The eddy-viscosity model for turbulence has some difficulty in predicting rotating and swirling flows. Turbulent swirling flow in a straight pipe is a typical example. A rapidly rotating core in the pipe decays too quickly in results obtained from...

10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017 2 Jan 2017

The energy spectrum must be useful in describing the energy transfer not only in homogeneous isotropic turbulence but also in inhomogeneous turbulence. Instead of the energy spectrum in the wavenumber space, the energy density in the scale space c...

Mechanical rotation of a magnetic stirrer or a rotary evaporator can induce an enantiomeric excess of supramolecular species. In this study, we investigate the effect of fluid motion in a rotary evaporator on chiral supramolecular species. It is s...

Two-equation models that treat the transport equations for two variables are typical models for the Reynolds-averaged Navier-Stokes equation. Compared to the equation for the turbulent kinetic energy, the equation for the second variable such as t...

Journal of the Physical Society of Japan 81 Nov 2012

In the reverse simulation for identifying pollutant sources the transport equations for the computational fluid dynamics model are solved backward in time. Some filtering methods are used to suppress the numerical instability of the reverse simula...

When a hazardous substance is diffused, it is necessary to identify the pollutant source and respond immediately. However, there are many cases in which damage is caused without a clear understanding of where the pollutant source is located. There...

Journal of Environmental Engineering 77 27-35 Jan 2012

Reverse simulation, which is the solution of the transport equation in negative time, is a method for identifying pollutant source with CFD. Then the negative diffusion amplifies numerical errors and reverse simulation cannot be carried out. We pr...

Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE 5 193-199 Dec 2011

Reverse simulation was carried out to specify the point source of pollutants in closed waters. If pollutants flow out into waters, their source must be specified as soon as possible to take a quick measure against the pollution problem. Actually, ...

Hybrid Reynolds-averaged Navier-Stokes/large eddy simulation (RANS/LES) is expected to accurately predict wall-bounded turbulent flows at high Reynolds numbers. It is known that extra terms due to the noncommutivity between the hybrid filter and t...

Journal of Physics: Conference Series 318 Jan 2011

An analytical way for investigating the inhomogeneous turbulent flow has been proposed by introducing Lagrangian-like view. The present method is developed based on TSDIA (Two-Scale Direct Interaction Approximation) which is one of the few theoret...

A large eddy simulation of magnetohydrodynamic (MHD) turbulent channel flow is carried out to investigate the dynamo mechanism. It is shown that the streamwise component of the mean magnetic field is generated and sustained due to the effect of th...

International Journal of Heat and Fluid Flow 30 20-31 Feb 2009

Hybrid approach combining large eddy simulation (LES) with the Reynolds-averaged Navier-Stokes equation (RANS) is expected to accurately simulate wall-bounded turbulent flows at high Reynolds numbers. As an important issue in developing hybrid met...

Solid Mechanics and its Applications 4 267-272 Dec 2008

An exact nonlocal expression for the Reynolds stress in rotating frames is described using the Green's function for the velocity fluctuation. This expression is applied to the DNS of non-rotating and rotating channel flows. Spatially- and temporal...

Nobumitsu Yokoi, Robert Rubinstein, Akira Yoshizawa, Fujihiro Hamba

Journal of Turbulence 9 1-25 Nov 2008

The statistical theory of inhomogeneous turbulence is applied to develop a system of model equations for magnetohydrodynamic (MHD) turbulence. The statistical descriptors of MHD turbulence are taken to be the turbulent MHD energy, its dissipation ...

The turbulent electromotive force in the mean-field equation needs to be modeled to predict a large-scale magnetic field in magnetohydrodynamic turbulence at high Reynolds number. Using a statistical theory for inhomogeneous turbulence, model expr...

A magnetohydrodynamic (MHD) turbulence model incorporating the turbulent MHD residual energy (difference between the kinetic and magnetic energies) is applied to solar-wind turbulence. In the model, the dynamics of the turbulent cross-helicity (cr...

Taking into account the frame-invariance of a model expression under arbitrarily rotating transformations, Weis & Hutter (J. Fluid Mech. vol. 476, 2003, p. 63) proposed a Euclidean-objective weak-equilibrium condition for the algebraic Reynolds st...

In the core region of spanwise rotating channel flows, the mean velocity profile is approximately linear with a slope of twice the system rotation rate. The mechanism of this zero mean absolute vorticity state is investigated from the turbulence m...

Theoretical and Computational Fluid Dynamics 20 89-101 Apr 2006

A hybrid method combining large eddy simulation (LES) with the Reynolds-averaged Navier-Stokes (RANS) equation is used to simulate a turbulent channel flow at high Reynolds number. It is known that the mean velocity profile has a mismatch between ...

An exact expression for the Reynolds stress is derived using the response function for the velocity fluctuation. The nonlocal eddy viscosity in the expression represents a contribution to the Reynolds stress by the mean velocity gradient at remote...

4th International Symposium on Turbulence and Shear Flow Phenomena 1 147-152 Dec 2005

An exact expression for the Reynolds stress was derived using the Green's function for the velocity fluctuation. The nonlocal eddy viscosity involved in the expression represents a contribution to the Reynolds stress from the mean velocity gradien...

Numerical simulation of the magnetic field in a rotating spherical shell was carried out to assess and improve the Reynolds-averaged turbulence model for magnetohydrodynamic flows. In the three-equation model the transport equations for the turbul...

An exact expression for the scalar flux was derived using the Green's function for a scalar. The nonlocal eddy diffusivity involved in the expression represents a contribution to the scalar flux from the mean scalar gradient at remote points in sp...

Theoretical and Computational Fluid Dynamics 16 387-403 May 2003

Hybrid models combining large eddy simulation (LES) with Reynolds-averaged Navier-Stokes (RANS) simulation are expected to be useful for wall modeling in the LES of high Reynolds number flows. Some hybrid simulations of turbulent channel flow have...

A Reynolds mean turbulence model is presented, with attention focused on the applicability to supersonic free-shear layer and wall-bounded flows. In this model, the Reynolds stress is approximated by a nonequilibrium turbulent-viscosity representa...

Theoretical and Computational Fluid Dynamics 14 323-336 Dec 2001

Large eddy simulation (LES) is combined with the Reynolds-averaged Navier-Stokes (RANS) equation in a turbulent channel-flow calculation. A one-equation subgrid-scale model is solved in a three-dimensional grid in the near-wall region whereas the ...

Journal of the Physical Society of Japan 70 1565-1574 Jun 2001

The non-negativeness of the normal stress is one of the realizability conditions for the Reynolds stress. This condition is investigated to improve turbulence models. A statistical theory called the two-scale direct-interaction approximation is mo...

Direct numerical simulation results are used to study compressibility effects on turbulent energy growth in homogeneous shear flow. Normalized amplitude of the pressure fluctuations is shown to decrease as the turbulent Mach number increases. This...

Turbulence models for compressible flows are investigated using a statiscal theory called the two-scale direct-interaction approximation. Inertial-range spectra for velocity and density variances are assumed to derive models for several correlatio...

Journal of the Atmospheric Sciences 52 1084-1095 Jan 1995

The Green's function for scalar fluctuations is introduced into a large eddy simulation of the convective boundary layer to investigate nonlocal scalar transport. This Green's function is used to derive a nonlocal expression for the scalar flux an...

Journal of Geophysical Research 98 5173-5182 Jan 1993

The effect of cross diffusion is introduced; that is, the scalar flux of a species depends on the scalar gradients of other species. One-dimensional calculations are carried out for the convective boundary layer by using a K model, a modified K mo...

Journal of the Atmospheric Sciences 50 2800-2810 Jan 1993

In addition to the eddy diffusivity term, the model includes a term proportional to the second derivative of the mean scalar. The coefficient of the new term is closely related to the skewness of the vertical velocity component and to the inhomoge...

A three-dimensional direct simulation of inhomogeneous magnetohydrodynamic (MHD) turbulence is carried out to investigate the turbulent dynamo effect. The velocity field is driven by an external force so that the velocity and magnetic fields are s...

A one-dimensional simulation of reversed field pinches is performed using a turbulent dynamo model. Steady states with field reversal are obtained. Effects of the boundary condition at the wall are investigated to show the importance of injection ...

journal of the physical society of japan 58 2414-2422 Jan 1988

A numerical simulation of reversed field pinches is performed using a three-dimensional incompressible magnetohydrodynamic (MHD) code. A turbulence model called large eddy simulation is applied. Although field reversal is obtained in a simulation ...

Journal of the Physical Society of Japan 56 3771-3774 Jan 1987

The transport equation for the turbulent energy dissipation rate is investigated using a two-scale direct-interaction approximation. The time integral of a two-time velocity correlation is examined to obtain a statistical model for the dissipation...