**2. Mathematical formulation**

The two infinite plates are kept at *Y* ¼ �*h*<sup>1</sup> and *Y* ¼ *h*<sup>2</sup> initially as shown in **Figure 1** and the two sheets are isothermal with dissimilar temperatures T1 and T2 respectively. The distance �*h*<sup>1</sup> ≤*Y* ≤0 represents region-1 and the distance 0≤*Y* ≤*h*<sup>2</sup> represents region-2 where the first one occupies micropolar fluid and the other, viscous fluid. Here the buoyancy force determines the fluid flow.

**Figure 1.** *Schematic diagram of the problem.*

The governing conditions for the problem are developed based on the assumptions stated below:


5.*T*<sup>1</sup> >*T*2,*C*<sup>1</sup> >*C*2.
