Chandrashekhar Jog - Academia.edu (original) (raw)
Papers by Chandrashekhar Jog
Fluids, 2022
This work develops a new monolithic finite-element-based strategy for magnetohydrodynamics (MHD) ... more This work develops a new monolithic finite-element-based strategy for magnetohydrodynamics (MHD) involving a compressible fluid based on a continuous velocity–pressure formulation. The entire formulation is within a nodal finite element framework, and is directly in terms of physical variables. The exact linearization of the variational formulation ensures a quadratic rate of convergence in the vicinity of the solution. Both steady-state and transient formulations are presented for two- and three-dimensional flows. Several benchmark problems are presented, and comparisons are carried out against analytical solutions, experimental data, or against other numerical schemes for MHD. We show a good coarse-mesh accuracy and robustness of the proposed strategy, even at high Hartmann numbers.
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Solid Mechanics and Its Applications
ABSTRACT Conventional three-dimensional isoparametric elements are susceptible to problems of loc... more ABSTRACT Conventional three-dimensional isoparametric elements are susceptible to problems of locking when used to model plate/shell geometries or when the meshes are distorted etc. Hybrid elements that are based on a two-field variational formulation are immune to most of these problems, and hence can be used to efficiently model both “chunky” three-dimensional and plate/shell type structures. Thus, only one type of element can be used to model “all” types of structures, and also allows us to use a standard dual algorithm for carrying out the topology optimization of the structure. We also address the issue of manufacturability of the designs.
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Computing Systems in Engineering, 1992
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Computers & Mathematics with Applications, 2014
ABSTRACT The occurrence of spurious solutions is a well-known limitation of the standard nodal fi... more ABSTRACT The occurrence of spurious solutions is a well-known limitation of the standard nodal finite element method when applied to electromagnetic problems. The two commonly used remedies that are used to address this problem are (i) The addition of a penalty term with the penalty factor based on the local dielectric constant, and which reduces to a Helmholtz form on homogeneous domains (regularized formulation); (ii) A formulation based on a vector and a scalar potential. Both these strategies have some shortcomings. The penalty method does not completely get rid of the spurious modes, and both methods are incapable of predicting singular eigenvalues in non-convex domains. Some non-zero spurious eigenvalues are also predicted by these methods on non-convex domains. In this work, we develop mixed finite element formulations which predict the eigenfrequencies (including their multiplicities) accurately, even for nonconvex domains. The main feature of the proposed mixed finite element formulation is that no ad-hoc terms are added to the formulation as in the penalty formulation, and the improvement is achieved purely by an appropriate choice of finite element spaces for the different variables. We show that the formulation works even for inhomogeneous domains where ‘double noding’ is used to enforce the appropriate continuity requirements at an interface. For two-dimensional problems, the shape of the domain can be arbitrary, while for the three-dimensional ones, with our current formulation, only regular domains (which can be nonconvex) can be modeled. Since eigenfrequencies are modeled accurately, these elements also yield accurate results for driven problems.
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Structural Optimization, 1996
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Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2008
We consider the synchronous whirl of arbitrary axisymmetric rotors supported on rigid bearings. P... more We consider the synchronous whirl of arbitrary axisymmetric rotors supported on rigid bearings. Prior computational treatments of this problem were based on adding element-level gyroscopic terms to the governing equations. Here, we begin with a direct continuum formulation wherein gyroscopic terms need not be added on separately and explicitly: all gyroscopic effects are captured implicitly within the continuum elastodynamics. We present two new methods for obtaining the whirl speed, where we project the dynamic equilibrium equations of the rotor on to a few of its non-spinning vibration mode shapes. The first modal projection method is direct and more accurate, but requires numerical evaluation of more demanding integrals. The second method is iterative and involves a small approximation, but is simpler. Both the methods are based on one new insight: the gyroscopic terms used in other treatments are essentially the result of a prestress in the rotor caused by the non-zero spin rate...
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Journal of the Mechanics and Physics of Solids, 2000
We present a general approach for determining the equilibrium shape of isolated, coherent, misfit... more We present a general approach for determining the equilibrium shape of isolated, coherent, misfitting particles by minimizing the sum of elastic and interfacial energies using a synthesis of finite element and optimization techniques. The generality derives from the fact that there is no ...
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The Journal of the Acoustical Society of America, 2005
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Journal of Sound and Vibration, 2002
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Journal of Elasticity, 2008
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International Journal for Numerical Methods in Fluids, 2009
ABSTRACT Past studies that have compared LBB stable discontinuous- and continuous-pressure finite... more ABSTRACT Past studies that have compared LBB stable discontinuous- and continuous-pressure finite element formulations on a variety of problems have concluded that both methods yield solutions of comparable accuracy, and that the choice of interpolation is dictated by which of the two is more efficient. In this work, we show that using discontinuous-pressure interpolations can yield inaccurate solutions at large times on a class of transient problems, while the continuous-pressure formulation yields solutions that are in good agreement with the analytical solution. Copyright © 2009 John Wiley & Sons, Ltd.
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International Journal for Numerical Methods in Fluids, 2010
ABSTRACT This work presents a mixed three-dimensional finite element formulation for analyzing co... more ABSTRACT This work presents a mixed three-dimensional finite element formulation for analyzing compressible viscous flows. The formulation is based on the primitive variables velocity, density, temperature and pressure. The goal of this work is to present a ‘stable’ numerical formulation, and, thus, the interpolation functions for the field variables are chosen so as to satisfy the inf–sup conditions. An exact tangent stiffness matrix is derived for the formulation, which ensures a quadratic rate of convergence. The good performance of the proposed strategy is shown in a number of steady-state and transient problems where compressibility effects are important such as high Mach number flows, natural convection, Riemann problems, etc., and also on problems where the fluid can be treated as almost incompressible. Copyright © 2010 John Wiley & Sons, Ltd.
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International Journal for Numerical Methods in Engineering, 1994
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Computer Methods in Applied Mechanics and Engineering, 1996
... in the presence of thermal loading, the stresses are not proportional to the strains, even in... more ... in the presence of thermal loading, the stresses are not proportional to the strains, even in linearized thermoelasticity. ... This result is analogous to that obtained using the small-strain theory, hence, it would be reasonable to expect that the solid-void compliance optimization ...
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Fluids, 2022
This work develops a new monolithic finite-element-based strategy for magnetohydrodynamics (MHD) ... more This work develops a new monolithic finite-element-based strategy for magnetohydrodynamics (MHD) involving a compressible fluid based on a continuous velocity–pressure formulation. The entire formulation is within a nodal finite element framework, and is directly in terms of physical variables. The exact linearization of the variational formulation ensures a quadratic rate of convergence in the vicinity of the solution. Both steady-state and transient formulations are presented for two- and three-dimensional flows. Several benchmark problems are presented, and comparisons are carried out against analytical solutions, experimental data, or against other numerical schemes for MHD. We show a good coarse-mesh accuracy and robustness of the proposed strategy, even at high Hartmann numbers.
Bookmarks Related papers MentionsView impact
Solid Mechanics and Its Applications
ABSTRACT Conventional three-dimensional isoparametric elements are susceptible to problems of loc... more ABSTRACT Conventional three-dimensional isoparametric elements are susceptible to problems of locking when used to model plate/shell geometries or when the meshes are distorted etc. Hybrid elements that are based on a two-field variational formulation are immune to most of these problems, and hence can be used to efficiently model both “chunky” three-dimensional and plate/shell type structures. Thus, only one type of element can be used to model “all” types of structures, and also allows us to use a standard dual algorithm for carrying out the topology optimization of the structure. We also address the issue of manufacturability of the designs.
Bookmarks Related papers MentionsView impact
Computing Systems in Engineering, 1992
Bookmarks Related papers MentionsView impact
Computers & Mathematics with Applications, 2014
ABSTRACT The occurrence of spurious solutions is a well-known limitation of the standard nodal fi... more ABSTRACT The occurrence of spurious solutions is a well-known limitation of the standard nodal finite element method when applied to electromagnetic problems. The two commonly used remedies that are used to address this problem are (i) The addition of a penalty term with the penalty factor based on the local dielectric constant, and which reduces to a Helmholtz form on homogeneous domains (regularized formulation); (ii) A formulation based on a vector and a scalar potential. Both these strategies have some shortcomings. The penalty method does not completely get rid of the spurious modes, and both methods are incapable of predicting singular eigenvalues in non-convex domains. Some non-zero spurious eigenvalues are also predicted by these methods on non-convex domains. In this work, we develop mixed finite element formulations which predict the eigenfrequencies (including their multiplicities) accurately, even for nonconvex domains. The main feature of the proposed mixed finite element formulation is that no ad-hoc terms are added to the formulation as in the penalty formulation, and the improvement is achieved purely by an appropriate choice of finite element spaces for the different variables. We show that the formulation works even for inhomogeneous domains where ‘double noding’ is used to enforce the appropriate continuity requirements at an interface. For two-dimensional problems, the shape of the domain can be arbitrary, while for the three-dimensional ones, with our current formulation, only regular domains (which can be nonconvex) can be modeled. Since eigenfrequencies are modeled accurately, these elements also yield accurate results for driven problems.
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
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Foundations and Applications of Mechanics
Bookmarks Related papers MentionsView impact
Foundations and Applications of Mechanics
Bookmarks Related papers MentionsView impact
Structural Optimization, 1996
Bookmarks Related papers MentionsView impact
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2008
We consider the synchronous whirl of arbitrary axisymmetric rotors supported on rigid bearings. P... more We consider the synchronous whirl of arbitrary axisymmetric rotors supported on rigid bearings. Prior computational treatments of this problem were based on adding element-level gyroscopic terms to the governing equations. Here, we begin with a direct continuum formulation wherein gyroscopic terms need not be added on separately and explicitly: all gyroscopic effects are captured implicitly within the continuum elastodynamics. We present two new methods for obtaining the whirl speed, where we project the dynamic equilibrium equations of the rotor on to a few of its non-spinning vibration mode shapes. The first modal projection method is direct and more accurate, but requires numerical evaluation of more demanding integrals. The second method is iterative and involves a small approximation, but is simpler. Both the methods are based on one new insight: the gyroscopic terms used in other treatments are essentially the result of a prestress in the rotor caused by the non-zero spin rate...
Bookmarks Related papers MentionsView impact
Journal of the Mechanics and Physics of Solids, 2000
We present a general approach for determining the equilibrium shape of isolated, coherent, misfit... more We present a general approach for determining the equilibrium shape of isolated, coherent, misfitting particles by minimizing the sum of elastic and interfacial energies using a synthesis of finite element and optimization techniques. The generality derives from the fact that there is no ...
Bookmarks Related papers MentionsView impact
The Journal of the Acoustical Society of America, 2005
Bookmarks Related papers MentionsView impact
Journal of Sound and Vibration, 2002
Bookmarks Related papers MentionsView impact
Journal of Elasticity, 2008
Bookmarks Related papers MentionsView impact
International Journal for Numerical Methods in Fluids, 2009
ABSTRACT Past studies that have compared LBB stable discontinuous- and continuous-pressure finite... more ABSTRACT Past studies that have compared LBB stable discontinuous- and continuous-pressure finite element formulations on a variety of problems have concluded that both methods yield solutions of comparable accuracy, and that the choice of interpolation is dictated by which of the two is more efficient. In this work, we show that using discontinuous-pressure interpolations can yield inaccurate solutions at large times on a class of transient problems, while the continuous-pressure formulation yields solutions that are in good agreement with the analytical solution. Copyright © 2009 John Wiley & Sons, Ltd.
Bookmarks Related papers MentionsView impact
International Journal for Numerical Methods in Fluids, 2010
ABSTRACT This work presents a mixed three-dimensional finite element formulation for analyzing co... more ABSTRACT This work presents a mixed three-dimensional finite element formulation for analyzing compressible viscous flows. The formulation is based on the primitive variables velocity, density, temperature and pressure. The goal of this work is to present a ‘stable’ numerical formulation, and, thus, the interpolation functions for the field variables are chosen so as to satisfy the inf–sup conditions. An exact tangent stiffness matrix is derived for the formulation, which ensures a quadratic rate of convergence. The good performance of the proposed strategy is shown in a number of steady-state and transient problems where compressibility effects are important such as high Mach number flows, natural convection, Riemann problems, etc., and also on problems where the fluid can be treated as almost incompressible. Copyright © 2010 John Wiley & Sons, Ltd.
Bookmarks Related papers MentionsView impact
International Journal for Numerical Methods in Engineering, 1994
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Computer Methods in Applied Mechanics and Engineering, 1996
... in the presence of thermal loading, the stresses are not proportional to the strains, even in... more ... in the presence of thermal loading, the stresses are not proportional to the strains, even in linearized thermoelasticity. ... This result is analogous to that obtained using the small-strain theory, hence, it would be reasonable to expect that the solid-void compliance optimization ...
Bookmarks Related papers MentionsView impact