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Letteratura scientifica selezionata sul tema "Bow shock wave"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 7 settembre 2023

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Articoli di riviste sul tema "Bow shock wave"

1

Vuorinen, Laura, Rami Vainio, Heli Hietala e Terry Z. Liu. "Monte Carlo Simulations of Electron Acceleration at Bow Waves Driven by Fast Jets in the Earth’s Magnetosheath". Astrophysical Journal 934, n. 2 (1 agosto 2022): 165. http://dx.doi.org/10.3847/1538-4357/ac7f42.

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Abstract The shocked solar wind flows around the Earth’s magnetosphere in the magnetosheath downstream of the Earth’s bow shock. Within this region, faster flows of plasma, called magnetosheath jets, are frequently observed. These jets have been shown to sometimes exhibit supermagnetosonic speeds relative to the magnetosheath flow and to develop bow waves or shocks of their own. Such jet-driven bow waves have been observed to accelerate ions and electrons. We model electron acceleration by magnetosheath jet-driven bow waves using test-particle Monte Carlo simulations. Our simulations suggest that the energy increase of electrons with energies of a few hundred eV to 10 keV can be explained by a collapsing magnetic trap forming between the bow wave and the magnetopause with shock drift acceleration at the moving bow wave. Our simulations allow us to estimate the efficiency of acceleration as a function of different jet and magnetosheath parameters. Electron acceleration by jet-driven bow waves can increase the total acceleration in the parent shock environment, most likely also at shocks other than the Earth’s bow shock.

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2

Czaykowska, A., T. M. Bauer, R. A. Treumann e W. Baumjohann. "Magnetic field fluctuations across the Earth’s bow shock". Annales Geophysicae 19, n. 3 (31 marzo 2001): 275–87. http://dx.doi.org/10.5194/angeo-19-275-2001.

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Abstract. We present a statistical analysis of 132 dayside (LT 0700-1700) bow shock crossings of the AMPTE/IRM spacecraft. We perform a superposed epoch analysis of low frequency, magnetic power spectra some minutes up-stream and downstream of the bow shock. The events are devided into categories depending on the angle θBn between bow shock normal and interplanetary magnetic field, and on plasma-β. In the foreshock upstream of the quasi-parallel bow shock, the power of the magnetic fluctuations is roughly 1 order of magnitude larger (δB ~ 4 nT for frequencies 0.01–0.04 Hz) than upstream of the quasi-perpendicular shock. There is no significant difference in the magnetic power spectra upstream and downstream of the quasi-parallel bow shock; only at the shock itself, is the magnetic power enhanced by a factor of 4. This enhancement may be due to either an amplification of convecting upstream waves or to wave generation at the shock interface. On the contrary, downstream of the quasi-perpendicular shock, the magnetic wave activity is considerably higher than upstream. Down-stream of the quasi-perpendicular low-β bow shock, we find a dominance of the left-hand polarized component at frequencies just below the ion-cyclotron frequency, with amplitudes of about 3 nT. These waves are identified as ion-cyclotron waves, which grow in a low-β regime due to the proton temperature anisotropy. We find a strong correlation of this anisotropy with the intensity of the left-hand polarized component. Downstream of some nearly perpendicular (θBn ≈ 90°) high-β crossings, mirror waves are identified. However, there are also cases where the conditions for mirror modes are met downstream of the nearly perpendicular shock, but no mirror waves are observed.Key words. Interplanetary physics (plasma waves and turbulence) – Magnetospheric physics (magnetosheath; plasma waves and instabilities)

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3

ZHONG, XIAOLIN. "Leading-edge receptivity to free-stream disturbance waves for hypersonic flow over a parabola". Journal of Fluid Mechanics 441 (15 agosto 2001): 315–67. http://dx.doi.org/10.1017/s0022112001004918.

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The receptivity of hypersonic boundary layers to free-stream disturbances, which is the process of environmental disturbances initially entering the boundary layers and generating disturbance waves, is altered considerably by the presence of bow shocks in hypersonic flow fields. This paper presents a numerical simulation study of the generation of boundary layer disturbance waves due to free-stream waves, for a two-dimensional Mach 15 viscous flow over a parabola. Both steady and unsteady flow solutions of the receptivity problem are obtained by computing the full Navier–Stokes equations using a high-order-accurate shock-fitting finite difference scheme. The effects of bow-shock/free-stream-sound interactions on the receptivity process are accurately taken into account by treating the shock as a discontinuity surface, governed by the Rankine-Hugoniot relations. The results show that the disturbance waves generated and developed in the hypersonic boundary layer contain both first-, second-, and third-mode waves. A parametric study is carried out on the receptivity characteristics for different free-stream waves, frequencies, nose bluntness characterized by Strouhal numbers, Reynolds numbers, Mach numbers, and wall cooling. In this paper, the hypersonic boundary-layer receptivity is characterized by a receptivity parameter defined as the ratio of the maximum induced wave amplitude in the first-mode-dominated region to the amplitude of the free-stream forcing wave. It is found that the receptivity parameter decreases when the forcing frequency or nose bluntness increase. The results also show that the generation of boundary layer waves is mainly due to the interaction of the boundary layer with the acoustic wave field behind the bow shock, rather than interactions with the entropy and vorticity wave fields.

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4

Знаменская, И. А., Д. С. Наумов, Н. Н. Сысоев e В. А. Черников. "Исследование динамических процессов, реализующихся при генерации плазмоидных образований в сверхзвуковом потоке". Журнал технической физики 89, n. 6 (2019): 856. http://dx.doi.org/10.21883/jtf.2019.06.47631.349-18.

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An analysis of plasma dynamic processes and shock waves interactions in supersonic jet at plasma spherical formation initiation was made using the high-speed digital image recording. The dynamics of the spherical plasmoid which creates discontinuities, affecting the bow shock wave in front of the model was investigated with a high temporal resolution. It was shown that during the time of plasmoid electric current (about 100-130 microseconds) the structure of supersonic flow around the model changes: the shock layer is transformed, bow shock wave detached distance on the symmetry axis is significantly increased due to a change of oncoming flow parameters and structure.

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5

JIANG, QINGFANG, e RONALD B. SMITH. "V-waves, bow shocks, and wakes in supercritical hydrostatic flow". Journal of Fluid Mechanics 406 (10 marzo 2000): 27–53. http://dx.doi.org/10.1017/s0022112099007636.

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The structure of the bow shock, V-wave, and the related wave drag and wake in supercritical ambient flow are investigated for homogeneous hydrostatic single-layer flow with a free surface over an isolated two-dimensional (i.e. h(x, y)) obstacle. The two control parameters for this physical system are the ratio of obstacle height to fluid depth and the Froude number F = U/√gH. Based on theoretical analysis and numerical modelling, a steady-state regime diagram is constructed for supercritical flow. This study suggests that supercritical flow may have an upstream bow shock with a transition from the supercritical state to the subcritical state near the centreline, and a V-shock in the lee without a state transition. Unlike subcritical flow, neither a flank shock nor a normal lee shock is observed, due to the local supercritical environment. Both the bow shock and V-shock are dissipative and reduce the Bernoulli constant, but the vorticity generation is very weak in comparison with subcritical ambient flow. Thus, in supercritical flow, wakes are weak and eddy shedding is absent.Formulae for V-wave shape and V-wave drag are given using linear theory. Both formulae compare well with numerical model runs for small obstacles.These results can be applied to air flow over mountains, river hydraulics and coastal ocean currents with bottom topographies.

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6

Kosinov, Aleksandr, Maxim Golubev e Alexey Pavlov. "On Determination Of The Mechanism Of Mach Wave / Bow-Shock Interaction". Siberian Journal of Physics 12, n. 2 (1 giugno 2017): 20–27. http://dx.doi.org/10.54362/1818-7919-2017-12-2-20-27.

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The work presents the results of investigation of interaction of outer couple weak shock waves with a bow shock produced by a triangle plate at Mach number M = 2. The couple of waves were generated by a two-dimensional roughness on the wall of the test section of supersonic tunnel. Hotwire measurements showed generated to free flow perturbations to correspond to N-wave. Optical visualization was done applying schlieren technique and interferometric method using adaptive visualizing transparencies based on absorption saturation. Qualitative coincidence of hotwire and interference data was obtained. Inclination angle of weak waves passed through the bow shock was observed to change.

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7

Du, J., C. Wang, T. L. Zhang, M. Volwerk e C. Carr. "Mirror waves and mode transition observed in the magnetosheath by Double Star TC-1". Annales Geophysicae 27, n. 1 (22 gennaio 2009): 351–55. http://dx.doi.org/10.5194/angeo-27-351-2009.

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Abstract. The Double Star TC-1 magnetosheath pass on 26 February 2004 is used to investigate magnetic field fluctuations. Strong compressional signatures which last for more than an hour have been found near the magnetopause behind a quasi-perpendicular bow shock. These compressional structures are most likely mirror mode waves. There is a clear wave transition in the magnetosheath which probably results from the change of the interplanetary magnetic field (IMF) cone angle. The wave characteristics in the magnetosheath are strongly controlled by the type of the upstream bow shock.

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8

Mazelle, C., D. Le Quéau e K. Meziane. "Nonlinear wave-particle interaction upstream from the Earth's bow shock". Nonlinear Processes in Geophysics 7, n. 3/4 (31 dicembre 2000): 185–90. http://dx.doi.org/10.5194/npg-7-185-2000.

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Abstract. Well-defined ring-like backstreaming ion distributions have been recently reported from observations made by the 3DP/PESA-High analyzer onboard the WIND spacecraft in the Earth's foreshock at large distances from the bow shock, which suggests a local production mechanism. The maximum phase space density for these distributions remains localized at a nearly constant pitch-angle value for a large number of gyroperiods while the shape of the distribution remains very steady. These distributions are also observed in association with quasi-monochromatic low frequency (~ 50 mHz) waves with substantial amplitude (δB/B>0.2). The analysis of the magnetic field data has shown that the waves are propagating parallel to the background field in the right-hand mode. Parallel ion beams are also often observed in the same region before the observation of both the ring-like distributions and the waves. The waves appear in cyclotron resonance with the ion parallel beams. We investigate first the possibility that the ion beams could provide the free energy source for driving an ion/ion instability responsible for the ULF wave occurrence. For that, we solve the wave dispersion relation with the observed parameters. Second, we show that the ring-like distributions could then be produced by a coherent nonlinear wave-particle interaction. It tends to trap the ions into narrow cells in velocity space centered on a well-defined pitch-angle, directly related to the saturation wave amplitude in the analytical theory. The theoretical predictions are in good quantitative agreement with the observations

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9

Dimmock, A. P., M. A. Balikhin, S. N. Walker e S. A. Pope. "Dispersion of low frequency plasma waves upstream of the quasi-perpendicular terrestrial bow shock". Annales Geophysicae 31, n. 8 (9 agosto 2013): 1387–95. http://dx.doi.org/10.5194/angeo-31-1387-2013.

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Abstract. Low frequency waves in the foot of a supercritical quasi-perpendicular shock front have been observed since the very early in situ observations of the terrestrial bow shock (Guha et al., 1972). The great attention that has been devoted to these type of waves since the first observations is explained by the key role attributed to them in the processes of energy redistribution in the shock front by various theoretical models. In some models, these waves play the role of the intermediator between the ions and electrons. It is assumed that they are generated by plasma instability that exist due to the counter-streaming flows of incident and reflected ions. In the second type of models, these waves result from the evolution of the shock front itself in the quasi-periodic process of steepening and overturning of the magnetic ramp. However, the range of the observed frequencies in the spacecraft frame are not enough to distinguish the origin of the observed waves. It also requires the determination of the wave vectors and the plasma frame frequencies. Multipoint measurements within the wave coherence length are needed for an ambiguous determination of the wave vectors. In the main multi-point missions such as ISEE, AMPTE, Cluster and THEMIS, the spacecraft separation is too large for such a wave vector determination and therefore only very few case studies are published (mainly for AMPTE UKS AMPTE IRM pair). Here we present the observations of upstream low frequency waves by the Cluster spacecraft which took place on 19 February 2002. The spacecraft separation during the crossing of the bow shock was small enough to determine the wave vectors and allowed the identification of the plasma wave dispersion relation for the observed waves. Presented results are compared with whistler wave dispersion and it is shown that contrary to previous studies based on the AMPTE data, the phase velocity in the shock frame is directed downstream. The consequences of this finding for both types of models that were developed to explain the generation of these waves are discussed.

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10

Clausen, L. B. N., T. K. Yeoman, R. C. Fear, R. Behlke, E. A. Lucek e M. J. Engebretson. "First simultaneous measurements of waves generated at the bow shock in the solar wind, the magnetosphere and on the ground". Annales Geophysicae 27, n. 1 (22 gennaio 2009): 357–71. http://dx.doi.org/10.5194/angeo-27-357-2009.

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Abstract. On 5 September 2002 the Geotail satellite observed the cone angle of the Interplanetary Magnetic Field (IMF) change to values below 30° during a 56 min interval between 18:14 and 19:10 UT. This triggered the generation of upstream waves at the bow shock, 13 RE downstream of the position of Geotail. Upstream generated waves were subsequently observed by Geotail between 18:30 and 18:48 UT, during times the IMF cone angle dropped below values of 10°. At 18:24 UT all four Cluster satellites simultaneously observed a sudden increase in wave power in all three magnetic field components, independent of their position in the dayside magnetosphere. We show that the 10 min delay between the change in IMF direction as observed by Geotail and the increase in wave power observed by Cluster is consistent with the propagation of the IMF change from the Geotail position to the bow shock and the propagation of the generated waves through the bow shock, magnetosheath and magnetosphere towards the position of the Cluster satellites. We go on to show that the wave power recorded by the Cluster satellites in the component containing the poloidal and compressional pulsations was broadband and unstructured; the power in the component containing toroidal oscillations was structured and shows the existence of multi-harmonic Alfvénic continuum waves on field lines. Model predictions of these frequencies fit well with the observations. An increase in wave power associated with the change in IMF direction was also registered by ground based magnetometers which were magnetically conjunct with the Cluster satellites during the event. To the best of our knowledge we present the first simultaneous observations of waves created by backstreaming ions at the bow shock in the solar wind, the dayside magnetosphere and on the ground.

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Più fonti

Tesi sul tema "Bow shock wave"

1

Behlke, Rico. "Dissipation at the Earth's Quasi-Parallel Bow Shock". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6123.

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2

Zakrzewski, Sam Mechanical &amp Manufacturing Engineering Faculty of Engineering UNSW. "A Numerical and Experimental Investigation of High-Speed Liquid Jets - Their Characteristics and Dynamics". Awarded by:University of New South Wales. Mechanical and Manufacturing Engineering, 2002. http://handle.unsw.edu.au/1959.4/18653.

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A comprehensive understanding of high-speed liquid jets is required for their introduction into engine and combustion applications. Their transient nature, short lifetime, unique characteristics and the inability to take many experimental readings, has inhibited this need. This study investigates the outflow of a high-speed liquid jet into quiescent atmospheric air. The key characteristics present are, a bow shock wave preceding the jet head, an enhanced mixing layer and the transient deformation of the liquid jet core. The outflow regime is studied in an experimental and numerical manner. In the experimental investigation, a high-speed liquid water jet is generated using the momentum exchange by impact method. The jet velocity is supersonic with respect to the impinged gaseous medium. The resulting jet speed is Mach 1.8. The jet is visualised with the use of shadowgraph apparatus. Visualisation takes place over a variety of time steps in the liquid jet???s life span and illustrates the four major development stages. The stages progress from initial rapid core jet expansion to jet stabilisation and characteristic uniform gradient formation. The visualisation shows that at all stages of the jet???s life it is axi-symmetric. One dimensional nozzle analysis and a clean bow shock wave indicate that the pulsing jet phenomenon can be ignored. In the numerical investigation, a time marching finite volume scheme is employed. The bow shock wave characteristics are studied with the use of a blunt body analogy. The jet at a specific time frame is considered a solid body. The jet shape is found to have an important influence on the shock position and shape. Analysis of the results indicates a shock stand-off similar to that seen in experimental observations and the prediction of shock data. The jet life span is modelled using a species dependent density model. The transient calculations reproduce the key jet shape characteristics shown in experimental visualisation. The mushrooming effect and large mixing layer are shown to develop. These effects are strongest when the shock wave transience has yet to stabilise. Quantitative analysis of the mixing layer at varying time steps is presented.

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3

Blanco-Cano, Xochitl Guillermina. "Waves and particles upstream of the earth's bow shock". Thesis, Queen Mary, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362331.

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4

Narita, Yasuhito. "Low frequency waves upstream and downstream of the terrestrial bow shock". Katlenburg-Lindau Copernicus GmbH, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?idn=979493870.

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5

Shin, Koichi. "Study on electrostatic waves in the terrestrial bow shock region via spacecraft observations". 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136234.

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6

Narita, Yasuhito [Verfasser]. "Low frequency waves upstream and downstream of the terrestrial bow shock / von Yasuhito Narita". Katlenburg-Lindau : Copernicus GmbH, 2006. http://d-nb.info/979493870/34.

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7

g, Ufot Ekong Ufot. "Analysis of low frequency plasma waves in turbulent magnetosheath : downstream of the Earth's bow shock". Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6324/.

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The knowledge of the dynamics and characteristics of space plasma during solar-terrestrial coupling has been greatly enriched by process that aids the determination of the instantaneous frequencies which support the non-stationary and non-linear nature of signals. Such plasmas are observed in the magnetosheath in the downstream of bow shock. In this thesis a technique was applied which extracts the various contributing oscillatory modes reflecting the waveforms observed in the space by Cluster spacecraft instruments such as FGM, CIS and EFW, and decompose the frequency of each extracted mode using Instantaneous Frequency method that is based on Simple Hilbert Transform (SHT). This is achieved through the use of Empirical Mode Decomposition (EMD). To eliminate the negative frequency of the various extracted modes referred to as intrinsic mode function which appears with Fourier transform, we apply Hilbert transform leading to analytic representation of the signals. This process aids the determination of the instantaneous frequencies of the extracted modes. The combined process of EMD and Hilbert transform is called the Hilbert-Huang transform. The results in this thesis have been based on the improved EMD. To contribute to the understanding of plasma dynamics, the computed instantaneous frequencies are compared with the results obtained from the application of Simple Hilbert Transform. Instantaneous frequencies of overriding waves are easily separated as opposed to the application of just SHT. They offer the advantage of 3-dimensional study of the spatial characteristics of waves. The understanding of the instantaneous wave number has been achieved through the EMD and SHT combination. This provides the results which give the wave vector for a known frequency at a given instant of time. The instantaneous dispersion relation is determined using the knowledge of the instantaneous frequency and wave vector in the satellite frame, the plasma bulk velocity and the spacecraft velocity (found to be negligible compared with the plasma bulk velocity). This is accomplished using a Doppler shift relation. Wave modes identifications have been carried out by considering the proton temperature anisotropies, plasma beta and plasma bulk velocity and instantaneous phase velocity in the satellite frame. We report Alfvén mode close to the bow shock, spreading out to mirror mode which dominates the middle of magnetosheath. The mirror mode then diminishes towards the magnetopause.

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8

Khatta, Abhishek. "Experimental Studies on Shock-Shock Interactions in Hypersonic Shock Tunnels". Thesis, 2016. http://etd.iisc.ac.in/handle/2005/2927.

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Shock-shock interactions are among the most basic gas-dynamic problem, and are almost unavoidable in any high speed light, where shock waves generating from different sources crosses each other paths. These interactions when present very close to the solid surface lead to very high pressure and thermal loads on the surface. The related practical problem is that experienced at the cowl lip of a scramjet engine, where the interfering shock waves leads to high heat transfer rates which may also lead to the damage of the material. The classification by Edney (1968) on the shock-shock interaction patterns based on the visualization has since then served the basis for such studies. Though the problem of high heating on the surface in the vicinity of the shock-shock interactions has been studied at length at supersonic Mach numbers, the study on the topic at the hypersonic Mach numbers is little sparse. Even in the studies at hypersonic Mach numbers, the high speeds are not simulated, which is the measure of the kinetic energy of the ow. Very few experimental studies have addressed this problem by simulating the energy content of the ow. Also, some of the numerical studies on the shock-shock interactions suggest the presence of unsteadiness in the shock-shock interaction patterns as observed by Edney (1968), though this observation is not made very clearly in the experimental studies undertaken so far. In the present study, experiments are carried out in a conventional shock tunnel at Mach number of 5.62 (total enthalpy of 1.07 MJ/kg; freestream velocity of 1361 m/s), with the objective of mapping the surface pressure distribution and surface convective heat transfer rate distribution on the hemispherical body in the presence of the shock-shock interactions. A shock generator which is basically a wedge of angle = 25 , is placed at some dis-dance in front of the hemispherical body such that the planar oblique shock wave from the shock generator hits the bow shock wave in front of the hemi-spherical body. The relative distance between the wedge tip and the nose of the hemispherical body is allowed to change in di erent experiments to capture the whole realm of shock-shock interaction by making the planar oblique shock wave interact with the bow shock wave at different locations along its trajectory. The study results in a bulk of data for the surface pressure and heat transfer rates which were obtained by placing 5 kulites pressure transducers, 1 PCB pressure transducer and 21 platinum thin lm gauges along the surface of the hemispherical body in a plane normal to the freestream velocity direction. Along with the measurement of the surface pressure and the surface heat transfer rates, the schlieren visualization is carried out to capture the shock waves, expansion fans, slip lines, present in a certain shock-shock interaction pattern and the measured values were correlated with the captured schlieren images to evaluate the ow build up and steady and useful test time thereby helping in understanding the ow physics in the presence of the shock-shock interactions. From the present study it has been observed that in the presence of Edney Type-I and Edney Type-II interaction, the heat transfer rates on the hemi-spherical body are symmetrical about the centerline of the body, with the peak heating at the centerline which drops towards the shoulder. For Edney Type-III, Edney Type-IV, Edney Type-V and Edney Type-VI interaction pattern, the distribution in not symmetrical and shifts in peak heat transfer rates being on the side of the hemispherical from which planar oblique shock wave is incident. Also, it is observed that for the interactions which appear within the sonic circle, Edney Type-III and Edney Type-IV, the heat transfer rates observe an unsteadiness, such that the gauges located close to the interaction region experiencing varying heat transfer rates during the useful test time of the shock tunnel. Few experiments were conducted at Mach 8.36 (total enthalpy of 1.29 MJ/kg; freestream velocity of 1555.25 m/s) and Mach 10.14 (total enthalpy of 2.67 MJ/kg; freestream velocity of 2258.51 m/s) for the con gurations representing Edney Type-III interaction pattern to further evaluate the unsteady nature observed at Mach 5.62 ows. The unsteadiness was evident in both the cases. It is realized that the short test times in the shock tunnels pose a constraint in the study of unsteady flow fields, and the use of tailored mode operation of shock tunnel can alleviate this constraint. Also, limited number of experiments in the present study, which are carried out in a Free Piston Shock Tunnel, helps to understand the need to conduct such study in high enthalpy test conditions.

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9

Khatta, Abhishek. "Experimental Studies on Shock-Shock Interactions in Hypersonic Shock Tunnels". Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2927.

Testo completo

Abstract (sommario):

Shock-shock interactions are among the most basic gas-dynamic problem, and are almost unavoidable in any high speed light, where shock waves generating from different sources crosses each other paths. These interactions when present very close to the solid surface lead to very high pressure and thermal loads on the surface. The related practical problem is that experienced at the cowl lip of a scramjet engine, where the interfering shock waves leads to high heat transfer rates which may also lead to the damage of the material. The classification by Edney (1968) on the shock-shock interaction patterns based on the visualization has since then served the basis for such studies. Though the problem of high heating on the surface in the vicinity of the shock-shock interactions has been studied at length at supersonic Mach numbers, the study on the topic at the hypersonic Mach numbers is little sparse. Even in the studies at hypersonic Mach numbers, the high speeds are not simulated, which is the measure of the kinetic energy of the ow. Very few experimental studies have addressed this problem by simulating the energy content of the ow. Also, some of the numerical studies on the shock-shock interactions suggest the presence of unsteadiness in the shock-shock interaction patterns as observed by Edney (1968), though this observation is not made very clearly in the experimental studies undertaken so far. In the present study, experiments are carried out in a conventional shock tunnel at Mach number of 5.62 (total enthalpy of 1.07 MJ/kg; freestream velocity of 1361 m/s), with the objective of mapping the surface pressure distribution and surface convective heat transfer rate distribution on the hemispherical body in the presence of the shock-shock interactions. A shock generator which is basically a wedge of angle = 25 , is placed at some dis-dance in front of the hemispherical body such that the planar oblique shock wave from the shock generator hits the bow shock wave in front of the hemi-spherical body. The relative distance between the wedge tip and the nose of the hemispherical body is allowed to change in di erent experiments to capture the whole realm of shock-shock interaction by making the planar oblique shock wave interact with the bow shock wave at different locations along its trajectory. The study results in a bulk of data for the surface pressure and heat transfer rates which were obtained by placing 5 kulites pressure transducers, 1 PCB pressure transducer and 21 platinum thin lm gauges along the surface of the hemispherical body in a plane normal to the freestream velocity direction. Along with the measurement of the surface pressure and the surface heat transfer rates, the schlieren visualization is carried out to capture the shock waves, expansion fans, slip lines, present in a certain shock-shock interaction pattern and the measured values were correlated with the captured schlieren images to evaluate the ow build up and steady and useful test time thereby helping in understanding the ow physics in the presence of the shock-shock interactions. From the present study it has been observed that in the presence of Edney Type-I and Edney Type-II interaction, the heat transfer rates on the hemi-spherical body are symmetrical about the centerline of the body, with the peak heating at the centerline which drops towards the shoulder. For Edney Type-III, Edney Type-IV, Edney Type-V and Edney Type-VI interaction pattern, the distribution in not symmetrical and shifts in peak heat transfer rates being on the side of the hemispherical from which planar oblique shock wave is incident. Also, it is observed that for the interactions which appear within the sonic circle, Edney Type-III and Edney Type-IV, the heat transfer rates observe an unsteadiness, such that the gauges located close to the interaction region experiencing varying heat transfer rates during the useful test time of the shock tunnel. Few experiments were conducted at Mach 8.36 (total enthalpy of 1.29 MJ/kg; freestream velocity of 1555.25 m/s) and Mach 10.14 (total enthalpy of 2.67 MJ/kg; freestream velocity of 2258.51 m/s) for the con gurations representing Edney Type-III interaction pattern to further evaluate the unsteady nature observed at Mach 5.62 ows. The unsteadiness was evident in both the cases. It is realized that the short test times in the shock tunnels pose a constraint in the study of unsteady flow fields, and the use of tailored mode operation of shock tunnel can alleviate this constraint. Also, limited number of experiments in the present study, which are carried out in a Free Piston Shock Tunnel, helps to understand the need to conduct such study in high enthalpy test conditions.

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Libri sul tema "Bow shock wave"

1

Guoying, Zhao. Nonequilibrium phenomena behind a bow shock wave in a dusty gas. [S.l.]: [s.n.], 1985.

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2

United States. National Aeronautics and Space Administration., a cura di. ICE/ISEE plasma wave data analysis: Final report for period January 1992-September 1993. Redondo Beach, Calif: TRW Space And Technology Group, Applied Technology Division, 1993.

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3

United States. National Aeronautics and Space Administration., a cura di. ICE/ISEE plasma wave data analysis: Final report for period January 1990-December 1991. Redondo Beach, Calif: TRW Space And Technlogy Group, Applied Technology Division, 1992.

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4

Grabbe, Crockett L. Analytical MHD theory for Earth's bow shock at low Mach numbers. [Washington, DC: National Aeronautics and Space Administration, 1995.

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5

L, Grabbe Crockett, e United States. National Aeronautics and Space Administration., a cura di. Towards an MHD theory for the standoff distance of earth's bow shock. [Washington, DC: National Aeronautics and Space Administration, 1997.

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6

Ahuja, J. K. Numerical simulation of shock-induced combustion past blunt bodies using shock-fitting technique. Washington, D. C: American Institute of Aeronautics and Astronautiacs, 1994.

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7

B, Hospodarsky G., e United States. National Aeronautics and Space Administration., a cura di. The fine structure of Langmuir waves observed upstream of the bow shock at Venus. Iowa City, Iowa: Dept. of Physics and Astronomy, The University of Iowa, 1994.

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8

J, Singh D., Tiwari S. N e United States. National Aeronautics and Space Administration., a cura di. Numerical simulation of shock-induced combustion past blunt bodies using shock-fitting technique: Progress report for the period ended June 30, 1994. Norfolk, Va: Old Dominion University Research Foundation, 1994.

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9

J, Capone Francis, e Langley Research Center, a cura di. Impingement of boundary-reflected disturbances originating at the nose of a body of revolution in the Langley Research Center 16-foot transonic tunnel. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1998.

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10

Homayoun, Karimabadi, Krauss-Varban Dietmar e United States. National Aeronautics and Space Administration., a cura di. Physics of boundaries and their interactions in space plasmas: Interim contractor report #32 (final), 6/01/99-6/30/99. San Diego, CA: SciberNet, Inc., 1999.

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Più fonti

Capitoli di libri sul tema "Bow shock wave"

1

Georgievskiy, P. Y., e V. A. Levin. "Front separation regions for blunt and streamlined bodies initiated by temperature wake – bow shock wave interaction". In Shock Waves, 1273–78. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-85181-3_77.

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2

Shevchenko, A., A. Shmakov, I. Kavun, M. Golubev, Ya Ignatenko, A. Kharitonov, A. Pavlov e V. Zapryagaev. "Hypersonic Interaction of a Vortex Wake with a Bow Shock Wave". In 28th International Symposium on Shock Waves, 697–702. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-25685-1_106.

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3

Maekawa, Syozo, Shigeru Aso, Shigehide Nakao, Kazuo Arashi, Kenji Tomioka e Hiroyuki Yamao. "Aerodynamic Heating in Three-Dimensional Bow Shock Wave/Turbulent Boundary Layer Interaction Region". In Shock Waves @ Marseille I, 133–38. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78829-1_21.

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4

Seiler, F., e K. W. Naumann. "Bow Shock Wave Heating and Ablation of a Sharp-Nosed Projectile Flying inside a Ram Accelerator". In Shock Waves @ Marseille I, 183–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-78829-1_29.

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5

Krauss-Varban, D. "Bow Shock and Magnetosheath Simulations: Wave Transport and Kinetic Properties". In Solar Wind Sources of Magnetospheric Ultra-Low-Frequency Waves, 121–34. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm081p0121.

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Pushkar, E. A. "Features of the Impact of a Solar Wind Shock Wave on the Earth’s Bow Shock in a Strong Interplanetary Magnetic Field". In 28th International Symposium on Shock Waves, 743–49. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-25685-1_113.

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Anderson, K. A., C. W. Carlson, D. W. Curtis, R. P. Lin, H. Rème, J. A. Sauvaud, C. d’Uston, A. Korth, A. K. Richter e D. A. Mendis. "The upstream region, foreshock and bow shock wave at comet P/Halley from plasma electron measurements". In Exploration of Halley’s Comet, 290–92. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-82971-0_52.

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8

Sagdeev, R. Z., V. D. Shapiro, V. I. Shevchenko e K. Szegö. "The Effect of Mass Loading Outside Cometary Bow Shock for the Plasma and Wave Measurements in the Coming Cometary Missions". In Special Publications, 1131–37. Washington, D.C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/sp027p0017.

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Burgess, David. "Particle Acceleration at the Earth’s Bow Shock". In The High Energy Solar Corona: Waves, Eruptions, Particles, 161–91. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-71570-2_8.

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10

Sato, Y., Y. Suzuki, K. Yasue e N. Ohnishi. "Three-Dimensional Simulation of Bow-Shock Instability Using Discontinuous Galerkin Method". In 28th International Symposium on Shock Waves, 1027–33. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-25685-1_156.

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Atti di convegni sul tema "Bow shock wave"

1

Yamamoto, Satoru, e Shintaro Kano. "Structure of bow shock and compression wave interactions in unsteady hypersonic shock/shock interference flow". In Theroretical Fluid Mechanics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1996. http://dx.doi.org/10.2514/6.1996-2152.

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2

Liu, Yong C. M. "Ion Thermalization and Wave Excitation Downstream of Earth’s Bow Shock". In THE PHYSICS OF COLLISIONLESS SHOCKS: 4th Annual IGPP International Astrophysics Conference. AIP, 2005. http://dx.doi.org/10.1063/1.2032689.

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3

Georgievsky, Pavel, e Vladimir Levin. "Bow Shock Wave Structures Control by Pulse-Periodic Energy Input". In 42nd AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2004. http://dx.doi.org/10.2514/6.2004-1019.

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4

Marineau, Eric, e Hans Hornung. "Study of Bow-Shock Wave Unsteadiness in Hypervelocity Flow from Reservoir Fluctuations". In 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-382.

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5

Gorrell, Steven E., Theodore H. Okiishi e William W. Copenhaver. "Stator-Rotor Interactions in a Transonic Compressor: Part 2 — Description of a Loss Producing Mechanism". In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30495.

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Abstract (sommario):

A previously unidentified loss producing mechanism resulting from the interaction of a transonic rotor blade-row with an upstream stator blade-row is described. This additional loss occurs only when the two blade rows are spaced closer together axially. Time-accurate simulations of the flow and high-response static pressure measurements acquired on the stator blade surface reveal important aspects of the fluid dynamics of the production of this additional loss. At close spacing the rotor bow shock is chopped by the stator trailing edge. The chopped bow shock becomes a pressure wave on the upper surface of the stator that is nearly normal to the flow and that propagates upstream. In the reference frame relative to this pressure wave, the flow is supersonic and thus a moving shock wave that produces an entropy rise and loss is experienced. The effect of this outcome of blade-row interaction is to lower the efficiency, pressure ratio, and mass flow rate observed as blade-row axial spacing is reduced from far to close. The magnitude of loss production is affected by the strength of the bow shock and how much it turns as it interacts with the trailing edge of the stator. At far spacing the rotor bow shock degenerates into a bow wave before it interacts with the stator trailing edge and no significant pressure wave forms on the stator upper surface. For this condition, no additional loss is produced.

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6

Langford, Matthew D., Andrew Breeze-Stringfellow, Stephen A. Guillot, William Solomon, Wing F. Ng e Jordi Estevadeordal. "Experimental Investigation of the Effects of a Moving Shock Wave on Compressor Stator Flow". In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68722.

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Linear cascade testing was performed to simulate the flow conditions experienced by stator blades in an axial compressor with supersonic relative Mach numbers at the inlet to the downstream embedded rotors. Experiments were conducted in a transonic blow-down wind tunnel with a nominal inlet Mach number of 0.65. A single moving normal shock introduced at the exit of the stator cascade simulated the bow shock from a downstream rotor. The shock was generated using a shock tube external to the wind tunnel. Pressure measurements indicated that the stator matched its design intent loading, turning and loss under steady flow conditions. Effects of the passing shock on the stator flow-field were investigated using shadowgraph photography and Digital Particle Image Velocimetry (DPIV). Measurements were taken with three different shock strengths. In each case, the passing shock induced a vortex around the trailing edge of the stator. The size and strength of these vortices were directly related to the shock strength. A suction side separation on the trailing edge of the stator was observed and found to correlate with the vortex blockage.

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7

Kucharek, H., B. Miao e E. Möbius. "Wave excitation and turbulence at the Earth’s bow shock: cluster data and simulations". In TURBULENCE AND NONLINEAR PROCESSES IN ASTROPHYSICAL PLASMAS; 6th Annual International Astrophysics Conference. AIP, 2007. http://dx.doi.org/10.1063/1.2778969.

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8

Yang, Shuchi, Danny Liu, Zhicun Wang e Chunpei Cai. "Hypersonic Aerodynamics Using BGK Approach for Oscillatory Membrane-on-Ballute with Bow Shock Wave". In 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2009. http://dx.doi.org/10.2514/6.2009-1103.

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9

Parks, G., E. Lee, N. Lin, A. Teste, M. Wilber, I. Dandouras, H. Réme et al. "CURRENT DENSITY AND WAVE POLARIZATION OBSERVED IN DENSITY HOLES UPSTREAM OF EARTH’S BOW SHOCK". In PARTICLE ACCELERATION AND TRANSPORT IN THE HELIOSPHERE AND BEYOND: 7th Annual International Astrophysics Conference. AIP, 2008. http://dx.doi.org/10.1063/1.2982456.

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10

MAHANTA, ABHAY KUMAR. "UNDERWATER MINE EXPLOSION AND ITS IMPACT ON THE TARGET SHIP". In 32ND INTERNATIONAL SYMPOSIUM ON BALLISTICS. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/ballistics22/36068.

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Underwater mines are one of the major threats to surface ships and submarines. In the present work, detection, localization, and the shock loadings on a target ship due to explosion caused by an underwater multi-influence bottom mine containing most advanced PBX-charge have been studied. It was found that the keel shock factor (KSF) value is 0.50 kg1/2m-1 up to the water depth of 70 m. The shock wave energy at 70 m water depth is 14.8 kJm-2 where KSF equals to 0.50 kg1/2m-1. For a target ship, a significant drop in the blast pressure wave value (8.5-3.4 MPa) between the stern to the bow is noticeable with the total duration of shock loading of 0.0362s. The method proposed in the present study could be used for quick and reasonably accurate estimation of the impact of an incident shock wave underwater on the target ship.

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Rapporti di organizzazioni sul tema "Bow shock wave"

1

Monetary Policy Report - January 2023. Banco de la República, giugno 2023. http://dx.doi.org/10.32468/inf-pol-mont-eng.tr1-2023.

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1. Macroeconomic Summary In December, headline inflation (13.1%) and the average of the core inflation measures (10.3%) continued to trend upward, posting higher rates than those estimated by the Central Bank's technical staff and surpassing the market average. Inflation expectations for all terms exceeded the 3.0% target. In that month, every major group in the Consumer Price Index (CPI) registered higher-than-estimated increases, and the diffusion indicators continued to show generalized price hikes. Accumulated exchange rate pressures on prices, indexation to high inflation rates, and several food supply shocks would explain, in part, the acceleration in inflation. All of this is in a context of significant surplus demand, a tight labor market, and inflation expectations at different terms that exceed the 3.0% target. Compared to the October edition of the Monetary Policy Report, the forecast path for headline and core inflation (excluding food and regulated items: EFR) increased (Graphs 1.1 and 1.2), reflecting heightened accumulated exchange rate pressures, price indexation to a higher inflation rate (CPI and the producer price index: PPI), and the rise in labor costs attributed to a larger-than-estimated adjustment in the minimum wage. Nevertheless, headline inflation is expected to begin to ease by early 2023, although from a higher level than had been estimated in October. This would be supported initially by the slowdown forecast for the food CPI due to a high base of comparison, the end anticipated for the shocks that have affected the prices of these products, and the estimated improvement in external and domestic supply in this sector. In turn, the deterioration in real household income because of high inflation and the end of the effects of pent-up demand, plus tighter external and domestic financial conditions would contribute to diluting surplus demand in 2023 and reducing inflation. By the end of 2023, both headline and core (EFR) inflation would reach 8.7% and would be 3.5% and 3.8%, respectively, by December 2024. These forecasts are subject to a great deal of uncertainty, especially concerning the future behavior of international financial conditions, the evolution of the exchange rate, the pace of adjustment in domestic demand, the extent of indexation of nominal contracts, and the decisions taken regarding the domestic price of fuel and electricity. In the third quarter, economic activity surprised again on the upside and the growth projection for 2022 rose to 8.0% (previously 7.9%). However, it declined to 0.2% for 2023 (previously 0.5%). With this, surplus demand continues to be significant and is still expected to weaken during the current year. Annual economic growth in the third quarter (7.1 % SCA)1 was higher than estimated in October (6.4 % SCA), given stronger domestic demand specifically because of higher-than-expected investment. Private consumption fell from the high level witnessed a quarter earlier and net exports registered a more negative contribution than anticipated. For the fourth quarter, economic activity indicators suggest that gross domestic product (GDP) would have remained high and at a level similar to that observed in the third quarter, with an annual variation of 4.1%. Domestic demand would have slowed in annual terms, although at levels that would have remained above those for output, mainly because of considerable private consumption. Investment would have declined slightly to a value like the average observed in 2019. The real trade deficit would have decreased due to a drop in imports that was more pronounced than the estimated decline in exports. On the forecast horizon, consumption is expected to decline from current elevated levels, partly because of tighter domestic financial conditions and a deterioration in real income due to high inflation. Investment would also weaken and return to levels below those seen before the pandemic. In real terms, the trade deficit would narrow due to a lower momentum projection for domestic demand and higher cumulative real depreciation. In sum, economic growth for all of 2022, 2023, and 2024 would stand at 8.0%, 0.2% and 1.0%, respectively (Graph 1.3). Surplus demand remains high (as measured by the output gap) and is expected to decline in 2023 and could turn negative in 2024 (Graph 1.4). Although the macroeconomic forecast includes a marked slowdown in the economy, an even greater adjustment in domestic absorption cannot be ruled out due to the cumulative effects of tighter external and domestic financial conditions, among other reasons. These estimates continue to be subject to a high degree of uncertainty, which is associated with factors such as global political tensions, changes in international interest rates and their effects on external demand, global risk aversion, the effects of the approved tax reform, the possible impact of reforms announced for this year (pension, health, and labor reforms, among others), and future measures regarding hydrocarbon production. In 2022, the current account deficit would have been high (6.3 % of GDP), but it would be corrected significantly in 2023 (to 3.9 % of GDP) given the expected slowdown in domestic demand. Despite favorable terms of trade, the high external imbalance that would occur during 2022 would be largely due to domestic demand growth, cost pressures associated with high freight rates, higher external debt service payments, and good performance in terms of the profits of foreign companies.2 By 2023, the adjustment in domestic demand would be reflected in a smaller current account deficit especially due to fewer imports, a global moderation in prices and cost pressures, and a reduction in profits remitted abroad by companies with foreign direct investment (FDI) focused on the local market. Despite this anticipated correction in the external imbalance, its level as a percentage of GDP would remain high in the context of tight financial conditions. In the world's main economies, inflation forecasts and expectations point to a reduction by 2023, but at levels that still exceed their central banks' targets. The path anticipated for the Federal Reserve (Fed) interest rate increased and the forecast for global growth continues to be moderate. In the fourth quarter of 2022, logistics costs and international prices for some foods, oil and energy declined from elevated levels, bringing downward pressure to bear on global inflation. Meanwhile, the higher cost of financing, the loss of real income due to high levels of global inflation, and the persistence of the war in Ukraine, among other factors, have contributed to the reduction in global economic growth forecasts. In the United States, inflation turned out to be lower than estimated and the members of the Federal Open Market Committee (FOMC) reduced the growth forecast for 2023. Nevertheless, the actual level of inflation in that country, its forecasts, and expectations exceed the target. Also, the labor market remains tight, and fiscal policy is still expansionary. In this environment, the Fed raised the expected path for policy interest rates and, with this, the market average estimates higher levels for 2023 than those forecast in October. In the region's emerging economies, country risk premia declined during the quarter and the currencies of those countries appreciated against the US dollar. Considering all the above, for the current year, the Central Bank's technical staff increased the path estimated for the Fed's interest rate, reduced the forecast for growth in the country's external demand, lowered the expected path of oil prices, and kept the country’s risk premium assumption high, but at somewhat lower levels than those anticipated in the previous Monetary Policy Report. Moreover, accumulated inflationary pressures originating from the behavior of the exchange rate would continue to be important. External financial conditions facing the economy have improved recently and could be associated with a more favorable international context for the Colombian economy. So far this year, there has been a reduction in long-term bond interest rates in the markets of developed countries and an increase in the prices of risky assets, such as stocks. This would be associated with a faster-than-expected reduction in inflation in the United States and Europe, which would allow for a less restrictive course for monetary policy in those regions. In this context, the risks of a global recession have been reduced and the global appetite for risk has increased. Consequently, the risk premium continues to decline, the Colombian peso has appreciated significantly, and TES interest rates have decreased. Should this trend consolidate, exchange rate inflationary pressures could be less than what was incorporated into the macroeconomic forecast. Uncertainty about external forecasts and their impact on the country remains high, given the unpredictable course of the war in Ukraine, geopolitical tensions, local uncertainty, and the extensive financing needs of the Colombian government and the economy. High inflation with forecasts and expectations above 3.0%, coupled with surplus demand and a tight labor market are compatible with a contractionary stance on monetary policy that is conducive to the macroeconomic adjustment needed to mitigate the risk of de-anchoring inflation expectations and to ensure that inflation converges to the target. Compared to the forecasts in the October edition of the Monetary Policy Report, domestic demand has been more dynamic, with a higher observed level of output exceeding the productive capacity of the economy. In this context of surplus demand, headline and core inflation continued to trend upward and posted surprising increases. Observed and expected international interest rates increased, the country’s risk premia lessened (but remains at high levels), and accumulated exchange rate pressures are still significant. The technical staff's inflation forecast for 2023 increased and inflation expectations remain well above 3.0%. All in all, the risk of inflation expectations becoming unanchored persists, which would accentuate the generalized indexation process and push inflation even further away from the target. This macroeconomic context requires consolidating a contractionary monetary policy stance that aims to meet the inflation target within the forecast horizon and bring the economy's output to levels closer to its potential. 1.2 Monetary Policy Decision At its meetings in December 2022 and January 2023, Banco de la República’s Board of Directors (BDBR) agreed to continue the process of normalizing monetary policy. In December, the BDBR decided by a majority vote to increase the monetary policy interest rate by 100 basis points (bps) and in its January meeting by 75 bps, bringing it to 12.75% (Graph 1.5). 1/ Seasonally and calendar adjusted. 2/ In the current account aggregate, the pressures for a higher external deficit come from those companies with FDI that are focused on the domestic market. In contrast, profits in the mining and energy sectors are more than offset by the external revenue they generate through exports. Box 1 - Electricity Rates: Recent Developments and Indexation. Author: Édgar Caicedo García, Pablo Montealegre Moreno and Álex Fernando Pérez Libreros Box 2 - Indicators of Household Indebtedness. Author: Camilo Gómez y Juan Sebastián Mariño

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