Transient Flow Lab

Direct numerical simulation is performed of a transient flow in a channel consisting of a rough bottom wall made of close-packed 3-D pyramid roughness and a smooth top wall. The unsteady flow started from an initially statistically steady turbulent flow with  and increased linearly, within a very short time, to a final Reynolds number ranging from. The corresponding equivalent sand roughness Reynolds for the initial and final flows are respectively and, the research is looking into study unsteady flow behaviour in the transitionally-rough regime.

^{Figure 2. Turbulent-turbulent transient flow over rough surface.}

Using Direct Numerical Simulations DNS, this study examines the turbulent drag reduction for the novel implementation of the Backswimmer insect inspired texture geometry. Simulations are performed for a channel flow at low friction Reynolds number (Re = 180). Turbulence statistics and the detailed flow structures are compared against those used for the smooth channel flow.  Preliminary results shows drag reduction (DR) of 20%.

We use national, regional and Faculty-level high-performance computing (HPC) facilities. Our Faculty’s and departmental Linux-base HPC computer clusters comprise ~400 computational cores which are continuously being under development to be upgraded to higher computational cores. 

STOKES

STOKES is our local High Performance Computing (HPC) resource. It provides computing capabilities for our students and researchers within the centre.

CFD/FEA Packages

CHAPSim is an in-house CFD package which simulate channel and pipe flow using state-of-the-art DNS/LES approaches. It has mainly been developed by Dr Mehdi Seddighi, (Seddighi, 2011, He and Seddighi, 2013) based on the methods/subroutines proposed by Orlandi (2001); some further developments of the code have been carried out through contributions made by few PhD students and Post-docs under supervision of Dr Mehdi Seddighi and Prof. Shuisheng He (University of Sheffield). 

Abaqus

OpenFOAM

Experiments are carried out in a closed return wind tunnel at the Byrom Street Campus at Liverpool John Moores University. The working test section of the wind tunnel is 0.4m wide by 0.4m high. The normal range of air velocity is 0 to 35 m/s. The wind tunnel is equipped with a Plint and Partners Ltd. three component balance to measure various components of aerodynamic forces.

Seddighi M, He S. 2017. Turbulent-turbulent transient flow in a transitionally rough regime International Symposium on Turbulence and Shear Flow Phenomena, TSFP10 

Khosh Aghdam S, Ricco P, Seddighi M. 2015. Turbulent drag reduction by hydrophobic surfaces with shear-dependent slip length 15th European Turbulence Conference 

Seddighi M, He S, Vardy AE, O’Donoghue T, Dubravka P. 2015. Near-wall behaviour of transient flow in a channel with distributed 3-D roughnessInternational Symposium on Turbulence and Shear Flow Phenomena, TSFP9 

Seddighi M, He S. 2012. Turbulence structure in a rapidly accelerating channel flow

Mathur A, Seddighi M, He S. 2018. Transition of Transient Channel Flow with High Reynolds Number Ratios Entropy, 20(5)  >DOI

Mathur A, Gorji S, He S, Seddighi M, Vardy AE, ODonoghue T, Pokrajac D. 2018. Temporal acceleration of a turbulent channel flow Journal of Fluid Mechanics, 835 :471-490 >DOI

He S, He K, Seddighi M. 2016. Laminarisation of flow at low Reynolds number due to streamwise body force Journal of Fluid Mechanics, 809 :31-71 >DOI

He K, Seddighi M, He S. 2016. DNS study of a pipe flow following a step increase in flow rate International Journal of Heat and Fluid Flow, 57 :130-141 

Seddighi M, He S, Pokrajac D, O'Donoghue T, Vardy AE. 2015. Turbulence in a transient channel flow with a wall of pyramid roughness Journal of Fluid Mechanics, 781 :226-260 >DOI

He S, Seddighi M. 2015. Transition of transient channel flow after a change in Reynolds number Journal of Fluid Mechanics, 764 :395-427 >DOI

Seddighi M, He S, Vardy AE, Orlandi P. 2014. Direct numerical simulation of an accelerating channel flow Flow, Turbulence and Combustion, 92 :473-502 >DOI

Gorji S, Seddighi M, Ariyaratne C, Vardy AE, O'Donoghue T, Pokrajac D, He S. 2014. A comparative study of turbulence models in a transient channel flow Computers and Fluids, 89 :111-123 >DOI

He S, Seddighi M. 2013. Turbulence in transient channel flow Journal of Fluid Mechanics, 715 :60-102 >DOI

Seddighi M, He S, Orlandi P, Vardy AE. 2011. A comparative study of turbulence in ramp-up and ramp-down unsteady flows Flow, Turbulence and Combustion, 86 :439-454 >DOI