Analysis of Possible Risks in Aviation Safety Issues Associated with the Massive Introduction of Unmanned Aerial Systems

The flow around three staggered square cylinders at two different triangular arrangements has been numerically analyzed in the present work. The calculations are carried out for several values of Reynolds numbers ranging from 1 to 110. Three different states of flow are found in this study by systematically varying Re. The critical Reynolds number is determined for both two arrangements. It is clear that the point of bifurcation is strongly influenced by the type of the type of the triangular arrangement because both arrangements generate a large reduction in the value of the critical Reynolds number. The unsteady periodic wake is characterized by the Strouhal number, which varies with the Reynolds number and also the arrangement of the three cylinders. Hence, the values of vortex shedding frequencies are calculated for both triangular arrangements. Furthermore, the drag and lift coefficients of three staggered squares cylinders in different triangular arrangements are determined.

Keywords:Staggered square cylinders; Flow regimes; Triangular arrangement; Strouhal number; Numerical simulation; Critical Reynolds number; Lift and drag coefficients

Nomenclature:

Re - Reynolds number

l - channel width

h - channel height

(u, v) - velocity components, m s-1

x, y - dimensionless coordinates

St - Strouhal number

CD - drag coefficient

CL - lift coefficient

P - dimensionless pressure

Φ - generic variable

Greek symbols

ρ - density of fluid, kg m-3

ν - kinematic viscosity, m2s-1

Subscripts

Max, Min - maximum, minimum

c - Critical