Guglielmo Minelli

Numerical Investigation of Active Flow Control Around a Generic Truck A-Pillar

Large Eddy Simulations (LES) are conducted to study the actuated flow field around a bluff body. The model is a simplified section of a truck. The aim of the work is to model the separation of the flow acting at the front rounded corners, the so called A-pillars, and to minimize the separation of the flow by means of Zero Net Mass Flux synthetic jets. LES data show the interaction of the flow main structures, the separation mechanism and the effects of the actuation on the flow field. The flow is post processed using modal and frequency decompositions. Relevant results in terms of drag reduction were observed for the actuated flow. The principle flow mechanisms are discussed and an optimal actuation frequency, in terms of induced fluctuations and drag reduction, is identified.

Partially-Averaged Navier-Stokes Simulations of Flows Around Generic Vehicle at Yaw

Partially-Averaged Navier-Stokes Simulations (PANS) were made of flow around a generic vehicle influenced by side wind at four different yaw angles to investigate the prediction capabilities of PANS. Comparisons with results of LES show clear advantages of PANS in predicting pressure-induced separation resulting in the trailing vortices aligned with the direction of the flow. Poorer agreement was obtained in the near wake when the boundary layer separates at the end of the surface at the rear end. A possible explanation for the lack of accuracy at the rear end of the body was found in the formulation of the switching coefficient fk which produces too low values resulting in too low eddy viscosity in this region.

Status of PANS for Bluff Body Aerodynamics of Engineering Relevance

This paper is a review of the use of Partially-Averaged Navier-Stokes (PANS) simulations for various bluff body flows of engineering relevance. The application range from flows around generic bluff bodies such as a finite cylinder to flows around simplified road vehicles, trains and landing gears. Active flow control of bluff body flow is one of important application of PANS discussed in this paper. Judgment of the PANS performance is made in comparison with LES and other numerical techniques such as DES and RANS. The review illustrates the success of PANS and its advantage over LES in several bluff body flows, such as the flow around a rudimentary landing gear and the flow around finite cylinder. It also shows that there is a need of improvement in existing PANS methodology with variable \(f_k\) in flows with varying boundary conditions.

Partially-Averaged Navier-Stokes simulation of the flow around simplified vehicle

This paper presents Partially-Averaged Navier-Stokes (PANS) simulation of the flow around generic vehicle at different yaw angles. The results of PANS show not only excellent agreement with the experimental data but also large savings in the computer effort compared to LES predictions. Simulations on several computational grids show that PANS adapts to the existing grid making the prediction accurate on affordable computational grids

Numerical Investigation of the Actuated Flow on a Bluff Body

Large Eddy Simulations (LES) are conducted to study the Active Flow Control (AFC) of the separation of the boundary layer on a rounded leading edge frontstep. This bluff body imitates the flow around a section of a simplified truck cabin and focuses on the separation arising at the front rounded corner, the so called A-pillar. The LES data show the connection between the actuation and drag reduction. The actuated and unactuated flows are analysed using modal decomposition and frequency analysis. Two different actuation frequencies are tested and a strong influence of the control on both drag reduction and separation mechanism was observed. Relevant results, in terms of drag coefficient and recirculation bubble reduction, are achieved when the flow is actuated. LES shows an increased unsteadiness in the flow, introduced by the actuation. An analysis that investigates the connection between actuation and induced unsteadiness is presented.

A Flow Control Study of a Simplified, Oscillating Truck Cabin Using PANS

This work presents an application of the partially averaged Navier–Stokes (PANS) equations for an external vehicle flow. In particular, the flow around a generic truck cabin is simulated. The PANS method is first validated against experiments and resolved large eddy simulation (LES) on two static cases. As a consequence, PANS is used to study the effect of an active flow control (AFC) on a dynamic oscillating configuration. The oscillation of the model represents a more realistic ground vehicle flow, where gusts (of different natures) define the unsteadiness of the incoming flow. In the numerical study, the model is forced to oscillate with a yaw angle 10 deg > β > –10 deg and a nondimensional frequency St = fW/Uinf = 0.1. The effect of the periodic motion of the model is compared with the quasi-static flow condition. At a later stage, the dynamic configuration is actuated by means of a synthetic jet boundary condition. Overall, the effect of the actuation is beneficial. The actuation of the AFC decreases drag, stabilizes the flow, and reduces the size of the side recirculation bubble.

LES and PANS of turbulent flow through a staggered tube bundle

Two unsteady numerical techniques, Partially-Averaged Navier Stokes (PANS) and Large Eddy Simulation (LES), are used to predict the flow in a tube bundle. The results were compared with the existing experimental data. Both methods predicted the flow in a relatively good agreement with the experimental data although the PANS simulation used only fifty percent of the computational nodes compared to the LES. The results of the simulations are used to study the unsteadiness in the flow and identify a dominant frequency of the flow.

PANS study of the flow around an oscillating, simplified truck cabin with flow control

This work presents an application of the Partially-Averaged Navier-Stokes equations for an external vehicle flow. In particular, the flow around a generic truck cabin is simulated. The PANS method is first validated against experiments and resolved LES on two static cases. As a consequence, PANS is used to study the effect of an active flow control (AFC) on a dynamic oscillating configuration. The oscillation of the model represents a more realistic ground vehicle flow, where gusts (of different nature) define the unsteadiness of the incoming flow. In the numerical study, the model is forced to oscillate with a yaw angle 10 ◦ > β > −10 ◦ and a non-dimensional frequency St = fW /U in f = 0.1. The effect of the periodic motion of the model is compared with the quasi-steady flow condition. At a later stage, the dynamic configuration is actuated by means of a synthetic jet boundary condition. Overall, the effect of the actuation is beneficial. The actuation of the AFC decreases drag, stabilises the flow and reduces the size of the side recirculation bubble.