Novel design and experimental validation of a contraction nozzle for aerodynamic measurements in a subsonic wind tunnel

Abstract

A novel design for a contraction nozzle, based on a logarithmic profile, is presented and developed to enhance aerodynamic measurements in a low-speed wind tunnel. The improvements obtained with this new proposal are validated, both, numerical and experimentally. As a starting point, four different wind tunnel contraction profiles are firstly considered and tested using the Computational Fluid Dynamics (CFD) package ANSYS FLUENT®. Both polynomial, due to its classical inclusion for wind tunnels, and logarithmic profiles, due to its expected enhancement, have been studied in terms of avoidance of separation of the boundary layer, procurement of a maximum level of exit-flow uniformity, and minimum turbulence levels at the outlet. Numerical comparison between obtained results shows the benefits of the new logarithmic profile developed by the authors, which was finally employed to construct the nozzle. To characterize its real performance, intensive experimental measurements have been conducted using pressure transducers and both single and dual hot wire anemometry. The pressure coefficient along the nozzle sidewall reveals an optimal evolution, matching perfectly with the theoretical design. In addition, low levels of turbulence and high flow uniformity is confirmed at the nozzle discharge. Turbulence intensities below 0.7% are obtained for the whole range of velocities available in the wind tunnel, and even practically constant uniform flow is obtained for all the traverses tested for validation. These indicators conclude that the contraction designed with the new profile is a good enhancing of the wind tunnel benefits.

Comparison of various turbulence models in wind tunnels

“…. Previous research on wind tunnel experiments mainly focused on the implementation of wind tunnel plans [7][8]. There are also comments on wind tunnels, but they only provide a general description of the airflow [9].…”

Wall-Resolved LES Modeling of a Wind Turbine Airfoil at Different Angles of Attack

“…Regarding the boundary conditions, a pressure outlet condition was applied in the far boundary, while the velocity-inlet condition was specified for the rest of the far-field boundaries. A moderate-to low Re number of 350,000, based on the chord length, was used at the inlet with a characteristic 0.7% turbulence intensity and an integral length scale of 0.075 m (obtained in [29] by hot wire experimental measurements). The no-slip condition was used for the airfoil walls and the symmetry condition was applied in the spanwise boundaries (top and bottom).…”

Exact solutions for quasi-one-dimensional compressible viscous flows in conical nozzles

“…The one-dimensional models are popular in the engineering communities that deal with propulsion and power generation equipment (Maicke & Majdalani 2012): applications abound and include wind tunnels (Rodriguez Lastra et al. 2013), scramjets (Yu et al. 2020), rockets (Sutton 1992), ramjets, afterburners and a variety of gas turbine components through which gases are expanded (Maicke & Majdalani 2012; Cavazzuti & Corticelli 2017).…”