The following sections describe some output that occurs in transient blade row simulations:
There is a table that indicates, for each domain, the starting and ending time steps for the data compression algorithm, as well as the fundamental period.
An example of this table follows:
====================================================================== | Transient Blade Row Post-processing Information | +--------------------------------------------------------------------+ | | | Fourier coefficient | | Domain Name: | Disturbance | accumulation time step range | | | period |------------------------------+ | | | Start | End | +----------------------+--------------+--------------+---------------+ | R1 | 4.7619E-04 | 6120 | 6179 | +--------------------------------------------------------------------+ | S2 | 4.0816E-04 | 6120 | 6179 | +--------------------------------------------------------------------+
A description of the items in this table follows:
Domain Name: The name of a domain that accumulates transient blade row data.
Disturbance period: The fundamental periods (and their harmonics) used for the data compression algorithm. The period is given in time units as specified by the solution units. For details on solution units, see Setting the Solution Units in the CFX-Pre User's Guide.
Start: The time step at which the data compression algorithm starts for the applicable domain.
End : The time step at which the data compression algorithm ends for the applicable domain.
Note: If the solver run is stopped before the data compression algorithm finishes for all the listed domains, no data will be visible in the post-processor.
For Fourier transformation cases, there is a table that lists information about time steps and coefficient loops.
An example of this table follows:
====================================================================== | Fourier Transformation Information | ====================================================================== | | +--------------------------------------------------------------------+ | | Max. | Time Step Range | | | Coeff. |----------------------------+ | | Loops | Start | End | |-----------------------------+---------+-------------+--------------+ | Initialisation Period | 3 | 41 | 160 | ---------------------------------------------------------------------- | Startup Period | 3 | 161 | 220 | ---------------------------------------------------------------------- | Full Fourier Transformation | 10 | 221 | 640 | ======================================================================
For time transformation cases, there is a table that lists the acceptable range of pitch ratio for a stable run.
This pitch ratio is computed as follows:
For inlet disturbance cases with a stationary passage and a moving signal, the pitch ratio is computed as the passage pitch divided by the signal pitch.
For inlet disturbance cases with a moving passage and a stationary signal, the pitch ratio is computed as the signal pitch divided by the passage pitch.
For rotor-stator cases, the pitch ratio is computed as the pitch of the stator divided by the pitch of the rotor.
An example of this table follows:
====================================================================== | Time Transformation stability limits | | Pitch ratio computed using stationary/rotating component pitches | +--------------------------------------------------------------------+ | | Pitch ratio | | Disturbance name |--------------------------------| | | Minimum | Maximum | Current | +--------------------------------------------------------------------+ | Time Transformation 1 | 0.60 | 1.40 | 1.33 Poor | +--------------------------------------------------------------------+ | Poor: The pitch ratio is close to one of the stability limits. | | If the solution becomes unstable please do one of the | | following: | | (1) Modify the number of passages per components to obtain a | | pitch ratio within the stability limits. | | (2) For further information on Time Transformation stability | | limits please consult the Transient Blade Row guide. | +--------------------------------------------------------------------+