I am struggling with running the simulation of incompressible flow, I have tried for many times but it still doesnt work. Can anyone please help me.
URL: https://www.simscale.com/workbench/?pid=5873768082582250422&rru=44a93cf8-d59e-464c-aa11-46c5b59c8607&ci=ca449b81-838c-4e44-94e6-3bf568ed18ae&mt=SIMULATION_RESULT&ct=SOLUTION_FIELD
Hi @HenglongAng, thanks for posting on the forum and welcome to the SimScale Community 
Since your mesh looks good, the problem most likely comes from the “mean value” velocity inlet boundary condition:
Changing it to fixed value should solve the issues.
Cheers
Igor