Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Flow dynamics and aerodynamic forces on an adapted Ahmed body at moderate Reynolds Numbers through numerical simulation
Submission Author:
Marcos Heduardo Pereira da Silva , MS
Co-Authors:
Marcos Heduardo Pereira da Silva, Raul Rosseto, Fernando Augusto Alves Mendes, Augusto Bornschlegell
Presenter: Augusto Bornschlegell
doi://10.26678/ABCM.COBEM2021.COB2021-1151
Abstract
Conducting aerodynamics studies on land vehicles is very valuable, since it’s possible to reach increasingly better efficiency of land transport in terms of fuel consumption, lifespan and safety. One of its main fundamentals is related to the aerodynamic drag, which can be defined as the force contrary to the movement of a body immersed in fluid. In this work, we evaluate the flow dynamics around an adapted Ahmed's body and its implications on aerodynamic forces. A fillet between the top surface and the rear chanfer is added to the original Ahmed body benchmark considering the original chanfer angle of 30°. Different fillet radius and inlet velocities were evaluated, so that Reynolds Numbers ranged from 4.8x103 to 4.8x104. In order to predict the flow behavior and the aerodynamic forces, a numerical model was built in the OpenFOAM environment, considering a transient, bidimensional, incompressible and isothermal flow model with constant properties. The employed turbulence model was the standard OpenFOAM implementation of the Spalart-Allmaras model, with 3% of turbulent intensity. The advective terms were modeled using a first order Upwind scheme and the time integration was performed using a second order backward scheme. PISO algorithm was used to solve the pressure-velocity coupling by the pisoFoam solver and the modeled physical time was 1 second. The initital flow condition was the solution of the equivalent steady state problem using the simpleFoam solver. The boundary conditions were precribed velocity at the inlet, zero gradient implementation that allows reverse flow at outlet, slip condition at the top boundary and moving wall boundary condition at bottom, at the same inlet velocity, so that the relative motion between the ground and the Ahmed body could be represented. The expected results from this work is to evaluate the effect of the boundry layer reattachment behavior at the Ahmed body top surface as the fillet radius and inlet velocity increases and evaluate how this physical behavior may bring and benifits in terms of drag reduction.
Keywords
Ahmed Body, Aerodynamics, Turbulence, OpenFOAM, Open Source
