Search results for " Large Eddy Simulation"

Numerical simulation of internal boundary-layer development and comparison with atmospheric data

2006

A finite-volume numerical model is employed to investigate the adaptation of the atmospheric boundary layer to a change in the underlying surface roughness, such as that existing in the transition from land to the free surface of a water body. Numerical results are validated by comparison with neutral stratification atmospheric data and compared with the internal boundary-layer (IBL) heights computed using a number of existing empirical formulae. The numerical analysis allows an extension of the fetch range in which the existing formulae, calibrated only by comparison with short fetch data, may be applied. An argument is offered that the spatial variability of the water surface roughness sh…

Large Eddy Simulations of Rough Turbulent Channel Flows Bounded by Irregular Roughness: Advances Toward a Universal Roughness Correlation

2020

The downward shift of the mean velocity profile in the logarithmic region, known as roughness function, $$\Delta U^+$$ , is the major macroscopic effect of roughness in wall bounded flows. This speed decrease, which is strictly linked to the friction Reynolds number and the geometrical properties which define the roughness pattern such as roughness height, density, shape parameters, has been deeply investigated in the past decades. Among the geometrical parameters, the effective slope (ES) seems to be suitable to estimate the roughness function at fixed friction Reynolds number, Re $$_{\tau }$$ . In the present work, the effects of several geometrical parameters on the roughness function, i…

Large eddy simulations on the effect of the irregular roughness shape on turbulent channel flows

2019

Abstract Large Eddy Simulations (LES) are carried out to investigate on the mean flow in turbulent channel flows over irregular rough surfaces. Here the attention is focused to selectively investigate on the effect induced by crests or cavities of the roughness. The irregular shape is generated through the super-imposition of sinusoidal functions having random amplitude and four different wave-lengths. The irregular roughness profile is reproduced along the spanwise direction in order to obtain a 2D rough shape. The analysis of the mean velocity profiles shows that roughness crests induce higher effect in the outer-region whereas roughness cavities cause the highest effects in the inner-reg…

The effect of the slope of irregularly distributed roughness elements on turbulent wall-bounded flows

2008

Wall roughness produces a downward shift of the mean streamwise velocity profile in the log region, known as the roughness function. The dependence of the roughness function on the height and arrangement of roughness elements has been confirmed in several studies where regular rough walls were analysed; less attention has been paid to non-regular rough walls. Here, a numerical analysis of turbulent flows over irregularly shaped rough walls is performed, clearly identifying the importance of a parameter, called the effective slope (ES) of the wall corrugations, in characterizing the geometry of non-smooth irregular walls. The effective slope proves to be one of the fundamental geometric para…

Field and numerical study of river confluence flow structures

2010

River hydrodynamics Turbulent open channel flow and transport phenomena

INFLUENZA DELLA PENDENZA MEDIA DELLE CORRUGAZIONI DI UNA PARETE SCABRA SUL CAMPO DI MOTO TURBOLENTO

2008

Rapid Compression Machine. 2013.

2013

A rapid compression machine is a type of ideal internal combustion reactor which is well suited for gas phase kinetics studies and physical processes of combustion. These studies consist in recording the evolution of the reactivity and of the composition of the reacting mixtures as a function of temperature, pressure, residence time and the composition of the compressed mixture. Pressure measurement is used to analyse the evolution of the combustion process, but more recent studies couple pressure measurement with optical diagnostics in order to assess the homogeneity of the combustion process. Speciation based on rapid sampling of the intermediates formed, during the oxidation of the fuel,…