LES Boundary Conditions for Pipe Flow
 

Hello everyone,

I am currently trying to model some spray evaporation and chemistry and want to start using LES to resolve the spray velocity distribution better. I was previously using RANS w/k-epsilon and obtaining decent flow with the following BCs:

U: inlet = fixedValue (average U)
outlet = zeroGradient

p: inlet = inletOutlet
outlet = outletInlet

k: inlet = calculated
outlet = zeroGradient

When running the same case in LES, I get very peculiar velocity fluctuations (pictures attached). Not a ton of experience with LES, so I figure there is a better way to set the BC. Inlet is on the left side, outlet on the right. Cylindrical pipe with walls BC specified for each. Length is 8m, diameter is 0.3m. Using an O-grid, total cells are about 320K

Thanks!