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 LancelotCFD November 3, 2008 11:52

Acceleration in CFX Post

Hi everyone, I am looking for acceleration values in ansys cfx. I have searched in help and in forums but no one seem to know how can you compute and display acceleration chart in Ansys CFX. Any idea ? Thank you for your help .

 CycLone November 3, 2008 17:16

Re: Acceleration in CFX Post

Acceleration of what?

Are you looking for velocity gradients? If that's the case, there are 3 vector variables, Velocity u.Gradient, Velocity v.Gradient and Velocity w.Gradient, which represent the 9 components of the gradient of velocity.

-CycLone

 LancelotCFD November 4, 2008 03:45

Re: Acceleration in CFX Post

Acceleration of fluid . I dare say that velocity gradients and acceleration are not the same fluid. To make it clear, if V is velocity vector I am looking for dV/dt not for grad V or dV/dx ... So anyone has an idea on the subject ?

 Fahim November 4, 2008 07:29

Re: Acceleration in CFX Post

Hi

Are you doing Transient simulation?

 LancelotCFD November 4, 2008 09:13

Re: Acceleration in CFX Post

Yes, I'm pretty sure Ansys solver compute acceleration to solve the Navier stokes equation so why isn't it available? Is there some kind of tricks I should use ? I tried CEL expression but it does not have the derivation operator. I want them in Ansys CFX, rather than in a third party software ... Thanks for your help !

 CycLone November 4, 2008 11:42

Re: Acceleration in CFX Post

The transient term within a cell is not the same as acceleration. Note that since the fluid is moving, the acceleration is actually the dot product of the velocity and gradient (i.e. the gradient in the direction of the flow).

What do you need the "acceleration" for? What are you trying to compute? There is probably another way which you have not considered.

-CycLone

 LancelotCFD November 4, 2008 12:06

Re: Acceleration in CFX Post

All right, you're saying that I can consider the advection as an acceleration ? What I am doing is studying an oscillating flow, normal to a slender cylinder. The main purpose of this is getting an approximation of the added mass coefficient of the cylinder, the base equation being morison's equation.

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