Abstract
The aerodynamics of contra-rotating propellers is a complex three-dimensional problem of an unsteady flow, which is often approached by assuming numerous simplifications. Presented computational model combines a 3D panel method with a force-free vortex wake and a two-dimensional two-equation boundary layer model in an attempt to capture all the main contributing elements of the flow physics. An emphasis is placed on the interaction of the viscous boundary layer region with the inviscid region and the development of a portable method of their coupling. The kinematics of a force-free vortex wake is supplemented with a vortex aging due to a diffusion. Extra attention is paid to the process of the blade passing through the wake of another blade. To demonstrate the ability of the numerical model, several test cases are presented, illustrating the reaction of the system to various operational conditions.
Highlights
Numerical tools based on inviscid flow methods developed for specific types of open rotor aerodynamics are among the top choices for design and analysis purposes
The numerical model described in this paper has been developed for analysis of contra-rotating propellers but it is general enough to be applicable to a wide range of engineering problems of the external flow past lifting bodies, such as wing configurations, vertical and horizontal axis wind turbines and single propellers
Contra-rotating propellers are gaining new attention due to emerging fields of application in various unmanned aerial vehicles and for example, as a means of reducing an airliners turboprop engine fuel consumption. Existing numerical models such as that of Leishman and Ananthan [1] or those described in the review by Coleman [2], often approach the problem using the blade element momentum theory with Prandtl tip correction, or a lifting surface model with a vortex wake, neglecting the boundary layer and propeller thickness
Summary
Numerical tools based on inviscid flow methods developed for specific types of open rotor aerodynamics are among the top choices for design and analysis purposes. Contra-rotating propellers are gaining new attention due to emerging fields of application in various unmanned aerial vehicles and for example, as a means of reducing an airliners turboprop engine fuel consumption Existing numerical models such as that of Leishman and Ananthan [1] or those described in the review by Coleman [2], often approach the problem using the blade element momentum theory with Prandtl tip correction, or a lifting surface model with a vortex wake, neglecting the boundary layer and propeller thickness. Chosen elementary solutions used in the presented method are: flat constant source panels and quadrilateral vortex rings. The surface of each blade is discretized by a structured grid of quadrilateral panels containing both constant source and vortex ring elementary solutions. The solution to the system of N linear equations (eq 3) has to be found, where N is the number of collocation points in the domain and the number of unknown circulation values
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