Improving Euler computations at low Mach numbers
Koren, B.; Leer, van B.; Deconinck, H.; Koren, B.
1997-01-01
The paper consists of two parts, both dealing with conditioning techniques for lowMach-number Euler-flow computations, in which a multigrid technique is applied. In the first part, for subsonic flows and upwind-discretized, linearized 1-D Euler equations, the smoothing behavior of
Improving Euler computations at low Mach numbers
Koren, B.
1996-01-01
This paper consists of two parts, both dealing with conditioning techniques for low-Mach-number Euler-flow computations, in which a multigrid technique is applied. In the first part, for subsonic flows and upwind-discretized linearized 1-D Euler equations, the smoothing behavior of
Aeroacoustic computation of low Mach number flow
Energy Technology Data Exchange (ETDEWEB)
Dahl, K.S.
1996-12-01
This thesis explores the possibilities of applying a recently developed numerical technique to predict aerodynamically generated sound from wind turbines. 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 field 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 characteristic based condition. The technique is applied to the problems of the sound generation of a pulsating sphere, which is a monopole; a co-rotating vortex pair, which is a quadrupole, and the viscous flow over a circular cylinder, which is a dipole. The governing equations are written and solved for spherical, Cartesian, and cylindrical coordinates, respectively, thus, representing three common orthogonal coordinate systems. Numerical results agree very well with the analytical solutions for the problems of the pulsating sphere and the co-rotating vortex pair. Numerical results for the viscous flow over a cylinder are presented and evaluated qualitatively. The technique has potential for applications to airfoil flows as they are on a wind turbine blade, as well as for other low Mach number flows. (au) 2 tabs., 33 ills., 48 refs.
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
Physical and numerical modelling of low mach number compressible flows
International Nuclear Information System (INIS)
Paillerre, H.; Clerc, S.; Dabbene, F.; Cueto, O.
1999-01-01
This article reviews various physical models that may be used to describe compressible flow at low Mach numbers, as well as the numerical methods developed at DRN to discretize the different systems of equations. A selection of thermal-hydraulic applications illustrate the need to take into account compressibility and multidimensional effects as well as variable flow properties. (authors)
Very high Mach number shocks - Theory. [in space plasmas
Quest, Kevin B.
1986-01-01
The theory and simulation of collisionless perpendicular supercritical shock structure is reviewed, with major emphasis on recent research results. The primary tool of investigation is the hybrid simulation method, in which the Newtonian orbits of a large number of ion macroparticles are followed numerically, and in which the electrons are treated as a charge neutralizing fluid. The principal results include the following: (1) electron resistivity is not required to explain the observed quasi-stationarity of the earth's bow shock, (2) the structure of the perpendicular shock at very high Mach numbers depends sensitively on the upstream value of beta (the ratio of the thermal to magnetic pressure) and electron resistivity, (3) two-dimensional turbulence will become increasingly important as the Mach number is increased, and (4) nonadiabatic bulk electron heating will result when a thermal electron cannot complete a gyrorbit while transiting the shock.
Low-Mach number simulations of transcritical flows
Lapenna, Pasquale E.
2018-01-08
A numerical framework for the direct simulation, in the low-Mach number limit, of reacting and non-reacting transcritical flows is presented. The key feature are an efficient and detailed representation of the real fluid properties and an high-order spatial discretization. The latter is of fundamental importance to correctly resolve the largely non-linear behavior of the fluid in the proximity of the pseudo-boiling. The validity of the low-Mach number assumptions is assessed for a previously developed non-reacting DNS database of transcritical and supercritical mixing. Fully resolved DNS data employing high-fidelity thermodynamical models are also used to investigate the spectral characteristic as well as the differences between transcritical and supercritical jets.
Low Mach number asymptotics for reacting compressible fluid flows
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Petzeltová, Hana
2010-01-01
Roč. 26, č. 2 (2010), s. 455-480 ISSN 1078-0947 R&D Projects: GA ČR GA201/05/0164 Institutional research plan: CEZ:AV0Z10190503 Keywords : low Mach number * Navier-Stokes-Fourier system * reacting fluids Subject RIV: BA - General Mathematics Impact factor: 0.986, year: 2010 http://www.aimsciences.org/journals/displayArticles.jsp?paperID=4660
Low Mach number limits of compressible rotating fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2012-01-01
Roč. 14, č. 1 (2012), s. 61-78 ISSN 1422-6928 R&D Projects: GA ČR GA201/08/0315 Institutional research plan: CEZ:AV0Z10190503 Keywords : low Mach number limit * rotating fluid * compressible fluid Subject RIV: BA - General Mathematics Impact factor: 1.415, year: 2012 http://www.springerlink.com/content/635r1116j40t6428/
Numerical simulation of low Mach number reacting flows
International Nuclear Information System (INIS)
Bell, J B; Aspden, A J; Day, M S; Lijewski, M J
2007-01-01
Using examples from active research areas in combustion and astrophysics, we demonstrate a computationally efficient numerical approach for simulating multiscale low Mach number reacting flows. The method enables simulations that incorporate an unprecedented range of temporal and spatial scales, while at the same time, allows an extremely high degree of reaction fidelity. Sample applications demonstrate the efficiency of the approach with respect to a traditional time-explicit integration method, and the utility of the methodology for studying the interaction of turbulence with terrestrial and astrophysical flame structures
Mach Number effects on turbulent superstructures in wall bounded flows
Kaehler, Christian J.; Bross, Matthew; Scharnowski, Sven
2017-11-01
Planer and three-dimensional flow field measurements along a flat plat boundary layer in the Trisonic Wind Tunnel Munich (TWM) are examined with the aim to characterize the scaling, spatial organization, and topology of large scale turbulent superstructures in compressible flow. This facility is ideal for this investigation as the ratio of boundary layer thickness to test section spanwise extent ratio is around 1/25, ensuring minimal sidewall and corner effects on turbulent structures in the center of the test section. A major difficulty in the experimental investigation of large scale features is the mutual size of the superstructures which can extend over many boundary layer thicknesses. Using multiple PIV systems, it was possible to capture the full spatial extent of large-scale structures over a range of Mach numbers from Ma = 0.3 - 3. To calculate the average large-scale structure length and spacing, the acquired vector fields were analyzed by statistical multi-point methods that show large scale structures with a correlation length of around 10 boundary layer thicknesses over the range of Mach numbers investigated. Furthermore, the average spacing between high and low momentum structures is on the order of a boundary layer thicknesses. This work is supported by the Priority Programme SPP 1881 Turbulent Superstructures of the Deutsche Forschungsgemeinschaft.
The Variation of Slat Noise with Mach and Reynolds Numbers
Lockard, 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.
Angular dependence of high Mach number plasma interactions
International Nuclear Information System (INIS)
Thomas, V.A.; Brecht, S.H.
1987-01-01
In this paper a 2-1/2-dimensional hybrid code is used to examine the collisionless large spatial scale (kc/ω pi ∼ 1) low-frequency (ω ∼ ω ci ) interaction initiated by a plasma shell of finite width traveling at high Alfven Mach number relative to a uniform background plasma. Particular attention is given to the angle of the relative velocity relative to the ambient magnetic field for the range of angles O < θ < π/2. An attempt is made to parameterize some of the important physics including the Alfven ion cyclotron instability, the field-aligned electromagnetic ion counter streaming instability, mixing of the plasma shell with the background ions, and structuring of the interaction region. These results are applicable to various astrophysical interactions such as bow shocks and interplanetary shocks
Numerical solutions of unsteady flows with low inlet Mach numbers
Czech Academy of Sciences Publication Activity Database
Punčochářová, Petra; Furst, Jiří; Horáček, Jaromír; Kozel, Karel
2010-01-01
Roč. 80, č. 8 (2010), s. 1795-1805 ISSN 0378-4754 R&D Projects: GA AV ČR IAA200760613 Institutional research plan: CEZ:AV0Z20760514 Keywords : finite volume method * unsteady flow * low Mach number * viscous compressible fluid Subject RIV: BI - Acoustics Impact factor: 0.812, year: 2010 http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V0T-4Y0D67D-1-R&_cdi=5655&_user=640952&_pii=S0378475409003607&_origin=search&_coverDate=04%2F30%2F2010&_sk=999199991&view=c&wchp=dGLbVlb-zSkzk&md5=ed6eaf0a050968ee978714fd54e7f131&ie=/sdarticle.pdf
Effects of Mach number on pitot-probe displacement in a turbulent boundary layer
Allen, J. M.
1974-01-01
Experimental pitot-probe-displacement data have been obtained in a turbulent boundary layer at a local free-stream Mach number of 4.63 and unit Reynolds number of 6.46 million meter. The results of this study were compared with lower Mach number results of previous studies. It was found that small probes showed displacement only, whereas the larger probes showed not only displacement but also distortion of the shape of the boundary-layer profile. The distortion pattern occurred lower in the boundary layer at the higher Mach number than at the the lower Mach number. The maximum distortion occurred when the center of the probe was about one probe diameter off the test surface. For probes in the wall contact position, the indicated Mach numbers were, for all probes tested, close to the true profile. Pitot-probe displacement was found to increase significantly with increasing Mach number.
High-Mach number, laser-driven magnetized collisionless shocks
International Nuclear Information System (INIS)
Schaeffer, Derek B.; Fox, W.; Haberberger, D.; Fiksel, G.; Bhattacharjee, A.
2017-01-01
Collisionless shocks are ubiquitous in space and astrophysical systems, and the class of supercritical shocks is of particular importance due to their role in accelerating particles to high energies. While these shocks have been traditionally studied by spacecraft and remote sensing observations, laboratory experiments can provide reproducible and multi-dimensional datasets that provide complementary understanding of the underlying microphysics. We present experiments undertaken on the OMEGA and OMEGA EP laser facilities that show the formation and evolution of high-Mach number collisionless shocks created through the interaction of a laser-driven magnetic piston and magnetized ambient plasma. Through time-resolved, 2-D imaging we observe large density and magnetic compressions that propagate at super-Alfvenic speeds and that occur over ion kinetic length scales. Electron density and temperature of the initial ambient plasma are characterized using optical Thomson scattering. Measurements of the piston laser-plasma are modeled with 2-D radiation-hydrodynamic simulations, which are used to initialize 2-D particle-in-cell simulations of the interaction between the piston and ambient plasmas. The numerical results show the formation of collisionless shocks, including the separate dynamics of the carbon and hydrogen ions that constitute the ambient plasma and their effect on the shock structure. Furthermore, the simulations also show the shock separating from the piston, which we observe in the data at late experimental times.
Role of Turbulent Prandtl Number on Heat Flux at Hypersonic Mach Numbers
Xiao, X.; Edwards, J. R.; Hassan, H. A.; Gaffney, R. L., Jr.
2007-01-01
A new turbulence model suited for calculating the turbulent Prandtl number as part of the solution is presented. The model is based on a set of two equations: one governing the variance of the enthalpy and the other governing its dissipation rate. These equations were derived from the exact energy equation and thus take into consideration compressibility and dissipation terms. The model is used to study two cases involving shock wave/boundary layer interaction at Mach 9.22 and Mach 5.0. In general, heat transfer prediction showed great improvement over traditional turbulence models where the turbulent Prandtl number is assumed constant. It is concluded that using a model that calculates the turbulent Prandtl number as part of the solution is the key to bridging the gap between theory and experiment for flows dominated by shock wave/boundary layer interactions.
Effects of rocket jet on stability and control at high Mach numbers
Fetterman, David E , Jr
1958-01-01
Paper presents the results of an investigation to determine the jet-interference effects which may occur at high jet static-pressure ratios and high Mach numbers. Tests were made in the Langley 11-inch hypersonic tunnel at a Mach number of 6.86.
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
Dynamic pressure sensitivity determination with Mach number method
Sarraf, Christophe; Damion, Jean-Pierre
2018-05-01
Measurements of pressure in fast transient conditions are often performed even if the dynamic characteristic of the transducer are not traceable to international standards. Moreover, the question of a primary standard in dynamic pressure is still open, especially for gaseous applications. The question is to improve dynamic standards in order to respond to expressed industrial needs. In this paper, the method proposed in the EMRP IND09 ‘Dynamic’ project, which can be called the ‘ideal shock tube method’, is compared with the ‘collective standard method’ currently used in the Laboratoire de Métrologie Dynamique (LNE/ENSAM). The input is a step of pressure generated by a shock tube. The transducer is a piezoelectric pressure sensor. With the ‘ideal shock tube method’ the sensitivity of a pressure sensor is first determined dynamically. This method requires a shock tube implemented with piezoelectric shock wave detectors. The measurement of the Mach number in the tube allows an evaluation of the incident pressure amplitude of a step using a theoretical 1D model of the shock tube. Heat transfer, other actual effects and effects of the shock tube imperfections are not taken into account. The amplitude of the pressure step is then used to determine the sensitivity in dynamic conditions. The second method uses a frequency bandwidth comparison to determine pressure at frequencies from quasi-static conditions, traceable to static pressure standards, to higher frequencies (up to 10 kHz). The measurand is also a step of pressure generated by a supposed ideal shock tube or a fast-opening device. The results are provided as a transfer function with an uncertainty budget assigned to a frequency range, also deliverable frequency by frequency. The largest uncertainty in the bandwidth of comparison is used to trace the final pressure step level measured in dynamic conditions, owing that this pressure is not measurable in a steady state on a shock tube. A reference
Performance Limiting Flow Processes in High-State Loading High-Mach Number Compressors
National Research Council Canada - National Science Library
Tan, Choon S
2008-01-01
In high-stage loading high-Mach number (HLM) compressors, counter-rotating pairs of discrete vortices are shed at the trailing edge of the upstream blade row at a frequency corresponding to the downstream rotor blade passing frequency...
Derivation of the low Mach number diphasic system. Numerical simulation in mono-dimensional geometry
International Nuclear Information System (INIS)
Dellacherie, St.
2004-01-01
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)
Role of Turbulent Prandtl Number on Heat Flux at Hypersonic Mach Number
Xiao, X.; Edwards, J. R.; Hassan, H. A.
2004-01-01
Present simulation of turbulent flows involving shock wave/boundary layer interaction invariably overestimates heat flux by almost a factor of two. One possible reason for such a performance is a result of the fact that the turbulence models employed make use of Morkovin's hypothesis. This hypothesis is valid for non-hypersonic Mach numbers and moderate rates of heat transfer. At hypersonic Mach numbers, high rates of heat transfer exist in regions where shock wave/boundary layer interactions are important. As a result, one should not expect traditional turbulence models to yield accurate results. The goal of this investigation is to explore the role of a variable Prandtl number formulation in predicting heat flux in flows dominated by strong shock wave/boundary layer interactions. The intended applications involve external flows in the absence of combustion such as those encountered in supersonic inlets. This can be achieved by adding equations for the temperature variance and its dissipation rate. Such equations can be derived from the exact Navier-Stokes equations. Traditionally, modeled equations are based on the low speed energy equation where the pressure gradient term and the term responsible for energy dissipation are ignored. It is clear that such assumptions are not valid for hypersonic flows. The approach used here is based on the procedure used in deriving the k-zeta model, in which the exact equations that governed k, the variance of velocity, and zeta, the variance of vorticity, were derived and modeled. For the variable turbulent Prandtl number, the exact equations that govern the temperature variance and its dissipation rate are derived and modeled term by term. The resulting set of equations are free of damping and wall functions and are coordinate-system independent. Moreover, modeled correlations are tensorially consistent and invariant under Galilean transformation. The final set of equations will be given in the paper.
On the instabilities of supersonic mixing layers - A high-Mach-number asymptotic theory
Balsa, Thomas F.; Goldstein, M. E.
1990-01-01
The stability of a family of tanh mixing layers is studied at large Mach numbers using perturbation methods. It is found that the eigenfunction develops a multilayered structure, and the eigenvalue is obtained by solving a simplified version of the Rayleigh equation (with homogeneous boundary conditions) in one of these layers which lies in either of the external streams. This analysis leads to a simple hypersonic similarity law which explains how spatial and temporal phase speeds and growth rates scale with Mach number and temperature ratio. Comparisons are made with numerical results, and it is found that this similarity law provides a good qualitative guide for the behavior of the instability at high Mach numbers. In addition to this asymptotic theory, some fully numerical results are also presented (with no limitation on the Mach number) in order to explain the origin of the hypersonic modes (through mode splitting) and to discuss the role of oblique modes over a very wide range of Mach number and temperature ratio.
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)
A Parametric Study of a Constant-Mach-Number MHD Generator with Nuclear Ionization
International Nuclear Information System (INIS)
Braun, J.
1965-03-01
The influence of electrical and gas dynamical parameters on the length, of a linear constant-Mach-number MHD duct has been investigated. The gas has been assumed to be ionized by neutron irradiation in the expansion nozzle preceding the MHD duct. Inside the duct the electron recombination is assumed to be governed, by volume recombination. It is found that there exists a distinct domain from which the parameters must be chosen, pressure and Mach number being the most critical ones. If power densities in the order of magnitude 100 MW/m 3 are desired, high magnetic fields and Mach numbers in the supersonic range are needed. The influence of the variation of critical parameters on the channel length is given as a product of simple functions, each containing one parameter
Applicability of higher-order TVD method to low mach number compressible flows
International Nuclear Information System (INIS)
Akamatsu, Mikio
1995-01-01
Steep gradients of fluid density are the influential factor of spurious oscillation in numerical solutions of low Mach number (M<<1) compressible flows. The total variation diminishing (TVD) scheme is a promising remedy to overcome this problem and obtain accurate solutions. TVD schemes for high-speed flows are, however, not compatible with commonly used methods in low Mach number flows using pressure-based formulation. In the present study a higher-order TVD scheme is constructed on a modified form of each individual scalar equation of primitive variables. It is thus clarified that the concept of TVD is applicable to low Mach number flows within the framework of the existing numerical method. Results of test problems of the moving interface of two-component gases with the density ratio ≥ 4, demonstrate the accurate and robust (wiggle-free) profile of the scheme. (author)
A Parametric Study of a Constant-Mach-Number MHD Generator with Nuclear Ionization
Energy Technology Data Exchange (ETDEWEB)
Braun, J
1965-03-15
The influence of electrical and gas dynamical parameters on the length, of a linear constant-Mach-number MHD duct has been investigated. The gas has been assumed to be ionized by neutron irradiation in the expansion nozzle preceding the MHD duct. Inside the duct the electron recombination is assumed to be governed, by volume recombination. It is found that there exists a distinct domain from which the parameters must be chosen, pressure and Mach number being the most critical ones. If power densities in the order of magnitude 100 MW/m{sup 3} are desired, high magnetic fields and Mach numbers in the supersonic range are needed. The influence of the variation of critical parameters on the channel length is given as a product of simple functions, each containing one parameter.
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.
Numerical simulation of unsteady compressible low Mach number flow in a channel
Czech Academy of Sciences Publication Activity Database
Punčochářová-Pořízková, P.; Kozel, Karel; Horáček, Jaromír; Fürst, J.
2010-01-01
Roč. 17, č. 2 (2010), s. 83-97 ISSN 1802-1484 R&D Projects: GA MŠk OC09019 Institutional research plan: CEZ:AV0Z20760514 Keywords : CFD * finite volume method * unsteady flow * low Mach number Subject RIV: BI - Acoustics
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 (Msuccessive 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.
A two-dimensional, TVD numerical scheme for inviscid, high Mach number flows in chemical equilibrium
Eberhardt, S.; Palmer, G.
1986-01-01
A new algorithm has been developed for hypervelocity flows in chemical equilibrium. Solutions have been achieved for Mach numbers up to 15 with no adverse effect on convergence. Two methods of coupling an equilibrium chemistry package have been tested, with the simpler method proving to be more robust. Improvements in boundary conditions are still required for a production-quality code.
Study and discretization of kinetic models and fluid models at low Mach number
International Nuclear Information System (INIS)
Dellacherie, Stephane
2011-01-01
This thesis summarizes our work between 1995 and 2010. It concerns the analysis and the discretization of Fokker-Planck or semi-classical Boltzmann kinetic models and of Euler or Navier-Stokes fluid models at low Mach number. The studied Fokker-Planck equation models the collisions between ions and electrons in a hot plasma, and is here applied to the inertial confinement fusion. The studied semi-classical Boltzmann equations are of two types. The first one models the thermonuclear reaction between a deuterium ion and a tritium ion producing an α particle and a neutron particle, and is also in our case used to describe inertial confinement fusion. The second one (known as the Wang-Chang and Uhlenbeck equations) models the transitions between electronic quantified energy levels of uranium and iron atoms in the AVLIS isotopic separation process. The basic properties of these two Boltzmann equations are studied, and, for the Wang-Chang and Uhlenbeck equations, a kinetic-fluid coupling algorithm is proposed. This kinetic-fluid coupling algorithm incited us to study the relaxation concept for gas and immiscible fluids mixtures, and to underline connections with classical kinetic theory. Then, a diphasic low Mach number model without acoustic waves is proposed to model the deformation of the interface between two immiscible fluids induced by high heat transfers at low Mach number. In order to increase the accuracy of the results without increasing computational cost, an AMR algorithm is studied on a simplified interface deformation model. These low Mach number studies also incited us to analyse on cartesian meshes the inaccuracy at low Mach number of Godunov schemes. Finally, the LBM algorithm applied to the heat equation is justified
Turbulent mixing of a slightly supercritical van der Waals fluid at low-Mach number
International Nuclear Information System (INIS)
Battista, F.; Casciola, C. M.; Picano, F.
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 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 supercritical regime is characterized by the formation of finger-like structures – the so-called ligaments – in the shear layers separating the two streams. The mechanism of ligament formation at vanishing Mach number is extracted from the simulations and a detailed statistical characterization is provided. Ligaments always form whenever a high density contrast occurs, independently of real or perfect gas behaviors. The difference between real and perfect gas conditions is found in the ligament small-scale structure. More intense density gradients and thinner interfaces characterize the near critical fluid in comparison with the smoother behavior of the perfect gas. A phenomenological interpretation is here provided on the basis of the real gas thermodynamics properties
Turbulent mixing of a slightly supercritical van der Waals fluid at low-Mach number
Energy Technology Data Exchange (ETDEWEB)
Battista, F.; Casciola, C. M. [Department of Mechanical and Aerospace Engineering, Sapienza University, via Eudossiana 18, 00184 Rome (Italy); Picano, F. [Department of Industrial Engineering, University of Padova, via Venezia 1, 35131 Padova (Italy)
2014-05-15
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 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 supercritical regime is characterized by the formation of finger-like structures – the so-called ligaments – in the shear layers separating the two streams. The mechanism of ligament formation at vanishing Mach number is extracted from the simulations and a detailed statistical characterization is provided. Ligaments always form whenever a high density contrast occurs, independently of real or perfect gas behaviors. The difference between real and perfect gas conditions is found in the ligament small-scale structure. More intense density gradients and thinner interfaces characterize the near critical fluid in comparison with the smoother behavior of the perfect gas. A phenomenological interpretation is here provided on the basis of the real gas thermodynamics properties.
Application of a transitional boundary-layer theory in the low hypersonic Mach number regime
Shamroth, S. J.; Mcdonald, H.
1975-01-01
An investigation is made to assess the capability of a finite-difference boundary-layer procedure to predict the mean profile development across a transition from laminar to turbulent flow in the low hypersonic Mach-number regime. The boundary-layer procedure uses an integral form of the turbulence kinetic-energy equation to govern the development of the Reynolds apparent shear stress. The present investigation shows the ability of this procedure to predict Stanton number, velocity profiles, and density profiles through the transition region and, in addition, to predict the effect of wall cooling and Mach number on transition Reynolds number. The contribution of the pressure-dilatation term to the energy balance is examined and it is suggested that transition can be initiated by the direct absorption of acoustic energy even if only a small amount (1 per cent) of the incident acoustic energy is absorbed.
Assessment of a transitional boundary layer theory at low hypersonic Mach numbers
Shamroth, S. J.; Mcdonald, H.
1972-01-01
An investigation was carried out to assess the accuracy of a transitional boundary layer theory in the low hypersonic Mach number regime. The theory is based upon the simultaneous numerical solution of the boundary layer partial differential equations for the mean motion and an integral form of the turbulence kinetic energy equation which controls the magnitude and development of the Reynolds stress. Comparisions with experimental data show the theory is capable of accurately predicting heat transfer and velocity profiles through the transitional regime and correctly predicts the effects of Mach number and wall cooling on transition Reynolds number. The procedure shows promise of predicting the initiation of transition for given free stream disturbance levels. The effects on transition predictions of the pressure dilitation term and of direct absorption of acoustic energy by the boundary layer were evaluated.
Low Mach-number collisionless electrostatic shocks and associated ion acceleration
Pusztai, I.; TenBarge, J. M.; Csapó, A. N.; Juno, J.; Hakim, A.; Yi, L.; Fülöp, T.
2018-03-01
The existence and properties of low Mach-number (M≳ 1) electrostatic collisionless shocks are investigated with a semi-analytical solution for the shock structure. We show that the properties of the shock obtained in the semi-analytical model can be well reproduced in fully kinetic Eulerian Vlasov-Poisson simulations, where the shock is generated by the decay of an initial density discontinuity. Using this semi-analytical model, we study the effect of the electron-to-ion temperature ratio and the presence of impurities on both the maximum shock potential and the Mach number. We find that even a small amount of impurities can influence the shock properties significantly, including the reflected light ion fraction, which can change several orders of magnitude. Electrostatic shocks in heavy ion plasmas reflect most of the hydrogen impurity ions.
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.
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.
Surfing and drift acceleration at high mach number quasi-perpendicular shocks
International Nuclear Information System (INIS)
Amano, T.
2008-01-01
Electron acceleration in high Mach number collisionless shocks relevant to supernova remnant is discussed. By performing one- and two-dimensional particle-in-cell simulations of quasi-perpendicular shocks, we find that energetic electrons are quickly generated in the shock transition region through shock surfing and drift acceleration. The electron energization is strong enough to account for the observed injection at supernova remnant shocks. (author)
The Dynamics of Very High Alfvén Mach Number Shocks in Space Plasmas
Energy Technology Data Exchange (ETDEWEB)
Sundberg, Torbjörn; Burgess, David [School of Physics and Astronomy, Queen Mary University of London, London, E1 4NS (United Kingdom); Scholer, Manfred [Max-Planck-Institut für extraterrestrische Physik, Garching (Germany); Masters, Adam [The Blackett Laboratory, Imperial College London, Prince Consort Road, London, SW7 2AZ (United Kingdom); Sulaiman, Ali H., E-mail: torbjorn.sundberg@gmail.com [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States)
2017-02-10
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.
Acoustic-hydrodynamic-flame coupling—A new perspective for zero and low Mach number flows
Pulikkottil, V. V.; Sujith, R. I.
2017-04-01
A combustion chamber has a hydrodynamic field that convects the incoming fuel and oxidizer into the chamber, thereby causing the mixture to react and produce heat energy. This heat energy can, in turn, modify the hydrodynamic and acoustic fields by acting as a source and thereby, establish a positive feedback loop. Subsequent growth in the amplitude of the acoustic field variables and their eventual saturation to a limit cycle is generally known as thermo-acoustic instability. Mathematical representation of these phenomena, by a set of equations, is the subject of this paper. In contrast to the ad hoc models, an explanation of the flame-acoustic-hydrodynamic coupling, based on fundamental laws of conservation of mass, momentum, and energy, is presented in this paper. In this paper, we use a convection reaction diffusion equation, which, in turn, is derived from the fundamental laws of conservation to explain the flame-acoustic coupling. The advantage of this approach is that the physical variables such as hydrodynamic velocity and heat release rate are coupled based on the conservation of energy and not based on an ad hoc model. Our approach shows that the acoustic-hydrodynamic interaction arises from the convection of acoustic velocity fluctuations by the hydrodynamic field and vice versa. This is a linear mechanism, mathematically represented as a convection operator. This mechanism resembles the non-normal mechanism studied in hydrodynamic theory. We propose that this mechanism could relate the instability mechanisms of hydrodynamic and thermo-acoustic systems. Furthermore, the acoustic-hydrodynamic interaction is shown to be responsible for the convection of entropy disturbances from the inlet of the chamber. The theory proposed in this paper also unifies the observations in the fields of low Mach number flows and zero Mach number flows. In contrast to the previous findings, where compressibility is shown to be causing different physics for zero and low Mach
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.
Chu, Julio; Luckring, James M.
1996-01-01
An experimental wind tunnel test of a 65 deg. delta wing model with interchangeable leading edges was conducted in the Langley National Transonic Facility (NTF). The objective was to investigate the effects of Reynolds and Mach numbers on slender-wing leading-edge vortex flows with four values of wing leading-edge bluntness. Experimentally obtained pressure data are presented without analysis in tabulated and graphical formats across a Reynolds number range of 6 x 10(exp 6) to 84 x 10(exp 6) at a Mach number of 0.85 and across a Mach number range of 0.4 to 0.9 at Reynolds numbers of 6 x 10(exp 6) and 60 x 10(exp 6). Normal-force and pitching-moment coefficient plots for these Reynolds number and Mach number ranges are also presented.
Needleman, Kathy E.; Mack, Robert J.
1990-01-01
This paper presents and discusses trends in nose shock overpressure generated by two conceptual Mach 2.0 configurations. One configuration was designed for high aerodynamic efficiency, while the other was designed to produce a low boom, shaped-overpressure signature. Aerodynamic lift, sonic boom minimization, and Mach-sliced/area-rule codes were used to analyze and compute the sonic boom characteristics of both configurations with respect to cruise Mach number, weight, and altitude. The influence of these parameters on the overpressure and the overpressure trends are discussed and conclusions are given.
Low Mach number analysis of idealized thermoacoustic engines with numerical solution.
Hireche, Omar; Weisman, Catherine; Baltean-Carlès, Diana; Le Quéré, Patrick; Bauwens, Luc
2010-12-01
A model of an idealized thermoacoustic engine is formulated, coupling nonlinear flow and heat exchange in the heat exchangers and stack with a simple linear acoustic model of the resonator and load. Correct coupling results in an asymptotically consistent global model, in the small Mach number approximation. A well-resolved numerical solution is obtained for two-dimensional heat exchangers and stack. The model assumes that the heat exchangers and stack are shorter than the overall length by a factor of the order of a representative Mach number. The model is well-suited for simulation of the entire startup process, whereby as a result of some excitation, an initially specified temperature profile in the stack evolves toward a near-steady profile, eventually reaching stationary operation. A validation analysis is presented, together with results showing the early amplitude growth and approach of a stationary regime. Two types of initial excitation are used: Random noise and a small periodic wave. The set of assumptions made leads to a heat-exchanger section that acts as a source of volume but is transparent to pressure and to a local heat-exchanger model characterized by a dynamically incompressible flow to which a locally spatially uniform acoustic pressure fluctuation is superimposed.
Thermodynamic analysis on optimum performance of scramjet engine at high Mach numbers
International Nuclear Information System (INIS)
Zhang, Duo; Yang, Shengbo; Zhang, Silong; Qin, Jiang; Bao, Wen
2015-01-01
In order to predict the maximum performance of scramjet engine at flight conditions with high freestream Mach numbers, a thermodynamic model of Brayton cycle was utilized to analyze the effects of inlet pressure ratio, fuel equivalence ratio and the upper limit of gas temperature to the specific thrust and the fuel impulse of the scramjet considering the characteristics of non-isentropic compression in the inlet. The results show that both the inlet efficiency and the temperature limit in the combustor have remarkable effects on the overall engine performances. Different with the ideal Brayton cycles assuming isentropic compression without upper limit of gas temperature, both the maximum specific thrust and the maximum fuel impulse of a scramjet present non-monotonic trends against the fuel equivalence ratio in this study. Considering the empirical design efficiencies of inlet, there is a wide range of fuel equivalence ratios in which the fuel impulses remain at high values. Moreover, the maximum specific thrust can also be achieved with a fuel equivalence ratio near this range. Therefore, it is possible to achieve an overall high performance in a scramjet at high Mach numbers. - Highlights: • Thermodynamic analysis with Brayton cycle on overall performances of scramjet. • The compression loss in the inlet was considered in predicting scram-mode operation. • Non-monotonic trends of engine performances against fuel equivalence ratio.
Influences of mach number and flow incidence on aerodynamic losses of steam turbine blade
International Nuclear Information System (INIS)
Yoo, Seok Jae; Ng, Wing Fai
2000-01-01
An experiment was conducted to investigate the aerodynamic losses of high pressure steam turbine nozzle (526A) subjected to a large range of incident angles (-34 .deg. to 26 .deg. ) and exit Mach numbers (0.6 and 1.15). Measurements included downstream pitot probe traverses, upstream total pressure, and endwall static pressures. Flow visualization techniques such as shadowgraph and color oil flow visualization were performed to complement the measured data. When the exit Mach number for nozzles increased from 0.9 to 1.1 the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses measured at subsonic conditions (M 2 <0.9). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on the shadowgraphs taken during the experiment, it's believed that the large increase in losses at transonic conditions is due to strong shock/ boundary layer interaction that may lead to flow separation on the blade suction surface
Energy Technology Data Exchange (ETDEWEB)
Matsumoto, Yosuke [Department of Physics, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522 (Japan); Amano, Takanobu; Hoshino, Masahiro, E-mail: ymatumot@astro.s.chiba-u.ac.jp [Department of Earth and Planetary Science, University of Tokyo, Hongo 1-33, Bunkyo-ku, Tokyo 113-0033 (Japan)
2012-08-20
Electron accelerations at high Mach number collisionless shocks are investigated by means of two-dimensional electromagnetic particle-in-cell simulations with various Alfven Mach numbers, ion-to-electron mass ratios, and the upstream electron {beta}{sub e} (the ratio of the thermal pressure to the magnetic pressure). We find electrons are effectively accelerated at a super-high Mach number shock (M{sub A} {approx} 30) with a mass ratio of M/m = 100 and {beta}{sub e} = 0.5. The electron shock surfing acceleration is an effective mechanism for accelerating the particles toward the relativistic regime even in two dimensions with a large mass ratio. Buneman instability excited at the leading edge of the foot in the super-high Mach number shock results in a coherent electrostatic potential structure. While multi-dimensionality allows the electrons to escape from the trapping region, they can interact with the strong electrostatic field several times. Simulation runs in various parameter regimes indicate that the electron shock surfing acceleration is an effective mechanism for producing relativistic particles in extremely high Mach number shocks in supernova remnants, provided that the upstream electron temperature is reasonably low.
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.
Sensitivity of boundary-layer stability to base-state distortions at high Mach numbers
Park, Junho; Zaki, Tamer
2017-11-01
The stability diagram of high-speed boundary layers has been established by evaluating the linear instability modes of the similarity profile, over wide ranges of Reynolds and Mach numbers. In real flows, however, the base state can deviate from the similarity profile. Both the base velocity and temperature can be distorted, for example due to roughness and thermal wall treatments. We review the stability problem of high-speed boundary layer, and derive a new formulation of the sensitivity to base-state distortion using forward and adjoint parabolized stability equations. The new formulation provides qualitative and quantitative interpretations on change in growth rate due to modifications of mean-flow and mean-temperature in heated high-speed boundary layers, and establishes the foundation for future control strategies. This work has been funded by the Air Force Office of Scientific Research (AFOSR) Grant: FA9550-16-1-0103.
Spectroscopic studies of a high Mach-number rotating plasma flow
International Nuclear Information System (INIS)
Ando, Akira; Ashino, Masashi; Sagi, Yukiko; Inutake, Masaaki; Hattori, Kunihiko; Yoshinuma, Mikirou; Imasaki, Atsushi; Tobari, Hiroyuki; Yagai, Tsuyoshi
2001-01-01
Characteristics of an axially-magnetized rotating plasma are investigated by spectroscopy in the HITOP device of Tohoku University. A He plasma flows our axially and rotates azimuthally near the muzzle region of the MPD arcjet. Flow and rotational velocities and temperature of He ions and atoms are measured by Doppler shift and broadening of the HeII (γ=468.58 nm) and HeI (γ=587.56 nm) lines. Rotational velocity increases with the increase of axially-applied magnetic field strength and discharge current. As discharge current increases and mass flow rate decreases, the plasma flow velocity increases and T i increases. Ion acoustic Mach number of the plasma flow also increases, but tends to saturate at near 1. Radial profile of space potential is calculated from the obtained rotational velocity. The potential profile in the core region is parabolic corresponding to the observed rigid-body rotation of the core plasma. (author)
Spectroscopic studies of a high Mach-number rotating plasma flow
Energy Technology Data Exchange (ETDEWEB)
Ando, Akira; Ashino, Masashi; Sagi, Yukiko; Inutake, Masaaki; Hattori, Kunihiko; Yoshinuma, Mikirou; Imasaki, Atsushi; Tobari, Hiroyuki; Yagai, Tsuyoshi [Tohoku Univ., Dept. of Electrical Engineering, Sendai, Miyagi (Japan)
2001-07-01
Characteristics of an axially-magnetized rotating plasma are investigated by spectroscopy in the HITOP device of Tohoku University. A He plasma flows our axially and rotates azimuthally near the muzzle region of the MPD arcjet. Flow and rotational velocities and temperature of He ions and atoms are measured by Doppler shift and broadening of the HeII ({gamma}=468.58 nm) and HeI ({gamma}=587.56 nm) lines. Rotational velocity increases with the increase of axially-applied magnetic field strength and discharge current. As discharge current increases and mass flow rate decreases, the plasma flow velocity increases and T{sub i} increases. Ion acoustic Mach number of the plasma flow also increases, but tends to saturate at near 1. Radial profile of space potential is calculated from the obtained rotational velocity. The potential profile in the core region is parabolic corresponding to the observed rigid-body rotation of the core plasma. (author)
Engineering method for aero-propulsive characteristics at hypersonic Mach numbers
Goradia, Suresh; Torres, Abel O.; Stack, Sharon H.; Everhart, Joel L.
1991-01-01
An engineering method has been developed for the rapid analysis of external aerodynamics and propulsive performance characteristics of airbreathing vehicles at hypersonic Mach numbers. This method, based on the theory of characteristics, has been developed to analyze fuselage-wing body combinations and body flaps with blunt or sharp leading/trailing edges. Arbitrary ratio of specific heat for the flowing medium can be specified in the program. Furthermore, the capability exists in the code to compute the inviscid inlet mass capture and momentum flux. The method is under development for computations of pressure distribution, and flow characteristics in the inlet, along with the effect of viscosity. Correlative studies have been performed for representative hypersonic configurations using the current method. The results of these correlations for various aerodynamics parameters are encouraging.
Effect of Mach number on thermoelectric performance of SiC ceramics nose-tip for supersonic vehicles
International Nuclear Information System (INIS)
Han, Xiao-Yi; Wang, Jun
2014-01-01
This paper focus on the effects of Mach number on thermoelectric energy conversion for the limitation of aero-heating and the feasibility of energy harvesting on supersonic vehicles. A model of nose-tip structure constructed with SiC ceramics is developed to numerically study the thermoelectric performance in a supersonic flow field by employing the computational fluid dynamics and the thermal conduction theory. Results are given in the cases of different Mach numbers. Moreover, the thermoelectric performance in each case is predicted with and without Thomson heat, respectively. Due to the increase of Mach number, both the temperature difference and the conductive heat flux between the hot side and the cold side of nose tip are increased. This results in the growth of the thermoelectric power generated and the energy conversion efficiency. With respect to the Thomson effect, over 50% of total power generated converts to Thomson heat, which greatly reduces the thermoelectric power and efficiency. However, whether the Thomson effect is considered or not, with the Mach number increasing from 2.5 to 4.5, the thermoelectric performance can be effectively improved. -- Highlights: • Thermoelectric SiC nose-tip structure for aerodynamic heat harvesting of high-speed vehicles is studied. • Thermoelectric performance is predicted based on numerical methods and experimental thermoelectric parameters. • The effects of Mach number on thermoelectric performance are studied in the present paper. • Results with respect to the Thomson effect are also explored. • Output power and energy efficiency of the thermoelectric nose-tip are increased with the increase of Mach number
Energy Technology Data Exchange (ETDEWEB)
Correia, C.; De Medeiros, J. R. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, 59072-970 (Brazil); Burkhart, B.; Lazarian, A. [Astronomy Department, University of Wisconsin, Madison, 475 North Charter Street, WI 53711 (United States); Ossenkopf, V.; Stutzki, J. [Physikalisches Institut der Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln (Germany); Kainulainen, J. [Max-Planck-Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Kowal, G., E-mail: caioftc@dfte.ufrn.br [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, 05508-090 (Brazil)
2014-04-10
We study how the estimation of the sonic Mach number (M{sub s} ) from {sup 13}CO linewidths relates to the actual three-dimensional sonic Mach number. For this purpose we analyze MHD simulations that 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{sub s} to be overestimated by a factor of ≈1.16-1.3 when calculated from optically thick {sup 13}CO lines. We also find that there is a dependence on the magnetic field: super-Alfvénic turbulence shows increased line broadening compared with sub-Alfvénic turbulence for all values of optical depth for supersonic turbulence. Our results have implications for the observationally derived sonic Mach number-density standard deviation (σ{sub ρ/(ρ)}) relationship, σ{sub ρ/〈ρ〉}{sup 2}=b{sup 2}M{sub s}{sup 2}, and the related column density standard deviation (σ {sub N/(N)}) sonic Mach number relationship. In particular, we find that the parameter b, as an indicator of solenoidal versus compressive driving, will be underestimated as a result of opacity broadening. We compare the σ {sub N/(N)}-M{sub s} relation derived from synthetic dust extinction maps and {sup 13}CO linewidths with recent observational studies and find that solenoidally driven MHD turbulence simulations have values of σ {sub N/(N)}which are lower than real molecular clouds. This may be due to the influence of self-gravity which should be included in simulations of molecular cloud dynamics.
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.
Study of Perturbations on High Mach Number Blast Waves in Various Gasses
Edens, A.; Adams, R.; Rambo, P.; Shores, J.; Smith, I.; Atherton, B.; Ditmire, T.
2006-10-01
We have performed a series of experiments examining the properties of high Mach number blast waves. Experiments were conducted on the Z-Beamlet^1 laser at Sandia National Laboratories. We created blast waves in the laboratory by using 10 J- 1000 J laser pulses to illuminate millimeter scale solid targets immersed in gas. Our experiments studied the validity of theories forwarded by Vishniac and Ryu^2-4 to explain the dynamics of perturbations on astrophysical blast waves. These experiments consisted of an examination of the evolution of perturbations of known primary mode number induced on the surface of blast waves by means of regularly spaced wire arrays. The temporal evolution of the amplitude of the induced perturbations relative to the mean radius of the blast wave was fit to a power law in time. Measurements were taken for a number of different mode numbers and background gasses and the results show qualitative agreement with previously published theories for the hydrodynamics of thin shell blast wave. The results for perturbations on nitrogen gas have been recently published^5. .^1 P. K. Rambo, I. C. Smith, J. L. Porter, et al., Applied Optics 44, 2421 (2005). ^2 D. Ryu and E. T. Vishniac, Astrophysical Journal 313, 820 (1987). ^3 D. Ryu and E. T. Vishniac, Astrophysical Journal 368, 411 (1991). ^4 E. T. Vishniac, Astrophysical Journal 274, 152 (1983). ^5 A. D. Edens, T. Ditmire, J. F. Hansen, et al., Physical Review Letters 95 (2005).
Risius, Steffen; Costantini, Marco; Koch, Stefan; Hein, Stefan; Klein, Christian
2018-05-01
The influence of unit Reynolds number (Re_1=17.5× 106-80× 106 {m}^{-1}), Mach number (M= 0.35-0.77) and incompressible shape factor (H_{12} = 2.50-2.66) on laminar-turbulent boundary layer transition was systematically investigated in the Cryogenic Ludwieg-Tube Göttingen (DNW-KRG). For this investigation the existing two-dimensional wind tunnel model, PaLASTra, which offers a quasi-uniform streamwise pressure gradient, was modified to reduce the size of the flow separation region at its trailing edge. The streamwise temperature distribution and the location of laminar-turbulent transition were measured by means of temperature-sensitive paint (TSP) with a higher accuracy than attained in earlier measurements. It was found that for the modified PaLASTra model the transition Reynolds number (Re_{ {tr}}) exhibits a linear dependence on the pressure gradient, characterized by H_{12}. Due to this linear relation it was possible to quantify the so-called `unit Reynolds number effect', which is an increase of Re_{ {tr}} with Re_1. By a systematic variation of M, Re_1 and H_{12} in combination with a spectral analysis of freestream disturbances, a stabilizing effect of compressibility on boundary layer transition, as predicted by linear stability theory, was detected (`Mach number effect'). Furthermore, two expressions were derived which can be used to calculate the transition Reynolds number as a function of the amplitude of total pressure fluctuations, Re_1 and H_{12}. To determine critical N-factors, the measured transition locations were correlated with amplification rates, calculated by incompressible and compressible linear stability theory. By taking into account the spectral level of total pressure fluctuations at the frequency of the most amplified Tollmien-Schlichting wave at transition location, the scatter in the determined critical N-factors was reduced. Furthermore, the receptivity coefficients dependence on incidence angle of acoustic waves was used to
Investigation of side wall effects on an inward scramjet inlet at Mach number 8.6
Rolim, Tiago Cavalcanti
Experimental and computational studies were conducted to evaluate the performance of a scramjet inlet as the side cowl length is changed. A slender inward turning inlet of a total length of 304.8 mm, a span of 50.8 mm with the compression at 11.54 deg and CR = 4.79 was used. The side cowl lengths were of 0, 50.8 and 76.2 mm. The UTA Hypersonic Shock Tunnel facility was used in the reflected mode. The model was instrumented with nine piezoelectric pressure transducers, for static and total pressure measurements. A wedge was mounted at the rear of the inlet in order to accommodate a Pitot pressure rake. The driven tube was instrumented with three pressure transducers. Two of them were used to measure the incident shock wave speed, and a third one was used for stagnation pressure measurements during a test. Furthermore, a Pitot probe was installed below the model in order to measure the impact pressure on each run, this reading along with the driven sensor readings, allowed us for the calculation of freestream properties. During the experiments, nominal stagnation enthalpy of 0.67 MJ/kg and stagnation pressure of 3.67 MPa were achieved. Freestream conditions were Mach number 8.6 and Reynolds number of 1.94 million per m. Test times were 300 - 500 microseconds. Numerical simulations using RANS with the Wilcox K-w turbulence model were performed using ANSYS Fluent. The results from the static pressure measurements presented a good agreement with CFD predictions. Moreover, the uniformity at the inlet exit was achieved within the experimental precision. The experiments showed that the cowl length has a pronounced effect in the pressure distribution on the inlet and a minor effect in the exit flow Mach number. The numerical results confirmed these trends and showed that a complex flow structure is formed in the cowl-ramp corners; a non-uniform transverse shock structure was found to be related to the cowl leading edge position. Cross flow due to the side expansion
Analytic MHD Theory for Earth's Bow Shock at Low Mach Numbers
Grabbe, Crockett L.; Cairns, Iver H.
1995-01-01
A previous MHD theory for the density jump at the Earth's bow shock, which assumed the Alfven M(A) and sonic M(s) Mach numbers are both much greater than 1, is reanalyzed and generalized. It is shown that the MHD jump equation can be analytically solved much more directly using perturbation theory, with the ordering determined by M(A) and M(s), and that the first-order perturbation solution is identical to the solution found in the earlier theory. The second-order perturbation solution is calculated, whereas the earlier approach cannot be used to obtain it. The second-order terms generally are important over most of the range of M(A) and M(s) in the solar wind when the angle theta between the normal to the bow shock and magnetic field is not close to 0 deg or 180 deg (the solutions are symmetric about 90 deg). This new perturbation solution is generally accurate under most solar wind conditions at 1 AU, with the exception of low Mach numbers when theta is close to 90 deg. In this exceptional case the new solution does not improve on the first-order solutions obtained earlier, and the predicted density ratio can vary by 10-20% from the exact numerical MHD solutions. For theta approx. = 90 deg another perturbation solution is derived that predicts the density ratio much more accurately. This second solution is typically accurate for quasi-perpendicular conditions. Taken together, these two analytical solutions are generally accurate for the Earth's bow shock, except in the rare circumstance that M(A) is less than or = 2. MHD and gasdynamic simulations have produced empirical models in which the shock's standoff distance a(s) is linearly related to the density jump ratio X at the subsolar point. Using an empirical relationship between a(s) and X obtained from MHD simulations, a(s) values predicted using the MHD solutions for X are compared with the predictions of phenomenological models commonly used for modeling observational data, and with the predictions of a
Particle image velocimetry measurements of Mach 3 turbulent boundary layers at low Reynolds numbers
Brooks, J. M.; Gupta, A. K.; Smith, M. S.; Marineau, E. C.
2018-05-01
Particle image velocimetry (PIV) measurements of Mach 3 turbulent boundary layers (TBL) have been performed under low Reynolds number conditions, Re_τ =200{-}1000, typical of direct numerical simulations (DNS). Three reservoir pressures and three measurement locations create an overlap in parameter space at one research facility. This allows us to assess the effects of Reynolds number, particle response and boundary layer thickness separate from facility specific experimental apparatus or methods. The Morkovin-scaled streamwise fluctuating velocity profiles agree well with published experimental and numerical data and show a small standard deviation among the nine test conditions. The wall-normal fluctuating velocity profiles show larger variations which appears to be due to particle lag. Prior to the current study, no detailed experimental study characterizing the effect of Stokes number on attenuating wall-normal fluctuating velocities has been performed. A linear variation is found between the Stokes number ( St) and the relative error in wall-normal fluctuating velocity magnitude (compared to hot wire anemometry data from Klebanoff, Characteristics of Turbulence in a Boundary Layer with Zero Pressure Gradient. Tech. Rep. NACA-TR-1247, National Advisory Committee for Aeronautics, Springfield, Virginia, 1955). The relative error ranges from about 10% for St=0.26 to over 50% for St=1.06. Particle lag and spatial resolution are shown to act as low-pass filters on the fluctuating velocity power spectral densities which limit the measurable energy content. The wall-normal component appears more susceptible to these effects due to the flatter spectrum profile which indicates that there is additional energy at higher wave numbers not measured by PIV. The upstream inclination and spatial correlation extent of coherent turbulent structures agree well with published data including those using krypton tagging velocimetry (KTV) performed at the same facility.
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.
Vink, J.; Yamazaki, R.
2014-01-01
It is shown that, under some generic assumptions, shocks cannot accelerate particles unless the overall shock Mach number exceeds a critical value M > √5. The reason is that for M ≤ √5 the work done to compress the flow in a particle precursor requires more enthalpy flux than the system can sustain.
Effects of Mach Numbers on Side Force, Yawing Moment and Surface Pressure
Sohail, Muhammad Amjad; Muhammad, Zaka; Husain, Mukkarum; Younis, Muhammad Yamin
2011-09-01
In this research, CFD simulations are performed for air vehicle configuration to compute the side force effect and yawing moment coefficients variations at high angle of attack and Mach numbers. As the angle of attack is increased then lift and drag are increased for cylinder body configurations. But when roll angle is given to body then side force component is also appeared on the body which causes lateral forces on the body and yawing moment is also produced. Now due to advancement of CFD methods we are able to calculate these forces and moment even at supersonic and hypersonic speed. In this study modern CFD techniques are used to simulate the hypersonic flow to calculate the side force effects and yawing moment coefficient. Static pressure variations along the circumferential and along the length of the body are also calculated. The pressure coefficient and center of pressure may be accurately predicted and calculated. When roll angle and yaw angle is given to body then these forces becomes very high and cause the instability of the missile body with fin configurations. So it is very demanding and serious problem to accurately predict and simulate these forces for the stability of supersonic vehicles.
Effect of finite cavity width on flow oscillation in a low-Mach-number cavity flow
Energy Technology Data Exchange (ETDEWEB)
Zhang, Ke; Naguib, Ahmed M. [Michigan State University, East Lansing, MI (United States)
2011-11-15
The current study is focused on examining the effect of the cavity width and side walls on the self-sustained oscillation in a low Mach number cavity flow with a turbulent boundary layer at separation. An axisymmetric cavity geometry is employed in order to provide a reference condition that is free from any side-wall influence, which is not possible to obtain with a rectangular cavity. The cavity could then be partially filled to form finite-width geometry. The unsteady surface pressure is measured using microphone arrays that are deployed on the cavity floor along the streamwise direction and on the downstream wall along the azimuthal direction. In addition, velocity measurements using two-component Laser Doppler Anemometer are performed simultaneously with the array measurements in different azimuthal planes. The compiled data sets are used to investigate the evolution of the coherent structures generating the pressure oscillation in the cavity using linear stochastic estimation of the velocity field based on the wall-pressure signature on the cavity end wall. The results lead to the discovery of pronounced harmonic pressure oscillations near the cavity's side walls. These oscillations, which are absent in the axisymmetric cavity, are linked to the establishment of a secondary mean streamwise circulating flow pattern near the side walls and the interaction of this secondary flow with the shear layer above the cavity. (orig.)
Measurement and analysis of the noise radiated by low Mach numbers centrifugal blowers
Yeager, D. M.; Lauchle, G. C.
1987-11-01
The broad band, aerodynamically generated noise in low tip-speed Mach number, centrifugal air moving devices is investigated. An interdisciplinary 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 which was 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. 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. New frequency-domain expressions for the correlation area and dipole source strength per unit area on a surface immersed in turbulence were developed which can be used to characterize the noise generation process over a rigid surface immersed in turbulence. An investigation of the noise radiated from the single, isolated airfoil (impeller blade) was performed using modern correlation and spectral analysis techniques.
Plasma wave profiles of Earth's bow shock at low Mach number: ISEE 3 observations on the far flank
International Nuclear Information System (INIS)
Greenstadt, E.W.; Coroniti, F.V.; Moses, S.L.; Smith, E.J.
1992-01-01
The Earth's bow shock is weak along its distant flanks where the projected component of solar wind velocity normal to the hyperboloidal surface is only a fraction of the total free stream velocity, severely reducing the local Mach number. The authors present a survey of selected crossings far downstream from the subsolar shock, delineating the overall plasma wave (pw) behavior of a selected set of nearly perpendicular crossings and another set of limited Mach number but broad geometry; they include their immediate upstream regions. The result is a generalizable pw signature, or signatures, of low Mach number shocks and some likely implications of those signatures for the weak shock's plasma physical processes on the flank. They find the data consistent with the presence of ion beam interactions producing noise ahead of the shock in the ion acoustic frequency range. One subcritical case was found whose pw noise was presumably related to a reflected ion population just as in stronger events. The presence or absence, and the amplitudes, of pw activity are explainable by the presence or absence of a population of upstream ions controlled by the component of interplanetary magnetic field normal to the solar wind flow
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
Hruschka, R.; Klatt, D.
2018-03-01
The transient shock dynamics and drag characteristics of a projectile flying through a pipe 3.55 times larger than its diameter at transonic speed are analyzed by means of time-of-flight and pipe wall pressure measurements as well as computational fluid dynamics (CFD). In addition, free-flight drag of the 4.5-mm-pellet-type projectile was also measured in a Mach number range between 0.5 and 1.5, providing a means for comparison against in-pipe data and CFD. The flow is categorized into five typical regimes the in-pipe projectile experiences. When projectile speed and hence compressibility effects are low, the presence of the pipe has little influence on the drag. Between Mach 0.5 and 0.8, there is a strong drag increase due to the presence of the pipe, however, up to a value of about two times the free-flight drag. This is exactly where the nose-to-base pressure ratio of the projectile becomes critical for locally sonic speed, allowing the drag to be estimated by equations describing choked flow through a converging-diverging nozzle. For even higher projectile Mach numbers, the drag coefficient decreases again, to a value slightly below the free-flight drag at Mach 1.5. This behavior is explained by a velocity-independent base pressure coefficient in the pipe, as opposed to base pressure decreasing with velocity in free flight. The drag calculated by CFD simulations agreed largely with the measurements within their experimental uncertainty, with some discrepancies remaining for free-flying projectiles at supersonic speed. Wall pressure measurements as well as measured speeds of both leading and trailing shocks caused by the projectile in the pipe also agreed well with CFD.
Hess, Robert V; Gardner, Clifford S
1947-01-01
By using the Prandtl-Glauert method that is valid for three-dimensional flow problems, the value of the maximum incremental velocity for compressible flow about thin ellipsoids at zero angle of attack is calculated as a function of the Mach number for various aspect ratios and thickness ratios. The critical Mach numbers of the various ellipsoids are also determined. The results indicate an increase in critical Mach number with decrease in aspect ratio which is large enough to explain experimental results on low-aspect-ratio wings at zero lift.
Lattice Boltzmann method and gas-kinetic BGK scheme in the low-Mach number viscous flow simulations
International Nuclear Information System (INIS)
Xu Kun; He Xiaoyi
2003-01-01
Both lattice Boltzmann method (LBM) and the gas-kinetic BGK scheme are based on the numerical discretization of the Boltzmann equation with collisional models, such as, the Bhatnagar-Gross-Krook (BGK) model. LBM tracks limited number of particles and the viscous flow behavior emerges automatically from the intrinsic particle stream and collisions process. On the other hand, the gas-kinetic BGK scheme is a finite volume scheme, where the time-dependent gas distribution function with continuous particle velocity space is constructed and used in the evaluation of the numerical fluxes across cell interfaces. Currently, LBM is mainly used for low Mach number, nearly incompressible flow simulation. For the gas-kinetic scheme, the application is focusing on the high speed compressible flows. In this paper, we are going to compare both schemes in the isothermal low-Mach number flow simulations. The methodology for developing both schemes will be clarified through the introduction of operator splitting Boltzmann model and operator averaging Boltzmann model. From the operator splitting Boltzmann model, the error rooted in many kinetic schemes, which are based on the decoupling of particle transport and collision, can be easily understood. As to the test case, we choose to use the 2D cavity flow since it is one of the most extensively studied cases. Detailed simulation results with different Reynolds numbers, as well as the benchmark solutions, are presented
LES of Supersonic Turbulent Channel Flow at Mach Numbers 1.5 and 3
Raghunath, Sriram; Brereton, Giles
2009-11-01
LES of compressible, turbulent, body-force driven, isothermal-wall channel flows at Reτ of 190 and 395 at moderate supersonic speeds (Mach 1.5 and 3) are presented. Simulations are fully resolved in the wall-normal direction without the need for wall-layer models. SGS models for incompressible flows, with appropriate extensions for compressibility, are tested a priori/ with DNS results and used in LES. Convergence of the simulations is found to be sensitive to the initial conditions and to the choice of model (wall-normal damping) in the laminar sublayer. The Nicoud--Ducros wall adapting SGS model, coupled with a standard SGS heat flux model, is found to yield results in good agreement with DNS.
Numerical resolution of the Navier-Stokes equations for a low Mach number by a spectral method
International Nuclear Information System (INIS)
Frohlich, Jochen
1990-01-01
The low Mach number approximation of the Navier-Stokes equations, also called isobar, is an approximation which is less restrictive than the one due to Boussinesq. It permits strong density variations while neglecting acoustic phenomena. We present a numerical method to solve these equations in the unsteady, two dimensional case with one direction of periodicity. The discretization uses a semi-implicit finite difference scheme in time and a Fourier-Chebycheff pseudo-spectral method in space. The solution of the equations of motion is based on an iterative algorithm of Uzawa type. In the Boussinesq limit we obtain a direct method. A first application is concerned with natural convection in the Rayleigh-Benard setting. We compare the results of the low Mach number equations with the ones in the Boussinesq case and consider the influence of variable fluid properties. A linear stability analysis based on a Chebychev-Tau method completes the study. The second application that we treat is a case of isobaric combustion in an open domain. We communicate results for the hydrodynamic Darrieus-Landau instability of a plane laminar flame front. [fr
Yang, Zhongwei; Lu, Quanming; Liu, Ying D.; Wang, Rui
2018-04-01
Electron dynamics at low-Mach-number collisionless shocks are investigated by using two-dimensional electromagnetic particle-in-cell simulations with various shock normal angles. We found: (1) The reflected ions and incident electrons at the shock front provide an effective mechanism for the quasi-electrostatic wave generation due to the charge-separation. A fraction of incident electrons can be effectively trapped and accelerated at the leading edge of the shock foot. (2) At quasi-perpendicular shocks, the electron trapping and reflection is nonuniform due to the shock rippling along the shock surface and is more likely to take place at some locations accompanied by intense reflected ion-beams. The electron trapping process has a periodical evolution over time due to the shock front self-reformation, which is controlled by ion dynamics. Thus, this is a cross-scale coupling phenomenon. (3) At quasi-parallel shocks, reflected ions can travel far back upstream. Consequently, quasi-electrostatic waves can be excited in the shock transition and the foreshock region. The electron trajectory analysis shows these waves can trap electrons at the foot region and reflect a fraction of them far back upstream. Simulation runs in this paper indicate that the micro-turbulence at the shock foot can provide a possible scenario for producing the reflected electron beam, which is a basic condition for the type II radio burst emission at low-Mach-number interplanetary shocks driven by Coronal Mass Ejections (CMEs).
International Nuclear Information System (INIS)
Hendijanifard, Mohammad; Willis, David A
2011-01-01
Laser-matter interactions are frequently studied by measuring the propagation of shock waves caused by the rapid laser-induced material removal. An improved method for calculating the thermo-fluid parameters behind shock waves is introduced in this work. Shock waves in ambient air, induced by pulsed Nd : YAG laser ablation of aluminium films, are measured using a shadowgraph apparatus. Normal shock solutions are applied to experimental data for shock wave positions and used to calculate pressure, temperature, and velocity behind the shock wave. Non-dimensionalizing the pressure and temperature with respect to the ambient values, the dimensionless pressure and temperature are estimated to be as high as 90 and 16, respectively, at a time of 10 ns after the ablation pulse for a laser fluence of F = 14.5 J cm -2 . The results of the normal shock solution and the Taylor-Sedov similarity solution are compared to show that the Taylor-Sedov solution under-predicts pressure when the Mach number of the shock wave is small. At a fluence of 3.1 J cm -2 , the shock wave Mach number is less than 3, and the Taylor-Sedov solution under-predicts the non-dimensional pressure by as much as 45%.
Dodd, Michael; Ferrante, Antonino
2017-11-01
Our objective is to perform DNS of finite-size droplets that are evaporating in isotropic turbulence. This requires fully resolving the process of momentum, heat, and mass transfer between the droplets and surrounding gas. We developed a combined volume-of-fluid (VOF) method and low-Mach-number approach to simulate this flow. The two main novelties of the method are: (i) the VOF algorithm captures the motion of the liquid gas interface in the presence of mass transfer due to evaporation and condensation without requiring a projection step for the liquid velocity, and (ii) the low-Mach-number approach allows for local volume changes caused by phase change while the total volume of the liquid-gas system is constant. The method is verified against an analytical solution for a Stefan flow problem, and the D2 law is verified for a single droplet in quiescent gas. We also demonstrate the schemes robustness when performing DNS of an evaporating droplet in forced isotropic turbulence.
Peng, Naifu; Yang, Yue
2018-01-01
We investigate the evolution of vortex-surface fields (VSFs) in compressible Taylor-Green flows at Mach numbers (Ma) ranging from 0.5 to 2.0 using direct numerical simulation. The formulation of VSFs in incompressible flows is extended to compressible flows, and a mass-based renormalization of VSFs is used to facilitate characterizing the evolution of a particular vortex surface. The effects of the Mach number on the VSF evolution are different in three stages. In the early stage, the jumps of the compressive velocity component near shocklets generate sinks to contract surrounding vortex surfaces, which shrink vortex volume and distort vortex surfaces. The subsequent reconnection of vortex surfaces, quantified by the minimal distance between approaching vortex surfaces and the exchange of vorticity fluxes, occurs earlier and has a higher reconnection degree for larger Ma owing to the dilatational dissipation and shocklet-induced reconnection of vortex lines. In the late stage, the positive dissipation rate and negative pressure work accelerate the loss of kinetic energy and suppress vortex twisting with increasing Ma.
Harrington, Douglas E.; Burley, Richard R.; Corban, Robert R.
1986-01-01
Wall Mach number distributions were determined over a range of test-section free-stream Mach numbers from 0.2 to 0.92. The test section was slotted and had a nominal porosity of 11 percent. Reentry flaps located at the test-section exit were varied from 0 (fully closed) to 9 (fully open) degrees. Flow was bled through the test-section slots by means of a plenum evacuation system (PES) and varied from 0 to 3 percent of tunnel flow. Variations in reentry flap angle or PES flow rate had little or no effect on the Mach number distributions in the first 70 percent of the test section. However, in the aft region of the test section, flap angle and PES flow rate had a major impact on the Mach number distributions. Optimum PES flow rates were nominally 2 to 2.5 percent wtih the flaps fully closed and less than 1 percent when the flaps were fully open. The standard deviation of the test-section wall Mach numbers at the optimum PES flow rates was 0.003 or less.
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.
Influence of Mach Number and Dynamic Pressure on Cavity Tones and Freedrop Trajectories
2014-03-27
18 LU-SGS Lower Upper-Symmetric Gauss Seidel . . . . . . . . . . . . . . . . . . 18 SSOR Successive Symmetric Over...complexity, the number of iterations necessary to gain convergence causes the simulation to be too expensive. The modern CFD method of overset or...solvers are Alternating Direction Implicit (ADI) Beam-Warming, Steger- Warming, Lower Upper-Symmetric Gauss Seidel (LU-SGS), and Successive Symmetric
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...
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.
Nonaka, Andrew; Day, Marcus S.; Bell, John B.
2018-01-01
We present a numerical approach for low Mach number combustion that conserves both mass and energy while remaining on the equation of state to a desired tolerance. We present both unconfined and confined cases, where in the latter the ambient pressure changes over time. Our overall scheme is a projection method for the velocity coupled to a multi-implicit spectral deferred corrections (SDC) approach to integrate the mass and energy equations. The iterative nature of SDC methods allows us to incorporate a series of pressure discrepancy corrections naturally that lead to additional mass and energy influx/outflux in each finite volume cell in order to satisfy the equation of state. The method is second order, and satisfies the equation of state to a desired tolerance with increasing iterations. Motivated by experimental results, we test our algorithm on hydrogen flames with detailed kinetics. We examine the morphology of thermodiffusively unstable cylindrical premixed flames in high-pressure environments for confined and unconfined cases. We also demonstrate that our algorithm maintains the equation of state for premixed methane flames and non-premixed dimethyl ether jet flames.
Evaluation of Blended Wing-Body Combinations with Curved Plan Forms at Mach Numbers Up to 3.50
Holdaway, George H.; Mellenthin, Jack A.
1960-01-01
This investigation is a continuation of the experimental and theoretical evaluation of the effects of wing plan-form variations on the aerodynamic performance characteristics of blended wing-body combinations. The present report compares previously tested straight-edged delta and arrow models which have leading-edge sweeps of 59.04 and 70-82 deg., respectively, with related models which have plan forms with curved leading and trailing edges designed to result in the same average sweeps in each case. All the models were symmetrical, without camber, and were generally similar having the same span, length, and aspect ratios. The wing sections had an average value of maximum thickness ratio of about 4 percent of the local wing chords in a streamwise direction. The wing sections were computed by varying their shapes along with the body radii (blending process) to match the selected area distribution and the given plan form. The models were tested with transition fixed at Reynolds numbers of roughly 4,000,000 to 9,000,000, based on the mean aerodynamic chord of the wing. The characteristic effect of the wing curvature of the delta and arrow models was an increase at subsonic and transonic speeds in the lift-curve slopes which was partially reflected in increased maximum lift-drag ratios. Curved edges were not evaluated on a diamond plan form because a preliminary investigation indicated that the curvature considered would increase the supersonic zero-lift wave drag. However, after the test program was completed, a suitable modification for the diamond plan form was discovered. The analysis presented in the appendix indicates that large reductions in the zero-lift wave drag would be obtained at supersonic Mach numbers if the leading- and trailing-edge sweeps are made to differ by indenting the trailing edge and extending the root of the leading edge.
Esenwein, Fred T; Schueller, Carl F
1952-01-01
An analysis of inlet-turbojet-engine matching for a range of Mach numbers up to 2.0 indicates large performance penalties when fixed-geometry inlets are used. Use of variable-geometry inlets, however, nearly eliminates th The analysis was confirmed experimentally by investigating at Mach numbers of 0, 0.63, and 1.5 to 2.0 two single oblique-shock-type inlets of different compression-ramp angles, which simulated a variable-geometry configuration. The experimental investigation indicated that total-pressure recoveries comparable withose attainable with well designed nose inlets were obtained with the side inlets when all the boundary layer ahead of the inlets was removed. Serious drag penalties resulted at a Mach number of 2.0 from the use of blunt-cowl leading edges. However, sharp-lip inlets produced large losses in thrust for the take-off condition. These thrust penalties which are associated with the the low-speed operation of the sharp-lip inlet designs can probably be avoided without impairing the supersonic performance of the inlet by the use of auxiliary inlets or blow-in doors.
International Nuclear Information System (INIS)
Hou Bingxu; Yu Jiyang; Senechal, Dorothee; Mechitoua, Namane; Min Jiesheng; Chen Guofei
2015-01-01
During CFD simulations of the flows at low Mach number regime, the classical assumption which neglects the dilatable effect of gas is no longer applicable when the temperature variation or the concentration variation of the mixture's components is too large in the fluid domain. To be able to correctly predict the flow at such a regime, some authors have recourse to a Low Mach number algorithm. This algorithm is based on the well-known pressure-based algorithm or elliptic solver for incompressible flows, SIMPLE, with a modification for the treatment of the pressure which is split into two parts (the hydrodynamic pressure and the thermodynamic pressure) and a dilatable term added in the mass equation. This algorithm has been implemented in the CFD code, Code_—Saturne, developed by EDF R and D, and applied for the CFD simulations of the erosion phenomena of light gas stratification by air injection. This paper is devoted to the analytical work with the Low Mach number algorithm based on the ST1 series of the SETH-2 campaign provided by the OECD project on the PANDA test facility of PSI. The first part is focused on a mesh sensitivity analysis, which is a common procedure for CFD codes validation. The second part of the paper presents a comparison between the CFD results obtained with the standard algorithms used for incompressible flows and the Low Mach number algorithm. The third part is an analysis of the CFD results obtained on the reference mesh with both different Froude numbers corresponding to the tests ST1_—7 (Fr=6.04) and ST1_—10 (Fr=7.95) from the ST1 series. In the last part the authors perform the knowledge of the initial light gas distribution effect on the stratification erosion and the capability of the CFD codes to predict this phenomenon with an area governed by diffusion regime (at the top of the vessel) and another one by forced convection near the injection. (author)
Energy Technology Data Exchange (ETDEWEB)
Guo, Xinyi; Narayan, Ramesh [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Sironi, Lorenzo [NASA Einstein Postdoctoral Fellow. (United States)
2014-12-10
Electron acceleration to non-thermal energies is known to occur in low Mach number (M{sub s} ≲ 5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D) particle-in-cell (PIC) plasma simulations, we showed in Paper I that electrons are efficiently accelerated in low Mach number (M{sub s} = 3) quasi-perpendicular shocks via a Fermi-like process. The electrons bounce between the upstream region and the shock front, with each reflection at the shock resulting in energy gain via shock drift acceleration. The upstream scattering is provided by oblique magnetic waves that are self-generated by the electrons escaping ahead of the shock. In the present work, we employ additional 2D PIC simulations to address the nature of the upstream oblique waves. We find that the waves are generated by the shock-reflected electrons via the firehose instability, which is driven by an anisotropy in the electron velocity distribution. We systematically explore how the efficiency of wave generation and of electron acceleration depend on the magnetic field obliquity, the flow magnetization (or equivalently, the plasma beta), and the upstream electron temperature. We find that the mechanism works for shocks with high plasma beta (≳ 20) at nearly all magnetic field obliquities, and for electron temperatures in the range relevant for galaxy clusters. Our findings offer 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.
Spearman, M. L.
1983-01-01
An investigation has been made to determine the effects of external stores on the stability and control characteristics of a delta wing fighter airplane model at Mach numbers from 0.60 to 2.01 for a Reynolds number of 3.0 X 1 million per foot. The angle-of-attack range was from about -4 degrees to 20 degrees at a sideslip angle of 0 degrees for the transonic tests, and from about -4 degrees to 10 degrees at sideslip angles of 0 degrees and 3 degrees for the supersonic tests. In general, the results of the tests indicated no seriously detrimental effects of the stores on the stability and control characteristics of the model but did show an increase in the minimum drag level throughout the Mach number range. However, the drag-due-to-lift was such that for subsonic/transonic speeds, the drag at higher lifts was essentially unaffected and the indications are that the maneuvering capability may not be impaired by the stores.
Mack, Robert J.
1988-01-01
A wind-tunnel study was conducted to determine the capability of a method combining linear theory and shock-expansion theory to design optimum camber surfaces for wings that will fly at high-supersonic/low-hypersonic speeds. Three force models (a flat-plate reference wing and two cambered and twisted wings) were used to obtain aerodynamic lift, drag, and pitching-moment data. A fourth pressure-orifice model was used to obtain surface-pressure data. All four wing models had the same planform, airfoil section, and centerbody area distribution. The design Mach number was 4.5, but data were also obtained at Mach numbers of 3.5 and 4.0. Results of these tests indicated that the use of airfoil thickness as a theoretical optimum, camber-surface design constraint did not improve the aerodynamic efficiency or performance of a wing as compared with a wing that was designed with a zero-thickness airfoil (linear-theory) constraint.
Pittman, J. L.
1979-01-01
Aerodynamic predictions from supersonic linear theory and hypersonic impact theory were compared with experimental data for three hypersonic research airplane concepts over a Mach number range from 1.10 to 2.86. The linear theory gave good lift prediction and fair to good pitching-moment prediction over the Mach number (M) range. The tangent-cone theory predictions were good for lift and fair to good for pitching moment for M more than or equal to 2.0. The combined tangent-cone theory predictions were good for lift and fair to good for pitching moment for M more than or equal to 2.0. The combined tangent-cone/tangent-wedge method gave the least accurate prediction of lift and pitching moment. The zero-lift drag was overestimated, especially for M less than 2.0. The linear theory drag prediction was generally poor, with areas of good agreement only for M less than or equal to 1.2. For M more than or equal to 2.), the tangent-cone method predicted the zero-lift drag most accurately.
Energy Technology Data Exchange (ETDEWEB)
Choi, Seung Min [GyeongBuk Technopark, Gyeongsan (Korea, Republic of); Kang, Hui Bo; Kwon, Young Doo; Kwon, Soon Bum [Kyungpook Nat’l Univ., Daegu (Korea, Republic of)
2016-12-15
In the present study, the effects of non-equilibrium condensation on the drag divergence Mach number with the angle of attack in a transonic 2D moist air flow of NACA0012 are investigated using the TVD finite difference scheme. For the same α, the maximum upstream Mach number of the shock wave, Mmax, and the size of supersonic bubble decrease with the increase in Φ{sub 0}. For the same M{sub ∞}, Φ{sub 0}, and T{sub 0}, the length of the non-equilibrium condensation zone Δ{sub z} decreases with increasing Φ{sub 0}. On the other hand, because of the attenuating effect of non-equilibrium condensation on wave drag, which is related to the interaction between the shock wave and the boundary layer, the drag coefficient C{sub D} decreases with an increase in Φ{sub 0} for the same M{sub ∞} and α. For the same α, M{sub D} increases with increasing Φ{sub 0}, while M{sub D} decreases with an increase in α.
Nason, Martin L.; Brown, Clarence A., Jr.; Rock, Rupert S.
1955-01-01
A linear stability analysis and flight-test investigation has been performed on a rolleron-type roll-rate stabilization system for a canard-type missile configuration through a Mach number range from 0.9 to 2.3. This type damper provides roll damping by the action of gyro-actuated uncoupled wing-tip ailerons. A dynamic roll instability predicted by the analysis was confirmed by flight testing and was subsequently eliminated by the introduction of control-surface damping about the rolleron hinge line. The control-surface damping was provided by an orifice-type damper contained within the control surface. Steady-state rolling velocities were at all times less than 1 radian per second between the Mach numbers of 0.9 to 2.3 on the configurations tested. No adverse longitudinal effects were experienced in flight because of the tendency of the free-floating rollerons to couple into the pitching motion at the low angles of attack and disturbance levels investigated herein after the introduction of control-surface damping.
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)
International Nuclear Information System (INIS)
Barigozzi, Giovanna; Armellini, Alessandro; Mucignat, Claudio; Casarsa, Luca
2012-01-01
Highlights: ► Flow visualization and PIV documented the presence of large coherent structures. ► The presence of coherent structures is documented up to the vane trailing edge. ► Shape and direction of rotation of vortices change with injection conditions. ► Vortices morphology influences the film cooling effectiveness distributions. ► A Mach number increase moves vortices closer to the wall. - Abstract: The present paper shows the results of an experimental investigation into the unsteadiness of coolant ejection at the trailing edge of a highly loaded nozzle vane cascade. The trailing edge cooling scheme features a pressure side cutback with film cooling slots, stiffened by evenly spaced ribs in an inline configuration. Cooling air is also ejected through two rows of cylindrical holes placed upstream of the cutback. Tests were performed with a low inlet turbulence intensity level (Tu 1 = 1.6%), changing the cascade operating conditions from low speed (M 2is = 0.2) up to high subsonic regime (M 2is = 0.6), and with coolant to main stream mass flow ratio varied within the 0.5–2.0% range. Particle Image Velocimetry (PIV) and flow visualizations were used to investigate the unsteady mixing process taking place between coolant and main flow downstream of the cutback, up to the trailing edge. For all the tested conditions, the results show the presence of large coherent structures, which presence is still evident up to the trailing edge. Their shape and direction of rotation change with injection conditions, as a function of coolant to mainstream velocity ratio, strongly influencing the thermal protection capability of the injected coolant flow. The Mach number increase is only responsible for a positioning of such vortical structures closer to the wall, while the Strouhal number almost remains unchanged.
Carlson, H. W.
1979-01-01
A new linearized-theory pressure-coefficient formulation was studied. The new formulation is intended to provide more accurate estimates of detailed pressure loadings for improved stability analysis and for analysis of critical structural design conditions. The approach is based on the use of oblique-shock and Prandtl-Meyer expansion relationships for accurate representation of the variation of pressures with surface slopes in two-dimensional flow and linearized-theory perturbation velocities for evaluation of local three-dimensional aerodynamic interference effects. The applicability and limitations of the modification to linearized theory are illustrated through comparisons with experimental pressure distributions for delta wings covering a Mach number range from 1.45 to 4.60 and angles of attack from 0 to 25 degrees.
Energy Technology Data Exchange (ETDEWEB)
Jacobs, A. M.; Zingale, M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Nonaka, A.; Almgren, A. S.; Bell, J. B. [Center for Computational Sciences and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
2016-08-10
The dynamics of helium shell convection driven by nuclear burning establish the conditions for runaway in the sub-Chandrasekhar-mass, double-detonation model for SNe Ia, as well as for a variety of other explosive phenomena. We explore these convection dynamics for a range of white dwarf core and helium shell masses in three dimensions using the low Mach number hydrodynamics code MAESTRO. We present calculations of the bulk properties of this evolution, including time-series evolution of global diagnostics, lateral averages of the 3D state, and the global 3D state. We find a variety of outcomes, including quasi-equilibrium, localized runaway, and convective runaway. Our results suggest that the double-detonation progenitor model is promising and that 3D dynamic convection plays a key role.
Mason, M. L.; Putnam, L. E.
1979-01-01
The flow field behind a circular arc nozzle with exhaust jet was studied at subsonic free stream Mach numbers. A conical probe was used to measure the pitot pressure in the jet and free stream regions. Pressure data were recorded for two nozzle configurations at nozzle pressure ratios of 2.0, 2.9, and 5.0. At each set of test conditions, the probe was traversed from the jet center line into the free stream region at seven data acquisition stations. The survey began at the nozzle exit and extended downstream at intervals. The pitot pressure data may be applied to the evaluation of computational flow field models, as illustrated by a comparison of the flow field data with results of inviscid jet plume theory.
Pendergraft, O. C., Jr.; Bare, E. A.
1982-01-01
An investigation was conducted in the Langley 16 foot transonic tunnel to determine the longitudinal aerodynamic characteristics of twin two dimensional nozzles and twin baseline axisymmetric nozzles installed on a fully metric 0.047 scale model of the F-15 three surface configuration (canards, wing, horizontal tails). The effects on performance of two dimensional nozzle in flight thrust reversing, locations and orientation of the vertical tails, and deflections of the horizontal tails were also determined. Test data were obtained at static conditions and at Mach numbers from 0.60 to 1.20 over an angle of attack range from -2 deg to 15 deg. Nozzle pressure ratio was varied from jet off to about 6.5.
International Nuclear Information System (INIS)
Ansanay-Alex, G.
2009-01-01
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)
Loposer, J. Dan; Rumsey, Charles B.
1954-01-01
Measurement of average skin-friction coefficients have been made on six rocket-powered free-flight models by using the boundary-layer rake technique. The model configuration was the NACA RM-10, a 12.2-fineness-ratio parabolic body of revolution with a flat base. Measurements were made over a Mach number range from 1 to 3.7, a Reynolds number range 40 x 10(exp 6) to 170 x 10(exp 6) based on length to the measurement station, and with aerodynamic heating conditions varying from strong skin heating to strong skin cooling. The measurements show the same trends over the test ranges as Van Driest's theory for turbulent boundary layer on a flat plate. The measured values are approximately 7 percent higher than the values of the flat-plate theory. A comparison which takes into account the differences in Reynolds number is made between the present results and skin-friction measurements obtained on NACA RM-10 scale models in the Langley 4- by 4-foot supersonic pressure tunnel, the Lewis 8- by 6-foot supersonic tunnel, and the Langley 9-inch supersonic tunnel. Good agreement is shown at all but the lowest tunnel Reynolds number conditions. A simple empirical equation is developed which represents the measurements over the range of the tests.
Fisher, D. F.; Saltzman, E. J.
1973-01-01
Boundary-layer and local friction data for Mach numbers up to 2.5 and Reynolds numbers up to 3.6 x 10 to the 8th power were obtained in flight at three locations on the XB-70-1 airplane: the lower forward fuselage centerline (nose), the upper rear fuselage centerline, and the upper surface of the right wing. Local skin friction coefficients were derived at each location by using (1) a skin friction force balance, (2) a Preston probe, and (3) an adaptation of Clauser's method which derives skin friction from the rake velocity profile. These three techniques provided consistent results that agreed well with the von Karman-Schoenherr relationship for flow conditions that are quasi-two-dimensional. At the lower angles of attack, the nose-boom and flow-direction vanes are believed to have caused the momentum thickness at the nose to be larger than at the higher angles of attack. The boundary-layer data and local skin friction coefficients are tabulated. The wind-tunnel-model surface-pressure distribution ahead of the three locations and the flight surface-pressure distribution ahead of the wing location are included.
Berry, S. A.
1986-01-01
An incompressible boundary-layer stability analysis of Laminar Flow Control (LFC) experimental data was completed and the results are presented. This analysis was undertaken for three reasons: to study laminar boundary-layer stability on a modern swept LFC airfoil; to calculate incompressible design limits of linear stability theory as applied to a modern airfoil at high subsonic speeds; and to verify the use of linear stability theory as a design tool. The experimental data were taken from the slotted LFC experiment recently completed in the NASA Langley 8-Foot Transonic Pressure Tunnel. Linear stability theory was applied and the results were compared with transition data to arrive at correlated n-factors. Results of the analysis showed that for the configuration and cases studied, Tollmien-Schlichting (TS) amplification was the dominating disturbance influencing transition. For these cases, incompressible linear stability theory correlated with an n-factor for TS waves of approximately 10 at transition. The n-factor method correlated rather consistently to this value despite a number of non-ideal conditions which indicates the method is useful as a design tool for advanced laminar flow airfoils.
Driver, Cornelius
1956-01-01
Tests have been made in the Langley 4- by 4-foot supersonic pressure tunnel at Mach numbers of 1.41, 1.61, and 2.01 to determine the static longitudinal stability and control characteristics of various arrangements of the Grumman F11F-1 airplane. Tests were made of the complete model and various combinations of its component parts and, in addition, the effects of various body modifications, a revised vertical tail, and wing fences on the longitudinal characteristics were determined. The results indicate that for a horizontal-tail incidence of -10 deg the trim lift coefficient varied from 0.29 at a Mach number of 1.61 to 0.23 at a Mach number of 2.01 with a corresponding decrease in lift-drag trim from 3.72 to 3.15. Stick-position instability was indicated in the low-supersonic-speed range. A photographic-type nose modification resulted in slightly higher values of minimum drag coefficient but did not significantly affect the static stability or lift-curve slope. The minimum drag coefficient for the complete model with the production nose remained essentially constant at 0.047 throughout the Mach number range investigated.
Sinclair, Archibald R; Mace, William D
1956-01-01
A limited calibration of a combined pitot-static tube and vane-type flow-angularity indicator has been made in the Langley 4- by 4-foot supersonic pressure tunnel at Mach numbers of 1.61 and 2.01. The results indicated that the angle-of-yaw indications were affected by unsymmetric shock effects at low angles of attack.
Stack, John; Draley, Eugene C; Delano, James B; Feldman, Lewis
1950-01-01
As part of a general investigation of propellers at high forward speeds, tests of two 2-blade propellers having the NACA 4-(3)(8)-03 and NACA 4-(3)(8)-45 blade designs have been made in the Langley 8-foot high-speed tunnel through a range of blade angle from 20 degrees to 60 degrees for forward Mach numbers from 0.165 to 0.725 to establish in detail the changes in propeller characteristics due to compressibility effects. These propellers differed primarily only in blade solidity, one propeller having 50 percent and more solidity than the other. Serious losses in propeller efficiency were found as the propeller tip Mach number exceeded 0.91, irrespective of forward speed or blade angle. The magnitude of the efficiency losses varied from 9 percent to 22 percent per 0.1 increase in tip Mach number above the critical value. The range of advance ratio for peak efficiency decreased markedly with increase of forward speed. The general form of the changes in thrust and power coefficients was found to be similar to the changes in airfoil lift coefficient with changes in Mach number. Efficiency losses due to compressibility effects decreased with increase of blade width. The results indicated that the high level of propeller efficiency obtained at low speeds could be maintained to forward sea-level speeds exceeding 500 miles per hour.
Ferri, Antonio; Nucci, Louis M
1954-01-01
Contains theoretical and experimental analysis of circular inlets having a central body at Mach numbers of 3.30, 2.75, and 2.45. The inlets have been designed in order to have low drag and high pressure recovery. The pressure recoveries obtained are of the same order of magnitude as those previously obtained by inlets having very large external drag.
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.
Bond, Aleck C.; Swanson, Andrew G.
1953-01-01
A free-flight 0.12-scale rocket-boosted model of the North American MX-770 (X-10) missile has been tested in flight by the Pilotless Aircraft Research Division of the Langley Aeronautical Laboratory. Drag, longitudinal stability, and duct performance data were obtained at Mach numbers from 0.8 to 1.7 covering a Reynolds number range of about 9 x 10(exp 6) to 24 x 10(exp 6) based on wing mean aerodynamic chord. The lift-curve slope, static stability, and damping-in-pitch derivatives showed similar variations with Mach number, the parameters increasing from subsonic values in the transonic region and decreasing in the supersonic region. The variations were for the most part fairly smooth. The aerodynamic center of the configuration shifted rearward in the transonic region and moved forward gradually in the supersonic region. The pitching effectiveness of the canard control surfaces was maintained throughout the flight speed range, the supersonic values being somewhat greater than the subsonic. Trim values of angle of attack and lift coefficient changed abruptly in the transonic region, the change being associated with variations in the out-of-trim pitching moment, control effectiveness, and aerodynamic-center travel in this speed range. Duct total-pressure recovery decreased with increase in free-stream Mach number and the values were somewhat less than normal-shock recovery. Minimum drag data indicated a supersonic drag coefficient about twice the subsonic drag coefficient and a drag-rise Mach number of approximately 0.90. Base drag was small subsonically but was about 25 percent of the minimum drag of the configuration supersonically.
Montoya, L. C.; Economu, M. A.; Cissell, R. E.
1974-01-01
The use of a pitot-static probe to determine wing section drag at speeds from Mach 0.5 to approximately 1.0 was evaluated in flight. The probe unit is described and operational problems are discussed. Typical wake profiles and wing section drag coefficients are presented. The data indicate that the pitot-static probe gave reliable results up to speeds of approximately 1.0.
A Whitham-Theory Sonic-Boom Analysis of the TU-144 Aircraft at a Mach Number of 2.2
Mack, Robert J.
1999-01-01
. Therefore, an analysis of the Tu-144 was made to obtain predictions of pressure signature shape and shock strengths at cruise conditions so that the range and characteristics of the required pressure gages could be determined well in advance of the tests. Cancellation of the sonic-boom signature measurement part of the tests removed the need for these pressure gages. Since CFD methods would be used to analyze the aerodynamic performance of the Tu-144 and make similar pressure signature predictions, the relatively quick and simple Whitham-theory pressure signature predictions presented in this paper could be used for comparisons. Pressure signature predictions of sonic-boom disturbances from the Tu- 144 aircraft were obtained from geometry derived from a three-view description of the production aircraft. The geometry was used to calculate aerodynamic performance characteristics at supersonic-cruise conditions. These characteristics and Whitham/Walkden sonic-boom theory were employed to obtain F-functions and flow-field pressure signature predictions at a Mach number of 2.2, at a cruise altitude of 61000 feet, and at a cruise weight of 350000 pounds.
Schmeer, James W.; Cassetti, Marlowe D.
1960-01-01
An investigation of the performance, stability, and control characteristics of a variable-sweep arrow-wing model with the outer wing panels swept 75 deg. has been conducted in the Langley 16-foot transonic tunnel. Four outboard engines located above and below the wing provided propulsive thrust, and, by deflecting in the pitch direction and rotating in the lateral plane, also produced control forces. The engine nacelles incorporated swept lateral and vertical fins for aerodynamic stability and control. Jet-off data were obtained with flow-through nacelles, simulating inlet flow; jet thrust and hot-jet interference effects were obtained with faired-nose nacelles housing hydrogen peroxide gas generators. Six-component force and moment data were obtained at Mach numbers from 0.60 to 1.05 through a range of angles of attack and angles of side-slip. Control characteristics were obtained by deflecting the nacelle-fin combinations as elevators, rudders, and ailerons at several fixed angles for each control. The results indicate that the basic wing-body configuration becomes neutrally stable or unstable at a lift coefficient of 0.15; addition of nacelles with fins delayed instability to a lift coefficient of 0.30. Addition of nacelles to the wing-body configuration increased minimum drag from 0.0058 to 0.0100 at a Mach number of 0.60 and from 0.0080 to 0.0190 at a Mach number of 1.05 with corresponding reductions in maximum lift-drag ratio of 12 percent and 33 percent, respectively. The nacelle-fin combinations were ineffective as longitudinal controls but were adequate as directional and lateral controls. The model with nacelles and fins was directionally and laterally stable; the stability generally increased with increasing lift. Jet interference effects on stability and control characteristics were small but the adverse effects on drag were greater than would be expected for isolated nacelles.
Mccain, W. E.
1984-01-01
The unsteady aerodynamic lifting surface theory, the Doublet Lattice method, with experimental steady and unsteady pressure measurements of a high aspect ratio supercritical wing model at a Mach number of 0.78 were compared. The steady pressure data comparisons were made for incremental changes in angle of attack and control surface deflection. The unsteady pressure data comparisons were made at set angle of attack positions with oscillating control surface deflections. Significant viscous and transonic effects in the experimental aerodynamics which cannot be predicted by the Doublet Lattice method are shown. This study should assist development of empirical correction methods that may be applied to improve Doublet Lattice calculations of lifting surface aerodynamics.
Graves, E. B.; Fournier, R. H.
1979-01-01
The tests were performed at a Mach number of 2.50 and at angles of attack from about -4 deg to 32 deg. The results indicate that increasing nose bluntness increases zero lift drag and decreases both the maximum lift-drag ratio and the level of directional stability. The center of pressure generally moves forward with increasing nose size; however, small nose radii on the modified elliptical configurations move the center of pressure rearward. The circular bodied configurations exhibit the greatest longitudinal stability and the least directional stability. Concepts with the variable geometry afterbody contour display the most directional stability and the greatest zero lift drag.
Brown, Clarence A , Jr
1957-01-01
A full- scale rocket-powered model of a cruciform canard missile configuration with a low- aspect - ratio wing and blunt nose has been flight tested by the Langley Pilotless Aircraft Research Division. Static and dynamic longitudinal stability and control derivatives of this interdigitated canard-wing missile configuration were determined by using the pulsed- control technique at low angles of attack and for a Mach number range of 1.2 to 2.1. The lift - curve slope showed only small nonlinearities with changes in control deflection or angle of attack but indicated a difference in lift- .curve slope of approximately 7 percent for the two control deflections of delta = 3.0 deg and delta= -0.3 deg . The large tail length of the missile tested was effective in producing damping in pitch throughout the Mach number range tested. The aerodynamic- center location was nearly constant with Mach number for the two control deflections but was shown to be less stable with the larger control deflection. The increment of lift produced by the controls was small and positive throughout the Mach number range tested, whereas the pitching moment produced by the controls exhibited a normal trend of reduced effectiveness with increasing Mach number.The effectiveness of the controls in producing angle of attack, lift, and pitching moment was good at all Mach numbers tested.
Crabill, Norman L.
1956-01-01
The National Advisory Committee for Aeronautics has conducted a flight test of a model approximating the McDonnell F3H-lN airplane configuration to determine its pitch-up and buffet boundaries, as well as the usual longitudinal stability derivatives obtainable from the pulsed- tail technique. The test was conducted by the freely flying rocket- boosted model technique developed at the Langley Laboratory; results were obtained at Mach numbers from 0.40 to 1.27 at corresponding Reynolds numbers of 2.6 x 10(exp 6) and 9.0 x 10(exp 6). The phenomena of pitch-up, buffet, and maximum lift were encountered at Mach numbers between 0.42 and 0.85. The lift-curve slope and wing-root bending-moment slope increased with increasing angle of attack, whereas the static stability decreased with angle of attack at subsonic speeds and increased at transonic speeds. There was little change in trim at low lift at transonic speeds.
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...
Igoe, William B.; Re, Richard J.; Cassetti, Marlowe
1961-01-01
An investigation has been made of the effects of conical wing camber and supersonic body indentation on the aerodynamic characteristics of a wing-body configuration at transonic speeds. Wing aspect ratio was 3.0, taper ratio was 0.1, and quarter-chord line sweepback was 52.5 deg with airfoil sections of 0.03 thickness ratio. The tests were conducted in the Langley 16-foot transonic tunnel at various Mach numbers from 0.80 to 1.05 at angles of attack from -4 deg to 14 deg. The cambered-wing configuration achieved higher lift-drag ratios than a similar plane-wing configuration. The camber also reduced the effects of wing-tip flow separation on the aerodynamic characteristics. In general, no stability or trim changes below wing-tip flow separation resulted from the use of camber. The use of supersonic body indentation improved the lift-drag ratios at Mach numbers from 0.96 to 1.05.
International Nuclear Information System (INIS)
Samir, U.; Wildman, P.J.; Rich, F.; Brinton, H.C.; Sagalyn, R.C.
1981-01-01
Measurements of ion current, electron temperature, and density and values of satellite potential from the U.S. Air Force Satellite S3-2 together with ion composition measurements from the Atmosphere Explorer (AE-E) satellite were used to examine the variation of the ratio α = [I/sub +/(wake)]/[I/sub +/(ambient)] (where I/sub +/ is the ion current) with altitude and to examine the significance of the parametric interplay between ionic Mach number, normalized body size R/sub D/( = R0/lambda/sub D/, where R 0 is the satellite radius and lambda/sub D/ is the ambient debye length) and normalized body potenital phi/sub N/( = ephis/KT/sub e/, where phi/sub s/ is the satellite potential, T/sub e/ is the electron temperature, and e and K are constants). It was possible to separate between the influence of R/sub D/ and phi/sub N/ on α for a specific range parameters. Uncertainty, however, remains regarding the competiton between R/sub D/ and S(H + ) and S(O + ) are oxygen and hydrogen ionic Mach numbers, respectively) in determining the ion distribution in the nearest vicincity to the satellite surface. A brief discussion relevant to future experiments in the area of body plasma flow interactions to be conducted on board the Shuttle/Spacelab facility, is also included
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 angle-of-attack and sideslip regions studied.
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)
Bailey, R. O.; Brownson, J. J.
1979-01-01
Tests were conducted in the Ames 6 by 6 foot wind tunnel to determine the interaction of reaction jets for roll control on the M2-F2 lifting-body entry vehicle. Moment interactions are presented for a Mach number range of 0.6 to 1.7, a Reynolds number range of 1.2 x 10 to the 6th power to 1.6 x 10 to the 6th power (based on model reference length), an angle-of-attack range of -9 deg to 20 deg, and an angle-of-sideslip range of -6 deg to 6 deg at an angle of attack of 6 deg. The reaction jets produce roll control with small adverse yawing moment, which can be offset by horizontal thrust component of canted jets.
Hollinger, James A.; Mitcham, Grady L.
1955-01-01
A flight test of a rocket-propelled model of the Convair XFY-1 airplane was conducted to determine the lateral stability and control characteristics, The 0.133-scale model had windmilling propellers for this test, which covered a Mach number range of O.70 to 1.12. The center of gravity was located at 13.9 percent of the mean aerodynamic chord. The methods of analysis included both a solution by vector diagrams and simple one- and two-degree-of-freedom methods. The model was both statically and dynamically stable throughout the speed range of the testa The roll damping was good, and the slope of the side-force curve varied little with speed. The rudder was effective throughout the test speed range, although it was reduced to about 43 percent of its subsonic value at supersonic speeds.
Putnam, L. E.; Mercer, C. E.
1986-01-01
An investigation has been conducted in the Langley 16-Foot Transonic Tunnel to measure the flow field in and around the jet exhaust from a nonaxisymmetric nozzle configuration. The nozzle had a rectangular exit with a width-to-height ratio of 2.38. Pitot-pressure measurements were made at five longitudinal locations downstream of the nozzle exit. The maximum distance downstream of the exit was about 5 nozzle heights. These measurements were made at free-stream Mach numbers of 0.00, 0.60, and 1.20 with the nozzle operating at a ratio of nozzle total pressure to free-stream static pressure of 4.0. The jet exhaust was simulated with high-pressure air that had an exit total temperature essentially equal to the free-stream total temperature.
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
Garland, Benjamine J.; Chauvin, Leo T.
1957-01-01
Measurements of aerodynamic heat transfer have been made along the hemisphere and cylinder of a hemisphere-cylinder rocket-propelled model in free flight up to a Mach number of 3.88. The test Reynolds number based on free-stream condition and diameter of model covered a range from 2.69 x l0(exp 6) to 11.70 x 10(exp 6). Laminar, transitional, and turbulent heat-transfer coefficients were obtained. The laminar data along the body agreed with laminar theory for blunt bodies whereas the turbulent data along the cylinder were consistently lower than that predicted by the turbulent theory for a flat plate. Measurements of heat transfer at the stagnation point were, in general, lower than the theory for stagnation-point heat transfer. When the Reynolds number to the junction of the hemisphere-cylinder was greater than 6 x l0(exp 6), the transitional Reynolds number varied from 0.8 x l0(exp 6) to 3.0 x 10(exp 6); however, than 6 x l(exp 6) when the Reynolds number to the junction was less, than the transitional Reynolds number varied from 7.0 x l0(exp 6) to 24.7 x 10(exp 6).
International Nuclear Information System (INIS)
Khoury, Justin; Parikh, Maulik
2009-01-01
Mach's principle is the proposition that inertial frames are determined by matter. We put forth and implement a precise correspondence between matter and geometry that realizes Mach's principle. Einstein's equations are not modified and no selection principle is applied to their solutions; Mach's principle is realized wholly within Einstein's general theory of relativity. The key insight is the observation that, in addition to bulk matter, one can also add boundary matter. Given a space-time, and thus the inertial frames, we can read off both boundary and bulk stress tensors, thereby relating matter and geometry. We consider some global conditions that are necessary for the space-time to be reconstructible, in principle, from bulk and boundary matter. Our framework is similar to that of the black hole membrane paradigm and, in asymptotically anti-de Sitter space-times, is consistent with holographic duality.
Hastings, Earl C., Jr.; Dickens, Waldo L.
1957-01-01
A flight investigation was conducted to determine the effects of an inlet modification and rocket-rack extension on the longitudinal trim and low-lift drag of the Douglas F5D-1 airplane. The investigation was conducted with a 0.125-scale rocket-boosted model which was flight tested at the Langley Pilotless Aircraft Research Station at Wallops Island, Va. Results indicate that the combined effects of the modified inlet and fully extended rocket racks on the trim lift coefficient and trim angle of attack were small between Mach numbers of 0.94 and 1.57. Between Mach numbers of 1.10 and 1.57 there was an average increase in drag coefficient of about o,005 for the model with modified inlet and extended rocket racks. The change in drag coefficient due to the inlet modification alone is small between Mach numbers of 1.59 and 1.64
Hofstetter, William R.
1957-01-01
The static longitudinal and lateral stability charaetefistics of an 0 .065-scale model of the XRSSM-N-9a (REGULUS II) Missile at Mach number range of 1.6 to 2.0 at a Reynolds number per foot of 2.0(exp 8)
Hastings, Earl C., Jr.; Dickens, Waldo L.
1957-01-01
A flight investigation was conducted to determine the effects of inlet modification and rocket-rack extension on the longitudinal trim and low-lift drag of the Douglas F5D-1 airplane. The investigation was conducted with a 0.125-scale rocket-boosted model between Mach Numbers of 0.81 and 1.64. This paper presents the changes in trim angle of attack, trim lift coefficient, and low-lift drag caused by the modified inlets alone over a small part of the test Mach number range and by a combination of the modified inlets and extended rocket racks throughout the remainder of the test.
Photodensitometric tracing of Mach bands and its significance
International Nuclear Information System (INIS)
Yoo, Shi Joon; Cho, Kyung Sik; Kang, Heung Sik; Cho, Byung Jae
1984-01-01
Mach bands, a visual phenomenon resulting from lateral inhibitory impulses in the retina, are recognized as lucent or dense lines at the borders of different radiographic densities. A number of clinical situations have been described in which Mach bands may cause difficulty in radiographic diagnosis. Photodensitometric measurement of the film can differentiate the true change in film density from the Mach band which is an optical illusion. Authors present several examples of photodensitometric tracings of Mach bands, with the brief review of the mechanism of their production
Stevens, Joseph E.
1955-01-01
Low-lift drag data are presented herein for one 1/7.5-scale rocket-boosted model and three 1/45.85-scale equivalent-body models of the Grumman F9F-9 airplane, The data were obtained over a Reynolds number range of about 5 x 10(exp 6) to 10 x 10(exp 6) based on wing mean aerodynamic chord for the rocket model and total body length for the equivalent-body models. The rocket-boosted model showed a drag rise of about 0,037 (based on included wing area) between the subsonic level and the peak supersonic drag coefficient at the maximum Mach number of this test. The base drag coefficient measured on this model varied from a value of -0,0015 in the subsonic range to a maximum of about 0.0020 at a Mach number of 1.28, Drag coefficients for the equivalent-body models varied from about 0.125 (based on body maximum area) in the subsonic range to about 0.300 at a Mach number of 1.25. Increasing the total fineness ratio by a small amount raised the drag-rise Mach number slightly.
Sogukpinar, Haci
2018-02-01
In this paper, some of the NACA 64A series airfoils data are estimated and aerodynamic properties are calculated to facilitate great understandings effect of relative thickness on the aerodynamic performance of the airfoil by using COMSOL software. 64A201-64A204 airfoils data are not available in literature therefore 64A210 data are used as reference data to estimate 64A201, 64A202, 64A203, 64A204 airfoil configurations. Numerical calculations are then conducted with the angle of attack from -12° to +16° by using k-w turbulence model based on the finite-volume approach. The lift and drag coefficient are one of the most important parameters in studying the airplane performance. Therefore lift, drag and pressure coefficient around selected airfoil are calculated and compared at the Reynolds numbers of 6 × 106 and also stalling characteristics of airfoil section are investigated and presented numerically.
Cassetti, Marlowe D.; Re, Richard J.; Igoe, William B.
1961-01-01
An investigation has been made of the effects of conical wing camber and body indentation according to the supersonic area rule on the aerodynamic wing loading characteristics of a wing-body-tail configuration at transonic speeds. The wing aspect ratio was 3, taper ratio was 0.1, and quarter-chord-line sweepback was 52.5 deg. with 3-percent-thick airfoil sections. The tests were conducted in the Langley 16-foot transonic tunnel at Mach numbers from 0.80 to 1.05 and at angles of attack from 0 deg. to 14 deg., with Reynolds numbers based on mean aerodynamic chord varying from 7 x 10(exp 6) to 8 x 10(exp 6). Conical camber delayed wing-tip stall and reduced the severity of the accompanying longitudinal instability but did not appreciably affect the spanwise load distribution at angles of attack below tip stall. Body indentation reduced the transonic chordwise center-of-pressure travel from about 8 percent to 5 percent of the mean aerodynamic chord.
Hastings, Earl E., Jr.; Mitcham, Grady L.
1954-01-01
A flight test has been conducted to determine the longitudinal stability and control,characteristics of a 0.133-scale model of the Consolidated Vultee XFY-1 airplane without propellers for the Mach number range between 0.73 and 1.19.
Baber, Hal T , Jr; Moul, Martin T
1955-01-01
Two full-scale models of an inline, cruciform, canard missile configuration having a low-aspect-ratio wing equipped with flap-type controls were flight tested in order to determine the missile's longitudinal aerodynamic characteristics. Stability derivatives and control and drag characteristics are presented for a range of Mach number from 0.7 to 1.8. Nonlinear lift and moment curves were noted for the angle - of-attack range of this test (0 deg to 8 deg). The aerodynamic-center location for angles of attack near 50 remained nearly constant for supersonic speeds at 13.5 percent of the mean aerodynamic chord; whereas for angles of attack near 0 deg, there was a rapid forward movement of the aerodynamic center as the Mach number increased. At a control deflection of 0 deg, the missile's response to the longitudinal control was in an essentially fixed space plane which was not coincident with the pitch plane as a result of the missile rolling. As a consequence, stability characteristics were determined from the resultant of pitch and yaw motions. The damping-in-pitch derivatives for the two angle -of-attack ranges of the test are in close agreement and varied only slightly with Mach number. The horn-balanced trailing-edge flap was effective in producing angle of attack over the Mach number range.
Baber, H. T., Jr.; Moul, M. T.
1955-01-01
Two full-scale models of an inline, cruciform, canard missile configuration having a low-aspect-ratio wing equipped with flap-type controls were flight tested in order to determine the missile's longitudinal aerodynamic characteristics. Stability derivatives and control and drag characteristics are presented for a range of Mach number from 0.7 to 1.8. Nonlinear lift and moment curves were noted for the angle-of-attack range of this test (0 deg to 8 deg ). The aerodynamic-center location for angles of attack near 5 deg remained nearly constant for supersonic speeds at 13.5 percent of the mean aerodynamic chord; whereas for angles of attack near O deg, there was a rapid forward movement of the aerodynamic center as the Mach number increased. At a control deflection of O deg, the missile's response to the longitudinal control was in an essentially fixed space plane which was not coincident with the pitch plane as a result of the missile rolling. As a consequence, stability characteristics were determined from the resultant of pitch and yaw motions. The damping-in-pitch derivatives for the two angle-of-attack ranges of the test are in close agreement and varied only slightly with Mach number. The horn-balanced trailing-edge flap was effective in producing angle of attack over the Mach number range.
Runckel, Jack F.; Schmeer, James W.; Cassetti, Marlowe D.
1960-01-01
An investigation of the performance, stability, and control characteristics of a variable-sweep arrow-wing model (the "Swallow") with the outer wing panels swept 25 deg has been conducted in the Langley 16-foot transonic tunnel. The wing was uncambered and untwisted and had RAE 102 airfoil sections with a thickness-to-chord ratio of 0.14 normal to the leading edge. Four outboard engines located above and below the wing provided propulsive thrust, and, by deflecting in the pitch direction and rotating in the lateral plane, also produced control forces. A pair of swept lateral fins and a single vertical fin were mounted on each engine nacelle to provide aerodynamic stability and control. Jets-off data were obtained with flow-through nacelles, stimulating the effects of inlet flow; jet thrust and hot-jet interference effects were obtained with faired-nose nacelles housing hydrogen peroxide gas generators. Six-component force and moment data were obtained through a Mach number range of 0.40 to 0.90 at angles of attack and angles of sideslip from 0 deg to 15 deg. Longitudinal, directional, and lateral control were obtained by deflecting the nacelle-fin combinations as elevators, rudders, and ailerons at several fixed angles for each control.
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)
Mach's principle and rotating universes
International Nuclear Information System (INIS)
King, D.H.
1990-01-01
It is shown that the Bianchi 9 model universe satisfies the Mach principle. These closed rotating universes were previously thought to be counter-examples to the principle. The Mach principle is satisfied because the angular momentum of the rotating matter is compensated by the effective angular momentum of gravitational waves. A new formulation of the Mach principle is given that is based on the field theory interpretation of general relativity. Every closed universe with 3-sphere topology is shown to satisfy this formulation of the Mach principle. It is shown that the total angular momentum of the matter and gravitational waves in a closed 3-sphere topology universe is zero
Graham, John B., Jr.
1958-01-01
Heat-transfer and pressure measurements were obtained from a flight test of a 1/18-scale model of the Titan intercontinental ballistic missile up to a Mach number of 3.86 and Reynolds number per foot of 23.5 x 10(exp 6) and are compared with the data of two previously tested 1/18-scale models. Boundary-layer transition was observed on the nose of the model. Van Driest's theory predicted heat-transfer coefficients reasonably well for the fully laminar flow but predictions made by Van Driest's theory for turbulent flow were considerably higher than the measurements when the skin was being heated. Comparison with the flight test of two similar models shows fair repeatability of the measurements for fully laminar or turbulent flow.
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.)
Gyro precession and Mach's principle
International Nuclear Information System (INIS)
Eby, P.
1979-01-01
The precession of a gyroscope is calculated in a nonrelativistic theory due to Barbour which satisfies Mach's principle. It is shown that the theory predicts both the geodetic and motional precession of general relativity to within factors of order 1. The significance of the gyro experiment is discussed from the point of view of metric theories of gravity and this is contrasted with its significance from the point of view of Mach's principle. (author)
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
Mach's predictions and relativistic cosmology
International Nuclear Information System (INIS)
Heller, M.
1989-01-01
Deep methodological insight of Ernst Mach into the structure of the Newtonian mechanics allowed him to ask questions, the importance of which can be appreciated only today. Three such Mach's ''predictions'' are briefly presented, namely: the possibility of the existence of an allpervading medium which could serve as an universal frame of reference and which has actually been discovered in the form of the microwave background radiation, a certain ''smoothness'' of the Universe which is now recognized as the Robertson-Walker symmetries and the possibility of the experimental verification of the mass anisotropy. 11 refs. (author)
Czech Academy of Sciences Publication Activity Database
Těšínská, Emilie; Landa, Ivan; Drahoš, Jiří
2016-01-01
Roč. 66, č. 3 (2016), s. 167-174 ISSN 0009-0700 Institutional support: RVO:67985955 ; RVO:68378114 ; RVO:67985858 Keywords : Ernst Mach * pedagogy * experiments * general education * ballistics * Doppler principle Subject RIV: AB - History; CF - Physical ; Theoretical Chemistry (UCHP-M)
Elementary physical approach to Mach's principle and its observational basis
International Nuclear Information System (INIS)
Horak, Z.
1979-01-01
It is shown that Mach's principle and the general principle of relativity are logical consequences of a 'materialistic postulate' and that general relativity implies the validity of Mach's principle for a static (or quasistatic) homogeneous and isotropic universe, spatially self-enclosed. The finite velocity of propagation of gravitational field does not imply a retardation of inertial forces due to the distant masses and therefore does not exclude the validity of Mach's principle. Similarly, the experimentally verified isotropy of inertia is compatible with this principle. The recent observational evidence of very high isotropy of the actual universe proves that the 'anti-Machian' Godel world model must be rejected as a nonphysical one. This suggests the possibility of a renaissance of Einstein's first cosmological model by considering-in the spirit of an older idea of Herbert Dingle-a superlarge-scale quasistatic universe consisting of an unknown number of statistically oscillating regions similar to our own, momentarily expanding, metagalaxy. (author)
Local flow measurements at the inlet spike tip of a Mach 3 supersonic cruise airplane
Johnson, H. J.; Montoya, E. J.
1973-01-01
The flow field at the left inlet spike tip of a YF-12A airplane was examined using at 26 deg included angle conical flow sensor to obtain measurements at free-stream Mach numbers from 1.6 to 3.0. Local flow angularity, Mach number, impact pressure, and mass flow were determined and compared with free-stream values. Local flow changes occurred at the same time as free-stream changes. The local flow usually approached the spike centerline from the upper outboard side because of spike cant and toe-in. Free-stream Mach number influenced the local flow angularity; as Mach number increased above 2.2, local angle of attack increased and local sideslip angle decreased. Local Mach number was generally 3 percent less than free-stream Mach number. Impact-pressure ratio and mass flow ratio increased as free-stream Mach number increased above 2.2, indicating a beneficial forebody compression effect. No degradation of the spike tip instrumentation was observed after more than 40 flights in the high-speed thermal environment encountered by the airplane. The sensor is rugged, simple, and sensitive to small flow changes. It can provide accurate imputs necessary to control an inlet.
Diffusive wave in the low Mach limit for non-viscous and heat-conductive gas
Liu, Yechi
2018-06-01
The low Mach number limit for one-dimensional non-isentropic compressible Navier-Stokes system without viscosity is investigated, where the density and temperature have different asymptotic states at far fields. It is proved that the solution of the system converges to a nonlinear diffusion wave globally in time as Mach number goes to zero. It is remarked that the velocity of diffusion wave is proportional with the variation of temperature. Furthermore, it is shown that the solution of compressible Navier-Stokes system also has the same phenomenon when Mach number is suitably small.
Robert Musil versus Ernst Mach
Directory of Open Access Journals (Sweden)
Jalón, Mauricio
2010-06-01
Full Text Available On Mach’s Theories (DT of R. Musil rejects that the scientific representation tends to build a clear and complete inventory of facts. Mach finds himself obliged to presuppose constant relationships in nature; but this regularity of phenomena implies that the law is something more than a «table», that its mere dependencies are pushed into the background, and that a theoretical relationship in Physics is much more than an order relationship. His conception of scientific economy as a «natural adaptation» implies a biological monism opposed to the characteristic dualities of an empiricist.
Sobre las teorías de Mach (TD de R. Musil rebate que la representación científica tienda a construir un claro y completo inventario de hechos. Pues Mach se ve obligado a presuponer relaciones constantes en la naturaleza; pero esta regularidad de los fenómenos implica que la ley es algo más que cierto «cuadro», que las meras dependencias que defiende están en un segundo plano y que una relación teórica en física es mucho más que una relación de orden. Su concepción de la economía científica como «adaptación natural» significa un monismo biológico opuesto a las dualidades propias de un empirista.
Rotating detectors and Mach's principle
International Nuclear Information System (INIS)
Paola, R.D.M. de; Svaiter, N.F.
2000-08-01
In this work we consider a quantum version of Newton s bucket experiment in a fl;at spacetime: we take an Unruh-DeWitt detector in interaction with a real massless scalar field. We calculate the detector's excitation rate when it is uniformly rotating around some fixed point and the field is prepared in the Minkowski vacuum and also when the detector is inertial and the field is in the Trocheries-Takeno vacuum state. These results are compared and the relations with Mach's principle are discussed. (author)
Recovery Temperature, Transition, and Heat Transfer Measurements at Mach 5
Brinich, Paul F.
1961-01-01
Schlieren, recovery temperature, and heat-transfer measurements were made on a hollow cylinder and a cone with axes alined parallel to the stream. Both the cone and cylinder were equipped with various bluntnesses, and the tests covered a Reynolds number range up to 20 x 10(exp 6) at a free-stream Mach number of 4.95 and wall to free-stream temperature ratios from 1.8 to 5.2 (adiabatic). A substantial transition delay due to bluntness was found for both the cylinder and the cone. For the present tests (Mach 4.95), transition was delayed by a factor of 3 on the cylinder and about 2 on the cone, these delays being somewhat larger than those observed in earlier tests at Mach 3.1. Heat-transfer tests on the cylinder showed only slight effects of wall temperature level on transition location; this is to be contrasted to the large transition delays observed on conical-type bodies at low surface temperatures at Mach 3.1. The schlieren and the peak-recovery-temperature methods of detecting transition were compared with the heat-transfer results. The comparison showed that the first two methods identified a transition point which occurred just beyond the end of the laminar run as seen in the heat-transfer data.
Does the chromatic Mach bands effect exist?
Tsofe, Avital; Spitzer, Hedva; Einav, Shmuel
2009-06-30
The achromatic Mach bands effect is a well-known visual illusion, discovered over a hundred years ago. This effect has been investigated thoroughly, mainly for its brightness aspect. The existence of Chromatic Mach bands, however, has been disputed. In recent years it has been reported that Chromatic Mach bands are not perceived under controlled iso-luminance conditions. However, here we show that a variety of Chromatic Mach bands, consisting of chromatic and achromatic regions, separated by a saturation ramp, can be clearly perceived under iso-luminance and iso-brightness conditions. In this study, observers' eye movements were recorded under iso-brightness conditions. Several observers were tested for their ability to perceive the Chromatic Mach bands effect and its magnitude, across different cardinal and non-cardinal Chromatic Mach bands stimuli. A computational model of color adaptation, which predicted color induction and color constancy, successfully predicts this variation of Chromatic Mach bands. This has been tested by measuring the distance of the data points from the "achromatic point" and by calculating the shift of the data points from predicted complementary lines. The results suggest that the Chromatic Mach bands effect is a specific chromatic induction effect.
Cui, Peng; Xu, WanWu; Li, Qinglian
2018-01-01
Currently, the upper operating limit of the turbine engine is Mach 2+, and the lower limit of the dual-mode scramjet is Mach 4. Therefore no single power systems can operate within the range between Mach 2 + and Mach 4. By using ejector rockets, Rocket-based-combined-cycle can work well in the above scope. As the key component of Rocket-based-combined-cycle, the ejector rocket has significant influence on Rocket-based-combined-cycle performance. Research on the influence of rocket parameters on Rocket-based-combined-cycle in the speed range of Mach 2 + to Mach 4 is scarce. In the present study, influences of Mach number and total pressure of the ejector rocket on Rocket-based-combined-cycle were analyzed numerically. Due to the significant effects of the flight conditions and the Rocket-based-combined-cycle configuration on Rocket-based-combined-cycle performances, flight altitude, flight Mach number, and divergence ratio were also considered. The simulation results indicate that matching lower altitude with higher flight Mach numbers can increase Rocket-based-combined-cycle thrust. For another thing, with an increase of the divergent ratio, the effect of the divergent configuration will strengthen and there is a limit on the divergent ratio. When the divergent ratio is greater than the limit, the effect of divergent configuration will gradually exceed that of combustion on supersonic flows. Further increases in the divergent ratio will decrease Rocket-based-combined-cycle thrust.
Dark matter versus Mach's principle.
von Borzeszkowski, H.-H.; Treder, H.-J.
1998-02-01
Empirical and theoretical evidence show that the astrophysical problem of dark matter might be solved by a theory of Einstein-Mayer type. In this theory up to global Lorentz rotations the reference system is determined by the motion of cosmic matter. Thus one is led to a "Riemannian space with teleparallelism" realizing a geometric version of the Mach-Einstein doctrine. The field equations of this gravitational theory contain hidden matter terms where the existence of hidden matter is inferred safely from its gravitational effects. It is argued that in the nonrelativistic mechanical approximation they provide an inertia-free mechanics where the inertial mass of a body is induced by the gravitational action of the comic masses. Interpreted form the Newtonian point of view this mechanics shows that the effective gravitational mass of astrophysical objects depends on r such that one expects the existence of dark matter.
Determining integral density distribution in the mach reflection of shock waves
Shevchenko, A. M.; Golubev, M. P.; Pavlov, A. A.; Pavlov, Al. A.; Khotyanovsky, D. V.; Shmakov, A. S.
2017-05-01
We present a method for and results of determination of the field of integral density in the structure of flow corresponding to the Mach interaction of shock waves at Mach number M = 3. The optical diagnostics of flow was performed using an interference technique based on self-adjusting Zernike filters (SA-AVT method). Numerical simulations were carried out using the CFS3D program package for solving the Euler and Navier-Stokes equations. Quantitative data on the distribution of integral density on the path of probing radiation in one direction of 3D flow transillumination in the region of Mach interaction of shock waves were obtained for the first time.
Interplay between Mach cone and radial expansion in jet events
Energy Technology Data Exchange (ETDEWEB)
Tachibana, Y., E-mail: tachibana@nt.phys.s.u-tokyo.ac.jp [Theoretical Research Division, Nishina Center, RIKEN, Wako 351-0198 (Japan); Department of Engineering, Nishinippon Institute of Technology, Fukuoka 800-0344 (Japan); Department of Physics, Sophia University, Tokyo 102-8554 (Japan); Hirano, T., E-mail: hirano@sophia.ac.jp [Department of Physics, Sophia University, Tokyo 102-8554 (Japan)
2016-12-15
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.
Interplay between Mach cone and radial expansion in jet events
International Nuclear Information System (INIS)
Tachibana, Y.; Hirano, T.
2016-01-01
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.
Energy Technology Data Exchange (ETDEWEB)
Marc O Delchini; Jean E. Ragusa; Ray A. Berry
2015-07-01
We present a new version of the entropy viscosity method, a viscous regularization technique for hyperbolic conservation laws, that is well-suited for low-Mach flows. By means of a low-Mach asymptotic study, new expressions for the entropy viscosity coefficients are derived. These definitions are valid for a wide range of Mach numbers, from subsonic flows (with very low Mach numbers) to supersonic flows, and no longer depend on an analytical expression for the entropy function. In addition, the entropy viscosity method is extended to Euler equations with variable area for nozzle flow problems. The effectiveness of the method is demonstrated using various 1-D and 2-D benchmark tests: flow in a converging–diverging nozzle; Leblanc shock tube; slow moving shock; strong shock for liquid phase; low-Mach flows around a cylinder and over a circular hump; and supersonic flow in a compression corner. Convergence studies are performed for smooth solutions and solutions with shocks present.
Mach cones in space and laboratory dusty magnetoplasmas
International Nuclear Information System (INIS)
Mamun, A.A.; Shukla, P.K
2004-07-01
We present a rigorous theoretical investigation on the possibility for the formation of Mach cones in both space and laboratory dusty magnetoplasmas. We find the parametric regimes for which different types of Mach cones, such as dust acoustic Mach cones, dust magneto-acoustic Mach cones, oscillonic Mach cones, etc. are formed in space and laboratory dusty magnetoplasmas. We also identify the basic features of such different classes of Mach cones (viz. dust- acoustic, dust magneto-acoustic, oscillonic Mach cones, etc.), and clearly explain how they are relevant to space and laboratory dusty manetoplasmas. (author)
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.
Low Mach number limit for a model of accretion disk
Czech Academy of Sciences Publication Activity Database
Donatelli, D.; Ducomet, B.; Nečasová, Šárka
2018-01-01
Roč. 38, č. 7 (2018), s. 3239-3268 ISSN 1078-0947 R&D Projects: GA ČR GA13-00522S; GA ČR GA16-03230S Institutional support: RVO:67985840 Keywords : Navier-Stokes-Fourier-Poisson system * magnetohydrodynamics * radiating transfer Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.099, year: 2016 http://aimsciences.org/article/doi/10.3934/dcds.2018141
Low Mach number limit for a model of accretion disk
Czech Academy of Sciences Publication Activity Database
Donatelli, D.; Ducomet, B.; Nečasová, Šárka
2018-01-01
Roč. 38, č. 7 (2018), s. 3239-3268 ISSN 1078-0947 R&D Projects: GA ČR GA13-00522S; GA ČR GA16-03230S Institutional support: RVO:67985840 Keywords : Navier-Stokes-Fourier-Poisson system * magnetohydrodynamics * radiating transfer Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.099, year: 2016 http://aimsciences.org/ article /doi/10.3934/dcds.2018141
Miscellaneous: Various Low-Mach-Number Fluid Problems and Motions
Zeytounian, Radyadour Kh.
In this last chapter, we consider, first, in Sect. 7.1, mainly the asymptotic derivation of the KZK equation of nonlinear acoustics, which generalizes the well-known Burgers' unsteady one-dimensional dissipative model equation (Burgers 1948) to an equation with a diffraction and parabolic effect.
Modelling of high-enthalpy, high-Mach number flows
International Nuclear Information System (INIS)
Degrez, G; Lani, A; Panesi, M; Chazot, O; Deconinck, H
2009-01-01
A review is made of the computational models of high-enthalpy flows developed over the past few years at the von Karman Institute and Universite Libre de Bruxelles, for the modelling of high-enthalpy hypersonic (re-)entry flows. Both flows in local thermo-chemical equilibrium (LTE) and flows in thermo-chemical non-equilibrium (TCNEQ) are considered. First, the physico-chemical models are described, i.e. the set of conservation laws, the thermodynamics, transport phenomena and chemical kinetics models. Particular attention is given to the correct modelling of elemental (LTE flows) and species (chemical non-equilibrium-CNEQ-flows) transport. The numerical algorithm, based on a state-of-the-art finite volume discretization, is then briefly described. Finally, selected examples are included to illustrate the capabilities of the developed solver. (review article)
Acoustic Radiation From a Mach 14 Turbulent Boundary Layer
Zhang, Chao; Duan, Lian; Choudhari, Meelan M.
2016-01-01
Direct numerical simulations (DNS) are used to examine the turbulence statistics and the radiation field generated by a high-speed turbulent boundary layer with a nominal freestream Mach number of 14 and wall temperature of 0:18 times the recovery temperature. The flow conditions fall within the range of nozzle exit conditions of the Arnold Engineering Development Center (AEDC) Hypervelocity Tunnel No. 9 facility. The streamwise domain size is approximately 200 times the boundary-layer thickness at the inlet, with a useful range of Reynolds number corresponding to Re 450 ?? 650. Consistent with previous studies of turbulent boundary layer at high Mach numbers, the weak compressibility hypothesis for turbulent boundary layers remains applicable under this flow condition and the computational results confirm the validity of both the van Driest transformation and Morkovin's scaling. The Reynolds analogy is valid at the surface; the RMS of fluctuations in the surface pressure, wall shear stress, and heat flux is 24%, 53%, and 67% of the surface mean, respectively. The magnitude and dominant frequency of pressure fluctuations are found to vary dramatically within the inner layer (z/delta 0.< or approx. 0.08 or z+ < or approx. 50). The peak of the pre-multiplied frequency spectrum of the pressure fluctuation is f(delta)/U(sub infinity) approx. 2.1 at the surface and shifts to a lower frequency of f(delta)/U(sub infinity) approx. 0.7 in the free stream where the pressure signal is predominantly acoustic. The dominant frequency of the pressure spectrum shows a significant dependence on the freestream Mach number both at the wall and in the free stream.
Mach's principle and space-time structure
International Nuclear Information System (INIS)
Raine, D.J.
1981-01-01
Mach's principle, that inertial forces should be generated by the motion of a body relative to the bulk of matter in the universe, is shown to be related to the structure imposed on space-time by dynamical theories. General relativity theory and Mach's principle are both shown to be well supported by observations. Since Mach's principle is not contained in general relativity this leads to a discussion of attempts to derive Machian theories. The most promising of these appears to be a selection rule for solutions of the general relativistic field equations, in which the space-time metric structure is generated by the matter content of the universe only in a well-defined way. (author)
Mach's principle in spatially homogeneous spacetimes
International Nuclear Information System (INIS)
Tipler, F.J.
1978-01-01
On the basis of Mach's Principle it is concluded that the only singularity-free solution to the empty space Einstein equations is flat space. It is shown that the only singularity-free solution to the empty space Einstein equations which is spatially homogeneous and globally hyperbolic is in fact suitably identified Minkowski space. (Auth.)
All-optical negabinary adders using Mach-Zehnder interferometer
Cherri, A. K.
2011-02-01
In contrast to optoelectronics, all-optical adders are proposed where all-optical signals are used to represent the input numbers and the control signals. In addition, the all-optical adders use the negabinary modified signed-digit number representation (an extension of the negabinary number system) to represent the input digits. Further, the ultra-speed of the designed circuits is achieved due to the use of ultra-fast all-optical switching property of the semiconductor optical amplifier and Mach-Zehnder interferometer (SOA-MZI). Furthermore, two-bit per digit binary encoding scheme is employed to represent the trinary values of the negabinary modified signed-digits.
An implicit turbulence model for low-Mach Roe scheme using truncated Navier-Stokes equations
Li, Chung-Gang; Tsubokura, Makoto
2017-09-01
The original Roe scheme is well-known to be unsuitable in simulations of turbulence because the dissipation that develops is unsatisfactory. Simulations of turbulent channel flow for Reτ = 180 show that, with the 'low-Mach-fix for Roe' (LMRoe) proposed by Rieper [J. Comput. Phys. 230 (2011) 5263-5287], the Roe dissipation term potentially equates the simulation to an implicit large eddy simulation (ILES) at low Mach number. Thus inspired, a new implicit turbulence model for low Mach numbers is proposed that controls the Roe dissipation term appropriately. Referred to as the automatic dissipation adjustment (ADA) model, the method of solution follows procedures developed previously for the truncated Navier-Stokes (TNS) equations and, without tuning of parameters, uses the energy ratio as a criterion to automatically adjust the upwind dissipation. Turbulent channel flow at two different Reynold numbers and the Taylor-Green vortex were performed to validate the ADA model. In simulations of turbulent channel flow for Reτ = 180 at Mach number of 0.05 using the ADA model, the mean velocity and turbulence intensities are in excellent agreement with DNS results. With Reτ = 950 at Mach number of 0.1, the result is also consistent with DNS results, indicating that the ADA model is also reliable at higher Reynolds numbers. In simulations of the Taylor-Green vortex at Re = 3000, the kinetic energy is consistent with the power law of decaying turbulence with -1.2 exponents for both LMRoe with and without the ADA model. However, with the ADA model, the dissipation rate can be significantly improved near the dissipation peak region and the peak duration can be also more accurately captured. With a firm basis in TNS theory, applicability at higher Reynolds number, and ease in implementation as no extra terms are needed, the ADA model offers to become a promising tool for turbulence modeling.
Irie, T.; Yasunobu, T.; Kashimura, H.; Setoguchi, T.
2003-05-01
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.
Supersonic and transonic Mach probe for calibration control in the Trisonic Wind Tunnel
Directory of Open Access Journals (Sweden)
Alexandru Marius PANAIT
2017-12-01
Full Text Available A supersonic and high speed transonic Pitot Prandtl is described as it can be implemented in the Trisonic Wind Tunnel for calibration and verification of Mach number precision. A new calculation method for arbitrary precision Mach numbers is proposed and explained. The probe is specially designed for the Trisonic wind tunnel and would greatly simplify obtaining a precise Mach calibration in the critical high transonic and low supersonic regimes, where typically wind tunnels exhibit poor performance. The supersonic Pitot Prandtl combined probe is well known in the aerospace industry, however the proposed probe is a derivative of the standard configuration, combining a stout cone-cylinder probe with a supersonic Pitot static port which allows this configuration to validate the Mach number by three methods: conical flow method – using the pressure ports on a cone generatrix, the Schlieren-optical method of shock wave angle photogrammetry and the Rayleigh supersonic Pitot equation, while having an aerodynamic blockage similar to that of a scaled rocket model commonly used in testing. The proposed probe uses an existing cone-cylinder probe forebody and support, adding only an afterbody with a support for a static port.
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.
Chan, David T.; Balakrishna, Sundareswara; Walker, Eric L.; Goodliff, Scott L.
2015-01-01
Recent data quality improvements at the National Transonic Facility have an intended goal of reducing the Mach number variation in a data point to within plus or minus 0.0005, with the ultimate goal of reducing the data repeatability of the drag coefficient for full-span subsonic transport models at transonic speeds to within half a drag count. This paper will discuss the Mach stability improvements achieved through the use of an existing second throat capability at the NTF to create a minimum area at the end of the test section. These improvements were demonstrated using both the NASA Common Research Model and the NTF Pathfinder-I model in recent experiments. Sonic conditions at the throat were verified using sidewall static pressure data. The Mach variation levels from both experiments in the baseline tunnel configuration and the choked tunnel configuration will be presented and the correlation between Mach number and drag will also be examined. Finally, a brief discussion is given on the consequences of using the second throat in its location at the end of the test section.
Scramjet Combustor Characteristics at Hypervelocity Condition over Mach 10 Flight
Takahashi, M.; Komuro, T.; Sato, K.; Kodera, M.; Tanno, H.; Itoh, K.
2009-01-01
To investigate possibility of reduction of a scramjet combustor size without thrust performance loss, a two-dimensional constant-area combustor of a previous engine model was replaced with the one with 23% lower-height. With the application of the lower-height combustor, the pressure in the combustor becomes 50% higher and the combustor length for the optimal performance becomes 43% shorter than the original combustor. The combustion tests of the modified engine model were conducted using a large free-piston driven shock tunnel at flow conditions corresponding to the flight Mach number from 9 to 14. CFD was also applied to the engine internal flows. The results showed that the mixing and combustion heat release progress faster to the distance and the combustor performance similar to that of the previous engine was obtained with the modified engine. The reduction of the combustor size without the thrust performance loss is successfully achieved by applying the lower-height combustor.
Mach-Like Structure in a Patronic-Hadronic Transport Model at RHIC Energies
International Nuclear Information System (INIS)
Ma, Y.G.; Ma, G.L.; Zhang, S.
2008-01-01
Recent RHIC experimental results indicated an exotic partonic matter may be created in central Au + Au collisions at dollars sqrt (s ( NN))dollars =200 GeV. When a parton with high transverse momentum (jet) passes through the new matter, jet will quench. The lost energy will be redistributed into the medium. Experimentally the soft scattered particles which carry the lost energy have been reconstructed via di-hadron angular correlations of charged particles and a hump structure on away side in di-hadron $ Delta phi$ correlation has been observed in central Au + Au collisions [1,2]. Some interpretations, such as Mach-cone shock wave and gluon Cherenkov-like radiation mechanism etc, have been proposed to explain the splitting behavior of the away side peaks. However, quantitative understanding of the experimental observation has yet to be established. In this work, we use a multi-phase transport (AMPT) model to make a detailed simulation for di-hadron or tri-hadron azimuthal correlation for central Au + Au collisions at dollars sqrt(s ( NN)) dollars =200 GeV. The hump structure on away side (we called Mach-like structure later) in the di-hadron and tri-hadron azimuthal correlations has been observed [3,4,5]. Furthermore, the time evolution of Mach-like structure is presented [6]. With the increasing of the lifetime of partonic matter, Mach-like structure develops by strong parton cascade process. Not only the splitting parameter but also the number of associated hadrons (dollarsN ( h) (assoc)dollars) increases with the lifetime of partonic matter and partonic interaction cross section. Both the explosion of dollarsN ( h) (assoc)dollars following the formation of Mach-like structure and the corresponding results of three-particle correlation support that a partonic Mach-like behavior can be produced by a collective coupling of partons because of the strong parton cascade mechanism. Therefore, the studies about Mach-like structure may give us some critical information
Lezberg, Erwin A.; Metzler, Allen J.; Pack, William D.
1993-01-01
Results of in-stream combustion measurements taken during Mach 5 to 7 true simulation testing of the Hypersonic Research Engine/Aerothermodynamic Integration Model (HRE/AIM) are presented. These results, the instrumentation techniques, and configuration changes to the engine installation that were required to test this model are described. In test runs at facility Mach numbers of 5 to 7, an exhaust instrumentation ring which formed an extension of the engine exhaust nozzle shroud provided diagnostic measurements at 10 circumferential locations in the HRE combustor exit plane. The measurements included static and pitot pressures using conventional conical probes, combustion gas temperatures from cooled-gas pyrometer probes, and species concentration from analysis of combustion gas samples. Results showed considerable circumferential variation, indicating that efficiency losses were due to nonuniform fuel distribution or incomplete mixing. Results using the Mach 7 facility nozzle but with Mach 6 temperature simulation, 1590 to 1670 K, showed indications of incomplete combustion. Nitric oxide measurements at the combustor exit peaked at 2000 ppmv for stoichiometric combustion at Mach 6.
A fast spatial scanning combination emissive and mach probe for edge plasma diagnosis
International Nuclear Information System (INIS)
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.
The intellectual quadrangle: Mach-Boltzmann-Planck-Einstein
International Nuclear Information System (INIS)
Broda, E.
1981-01-01
These four men were influential in the transition from classical to modern physics. They interacted as scientists, often antagonistically. Thus Boltzmann was the greatest champion of the atom, while Mach remained unconvinced all his life. As a aphysicist, Einstein was greatly influenced by both Mach and Boltzmann, although Mach in the end rejected relativity as well. Because of his work on statistical mechanics, fluctuations, and quantum theory, Einstein has been called the natural successor to Boltzmann. Planck also was influenced by Mach at first. Hence he and Boltzmann were adversaries antil Planck converted to atomistics in 1900 and used the statistical interpretation of entropy to establish his radiation law. Planck accepted relativity early, but in quantum theory he was for a long time partly opposed to Einstein, and vice versa - Einstein considered Planck's derivation of his radiation law as unsound, while Planck could not accept the light quantum. In the case of all four physicists, science was interwoven with philosophy. Boltzmann consistently fought Mach's positivism, while Planck and Einstein moved from positivism to realism. All were also, though in very different ways, actively interested in public affairs. (orig.)
Heat transfer to surface and gaps of RSI tile arrays in turbulent flow at Mach 10.3
Throckmorton, D. A.
1974-01-01
Heat transfer to gap walls and surface of a simulated reusable surface insulation (RSI) tile array are presented. The data were obtained in the thick, turbulent tunnel wall boundary layer of the Langley Continuous Flow Hypersonic Tunnel at a freestream Mach number of 10.3 and a freestream unit Reynolds number of one million. Pertinent test variables were: (1) tile array orientation (staggered and in-line), (2) gap width, (3) flow angularity, and (4) tile mismatch.
Computation of Mach reflection from rigid and yielding surfaces
International Nuclear Information System (INIS)
Buckingham, A.C.; Wilson, S.S.
1976-01-01
The present discussion centers on a theoretical description of one aspect of the irregular or Mach reflection from solid surfaces. The discussion is restricted to analytical considerations and some preliminary results using model approximations to the surface interaction phenomena. Currently, full numerical simulations of the irregular reflection surface interaction dynamics have not been obtained since the method is still under development. Discussion of the numerical method is, therefore, restricted to some special procedures for the gas-solid surface boundary dynamics. The discussion is divided into an introductory section briefly describing a particular Mach reflection process. Subsequently, some of the considerations on boundary conditions are submitted for numerical treatment of the gas-solid interface. Analysis and discussion of a yielding solid surface subjected to impulsive loading from an intense gas shock wave follows. This is used as a guide for the development of the numerical procedure. Mach reflection processes are then briefly reviewed with special attention for similitude and singular perturbation features
MACH MIT: Deutsches Wochenende am Karlsfluss (MACH MIT: a German Week-End on the Charles River).
Reizes, Sonia; Kramsch, Claire J.
1980-01-01
Describes a joint high school/college pilot program planned by Massachusetts foreign language teachers and hosted by M.I.T. The success of the program dubbed "MACH MIT Total Immersion German Weekend" is attributed to the concept of active involvement, which was implemented through games, seminars, shows, cooking and other activities.…
Measurements of flows in the DIII-D divertor by Mach probes
International Nuclear Information System (INIS)
Boedo, J.A.; Lehmer, R.; Moyer, R.A.; Watkins, J.G.; Porter, G.D.; Evans, T.E.; Leonard, A.W.; Schaffer, M.J.
1998-06-01
First measurements of Mach number of background plasma in the DIII-D divertor are presented in conjunction with temperature T e and density n e using a fast scanning probe array. To validate the probe measurements, the authors compared the T e , n e and J sat data to Thomson scattering data and find good overall agreement in attached discharges and some discrepancy for T e and n e in detached discharges. The discrepancy is mostly due to the effect of large fluctuations present during detached plasmas on the probe characteristic; the particle flux is accurately measured in every case. A composite 2-D map of measured flows is presented for an ELMing H-mode discharge and they focus on some of the details. They have also documented the temperature, density and Mach number in the private flux region of the divertor and the vicinity of the X-point, which are important transition regions that have been little studied or modeled. Background parallel plasma flows and electric fields in the divertor region show a complex structure
Blunt body near wake flow field at Mach 6
Horvath, Thomas J.; McGinley, Catherine B.; Hannemann, Klaus
1996-01-01
Tests were conducted in a Mach 6 flow to examine the reattachment process of an axisymmetric free shear layer associated with the near wake of a 70 deg. half angle, spherically blunted cone with a cylindrical after body. Model angle of incidence was fixed at 0 deg. and free-stream Reynolds numbers based on body diameter ranged from 0.5 x 10(exp 6) to 4 x 10(exp 6). The sensitivity of wake shear layer transition on reattachment heating was investigated. The present perfect gas study was designed to compliment results obtained previously in facilities capable of producing real gas effects. The instrumented blunted cone model was designed primarily for testing in high enthalpy hypervelocity shock tunnels in both this country and abroad but was amenable for testing in conventional hypersonic blowdown wind tunnels as well. Surface heating rates were inferred from temperature - time histories from coaxial surface thermocouples on the model forebody and thin film resistance gages along the model base and cylindrical after body. General flow feature (bow shock, wake shear layer, and recompression shock) locations were visually identified by schlieren photography. Mean shear layer position and growth were determined from intrusive pitot pressure surveys. In addition, wake surveys with a constant temperature hot-wire anemometer were utilized to qualitatively characterize the state of the shear layer prior to reattachment. Experimental results were compared to laminar perfect gas predictions provided by a 3-D Navier Stokes code (NSHYP). Shear layer impingement on the instrumented cylindrical after body resulted in a localized heating maximum that was 21 to 29 percent of the forebody stagnation point heating. Peak heating resulting from the reattaching shear layer was found to be a factor of 2 higher than laminar predictions, which suggested a transitional shear layer. Schlieren flow visualization and fluctuating voltage time histories and spectra from the hot wire surveys
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;
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.
Laser produced plasma density measurement by Mach-Zehnder interferometry
International Nuclear Information System (INIS)
Vaziri, A.; Kohanzadeh, Y.; Mosavi, R.K.
1976-06-01
This report describes an optical interferometric method of measuring the refractive index of the laser-produced plasma, giving estimates of its electron density. The plasma is produced by the interaction of a high power pulsed CO 2 laser beam with a solid target in the vacuum. The time varying plasma has a transient electron density. This transient electron density gives rise to a changing plasma refractive index. A Mach-Zehnder ruby laser interferometer is used to measure this refractive index change
Optimization of OT-MACH Filter Generation for Target Recognition
Johnson, Oliver C.; Edens, Weston; Lu, Thomas T.; Chao, Tien-Hsin
2009-01-01
An automatic Optimum Trade-off Maximum Average Correlation Height (OT-MACH) filter generator for use in a gray-scale optical correlator (GOC) has been developed for improved target detection at JPL. While the OT-MACH filter has been shown to be an optimal filter for target detection, actually solving for the optimum is too computationally intensive for multiple targets. Instead, an adaptive step gradient descent method was tested to iteratively optimize the three OT-MACH parameters, alpha, beta, and gamma. The feedback for the gradient descent method was a composite of the performance measures, correlation peak height and peak to side lobe ratio. The automated method generated and tested multiple filters in order to approach the optimal filter quicker and more reliably than the current manual method. Initial usage and testing has shown preliminary success at finding an approximation of the optimal filter, in terms of alpha, beta, gamma values. This corresponded to a substantial improvement in detection performance where the true positive rate increased for the same average false positives per image.
High Mach Number Scramjet Test Flows in the X3 Expansion Tube
Gildfind, D. E.; Sancho, J.; Morgan, R. G.
The University of Queensland (UQ) has two free-piston driven expansion tube facilities; X2 has a total length of 23 m and was originally commissioned in 1995 [1]; X3 is much longer at 62 m, and was commissioned in 2001 [2].
ASYMPTOTIC STEADY-STATE SOLUTION TO A BOW SHOCK WITH AN INFINITE MACH NUMBER
Energy Technology Data Exchange (ETDEWEB)
Yalinewich, Almog; Sari, Re’em [Racah Institute of Physics, the Hebrew University, 91904, Jerusalem (Israel)
2016-08-01
The problem of a cold gas flowing past a stationary obstacle is considered. We study the bow shock that forms around the obstacle and show that at large distances from the obstacle the shock front forms a parabolic solid of revolution. The profiles of the hydrodynamic variables in the interior of the shock are obtained by solution of the hydrodynamic equations in parabolic coordinates. The results are verified with a hydrodynamic simulation. The drag force on the obstacle is also calculated. Finally, we use these results to model the bow shock around an isolated neutron star.
Stability with respect to domain of the low Mach number limit of compressible viscous fluids
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Karper, T.; Kreml, Ondřej; Stebel, Jan
2013-01-01
Roč. 23, č. 13 (2013), s. 2465-2493 ISSN 0218-2025 R&D Projects: GA ČR GA201/09/0917 Institutional research plan: CEZ:AV0Z10190503 Keywords : incompressible limit * domain dependence * Navier-Stokes system Subject RIV: BA - General Mathematics Impact factor: 2.351, year: 2013 http://www.worldscientific.com/doi/abs/10.1142/S0218202513500371
On the low Mach number limit of compressible flows in exterior moving domains
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Kreml, Ondřej; Mácha, Václav; Nečasová, Šárka
2016-01-01
Roč. 16, č. 3 (2016), s. 705-722 ISSN 1424-3199 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : compressible Navier-Stokes system * incompressible limit * moving domain Subject RIV: BA - General Mathematics Impact factor: 1.038, year: 2016 http://link.springer.com/article/10.1007%2Fs00028-016-0338-2
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...
Investigation of Shock Diffusers at Mach Number 1.85. 1 - Projecting Single Shock Cones
1947-06-17
cylindrical simulated combustion chamber was used to vary the outlet area of the flow through the diffuser. The pitot -static rake, located as shown in the...and II. Proc. Roy. Soc. (London), ser. A, vol. 139, no 838, Feb. 1, 1933, pp. 278-311. 5. Wyatt, DeMarquis D., and Hunczak, Henry R.: An...Simulated combustion u chamber A 90° W •—Conical damper S Static-pressure orifice ps pitot -static ""rake’ NATIONAL ADVISORY
Measurement and Analysis of the Noise Radiated by Low Mach Numbers Centrifugal Blowers
1987-11-01
Lang, V Manager of the IBM Poughkeepsie Acoustics Laboratory, for his understanding and support. I would also like to express my gratitude to the IBM...ficl.l. Knowlede p of these quantities provides important information on the relative strength of thL :cro- a dynamic noise sources on the blade... manageability . The model blower design was thus determined by scaling all of the linear dimensions of the reference device by 2.0 and by maintaining • all of
High Angle of Attack Missile Aerodynamics at Mach Numbers 0.30 to 1.5
1980-11-01
I AFWAL-TR-80-3070 I 45~//1° 4. N3B2 Cn 3d . 35 10 -2 36 30 37 50 2- S Cy ’ -1I __- 40 0 45 CAh ------ 50 -555 70- * 6C 50 504 40 ZS 8 9 LO R*N a 4. 5...Continued) 36. Drescher, H., "Messung Der Auf Querange-Sti"mte Zylinder Ausgeubten Zeitlich Verabderten Druck ," Z.F. Flugwss, Vol. 4, No. 1/2, 1956
Low Mach and Peclet number limit for a model of stellar tachocline and upper radiative zones
Czech Academy of Sciences Publication Activity Database
Donatelli, D.; Ducomet, B.; Kobera, M.; Nečasová, Šárka
2016-01-01
Roč. 2016, Č. 245 (2016), s. 1-31 ISSN 1072-6691 R&D Projects: GA ČR GA16-03230S Institutional support: RVO:67985840 Keywords : Navier-Stokes-Fourier-Poisson system * radiation transfer * compressible magnetohydrodynamics Subject RIV: BA - General Math ematics Impact factor: 0.954, year: 2016 http://ejde. math .txstate.edu/Volumes/2016/245/abstr.html
Turbulent boundary layer noise : direct radiation at Mach number 0.5
Gloerfelt , Xavier; Berland , Julien
2013-01-01
International audience; Boundary layers constitute a fundamental source of aerodynamic noise. A turbulent boundary layer over a plane wall can provide an indirect contribution to the noise by exciting the structure, and a direct noise contribution. The latter part can play a significant role even if its intensity is very low, explaining why it is hardly measured unambiguously. In the present study, the aerodynamic noise generated by a spatially developing turbulent boundary layer is computed ...
Rotating detectors and Mach's principle
Energy Technology Data Exchange (ETDEWEB)
Paola, R.D.M. de; Svaiter, N.F
2000-08-01
In this work we consider a quantum version of Newton{sup s} bucket experiment in a fl;at spacetime: we take an Unruh-DeWitt detector in interaction with a real massless scalar field. We calculate the detector's excitation rate when it is uniformly rotating around some fixed point and the field is prepared in the Minkowski vacuum and also when the detector is inertial and the field is in the Trocheries-Takeno vacuum state. These results are compared and the relations with Mach's principle are discussed. (author)
Reflected rarefactions, double regular reflection, and mach waves in aluminum and beryllium
International Nuclear Information System (INIS)
Neal, T.
1975-01-01
A number of shock techniques which can be used to obtain high-pressure equation-of-state information between the principal Hugoniot and the principal adiabat are illustrated. A rarefaction wave in aluminum shocked to 27.7 GPa [277 kbar] is examined with radiographic techniques and the bulk sound speed is determined. The two stage compression which occurs in a double shock may be attained by colliding two shocks and observing regular reflection. A radiographic method which uses this phenomenon to measure a three-stage compression of aluminum to a density of 4.7 Mg/m 3 and beryllium to a density of 3.1 Mg/m 3 is presented. The results of a Mach reflection experiment in aluminum are found to disagree substantially with the simple three-shock model. A modified model, consistent with observations, is discussed. In all cases the Gruneisen parameter is determined. (U.S.)
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.
Iodine Tagging Velocimetry in a Mach 10 Wake
Balla, Robert Jeffrey
2013-01-01
A variation on molecular tagging velocimetry (MTV) [1] designated iodine tagging velocimetry (ITV) is demonstrated. Molecular iodine is tagged by two-photon absorption using an Argon Fluoride (ArF) excimer laser. A single camera measures fluid displacement using atomic iodine emission at 206 nm. Two examples ofMTVfor cold-flowmeasurements areN2OMTV [2] and Femtosecond Laser Electronic Excitation Tagging [3]. These, like most MTV methods, are designed for atmospheric pressure applications. Neither can be implemented at the low pressures (0.1- 1 Torr) in typical hypersonic wakes. Of all the single-laser/singlecamera MTV approaches, only Nitric-Oxide Planar Laser Induced Fluorescence-based MTV [4] has been successfully demonstrated in a Mach 10 wake. Oxygen quenching limits transit times to 500 ns and accuracy to typically 30%. The present note describes the photophysics of the ITV method. Off-body velocimetry along a line is demonstrated in the aerothermodynamically important and experimentally challenging region of a hypersonic low-pressure near-wake in a Mach 10 air wind tunnel. Transit times up to 10 µs are demonstrated with conservative errors of 10%.
Quantum Anatomy of the Classical Interference of n-Photon States in a Mach-Zehnder Interferometer
International Nuclear Information System (INIS)
Ramírez-Cruz, N; Velázquez, V; Bastarrachea-Magnani, M A
2016-01-01
In this work we present the theory for the quantum interference of states with an arbitrary number of photons in a Mach-Zehnder interferometer. We express the mathematical description of the interference in an algebraic way. We show the interference pattern of an average of a n photons input state corresponds to the classical interference pattern, which tells us the last comes from a quantum interference statistical average. Then, we propose to use this scheme to study the statistical transition from quantum to classical interference. (paper)
Ernst Mach, George Sarton and the Empiry of Teaching Science Part I
Siemsen, Hayo
2012-01-01
George Sarton had a strong influence on modern history of science. The method he pursued throughout his life was the method he had discovered in Ernst Mach's "Mechanics" when he was a student in Ghent. Sarton was in fact throughout his life implementing a research program inspired by the epistemology of Mach. Sarton in turn inspired many…
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…
Germanium on silicon mid-infrared waveguides and Mach-Zehnder interferometers
Malik, A.; Muneeb, M.; Shimura, Y.; Campenhout, van J.; Loo, van de R.; Roelkens, G.C.
2013-01-01
In this paper we describe Ge-on-Si waveguides and Mach-Zehnder interferometers operating in the 5.2 - 5.4 µm wavelength range. 3dB/cm waveguide losses and Mach-Zehnder interferometers with 20dB extinction ratio are presented.
Sub-shot-noise phase sensitivity with a Bose-Einstein condensate Mach-Zehnder interferometer
International Nuclear Information System (INIS)
Pezze, L.; Smerzi, A.; Collins, L.A.; Berman, G.P.; Bishop, A.R.
2005-01-01
Bose-Einstein condensates (BEC), with their coherence properties, have attracted wide interest for their possible application to ultraprecise interferometry and ultraweak force sensors. Since condensates, unlike photons, are interacting, they may permit the realization of specific quantum states needed as input of an interferometer to approach the Heisenberg limit, the supposed lower bound to precision phase measurements. To this end, we study the sensitivity to external weak perturbations of a representative matter-wave Mach-Zehnder interferometer whose input are two Bose-Einstein condensates created by splitting a single condensate in two parts. The interferometric phase sensitivity depends on the specific quantum state created with the two condensates, and, therefore, on the time scale of the splitting process. We identify three different regimes, characterized by a phase sensitivity Δθ scaling with the total number of condensate particles N as (i) the standard quantum limit Δθ∼1/N 1/2 (ii) the sub shot-noise Δθ∼1/N 3/4 , and the (iii) the Heisenberg limit Δθ∼1/N. However, in a realistic dynamical BEC splitting, the 1/N limit requires a long adiabaticity time scale, which is hardly reachable experimentally. On the other hand, the sub-shot-noise sensitivity Δθ∼1/N 3/4 can be reached in a realistic experimental setting. We also show that the 1/N 3/4 scaling is a rigorous upper bound in the limit N→∞, while keeping constant all different parameters of the bosonic Mach-Zehnder interferometer
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.
Mach's principle and the rest mass of the graviton
International Nuclear Information System (INIS)
Woodward, J.F.; Crowley, R.J.; Yourgrau, W.
1975-01-01
The question of the graviton rest mass is briefly discussed and then it is shown that the Sciama-Dicke formulation of Mach's principle admits, in the linear approximation, the calculation of the graviton rest mass. One finds that the value of the graviton rest mass depends on the cosmological model adopted, the mean matter density in the universe, the speed of light, and the constant of gravitation. The value obtained for an infinite, stationary universe is 7.6 times 10 -67 g. The value for evolutionary cosmological models is found to depend critically on the mass and ''radius'' of the universe, both null and non-null values occurring only for certain values of these parameters. Problems that arise as a consequence of the linear approximation are pointed out
On-chip Mach-Zehnder interferometer for OCT systems
van Leeuwen, Ton G.; Akca, Imran B.; Angelou, Nikolaos; Weiss, Nicolas; Hoekman, Marcel; Leinse, Arne; Heideman, Rene G.
2018-04-01
By using integrated optics, it is possible to reduce the size and cost of a bulky optical coherence tomography (OCT) system. One of the OCT components that can be implemented on-chip is the interferometer. In this work, we present the design and characterization of a Mach-Zehnder interferometer consisting of the wavelength-independent splitters and an on-chip reference arm. The Si3N4 was chosen as the material platform as it can provide low losses while keeping the device size small. The device was characterized by using a home-built swept source OCT system. A sensitivity value of 83 dB, an axial resolution of 15.2 μm (in air) and a depth range of 2.5 mm (in air) were all obtained.
How the mach phenomenon and shape affect the radiographic appearance of skeletal structures
International Nuclear Information System (INIS)
Papageorges, M.
1991-01-01
The shape of skeletal structures and their position relative to the x-ray beam have a considerable effect on their radiographic appearance. Depending on the thickness of the cortical or subchondral bone, skeletal structures display the characteristics of either homogeneous or compound lamellar structures. Convex homogeneous structures are associated with a negative Mach line, and concave homogeneous structures are associated with a positive Mach line. Convex compound lamellar structures are associated with a negative Mach band and visualization of the lamina (subchondral or cortical bone) is reduced. Concave compound lamellar structures are associated with a positive Mach band and visualization of the lamina is enhanced. The combined effect of Mach phenomenon, shape, and thickness enhances visualization of some skeletal surfaces and make others imperceptible. These principles are very useful to correctly identify complex skeletal structures and avoid misinterpretations
[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.
The Red Rectangle: An Astronomical Example of Mach Bands?
Brecher, K.
2005-12-01
Recently, the Hubble Space Telescope (HST) produced spectacular images of the "Red Rectangle". This appears to be a binary star system undergoing recurrent mass loss episodes. The image-processed HST photographs display distinctive diagonal lightness enhancements. Some of the visual appearance undoubtedly arises from actual variations in the luminosity distribution of the light of the nebula itself, i.e., due to limb brightening. Psychophysical enhancement similar to the Vasarely or pyramid effect also seems to be involved in the visual impression conveyed by the HST images. This effect is related to Mach bands (as well as to the Chevreul and Craik-O'Brien-Cornsweet effects). The effect can be produced by stacking concentric squares (or other geometrical figures such as rectangles or hexagons) of linearly increasing or decreasing size and lightness, one on top of another. We have constructed controllable Flash applets of this effect as part of the NSF supported "Project LITE: Light Inquiry Through Experiments". They can be found in the vision section of the LITE web site at http://lite.bu.edu. Mach band effects have previously been seen in medical x-ray images. Here we report for the first time the possibility that such effects play a role in the interpretation of astronomical images. Specifically, we examine to what extent the visual impressions of the Red Rectangle and other extended astronomical objects are purely physical (photometric) in origin and to what degree they are enhanced by psychophysical processes. To help assess the relative physical and psychophysical contributions to the perceived lightness effects, we have made use of a center-surround (Difference of Gaussians) filter we developed for MatLab. We conclude that local (lateral inhibition) and longer range human visual perception effects probably do contribute to the lightness features seen in astronomical objects like the Red Rectangle. Project LITE is supported by NSF Grant # DUE-0125992.
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....
Modeling Turbulent Combustion for Variable Prandtl and Schmidt Number
Hassan, H. A.
2004-01-01
This report consists of two abstracts submitted for possible presentation at the AIAA Aerospace Science Meeting to be held in January 2005. Since the submittal of these abstracts we are continuing refinement of the model coefficients derived for the case of a variable Turbulent Prandtl number. The test cases being investigated are a Mach 9.2 flow over a degree ramp and a Mach 8.2 3-D calculation of crossing shocks. We have developed an axisymmetric code for treating axisymmetric flows. In addition the variable Schmidt number formulation was incorporated in the code and we are in the process of determining the model constants.
International Nuclear Information System (INIS)
Kolosov, G L; Kosinov, A D
2016-01-01
Experimental data on the linear and nonlinear wave train development in 3D supersonic boundary layer over a 45° swept-wing at Mach number 2.5 are presented. Travelling artificial disturbances were introduced in the boundary layer by periodical glow discharge at frequencies 10 and 20 kHz. The spatial-temporal and spectral-wave characteristics of the wave train of unstable disturbances in the linear region are obtained. It is shown that the additional peaks in β '-spectra arise for both subharmonic and fundamental frequencies. The experiments indicate the presence of subharmonic resonance mechanism in 3D boundary layer at Mach number 2.5. (paper)
Laser-driven Mach waves for gigabar-range shock experiments
Swift, Damian; Lazicki, Amy; Coppari, Federica; Saunders, Alison; Nilsen, Joseph
2017-10-01
Mach reflection offers possibilities for generating planar, supported shocks at higher pressures than are practical even with laser ablation. We have studied the formation of Mach waves by algebraic solution and hydrocode simulation for drive pressures at much than reported previously, and for realistic equations of state. We predict that Mach reflection continues to occur as the drive pressure increases, and the pressure enhancement increases monotonically with drive pressure even though the ``enhancement spike'' characteristic of low-pressure Mach waves disappears. The growth angle also increases monotonically with pressure, so a higher drive pressure seems always to be an advantage. However, there are conditions where the Mach wave is perturbed by reflections. We have performed trial experiments at the Omega facility, using a laser-heated halfraum to induce a Mach wave in a polystyrene cone. Pulse length and energy limitations meant that the drive was not maintained long enough to fully support the shock, but the results indicated a Mach wave of 25-30 TPa from a drive pressure of 5-6 TPa, consistent with simulations. A similar configuration should be tested at the NIF, and a Z-pinch driven configuration may be possible. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Working with Instruments: Ernst Mach as Material Epistemologist, a Short Introduction.
Hoffmann, Christoph; Métraux, Alexandre
2016-12-01
With the death of Ernst Mach on February 19, 1916, one day after his seventy-eighth birthday, a question finally became explicit that had been looming for some time. It was as simple as it was fundamental: who, in the end, was this man, a scientist or a philosopher? The importance of this question for contemporaries can easily be gleaned from the obituaries that appeared in the weeks following Mach's death: one in the Physikalische Zeitschrift, written by Albert Einstein, and another in the Archiv für die Geschichte der Philosophie, written by Mach's former student Heinrich Gomperz. They both addressed this critical issue in plain words. Einstein stressed that Mach "was not a philosopher who chose the natural sciences as the object of his speculation, but a many-sided, interested, diligent scientist who also took visible pleasure in detailed questions outside the burning issues of general interest" (Einstein 1916, 104; translation cited in Blackmore 1992, 158). Gomperz in turn first emphasized the great loss science had experienced with Mach's death, asking subsequently whether "the suffering science is physics or philosophy?" (Gomperz 1916, 321). His answer broadly followed Einstein's conclusion; relying on Mach's own words, he reminded his readers that Mach never claimed to be a philosopher, but merely was looking for a viewpoint that transcended the disciplinary constraints of particular scientific activities.
Boundary-Layer Instability Measurements in a Mach-6 Quiet Tunnel
Berridge, Dennis C.; Ward, Christopher, A. C.; Luersen, Ryan P. K.; Chou, Amanda; Abney, Andrew D.; Schneider, Steven P.
2012-01-01
Several experiments have been performed in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University. A 7 degree half angle cone at 6 degree angle of attack with temperature-sensitive paint (TSP) and PCB pressure transducers was tested under quiet flow. The stationary crossflow vortices appear to break down to turbulence near the lee ray for sufficiently high Reynolds numbers. Attempts to use roughness elements to control the spacing of hot streaks on a flared cone in quiet flow did not succeed. Roughness was observed to damp the second-mode waves in areas influenced by the roughness, and wide roughness spacing allowed hot streaks to form between the roughness elements. A forward-facing cavity was used for proof-of-concept studies for a laser perturber. The lowest density at which the freestream laser perturbations could be detected was 1.07 x 10(exp -2) kilograms per cubic meter. Experiments were conducted to determine the transition characteristics of a streamwise corner flow at hypersonic velocities. Quiet flow resulted in a delayed onset of hot streak spreading. Under low Reynolds number flow hot streak spreading did not occur along the model. A new shock tube has been built at Purdue. The shock tube is designed to create weak shocks suitable for calibrating sensors, particularly PCB-132 sensors. PCB-132 measurements in another shock tube show the shock response and a linear calibration over a moderate pressure range.
Experiments on a smooth wall hypersonic boundary layer at Mach 6
Neeb, Dominik; Saile, Dominik; Gülhan, Ali
2018-04-01
The turbulent boundary layer along the surface of high-speed vehicles drives shear stress and heat flux. Although essential to the vehicle design, the understanding of compressible turbulent boundary layers at high Mach numbers is limited due to the lack of available data. This is particularly true if the surface is rough, which is typically the case for all technical surfaces. To validate a methodological approach, as initial step, smooth wall experiments were performed. A hypersonic turbulent boundary layer at Ma = 6 (Ma_e=5.4) along a 7{}° sharp cone model at low Reynolds numbers Re_{θ } ≈ 3000 was characterized. The mean velocities in the boundary layer were acquired by means of Pitot pressure and particle image velocimetry (PIV) measurements. Furthermore, the PIV data were used to extract turbulent intensities along the profile. The mean velocities in the boundary layer agree with numerical data, independent of the measurement technique. Based on the profile data, three different approaches to extract the skin friction velocity were applied and show favorable comparison to literature and numerical data. The extracted values were used for inner and outer scaling of the van Driest transformed velocity profiles which are in good agreement to incompressible theoretical data. Morkovin scaled turbulent intensities show ambiguous results compared to literature data which may be influenced by inflow turbulence level, particle lag and other measurement uncertainties.
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.
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.
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.
Mach-Zehnder atom interferometer inside an optical fiber
Xin, Mingjie; Leong, Wuiseng; Chen, Zilong; Lan, Shau-Yu
2017-04-01
Precision measurement with light-pulse grating atom interferometry in free space have been used in the study of fundamental physics and applications in inertial sensing. Recent development of photonic band-gap fibers allows light for traveling in hollow region while preserving its fundamental Gaussian mode. The fibers could provide a very promising platform to transfer cold atoms. Optically guided matter waves inside a hollow-core photonic band-gap fiber can mitigate diffraction limit problem and has the potential to bring research in the field of atomic sensing and precision measurement to the next level of compactness and accuracy. Here, we will show our experimental progress towards an atom interferometer in optical fibers. We designed an atom trapping scheme inside a hollow-core photonic band-gap fiber to create an optical guided matter waves system, and studied the coherence properties of Rubidium atoms in this optical guided system. We also demonstrate a Mach-Zehnder atom interferometer in the optical waveguide. This interferometer is promising for precision measurements and designs of mobile atomic sensors.
Mach-Zehnder interferometry with interacting Bose-Einstein condensates in a double-well potential
International Nuclear Information System (INIS)
Berrada, T.
2014-01-01
Mach-Zehnder interferometry with interacting Bose-Einstein condensates in a double-well potential Particle-wave duality has enabled the construction of interferometers for massive particles such as electrons, neutrons, atoms or molecules. Implementing atom interferometry has required the development of analogues to the optical beam-splitters, phase shifters or recombiners to enable the coherent, i.e. phase-preserving manipulation of quantum superpositions. While initially demonstrating the wave nature of particles, atom interferometers have evolved into some of the most advanced devices for precision measurement, both for technological applications and tests of the fundamental laws of nature. Bose- Einstein condensates (BEC) of ultracold atoms are particular matter waves: they exhibit a collective many-body wave function and macroscopic coherence properties. As such, they have often been considered as an analogue to optical laser elds and it is natural to wonder whether BECs can provide to atom interferometry a similar boost as the laser brought to optical interferometry. One fundamental dierence between atomic BECs and lasers elds is the presence of atomic interactions, yielding an intrinsic non-linearity. On one hand, interactions can lead to eects destroying the phase coherence and limiting the interrogation time of trapped BEC interferometers. On the other hand, they can be used to generate nonclassical (e.g. squeezed) states to improve the sensitivity of interferometric measurements beyond the standard quantum limit (SQL). In this thesis, we present the realization of a full Mach-Zehnder interferometric sequence with trapped, interacting BECs con ned on an atom chip. Our interferometer relies on the coherent manipulation of a BEC in a magnetic double-well potential. For this purpose, we developed a novel type of matter-wave recombiner, an element which so far was missing in BEC atom optics. We have been able to exploit interactions to generate a squeezed
Hadron Azimuthal Correlations and Mach-like Structures in a Partonic/Hadronic Transport Model
International Nuclear Information System (INIS)
Ma, G.L.; Zhang, S.; Ma, Y.G.; Cai, X.Z.; Chen, J.H.; He, Z.J.; Huang, H.Z.; Long, J.L.; Shen, W.Q.; Shi, X.H.; Zhong, C.; Zuo, J.X.
2007-01-01
With a multi-phase transport model (AMPT) with both partonic and hadronic interactions, two- and three-particle azimuthal correlations in Au + Au collisions at s NN =200 GeV have been studied by the mixing-event technique. A Mach-like structure has been observed in two- and three-particle correlations in central collisions. It has been found that both partonic and hadronic dynamical mechanisms contribute to the Mach-like structure. However, only hadronic rescattering is unable to reproduce experimental amplitude of Mach-like structure, and parton cascade process is indispensable. The results of three-particle correlation indicate a partonic Mach-like shock wave can be produced by strong parton cascade in central Au+Au collisions
Hypervelocity Wind Tunnel No. 9 Mach 7 Thermal Structural Facility Verification and Calibration
National Research Council Canada - National Science Library
Lafferty, John
1996-01-01
This report summarizes the verification and calibration of the new Mach 7 Thermal Structural Facility located at the White Oak, Maryland, site of the Dahlgren Division, Naval Surface Warfare Center...
Electrical crosstalk in integrated Mach-Zehnder modulators caused by a shared ground path
Yao, W.; Gilardi, G.; Smit, M.K.; Wale, M.J.
2015-01-01
We show that the majority of electrical crosstalk between integrated Mach-Zehnder modulators can be caused by a shared ground path and demonstrate that in its absence crosstalk and related transmission penalty is greatly reduced.
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.
[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.
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.
Directory of Open Access Journals (Sweden)
Najafian Ashrafi Zabihollah
2016-01-01
Full Text Available An experimental study was conducted to investigate the influence of Reynolds number and equivalence ratio on flame temperature field and thermal flame height of laminar premixed LFG fuel. Mach-Zehnder interferometry technique is used to obtain an insight to the overall temperature field. The slot burner with large aspect ratio (L/W, length of L=60 mm and width of W=6 mm was used to eliminate the three- dimensional effect of temperature field. Two kinds of mixed fuels, LFG70 (70%CH4- 30%CO2 on volume basis and LFG50 (50%CH4- 50%CO2 were used to investigate flame characteristics under the test conditions of 100 ≤ Re ≤ 600 and 0.7 ≤ φ ≤ 1.3. The present measurement reveals that the variation of maximum flame temperature with increment of Reynolds number is mainly due to heat transfer effects and is negligible. On the other hand, the equivalence ratio and fuel composition have a noticeable effect on flame temperature. In addition, the results show that the LFG flames compared to the CH4 ones have a lower flame temperature. With increment of CO2 volume fraction at lean combustion, thermal flame height is augmented while at stoichiometric and rich combustion, its value reduced. Thermal flame height augments linearly by Reynolds number increase, while its increment at rich mixture is higher and the effect of Reynolds number at lean mixtures is insignificant. For validation of experimental results from Mach-Zehnder Interferometry, K-type thermocouples are used at peripherally low and moderate isotherm lines.
Experimental investigation of liquid jet injection into Mach 6 hypersonic crossflow
Energy Technology Data Exchange (ETDEWEB)
Beloki Perurena, J. [von Karman Institute for Fluid Dynamics, Rhode-Saint-Genese (Belgium)]|[RWTH Aachen University, Shock Wave Laboratory, Aachen (Germany); Asma, C.O. [von Karman Institute for Fluid Dynamics, Rhode-Saint-Genese (Belgium)]|[Ghent University, Department of Flow, Heat and Combustion Mechanics, Ghent (Belgium); Theunissen, R. [von Karman Institute for Fluid Dynamics, Rhode-Saint-Genese (Belgium)]|[Delft University of Technology, Faculty of Aerospace Engineering, Delft (Netherlands); Chazot, O. [von Karman Institute for Fluid Dynamics, Rhode-Saint-Genese (Belgium)
2009-03-15
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 resolution to capture small scale effects was obtained by high-speed recording, while directional illumination allowed variation in field of view. Shock pattern and flow topology were visualized by Schlieren-technique. Correlations are proposed on relating water jet penetration height and lateral extension with the injection ratio and orifice diameter for circular injector jets. Penetration height and lateral extension are compared for different injector shapes at relevant jet-to-air momentum-flux ratios showing that penetration height and lateral extension decrease and increase, respectively, with injector's aspect ratio. Probability density function analysis has shown that the mixing of the jet with the crossflow is completed at a distance of x/d{sub j}{proportional_to} 40, independent of the momentum-flux ratio. Mean velocity profiles related with the liquid jet have been extracted by means of an ensemble correlation PIV algorithm. Finally, frequency analyses of the jet breakup and fluctuating shock pattern are performed using a fast Fourier algorithm and characteristic Strouhal numbers of St=0.18 for the liquid jet breakup and of St=0.011 for the separation shock fluctuation are obtained. (orig.)
Patterned Roughness for Cross-flow Transition Control at Mach 6
Arndt, Alexander; Matlis, Eric; Semper, Michael; Corke, Thomas
2017-11-01
Experiments are performed to investigate patterned discrete roughness for transition control on a sharp right-circular cone at an angle of attack at Mach 6.0. The approach to transition control is based on exciting less-amplified (subcritical) stationary cross-flow (CF) modes that suppress the growth of the more-amplified (critical) CF modes, and thereby delay transition. The experiments were performed in the Air Force Academy Ludwieg Tube which is a conventional (noisy) design. The cone model is equipped with a motorized 3-D traversing mechanism that mounts on the support sting. The traversing mechanism held a closely-spaced pair of fast-response total pressure Pitot probes. The model utilized a removable tip to exchange between different tip-roughness conditions. Mean flow distortion x-development indicated that the transition Reynolds number increased by 25% with the addition of the subcritical roughness. The energy in traveling disturbances was centered in the band of most amplified traveling CF modes predicted by linear theory. The spatial pattern in the amplitude of the traveling CF modes indicated a nonlinear (sum and difference) interaction between the stationary and traveling CF modes that might explain differences in Retrans between noisy and quiet environments. Air Force Grant FA9550-15-1-0278.
Mach's Principle to Hubble's Law and Light Relativity
Zhang, Tianxi
2018-01-01
Discovery of the redshift-distance relation to be linear (i.e. Hubble's law) for galaxies in the end of 1920s instigated us to widely accept expansion of the universe, originated from a big bang around 14 billion years ago. Finding of the redshift-distance relation to be weaker than linear for distant type Ia supernovae nearly two decades ago further precipitated us to largely agree with recent acceleration of the universe, driven by the mysterious dark energy. The time dilation measured for supernovae has been claimed as a direct evidence for the expansion of the universe, but scientists could not explain why quasars and gamma-ray bursts had not similar time dilations. Recently, an anomaly was found in the standard template for the width of supernova light curves to be proportional to the wavelength, which exactly removed the time dilation of supernovae and hence was strongly inconsistent with the conventional redshift mechanism. In this study, we have derived a new redshift-distance relation from Mach's principle with light relativity that describes the effect of light on spacetime as well as the influence of disturbed spacetime on the light inertia or frequency. A moving object or photon, because of its continuously keeping on displacement, disturbs the rest of the entire universe or distorts/curves the spacetime. The distorted or curved spacetime then generates an effective gravitational force to act back on the moving object or photon, so that reduces the object inertia or photon frequency. Considering the disturbance of spacetime by a photon is extremely weak, we have modelled the effective gravitational force to be Newtonian and derived the new redshift-distance relation that can not only perfectly explain the redshift-distance measurement of distant type Ia supernovae but also inherently obtain Hubble's law as an approximate at small redshift. Therefore, the result obtained from this study does neither support the acceleration of the universe nor the
Computational Fluid Dynamics (CFD) Image of Hyper-X Research Vehicle at Mach 7 with Engine Operating
1997-01-01
This computational fluid dynamics (CFD) image shows the Hyper-X vehicle at a Mach 7 test condition with the engine operating. The solution includes both internal (scramjet engine) and external flow fields, including the interaction between the engine exhaust and vehicle aerodynamics. The image illustrates surface heat transfer on the vehicle surface (red is highest heating) and flowfield contours at local Mach number. The last contour illustrates the engine exhaust plume shape. This solution approach is one method of predicting the vehicle performance, and the best method for determination of vehicle structural, pressure and thermal design loads. The Hyper-X program is an ambitious series of experimental flights to expand the boundaries of high-speed aeronautics and develop new technologies for space access. When the first of three aircraft flies, it will be the first time a non-rocket engine has powered a vehicle in flight at hypersonic speeds--speeds above Mach 5, equivalent to about one mile per second or approximately 3,600 miles per hour at sea level. Hyper-X, the flight vehicle for which is designated as X-43A, is an experimental flight-research program seeking to demonstrate airframe-integrated, 'air-breathing' engine technologies that promise to increase payload capacity for future vehicles, including hypersonic aircraft (faster than Mach 5) and reusable space launchers. This multiyear program is currently underway at NASA Dryden Flight Research Center, Edwards, California. The Hyper-X schedule calls for its first flight later this year (2000). Hyper-X is a joint program, with Dryden sharing responsibility with NASA's Langley Research Center, Hampton, Virginia. Dryden's primary role is to fly three unpiloted X-43A research vehicles to validate engine technologies and hypersonic design tools as well as the hypersonic test facility at Langley. Langley manages the program and leads the technology development effort. The Hyper-X Program seeks to significantly
Rayleigh Scattering Density Measurements, Cluster Theory, and Nucleation Calculations at Mach 10
Balla, R. Jeffrey; Everhart, Joel L.
2012-01-01
In an exploratory investigation, quantitative unclustered laser Rayleigh scattering measurements of density were performed in the air in the NASA Langley Research Center's 31 in. Mach 10 wind tunnel. A review of 20 previous years of data in supersonic and Mach 6 hypersonic flows is presented where clustered signals typically overwhelmed molecular signals. A review of nucleation theory and accompanying nucleation calculations are also provided to interpret the current observed lack of clustering. Data were acquired at a fixed stagnation temperature near 990Kat five stagnation pressures spanning 2.41 to 10.0 MPa (350 to 1454 psi) using a pulsed argon fluoride excimer laser and double-intensified charge-coupled device camera. Data averaged over 371 images and 210 pixels along a 36.7mmline measured freestream densities that agree with computed isentropic-expansion densities to less than 2% and less than 6% at the highest and lowest densities, respectively. Cluster-free Mach 10 results are compared with previous clustered Mach 6 and condensation-free Mach 14 results. Evidence is presented indicating vibrationally excited oxygen and nitrogen molecules are absorbed as the clusters form, release their excess energy, and inhibit or possibly reverse the clustering process. Implications for delaying clustering and condensation onset in hypersonic and hypervelocity facilities are discussed.
Human vision model in relation to characteristics of shapes for the Mach band effect.
Wu, Bo-Wen; Fang, Yi-Chin
2015-10-01
For human vision to recognize the contours of objects means that, as the contrast variation at the object's edges increases, so will the Mach band effect of human vision. This paper more deeply investigates the relationship between changes in the contours of an object and the Mach band effect of human vision. Based on lateral inhibition and the Mach band effect, we studied subjects' eyes as they watched images of different shapes under a fixed brightness at 34 cd/m2, with changes of contrast and spatial frequency. Three types of display were used: a television, a computer monitor, and a projector. For each display used, we conducted a separate experiment for each shape. Although the maximum values for the contrast sensitivity function curves of the displays were different, their variations were minimal. As the spatial frequency changed, the diminishing effect of the different lines also was minimal. However, as the shapes at the contour intersections were modified by the Mach band effect, a greater degree of variation occurred. In addition, as the spatial frequency at a contour intersection increased, the Mach band effect became lower, along with changes in the corresponding contrast sensitivity function curve. Our experimental results on the characteristics of human vision have led to what we believe is a new vision model based on tests with different shapes. This new model may be used for future development and implementation of an artificial vision system.
High Mach flow associated with plasma detachment in JT-60U
International Nuclear Information System (INIS)
Hatayama, A.; Hoshino, K.; Miyamoto, K.
2003-01-01
Recent new results of the high Mach flows associated with plasma detachment are presented on the basis of numerical simulations by a 2-D edge simulation code (the B2-Eirene code) and their comparisons with experiments in JT-60U W-shaped divertor plasma. High Mach flows appear near the ionization front away from the target plate. The plasma static pressure rapidly drops, while the total pressure is kept almost constant near the ionization front, because the ionization front near the X-point is clearly separated from the momentum loss region near the target plate. Redistribution from static to dynamic pressure without a large momentum loss is confirmed to be a possible mechanism of the high Mach flows. It has been also shown that the radial structure of the high Mach flow near the X point away from the target plate has a strong correlation with the DOD (Degree of Detachment) at the target plate. Also, we have made systematic analyses on the high Mach flows for both the 'Open' geometry and the 'W-shaped' geometry of JT-60U in order to clarify the geometric effects on the flows. (author)
Guzzardi, Luca
2014-06-01
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 antireductionist view of science. Mach expounds his thesis about EC in his first historical-epistemological essay, Die Geschichte und die Wurzel des Satzes von der Erhaltung der Arbeit (1872): far from being a new principle, it is used from the early beginnings of mechanics independently from other principles; in fact, EC is a pre-mechanical principle which is generally applied in investigating nature: it is, indeed, nothing but a form of the principle of causality. The paper focuses on the scientific-historical premises and philosophical underpinnings of Mach's thesis, beginning with the classic debate on the validity and limits of the notion of cause by Hume, Kant, and Helmholtz. Such reference also implies a discussion of the relationship between causality on the one hand and space and time on the other. This connection plays a major role for Mach, and in the final paragraphs its importance is argued in order to understand his antireductionist perspective, i.e. the rejection of any attempt to give an ultimate explanation of the world via reduction of nature to one fundamental set of phenomena.
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.
Bennett, Ruth, Ed.; And Others
An introduction to the Hupa number system is provided in this workbook, one in a series of numerous materials developed to promote the use of the Hupa language. The book is written in English with Hupa terms used only for the names of numbers. The opening pages present the numbers from 1-10, giving the numeral, the Hupa word, the English word, and…
Indian Academy of Sciences (India)
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Triangular number, figurate num- ber, rangoli, Brahmagupta–Pell equation, Jacobi triple product identity. Figure 1. The first four triangular numbers. Left: Anuradha S Garge completed her PhD from. Pune University in 2008 under the supervision of Prof. S A Katre. Her research interests include K-theory and number theory.
Directory of Open Access Journals (Sweden)
Schwarzweller Christoph
2015-02-01
Full Text Available In this article we introduce Proth numbers and prove two theorems on such numbers being prime [3]. We also give revised versions of Pocklington’s theorem and of the Legendre symbol. Finally, we prove Pepin’s theorem and that the fifth Fermat number is not prime.
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
Cost-effective evolution of research prototypes into end-user tools: The MACH case study
DEFF Research Database (Denmark)
Störrle, Harald
2017-01-01
's claim by fellow scientists, and (3) demonstrate the utility and value of the research contribution to any interested parties. However, turning an exploratory prototype into a “proper” tool for end-users often entails great effort. Heavyweight mainstream frameworks such as Eclipse do not address...... this issue; their steep learning curves constitute substantial entry barriers to such ecosystems. In this paper, we present the Model Analyzer/Checker (MACH), a stand-alone tool with a command-line interpreter. MACH integrates a set of research prototypes for analyzing UML models. By choosing a simple...... command line interpreter rather than (costly) graphical user interface, we achieved the core goal of quickly deploying research results to a broader audience while keeping the required effort to an absolute minimum. We analyze MACH as a case study of how requirements and constraints in an academic...
Hyper-X Mach 7 Scramjet Design, Ground Test and Flight Results
Ferlemann, Shelly M.; McClinton, Charles R.; Rock, Ken E.; Voland, Randy T.
2005-01-01
The successful Mach 7 flight test of the Hyper-X (X-43) research vehicle has provided the major, essential demonstration of the capability of the airframe integrated scramjet engine. This flight was a crucial first step toward realizing the potential for airbreathing hypersonic propulsion for application to space launch vehicles. However, it is not sufficient to have just achieved a successful flight. The more useful knowledge gained from the flight is how well the prediction methods matched the actual test results in order to have confidence that these methods can be applied to the design of other scramjet engines and powered vehicles. The propulsion predictions for the Mach 7 flight test were calculated using the computer code, SRGULL, with input from computational fluid dynamics (CFD) and wind tunnel tests. This paper will discuss the evolution of the Mach 7 Hyper-X engine, ground wind tunnel experiments, propulsion prediction methodology, flight results and validation of design methods.
Directory of Open Access Journals (Sweden)
Erinc Erdem
2014-12-01
Full Text Available An experimental investigation of sonic air, CO2 and Helium transverse jets in Mach 5 cross flow was carried out over a flat plate. The jet to freestream momentum flux ratio, J, was kept the same for all gases. The unsteady flow topology was examined using high speed schlieren visualisation and PIV. Schlieren visualisation provided information regarding oscillating jet shear layer structures and bow shock, Mach disc and barrel shocks. Two-component PIV measurements at the centreline, provided information regarding jet penetration trajectories. Barrel shocks and Mach disc forming the jet boundary were visualised/quantified also jet penetration boundaries were determined. Even though J is kept the same for all gases, the penetration patterns were found to be remarkably different both at the nearfield and the farfield. Air and CO2 jet resulted similar nearfield and farfield penetration pattern whereas Helium jet spread minimal in the nearfield.
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.
On integral formulation of the Mach principle in a conformally flat space
International Nuclear Information System (INIS)
Mal'tsev, V.K.
1976-01-01
The integral formulation of the Mach principle represents a rather complicated mathematical formalism in which many aspects of the physical content of theory are not clear. Below an attempt is made to consider the integral representation for the most simple case of conformally flat spaces. The fact that this formalism there is only one scalar function makes it possible to analyse in more detail many physical peculiarities of this representation of the Mach principle: the absence of asymptotically flat spaces, problems of inertia and gravity, constraints on state equations, etc
MACHe3: A new generation detector for non-baryonic dark matter direct detection
International Nuclear Information System (INIS)
Santos, D.; Mayet, F.; Perrin, G.; Moulin, E.; Bunkov, Yu. M.; Godfrin, H.; Krusius, M.
2002-01-01
MACHe3 (MAtrix of Cells of superfluid 3 H e) is a project of a new detector for direct Dark Matter (DM) search, using superfluid 3 He as a sensitive medium. An experiment on a prototype cell has been performed and the st results reported here are encouraging to develop of a multicell prototype. In order to investigate the discovery potential of MACHe3, and its complementarity with other DM detectors, a phenomenological study done with the DarkSUSY code is shown. (authors)
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, ...
Siemsen, Hayo
2013-01-01
George Sarton had a strong influence on modern history of science. The method he pursued throughout his life was the method he had discovered in Ernst Mach's "Mechanics" when he was a student in Ghent. Sarton was in fact throughout his life implementing a research program inspired by the epistemology of Mach. Sarton in turn inspired many…
Indian Academy of Sciences (India)
Transfinite Numbers. What is Infinity? S M Srivastava. In a series of revolutionary articles written during the last quarter of the nineteenth century, the great Ger- man mathematician Georg Cantor removed the age-old mistrust of infinity and created an exceptionally beau- tiful and useful theory of transfinite numbers. This is.
Ji, Caleb; Khovanova, Tanya; Park, Robin; Song, Angela
2015-01-01
In this paper, we consider a game played on a rectangular $m \\times n$ gridded chocolate bar. Each move, a player breaks the bar along a grid line. Each move after that consists of taking any piece of chocolate and breaking it again along existing grid lines, until just $mn$ individual squares remain. This paper enumerates the number of ways to break an $m \\times n$ bar, which we call chocolate numbers, and introduces four new sequences related to these numbers. Using various techniques, we p...
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
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…
All-silicon thermal independent Mach-Zehnder interferometer with multimode waveguides
DEFF Research Database (Denmark)
Guan, Xiaowei; Frandsen, Lars Hagedorn
2016-01-01
A novel all-silicon thermal independent Mach-Zehnder interferometer consisting of two multimode waveguide arms having equal lengths and widths but transmitting different modes is proposed and experimentally demonstrated. The interferometer has a temperature sensitivity smaller than 8pm/°C in a wa...
A versatile all-optical modulator based on nonlinear Mach-Zehnder interferometers
Krijnen, Gijsbertus J.M.; Villeneuve, A.; Stegeman, G.I.; Lambeck, Paul; Hoekstra, Hugo
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
Experiments on a hot plume base flow interaction at Mach 2
Blinde, P.L.; Schrijer, F.F.J.; Powell, S.J.; Werner, R.M.; Van Oudheusden, B.W.
2015-01-01
A wind tunnel model containing a solid rocket motor was tested at Mach 2 to assess the feasibility of investigating the interaction between a hot plume and a high-speed outer stream. In addition to Schlieren visualisation, the feasibility of applying PIV was explored. Recorded particle images
Mach probe interpretation in the presence of supra-thermal electrons
Czech Academy of Sciences Publication Activity Database
Fuchs, Vladimír; Gunn, J. P.
2007-01-01
Roč. 14, č. 3 (2007), 032501-1 ISSN 1070-664X R&D Projects: GA ČR GA202/04/0360 Institutional research plan: CEZ:AV0Z20430508 Keywords : Mach probes * supra -thermal electrons * quasi-neutral PIC codes Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.325, year: 2007
Quantum nonlocality of photon pairs in interference in a Mach-Zehnder interferometer
Czech Academy of Sciences Publication Activity Database
Trojek, P.; Peřina ml., Jan
2003-01-01
Roč. 53, č. 4 (2003), s. 335-349 ISSN 0011-4626 R&D Projects: GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z1010921 Keywords : entangled photon pairs * nonlocal interference * Mach-Zehender interferometer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.263, year: 2003
The realization of an integrated Mach-Zehnder waveguide immunosensor in silicon technology
Schipper, E.F.; Schipper, E.F.; Brugman, A.M.; Lechuga, L.M.; Lechuga, L.M.; Kooyman, R.P.H.; Greve, Jan; 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
Design of an Optical OR Gate using Mach-Zehnder Interferometers
Choudhary, Kuldeep; Kumar, Santosh
2018-04-01
The optical switching phenomenon enhances the speed of optical communication systems. It is widely used in the wavelength division multiplexing (WDM). In this work, an optical OR gate is proposed using the Mach-Zehnder interferometer (MZI) structure. The detailed derivation of mathematical expression have been shown. The analysis is carried out by simulating the proposed device with MATLAB and Beam propagation method.
Consistency of the Mach principle and the gravitational-to-inertial mass equivalence principle
International Nuclear Information System (INIS)
Granada, Kh.K.; Chubykalo, A.E.
1990-01-01
Kinematics of the system, composed of two bodies, interacting with each other according to inverse-square law, was investigated. It is shown that the Mach principle, earlier rejected by the general relativity theory, can be used as an alternative for the absolute space concept, if it is proposed, that distant star background dictates both inertial and gravitational mass of a body
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...
Re, Richard J.
2005-01-01
Force balance and wing pressure data were obtained on a 0.017-Scale Model of a blended-wing-body configuration (without a simulated propulsion system installation) to validate the capability of computational fluid dynamic codes to predict the performance of such thick sectioned subsonic transport configurations. The tests were conducted in the National Transonic Facility of the Langley Research Center at Reynolds numbers from 3.5 to 25.0 million at Mach numbers from 0.25 to 0.86. Data were obtained in the pitch plane only at angles of attack from -1 to 8 deg at Mach numbers greater than 0.25. A configuration with winglets was tested at a Reynolds number of 25.0 million at Mach numbers from 0.83 to 0.86.
Measurements in a Transitioning Cone Boundary Layer at Freestream Mach 3.5
King, Rudolph A.; Chou, Amanda; Balakumar, Ponnampalam; Owens, Lewis R.; Kegerise, Michael A.
2016-01-01
An experimental study was conducted in the Supersonic Low-Disturbance Tunnel to investigate naturally-occurring instabilities in a supersonic boundary layer on a 7 deg half- angle cone. All tests were conducted with a nominal freestream Mach number of M(sub infinity) = 3:5, total temperature of T(sub 0) = 299:8 K, and unit Reynolds numbers of Re(sub infinity) x 10(exp -6) = 9:89, 13.85, 21.77, and 25.73 m(exp -1). Instability measurements were acquired under noisy- ow and quiet- ow conditions. Measurements were made to document the freestream and the boundary-layer edge environment, to document the cone baseline flow, and to establish the stability characteristics of the transitioning flow. Pitot pressure and hot-wire boundary- layer measurements were obtained using a model-integrated traverse system. All hot- wire results were single-point measurements and were acquired with a sensor calibrated to mass ux. For the noisy-flow conditions, excellent agreement for the growth rates and mode shapes was achieved between the measured results and linear stability theory (LST). The corresponding N factor at transition from LST is N 3:9. The stability measurements for the quiet-flow conditions were limited to the aft end of the cone. The most unstable first-mode instabilities as predicted by LST were successfully measured, but this unstable first mode was not the dominant instability measured in the boundary layer. Instead, the dominant instabilities were found to be the less-amplified, low-frequency disturbances predicted by linear stability theory, and these instabilities grew according to linear theory. These low-frequency unstable disturbances were initiated by freestream acoustic disturbances through a receptivity process that is believed to occur near the branch I locations of the cone. Under quiet-flow conditions, the boundary layer remained laminar up to the last measurement station for the largest Re1, implying a transition N factor of N greater than 8:5.
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...... 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....
1944-11-01
SS SUBJECT HEADIN6S: Pressure distribution - Flow research - Methods (40950) Wings (74500); DMiion, Intolilfjonco Air Kkrtcricl Command AIQ TECHNICAL INDGK Wrl0ht- Patto *son Air Forco ( Dayton, Ohio ///¥
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Medviďová-Lukáčová, M.; Nečasová, Šárka; Novotný, A.; She, Bangwei
2018-01-01
Roč. 16, č. 1 (2018), s. 150-183 ISSN 1540-3459 R&D Projects: GA ČR GA16-03230S EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : Navier-Stokes system * finite element numerical method * finite volume numerical method * asymptotic preserving schemes Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.865, year: 2016 http://epubs.siam.org/doi/10.1137/16M1094233
Olsen, W. A.; Krejsa, E. A.; Coats, J. W.
1972-01-01
Noise attenuation was measured for several types of cylindrical suppressors that use a duct lining composed of honeycomb cells covered with a perforated plate. The experimental technique used gave attenuation data that were repeatable and free of noise floors and other sources of error. The suppressor length, the effective acoustic diameter, suppressor shape and flow velocity were varied. The agreement among the attenuation data and two widely used analytical models was generally satisfactory. Changes were also made in the construction of the acoustic lining to measure their effect on attenuation. One of these produced a very broadband muffler.
International Nuclear Information System (INIS)
Zaytsev, S.G.; Lazareva, E.V.; Mikhailova, A.V.; Nikolaev-Kozlov, V.L.; Chebotareva, E.I.
1979-01-01
Propagation of intensive shock waves with a temperature of about 1 eV has been studied in a two-dimensional reflection nozzle mounted at the exit of a shock tube. The Toepler technique has been involved along with the interference scheme with a laser light source allowing the multiple-frame recording to be done. Density distribution in the nozzle as well as the wave pattern occurring at the shock propagation are presented. (author)
Directory of Open Access Journals (Sweden)
Theodore M. Porter
2012-12-01
Full Text Available The struggle over cure rate measures in nineteenth-century asylums provides an exemplary instance of how, when used for official assessments of institutions, these numbers become sites of contestation. The evasion of goals and corruption of measures tends to make these numbers “funny” in the sense of becoming dis-honest, while the mismatch between boring, technical appearances and cunning backstage manipulations supplies dark humor. The dangers are evident in recent efforts to decentralize the functions of governments and corporations using incen-tives based on quantified targets.
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.
Indian Academy of Sciences (India)
this is a characteristic difference between finite and infinite sets and created an immensely useful branch of mathematics based on this idea which had a great impact on the whole of mathe- matics. For example, the question of what is a number (finite or infinite) is almost a philosophical one. However Cantor's work turned it ...
Ernst Mach, George Sarton and the Empiry of Teaching Science Part I
Siemsen, Hayo
2012-04-01
George Sarton had a strong influence on modern history of science. The method he pursued throughout his life was the method he had discovered in Ernst Mach's Mechanics when he was a student in Ghent. Sarton was in fact throughout his life implementing a research program inspired by the epistemology of Mach. Sarton in turn inspired many others (James Conant, Thomas Kuhn, Gerald Holton, etc.). What were the origins of these ideas in Mach and what can this origin tell us about the history of science and science education nowadays? Which ideas proved to be successful and which ones need to be improved upon? The following article will elaborate the epistemological questions, which Darwin's "Origin" raised concerning human knowledge and scientific knowledge and which led Mach to adapt the concept of what is "empirical" in contrast to metaphysical a priori assumptions a second time after Galileo. On this basis Sarton proposed "genesis and development" as the major goal of Isis. Mach had elaborated this epistemology in La Connaissance et l'Erreur ( Knowledge and Error), which Sarton read in 1913 (Hiebert 1905/1976; de Mey 1984). Accordingly for Sarton, history becomes not only a subject of science, but a method of science education. Culture—and science as part of culture—is a result of a genetic process. History of science shapes and is shaped by science and science education in a reciprocal process. Its epistemology needs to be adapted to scientific facts and the philosophy of science. Sarton was well aware of the need to develop the history of science and the philosophy of science along the lines of this reciprocal process. It was a very fruitful basis, but a specific part of it, Sarton did not elaborate further, namely the psychology of science education. This proved to be a crucial missing element for all of science education in Sarton's succession, especially in the US. Looking again at the origins of the central questions in the thinking of Mach, which provided
International Nuclear Information System (INIS)
Girardin, Mathieu
2014-01-01
Two-phase flows in Pressurized Water Reactors belong to a wide range of Mach number flows. Computing accurate approximate solutions of those flows may be challenging from a numerical point of view as classical finite volume methods are too diffusive in the low Mach regime. In this thesis, we are interested in designing and studying some robust numerical schemes that are stable for large time steps and accurate even on coarse meshes for a wide range of flow regimes. An important feature is the strategy to construct those schemes. We use a mixed implicit-explicit strategy based on an operator splitting to solve fast and slow phenomena separately. Then, we introduce a modification of a Suliciu type relaxation scheme to improve the accuracy of the numerical scheme in some regime of interest. Two approaches have been used to assess the ability of our numerical schemes to deal with a wide range of flow regimes. The first approach, based on the asymptotic preserving property, has been used for the gas dynamics equations with stiff source terms. The second approach, based on the all-regime property, has been used for the gas dynamics equations and the homogeneous two-phase flows models HRM and HEM in the low Mach regime. We obtained some robustness and stability properties for our numerical schemes. In particular, some discrete entropy inequalities are shown. Numerical evidences, in 1D and in 2D on unstructured meshes, assess the gain in term of accuracy and CPU time of those asymptotic preserving and all-regime numerical schemes in comparison with classical finite volume methods. (author) [fr
Saxena, Anand
The focus of this research was to demonstrate a four blade rotor trim in forward flight using integrated trailing edge flaps instead of using a swashplate controls. A compact brushless DC motor was evaluated as an on-blade actuator, with the possibility of achieving large trailing edge flap amplitudes. A control strategy to actuate the trailing edge flap at desired frequency and amplitude was developed and large trailing edge flap amplitudes from the motor (instead of rotational motion) were obtained. Once the actuator was tested on the bench-top, a lightweight mechanism was designed to incorporate the motor in the blade and actuate the trailing edge flaps. A six feet diameter, four bladed composite rotor with motor-flap system integrated into the NACA 0012 airfoil section was fabricated. Systematic testing was carried out for a range of load conditions, first in the vacuum chamber followed by hover tests. Large trailing edge flap deflections were observed during the hover testing, and a peak to peak trailing edge flap amplitude of 18 degree was achieved at 2000 rotor RPM with hover tip Mach number of 0.628. A closed loop controller was designed to demonstrate trailing edge flap mean position and the peak to peak amplitude control. Further, a soft pitch link was designed and fabricated, to replace the stiff pitch link and thereby reduce the torsional stiffness of the blade to 2/rev. This soft pitch link allowed for blade root pitch motion in response to the trailing edge flap inputs. Blade pitch response due to both steady as well as sinusoidal flap deflections were demonstrated. Finally, tests were performed in Glenn L. Martin wind tunnel using a model rotor rig to assess the performance of motor-flap system in forward flight. A swashplateless trim using brushless DC motor actuated trailing edge flaps was achieved for a rotor operating at 1200 RPM and an advance ratio of 0.28. Also, preliminary exploration was carried out to test the scalability of the motor
Mach-Zehnder interferometer implementation for thermo-optical and Kerr effect study
Bundulis, Arturs; Nitiss, Edgars; Busenbergs, Janis; Rutkis, Martins
2018-04-01
In this paper, we propose the Mach-Zehnder interferometric method for third-order nonlinear optical and thermo-optical studies. Both effects manifest themselves as refractive index dependence on the incident light intensity and are widely employed for multiple opto-optical and thermo-optical applications. With the implemented method, we have measured the Kerr and thermo-optical coefficients of chloroform under CW, ns and ps laser irradiance. The application of lasers with different light wavelengths, pulse duration and energy allowed us to distinguish the processes responsible for refractive index changes in the investigated solution. Presented setup was also used for demonstration of opto-optical switching. Results from Mach-Zehnder experiment were compared to Z-scan data obtained in our previous studies. Based on this, a quality comparison of both methods was assessed and advantages and disadvantages of each method were analyzed.
The Interaction of Boltzmann with Mach, Ostwald and Planck, and his influence on Nernst and Einstein
International Nuclear Information System (INIS)
Broda, E.
1981-01-01
Boltzmann esteemed both Mach and Ostwald personally and as experimentalists, but consistently fought them in epistemology. He represented atomism and realism against energism and positivism. In the early period Boltzmann also had to struggle against Planck as a phenomenologist, but he welcomed his quantum hypothesis. As a scientist Nernst was also under Boltzmann's influence. Einstein learned atomism from (Maxwell and) Boltzmann. After Einstein had overcome Mach's positivist influence, he unknowingly approached Boltzmann's philosophical views. Some sociopolitlcal aspects of the lives of the great physicists will be discussed. It will be shown how they all, and many of Boltzmann's most eminent students, in one way or other conflicted with evil tendencies and developments in existing society. (author)
The three-grating Mach-Zehnder optical interferometer: a tutorial approach using particle optics
International Nuclear Information System (INIS)
Miffre, A; Delhuille, R; Viaris Lesegno, B de; Buechner, M; Rizzo, C; Vigue, J
2002-01-01
In this paper, we present a tutorial set-up based on an optical three-grating Mach-Zehnder interferometer. As this apparatus is very similar in its principle to the Mach-Zehnder interferometers used with matter waves (neutrons, atoms and molecules), it can be used to familiarize students with particle optics, and in our explanations, we use the complementary points of view of wave optics and particle optics. Finally, we have used this interferometer to measure the index of refraction of BK7 glass for red light at 633 nm, with a technique equivalent to the one used to measure the index of refraction of solid matter for thermal neutrons. The dimensions of this interferometer and its cost make it very interesting for laboratory courses and the experiment described here can be reproduced by students
Comparison between Hydrogen and Methane Fuels in a 3-D Scramjet at Mach 8
2016-06-24
scramjet using a cavity based flame holder in the T4 shock tunnel at The University of Queensland, as well as a companion fundamental CFD study. The...shock tunnel. 15. SUBJECT TERMS Airbreathing Engines, Hypersonics , Propulsion, AOARD 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18...Report Comparison between hydrogen, methane and ethylene fuels in a 3-D Scramjet at Mach 8 Professor Michael K. Smart Chair of Hypersonic Propulsion
Comparison between Hydrogen, Methane and Ethylene Fuels in a 3-D Scramjet at Mach 8
2016-06-24
scramjet using a cavity based flame holder in the T4 shock tunnel at The University of Queensland, as well as a companion fundamental CFD study. The...shock tunnel. 15. SUBJECT TERMS Airbreathing Engines, Hypersonics , Propulsion, AOARD 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18...Report Comparison between hydrogen, methane and ethylene fuels in a 3-D Scramjet at Mach 8 Professor Michael K. Smart Chair of Hypersonic Propulsion
CFD Validation Experiment of a Mach 2.5 Axisymmetric Shock-Wave/Boundary-Layer Interaction
Davis, David Owen
2015-01-01
Preliminary results of an experimental investigation of a Mach 2.5 two-dimensional axisymmetric shock-wave/ boundary-layer interaction (SWBLI) are presented. The purpose of the investigation is to create a SWBLI dataset specifically for CFD validation purposes. Presented herein are the details of the facility and preliminary measurements characterizing the facility and interaction region. These results will serve to define the region of interest where more detailed mean and turbulence measurements will be made.
NASA Administrator Sean O'Keefe, left, learned about the Mach 10 X-43 research vehicle from manager
2002-01-01
NASA Administrator Sean O'Keefe left, learned about the Mach 10 X-43 research vehicle from manager, Joel Sitz during O'Keefe's visit to the NASA Dryden Flight Research Center, Edwards, California, January 31, 2002.
International Nuclear Information System (INIS)
Mosquera, L; Osorio, Jonas H; Hayashi, Juliano G; Cordeiro, Cristiano M B
2011-01-01
A refractometric sensor based on mechanically induced interferometers formed with long period gratings is reported. It is also shown two different setups based on a Michelson and Mach-Zehnder interferometer and its application to measure ethanol concentration in gasoline.
International Nuclear Information System (INIS)
Zaza, Chady
2015-01-01
The numerical simulation of steam generators of pressurized water reactors is a complex problem, involving different flow regimes and a wide range of length and time scales. An accidental scenario may be associated with very fast variations of the flow with an important Mach number. In contrast in the nominal regime the flow may be stationary, at low Mach number. Moreover whatever the regime under consideration, the array of U-tubes is modelled by a porous medium in order to avoid taking into account the complex geometry of the steam generator, which entails the issue of the coupling conditions at the interface with the free-fluid. We propose a new pressure-correction scheme for cell-centered finite volumes for solving the compressible Navier-Stokes and Euler equations at all Mach number. The existence of a discrete solution, the consistency of the scheme in the Lax sense and the positivity of the internal energy were proved. Then the scheme was extended to the homogeneous two-phase flow models of the GENEPI code developed at CEA. Lastly a multigrid-AMR algorithm was adapted for using our pressure-correction scheme on adaptive grids. Regarding the second issue addressed in this work, the numerical simulation of a fluid flow over a porous bed involves very different length scales. Macroscopic interface models - such as Ochoa-Tapia-Whitaker or Beavers-Joseph law for a viscous flow - represent the transition region between the free-fluid and the porous region by an interface of discontinuity associated with specific transmission conditions. An extension to the Beavers-Joseph law was proposed for the convective regime. By introducing a jump in the kinetic energy at the interface, we recover an interface condition close to the Beavers-Joseph law but with a non-linear slip coefficient, which depends on the free-fluid velocity at the interface and on the Darcy velocity. The validity of this new transmission condition was assessed with direct numerical simulations at
Bodony, Daniel; Ostoich, Christopher; Geubelle, Philippe
2013-11-01
The interaction between a thin metallic panel and a Mach 2.25 turbulent boundary layer is investigated using a direct numerical simulation approach for coupled fluid-structure problems. The solid solution uses a finite-strain, finite-deformation formulation, while the direct numerical simulation of the boundary layer uses a finite-difference compressible Navier-Stokes solver. The initially laminar boundary layer contains low amplitude unstable eigenmodes that grow in time and excite traveling bending waves in the panel. As the boundary layer transitions to a fully turbulent state, with Reθ ~ 1200 , the panel's bending waves coalesce into a standing wave pattern exhibiting flutter with a final amplitude approximately 20 times the panel thickness. The corresponding panel deflection is roughly 25 wall units and reaches across the sonic line in the boundary layer profile. Once it reaches a limit cycle state, the panel/boundary layer system is examined in detail where it is found that turbulence statistics, especially the main Reynolds stress - , appear to be modified by the presence of the compliant panel, the effect of which is forgotten within one integral length downstream of the panel. Supported by the U.S. Air Force Research Laboratory Air Vehicles Directorate under contract number FA8650-06-2-3620.
Qu, Kun; Zhao, Shanghong; Li, Xuan; Tan, Qinggui; Zhu, Zihang
2018-04-01
A novel scheme for the generation of ultraflat and broadband optical frequency comb (OFC) is proposed based on cascaded two dual-electrode Mach-Zehnder modulators (DE-MZM). The first DE-MZM can generate a four-comb-line OFC, then the OFC is injected into the second DE-MZM as a carrier, which can increase the number of comb lines. Our modified scheme finally can generate a broadband OFC with high flatness by simply modifying the electrical power and the bias voltage of the DE-MZM. Theoretical analysis and simulation results reveal that a 16-comb-line OFC with a frequency spacing that two times the frequency of the RF signal can be obtained. The power fluctuation of the OFC lines is 0.48 dB and the unwanted-mode suppression ratio (UMSR) can reach 16.5 dB. Additionally, whether the bias drift of the DE-MZMs has little influence on the power fluctuation is also analyzed. These results demonstrate the robustness of our scheme and verify its good accuracy and high stability with perfect flatness.
Indian Academy of Sciences (India)
space was postulated arbitrarily and in an abstract man- ner. Why does ... moves with uniform velocity. But we now no .... action. The reaction from B to A, however travels back along the same route, arriving at A earlier than it left. B. Such an ...
The Influence of Ernst Mach and Ludwig Boltzmann on Albert Einstein
International Nuclear Information System (INIS)
Broda, E.
1979-01-01
This document, written by Engelbert Broda in 1979, analyses the influence of Ernst Mach and Ludwig Boltzmann on Albert Einstein. Broda describes how Einstein and his scientific thinking benefited from Mach’s criticism on classical mechanics and its basic concepts like absolute time and absolute space. This criticism encouraged Einstein in the time he worked on his special relativity. On the other side Broda writes about the influence of Ludwig Boltzman, an atomist, whose scientific work and research prepared the ground for Einsteins work on the quantum-structure of electromagnetic radiation or the discovery of the photoelectric effect. (nowak)
Goedel, Penrose, anti-Mach: extra supersymmetries of time-dependent plane waves
International Nuclear Information System (INIS)
Blau, Matthias; O'Loughlin, Martin; Meessen, Patrick
2003-01-01
We prove that M-theory plane waves with extra supersymmetries are necessarily homogeneous (but possibly time-dependent), and we show by explicit construction that such time-dependent plane waves can admit extra supersymmetries. To that end we study the Penrose limits of Goedel-like metrics, show that the Penrose limit of the M-theory Goedel metric (with 20 supercharges) is generically a time-dependent homogeneous plane wave of the anti-Mach type, and display the four extra Killings spinors in that case. We conclude with some general remarks on the Killing spinor equations for homogeneous plane waves. (author)
Temperature effects of Mach-Zehnder interferometer using a liquid crystal-filled fiber
DEFF Research Database (Denmark)
Ho, Bo-Yan; Su, Hsien-Pin; Tseng, Yu-Pei
2015-01-01
We demonstrated a simple and cost-effective method to fabricate all fiber Mach-Zehnder interferometer (MZI) based on cascading a short section of liquid crystal (LC)-filled hollow-optic fiber (HOF) between two single mode fibers by using automatically splicing technique. The transmission spectra...... of the proposed MZI with different LC-infiltrated length were measured and the temperature-induced wavelength shifts of the interference fringes were recorded. Both blue shift and red shift were observed, depending the temperature range. Based on our experimental results, interference fringe was observed...
Asymmetric Mach-Zehnder Interferometer Based Biosensors for Aflatoxin M1 Detection.
Chalyan, Tatevik; Guider, Romain; Pasquardini, Laura; Zanetti, Manuela; Falke, Floris; Schreuder, Erik; Heideman, Rene G; Pederzolli, Cecilia; Pavesi, Lorenzo
2016-01-06
In this work, we present a study of Aflatoxin M1 detection by photonic biosensors based on Si₃N₄ Asymmetric Mach-Zehnder Interferometer (aMZI) functionalized with antibodies fragments (Fab'). We measured a best volumetric sensitivity of 10⁴ rad/RIU, leading to a Limit of Detection below 5 × 10(-7) RIU. On sensors functionalized with Fab', we performed specific and non-specific sensing measurements at various toxin concentrations. Reproducibility of the measurements and re-usability of the sensor were also investigated.
Analisis Perbandingan Kinerja Mach-Zehnder berdasarkan Ragam Format Modulasi pada Jaringan FTTH
Directory of Open Access Journals (Sweden)
ZULIA NURUL KARIMAH
2018-03-01
Full Text Available ABSTRAK Pada jurnal ini dibuat pemodelan link FTTH pada software Optisystem 7.0 untuk mengetahui pengaruh dari Kerr effect dengan membandingkan performansi serat optik kaca dan serat optik plastik berdasarkan format modulasi berupa NRZ, RZ, RZ-DPSK, RZ-DQPSK dan CSRZ. Terdapat dua skenario, dengan skenario pertama, variabel input yang diubah adalah format modulasi pada Mach-zehnder, sedangkan pada skenario kedua, variabel yang diubah adalah pemakaian serat optik yang dipakai, yaitu serat optik bahan kaca, plastik dan hybrid kaca plastik. Hasil simulasi menunjukkan dengan efek linier dan non-linier pada kabel kaca yang menghasilkan performansi jaringan dari yang terbaik, dengan Q factor di atas 6 dan BER di bawah 10-9 adalah NRZ, RZ, RZ-DPSK, CSRZ dan RZ-DQPSK. Sedangkan dengan penggunaan kabel PMMA, yang menunjukkan performansi jaringan yang baik adalah dengan konfigurasi G652D-G652D-PMMA pada format modulasi NRZ, RZ, RZ-DPSK dan RZ-DQPSK. Efek non-linier yang terjadi pada jaringan ini hanya SPM dan XPM. Kata kunci: FTTH, mach-zehnder, format modulasi, efek non-linier, GOF, POF. ABSTRACT In this journal is creating a FTTH link on Optisystem software 7.0 to determine the effect of Kerr effect by comparing the performance of fiber optic glass and plastic optical fiber based on modulation formats such as NRZ, RZ, RZ-DPSK, RZ-DQPSK and CSRZ. There are two scenarios, first, input variables are changed based on format in Mach-zehnder modulator, while in the second scenario, the changed variable is the material of optical fiber, the materials are optical fiber glass, plastic and hybrid plastic and glass. The simulation results based on comparison with linear and nonlinear effects on glass optical fiber, which produce Q factor above 6 and BER below 10-9 are NRZ, RZ, RZ-DPSK, CSRZ and RZ-DQPSK. While the use of PMMA cable, which indicates good network performance is the configuration G652D-G652D-PMMA on the modulation format NRZ, RZ, RZ-DPSK and RZ
A Concept of Multi-Mode High Spectral Resolution Lidar Using Mach-Zehnder Interferometer
Directory of Open Access Journals (Sweden)
Jin Yoshitaka
2016-01-01
Full Text Available In this paper, we present the design of a High Spectral Resolution Lidar (HSRL using a laser that oscillates in a multi-longitudinal mode. Rayleigh and Mie scattering components are separated using a Mach-Zehnder Interferometer (MZI with the same free spectral range (FSR as the transmitted laser. The transmitted laser light is measured as a reference signal with the same MZI. By scanning the MZI periodically with a scanning range equal to the mode spacing, we can identify the maximum Mie and the maximum Rayleigh signals using the reference signal. The cross talk due to the spectral width of each laser mode can also be estimated.
Femtosecond laser writing of a flat-top interleaver via cascaded Mach-Zehnder interferometers.
Ng, Jason C; Li, Chengbo; Herman, Peter R; Qian, Li
2012-07-30
A flat-top interleaver consisting of cascaded Mach-Zehnder interferometers (MZIs) was fabricated in bulk glass by femtosecond laser direct writing. Spectral contrast ratios of greater than 15 dB were demonstrated over a 30 nm bandwidth for 3 nm channel spacing. The observed spectral response agreed well with a standard transfer matrix model generated from responses of individual optical components, demonstrating the possibility for multi-component optical design as well as sufficient process accuracy and fabrication consistency for femtosecond laser writing of advanced optical circuits in three dimensions.
Analisis Perbandingan Kinerja Mach-Zehnder berdasarkan Ragam Format Modulasi pada Jaringan FTTH
Directory of Open Access Journals (Sweden)
ZULIA NURUL KARIMAH
2017-06-01
Full Text Available ABSTRAKPada jurnal ini dibuat pemodelan link FTTH pada software Optisystem 7.0 untuk mengetahui pengaruh dari Kerr effect dengan membandingkan performansi serat optik kaca dan serat optik plastik berdasarkan format modulasi berupa NRZ, RZ, RZ-DPSK, RZ-DQPSK dan CSRZ. Terdapat dua skenario, dengan skenario pertama, variabel input yang diubah adalah format modulasi pada Mach-zehnder, sedangkan pada skenario kedua, variabel yang diubah adalah pemakaian serat optik yang dipakai, yaitu serat optik bahan kaca, plastik dan hybrid kaca plastik. Hasil simulasi menunjukkan dengan efek linier dan non-linier pada kabel kaca yang menghasilkan performansi jaringan dari yang terbaik, dengan Q factor di atas 6 dan BER di bawah 10-9 adalah NRZ, RZ, RZ-DPSK, CSRZ dan RZ-DQPSK. Sedangkan dengan penggunaan kabel PMMA, yang menunjukkan performansi jaringan yang baik adalah dengan konfigurasi G652D-G652D-PMMA pada format modulasi NRZ, RZ, RZ-DPSK dan RZ-DQPSK. Efek non-linier yang terjadi pada jaringan ini hanya SPM dan XPM.Kata kunci: FTTH, mach-zehnder, format modulasi, efek non-linier, GOF, POF.ABSTRACTIn this journal is creating a FTTH link on Optisystem software 7.0 to determine the effect of Kerr effect by comparing the performance of fiber optic glass and plastic optical fiber based on modulation formats such as NRZ, RZ, RZ-DPSK, RZ-DQPSK and CSRZ. There are two scenarios, first, input variables are changed based on format in Mach-zehnder modulator, while in the second scenario, the changed variable is the material of optical fiber, the materials are optical fiber glass, plastic and hybrid plastic and glass. The simulation results based on comparison with linear and nonlinear effects on glass optical fiber, which produce Q factor above 6 and BER below 10-9 are NRZ, RZ, RZ-DPSK, CSRZ and RZ-DQPSK. While the use of PMMA cable, which indicates good network performance is the configuration G652D-G652D-PMMA on the modulation format NRZ, RZ, RZ-DPSK and RZ
Oxidation of a Silica-Containing Material in a Mach 0.3 Burner Rig
Nguyen, QuynhGiao N.; Cuy, Michael D.; Gray, Hugh R. (Technical Monitor)
2002-01-01
A primarily silica-containing material with traces of organic compounds, as well as aluminum and calcium additions, was exposed to a Mach 0.3 burner rig at atmospheric pressure using jet fuel. The sample was exposed for 5 continuous hours at 1370 C. Post exposure x-ray diffraction analyses indicate formation of cristobalite, quartz, NiO and Spinel (Al(Ni)CR2O4). The rig hardware is composed of a nickel-based superalloy with traces of Fe. These elements are indicated in the energy dispersive spectroscopy (EDS) results. This material was studied as a candidate for high temperature applications under an engine technology program.
Gravitational Lagrangians, Mach's Principle, and the Equivalence Principle in an Expanding Universe
Essén, Hanno
2014-08-01
Gravitational Lagrangians as derived by Fock for the Einstein-Infeld-Hoffmann approach, and by Kennedy assuming only a fourth rank tensor interaction, contain long range interactions. Here we investigate how these affect the local dynamics when integrated over an expanding universe out to the Hubble radius. Taking the cosmic expansion velocity into account in a heuristic manner it is found that these long range interactions imply Mach's principle, provided the universe has the critical density, and that mass is renormalized. Suitable higher order additions to the Lagrangians make the formalism consistent with the equivalence principle.
Goedel, Penrose, anti-Mach: extra supersymmetries of time-dependent plane waves
Energy Technology Data Exchange (ETDEWEB)
Blau, Matthias; O' Loughlin, Martin; Meessen, Patrick [SISSA/ISAS, Via Beirut 2-4, 34014 Trieste (Italy)]. E-mail: meessen@sissa.it
2003-09-01
We prove that M-theory plane waves with extra supersymmetries are necessarily homogeneous (but possibly time-dependent), and we show by explicit construction that such time-dependent plane waves can admit extra supersymmetries. To that end we study the Penrose limits of Goedel-like metrics, show that the Penrose limit of the M-theory Goedel metric (with 20 supercharges) is generically a time-dependent homogeneous plane wave of the anti-Mach type, and display the four extra Killings spinors in that case. We conclude with some general remarks on the Killing spinor equations for homogeneous plane waves. (author)
SPIROMETRIC EVALUATION OF LUNG FUNCTION OF COAL WORKERS WORKING AT MACH (BOLAN DISTRICT)
Ghulam Sarwar, Muhammad Younis, Shafi Muhammad, Tanzeel Ahmed*, Muhammad Siddique, Bashir Ahmed, Munir Ahmed, Jahanzaib
2017-01-01
To evaluate the coal dust effect on lung function among coal workers and non-coal workers. This was case-control study. The 144 male coal workers and non-coal workers, 20-50 years more than one year of working skill were selected. Study was carried out in the Mach, Bolan district in Balochistan, Pakistan. The Spirometer and selfdesigned survey form were used. The interview was accompanied and information was documented in the survey form and Spirometry was done for coal workers and non-coal w...
Fiber optic sensor based on Mach-Zehnder interferometer for securing entrance areas of buildings
Nedoma, Jan; Fajkus, Marcel; Martinek, Radek; Mec, Pavel; Novak, Martin; Bednarek, Lukas; Vasinek, Vladimir
2017-10-01
Authors of this article focused on the utilization of fiber optic sensors based on interferometric measurements for securing entrance areas of buildings such as windows and doors. We described the implementation of the fiber-optic interferometer (type Mach-Zehnder) into the window frame or door, sensor sensitivity, analysis of the background noise and methods of signal evaluation. The advantage of presented solution is the use of standard telecommunication fiber standard G.652.D, high sensitivity, immunity of sensor to electromagnetic interference (EMI) and passivity of the sensor regarding power supply. Authors implemented the Graphical User Interface (GUI) which offers the possibility of remote monitoring presented sensing solution.
Di-hadron azimuthal correlation and Mach-like cone structure in a parton/hadron transport model
International Nuclear Information System (INIS)
Ma, G.L.; Zhang, S.; Ma, Y.G.; Huang, H.Z.; Cai, X.Z.; Chen, J.H.; He, Z.J.; Long, J.L.; Shen, W.Q.; Shi, X.H.; Zuo, J.X.
2006-01-01
In the framework of a multi-phase transport model (AMPT) with both partonic and hadronic interactions, azimuthal correlations between trigger particles and associated scattering particles have been studied by the mixing-event technique. The momentum ranges of these particles are 3 T trig T assoc T trig T assoc NN =200 GeV. A Mach-like structure has been observed in correlation functions for central collisions. By comparing scenarios with and without parton cascade and hadronic rescattering, we show that both partonic and hadronic dynamical mechanisms contribute to the Mach-like structure of the associated particle azimuthal correlations. The contribution of hadronic dynamical process cannot be ignored in the emergence of Mach-like correlations of the soft scattered associated hadrons. However, hadronic rescattering alone cannot reproduce experimental amplitude of Mach-like cone on away-side, and the parton cascade process is essential to describe experimental amplitude of Mach-like cone on away-side. In addition, both the associated multiplicity and the sum of p T decrease, while the T > increases, with the impact parameter in the AMPT model including partonic dynamics from string melting scenario
Creel, T. R.; Beckwith, I. E.
1983-01-01
A method of shielding a wind-tunnel model from noise radiated by the tunnel-wall boundary layer has been developed and tested at the Langley Research Center. The shield consists of a rectangular array of longitudinal rods with boundary-layer suction through gaps between the rods. Tests were conducted at Mach 5 over a unit Reynolds number range of 1.0-3.5 x 10 to the 7th/m. Hot-wire measurements indicated the freestream noise, expressed in terms of the rms pressure fluctuations normalized by the mean pressure, was reduced from about 1.4 percent just upstream of the shielded region of a minimum level of about 0.4 percent in the forward portion of the shielded flow.
Software-aided discussion about classical picture of Mach-Zehnder interferometer
Cavalcanti, C. J. H.; Ostermann, F.; Lima, N. W.; Netto, J. S.
2017-11-01
The Mach-Zehnder interferometer has played an important role both in quantum and classical physics research over the years. In physics education, it has been used as a didactic tool for quantum physics teaching, allowing fundamental concepts, such as particle-wave duality, to be addressed from the very beginning. For a student to understand the novelties of the quantum scenario, it is first worth introducing the classical picture. In this paper, we introduce a new version of the software developed by our research group to deepen the discussion on the classical picture of the Mach-Zehnder interferometer. We present its equivalence with the double slit experiment and we derive the mathematical expressions relating to the interference pattern. We also explore the concept of visibility (which is very important for understanding wave-particle complementarity in quantum physics) to help students become familiar with this experiment and to enhance their knowledge of its counterintuitive aspects. We use the software articulated by the mathematical formalism and phenomenological features. We also present excerpts of the discursive interactions of students using the software in didactic situations.
Single Mode SU8 Polymer Based Mach-Zehnder Interferometer for Bio-Sensing Application
Boiragi, Indrajit; Kundu, Sushanta; Makkar, Roshan; Chalapathi, Krishnamurthy
2011-10-01
This paper explains the influence of different parameters to the sensitivity of an optical waveguide Mach-Zehnder Interferometer (MZI) for real time detection of biomolecules. The sensing principle is based on the interaction of evanescence field with the biomolecules that get immobilized on sensing arm. The sensitivity has been calculated by varying the sensing window length, wavelength and concentration of bio-analyte. The maximum attainable sensitivity for the preferred design is the order of 10-8 RIU at 840 nm wavelength with a sensing window length of 1cm. All the simulation work has been carried out with Opti-BPMCAD for the optimization of MZI device parameters. The SU8 polymers are used as a core and clad material to fabricate the waveguide. The refractive index of cladding layer is optimized by varying the curing temperature for a fixed time period and the achieved index difference between core and clad is Δn = 0.0151. The fabricated MZI device has been characterized with LASER beam profiler at 840 nm wavelength. This study demonstrates the effectiveness of the different parameter to the sensitivity of a single mode optical waveguide Mach-Zehnder Interferometer for bio-sensing application.
Optical Coupling Structures of Fiber-Optic Mach-Zehnder Interferometers Using CO2 Laser Irradiation
Directory of Open Access Journals (Sweden)
Chien-Hsing Chen
2014-01-01
Full Text Available The Mach-Zehnder interferometer (MZI can be used to test changes in the refractive index of sucrose solutions at different concentrations. However, the popularity of this measurement tool is limited by its substantial size and portability. Therefore, the MZI was integrated with a small fiber-optic waveguide component to develop an interferometer with fiber-optic characteristics, specifically a fiber-optic Mach-Zehnder interferometer (FO-MZI. Optical fiber must be processed to fabricate two optical coupling structures. The two optical coupling structures are a duplicate of the beam splitter, an optical component of the interferometer. Therefore, when the sensor length and the two optical coupling structures vary, the time or path for optical transmission in the sensor changes, thereby influencing the back-end interference signals. The researchers successfully developed an asymmetrical FO-MZI with sensing abilities. The spacing value between the troughs of the sensor length and interference signal exhibited an inverse relationship. In addition, image analysis was employed to examine the size-matching relationship between various sensor lengths and the coupling and decoupling structure. Furthermore, the spectral wavelength shift results measured using a refractive index sensor indicate that FO-MZIs with a sensor length of 38 mm exhibited excellent sensitivity, measuring 59.7 nm/RIU.
Air Density Measurements in a Mach 10 Wake Using Iodine Cordes Bands
Balla, Robert J.; Everhart, Joel L.
2012-01-01
An exploratory study designed to examine the viability of making air density measurements in a Mach 10 flow using laser-induced fluorescence of the iodine Cordes bands is presented. Experiments are performed in the NASA Langley Research Center 31 in. Mach 10 air wind tunnel in the hypersonic near wake of a multipurpose crew vehicle model. To introduce iodine into the wake, a 0.5% iodine/nitrogen mixture is seeded using a pressure tap at the rear of the model. Air density was measured at 56 points along a 7 mm line and three stagnation pressures of 6.21, 8.62, and 10.0 MPa (900, 1250, and 1450 psi). Average results over time and space show rho(sub wake)/rho(sub freestream) of 0.145 plus or minus 0.010, independent of freestream air density. Average off-body results over time and space agree to better than 7.5% with computed densities from onbody pressure measurements. Densities measured during a single 60 s run at 10.0 MPa are time-dependent and steadily decrease by 15%. This decrease is attributed to model forebody heating by the flow.
Energy Technology Data Exchange (ETDEWEB)
Hull, Lawrence Mark [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Miller, Phillip Isaac [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moro, Erik Allan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-11-28
In the instance of multiple fragment impact on cased explosive, isolated curved shocks are generated in the explosive. These curved shocks propagate and may interact and form irregular or Mach reflections along the interaction loci, thereby producing a single shock that may be sufficient to initiate PBX-9501. However, the incident shocks are divergent and their intensity generally decreases as they expand, and the regions behind the Mach stem interaction loci are generally unsupported and allow release waves to rapidly affect the flow. The effects of release waves and divergent shocks may be considered theoretically through a “Shock Change Equation”.
Energy Technology Data Exchange (ETDEWEB)
Staudhammer, Karl P.
2004-01-01
The Mach stem region in an axial symmetric shock implosion has generally been avoided in the dynamic consolidation of powders for a number of reasons. The prime reason being that the convergence of the shock waves in the cylindrical axis produce enormous pressures and concomitant temperatures that have melted tungsten. This shock wave convergence consequently results in a discontinuity in the hydro-code calculations. Dynamic deformation experiments on gold plated 304L stainless steel powders were undertaken. These experiments utilized pressures of 0.08 to 1.0 Mbar and contained a symmetric radial melt region along the central axis of the sample holder. To understand the role of deformation in a porous material, the pressure, and temperature as well as the deformation heat and associated defects must be accounted for. When the added heat of consolidation deformation exceeds the melt temperature of the 304 powders, a melt zone results that can consume large regions of the compact while still under the high-pressure pulse. As the shock wave traverses the sample and is removed in a momentum trap, its pressure/temperature are quenched. It is within this region that very high diffusion/alloying occurs and has been observed in the gold plated powders. Anomalous increases of gold diffusion into 304 stainless steel have been observed via optical microscopy, scanning electron microscopy and EDAX measurements. Values exceeding 1200 m/sec have been measured and correlated to the powder sizes, size distribution and packing density, concomitant with sample container strains ranging from 2.0% to 26%.
Classical and quantum non-linear optical applications using the Mach-Zehnder interferometer
Prescod, Andru
Mach Zehnder (MZ) modulators are widely employed in a variety of applications, such as optical communications, optical imaging, metrology and encryption. In this dissertation, we explore two non-linear MZ applications; one classified as classical and one as quantum, in which the Mach Zehnder interferometer is used. In the first application, a classical non-linear application, we introduce and study a new electro-optic highly linear (e.g., >130 dB) modulator configuration. This modulator makes use of a phase modulator (PM) in one arm of the MZ interferometer (MZI) and a ring resonator (RR) located on the other arm. The modulator performance is obtained through the control of a combination of internal and external parameters. These parameters include the RR-coupling ratio (internal parameter); the RF power split ratio and the RF phase bias (external parameters). Results show the unique and superior features, such as high linearity (SFDR˜133 dB), modulation bandwidth extension (as much as 70%) over the previously proposed and demonstrated Resonator-Assisted Mach Zehnder (RAMZ) design. Furthermore the proposed electro-optic modulator of this dissertation also provides an inherent SFDR compensation capability, even in cases where a significant waveguide optical loss exists. This design also shows potential for increased flexibility, practicality and ease of use. In the second application, a quantum non-linear application, we experimentally demonstrate quantum optical coherence tomography (QOCT) using a type II non-linear crystal (periodically-poled potassium titanyl phosphate (KTiOPO4) or PPKTP). There have been several publications discussing the merits and disadvantages of QOCT compared to OCT and other imaging techniques. First, we discuss the issues and solutions for increasing the efficiency of the quantum entangled photons. Second, we use a free space QOCT experiment to generate a high flux of these quantum entangled photons in two orthogonal polarizations, by
CSIR Research Space (South Africa)
Naidoo, K
2011-06-01
Full Text Available research by Ernst Mach in 1878. The steady, two-dimensional transition criteria between regular and Mach reflection are well established. There has been little done to consider the dynamic effect of a rapidly rotating wedge on the transition between regular...
Polymer/silica hybrid waveguide temperature sensor based on asymmetric Mach-Zehnder interferometer
Niu, Donghai; Wang, Xibin; Sun, Shiqi; Jiang, Minghui; Xu, Qiang; Wang, Fei; Wu, Yuanda; Zhang, Daming
2018-04-01
A highly sensitive waveguide temperature sensor based on asymmetric Mach-Zehnder interferometer was designed and experimentally demonstrated. The interferometer is based on the polymer/silica hybrid waveguide structure, and Norland Optical Adhesive 73 (NOA 73) was employed as the waveguide core to enhance the temperature sensitivity. The influence of the different length differences between the two interferometer arms on the sensitivity of the sensor was systemically studied. It is shown that the maximum temperature sensitivity of -431 pm °C-1 can be obtained in the range of 25 °C-75 °C, while the length difference is 92 μm. Moreover, the temperature sensitivity contributions from different core materials were also investigated experimentally. It is shown that the waveguide material and microstructure of the device have significant influences on the sensitivity of the waveguide temperature sensor.
Xiong, Qiao; Tong, Xinglin; Deng, Chengwei; Zhang, Cui; Wang, Pengfei; Zheng, Zhiyuan; Liu, Fang
2018-05-13
A novel Mach-Zehnder interferometer using eccentric-core fiber (ECF) design for optical coherence tomography (OCT) is proposed and demonstrated. Instead of the commercial single-mode fiber (SMF), the ECF is used as one interference arm of the implementation. Because of the offset location of the eccentric core, it is sensitive to directional bending and the optical path difference (OPD) of two interference arms can be adjusted with high precision. The birefringence of ECF is calculated and experimentally measured, which demonstrates the polarization sensitivity of the ECF proposed in the paper is similar to that of SMF. Such a structure can replace the reference optical delay line to form an all-fiber passive device. A mirror is used as a sample for analyzing the ECF bending responses of the system. Besides, four pieces of overlapping glass slides as sample are experimentally measured as well.
Asselmeyer-Maluga, Torsten
2016-01-01
In this book, leading theorists present new contributions and reviews addressing longstanding challenges and ongoing progress in spacetime physics. In the anniversary year of Einstein's General Theory of Relativity, developed 100 years ago, this collection reflects the subsequent and continuing fruitful development of spacetime theories. The volume is published in honour of Carl Brans on the occasion of his 80th birthday. Carl H. Brans, who also contributes personally, is a creative and independent researcher and one of the founders of the scalar-tensor theory, also known as Jordan-Brans-Dicke theory. In the present book, much space is devoted to scalar-tensor theories. Since the beginning of the 1990s, Brans has worked on new models of spacetime, collectively known as exotic smoothness, a field largely established by him. In this Festschrift, one finds an outstanding and unique collection of articles about exotic smoothness. Also featured are Bell's inequality and Mach's principle. Personal memories and hist...
Double-pass Mach-Zehnder fiber interferometer pH sensor.
Tou, Zhi Qiang; Chan, Chi Chiu; Hong, Jesmond; Png, Shermaine; Eddie, Khay Ming Tan; Tan, Terence Aik Huang
2014-04-01
A biocompatible fiber-optic pH sensor based on a unique double-pass Mach-Zehnder interferometer is proposed. pH responsive poly(2-hydroxyethyl methacrylate-co-2-(dimethylamino)ethyl methacrylate) hydrogel coating on the fiber swells/deswells in response to local pH, leading to refractive index changes that manifest as shifting of interference dips in the optical spectrum. The pH sensor is tested in spiked phosphate buffer saline and demonstrates high sensitivity of 1.71 nm/pH, pH 0.004 limit of detection with good responsiveness, repeatability, and stability. The proposed sensor has been successfully applied in monitoring the media pH in cell culture experiments to investigate the relationship between pH and cancer cell growth.
Analytical and Experimental Verification of a Flight Article for a Mach-8 Boundary-Layer Experiment
Richards, W. Lance; Monaghan, Richard C.
1996-01-01
Preparations for a boundary-layer transition experiment to be conducted on a future flight mission of the air-launched Pegasus(TM) rocket are underway. The experiment requires a flight-test article called a glove to be attached to the wing of the Mach-8 first-stage booster. A three-dimensional, nonlinear finite-element analysis has been performed and significant small-scale laboratory testing has been accomplished to ensure the glove design integrity and quality of the experiment. Reliance on both the analysis and experiment activities has been instrumental in the success of the flight-article design. Results obtained from the structural analysis and laboratory testing show that all glove components are well within the allowable thermal stress and deformation requirements to satisfy the experiment objectives.
The cosmological constant and Pioneer anomaly from Weyl spacetimes and Mach's principle
International Nuclear Information System (INIS)
Castro, Carlos
2009-01-01
It is shown how Weyl's geometry and Mach's holographic principle furnishes both the magnitude and sign (towards the sun) of the Pioneer anomalous acceleration a P ∼-c 2 /R Hubble firstly observed by Anderson et al. Weyl's geometry can account for both the origins and the value of the observed vacuum energy density (dark energy). The source of dark energy is just the dilaton-like Jordan-Brans-Dicke scalar field that is required to implement Weyl invariance of the most simple of all possible actions. A nonvanishing value of the vacuum energy density of the order of 10 -123 M Planck 4 is found consistent with observations. Weyl's geometry accounts also for the phantom scalar field in modern Cosmology in a very natural fashion.
Study on the high speed scramjet characteristics at Mach 10 to 15 flight condition
Takahashi, M.; Itoh, K.; Tanno, H.; Komuro, T.; Sunami, T.; Sato, K.; Ueda, S.
A scramjet engine model, designed to establish steady and strong combustion at free-stream conditions corresponding to Mach 12 flight, was tested in a large free-piston driven shock tunnel. Combustion tests of a previous engine model showed that combustion heat release obtained in the combustor was not sufficient to maintain strong combustion. For a new scramjet engine model, the inlet compression ratio was increased to raise the static temperature and density of the flow at the combustor entrance. As a result of the aerodynamic design change, the pressure rise due to combustion increased and the duration of strong combustion conditions in the combustor was extended. A hyper-mixer injector designed to enhance mixing and combustion by introducing streamwise vortices was applied to the new engine model. The results showed that the hyper mixer injector was very effective in promoting combustion heat release and establishing steady and strong combustion in the combustor.
Sense data and the philosophy of mind: Russell, James, and Mach
Directory of Open Access Journals (Sweden)
Gary Hatfield
2002-12-01
Full Text Available The theory of knowledge in early twentieth-century Anglo American philosophy was oriented toward phenomenally described cognition There was a healthy respect for the mind body problem, which meant that phenomena in both the mental and physical domain were taken sinuously Bertrand Russell's developing position on sense-data and momentary particulars drew upon, and ultimately became like, the neutral monism of Ernst Mach and William James Due to a more recent behaviorist and physicalist inspired "fear of the mental", this development has been down played in historical work on early analytic philosophy Such neglect as sumes that the "linguistic turn" is a proper and permanent effect of twentieth century philosophy, an assumption that distorts early analytic historiography, and begs a substantive philosophical question about thought and cognition.
Investigation of Mach-Zehnder interferometer properties based on PLC technology
Ren, Mei-zhen; Zhang, Jia-shun; An, Jun-ming; Wang, Yue; Wang, Liang-liang; Li, Jian-guang; Wu, Yuan-da; Yin, Xiao-jie; Hu, Xiong-wei
2018-05-01
We report investigations of three types of silica-based thermo-optic modulating Mach-Zehnder interferometers (MZIs). They are widely used in optical communication and quantum photonics. Three types of MZIs are fabricated. The waveguide structure and fabrication process are paid special attention. The power consumption is less than 250 mW for all MZIs. The polarization dependent loss (PDL) at the same attenuation using the upper heater is less than that using the lower heater for the three types of MZIs. In addition, it is found that the PDL at the same attenuation increases gradually for π, 2π and 0 phase differences. The measured response time of the three types of MZIs is less than 1.8 ms.
Asymmetry reversal of ion collection by mach probes in flowing unmagnetized plasmas
International Nuclear Information System (INIS)
Ko, E; Hershkowitz, N
2006-01-01
Measurements of ion current in flowing unmagnetized plasmas were performed with planar and spherical Mach probes in two different devices, one a dc multi-dipole plasma device for subsonic flow within a presheath region and the other a double plasma device for supersonic flow. Asymmetry reversal, which is higher ion current to the downstream side of the probe compared with the upstream side current, was observed for high probe bias compared with the electron temperature, relatively low ion drift velocity and Debye length comparable to probe radius. These data are in qualitative agreement with a recent numerical calculation by Hutchinson. As suggested by Hutchinson, it was found that the current ratio depended on the plasma parameters, especially for finite Debye length and high probe bias. Asymmetry reversal emphasizes the lack of validity of using the current ratio except for narrow parameter ranges. This study is the first experiment to demonstrate the non-intuitive phenomenon predicted by Hutchinson's numerical calculation
Everhart, Joel L.; Ashby, George C., Jr.; Monta, William J.
1992-01-01
A propulsion/airframe integration experiment conducted in the NASA Langley 20-Inch Mach 6 Tunnel using a 16.8-in.-long version of the Langley Test Technique Demonstrator configuration with simulated scramjet propulsion is described. Schlieren and vapor screen visualization of the nozzle flow field is presented and correlated with pitot-pressure flow-field surveys. The data were obtained at nominal free-stream conditions of Re = 2.8 x 10 exp 6 and a nominal engine total pressure of 100 psia. It is concluded that pitot-pressure surveys coupled to schlieren and vapor-screen photographs, and oil flows have revealed flow features including vortices, free shear layers, and shock waves occurring in the model flow field.
Mach 0.3 Burner Rig Facility at the NASA Glenn Materials Research Laboratory
Fox, Dennis S.; Miller, Robert A.; Zhu, Dongming; Perez, Michael; Cuy, Michael D.; Robinson, R. Craig
2011-01-01
This Technical Memorandum presents the current capabilities of the state-of-the-art Mach 0.3 Burner Rig Facility. It is used for materials research including oxidation, corrosion, erosion and impact. Consisting of seven computer controlled jet-fueled combustors in individual test cells, these relatively small rigs burn just 2 to 3 gal of jet fuel per hour. The rigs are used as an efficient means of subjecting potential aircraft engine/airframe advanced materials to the high temperatures, high velocities and thermal cycling closely approximating actual operating environments. Materials of various geometries and compositions can be evaluated at temperatures from 700 to 2400 F. Tests are conducted not only on bare superalloys and ceramics, but also to study the behavior and durability of protective coatings applied to those materials.
Mach-Zehnder interferometric photonic crystal fiber for low acoustic frequency detections
Energy Technology Data Exchange (ETDEWEB)
Pawar, Dnyandeo; Rao, Ch. N.; Kale, S. N., E-mail: sangeetakale2004@gmail.com [Department of Applied Physics, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411 025, Maharashtra (India); Choubey, Ravi Kant [Department of Applied Physics, Amity Institute of Applied Sciences, Amity University, Noida 201 313 (India)
2016-01-25
Low frequency under-water acoustic signal detections are challenging, especially for marine applications. A Mach-Zehnder interferometric hydrophone is demonstrated using polarization-maintaining photonic-crystal-fiber (PM-PCF), spliced between two single-mode-fibers, operated at 1550 nm source. These data are compared with standard hydrophone, single-mode and multimode fiber. The PM-PCF sensor shows the highest response with a power shift (2.32 dBm) and a wavelength shift (392.8 pm) at 200 Hz. High birefringence values and the effect of the imparted acoustic pressure on this fiber, introducing the difference between the fast and slow axis changes, owing to the phase change in the propagation waves, demonstrate the strain-optic properties of the sensor.
High-speed carrier-depletion silicon Mach-Zehnder optical modulators with lateral PN junctions
Directory of Open Access Journals (Sweden)
Graham Trevor Reed
2014-12-01
Full Text Available This paper presents new experimental data from a lateral PN junction silicon Mach-Zehnder optical modulator. Efficiencies in the 1.4V.cm to 1.9V.cm range are demonstrated for drive voltages between 0V and 6V. High speed operation up to 52Gbit/s is also presented. The performance of the device which has its PN junction positioned in the centre of the waveguide is then compared to previously reported data from a lateral PN junction device with the junction self-aligned to the edge of the waveguide rib. An improvement in modulation efficiency is demonstrated when the junction is positioned in the centre of the waveguide. Finally we propose schemes for achieving high modulation efficiency whilst retaining self-aligned formation of the PN junction.
Up-taper-based Mach-Zehnder interferometer for temperature and strain simultaneous measurement.
Kang, Zexin; Wen, Xiaodong; Li, Chao; Sun, Jiang; Wang, Jing; Jian, Shuisheng
2014-04-20
A novel all-fiber sensing configuration for simultaneous measurements of temperature and strain based on the up-taper Mach-Zehnder interferometer (MZI) with an in-line embedded fiber Bragg grating (FBG) is proposed and experimentally demonstrated. This configuration consists of two up-tapers fabricated by an excessive fusion splicing method and a short segment of inscribed FBG. Due to the different responses of the up-taper MZI and the FBG to the uniform variation of temperature and strain, the simultaneous measurement for these two variables could be achieved by real-time monitoring the transmission spectrum. For 0.01 nm wavelength resolution, a resolution of 0.311°C in temperature can be achieved, and the average strain resolution is 10.07 με.
Simulation of acousto-optical interaction in a Mach-Zehnder interferometer
DEFF Research Database (Denmark)
Dühring, Maria Bayard; Sigmund, Ole; Jensen, Jakob Søndergaard
of half the SAW wavelength the light at the output waveguide will interfere constructively and destructively in a periodic way and the MZI can hence be used as an optical switch. To understand and improve the interaction of the elastic field from the SAW with the optical field in the waveguides......The acousto-optical modulation of light in a Mach-Zehnder interferometer affected by a surface acoustic wave, is simulated by the finite element method. It is discussed how the modulation can be improved based on a parameter study of the geometry. Summary A new way to control and modulate light...... introduced by the SAW the changes in refractive indices are obtained from Pockels constants. This model is then coupled to an optical model where the time independent wave equation is solved as an eigenvalue problem giving the effective refractive index of the lowest modes in the waveguide arms. Numerical...
Directory of Open Access Journals (Sweden)
Jun Huang
2018-01-01
Full Text Available A novel humidity sensor based on Mach-Zehnder interferometer (MZI with the single-mode fiber (SMF coated with methylcellulose (MC is proposed and experimentally demonstrated. The MZI consists of two waist enlarged structures. Such an all-fiber MZI incorporates an intermodal interference between the core mode and cladding modes. The MC is coated on the surface of the SMF. External humidity changes the refractive index of MC, causing the intensity changes of the interference pattern. The proposed sensor is linearly responsive to refractive humidity (RH within the range from 45% to 85% RH, with sensitivity of 0.094 dB/%RH. Moreover the insensitivity of the fiber to the temperature makes this structure more suitable for practical measurement.
Mach-Zehnder Fiber-Optic Links for Reaction History Measurements at the National Ignition Facility
International Nuclear Information System (INIS)
Miller, E. Kirk; Herrmann, H.W.; Stoeffl, W.; Horsfield, C.J.
2009-01-01
We present the details of the analog fiber-optic data link that will be used in the chamber-mounted Gamma Reaction History (GRH) diagnostic at the National Ignition Facility (NIF) located at the Lawrence Livermore Laboratory in Livermore, California. The system is based on Mach-Zehnder (MZ) modulators integrated into the diagnostic, with the source lasers and bias control electronics located remotely to protect the active electronics. A complete recording system for a single GRH channel comprises two MZ modulators, with the fiber signals split onto four channels on a single digitizer. By carefully selecting the attenuation, the photoreceiver, and the digitizer settings, the dynamic range achievable is greater than 1000:1 at the full system bandwidth of greater than 10 GHz. The system is designed to minimize electrical reflections and mitigate the effects of transient radiation darkening on the fibers.
SIERRA Low Mach Module: Fuego Theory Manual Version 4.44
Energy Technology Data Exchange (ETDEWEB)
Sierra Thermal/Fluid Team
2017-04-01
The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the core architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.
SIERRA Low Mach Module: Fuego Theory Manual Version 4.46.
Energy Technology Data Exchange (ETDEWEB)
Sierra Thermal/Fluid Team
2017-09-01
The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the core architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.
SIERRA Low Mach Module: Fuego User Manual Version 4.44
Energy Technology Data Exchange (ETDEWEB)
Sierra Thermal/Fluid Team
2017-04-01
The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the core architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.
SIERRA Low Mach Module: Fuego User Manual Version 4.46.
Energy Technology Data Exchange (ETDEWEB)
Sierra Thermal/Fluid Team
2017-09-01
The SIERRA Low Mach Module: Fuego along with the SIERRA Participating Media Radiation Module: Syrinx, henceforth referred to as Fuego and Syrinx, respectively, are the key elements of the ASCI fire environment simulation project. The fire environment simulation project is directed at characterizing both open large-scale pool fires and building enclosure fires. Fuego represents the turbulent, buoyantly-driven incompressible flow, heat transfer, mass transfer, combustion, soot, and absorption coefficient model portion of the simulation software. Syrinx represents the participating-media thermal radiation mechanics. This project is an integral part of the SIERRA multi-mechanics software development project. Fuego depends heavily upon the core architecture developments provided by SIERRA for massively parallel computing, solution adaptivity, and mechanics coupling on unstructured grids.
O Naturalismo como Atitude: Mach em Disputa com a Metafísica
Directory of Open Access Journals (Sweden)
Antonio Augusto Passos Videira
2009-01-01
Full Text Available http://dx.doi.org/10.5007/1808-1711.2009v13n3p371 Este artigo defende a hipótese de que Ernst Mach (1838-1916 recorreu ao naturalismo (termo que ele não usou — atitude derivada da sua aceitação da teoria da evolução de Darwin — como arma contra a metafísica (aqui compreendida como uma atitude em favor da busca por fundamentação última, fixa e definitiva, já que procuraria estabelecer critérios de avaliação, incluindo os relativos à escolha de teorias científicas, efetivamente capazes de serem usados pelos seres humanos.
Trujillo, Caleb M.; Anderson, Trevor R.; Pelaez, Nancy J.
2016-01-01
When undergraduate biology students learn to explain biological mechanisms, they face many challenges and may overestimate their understanding of living systems. Previously, we developed the MACH model of four components used by expert biologists to explain mechanisms: Methods, Analogies, Context, and How. This study explores the implementation of…
Mariscal, Jean-François; Bruneau, Didier; Pelon, Jacques; Van Haecke, Mathilde; Blouzon, Frédéric; Montmessin, Franck; Chepfer, Hélène
2018-04-01
We present the measurement principle and the optical design of a Quad Mach Zehnder (QMZ) interferometer as HSRL technique, allowing simultaneous measurements of particle backscattering and wind velocity. Key features of this concept is to operate with a multimodal laser and do not require any frequency stabilization. These features are relevant especially for space applications for which high technical readiness level is required.
Hoekman, M.; Dijkstra, Marcel; Dijkstra, Mindert; Hoekstra, Hugo
2006-01-01
The modeling and design of a spiral-shaped Mach-Zehnder Interferometric sensor (sMZI sensor) for refractive index sensing of watery solutions is presented. The goal of the running project is to realise a multi-sensing array by placing multiple sMZIs in series to form a sensing branch, and to place
Use of Vortex Generators to Reduce Distortion for Mach 1.6 Streamline-Traced Supersonic Inlets
Baydar, Ezgihan; Lu, Frank; Slater, John W.; Trefny, Chuck
2016-01-01
Reduce the total pressure distortion at the engine-fan face due to low-momentum flow caused by the interaction of an external terminal shock at the turbulent boundary layer along a streamline-traced external-compression (STEX) inlet for Mach 1.6.
Czech Academy of Sciences Publication Activity Database
Bartkiewicz, K.; Černoch, A.; Javůrek, D.; Lemr, K.; Soubusta, Jan; Svozilík, J.
2015-01-01
Roč. 91, č. 1 (2015), "012103-1"-"012103-4" ISSN 1050-2947 Institutional support: RVO:68378271 Keywords : one-state vector * quantum state * Mach-Zehnder interferometer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.808, year: 2014
Pérez, Daniel; Gasulla, Ivana; Capmany, José; Fandiño, Javier S; Muñoz, Pascual; Alavi, Hossein
2016-09-05
We develop, analyze and apply a linearization technique based on dual parallel Mach-Zehnder modulator to self-beating microwave photonics systems. The approach enables broadband low-distortion transmission and reception at expense of a moderate electrical power penalty yielding a small optical power penalty (<1 dB).
Trimmer, L. L.; Love, D. A.; Decker, J. P.; Blackwell, K. L.; Strike, W. T.; Rampy, J. M.
1972-01-01
Aerodynamic data obtained from a space shuttle abort stage separation wind tunnel test are presented. The .00556 scale models of the orbiter and booster configuration were tested in close proximity using dual balances during the time period of April 21 to April 27 1971. Data were obtained for both booster and orbiter over an angle of attack range from -10 to 10 deg for zero degree sideslip angle. The models were tested at several relative incidence angles and separation distances and power conditions. Plug nozzles utilizing air were used to simulate booster and orbiter plumes at various altitudes along a nominal ascent trajectory. Powered conditions were 100, 50, 25 and 0 percent of full power for the orbiter and 100, 50 and 0 percent of full power for the booster. Pitch control effectiveness data were obtained for both booster and orbiter with power on and off. In addition, launch vehicle data with and without booster power were obtained utilizing a single balance in the booster model. Data were also obtained with the booster canard off in close proximity and for the launch configuration.
Low-Reynolds number compressible flow around a triangular airfoil
Munday, Phillip; Taira, Kunihiko; Suwa, Tetsuya; Numata, Daiju; Asai, Keisuke
2013-11-01
We report on the combined numerical and experimental effort to analyze the nonlinear aerodynamics of a triangular airfoil in low-Reynolds number compressible flow that is representative of wings on future Martian air vehicles. The flow field around this airfoil is examined for a wide range of angles of attack and Mach numbers with three-dimensional direct numerical simulations at Re = 3000 . Companion experiments are conducted in a unique Martian wind tunnel that is placed in a vacuum chamber to simulate the Martian atmosphere. Computational findings are compared with pressure sensitive paint and direct force measurements and are found to be in agreement. The separated flow from the leading edge is found to form a large leading-edge vortex that sits directly above the apex of the airfoil and provides enhanced lift at post stall angles of attack. For higher subsonic flows, the vortical structures elongate in the streamwise direction resulting in reduced lift enhancement. We also observe that the onset of spanwise instability for higher angles of attack is delayed at lower Mach numbers. Currently at Mitsubishi Heavy Industries, Ltd., Nagasaki.
Number Sense on the Number Line
Woods, Dawn Marie; Ketterlin Geller, Leanne; Basaraba, Deni
2018-01-01
A strong foundation in early number concepts is critical for students' future success in mathematics. Research suggests that visual representations, like a number line, support students' development of number sense by helping them create a mental representation of the order and magnitude of numbers. In addition, explicitly sequencing instruction…
Richardson, Thomas M.
2014-01-01
We introduce the super Patalan numbers, a generalization of the super Catalan numbers in the sense of Gessel, and prove a number of properties analagous to those of the super Catalan numbers. The super Patalan numbers generalize the super Catalan numbers similarly to how the Patalan numbers generalize the Catalan numbers.
Siemsen, Hayo
2013-05-01
George Sarton had a strong influence on modern history of science. The method he pursued throughout his life was the method he had discovered in Ernst Mach's Mechanics when he was a student in Ghent. Sarton was in fact throughout his life implementing a research program inspired by the epistemology of Mach. Sarton in turn inspired many others in several generations (James Conant, Thomas Kuhn, Gerald Holton, etc.). What were the origins of these ideas in Mach and what can this origin tell us about the history of science and science education nowadays? Which ideas proved to be successful and which ones need to be improved upon? The following article will elaborate the epistemological questions, which Charles Darwin's "Origin" raised concerning human knowledge and scientific knowledge and which led Mach to adapt the concept of what is "empirical" in contrast to metaphysical a priori assumptions a second time after Galileo. On this basis Sarton proposed "genesis and development" as the major goal of his journal Isis. Mach had elaborated this epistemology in La Connaissance et l'Erreur ( Knowledge and Error), which Sarton read in 1911 (Hiebert in Knowledge and error. Reidel, Dordrecht, 1976; de Mey in George Sarton centennial. Communication & Cognition, Ghent, pp. 3-6, 1984). Accordingly for Sarton, history becomes not only a subject of science, but a method of science education. Culture—and science as part of culture—is a result of a genetic process. History of science shapes and is shaped by science and science education in a reciprocal process. Its epistemology needs to be adapted to scientific facts and the philosophy of science. Sarton was well aware of the need to develop the history of science and the philosophy of science along the lines of this reciprocal process. It was a very fruitful basis, but a specific part of it Sarton did not elaborate further, namely the erkenntnis-theory and psychology of science education. This proved to be a crucial missing
Jet propagation and Mach-cone formation in (3+1)-dimensional ideal hydrodynamics
International Nuclear Information System (INIS)
Betz, Barbara
2009-01-01
This thesis investigates the jet-medium interactions in a Quark-Gluon Plasma using a hydrodynamical model. Such a Quark-Gluon Plasma represents a very early stage of our universe and is assumed to be created in heavy-ion collisions. Its properties are subject of current research. Since the comparison of measured data to model calculations suggests that the Quark-Gluon Plasma behaves like a nearly perfect liquid, the medium created in a heavy-ion collision can be described applying hydrodynamical simulations. One of the crucial questions in this context is if highly energetic particles (so-called jets), which are produced at the beginning of the collision and traverse the formed medium, may lead to the creation of a Mach cone. Such a Mach cone is always expected to develop if a jet moves with a velocity larger than the speed of sound relative to the medium. In that case, the measured angular particle distributions are supposed to exhibit a characteristic structure allowing for direct conclusions about the Equation of State and in particular about the speed of sound of the medium. Several different scenarios of jet energy loss are examined (the exact form of which is not known from first principles) and different mechanisms of energy and momentum loss are analyzed, ranging from weak interactions (based on calculations from perturbative Quantum Chromodynamics, pQCD) to strong interactions (formulated using the Anti-de-Sitter/Conformal Field Theory Correspondence, AdS/CFT). Though they result in different angular particle correlations which could in principle allow to distinguish the underlying processes (if it becomes possible to analyze single-jet events), it is shown that the characteristic structure observed in experimental data can be obtained due to the different contributions of several possible jet trajectories through an expanding medium. Such a structure cannot directly be connected to the Equation of State. In this context, the impact of a strong flow
Allen, J. M.; Hernandez, G.; Lamb, M.
1983-01-01
Tabulated body surface pressure data for two monoplane-wing missile configurations are presented and analyzed. Body pressure data are presented for body-alone, body-tail, and body-wing-tail combinations. For the lost combination, data are presented for tail-fin deflection angles of 0 deg and 30 deg to simulate pitch, yaw, and roll control for both configurations. The data cover angles of attack from -5 deg to 25 deg and angles of roll from 0 deg to 90 deg at a Mach number of 2.50 and a Reynolds number of 6.56 x 1,000,000 per meter. Very consistent, systematic trends with angle of attack and angle of roll were observed in the data, and very good symmetry was found at a roll angle of 0 deg. Body pressures depended strongly on the local body cross-section shape, with very little dependence on the upstream shape. Undeflected fins had only a small influence on the pressures on the aft end of the body; however, tail-fin deflections caused large changes in the pressures.
Multi-band microwave photonic satellite repeater scheme employing intensity Mach-Zehnder modulators
Institute of Scientific and Technical Information of China (English)
Yin Jie; Dong Tao; Zhang Bin; Hao Yan; Cao Guixing; Cheng Zijing; Xu Kun; Zhou Yue; Dai Jian
2017-01-01
To solve the satellite repeater's flexible and wideband frequency conversion problem,we propose a novel microwave photonic repeater system,which can convert the upload signal's carrier to six different frequencies.The scheme employs one 20 GHz bandwidth dual-drive Mach-Zehnder modulator (MZM) and two 10 GHz bandwidth MZMs.The basic principle of this scheme is filtering out two optical sidebands after the optical carrier suppression (OCS) modulation and combining two sidebands modulated by the input radio frequency (RF) signal.This structure can realize simultaneous multi-band frequency conversion with only one frequency-fixed microwave source and prevent generating harmful interference sidebands by using two corresponding optical filters after optical modulation.In the simulation,one C-band signal of 6 GHz carrier can be successfully converted to 12 GHz (Ku-band),28 GHz,34 GHz,40 GHz,46 GHz (Ka-band) and 52 GHz (V-band),which can be an attractive method to realize multi-band microwave photonic satellite repeater.Alternatively,the scheme can be configured to generate multi-band local oscillators (LOs) for widely satellite onboard clock distribution when the input RF signal is replaced by the internal clock source.
Ernst Mach and the Epistemological Ideas Specific for Finnish Science Education
Siemsen, Hayo
2011-03-01
Where does Finnish science education come from? Where will it go? The following outside view reflects on relations, which Finns consider "normal" (and thus unrecognizable in introspection) in science education. But what is "normal" in Finnish culture cannot be considered "normal" for science education in other cultures, for example in Germany. The following article will trace the central ideas, which had a larger influence in the development of this difference. The question is, if and why the Finnish uniqueness in the philosophy of science education is empirically important. This puts Finnish science education into the perspective of a more general epistemological debate around Ernst Mach's Erkenntnistheorie (a German term similar to the meaning of history and philosophy of science, though more general; literally translated "cognition/knowledge theory"). From this perspective, an outlook will be given on open questions within the epistemology of Finnish science education. Following such questions could lead to the adaptation of the "successful" ideas in Finnish science education (indicated by empirical studies, such as the OECD PISA study) as well as the further development of the central ideas of Finnish science education.
Generation of cylindrically convergent shockwaves in water on the MACH facility
Bland, Simon; Krasik, Ya. E.; Yanuka, D.; Gardner, R.; MacDonald, J.; Virozub, A.; Efimov, S.; Gleizer, S.; Chaturvedi, N.
2017-06-01
We report on the first experiments utilizing MACH facility at Imperial College London to explode copper wire arrays in water, generating extremely symmetric, cylindrical convergent shockwaves. The experiments were carried out with 10mm diameter arrays consisting of 60 × 130 μm wires, and currents >500 kA were achieved despite the high inductance load. Laser backlit framing images and streak photography of the implosion showed a highly uniform, stable shockwave that travelled towards the axis at velocities up to 7.5 kms-1. For the first time, imaging of the shock front has been carried at radii 1 Mbar are produced within 10 μm of the axis, with water densities 3 gcm-3 and temperatures of many 1000 s of Kelvin. The results represent a significant step in the application of the technique to drive different material samples, and calculations of scaling the technique to larger pulsed power facilities are presented. This work was supported by the Institute of Shock Physics, funded by AWE Aldermaston, and the NNSA under DOE Cooperative Agreement Nos. DE-F03-02NA00057 and DE-SC-0001063.
Comment on "Particle path through a nested Mach-Zehnder interferometer"
Salih, Hatim
2018-02-01
In a recent paper [Phys. Rev. A 94, 032115 (2016), 10.1103/PhysRevA.94.032115], Griffiths questioned—based on an interesting consistent-histories (CH) argument—the counterfactuality, for one of the bit choices, of the protocol of Salih et al. for communicating without sending physical particles [Phys. Rev. Lett. 110, 170502 (2013), 10.1103/PhysRevLett.110.170502]. Here, we first show that for the Mach-Zehnder version used to explain our protocol, contrary to Griffiths's claim, no family of consistent histories exists where any history has the photon traveling through the communication channel, thus rendering the question of whether the photon was in the communication channel meaningless from a CH viewpoint. We then show that for the actual Michelson-type protocol, there is a consistent-histories family for each cycle that includes histories where the photon travels through the communication channel. We show that the probability of finding the photon in the communication channel at any time is zero—proving complete counterfactuality.
A supersonic fan equipped variable cycle engine for a Mach 2.7 supersonic transport
Tavares, T. S.
1985-01-01
The concept of a variable cycle turbofan engine with an axially supersonic fan stage as powerplant for a Mach 2.7 supersonic transport was evaluated. Quantitative cycle analysis was used to assess the effects of the fan inlet and blading efficiencies on engine performance. Thrust levels predicted by cycle analysis are shown to match the thrust requirements of a representative aircraft. Fan inlet geometry is discussed and it is shown that a fixed geometry conical spike will provide sufficient airflow throughout the operating regime. The supersonic fan considered consists of a single stage comprising a rotor and stator. The concept is similar in principle to a supersonic compressor, but differs by having a stator which removes swirl from the flow without producing a net rise in static pressure. Operating conditions peculiar to the axially supersonic fan are discussed. Geometry of rotor and stator cascades are presented which utilize a supersonic vortex flow distribution. Results of a 2-D CFD flow analysis of these cascades are presented. A simple estimate of passage losses was made using empirical methods.
Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer
International Nuclear Information System (INIS)
Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro
2011-01-01
Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n e and the electron temperature T e profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO 2 laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n e and T e were, respectively, about 2 x 10 24 m -3 and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n e at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.
Effects of temperature distribution on boundary layer stability for a circular cone at Mach 10
Rigney, Jeffrey M.
A CFD analysis was conducted on a circular cone at 3 degrees angle of attack at Mach 10 using US3D and STABL 3D to determine the effect of wall temperature on the stability characteristics that lead to laminar-to-turbulent transition. Wall temperature distributions were manipulated while all other flow inputs and geometric qualities were held constant. Laminar-to-turbulent transition was analyzed for isothermal and adiabatic wall conditions, a simulated short-duration wind tunnel case, and several hot-nose temperature distributions. For this study, stability characteristics include maximum N-factor growth and the corresponding frequency range, disturbance spatial amplification rate and the corresponding modal frequency, and stability neutral point location. STABL 3D analysis indicates that temperature distributions typical of those in short-duration hypersonic wind tunnels do not result in any significant difference on the stability characteristics, as compared to an isothermal wall boundary condition. Hypothetical distributions of much greater temperatures at and past the nose tip do show a trend of dampening of second-mode disturbances, most notably on the leeward ray. The most pronounced differences existed between the isothermal and adiabatic cases.
Optical fiber temperature sensor based on dumbbell-shaped Mach-Zehnder interferometer
Tan, Jianchang; Feng, Guoying; Liang, Jingchuan; Zhang, Shulin
2018-01-01
A dumbbell-shaped and core-disconnected microstructure all-fiber temperature sensor based on the Mach-Zehnder interferometer (MZI) is designed and implemented. To the best of our knowledge, the MZI with this configuration was produced and applied to sense temperature for the first time. It demonstrated that this all-fiber interferometer incorporates intermodal interference between the LP01 mode and a high-order cladding mode of LP07. Theoretical and experimental results indicate that the linearity of the spectral shift due to the temperature change is ˜0.999 and the sensitivity at 25°C to 400°C is ˜26.03 pm/°C and at -25°C to 20°C is ˜23.87 pm/°C. The reproducibility error of this all-fiber temperature sensor at 25°C to 400°C is innovative micro-nano all-fiber sensors.
Combined Experimental and Numerical Investigation of Electric-Arc Airspikes For Blunt Body at Mach 3
Misiewicz, C.; Myrabo, L. N.; Shneider, M. N.; Raizer, Y. P.
2005-04-01
Electric-arc airspike experiments were performed with a 1.25-inch diameter blunt body in the vacuum-driven Mach 3 wind tunnel at Rensselaer Polytechnic Institute. Schlieren movies at 30-Hz frame rate were recorded of the airspike flowfields, revealing substantial evolution over the 6-second run durations. Arc powers up to 2-kW were delivered into the airspike by an arc-welding power supply, using zirconiated tungsten electrodes. Aerodynamic drag was measured with a piezo-electric load cell, revealing reductions up to 70% when the airspike was energized. The test article was a small-scale model of the Mercury lightcraft, a laser-propelled transatmospheric vehicle designed to transport one-person into orbit. Numerical modeling of this airspike is based on the Euler gasdynamic equations for conditions identical to those tested in the RPI supersonic tunnel. Excellent agreement between the shock wave shapes given by first-order asymptotic theory, numerical modeling, and experiment is demonstrated. Results of the numerical modeling confirm both the significant drag reduction potential and the energy efficiency of the airspike concept.
Near-Field Antenna Measurements Using Photonic Sensor of Mach-Zehnder Interferometer
Directory of Open Access Journals (Sweden)
Masanobu Hirose
2012-01-01
Full Text Available We have been developing a photonic sensor system to measure the electric near-field distribution at a distance shorter than one wavelength from the aperture of an antenna. The photonic sensor is a type of Mach-Zehnder interferometer and consists of an array antenna of 2.4 mm height and 2 mm width on a LiNbO3 substrate (0.5 mm thickness, 8 mm length, and 3 mm width supported by a glass pipe. The photonic sensor can be considered to be a receiving infinitesimal dipole antenna that is a tiny metallic part printed on a small dielectric plate at microwave frequency. Those physical and electrical features make the photonic sensor attractive when used as a probe for near-field antenna measurements. We have demonstrated that the system can be applied to planar, spherical, and cylindrical near-field antenna measurements without any probe compensation approximately below 10 GHz. We show the theories and the measurements using the photonic sensor in the three near-field antenna measurement methods.
International Nuclear Information System (INIS)
Zhou, X.; Zeng, R.; Zhuang, C.; Chen, S.
2015-01-01
Leader discharge is one of the main phases in long air gap breakdown, which is characterized by high temperature and high conductivity. It is of great importance to determine thermal characteristics of leader discharges. In this paper, a long-optical-path Mach-Zehnder interferometer was set up to measure the thermal parameters (thermal diameter, gas density, and gas temperature) of positive leader discharges in atmospheric air. IEC standard positive switching impulse voltages were applied to a near-one-meter point-plane air gap. Filamentary channels with high gas temperature and low density corresponding to leader discharges were observed as significant distortions in the interference fringe images. Typical diameters of the entire heated channel range from 1.5 mm to 3.5 mm with an average expansion velocity of 6.7 m/s. In contrast, typical diameters of the intensely heated region with a sharp gas density reduction range from 0.4 mm to 1.1 mm, about one third of the entire heated channel. The radial distribution of the gas density is calculated from the fringe displacements by performing an Abel inverse transform. The typical calculated gas density reduction in the center of a propagating leader channel is 80% to 90%, corresponding to a gas temperature of 1500 K to 3000 K based on the ideal gas law. Leaders tend to terminate if the central temperature is below 1500 K
On the use of microjets to suppress turbulence in a Mach 0.9 axisymmetric jet
Arakeri, V. H.; Krothapalli, A.; Siddavaram, V.; Alkislar, M. B.; Lourenco, L. M.
2003-09-01
We have experimentally studied the effect of microjets on the flow field of a Mach 0.9 round jet. Planar and three-dimensional velocity field measurements using particle image velocimetry show a significant reduction in the near-field turbulent intensities with the activation of microjets. The axial and normal turbulence intensities are reduced by about 15% and 20%, respectively, and an even larger effect is found on the peak values of the turbulent shear stress with a reduction of up to 40%. The required mass flow rate of the microjets was about 1% of the primary jet mass flux. It appears that the microjets influence the mean velocity profiles such that the peak normalized vorticity in the shear layer is significantly reduced, thus inducing an overall stabilizing effect. Therefore, we seem to have exploited the fact that an alteration in the instability characteristics of the initial shear-layer can influence the whole jet exhaust including its noise field. We have found a reduction of about 2 dB in the near-field overall sound pressure level in the lateral direction with the use of microjets. This observation is qualitatively consistent with the measured reduced turbulence intensities.
Energy Technology Data Exchange (ETDEWEB)
Zhou, X., E-mail: zhouxuan12@mails.thu.edu.cn; Zeng, R.; Zhuang, C.; Chen, S. [Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China)
2015-06-15
Leader discharge is one of the main phases in long air gap breakdown, which is characterized by high temperature and high conductivity. It is of great importance to determine thermal characteristics of leader discharges. In this paper, a long-optical-path Mach-Zehnder interferometer was set up to measure the thermal parameters (thermal diameter, gas density, and gas temperature) of positive leader discharges in atmospheric air. IEC standard positive switching impulse voltages were applied to a near-one-meter point-plane air gap. Filamentary channels with high gas temperature and low density corresponding to leader discharges were observed as significant distortions in the interference fringe images. Typical diameters of the entire heated channel range from 1.5 mm to 3.5 mm with an average expansion velocity of 6.7 m/s. In contrast, typical diameters of the intensely heated region with a sharp gas density reduction range from 0.4 mm to 1.1 mm, about one third of the entire heated channel. The radial distribution of the gas density is calculated from the fringe displacements by performing an Abel inverse transform. The typical calculated gas density reduction in the center of a propagating leader channel is 80% to 90%, corresponding to a gas temperature of 1500 K to 3000 K based on the ideal gas law. Leaders tend to terminate if the central temperature is below 1500 K.
In-fiber torsion sensor based on dual polarized Mach-Zehnder interference.
Chen, Lei; Zhang, Wei-Gang; Wang, Li; Zhang, Hao; Sieg, Jonathan; Zhou, Quan; Zhang, Li-Yu; Wang, Biao; Yan, Tie-Yi
2014-12-29
This paper presents a novel optical fiber torsion sensor based on dual polarized Mach-Zehnder interference (DPMZI). Unlike the conventional fiber sensor, the proposed sensor is composed of a sensor part and a demodulator. The demodulator is made by a bared single mode fiber (SMF) loop, and the sensor part is a segment of a coated SMF placed before the loop. A mathematical model is proposed based on DPMZI mechanism and from the model when the sensor part is twisted, the E-field rotational angle will bring a quasi-linear impact on the resonance dip wavelength in their matched detecting range. A proof-of-concept experiment was performed to verify the theoretical prediction. From the experimental data, a sensitivity of -0.3703, -1.00962, and -0.59881 nm•m/rad is achieved with the determining range of 12.0936, 7.6959, and 10.4444 rad/m respectively. The sensor which is composed only of the SMF has the advantages of low insertion loss (~-2dB), healthy structure, low manufacture cost, and easy assembly and application.
Secondary Instability of Stationary Crossflow Vortices in Mach 6 Boundary Layer Over a Circular Cone
Li, Fei; Choudhari, Meelan M.; Paredes-Gonzalez, Pedro; Duan, Lian
2015-01-01
Hypersonic boundary layer flows over a circular cone at moderate incidence can support strong crossflow instability. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7-degree half-angle circular cone in a Mach 6 free stream. Depending on the local amplitude of the stationary crossflow mode, the most unstable secondary disturbances either originate from the second (i.e., Mack) mode instabilities of the unperturbed boundary layer or correspond to genuine secondary instabilities that reduce to stable disturbances at sufficiently small amplitudes of the stationary crossflow vortex. The predicted frequencies of dominant secondary disturbances are similar to those measured during wind tunnel experiments at Purdue University and the Technical University of Braunschweig, Germany.
Energy Technology Data Exchange (ETDEWEB)
Zhukhovitskii, D. I., E-mail: dmr@ihed.ras.ru; Fortov, V. E.; Molotkov, V. I.; Lipaev, A. M.; Naumkin, V. N. [Joint Institute of High Temperatures, Russian Academy of Sciences, Izhorskaya 13, Bd. 2, 125412 Moscow (Russian Federation); Thomas, H. M. [Research Group Complex Plasma, DLR, Oberpfaffenhofen, 82234 Wessling (Germany); Ivlev, A. V.; Morfill, G. E. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Schwabe, M. [Department of Chemical and Biomolecular Engineering, Graves Lab, D75 Tan Hall, University of California, Berkeley, CA 94720 (United States)
2015-02-15
We report the first observation of the Mach cones excited by a larger microparticle (projectile) moving through a cloud of smaller microparticles (dust) in a complex plasma with neon as a buffer gas under microgravity conditions. A collective motion of the dust particles occurs as propagation of the contact discontinuity. The corresponding speed of sound was measured by a special method of the Mach cone visualization. The measurement results are incompatible with the theory of ion acoustic waves. The estimate for the pressure in a strongly coupled Coulomb system and a scaling law for the complex plasma make it possible to derive an evaluation for the speed of sound, which is in a reasonable agreement with the experiments in complex plasmas.
International Nuclear Information System (INIS)
Zhukhovitskii, D. I.; Fortov, V. E.; Molotkov, V. I.; Lipaev, A. M.; Naumkin, V. N.; Thomas, H. M.; Ivlev, A. V.; Morfill, G. E.; Schwabe, M.
2015-01-01
We report the first observation of the Mach cones excited by a larger microparticle (projectile) moving through a cloud of smaller microparticles (dust) in a complex plasma with neon as a buffer gas under microgravity conditions. A collective motion of the dust particles occurs as propagation of the contact discontinuity. The corresponding speed of sound was measured by a special method of the Mach cone visualization. The measurement results are incompatible with the theory of ion acoustic waves. The estimate for the pressure in a strongly coupled Coulomb system and a scaling law for the complex plasma make it possible to derive an evaluation for the speed of sound, which is in a reasonable agreement with the experiments in complex plasmas
Directory of Open Access Journals (Sweden)
Mariscal Jean-François
2018-01-01
Full Text Available We present the measurement principle and the optical design of a Quad Mach Zehnder (QMZ interferometer as HSRL technique, allowing simultaneous measurements of particle backscattering and wind velocity. Key features of this concept is to operate with a multimodal laser and do not require any frequency stabilization. These features are relevant especially for space applications for which high technical readiness level is required.
DEFF Research Database (Denmark)
Zhao, Ying; Pang, Xiaodan; Deng, Lei
2011-01-01
A novel approach for broadband microwave frequency measurement by employing a single-drive dual-parallel Mach-Zehnder modulator is proposed and experimentally demonstrated. Based on bias manipulations of the modulator, conventional frequency-to-power mapping technique is developed by performing a...... 10−3 relative error. This high accuracy frequency measurement technique is a promising candidate for high-speed electronic warfare and defense applications....
Cammarata, Simone
2017-01-01
Silicon Photonics may well provide the opportunity for new levels of integration between detectors and their readout electronics. This technology is thus being evaluated at CERN in order to assess its suitability for use in particle physics experiments. In order to check the agreement with measurements and the validity of previous device simulations, a pure Synopsys Sentaurus™ simulation of an un-irradiated Mach-Zehnder silicon modulator has been carried out during the Summer Student project.
CFD Validation Experiment of a Mach 2.5 Axisymmetric Shock-Wave Boundary-Layer Interaction
Davis, David O.
2015-01-01
Preliminary results of an experimental investigation of a Mach 2.5 two-dimensional axisymmetric shock-wave/boundary-layer interaction (SWBLI) are presented. The purpose of the investigation is to create a SWBLI dataset specifically for CFD validation purposes. Presented herein are the details of the facility and preliminary measurements characterizing the facility and interaction region. The results will serve to define the region of interest where more detailed mean and turbulence measurements will be made.
Sun, Y. H.; Sainio, W. C.
1975-01-01
Test results of the Aerothermodynamic Integration Model are presented. A program was initiated to develop a hydrogen-fueled research-oriented scramjet for operation between Mach 3 and 8. The primary objectives were to investigate the internal aerothermodynamic characteristics of the engine, to provide realistic design parameters for future hypersonic engine development as well as to evaluate the ground test facility and testing techniques. The engine was tested at the NASA hypersonic tunnel facility with synthetic air at Mach 5, 6, and 7. The hydrogen fuel was heated up to 1500 R prior to injection to simulate a regeneratively cooled system. The engine and component performance at Mach 6 is reported. Inlet performance compared very well both with theory and with subscale model tests. Combustor efficiencies up to 95 percent were attained at an equivalence ratio of unity. Nozzle performance was lower than expected. The overall engine performance was computed using two different methods. The performance was also compared with test data from other sources.
Trujillo, Caleb M.; Anderson, Trevor R.; Pelaez, Nancy J.
2016-01-01
When undergraduate biology students learn to explain biological mechanisms, they face many challenges and may overestimate their understanding of living systems. Previously, we developed the MACH model of four components used by expert biologists to explain mechanisms: Methods, Analogies, Context, and How. This study explores the implementation of the model in an undergraduate biology classroom as an educational tool to address some of the known challenges. To find out how well students’ written explanations represent components of the MACH model before and after they were taught about it and why students think the MACH model was useful, we conducted an exploratory multiple case study with four interview participants. We characterize how two students explained biological mechanisms before and after a teaching intervention that used the MACH components. Inductive analysis of written explanations and interviews showed that MACH acted as an effective metacognitive tool for all four students by helping them to monitor their understanding, communicate explanations, and identify explanatory gaps. Further research, though, is needed to more fully substantiate the general usefulness of MACH for promoting students’ metacognition about their understanding of biological mechanisms. PMID:27252295
A Study of Mach-Zehnder Interferometer Type Optical Modulator Applicable to an Accelerometer
Suzuki, Masato; Takahashi, Tomokazu; Aoyagi, Seiji; Amemiya, Yoshiteru; Fukuyama, Masataka; Yokoyama, Shin
2011-04-01
A novel Mach-Zehnder interferometer (MZI)-type optical modulator based on micro electro mechanical systems (MEMS) technology is developed in this study. In this optical modulator, one of two branched waveguides in the MZI has a floating beam structure (air-bridge type). Additionally, a cantilever supporting a proof mass intersects with the floating optical waveguide. When an inertial force due to acceleration is applied to the proof mass, the floating waveguide is expanded and the output of the MZI is modulated. Therefore, this optical modulator will be applicable to an accelerometer in the future. To decrease optical loss at the intersectional point between the floating waveguide and the cantilever in the MZI, the multi-mode interference (MMI) waveguide is serially connected with the floating waveguide and the cantilever crosses to the MMI waveguide. An optimization of the MMI waveguide and an estimation of deflection of the floating waveguide due to applying force are carried out by using optical and mechanical simulation, respectively. The proposed optical modulator is fabricated by inductively coupled plasma (ICP) etching of the top layer of a silicon-on-insulator (SOI) wafer, which is made of crystal Si. The floating waveguide in the modulator is formed by removal of its underlying buried oxide (BOX) layer of SOI. As a result of evaluation, we have succeeded in changing the output of the MZI by applying a force to the cantilever. However, the modulation is smaller than the expected value. Improvement of the modulation and detection of the inertial force due to the applied acceleration are future tasks.
Number words and number symbols a cultural history of numbers
Menninger, Karl
1992-01-01
Classic study discusses number sequence and language and explores written numerals and computations in many cultures. "The historian of mathematics will find much to interest him here both in the contents and viewpoint, while the casual reader is likely to be intrigued by the author's superior narrative ability.
Directory of Open Access Journals (Sweden)
T. Pathinathan
2015-01-01
Full Text Available In this paper we define diamond fuzzy number with the help of triangular fuzzy number. We include basic arithmetic operations like addition, subtraction of diamond fuzzy numbers with examples. We define diamond fuzzy matrix with some matrix properties. We have defined Nested diamond fuzzy number and Linked diamond fuzzy number. We have further classified Right Linked Diamond Fuzzy number and Left Linked Diamond Fuzzy number. Finally we have verified the arithmetic operations for the above mentioned types of Diamond Fuzzy Numbers.
Koninck, Jean-Marie De
2009-01-01
Who would have thought that listing the positive integers along with their most remarkable properties could end up being such an engaging and stimulating adventure? The author uses this approach to explore elementary and advanced topics in classical number theory. A large variety of numbers are contemplated: Fermat numbers, Mersenne primes, powerful numbers, sublime numbers, Wieferich primes, insolite numbers, Sastry numbers, voracious numbers, to name only a few. The author also presents short proofs of miscellaneous results and constantly challenges the reader with a variety of old and new n
2011-08-29
current (state of the art) and future technology. The military mission shows in-flight delivery/release of the “payload” but we have to cater for the...for the aircraft in airline service. The aircraft featured fuel transfer tanks for trim and most probably, there was insufficient capacity for the
Directory of Open Access Journals (Sweden)
Jean-François Ciparisse
2018-04-01
Full Text Available ITER (International Thermonuclear Experimental Reactor is a magnetically confined plasma nuclear reactor. Inside it, due to plasma disruptions, the formation of neutron-activated powders, which are essentially made out of tungsten and beryllium, occurs. As many windows for diagnostics are present on the reactor, which operates at very low pressure, a LOVA (Loss of Vacuum Accident could be possible and may lead to dust mobilisation and a toxic and radioactive fallout inside the plant. This study is aimed at reproducing numerically the first seconds of a LOVA in ITER, in order to get information about the dust resuspension risk. This work has been carried out by means of a CFD (Computational Fluid Dynamics simulation of the beginning of the pressurisation transient inside the whole Tokamak. It has been found that the pressurization transient is extremely slow, and that the friction speed on the walls is very high, and therefore a high mobilization risk of the dust is expected on the entire internal surface of the reactor. It has been observed that a LOVA in a real-scale reactor is more severe than the one reproduced in reduced-scale facilities, as STARDUST-U, because the speeds are higher, and the dust resuspension capacity of the flow is greater.
1993-01-01
WOWOLICF IcFO OaF OOI cFCF CODFFt Ft~ ~~~~~~~~ FC,0~FO0OaF~ F7 Fz00 F ,FF F O O 7** 0 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ u .0F F 0 F0’L F 0NN F 0 4 444 F F FO C H...Z z Z ~0424 0 1:, ’o 0C wC C" I C-4 cc 0- a j > 4v Lo.- C) U - u 0 M I- . to a aL a aA acca . ) 0 a- C a T 0 (0 CC cc 4 w w 0124) aa aw0 4 -- I
Axelson, John A.; Crown, J. Conrad
1948-01-01
An analysis is presented of the influence of wing aspect ratio and tail location on the effects of compressibility upon static longitudinal stability. The investigation showed that the use of reduced wing aspect ratios or short tail lengths leads to serious reductions in high-speed stability and the possibility of high-speed instability.
Reuter, William H.; Buning, Pieter G.; Hobson, Garth V.
1993-01-01
An effective control canard design to provide enhanced controllability throughout the flight regime is described which uses a 3D, Navier-Stokes computational solution. The use of canard by the Space Shuttle Orbiter in both hypersonic and subsonic flight regimes can enhance its usefullness by expanding its payload carrying capability and improving its static stability. The canard produces an additional nose-up pitching moment to relax center-of-gravity constraint and alleviates the need for large, lift-destroying elevon deflections required to maintain the high angles of attack for effective hypersonic flight.
Violato, D.; Bryon, K.; Moore, P.; Scarano, F.
2010-01-01
This paper describes an experimental investigation by time-resolved planar and tomographic PIV on the sound production mechanism of vortex pairing of a transitional water-jet flow at Re=5000. The shear layer is characterized by axisymmetric vortex rings which undergo pairing with a varicose mode.
International Nuclear Information System (INIS)
Le Quere, P.; Weisman, C.; Paillere, H.; Vierendeels, J.; Dick, E.; Becker, R.; Braack, M.; Locke, J.
2005-01-01
Heat transfer by natural convection and conduction in enclosures occurs in numerous practical situations including the cooling of nuclear reactors. For large temperature difference, the flow becomes compressible with a strong coupling between the continuity, the momentum and the energy equations through the equation of state, and its properties (viscosity, heat conductivity) also vary with the temperature, making the Boussinesq flow approximation inappropriate and inaccurate. There are very few reference solutions in the literature on non-Boussinesq natural convection flows. We propose here a test case problem which extends the well-known De Vahl Davis differentially heated square cavity problem to the case of large temperature differences for which the Boussinesq approximation is no longer valid. The paper is split in two parts: in this first part, we propose as yet unpublished reference solutions for cases characterized by a non-dimensional temperature difference of 0.6, Ra 10 6 (constant property and variable property cases) and Ra = 10 7 (variable property case). These reference solutions were produced after a first international workshop organized by Cea and LIMSI in January 2000, in which the above authors volunteered to produce accurate numerical solutions from which the present reference solutions could be established. (authors)
Burkhart, Jerry
2009-01-01
Prime numbers are often described as the "building blocks" of natural numbers. This article shows how the author and his students took this idea literally by using prime factorizations to build numbers with blocks. In this activity, students explore many concepts of number theory, including the relationship between greatest common factors and…
Vazzana, Anthony; Garth, David
2007-01-01
One of the oldest branches of mathematics, number theory is a vast field devoted to studying the properties of whole numbers. Offering a flexible format for a one- or two-semester course, Introduction to Number Theory uses worked examples, numerous exercises, and two popular software packages to describe a diverse array of number theory topics.
Powers, Sheryll Goecke
1997-01-01
This monograph discusses the working and living environment of women involved with flight research at NASA Dryden Flight Research Center during the late 1940s and early 1950s. The women engineers, their work and the airplanes they worked on from 1960 to December 1995 are highlighted. The labor intensive data gathering and analysis procedures and instrumentation used before the age of digital computers are explained by showing and describing typical instrumentation found on the X-series aircraft from the X-1 through the X-15. The data reduction technique used to obtain the Mach number position error curve for the X-1 aircraft and which documents the historic first flight to exceed the speed of sound is described and a Mach number and altitude plot from an X-15 flight is shown.
Silicon opto-electronic wavelength tracker based on an asymmetric 2x3 Mach-Zehnder Interferometer
Doménech Gómez, José David; Sanchez Fandiño, Javier Antonio; Gargallo Jaquotot, Bernardo Andrés; Baños Lopez, Rocio; Muñoz Muñoz, Pascual
2014-01-01
In this paper we report on the experimental demonstration of a Silicon-on-Insulator opto-electronic wavelength tracker for the optical telecommunication C-band. The device consist of a 2x3 Mach-Zehnder Interferometer (MZI) with 10 pm resolution and photo-detectors integrated on the same chip. The MZI is built interconnecting two Multimode Interference (MMI) couplers with two waveguides whose length difference is 56 mm. The first MMI has a coupling ratio of 95:05 to com...
DEFF Research Database (Denmark)
Guan, Xiaowei; Wang, Xiaoyan; Frandsen, Lars Hagedorn
2016-01-01
We report on a novel design of an on-chip optical temperature sensor based on a Mach-Zehnder interferometer configuration where the two arms consist of hybrid waveguides providing opposite temperature-dependent phase changes to enhance the temperature sensitivity of the sensor. The sensitivity...... of the fabricated sensor with silicon/polymer hybrid waveguides is measured to be 172 pm/°C, which is two times larger than a conventional all-silicon optical temperature sensor (∼80 pm/°C). Moreover, a design with silicon/titanium dioxide hybrid waveguides is by calculation expected to have a sensitivity as high...
Sun, Xiao-Yan; Chu, Dong-Kai; Dong, Xin-Ran; Zhou, Chu; Li, Hai-Tao; Luo-Zhi; Hu, You-Wang; Zhou, Jian-Ying; Cong-Wang; Duan, Ji-An
2016-03-01
A High sensitive refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed, which is fabricated by femtosecond laser transversal-scanning inscription method and chemical etching. A rectangular cavity structure is formed in part of fiber core and cladding interface. The MZI sensor shows excellent refractive index sensitivity and linearity, which exhibits an extremely high RI sensitivity of -17197 nm/RIU (refractive index unit) with the linearity of 0.9996 within the refractive index range of 1.3371-1.3407. The experimental results are consistent with theoretical analysis.
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...... point is specified suitably and a simple transition length model is incorporated to determine the extent of the laminar separation bubble. The thin-layer approximations of compressible, Reynolds-averaged, Navier-Stokes equations are used for the numerical solution, with an implicit, upwind-biased, third...
On the number of special numbers
Indian Academy of Sciences (India)
without loss of any generality to be the first k primes), then the equation a + b = c has .... This is an elementary exercise in partial summation (see [12]). Thus ... This is easily done by inserting a stronger form of the prime number theorem into the.
Grešak, Rozalija
2015-01-01
The field of real numbers is usually constructed using Dedekind cuts. In these thesis we focus on the construction of the field of real numbers using metric completion of rational numbers using Cauchy sequences. In a similar manner we construct the field of p-adic numbers, describe some of their basic and topological properties. We follow by a construction of complex p-adic numbers and we compare them with the ordinary complex numbers. We conclude the thesis by giving a motivation for the int...
On the number of special numbers
Indian Academy of Sciences (India)
We now apply the theory of the Thue equation to obtain an effective bound on m. Indeed, by Lemma 3.2, we can write m2 = ba3 and m2 − 4 = cd3 with b, c cubefree. By the above, both b, c are bounded since they are cubefree and all their prime factors are less than e63727. Now we have a finite number of. Thue equations:.
International Nuclear Information System (INIS)
Kaneko, K.
1987-01-01
A relationship between the number projection and the shell model methods is investigated in the case of a single-j shell. We can find a one-to-one correspondence between the number projected and the shell model states
Gallistel, C R
2017-12-01
The representation of discrete and continuous quantities appears to be ancient and pervasive in animal brains. Because numbers are the natural carriers of these representations, we may discover that in brains, it's numbers all the way down.
Astronomical random numbers for quantum foundations experiments
Leung, Calvin; Brown, Amy; Nguyen, Hien; Friedman, Andrew S.; Kaiser, David I.; Gallicchio, Jason
2018-04-01
Photons from distant astronomical sources can be used as a classical source of randomness to improve fundamental tests of quantum nonlocality, wave-particle duality, and local realism through Bell's inequality and delayed-choice quantum eraser tests inspired by Wheeler's cosmic-scale Mach-Zehnder interferometer gedanken experiment. Such sources of random numbers may also be useful for information-theoretic applications such as key distribution for quantum cryptography. Building on the design of an astronomical random number generator developed for the recent cosmic Bell experiment [Handsteiner et al. Phys. Rev. Lett. 118, 060401 (2017), 10.1103/PhysRevLett.118.060401], in this paper we report on the design and characterization of a device that, with 20-nanosecond latency, outputs a bit based on whether the wavelength of an incoming photon is greater than or less than ≈700 nm. Using the one-meter telescope at the Jet Propulsion Laboratory Table Mountain Observatory, we generated random bits from astronomical photons in both color channels from 50 stars of varying color and magnitude, and from 12 quasars with redshifts up to z =3.9 . With stars, we achieved bit rates of ˜1 ×106Hz/m 2 , limited by saturation of our single-photon detectors, and with quasars of magnitudes between 12.9 and 16, we achieved rates between ˜102 and 2 ×103Hz /m2 . For bright quasars, the resulting bitstreams exhibit sufficiently low amounts of statistical predictability as quantified by the mutual information. In addition, a sufficiently high fraction of bits generated are of true astronomical origin in order to address both the locality and freedom-of-choice loopholes when used to set the measurement settings in a test of the Bell-CHSH inequality.
DEFF Research Database (Denmark)
Andersen, Torben
2014-01-01
had a marked singular and an unmarked plural. Synchronically, however, the singular is arguably the basic member of the number category as revealed by the use of the two numbers. In addition, some nouns have a collective form, which is grammatically singular. Number also plays a role...
DEFF Research Database (Denmark)
Elvik, Rune; Bjørnskau, Torkel
2017-01-01
Highlights •26 studies of the safety-in-numbers effect are reviewed. •The existence of a safety-in-numbers effect is confirmed. •Results are consistent. •Causes of the safety-in-numbers effect are incompletely known....
de Mestre, Neville
2008-01-01
Prime numbers are important as the building blocks for the set of all natural numbers, because prime factorisation is an important and useful property of all natural numbers. Students can discover them by using the method known as the Sieve of Eratosthenes, named after the Greek geographer and astronomer who lived from c. 276-194 BC. Eratosthenes…
Siemsen, Hayo; Siemsen, Karl Hayo
2009-04-01
Although it is generally assumed that the thoughts of Ernst Mach and the scientific fields he influenced (in this case psychophysics and Gestalt psychology) emigrated from Europe during Second World War they apparently survived in Finland, influencing the Finnish education system. The following article evaluates this relationship and its implications from a historical and an empirical perspective. In empirical studies comparing the education systems of different countries, such as PISA, the Finns are in general regarded as being very successful with their school system. Does this apparent success have anything to do with a Machian influence? Our current research has so far revealed that the Finns have gone through an independent cultural development in two specific aspects: in the idea of the development of the individual personality (Snellman) and in a specific phenomenalism (developed primarily by Eino Kaila, in which Kaila was heavily influenced in this by Ernst Mach). The result can be regarded as a nation-wide “Experiment”, the empirical evaluation of which can be found partly in the statistics of the PISA Studies, especially the evaluation of Finland in relation to other countries.
Convective and global stability analysis of a Mach 5.8 boundary layer grazing a compliant surface
Dettenrieder, Fabian; Bodony, Daniel
2016-11-01
Boundary layer transition on high-speed vehicles is expected to be affected by unsteady surface compliance. The stability properties of a Mach 5.8 zero-pressure-gradient laminar boundary layer grazing a nominally-flat thermo-mechanically compliant panel is considered. The linearized compressible Navier-Stokes equations describe small amplitude disturbances in the fluid while the panel deformations are described by the Kirchhoff-Love plate equation and its thermal state by the transient heat equation. Compatibility conditions that couple disturbances in the fluid to those in the solid yield simple algebraic and robin boundary conditions for the velocity and thermal states, respectively. A local convective stability analysis shows that the panel can modify both the first and second Mack modes when, for metallic-like panels, the panel thickness exceeds the lengthscale δ99 Rex- 0 . 5 . A global stability analysis, which permits finite panel lengths with clamped-clamped boundary conditions, shows a rich eigenvalue spectrum with several branches. Unstable modes are found with streamwise-growing panel deformations leading to Mach wave-type radiation. Stable global modes are also found and have distinctly different panel modes but similar radiation patterns. Air Force Office of Scientific Research.
International Nuclear Information System (INIS)
Feldman, M.; Mockler, D.J.; English, R.E. Jr.; Byrd, J.L.; Salmon, J.T.
1991-01-01
We are incorporating a novel self-referencing Mach-Zehnder interferometer into a large scale laser system as a real time, interactive diagnostic tool for wavefront measurement. The instrument is capable of absolute wavefront measurements accurate to better than λ/10 pv over a wavelength range > 300 nm without readjustment of the optical components. This performance is achieved through the design of both refractive optics and catadioptric collimator to achromatize the Mach-Zehnder reference arm. Other features include polarization insensitivity through the use of low angles of incidence on all beamsplitters as well as an equal path length configuration that allows measurement of either broad-band or closely spaced laser-line sources. Instrument accuracy is periodically monitored in place by means of a thermally and mechanically stable wavefront reference source that is calibrated off-line with a phase conjugate interferometer. Video interferograms are analyzed using Fourier transform techniques on a computer that includes dedicated array processor. Computer and video networks maintain distributed interferometers under the control of a single analysis computer with multiple user access. 7 refs., 11 figs
Nozzle design study for a quasi-axisymmetric scramjet-powered vehicle at Mach 7.9 flight conditions
Tanimizu, Katsuyoshi; Mee, David J.; Stalker, Raymond J.; Jacobs, Peter A.
2013-09-01
A nozzle shape optimization study for a quasi-axisymmetric scramjet has been performed for a Mach 7.9 operating condition with hydrogen fuel, aiming at the application of a hypersonic airbreathing vehicle. In this study, the nozzle geometry which is parameterized by a set of design variables, is optimized for the single objective of maximum net thrust using an in-house CFD solver for inviscid flowfields with a simple force prediction methodology. The combustion is modelled using a simple chemical reaction code. The effects of the nozzle design on the overall vehicle performance are discussed. For the present geometry, net thrust is achieved for the optimized vehicle design. The results of the nozzle-optimization study show that performance is limited by the nozzle area ratio that can be incorporated into the vehicle without leading to too large a base diameter of the vehicle and increasing the external drag of the vehicle. This study indicates that it is very difficult to achieve positive thrust at Mach 7.9 using the basic geometry investigated.
A study of direct-current surface discharge plasma for a Mach 3 supersonic flow control
Shin, Jichul
A direct-current, non-equilibrium surface glow discharge plasma in the presence of a Mach 2.85 flow is studied experimentally for flow control applications. The discharge is generated with pin-like electrodes flush mounted on a ceramic plate with sustaining currents from 25 mA to 300 mA. In the presence of a supersonic flow, two distinct discharge modes - diffuse and constricted - are observed depending on the flow and discharge operating conditions. In cathode upstream location, both diffuse and constricted discharges are observed while in cathode downstream location, the discharge mostly exhibits either constricted mode or bistable mixed mode. The effect of the discharge on the flow ("plasma actuation'') is characterized by the appearance of a weak shock wave in the vicinity of the discharge. The shock is observed at low powers (˜10 W) for the diffuse discharge mode but is absent for the higher power (˜100 W) constricted mode. High speed laser schlieren imaging suggests that the diffuse mode plasma actuation is rapid as it occurs on a time scale that is less than 100 microsec. Rotational (gas) and vibrational temperatures within the discharge are estimated by emission spectral line fits of N 2 and N+2 rovibronic bands near 365-395 nm. The electronic temperatures are estimated by using the Boltzmann plot method for Fe(I) atomic lines. Rotational temperatures are found to be high (˜1500 K) in the absence of a flow but drop sharply (˜500 K) in the presence of a supersonic flow for both the diffuse and constricted discharge modes. The vibrational and electronic temperatures are measured to be about 3000 K and 1.25 eV (14500 K), respectively, and these temperatures are the same with and without flow. The gas (rotational) temperature spatial profiles above the cathode surface are found to be similar for the diffuse and constricted modes indicating that dilatational effects due to gas heating are similar. However, complete absence of flow actuation for the
International Nuclear Information System (INIS)
Todorov, T.D.
1980-01-01
The set of asymptotic numbers A as a system of generalized numbers including the system of real numbers R, as well as infinitely small (infinitesimals) and infinitely large numbers, is introduced. The detailed algebraic properties of A, which are unusual as compared with the known algebraic structures, are studied. It is proved that the set of asymptotic numbers A cannot be isomorphically embedded as a subspace in any group, ring or field, but some particular subsets of asymptotic numbers are shown to be groups, rings, and fields. The algebraic operation, additive and multiplicative forms, and the algebraic properties are constructed in an appropriate way. It is shown that the asymptotic numbers give rise to a new type of generalized functions quite analogous to the distributions of Schwartz allowing, however, the operation multiplication. A possible application of these functions to quantum theory is discussed
Niederreiter, Harald
2015-01-01
This textbook effectively builds a bridge from basic number theory to recent advances in applied number theory. It presents the first unified account of the four major areas of application where number theory plays a fundamental role, namely cryptography, coding theory, quasi-Monte Carlo methods, and pseudorandom number generation, allowing the authors to delineate the manifold links and interrelations between these areas. Number theory, which Carl-Friedrich Gauss famously dubbed the queen of mathematics, has always been considered a very beautiful field of mathematics, producing lovely results and elegant proofs. While only very few real-life applications were known in the past, today number theory can be found in everyday life: in supermarket bar code scanners, in our cars’ GPS systems, in online banking, etc. Starting with a brief introductory course on number theory in Chapter 1, which makes the book more accessible for undergraduates, the authors describe the four main application areas in Chapters...
Mora, José; Ortigosa-Blanch, Arturo; Pastor, Daniel; Capmany, José
2006-08-21
We present a full theoretical and experimental analysis of a novel all-optical microwave photonic filter combining a mode-locked fiber laser and a Mach-Zenhder structure in cascade to a 2x1 electro-optic modulator. The filter is free from the carrier suppression effect and thus it does not require single sideband modulation. Positive and negative coefficients are obtained inherently in the system and the tunability is achieved by controlling the optical path difference of the Mach-Zenhder structure.
Cammarata, Simone
2017-01-01
Silicon Photonics may well provide the opportunity for new levels of integration between detectors and their readout electronics. This technology is thus being evaluated at CERN in order to assess its suitability for use in particle physics experiments. In order to check the agreement with measurements and the validity of previous device simulations, a pure Synopsys SentaurusTM simulation of an un-irradiated Mach-Zehnder silicon modulator has been carried out during the Summer Student project. Index Terms—Silicon Photonics, Mach-Zehnder modulator, electro-optic simulation, Synopsys SentaurusTM, electro-optic measurement, HEP.
DEFF Research Database (Denmark)
Jørgensen, Claus Bjørn; Suetens, Sigrid; Tyran, Jean-Robert
numbers based on recent drawings. While most players pick the same set of numbers week after week without regards of numbers drawn or anything else, we find that those who do change, act on average in the way predicted by the law of small numbers as formalized in recent behavioral theory. In particular......We investigate the “law of small numbers” using a unique panel data set on lotto gambling. Because we can track individual players over time, we can measure how they react to outcomes of recent lotto drawings. We can therefore test whether they behave as if they believe they can predict lotto......, on average they move away from numbers that have recently been drawn, as suggested by the “gambler’s fallacy”, and move toward numbers that are on streak, i.e. have been drawn several weeks in a row, consistent with the “hot hand fallacy”....
Ore, Oystein
2017-01-01
Number theory is the branch of mathematics concerned with the counting numbers, 1, 2, 3, … and their multiples and factors. Of particular importance are odd and even numbers, squares and cubes, and prime numbers. But in spite of their simplicity, you will meet a multitude of topics in this book: magic squares, cryptarithms, finding the day of the week for a given date, constructing regular polygons, pythagorean triples, and many more. In this revised edition, John Watkins and Robin Wilson have updated the text to bring it in line with contemporary developments. They have added new material on Fermat's Last Theorem, the role of computers in number theory, and the use of number theory in cryptography, and have made numerous minor changes in the presentation and layout of the text and the exercises.
Monta, William J.
1992-01-01
A pitot-rake survey of the simulated exhaust of a half-span scramjet nozzle model was conducted in the Langley 20-Inch Mach 6 Tunnel to provide an additional data set for computational fluid dynamics (CFD) code comparisons. A wind-tunnel model was tested with a 26-tube pitot rake that could be manually positioned along the mid-semispan plane of the model. The model configuration had an external expansion surface of 20 degrees and an internal cowl expansion of 12 degrees; tests were also performed with a flow fence. Tests were conducted at a free-stream Reynolds number of approximately 6.5 x 10(exp 6) per foot and a model angle of attack of -0.75 degrees. The two exhaust gas mediums that were tested were air and a Freon 12-argon mixture. Each medium was tested at two jet total pressures at approximately 28 and 14 psia. This document presents the flow-field survey results in graphical as well as tabular form, and several observations concerning the results are discussed. The surveys reveal the major expected flow-field characteristics for each test configuration. For a 50-percent freon 12 and 50-percent argon mixture by volume (Fr-Ar), the exhaust jet pressures were slightly higher than those for air. The addition of a flow fence slightly raised the pitot pressure for the Fr-Ar mixture, but it produced little change for air. For the Fr-Ar exhaust, the plume was larger and the region between the shock wave and plume was smaller.
Godefroy, Gilles
2004-01-01
Numbers are fascinating. The fascination begins in childhood, when we first learn to count. It continues as we learn arithmetic, algebra, geometry, and so on. Eventually, we learn that numbers not only help us to measure the world, but also to understand it and, to some extent, to control it. In The Adventure of Numbers, Gilles Godefroy follows the thread of our expanding understanding of numbers to lead us through the history of mathematics. His goal is to share the joy of discovering and understanding this great adventure of the mind. The development of mathematics has been punctuated by a n
DEFF Research Database (Denmark)
Suetens, Sigrid; Galbo-Jørgensen, Claus B.; Tyran, Jean-Robert Karl
2016-01-01
We investigate the ‘law of small numbers’ using a data set on lotto gambling that allows us to measure players’ reactions to draws. While most players pick the same set of numbers week after week, we find that those who do change react on average as predicted by the law of small numbers...... as formalized in recent behavioral theory. In particular, players tend to bet less on numbers that have been drawn in the preceding week, as suggested by the ‘gambler’s fallacy’, and bet more on a number if it was frequently drawn in the recent past, consistent with the ‘hot-hand fallacy’....
Diamond, Harold G; Cheung, Man Ping
2016-01-01
"Generalized numbers" is a multiplicative structure introduced by A. Beurling to study how independent prime number theory is from the additivity of the natural numbers. The results and techniques of this theory apply to other systems having the character of prime numbers and integers; for example, it is used in the study of the prime number theorem (PNT) for ideals of algebraic number fields. Using both analytic and elementary methods, this book presents many old and new theorems, including several of the authors' results, and many examples of extremal behavior of g-number systems. Also, the authors give detailed accounts of the L^2 PNT theorem of J. P. Kahane and of the example created with H. L. Montgomery, showing that additive structure is needed for proving the Riemann hypothesis. Other interesting topics discussed are propositions "equivalent" to the PNT, the role of multiplicative convolution and Chebyshev's prime number formula for g-numbers, and how Beurling theory provides an interpretation of the ...
Intuitive numbers guide decisions
Directory of Open Access Journals (Sweden)
Ellen Peters
2008-12-01
Full Text Available Measuring reaction times to number comparisons is thought to reveal a processing stage in elementary numerical cognition linked to internal, imprecise representations of number magnitudes. These intuitive representations of the mental number line have been demonstrated across species and human development but have been little explored in decision making. This paper develops and tests hypotheses about the influence of such evolutionarily ancient, intuitive numbers on human decisions. We demonstrate that individuals with more precise mental-number-line representations are higher in numeracy (number skills consistent with previous research with children. Individuals with more precise representations (compared to those with less precise representations also were more likely to choose larger, later amounts over smaller, immediate amounts, particularly with a larger proportional difference between the two monetary outcomes. In addition, they were more likely to choose an option with a larger proportional but smaller absolute difference compared to those with less precise representations. These results are consistent with intuitive number representations underlying: a perceived differences between numbers, b the extent to which proportional differences are weighed in decisions, and, ultimately, c the valuation of decision options. Human decision processes involving numbers important to health and financial matters may be rooted in elementary, biological processes shared with other species.
Hirst, Keith
1994-01-01
Number and geometry are the foundations upon which mathematics has been built over some 3000 years. This book is concerned with the logical foundations of number systems from integers to complex numbers. The author has chosen to develop the ideas by illustrating the techniques used throughout mathematics rather than using a self-contained logical treatise. The idea of proof has been emphasised, as has the illustration of concepts from a graphical, numerical and algebraic point of view. Having laid the foundations of the number system, the author has then turned to the analysis of infinite proc
Templates, Numbers & Watercolors.
Clemesha, David J.
1990-01-01
Describes how a second-grade class used large templates to draw and paint five-digit numbers. The lesson integrated artistic knowledge and vocabulary with their mathematics lesson in place value. Students learned how draftspeople use templates, and they studied number paintings by Charles Demuth and Jasper Johns. (KM)
Evaluación Integral del Riesgo Volcánico del Cerro Machín, Colombia
Leonel Vega Mora; Fernando Javier Diaz
2013-01-01
El volcán Cerro Machín (VCM) se encuentra situado en la Cordillera Central de Colombia. Por la composición química, magnitud y extensión de sus erupciones pasadas se reconoce como un volcán explosivo de gran potencial de daño, cuya actividad futura podría afectar intensamente y durante mucho tiempo (meses hasta años) una región estratégica para la economía del país, que cubre áreas pertenecientes a los departamentos de Tolima, Quindío, Valle del Cauca y Cundinamarca, en las cuales habitan cer...
Qi, Yanwen; Zhang, Siyao; Feng, Shengfei; Wang, Xinke; Sun, Wenfeng; Ye, Jiasheng; Han, Peng; Zhang, Yan
2018-01-01
A sensitive, real-time seven core optical fiber based Mach-Zehnder interferometer (MZI) sensor for liquid refractive index detection is proposed, fabricated and characterized. A trapezoid body with an inverted wedge shape groove in the center is used to design the MZI. The two ends of the trapezoid body play the roles of micro-prisms, and the middle parts of the trapezoid body and the groove play the roles of reference and sensing arms. A series of performance tests were carried out by immersing the sensor in different kinds of solutions to verify the universal applicability of the sensor. The MZI sensor is as small as only 43 μm × 8 μm, and at the same time with sensitivity of 1616 nm/RIU. Nominally, we realized a completely integrated optical sensing system. And, this system actually could be the building block of more powerful integrated chemical sensing chip for health, security and industry application.
International Nuclear Information System (INIS)
Husain, Z.
1991-01-01
During manufacture and assembly of steam and gas turbine blades there are always some technological deviation and is meant local increase or decrease in dimension at certain sections of the profile improper stagger angle of long blades during assembly etc. In this paper the effect of oversize in dimensions at certain important places along a reaction profile has been studied. The technological deviation has been made by sticking thin aluminium foils of 0.3 mm thickness and 15 mm width at inlet and exit tips of reactive profiles and its effect on aerodynamic efficiency at mach. nos ranging from 0.7 to 1.1. The object of performing these tests was to obtain comprehensive data based on which information suitable tolerances could be recommended during manufacture of these blades
Xiao, Jiangnan; Li, Xinying; Xu, Yuming; Zhang, Ziran; Chen, Long; Yu, Jianjun
2015-09-07
We present a simple radio-over-fiber (RoF) link architecture for millimeter-wave orthogonal frequency division multiplexing (OFDM) transmission using only one Mach-Zehnder modulator (MZM) and precoding technique. In the transmission system, the amplitudes and the phase of the driving radio-frequency (RF) OFDM signal on each sub-carrier are precoded, to ensure that the OFDM signal after photodetector (PD) can be restored to original OFDM signal. The experimental results show that the bit-error ratios (BERs) of the transmission system are less than the forward-error-correction (FEC) threshold of 3.8 × 10(-3), which demonstrates that the generation of OFDM vector signal based on our proposed scheme can be employed in our system architecture.
Mao, Mingzhi; Qian, Chen; Cao, Bingyao; Zhang, Qianwu; Song, Yingxiong; Wang, Min
2017-09-01
A digital signal process enabled dual-drive Mach-Zehnder modulator (DD-MZM)-based spectral converter is proposed and extensively investigated to realize dynamically reconfigurable and high transparent spectral conversion. As another important innovation point of the paper, to optimize the converter performance, the optimum operation conditions of the proposed converter are deduced, statistically simulated, and experimentally verified. The optimum conditions supported-converter performances are verified by detail numerical simulations and experiments in intensity-modulation and direct-detection-based network in terms of frequency detuning range-dependent conversion efficiency, strict operation transparency for user signal characteristics, impact of parasitic components on the conversion performance, as well as the converted component waveform are almost nondistortion. It is also found that the converter has the high robustness to the input signal power, optical signal-to-noise ratio variations, extinction ratio, and driving signal frequency.
Hiraki, Tatsurou; Fukuda, Hiroshi; Yamada, Koji; Yamamoto, Tsuyoshi
2015-03-01
We demonstrated a small sensitivity to temperature variations of delay-line Mach-Zehnder interferometer (DL MZI) on a Si photonics platform. The key technique is to balance a thermo-optic effect in the two arms by using waveguide made of different materials. With silicon and silicon nitride waveguides, the fabricated DL MZI with a free-spectrum range of ~40 GHz showed a wavelength shift of -2.8 pm/K with temperature variations, which is 24 times smaller than that of the conventional Si-waveguide DL MZI. We also demonstrated the decoding of the 40-Gbit/s differential phase-shift keying signals to on-off keying signals with various temperatures. The tolerable temperature variation for the acceptable power penalty was significantly improved due to the small wavelength shifts.
Eklund, Dean R.; Northam, G. B.; Mcdaniel, J. C.; Smith, Cliff
1992-01-01
A CFD (Computational Fluid Dynamics) competition was held at the Third Scramjet Combustor Modeling Workshop to assess the current state-of-the-art in CFD codes for the analysis of scramjet combustors. Solutions from six three-dimensional Navier-Stokes codes were compared for the case of staged injection of air behind a step into a Mach 2 flow. This case was investigated experimentally at the University of Virginia and extensive in-stream data was obtained. Code-to-code comparisons have been made with regard to both accuracy and efficiency. The turbulence models employed in the solutions are believed to be a major source of discrepancy between the six solutions.
Canagasabey, Albert; Michie, Andrew; Canning, John; Holdsworth, John; Fleming, Simon; Wang, Hsiao-Chuan; Aslund, Mattias L
2011-01-01
Linewidth measurements of a distributed feedback (DFB) fibre laser are made using delayed self heterodyne interferometry (DHSI) with both Mach-Zehnder and Michelson interferometer configurations. Voigt fitting is used to extract and compare the Lorentzian and Gaussian linewidths and associated sources of noise. The respective measurements are w(L) (MZI) = (1.6 ± 0.2) kHz and w(L) (MI) = (1.4 ± 0.1) kHz. The Michelson with Faraday rotator mirrors gives a slightly narrower linewidth with significantly reduced error. This is explained by the unscrambling of polarisation drift using the Faraday rotator mirrors, confirmed by comparing with non-rotating standard gold coated fibre end mirrors.
Directory of Open Access Journals (Sweden)
Simon Fleming
2011-09-01
Full Text Available Linewidth measurements of a distributed feedback (DFB fibre laser are made using delayed self heterodyne interferometry (DHSI with both Mach-Zehnder and Michelson interferometer configurations. Voigt fitting is used to extract and compare the Lorentzian and Gaussian linewidths and associated sources of noise. The respective measurements are wL (MZI = (1.6 ± 0.2 kHz and wL (MI = (1.4 ± 0.1 kHz. The Michelson with Faraday rotator mirrors gives a slightly narrower linewidth with significantly reduced error. This is explained by the unscrambling of polarisation drift using the Faraday rotator mirrors, confirmed by comparing with non-rotating standard gold coated fibre end mirrors.
El Nasr-Storey, Sarah Seif; Baudot, Charles; Detraz, Stephane; Fedeli, Jean Marc; Marris-Morini, Delphine; Olantera, Lauri; Pezzullo, Giuseppe; Sigaud, Christophe; Soos, Csaba; Troska, Jan; Vasey, Francois; Vivien, Laurent; Zeiler, Marcel; Ziebell, Melissa
2015-01-01
High-speed Mach-Zehnder interferometer silicon modulators were irradiated with neutrons and X-rays in two separate radiation tests. The devices were exposed to a total fluence of 1.2 x 10$^{15}$ neutrons/cm$^2$ and a total ionizing dose of 1.3 MGy; levels comparable to the worst radiation levels for a tracking detector after 10 years of operation at the High- Luminosity LHC. Our measurements indicate that the devices performance does not significantly degrade after exposure to nonionizing radiation and begins to be affected by ionizing radiation after a dose of a few hundred kGy; the phase-shift for an applied reverse bias of 1 V is 10% of its pre-irradiated value after 600 kGy of received ionizing dose.
International Nuclear Information System (INIS)
Coveyou, R.R.
1974-01-01
The subject of random number generation is currently controversial. Differing opinions on this subject seem to stem from implicit or explicit differences in philosophy; in particular, from differing ideas concerning the role of probability in the real world of physical processes, electronic computers, and Monte Carlo calculations. An attempt is made here to reconcile these views. The role of stochastic ideas in mathematical models is discussed. In illustration of these ideas, a mathematical model of the use of random number generators in Monte Carlo calculations is constructed. This model is used to set up criteria for the comparison and evaluation of random number generators. (U.S.)
Weiss, Edwin
1998-01-01
Careful organization and clear, detailed proofs characterize this methodical, self-contained exposition of basic results of classical algebraic number theory from a relatively modem point of view. This volume presents most of the number-theoretic prerequisites for a study of either class field theory (as formulated by Artin and Tate) or the contemporary treatment of analytical questions (as found, for example, in Tate's thesis).Although concerned exclusively with algebraic number fields, this treatment features axiomatic formulations with a considerable range of applications. Modem abstract te
Cohn, Harvey
1980-01-01
""A very stimulating book ... in a class by itself."" - American Mathematical MonthlyAdvanced students, mathematicians and number theorists will welcome this stimulating treatment of advanced number theory, which approaches the complex topic of algebraic number theory from a historical standpoint, taking pains to show the reader how concepts, definitions and theories have evolved during the last two centuries. Moreover, the book abounds with numerical examples and more concrete, specific theorems than are found in most contemporary treatments of the subject.The book is divided into three parts
Crossley, John N
1987-01-01
This book presents detailed studies of the development of three kinds of number. In the first part the development of the natural numbers from Stone-Age times right up to the present day is examined not only from the point of view of pure history but also taking into account archaeological, anthropological and linguistic evidence. The dramatic change caused by the introduction of logical theories of number in the 19th century is also treated and this part ends with a non-technical account of the very latest developments in the area of Gödel's theorem. The second part is concerned with the deve
Professor Stewart's incredible numbers
Stewart, Ian
2015-01-01
Ian Stewart explores the astonishing properties of numbers from 1 to10 to zero and infinity, including one figure that, if you wrote it out, would span the universe. He looks at every kind of number you can think of - real, imaginary, rational, irrational, positive and negative - along with several you might have thought you couldn't think of. He explains the insights of the ancient mathematicians, shows how numbers have evolved through the ages, and reveals the way numerical theory enables everyday life. Under Professor Stewart's guidance you will discover the mathematics of codes,
LeVeque, William J
1996-01-01
This excellent textbook introduces the basics of number theory, incorporating the language of abstract algebra. A knowledge of such algebraic concepts as group, ring, field, and domain is not assumed, however; all terms are defined and examples are given - making the book self-contained in this respect.The author begins with an introductory chapter on number theory and its early history. Subsequent chapters deal with unique factorization and the GCD, quadratic residues, number-theoretic functions and the distribution of primes, sums of squares, quadratic equations and quadratic fields, diopha
Kneusel, Ronald T
2015-01-01
This is a book about numbers and how those numbers are represented in and operated on by computers. It is crucial that developers understand this area because the numerical operations allowed by computers, and the limitations of those operations, especially in the area of floating point math, affect virtually everything people try to do with computers. This book aims to fill this gap by exploring, in sufficient but not overwhelming detail, just what it is that computers do with numbers. Divided into two parts, the first deals with standard representations of integers and floating point numb
Sierpinski, Waclaw
1988-01-01
Since the publication of the first edition of this work, considerable progress has been made in many of the questions examined. This edition has been updated and enlarged, and the bibliography has been revised.The variety of topics covered here includes divisibility, diophantine equations, prime numbers (especially Mersenne and Fermat primes), the basic arithmetic functions, congruences, the quadratic reciprocity law, expansion of real numbers into decimal fractions, decomposition of integers into sums of powers, some other problems of the additive theory of numbers and the theory of Gaussian
Directory of Open Access Journals (Sweden)
R. A. Mollin
1986-01-01
Full Text Available A powerful number is a positive integer n satisfying the property that p2 divides n whenever the prime p divides n; i.e., in the canonical prime decomposition of n, no prime appears with exponent 1. In [1], S.W. Golomb introduced and studied such numbers. In particular, he asked whether (25,27 is the only pair of consecutive odd powerful numbers. This question was settled in [2] by W.A. Sentance who gave necessary and sufficient conditions for the existence of such pairs. The first result of this paper is to provide a generalization of Sentance's result by giving necessary and sufficient conditions for the existence of pairs of powerful numbers spaced evenly apart. This result leads us naturally to consider integers which are representable as a proper difference of two powerful numbers, i.e. n=p1−p2 where p1 and p2 are powerful numbers with g.c.d. (p1,p2=1. Golomb (op.cit. conjectured that 6 is not a proper difference of two powerful numbers, and that there are infinitely many numbers which cannot be represented as a proper difference of two powerful numbers. The antithesis of this conjecture was proved by W.L. McDaniel [3] who verified that every non-zero integer is in fact a proper difference of two powerful numbers in infinitely many ways. McDaniel's proof is essentially an existence proof. The second result of this paper is a simpler proof of McDaniel's result as well as an effective algorithm (in the proof for explicitly determining infinitely many such representations. However, in both our proof and McDaniel's proof one of the powerful numbers is almost always a perfect square (namely one is always a perfect square when n≢2(mod4. We provide in §2 a proof that all even integers are representable in infinitely many ways as a proper nonsquare difference; i.e., proper difference of two powerful numbers neither of which is a perfect square. This, in conjunction with the odd case in [4], shows that every integer is representable in
Corry, Leo
2015-01-01
The world around us is saturated with numbers. They are a fundamental pillar of our modern society, and accepted and used with hardly a second thought. But how did this state of affairs come to be? In this book, Leo Corry tells the story behind the idea of number from the early days of the Pythagoreans, up until the turn of the twentieth century. He presents an overview of how numbers were handled and conceived in classical Greek mathematics, in the mathematics of Islam, in European mathematics of the middle ages and the Renaissance, during the scientific revolution, all the way through to the
Dudley, Underwood
2008-01-01
Ideal for a first course in number theory, this lively, engaging text requires only a familiarity with elementary algebra and the properties of real numbers. Author Underwood Dudley, who has written a series of popular mathematics books, maintains that the best way to learn mathematics is by solving problems. In keeping with this philosophy, the text includes nearly 1,000 exercises and problems-some computational and some classical, many original, and some with complete solutions. The opening chapters offer sound explanations of the basics of elementary number theory and develop the fundamenta
International Nuclear Information System (INIS)
Gajos, Katarzyna; Angelopoulou, Michailia; Petrou, Panagiota; Awsiuk, Kamil; Kakabakos, Sotirios; Haasnoot, Willem; Bernasik, Andrzej; Rysz, Jakub; Marzec, Mateusz M.; Misiakos, Konstantinos; Raptis, Ioannis; Budkowski, Andrzej
2016-01-01
Highlights: • Optimization of probe immobilization with robotic spotter printing overlapping spots. • In-situ inspection of microstructured surfaces of biosensors integrated on silicon. • Imaging and chemical analysis of immobilization, surface blocking and immunoreaction. • Insight with molecular discrimination into step-by-step sensor surface modifications. • Optimized biofunctionalization improves sensor sensitivity and response repeatability. - Abstract: Time-of-flight secondary ion mass spectrometry (imaging, micro-analysis) has been employed to evaluate biofunctionalization of the sensing arm areas of Mach-Zehnder interferometers monolithically integrated on silicon chips for the immunochemical (competitive) detection of bovine κ-casein in goat milk. Biosensor surfaces are examined after: modification with (3-aminopropyl)triethoxysilane, application of multiple overlapping spots of κ-casein solutions, blocking with 100-times diluted goat milk, and reaction with monoclonal mouse anti-κ-casein antibodies in blocking solution. The areas spotted with κ-casein solutions of different concentrations are examined and optimum concentration providing homogeneous coverage is determined. Coverage of biosensor surfaces with biomolecules after each of the sequential steps employed in immunodetection is also evaluated with TOF-SIMS, supplemented by Atomic force microscopy and X-ray photoelectron spectroscopy. Uniform molecular distributions are observed on the sensing arm areas after spotting with optimum κ-casein concentration, blocking and immunoreaction. The corresponding biomolecular compositions are determined with a Principal Component Analysis that distinguished between protein amino acids and milk glycerides, as well as between amino acids characteristic for Mabs and κ-casein, respectively. Use of the optimum conditions (κ-casein concentration) for functionalization of chips with arrays of ten Mach-Zehnder interferometers provided on-chips assays
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.
Energy Technology Data Exchange (ETDEWEB)
Gajos, Katarzyna, E-mail: kasia.fornal@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków (Poland); Angelopoulou, Michailia; Petrou, Panagiota [Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, NCSR Demokritos, P. Grigoriou & Neapoleos St, Aghia Paraksevi 15310, Athens (Greece); Awsiuk, Kamil [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków (Poland); Kakabakos, Sotirios [Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, NCSR Demokritos, P. Grigoriou & Neapoleos St, Aghia Paraksevi 15310, Athens (Greece); Haasnoot, Willem [RIKILT Wageningen UR, Akkermaalsbos 2, 6708 WB Wageningen (Netherlands); Bernasik, Andrzej [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków (Poland); Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków (Poland); Rysz, Jakub [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków (Poland); Marzec, Mateusz M. [Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków (Poland); Misiakos, Konstantinos; Raptis, Ioannis [Department of Microelectronics, Institute of Nanoscience and Nanotechnology, NCSR Demokritos, P. Grigoriou & Neapoleos St, Aghia Paraksevi 15310, Athens (Greece); Budkowski, Andrzej [M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków (Poland)
2016-11-01
Highlights: • Optimization of probe immobilization with robotic spotter printing overlapping spots. • In-situ inspection of microstructured surfaces of biosensors integrated on silicon. • Imaging and chemical analysis of immobilization, surface blocking and immunoreaction. • Insight with molecular discrimination into step-by-step sensor surface modifications. • Optimized biofunctionalization improves sensor sensitivity and response repeatability. - Abstract: Time-of-flight secondary ion mass spectrometry (imaging, micro-analysis) has been employed to evaluate biofunctionalization of the sensing arm areas of Mach-Zehnder interferometers monolithically integrated on silicon chips for the immunochemical (competitive) detection of bovine κ-casein in goat milk. Biosensor surfaces are examined after: modification with (3-aminopropyl)triethoxysilane, application of multiple overlapping spots of κ-casein solutions, blocking with 100-times diluted goat milk, and reaction with monoclonal mouse anti-κ-casein antibodies in blocking solution. The areas spotted with κ-casein solutions of different concentrations are examined and optimum concentration providing homogeneous coverage is determined. Coverage of biosensor surfaces with biomolecules after each of the sequential steps employed in immunodetection is also evaluated with TOF-SIMS, supplemented by Atomic force microscopy and X-ray photoelectron spectroscopy. Uniform molecular distributions are observed on the sensing arm areas after spotting with optimum κ-casein concentration, blocking and immunoreaction. The corresponding biomolecular compositions are determined with a Principal Component Analysis that distinguished between protein amino acids and milk glycerides, as well as between amino acids characteristic for Mabs and κ-casein, respectively. Use of the optimum conditions (κ-casein concentration) for functionalization of chips with arrays of ten Mach-Zehnder interferometers provided on-chips assays
Noise reduction in a Mach 5 wind tunnel with a rectangular rod-wall sound shield
Creel, T. R., Jr.; Keyes, J. W.; Beckwith, I. E.
1980-01-01
A rod wall sound shield was tested over a range of Reynolds numbers of 0.5 x 10 to the 7th power to 8.0 x 10 to the 7th power per meter. The model consisted of a rectangular array of longitudinal rods with boundary-layer suction through gaps between the rods. Suitable measurement techniques were used to determine properties of the flow and acoustic disturbance in the shield and transition in the rod boundary layers. Measurements indicated that for a Reynolds number of 1.5 x 10 to the 9th power the noise in the shielded region was significantly reduced, but only when the flow is mostly laminar on the rods. Actual nozzle input noise measured on the nozzle centerline before reflection at the shield walls was attenuated only slightly even when the rod boundary layer were laminar. At a lower Reynolds number, nozzle input noise at noise levels in the shield were still too high for application to a quiet tunnel. At Reynolds numbers above 2.0 x 10 the the 7th power per meter, measured noise levels were generally higher than nozzle input levels, probably due to transition in the rod boundary layers. The small attenuation of nozzle input noise at intermediate Reynolds numbers for laminar rod layers at the acoustic origins is apparently due to high frequencies of noise.
DEFF Research Database (Denmark)
Jepsen, Kim Stokholm; Mikkelsen, Benny; Vaa, Michael
1998-01-01
Simultaneous all-optical add and drop multiplexing of a 40-Gbit/s OTDM signal using a monolithically integrated semiconductor optical amplifier/Mach Zehnder interferometer (SOA-MZI) is demonstrated. While maintaining a penalty of 1.3 dB for the add operation the sensitivity for the demultiplexed ...... signal is -34.4 dBm...
DEFF Research Database (Denmark)
Bischoff, Svend; Mørk, Jesper
2000-01-01
Summary form only given. All-optical signal regeneration and processing are interesting for high bit-rate transmission systems. The Mach-Zehnder interferometer (MZI) is a promising device for functionalities like all-optical add/drop and signal regeneration. Wavelength conversion up-to 20 Gbit...... and optimization issues....
DEFF Research Database (Denmark)
Fischer, St.; Dülk, M.; Gamper, E.
2000-01-01
We present a novel method for all-optical add-drop multiplexing having regenerative capability for 40-Gb/s optical time-division multiplexed (OTDM) data using a semiconductor optical amplifier (SOA) based, monolithic Mach-Zehnder interferometer (MZI). Simultaneous dropping of one 10-Gb/s channel ...
Czech Academy of Sciences Publication Activity Database
Bartkiewicz, K.; Černoch, A.; Javůrek, D.; Lemr, K.; Soubusta, Jan; Svozilík, J.
2016-01-01
Roč. 93, č. 3 (2016), 1-2, č. článku 036104. ISSN 2469-9926 Institutional support: RVO:68378271 Keywords : one-state vector * quantum state * Mach-Zehnder interferometer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.925, year: 2016
Pavlovic, Radenko; Chen, Jack; Beaulieu, Paul-Andre; Anselmp, David; Gravel, Sylvie; Moran, Mike; Menard, Sylvain; Davignon, Didier
2014-05-01
A wildfire emissions processing system has been developed to incorporate near-real-time emissions from wildfires and large prescribed burns into Environment Canada's real-time GEM-MACH air quality (AQ) forecast system. Since the GEM-MACH forecast domain covers Canada and most of the U.S.A., including Alaska, fire location information is needed for both of these large countries. During AQ model runs, emissions from individual fire sources are injected into elevated model layers based on plume-rise calculations and then transport and chemistry calculations are performed. This "on the fly" approach to the insertion of the fire emissions provides flexibility and efficiency since on-line meteorology is used and computational overhead in emissions pre-processing is reduced. GEM-MACH-FireWork, an experimental wildfire version of GEM-MACH, was run in real-time mode for the summers of 2012 and 2013 in parallel with the normal operational version. 48-hour forecasts were generated every 12 hours (at 00 and 12 UTC). Noticeable improvements in the AQ forecasts for PM2.5 were seen in numerous regions where fire activity was high. Case studies evaluating model performance for specific regions and computed objective scores will be included in this presentation. Using the lessons learned from the last two summers, Environment Canada will continue to work towards the goal of incorporating near-real-time intermittent wildfire emissions into the operational air quality forecast system.
African Journals Online (AJOL)
OLUWOLE
Agro-Science Journal of Tropical Agriculture, Food, Environment and Extension. Volume 9 Number 1 ... of persistent dumping of cheap subsidized food imports from developed ... independence of the inefficiency effects in the two estimation ...
High Reynolds Number Turbulence
National Research Council Canada - National Science Library
Smits, Alexander J
2007-01-01
The objectives of the grant were to provide a systematic study to fill the gap between existing research on low Reynolds number turbulent flows to the kinds of turbulent flows encountered on full-scale vehicles...
International Development Research Centre (IDRC) Digital Library (Canada)
Operating a Demographic Surveillance System (DSS) like this one requires a blend of high-tech number-crunching ability and .... views follow a standardized format that takes several ... general levels of health and to the use of health services.
Quantum random number generator
Pooser, Raphael C.
2016-05-10
A quantum random number generator (QRNG) and a photon generator for a QRNG are provided. The photon generator may be operated in a spontaneous mode below a lasing threshold to emit photons. Photons emitted from the photon generator may have at least one random characteristic, which may be monitored by the QRNG to generate a random number. In one embodiment, the photon generator may include a photon emitter and an amplifier coupled to the photon emitter. The amplifier may enable the photon generator to be used in the QRNG without introducing significant bias in the random number and may enable multiplexing of multiple random numbers. The amplifier may also desensitize the photon generator to fluctuations in power supplied thereto while operating in the spontaneous mode. In one embodiment, the photon emitter and amplifier may be a tapered diode amplifier.
Solar Indices - Sunspot Numbers
National Oceanic and Atmospheric Administration, Department of Commerce — Collection includes a variety of indices related to solar activity contributed by a number of national and private solar observatories located worldwide. This...
Schwartz, Richard Evan
2014-01-01
In the American Mathematical Society's first-ever book for kids (and kids at heart), mathematician and author Richard Evan Schwartz leads math lovers of all ages on an innovative and strikingly illustrated journey through the infinite number system. By means of engaging, imaginative visuals and endearing narration, Schwartz manages the monumental task of presenting the complex concept of Big Numbers in fresh and relatable ways. The book begins with small, easily observable numbers before building up to truly gigantic ones, like a nonillion, a tredecillion, a googol, and even ones too huge for names! Any person, regardless of age, can benefit from reading this book. Readers will find themselves returning to its pages for a very long time, perpetually learning from and growing with the narrative as their knowledge deepens. Really Big Numbers is a wonderful enrichment for any math education program and is enthusiastically recommended to every teacher, parent and grandparent, student, child, or other individual i...
Indian Academy of Sciences (India)
One could endlessly churn out congruent numbers following the method in Box 1 without being certain when a given number n (or n x m 2, for some integer m) will ap- pear on the list. Continuing in this way ·would exhaust one's computing resources, not to mention one's patience! Also, this procedure is of no avail if n is not ...
DEFF Research Database (Denmark)
Korsby, Trine Mygind
2017-01-01
Taking a point of departure in negotiations for access to a phone number for a brothel abroad, the article demonstrates how a group of pimps in Eastern Romania attempt to extend their local business into the rest of the EU. The article shows how the phone number works as a micro-infrastructure in......Taking a point of departure in negotiations for access to a phone number for a brothel abroad, the article demonstrates how a group of pimps in Eastern Romania attempt to extend their local business into the rest of the EU. The article shows how the phone number works as a micro...... in turn cultivate and maximize uncertainty about themselves in others. When making the move to go abroad into unknown terrains, accessing the infrastructure generated by the phone number can provide certainty and consolidate one’s position within criminal networks abroad. However, at the same time......, mishandling the phone number can be dangerous and in that sense produce new doubts and uncertainties....
Energy Technology Data Exchange (ETDEWEB)
Nelson, R.N. (ed.)
1985-05-01
This publication lists all report number codes processed by the Office of Scientific and Technical Information. The report codes are substantially based on the American National Standards Institute, Standard Technical Report Number (STRN)-Format and Creation Z39.23-1983. The Standard Technical Report Number (STRN) provides one of the primary methods of identifying a specific technical report. The STRN consists of two parts: The report code and the sequential number. The report code identifies the issuing organization, a specific program, or a type of document. The sequential number, which is assigned in sequence by each report issuing entity, is not included in this publication. Part I of this compilation is alphabetized by report codes followed by issuing installations. Part II lists the issuing organization followed by the assigned report code(s). In both Parts I and II, the names of issuing organizations appear for the most part in the form used at the time the reports were issued. However, for some of the more prolific installations which have had name changes, all entries have been merged under the current name.
International Nuclear Information System (INIS)
Nelson, R.N.
1985-05-01
This publication lists all report number codes processed by the Office of Scientific and Technical Information. The report codes are substantially based on the American National Standards Institute, Standard Technical Report Number (STRN)-Format and Creation Z39.23-1983. The Standard Technical Report Number (STRN) provides one of the primary methods of identifying a specific technical report. The STRN consists of two parts: The report code and the sequential number. The report code identifies the issuing organization, a specific program, or a type of document. The sequential number, which is assigned in sequence by each report issuing entity, is not included in this publication. Part I of this compilation is alphabetized by report codes followed by issuing installations. Part II lists the issuing organization followed by the assigned report code(s). In both Parts I and II, the names of issuing organizations appear for the most part in the form used at the time the reports were issued. However, for some of the more prolific installations which have had name changes, all entries have been merged under the current name
DEFF Research Database (Denmark)
Levin, Bruce R; McCall, Ingrid C.; Perrot, Veronique
2017-01-01
We postulate that the inhibition of growth and low rates of mortality of bacteria exposed to ribosome-binding antibiotics deemed bacteriostatic can be attributed almost uniquely to these drugs reducing the number of ribosomes contributing to protein synthesis, i.e., the number of effective......-targeting bacteriostatic antibiotics, the time before these bacteria start to grow again when the drugs are removed, referred to as the post-antibiotic effect (PAE), is markedly greater for constructs with fewer rrn operons than for those with more rrn operons. We interpret the results of these other experiments reported...... here as support for the hypothesis that the reduction in the effective number of ribosomes due to binding to these structures provides a sufficient explanation for the action of bacteriostatic antibiotics that target these structures....
Quantum random number generator
Soubusta, Jan; Haderka, Ondrej; Hendrych, Martin
2001-03-01
Since reflection or transmission of a quantum particle on a beamsplitter is inherently random quantum process, a device built on this principle does not suffer from drawbacks of neither pseudo-random computer generators or classical noise sources. Nevertheless, a number of physical conditions necessary for high quality random numbers generation must be satisfied. Luckily, in quantum optics realization they can be well controlled. We present an easy random number generator based on the division of weak light pulses on a beamsplitter. The randomness of the generated bit stream is supported by passing the data through series of 15 statistical test. The device generates at a rate of 109.7 kbit/s.
Alizée Dauvergne
2010-01-01
What makes the LHC the biggest particle accelerator in the world? Here are some of the numbers that characterise the LHC, and their equivalents in terms that are easier for us to imagine. Feature Number Equivalent Circumference ~ 27 km Distance covered by beam in 10 hours ~ 10 billion km a round trip to Neptune Number of times a single proton travels around the ring each second 11 245 Speed of protons first entering the LHC 299 732 500 m/s 99.9998 % of the speed of light Speed of protons when they collide 299 789 760 m/s 99.9999991 % of the speed of light Collision temperature ~ 1016 °C ove...
Samuel, Pierre
2008-01-01
Algebraic number theory introduces students not only to new algebraic notions but also to related concepts: groups, rings, fields, ideals, quotient rings and quotient fields, homomorphisms and isomorphisms, modules, and vector spaces. Author Pierre Samuel notes that students benefit from their studies of algebraic number theory by encountering many concepts fundamental to other branches of mathematics - algebraic geometry, in particular.This book assumes a knowledge of basic algebra but supplements its teachings with brief, clear explanations of integrality, algebraic extensions of fields, Gal
Iwaniec, Henryk
2004-01-01
Analytic Number Theory distinguishes itself by the variety of tools it uses to establish results, many of which belong to the mainstream of arithmetic. One of the main attractions of analytic number theory is the vast diversity of concepts and methods it includes. The main goal of the book is to show the scope of the theory, both in classical and modern directions, and to exhibit its wealth and prospects, its beautiful theorems and powerful techniques. The book is written with graduate students in mind, and the authors tried to balance between clarity, completeness, and generality. The exercis
CONFUSION WITH TELEPHONE NUMBERS
Telecom Service
2002-01-01
he area code is now required for all telephone calls within Switzerland. Unfortunately this is causing some confusion. CERN has received complaints that incoming calls intended for CERN mobile phones are being directed to private subscribers. This is caused by mistakenly dialing the WRONG code (e.g. 022) in front of the mobile number. In order to avoid these problems, please inform your correspondents that the correct numbers are: 079 201 XXXX from Switzerland; 0041 79 201 XXXX from other countries. Telecom Service
CONFUSION WITH TELEPHONE NUMBERS
Telecom Service
2002-01-01
The area code is now required for all telephone calls within Switzerland. Unfortunately this is causing some confusion. CERN has received complaints that incoming calls intended for CERN mobile phones are being directed to private subscribers. This is caused by mistakenly dialing the WRONG code (e.g. 022) in front of the mobile number. In order to avoid these problems, please inform your correspondents that the correct numbers are: 079 201 XXXX from Switzerland; 0041 79 201 XXXX from other countries. Telecom Service
Earthquake number forecasts testing
Kagan, Yan Y.
2017-10-01
We study the distributions of earthquake numbers in two global earthquake catalogues: Global Centroid-Moment Tensor and Preliminary Determinations of Epicenters. The properties of these distributions are especially required to develop the number test for our forecasts of future seismic activity rate, tested by the Collaboratory for Study of Earthquake Predictability (CSEP). A common assumption, as used in the CSEP tests, is that the numbers are described by the Poisson distribution. It is clear, however, that the Poisson assumption for the earthquake number distribution is incorrect, especially for the catalogues with a lower magnitude threshold. In contrast to the one-parameter Poisson distribution so widely used to describe earthquake occurrences, the negative-binomial distribution (NBD) has two parameters. The second parameter can be used to characterize the clustering or overdispersion of a process. We also introduce and study a more complex three-parameter beta negative-binomial distribution. We investigate the dependence of parameters for both Poisson and NBD distributions on the catalogue magnitude threshold and on temporal subdivision of catalogue duration. First, we study whether the Poisson law can be statistically rejected for various catalogue subdivisions. We find that for most cases of interest, the Poisson distribution can be shown to be rejected statistically at a high significance level in favour of the NBD. Thereafter, we investigate whether these distributions fit the observed distributions of seismicity. For this purpose, we study upper statistical moments of earthquake numbers (skewness and kurtosis) and compare them to the theoretical values for both distributions. Empirical values for the skewness and the kurtosis increase for the smaller magnitude threshold and increase with even greater intensity for small temporal subdivision of catalogues. The Poisson distribution for large rate values approaches the Gaussian law, therefore its skewness
Reduced-Order Modeling of Unsteady Aerodynamics Across Multiple Mach Regimes
2013-01-01
elastic deformation, has been the subject of intensive study and has been treated in a number of textbooks , including Refs. 9–11, as well as review...simulations, which can be quite computationally-intensive. Reduced-order models (ROMs) o er a solution to these competing demands of accuracy and e ciency...regimes, from subsonic to hypersonic ight. The correction factor term allows the ROM to be accurate over a range of vehicle elastic modal deformation
Wetherell, Chris
2017-01-01
This is an edited extract from the keynote address given by Dr. Chris Wetherell at the 26th Biennial Conference of the Australian Association of Mathematics Teachers Inc. The author investigates the surprisingly rich structure that exists within a simple arrangement of numbers: the times tables.
Bell, Eric Temple
1991-01-01
From one of the foremost interpreters for lay readers of the history and meaning of mathematics: a stimulating account of the origins of mathematical thought and the development of numerical theory. It probes the work of Pythagoras, Galileo, Berkeley, Einstein, and others, exploring how ""number magic"" has influenced religion, philosophy, science, and mathematics
International Nuclear Information System (INIS)
Khan, T.A.; Baum, J.W.; Beckman, M.C.
1993-10-01
This document contains information dealing with the lessons learned from the experience of nuclear plants. In this issue the authors tried to avoid the 'tyranny' of numbers and concentrated on the main lessons learned. Topics include: filtration devices for air pollution abatement, crack repair and inspection, and remote handling equipment
Uniform random number generators
Farr, W. R.
1971-01-01
Methods are presented for the generation of random numbers with uniform and normal distributions. Subprogram listings of Fortran generators for the Univac 1108, SDS 930, and CDC 3200 digital computers are also included. The generators are of the mixed multiplicative type, and the mathematical method employed is that of Marsaglia and Bray.
International Nuclear Information System (INIS)
1994-01-01
The key numbers of energy give statistical data related to production, consumption, and to foreign trade of each energy in the World and in France. A chapter is dedicated to environment and brings quantitative elements on pollutant emissions connected to energy uses
Directory of Open Access Journals (Sweden)
Oli Brown
2008-10-01
Full Text Available Estimates of the potential number of ‘climate changemigrants’ vary hugely. In order to persuade policymakers ofthe need to act and to provide a sound basis for appropriateresponses, there is an urgent need for better analysis, betterdata and better predictions.
Trudgian, Timothy
2009-01-01
One of the difficulties in any teaching of mathematics is to bridge the divide between the abstract and the intuitive. Throughout school one encounters increasingly abstract notions, which are more and more difficult to relate to everyday experiences. This article examines a familiar approach to thinking about negative numbers, that is an…
Indian Academy of Sciences (India)
First page Back Continue Last page Overview Graphics. Typical Complexity Numbers. Say. 1000 tones,; 100 Users,; Transmission every 10 msec. Full Crosstalk cancellation would require. Full cancellation requires a matrix multiplication of order 100*100 for all the tones. 1000*100*100*100 operations every second for the ...
Indian Academy of Sciences (India)
IAS Admin
improved by Selberg [4] in 1941 who showed that a pos- ... be seen by entries of his first letter to G H Hardy in ... tary in the technical sense of the word, employed com- ..... III: On the expression of a number as a sum of primes, Acta Math.,.
1985-02-01
of the blade. The Darrieus VAWT has more complex aerodynamics. This type of wind turbine produces power as a result of the tangential thrust as...Horizontal Axis Propeller-Type b) Verticle Axis Darrieus -Type Figure 78. Wind Turbine Configurations 0 6 Q K [_ 2 -, C 4 UJ UJ...Sailplanes 23 5.2 Wind Turbines 23 6. CONCLUDING REMARKS 24 7. RECOMMENDATIONS FOR FUTURE RESEARCH 24 REFERENCES 25 FIGURES 32 yv/ LOW REYNOLDS NUMBER
CFD Validation Experiment of a Mach 2.5 Axisymmetric Shock-Wave/Boundary-Layer Interaction
Davis, David O.
2015-01-01
Experimental investigations of specific flow phenomena, e.g., Shock Wave Boundary-Layer Interactions (SWBLI), provide great insight to the flow behavior but often lack the necessary details to be useful as CFD validation experiments. Reasons include: 1.Undefined boundary conditions Inconsistent results 2.Undocumented 3D effects (CL only measurements) 3.Lack of uncertainty analysis While there are a number of good subsonic experimental investigations that are sufficiently documented to be considered test cases for CFD and turbulence model validation, the number of supersonic and hypersonic cases is much less. This was highlighted by Settles and Dodsons [1] comprehensive review of available supersonic and hypersonic experimental studies. In all, several hundred studies were considered for their database.Of these, over a hundred were subjected to rigorous acceptance criteria. Based on their criteria, only 19 (12 supersonic, 7 hypersonic) were considered of sufficient quality to be used for validation purposes. Aeschliman and Oberkampf [2] recognized the need to develop a specific methodology for experimental studies intended specifically for validation purposes.
Design-order, non-conformal low-Mach fluid algorithms using a hybrid CVFEM/DG approach
Domino, Stefan P.
2018-04-01
A hybrid, design-order sliding mesh algorithm, which uses a control volume finite element method (CVFEM), in conjunction with a discontinuous Galerkin (DG) approach at non-conformal interfaces, is outlined in the context of a low-Mach fluid dynamics equation set. This novel hybrid DG approach is also demonstrated to be compatible with a classic edge-based vertex centered (EBVC) scheme. For the CVFEM, element polynomial, P, promotion is used to extend the low-order P = 1 CVFEM method to higher-order, i.e., P = 2. An equal-order low-Mach pressure-stabilized methodology, with emphasis on the non-conformal interface boundary condition, is presented. A fully implicit matrix solver approach that accounts for the full stencil connectivity across the non-conformal interface is employed. A complete suite of formal verification studies using the method of manufactured solutions (MMS) is performed to verify the order of accuracy of the underlying methodology. The chosen suite of analytical verification cases range from a simple steady diffusion system to a traveling viscous vortex across mixed-order non-conformal interfaces. Results from all verification studies demonstrate either second- or third-order spatial accuracy and, for transient solutions, second-order temporal accuracy. Significant accuracy gains in manufactured solution error norms are noted even with modest promotion of the underlying polynomial order. The paper also demonstrates the CVFEM/DG methodology on two production-like simulation cases that include an inner block subjected to solid rotation, i.e., each of the simulations include a sliding mesh, non-conformal interface. The first production case presented is a turbulent flow past a high-rate-of-rotation cube (Re, 4000; RPM, 3600) on like and mixed-order polynomial interfaces. The final simulation case is a full-scale Vestas V27 225 kW wind turbine (tower and nacelle omitted) in which a hybrid topology, low-order mesh is used. Both production simulations
LeVeque, William J
2002-01-01
Classic two-part work now available in a single volume assumes no prior theoretical knowledge on reader's part and develops the subject fully. Volume I is a suitable first course text for advanced undergraduate and beginning graduate students. Volume II requires a much higher level of mathematical maturity, including a working knowledge of the theory of analytic functions. Contents range from chapters on binary quadratic forms to the Thue-Siegel-Roth Theorem and the Prime Number Theorem. Includes numerous problems and hints for their solutions. 1956 edition. Supplementary Reading. List of Symb
DEFF Research Database (Denmark)
Wanscher, Jørgen Bundgaard; Sørensen, Majken Vildrik
2006-01-01
Random numbers are used for a great variety of applications in almost any field of computer and economic sciences today. Examples ranges from stock market forecasting in economics, through stochastic traffic modelling in operations research to photon and ray tracing in graphics. The construction...... distributions into others with most of the required characteristics. In essence, a uniform sequence which is transformed into a new sequence with the required distribution. The subject of this article is to consider the well known highly uniform Halton sequence and modifications to it. The intent is to generate...
Deveikis, W. D.
1983-01-01
External and internal pressure and cold-wall heating-rate distributions were obtained in hypersonic flow on a full-scale heat-sink representation of the space shuttle orbiter wing-elevon-cove configuration in an effort to define effects of flow separation on cove aerothermal environment as a function of cove seal leak area, ramp angle, and free-stream unit Reynolds number. Average free-stream Mach number from all tests was 6.9; average total temperature from all tests was 3360 R; free-stream dynamic pressure ranged from about 2 to 9 psi; and wing angle of attack was 5 deg (flow compression). For transitional and turbulent flow separation, increasing cove leakage progressively increased heating rates in the cove. When ingested mass flow was sufficient to force large reductions in extent of separation, increasing cove leakage reduced heating rates in the cove to those for laminar attached flow. Cove heating-rate distributions calculated with a method that assumed laminar developing channel flow agreed with experimentally obtained distributions within root-mean-square differences that varied between 11 and 36 percent where cove walls were parallel for leak areas of 50 and 100 percent.
Discrete-Roughness-Element-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers
Malik, Mujeeb; Liao, Wei; Li, Fei; Choudhari, Meelan
2015-01-01
Nonlinear parabolized stability equations and secondary-instability analyses are used to provide a computational assessment of the potential use of the discrete-roughness-element technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural-laminar-flow airfoil with a leading-edge sweep angle of 34.6 deg, freestream Mach number of 0.75, and chord Reynolds numbers of 17 × 10(exp 6), 24 × 10(exp 6), and 30 × 10(exp 6) suggest that discrete roughness elements could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small-wavelength stationary crossflow disturbances (i.e., discrete roughness element) also suppresses the growth of most amplified traveling crossflow disturbances.
DRE-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers
Malik, Mujeeb; Liao, Wei; Li, Fe; Choudhari, Meelan
2013-01-01
Nonlinear parabolized stability equations and secondary instability analyses are used to provide a computational assessment of the potential use of the discrete roughness elements (DRE) technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural laminar flow airfoil with a leading-edge sweep angle of 34.6deg, free-stream Mach number of 0.75 and chord Reynolds numbers of 17 x 10(exp 6), 24 x 10(exp 6) and 30 x 10(exp 6) suggest that DRE could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small wavelength stationary crossflow disturbances (i.e., DRE) also suppresses the growth of most amplified traveling crossflow disturbances.
Kristament, Christian; Schwaighofer, Andreas; Montemurro, Milagros; Lendl, Bernhard
2018-02-01
One of the advantages of mid-IR spectroscopy in biomedical research lies in its capability to provide direct information on the secondary structure of proteins in their natural, often aqueous, environment. One impediment of direct absorption measurements in the correspondent spectral region is the strong absorbance of the native solvent (H2O). In this regard, the advent of broadly-tunable external cavity quantum cascade lasers (EC-QCL) allowed to significantly increasing the optical path length employed in transmission measurements due to their high spectral power densities. Low measured S/N ratios were improved by elaborated data analysis protocols that corrected mechanical flaws in the tuning mechanism of ECQCLs and allow for S/N ratios comparable to research grade FTIR spectrometers. Recent development of new optical set-ups outpacing direct absorption measurements led to further advancements. We present a dedicated Mach-Zehnder interferometer for photothermal measurements in balanced detection mode. In this highly sensitive design, the interferometer is illuminated by a HeNe laser to detect the refractive index change induced by the heat insertion of the EC-QCL. Here, we present photothermal phase shift interferometry measurements of caffeine in ethanol as well as casein in water. Further, the dependency of the signal amplitude on varying modulation frequencies was investigated for different liquids.
International Nuclear Information System (INIS)
Dai Hui; Hajima, Ryoichi
2008-11-01
For future advanced energy recovery linac to generate femtosecond X-ray pulses, precise synchronization between sub-systems is highly desired. Typical synchronization methods based on direct photo detection are limited by detector nonlinearities, which lead to amplitude-to-phase conversion and introduce excess timing jitter. In this paper, we experimentally demonstrate an optical-electronic mixed phase lock loop to synchronize the RF signal and laser pulses. In this synchronism setup, a Sagnac-loop Mach-Zehnder interferometer has been used to suppress the excess noise of direct photo detection. This scheme transfers the timing information into a intensity imbalance between the two output beams of the interferometer. As experimental demonstration, the single side-band phase noise of RF signal from the VCO is locked to the mode-locked Ti:Sapphire laser in the spectrum covering the range of 10 kHz to 1 MHz. This synchronization scheme greatly reduces the phase noise and timing jitter of the RF signal. (author)
Bastos, Ana R; Vicente, Carlos M S; Oliveira-Silva, Rui; Silva, Nuno J O; Tacão, Marta; Costa, João P da; Lima, Mário; André, Paulo S; Ferreira, Rute A S
2018-03-12
The development of portable low-cost integrated optics-based biosensors for photonics-on-a-chip devices for real-time diagnosis are of great interest, offering significant advantages over current analytical methods. We report the fabrication and characterization of an optical sensor based on a Mach-Zehnder interferometer to monitor the growing concentration of bacteria in a liquid medium. The device pattern was imprinted on transparent self-patternable organic-inorganic di-ureasil hybrid films by direct UV-laser, reducing the complexity and cost production compared with lithographic techniques or three-dimensional (3D) patterning using femtosecond lasers. The sensor performance was evaluated using, as an illustrative example, E. coli cell growth in an aqueous medium. The measured sensitivity (2 × 10 -4 RIU) and limit of detection (LOD = 2 × 10 -4 ) are among the best values known for low-refractive index contrast sensors. Furthermore, the di-ureasil hybrid used to produce this biosensor has additional advantages, such as mechanical flexibility, thermal stability, and low insertion losses due to fiber-device refractive index mismatch (~1.49). Therefore, the proposed sensor constitutes a direct, compact, fast, and cost-effective solution for monitoring the concentration of lived-cells.
Hunter, W. W., Jr.; Ocheltree, S. L.; Russ, C. E., Jr.
1991-01-01
Laser transit anemometer (LTA) measurements of a 7 degree sharp cone boundary layer were conducted in the Air Force/AEDC Supersonic Tunnel A Mach 4 flow field. These measurements are compared with Pitot probe measurements and tricone theory provided by AEDC staff. Measurements were made both in laminar and turbulent boundary layers of the model. Comparison of LTA measurements with theory showed agreement to better than 1 percent for the laminar boundary layer cases. This level of agreement was obtained after small position corrections, 0.01 to 0.6 mm, were applied to the experimental data sets. Pitot probe data when compared with theory also showed small positioning errors. The Pitot data value was also limited due to probe interference with the flow near the model. The LTA turbulent boundary layer data indicated a power law dependence of 6.3 to 6.9. The LTA data was analyzed in the time (Tau) domain in which it was obtained and in the velocity domain. No significant differences were noted between Tau and velocity domain results except in one turbulent boundary layer case.
Jasim, A. A.; Ahmad, H.
2017-12-01
The generation and switching of dual-wavelength laser based on compact coupled microfiber Mach-Zehnder interferometer (CM-MZI) is reported. The CM-MZI is constructed by overlapping two portions of a single tapered optical fiber which has a diameter of 9 μm as to create multi-mode interference and also to produce spatial mode beating as to suppress mode competition in the homogeneous gain medium. The system is able to generate a dual-wavelength laser output that can be switched with the aid of the polarization rotation technique. Four dual-wavelength oscillation pairs are obtained from the interference fringe peaks of the CM-MZI comb filter with a switched channel spacing of 1.5 nm, 3.0 nm, and 6.0 nm. The wavelength spacing is stable at different pump powers. The lasing wavelength has a 3-dB linewidth of about 30 pm and peak-to-floor ration of about 55 dB at a pump power of 38 mW.
Energy Technology Data Exchange (ETDEWEB)
Gao, Shecheng [Key Laboratory of Optical Information Science and Technology, Ministry of Education, Institute of Modern Optics, Nankai University, Tianjin 300071 (China); Institute of Micro and Nano Optics, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Zhang, Weigang, E-mail: zhangwg@nankai.edu.cn, E-mail: haozhang@nankai.edu.cn; Zhang, Hao, E-mail: zhangwg@nankai.edu.cn, E-mail: haozhang@nankai.edu.cn [Key Laboratory of Optical Information Science and Technology, Ministry of Education, Institute of Modern Optics, Nankai University, Tianjin 300071 (China); Zhang, Chonglei [Institute of Micro and Nano Optics, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China)
2015-02-23
A reconfigurable Mach-Zenhnder interferometer (MZI) based on a microfluidic cavity (MFC) constructed by embedding a microfiber between two segments of single-mode fibers with pre-designed lateral offset has been proposed and experimentally demonstrated. The MFC serves as an interference arm with an eccentric annular cross section and allows convenient sample (gas or liquids) replacement procedure. The microfiber works as the other interference arm that provides the proposed device with ease of reconstruction and also enhances the force sensitivity. The re-configurability and the ultra-wide tuning sensitivity range are demonstrated by immersing the MZI constructed with a 484 μm-long-MFC and a microfiber 44 μm in diameter in different droplets. Ultrahigh sensitivities of 34.65 nm/°C (∼88 380 nm/RIU) and −493.7 nm/N (∼−590 pm/με) are experimentally achieved using a droplet with a refractive index of ∼1.44.
Chen, Feifei; Jiang, Yi; Zhang, Liuchao; Jiang, Lan; Wang, Sumei
2018-04-01
A compact microhole-induced fiber optic inline Mach-Zehnder interferometer (MZI) is demonstrated for measurements of refractive index (RI) and magnetic field. Inline MZIs with different etched diameters, different interaction lengths and different sizes of microholes are fabricated and assessed. The optical transmission spectra of the inline MZIs immersed into a series of liquids are characterized and analysed. Experimental results show that liquid RI sensitivity as high as 539.8436 nm RIU-1 in the RI range of 1.3352-1.4113 RIU is achieved and also exhibits good linearity with a correlation coefficient >93%. An inline MZI is also fabricated to be a magnetic field sensor by using magnetic fluid material. The experimental results show that this magnetic field sensor has a high sensitivity of -275.6 pm Oe-1. The inline MZI-based fiber optic sensors possess many advantages, such as small size, simple fabrication, high sensitivity and good linearity, which has a wide application potential in chemical, biological and environmental sensing fields.
International Nuclear Information System (INIS)
Gao, Shecheng; Zhang, Weigang; Zhang, Hao; Zhang, Chonglei
2015-01-01
A reconfigurable Mach-Zenhnder interferometer (MZI) based on a microfluidic cavity (MFC) constructed by embedding a microfiber between two segments of single-mode fibers with pre-designed lateral offset has been proposed and experimentally demonstrated. The MFC serves as an interference arm with an eccentric annular cross section and allows convenient sample (gas or liquids) replacement procedure. The microfiber works as the other interference arm that provides the proposed device with ease of reconstruction and also enhances the force sensitivity. The re-configurability and the ultra-wide tuning sensitivity range are demonstrated by immersing the MZI constructed with a 484 μm-long-MFC and a microfiber 44 μm in diameter in different droplets. Ultrahigh sensitivities of 34.65 nm/°C (∼88 380 nm/RIU) and −493.7 nm/N (∼−590 pm/με) are experimentally achieved using a droplet with a refractive index of ∼1.44
Ahmad, H.; Jasim, A. A.
2017-07-01
A compact coupled microfiber Mach-Zehnder interferometer (CM-MZI) is proposed and experimentally demonstrated for C-band region multi-wavelength tuning and switching in a fiber laser. The CM-MZI is fabricated using a 9 μm single tapered silica optical microfiber fabricated by flame-drawing technique and exploits multi-mode interference to produce spatial mode beating and suppress mode competition of the homogeneous gain medium. The output wavelength spacing is immune to changes in the external environment, but can be changed from 1.5 nm to 1.4 nm by slightly modifying the path-length difference of the CM-MZI. The proposed laser is capable of generating single, dual, triple, quintuple, and sextuple stabilize wavelengths outputs over a range of more than 32 nm using polarization rotation (PR) and macro-bending. The lasers having a 3 dB line-width of less than ∼30 pm and peak-to-floor of about 55 dB at a pump power of 38 mW.
A perfect spin filtering device through Mach-Zehnder interferometry in a GaAs/AlGaAs electron gas
Energy Technology Data Exchange (ETDEWEB)
Lopez, Alexander; Medina, Ernesto [Centro de Fisica, Instituto Venezolano de Investigaciones CientIficas, Apartado 21874, Caracas 1020-A (Venezuela, Bolivarian Republic of); BolIvar, Nelson [Departamento de Fisica, Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of); Berche, Bertrand [Statistical Physics Group, P2M, Institut Jean Lamour, Nancy Universite, BP70239, F-54506 Vandoeuvre les Nancy (France)
2010-03-24
A spin filtering device based on quantum spin interference is addressed, for use with a two-dimensional GaAs/AlGaAs electron gas that has both Rashba and Dresselhaus spin-orbit (SO) couplings and an applied external magnetic field. We propose an experimentally feasible electronic Mach-Zehnder interferometer and derive a map, in parameter space, that determines perfect spin filtering conditions. We find two broad spin filtering regimes: one where filtering is achieved in the original incoming quantization basis, that takes advantage of the purely non-Abelian nature of the spin rotations; and another where one needs a tilted preferential axis in order to observe the polarized output spinor. Both solutions apply for arbitrary incoming electron polarization and energy, and are only limited in output amplitude by the randomness of the incoming spinor state. Including a full account of the beam splitter and mirror effects on spin yields solutions only for the tilted basis, but encompasses a broad range of filtering conditions.
A perfect spin filtering device through Mach-Zehnder interferometry in a GaAs/AlGaAs electron gas
International Nuclear Information System (INIS)
Lopez, Alexander; Medina, Ernesto; BolIvar, Nelson; Berche, Bertrand
2010-01-01
A spin filtering device based on quantum spin interference is addressed, for use with a two-dimensional GaAs/AlGaAs electron gas that has both Rashba and Dresselhaus spin-orbit (SO) couplings and an applied external magnetic field. We propose an experimentally feasible electronic Mach-Zehnder interferometer and derive a map, in parameter space, that determines perfect spin filtering conditions. We find two broad spin filtering regimes: one where filtering is achieved in the original incoming quantization basis, that takes advantage of the purely non-Abelian nature of the spin rotations; and another where one needs a tilted preferential axis in order to observe the polarized output spinor. Both solutions apply for arbitrary incoming electron polarization and energy, and are only limited in output amplitude by the randomness of the incoming spinor state. Including a full account of the beam splitter and mirror effects on spin yields solutions only for the tilted basis, but encompasses a broad range of filtering conditions.
A perfect spin filtering device through Mach-Zehnder interferometry in a GaAs/AlGaAs electron gas
López, Alexander; Medina, Ernesto; Bolívar, Nelson; Berche, Bertrand
2010-03-01
A spin filtering device based on quantum spin interference is addressed, for use with a two-dimensional GaAs/AlGaAs electron gas that has both Rashba and Dresselhaus spin-orbit (SO) couplings and an applied external magnetic field. We propose an experimentally feasible electronic Mach-Zehnder interferometer and derive a map, in parameter space, that determines perfect spin filtering conditions. We find two broad spin filtering regimes: one where filtering is achieved in the original incoming quantization basis, that takes advantage of the purely non-Abelian nature of the spin rotations; and another where one needs a tilted preferential axis in order to observe the polarized output spinor. Both solutions apply for arbitrary incoming electron polarization and energy, and are only limited in output amplitude by the randomness of the incoming spinor state. Including a full account of the beam splitter and mirror effects on spin yields solutions only for the tilted basis, but encompasses a broad range of filtering conditions.