# Moving Mesh Velocity Issue: Mesh velocity does not equal displacement

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 September 8, 2011, 10:44 Moving Mesh Velocity Issue: Mesh velocity does not equal displacement #1 Member   anonymous Join Date: Jun 2011 Posts: 58 Rep Power: 7 Hello everyone I'm modeling a blade moving through a liquid by using a subdomain that surrounds a blade within a large domain and applying a moving mesh to the subdomain. I want the blade to start at a stand still and accelerate linearly to 2 m/s over 1s in the x direction. These are the CEL functions I use to define the moving mesh. Specified mesh location X is: X Still + X New Tran X Still = (x-X0) - Total Mesh Displacement X X New Tran = X Vel * t X Vel = 2 [m s^-2] * t Total time of simulation = 1s Time steps = Total time/500 The issue i have is very odd. After running the simulation, the velocity which the blade/inner subdomain moves is twice what it should. What is strange is that the distance that the blade moves is normal. example to explain at t=1 Blade mesh velocity should be 2m/s but it actual is 4m/s Mesh Displacement at the blade is 4/500 however Total mesh Displacement at the blade is 2m. The total displacement of the blade does not equal the mesh velocity or the sum of the timestep displacements, throughout the entire simulation, the mesh velocity is double compared to the mesh displacement at that timestep I'm really confused as to why or how this is happening so any help would be great. Thank You, DM

 September 8, 2011, 11:42 #2 Senior Member   Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 512 Rep Power: 12 For constant accel: v=at s=integral(at)dt=1/2*a*t^2 you have s=a*t^2

September 8, 2011, 12:02
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anonymous
Join Date: Jun 2011
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Quote:
 Originally Posted by singer1812 For constant accel: v=at s=integral(at)dt=1/2*a*t^2 you have s=a*t^2
Wow. I'm an idiot for missing that one. Thanks

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