Numerical investigation of TNTI in a turbulent channel flow

Many turbulent flows are characterised by a sharpand thin interface which divides the flow field intotwo distinct regions. In one of these regions flow isturbulent while in the other region, flow is mainlyirrotational and non-turbulent. This thin layer iscalled turbulent/non-turbulent interface (TNTI). Inthis research, TNTI is detected, by using directnumerical simulations (DNS) data for turbulentchannel flow at turbulent Reynolds numberReτ=۱۸۰. TNTI is identified using passive scalar andvorticity techniques. Both techniques are applied tothe turbulent kinetic energy (TKE) field andcompared to each other. Both the exact value ofthresholds is estimated using the conditionalprobability density function (PDF) curves of thepassive scalar (normalized TKE) and normalizedvorticity. Using the algorithm used in this paper,TNTI can be determined at TKE field of turbulentchannel flow. Thus, it is possible to measure thesizes of turbulent structures. However, the detectionof the turbulent region depends on the thresholdvalue. In passive scalar method, When the thresholdvalue is low, new turbulent regions are detected andsome of them merge with the previously identifiedregions.

Keywords:

DNS , TNTI , Turbulence , Channel flow.