Abstract
The effect of manufacturing geometry deviations on the flow past a NACA 64(3)-618 asymmetric airfoil is studied. This airfoil is 3D printed according to the coordinates from a public database. An optical high-precision 3D scanner, GOM Atos, measures the difference from the idealized model. Based on this difference, another model is prepared with a physical output closer to the ideal model. The velocity in the near wake (0–0.4 chord) is measured by using the Particle Image Velocimetry (PIV) technique. This work compares the wakes past three airfoil realizations, which differ in their similarity to the original design (none of the realizations is identical to the original design). The chord-based Reynolds number ranges from 1.6×104 to 1.6×105. The ensemble average velocity is used for the determination of the wake width and for the rough estimation of the drag coefficient. The lift coefficient is measured directly by using force balance. We discuss the origin of turbulent kinetic energy in terms of anisotropy (at least in 2D) and the length-scales of fluctuations across the wake. The spatial power spectral density is shown. The autocorrelation function of the cross-stream velocity detects the regime of the von Karmán vortex street at lower velocities.
Highlights
IntroductionOne of the general effects of non-linearity is the unpredictable response to even small perturbations or changes of the boundary conditions
Fluid flow is a highly non-linear problem that still lacks a reasonable solution
The statistical properties can be predicted quite reasonably. This feature is used in modern computational fluid dynamics, which does not solve the non-linear Navier–Stokes equations on a fine mesh with the resolution of the Kolmogorov length-scale, but it solves only much larger cells with a direct link to the geometry of the boundary conditions under the assumption that the behavior at smaller scales follows some of the turbulence models
Summary
One of the general effects of non-linearity is the unpredictable response to even small perturbations or changes of the boundary conditions. The scale of possible responses to a small geometry perturbation ranges from almost zero effect to a linear response and up to a complex change of flow state. The statistical properties can be predicted quite reasonably This feature is used in modern computational fluid dynamics, which does not solve the non-linear Navier–Stokes equations on a fine mesh with the resolution of the Kolmogorov length-scale, but it solves only much larger cells with a direct link to the geometry of the boundary conditions under the assumption that the behavior at smaller scales follows some of the turbulence models
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
