Evaluation of Reynolds stress, k-ε and RNG k-ε turbulence models in street canyon flows using various experimental datasets

Abstract

In this study the Reynolds-averaged Navier-Stokes computational fluid dynamics methodology is used, which has proved to be a powerful tool for the simulations of the airflow and pollutant dispersion in the atmospheric environment. The interest is focused on the urban areas and more specifically on the street canyons, several types of which are examined in order to evaluate the performance of various turbulence models, including a Reynolds-stress model and variations of the k-ε model. The results of the two-dimensional simulations are compared with measurements from a diversity of independent street canyon experimental datasets, covering a wide range of aspect ratios, free stream velocities and roughnesses. This way more general and reliable conclusions can be reached about the applicability, accuracy and ease of use of each turbulence model. In this work, the renormalization group k-ε presented better results in most cases examined, while the Reynolds-stress model did not stand up for the expectations and also exhibited convergence problems.

Optimization and field application of water jet for coal bed methane stimulation

“…For high‐pressure water jet flow field, the RNG k–ε turbulence model was used in this paper. The governing equations for the standard k–ε turbulence model are as follows: Mass balance equation where ρ is density of fluid; t is time; u, v and w are the components of velocity in the x, y, and z directions, respectively.…”

CFD simulation of near-field pollutant dispersion in the urban environment: A review of current modeling techniques

“…A considerable amount of research has investigated both the influence of pollutant transport modeling and the influence of inflow conditions, canyon configurations, and other modeling considerations with two-dimensional (2-D) street canyons using RANS (Meroney et al, 1996;Baik and Kim, 1999;Chan et al, 2002;Liu and Barth, 2002;Baik and Kim, 2002;Kim and Baik, 2003;Nazridoust and Ahmadi, 2006) and LES (Liu et al, 2005;Li et al, 2008Li et al, , 2009Cai et al, 2008;Zhang et al, 2011;Cheng and Liu, 2011a,b). Moreover, significant research has been conducted for generic three-dimensional (3-D) street canyon model using various turbulence models (Hunter et al, 1992;Chang and Meroney, 2001;Chang and Meroney, 2003;Baik et al, 2003;Yang and Shao, 2008;Murena et al, 2009;Solazzo et al, 2009;Tominaga and Stathopoulos, 2011;Salim et al, 2011;Koutsourakis et al, 2012). A 3-D street canyon, which consists of two or more building blocks, has three determining factors of flow regime, namely the relative height (H), width (W) and length (L) of the canyon, in contrast to a 2-D canyon with two factors, H and W. Therefore, the flow field formed in a 3-D street canyon is highly complex in comparison to the 2-D case.…”

“…The differences of the results between SKE and the modified k-ε models are rather small for dispersion in street canyons and building complexes, where turbulence produced by surrounding buildings is dominant (Chang and Meroney, 2001;Nazridoust and Ahmadi, 2006). The Reynolds-stress models (RSM; Launder et al, 1975) has often provided the worst results in comparative studies of various turbulence models, although it can occasionally capture the near-wall flow phenomena (Murakami et al, 1996;Wang and McNamara, 2006;Koutsourakis et al, 2012). This is mainly because RSM requires optimization of many numerical parameters due to the comparatively high number of differential equations to be solved, and the simulations generally have a higher dependency on the chosen mesh and more difficulty converging when compared to the k-ε models.…”

A CFD modeling study in an urban street canyon for ultrafine particles and population exposure: The intake fraction approach

“…This is extracted from the basic principles of conservation of mass, momentum and energy. The turbulence model that is adopted in our study is the RNG model (Kim and Baik, 2004;Koutsourakis et al, 2012;Yakhot and Orszag, 1986). This scheme differs from the standard k-ε model turbulence scheme.…”