IMPLEMENTATION AND VALIDATION OF A NON-CUT CELL IMMERSED BOUNDARY METHOD FOR USE IN ICING SMIULATIONS

Open Access
Author:
Sarofeen, Christian
Graduate Program:
Mechanical Engineering
Degree:
Master of Engineering
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Eric Patterson, Thesis Advisor
  • Dr Eric Paterson, Thesis Advisor
  • Philip John Morris, Thesis Advisor
Keywords:
  • Simulation
  • Computational
  • IBM
  • Immersed Boundary Method
  • CFD
  • Icing
  • Rotorcraft
Abstract:
This thesis describes the development of a computational fluid dynamic method for the purpose of modeling changing aircraft geometry due to icing. As a computational simulation predicts the ice shape growth of an aircraft, the change in geometry has to be taken into consideration dynamically during the simulation process. A non-cut cell Immersed Boundary Method (IBM) approach is used to represent the ice on the surface of an aircraft during the icing simulation process. The IBM allows computational cells to be changed from a normal field cell in the computational domain to a cell that will enforce a no-slip boundary condition at its nodes. This process begins with the identification of the body of interest relative to the computational grid. The nodes that are in the computational domain are also inside the body of interest are marked with an integer value signifying that they are immersed nodes. The governing equations are modified so that throughout the solution process the independent variables of the nodes at the interface of the immersed nodes and the rest of the computational domain are set to a solid wall boundary condition values (this interface is aligned with the surface of the body being represented). This is done by enforcing a zero velocity to immersed nodes relative to the grid motion and by enforcing the independent turbulence variables to their boundary condition values. This method has been implemented in NASA's finite volume, node centered computational code (FUN3D). The formulation and implementation of this method is explained in detail including the governing equations, the implementation, and the programs used. The IBM capability is tested for two-dimensional airfoils including clean airfoils, an iced airfoil, and an airfoil in harmonic pitching motion about its quarter chord. For these simulations velocity contours, pressure distributions, coefficients of lift, coefficients of drag, and coefficients of pitching moment about the airfoil's quarter chord are computed and used for comparison against experimental results and the results from FUN3D's normal solution process. The results of the IBM simulations show that the accuracy of the IBM compares satisfactorily with the experimental results and the results from FUN3D's normal solution process.