Fluid Friction Overview
Friction is the force that prevents solid surfaces, fluid layers, and material components from sliding against each other. The force that resists the flow of liquid inside itself or in another medium is referred to as "fluid friction." Because of the less attractive interactions between the molecules in a liquid, they move continually. The liquid friction is affected by the fluid's thickness. It is commonly used in water slides to allow people to glide down smoothly.
What is Friction?
Friction is described as the resistance provided by surfaces in contact as they move past each other. Friction gives the traction required to walk without slipping. In most circumstances, friction is beneficial. They do, however, provide significant resistance to the move. Furthermore, around 20% of automotive engine power is spent overcoming frictional forces in moving components.
Read more about What Is Friction?
What is a Fluid?
A fluid, as opposed to a solid, is a substance that deforms continuously when forced by an outside force. Fluids are commonly associated with water and coffee; however, gases such as air and compounds such as motor oil are also fluids. Viscosity is the trait that distinguishes them from one another. The viscosity of a fluid is a measure of its resistance to flow due to internal friction. This is why honey is far more difficult to extract from a container than ketchup. It also explains why moving in a swimming pool is more difficult than moving on dry land.
What is Fluid Friction?
Fluid friction arises when fluid layers move relative to one another. The term for this internal resistance to flow is viscosity. The viscosity of a fluid is commonly referred to as its "thickness" in ordinary parlance. Because all-natural fluids resist shearing, they are vicious. It is useful to consider an inviscid fluid or an ideal fluid that has no resistance to shearing and is therefore not vicious. It depicts the friction that occurs between the moving layers of a viscous liquid. Viscosity refers to the internal resistance to flow. The higher the ease of movement or frictional force, the less dense the fluid. Fluid friction is commonly employed in water slides to gently encourage or glide down.
What is Drag in Fluid Friction?
Drag is the frictional force exerted by a fluid and is a type of frictional force exerted by a fluid that resists an object's motion through that fluid. Drag force works in the opposite direction of the object's motion.
Examples of Fluid Friction
There are several examples of friction in everyday life. Below are a few examples-
- An aircraft soaring across the sky.
- A person in the water swimming.
- A sailing ship on the water.
- The movement of coffee when stirred.
- The flow of honey when smeared on toast The flow of water when sucked through a straw.
Types of Friction
The following are some of the types of fluid friction-
Dry Friction
It is the resistance to relative lateral motion between two solid surfaces in contact.
Fluid Friction
It is friction that occurs between moving layers of a viscous fluid.
Internal Friction
It is the force that resists motion between the components that make up a solid substance when it deforms.
Lubricated Friction
It is a type of fluid friction in which two solid surfaces are separated by a lubricating fluid.
Skin Friction
It is a component of drag, which is the force that resists fluid motion across the surface of a body.
How does Fluid Friction function?
Friction occurs when two fluid layers move in opposite directions. Viscosity refers to the internal resistance to flow. The term "viscosity" refers to the "thickness" of a fluid. All real fluids are viscous because they resist shearing in some way. The concept of an inviscid fluid, or an ideal fluid with no resistance to shearing and so is not viscous, can be advantageous.
Laws of Fluid Friction
The fluid friction laws are as follows-
First Law
As the area of contact between the surface and the fluid rises, so does the fluid friction.
Second Law
As the velocity gradient of the material grows, so does the fluid friction.
Third Law
A fluid with a greater coefficient of fluid friction, or eta (), has a higher fluid frictional force.
Read more about the Mechanical Properties of Fluids.
Factors Affecting the Fluid Friction
Fluid friction is determined by the following factors-
Nature of the Fluid
The lower the fluid friction, the thinner the fluid, and vice versa. Different fluids provide varying degrees of resistance or viscous drag to the thing moving through them.
For Example: An object traveling in honey experiences far more viscous force than an object traveling in plain water because the density of honey is much greater than the density of water and hence presents greater resistance to the flow of the object.
The Pressure on the Body
Friction and speed are proportional to one another. The fluid friction or drag rises proportionately as the speed increases.
For Example: An airplane traveling at its maximum speed of 1000 km/hr will experience more air frictional force or drag than another similar airplane traveling at 600 km/hr. Similarly, a fast watercraft feels less fluid friction than a slow-moving fish.
The Shape of the Body
Other figures experience greater drag than the body with a streamlined shape that begins and finishes in points like a fish shape. Vehicle designs are meant to minimize surface contact while moving. It contributes significantly to the smoother movement of liquids and gases. The body's form must be in agreement with the medium in which it is flowing or moving, or else it faces significant resistance to movement, making the activity time-consuming. As a result, most bodies have a streamlined form to decrease this. This guarantees that the surface of contact and hence fluid friction are minimized at the beginning and end.
The Speed of the Body
Friction and speed are proportional to one another. The fluid friction or drag rises proportionately as the speed increases.
For Example: An airplane traveling at a maximum speed of 1000 km/hr will experience more air frictional force or drag than another similar airplane traveling at 600 km/hr. Similarly, a fast watercraft feels less fluid friction than a slow-moving fish.
The Surface Area of the Body
The greater the surface area of the body, the greater the fluid friction.
For Example: A horizontally traveling body may cut through liquid more easily than a vertically moving body. Fluid friction increases as the surface area of a body grows, making movement or flow more difficult.
The Temperature
Because the fluid friction of gas is precisely proportional to the square root of the absolute temperature, the fluid friction of all gases increases as the temperature rises. The fluid friction of liquids and other things increases proportionately as the temperature rises.
The Viscosity of Fluid
The viscosity of a fluid is an important factor in influencing the velocity of an object passing through it. The more viscous the fluid, the denser it is, and hence the mobility of any substance contained inside it is restricted or encounters resistance to motion. The more viscous the drag, the denser the liquid.
Read more about the Difference Between Solid, Liquid and Gas.
Disadvantages of Fluid Friction
The disadvantages of fluid friction-
- The major drawbacks of fluid friction are that it slows things moving through fluids.
- It makes it more difficult to accelerate.
- When things move through fluids, they expend some energy overcoming fluid friction. This reduces their effectiveness.
- When a car is on the road, part of its energy is expended or lost in overcoming the friction of the air that resists its motion. When a fast boat speeds over water, part of its energy is used or lost in overcoming water friction.
- A streamlined form is one that has relatively minimal resistance to the flow of air or water around it.
- A streamlined form resembles a narrow wedge or triangular item lying on its base and gradually rising upwards.
Points to Remember
- Fluid friction is the force that resists the movement of molecules inside a fluid and the external medium with which it comes into contact.
- Fluid friction is affected by the shape, size, speed, and nature of the fluid or object.
- Fluid friction arises owing to two conditions: internal movement of molecules and fluid contact with the external medium.
- Fluid friction, skin friction, lubricant friction, dry friction, and internal friction are the five forms of friction.