Why does RAMMS display momentum with units of m²/s instead of kg·m/s?

Great question — and you’re absolutely right to notice the discrepancy. In classical mechanics, momentum is defined as the product of mass and velocity, with units of kg·m/s. However, in RAMMS::DEBRIS FLOW, the momentum output is simplified for performance and visualization purposes.

Since the model assumes a constant flow density and uses a uniform grid (with equal X and Y resolution), we represent momentum as the product of flow height (H) and flow velocity (V), resulting in units of m²/s. This simplification omits constant factors like density and grid area for clarity and computational efficiency.

To convert this value to physical momentum (kg·m/s), simply multiply the RAMMS output by:

• The flow density (kg/m³), and
• The square of the grid resolution (m²).

This gives you the full physical momentum:
Momentum = H × V × ρ × (grid_res)² (in kg·m/s)

This approach allows for more efficient calculations and visualization while maintaining physical consistency when properly interpreted.