Y+ value variation

- April 5, 2024 at 2:04 pm
  
  Simranjeet Singh
  Subscriber
  
  Hello everyone,
  
  I'm new to Fluent and have been working on simulating nozzle flow in a 2D axisymmetric case. I've learned that Y+ is an important value for assessing mesh quality. When I ran simulations using the pressure-based solver (PBS), I got Y+ values ranging from a minimum of 0.003 to a maximum of 3.216. However, with the density-based solver (DBS), I observed Y+ values ranging from a minimum of 0 to a maximum of 5.38e-7.
  
  I'm wondering what could be causing this discrepancy between the two solver types. Additionally, I've noticed that the PBS simulation converges in 356 iterations, while the DBS struggles to converge even after 2000 iterations.
  
  I would appreciate any insights or suggestions to help me understand and address these differences. I've added 15 inflation layers along the nozzle wall.
- April 11, 2024 at 2:11 pm
  
  SRP
  Ansys Employee
  
  Hi,
  The pressure-based solver typically uses the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm or its variants, such as PISO (Pressure-Implicit with Splitting of Operators). These algorithms are designed to solve the pressure-velocity coupling iteratively.
  The density-based solver, on the other hand, solves the compressible Navier-Stokes equations directly. It may use different numerical methods and algorithms compared to the pressure-based solver.
  I suggest you to choose correct solver based on the physics you are monitoring.
  You can also refer to What are pressure-based solver vs. density-based solver in FLUENT? - Ansys Knowledge
  Hope this helps.