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Subsonic Flow and Discharge Coefficients
Published in Frank E. Jones, Techniques and Topics in FLOW MEASUREMENT, 2020
where T1 is the upstream temperature; γ is the ratio of specific heats of the gas; M1 is the upstream Mach number; and F is the recovery factor for the temperature sensor, a factor by which the indicated temperature is corrected to the true temperature. The Mach number is defined as the ratio of the velocity of the gas to the speed of sound. () P0≡P1[1+(γ−1)M12/2]γ/(γ-1)
Introduction
Published in Mohamed Gad-el-Hak, MEMS, 2005
where vo is a characteristic velocity and v is the kinematic viscosity of the fluid. The Mach number is the ratio of flow velocity to the speed of sound Ma=voao
Speed of Sound and Mach Number
Published in Rose G. Davies, Aerodynamics Principles for Air Transport Pilots, 2020
The free-stream Mach number of an aircraft is used to classify the flights. Subsonic flights: The free-stream Mach number of aircraft is less than its critical Mach number, Mfs < Mcrit. The airflow around the subsonic aircraft is always subsonic, i.e., the local air flow speed around a subsonic aircraft is always less than the local speed of sound. The airflow can be treated as incompressible if the true airspeed of the aircraft is less than 250 kt, low subsonic. Otherwise, the airflow around the subsonic is compressible.Transonic flights: The free-stream Mach number of aircraft is greater than its critical Mach number, and less than, approximately, 1.2, Mcrit < Mfs < 1.2. The airflow around transonic aircraft can be subsonic, as well supersonic, even when the free-stream Mach number is less than 1. The air definitely is compressible, and shockwaves may be formed on aerofoils and on other parts of the aircraft body.Supersonic flights: The free-stream Mach number of aircraft is greater than 1.2, Mfs > 1.2. This is also called hypersonic if the free-stream Mach number of any traveling object is greater than 5 or 6. Airflow around the supersonic aircraft is supersonic in general, except the airflow behind a normal shockwave, and within boundary layers. The air is highly compressible, and the kinetic heating is a significant concern due to the speed change of airflow around supersonic aircraft.
Using an optimisation strategy to design a supercritical CO2 radial inflow turbine transonic stator
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Jianhui Qi, Bingkun Ma, Kan Qin, Kuihua Han, Jiangwei Liu, Jinliang Xu, Yueming Yang, Yongqing Xiao, Xujiang Wang
It can be seen from Figure 10(a) that the flow accelerates from a low Mach number to a supersonic state at the nozzle throat. A maximum Mach number of approximately 1.3 is reached. The streamlines show the flow directions in the nozzle. It can be noticed that a large separation occurs near the outside wall, and the streamlines of the separation show that a large vortex is formed near the outside wall. This is due to the limited from the given inlet condition, which cannot fully occupy the downstream nozzle. This large vortex pushes the mean stream towards the inside wall, which confirms again that the optimiser can find a correct nozzle shape to constrain the via ‘smartly manipulating’ the vortex.
Study of the thermal erosion, ejection and solidification processes of electrode materials during EDM
Published in Engineering Applications of Computational Fluid Mechanics, 2019
Shengfang Zhang, Wenchao Zhang, Hao Chang, Yu Liu, Fujian Ma, Dapeng Yang, Zhihua Sha
According to the gas flow theory, the relationship between the maximum outlet pressure of the vapor at the time of ejection and the environmental pressure on the electrode surface can be expressed as follows (Yang, Zhao, & Huang, 2011): where Ma is the Mach number, P0 is the environmental pressure, and P is the vapor pressure. Upon substituting Equation (7) into Equation (6), the expression of the relationship between the Mach number of vapor outlet airflow and discharge energy can be expressed as follows: The Mach number is essentially the ratio of the velocity v to the speed of sound a under the current environmental conditions, namely, Ma = v/a. Therefore, an equation of the maximum velocity of vapor ejection is finally obtained: Thus, the maximum velocity of the vapor ejection generated under different discharge parameter conditions can be obtained by Equation (9). Since the magnitude of the impact pressure generated by the vaporization explosion of the material is related to the energy released, the amount of energy released is linearly related to the heat absorbed by the material per unit time. It was concluded that the impact pressure generated by the vaporization explosion also satisfies the Boltzmann distribution, and the impact pressure is proportional to the impact velocity. Therefore, the vapor jet velocity generated at the distance r from any point on the surface of the material to the center of the discharge point can be expressed by Equation (10):
Aerothermodynamic design and performance analysis of modified nose cones for space reentry vehicles
Published in International Journal of Ambient Energy, 2022
Raja Muthu, S. Siva Lakshmi, Santhoshini Babu
The solver used is density-based formulation since the problem is a compressible flow (hypersonic velocity model). The Mach number for simulation is chosen as 5 (hypersonic speed). SST k–ω (shear stress transport k–omega) turbulence model is chosen (Deepak, Vinu, and Chandran 2017). It is a hybrid two equation model combining the Wilcox k–ω and the k–ϵ models. The k–ϵ model predicts well far from the boundaries (wall) and k–ω model predicts well near wall.