Stratus cloud Stratus cloud Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds that are formed by rising thermals. More specifically, the term "stratus" is used to describe flat, hazy, featureless clouds of low altitude varying in color from dark gray to nearly white. The word "stratus" comes from the Latin prefix "strato-", meaning "layer". Stratus clouds may produce a light drizzle or a small amount of snow. These clouds are essentially above-ground fog formed either through the lifting of morning fog or through cold air moving at low altitudes over
Vortex sheet of a vortex sheet by vortex panels with arc wise diffusion of circulation density also shows that the sheet rolls-up into a double branched spiral. In many engineering and physical applications the growth of a temporal free shear layer is of interest. The thickness of a free shear layer is usually measured by momentum thickness, which is defined as formula_28 where formula_29 and formula_30 is the freestream velocity. Momentum thickness has the dimension of length and the non-dimensional momentum thickness is given by formula_31. Momentum thickness can be used to measure the thickness of a vortex layer. Vortex sheet A