A molecular dynamics study on obstructed flow around single and two paratactic circular cylinders

Obstructed flow around single and two paratactic circular cylinders were investigated with two-dimensional molecular dynamics simulation (MDS) methods in the view of discrete particles. The transient and time-averaged profiles of streamline and density were obtained in order to analyze the characteristics of the wake flow. For single cylinder case, different flow patterns, i.e. Stokes flow, steady vortices flow, periodic vortices-shedding flow with the Kármán vortex street and supersonic flow, were divided based on Reynolds number (Re), 4<Re<12, 12<Re<20, 20<Re<62 and Re>62 respectively. For two paratactic cylinders case, different flow patterns, namely periodic vortices-shedding flow, periodic vortices-shedding flow with gap-flow, bistable flow and synchronized vortex-shedding flow, were observed with different center-to-center pitch ratios (D*/d*), D*/d*=1.0, 1.0< D*/d*<1.1, 1.1<D*/ d*<1.8 and D*/d*>1.8 respectively. The results show qualitative or quantitative agreement with those obtained from experiments and other MDS and indicate that most macroscopic obstructed flow patterns still exist even in nanoscale.