Monitors
While Virtualwind executes the simulation, it generates the wind data at each time step on the fly. The wind data include quantities such as velocity, pressure, vorticity, etc. In order to record the data, however, you need to set up Monitors to specify parameters to identify what quantities you want to monitor/store, where in the Domain you want to monitor the data, and when you want to start and end the monitoring.
Four Types of Monitors
Virtualwind supports the following four types of monitors:
- Domain Wind Monitor: monitoring the specified quantities in the entire Domain;
- Point Wind Monitor*: monitoring the specified quantities only at a particular point of the Domain;
- Domain Fluid Species Monitor*: monitoring a particular smoke (released by Smokebombs) in the entire Domain;
- Tracer Particle Monitor*: monitoring particles released by a particular Tracer Particle Generator.
A detailed explanation of each Monitor type can be found by accessing the links at the bottom of this page.
Common Settings
Output
One common setting for all the Monitors is how and when you want to record the monitored data. You can choose to record the data in either the SNAPSHOT mode or the ANIMATION mode by setting up the Frame Writing Mode in its "Output" item. By SNAPSHOT, we mean that the Monitor only saves the wind data (for the specified quantities) at one particular time spot – if the Monitor outputs the data multiple times during the output period, the latest data to be recorded will overwrite the previous data and eventually you will have only one "frame" of the wind information at the time of the last output. However, in the ANIMATION mode, the Monitor records every output in the time series and later on you can play them as an animation.
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As shown above, you need to specify the start time and stop time of the output process (in seconds). You also need to specify how often (output interval) you want to record the data (also in seconds).
Sampling
If the Monitor is checking quantities of a statistical nature, such as mean velocity, mean wind speed, and GEM wind speed, you also need to configure the "Sampling" item of the monitor. This item controls the method to obtain a sample, from which the statistics (i.e., the mean value) are calculated. Similar to the output item, you need to specify the start time and the stop time of the sampling (in seconds), and you also need to specify the sampling interval (also in seconds).
The statistics are computed in an "accumulated" sense. What this means is that over the specified sampling time, the sample keeps growing–one new sample element is added into the sample over each period of the sampling interval– and the statistics (such as the mean value) are therefore re-computed based on the updated sample. Therefore, if you look at the value of the quantity at each output time, you will find that it tends to become stable over time. (i.e., it may vary significantly at the beginning of the output sequence but converges to a certain value at later output times).
You can choose to synchronize the output with the sampling, meaning that the Monitor will output the data at the same pace as the sampling – basically it outputs whatever its samples. Otherwise, you can specify two different sets of start time, stop time, and interval for output and sampling, respectively.
By default, the Monitors' writing mode is set to ANIMATION and the output is set to be independent of the sampling – they are not necessarily synchronized.