The Model Selection dialog will first appear as it looks below for a continuum that has not yet been defined.
The Enabled Models group box on the right-hand side of the dialog will be empty, indicating that no models have yet been selected. Two models are available for selection, the Motion model and the Material model. The <Optional> labels indicate that the selection of these items is not mandatory. The Auto-select recommended models checkbox provides an option for the automatic selection of recommended models.
The Model Selection dialog changes dynamically in response to previous selections. For instance if the Stationary and Single-Phase Material model options are selected, it will appear as below. Now, you will be prompted to select a Space model and a specific Single-Phase Material model. The <Additional model selections are required> label tells you that the model selection is incomplete. An incomplete model selection means that the continuum cannot be initialized in its current state.
Trying to iterate when you have not completed the model selection results in an error similar to that shown below.
The most effective way to make model selections is to keep making choices from the model family that appears at the top of the available models side of the dialog. This will add models to the Enabled Models group box in the same order that they were selected (by you or by STAR-CCM+when in auto select mode).
The dialog is "live" in that the server is updated each time you change the state of a checkbox or radio button, and this will be reflected in the tree if you have the relevant nodes open.