On the non-intrusive evaluation of fluid forces with the momentum equation approach

The aim of this paper is to discuss the advantages and difficulties linked with the experimental application of the momentum equation approach as a non-intrusive way to predict the unsteady loads experienced by an airfoil in motion. First, in order to evaluate the influence of the varying parameters relative to the calculation of the corresponding drag and lift coefficients, numerical flow fields obtained by means of DNS are used. The comprehension of the impact of the spatial and temporal resolutions, velocity accuracy or third velocity component on the estimation of forces allows us to quantify the accuracy of the approach and helps in specifying the parameters setting which could lead to a consistent experimental application. In a second step, the approach is applied to experimental flow fields measured through the use of time resolved particle image velocimetry (TR-PIV). A low Reynolds number flow around an impulsively started airfoil is considered. The loads and vorticity flow fields are correlated and compared with those obtained by DNS.

[1]  Dilek Funda Kurtulus,et al.  Unsteady aerodynamic forces estimation on a square cylinder by TR-PIV , 2007 .

[2]  James Lighthill,et al.  Fundamentals concerning wave loading on offshore structures , 1986, Journal of Fluid Mechanics.

[3]  D. Kurtulus,et al.  Aerodynamic characteristics of flapping motion in hover , 2007 .

[4]  Bartosz Protas,et al.  An Effective Approach to Computation of Forces in Viscous Incompressible Flows , 2000 .

[5]  Alain Farcy,et al.  Characterization of vortical structures and loads based on time-resolved PIV for asymmetric hovering flapping flight , 2009 .

[6]  D. Rockwell,et al.  FORCE PREDICTION BY PIV IMAGING: A MOMENTUM-BASED APPROACH , 1997 .

[7]  L. Quartapelle,et al.  Force and moment in incompressible flows , 1983 .

[8]  Flavio Noca,et al.  Measuring instantaneous fluid dynamic forces on bodies, using only velocity fields and their derivatives , 1997 .

[9]  F. Noca,et al.  A COMPARISON OF METHODS FOR EVALUATING TIME-DEPENDENT FLUID DYNAMIC FORCES ON BODIES, USING ONLY VELOCITY FIELDS AND THEIR DERIVATIVES , 1999 .

[10]  Fulvio Scarano,et al.  Instantaneous planar pressure field determination around a square-section cylinder based on time resolved stereo-PIV , 2008 .

[11]  Michel Stanislas,et al.  Main results of the Second International PIV Challenge , 2005 .

[12]  Fulvio Scarano,et al.  Non-intrusive load characterization of an airfoil using PIV , 2006 .

[13]  Donald Rockwell,et al.  FORCE IDENTIFICATION BY VORTICITY FIELDS: TECHNIQUES BASED ON FLOW IMAGING , 1996 .