analysis of flow over fixed wing micro air vehicle (mav ... web viewt. j. mueller,...

Visit techris.in/iwy for full explanation of this project Idea

Visit techris.in/iwy for full explanation of this project

Chapter 1

Analysis of flow over fixed wing micro

air vehicle (MAV) with bio inspired

winglets

Micro Air Vehicle(MAV), as shown in fig 1.1, is a tiny flying vehicle which generally flies in low Reynolds

number regime (Fig 1.2). The typical dimension, payload, endurance and the airspeed for the MAV is

defined by the The American Defense Advanced Research Projects Agency (DARPA)[1] and they are

150mm, 20 to 60 minutes and 15 to 20 m/s respectively.

The dimensional constraint forces the MAV to use a lower aspect ratio which will be usually in the range

of 1. This low aspect ratio can be advantageous since it can offer higher stall angles compared to

conventional large aspect ratio wings but also offers higher induced drag due to the wing tip vortex.

The major challenge for the designer of a MAV is to have a highest L/D ratio possible. This can be done

by reducing te drag. Since the induced drag is a major portion of the frag, by reducing the induced drag,

the L/D ratio can be increased.

The induced drag is usually reduced in wings by using winglets. Spiroid, flat-plate and blended winglets

are some of the winglets used for reducing induced drag. The size and position of the winglet plays

important role in reducing the drag.

Birds use tiny feathers at the tip of their wing (Fig 1.3) to reduce the induced drag. This inspires us to

use similar winglets on MAV to achieve the same as shown in fig 1.4.

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The dimensions of both MAV and winglet, and the operational regime will be decided based on literature

review.

1.1 Flow field variables to be analyzed

• Pressure field

• Velocity field

• Lift, drag and pitching moment

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1.2 Images

Figure 1.1: Picture of typical fixed wing MAV, from [1]

Figure 1.2: Reynolds number range of MAV, from [2]

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Figure 1.3: Tiny feathers acting like winglets in birds, from pixabay.com

Figure 1.4: Concept of MAV with winglet

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References

[1] J. M. McMichael and M. S. Francis, “Micro air vehicles-toward a new dimension in flight,” DARPA

document, 1997.

[2] T. J. Mueller, “Aerodynamic measurements at low raynolds numbers for fixed wing micro-air

vehicles,” tech. rep., DTIC Document, 2000.

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