Discussion Forum

Hello Chiara,

1/ The integration coupling operator already performs an integration. You don't need to further integrate in Derived Values, instead in Derived Values, do a Global Evaluation of intop1(1). The "perform integral in revolved geometry" checkbox takes care of the 2pir term in the integral, BTW.

2/ If it's a sphere you want, in 2D axisymmetry you need to draw a half-circle with its straight side on the r=0 axis. What you drew corresponds to a torus of zero inner radius.

To evaluate the change in volume, you'll want to integrate the trace of the strain tensor, assuming you're operating under small strains assumptions.

Best,

Jeff

Hi Jeff, thanks for your answers. I, previously, tried the Global Evaluation but I didn't get the right volume so I thought that to be wrong. But, I was not considering to build the circle with its straight side on the r=0 axis. Now, I got the right volume value. Thank you.

To evaluate the change in volume, you'll want to integrate the trace of the strain tensor, assuming you're operating under small strains assumptions.

As for the part about the evaluation of the volume change, I don't understand exactly what to do. Is there some documentation that I can refer to??

Chiara

Hello Chiara,

See the attached model. I set it up so that the sphere is in a state of pure pressure and therefore shrinks into a smaller sphere. You can see from one of the plots that its diameter is reduced by ~5.45e-6 meters. The global evaluation node computes the change in volume as ~-3.427e-5 cubic meters. You can check that that value matches the analytical value for the change in volume of a sphere going from a diameter of 2 meters to a diameter of 2-5.45e-6 meters.

Best regrds,

Jeff

Hi Jeff,

you have been very kind to attach the model. I really appreciate the help. Thank you!!

Best, Chiara

Hi Jeff, sorry to bother you again but I was wondering about to build the model in the reverse way. I will explain myself better. Is it possible to impose directly a volume variation on the sphere without using the pressure? 1) For example, I have the initial volume, V1, and a final volume, V2 and I want that my sphere (or some other geometry) moves from V1 to V2. I was thinking something about using the interpolation function with the two points: (V1,t1) and (V2,t2), but I am not sure how to impose it on the domains or the boundaries of the sphere. t1 and t2 are for the time. 2) Is there the chance to do it without using a time dependent condition? Thanks in advance.

Best, Chiara

I don't understand what you are trying to achieve. There are many different deformation fields that would result in an object going from its initial volume V1 to a pre-selected other volume V2. If you know the entire deformation field, not just the overall volume change, then read into the use of moving geometry and moving mesh interfaces, this may be what you are after.

Best,

Jeff

I don't understand what you are trying to achieve. There are many different deformation fields that would result in an object going from its initial volume V1 to a pre-selected other volume V2. If you know the entire deformation field, not just the overall volume change, then read into the use of moving geometry and moving mesh interfaces, this may be what you are after.

Best,

Jeff

Hi Jeff, thanks for your answer. At the present moment, I was wondering if it possible only to apply a volume change on an object (and not to apply the pressure to see the change in the original shape) and, eventually to control this change thorough time. I think I have only the overall volume change, but thanks for the suggestion about the moving mesh and geometry. I will check on that.

Best, Chiara