The following references are free available (and the first paragraph in spanish but) I will write the topics in english (I hope that my translation is right for the specification of this topics is right). I write this literature and you can search such key words to find the literature or ideas that is required for your class.
In the hope page of professor Chamizo, from Universidad Autónoma de Madrid Apuntes de Modelización II, there are topics as gyroscopic movement (pages 19-22), soap bubbles (25-30), and so other topics for which I no longer wrote the page, for example heat transfer, or the Radon transform and tomography, the JPEG format.
In his lecture notes : Chamizo, Geometría IV (tensores, formas, curvatura, relatividad y todo eso), you can find a section dedicated for example to de Rham cohomology, the Schwarzschild metric and black holes or Einstein field equations.
Additionally you can think in topics (at least I think that are beatiful) as what's an invariant in physic or mathematics?, Paul Dirac and the beauty of the equations (I am saying the study of the symmetries of some equation related with Paul Dirac), what's the Church–Turing thesis? (or a different work of Alan Turing, for example with respect the how he did the cryptanalysis of the Enigma), Euler equations in fluid dynamics (Córdoba, Fontelos and Rodrigo, Las matemáticas de los fluidos: torbellinos, gotas y olas. La GACETA de la Real Sociedad Matemática Española Vol. 8, No. 3 (2005)), flamenco and mathematics (Díaz-Báñez, Sobre problemas de matemáticas
en el estudio del cante flamenco, La Gaceta de la RSME, Vol. 16 No. 3, (2013), ), Interpolation (spaces, interpolation of operators) and PDE (see Lunardi, How to use interpolation in PDE's, Summer School on Harmonic Analysis and PDE's, Helsinki, August 2003.) Orbifolds (here I haven't find a free access, but as previous this has the more high quality: Montesinos Amilibia, Orbifolds in the Alhambra. Memorias de la Real Academia de Ciencias Exactas, Fisicas y Naturales de Madrid. Serie de ciencias exactas, 23 . p. 44. ISSN 0211-1721).
Mathematics and oceanography (see Tartar, An Introduction to Navier-Stokes Equation and Oceanography, Springer, (2006) see www.springer.com; I presume that one can find information about mathematics and..., for example mathematics and the exploration of Mars. A proof or detailed examples of the Cauchy–Kowalevski theorem. Or mathematics and quantum mechanics (I found this Heathcote, Undounded operators and the incompleteness of quantum mechanics Philosophy of Science 57 (3):523-534 (1990)). See Ratlif, Linear Algebra and Robot Modeling ,also as a second example of topics that you can find in papers, from Institut für Parallele und Verteilte Systeme (Universität Stuttgart). Also you can find literatue about, for example, applications of fractals in the real life and the mathematics beyond this ideas (fractal antenna or fractal geometry in medicine...).