11428

# Solutions of the Elliptic Membrane Problem

The problem of the free oscillations of an elliptic membrane was studied by Mathieu in 1868. The membrane is anchored to the perimeter of the ellipse. Mathieu functions can appear in problems with elliptical geometry and in certain periodic phenomena.

### DETAILS

Consider the two-dimensional Helmholtz equation
and use elliptic coordinates
,
with ( is the semiminor axis of the ellipse). Solutions of the type lead to separation of variables, with the pair of differential equations
,
.
Now, consider the wave equation
.
Here , where is the tension and is the surface mass density, and we assume the harmonic dependence . The wave equation can be rewritten as the Helmholtz equation, with solutions with Dirichlet boundary conditions . Thus
where and are even and odd angular solutions. These functions are represented in Mathematica as MathieuC[a,q,z] and MathieuS[a,q,z], respectively; is the characteristic (MathieuCharacteristicA[n,q] and MathieuCharacteristicB[n,q]), a value for which the Mathieu functions are periodic. The radial functions and correspond to the same functions with . The solutions have angular nodes and radial nodes, with for even modes and for the odd ones.
Reference
[1] J. C. Gutiérrez-Vega, R. M. Rodrı́guez-Dagnino, M. A. Meneses-Nava, and S. Chávez-Cerda, "Mathieu Functions, a Visual Approach," American Journal of Physics, 71(3), 2003 pp. 233–242. doi:10.1119/1.1522698.

### PERMANENT CITATION

 Share: Embed Interactive Demonstration New! Just copy and paste this snippet of JavaScript code into your website or blog to put the live Demonstration on your site. More details » Download Demonstration as CDF » Download Author Code »(preview ») Files require Wolfram CDF Player or Mathematica.

#### Related Topics

 RELATED RESOURCES
 The #1 tool for creating Demonstrations and anything technical. Explore anything with the first computational knowledge engine. The web's most extensive mathematics resource. An app for every course—right in the palm of your hand. Read our views on math,science, and technology. The format that makes Demonstrations (and any information) easy to share and interact with. Programs & resources for educators, schools & students. Join the initiative for modernizing math education. Walk through homework problems one step at a time, with hints to help along the way. Unlimited random practice problems and answers with built-in step-by-step solutions. Practice online or make a printable study sheet. Knowledge-based programming for everyone.