Moving regions usually belong to the sample cartridge assembly (SCA) and require time-dependent computation (full implicit time model). You specify either constant velocities in radial (r) or axial (z) direction or you specify a file containing time-dependent position or velocity profiles. The file must be a text file with the extension *.mov and has to correspond to the following format:
Time (col. 1) | r-coordinate (col. 2) | z-coordinate (col. 3) |
|---|---|---|
0 | 0. | 0. |
100 | 0. | 0. |
500 | 0. | 0.5 |
1000 | 0. | 0.5 |
In this example the region will not move at all in the interval from 0 to 100 seconds. Then the region will move 5 cm in z-direction within the next 400 seconds and remain in this position until 1000 seconds have elapsed.
The program will take the information about the position from columns 2 and 3 for the first moving region. In the dialog you only specify the column of the r-coordinate, the program takes the next column automatically as z-coordinate. If you want to specify time profiles for more than one moving region in the profile file, you add column 4 and 5 for the second moving region, 6 and 7 for the third and so on.
If you want to specify time-dependent velocity profiles, the *.mov file has a similar format, but instead of coordinates you have to write the values of r and z-velocity.
The following prerequisites should be considered when working with moving regions:
A moving region shall not intersect a line of a fixed region or collide with other parts of the geometry.
By default, monitor points in moving regions stay in their original position. However, if you check the moving button in the Monitor/Write Profile dialog, they move together with the region. You will be able to monitor the temperature at this point moving through the furnace.
Do not define more moving regions than necessary. For instance, if you have a sample mounted on a rod which is moving through the furnace, only assign the sample as moving region. The rod will automatically be detected as a distorting region. If the distorting region has a non-zero velocity component perpendicular to an outer boundary, also convective heat fluxes resulting from the movement will be taken into account.
Fixed regions adjoining a moving region (e.g. floating sealing) will be distorted (distorting region), because their form is adjusted at every time step in order to stay connected with their neighbors. Usually this distortion can be neglected, because only the result for the moving region is of interest. The changing shape of the fixed region (shortening or elongating, depending on the direction of movement) does not have any impact on the results for the moving regions. The following figure illustrates this fact:
Moving region
Fixed region
Fixed region, to be re-meshed
If a moving region is enclosed in a radiation cavity, the view factors of this cluster will be recomputed at every time step. The contact line between a fixed region and a moving region can be labeled as “sliding”, see Assigning labels. The moving region will slide along the fixed region and the fixed region will not be distorted.
The line upstream on the moving region must not have any intersections nor lose contact to the sliding line:
Sliding line
Proper sliding line between fixed and moving regions
Not allowed: Sliding line meeting intersection
Not allowed: Sliding line losing contact
Pay attention, that the sliding line between the moving regions and environment should be directed parallel to the movement vector.
The distortion of the neighbor regions attached with the moving region can be avoided by introducing a label at the shared line, along which slides the moving region.
Open the dialog Labels , select the sliding line and mark it as Sliding . For details see section Labels and Joiner. The labeled line will remain unmovable, the moving region will slide with respect to it.
Note
If the only line at side of the unmovable regions is attached to the sliding boundary, then an additional line can be introduced in Geometry mode in order to create the second vertex at the sliding line. The line between these two vertexes can be then labeled as described above and the distortion of the geometry around moving regions will be avoided.