<P> Vorticity in two dimensional flows in the r − θ (\ displaystyle r - \ theta) plane can be expressed as--</P> <Dl> <Dd> ω _̄ = ω z k ^ (\ displaystyle (\ bar (\ boldsymbol (\ omega))) = \ omega _ (z) (\ hat (\ boldsymbol (k)))) </Dd> </Dl> <Dd> ω _̄ = ω z k ^ (\ displaystyle (\ bar (\ boldsymbol (\ omega))) = \ omega _ (z) (\ hat (\ boldsymbol (k)))) </Dd> <Dl> <Dd> ω z = 1 r ∂ ∂ r (r ∂ ψ ∂ r) + 1 r 2 ∂ 2 ψ ∂ r 2 . (\ displaystyle \ omega _ (z) = (\ frac (1) (r)) (\ frac (\ partial) (\ partial r)) (r (\ frac (\ partial \ psi) (\ partial r))) + (\ frac (1) (r ^ (2))) (\ frac (\ partial ^ (2) \ psi) (\ partial r ^ (2))).) </Dd> </Dl>

What is one two and three dimensional flow