Skin-Friction and Forced Convection from Rough and Smooth Plates

The current models for skin-friction drag from a plate with a rough surface are derived by analogy to flow within pipes having rough interiors. But this analogy fails at low Reynolds number (Re) flow rates because the boundary-layer must compress into the center of the pipe, while the plate boundary-layer is unbounded. A significant discrepancy from the pipe analogy at low Re was found by the rough plate experiments of Pimenta, Moffat, and Kays (1975) and by experiments conducted by the present author (2019). An additional problem is that the roughness parameter in pipe analogy theories is tied to the drag measurements of flows inside Nikuradse's assortment of sand-roughened pipes (1933). Prandtl and Schlichting (1934) caution that their theory applies only to sand-roughness. More useful would be a theory based on direct measurements of roughness profiles. The present work derives the formula for a plate's skin-friction drag coefficient given its root-mean-squared height-of-roughness, and Re bounds from the roughness spatial frequency spectrum. The present theory is in close agreement with the Mills-Hang (1983) theory, the Pimenta et al measurements, and the experiments conducted by the author over their respective Re ranges. From boundary conditions of its rough plate analysis, the present work also derives an exact formula for skin-friction from a smooth plate; this formula is in very close agreement with measurements from Smith and Walker (1959) and Spalding and Chi (1964) over 4 decades of Re.Comment: Rewritten to include skin-friction from smooth plates. 20 pages; 17 figures; 16 reference

Matching Dependencies with Arbitrary Attribute Values: Semantics, Query Answering and Integrity Constraints

Matching dependencies (MDs) were introduced to specify the identification or matching of certain attribute values in pairs of database tuples when some similarity conditions are satisfied. Their enforcement can be seen as a natural generalization of entity resolution. In what we call the "pure case" of MDs, any value from the underlying data domain can be used for the value in common that does the matching. We investigate the semantics and properties of data cleaning through the enforcement of matching dependencies for the pure case. We characterize the intended clean instances and also the "clean answers" to queries as those that are invariant under the cleaning process. The complexity of computing clean instances and clean answers to queries is investigated. Tractable and intractable cases depending on the MDs and queries are identified. Finally, we establish connections with database "repairs" under integrity constraints.Comment: 13 pages, double column, 2 figure

Small step for a big cause

My name is Jasna Jaffer. I am a second year Degree student studying in KMEA College, Aluva. I belong to Nettoor and is a part of Maradu Muncipality, Ernakulam. Near to our area is the International vegetable market and besides this market is situated the water treatment plants, post Office, agriculture training centres and soil testing centre. I am a student, social activist and a farmer. I have been honored with the School topper award, Best student of the School, Eastern bhoomika iconic women award for social activities, Best agriculture student of Maradu Municipality, Akshayasree award, Inpham award and also treceived the District level agriculture student award by state government

Fish catch composition in relation to some hydrographic observations along the Bombay Ratnagiri coast

Hydrographic parameters in relation to fish catch composition within the depth range of 30 m to 97 m at 15 different stations off the Bombay to Ratnagiri coast were studied from onboard the vessel M.V. Saraswathi, a 36.5 meter deepsea going research-cum-training vessel during her 58th cruise from the 17th to the 27th December 1986. The study indicates the abundance of Trichiurus sp, Priacanthus sp and Arius sp. Fluctuations in the zooplankton biomass and faunistic composition in the area are examined in relation to some important hydrographic parameters