Measurements of directed, elliptic, and triangular flow in Cu + Au collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mi mathvariant="italic">NN</mml:mi></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>200</mml:mn></mml:mrow></mml:math> GeV

Measurements of anisotropic flow Fourier coefficients (${v}_{n}$) for inclusive charged particles and identified hadrons ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}, {K}^{\ifmmode\pm\else\textpm\fi{}}, p$, and $\overline{p}$ produced at midrapidity in $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{{s}_{{}_{\mathit{NN}}}}=200$ GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes ${\mathrm{\ensuremath{\Psi}}}_{n}$, for $n=1$, 2, and 3 are studied as a function of transverse momentum ${p}_{T}$ over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. We also compare these $\mathrm{Cu}+\mathrm{Au}$ results with those in $\mathrm{Cu}+\mathrm{Cu}$ and $\mathrm{Au}+\mathrm{Au}$ collisions at the same $\sqrt{{s}_{\mathit{NN}}}$ and find that the ${v}_{2}$ and ${v}_{3}$, as a function of transverse momentum, follow a common scaling with $1/({\ensuremath{\varepsilon}}_{n}{N}_{\mathrm{part}}^{1/3})$.