Analysis of Measured Helicopter Rotor Pressure Distributions
Abstract
The purpose of this research was to determine a rational basis for interpretation of the aerodynamic force characteristics of helicopter rotors. The approach consisted of three elements. The first was the parallel development of series expressions for: flight measurements of rotor differential pressure distribution; corresponding two-dimensional wind tunnel pressure distributions for the same airfoil geometry; and theoretical pressure distributions for the two-dimensional airfoil. Second, there was a comparison between pressure differential distribution components determined from flight measurements and pressure distribution components computed by an approximate, unsteady, three- dimensional theory developed previously at CAL for the U. S. Army. Third, the sensitivity of the airfoil drag characteristics to variations in the pressure differential distributions was investigated on the basis of two-dimensional steady boundary layer theory. The fundamental technique employed was a curve- fitting process based on an expansion of the pressure distributions in terms of Glauert coefficients. Glauert coefficients derived from rotor pressure differentials measured in flight had many of the characteristics of the Glauert coefficients derived from measured two-dimensional pressure distributions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1970
- Accession Number
- AD0877463
Entities
People
- Chee Tung
- Frank A. Duwaldt
Organizations
- Calspan