What is Viscous Drag?

A resistance force exerted on a moving object by the fluid is called Viscous drag. The speed at which the viscous drag of an object falling in a viscous fluid is equal to the other forces acting on the object (such as gravity) so that the acceleration of the object is zero. Everyone has seen fluids flow. From pouring a glass of water to watching maple syrup creep towards the edge of a stack of pancakes. Viscosity is the intrinsic resistance of a fluid to flow under an applied force.

Let’s go through a more technical explanation of viscous drag and viscosity by the following diagram:

Let’s go back to the maple syrup again and pretend we are freezing it into thin slabs that are stacked one on top of another.

Diagram 1: Shows these layers and a force, F, applied to the top slab of frozen syrup.

Since the applied force is acting on the top layer, we would expect the top layer to be pushed out right?

The friction between the top layer and the second layer would drag the second layer along. This will continue down through the layers of slabs with each towards the bottom moving less than the layer above it.

Diagram 2: Shows this effect in action.

Fluid friction occurs between fluid layers that are moving relative to each other. This internal resistance to flow is called viscosity or viscous drag or fluid friction. In normal terms, the viscosity of a fluid is described as its “thickness” of the fluid. Thus, water is “thin”, having a lower viscosity, while honey is “thick”, having a higher viscosity. The less viscous the fluid, the greater its ease of deformation or movement.

All real fluids (except superfluids) offer some resistance to shearing and therefore are viscous. Although the term “fluid” includes both the liquid and gas phases, in common usage, “fluid” is often used synonymously with “liquid”. Liquids and gases are called fluids because they can be made to flow or move. In any fluid, the molecules themselves are in constant, random motion, colliding with each other and with the walls of any container. In this article, we will learn in detail about fluid friction, its properties, example and more.