The x-momentum equation for the boundary layer in free convection is given below.
$u\frac{\partial u}{\partial x} + v\frac{\partial u}{\partial y} = -\frac{1}{\rho}\frac{dp_\infty}{dx} - g + \nu\frac{\partial^2 u}{\partial y^2}$
The different terms in the equation represent:
O 1 and 2: convection, 3: pressure force, 4: body force, and 5: viscous force.
O 1 and 2: net advection, 3 and 4: body forces, and 5: net viscous force.
O 1 and 2: advection, 3 and 4: pressure forces, and 5: viscous force.
O 1 and 2: advection, 3: pressure force, 4: body force, and 5: viscous force.
