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Flow Sounds 2.2

It has more than 25 high-quality soundscapes + a Pomodoro timer (25/5) + a minimalist design, + and is usable offline. You can enjoy your new productivity tool to create the perfect environment for your working mood. Pick your favorite sound, and start your Pomodoro session: 25 focus time + 5 minutes break. Your progress will be tracked right in the menu bar.

Flow Sounds 2.2

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Mach number (M or Ma) (/mɑːk/; German: [max]) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.[1][2]It is named after the Austrian physicist and philosopher Ernst Mach.

By definition, at Mach 1, the local flow velocity u is equal to the speed of sound. At Mach 0.65, u is 65% of the speed of sound (subsonic), and, at Mach 1.35, u is 35% faster than the speed of sound (supersonic). Pilots of high-altitude aerospace vehicles use flight Mach number to express a vehicle's true airspeed, but the flow field around a vehicle varies in three dimensions, with corresponding variations in local Mach number.

The local speed of sound, and hence the Mach number, depends on the temperature of the surrounding gas. The Mach number is primarily used to determine the approximation with which a flow can be treated as an incompressible flow. The medium can be a gas or a liquid. The boundary can be traveling in the medium, or it can be stationary while the medium flows along it, or they can both be moving, with different velocities: what matters is their relative velocity with respect to each other. The boundary can be the boundary of an object immersed in the medium, or of a channel such as a nozzle, diffuser or wind tunnel channeling the medium. As the Mach number is defined as the ratio of two speeds, it is a dimensionless number. If M

While the terms subsonic and supersonic, in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a transonic regime around flight (free stream) M = 1 where approximations of the Navier-Stokes equations used for subsonic design no longer apply; the simplest explanation is that the flow around an airframe locally begins to exceed M = 1 even though the free stream Mach number is below this value.

Meanwhile, the supersonic regime is usually used to talk about the set of Mach numbers for which linearised theory may be used, where for example the (air) flow is not chemically reacting, and where heat-transfer between air and vehicle may be reasonably neglected in calculations.

The subsonic speed range is that range of speeds within which, all of the airflow over an aircraft is less than Mach 1. The critical Mach number (Mcrit) is lowest free stream Mach number at which airflow over any part of the aircraft first reaches Mach 1. So the subsonic speed range includes all speeds that are less than Mcrit.

The transonic speed range is that range of speeds within which the airflow over different parts of an aircraft is between subsonic and supersonic. So the regime of flight from Mcrit up to Mach 1.3 is called the transonic range.

Aircraft designed to fly at supersonic speeds show large differences in their aerodynamic design because of the radical differences in the behavior of flows above Mach 1. Sharp edges, thin aerofoil-sections, and all-moving tailplane/canards are common. Modern combat aircraft must compromise in order to maintain low-speed handling; "true" supersonic designs include the F-104 Starfighter, MiG-31, North American XB-70 Valkyrie, SR-71 Blackbird, and BAC/Aérospatiale Concorde.

At transonic speeds, the flow field around the object includes both sub- and supersonic parts. The transonic period begins when first zones of M > 1 flow appear around the object. In case of an airfoil (such as an aircraft's wing), this typically happens above the wing. Supersonic flow can decelerate back to subsonic only in a normal shock; this typically happens before the trailing edge. (Fig.1a)

As the speed increases, the zone of M > 1 flow increases towards both leading and trailing edges. As M = 1 is reached and passed, the normal shock reaches the trailing edge and becomes a weak oblique shock: the flow decelerates over the shock, but remains supersonic. A normal shock is created ahead of the object, and the only subsonic zone in the flow field is a small area around the object's leading edge. (Fig.1b)

At fully supersonic speed, the shock wave starts to take its cone shape and flow is either completely supersonic, or (in case of a blunt object), only a very small subsonic flow area remains between the object's nose and the shock wave it creates ahead of itself. (In the case of a sharp object, there is no air between the nose and the shock wave: the shock wave starts from the nose.)

As the Mach number increases, so does the strength of the shock wave and the Mach cone becomes increasingly narrow. As the fluid flow crosses the shock wave, its speed is reduced and temperature, pressure, and density increase. The stronger the shock, the greater the changes. At high enough Mach numbers the temperature increases so much over the shock that ionization and dissociation of gas molecules behind the shock wave begin. Such flows are called hypersonic.

As a flow in a channel becomes supersonic, one significant change takes place. The conservation of mass flow rate leads one to expect that contracting the flow channel would increase the flow speed (i.e. making the channel narrower results in faster air flow) and at subsonic speeds this holds true. However, once the flow becomes supersonic, the relationship of flow area and speed is reversed: expanding the channel actually increases the speed.

The obvious result is that in order to accelerate a flow to supersonic, one needs a convergent-divergent nozzle, where the converging section accelerates the flow to sonic speeds, and the diverging section continues the acceleration. Such nozzles are called de Laval nozzles and in extreme cases they are able to reach hypersonic speeds (Mach 13 (15,900 km/h; 9,900 mph) at 20 C).

If the speed of sound is not known, Mach number may be determined by measuring the various air pressures (static and dynamic) and using the following formula that is derived from Bernoulli's equation for Mach numbers less than 1.0. Assuming air to be an ideal gas, the formula to compute Mach number in a subsonic compressible flow is:[9]

The annual average river flow into the Sound is about 1,174 m3 s-1, and a third to a half of this comes from the Skagit River flowing into Whidbey Basin. It would take about 5 years for all the rivers flowing into the Sound to fill up its volume, which suggests, correctly, that rivers alone do not play a dominant role in circulating water through the Sound. This is also apparent in the salinity of the Sound, which averages about 28.5 parts per thousand, compared to about 34 for the nearby Pacific. This means that the Sound is roughly 83% seawater. Even as far south as Budd Inlet near Olympia it is still two-thirds seawater. The sum of rivers entering the Chesapeake is about twice that of those entering Puget Sound, and they would fill the Bay in just a year. Because of the stronger river forcing, and because it is shallower, the Chesapeake is about 50% seawater, with salinity varying smoothly from oceanic to fresh over its length.3

Highlight Box 1 discusses how the seven sources of congestion are related to the underlying traffic flow characteristics that create a disruption in traffic. We typically think of a bottleneck as a physical restriction on capacity (Category 3 above). However, disorderly vehicle maneuvers caused by events have a similar effect on traffic flow as restricted physical capacity.

Because the traffic flow effects are similar, traffic disruptions of all types can be thought of as producing losses in highway capacity, at least temporarily. In the past, the primary focus of congestion responses was oriented to adding more physical capacity: changing highway alignment, adding more lanes (including turning lanes at signals), and improving merging and weaving areas at interchanges. But addressing the "temporary losses in capacity" from other sources is equally important.

When a person has the urge or intention to speak, her or his brain formsa sentence with the intended meaning and maps the sequence of words intophysiological movements required to produce the corresponding sequenceof speech sounds. The neural part of speech production is not discussedfurther here.

The physical activity begins by contracting the lungs, pushing out airfrom the lungs, through the throat, oral and nasal cavities. Airflow initself is not audible as a sound - sound is an oscillation in airpressure. To obtain a sound, we therefore need to obstruct airflow toobtain an oscillation or turbulence. Oscillations are primarily producedwhen the vocal folds aretensioned appropriately. This produces voiced sounds and is perhapsthe most characteristic property of speech signals. Oscillations canalso be produced by other parts of the speech production organs, such asletting the tongue oscillate against the teeth in a rolling /r/, or byletting the uvula oscillate in the airflow, known as the uvular trill(viz. something like a guttural /r/). Such trills, both with the tongueand the uvula, should however not be confused with voiced sounds, whichare always generated by oscillations in the vocal folds. Sounds withoutoscillations in the vocal folds are known as unvoiced sounds.

Most typical unvoiced sounds are caused by turbulences produced bystatic constrictions of airflow in any part of the air spaces above thevocal folds (viz. larynx, pharynx and oral or nasal cavities). Forexample, by letting the tongue rest close to the teeth, we obtain theconsonant /s/, and by stopping and releasing airflow by closing andopening the lips, we obtain the consonant /p/. A further particularclass of phonemes are nasal consonants, where airflow through the mouthis stopped entirely or partially, such that a majority of the air flowsthrough the nose. 041b061a72


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