Fluid Movement

Fluids

Define laminar flow.

A type of fluid flow in which the fluid moves in smooth, uniform layers and the velocity at any particular point remains constant over time.

What is another name for laminar flow?

Streamline flow.

Describe the movement of fluid during laminar flow.

The fluid moves in smooth layers that slide past each other without mixing significantly.

What happens to the velocity of fluid at a particular point during laminar flow?

It remains constant over time.

Does fluid necessarily have the same velocity at every point during laminar flow?

No. The velocity can vary between different positions, but at any particular position it remains constant over time.

What is a streamline?

A line representing laminar fluid flow along which the velocity is constant over time at each point.

What do streamlines show?

The direction in which a fluid is moving.

What does the spacing of streamlines help indicate?

The relative speed of the fluid flow.

Why is laminar flow described as predictable?

The fluid follows smooth streamlines and the velocity at each point remains constant over time.

Describe laminar flow through a pipe.

The fluid flows in parallel layers, with different layers able to move at different speeds.

Where is fluid flow fastest in a pipe during laminar flow?

Near the centre of the pipe.

Where is fluid flow slowest in a pipe during laminar flow?

Near the walls of the pipe.

Why is fluid slower near the walls of a pipe?

Friction between the fluid and the pipe walls slows the fluid down.

Why can layers of fluid move at different speeds in laminar flow?

Frictional forces act between adjacent layers of the fluid.

Define turbulent flow.

Fluid flow in which the velocity at a particular point changes over time, often unpredictably.

Describe the movement of fluid during turbulent flow.

The fluid moves chaotically with irregular changes in speed and direction.

What are eddies?

Swirling circular movements of fluid that form during turbulent flow.

What happens to the velocity at a point during turbulent flow?

Both its magnitude and direction can change over time.

What can cause laminar flow to become turbulent?

Increasing the speed of the fluid.

How does increasing fluid speed affect the likelihood of turbulence?

Higher speeds make turbulent flow more likely.

How can an obstacle affect fluid flow?

It can disrupt smooth streamlines and produce turbulent flow.

How does the shape of an obstacle affect turbulence?

Smooth, curved shapes generally produce less turbulence than sharp or square shapes.

What is streamlining?

Designing an object's shape so that fluid can flow smoothly around it with minimal turbulence.

Why are vehicles streamlined?

To reduce turbulent flow and therefore reduce drag.

What is drag?

A resistive force acting against the motion of an object through a fluid.

How does turbulent flow affect drag?

Turbulent flow generally increases drag.

How does increased drag affect a vehicle?

More force and energy are required to maintain its speed.

Why can turbulent airflow increase a car's fuel consumption?

Increased turbulence increases drag, so the engine must transfer more energy to maintain the car's speed.

How can a wind tunnel be used to investigate airflow?

Smoke can be passed over an object so the pattern of airflow around it can be observed.

What does smooth smoke flow in a wind tunnel indicate?

Laminar flow.

What does irregular or swirling smoke flow indicate?

Turbulent flow.

Why are streamlines useful when designing vehicles?

They show how air flows around the vehicle and help identify regions where turbulence and drag may occur.

What happens to streamlines around a well-designed streamlined car?

They follow the shape of the car smoothly with relatively little turbulence.

How can engineers investigate when laminar flow becomes turbulent?

They can gradually increase the fluid speed and observe when the smooth streamlines become irregular.

How can different object shapes be compared for turbulence?

Place them in the same fluid flow and observe how much they disrupt the streamlines.

Which generally produces less turbulence: a curved obstacle or a square obstacle?

A curved obstacle.

Give an example of laminar flow.

Smooth airflow over a streamlined vehicle at an appropriate speed.

Give an example of turbulent flow.

Water flowing rapidly around an obstacle or through a narrow opening.

What is the main difference between laminar and turbulent flow?

Laminar flow is smooth and predictable, whereas turbulent flow is chaotic and its velocity changes over time.