A team of MIT engineers claims that they have found an easy equation that can calculate the amount of force needed to push an “intruder” or shovel through sand. They also discovered that this concept that is technically known as Resistive Force Theory can produce several useful equations for other cohesive substances like mud and others. Apart from calculating the elbow grease that is required to carve the beachside moat, the researchers claim that this equation is capable of optimizing the driving of vehicles over sand, gravel, soil, and other rough materials. The application can go as high as up to the rovers that are being used for navigation in the Martian landscapes. It will also help in understanding the manner in which animals like worms and lizards borrow under the earth’s surface.
Figure 1: Square-shaped Intruder
Resistive Force Theory (RTF) is not a new thing for engineering professionals, it was introduced somewhere in 1950s to describe the manner in which objects move through viscous fluids like honey and oil. However, it was until several years later when scientists decided to apply this idea to other granular materials like sand. Ken Kamrin, an associate professor for mechanical engineering at MIT, quotes that scientists from all over the world refer to RFT as a magical phenomenon because nobody has been successful in predicting how this theory that was initially founded for fluids became successful in finding the solutions for granular things like sand.
As per a recently published paper, Karin and his associates have been successful in solving this mystery to some extent. They say they have discovered a mechanical explanation as for how the equation works in favor of granular materials. As per them, it is rational for scientists to rely on the RFT for estimating the correct amount of force needed for sand, gels, and mud. Karin further adds, “People observed this concept worked but didn’t know why, and that’s really shaky ground for scientists — is it just a coincidence? Now we can explain the backbone of the granular resistive force theory, so you can close your eyes and have confidence that it’s going to work. It gives us some fleeting hope that we might be able to design something that more efficiently moves, swims, or dives over sand.”
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