Set-valued problems under bounded variation assumptions involving the Hausdorff excess

<p style='text-indent:20px;'>In the very general framework of a (possibly infinite dimensional) Banach space <inline-formula><tex-math id="M1">\begin{document}$ X $\end{document}</tex-math></inline-formula>, we are concerned with the existence of bounded variation solutions for measure differential inclusions</p><p style='text-indent:20px;'><disp-formula> <label/> <tex-math id="FE100"> \begin{document}$ \begin{equation} \begin{split} &amp;dx(t) \in G(t, x(t)) dg(t),\\ &amp;x(0) = x_0, \end{split} \end{equation}\;\;\;\;\;\;(1) $\end{document} </tex-math></disp-formula></p><p style='text-indent:20px;'>where <inline-formula><tex-math id="M2">\begin{document}$ dg $\end{document}</tex-math></inline-formula> is the Stieltjes measure generated by a nondecreasing left-continuous function.</p><p style='text-indent:20px;'>This class of differential problems covers a wide variety of problems occuring when studying the behaviour of dynamical systems, such as: differential and difference inclusions, dynamic inclusions on time scales and impulsive differential problems. The connection between the solution set associated to a given measure <inline-formula><tex-math id="M3">\begin{document}$ dg $\end{document}</tex-math></inline-formula> and the solution sets associated to some sequence of measures <inline-formula><tex-math id="M4">\begin{document}$ dg_n $\end{document}</tex-math></inline-formula> strongly convergent to <inline-formula><tex-math id="M5">\begin{document}$ dg $\end{document}</tex-math></inline-formula> is also investigated.</p><p style='text-indent:20px;'>The multifunction <inline-formula><tex-math id="M6">\begin{document}$ G : [0,1] \times X \to \mathcal{P}(X) $\end{document}</tex-math></inline-formula> with compact values is assumed to satisfy excess bounded variation conditions, which are less restrictive comparing to bounded variation with respect to the Hausdorff-Pompeiu metric, thus the presented theory generalizes already known existence and continuous dependence results. The generalization is two-fold, since this is the first study in the setting of infinite dimensional spaces.</p><p style='text-indent:20px;'>Next, by using a set-valued selection principle under excess bounded variation hypotheses, we obtain solutions for a functional inclusion</p><p style='text-indent:20px;'><disp-formula> <label/> <tex-math id="FE102"> \begin{document}$ \begin{equation} \begin{split} &amp;Y(t)\subset F(t,Y(t)),\\ &amp;Y(0) = Y_0. \end{split} \end{equation}\;\;\;\;(2) $\end{document} </tex-math></disp-formula></p><p style='text-indent:20px;'>It is shown that a recent parametrized version of Banach's Contraction Theorem given by V.V. Chistyakov follows from our result.</p>

Measure Differential Inclusions: Existence Results and Minimum Problems

We focus on a very general problem in the theory of dynamic systems, namely that of studying measure differential inclusions with varying measures. The multifunction on the right hand side has compact non-necessarily convex values in a real Euclidean space and satisfies bounded variation hypotheses with respect to the Pompeiu excess (and not to the Hausdorff-Pompeiu distance, as usually in literature). This is possible due to the use of interesting selection principles for excess bounded variation set-valued mappings. Conditions for the minimization of a generic functional with respect to a family of measures generated by equiregulated left-continuous, nondecreasing functions and to associated solutions of the differential inclusion driven by these measures are deduced, under constraints only on the initial point of the trajectory.

Nonsmooth Thermoelastic Simulations of Blade–Casing Contact Interactions

In turbomachinery, it is well known that tighter operating clearances improve the efficiency. However, this leads to unwanted potential unilateral and frictional contact occurrences between the rotating (blades) and stationary components (casings) together with attendant thermal excitations. Unilateral contact induces discontinuities in the velocity at impact times, hence the terminology nonsmooth dynamics. Current modeling strategies of rotor–stator interactions are either based on regularizing penalty methods or on explicit time-marching methods derived from Carpenter's forward Lagrange multiplier method. Regularization introduces an artificial time scale in the formulation corresponding to numerical stiffness, which is not desirable. Carpenter's scheme has been successfully applied to turbomachinery industrial models in the sole mechanical framework, but faces serious stability issues when dealing with the additional heat equation. This work overcomes the above issues by using the Moreau–Jean nonsmooth integration scheme within an implicit θ-method. This numerical scheme is based on a mathematically sound description of the contact dynamics by means of measure differential inclusions and enjoys attractive features. The procedure is unconditionally stable opening doors to quick preliminary simulations with time-steps one hundred times larger than with previous algorithms. It can also deal with strongly coupled thermomechanical problems.

Nonsmooth Thermoelastic Simulations of Blade-Casing Contact Interactions

In turbomachinery, it is well known that tighter operating clearances improve the efficiency. However, this leads to unwanted potential unilateral and frictional contact occurrences between the rotating (blades) and stationary components (casings) together with attendant thermal excitations. Unilateral contact induces discontinuities in the velocity at impact times, hence the terminology nonsmooth dynamics. Current modeling strategies of rotor-stator interactions are either based on regularizing penalty methods or on explicit time-marching methods derived from Carpenter’s forward Lagrange multiplier method. Regularization introduces an artificial time scale in the formulation corresponding to numerical stiffness which is not desirable. Carpenter’s scheme has been successfully applied to turbomachinery industrial models in the sole mechanical framework, but faces serious stability issues when dealing with the additional heat equation. This work overcomes the above issues by using the Moreau–Jean nonsmooth integration scheme within an implicit θ-method. This numerical scheme is based on a mathematically sound description of the contact dynamics by means of measure differential inclusions and enjoys attractive features. The procedure is unconditionally stable opening doors to quick preliminary simulations with time-steps one hundred times larger than with previous algorithms. It can also deal with strongly coupled thermomechanical problems.