OpenLabs - Recent Threads

Problems with openLabs

sriluta — Mon, 03 Apr 2023 10:38:59 GMT

Hey,

iam using OpenLabs because my inlet boundary conditions change with the time and the azimuth angle in the unsteady Simulation. So OpenLabs works with SI Units. In the first time, I defined the pressure in bar ( since didn't know that OpenLabs works with SI Units and there the pressure is defined in pascal ). So with the following function implemented in OpenLabs for the absolut total pressure I didn't got Problems:

3.853 + (-0.9863)*cos(tCoord*1.966 + 2*PI*Time/timePeriod) + 0.08183*sin(tCoord*1.966+ 2*PI*Time/timePeriod) + (-0.2735)*cos(tCoord*3.932+ 2*PI*Time/timePeriod) + 0.6356*sin(tCoord*3.932+ 2*PI*Time/timePeriod) + 0.588*cos(tCoord*5.88 + 2*PI*Time/timePeriod) + (-0.1489)*sin(tCoord*5.88 + 2*PI*Time/timePeriod) + (-0.07768)*cos(tCoord*7.864 + 2*PI*Time/timePeriod) + (-0.2232)*sin(tCoord*7.864 + 2*PI*Time/timePeriod) + (-0.3242)*cos(tCoord*9.83 + 2*PI*Time/timePeriod) + 0.01536*sin(tCoord*9.83 + 2*PI*Time/timePeriod) + 0.1678*cos(tCoord*11.796+ 2*PI*Time/timePeriod) + 0.2214*sin(tCoord*11.796 + 2*PI*Time/timePeriod) + 0.1408*cos(tCoord*13.762 + 2*PI*Time/timePeriod) + (-0.0754)*sin(tCoord*13.762+ 2*PI*Time/timePeriod) + (-0.1216)*cos(tCoord*15.728 + 2*PI*Time/timePeriod) + (-0.1922)*sin(tCoord*15.728 + 2*PI*Time/timePeriod)

when I found out that OpenLabs works in SI units, I converted the sizes from bar to pascal and created the new following function:

390101.438+ (−99956.492)*cos(1.963*tCoord + 2*PI*Time/timePeriod)+ 9062.116*sin(1.963*tCoord + 2*PI*Time/timePeriod)+ (−26626.657)*cos(3.927*tCoord + 2*PI*Time/timePeriod)+63969.754*sin(3.927*tCoord + 2*PI*Time/timePeriod)+57284.906*cos(5.890*tCoord + 2*PI*Time/timePeriod) + (−15828.864)*sin(5.890*tCoord + 2*PI*Time/timePeriod) + (−8525.752)*cos(7.854*tCoord + 2*PI*Time/timePeriod) + (−21014.003)*sin(7.854*tCoord + 2*PI*Time/timePeriod) + (−30331.247)*cos(9.817*tCoord + 2*PI*Time/timePeriod)+2857.566*sin(9.817*tCoord + 2*PI*Time/timePeriod)+15956.411*cos(11.781*tCoord + 2*PI*Time/timePeriod)+19562.181*sin(11.781*tCoord + 2*PI*Time/timePeriod)+11641.815*cos(13.744*tCoord + 2*PI*Time/timePeriod) + (−6956.443)*sin(13.744*tCoord + 2*PI*Time/timePeriod) + (−10933.721)*cos(15.708*tCoord + 2*PI*Time/timePeriod) + (−14834.89)*sin(15.708*tCoord + 2*PI*Time/timePeriod).

If I click in OpenLabs at validate labs everything is fine, if I start the Simulation, the Simulation stops from beginning and say there is a problem with OpenLabs. I also defined the functions for the absolut Total Temperature and arctg( Vt/Vz) and there are no Problems but just with the pressure. Now I dont know what to do,

greetings 🙂

Unsteady inlet boundary condition with OpenLabs

sriluta — Wed, 15 Feb 2023 11:30:41 GMT

Hey, I have at my inlet three Boundary conditions that changes with time and the azimuth angle. Arctg (Vt/Vz), Absolute total pressure and the absolute temperature. In the Inlet of my domain, I import the profiles, that changes with the azimuth angle. Now I want to change these profiles with the time too and I need to use OpenLabs for. In the tutotorial of OpenLabs I saw a expression with a sine function ( tutorial 2: customized unsteady Inlet boundary condition), but I don't like to use that. Is it possible to use an array of values ?

For example my time step is 0.000011s. At an azimuth angle of 0 degree I have a total pressure of 1 Bar and the time is 0. At an azimuth angle of 90 degree a have a total pressure of 2 bar and the time is 0.000011s. At an azimuth angle of 180 degree I have a total pressure of 3 bar and the time is 0.000022s and so on, is that possible ? I don't like to use a function here for.

Iam simulating a stator..

greetings Hussein

Cavitation with Thermodynamics table issue

JosephSmith — Wed, 04 Jan 2023 15:54:01 GMT

Greetings,

I have been attempting to use thermodynamic tables to simulate cavitation within a turbopump. Water was the working fluid. However, I have been getting a run time error right at the beginning of the simulation – this is seen in the attached log file I copied.

community.cadence.com/.../3146.thermotable-error.txt

I followed the parameter guidelines in the FINE Open user and theory guide when using the thermodynamic tables option (I first changed the iCavitation_ value to 2 then changed the rest of the parameters locally in the advanced Control variables tab). The initial solution was taken from a converged run without cavitation models. This initial solution worked with the Barotropic cavitation model but not with Thermodynamic tables.

I’m still in the process of troubleshooting possible ways of where the error lies. Not certain if its relevant to the error, but I did not understand what the user manual meant by using thermodynamics tables in the Physical configuration > Fluid model page, seen in attached image.

I would appreciate any assistance on the error or to what the manual referred to for the former.

Kind regards,

Joseph

Actuator disk modeling in OpenLabs

Colinda — Fri, 16 Dec 2022 15:02:45 GMT

To avoid meshing a full propeller, using an actuator disk model may be more suited to save cell count. The validity of such approximation depends of course on the objectives of the simulation and the required accuracy.

The actuator model adds source terms to the Navier-Stokes equations.

pressure far field boundary condition

sriluta — Thu, 07 Jul 2022 09:23:00 GMT

Hey, I am investigating the flow in a turbine with only one stator. For the outlet I would like to set a pressure far field BC, because I don't now the static pressure in the outlet. For this I have extended my domain length by 20 times the chord length of the blade. So how can I set this BC, with the Bc external for the outlet ? Iam using Omnis v2,
thx

Undefined variable

Colinda — Tue, 22 Mar 2022 14:35:56 GMT

When I validate a lab it writes: Undefined variable “Xpc_1,Xpc_1” in the expression of Exprfbx_i.How to solve this?