844 simulation stability the hysys olga link relies

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8.4.4 Simulation Stability The HYSYS-OLGA Link relies on the linking of two simultaneous hydraulic solvers. This means that the simulation will not necessarily be stable nor accurate if rapid transients occur at the Link boundaries. This instability is usually seen when you try to stop the flow completely. It is recommended that you either: Put the valve or other flow control device (pumps included) at the immediate boundary of the link. Put the valve or other flow control device (pumps included) within either the OLGA or HYSYS model to give sufficient capacitance to stabilize this tearing of the hydraulic solutions. 8.4.5 Errors The HYSYS-OLGA Link will report a number of different types of errors if problems are experienced. You have the option of reporting the errors to the HYSYS Trace window or having the errors appear as a message dialogue box that has to be acknowledged. You can change this behavior via the Trace Errors checkbox on the Connections page of the Setup tab. Most errors will just be of some descriptive text, which should be self-explanatory. Other categories of messages are described below. If a message is preceded with the words OLGA_SERVER Reported Error (OLGA_ERROR - Log All Communication and review log file): , then this indicates the OLGA Server responded with an error The convention for an OLGA SOURCE is to have positive flow mean flow into the OLGA pipe. Negative flow means material removal. This means for an Outlet from a HYSYS-OLGA Link which is connected to a SOURCE, the OLGA GGSOUR, GLHLMA and GLWTMA flow variables will be negative but this sign is negated when used in HYSYS since the HYSYS Outlet flow is actually positive.
OLGA Link 8-47 8-47 message to one of the messages sent by the Client. The error message from OLGA follows in either the HYSYS Trace window or message dialogue box. To see these warning messages, you need to use the Log All Communication checkbox and view the special HYSYS trace log file. These error messages should be reviewed in conjunction with your OLGA documentation and perhaps running the OLGA model standalone through the same operating scenario. If a message is preceded with the words METHOD - then this indicates that Visual Basic has experienced an exception in the extension code. The Link was written to be as robust as possible and the VB code will just report this exception with its associated error message and then carry on. 8.4.6 Trace Debugging If problems are experienced while using the HYSYS-OLGA Link, then you can try turning on the Log All Communication checkbox on the OLGA page of the Dynamics tab. This will trace all client to server (and vice versa) messages by opening two new files. One will be on the HYSYS side and will be located in the same directory as where your HYSYS case resides. The file will have a name of OLGA2000Client- dd_mmm_yy-hh_mm.log where the date and time stamp are appended. This file contains all messaging as logged by the client (that is the HYSYS extension code).

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