Double Ducted Fan (DDF) as a novel ducted fan inlet lip separation control device

Ali Akturk, Cengiz Camci

Research output: Chapter in Book/Report/Conference proceedingConference contribution

8 Scopus citations


This paper describes computational study of a novel ducted fan inlet flow conditioning concept that will significantly improve the performance and controllability of VTOL UAVs and many other ducted fan based systems. The new concept that will significantly reduce the inlet lip separation related performance penalties in the edgewise flight zone is named "DOUBLE DUCTED FAN" (DDF). The current concept uses a secondary stationary duct system to control "inlet lip separation" related momentum deficit at the inlet of the fan rotor typically occurring at elevated edgewise flight velocities. DDF is self-adjusting in a wide edgewise flight velocity range and its corrective aerodynamic influence becomes more pronounced with increasing flight velocity due to its inherent design properties. Most axial flow fans are designed for an inlet flow with zero or minimal inlet flow distortion. The DDF concept is proven to be an effective way of dealing with inlet flow distortions occurring near the Up section of a typical axial flow fan rotor system. In this paper, a conventional baseline duct is compared to two dif-ferent double ducted fans named DDF CASE-A and DDF CASE-B via 3D, viscous and turbulent flow computational analysis. Both hover and edgewise flight conditions are considered. Significant relative improvements from DDF CASE-A and DDF CASE-B are in the areas of thrust enhancement, nose-up pitching moment control and recovery of fan through-flow mass flow rate. The results clearly show a major reduction of highly 3D and recirculatory inlet lip separation zone when the DDF concept is implemented. The improved uniformity of fan exit flow and reduced differentials between the leading side and trailing side are other performance enhancing features of the novel concept. The local details of the flow near the entrance area of the leading side of the ducted fan are explained via detailed static pressure distributions obtained from 3D computational analysis including a simulated rotor in the duct.

Original languageEnglish (US)
Title of host publicationInternational Powered Lift Conference 2010
Number of pages23
StatePublished - Dec 1 2010
EventInternational Powered Lift Conference 2010 - Philadelphia, PA, United States
Duration: Oct 5 2010Oct 7 2010

Publication series

NameInternational Powered Lift Conference 2010


OtherInternational Powered Lift Conference 2010
Country/TerritoryUnited States
CityPhiladelphia, PA

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering
  • Control and Systems Engineering


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