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BTU
The One-Dimensional Turbulence model is modified in this work for its application to a classical electrohydrodynamic (EHD) problem. Being the first study case, this work is focused on the influence of electrostatic fields and space charge on the velocity field inside a wire-plate Electrostatic Precipitator (ESP) with one-way-coupling dynamics. The study case is an attempt to replicate velocity profiles and Turbulent Kinetic Energy (TKE) budgets obtained in the Direct Numerical Simulation (DNS) carried out by Soldati and Banerjee (1998). Qualitative trends are confirmed in preliminary ODT results, thus showing the potential of the stochastic ODT modeling approach for other types of EHD flows.
The stochastic One-Dimensional Turbulence (ODT) model is used in combination with a Large Eddy Simulation (LES) approach in order to illustrate the potential of the fully coupled model (ODTLES) for highly turbulent flows. In this work, we use a new C++ implementation of the ODTLES code in order to analyze the computational performance in a classical incompressible turbulent channel flow problem. The parallelization potential of the model, as well as its physical and numerical consistency are evaluated and compared to Direct Numerical Simulations (DNSs). The numerical results show that the model is capable of reproducing a representative part of the DNS data at a cheaper computational cost. This advantage can be enhanced in the future by the implementation of a straightforward parallelization approach.
Electrohydrodynamic‐enhanced internal pipe flows from a One‐Dimensional Turbulence perspective
(2020)
The computational cost of Direct Numerical Simulations (DNS) that resolve all scales rises with the cube of the Reynolds numberand is currently not feasible for real world applications. Large Eddy Simulations (LES) overcome this limitation by only resolving the large scale effects and completely model the small scaleeffects. This results in a strong dependence of the accuracy onthe chosen subgrid-scale model. The model adaptivity concept discussed in [Schmidt et al., ICDERS, 2007] dynamically uses different Linear Eddy Model (LEM) types [Kerstein, LEM, 1988] for stochastic closure to model the turbulent flame speed of apremixed flame within LES. In the talk, we will first summarize the progress of our group on One Dimensional Turbulence (ODT) [Kerstein, ODT, 1999] and Hierarchical Parcel Swapping (HiPS) [Kerstein, HiPS, 2013] based on reactive stand-alone simulations, [Jozefik et al., Combust. Flame, 2015] [Jozefik et al., Combust. Flame, 2016] [Medina et al., Combust. Flame, 2018]. Second,we will sketch a possible combination of the model adaptivity concept [Schmidt et al., ICDERS, 2007] and recent efficient ODTLES implementations [Glawe et al., Z. Angew. Math. Mech.,2018] to dynamically use LEM, ODT and HIPS together inside ofLES solvers to simulate turbulent reactive flows.
Zur jüngsten Entwicklung in der Modellierung von turbulenten Verbrennungsprozessen mittels ODT
(2019)
Joint predictive modeling of hydrodynamics and electrokinetics is a standing numerical challenge but crucial for various applications in electrochemistry and power engineering. The present lack in modeling of electrohydrodynamic (EHD) turbulent flows lies in the treatment of small-scale processes and scale interactions. To overcome these limitations, a stochastic one-dimensional turbulence (ODT) model is utilized. The model aims to resolve all scales of the flow, but only on a notional line-of-sight, modeling turbulent advection by a stochastically sampled sequence of eddy events that punctuate deterministic molecular diffusive advancement. In this study, two canonical flow configurations are investigated that address different coupling strategies and flow physics. First, EHD effects in a variable-density vertical pipe flow of an ideal gas with an inner concentric electrode are investigated with a one-way coupled model formulation. Electric fields are generated by means of a corona discharge and the corresponding effect of a fixed ionic charge density field. Second, in order to reduce physical complexity, EHD effects the turbulent boundary layers in plane Couette flow of an isothermal univalent ionic liquid are investigated with a fully coupled model formulation. Both application cases demonstrate that ODT has predictive capabilities due to multiscale resolution of transport processes. Present results suggest that more expensive fully than one-way coupling of electrokinetics is crucial when charge relaxation times are significantly larger than the mean advection time scale.
The incompressible temporally developing turbulent boundary layer
(TBL) is analysed using the map-based stochastic one-dimensional
turbulence (ODT) model. The TBL is a canonical flow problem, which is, in the present study, formed by a planar moving wall and a free stream at rest. An understanding of this idealised flow is of fundamental relevance for the numerical analysis of turbulent boundary-layer-type flows. In the present ODT simulations, the flow variables are resolved on all scales along a wall-normal, one-dimensional domain. These variables are evolved by a deterministic and a stochastic process. The latter models the effect of turbulent advection and pressure fluctuations, whereas the former represents molecular diffusion. The model is appropriate for high Reynolds numbers for
which the turbulence field exhibits a broad range of scales and is notionally featureless. We show that ODT is able to capture salient features of the TBL by comparing the various statistics with available reference direct numerical simulation (DNS) results for different bulk Reynolds numbers in the range 250 ≤ Reb ≤ 2000 using fixed model parameters. The influence of the model parameters is analysed for Reb = 1000 and optimal parameter values are provided. The results discussed in this paper suggest that ODT is an economical and reasonably accurate approach for the simulation of transient turbulent boundary-layer-type flows.