18 citations · 87 across the 20 of their papers we have counts for
20 papers
An example from turbulence how not to use the invariant function method of Lie-group symmetries
Michael Frewer, George Khujadze
The recent Reply by Oberlack et al. [Phys. Rev. Lett. 130, 069403 (2023)] fails to rebut the critique that a mathematical solution method has been misapplied in their original work…
No new scaling laws of passive scalar with a constant mean gradient in decaying isotropic turbulence
Michael Frewer
In the study by Sadeghi & Oberlack [JFM 899, A10 (2020)] it is claimed that new scaling laws are derived for the case of passive scalar dynamics under the influence of a constant m…
A closer look at predicting turbulence statistics of arbitrary moments when based on a non-modelled symmetry approach
Michael Frewer, George Khujadze
A recent Letter by Oberlack et al. [Phys. Rev. Lett. 128, 024502 (2022)] claims to have derived new symmetry-induced solutions of the non-modelled statistical Navier-Stokes equatio…
A critical examination of the conformal invariance in the statistical equations of 2D turbulent scalar fields
Michael Frewer, George Khujadze
The recent study by Waclawczyk et al. [Phys. Rev. Fluids 6, 084610 (2021)] on conformal invariance in 2D turbulence is misleading as it makes three incorrect claims that form the c…
Refuting the claim of conformal invariance for a zero-vorticity characteristic equation in 2D turbulence
Michael Frewer, George Khujadze
Although the current Reply by Grebenev et al. (2021a) makes their original analysis in Grebenev et al. (2017) more transparent, the actual problem remains. Their claim to have anal…
Comment on 'Conformal invariance of the zero-vorticity Lagrangian path in 2D turbulence'
Michael Frewer, George Khujadze
The current claim by Grebenev et al. [J. Phys. A: Math. Theor. 52, 335501 (2019)], namely that the inviscid and unclosed 2D Lundgren-Monin-Novikov (LMN) equations on a zero-vortici…
Symmetries and turbulence modeling. A critical examination
George Khujadze, Michael Frewer
The recent study by Klingenberg, Oberlack & Pluemacher (2020) proposes a new strategy for modeling turbulence in general. A proof-of-concept is presented therein for the particular…
Conformal invariance and the Lundgren-Monin-Novikov equations for vorticity fields in 2D turbulence: Refuting a recent claim
Michael Frewer, George Khujadze
The recent claim by Grebenev et al. [J. Phys. A: Math. Theor. 50, 435502 (2017)] that the inviscid 2D Lundgren-Monin-Novikov (LMN) equations on a zero vorticity characteristic natu…
On physically redundant and irrelevant features when applying Lie-group symmetry analysis to hydrodynamic stability analysis
Michael Frewer
Every linear system of partial differential equations (PDEs) admits a scaling symmetry in its dependent variables. In conjunction with other admitted symmetries of linear type, the…
Comment on 'Lie symmetry analysis of the Lundgren-Monin-Novikov equations for multi-point probability density functions of turbulent flow'
Michael Frewer, George Khujadze, Holger Foysi
The recent study by Waclawczyk et al. [J. Phys. A: Math. Theor. 50, 175501 (2017)] possesses three shortcomings: (i) The analysis misses a key aspect of the LMN equations which mak…
Covariance and objectivity in mechanics and turbulence
Michael Frewer
Form-invariance (covariance) and frame-indifference (objectivity) are two notions in classical continuum mechanics which have attracted much attention and controversy over the past…
On the use of applying Lie-group symmetry analysis to turbulent channel flow with streamwise rotation
Michael Frewer, George Khujadze
The study by Oberlack et al. (2006) consists of two main parts: a direct numerical simulation (DNS) of a turbulent plane channel flow with streamwise rotation and a preceding Lie-g…
Revisiting the Lie-group symmetry method for turbulent channel flow with wall transpiration
George Khujadze, Michael Frewer
The Lie-group-based symmetry analysis, as first proposed in Avsarkisov et al. (2014) and then later modified in Oberlack et al. (2015), to generate invariant solutions in order to…
A note on the notion "statistical symmetry"
Michael Frewer, George Khujadze, Holger Foysi
A critical review is presented on the most recent attempt to generally explain the notion of "statistical symmetry". This particular explanation, however, is incomplete and misses…
Application of Lie-group symmetry analysis to an infinite hierarchy of differential equations at the example of first order ODEs
Michael Frewer
This study will explicitly demonstrate by example that an unrestricted infinite and forward recursive hierarchy of differential equations must be identified as an unclosed system o…
An example elucidating the mathematical situation in the statistical non-uniqueness problem of turbulence
Michael Frewer
An instructive example is presented to elucidate the mathematical situation in the non-uniqueness problem of the infinite Friedmann-Keller hierarchy of equations for all multi-poin…
A critical examination of the statistical symmetries admitted by the Lundgren-Monin-Novikov hierarchy of unconfined turbulence
Michael Frewer, George Khujadze, Holger Foysi
We present a critical examination of the recent article by Waclawczyk et al. (2014) which proposes two new statistical symmetries in the classical theory for turbulent hydrodynamic…
Is the log-law a first principle result from Lie-group invariance analysis?
Michael Frewer, George Khujadze, Holger Foysi
The invariance method of Lie-groups in the theory of turbulence carries the high expectation of being a first principle method for generating statistical scaling laws. The purpose…
On the physical inconsistency of a new statistical scaling symmetry in incompressible Navier-Stokes turbulence
Michael Frewer, George Khujadze, Holger Foysi
A detailed theoretical investigation is given which demonstrates that a recently proposed statistical scaling symmetry is physically void. Although this scaling is mathematically a…
Renormalization of an effective model Hamiltonian by a counter term
Michael Frewer, Tobias Frederico, Hans-Christian Pauli
An ill-defined integral equation for modeling the mass-spectrum of mesons is regulated with an additional but unphysical parameter. This parameter dependance is removed by renormal…