The Experts below are selected from a list of 19671 Experts worldwide ranked by ideXlab platform
Dehua Wang - One of the best experts on this subject based on the ideXlab platform.
-
vanishing viscosity method for Transonic Flow
Archive for Rational Mechanics and Analysis, 2008Co-Authors: Guiqiang Chen, Marshall Slemrod, Dehua WangAbstract:A vanishing viscosity method is formulated for two-dimensional Transonic steady irrotational compressible fluid Flows with adiabatic constant $$\gamma \in [1,3)$$ . This formulation allows a family of invariant regions in the phase plane for the corresponding viscous problem, which implies an upper bound uniformly away from cavitation for the viscous approximate velocity fields. Mathematical entropy pairs are constructed through the Loewner–Morawetz relation via entropy generators governed by a generalized Tricomi equation of mixed elliptic–hyperbolic type, and the corresponding entropy dissipation measures are analyzed so that the viscous approximate solutions satisfy the compensated compactness framework. Then the method of compensated compactness is applied to show that a sequence of solutions to the artificial viscous problem, staying uniformly away from stagnation with uniformly bounded velocity angles, converges to an entropy solution of the inviscid Transonic Flow problem.
-
vanishing viscosity method for Transonic Flow
arXiv: Analysis of PDEs, 2006Co-Authors: Guiqiang Chen, Marshall Slemrod, Dehua WangAbstract:A vanishing viscosity method is formulated for two-dimensional Transonic steady irrotational compressible fluid Flows with adiabatic constant $\gamma\in [1,3)$. This formulation allows a family of invariant regions in the phase plane for the corresponding viscous problem, which implies an upper bound uniformly away from cavitation for the viscous approximate velocity fields. Mathematical entropy pairs are constructed through the Loewner-Morawetz relation by entropy generators governed by a generalized Tricomi equation of mixed elliptic-hyperbolic type, and the corresponding entropy dissipation measures are analyzed so that the viscous approximate solutions satisfy the compensated compactness framework. Then the method of compensated compactness is applied to show that a sequence of solutions to the artificial viscous problem, staying uniformly away from stagnation, converges to an entropy solution of the inviscid Transonic Flow problem.
Vishwas Rao - One of the best experts on this subject based on the ideXlab platform.
-
machine learning for nonintrusive model order reduction of the parametric inviscid Transonic Flow past an airfoil
Physics of Fluids, 2020Co-Authors: Ashwin S Renganathan, Romit Maulik, Vishwas RaoAbstract:Fluid Flow in the Transonic regime finds relevance in aerospace engineering, particularly in the design of commercial air transportation vehicles. Computational fluid dynamics models of Transonic Flow for aerospace applications are computationally expensive to solve because of the high degrees of freedom as well as the coupled nature of the conservation laws. While these issues pose a bottleneck for the use of such models in aerospace design, computational costs can be significantly minimized by constructing special, structure-preserving surrogate models called reduced-order models. In this work, we propose a machine learning method to construct reduced-order models via deep neural networks and we demonstrate its ability to preserve accuracy with a significantly lower computational cost. In addition, our machine learning methodology is physics-informed and constrained through the utilization of an interpretable encoding by way of proper orthogonal decomposition. Application to the inviscid Transonic Flow past the RAE2822 airfoil under varying freestream Mach numbers and angles of attack, as well as airfoil shape parameters with a deforming mesh, shows that the proposed approach adapts to high-dimensional parameter variation well. Notably, the proposed framework precludes the knowledge of numerical operators utilized in the data generation phase, thereby demonstrating its potential utility in the fast exploration of design space for diverse engineering applications. Comparison against a projection-based nonintrusive model order reduction method demonstrates that the proposed approach produces comparable accuracy and yet is orders of magnitude computationally cheap to evaluate, despite being agnostic to the physics of the problem.
Guiqiang Chen - One of the best experts on this subject based on the ideXlab platform.
-
Existence and stability of multi-dimensional Transonic Flows through an infinite nozzle of arbitrary cross-sections
2015Co-Authors: Guiqiang Chen, Mikhail FeldmanAbstract:Abstract. We establish the existence and stability of multidimensional steady Transonic Flows with Transonic shocks through an infinite nozzle of arbitrary cross-sections, including a slowly varying de Laval nozzle. The Transonic Flow is governed by the inviscid potential Flow equation with supersonic upstream Flow at the entrance, uniform subsonic downstream Flow at the exit at infinity, and the slip boundary condition on the nozzle boundary. Our results indicate that, if the supersonic upstream Flow at the entrance is sufficiently close to a uniform Flow, there exists a solution that consists of a C1,α subsonic Flow in the unbounded downstream region, converging to a uniform velocity state at infinity, and a C1,α multidimensional Transonic shock dividing the subsonic Flow from the supersonic upstream Flow; the uniform velocity state at the exit at infinity in the downstream direction is uniquely determined by the supersonic upstream Flow; and the shock is orthogonal to the nozzle boundary at every point of their intersection. In order to construct such a Transonic Flow, we reformulate the multidimensional Transonic nozzle problem into a free boundary problem for the subsonic phase, in which the equation is elliptic and the free boundary is a Transonic shock. The free boundary conditions are determined by the Rankine-Hugoniot conditions along the shock. We further develop a nonlinear iteration approach and employ its advantages to deal with such a free boundary problem in the unbounded domain. We also prove that the Transonic Flow with a Transonic shock is unique and stable with respect to the nozzle boundary and the smooth supersonic upstream Flow at the entrance. 1
-
vanishing viscosity method for Transonic Flow
Archive for Rational Mechanics and Analysis, 2008Co-Authors: Guiqiang Chen, Marshall Slemrod, Dehua WangAbstract:A vanishing viscosity method is formulated for two-dimensional Transonic steady irrotational compressible fluid Flows with adiabatic constant $$\gamma \in [1,3)$$ . This formulation allows a family of invariant regions in the phase plane for the corresponding viscous problem, which implies an upper bound uniformly away from cavitation for the viscous approximate velocity fields. Mathematical entropy pairs are constructed through the Loewner–Morawetz relation via entropy generators governed by a generalized Tricomi equation of mixed elliptic–hyperbolic type, and the corresponding entropy dissipation measures are analyzed so that the viscous approximate solutions satisfy the compensated compactness framework. Then the method of compensated compactness is applied to show that a sequence of solutions to the artificial viscous problem, staying uniformly away from stagnation with uniformly bounded velocity angles, converges to an entropy solution of the inviscid Transonic Flow problem.
-
vanishing viscosity method for Transonic Flow
arXiv: Analysis of PDEs, 2006Co-Authors: Guiqiang Chen, Marshall Slemrod, Dehua WangAbstract:A vanishing viscosity method is formulated for two-dimensional Transonic steady irrotational compressible fluid Flows with adiabatic constant $\gamma\in [1,3)$. This formulation allows a family of invariant regions in the phase plane for the corresponding viscous problem, which implies an upper bound uniformly away from cavitation for the viscous approximate velocity fields. Mathematical entropy pairs are constructed through the Loewner-Morawetz relation by entropy generators governed by a generalized Tricomi equation of mixed elliptic-hyperbolic type, and the corresponding entropy dissipation measures are analyzed so that the viscous approximate solutions satisfy the compensated compactness framework. Then the method of compensated compactness is applied to show that a sequence of solutions to the artificial viscous problem, staying uniformly away from stagnation, converges to an entropy solution of the inviscid Transonic Flow problem.
Tooru Suita - One of the best experts on this subject based on the ideXlab platform.
-
detailed Flow study of mach number 1 6 high Transonic Flow with a shock wave in a pressure ratio 11 centrifugal compressor impeller
Journal of Turbomachinery-transactions of The Asme, 2004Co-Authors: Hirotaka Higashimori, Kiyoshi Hasagawa, Kunio Sumida, Tooru SuitaAbstract:Requirements for aeronautical gas turbine engines for helicopters include small size, low weight, high output, and low fuel consumption. In order to achieve these requirements, development work has been carried out on high efficiency and high pressure ratio compressors. As a result, we have developed a single stage centrifugal compressor with a pressure ratio of 11 for a 1000 shp class gas turbine. The centrifugal compressor is a high Transonic compressor with an inlet Mach number of about 1.6. In high inlet Mach number compressors, the Flow distortion due to the shock wave and the shock boundary layer interaction must have a large effect on the Flow in the inducer. In order to ensure the reliability of aerodynamic design technology, the actual supersonic Flow phenomena with a shock wave must be ascertained using measurement and Computational Fluid Dynamics (CFD). This report presents the measured results of the high Transonic Flow at the impeller inlet using Laser Doppler Velocimeter (LDV) and verification of CFD, with respect to the high Transonic Flow velocity distribution, pressure distribution, and shock boundary layer interaction at the inducer. The impeller inlet tangential velocity is about 460 m/s and the relative Mach number reaches about 1.6. Using a LDV, about 500 m/s relative velocity was measured preceding a steep deceleration of velocity. The following steep deceleration of velocity at the middle of blade pitch clarified the cause as being the pressure rise of a shock wave, through comparison with CFD as well as comparison with the pressure distribution measured using a high frequency pressure transducer. Furthermore, a reverse Flow is measured in the vicinity of casing surface. It was clarified by comparison with CFD that the reverse Flow is caused by the shock-boundary layer interaction. Generally CFD shows good agreement with the measured velocity distribution at the inducer and splitter inlet, except in the vicinity of the casing surface.
-
detailed Flow study of mach number 1 6 high Transonic Flow with a shock wave in a pressure ratio 11 centrifugal compressor impeller
ASME Turbo Expo 2004: Power for Land Sea and Air, 2004Co-Authors: Hirotaka Higashimori, Kiyoshi Hasagawa, Kunio Sumida, Tooru SuitaAbstract:Requirements for aeronautical gas turbine engines for helicopters include small size, low weight, high output, and low fuel consumption. In order to achieve these requirements, development work has been carried out on high efficiency and high pressure ratio compressors. As a result, we have developed a single stage centrifugal compressor with a pressure ratio of 11 for a 1000 shp class gas turbine. The centrifugal compressor is a high Transonic compressor with an inlet Mach number of about 1.6. In high inlet Mach number compressors, the Flow distortion due to the shock wave and the shock boundary layer interaction must have a large effect on the Flow in the inducer. In order to ensure the reliability of aerodynamic design technology, the actual supersonic Flow phenomena with a shock wave must be ascertained using measurement and CFD. This report presents the measured results of the high Transonic Flow at the impeller inlet using LDV and verification of CFD, with respect to the high Transonic Flow velocity distribution, pressure distribution and shock boundary layer interaction at the inducer. The impeller inlet tangential velocity is about 460m/s and the relative Mach number reaches about 1.6. Using an LDV, about 500m/s relative velocity was measured preceding a steep deceleration of velocity. The following steep deceleration of velocity at the middle of blade pitch clarified the cause as being the pressure rise of a shock wave, through comparison with CFD as well as comparison with the pressure distribution measured using a high frequency pressure transducer. Furthermore, a reverse Flow is measured in the vicinity of casing surface. It was clarified by comparison with CFD that the reverse Flow is caused by the shock-boundary layer interaction. Generally CFD shows good agreement with the measured velocity distribution at the inducer and splitter inlet, except in the vicinity of the casing surface.© 2004 ASME
Ashwin S Renganathan - One of the best experts on this subject based on the ideXlab platform.
-
machine learning for nonintrusive model order reduction of the parametric inviscid Transonic Flow past an airfoil
Physics of Fluids, 2020Co-Authors: Ashwin S Renganathan, Romit Maulik, Vishwas RaoAbstract:Fluid Flow in the Transonic regime finds relevance in aerospace engineering, particularly in the design of commercial air transportation vehicles. Computational fluid dynamics models of Transonic Flow for aerospace applications are computationally expensive to solve because of the high degrees of freedom as well as the coupled nature of the conservation laws. While these issues pose a bottleneck for the use of such models in aerospace design, computational costs can be significantly minimized by constructing special, structure-preserving surrogate models called reduced-order models. In this work, we propose a machine learning method to construct reduced-order models via deep neural networks and we demonstrate its ability to preserve accuracy with a significantly lower computational cost. In addition, our machine learning methodology is physics-informed and constrained through the utilization of an interpretable encoding by way of proper orthogonal decomposition. Application to the inviscid Transonic Flow past the RAE2822 airfoil under varying freestream Mach numbers and angles of attack, as well as airfoil shape parameters with a deforming mesh, shows that the proposed approach adapts to high-dimensional parameter variation well. Notably, the proposed framework precludes the knowledge of numerical operators utilized in the data generation phase, thereby demonstrating its potential utility in the fast exploration of design space for diverse engineering applications. Comparison against a projection-based nonintrusive model order reduction method demonstrates that the proposed approach produces comparable accuracy and yet is orders of magnitude computationally cheap to evaluate, despite being agnostic to the physics of the problem.
