# Boundary Conditions - Transient Simulation

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 May 16, 2012, 15:40 Boundary Conditions - Transient Simulation #1 New Member   Krumov Join Date: Jul 2011 Posts: 2 Rep Power: 0 Dear friends, I would like to make a transient simulation of combustion process in Ansys CFX 13.0 and I have need to set Normal Speed for Air flow as follow (for steady-state simulation): Insert Boundary>Boundary Details>Mass And Momentum>Option – Normal Speed>Normal Speed>15 m.s^-1 But if I want to make a transient simulation I would like to define Normal Speed for Air flow as function of time. For example: Vair flow= A*t^3+B*t^2+C*t+D,m/s where A,B,C,D are constants, t-time,s or Insert Boundary>Boundary Details>Mass And Momentum>Option – Normal Speed>Normal Speed> Enter Expression>2,5*t^3+6*t^2+2*t+1,8. So, how can I express this dependence if I want to do this transient simulation? Thank you in advance miki

 May 16, 2012, 19:23 #2 Senior Member   Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,122 Rep Power: 21 A[m*s^-4]*t^3+B[m^s^-3]*t^2+C[m*s^-s]*t+D[m*s^-1]

 May 18, 2012, 02:22 #3 New Member   Krumov Join Date: Jul 2011 Posts: 2 Rep Power: 0 Dear evcelica, Thank you so much!