Drag Coefficient

Drag Coefficient – Sphere

- April 17, 2020 at 2:49 pm
  
  moritz.mantel
  Subscriber
  
  Hello,
  
  i am currently working on a quite simple fluent simulation, with a steady water stream and a 1m-diameter sphere in the middle of the stream. My goal is to reach the known drag coefficient an drag force values for the sphere just to get some validation for a more complicated simulation i am working on. But actually the solutions i get in my fluent simulations are very different then what i found in the literature. I chose the k-omega SST viscous model for the simulation. I did also set the reference values and generated a fine mesh.
  
  I created a little table with the values i got from my simulation and the literature i found.
  
  Does anyone know where the problem might be or what i am doing wrong ? Thanks for every help.
- April 20, 2020 at 9:03 pm
  
  RK
  Ansys Employee
  
  Hello,
  
  Can you please specify the boundary conditions and the solution methods you using for the simulation?
  
  Regards,
  
  Rahul
- April 21, 2020 at 11:50 am
  
  moritz.mantel
  Subscriber
  
  I have a large fluid body with a little "hole" in it which is my sphere. The sphere walls are no slip walls.
  
  Velocity Inlet - pressure outlet with 0 gauge pressure
  
  By now i tried all viscous models from laminar to LES but got similar results with all. For the solution methods i always kept the Fluent default settings for the calculation.
- April 21, 2020 at 2:32 pm
  
  RK
  Ansys Employee
  
  From the table you have provided, the deviation from the Ansys Fluent results from the diagram is large when the Re is of the order of e5 and greater.
  
  It is important in this case to resolve the boundary layer region. Here are links which gives some tips in resolving the y+.
  
  https://www.computationalfluiddynamics.com.au/tips-tricks-turbulence-part-4-reviewing-how-well-you-have-resolved-the-boundary-layer/
  
  https://www.computationalfluiddynamics.com.au/tips-tricks-cfd-estimate-first-cell-height/
  
  Regards,
  
  Rahul
- April 23, 2020 at 2:06 pm
  
  moritz.mantel
  Subscriber
  
  Hi Rahul, thanks a lot for your answer.
  
  What i don´t really get is how i can calculate or determine the y+ value i need. Is there any trick to this ?
  
  Regards, Moritz
- November 30, 2022 at 6:12 am
  
  Andrés Rivera
  Subscriber
  
  I am currently working on the same validation of my results. Did you find the correct setting?