Direct numerical simulation (DNS) of combustion in globally lean non-homogeneous propane-air mixtures has been performed for several initial distributions of non-homogeneities. Results have shown a strong influence of the scale and asymmetry of this distribution on both the combustion efficiency and thermal NO production, in accordance with experimental results. The simulations also have made p...

Direct numerical simulation (DNS) can be used to extract information implicit in the equations of fluid-particle motion. We have investigated the lift-off of a single particle and many particles in pressure driven flows by 2D DNS (N.A. Patankar, Huang, Ko & Joseph 2001a, Ko, N.A. Patankar & Joseph 2001, Joseph, & Ocando 2001, Choi & Joseph 2001, N.A. Patankar, Ko, Choi & Joseph 2001b). We show ...

A laminar boundary layer separates in a region of adverse pressure gradient on a flat plate, undergoes transition, and finally the turbulent boundary layer reattaches. Laminar-turbulent transition within this laminar separation bubble (LSB) is investigated by means of measurements with a Laser-Doppler-Anemometer (LDA), flow visualization in water and direct numerical simulation (DNS). The role ...

We perform a direct numerical simulation (DNS) of forced homogeneous isotropic turbulence with a passive scalar that is forced by mean gradient. The DNS data are used to study the properties of subgrid-scale flux of a passive scalar in the framework of large eddy simulation (LES), such as alignment trends between the flux, resolved, and subgrid-scale flow structures. It is shown that the direct...

Methods motivated by non-equilibrium statistical mechanics of turbulence are applied to solve an important practical problem in geophysical fluid dynamics, namely the parametrization of subgrid-scale eddies needed in large-eddy simulations (LESs). A direct stochastic modelling scheme that is closely related to techniques based on statistical closure theories, but which is more generally applica...

Combustion is a natural phenomenon. It happens in forest, automotive engine and gas cooker. In Computational Fluid Dynamics (CFD), the combustion phenomenon complies with a set of partial differential equations. According to the resolution scale, from big to small, the simulation methods in combustion are Reynolds Averaged Navior Stokes method (RANS), Large Eddy Simulation (LES), and Direct Num...

In this paper we present a Large-eddy-simulation (LES)-informed resolvent-based estimator to obtain estimates on the space-time domain of pipe flows after low-rank measurements wall shear-stress. It is shown that an LES with approximately one order magnitude less grid points than Direct numerical simulation (DNS) has similar performance regarding quality.

The objective has been to study turbulent boundary layers under adverse pressure gradients (APG) through direct numerical simulation (DNS). The numerical code is based on a pseudo-spectral technique which is suitable for the simple geometry (flat plate) considered here. A large effort has been put into the optimization of the numerical code on various super computers. Five large simulations hav...

Large eddy simulation (LES) and direct numerical simulation (DNS) of polydisperse evaporating sprays with Eulerian models are very promising tools for high performance computing of combustion applications since they are able to predict the turbulent dispersion and evaporation. However, the spray system of conservation equations has a convective part which is similar either to gas dynamics Euler...

The concept of flow field velocimetry based on scalar imaging measurements @Phys. Fluids A 4, 2191 ~1992!# is here formulated in terms of an integral minimization implementation, where the velocity field u~x,t! is found by minimizing weighted residuals of the conserved scalar transport equation, along with the continuity condition and a smoothness condition. We apply this technique to direct nu...