Ioannis W. Kokkinakis

On the propagation and multiple reflections of a blast wave travelling through a dusty gas in a closed box

This paper concerns the propagation of shock waves in an enclosure filled with dusty gas. The main motivation for this problem is to probe the effect on such dynamics of solid particles dispersed in the fluid medium. This subject, which has attracted so much attention over recent years given its important implications in the study of the structural stability of systems exposed to high-energy internal detonations, is approached here in the framework of a hybrid numerical two-way coupled Eulerian-Lagrangian methodology. In particular, insights are sought by considering a relatively simple archetypal setting corresponding to a shock wave originating from a small spherical region initialized on the basis of available analytic solutions. The response of the system is explored numerically with respect to several parameters, including the blast intensity (via the related value of the initial shock Mach number), the solid mass fraction (mass load), and the particle size (Stokes number). Results are presented in t...

Implicit large eddy simulation of acoustic loading in supersonic turbulent boundary layers

This paper investigates the accuracy of implicit large eddy simulation in the prediction of acoustic phenomena associated with pressure fluctuations within a supersonic turbulent boundary layer. We assess the accuracy of implicit large eddy simulation against direct numerical simulation and experiments for attached turbulent supersonic flow with zero-pressure gradient, and further analyze and discuss the effects of turbulent boundary layer pressure fluctuations on acoustic loading both at the high and low frequency regimes. The results of high-order variants of the simulations show good agreement with theoretical models, experiments, as well as previously published direct numerical simulations.

Comparison of the Finite Volume and Discontinuous Galerkin schemes for the Double Vortex Pairing Problem using the SU2 Software Suite

A numerical investigation of finite volume (FV) and discontinuous Galerkin (DG) finite element methods in the framework of the SU2 software is presented. The accuracy of different numerical variants is assessed with reference to the low Mach double vortex pairing flow problem, which has recently been proposed as a benchmark for studying the properties of structured and unstructured grid based methods with respect to turbulent-like vortices. The present study reveals that low-Mach corrections significantly improve the accuracy of second- and third-order, unstructured grid based schemes, at flow speeds in the incompressible limit. Furthermore, the 3rd-order DG method produces results similar to 11th-order accurate FV volume schemes.

Physical insight into a Mach 7.2 compression corner flow

High-order implicit Large Eddy Simulations were conducted to study shock-boundary layer interaction around a 33° compression corner at Mach 7.2 and Reynolds number of Reθ = 3,500 based on the momentum thickness. A grid-convergence study was performed to reduce the computational uncertainty and the results were compared with experiments and theoretical predictions. Furthermore, the turbulent flow properties were analysed with respect to the Reynolds normal stress, skewness and flatness, and conclusions were drawn regarding the shock boundary layer interaction behavior.

Thermoacoustic effects in high-speed compressible transitional and turbulent boundary layers

A numerical investigation of the thermal and acoustic effects in high-speed compressible flows is presented. Two case studies are considered: i) transition to turbulence in supersonic flows over a flat plate, and ii) supersonic shock wave turbulent boundary layer interaction (SWTBLI) over a compression ramp. Implicit Large Eddy Simulations (iLES) are performed using the second and fifth order Monotone-Upstream Central Scheme for Conservation Laws (MUSCL) and the ninth order Weighted Essentially Non-Oscillatory (WENO) schemes. The aim of this study is twofold: i) to examine the acoustic and thermal effects associated with transitional and turbulent boundary layers, particularly in the near wall region; ii) to investigate the effects of numerical accuracy on acoustic and thermal loading. The results are compared with theoretical models, Direct Numerical Simulations (DNS) and experiments.

Near-wall behaviour of implicit large eddy simulations

This paper investigates the accuracy of implicit large eddy simulations (ILES) in compressible turbulent boundary layers (TBL). ILES are conducted in conjunction with Monotonic Upstream-Centred Scheme for Conservation Laws (MUSCL) and Weighted Essentially Non-Oscillatory (WENO), ranging from 2nd to 9th-order. The excess artificial dissipation occurring at low Mach numbers is counter-balanced by using low Mach corrections. The study concludes that high-order ILES provide accurate predictions of TBL even on relatively coarse grids.