SPH Toolbox Features for Shell Volume Method

 

1. 'Create¡¯ option enables the creation of lumped mass elements of the type SPH.

2. ¡®Method¡¯ menu provides the choice of methods that can be employed in the creation of SPH elements.

The method of interest in this document is ¡®Shell Volume¡¯

Creation of SPH elements through ¡®Shell Volume¡¯ requires a closed volume of shell elements, with no free edges. However, the shell normals need not be consistent.

3. ¡®Del Old Parts¡¯ option, when turned on, would delete the parts corresponding to shell volume after the creation of SPH elements.

4. ¡®SPH Name¡¯ input corresponds to the title of the SPH part in the *PART card.

5. ¡®Add¡¯ enables the creation of a new SPH part with similar or different parameters.

6. The input to the parameters N1, N2 and N3 (Generation Direction) corresponds to the nodal ids of 3 nodes, employed to define a local coordinate system, which aids in setting the direction of filling the SPH elements.

The ids of the 3 nodes can be input manually or selected from the display panel, by initially checking N1/N2/N3.

The N1 to N2 direction defines the X-axis, while N1-N2-N3 together defines the X-Y plane such that:

(N1-N2) X (N1-N3) --> Z axis

(Z axis) X (X-axis) --> Y-axis.

 

7. The parameters PitX, PitY and PitZ (Num Particles Definition), are employed to input the space between adjacent SPH elements, along the X, Y and Z directions, respectively.

The X, Y and Z directions are determined by the Local Coordinate system, if defined, in Generation Direction.

Else, Global Coordinate System would be employed.

8. The percentage of closed shell volume to be filled can be established through the ¡®Ratio¡¯ parameter (Filling Property).

This parameter can be set manually or by employing the available values.

9. Further, the direction of partial filling can be set by entering the X, Y and Z directions of the vector along which partial filling has to be implemented, in DirX, DirY and DirZ parameters, respectively.

Note:The X, Y and Z directions, correspond to the global coordinate system. Hence, the normal directions should be adjusted appropriately for any given enclosed volume (if needed).

Thus DirX =1, DirY=0 and DirZ=0, would partially fill the closed volume by Ratio percentage along the X direction.

Similarly, DirX=1, DirY=1 and DirZ=0, would implement partial filling in the direction of a line in the XY plane, inclined at 45 deg to the X-axis.

Note:Negative values can also be input while defining the direction of fill.

10. While implementing a partial fill, the unfilled volume can be automatically filled with SPH elements belonging to another part by checking the PID option, in the ¡®Create SPH Part for Unfilled part¡¯

The input of ¡®Density¡¯ (optional) enables the determination of ¡®MASS¡¯ in *ELEMENT_SPH¡¯ card.

The method of determination of the ¡®MASS¡¯ is explained in the following section.

This function of creating a SPH part for the unfilled volume can be employed in instances, such as filling a closed volume with a liquid-liquid or liquid-air mixture, among others.

 

 

 

11. The SPH elements can be filled in the closed volume, such that a gap exists between the shell part and the SPH element closest to it.

12. A density value needs to be defined to determine the ¡®MASS¡¯ of the SPH elements (which can be considered as lumped mass elements assigned to nodal points), as defined in the *ELEMENT_SPH card.

Note(a)£ºFor a positive value of ¡®Density¡¯, the mass of each SPH element in the created part is computed as:

Note(b):The Number of SPH elements filled is determined by the volume of the closed shell parts and PitX, PitY and PitZ.

Similarly, the default radius of representation of each SPH element is dependent upon the above parameters.

Note(c):If the ¡®Density¡¯ is input as a negative value, the absolute value of ¡®Density¡¯ would be considered as the volume of each SPH element.

Hence, the mass of a SPH element would be equivalent to density retrieved from the material card defined in the PID (of the SPH part) times absolute value of Density.

13.Upon defining the necessary parameters, as discussed in the above section, the ¡®Set Params¡¯ option should be invoked to set the selected parameters for a selected shell volume, prior to the generation of the SPH elements.

Note:If multiple shell volumes were to be filled with SPH elements, with same parameters such as pitch, generation directions and density, among others, check the option ¡®Same Para¡¯ prior to clicking upon ¡®Set Params¡¯.

14.¡®Start NID¡¯ and ¡®Start PID¡¯ indicate the starting id of the SPH elements (where NID and EID are the same) and SPH parts, respectively.

15.¡®Apply¡¯ option generates the SPH elements for visualization, prior to their acceptance (through ¡®Accept¡¯) or rejection (through ¡®Reject¡¯).

 

SPH Element Visualization

The visualization of the SPH elements can be controlled through the ¡®General Settings¡¯ available in the ¡®Settings¡¯ option, on the top menu in LSPP.

Among the available options in ¡®SPH/Particle¡¯:

1. ¡®Radius Scale¡¯ scales the default radius of the SPH elements (determined as described in section 12 of the above discussion on the SPH element generation toolbox).

2. ¡®Style¡¯ determines the visualization style of the SPH elements.

Note:The default style might be particle, but alternative visualizations such as smooth, flat and wire can be selected.

3. ¡®Sphere divs¡¯ determines the number of divisions in styles such as smooth, flat and wire.

Note:The representation of the SPH elements would be smoother with the increase in number of divisions.

4. ¡®Apply¡¯ would enable the application of the settings to the entities on display.