Yunpeng Wang

Starting Process in a Large-Scale Shock Tunnel

The starting process of the flow in an expansion nozzle (nominal Mach number 6) with an outlet diameter of 1.5 m and 8.9 m length, which is used for a large-scale hypersonic shock tunnel in the Key Laboratory of High-Temperature Gas Dynamics, was simulated and analyzed at incident Mach number M-s = 3.9. The calculating domains include the driven section (the shock-tube end, about 4.8m length), the nozzle with about 8.9 m length, and part of the test section (more than 3 m). The characteristics of unsteady nozzle flow, including the shock wave patterns in the nozzle inlet region and inside the nozzle, were analyzed numerically in the viscous and inviscid flow regimes, respectively. The pressure and Mach number results were presented and discussed by comparing with the experimental findings, where the simulated results of the reflected shock wave in the shock tube and the transmitted shock wave inside the nozzle were found to agree well with the test data. Additionally, the case without a contraction section for the throat configuration was also calculated and compared with the case with a contraction section. The effect of the starting flow in these two cases on the flowfield uniformity is discussed in detail in this paper.

Simulation of Supersonic Stage Separation of Capsule-Shaped Abort System by Aerodynamic Interaction

Abort separation of the capsule-shaped abort system boosted by supersonic aerodynamic interferences is studied by experiment and CFD. The objective of this study is to examine the effects of aerodynamic interaction on the abort process between two bodies: a capsule and a rocket. For this problem, four models are considered; model A has no disk, model B-1 has a disk, and model B-2 and B-3 have one and two fences, respectively, in addition to a disk. The capsule is modeled by a cone as a Launch Abort Vehicle (LAV), and the rocket by a circular cylinder as a Service Module (SM). To enhance the abort separation, ad isk and af ence are installed in order to increase the thrust force acting on the capsule, and their effects are investigated by experimental measurements and numerical simulations. The effects of aerodynamic interaction during an abort separation are examined from static and dynamic simulations for various separation distances. The role of fence vanishes and the effect of disk becomes very weak when the non-dimensional separation distances are larger than 0.6 and 0.8, respectively. For this reason, the capsule has a return in the case with disk when the separation distance is more than 2.0. However, the capsule has no possibility of recontact with the rocket due to the strong interferences.

SUPERSONIC UNSTEADY FLOW AROUND A CAPSULE-SHAPED ABORT SYSTEM WITH ANGLE OF ATTACK

Supersonic flow over a capsule-shaped abort system with angle of attack (AoA) of �, which is boosted by supersonic aerodynamic interference, is investigated numerically through the 3D simulation. The objective of this study is to examine the effects of AoA on aerodynamic stability. In the previous study, the flowfield around this system at � = 0 � is unsteady and has a strong periodic flow oscillation in the case without the clearance between the capsule and rocket. In the present study, this system has the angle of attack and a disk is installed to enhance the abort separation. The self-sustaining flow oscillation in the case with AoA is described and is visualized using the phase-averaged analysis of simulated results. With increasing AoA, the oscillating flow is divided into two parts, which correspond to the lower and upper surfaces of the cone. These two flows have a phase difference which becomes larger with increasing AoA. The present findings show it is about 0.28� and 0.4�, respectively. At the same time, the lower flow oscillation is out of step with the upper one, and an inharmonic flow oscillation occurs because of strong aerodynamic interaction in the lower flow. This unstable flow will lead to a risky abort separation and this phenomenon is analyzed in detail in this paper.

Force measurement using strain-gauge balance in a shock tunnel with long test duration

Force tests were conducted at the long-duration-test shock tunnel JF12, which has been designed and built in the Institute of Mechanics, Chinese Academy of Sciences. The performance tests demonstrated that this facility is capable of reproducing a flow of dry air at Mach numbers from 5 to 9 at more than 100 ms test duration. Therefore, the traditional internal strain-gauge balance was considered for the force tests use in this large impulse facility. However, when the force tests are conducted in a shock tunnel, the inertial forces lead to low-frequency vibrations of the test model and its motion cannot be addressed through digital filtering because a sufficient number of cycles cannot be found during a shock tunnel run. The post-processing of the balance signal thus becomes extremely difficult when an averaging method is employed. Therefore, the force measurement encounters many problems in an impulse facility, particularly for large and heavy models. The objective of the present study is to develop pulse-type sting balance by using a strain-gauge sensor that can be applied in the force measurement of 100 ms test time, especially for the force test of the large-scale model. Different structures of the S-series (i.e., sting shaped balances) strain-gauge balance are proposed and designed, and the measuring elements are further optimized to overcome the difficulties encountered during the measurement of aerodynamic force in a shock tunnel. In addition, the force tests were conducted using two large-scale test models in JF12 and the S-series strain-gauge balances show good performance in the force measurements during the 100 ms test time.

Force measurement in a shock tunnel with 100 milliseconds test duration

Force tests were conducted at the long-duration-test shock tunnel JF12, which has been designed and built in the Institute of Mechanics, Chinese Academy of Sciences. The performance tests demonstrated that this facility is capable of reproducing a flow of dry air at Mach numbers from 5–9 at more than 100 ms test duration. Therefore, the traditional internal strain-gauge balance was considered for the force tests use in this large impulse facility. However, when the force tests are conducted in a shock tunnel, the inertial forces lead to low-frequency vibrations of the test model and its motion cannot be addressed through digital filtering because a sufficient number of cycles cannot be found during a shock tunnel run. The post-processing of the balance signal thus becomes extremely difficult when an averaging method is employed. Therefore, the force measurement encounters many problems in an impulse facility, particularly for large and heavy models. The objective of the present study is to develop pulse-type sting balance by using a strain-gauge sensor, that can be applied in the force measurement that 100 ms test time, especially for the force test of the large-scale model. Different structures of the S-series (i.e., sting shaped balances) strain-gauge balance are proposed and designed, and the measuring elements are further optimized to overcome the difficulties encountered during the measurement of aerodynamic force in a shock tunnel. In addition, the force tests were conducted using two large-scale test models in JF12 and the S-series strain-gauge balances show good performance in the force measurements during the 100 ms test time.