ORCID Profile
0000-0002-3300-7669
Current Organisation
University of Nicosia
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Publisher: AIP Publishing
Date: 10-2021
DOI: 10.1063/5.0065257
Abstract: This paper concerns implicit large eddy simulations of subsonic flows through a symmetric suddenly expanded channel. We aim at shedding light on the flow physics at a relatively high Reynolds number of 10 000, based on the inlet bulk velocity and the step height of the channel, and examine the compressibility effects for two Mach numbers, Ma = 0.1 and Ma = 0.5. Comparisons with experimental measurements are provided. In addition, we investigate the structure of the separated regions, turbulence structures—through the Reynolds stress anisotropy componentality—and turbulence kinetic energy budgets. The results reveal that compressibility influences particular flow physics.
Publisher: Elsevier BV
Date: 05-2011
Publisher: ASME International
Date: 09-07-2014
DOI: 10.1115/1.4027367
Abstract: This paper presents an investigation into the use of a moving mesh algorithm for solving unsteady turbulent mixing problems. The growth of a shock induced mixing zone following reshock, using an initial setup comparable to that of existing experimental work, is used to evaluate the behavior of the numerical scheme for single-mode Richtmyer–Meshkov instability (SM-RMI). Subsequently the code is used to evaluate the growth rate for a range of different initial conditions. The initial growth rate for three-dimensional (3D) SM Richtmyer–Meshkov is also presented for a number of different initial conditions. This numerical study details the development of the mixing layer width both prior to and after reshock. The numerical scheme used includes an arbitrary Lagrangian–Eulerian grid motion which is successfully used to reduce the mesh size and computational time while retaining the accuracy of the simulation results. Varying initial conditions shows that the growth rate after reshock is independent of the initial conditions for a SM provided that the initial growth remains in the linear regime.
Publisher: Informa UK Limited
Date: 2011
Publisher: ASME International
Date: 29-06-2007
DOI: 10.1115/1.2801367
Abstract: The paper presents implicit large-eddy simulation (ILES) simulation of a shock tube experiment involving compressible turbulent mixing. A new characteristic-based approximate Riemann solver is derived, and employed in a second-order and fifth-order finite volume Godunov-type ILES framework. The methods are validated against (qualitative) experimental data and then compared and contrasted in terms of resolved turbulent kinetic energy and mixing parameters as a function of grid resolution. It is concluded that both schemes represent the experiment with good accuracy. However, the fifth-order results are approximately equivalent to results gained on double the grid size at second order, whereas the fifth-order method requires only approximately 20% extra computational time.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 10-2008
DOI: 10.2514/1.36856
Publisher: Wiley
Date: 11-10-2007
DOI: 10.1002/FLD.1628
Publisher: Informa UK Limited
Date: 2013
Publisher: Elsevier BV
Date: 08-2008
Publisher: The Royal Society
Date: 28-07-2009
Abstract: Restrictions on computing power make direct numerical simulation too expensive for complex flows thus, the development of accurate large eddy simulation (LES) methods, which are industrially applicable and efficient, is required. This paper reviews recent findings about the leading order dissipation rate associated with high-resolution methods and improvements to the standard schemes for use in highly turbulent flows. Results from implicit LES are presented for a broad range of flows and numerical schemes, ranging from the second-order monotone upstream-centered schemes for conservation laws to very high-order (up to ninth-order) weighted essentially non-oscillatory schemes.
Publisher: Elsevier BV
Date: 10-2007
Publisher: Informa UK Limited
Date: 2012
Publisher: AIP Publishing
Date: 09-2011
DOI: 10.1063/1.3638616
Abstract: This paper presents a numerical study of a reshocked turbulent mixing layer using high-order accurate Implicit Large-Eddy-Simulations (ILES). Existing theoretical approaches are discussed, and the theory of Youngs (detailed in Ref. 1) is extended to predict the behaviour of a reshocked mixing layer formed initially from a shock interacting with a broadband instability. The theory of Mikaelian2 is also extended to account for molecular mixing in the single-shocked layer prior to reshock. Simulations are conducted for broadband and narrowband initial perturbations and results for the growth rate of the reshocked layer and the decay rate of turbulent kinetic energy show excellent agreement with the extended theoretical approach. Reshock causes a marginal decrease in mixing parameters for the narrowband layer, but a significant increase for the broadband initial perturbation. The layer properties are observed to be very similar post-reshock, however, the growth rate exponent for the mixing layer width is higher in the broadband case, indicating that the reshocked layer still has a dependence (although weakened) on the initial conditions. These results have important implications for Unsteady Reynolds Averaged Navier Stokes modelling of such instabilities.
Publisher: AIP Publishing
Date: 04-2011
DOI: 10.1063/1.3570692
Abstract: Jet injection into a supersonic cross-flow is a challenging fluid dynamics problem in the field of aerospace engineering which has applications as part of a rocket thrust vector control system for noise control in cavities and fuel injection in scramjet combustion chambers. Several experimental and theoretical/numerical works have been conducted to explore this flow however, there is a dearth of literature detailing the instantaneous flow which is vital to improve the efficiency of the mixing of fluids. In this paper, a sonic jet in a Mach 1.6 free-stream is studied using a finite volume Godunov type implicit large eddy simulations technique, which employs fifth-order accurate MUSCL (Monotone Upstream-centered Schemes for Conservation Laws) scheme with modified variable extrapolation and a three-stage second-order strong-stability-preserving Runge–Kutta scheme for temporal advancement. A digital filter based turbulent inflow data generation method is implemented in order to capture the physics of the supersonic turbulent boundary layer. This paper details the averaged and instantaneous flow features including vortex structures downstream of the jet injection, along with the jet penetration, jet mixing, pressure distributions, turbulent kinetic energy, and Reynolds stresses in the downstream flow. It demonstrates that Kelvin–Helmholtz type instabilities in the upper jet shear layer are primarily responsible for mixing of the two fluids. The results are compared to experimental data and recently performed classical large eddy simulations (LES) with the same initial conditions in order to demonstrate the accuracy of the numerical methods and utility of the inflow generation method. Results here show equivalent accuracy for 1∕45th of the computational resources used in the classical LES study.
Publisher: Elsevier BV
Date: 05-2008
Publisher: Cambridge University Press (CUP)
Date: 12-05-2010
DOI: 10.1017/S0022112010000492
Abstract: This paper investigates the influence of different three-dimensional multi-mode initial conditions on the rate of growth of a mixing layer initiated via a Richtmyer–Meshkov instability through a series of well-controlled numerical experiments. Results are presented for large-eddy simulation of narrowband and broadband perturbations at grid resolutions up to 3 × 10 9 points using two completely different numerical methods, and comparisons are made with theory and experiment. It is shown that the mixing-layer growth is strongly dependent on initial conditions, the narrowband case giving a power-law exponent θ ≈ 0.26 at low Atwood and θ ≈ 0.3 at high Atwood numbers. The broadband case uses a perturbation power spectrum of the form P ( k ) ∝ k −2 with a proposed theoretical growth rate of θ = 2/3. The numerical results confirm this however, they highlight the necessity of a very fine grid to capture an appropriately broad range of initial scales. In addition, an analysis of the kinetic energy decay rates, fluctuating kinetic energy spectra, plane-averaged volume fraction profiles and mixing parameters is presented for each case.
Publisher: Elsevier BV
Date: 05-2008
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Dimitris Drikakis.