CFD Simulations

Computational Fluid Dynamics (CFD) simulations have emerged as a valuable tool for augmenting laboratory wind testing in predicting wind-induced loads at full scale, particularly when realistic inflow turbulence is considered. By precisely controlling boundary conditions and employing a virtual boundary-layer wind laboratory as the computational domain, which incorporates all floor roughness elements found in the test model, a direct comparison between CFD and experimental results can be achieved, facilitating the emulation of physical testing. Unlike physical experiments, CFD simulations offer the advantage of not requiring the incorporation of instruments that may interfere with the test object, thereby enhancing prediction accuracy.

Furthermore, CFD simulations enable full-scale modeling, a significant challenge in physical experiments conducted in artificial winds due to the absence of fully developed turbulence with a realistic integral length scale. However, a notable drawback of the CFD-based approach is the high computational cost associated with predicting peak loads on structures under turbulent flows. Integrating a relatively accurate turbulence model, such as Large Eddy Simulations (LES), into numerical modeling at high Reynolds numbers may necessitate high-performance computing capabilities for CFD simulations. This computational challenge, coupled with the expense of commercial CFD licenses for parallel computing, limits the practicality of CFD simulations for design wind load evaluation. Therefore, wind experiments remain a more cost-effective option for wind load applications. Nevertheless, concurrent CFD studies provide additional opportunities to elucidate and enhance laboratory wind studies.


We have successfully implemented CFD with Large Eddy Simulation (LES) turbulence closure on a 1:1 scale prototype building. A computational proximity study was conducted using CFD with LES, leading to novel recommendations regarding the sizing of the computational domain preceding a building model. These recommendations differ from conventional guidelines based on Reynolds-Averaged Navier-Stokes (RANS), such as COST and AIJ.

Our research findings demonstrate that the placement of the test building deviates from existing procedures, and the proximity of the inflow boundary significantly impacts pressure correlation and the accurate representation of peak loads. We compared the CFD LES results with corresponding pressures obtained from open jet, full-scale measurements, as well as the American Society of Civil Engineers (ASCE) 7 standard for roof Components & Cladding design.

The results indicate that CFD LES is capable of accurately reproducing peak pressures and loads on buildings, as it successfully captures the spectral characteristics of the inflow at a 1:1 scale, in agreement with field pressure observations. This demonstrates the adequacy of CFD LES for simulating realistic flow conditions in building environments.


Fig. 08 LES

Velocity contours, from ParaView, at different times. All subfigures on the left are of full domain height and clipped at mid-width, and all subfigures on the right are clipped at mid-height of the computational domain.


 fig 12 les
Scatter plot for comparison of turbulence intensities provided at the inlet with the target ones and with those obtained from different DES cases at locations A (a), C (b), and E (c). 

Large Eddy Simulation (LES) has emerged as a highly accurate computational tool in the field of wind engineering. Nevertheless, the extensive computational requirements associated with LES pose a significant challenge compared to RANS models. In this study, we propose several methodologies to mitigate the computational expense of LES while maintaining its precision.

Through our investigation, we demonstrate that incorporating the wall-adapting eddy viscosity (WALE) subgrid-scale (SGS) model within LES leads to a notable reduction in computational time while preserving a minimal level of error. Additionally, when aiming for a comparable level of precision, both Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) hybrid models exhibit substantial computational cost reductions relative to LES, particularly when utilizing the dynamic one-equation eddy-viscosity SGS model.

By exploring these alternative modeling approaches, our research contributes to advancing the efficiency and accuracy of computational wind engineering, offering valuable insights for practical applications in the field.

CFD has emerged as a valuable tool for investigating and mitigating the Urban Heat Island (UHI) phenomenon, which has gained global attention due to the proliferation of urbanized areas. This research focuses on the impact of altering geometrical canyons on wind flow patterns and air temperatures, key factors governing the UHI phenomenon. Through comprehensive CFD simulations encompassing various urban building configurations, we explore the effects of spacing ratio, shape, and other pertinent factors on wind velocity within the canyon. Our study reveals that employing larger y+ values, exceeding recommendations from existing literature, still yield accurate results for velocity and temperature dynamics around buildings. Notably, step-up building configurations substantially enhance canyon wind speed. Furthermore, our findings demonstrate an inverse relationship between building spacing ratio and average canyon temperatures, indicating that higher spacing ratios result in lower temperatures within the canyon. This research deepens our understanding of the intricate relationship between geometrical canyon alterations, wind flow patterns, and air temperatures, shedding light on potential strategies to mitigate the UHI phenomenon in urban environments.
In the realm of hydraulic engineering, CFD plays a crucial role in understanding scouring mechanisms and mitigating their impact on various structures exposed to flood conditions, including bridges and offshore wind turbines. This study investigates the optimization of pier design to effectively mitigate scour. We propose employing CFD simulations using LES and RANS to study bridge scour. The LES simulations focus specifically on local scour-induced effects and are compared with findings obtained from RANS simulations. Additionally, two countermeasures, namely delta vanes and plate footings, are modeled to alleviate scour around piers. Our results demonstrate the effective reduction of shear stress by both countermeasures. Notably, a combination of delta vanes and plate footings emerges as a promising solution to reduce upstream and downstream bed shear stress. This study emphasizes the significance of comprehensive investigations into bridge scour and the imperative for effective countermeasures to safeguard critical infrastructure against scour-related damage or potential collapse. The recommended countermeasures hold substantial promise for reducing construction and maintenance costs while enhancing the longevity of infrastructure.

Selected Publications