TY - JOUR
T1 - DNS of passive scalar transport in turbulent channel flow at high Schmidt numbers
AU - Schwertfirm, Florian
AU - Manhart, Michael
PY - 2007/12
Y1 - 2007/12
N2 - We perform DNS of passive scalar transport in low Reynolds number turbulent channel flow at Schmidt numbers up to Sc = 49. The high resolutions required to resolve the scalar concentration fields at such Schmidt numbers are achieved by a hierarchical algorithm in which only the scalar fields are solved on the grid dictated by the Batchelor scale. The velocity fields are solved on coarser grids and prolonged by a conservative interpolation to the fine-grid. The trends observed so far at lower Schmidt numbers Sc ≤ 10 are confirmed, i.e. the mean scalar gradient steepens at the wall with increasing Schmidt number, the peaks of turbulent quantities increase and move towards the wall. The instantaneous scalar fields show a dramatic change. Observable structures get longer and thinner which is connected with the occurrence of steeper gradients, but the wall concentrations penetrate less deeply into the plateau in the core of the channel. Our data shows that the thickness of the conductive sublayer, as defined by the intersection point of the linear with the logarithmic asymptote scales with Sc-0.29. With this information it is possible to derive an expression for the dimensionless transfer coefficient K+ which is only dependent on Sc and Reτ. This expression is in full accordance to previous results which demonstrates that the thickness of the conductive sublayer is the dominating quantity for the mean scalar profile.
AB - We perform DNS of passive scalar transport in low Reynolds number turbulent channel flow at Schmidt numbers up to Sc = 49. The high resolutions required to resolve the scalar concentration fields at such Schmidt numbers are achieved by a hierarchical algorithm in which only the scalar fields are solved on the grid dictated by the Batchelor scale. The velocity fields are solved on coarser grids and prolonged by a conservative interpolation to the fine-grid. The trends observed so far at lower Schmidt numbers Sc ≤ 10 are confirmed, i.e. the mean scalar gradient steepens at the wall with increasing Schmidt number, the peaks of turbulent quantities increase and move towards the wall. The instantaneous scalar fields show a dramatic change. Observable structures get longer and thinner which is connected with the occurrence of steeper gradients, but the wall concentrations penetrate less deeply into the plateau in the core of the channel. Our data shows that the thickness of the conductive sublayer, as defined by the intersection point of the linear with the logarithmic asymptote scales with Sc-0.29. With this information it is possible to derive an expression for the dimensionless transfer coefficient K+ which is only dependent on Sc and Reτ. This expression is in full accordance to previous results which demonstrates that the thickness of the conductive sublayer is the dominating quantity for the mean scalar profile.
KW - DNS
KW - High Schmidt number
KW - Mass transfer coefficient
KW - Passive scalar
KW - Turbulent channel flow
UR - http://www.scopus.com/inward/record.url?scp=36248976201&partnerID=8YFLogxK
U2 - 10.1016/j.ijheatfluidflow.2007.05.012
DO - 10.1016/j.ijheatfluidflow.2007.05.012
M3 - Article
AN - SCOPUS:36248976201
SN - 0142-727X
VL - 28
SP - 1204
EP - 1214
JO - International Journal of Heat and Fluid Flow
JF - International Journal of Heat and Fluid Flow
IS - 6
ER -