Relative Mach number

Increased blade relative velocities, resulting in higher blade relative Mach numbers and lower efficiencies. 

Free-vortex prewhirl. This type is represented by r Ve = constant with respect to the inducer inlet radius. This prewhirl distribution is shown in Figure 6-13. Vg is at a minimum at the inducer inlet shroud radius. Therefore, it is not effective in decreasing the relative Mach number in this manner. 

Fig. (2) Inlet Relative Mach Number Versus Flow Coefficient...

Most often, the Mach number is calculated using the speed of sound evaluated at the local pressure and temperature. When M = 1, the flow is critical or sonic and the velocity equals the local speed of sound. For subsonic flowM < 1 while supersonic flows have M > 1. Compressibility effects are important when the Mach number exceeds 0.1 to 0.2. A common error is to assume that compressibihty effects are always negligible when the Mach number is small. The proper assessment of whether compressibihty is important should be based on relative density changes, not on Mach number. 

The helical-lobe compressor is further divided into a dry and a flooded form. The dry fonn uses timing gears to hold a prescribed timing to tlie relative motion of the rotors the flooded form uses a liquid media to keep the rotors from touching. The helical-lobe compressor is the most sophisticated and versatile of the rotary compressor group and operates at the highest rotor tip Mach number of any of the compressors in the rotary family. This compressor is usually referred to as the screw compressor or the SRM compressor. ... 

Turner et al. (2004) studied the independent variables relative surface roughness, Knudsen number and Mach number and their influence on the friction factor. The micro-channels were etched into silicon wafers, capped with glass, with hydraulic diameters between 5 and 96 pm. Their surface roughness was 0.002 < ks< 0.06 pm for the smooth channels, and 0.33 < / < 1 -6 pm for the glass-capped ones. The surface roughness of the glass micro-channels was measured to be in the range 0.0014 [Pg.39]

The influence of compressibility was assessed by varying the Mach number in the range 0 < Ma < 0.38, while Kn and ks/H were kept low. Friction factor data were reported only with Ma < 1 at the exit, to ensure the flow rate was controlled by viscous forces alone. A mild increase in the friction factor (8%) was observed as Ma approached 0.38. This effect was verified independently by numerical analysis for the same conditions as in the experiment. The range of relative surface roughness tested was 0.001 < ka/H < 0.06, yet there was no significant influence on the friction factor for laminar gas flow. 

Fig. 3.28. Schematic picture of conditions surrounding a supernova shock. M is the Mach number, B the magnetic field and velocities are relative to the shock front.

Drag coefficient Q/l. .Re) is the drag coefficient calculated using the correlation for subsonic flow with Ma=l. f V/1.75, Re ) is the drag coefficient calculated using the correlation for supersonic flow with Ma00=1.75 Mach number based on relative velocity between gas and sphere ... 

As the relative velocity difference is increased, however, coherent structure development is suppressed by compressibility effect [7, 8] and thus the effect on mixing by coherent structures diminishes. The compressibility effect can be quantified in terms of the convective Mach number, which is defined as the... 

Elsewhere in this book attention is focused on particles whose Mach and Knudsen numbers are small. The Mach number is defined as the ratio of the relative velocity between the particle and the fluid to the speed of sound in the fluid ... 

The induction time data and density profiles pf detonations in oxy-hydrogen and oxy-methane mixtures were analyzed on the basis of the kinetic data obtained by the reflected-wave technique and similar methods. A plot of the ignition delay vs 1/T in oxy-ammonia mixtures gave a straight line with a slope corresponding to an activation energy of 42.5 kcal/mole. In these mixtures the induction zone is not uniform, but the shock front is flat and end of the reaction zone is clearly discernible. Onedimensional detonation waves of low Mach number but relatively stable were obtained in a gas preheated to 600-1800°K ahead of the shock front... 

The instant at which combination of the combustion and shock waves begins is not necessarily the point at which the steady-state detonation velocity has been reached. Because of the turbulence generated by the flame, the velocity of the products relative to the initially forming detonation front may be subsonic. This state cannot last very long because rarefaction waves thru the burnt gas can move right up to the detonation wave and weaken it until its speed drops to unit Mach number relative to the products... 

The Mach number is used in fluid mechanics and is especially useful in studies involving supersonic aerodynamics. It is named after Ernst Mach (1838-1916), the Austrian physicist and philosopher who pioneered the study of supersonic projectiles. The Mach number is the ratio of the velocity of a fluid to the velocity of sotmd in that same fluid. In the case of a body moving through a fluid, the Mach number is the velocity of the body relative to the fluid divided by the velocity of sound in the fluid. The velocity of sound varies with temperature and also varies from one fluid to another. At sea level, for example, the velocity of sound in air at 59°F (15°C) is about 760 MPH (1,223 km/h). At an elevation of 40,000 ft (12,200 m), however, the temperature is about -70°F (-57°C), and the velocity of sound in air is only 660 MPH (1,062 km/h). Thus, an airplane flying at 760 MPH at sea level would have a Mach number of 1.0, while at an elevation of 40,000 ft it would have a higher Mach number of almost 1.2. 

To be able to apply the ID equations one often has to estimate terms that cannot be calculated directly without further empirical information, or we might simply neglect the insignificant terms for each particular application. The work associated with the term ((T) (v) ) e, can be split into two contributions. In chemical reactor analysis (and many other low Mach number flows in chemical engineering [13]) the viscous work ((g) A (v)a) ez is normally neglectable relative to the pressure work (p)a vz)a-... 

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