Effect of Mach number on the structure of turbulent spots

Direct numerical simulations have been performed to study the dynamics of isolated turbulent spots in compressible isothermal-wall boundary layers. Results of a bypass transition scenario at Mach 2, 4 and 6 are presented. At all Mach numbers the evolved spots have a leading-edge overhang, followed by a turbulent core and a calmed region at the rear interface. The spots have an upstream-pointing arrowhead shape when visualized by near-wall slices, but a downstream-pointing arrowhead in slices away front the wall. The lateral spreading of the spot decreases substantially with the Mach number, consistent with a growth mechanism based on the instability of lateral shear layers. Evidence for a supersonic (Mach) mode substructure is found in the Mach 6 case, where coherent spanwise structures are observed under the spot overhang region

Strong interaction of a turbulent spot with a shock-induced separation bubble

Direct numerical simulations have been conducted to study the passage of a turbulent spot through a shock-induced separation bubble. Localized blowing is used to trip the boundary layer well upstream of the shock impingement, leading to mature turbulent spots at impingement, with a length comparable to the length of the separation zone. Interactions are simulated at free stream Mach numbers of two and four, for isothermal (hot) wall boundary conditions. The core of the spot is seen to tunnel through the separation bubble, leading to a transient reattachment of the flow. Recovery times are long due to the influence of the calmed region behind the spot. The propagation speed of the trailing interface of the spot decreases during the interaction and a substantial increase in the lateral spreading of the spot was observed. A conceptual model based on the growth of the lateral shear layer near the wingtips of the spot is used to explain the change in lateral growth rat

Marginalizing the likelihood function for modeled gravitational wave searches

Matched filtering is a commonly used technique in gravitational wave searches for signals from compact binary systems and from rapidly rotating neutron stars. A common issue in these searches is dealing with four extrinsic parameters which do not affect the phase evolution of the system: the overall amplitude, initial phase, and two angles determining the overall orientation of the system. The F-statistic maximizes the likelihood function analytically over these parameters, while the B-statistic marginalizes over them. The B-statistic, while potentially more powerful and capable of incorporating astrophysical priors, is not as widely used because of the computational difficulty of performing the marginalization. In this paper we address this difficulty and show how the marginalization can be done analytically by combining the four parameters into a set of complex amplitudes. The results of this paper are applicable to both transient non-precessing binary coalescence events, and to long lived signals from rapidly rotating neutron stars.Comment: 26 page

Finfish larval culture

The success of any large-scale finfish culture is mainly dependent upon the continuous and adequate supply offish seed. Although fish seed may be collected from the wild, natural sources of fish seed are unreliable and mostly seasonal. Here comes the importance of controlled breeding and mass scale larval rearing. [n the background of the increased emphasis given by the Government oflndia to aquaculture, the present status oflarval rearing of important cultivable ornamental marine finfishes in our country is reviewed in this paper giving stress on the constraints in the progress of the research in this line

Marine ornamental resources and Management Strategies

Coral reefs form a very dynamic and productive ecosystem of the oceans. Marine ornamentals as well as a wide variety of invertebrates thrive in coral reefs making it a virtual paradis

Assessment of maturation and induction of spawning in marine finfish- Winter School on Recent Advances in Breeding and Larviculture of Marine Finfish and Shellfish

The cultivation of many economically important species has been helped greatly by the growing use of the technique of artificial fertilization and incubation. The discovery of artificial fertilization is supposed to be very old and this technique is said to have been practiced in the middle ages by the monk Don Pinchon in trout. The rediscovery of wet artificial fertilization in salmonids in 1842 by two anglers Gehin and Remy and the discovery of dry fertilization by the Russian Vrassky and its application between 1856 and 1870 led to great technical progress. Artificial spawning was first achieved in striped mullet in 1930 in Italy. In general the technique of hypophysation has triggered rapid progress in the induced breeding of cultured species, in the controlled rearing of fish larvae and in selective breeding

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