Our research aim is to investigate the buffet alleviation effect of static or vibrating bulges attached on the forebody surface of the model.Experiments and numerical simulations on a model consisting of a sharp-edged,70°-leading edge sweep delta wing and twin swept back vertical tails were conducted.Models with different bulges were tested and computed at 10 and 20 m/s of free stream velocity at angles of attack ranging from 20°–50°.Dynamic strain gauge and multichannel data acquisition and analysis system were employed for the measurement of unsteady root strain on the vertical tails.Experimental and computational results show that both static and vibrating bulges behave effectively as a novel tool to alleviate tail buffet,and the alleviation effect depends largely on the vibrating frequency.Besides,one-sided bulge can only alleviate the buffeting response for the tail of the same side,and it has no obvious alleviation effect for the opposite tail.Results of the spectral analysis reveal that there are generally three peaks of spectral density for aircrafts of this configuration,and bulges used in this paper could alleviate tail buffeting,but the total lift and drag of the whole model show no obvious deviation compared to the base model and the dominant frequency of the vibration of the tails has not shifted.
Side loads and aeroelastic stability of rocket nozzle were studied by solving Navier-Stokes equation coupled with structural equation of motion.The computation was implemented at different total pressure inlet conditions,and flow phenomena of free shock separation(FSS) and restricted shock separation(RSS) were captured.At certain total pressure inlet conditions,it was found that both kinds of separations existed in nozzle flow filed,while RSS exhibited combined space asymmetry and time unsteady characteristics.The corresponding asymmetric circumferential pressure distribution,strong pressure fluctuation in separation region and large range of displacement of shock wave all led to severe side loads.Besides,for flexible nozzles,the low pressure gradient in separation region might reduce structure stability at nozzle exit,resulting in large local deformation.It was also found that aeroelasticity exhibited buffeting characteristic due to the asymmetric separation,resulting in reduction of aeroelastic stability,even structure destruction.Moreover,aeroelasticity might amplify side loads and aggravate its growth rate.However,with increment of inlet pressure,nozzle aeroelastic stability was also increased when a full flow was nearly reached.
