Run Management in Simulation CFD

Autodesk Simulation CFD has several output windows and utility programs to track run progress and manage the solving of multiple simulations. Queuing multiple runs can make your simulations more efficient.

Convergence Monitor

Once the solver initiates the CFD computations, the Convergence Plot tab is activated in the Output bar.  As the solution progresses, the general objective is for the lines to flatten out, which is an indication that the change in results between iterations is decreasing (note that for certain transient runs this will be an exception since input variables may be changing during the simulation).  More information on convergence is located here:

A typical steady-state simulation run (top) is not fully converged in the initial iterations (1).  As the solver continues to iterate, the smooth lines flatten out until full convergence is achieved (2).  By contrast, poor convergence (bottom), in this case from invalid boundary conditions, is erratic in nature.

NOTE: Certain applications take more iterations to converge than others.  For example, a mixed convection simulation will typically take longer to converge than a forced convection simulation for the same geometry.

Runs that either demonstrate poor convergence or diverge entirely can be detected by observing the Convergence Plot.  The run can then be stopped and diagnosed for potential problems which could include poor mesh quality, incorrect boundary conditions, or invalid solver settings. 

Managing Multiple Runs

The purpose of a design study is to run multiple simulations to fully evaluate geometry or environmental changes; it is rare when only a single simulation will provide all of the design insight needed.  For example, when evaluating external flow over a building, it may be necessary to test at least several prevailing wind directions.

The ability to queue up and run multiple simulations is very useful since it keeps the computer running consecutive simulations without requiring further user interaction.  AEC applications benefit from this since they can be rather large simulations and computer resources may need to be used overnight or through the weekend to meet design deadlines.

The process of queuing runs is as simple as loading the design study file, activating the scenario to run, and clicking the Solve button as detailed here Simulation Queue.

The Solver Manager utility streamlines the queuing process by avoiding the need to activate individual scenarios in a design study. 

The Solution Monitor is a small utility which provides a convenient snapshot to the status of all runs that have been placed in the local run queue. 

For solutions sent to the cloud, the Simulation Job Manager  is used to monitor their status.

NOTE:  Runs that are solved locally are completed in sequence (current run has to finish before the next one starts).  Runs that are sent to the cloud are completed in parallel on cloud resources.

TIP: The software interface and solver are separate and distinct processes.  During a simulation run, the interface can be closed (e.g. to save memory) or another file can be opened and the solver will keep on running.  If the interface is launched again and the running scenario is opened, the interface will automatically reconnect to the solver and update the results in the graphics window.