# Test the accuracy of using the radial center point velocity to provide the characteristic velocity. For the

## Question:

Test the accuracy of using the radial center point velocity to provide the characteristic velocity. For the single rotor with two blades case, with C = 1.0m, divide the blade into four radial elements. Use the velocity at the radial center point of each element as the characteristic velocity for that element.

Determine if a human powered helicopter is feasible by calculating the required power.

The helicopter has a total mass of 100 kg. The rotor blades a lifting extending from radius r = 1m to r = 11 m. assume a lift coefficient of C _{L } ^{ } = 1.0

The lift force is,

FL = ½ C _{Lp }.AV _{2 },

Where the plan area of the lifting surface A = LC, With L the length of the lifting surface (10m) and C the chord, and the density is p = 1.225 kg/m ^{3 }. V is the velocity of the flow over the lifting surface. As the blade is rotating the velocity will vary along the lifting surface, so the velocity at the Centre point, in radial direction, of the lifting surface, as the characteristic velocity.

The drag coefficient is

C _{D } = 0.01 + C _{L } / πar

Where ar = L /c is the aspect ratio of the lifting surface.

**Related Book For**

## Vector Mechanics for Engineers Statics and Dynamics

ISBN: 978-0073212227

8th Edition

Authors: Ferdinand Beer, E. Russell Johnston, Jr., Elliot Eisenberg, William Clausen, David Mazurek, Phillip Cornwell