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TransAT Tutorial Manual                                 10.3. Droplet Impact on a Flat Plate



                   • Proceed as above to set the initial state of the remaining quantities as follows
                     V−Velocity
                         Method : Constant
                         Value :  0

                     Pressure
                         Method : Constant
                         Value :  0



               User-defined Initial Conditions


                     In TransAT, the user has the possibility to create custom initial conditions. For two–phase
               flow simulations especially, the initial gas–liquid interface topology has to be specified by the
               user. In this case, this is achieved in TransAT using an XML file initialconditions.xml.


                     For this specific case, the only variables that are being initialized are simply the ones that
               are solved for, i.e. velocity, pressure, and the Level-Set function which defines the topology of
               the gas–liquid interface.


                     At the initial time step, pressure and velocity are set to constant values over the whole
               domain as done in the Initial Conditions tab.


                     As for the two phases, they are initially confined in two distinct areas. The liquid is confined
               in a circular area and that represents the droplet and the gas occupies the rest of the domain.
               The interface between the two fluids is defined by the Level-Set function which is positive for one
               fluid and negative for the other. To create the initial interface, a circular shape is defined in the
               Level-set node of initialconditions.xml.


                     To be able to use custom initial conditions in this case, the file initialconditions.xml has to
               be placed in the project folder. For this case, a ready-made initial conditions file available in the
               TransAT Tutorials folder will be used to initialise variables over the domain. More information
               can be found on the generation of custom initial conditions in the Custom Initial Conditions
               chapter of the TransAT User Manual .


                   • Click Files in the top left corner then select Save to save the settings of the simulation

                   • Copy the file initialconditions.xml from the folder
                     Public/Documents/TransAT5.7/Tutorials/10.3 - droplet impact to your project folder.






                c 
Ascomp AG Switzerland                    423                                  Version 5.7
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