Gravity
 

If X-Z axis is in horizontal plane and +Y axis is upwards( gravity is in -Y axis). Now if the flow is in -Y direction what shud be the value of 'g'?? Is it -9.81 or +9.81??? Does the value of gravity depends on the direction of flow or it depends on the orientation of the coorodinate axis??

Re: Gravity
 

Gravity depends only on the orientation of the coordinate axis.

Re: Gravity
 

If my model is drawn such that flow is in +Y direction and hence g =-9.81m/s^2. Now I rotate the model and the axis by 180 degrees such that the flow is again in +Y axis but the difference is that +Y axis is now pointing down in the direction of gravity. Would g=+9.81 in this case?????

Re: Gravity
 

yes I guess,

it should be +9.81, in case you rotate the model about 180 degrees, since the flow is now towards the -Y direction which adds aditionally the gravitational force to the original acceleration of the flow.

-mp