In other words, kinetic energy is converted into heated air via ram pressure, and that heated air is quickly moved away from object surface with minimal physical interaction, and hence minimal heating of the body. Eggers of NACA used an insight about ram pressure to propose the blunt-body concept: a large, blunt body entering the atmosphere creates a boundary layer of compressed air which serves as a buffer between the body surface and the compression-heated air. It is primarily this ram pressure (rather than friction) that heats the air that in turn heats the meteoroid as it flows around it. Ram pressure and atmospheric (re)entry Ī meteoroid traveling supersonically through Earth's atmosphere produces a shock wave generated by the extremely rapid compression of air in front of the meteoroid. This is an attractive mechanism to explain not only the presence of isolated dwarf galaxies away from galaxy clusters with particularly low hydrogen abundance to stellar mass ratio, but also the compression of gas in the centre of a dwarf galaxy and the subsequent reignition of star formation. Although the typical overdensity within the cosmic web is significantly lower than that found in the environment of galaxy clusters, the high relative speed between a dwarf and the cosmic web renders ram pressure efficient. More recently, it has been shown that ram pressure can also lead to the removal of gas in isolated dwarf galaxies that plunge through the cosmic web (the so-called cosmic web stripping process). Increased Hα emission, a sign of star formation, corresponds to the compressed CO region, suggesting that star formation may be accelerated, at least temporarily, while ram pressure stripping of neutral hydrogen is ongoing. Recent radio observation of carbon monoxide (CO) emission from three galaxies ( NGC 4330, NGC 4402, and NGC 4522) in the Virgo cluster point to the molecular gas not being stripped but instead being compressed by the ram pressure. Spiral galaxies that have fallen at least to the core of both the Virgo and Coma clusters have had their gas (neutral hydrogen) depleted in this way and simulations suggest that this process can happen relatively quickly, with 100% depletion occurring in 100 million years to a more gradual few billion years. As galaxies fall toward the center of a cluster, more and more of their gas is stripped out, including the cool, denser gas that is the source of continued star formation. Ram pressure stripping is thought to have profound effects on the evolution of galaxies.
These ram pressure stripped galaxies will often have a large trailing tail and because of this they are commonly called "Jellyfish galaxies." Evidence of this ram pressure stripping can be seen in the image of NGC 4402. This pressure can strip gas out of the galaxy where, essentially, the gas is gravitationally bound to the galaxy less strongly than the force from the intracluster medium 'wind' due to the ram pressure. Ram pressure is given in tensor form as P ram = ρ u i u j the speed of the galaxy relative to the medium. It causes a drag force to be exerted on the body.
Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. Note the dust (brown) trailing behind (toward upper right) the galaxy, versus the dust-free (blue-white) leading edge. Ram pressure stripping in NGC 4402 as it falls towards the Virgo Supercluster (off image, toward bottom left).
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