Effect of waveform on turbulence transition in pulsatile pipe flow

Pulsatile flow in a straight pipe is a model system for unsteady internal flows in industrial engineering and physiology. In some parameter regimes, the laminar flow is susceptible to helical perturbations, whose transient energy growth scales exponentially with the Reynolds number (Re). We link the transient growth of these perturbations to the instantaneous linear instability of the laminar flow. We exploit this link to study the effect of the waveform on turbulence transition by performing linear stability and transient growth analyses of flows driven with different waveforms. We find a higher-energy growth in flows driven with longer low-velocity phases as well as with steeper deceleration and acceleration phases. Finally, we perform direct numerical simulations and show that, in pulsatile flows, the linear mechanisms responsible for turbulence transition are distinctly different from the nonlinear mechanisms sustaining turbulence. In this dataset we include all the codes used to perform the analysis: from the codes in Matlab to perform transient growth and stability analyses of pulsatile pipe flow, to the Fortran code we use to perform direct numerical simulations. Additionally we include the codes in Matlab we use to fit our data to a physically inspired formula and to initialize the direct numerical simulations. Our strategy is to first postprocess the results of the codes we use, and save them as '.mat' files. We then generate the figures using these '.mat' files. These '.mat' files can be found in this dataset. They are saved in compressed folders, named following the figures of the paper this dataset is linked to.