Wake Function

The generalized velocity derivative in Plus units.

$$\frac{\partial u^{+}}{\partial y^{+}}=\frac{1}{y^{+}}\Phi \left(\frac{y}{{\delta }_v}\right)$$

Here the $\Phi$ represents the universal Wake function which accounts for the wakes in the flow i.e turbulent behaviour. Depending on which layer of the wall bounded flow it is in, different Wake functions can be used.