Previous research has shown that aircraft employed in fire-fighting endeavors experience increases in lift when releasing large volumes of water in order to extinguish large scale flames.  One particular research study has shown that these increases in lift do not directly correlate to the mass exchange but have added effects due to air-water interactions. In this previous work, panel methods were used to replicate the water column as a solid body in order to solve for an approximate flow behavior.   Specifically, it was found that these water columns altered the flow characteristics about the lifting surfaces and aided the aerodynamic lift. In this effort, these effects are further investigated using numerical methods.

In this work, the concept is evolved in the context of utilizing fluid sprays to enhance aerodynamics. Here, a two-dimensional NACA 0012 airfoil is used to understand the behavior behind water spray formations and gas interactions. Multiple parametric studies are conducted to learn more about which factors affects the aerodynamic performance of a NACA 0012 airfoil with a spray formation on its­­ lower surface. This simplified model is used to learn more about isolated parameter behavior and is used to guide a novel understanding of these multi-phase fluid interactions. We evaluate the lift-to-drag ratio for each parameter combination to evaluate the aerodynamic performance of the liquid spray. Our main focus of this research is to understand the gas behavior with respect to liquid interaction as compared to a single-phase gas over the bottom surface of the airfoil. We hypothesize that the main effects are related to a ‘pseudo-geometry’ that is created on the lower surface due to the liquid spraying.

Numerical simulations of the unsteady, iso-thermal, two-phase flows were solved using second-order schemes and first-order discretization on space and time, respectively. The interactions between the water and gas phases were calculated by the Dispersed Multiphase (DM) model, which solves the dispersed phase (water) in a Euler-Euler approach. Similarly to the Euler-Lagrange approach, the DM model is able to represent the particles dispersed in a continuous flow at low volume fractions, but at a lower computational cost. Since we are more interested in investigating the aerodynamics effects caused by the liquid spray, liquid column and droplet breakups are not considered. Thus, the liquid jet is represented by liquid droplets with constant diameter and the mass flow is calculated for a momentum ratio of 10. Mesh and time-step refinements are conducted to certify numerical accuracy and help build confidence in the analysis.


Using Liquid Spray Formations to Improve Aerodynamic Performance of Airfoils

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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