Eigenvalues and Eigenvectors in Thermal Instabilities — Lesson 2

This lesson covers the Craya-Herring method and its application in deriving the equation of motion for a single triad. The lesson explains the concept of wavenumbers, convolution, cross product, and dot product. It also discusses the condition of symmetry in the equation and the importance of vector addition. The lesson further elaborates on the use of 2D physics to simplify the equation of motion. The instructor provides an illustrative example of a triangle to explain the angles and their relation to the equation. The lesson concludes with the application of the Craya-Herring method to solve complex examples.

Video Highlights

01:08 - Explanation of how eigenvalues and eigenvectors affect the direction of growth
06:43 - Explanation of the concept of neutral stability and its implications
17:22 - Discussion on the relationship between Rayleigh number and eigenvalues
25:29 - Discussion on the concept of stationary rolls and their characteristics
30:39 - Discussion on the impact of Prandtl number on Rayleigh critical

Key Takeaways

- Eigenvalues can indicate whether a system will grow or not, with positive eigenvalues indicating growth and negative ones indicating decay.
- Eigenvectors show the direction of growth or decay in a system.
- The concept of neutral stability is when the determinant is zero, indicating a state where the system neither grows nor decays.
- The Rayleigh number, wave number, and the onset of instability in a system are interconnected. The Rayleigh number at which stability starts can be determined given the wave number.
- The velocity field and temperature field are related at neutral stability.