Direct Numerical Simulation of Passive Scalar Field in a Turbulent Channel Flow

Abstract

A direct numerical simulation (DNS) of the fully developed thermal field in a two-dimensional turbulent channel flow of air was carried out. The isoflux condition was imposed on the two walls so that the local mean temperature increased linearly in the streamwise direction. With any buoyancy effect neglected, temperature was considered as a passive scalar. The computation was executed on 1,589,248 grid points by using a spectral method. The statistics obtained were root-mean-square temperature fluctuations, turbulent heat fluxes, turbulent Prandtl number, and dissipation time scales. They agreed fairly well with existing experimental and numerical simulation data. Each term in the budget equations of temperature variance, its dissipation rate, and turbulent heat fluxes was also calculated. It was found that the temperature fluctuation θ′ was closely correlated with the streamwise velocity fluctuation u′, particularly in the near-wall region. Hence, the distribution of budget terms for the streamwise and wall-normal heat fluxes, u′θ′ and v′θ′, were very similar to those for the two Reynolds stress components, u′u′ and u′v′.

A bridge between projection methods and SIMPLE type methods for incompressible Navier–Stokes equations

“…The root-mean-square velocity and temperature fluctuations, normalized by the Figure 2, we can see all of the results agree closely with the results of Kasagi et al [35], which were acquired by the high accurate spectral method. This illustrates that the general projection method with a Runge-Kutta technique for the update of the convective term and the Crank-Nicholson technique for the diffusion term can be applied on non-uniform meshes to get high accurate results.…”

Direct Numerical Simulation of Turbulence with Scalar Transfer around Complex Geometries Using the Immersed Boundary Method and Fully Conservative Higher-Order Finite-Difference Schemes

“…The results are compared with those obtained by the spectral method (Iwamoto et al 2002;Kasagi et al 1992). Figure 1 shows the computational domain for the channel flow with scalar transfer (with a constant heat flux q w ).…”

“…1), ν the kinematic viscosity, and κ the thermal diffusivity. In Equation (4), T + m is the mixed mean temperature averaged over the channel section, defined as (Kasagi et al 1992)…”

“…In this chapter, we demonstrate the method for performing DNS of incompressible turbulent flows with scalar transfer around complex geometries. In the first section, we present the results for the canonical channel flow with scalar transfer obtained using our DNS code and compare them with results obtained using the spectral method (Iwamoto et al 2002;Kasagi et al 1992). Then, we describe the numerical methods for the DNS of turbulent fields with scalar transfer around and downstream of regular and fractal grids (Hurst & Vassilicos 2007;Seoud & Vassilicos 2007;Mazellier & Vassilicos 2010) as an example of flow around complex geometries.…”

Direct numerical simulation of the passive heat transfer in a turbulent flow with particle

“…While there are a large number of applications from this including combustion, spray drying, and heat exchanger, very small attention has been paid to particle analysis in the non-isothermal flow [14][15][16]. This type of flow is known to be affected by the thermal layer through various mechanisms [17][18][19].…”