An easy-to-use turbulent inlet boundary condition for large-eddy simulation of radial diffusers

Pekka Saarinen*, Hannu Koskela, Timo Siikonen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


When applying time-accurate computational fluid dynamics, large-eddy simulation (CFD LES) to room ventilation, a common problem is that the supply jets do not model properly if there is no realistic turbulence in the inflow boundary. In this paper we introduce a novel, easy-to-use method of generating a turbulent inlet boundary condition for simulating a radial diffuser. The basic idea is to apply a time-independent velocity distribution with realistic spatial statistics, and to add temporal fluctuations by rotation. The method is simple to use, requires only one extra parameter, and does not necessitate large storage files. It needs a momentary velocity distribution on the inflow surface with the desired volume flow rate obtained from a time-accurate internal simulation of the diffuser alone. In a room-scale simulation, this velocity distribution is put in rotating movement in order to mimic a turbulent inlet boundary. The method is verified by comparing the outcome with published measurements and with a simulation containing the interior of the diffuser.

Original languageEnglish
Pages (from-to)569-581
Number of pages13
Issue number5
Publication statusPublished - 1 Oct 2016
MoE publication typeA1 Journal article-refereed


  • CFD
  • inlet boundary condition
  • large-eddy simulation
  • radial diffuser
  • radial jet
  • turbulent inflow

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