Concave Wedge Research Articles

Experimental Studies on the Hypersonic Flow past Plane, Convex and Concave Wedges

In this paper, the phenomena of viscous-inviscid interaction effects at M ∞ =6.2 over the front part of bodies have been investigated. The models tested are a flat plate and wedges having a plane, a convex or a concave surface, respectively. A uniform flow of R ∞ =2.0×10 5 per cm was established using a divergent shock tube. The measurements of the flow field were made by optical methods (interferometer and schlieren photograph), and in order to supplement the data the X-ray technique was employed near the leading edge of the model. The results are as follows. (1) For a flat plate: i) the pressure distribution on the sharp-nosed plate is about 5 per cent higher than Nagakura-Naruse's theoretical values; ii) the boundary layer thickness agrees almost perfectly with Naruse's theoretical values; iii) the shock wave location is in good agreement with the empirical formulae of Kendall and of Bogdonoff and Hammitt. (2) For wedges: i) near the leading edge, the boundary layer growth on a concave wedge is more ra...

A search for globules in the Palomar Sky Atlas.

view Abstract Citations (2) References (1) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A search for globules in the Palomar Sky Atlas. Fleischer, Robert ; Conti, Peter S. Abstract A search has been made on prints of the Palomar Sky Atlas for globules, or small roundish dark nebulae. On the blue exposures 0-175 with galactic longitude 3330, latitude - 10, and 0-159 with longitude 3370, latitude +~0, a first survey has resulted in not less than 10,000 and 7000 globules, respectively. The diameter of a typical object is I millimeter on the prints, or about I minute of arc. The reality of these suspected globules is plausible in view of the a priori probability of I in 4000 of finding a one-millimeter circle with zero stars on a similar plate of randomly distributed stars, and also in view of the improbability of the star formations, rings, loops, and concave wedges, which mark their boundaries. Attempts to show that random distributions of dots would show "globules" failed due to the difficulty of producing true random distributions. A count of stars in 340 one-millimeter squares in a typical region of print 0-175 showed that the stars were not distributed at random in the squares. The assumption of a random distribution of stars overlain with the 21 globules marked in this region led to a predicted distribution of star numbers with a ~` probability of 5 per cent that it represents the observed star numbers. This is considered satisfactory evidence that the large number of globules is probably real. Our typical globules are about 3 times the diameter of those marked by Bok and Reilly (1947). They supposed their globules to be at an average maximum distance of 1260 parsecs. If we assume ours to be closer in proportion to the apparent diameters, or at 420 parsecs, we find a space density of not less than 0.03 globules per cubic parsec, which may be compared with an average space density in the vicinity of the sun of 0.1 stars per cubic parsec. As this is a preliminary progress report, no more extensive publication is intended in the immediate future. A mimeographed report is available giving more details on the above points and some other provisional results of the search. Acknowledgment is made with thanks to the Research Grants Committee of Rensselaer Polytechnic Institute for a grant to the senior author for partial support of the purchase of the Atlas. Bok, B. J. and Reilly, E. F. 1947, Ap. J. 105, 255. Observatory, Rensselaer Polytechnic Institute, Troy, N. V. Publication: The Astronomical Journal Pub Date: February 1956 DOI: 10.1086/107269 Bibcode: 1956AJ.....61....4F full text sources ADS |