Numerical simulation of flow over an airfoil with a cross flow fan as a lift generating member in a new aircraft model

摘要

Purpose - The purpose of this paper is to show how flow over the airfoil comprising a cross flow fan has been solved by developing a computational fluid dynamics (CFD) code. This research was going to find aerodynamic coefficients and static pressure distribution over the airfoil surfaces. The eccentric vortex motion observed earlier by other researchers in cross flow fan has been studied by numerical method. Also, the airfoil trailing vortex size variation by free stream and fan rotational speed has been surveyed. Design/methodology/approach - Flow over the airfoil has been investigated by CFD. At the airfoil solid walls no slip condition (zero velocity) was applied. Re-normalization group k-[varepsilon] model was used for turbulence modeling. The pressure-velocity coupling was calculated by the SIMPLEC algorithm. Second-order upwind discretization was considered for the convection terms. Finite volume method with rectangular computational cells was used for whole the solution domain. Findings - CFD predicted lift force was in good agreement with experimental data with the error of 8.26 percent, while the error of thrust prediction was 14.17 percent. Both errors are generally acceptable for an engineering application. Some key flow features observed previously by experiments has also been reproduced by simulation, notably motion of the eccentric and trailing vortices. At low-fan rotational speed, the eccentric vortex formed below the shaft of the fan but at high-rotational speed, eccentric vortex came up and moved toward the airfoil leading edge. It was shown that increasing free stream velocity or decreasing fan rotational speed leads to a larger trailing vortex and vice versa. It was showed that the airfoil lift and thrust are highly depended on the fan rotational speed. These forces will increase by enhancing the fan rotational speed. Research limitations/implications - Because of complicated geometry of the airfoil, 2D analysis of the flow over the airfoil has been carried out. This simplification leads to higher discrepancies between experimental data and numerical solution. Practical implications - This paper provides a detailed study of the Fanwing airfoil. This airfoil is very new and researches in this area are very limited. So, this paper can be helpful for other researches involved in this topic as well as aerospace industries. Originality/value - This paper is valuable for researchers in the new and up-to-date concept of the airfoil comprising a cross flow fan (Fanwing airfoil). This work is original.