The three‐dimensional time‐dependence velocity of incompressible fluids satisfying linearized incompressible Navier–Stokes equations can often be expressed in terms of a singlehbyv=A∇h+B(lˆ×∇h)+Cl×(l×∇h), where l is a constant vector andA,B,Care scalar operators. ForB,C≠0,curl v≠0.