The image shows a complex equation, which is a form of the Navier-Stokes equation, often used in fluid dynamics to describe the motion of fluid substances. Let's break down each part of this specific version:

1. Inertia (per volume):
   $\frac{\partial \mathbf{u}}{\partial t}$ This represents the time variation of velocity, accounting for the rate of change of velocity with respect to time.

2. Convection:
   $(\mathbf{u} \cdot \nabla) \mathbf{u}$ This term accounts for the non-linear advection (or convection) of the velocity, which is how the fluid's motion moves itself around.

3. Diffusion:
   $-\nu \nabla^2 \mathbf{u}$ Here, $\nu$ is the kinematic viscosity, and this term accounts for the diffusion or spreading of momentum through the fluid, representing the viscous effects.

4. Internal Source:
   $-\nabla w$ This represents internal forces within the fluid, which might be pressure forces or other effects acting on the fluid.

5. External Source:
   $+ \mathbf{g}$ This accounts for external forces, such as gravity, acting on the fluid.

The equation as a whole is a momentum balance, taking into account various factors like inertia, convection, diffusion, internal, and external forces. It's part of the fundamental mathematical description of fluid flow.

Would you like more details or have any specific questions about this?

Here are 5 related questions to deepen understanding:

1. How is the Navier-Stokes equation used to model different types of fluids, such as incompressible vs. compressible fluids?
2. What is the significance of the kinematic viscosity $\nu$ in fluid dynamics?
3. How can boundary conditions be applied to solve the Navier-Stokes equation in specific physical problems?
4. What is the role of the external force $\mathbf{g}$ in practical fluid dynamics applications?
5. Can the Navier-Stokes equation be solved analytically for specific flow conditions, or does it require numerical methods?

Tip: The Navier-Stokes equation is highly non-linear and, in many cases, can only be solved numerically using methods like computational fluid dynamics (CFD).