The tripole vortex: Experimental evidence and explicit solutions

Based on experimental evidence, explicit vorticity-distributed solutions to the Euler equations in two dimensions are constructed describing the tripole vortex. The vortex form and the solution outside the region of nonzero vorticity are derived analytically, while the interior is solved numerically. The continuous-vorticity solution reproduces the main features of the tripoles observed in laboratory experiments and numerical simulations-their shape, flow pattern, and the form of the nonlinear vorticity vs streamfunction relation. The approach followed in the construction of a tripole proves to be beneficial in the search for higher-order multipoles, an example being a smooth quadrupole solution.