Jet vectoring using secondary Coanda synthetic jets

Abstract

In recent years, studies on the fundamental principle of thrust vectoring using jets have been conducted to realize next-generation aircraft applications. Various methods for vector control of jet flow have been proposed, such as methods that achieve control via steady, continuous jets under the Coanda effect, steady suction flows near the Coanda surface, and synthetic jets from a neighbor slot as secondary jets. However, there are no studies on the flow direction control of jets using the secondary synthetic Coanda jet. In this study, the influence of synthetic jets near a circular cylinder on the flow characteristics of a primary jet was experimentally investigated. The main results obtained in the study were that the direction of the primary jet flow can be controlled using the secondary synthetic jet, and the degree of jet deflection depends on the frequency of the velocity oscillation for the secondary synthetic jet under an identical momentum ratio. Furthermore, when using the synthetic jet as the secondary flow, a controllable region larger than that obtained when using a steady and continuous injection or suction flow is expected. This is because secondary flow is generated using the ratio of the momentum between the primary jet and the secondary flow at the slot exit in conjunction with the dimensionless frequency of the synthetic jet based on the velocity of the primary flow at the slot exit.

Influence of Amplitude of Excited Secondary Flow on the Direction of Jets

“…In previous studies, although the "control region" (i.e., range in which the deflection angle can be treated as a function of the momentum coefficient) is narrow, it is effective to apply suction to the secondary flow to deflect the jet. As previously reported, 9,17,25) the results of this study correspond to the results obtained in the previous study.…”

“…Results for three ratios of steady-state velocity to velocity fluctuation amplitude, ¼ À1, ¹1, and 0, and dimensionless frequencies, f à ¼ 0:02, 0.05, and 0.08, are discussed. Similar to the results of Kobayashi et al, 25) it can be confirmed that the deflection angle c depends on both the momentum ratio ² and dimensionless frequency f à . Furthermore, it also clearly depends on the ratio ¦ between the steady velocity and velocity fluctuation amplitude, as previously described.…”

“…A previous study demonstrated that the deflection angle of the jet depends on the momentum ratio ² and dimensionless frequency f à when the synthetic jet is applied as the secondary flow. 25) However, the results presented here confirm that the deflection angle also depends on the ratio of the time-averaged velocity of the continuous flow to the timefluctuating velocity amplitude ¦. Figure 8 also shows that the total flow rate of the primary and secondary flows decreases as the value of ¦ decreases.…”

“…Therefore, it is a subject for further study. For example, by combining ¦, it is possible to adjust the angle arbitrarily while retaining a small change in the flow field and maintaining the frequency constant with high-frequency conditions, which has not been achievable 25) until now. For instance, the deflection angle c can be controlled in the range of the range of the adjustable angle is wider as f à increases.…”

“…If the deflection angle of the jet can be arbitrarily adjusted using parameters different from the momentum ratio, fluidic thrust vectoring can be applied not only to aeronautical engineering, but also to a wide range of fields, such as manufacturing sites and home appliances. Therefore, Kobayashi et al 25) proposed a jet vectoring method that applies a synthetic jet to the secondary flow. There are two dimensionless parameters that do not involve geometrical shape changes for jet direction control: the momentum ratio of the jet and the dimensionless frequency.…”