Empirical correlations in B-C transition model were calibrated with experimental values of zero pressure gradient plates. Calibrated B-C transition model predicts reasonably transition positions with low inlet turbulence intensity. However, due to limitations of RANS method, B-C transition model’s accuracy diminishes for massively separated flows. A turbulence closure named transitional Delayed Detached-Eddy Simulation (BC-DDES) method is proposed which combines traditional SA-DDES method and B-C transition model. This method has the potential for accurately capturing massively separated boundary layers in transitional Reynolds number range. Numerical simulation of three-dimensional S-K flat plate shows that BC-DDES method obtains transition prediction consistent with baseline transition model. Comparisons are evaluated on circular cylinder in crossflow. It shows that pressure distribution and drag coefficient of cylinder calculated with BC-DDES method agree well with experimental data, with less computational costs than tHRLES method.