Browsing by Author "Christopherson, Charles D."

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    Description of a Ten-Inch Free-Jet Water Tunnel
    (St. Anthony Falls Hydraulic Laboratory, 1953-01) Christopherson, Charles D.
    A water tunnel is a device used in hydraulic research and design studies for the purpose of observing the relative motion between a solid body and a liquid and the effect which this motion has on the body. Its basic function is the production of a test stream of water of uniform and controllable pressure and velocity in which solid bodies can be supported under varying conditions. The free-jet type of water tunnel has a test stream which, ideally, is surrounded by a gaseous medium and which, practically, has only a partial solid-contact boundary required to permit observation of the interior of the stream. This type of tunnel thus differs from conventional water tunnels such as the closed-jet water tunnel, which has a test stream completely surrounded by a solid-contact surface, and the open-jet water tunnel, which has a test stream surrounded by water and which thus resembles a submerged jet. The essentially unbounded nature of the test stream of the free-jet water tunnel permits deformation of the test stream and avoids formation of adverse pressure and velocity gradients which form in conventional water tunnels because of gravitational effects and boundary layer formation; the result is that in the free-jet water tunnel, natural cavitation about solid bodies in the test stream can be studied at lower cavitation indices and with less influence due to the finite extent of the test stream than is possible in conventional tunnels.
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    Experimental Design Studies on Free-jet Water Tunnels
    (St. Anthony Falls Hydraulic Laboratory, 1951-09) Christopherson, Charles D.
    A study of the design and operating characteristics of free-jet water tunnels is presented. Included is a brief analysis indicating that this type of water tunnel is particularly well suited for the empirical analysis of steady-state cavities which form about solid bodies moving through water at extremely low cavitation indices. It is pointed out that the conventional closed-jet and open-jet types possess inherent limitations on the quality of the test-section flow and the accuracy and applicability of the measurable flow properties at these low cavitation indices. The experimental apparatus is described verbally and photographically. It was designed for the production and study of a test jet of circular cross section having a 2-in. diameter and an effective length of 6 diameters. The jet could be directed vertically upward, vertically downward, and horizontally. Facilities for the production and analysis of steady state cavities within the jet are also described. The experimental studies and the results are discussed. Included are observations concerning air entrainment by the jet, visual qualities of the jet, total head Pitot tube traverses of the jet, and steady~state cavities within the jet at cavitation indices as low as 0.015. The report concludes with general recommendations concerning the design of free-jet water tunnels.