Dilatant refers to a type of non-Newtonian fluid whose viscosity increases with the rate of shear strain. This means that as you apply more stress or force to the fluid, it becomes thicker and more resistant to flow. This behavior contrasts with other fluids, like Newtonian fluids, which maintain a constant viscosity regardless of the applied stress.
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Dilatant fluids often exhibit a behavior where they become more solid-like under stress, making them useful in applications like body armor or protective gear.
Common examples of dilatant fluids include cornstarch mixed with water (often called oobleck) and certain types of silicone.
The phenomenon of dilatancy can be attributed to the interaction between particles in the fluid, which can become jammed together under stress.
Dilatant behavior is typically observed in suspensions or colloids, where solid particles are dispersed in a liquid medium.
Understanding dilatant behavior is essential for various industrial processes, particularly in the food and cosmetic industries where texture and flow properties are crucial.
Review Questions
How does the viscosity of dilatant fluids change with varying shear rates, and what practical implications does this have?
Dilatant fluids exhibit an increase in viscosity when subjected to higher shear rates. This means that the harder you stir or push the fluid, the thicker it becomes. This property has practical implications in various fields such as manufacturing and materials science, where controlling fluid viscosity can affect processes like mixing and product stability.
Compare and contrast dilatant fluids with Bingham plastics in terms of their flow behavior under stress.
Dilatant fluids become more viscous with increased shear stress, while Bingham plastics behave as solids until a specific yield stress is reached. After overcoming this yield stress, Bingham plastics flow like a viscous fluid. The key difference lies in their response to applied stress: dilatants thicken under stress whereas Bingham plastics require an initial force to begin flowing.
Evaluate the significance of dilatancy in industrial applications and how it influences product formulation.
Dilatancy plays a crucial role in various industrial applications, especially in sectors like food production, cosmetics, and pharmaceuticals. The ability of a product to thicken under stress can enhance its usability and performance. For instance, cosmetics may require dilatant properties for better application consistency while ensuring stability during storage. Understanding how dilatant behavior affects flow characteristics allows manufacturers to tailor products to meet specific consumer needs effectively.
Related terms
Non-Newtonian Fluid: A fluid whose viscosity changes with the applied shear rate or stress, unlike Newtonian fluids which have a constant viscosity.
The force per unit area applied parallel to the surface of a material, which causes deformation and is crucial in determining fluid behavior.
Bingham Plastic: A type of non-Newtonian fluid that behaves as a solid until a certain yield stress is applied, after which it flows like a viscous fluid.