Learning Forum

[ShubhamG]

Hello, I am trying to perform a Fluid Structure Interaction of a Building in ansys. I have used a coupled Transient Fluent framework. I have modelled my building using line and shell elements. I have modelled Fluid domain such that the meshing near building is fine while it is coarser away from the building. I have suppressed the fluid in transient module and the building model in fluent module. I have defined a fluid solid interface also. The named selections include inlet, outlet, fluid, wall and building. The dynamic mesh properties include inlet and outlet as stationary, Fluid as deformable and building as system coupling. In co-sim sequence in system coupling I have assigned fluid as 1 and transient as 2. I have considered data transfer region as building.

I am getting an error as "Update failed for the Solution component in system coupling. The coupled update for system Transient Structural threw an exception. Error updating cell solution in system Transient Structural." Does anyone know how to solve this error. The photos and procedure used have been attached.

[Stephen Orlando]

Array, can you provide some more details on the physics and goals of this simulation? If the deflection of the building doesn't have a significant affect on the flow, then this can be modelled with a 1-way transfer of pressure from Fluent (steady) to Mechanical (static structural) with a direct connection in Workbench. This 1-way method doesn't use System Coupling. If the deflection does affect the flow, you'll need to use a 2-way transfer with System Coupling. nWhen running System Coupling and it stops running, the first thing to do is examine the output files for each solver to look for clues to what happened. For Fluent, look at the transcript .trn file. For Mechanical, look at the .out file. For CFX, look at the .out file. Also, look at the System Coupling log file, .scl.nI recommend going over this tutorial in the Ansys documentation that shows a 2-way FSI simulation with Fluent and Mechanical. https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v202/en/sysc_tut/sysc_tut_oscplate_wb_fluent.htmlnSystem Coupling Tutorials \\ Tutorials with Workbench-Setup Workflows \\ Tutorials with Workbench Setup and Execution \\ Oscillating Plate FSI with Fluent and MechanicalnYou can also look at the following for a similar tutorial but run with the System Coupling GUI outside of Workbench. The new System Coupling GUI (run outside of Workbench) is available by searching for System Coupling 2019R3 (or newer) in the Windows Start menu. https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/sysc_tut/sysc_tut_reedvalve_fluent.htmlnFSI simulations with very soft materials or membranes are prone to numerical instabilities. In 2020R1 we have introduced a stabilization method in System Coupling called the Quasi-Newton Stabilization Algorithm. Note that this has to be used with the new System Coupling GUI or Command Line Interface that is run outside of Workbench. More information here: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/sysc_ug/sysc_gen_scservice_dt_supplemental_iqnils.htmlnSystem Coupling User's Guide \\ System Coupling Data Transfers \\ Supplemental Processing Algorithms \\ Quasi-Newton Stabilization AlgorithmnIt is very important to build up the FSI simulation in stages as opposed to setting up the 2-way FSI right at the start. This document Best Practices for Coupled Fluid-Structure Interaction (FSI) describes this process and is available here: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v211/en/sysc_ug/sysc_bestpractices_fsi.htmlnSystem Coupling User's Guide \\ Best Practices for System Coupling \\ Best Practices for Coupled Fluid-Structure Interaction (FSI)n

[ShubhamG]

Thankyou for your suggestion sir. I tried to do the 1-way FSI as you said. But now I am getting this error, 'The normal of target element 184247 is not consistent with the normal of target element 184309 in real set 6561. Please use the ENORM command to correct it'. I read about it that the local axis of the two elements must not be matching so flip the element. Am I correct, But how can I find these elements. And also how can I use ENORM command or flip the same element. Note : I have got around 7000 elements in my model.nn

[Stephen Orlando]

Hi, for a 1-way FSI simulation, it's best not to use System Coupling. Instead, connect Fluent directly to Mechanical, ie connect Fluent cell C5 to Mechanical cell B5 in Workebench.nSteven