Investigations On Aerodynamics Of A Spike-tipped Hypersonic Vehicle

A blunt vehicle travelling at hypersonic speed generates a strong bow shock aheadof the blunt nose, which brings a rather high pressure and temperature. The high surfacepressure causes a large body drag. A spike tipped on the nose of hypersonic bluntvehicle is suitable for drag reduction and thermal load reduction, and it is widelyapplied in engineering. But the spike-tipped vehicles have some practical problems. Thecondition of optimal rate of drag reduction is rigorous. Unsteady flow induces unsteadyloads. It requires higher for the structural design.In this thesis，flow structure, the principle and the law of drag reduction and thesensitive parameters of the spike-tipped vehicle are investigated utilizing hypersonicwind tunnel experiment. Unsteady aerodynamics, separated flow and shock-boundarylayer interaction of the spiked-tipped blunt bodies are simulated numerically and themechanism of unsteady force and moment is explored. The main conclusions are asfollows.1. The measure and analysis at Mach number5by hypersonic wind tunnelexperiment indicates that the principle of drag reduction is related with the flowreconstruction and the inclination of the spiked bow shock. The reconstruction of flowstructure is sensitive to the length of spike as well as the diameter of tip disk and theangle of attacks. So Drag reduction is tightly associated with the sensitive parametersmentioned above.2．At small angle of attack, the longer spike and the bigger tip disk bring the moreobvious drag reduction to the extent of saturation. The maximum of drag reduction ishigher than60%. However, the spike-tipped vehicle will bring about somedisadvantages such as weak stability, heat spot and unsteady flow fluctuation.3. Unsteady numerical simulation suggests that unsteady flow around the spikebrings aerodynamics characteristics including the amplitude and the frequency of thepressure pulsation as well as the unsteady loads. The pressure pulsation in the separationregion of the spiked tip is low frequency, while the pressure pulsation arising from theshock oscillation is the relative high frequency. The most intense pressure pulsationappears at the nose of blunt vehicle where shock wave interacts with the boundary layer.Also the normal force and the axial force of the hypersonic spiked-tipped vehicle appearsimilar pulsation. The axial force behaves low-frequency oscillation and the normalforce behaves high-frequency oscillation.4．The comparability of unsteadiness appears among the different Mach numbers.Deduced from such comparability, the pulsation frequency of the real vehicle in theactual condition is quite close to that of its structural vibration. It is worthy of attention.