I will discuss a cartoon model for the onset of hydrodynamic behavior in an electron fluid with a polygon Fermi surface. Some interesting features of this model include new dissipative components to the viscosity tensor, a separation of fast and slow scattering rates, and the possibility of non-monotonic temperature dependence in conductance in the ballistic-to-hydrodynamic crossover in flows in channels. Our work is inspired by the possibility of electron hydrodynamics in PdCoO_2, which has an approximately hexagonal Fermi surface. We revisit data on possible hydrodynamic flow from earlier experiments in light of our model.
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