# Mathematics Gives You Wings | Summary and Q&A

1.3M views
November 8, 2010
by
Stanford
Mathematics Gives You Wings

## Summary

In this video, the speaker discusses the field of computational mathematics and its application to fluid flow problems. They explain how equations govern fluid flow processes and how these equations can be simplified to understand the behavior of various flow systems. The speaker also introduces the concept of using grids to approximate solutions and the importance of interpolation between grid points. They provide examples of simulations and how these equations can be applied in real-life scenarios, such as sail design and airplane wing optimization.

### Q: What is the speaker's background in computational mathematics?

The speaker mentions that they obtained their PhD in computer science and energy resources from Stanford University. They are currently the director of the Institute of Computational Mathematical Engineering at Stanford and have worked on various fluid flow projects throughout their career.

### Q: How are equations used to describe fluid flow?

Equations are used to describe various properties of fluid flow, such as velocity, pressure, and energy. These properties can be measured and understood through the equations, which help predict and analyze the behavior of fluid flow in different systems. The speaker emphasizes that while the equations may appear complex, they can be simplified and understood to reveal the underlying connections between different flow processes.

### Q: How are the equations translated into solutions for fluid flow problems?

The speaker explains that the equations are solved using numerical methods on a grid. Instead of finding the exact solution at every point in a domain, a grid is created and solutions are computed at grid points. These grid points represent approximations of the solution in the region. Interpolation is used to estimate the solution at points that are not on the grid. This allows for efficient computation of solutions while maintaining accuracy.

### Q: What are some examples of fluid flow problems that can be solved using computational mathematics?

The speaker provides examples of fluid flow problems they have worked on, such as optimizing wing designs for pterosaurs, studying fluid flow in oil and gas reservoirs, and analyzing airflow around sailboats. They highlight how the same set of equations can be applied to various scenarios, demonstrating the universality of computational mathematics in fluid flow problems.

### Q: How is approximation used to simplify the computational process?

The speaker explains that approximation is used to simplify the computation process. Instead of finding the solution at every point in the domain, calculations are focused on a grid of points. This reduces the complexity and computational load while still providing accurate approximations of the solution. Interpolation is used to estimate the solution at points not covered by the grid, further simplifying the computational process.

### Q: How are grid points determined in computational mathematics?

Grid points are determined based on the specific problem and the desired level of accuracy. In some cases, a coarse grid with fewer points may be used in regions with steady flow or less complex behavior. In areas with rapid changes or complex flow patterns, a denser grid with more points is employed. The grid points are strategically chosen to capture the important features and behavior of the flow system.

### Q: Can the grid be adjusted to include specific points of interest?

Yes, the grid can be adjusted to include specific points of interest. If a point of interest is not on the grid, interpolation can be used to estimate the solution at that point. However, it may not always be practical to include every specific point of interest, as the computational load may become too high. Strategic placement of grid points is necessary to balance accuracy and computational efficiency.

### Q: What are some challenges in translating the equations onto the grid?

One of the challenges in translating the equations onto the grid is ensuring that the grid is well-suited to the specific problem and accurately represents the flow behavior. Skewed grids, where the angles of the grid lines are too extreme, can lead to computational issues and inaccuracies. It requires careful planning and consideration to design a grid that effectively captures the flow characteristics and produces accurate solutions.

### Q: How can computational mathematics be used in practical applications like sail design?

Computational mathematics can be used in practical applications like sail design by simulating the behavior of fluid flow around the sail. By solving the equations on a grid and approximating the solution, designers can analyze different designs and configurations without the need for physical prototypes. This allows for faster and more efficient testing of new sail designs to improve performance and optimize their shape.

### Q: How does the accuracy of the solutions depend on the grid and interpolation?

The accuracy of the solutions depends on the grid density, with denser grids providing more accurate solutions. Interpolation is used to estimate the solution at points not on the grid, and the accuracy of interpolation also affects the overall accuracy of the solutions. A balance must be struck between grid density and computational efficiency to achieve accurate solutions while managing computational resources.

## Takeaways

Computational mathematics plays a crucial role in understanding and analyzing fluid flow problems. By translating complex equations onto a grid and approximating the solution, researchers and engineers can simulate and study various flow systems. The use of grids allows for efficient computation and enables interpolation to estimate the solution at points not on the grid. This approach has applications in sail design, aircraft wing optimization, and many other fields where fluid flow is a critical factor.