ANALYSIS OF DUCTED FAN FLOWS USING AN IMMERSED BOUNDARY METHOD

Open Access
Author:
Karachun, Kateryna
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Philip John Morris, Thesis Advisor
Keywords:
  • Immersed boundary method
  • CARIBOU
Abstract:
The Cartesian immersed boundary code “CARIBOU” has been used for several validation cases and to compute the flow field for a rotating blade and a ducted fan. First, the code is used to calculate the flow solution for a rotating cylinder in a quiescent medium. Second, the code is used to model the Stokes’s second problem of a wall oscillating in its plane. Third, the relationship between the viscous and inviscid versions of the CARIBOU code is established by initiating flow over NACA0009 airfoil. If the grid spacing in the inviscid code is such that, , then the viscous code with that particular Reynolds number yields the same flow solution as the inviscid code. After these tests, the 3D inviscid version of the code is used for the remainder of the project work. The last validation of CARIBOU confirms that if all parameters are initiated identically, stationary and moving coordinate systems in CARIBOU calculate identical flow solutions. Hence, modeling of the flow for a rotating blade used only moving grids in order to keep the number of points as small as possible and to reduce the computational time. A comparison between a rotating blade far from the point of rotation with a translating blade was satisfactory. For both cases, the lift force distribution was similar. Although the inviscid code with a moving grid was used for the rotating blade study, the full analysis of the flow was not carried out due to the unreasonably long time required by the computations. Nevertheless, collected data show that the lift force, for the early stages of flow development, oscillates about the average lift curve, which is also predicted theoretically. For the ducted fan study the fan is represented by a classical pressure jump. Three duct geometries are analyzed with the 2D serial version of the CARIBOU code. The flow computations, for all three ducts, show wake expansion at the exit of the duct, which agrees well with theory. However, the flow analyses show that duct geometry influences the wake development downstream.