A Computer Model for the Evaluation of Helicopter Fire Control Systems

Elwell, John; Mathewson, G. Frank

doi:10.4050/jahs.15.3

Cited by 24 publications

(1 citation statement)

References 5 publications

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“…As the circulation varies from one blade element to the next, trailing vortices spring from the blade-element boundaries according to the vortex theorems stated by Helmholtz [26]. The trailing vortices follow approximately a helical trajectory, which can be prescribed [27] or calculated freely [28,29]. The interaction between blade elements is represented by the velocities induced by the bound and trailing vortices, which are calculated using the law of Biot-Savart [30,31].…”

Section: Methods Invalid Outside Available Propeller Spectrummentioning

confidence: 99%

Toward a Scalable Propeller Performance Map

Giannakakis

Laskaridis

Nikolaidis

et al. 2015

Journal of Propulsion and Power

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Propeller performance is traditionally represented by a performance map that gives propeller efficiency as a function of the flight Mach number, the power coefficient C P , and the advance ratio J. This work aims to demonstrate how this map changes when the design C P and J change and to propose a novel map format that is able to capture the performance of different propeller designs. For this purpose, the propeller performance is simulated using a propeller lifting-line method validated for the SR3 propfan. Subsequently, the propeller model is used within a sequential quadratic programming framework to optimize the blade twist and chord distribution for different sets of design C P and J. A complete propeller performance map is then generated for each one of the optimized designs. The results demonstrate that all the investigated propellers can be modeled by a common map, which determines separately the ideal efficiency and the viscous losses. The ideal efficiency is given in the traditional format of η i fC P ;J, whereas the viscous losses are represented as a function of the relative variables C P ∕C Pdes and J∕J des .

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Section: Methods Invalid Outside Available Propeller Spectrummentioning

confidence: 99%

Toward a Scalable Propeller Performance Map

Giannakakis

Laskaridis

Nikolaidis

et al. 2015

Journal of Propulsion and Power

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Rotor in Vertical Flight: Momentum Theory and Wake Analysis

Seddon

Newman

2011

Basic Helicopter Aerodynamics

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Challenges in modelling the unsteady aerodynamics of wind turbines

2002

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Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately. This article emphasizes two key areas that need continued serious consideration for wind turbine predictive analyses: the modelling of the rotor wake and the modelling of the unsteady aerodynamics of the blade sections. Issues discussed herein include the modelling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the non-linear intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and ambiguities can also arise in how these models should be properly applied. A challenge for analysts of the future is to use complementary experimental measurements and modelling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.The aerodynamic modelling of wind turbines has spanned the gamut from parsimonious models based on simple momentum and blade element momentum (BEM) theories, through 'engineering models' based on blade element and dynamic inflow or vortex wake methods, to computational fluid dynamics (CFD) methods that solve numerically the Euler or Navier-Stokes equations. In this article, the focus will be on the use of engineering methods, which represent a majority of the methods currently being used to design wind turbines. While the other approaches using BEM theory, and perhaps even CFD, can play a useful role in the design * Only for k < O 0Ð01 can the flow be assumed steady or quasi-steady.

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A Computer Model for the Evaluation of Helicopter Fire Control Systems

Cited by 24 publications

References 5 publications

Toward a Scalable Propeller Performance Map

Toward a Scalable Propeller Performance Map

Rotor in Vertical Flight: Momentum Theory and Wake Analysis

Challenges in modelling the unsteady aerodynamics of wind turbines

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