**Fluid flow separation: **The fluid flow becomes detached from the surface of the object, and instead takes the forms of eddies and vortices.Courtesy jaganath

### Fluid flow separation explained with mathematics in 1904

In 1904, Ludwig Prandtl, considered the father of modern aerodynamics, derived the exact mathematical conditions for flow separation to occur, but only in two dimensions for steady flows.

### Unsteady fluid flow in three dimensions explained with mathematics in 2008

A century later, George Haller, a visiting professor in the Department of Mechanical Engineering at MIT led a group that explained the mathematics behind unsteady separation in two dimensions. This month, his team reports completing the theory by extending it to three dimensions. Papers on the experiments and theory are being published in the Sept. 25 issue of the Journal of Fluid Mechanics and in the September issue of Physics of Fluids, respectively. Haller's coauthors are Amit Surana, now at United Technologies; MIT student Oliver Grunberg; and Gustaaf Jacobs, now on the faculty at San Diego State University.

### Fluid mechanics theorists are excited

The equation will forever change the face of advanced fluid dynamics and will have a profound impact on many industries, including the aerospace and automotive industries. This quote from Daily Tech Review shows that this breakthough has theorists in fluid mechanics excited;

The new work -- if it survives the extensive peer review that is to come -- will likely go down as the greatest scientific advance of the decade. The research has already survived a strenuous initial round of peer review.

Equally important, this month Thomas Peacock, the Atlantic Richfield Career Development Associate Professor and his colleagues report important experimental work verifying the theory.

"This is the tip of the iceberg, but we've shown that this theory works," Peacock said.

### Fluid dynamics makes a difference

Understanding how surfaces effect how an object flows through a fluid (including air) can make big differences in maximizing performance. Did the new swimsuits make a difference in breaking world records in Olympic swimming competition? How about the surfaces of baseballs, golf balls, and tennis balls? The effects on miles per gallon for autos and airplanes can save millions (billions?) of dollars.

**Source**: MIT News