How to consider the elevation in the scaled model for free surface flow

[eng.abass5]

Hi, could you please advise me. 

I want to analyze the flow in the river with waterfall, suppose the ratio between the model and the prototype is 

1:50, to scale the flow velocity i use Froude number. But i have a doubt when it comes to waterfall elevation. 

Do i need to multiply the gravity with 50 like this (0,0,-50) instead of (0,0,-1)  or not ? 

Do i need to activate hydrostatic pressure or it's already considered in free surface analysis. 

another question 

First figure, this guy in his tutorial  defined the gravity direction and the gravity acceleration value below:

in this figure  from Autodesk webinar, they kept the value of the component as 0 

which one is correct 

[frederic.gaillard.7]

Hello @eng.abass5, 

• Do i need to multiply the gravity with 50 like this (0,0,-50) instead of (0,0,-1)  or not ? 
  • the original model and the prototype are operating in the same gravitional field, so the constant g will remain the same. gprotype=gmodel
• Do i need to activate hydrostatic pressure or it's already considered in free surface analysis. 
  • No, it's already considered in free surface analysis flow. 

Fred

[eng.abass5]

I am grateful for your replay, but how can i transform the effect elevation on velocity profile   between the model and the prototype ? is it a linear transformation ?

[frederic.gaillard.7]

with the caracteristic lenght 

[eng.abass5]

this for the  flow at the same horizontal level, basically Froude number. 

what i am talking about is the waterfall, when water fall from the top. 

[frederic.gaillard.7 · Accepted solution]

Hello @eng.abass5 

You can understand the Froude number as a ratio between the kinematic energy and the potential energy. In your  case the characteristic lenght ''l'' will become h, the height. 

hope it helps

Fred