Abstract
We return to the conservation law (1.2), but now study the case of systems, i.e.,
where \(u=u(x,t)=(u_{1},\dots,u_{n})\) and \(f=f(u)=(f_{1},\dots,f_{n})\in C^{2}\) are vectors in \(\mathbb{R}^{n}\). (We will not distinguish between row and column vectors, and use whatever is more convenient.) Furthermore, in this chapter we will consider only systems on the line; i.e., the dimension of the underlying physical space is still one. In Chapt. 2 we proved existence, uniqueness, and stability of the Cauchy problem for the scalar conservation law in one space dimension, i.e., well-posedness in the sense of Hadamard. However, this is a more subtle question in the case of systems of hyperbolic conservation laws. We will here first discuss the basic concepts for systems: fundamental properties of shock waves and rarefaction waves. In particular, we will discuss various entropy conditions to select the right solutions of the Rankine–Hugoniot relations.
Using these results, we will eventually be able to prove well-posedness of the Cauchy problem for systems of hyperbolic conservation laws with small variation in the initial data.
Diese Untersuchung macht nicht darauf Anspruch, der experimentellen Forschung nützliche Ergebnisse zu liefern; der Verfasser wünscht sie nur als einen Beitrag zur Theorie der nicht linearen partiellen Differentialgleichungen betrachtet zu sehen.The present work does not claim to lead to results in experimental research; the author asks only that it be considered as a contribution to the theory of nonlinear partial differential equations. — G. F. B. Riemann [156] Diese Untersuchung macht nicht darauf Anspruch, der experimentellen Forschung nützliche Ergebnisse zu liefern;der Verfasser wünscht sie nur als einen Beitrag zur Theorie der nicht linearen partiellen Differentialgleichungen betrachtet zu sehen. — G. F. B. Riemann [156] The present work does not claim to lead to results in experimental research; the author asks only that it be considered as a contribution to the theory of nonlinear partial differential equations.
Diese Untersuchung macht nicht darauf Anspruch, der experimentellen Forschung nützliche Ergebnisse zu liefern;der Verfasser wünscht sie nur als einen Beitrag zur Theorie der nicht linearen partiellen Differentialgleichungen betrachtet zu sehen.
— G. F. B. Riemann 156;
The present work does not claim to lead to results in experimental research; the author asks only that it be considered as a contribution to the theory of nonlinear partial differential equations.
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- 1.
A word of warning. There are several different equations that are called the shallow-water equations. Also the name Saint-Venant equation is used.
- 2.
Thanks to Harald Hanche-Olsen.
- 3.
In tidal waves, say in the North Sea, we have \(H\approx 100\,{\mathrm{m}}\), \(T=6\,{\mathrm{h}}\), \(\nu=10^{-6}\,{\mathrm{m}}^{2}{\mathrm{s}}^{-1}\), which yields \(\varepsilon\approx 2\cdot 10^{-4}\) and \(\mathrm{Re}\approx 3\cdot 10^{9}\).
- 4.
Nature does not make jumps.
- 5.
The properties of the eigenvalues follow from the implicit function theorem used on the determinant of \(\mu I-M(u,u_{l})\), and for the eigenvectors by considering the one-dimensional eigenprojections \(\int\left(M(u,u_{l})-\mu\right)^{-1}d\mu\) integrated around a small curve enclosing each eigenvalue \(\lambda_{j}(u_{l})\).
- 6.
The theory of nonlinear equations can, it seems, achieve the most success if our attention is directed to special problems of physical content with thoroughness and with a consideration of all auxiliary conditions. In fact, the solution of the very special problem that is the topic of the current paper requires new methods and concepts and leads to results which probably will also play a role in more general problems.
- 7.
Lo and behold; the second derivative of \(w_{k}(u(\epsilon),u_{l})\) is immaterial, since it is multiplied by \(u(\epsilon)-u_{l}\) at \(\epsilon=0\).
- 8.
Recall that this is in \((\rho,q,E)\) coordinates.
- 9.
In our notation we have \(\nabla(f(u)V(u))=V(u)(\nabla f(u))^{T}+f(u)\nabla V(u)\), where f is a scalar-valued function and V is (column) vector-valued. The result \(\nabla(fV)\) is a matrix.
- 10.
A word of caution: To show that \((\nabla\eta(u))^{T}df(u)=(\nabla(v\eta(u)))^{T}\) is strenuous. It is better done in nonconservative coordinates; see Exercise 5.12.
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Holden, H., Risebro, N.H. (2015). The Riemann Problem for Systems. In: Front Tracking for Hyperbolic Conservation Laws. Applied Mathematical Sciences, vol 152. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-662-47507-2_5
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DOI: https://doi.org/10.1007/978-3-662-47507-2_5
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