Difference between revisions of "Dynamic stall NACA0012 Michael Alletto"

From OpenFOAM Wiki
Jump to navigation Jump to search
(Created page with "category:mesh * '''contributor''': Michael Alletto * '''affiliation''': WRD MS * '''contact''': <mail address='michael.alletto@gmx.de' description='author'>click here for...")
 
Line 15: Line 15:
  
 
==Introduction==
 
==Introduction==
 +
 +
In this tutorial we will look at the simulation of the dynamic stall of a periodically pitching NACA0012 airfoil in an incompressbile flow. We will compare 2D RANS simulations with the experiments by \cite{lee2004}. The periodically pitching motion is achieved by an arbitrary mesh interphase (AMI). The same periodically pitching motion can be achieved also using the morphing mesh approach or using the overset mesh method. Unfortunately a few test with the morphing mesh lead to a deterioration of the mesh due to the large deformation of the mesh for the present case. Regarding the overset mesh such problem do not occur since the mesh topology is not changed. A few test however, lead to a much higher computational time compared to the AMI strategy. For this reason the AMI is chosen. The same method shown in this tutorial, could be also applied to the pitching motion of the wings of a wind turbines or a helicopters. 
 +
 +
Dynamic stall is a phenomena occurring in many technical application like vertical axis turbines (see \cite{wang2010}), airfoils under the influence of gusts, maneuvering aircraft and also horizontal axis wind turbines (see \cite{visbal2018}). Dynamic stall on a periodically pitching airfoil is characterized by the increase of the lift coefficient $C_l$ and the drag coefficient $C_d$ well beyond the maximum values obtained for a static airfoil. The stall angel $\alpha_s$ is also much higher for pitching airfoils compared to static airfoils (see \cite{lee2004}). Main cause of the increased lift and drag coefficient is the development of a large attached dynamic stall vertex (DSV) developing on the suction side of the airfoil as the angle of attach increases. This vortex is swept towards the trailing edge causing the pressure minima to move towards the trailing edge. This causes a strong nose down moment (see \cite{visbal2018}). As the angle of attach decreases the flow becomes attached again with a large hysteresis in the lift. The strong variation of the lift and drag leads to large oscillatory forces and the change in the moment coefficient $C_m$ leads to large torsion of the airfoil. Since this large forces and moment can severely damage the structure, it is a must to have numerical tools which can accurately predict this phenomena.

Revision as of 09:47, 8 January 2022

Go back to Collection by authors.

Go back to Meshing.

Vortex induced vibration of a 2D cylinder

You can download the case file https://gitlab.com/mAlletto/openfoamtutorials/-/tree/master/dynamicStall] here.

Introduction

In this tutorial we will look at the simulation of the dynamic stall of a periodically pitching NACA0012 airfoil in an incompressbile flow. We will compare 2D RANS simulations with the experiments by \cite{lee2004}. The periodically pitching motion is achieved by an arbitrary mesh interphase (AMI). The same periodically pitching motion can be achieved also using the morphing mesh approach or using the overset mesh method. Unfortunately a few test with the morphing mesh lead to a deterioration of the mesh due to the large deformation of the mesh for the present case. Regarding the overset mesh such problem do not occur since the mesh topology is not changed. A few test however, lead to a much higher computational time compared to the AMI strategy. For this reason the AMI is chosen. The same method shown in this tutorial, could be also applied to the pitching motion of the wings of a wind turbines or a helicopters.

Dynamic stall is a phenomena occurring in many technical application like vertical axis turbines (see \cite{wang2010}), airfoils under the influence of gusts, maneuvering aircraft and also horizontal axis wind turbines (see \cite{visbal2018}). Dynamic stall on a periodically pitching airfoil is characterized by the increase of the lift coefficient $C_l$ and the drag coefficient $C_d$ well beyond the maximum values obtained for a static airfoil. The stall angel $\alpha_s$ is also much higher for pitching airfoils compared to static airfoils (see \cite{lee2004}). Main cause of the increased lift and drag coefficient is the development of a large attached dynamic stall vertex (DSV) developing on the suction side of the airfoil as the angle of attach increases. This vortex is swept towards the trailing edge causing the pressure minima to move towards the trailing edge. This causes a strong nose down moment (see \cite{visbal2018}). As the angle of attach decreases the flow becomes attached again with a large hysteresis in the lift. The strong variation of the lift and drag leads to large oscillatory forces and the change in the moment coefficient $C_m$ leads to large torsion of the airfoil. Since this large forces and moment can severely damage the structure, it is a must to have numerical tools which can accurately predict this phenomena.