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Some Fluid Flows and D’Arcy Equation
Published in Prem K. Kythe, An introduction to BOUNDARY ELEMENT METHODS, 2020
With altitude the Mach number M increases while the speed of sound decreases. Also, the kinematic viscosity increases rapidly with increase in altitude and thus the Reynolds number decreases considerably. The potential flow theory does not remain valid in this case.
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)
An Introduction to Sound, Hearing and Perception
Published in Nick Zacharov, Sensory Evaluation of Sound, 2018
The vibration of an object causes movement or displacement in its surface, which displaces the molecules of surrounding medium. This causes a disturbance in the sound field, which then travels through the medium with the speed of sound (Beranek and Mellow, 2012). The speed depends on characteristics of the medium such as the density, temperature and moisture. The speed of sound can be approximated to be 340 m/s in air in normal room temperature.
Real-time DSP-based time delay estimation using two sensors
Published in International Journal of Electronics, 2018
Seyed Mehdi Hosseini, Rohollah Abdollahi
where is the flooring operator, is the total length of each block, is the distance between the two sensors and is the speed of the sound. The speed of the sound depends on the propagation medium. It is fixed for a given medium. At room temperature (20°C), the speed of sound is 343 m/s (Myers, 2004). To have simple calculation in localising a sound source based on far field assumption, the distance between the two microphones should be much less than the distance of the sound source to the microphone pairs. In this case, two incident sound rays may be assumed as parallel, which leads to the simple calculation (Valin, 2005). On the other hand, should be enough larger than the sampling period to have a finer resolution in localisation. For example, for speech signals, if the sound source is placed at the distance of order metres from the microphone pairs, then d should be in the order of 10 cm.
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):
Hydro-acoustic and noise analysis of DTMB4119 marine propeller at different advance coefficients using DES turbulence model
Published in Journal of Marine Engineering & Technology, 2023
Ehsan Yari, Mohammad Reza Nateghi
In this section, the settings of the hydrodynamic solver are discussed. The flow is considered turbulent. According to the properties of water fluid and the definition of Reynolds number , it is clear that the Reynolds number is of the order of 106 or 107. Water fluid is considered incompressible because the Mach number is less than 0.3. The speed of sound in water is 1500 m/s; the water density is 1026 Kg/m3. Reference Pressure Acoustic for water is equal to .