The University of Southampton
University of Southampton Institutional Repository

An experimental and a theoretical investigation of rotor pitch damping using a model rotor

An experimental and a theoretical investigation of rotor pitch damping using a model rotor
An experimental and a theoretical investigation of rotor pitch damping using a model rotor

An experimental investigation was conducted to study rotor pitch damping in hover, axial flight (climb speed to tip speed ratios: 0 - 0.549), and low speed forward flight (advance ratios: 0.05 - 0.088), for a variation in rotor thrust coefficient 0.001 - 0.013, and for the range of flapping frequency ratios squared 1.0 - 1.11. The tests were conducted at the following oscillation ratio frequencies, (frequency of oscillation divided by rotor angular speed), 0.186 for hover and axial flight and 0.1068 for low speed forward flight and in hover for the case of flapping frequency equal to unity. The nature of the damping of the rig was investigated since it was found that frictional effects contaminated the estimates of the rotor aerodynamic damping. To do this a parameter estimation method, based on a nonlinear minimisation procedure, was developed that does not require a large amount of data to identify the viscous and frictional damping coefficients from the free response of the rotor. A theoretical model for low frequency coupled rotor body dynamics was developed and the effects of rotor and inflow degrees of freedom on rotor damping were investigated. Results indicate that both rotor and inflow degrees of freedom are required in the mathematical description of low frequency coupled rotor-body dynamics for the adequate estimation of rotor damping. The dynamic inflow degrees of freedom were described by using momentum theory and by assuming a nonuniform distribution for the steady induced velocity given by a Glauert wake. A blade flexibility study was conducted to define the flapping frequency for blade-linear spring configurations producing both time invariant and time dependent boundary conditions at the spring location. Comparison of theoretical damping estimates with the experimental data in hover and axial flight show that at oscillation ratio frequency 0.186, the no-inflow model is in reasonable agreement with the experimental data and that the inclusion of dynamic inflow theory produces no improvement in the experimental data correlation. In hover and in low speed forward flight at oscillation frequency ratio 0.1068, the inclusion of dynamic inflow theory provides an improvement in the experimental data correlation indicating that for these conditions inflow degrees of freedom are also required for the adequate prediction of rotor pitch damping.

University of Southampton
Sotiriou, Constantinos Panteli
Sotiriou, Constantinos Panteli

Sotiriou, Constantinos Panteli (1990) An experimental and a theoretical investigation of rotor pitch damping using a model rotor. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

An experimental investigation was conducted to study rotor pitch damping in hover, axial flight (climb speed to tip speed ratios: 0 - 0.549), and low speed forward flight (advance ratios: 0.05 - 0.088), for a variation in rotor thrust coefficient 0.001 - 0.013, and for the range of flapping frequency ratios squared 1.0 - 1.11. The tests were conducted at the following oscillation ratio frequencies, (frequency of oscillation divided by rotor angular speed), 0.186 for hover and axial flight and 0.1068 for low speed forward flight and in hover for the case of flapping frequency equal to unity. The nature of the damping of the rig was investigated since it was found that frictional effects contaminated the estimates of the rotor aerodynamic damping. To do this a parameter estimation method, based on a nonlinear minimisation procedure, was developed that does not require a large amount of data to identify the viscous and frictional damping coefficients from the free response of the rotor. A theoretical model for low frequency coupled rotor body dynamics was developed and the effects of rotor and inflow degrees of freedom on rotor damping were investigated. Results indicate that both rotor and inflow degrees of freedom are required in the mathematical description of low frequency coupled rotor-body dynamics for the adequate estimation of rotor damping. The dynamic inflow degrees of freedom were described by using momentum theory and by assuming a nonuniform distribution for the steady induced velocity given by a Glauert wake. A blade flexibility study was conducted to define the flapping frequency for blade-linear spring configurations producing both time invariant and time dependent boundary conditions at the spring location. Comparison of theoretical damping estimates with the experimental data in hover and axial flight show that at oscillation ratio frequency 0.186, the no-inflow model is in reasonable agreement with the experimental data and that the inclusion of dynamic inflow theory produces no improvement in the experimental data correlation. In hover and in low speed forward flight at oscillation frequency ratio 0.1068, the inclusion of dynamic inflow theory provides an improvement in the experimental data correlation indicating that for these conditions inflow degrees of freedom are also required for the adequate prediction of rotor pitch damping.

This record has no associated files available for download.

More information

Published date: 1990

Identifiers

Local EPrints ID: 461810
URI: http://eprints.soton.ac.uk/id/eprint/461810
PURE UUID: 8066e105-acbc-4534-b837-d96a75477b29

Catalogue record

Date deposited: 04 Jul 2022 18:55
Last modified: 04 Jul 2022 18:55

Export record

Contributors

Author: Constantinos Panteli Sotiriou

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×