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Jens Chluba - One of the best experts on this subject based on the ideXlab platform.

  • mixing of blackbodies Entropy production and dissipation of sound waves in the early universe
    Astronomy and Astrophysics, 2012
    Co-Authors: Rishi Khatri, R Sunyaev, Jens Chluba
    Abstract:

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of cosmic microwave background (CMB) photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing sound waves on entering the sound horizon. Photons from different phases of the sound waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates sound waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/ 3r aises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 10 5 < z < 2 × 10 6 , comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with Entropy Creation. This allows us to obtain the main results connected with the dissipation of sound waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of sound waves in particular, leads to Creation of Entropy.

  • mixing of blackbodies Entropy production and dissipation of sound waves in the early universe
    arXiv: Cosmology and Nongalactic Astrophysics, 2012
    Co-Authors: Rishi Khatri, R Sunyaev, Jens Chluba
    Abstract:

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of CMB photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing sound waves on entering the sound horizon. Photons from different phases of the sound waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates sound waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/3 raises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 10^5< z< 2x10^6, comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with Entropy Creation. This allows us to obtain the main results connected with the dissipation of sound waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of sound waves in particular, leads to Creation of Entropy.

Rishi Khatri - One of the best experts on this subject based on the ideXlab platform.

  • mixing of blackbodies Entropy production and dissipation of sound waves in the early universe
    Astronomy and Astrophysics, 2012
    Co-Authors: Rishi Khatri, R Sunyaev, Jens Chluba
    Abstract:

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of cosmic microwave background (CMB) photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing sound waves on entering the sound horizon. Photons from different phases of the sound waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates sound waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/ 3r aises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 10 5 < z < 2 × 10 6 , comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with Entropy Creation. This allows us to obtain the main results connected with the dissipation of sound waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of sound waves in particular, leads to Creation of Entropy.

  • mixing of blackbodies Entropy production and dissipation of sound waves in the early universe
    arXiv: Cosmology and Nongalactic Astrophysics, 2012
    Co-Authors: Rishi Khatri, R Sunyaev, Jens Chluba
    Abstract:

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of CMB photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing sound waves on entering the sound horizon. Photons from different phases of the sound waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates sound waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/3 raises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 10^5< z< 2x10^6, comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with Entropy Creation. This allows us to obtain the main results connected with the dissipation of sound waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of sound waves in particular, leads to Creation of Entropy.

Yuz Juan - One of the best experts on this subject based on the ideXlab platform.

  • On port-Hamiltonian formulations of 3-dimensional compressible Newtonian fluids
    'AIP Publishing', 2022
    Co-Authors: Mora, Luis A., Le Gorrec Yann, Matignon Denis, Ramirez Hector, Yuz Juan
    Abstract:

    In this manuscript, a general formulation of 3-dimensional compressible fluids based on the port-Hamiltonian framework is presented, both for isentropic and non-isentropic assumptions, describing the energy flux between the mechanical, chemical, and thermal domains, with an explicit characterization of the first and the second law of thermodynamics. For isentropic fluids, the conversion of kinetic energy into heat by viscous friction is considered as energy dissipation associated with the rotation and compression of the fluid. A dissipative port-Hamiltonian formulation is derived for this class of fluids, including vorticity boundary conditions in the port variables. For non-isentropic fluids, we consider a fluid mixture with multiple chemical reactions. To describe the energy fluxes, we propose a pseudo port-Hamiltonian formulation, which includes the rate of irreversible Entropy Creation by heat flux, chemical reaction, diffusion of matter, and viscous friction

  • About Dissipative and Pseudo Port-Hamiltonian Formulations of Irreversible Newtonian Compressible Flows
    'Elsevier BV', 2020
    Co-Authors: Mora, Luis A., Matignon Denis, Ramirez Hector, Yann Le Gorrec, Yuz Juan
    Abstract:

    International audienceIn this paper we consider the physical-based modeling of 3D and 2D Newtonian fluids including thermal effects in order to cope with the first and second principles of thermodynamics. To describe the energy fluxes of non-isentropic fluids we propose a pseudo port-Hamiltonian formulation, which includes the rate of irreversible Entropy Creation by heat flux. For isentropic fluids, the conversion of kinetic energy into heat by viscous friction is considered as an energy dissipation associated with the rotation and compression of the fluid. Then, a dissipative port-Hamiltonian formulation is derived for this class of fluids. In the 2D case we modify the vorticity operators in order to preserve the structure of the proposed models. Moreover, we show that a description for inviscid or irrotational fluids can be derived from the proposed models under the corresponding assumptions leading to a pseudo or dissipative port-Hamiltonian structures

  • About Dissipative and Pseudo Port-Hamiltonian Formulations of Irreversible Newtonian Compressible Flows
    'Elsevier BV', 2020
    Co-Authors: Mora, Luis A., Matignon Denis, Ramirez Hector, Yann Le Gorrec, Yuz Juan
    Abstract:

    In this paper we consider the physical-based modeling of 3D and 2D Newtonian fluids including thermal effects in order to cope with the first and second principles of thermodynamics. To describe the energy fluxes of non-isentropic fluids we propose a pseudo port-Hamiltonian formulation, which includes the rate of irreversible Entropy Creation by heat flux. For isentropic fluids, the conversion of kinetic energy into heat by viscous friction is considered as an energy dissipation associated with the rotation and compression of the fluid. Then, a dissipative port-Hamiltonian formulation is derived for this class of fluids. In the 2D case we modify the vorticity operators in order to preserve the structure of the proposed models. Moreover, we show that a description for inviscid or irrotational fluids can be derived from the proposed models under the corresponding assumptions leading to a pseudo or dissipative port-Hamiltonian structures

R Sunyaev - One of the best experts on this subject based on the ideXlab platform.

  • mixing of blackbodies Entropy production and dissipation of sound waves in the early universe
    Astronomy and Astrophysics, 2012
    Co-Authors: Rishi Khatri, R Sunyaev, Jens Chluba
    Abstract:

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of cosmic microwave background (CMB) photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing sound waves on entering the sound horizon. Photons from different phases of the sound waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates sound waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/ 3r aises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 10 5 < z < 2 × 10 6 , comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with Entropy Creation. This allows us to obtain the main results connected with the dissipation of sound waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of sound waves in particular, leads to Creation of Entropy.

  • mixing of blackbodies Entropy production and dissipation of sound waves in the early universe
    arXiv: Cosmology and Nongalactic Astrophysics, 2012
    Co-Authors: Rishi Khatri, R Sunyaev, Jens Chluba
    Abstract:

    Mixing of blackbodies with different temperatures creates a spectral distortion which, at lowest order, is a y-type distortion, indistinguishable from the thermal y-type distortion produced by the scattering of CMB photons by hot electrons residing in clusters of galaxies. This process occurs in the radiation-pressure dominated early Universe, when the primordial perturbations excite standing sound waves on entering the sound horizon. Photons from different phases of the sound waves, having different temperatures, diffuse through the electron-baryon plasma and mix together. This diffusion, with the length defined by Thomson scattering, dissipates sound waves and creates spectral distortions in the CMB. Of the total dissipated energy, 2/3 raises the average temperature of the blackbody part of spectrum, while 1/3 creates a distortion of y-type. It is well known that at redshifts 10^5< z< 2x10^6, comptonization rapidly transforms y-distortions into a Bose-Einstein spectrum. The chemical potential of the Bose-Einstein spectrum is again 1/3 the value we would get if all the dissipated energy was injected into a blackbody spectrum but no extra photons were added. We study the mixing of blackbody spectra, emphasizing the thermodynamic point of view, and identifying spectral distortions with Entropy Creation. This allows us to obtain the main results connected with the dissipation of sound waves in the early Universe in a very simple way. We also show that mixing of blackbodies in general, and dissipation of sound waves in particular, leads to Creation of Entropy.

Wei Zhao - One of the best experts on this subject based on the ideXlab platform.

  • aerodynamic design and analysis of a multistage vaneless counter rotating turbine
    Journal of Turbomachinery-transactions of The Asme, 2015
    Co-Authors: Wei Zhao
    Abstract:

    A multistage vaneless counter-rotating turbine (MVCRT) eliminates vanes between rotors, which reduces the weight and size of the turbine and avoids viscous losses associated with vanes pronouncedly. An aircraft engine employing such a turbine would have greater thrust to weight ratio and smaller specific fuel consumption. This paper presents the aerodynamic design philosophy and performance analysis of the MVCRTs for gas turbine engines by a case study. The case is about a 1/2*4 turbine, which consists of a rotating frame and four rotors without any vanes between them. The first rotor and the third rotor are connected by a shaft to drive a compressor with a pressure ratio of 11.8, and the second rotor and the fourth rotor are connected by the rotating frame to deliver a total shaft power of around 2 MW. The stage loading of each rotor and flow axial acceleration of each duct are controlled to provide sufficient inlet swirls for their subsequent rotors. The stage work coefficients of each rotor are 0.95, 2.9, 1.4, and 1.0, respectively. Nonuniform radial circulation distributions are also used to maximize the turbine power output. Centrifugal forces in the outer rotor of the turbine are captured by carrying out a finite element analysis (FEA) to validate the aerodynamic design results. Three-dimensional viscous numerical results show that an adiabatic total-to-total efficiency of 91.47% with a pressure ratio of 9.8 at design condition is obtained and achieves the initial design objective very well. Entropy Creation associated with the tip leakage and secondary flow is also illustrated for understanding the origins and effects of losses in the turbine. Pressure ratios and efficiency at the speed combinations of the 80% to 100% inner and outer rotor design speeds are discussed to reveal the turbine characteristics at off-design conditions.

  • aerodynamic design and analysis of a multistage vaneless counter rotating turbine
    ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, 2014
    Co-Authors: Wei Zhao
    Abstract:

    Multistage vaneless counter-rotating turbines eliminate vanes between rotors, which reduces the weight of the turbine pronouncedly and avoids viscous losses associated with vanes. As a result, a gas turbine engine employing such a turbine would have greater thrust to weight ratio and smaller specific fuel consumption. This paper presents aerodynamic design and analysis for a multistage vaneless counter-rotating turbine, named as a 4*1/2 turbine, which consists of a rotating frame and four rotors without any vanes. The first rotor and the third rotor drive a single-shaft compressor with a pressure ratio of 11.8, and the second rotor and the forth rotor deliver a total shaft power of around 2MW. Stage loading and flow axial acceleration in blades and ducts are selected to provide sufficient inlet swirl for downstream vaneless rotor to produce required power output with acceptable performance. The stage work coefficients of each rotor are 0.95, 2.9, 1.4 and 1.0, respectively. Non-uniform radial circulation distributions and tapered blades are also used to maximize the turbine power output. Centrifugal forces in the outer rotor of the turbine are captured by carrying out a finite element analysis to validate the aerodynamic design results. Three dimensional viscous numerical results show that an adiabatic total-to-total efficiency of 91.5% with a pressure ratio of 9.8 at design condition is obtained and achieves the initial design objective very well. Entropy Creation associated with the tip leakage and secondary flow in each rotor is also illustrated for understanding the origins and effects of losses in such turbines. Pressure ratios and efficiency at speed combinations of the 80% to 100% design speeds of the inner and outer rotors are discussed to reveal the turbine characteristics at off-design conditions.Copyright © 2014 by ASME