hydrodynamic force acting on pile group driven in the river
 

i use ansys for modelling system of river current and pile grup with ansys fluent, i use 2 dimension model top view of pile and river current.
my purpose of this modelling is to know the force distribution for each pile from the effect of the river current, the look of my model is attached, zone 1 and 2 is the cylinder pile
https://ibb.co/iGdr2d
https://ibb.co/iGdr2d
i use velocity inlet for input velocity of the rive, pressure outlet in the as outle BC, and wall for the side of the river and all the cylinder pile.
for the solution, i use laminar model and steady flow and water liqiud as fluid material, and for solution method and initialization i use this
https://ibb.co/jHqcay
https://ibb.co/jHqcay
https://ibb.co/nPgEoJ
https://ibb.co/nPgEoJ
my problem is, i expected that the force result for each pile is in the same direction of the flow, however the result is different, for example for the pile in zone 1 and 2 the force is acting in positive y for pile 1 and negative y direction for zone 2, i just dont know how this is happen? and is it true if i am expected there are symetrycal flow in y direction for each pile in the river, because the contour velocity result is not symetry
https://ibb.co/j3aoyJ
https://ibb.co/j3aoyJ