Finite Element Methods for Higher Order Variational Inequalities

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Elliptic variational inequalities are fundamental mathematical tools for modeling phenomena that involve elliptic partial differential operators and constrained optimization. This project will develop and analyze finite element methods for fourth and higher order elliptic variational inequalities, which arise naturally for example in mechanics and elliptic optimal control problems. A recent theoretical advance by the PIs demonstrates that, for the displacement obstacle problems of Kirchhoff plates, the heart of the error analysis involves only problems at the continuous level and therefore any finite element method that works for fourth order boundary value problems can also be adapted for obstacle problems. This new approach will be extended to other fourth and higher order variational inequalities with different types of constraints, which will bring well-developed finite element methodologies for boundary value problems (conforming and nonconforming methods, discontinuous Galerkin methods, generalized finite element methods, isoparametric finite element methods, local mesh refinement, singular function method, etc.) into the study of numerical solution of higher order variational inequalities. Fast solvers for higher order variational inequalities, such as multigrid methods, domain decomposition methods and adaptive methods, will also be developed. In particular this project will lead to new algorithms for second order elliptic distributed optimal control problems with pointwise state and/or control constraints that are fundamentally different from existing algorithms. The results from this project will provide new insights to the numerical solution of higher order variational inequalities, an area that is becoming increasingly important as more and more complex phenomena in science, engineering and finance are being modeled by higher order differential equations. The outcomes of this project will impact diverse areas that require reliable and efficient numerical algorithms for the solution of such inequalities.