A method for regulating fluid flow through a gas turbine engine is provided. The method includes coupling an outer fairing to a radially outer duct wall and coupling an inner fairing to a radially inner duct wall. An annular valve is coupled between the radially outer and the radially inner duct walls such that an outer bypass flow area is at least partially defined between the annular valve and the outer fairing, and such that an inner bypass flow area is at least partially defined between the annular valve and the inner fairing. The annular valve is selectively positioned between a first operational position and a second operational position, such that at least one of the outer bypass and the inner bypass flow areas is varied during a transition from a first turbine operation to a second turbine operation.