During our last projects, we provided one direction of surge force parallel to straight running line direction only at both end of th elbow point for water service piping system.

A new project requests that a surge force have to be applied in two direction, piping axial direction and lateral direction.

Please let me know which one is correct based on behavior of surge force.

I guess the first approach is the right one

Right, and also consider both flow direction forece and counter flow direction.

I dont think surge force can be lateral direction