Cannot Define Run without a valid definition file!
 

I am trying to achieve two way FSI using CFX, but every time I am getting same error like "Cannot Define Run without a valid definition file!" can anyone tell me how to rectify this.

I would have thought creating a valid definition file would probably fix it. Sarcasm aside, the error message is very clear, and you have provided no information about what you are doing so we cannot help you.

I am very new to ANSYS, I am trying to run simulation of two way FSI oscillating plate.

If you want further explanation I am using ANSYS 18.0 Workbench for Two way FSI of Oscillating Plate. I don't require .def files but some how I am getting that error.

Have you done the tutorial examples for FSI simulations? They are available on the ANSYS Customer webpage.

FSI simulations are relatively easy to do if you are familiar with both packages: structural (ANSYS), and fluids (CFX/Fluent); however, if you are new to both packages, you are better off following the tutorials step by step and familiarize yourself with the vocabulary used by the packages used.

For two-way FSI simulation, both packages must be run, and they require some kind of input file regardless if you see it or not during the process.