Computational visualization of unsteady flow around vehicles using high performance computing

Abstract

One of the largest-scale unstructured Large Eddy Simulation (LES) of flow around a full-scale road vehicle is conducted on the Earth Simulator in Japan. The main objective of our study is to look into the validity of LES for the assessment of vehicle aerodynamics, especially in the context of its possibility for unsteady or transient aerodynamic forces. Firstly, the aerodynamic LES proposed is quantitatively validated on the ASMO simplified model by comparing the mean pressure distributions on the vehicle surface with those obtained by a conventional Reynolds-Averaged Navier-Stokes simulation (RANS) or a wind tunnel measurement. Then, the method is applied to the full-scale vehicle with complicated geometry to qualitatively investigate the capability of capturing organized flow structures around the vehicle. Finally, unsteady aerodynamic forces acting on the vehicle in transient yawing-angle change are estimated and relationship between the flow structures and the transient aerodynamic forces is mentioned. As a result, it is demonstrated that LES will be a powerful tool for the vehicle aerodynamic assessment in the foreseeable future, because it can provide precious aerodynamic data which conventional wind tunnel tests or RANS simulations are difficult to provide.

A numerical analysis of transient flow past road vehicles subjected to pitching oscillation

“…2.8", which was originally developed for the "Frontier Simulation Software for Industrial Science" project and optimized for vehicle aerodynamics simulation by Tsubokura et al (2009b), was adopted in the present study. The code has been validated successfully in the previous works (Tsubokura et al, 2009a) where good agreement is attained in the comparison between the numerical results and wind tunnel measurements for pressure distribution along the centerline of ASMO model and flow field around a full-scale production vehicle including complicated engine room and under body geometry.…”

“…To date, LES has been implemented successfully to assess aerodynamics performance of road vehicle, as may be evidenced in the literature (e.g., Verzicco et al, 2002;Krajnovic and Davidson, 2005;Kobayashi et al, 2008;Tsubokura et al, 2009a;Nakashima et al, 2009). In the present study, LES was applied to study the flow past simplified vehicle models representing the real passenger cars with different body shape configurations.…”

Roof Box Shape Streamline Adaptation and the Impact towards Fuel Consumption

“…5 exhibit that back area of common roof box has a bigger flow layer separation compare to optimize roof box. According to Tsubokura [13] this phenomena contribute the value of drag coefficient. This separation contribute to a pressure difference over the roof box body where the larger pressure difference the higher the drag will be.…”

Numerical Investigation of Cross Flow on the Performance of Polymer Electrolyte Fuel Cell

“…This is non-commercial software and open to use as free for all [37]. The computational code FrontFlow/red, which was originally developed under the project of "Frontier Simulation Software for industrial Science" and optimized for vehicle aerodynamics simulation by Tsubokura et al [38][39]. Later on, the PEFC model is implemented into the software FrontFlow/red under the project of "New Energy and Industrial Technology Development Organization" (NEDO).…”