1 Introduction
2 Study of the curvature term in uniform meshes
2.1 Curvature term for the Lagrange reconstruction
2.2 Curvature term for the PPH reconstruction
3 Study of the curvature term in nonuniform meshes
3.1 Curvature term for the Lagrange reconstruction in nonuniform meshes
3.2 Curvature term for the PPH reconstruction in nonuniform meshes
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Case 1.2 will only take place around inflection points on the underlying function. Therefore, if we work with data corresponding to strictly convex or concave functions this case will never happen.
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Case \(1.2.2\) will not occur around discontinuities except for extremely nonuniform grids where \(w_{j} \approx 1\), since \(M_{j}\) and \(D_{j}\) have the same sign if and only if \(|\frac{D_{j+1}}{D_{j}}|<\frac{w _{j}}{w_{j+1}}\).
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Under the assumption that for the given data condition in Case \(1.2.1\) is not satisfied, although this is a rare situation, we can consider the replacement at this concrete interval of the original data \(f_{j-1}\) by \(\tilde{f}_{j-1}\) according to (27a) instead of \(f_{j+2}\) by \(\tilde{f}_{j+2}\) in order to attain \(C_{L} \geq C _{H}\). This observation is easily proven because we go directly to Case \(2.2.1\). Thus, we give priority to the minimization of the curvature instead to the adaption to possible singularities. Notice that as mentioned in the previous point, there should not be a singularity at the considered interval but for exceptional cases.
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Case 2.2 will only appear around inflection points. Therefore, the case is avoided if we consider only data corresponding to strictly convex or concave functions.
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Case \(2.2.2\) will not occur around discontinuities except for extremely nonuniform grids where \(w_{j+1} \approx 1\), since \(M_{j}\) and \(D_{j+1}\) have the same sign if and only if \(|\frac{D_{j}}{D_{j}+1}|<\frac{w _{j+1}}{w_{j}}\).
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Under the assumption that for the given data condition in Case \(2.2.1\) is not satisfied, albeit this is not a common situation, we can give priority, as it happened in Case \(1.2.2\), to the minimization of the curvature instead to the adaption to possible singularities. Then, we consider in this case the replacement at this particular interval of the original data \(f_{j+2}\) by \(\tilde{f}_{j+2}\) according to (27b) instead of \(f_{j-1}\) by \(\tilde{f}_{j-1}\) in order to attain \(C_{L} \geq C_{H}\). Again this observation is trivial to prove. □