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An empirical model for transition to turbulence in oscillatory flows in straight tubes is proposed. The model, fashioned after a correlation for transition of a boundary layer on a flat plate, yields the laminar flow momentum thickness Reynolds number that must be met before transition to turbulence will occur. The transition point is located by comparing this to the actual momentum thickness Reynolds number. Since in one-dimensional computation, as is typically employed in engine simulation codes, the momentum thickness Reynolds number cannot be computed, a scheme is proposed for estimating it in terms of the position within the cycle, the maximum value of the diameter Reynolds number within the cycle, Remax, and the dimensionless frequency, Valensi number, Va. Another parameter required in the calculation of the point of transition is the turbulence intensity value within the core flow and external to the boundary layer.