Influence of nose perturbations on behaviors of asymmetric vortices over slender body

Abstract

The influence of nose perturbations on the behaviors of asymmetric vortices over a slender body with a three-caliber ogive nose is studied in this paper.The tests of a nose-disturbed slender body with surface pressure measurement were conducted at a low speed wind tunnel with subcritical Reynolds number of I • 105 at angle of attack (~ = 50 ~ The experiment results show that the behaviors and structure of asymmetric vortices over the slender body are mainly controlled by manual perturbation on the nose of body as compared with geometrical minute irregularities on the test model from the machining tolerances. The effect of the perturbation axial location on asymmetric vortices is the strongest if its location is near the model apex. There are four sensitive circumferential locations of manual perturbation at which bistable vortices over the slender body are switched by the perturbation. The flowfleld near the reattachment line of lee side is more sensitive to the perturbation, because the saddle point to saddle point topological structure in this reattachment flowfield is unstable. Various types of perturbation do not change the perturbation effect on the behaviors of bistable asymmetric vortices.KEY WORDS: asymmetric vortex, slender body of revolution, bistable flow, high angle of attack aerodynamics

Investigation of periodic characteristics of perturbed flow over a slender body

“…The relationship between side-force and a circumferential location of perturbation changed from a single period to an irregular double period. The sensitivity of asymmetric flow to perturbation weakened as the perturbation moved backward [ 16 ], thus, the double period presented irregular fluctuation. Meanwhile, Fig.…”

“…Based on the previous studies [ 16 , 17 , 32 ]; on the asymmetric flow over a slender body, the artificial perturbation near the tip of the slender body eliminates the uncertainty of flow and provide a stable asymmetric flow structure to study. In the present study, a micro particle with a diameter of d = 0.004 D was taken as the artificial perturbation onto the nose of the slender body.…”

“…Meanwhile, Rao [ 15 ] pasted a pair of transitional wires onto both sides of the nose of the slender body to disrupt the flow separation, thereby resulting in no obvious vortex structure occurring, hence, the side force was reduced. Chen [ 16 ] and Deng et al [ [17] , [18] , [19] ] employed a 0.2 mm diameter particle onto the tip of the slender body to disturb the asymmetric flow at high AoA. The asymmetric flow pattern was associated with the parameters of the particle.…”

Investigation on asymmetric flow over a blunt-nose slender body at high angle of attack

“…The microperturbation was then placed on the tip of the pointed-nose slender body. The vortex pattern was fairly manageable in the presence of the microperturbation, and the square wave, which is doubly periodic, was observed for the side-force variation with a roll angle from 0°to 360° (Chen et al 2002, Deng 2004, 2008.…”

“…Given the predominant role of microperturbation in asymmetric vortex patterns, a singly periodic square wave was observed for the side-force variation with the circumferential angle (θ) of microperturbation set from 0°to 360°around the body axis (figure 4). However, the characteristic of a single period differed from that of a double period in a pointed-nose slender body (Chen et al 2002). The flow structure over a pointed-nose body at a high AoA was described in detail by Deng and Wang (2004), but no study has described the flow structure over a blunt-nose body at a high AoA.…”