Physics · Study 023
Wind Tunnel
Streamlines of ideal flow part around a cylinder, speed up over its shoulders and close behind it. Drag the cylinder through the tunnel.
What you're looking at
Seven hundred tracer particles ride a velocity field given by a closed formula: uniform flow plus a doublet, which together describe frictionless fluid passing a circular obstacle. Lines crowd together above and below the cylinder, which is where the fluid moves fastest.
The idea behind it
This ideal solution famously predicts zero drag, a result known as d'Alembert's paradox. Real air has viscosity, which separates the flow behind the body into a turbulent wake. The neat symmetric picture is still the starting point for every aerodynamics course.
Try this
Move the pointer to reposition the cylinder and watch the streamlines re-form around it.
