-
Notifications
You must be signed in to change notification settings - Fork 67
Potential Research Topics
Although CFAST is not currently under active development, there still remain issues related to the existing model that could use further validation. A list of potential topics is listed below. The goal of any research related to these topics ought to be:
- Modification of the CFAST Technical Reference Guide, if necessary.
- A change in the CFAST source code, if necessary.
- Several verification cases added to the CFAST Software Development and Evaluation Guide.
- At least one comparison with full-scale experiments added to the Evaluation Guide.
The empirical model of flow through a ceiling vent was developed by Len Cooper at NIST in the late 1980s and early 1990s. It is similar to other models developed around that time, but there are few validation data sets (that we know of) that we can use to validate how it is used in CFAST. One particular issue related to flow through ceiling vents has to do with "plug-holing"; that is, the relative amount of gas from the upper and lower layers of the lower compartment that is entrained into the vent flow. A simple correlation based on the Froude number was developed using FDS to indicate how much of the lower layer air is entrained into the flow. This simple result has not been thoroughly evaluated experimentally. See the CFAST Technical Reference Guide, section "Horizontally-Oriented Vents (Ceiling Vents)".
CFAST uses Heskestad's correlations of plume temperature, velocity and entrainment. These correlations were developed for unobstructed plumes with no upper layer. However, in CFAST, we must compute the centerline temperature and velocity of the plume both below and above the interface between the lower and upper layers. The CFAST Technical Reference Guide contains a variation of Heskestad's plume temperature correlation for the region above the interface. The basic idea is that the temperature of the entrained gases are not ambient but rather that of the upper layer. This assumption has not been rigorously validated experimentally.