PHENIX results on flow observables in Cu$+$Au collisions at $\surd $sNN $=$ 200 GeV

High-energy collisions of asymmetric, large nuclei offer a unique window into many aspects of excited medium formation and evolution. Unlike symmetric collisions, an asymmetric system can have non-zero odd-order moments in its average transverse distribution of participants; and, the patterns of participants from the two nuclei can have different shapes on average. The PHENIX experiment has measured particle production from Cu$+$Au collisions at RHIC at full energy ($\surd $sNN $=$ 200 GeV) during the 2012 running period. We report here measurements of azimuthal anisotropies v1, v2 and v3 (directed, elliptic and triangular flow) for inclusive and identified charged hadrons produced at mid-rapidity in Cu$+$Au collisions. Implications for diagnosing a variety of unique initial-state geometry effects will be discussed.