Analysis of hammer shock load characteristics in S-duct

To analyze the effect of instantaneous high pressure profile caused by engine surge on the hammer shock propagation, an S-duct model was simulated under conditions of both subsonic and supersonic inflow, based on improved delayed detached eddy simulation (IDDES) method. Results showed that when hammer shock was generated, it propagated upward along the inlet rapidly with approximate constant speed and the strength of hammer shock increased. Meanwhile, the aerodynamic load of S-duct inner wall was uneven under the influence of centrifugal force field; the aerodynamic load on side wall with the larger radius was greater. Increasing the pressure loading gradient led to quicker hammer shock propagation speed and enhanced strength, however different unloading pressure profiles had no obvious effect on the hammer shock propagation speed and strength. Under both subsonic and supersonic inflow conditions, the intensity of hammer shock increased with the growth of maximum value of instantaneous high pressure, approximately matching the quadratic function distribution law. The hammer shock intensity of supersonic inflow was greater than the subsonic inflow.