A three dimensional unsteady fluid dynamics simulation was conducted to produce aerodynamic data used as the acoustic source for an aeroacoustics simulation. Two acoustic models were developed: one modeling the forces on the rotating fan blades as a set of rotating dipoles located at the center of mass of each fan blade and one modeling the forces on the stationary fan shroud as a field of distributed stationary dipoles. Predicted acoustic response was compared to experimental data measured at two operating speeds using three different outlet restrictions. The blade source model predicted overall far field sound power levels within 5 dB averaged over the six different operating conditions while the shroud model predicted overall far field sound power levels within 7 dB averaged over the same conditions. Doubling the density of the computational fluids mesh and using a scale adaptive simulation turbulence model increased broadband noise accuracy. However, computation time doubled and the accuracy of the overall sound power level prediction improved by only 1 dB.
Self-similar solution of the subsonic radiative heat equations using a binary equation of state
Heizler, Shay I; Malka, Elad
2016-01-01
Radiative subsonic heat waves, and their radiation driven shock waves, are important hydro-radiative phenomena. The high pressure, causes hot matter in the rear part of the heat wave to ablate backwards. At the front of the heat wave, this ablation pressure generates a shock wave which propagates ahead of the heat front. Although no self-similar solution of both the ablation and shock regions exists, a solution for the full problem was found in a previous work. Here, we use this model in order to investigate the effect of the equation of state (EOS) on the propagation of radiation driven shocks. We find that using a single ideal gas EOS for both regions, as used in previous works, yields large errors in describing the shock wave. We use the fact that the solution is composed of two different self-similar solutions, one for the ablation region and one for the shock, and apply two ideal gas EOS (binary-EOS), one for each region, by fitting a detailed tabulated EOS to power laws at different regimes. By comparin...
A Mach-Zender Holographic Microscope for Quantifying Bacterial Motility
Niraula, B.; Nadeau, J. L.; Serabyn, E.; Wallace, J. K.; Liewer, K.; Kuhn, J.; Graff, E.; Lindensmith, C.
2014-12-01
New microscopic techniques have revolutionized cell biology over the past two decades. However, there are still biological processes whose details elude us, especially those involving motility: e.g. feeding behavior of microorganisms in the ocean, or migration of cancer cells to form metastases. Imaging prokaryotes, which range in size from several hundred nm to a few microns, is especially challenging. An emerging technique to address these issues is Digital Holographic Microscopy (DHM). DHM is an imaging technique that uses the interference of light to record and reproduce three-dimensional magnified images of objects. This approach has several advantages over ordinary brightfield microscopy for fieldwork: a larger depth of field, hands-off operation, robustness regarding environmental conditions, and large sampling volumes with quantitative 3D records of motility behavior. Despite these promising features, real-time DHM was thought to be impractical for technological and computational reasons until recently, and there has so far been very limited application of DHM to biology. Most existing instruments are limited in performance by their particular (e.g. in-line, lens-less, phase-shifting) approach to holography. These limitations can be mitigated with an off-axis dual-path configuration. Here we describe the design and implementation of a design for a Mach-Zehnder-type holographic microscope with diffraction-limited lateral resolution, with intended applications in environmental microbiology. We have achieved sub-micron resolution and three-dimensional tracking of prokaryotic and eukaryotic test strains designed to represent different modes and speeds of microbial motility. Prokaryotes are Escherichia coli, Vibrio alginolyticus, and Bacillus subtilis. Each shows a characteristic motility pattern, as we illustrate in holographic videos in sample chambers 0.6 mm in depth. The ability to establish gradients of attractants with bacterial taxis towards the
Petersen, T Kyle
2015-01-01
This text presents the Eulerian numbers in the context of modern enumerative, algebraic, and geometric combinatorics. The book first studies Eulerian numbers from a purely combinatorial point of view, then embarks on a tour of how these numbers arise in the study of hyperplane arrangements, polytopes, and simplicial complexes. Some topics include a thorough discussion of gamma-nonnegativity and real-rootedness for Eulerian polynomials, as well as the weak order and the shard intersection order of the symmetric group. The book also includes a parallel story of Catalan combinatorics, wherein the Eulerian numbers are replaced with Narayana numbers. Again there is a progression from combinatorics to geometry, including discussion of the associahedron and the lattice of noncrossing partitions. The final chapters discuss how both the Eulerian and Narayana numbers have analogues in any finite Coxeter group, with many of the same enumerative and geometric properties. There are four supplemental chapters throughout, ...
Hydrogen film cooling with incident and swept-shock interactions in a Mach 6.4 nitrogen free stream
Olsen, George C.; Nowak, Robert J.
1995-01-01
The effectiveness of slot film cooling of a flat plate in a Mach 6.4 flow with and without incident and swept oblique shock interactions was experimentally investigated. Hydrogen was the primary coolant gas, although some tests were conducted using helium as the coolant. Tests were conducted in the Calspan 48-Inch Shock Tunnel with a nitrogen flow field to preclude combustion of the hydrogen coolant gas. A two-dimensional highly instrumented model developed in a previous test series was used. Parameters investigated included coolant mass flow rate, coolant gas, local free-stream Reynolds number, incident oblique shock strength, and a swept oblique shock. Both gases were highly effective coolants in undisturbed flow; however, both incident and swept shocks degraded that effectiveness.
Directory of Open Access Journals (Sweden)
Tiago Cavalcanti Rolim
2011-05-01
Full Text Available This paper presents a research in the development of the 14-X hypersonic airspace vehicle at Institute for Advanced Studies (IEAv from Department of Science and Aerospace Technology (DCTA of the Brazilian Air Force (FAB. The 14-X project objective is to develop a higher efficient satellite launch alternative, using a Supersonic Combustion Ramjet (SCRAMJET engine and waverider aerodynamics. For this development, the waverider technology is under investigation in Prof. Henry T. Nagamatsu Aerothermodynamics and Hypersonics Laboratory (LHTN, in IEAv/DCTA. The investigation has been conducted through ground test campaigns in Hypersonic Shock Tunnel T3. The 14-X Waverider Vehicle characteristic was verified in shock tunnel T3 where surface static pressures and pitot pressure for Mach number 10 were measured and, using Schlieren photographs Diagnostic Method, it was possible to identify a leading-edge attached shock wave in 14-X lower surface.
MHz-rate nitric oxide planar laser-induced fluorescence imaging in a Mach 10 hypersonic wind tunnel.
Jiang, Naibo; Webster, Matthew; Lempert, Walter R; Miller, Joseph D; Meyer, Terrence R; Ivey, Christopher B; Danehy, Paul M
2011-02-01
Nitric oxide planar laser-induced fluorescence (NO PLIF) imaging at repetition rates as high as 1 MHz is demonstrated in the NASA Langley 31 in. Mach 10 hypersonic wind tunnel. Approximately 200 time-correlated image sequences of between 10 and 20 individual frames were obtained over eight days of wind tunnel testing spanning two entries in March and September of 2009. The image sequences presented were obtained from the boundary layer of a 20° flat plate model, in which transition was induced using a variety of different shaped protuberances, including a cylinder and a triangle. The high-speed image sequences captured a variety of laminar and transitional flow phenomena, ranging from mostly laminar flow, typically at a lower Reynolds number and/or in the near wall region of the model, to highly transitional flow in which the temporal evolution and progression of characteristic streak instabilities and/or corkscrew-shaped vortices could be clearly identified.
Nielsen, Jack N; Kaattari, George E; Anastasio, Robert F
1953-01-01
A method is presented for calculating the lift and pitching-moment characteristics of circular cylindrical bodies in combination with triangular, rectangular, or trapezoidal wings or tails through the subsonic, transonic, and supersonic speed ranges. The method covers unbanked wings, sweptback leading edges or sweptforward trailing edges, low angles of attack, and the effects of wing and tail incidence. The wing-body interference is handled by the method presented in NACA RM's A51J04 and A52B06, and the wing-tail interference is treated by assuming one completely rolled-up vortex per wing panel and evaluating the tail load by strip theory. A computing table and set of design charts are presented which reduce the calculations to routine operations. Comparison is made between the estimated and experimental characteristics for a large number of wing-body and wing-body-tail combinations. Generally speaking, the lifts were estimated to within plus-or-minus 10 percent and the centers of pressure were estimated to within plus-or-minus 0.02 of the body length. The effect of wing deflection on wing-tail interference at supersonic speeds was not correctly predicted for triangular wings with supersonic leading edges.
Numerical Model of a Variable-Combined-Cycle Engine for Dual Subsonic and Supersonic Cruise
Directory of Open Access Journals (Sweden)
Victor Fernandez-Villace
2013-02-01
Full Text Available Efficient high speed propulsion requires exploiting the cooling capability of the cryogenic fuel in the propulsion cycle. This paper presents the numerical model of a combined cycle engine while in air turbo-rocket configuration. Specific models of the various heat exchanger modules and the turbomachinery elements were developed to represent the physical behavior at off-design operation. The dynamic nature of the model allows the introduction of the engine control logic that limits the operation of certain subcomponents and extends the overall engine operational envelope. The specific impulse and uninstalled thrust are detailed while flying a determined trajectory between Mach 2.5 and 5 for varying throttling levels throughout the operational envelope.
Positioning approach based on Mach-Zehnder fiber sensors and a DSP processor
Wan, Xiong; Du, Tingting; Zhang, Zhimin; Zhang, Huaming; Wang, Peng
2013-12-01
A positioning system based on Mach-Zehnder optical fiber interferometer is proposed, which can sense vibration information along the circumference of the fiber sensor and hence be applied to positioning invasions as a safe-guard system in residence communities. A cross-correlation algorithm fulfilled with a DSP processor has been adopted to calculate the time difference of two channels of the Mach-Zehnder optical fiber interferometer. A signal identification algorithm is proposed to decrease the workload of the DSP when no vibration occurs. An experiment with 11.28 kilometers sensing fiber has been carried out, whose results show the Mach-Zehnder positioning system identifies the position of vibration instantaneously and has a 44 meters positioning error within the total sensing distance.
Concept development of a Mach 3.0 high-speed civil transport
Robins, A. Warner; Dollyhigh, Samuel M.; Beissner, Fred L., Jr.; Geiselhart, Karl; Martin, Glenn L.; Shields, E. W.; Swanson, E. E.; Coen, Peter G.; Morris, Shelby J., Jr.
1988-01-01
A baseline concept for a Mach 3.0 high-speed civil transport concept was developed as part of a national program with the goal that concepts and technologies be developed which will enable an effective long-range high-speed civil transport system. The Mach 3.0 concept reported represents an aggressive application of advanced technology to achieve the design goals. The level of technology is generally considered to be that which could have a demonstrated availability date of 1995 to 2000. The results indicate that aircraft are technically feasible that could carry 250 passengers at Mach 3.0 cruise for a 6500 nautical mile range at a size, weight and performance level that allows it to fit into the existing world airport structure. The details of the configuration development, aerodynamic design, propulsion system design and integration, mass properties, mission performance, and sizing are presented.
Bizzarri, A.; Dunham, Eric M.; Spudich, P.
2010-01-01
We study how heterogeneous rupture propagation affects the coherence of shear and Rayleigh Mach wavefronts radiated by supershear earthquakes. We address this question using numerical simulations of ruptures on a planar, vertical strike-slip fault embedded in a three-dimensional, homogeneous, linear elastic half-space. Ruptures propagate spontaneously in accordance with a linear slip-weakening friction law through both homogeneous and heterogeneous initial shear stress fields. In the 3-D homogeneous case, rupture fronts are curved owing to interactions with the free surface and the finite fault width; however, this curvature does not greatly diminish the coherence of Mach fronts relative to cases in which the rupture front is constrained to be straight, as studied by Dunham and Bhat (2008a). Introducing heterogeneity in the initial shear stress distribution causes ruptures to propagate at speeds that locally fluctuate above and below the shear wave speed. Calculations of the Fourier amplitude spectra (FAS) of ground velocity time histories corroborate the kinematic results of Bizzarri and Spudich (2008a): (1) The ground motion of a supershear rupture is richer in high frequency with respect to a subshear one. (2) When a Mach pulse is present, its high frequency content overwhelms that arising from stress heterogeneity. Present numerical experiments indicate that a Mach pulse causes approximately an ω−1.7 high frequency falloff in the FAS of ground displacement. Moreover, within the context of the employed representation of heterogeneities and over the range of parameter space that is accessible with current computational resources, our simulations suggest that while heterogeneities reduce peak ground velocity and diminish the coherence of the Mach fronts, ground motion at stations experiencing Mach pulses should be richer in high frequencies compared to stations without Mach pulses. In contrast to the foregoing theoretical results, we find no average elevation
Institute of Scientific and Technical Information of China (English)
无
2004-01-01
THE last digit of my home phone number in Beijing is 4. “So what?” European readers might ask.This was my attitude when I first lived in China; I couldn't understand why Chinese friends were so shocked at my indifference to the number 4. But China brings new discoveries every day, and I have since seen the light. I know now that Chinese people have their own ways of preserving their well being, and that they see avoiding the number 4 as a good way to stay safe.
Andrews, George E
1994-01-01
Although mathematics majors are usually conversant with number theory by the time they have completed a course in abstract algebra, other undergraduates, especially those in education and the liberal arts, often need a more basic introduction to the topic.In this book the author solves the problem of maintaining the interest of students at both levels by offering a combinatorial approach to elementary number theory. In studying number theory from such a perspective, mathematics majors are spared repetition and provided with new insights, while other students benefit from the consequent simpl
CFD Simulation and Experimental Study of Winglets at Low Subsonic Flow
Directory of Open Access Journals (Sweden)
Sanjay Kumar Sardiwal
2014-05-01
Full Text Available A winglet is a device attached at the wingtip, used to improve aircraft efficiency by lowering the induced drag caused by wingtip vortices. It is a vertical or angled extension at the tips of each wing. Winglets work by increasing the effective aspect ratio of a wing without adding greatly to the structural stress and hence necessary weight of the wing structure. This paper describes a CFD 3-dimensional winglets analysis that was performed on a rectangular wing of NACA653218 cross sectional airfoil. The wing is of 660 mm span and 121 mm chord and was analyzed for two shape configurations, semicircle and elliptical. The objectives of the analysis were to compare the aerodynamic characteristics of the two winglet configurations and to investigate the performance of the two winglets shape simulated at selected cant angle of 0, 45 and 60 degrees. The computational simulation was carried out by FLUENT 6.2 solver using Finite Volume Approach. The simulation was done at low subsonic flow and at various angles of attack using Spalart-Allmaras couple implicit solver. A comparison of aerodynamics characteristics of lift coefficient CL , drag coefficient CD and lift to drag ratio, L/D was made and it was found that the addition of the elliptical and semi circular winglet gave a larger lift curve slope and higher Lift-to-Drag Ratio in comparison to the baseline wing alone. Elliptical winglet with 45 degree cant angle was the best overall design giving about 8 percent increase in lift curve slope and the best Lift-to-Drag Ratio.
Mach-wave coherence in 3D media with random heterogeneities
Vyas, Jagdish C.; Mai, P. Martin; Galis, Martin; Dunham, Eric M.; Imperatori, Walter
2016-04-01
We investigate Mach-waves coherence for complex super-shear ruptures embedded in 3D random media that lead to seismic scattering. We simulate Mach-wave using kinematic earthquake sources that include fault-regions over which the rupture propagates at super-shear speed. The local slip rate is modeled with the regularized Yoffe function. The medium heterogeneities are characterized by Von Karman correlation function. We consider various realizations of 3D random media from combinations of different values of correlation length (0.5 km, 2 km, 5 km), standard deviation (5%, 10%, 15%) and Hurst exponent (0.2). Simulations in a homogeneous medium serve as a reference case. The ground-motion simulations (maximum resolved frequency of 5 Hz) are conducted by solving the elasto-dynamic equations of motions using a generalized finite-difference method, assuming a vertical strike-slip fault. The seismic wavefield is sampled at numerous locations within the Mach-cone region to study the properties and evolution of the Mach-waves in scattering media. We find that the medium scattering from random heterogeneities significantly diminishes the coherence of Mach-wave in terms of both amplitude and frequencies. We observe that Mach-waves are considerably scattered at distances RJB > 20 km (and beyond) for random media with standard deviation 10%. The scattering efficiency of the medium for small Hurst exponents (H seismic scattering. We suggest that if an earthquake is recorded within 10-15 km fault perpendicular distance and has high PGA, then inversion should be carried out by allowing rupture speed variations from sub-Rayleigh to super-shear.
Barnes, John
2016-01-01
In this intriguing book, John Barnes takes us on a journey through aspects of numbers much as he took us on a geometrical journey in Gems of Geometry. Similarly originating from a series of lectures for adult students at Reading and Oxford University, this book touches a variety of amusing and fascinating topics regarding numbers and their uses both ancient and modern. The author intrigues and challenges his audience with both fundamental number topics such as prime numbers and cryptography, and themes of daily needs and pleasures such as counting one's assets, keeping track of time, and enjoying music. Puzzles and exercises at the end of each lecture offer additional inspiration, and numerous illustrations accompany the reader. Furthermore, a number of appendices provides in-depth insights into diverse topics such as Pascal’s triangle, the Rubik cube, Mersenne’s curious keyboards, and many others. A theme running through is the thought of what is our favourite number. Written in an engaging and witty sty...
Mach-Zehnder Modulator Performance on the NIF South Pole Bang Time Diagnostic
Energy Technology Data Exchange (ETDEWEB)
Beeman, B.; MacPhee, A. G.; Kimbrough, J. R.; Chow, R.; Carpenter, A.; Bond, E.; Zayas-Rivera, Z.; Bell, P.; Celeste, J.; Clancy, T.; Miller, E. K.; Edgell, D.; Donaldson, W. R.
2013-09-01
We present performance data for Mach-Zehnder optical modulators fielded on the National Ignition Facility (NIF) as a potential signal path upgrade for the South Pole Bang Time diagnostic. A single channel demonstration system has been deployed utilizing two modulators operating in a 90-degree In phase and Quadrature (I/Q) configuration. X-ray target emission signals are split and fed into two recording systems: a reference CRT based oscilloscope, Greenfield FTD10000, and the dual Mach-Zehnder system. Results of X-ray implosion time (bang time) determination from these two recording systems are compared and presented.
Hydrodynamic Flow and Jet Induced Mach Shocks at RHIC and LHC
Stöcker, H; Rau, P; Betz, Barbara; Rau, Philip; St\\"ocker, Horst
2007-01-01
We discuss the present collective flow signals for the phase transition to quark-gluon plasma (QGP) and the collective flow as a barometer for the equation of state (EoS). A study of Mach shocks induced by fast partonic jets propagating through the QGP is given. We predict a significant deformation of Mach shocks in central Au+Au collisions at RHIC and LHC energies as compared to the case of jet propagation in a static medium. Results of a hydrodynamical study of jet energy loss are presented.
Analysis of compressible light dynamic stall flow at transitional Reynolds numbers
DEFF Research Database (Denmark)
Dyken, R.D. Van; Ekaterinaris, John A.; Chandrasekhara, M.S.;
1996-01-01
Numerical and experimental results of steady and light dynamic stall flow over an oscillating NACA 0012 airfoil at a freestream Mach number of 0.3 and Reynolds number of 0.54 x 10(6) are compared, The experimental observation that dynamic stall is induced from the bursting of a laminar separation...
1947-02-21
appendix D. Bra» coefficient of swot -tack wlnfl at Mach number of 1.0. - Tho solution of the equations for c. fiven in appendix 3 shown tliat, for...gm’’ A’U " "^ ’ I*’ ’ «’I a»-2 - (a» - 3m A’ • A»3) Cosh-l 5^ " A’k + ". jam’fm’ - A’)I A , -1 an’ - A’ A’ . s\\ + cosh
Energy Technology Data Exchange (ETDEWEB)
Starik, A.M.; Lebedev, A.B.; Titova, N.S. [Central Inst. of Aviation Motors, Moscow (Russian Federation)
1997-12-31
On the basic of quasi one dimensional mixing model the numerical analysis of nonequilibrium chemical processes in the plume of subsonic and hypersonic aircraft is presented. It was found that species HNO, HNO{sub 3}, HNO{sub 4}, N{sub 2}O{sub 5}, ClO{sub 2}, CH{sub 3}NO{sub 2} could be formed as a result of nonequilibrium processes in the plume and their concentrations can essentially exceed both background values in free stream of atmosphere and their values at the nozzle exit plane. (author) 10 refs.
Hague, D. S.; Woodbury, N. W.
1975-01-01
The Mars system is a tool for rapid prediction of aircraft or engine characteristics based on correlation-regression analysis of past designs stored in the data bases. An example of output obtained from the MARS system, which involves derivation of an expression for gross weight of subsonic transport aircraft in terms of nine independent variables is given. The need is illustrated for careful selection of correlation variables and for continual review of the resulting estimation equations. For Vol. 1, see N76-10089.
Aero-acoustic simulation of a subsonic hot jet; Simulation aeroacoustique d'un jet chaud subsonique
Energy Technology Data Exchange (ETDEWEB)
Biancherin, A.; Rahier, G.; Prieur, J.; Vuillot, F.; Lupoglazoff, N.
2002-07-01
This paper presents a numerical simulation of subsonic a hot jet (M 0,7) and its acoustic analysis. The MSD code of the ONERA is used to resolve the Navier-Stokes equations. A detailed study, parametric and theoretical is realized to analyze the influence of the formulation, the position, the part and the nature of the control surface on the acoustic calculation results. The acoustic predictions in far field are compared to measures realized by the ONERA in the anechoic CEPRA 19 wind tunnel. (A.L.B.)
Murty, M Ram
2014-01-01
This book provides an introduction to the topic of transcendental numbers for upper-level undergraduate and graduate students. The text is constructed to support a full course on the subject, including descriptions of both relevant theorems and their applications. While the first part of the book focuses on introducing key concepts, the second part presents more complex material, including applications of Baker’s theorem, Schanuel’s conjecture, and Schneider’s theorem. These later chapters may be of interest to researchers interested in examining the relationship between transcendence and L-functions. Readers of this text should possess basic knowledge of complex analysis and elementary algebraic number theory.
Guzzardi, Luca
2014-01-01
This paper discusses Ernst Mach's interpretation of the principle of energy conservation (EC) in the context of the development of energy concepts and ideas about causality in nineteenth-century physics and theory of science. In doing this, it focuses on the close relationship between causality, energy conservation and space in Mach's…
Thelin, John R.
2013-01-01
What topic would you choose if you had the luxury of writing forever? In this article, John Thelin provides his response: He would opt to write about the history of higher education in a way that relies on quantitative data. "Numbers, please!" is his research request in taking on a longitudinal study of colleges and universities over…
Thelin, John R.
2013-01-01
What topic would you choose if you had the luxury of writing forever? In this article, John Thelin provides his response: He would opt to write about the history of higher education in a way that relies on quantitative data. "Numbers, please!" is his research request in taking on a longitudinal study of colleges and universities over…
Galbraith, Mary J.
1974-01-01
Examination of models for representing integers demonstrates that formal operational thought is required for establishing the operations on integers. Advocated is the use of many models for introducing negative numbers but, apart from addition, it is recommended that operations on integers be delayed until the formal operations stage. (JP)
Experimental investigation of liquid jet injection into Mach 6 hypersonic crossflow
Beloki Perurena, J.; Asma, C.O.; Theunissen, R.; Chazot, O.
2008-01-01
The injection of a liquid jet into a crossing Mach 6 air flow is investigated. Experiments were conducted on a sharp leading edge flat plate with flush mounted injectors. Water jets were introduced through different nozzle shapes at relevant jet-to-air momentum-flux ratios. Sufficient temporal
Event-based simulation of single-photon beam splitters and Mach-Zehnder interferometers
De Raedt, H; De Raedt, K; Michielsen, K
2005-01-01
We demonstrate that networks of locally connected processing units with a primitive learning capability exhibit a behavior that is usually only attributed to quantum systems. We describe networks that simulate single-photon beam splitter and Mach-Zehnder interferometer experiments on a causal, event
Kashif, Muhammad; Bakar, A. Ashrif A.; Hashim, Fazida Hanim
2016-12-01
Surface Plasmon Resonance (SPR) based on Mach-Zehnder interferometer (MZI) is a very accurate tool for the detection and analysis of molecular interactions. The performance of the proposed SPR phase sensor is dependent upon multiple performance parameters that include sensitivity, repeatability, drift and the induction speed of fluid into the flow cell. The SPR Mach-Zehnder interferometer is tested for different glycerin-water concentrations to check its performance based on the different parameters. This paper highlights the enhancement of the performance of SPR phase technique based on MZI that is influenced by different parameters, measured using glycerin solutions. These four performance parameters can affect the performance of SPR based on MZI and have a particular impact on the sensor output. It also provides us information about suitable working conditions for the SPR Mach-Zehnder interferometer sensor. The experiment data shows that the sensor's sensitivity is high for small concentrations of glycerin-water mixtures. Also, any change in drift as well as in induction speed of fluid can affect the performance of SPR Mach-Zehnder interferometer. The sensitivity of SPR phase sensor is high as it can measure glycerin concentration as low as 0.05%.
Experimental investigation of liquid jet injection into Mach 6 hypersonic crossflow
Beloki Perurena, J.; Asma, C.O.; Theunissen, R.; Chazot, O.
2008-01-01
The injection of a liquid jet into a crossing Mach 6 air flow is investigated. Experiments were conducted on a sharp leading edge flat plate with flush mounted injectors. Water jets were introduced through different nozzle shapes at relevant jet-to-air momentum-flux ratios. Sufficient temporal resol
All optical wavelength conversion by SOA's in a Mach-Zehnder configuration
DEFF Research Database (Denmark)
Durhuus, T.; Jørgensen, C.; Mikkelsen, Benny
1994-01-01
Penalty free wavelength conversion is demonstrated at 2.5 Gbit/s over a wavelength span of 12 nm by the use of semiconductor optical amplifier (SOA)'s in a Mach-Zehnder configuration. An increase in the extinction ratio is measured for the converted signal compared to the input signal implying si...... signal regeneration as well as wavelength conversion...
A versatile all-optical modulator based on nonlinear Mach-Zehnder interferometers
Krijnen, G.J.M.; Villeneuve, A.; Stegeman, G.I.; Lambeck, P.V.; Hoekstra, H.J.W.M.
1994-01-01
A device based on a Nonlinear Mach-Zehnder interferometer (NMI) which exploits cross-phase modulation of two co-propagating modes in bimodal branches has been described in this paper. The advantage of this device is that it becomes polarisation independent while keeping phase insensitive by using di
Iseke, Judy
2009-01-01
Misrepresentation, appropriation, and denigrating Indigenous knowledge is still common practice in educational institutions despite efforts of critical educators to challenge these practices. One such challenge was to papier mache totem poles in an education institution's library in a faculty of education that houses teacher education programs. A…
Incorporation of Mach's Principle in ΛFRW Cosmology that depends dynamically of the distance range
Falcon, N.
2017-07-01
It postulates a FRW cosmological model without dark matter and cosmological term depending the distance scale, in addition to incorporate Mach's principle, is consistent with the observations: rotation curves of the galaxies, the nucleosynthesis primordial and CMB. The dynamic expression of Cosmological term is an alternative to non-baryonic dark matter and a reinterpretation of dark energy.
The realization of an integrated Mach-Zehnder waveguide immunosensor in silicon technology
Schipper, E.F.; Brugman, A.M.; Lechuga, L.M.; Kooyman, R.P.H.; Greve, J.; Dominguez, C.
1997-01-01
We describe the realization of a symmetric integrated channel waveguide Mach-Zehnder sensor which uses the evanescent field to detect small refractive-index changes (¿nmin ¿ 1 × 10¿4) near the guiding-layer surface. This guiding layer consists of ridge structures with a height of 3 nm and a width of
On the Use of a Virtual Mach-Zehnder Interferometer in the Teaching of Quantum Mechanics
Pereira, Alexsandro; Ostermann, Fernanda; Cavalcanti, Claudio
2009-01-01
For many students, the conceptual learning of quantum mechanics can be rather painful owing to the counter-intuitive nature of quantum phenomena. In order to enhance students' understanding of the odd behaviour of photons and electrons, we introduce a computational simulation of the Mach-Zehnder interferometer, developed by our research group. An…
On the Use of a Virtual Mach-Zehnder Interferometer in the Teaching of Quantum Mechanics
Pereira, Alexsandro; Ostermann, Fernanda; Cavalcanti, Claudio
2009-01-01
For many students, the conceptual learning of quantum mechanics can be rather painful owing to the counter-intuitive nature of quantum phenomena. In order to enhance students' understanding of the odd behaviour of photons and electrons, we introduce a computational simulation of the Mach-Zehnder interferometer, developed by our research group. An…
The Contribution of Ernst Mach to Embodied Cognition and Mathematics Education
Zudini, Verena; Zuccheri, Luciana
2016-01-01
A study of the interactions between mathematics and cognitive science, carried out within a historical perspective, is important for a better understanding of mathematics education in the present. This is evident when analysing the contribution made by the epistemological theories of Ernst Mach. On the basis of such theories, a didactic method was…
Development of a Microphone Phased Array Capability for the Langley 14- by 22-Foot Subsonic Tunnel
Humphreys, William M.; Brooks, Thomas F.; Bahr, Christopher J.; Spalt, Taylor B.; Bartram, Scott M.; Culliton, William G.; Becker, Lawrence E.
2014-01-01
A new aeroacoustic measurement capability has been developed for use in open-jet testing in the NASA Langley 14- by 22-Foot Subsonic Tunnel (14x22 tunnel). A suite of instruments has been developed to characterize noise source strengths, locations, and directivity for both semi-span and full-span test articles in the facility. The primary instrument of the suite is a fully traversable microphone phased array for identification of noise source locations and strengths on models. The array can be mounted in the ceiling or on either side of the facility test section to accommodate various test article configurations. Complementing the phased array is an ensemble of streamwise traversing microphones that can be placed around the test section at defined locations to conduct noise source directivity studies along both flyover and sideline axes. A customized data acquisition system has been developed for the instrumentation suite that allows for command and control of all aspects of the array and microphone hardware, and is coupled with a comprehensive data reduction system to generate information in near real time. This information includes such items as time histories and spectral data for individual microphones and groups of microphones, contour presentations of noise source locations and strengths, and hemispherical directivity data. The data acquisition system integrates with the 14x22 tunnel data system to allow real time capture of facility parameters during acquisition of microphone data. The design of the phased array system has been vetted via a theoretical performance analysis based on conventional monopole beamforming and DAMAS deconvolution. The performance analysis provides the ability to compute figures of merit for the array as well as characterize factors such as beamwidths, sidelobe levels, and source discrimination for the types of noise sources anticipated in the 14x22 tunnel. The full paper will summarize in detail the design of the instrumentation
Plasma Sensor for High Bandwidth Mass-Flow Measurements at High Mach Numbers with RF Link Project
National Aeronautics and Space Administration — The proposal is aimed at the development of a miniature high bandwidth (1 MHz class) plasma sensor for flow measurements at high enthalpies. This device uses a...
Vortex sound in the presence of a low Mach number flow across a drum-like silencer.
Tang, S K
2011-05-01
The sound generated by a vortex propagating across a two-dimensional duct section with flexible walls (membranes) in an infinitely long rigid duct conveying a flow is investigated numerically using the matched asymptotic expansion technique and the potential theory. The effects of the initial vortex position, the mechanical properties of the flexible walls, and the mean flow on the sound generation are examined in detail. Results show that the presence of a vortex inside a uniform mean flow can strengthen or attenuate the sound generation, depending on the phase of the membrane vibration when the vortex starts vigorous interaction with the membranes and the strength of the mean flow. The results tend to imply that there is a higher chance of sound amplification when a vortex stream is moving closer to the lighter membrane under a relatively strong mean flow or when the mean flow is weak. The chances of sound amplification or attenuation are equal otherwise.
Experimental study of nonlinear processes in a swept-wing boundary layer at the mach number M=2
Yermolaev, Yu. G.; Kosinov, A. D.; Semionov, N. V.
2014-09-01
Results of experiments aimed at studying the linear and nonlinear stages of the development of natural disturbances in the boundary layer on a swept wing at supersonic velocities are presented. The experiments are performed on a swept wing model with a lens-shaped airfoil, leading-edge sweep angle of 45°, and relative thickness of 3%. The disturbances in the flow are recorded by a constant-temperature hot-wire anemometer. For determining the nonlinear interaction of disturbances, the kurtosis and skewness are estimated for experimentally obtained distributions of the oscillating signal over the streamwise coordinate or along the normal to the surface. The disturbances are found to increase in the frequency range from 8 to 35 kHz in the region of their linear development, whereas enhancement of high-frequency disturbances is observed in the region of their nonlinear evolution. It is demonstrated that the growth of disturbances in the high-frequency spectral range ( f > 35 kHz) is caused by the secondary instability.
Number names and number understanding
DEFF Research Database (Denmark)
Ejersbo, Lisser Rye; Misfeldt, Morten
2014-01-01
This paper concerns the results from the first year of a three-year research project involving the relationship between Danish number names and their corresponding digits in the canonical base 10 system. The project aims to develop a system to help the students’ understanding of the base 10 syste...
Kawai, Ronald T. (Compiler)
2011-01-01
This investigation was conducted to: (1) Develop a hybrid wing body subsonic transport configuration with noise prediction methods to meet the circa 2007 NASA Subsonic Fixed Wing (SFW) N+2 noise goal of -52 dB cum relative to FAR 36 Stage 3 (-42 dB cum re: Stage 4) while achieving a -25% fuel burned compared to current transports (re :B737/B767); (2) Develop improved noise prediction methods for ANOPP2 for use in predicting FAR 36 noise; (3) Design and fabricate a wind tunnel model for testing in the LaRC 14 x 22 ft low speed wind tunnel to validate noise predictions and determine low speed aero characteristics for an efficient low noise Hybrid Wing Body configuration. A medium wide body cargo freighter was selected to represent a logical need for an initial operational capability in the 2020 time frame. The Efficient Low Noise Hybrid Wing Body (ELNHWB) configuration N2A-EXTE was evolved meeting the circa 2007 NRA N+2 fuel burn and noise goals. The noise estimates were made using improvements in jet noise shielding and noise shielding prediction methods developed by UC Irvine and MIT. From this the Quiet Ultra Integrated Efficient Test Research Aircraft #1 (QUIET-R1) 5.8% wind tunnel model was designed and fabricated.
Cooper, B. P., Jr.
1979-01-01
A model for the boundary layer at the exit plane of a rocket nozzle was developed which, unlike most previous models, includes the subsonic sublayer. The equations for the flow near the nozzle exit plane are presented and the method by which the subsonic sublayer transitions to supersonic flow in the plume is described. The resulting model describes the entire boundary layer and can be used to provide a startline for method-of-characteristics calculations of plume flowfields. The model was incorporated into a method of characteristics computer program and comparisons of computed results to experimental data show good agreement. The data used in the comparisons were obtained in tests in which mass fluxes from a 22.2-N (5 lbf) thrust engine were measured at angles off the nozzle centerline of up to 150 deg. Additional comparisons were made with data obtained during tests of a 0.89-N (0.2 lbr) monopropellant thruster and from the OH-64 space shuttle heating tests. The agreement with the data indicates that the model can be used for calculating plume backflow properties.