Fundamental analysis of turbulent flows
It is well known that in turbulent flows, some statistics of the velocity gradient tensor are universal, for example the shape of Q-R diagram, the alignment of the vorticity vector with the intermediate strain-rate eigenvector etc. Our work focuses on the emergence of these universal features in the wake of a square grid element, i.e. from the potential to transitional and then to fully developed turbulent regions. We have performed very high resolution DNS simulations (with resolution smaller than the Kolmogorov length scale). This has allowed us to capture accurately higher moments of the fluctuating fields, and analyse the inception and subsequent evolution of these universal features.
We study also the interscale energy transfer in inhomogeneous and anisotropic flows using the Kármán–Howarth–Monin–Hill equation. This is a generalised scale-by-scale energy balance equation which, unlike the standard Kármán–Howarth equation, does not require the homogeneity or isotropy assumptions. We have used this equation to study the interscale energy transfer in the turbulent wake behind a square prism and the effect of large scale vortex shedding motion on the transfer process. This work was carried out in collaboration with Prof. J.C. Vassilicos.
Current work focuses on the analysis of interscale energy transfer in transitional boundary layers.
- H. Yao, F. Alves-Portela, and G. Papadakis (2020) Evolution of conditionally-averaged second order structure functions in a transitional boundary layer, Physical Review Fluids, 5, 093902
- F. Alves Portela, G. Papadakis and J. C. Vassilicos (2020) The role of Coherent Structures and Inhomogeneity in Near-Field Inter-Scale Turbulent Energy Transfers, J. Fluid Mech., vol. 896, A16. [selected for a Focus on Fluids paper].
- Paul, I., Papadakis, G. and Vassilicos, J.C. (2017) Genesis and spatial evolution of velocity gradients from production to decay regions of grid turbulence, J. Fluid Mech., Vol. 815, pp. 295-332.
- F. Portela, G. Papadakis, J.C. Vassilicos (2017) The Turbulence Cascade in the Near Wake of a Square Prism, J. Fluid Mech. vol. 825, pp. 315-352.
- I. Paul, G. Papadakis and J.C. Vassilicos (2018) DNS of heat transfer from a cylinder immersed in the production and decay regions of grid-element turbulence J. Fluid Mech., 847:452-488.
- Paul, I., Papadakis, G. and Vassilicos, J.C. (2018) Evolution of passive scalar statistics in a spatially developing turbulence, Physical Review Fluids, 3(1): 014612.
- F. Portela, G. Papadakis, J.C.Vassilicos (2018) Turbulence dissipation and the role of coherent structures in the near wake of a square prism, Physical Review Fluids, 3, 124609
- I.Paul (2017)Evolution of velocity and scalar gradients in a spatially developing turbulence, PhD thesis, Dept. of Aeronautics, Imperial College London.
- Alves Portela, Felipe (2017) Turbulence cascade in an inhomogeneous turbulent flow, PhD thesis, Dept. of Aeronautics, Imperial College London.