### What has Harry Potter to do with Maths?

### Watch this video of Harry Potter and the Half Blood Prince: Death Eater Attack.

### You can click on the link here or below (Video will only play on You Tube site):

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### A recent article in The Guardian, UK, explained the link between Harry Potter and Maths:

*‘(Alex)Hope, managing director of the visual effects firm Double Negative said: “In Harry Potter [and the Half Blood Prince], the opening sequence has Death Eaters flying across the river Thames, destroying the (Millennium) Bridge between St Paul’s and the Tate Modern.’*

*“The way you create that is people who understand computational fluid dynamics, they know how water moves. They take the physics that’s used in modelling rivers and the flow of water and apply that in our world. People doing it need an artistic sensibility as well. An understanding of maths and science is fundamental to many of the disciplines in our industry.”*

### Fluid Dynamics is the study of fluid flow. You can look at this picture (below) and see the similarity to the Death Eaters water-flowy appearance.

### Here is a experiment showing lamina Vs turbulent flow in water. Mathspig did experiments like this at university in Chemical Engineering. Equations can be scary, mathspigs, but not necessarily.

### Here is a water flow equation for a sharp edged weir with a V notch out let from AQUATEXT:

## Q = 0.266 x cB x (2g)^{0.5} x H^{1.5}

### where;

*Q = water flow rate, m*^{3}/sec

^{3}/sec

*B = width of the weir at the flowing rate*

*c = discharge coefficient, average 0.62*

*g = gravitational constant, 9.81*

*H = Height of the water over the weir, measured behind the weir edge, m*

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### Here is a real flood caused when water was released from a real weir or dam.

### In 2011 operators of the Wivenhoe Dam in Queensland (above) had to release water to stop the dam collapsing during severe floods. 8,000 properties were flooded.

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### More @ News Limited

### Combine the flow maths for a weir (equation above) with computer graphics and you have a realistic flood film sequence!!!!!!

### Or maybe a really unrealistic but terrrrrrrrifying sequence:

## Aghhhhhhhhhh!!! We’re all gonna die or …. like …