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Flow and Circulation of Matter
Published in Masanori Shukuya, Bio-Climatology for Built Environment, 2019
In order to make it possible to calculate exergy consumption rate, XC (= ΔPfV), we need to characterize how the pressure decreases in the course of air (or water) flowing inside a duct (or pipe). In general, the decrease in pressure expressed as ΔPf becomes larger as the duct is made longer or its diameter smaller. The pressure decrease also becomes larger as the fluid velocity increases, that is, the dynamic pressure increases. The whole of such relationship may be expressed with one single formula as () ΔPf=fLD(12ρv2), where f is the proportional coefficient, which is called Darcy-Weisbach friction factor or Darcy’s friction factor. The form of Eq. (11.16) was first conceived by J. Weisbach (1806–1871) and H. Darcy (1803–1859) identified the importance of surface roughness in determining the value of friction factor (Simmons 2008). L is the duct (or pipe) length [m], D is the duct (or pipe) diameter [m], ρ is the fluid density [kg/m3], and v is the fluid velocity [m/s].
Navigation
Published in Cary R. Spitzer, Uma Ferrell, Thomas Ferrell, Digital Avionics Handbook, 2017
The usual speed sensor on an aircraft or helicopter is a pitot tube that measures the dynamic pressure of the air stream from which airspeed is derived in an air-data computer. To compute ground speed, the velocity of the wind must be vectorially added to that of the aircraft (Figure 3.2). Hence, unpredicted wind will introduce an error into the dead-reckoning computation. Most pitot tubes are insensitive to the component of airspeed normal to their axis, called drift. Pitot tubes must be heated to prevent ice from blocking the orifices.
Equations of motion
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
As stated in Section 2.5.1, the pitot and static tube combination provides a means of measuring the dynamic pressure. It does not provide speed directly, but we can calculate the speed if we know the air density using Equation 2.44. In an aircraft with no processor, there is no simple method of measuring air density, so all that could be done is to assume a constant value for air density (usually equivalent to sea-level air density). This means that this airspeed would correspond to that at the standard sea-level air density. This instrument is called an airspeed indicator. Since the instrument is calibrated assuming one constant standard sea-level value of air density (ISA condition), it does not give the TAS, unless the aircraft is flying at a height where the density just happens to be equal to the standard sea-level value. The value of the IAS at which this occurs will always be the same whatever be the height. With the advance of technology, there are devices that can measure the true ground speed (e.g., GPS), but the airspeed indicator described earlier is still an important item on most cockpit instrument panels.
Influence of the wind tunnel model characteristics on the loading and response of cable-net hyperbolic paraboloid roofs
Published in Structure and Infrastructure Engineering, 2023
Fabio Rizzo, Francesco Ricciardelli, Aleksander Pistol, Renata Klaput, Łukasz Flaga
A single-stage, 220 V AC/200 kW axial fan with an efficiency of 0.8 to 0.9 acts as a propeller. The outer diameter is 2.72 m and the maximum velocity at the fan outlet is 100 m/s. Rotational speed is controlled by an inverter, with a nominal value of 750 rpm. Maximum speed in the test section is Drawings of the tunnel are given as Figure 2. Speed measurements were made using ATU2001 hot-wire anemometers connected to a multipurpose data acquisition module National Instruments NI-USB 6009. Reference dynamic pressure value is measured at the reference point as the difference between total pressure and static pressure obtained from the Pitot tube and static pressure probe. Time series of pressure at measurement points located on the roof of the models were recorded with multichannel differential pressure scanners DTC Initium. Analogue voltage signals obtained from pressure scanners are collected with the DTC Initium Utility Software system.
Investigation of methane-air explosions and its destruction at longwall coalface in underground coalmines
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Yunfei Zhu, Wendong Zhou, Deming Wang, Zhenlu Shao, Chaohang Xu, Min Li, Zhang Yutao
The dynamic pressure is the pressure increase that a moving fluid would have if it was brought to rest by an isentropic flow against a pressure gradient (Crowl, 2003). Velocity is a parameter directly perceived through human senses to assess the destruction of dynamic pressure. Figure 14 presents the peak-dynamic-pressure record in the simulation domain. The zone from the lower edge of the methane-air mixture to 3# crosscut in rail roadway and the strip near the coalface bottom experience high dynamic pressures. To evaluate the dynamic pressure destruction, the peak velocity of the blast wave at the locations mentioned above is illustrated in Figure 15.
Multi objective optimization of aerodynamic design of high speed railway windbreaks using Lattice Boltzmann Method and wind tunnel test results
Published in International Journal of Rail Transportation, 2018
Masoud Mohebbi, Mohammad Ali Rezvani
A pitot tube is installed on the upstream in the middle of the test section to measure the total pressure and the static pressure that are needed for determining the air flow dynamic pressure. A view of the pressure monitoring devices and the coupled hoses is presented in Figure 6.