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文摘 2024-07-23 02:59 意大利

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第2题

热门题型详解

Examples

2.Helicopter Momentum Theory(Actuator Disk)

Answer:

Perhaps the most simple model that we can use to analyse the helicopter power requirements is theactuator disk theory. It considers the helicopter rotor as a thin disk that generates a uniform flow of air through its rotation, and the air is accelerated and decelerated through the disk. The actuator disk model is useful for analysing the overall performance of a helicopter, including its lift, power requirements, and efficiency, but does not capture the complex details of the flow around the rotor, and more advanced models are required for detailed analysis and design. The main assumptions of the actuator disk theory are:

• The details of the flow around the blades are not considered.

• Rotor is considered as an actuator disk (infinite number of infinitesimal small blades) which

adds momentum and energy to the flow.

• Incompressible flow.

• Steady, inviscid(no dissipation), and irrotational flow.

• Flow is 1-D, and uniform through the rotor disk, and in the far wake.(don't need to consider the details in the flow enviroment)

• No swirl in the wake.

• No tip vorticies.

• Well defined slipstream.

• The far stream is at ambient pressure.

The basic principles applied by the actuator disk theory are the mass, momentum, and energy balance equations that we already know must be valid for any material volume.

本题图片内容感谢Marco Fiorito先生的支持

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