Annotation: During experimental investigation of the dynamic characteristics of a pneumatic test bench for testing liquid rocket engine high-flowrate automatic units, the effect was detected of 20-35% sound speed increase in the gas flow moving along the channel with corrugated wall (metal hose) which is a part of test bench drain system. The article presents the results of experiments and the task of theoretical justification of the effect is solved. It is indicated that its causes may be two mutually complementary factors – a decrease of gas compressibility at eddy motion and oscillations of metal hose wall. The physical model is considered that describes variation of gas elasticity and density in the conditions of high flow vorticity. It is supposed that in the near-wall layer of the channel, toroidal vortexes (vortex rings) are formed, which move into turbulent core of the flow where their size decreases and the velocity of rotation around the ring axis of torus increases. The spiral shape of the corrugation ensures also axial rotation, which increases vortexes stability. The intensive rotation around the ring axis creates considerable centrifugal forces; as a result, the dependence of pressure on gas density and the sound speed increase. The mathematical model has been developed that describes coupled longitudinal-lateral oscillations of gas and channel’s corrugated shell. It is indicated that in the investigated system, two mutually influencing wave types are present – longitudinal, which mainly transfer gas pressure pulses along the channel and lateral ones, which transfer the shell radial deformation pulses. As a result of modeling, it has been ascertained that because of the lateral oscillations of the wall, the propagation rate of gas pressure longitudinal waves (having the same wave length as in the experiments at test bench) turns out to be higher than adiabatic sound speed.

Annotation: This paper describes the effective approach for the technology of the rocket airframe development testing, based on the method of numerical modelling, which enables the virtual experimental runs prior to the beginning of the development testing to check the performance of the standard airframes and predict issues of concern. The method is realized based on the computer models developed in the ANSYS Workbench environment. Based on the offered method the complex mechanical system, which attaches the cluster projectiles in the conditions of the temperature exposure and heat cycling, underwent the virtual tests. Computational models, criteria and test procedures necessary for the analysis of the mechanical condition and prediction of the performance of the actual airframe of the warhead were developed. Moreover, computational models consider all the design and technological features of the airframe: layout of the projectiles attachments, initial stress-strain state of the system after the tightening of the threaded connections, friction between the components of the system and their mutual displacement, temperature dependence of the physical and mechanical characteristics and ultimate stress of materials. For the specified loading conditions during the ground operations with the warhead, the most dangerous computational cases are determined which have been implemented during the virtual tests. Test results were used to conduct the static analysis of the mechanical condition, strength and conditions for performance of the actual structure of the attachment under the impact of the operating levels of temperature exposure and heat cycling. Results of the virtual tests confirm the performance of the projectiles attachment system and are introduced into production in the phase of engineering development.