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Fluid Dynamics
Published in Wen-Jei Yang, Handbook of Flow Visualization, 2018
Tsuyoshi Asanuma, Yoshimichi Tanida
Figure 18 shows the change of the flow past a thin aerofoil, depending on the Mach number. With increasing Mach number of the free stream, a supersonic flow region appears on a part of the aerofoil surface. The Mach number at which the flow velocity becomes exactly sonic at a point on the aerofoil is called the critical Mach number. With further increase of the Mach number, shocks which produce discontinuous changes appear at the lee side of the supersonic region. With increasing Mach number, the shocks shift downstream, getting stronger until they reach the trailing edge of the aerofoil. Then, the flow becomes wholly supersonic. The subsonic region around the leading edge is caused by the thickness effect of the aerofoil, when the front shock is detached from the aerofoil (see Sec. V.C).
Transonic Flight and Aerofoils
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
When air flows over an aerofoil along its chord increases to become sonic, the aircraft’s Mach number reaches its critical Mach number Mcrit. The aircraft with sweep back wings can have relatively higher Mcrit.
Aeroelastic flutter analysis of tilted curved nanopipe in supersonic flow
Published in Mechanics of Advanced Materials and Structures, 2023
Ke Wu, Gang Wang, Xin Li, Yasuo Liu
The effects of different parameters on the state of stability in nanopipe in supersonic two-phase flow are examined in this section. In Figure 3, the effect of gas volume fraction is shown on the natural frequency versus Mach number curves. As seen, the fluids with pure liquid enhance the stability of the FG nanopipe against flutter behavior. Moreover, the natural frequency in which flutter initiates is slightly higher in the case of Therefore, having a more liquid phase in the two-phase flow aids the stability of the nanopipe structure. Moreover, the velocity of the flow narrows the vibrational stability region with a decrease in the critical Mach number. The increase in the velocity also reduces the frequency of occurrence of instability but this effect is not comparable to the effect on the Mach number.
Effects of blocking ratio and Mach number on aerodynamic characteristics of the evacuated tube train
Published in International Journal of Rail Transportation, 2020
Peng Zhou, Jiye Zhang, Tian Li
Combining (13) and (15) equations, variation curve of throat ratio to Mach number in the critical choked flow state can be plotted as shown in Figure 2. For a certain critical throat ratio corresponding to the incoming flow Mach number, the velocity increase of the incoming flow can inevitably result in the choked flow. In other words, for a critical Mach number, an increase in the throat ratio will inevitably result in the choked flow. By comparing the two limits, it is easily found that isentropic limit and Kantrowitz limit are stricter for subsonic incoming flow and supersonic incoming flow, respectively. Obviously, there will inevitably be choked flow as the Mach number of the incoming flow is about 1.0. In this study, the incoming flow Mach number mainly varies from 0.5 to 1.0, corresponding to the isentropic limit.
Latest technologies and novel approaches in coal seam gas centrifugal compressor trains in Australia
Published in Australian Journal of Mechanical Engineering, 2019
The maximum tip speed is governed by the followings (Bloch 2006a, 2006b; Brown 2005; Forsthoffer 2011):The strength limitation: The majority of impellers are manufactured from low alloy steels and trip speeds for closed-type impellers would be limited to approximately 330 m/s. For semi-open impellers, particularly overhung ones, tip speeds up to 410 m/s have been acceptable. However, these impellers are not commonly used for CSG applications.Mach number: Maximum tip speed is restricted by gas dynamics. Mach number in flow-paths of impellers should be restricted within some constrains (Bloch 2006a, 2006b; Brown 2005; Forsthoffer 2011). The critical Mach number occurs at the eye of impeller, and as a very rough indication it should be kept below about 0.85 to avoid choking at inlet. The inlet Mach numbers of up to 0.96 (or sometime more) have been used previously. It is extremely complicated to calculate this Mach number; for this reason the impeller tip Mach number (Ma) which is easy to calculate is usually used. It is defined as ‘Ma = impeller tip speed/speed of sound at inlet conditions’.