👉 A permanent fluid, also known as a viscous fluid or non-Newtonian fluid, is a substance that maintains its shape when applied with force but flows under the influence of gravity or other external forces. Unlike Newtonian fluids, which have a constant viscosity regardless of applied stress, permanent fluids exhibit varying viscosity depending on the force applied. This property means they can behave like a solid under low stress and like a liquid under high stress, as seen in materials like ketchup, blood, and certain gels. The permanent nature of these fluids is due to their internal structure, which can be broken or reformed when stress is applied, allowing them to retain their shape until the stress is removed.
