Bluff Body and Pressure Drag

Bluff Body: A bluff body is a three-dimensional object that has a blunt shape and has a high drag coefficient. Examples of bluff bodies are cylinders, spheres, cubes, and other shapes that have a large cross-sectional area perpendicular to the flow direction.

Pressure Drag: Pressure drag is the force that opposes the motion of a body through a fluid due to the pressure difference between the front and rear of the body. It is caused by the separation of the fluid flow from the surface of the body, resulting in a low-pressure region behind the body.

Explanation

Bluff bodies have a high drag coefficient because they create a large wake behind them, which creates a low-pressure region. The pressure difference between the front and rear of the body causes the pressure drag. As the cross-sectional area of the body increases, the pressure drag also increases. The friction drag is also present in bluff bodies, but it is relatively small compared to the pressure drag.

Bluff bodies have a higher pressure drag coefficient than streamlined bodies, which have a low drag coefficient due to their streamlined shape, and the fluid can flow smoothly over them without any separation. In other words, the pressure drag of a bluff body is more than the friction drag.

Conclusion

In conclusion, the correct answer to the question is option B) more. Bluff bodies have a high drag coefficient due to their shape, resulting in a larger wake behind them, creating a low-pressure region. As a result, the pressure drag is higher than the friction drag.