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\begin{equation}  \begin{aligned}  &(1) (2) (3) \\  {\frac{\partial u}{\partial t}} &+u\frac{\partial & +u\frac{\partial  u}{\partial x}+v\frac{\partial u}{\partial y}-K\left(\frac{{\partial }^2u}{\partial x^2}+\frac{{\partial }^2u}{\partial y^2}\right)&=0 \\ \frac{\partial &\frac{\partial  v}{\partial t}&+u\frac{\partial t}+u\frac{\partial  v}{\partial x}+v\frac{\partial v}{\partial y}-K\left(\frac{{\partial }^2v}{\partial x^2}+\frac{{\partial }^2v}{\partial y^2}\right)&=0\ \end{aligned}  \end{equation}