  Many metallic quantum materials display anomalous transport phenomena that
defy a Fermi liquid description. Here, we use numerical methods to calculate
thermal and charge transport in the doped Hubbard model and observe a
cross-over separating high- and low-temperature behaviors. Distinct from the
behavior at high temperatures, the Lorenz number $L$ becomes weakly doping
dependent and less sensitive to parameters at low temperatures. At the lowest
numerically accessible temperatures, $L$ roughly approaches the Wiedemann-Franz
constant $L_0$, even in a doped Mott insulator that lacks well-defined
quasiparticles. Decomposing the energy current operator indicates a
compensation between kinetic and potential contributions, which may help to
clarify the interpretation of transport experiments beyond Boltzmann theory in
strongly correlated metals.
