Statistically Targeted Forcing (STF) Method for Synthetic Turbulence Generation of Initial Conditions in Three-Dimensional Turbulent Mixing Layer Flow

2021 ◽  
Author(s):  
Olalekan O. Shobayo ◽  
D. Keith Walters
Keyword(s):  
Vortex Dynamics ◽  
Turbulent Mixing ◽  
Initial Conditions ◽  
Numerical Study ◽  
Mixing Layer ◽  
Turbulent Stress ◽  
Mean Velocity ◽  
Turbulent Mixing Layer ◽  
Layer Flow ◽  
Turbulence Generation

Abstract Computational fluid dynamics (CFD) results are presented for synthetic turbulence generation of initial conditions for the canonical test case of a temporally-developing turbulent mixing layer (TTML) flow. This numerical study investigates the performance of a newly proposed Statistically Targeted Forcing (STF) method, and its capability to act as a restoring force to match the target mean velocity and turbulent stress in a temporally-developing flow where highly unsteady destabilizing mechanisms and influence are evident. Several previous investigations exist documenting vortex dynamics of the turbulent mixing layer, but limited investigations exist on synthetic turbulence generation forcing methods to prescribe initial conditions. The objective of this study is to evaluate the performance of the newly proposed STF method to capture the vortex dynamics and effectively match target mean velocity and resolved turbulent stress predictions using large-eddy simulation. Results are interrogated and compared to statistical velocity and turbulent stress distributions obtained from DNS simulations available in the literature. Results show that the STF method can successfully reproduce desired statistical distributions in a turbulent mixing layer flow.

The effect of initial conditions on the development of a free shear layer

1966 ◽  
Vol 26 (2) ◽  
pp. 225-236 ◽  
Author(s):  
P. Bradshaw
Keyword(s):  
Turbulent Mixing ◽  
Initial Conditions ◽  
Mixing Layer ◽  
Initial Boundary ◽  
Shear Layers ◽  
Free Shear Layer ◽  
Turbulent Mixing Layer ◽  
Free Shear Layers ◽  
Final Approach ◽  
Reynolds Number Effects

The distance between the separation point and the final approach to a fully developed turbulent mixing layer is found to be of the order of a thousand times the momentum-deficit thickness of the initial boundary layer, whether the latter be laminar or turbulent. There are correspondingly large shifts in the virtual origin of the mixing layer, resulting in spurious Reynolds-number effects which cause considerable difficulties in tests of model jets or blunt-based bodies, and which are probably responsible for the disagreements over the influence of Mach number on the development of free shear layers. These effects are explained.

Entrainment in a shear-free turbulent mixing layer

1996 ◽  
Vol 310 ◽  
pp. 215-241 ◽  
Author(s):  
D. A. Briggs ◽  
J. H. Ferziger ◽  
J. R. Koseff ◽  
S. G. Monismith
Keyword(s):  
Kinetic Energy ◽  
Turbulent Mixing ◽  
Initial Conditions ◽  
Strain Tensor ◽  
Mixing Layer ◽  
Turbulence Models ◽  
Integral Scale ◽  
Turbulent Mixing Layer ◽  
Anisotropic Models ◽  
Forced Mixing

Results from a direct numerical simulation of a shear-free turbulent mixing layer are presented. The mixing mechanisms associated with the turbulence are isolated. In the first set of simulations, the turbulent mixing layer decays as energy is exchanged between the layers. Energy spectra with E(k) ∼ k2 and E(k) ∼ k4 dependence at low wavenumber are used to initialize the flow to investigate the effect of initial conditions. The intermittency of the mixing layer is quantified by the skewness and kurtosis of the velocity fields: results compare well with the shearless mixing layer experiments of Veeravalli & Warhaft (1989). Eddies of size of the integral scale (k3/2/∈) penetrate the mixing layer intermittently, transporting energy and causing the layer to grow. The turbulence in the mixing layer can be characterized by eddies with relatively large vertical kinetic energy and vertical length scale. In the second set of simulations, a forced mixing layer is created by continuously supplying energy in a local region to maintain a stationary kinetic energy profile. Assuming the spatial decay of r.m.s. velocity is of the form u &∞ yn, predictions of common two-equation turbulence models yield values of n ranging from -1.25 to -2.5. An exponent of -1.35 is calculated from the forced mixing layer simulation. In comparison, oscillating grid experiments yield decay exponents between n = -1 (Hannoun et al. 1989) and n = -1.5 (Nokes 1988). Reynolds numbers of 40 and 58, based on Taylor microscale, are obtained in the decaying and forced simulations, respectively. Components of the turbulence models proposed by Mellor & Yamada (1986) and Hanjalić & Launder (1972) are analysed. Although the isotropic models underpredict the turbulence transport, more complicated anisotropic models do not represent a significant improvement. Models for the pressure-strain tensor, based on the anisotropy tensor, performed adequately.

scholarly journals Numerical investigation of algebraic oceanic turbulent mixing-layer models

2013 ◽  
Vol 20 (6) ◽  
pp. 945-954 ◽  
Author(s):  
T. Chacón-Rebollo ◽  
M. Gómez-Mármol ◽  
S. Rubino
Keyword(s):  
Turbulent Mixing ◽  
Finite Time ◽  
Eddy Viscosity ◽  
Initial Conditions ◽  
Mixing Layer ◽  
Turbulence Models ◽  
Warm Pool ◽  
Oceanic Circulation ◽  
Turbulent Mixing Layer ◽  
Numerical Instabilities

Abstract. In this paper we investigate the finite-time and asymptotic behaviour of algebraic turbulent mixing-layer models by numerical simulation. We compare the performances given by three different settings of the eddy viscosity. We consider Richardson number-based vertical eddy viscosity models. Two of these are classical algebraic turbulence models usually used in numerical simulations of global oceanic circulation, i.e. the Pacanowski–Philander and the Gent models, while the other one is a more recent model (Bennis et al., 2010) proposed to prevent numerical instabilities generated by physically unstable configurations. The numerical schemes are based on the standard finite element method. We perform some numerical tests for relatively large deviations of realistic initial conditions provided by the Tropical Atmosphere Ocean (TAO) array. These initial conditions correspond to states close to mixing-layer profiles, measured on the Equatorial Pacific region called the West-Pacific Warm Pool. We conclude that mixing-layer profiles could be considered as kinds of "absorbing configurations" in finite time that asymptotically evolve to steady states under the application of negative surface energy fluxes.

scholarly journals The density of organized vortices in a turbulent mixing layer

1975 ◽  
Vol 69 (3) ◽  
pp. 465-473 ◽  
Author(s):  
D. W. Moore ◽  
P. G. Saffman
Keyword(s):  
Exact Solutions ◽  
Cross Section ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Negligible Effect ◽  
Mean Velocity ◽  
Maximum Slope ◽  
Turbulent Mixing Layer ◽  
Average Spacing ◽  
The Mean

It is argued on the basis of exact solutions for uniform vortices in straining fields that vortices of finite cross-section in a row will disintegrate if the spacing is too small. The results are applied to the organized vortex structures observed in turbulent mixing layers. An explanation is provided for the disappearance of these structures as they move downstream and it is deduced that the ratio of average spacing to width should be about 3·5, the width being defined by the maximum slope of the mean velocity. It is shown in an appendix that walls have negligible effect.

scholarly journals A numerical study of a turbulent mixing layer and its generated noise

2013 ◽  
Vol 56 (6) ◽  
pp. 1157-1164 ◽  
Author(s):  
Dong Li ◽  
Li Guo ◽  
Xing Zhang ◽  
GuoWei He
Keyword(s):  
Turbulent Mixing ◽  
Numerical Study ◽  
Mixing Layer ◽  
Turbulent Mixing Layer
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