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Showing results 1 to 25 of 26 Search took 0.00 seconds. Search: Posts Made By: ghorrocks

Forum: CFX November 2, 2019, 04:52

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks It's an FAQ:... It's an FAQ: https://www.cfd-online.com/Wiki/Ansys_FAQ#The_solver_terminates_with_the_error_message_.22A_negative_volume_appeared.22._What_went_wrong.3F

Forum: CFX January 7, 2016, 18:45

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks In future please start a new thread for a new... In future please start a new thread for a new question. The easiest way of doing this is as you have done, by making the material properties a function as you have done. Note that this is quite...

Forum: CFX July 13, 2015, 18:53

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks It means the Piston location = f(known... It means the Piston location = f(known variables). It is not an ODE or PDE or implicit function.

Forum: CFX July 13, 2015, 08:09

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks If there is no interia then the piston will move... If there is no interia then the piston will move such that the fluid force equals the accumulator pressure force. So the piston location is an algebraic function of the fluid pressure, and you do not...

Forum: CFX July 13, 2015, 07:55

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks If the accumulator piston has no inertia then you... If the accumulator piston has no inertia then you can model its motion using CEL expressions in CFX. If the accumulator has inertia you will need to use a rigid body solver.

Forum: CFX July 11, 2015, 06:06

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks Elastic constants? You mean the piston has a... Elastic constants? You mean the piston has a diaphragm which deforms? Then this is an FSI simulation, or possibly a moving mesh with the motion prescribed by the force on the diaphragm.

Forum: CFX May 23, 2015, 06:18

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks FAQ:... FAQ: http://www.cfd-online.com/Wiki/Ansys_FAQ#The_solver_terminates_with_the_error_message_.22A_negative_volume_appeared.22._What_went_wrong.3F

Forum: CFX May 6, 2015, 19:14

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks For a 3D region you need to define it in your... For a 3D region you need to define it in your mesh. So you will need to set this up in the meshing software.

Forum: CFX May 6, 2015, 19:14

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks For a 3D region you need to define it in your... For a 3D region you need to define it in your mesh. So you will need to set this up in the meshing software.

Forum: CFX April 23, 2015, 07:18

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks To make your latest CEL expression work you... To make your latest CEL expression work you simply need to make it return a non-zero value when outside the region. A simple if statement will do that: a = if(Shear Strain Rate >= 0.001[s^-1],...

Forum: CFX April 23, 2015, 05:53

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks Your function returns 0 if you are outside the... Your function returns 0 if you are outside the region. You cannot set the viscosity to be zero.

Forum: CFX April 20, 2015, 07:40

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks Isn't that high school level maths? -... Isn't that high school level maths? - http://www.purplemath.com/modules/distform.htm

Forum: CFX April 12, 2015, 07:52

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks Fix the negative volume element issue first. It... Fix the negative volume element issue first. It might the cause of the overflow error as well. Rerun the simulation generating transient results files on every time step, or at least the time...

Forum: CFX April 1, 2015, 07:03

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks How about this: PistonX = 0.0425[m]*sin(t/1... How about this: PistonX = 0.0425[m]*sin(t/1 [s]) Tolerance = 0.1 [m] CloseToPiston = if(abs(x-PistonX)<Tolerance,1,0) Viscosity = if(Shear Strain Rate >= 15[s^-1], (5000[kg m^-1 s^-2]/Shear...

Forum: CFX March 31, 2015, 17:23

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks You just include the x, y or z displacement of... You just include the x, y or z displacement of the piston in the CEL expression - it is not that hard. You just need to be careful about getting the units right.

Forum: CFX March 31, 2015, 07:00

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks I would expect convergence difficulties with a... I would expect convergence difficulties with a viscosity function like that. It has a big step in viscosity at SSR=15[s^-1]. Are you sure it is realistic? Looking back on this thread you state...

Forum: CFX March 19, 2015, 16:36

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks I do not have time to go through your simulation... I do not have time to go through your simulation in detail. The forum works best when you identify a specific problem you are having and post a question about that problem. Make sure you include...

Forum: CFX March 19, 2015, 06:17

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks I have no idea what you are modelling so I cannot... I have no idea what you are modelling so I cannot say whether it is correct. You also have not shown how you implemented anything. The equations you describe are the Bingham model, but as I said I...

Forum: CFX March 19, 2015, 06:06

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks The function you describe is a simple CEL... The function you describe is a simple CEL expression. A couple of if functions and some other basic operators should do it. Have a look in the CFX reference guide for the available functions and CEL...

Forum: CFX March 19, 2015, 01:29

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks The Bingham non-Newtonian model is already a... The Bingham non-Newtonian model is already a built in model in CFX. There is no need to write the equations to define it. Just use the existing model. The built in model also has the advantage...

Forum: CFX February 24, 2015, 01:05

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks The CEL expressions to do material properties are... The CEL expressions to do material properties are similar to any other expressions (for example your piston motion equations). Have a look in the tutorials for examples of CEL expressions.

Forum: CFX January 20, 2015, 04:25

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks There used to be example tutorials of pure mesh... There used to be example tutorials of pure mesh motion but they don't seem to be in V15. Have a look on the ANSYS community website, there might be some examples there.

Forum: CFX January 20, 2015, 01:03

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks OK, thanks. In that case you definitely do... OK, thanks. In that case you definitely do not want to use the rigid body solver. Use mesh motion and put your equation of motion on the moving piston. Put unspecified motion on the side...

Forum: CFX January 19, 2015, 16:19

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks What do you mean by force velocity distribution?... What do you mean by force velocity distribution? How does that fit in with your original request of how to put a sinusoidal motion on the piston?

Forum: CFX January 18, 2015, 22:29

Replies: 58 CEL Code for Sinusoidal Movement of Piston Views: 6,354 Posted By ghorrocks Please do not use jargon. What is a MR damper?... Please do not use jargon. What is a MR damper? .... I just looked it up on google, is it a Magnetorheological damper? What are you trying to learn with this simulation? What are you trying to do?...

Showing results 1 to 25 of 26

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