DNS, experimental and modelling study of axially compressed in-cylinder swirling flow

The paper reports on recent progress in the investigation and modelling of joint effects of compression and swirl on turbulence in a cylinder of a sin gle-stroke rapid compression machine (RCM). Experimental and modelling inve stigations cover a flat cylinder geometry and a 'squish' configuration with a bowl-in-cylinder head. In addition, the direct numerical simulations (DN S) of all three operational modes of RCM have been performed: steady rotati on, transient spin-down without compression and transient spin-down with co mpression. The Reynolds-averaged Navier-Stokes simulation (RANS) was perfor med using a low-Re-number second-moment closure. The results obtained are c ompared with the experimental results and with DNS. Prior to the computatio n of the RCM, the applied turbulence model was validated in several generic flows relevant to the RCM: developed and developing flows in an axially ro tating pipe, swirling flows in combustion chamber geometries and long strai ght pipes and several flows with mean compression, ranging from homogeneous compression to the compression in a closed cylinder. It is demonstrated th at in all cases considered including the RCM, the applied RANS model reprod uces reasonably well both the DNS and experimental results, without any mod el or coefficient modifications. (C) 2000 Begell House Inc. Published by El sevier Science Inc. All rights reserved.