In-pipe Pipe flow 2 Reynolds number 2 Basic building block 1 Coherent state 1 Coherent structure 1 Diameter ratio 1 Induced transitions 1 Large diameter 1 Moderate Reynolds numbers 1 Neutrally buoyant suspension 1 Occurrence probability 1 Onset of turbulence 1 Organisational 1 Particle-laden 1 Perturbation amplitude 1 Pipe diameter 1 Poisson distribution 1 Reynold number 1 Stereo image processing 1 Stereoscopic particle image velocimetry 1 Suspended particles 1 Suspensions (fluids) 1 Turbulence 1 Turbulent flow 1 Turbulent pipe flow 1 Velocity measurement 1