Fluid friction is the frictional force experienced by liquids or any object moving relatively with a liquid. It is generally weaker than dry friction. It is also known as fluid inertia, fluid drag, or viscous resistance. In this article, we look at the definition, examples, and factors affecting fluid friction.
Fluid friction definition
The frictional force exerted by fluids that resist motion within the fluid itself or resist the motion of any body moving relative to the fluid is called fluid friction. For example, When a speed boat moves in water, its speed is reduced due to fluid resistance.
Image by Military_Material from Pixabay
Example: We say honey is thicker than water, why? Because honey moves slower compared to water. It is because the molecules in any fluid face internal friction called viscosity, and this is what we call thickness or resistance to flow. Hence, the molecules in honey move at a slower pace as compared to water and eventually, honey seems thicker than water.
Synonyms of fluid friction
- Viscous resistance
- Frictional force in fluid
- Fluidic friction
- Force of fluid friction
- Drag in fluid
- Fluid inertia
Fluid friction examples
- Resistance is experienced by a swimmer in the water.
- Lubrication can reduce friction between two solid surfaces due to fluidic friction. Lubrication can be seen in door hinges, machine parts, etc. So, lubrication friction can be considered as an example of fluid friction.
- The friction of water in the river with the riverbed is an important factor in flooding.
- Water moving in pipelines also experiences friction with the pipe surface. This is specially studied as pipe friction.
- The flow of honey from the bottle is slow due to the internal friction experienced by the molecules.
You may read this article, “50 examples of friction in our daily life” for more examples of fluid friction.
What substances can be considered as fluid?
A substance that flows and takes the shape of a container can be considered a fluid. All liquids and gases can be considered fluids.
Is air resistance the same as fluid friction?
You might also find that gases are also sometimes included as fluids. Resistance exerted by air is studied separately as air resistance or air friction, it can be considered as a type of fluid friction.
Laws of fluid friction/factors affecting fluid friction
1)Design of the object: Objects with a streamlined design will help in the reduction of friction as the fluid molecules can easily move across the body of the object. Fishes have a streamlined body to assist them in swimming across the water. Ships have used this streamlined design for ages, mimicking nature.
2) Speed of the object: More the speed more the friction. Consider a speedboat, it experiences more force of resistance than a normal slow-moving boat. That is why the body of speed boats is made of strong materials to withstand such large resistive forces. In dry friction, the friction is not related to velocity but in fluid or air resistance, the friction is directly proportional to the velocity of the object.
3) Size of the object: The larger the object, the greater the resistive force. A blue whale will experience more friction compared to a man swimming in water [ship pic]
4) Nature of fluid: Fluids with high inner resistance show high fluid friction. Watch this animation to understand. We say honey is thicker than water, so it is difficult for objects to flow through honey as compared to water. This is the effect of fluid resistance.
You may read this article to learn more about factors affecting friction in general.
How does fluid friction occur?
In fluids, the molecules are not as closely faced as in the case of solids. So, the molecules can easily move against each other. Hence the friction offered by fluids is generally less than solids.
Quiz
What is lubrication, and how is it related to fluid friction?
Lubrication is the process of reducing friction between two surfaces by adding a material called lubricant. Lubricants are always slippery, or greasy, as we call them.
Lubricant acts as a layer between 2 sliding surfaces and converts the friction into fluidic friction. Fluidic friction is generally less as compared to friction in solids.
Examples of lubricants: any kind of oil, or grease.
What is pipe friction?
When water or any fluid passes through pipes there is friction develops between the liquid and the surface of the pipes which reduces the pressure of water. It is a problem that engineers come across while designing pipe systems. It is also called head loss.
What is drag in fluids?
Drag is a term used in fluid dynamics, which is a synonym for fluid friction. It is generally used in the study of the speed of an object across a fluid. Drag force is directly proportional to velocity and acts in the opposite direction to motion.
What is skin friction?
Skin friction is a type of fluid friction. This term is used while studying the resistance to motion when a fluid moves across the surfaces of objects. Example: movement of water across a pipe or canal.
What is the difference between viscosity and fluid friction?
Viscosity is usually used to refer to the internal resistive forces between the movement of molecules in a fluid, and fluid friction is used to refer to friction where there is resistance to relative motion with respect to the fluid.
How can we reduce fluid friction?
- Reduce the viscosity of the fluid
- Make the shape of the object streamlined
- Increase the speed of the object
- Reduce the surface area of exposure
Can we reduce fluid friction to zero?
This is a case where, ideally, no molecules should exist. Outer space might be a good example of this case.
See Also:
- Examples of fluid friction
- What is a frictional force?
- Factors affecting friction
- Applications of friction
- How can we decrease friction? What are the ways of doing it?
- How can we increase friction?
- What is rolling friction?
- What is static friction?
- 50 Examples of friction in our daily lives
- Friction is a necessary evil
