The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform

Yukio Sano - One of the best experts on this subject based on the ideXlab platform.

  • Shock jump equations for unsteady wave fronts of finite rise time
    Journal of Applied Physics, 1998
    Co-Authors: Yukio Sano, Isamu Miyamoto
    Abstract:

    First, generalized Rankine–Hugoniot equations for unsteady wave fronts of finite width are derived. It is clarified from these jump equations for particle velocity, stress, and Specific Internal Energy that shock jump conditions involve the effects of rise time of the front or the change in its velocity with time, in addition to that of strain rate and acceleration, and that the treatment in the previous study [Sano, J. Appl. Phys. 82, 5382 (1997)] where the rise time is reduced to an infinitesimal eliminates the terms of this change in the jump equations. Furthermore, the jump equations of the general form derived here support this elimination. Next, the influence of the rise time on the three jumps at the impacted surface of a lithium fluoride single crystal is calculated based on its experimental data and shown to be negligibly small. However, its influence, calculated for sandstone in a similar manner, is great. Finally, a parametric investigation of the influence is carried out for Specific strain waves.

  • Shock jump equations for unsteady wave fronts
    Journal of Applied Physics, 1997
    Co-Authors: Yukio Sano
    Abstract:

    First, the Rankine–Hugoniot (R–H) relations are generalized for unsteady shock wave fronts of infinitesimal risetime. The equation for particle velocity has a term of strain rate, while that for stress contains terms of strain rate and acceleration. Next, shock jump equations of general form for particle velocity, stress, and Specific Internal Energy are derived. They involve the combined effect of strain wave form, its change with time, and the path in time of strain. The effect, as well as the terms of strain rate and acceleration in the generalized R–H equations, indicates uncertainty about the applicability of familiar R–H equations to the shock fronts. Finally, jump equations for Specific strain waves are evaluated: Jumps in the three quantities are influenced greatly by the effect. If both the wave form and the path are linear, then the equations are of the same form as the R–H equations.

Manuel Perucho - One of the best experts on this subject based on the ideXlab platform.

  • Resonant Kelvin-Helmholtz modes in sheared relativistic flows.
    Physical Review E, 2007
    Co-Authors: Manuel Perucho, Michał Hanasz, J. M. Marti, J. A. Miralles
    Abstract:

    Certain aspects of the (linear and nonlinear) stability of sheared relativistic (slab) jets are analyzed. The linear problem has been solved for a wide range of jet models well inside the ultrarelativistic domain (flow Lorentz factors up to 20, Specific Internal energies $\ensuremath{\approx}60{c}^{2}$). As a distinct feature of our work, we have combined the analytical linear approach with high-resolution relativistic hydrodynamical simulations, which has allowed us (i) to identify, in the linear regime, resonant modes Specific to the relativistic shear layer, (ii) to confirm the result of the linear analysis with numerical simulations, and (iii) more interestingly, to follow the instability development through the nonlinear regime. We find that very-high-order reflection modes with dominant growth rates can modify the global, long-term stability of the relativistic flow. We discuss the dependence of these resonant modes on the jet flow Lorentz factor and Specific Internal Energy and on the shear-layer thickness. The results could have potential applications in the field of extragalactic relativistic jets.

  • Resonant Kelvin-Helmholtz modes in sheared relativistic flows.
    Physical review. E Statistical nonlinear and soft matter physics, 2007
    Co-Authors: Manuel Perucho, Michal Hanasz, José-maría Martí, J. A. Miralles
    Abstract:

    Certain aspects of the (linear and nonlinear) stability of sheared relativistic (slab) jets are analyzed. The linear problem has been solved for a wide range of jet models well inside the ultrarelativistic domain (flow Lorentz factors up to 20, Specific Internal energies approximately 60c2). As a distinct feature of our work, we have combined the analytical linear approach with high-resolution relativistic hydrodynamical simulations, which has allowed us (i) to identify, in the linear regime, resonant modes Specific to the relativistic shear layer, (ii) to confirm the result of the linear analysis with numerical simulations, and (iii) more interestingly, to follow the instability development through the nonlinear regime. We find that very-high-order reflection modes with dominant growth rates can modify the global, long-term stability of the relativistic flow. We discuss the dependence of these resonant modes on the jet flow Lorentz factor and Specific Internal Energy and on the shear-layer thickness. The results could have potential applications in the field of extragalactic relativistic jets.

  • Stability of hydrodynamical relativistic planar jets. I. Linear evolution and saturation of Kelvin-Helmholtz modes
    Astronomy & Astrophysics, 2004
    Co-Authors: Manuel Perucho, Michał Hanasz, J. M. Marti, Helene Sol
    Abstract:

    The effects of relativistic dynamics and thermodynamics in the development of Kelvin-Helmholtz instabilities in planar, relativistic jets along the early phases (namely linear and saturation phases) of evolution has been studied by a combination of linear stability analysis and high-resolution numerical simulations for the most unstable first reflection modes in the temporal approach. Three different values of the jet Lorentz factor (5, 10 and 20) and a few different values of Specific Internal Energy of the jet matter (from 0.08 to $60.0 c^2$) have been considered. Figures illustrating the evolution of the perturbations are also shown.

  • INFLUENCE OF Internal Energy ON THE STABILITY OF RELATIVISTIC FLOWS
    Highlights of Spanish Astrophysics III, 2003
    Co-Authors: Manuel Perucho, Michał Hanasz, J. M. Marti, Helene Sol
    Abstract:

    A set of simulations concerning the influence of Internal Energy on the stability of relativistic jets is presented. Results show that perturbations saturate when the amplitude of the velocity perturbation approaches the speed of light limit. Also, contrary to what predicted by linear stability theory, jets with higher Specific Internal Energy appear to be more stable.

Isamu Miyamoto - One of the best experts on this subject based on the ideXlab platform.

  • Shock jump equations for unsteady wave fronts of finite rise time
    Journal of Applied Physics, 1998
    Co-Authors: Yukio Sano, Isamu Miyamoto
    Abstract:

    First, generalized Rankine–Hugoniot equations for unsteady wave fronts of finite width are derived. It is clarified from these jump equations for particle velocity, stress, and Specific Internal Energy that shock jump conditions involve the effects of rise time of the front or the change in its velocity with time, in addition to that of strain rate and acceleration, and that the treatment in the previous study [Sano, J. Appl. Phys. 82, 5382 (1997)] where the rise time is reduced to an infinitesimal eliminates the terms of this change in the jump equations. Furthermore, the jump equations of the general form derived here support this elimination. Next, the influence of the rise time on the three jumps at the impacted surface of a lithium fluoride single crystal is calculated based on its experimental data and shown to be negligibly small. However, its influence, calculated for sandstone in a similar manner, is great. Finally, a parametric investigation of the influence is carried out for Specific strain waves.

J. A. Miralles - One of the best experts on this subject based on the ideXlab platform.

  • Resonant Kelvin-Helmholtz modes in sheared relativistic flows.
    Physical Review E, 2007
    Co-Authors: Manuel Perucho, Michał Hanasz, J. M. Marti, J. A. Miralles
    Abstract:

    Certain aspects of the (linear and nonlinear) stability of sheared relativistic (slab) jets are analyzed. The linear problem has been solved for a wide range of jet models well inside the ultrarelativistic domain (flow Lorentz factors up to 20, Specific Internal energies $\ensuremath{\approx}60{c}^{2}$). As a distinct feature of our work, we have combined the analytical linear approach with high-resolution relativistic hydrodynamical simulations, which has allowed us (i) to identify, in the linear regime, resonant modes Specific to the relativistic shear layer, (ii) to confirm the result of the linear analysis with numerical simulations, and (iii) more interestingly, to follow the instability development through the nonlinear regime. We find that very-high-order reflection modes with dominant growth rates can modify the global, long-term stability of the relativistic flow. We discuss the dependence of these resonant modes on the jet flow Lorentz factor and Specific Internal Energy and on the shear-layer thickness. The results could have potential applications in the field of extragalactic relativistic jets.

  • Resonant Kelvin-Helmholtz modes in sheared relativistic flows.
    Physical review. E Statistical nonlinear and soft matter physics, 2007
    Co-Authors: Manuel Perucho, Michal Hanasz, José-maría Martí, J. A. Miralles
    Abstract:

    Certain aspects of the (linear and nonlinear) stability of sheared relativistic (slab) jets are analyzed. The linear problem has been solved for a wide range of jet models well inside the ultrarelativistic domain (flow Lorentz factors up to 20, Specific Internal energies approximately 60c2). As a distinct feature of our work, we have combined the analytical linear approach with high-resolution relativistic hydrodynamical simulations, which has allowed us (i) to identify, in the linear regime, resonant modes Specific to the relativistic shear layer, (ii) to confirm the result of the linear analysis with numerical simulations, and (iii) more interestingly, to follow the instability development through the nonlinear regime. We find that very-high-order reflection modes with dominant growth rates can modify the global, long-term stability of the relativistic flow. We discuss the dependence of these resonant modes on the jet flow Lorentz factor and Specific Internal Energy and on the shear-layer thickness. The results could have potential applications in the field of extragalactic relativistic jets.

Helene Sol - One of the best experts on this subject based on the ideXlab platform.

  • Stability of hydrodynamical relativistic planar jets. I. Linear evolution and saturation of Kelvin-Helmholtz modes
    Astronomy & Astrophysics, 2004
    Co-Authors: Manuel Perucho, Michał Hanasz, J. M. Marti, Helene Sol
    Abstract:

    The effects of relativistic dynamics and thermodynamics in the development of Kelvin-Helmholtz instabilities in planar, relativistic jets along the early phases (namely linear and saturation phases) of evolution has been studied by a combination of linear stability analysis and high-resolution numerical simulations for the most unstable first reflection modes in the temporal approach. Three different values of the jet Lorentz factor (5, 10 and 20) and a few different values of Specific Internal Energy of the jet matter (from 0.08 to $60.0 c^2$) have been considered. Figures illustrating the evolution of the perturbations are also shown.

  • INFLUENCE OF Internal Energy ON THE STABILITY OF RELATIVISTIC FLOWS
    Highlights of Spanish Astrophysics III, 2003
    Co-Authors: Manuel Perucho, Michał Hanasz, J. M. Marti, Helene Sol
    Abstract:

    A set of simulations concerning the influence of Internal Energy on the stability of relativistic jets is presented. Results show that perturbations saturate when the amplitude of the velocity perturbation approaches the speed of light limit. Also, contrary to what predicted by linear stability theory, jets with higher Specific Internal Energy appear to be more stable.