This paper presents an overview of the current state-of-the-art in scale modeling of liquefied natural gas sloshing in ship tanks. The numerous potentially significant scaling parameters are discussed in detail and laboratory test data illustrating the effects of the important scaling parameters are presented. In view of current knowledge, an indication of appropriate scaling criteria is presented and recommendations for additional research efforts are outlined.
This paper presents an extensive review of some recent experimental results for developing turbulent free shear layers in isoenergetic flow with free stream Mach numbers up to eight. Experimental longitudinal variations of a midprofile velocity and a characteristic layer width are compared with corresponding predictions from a recent theory for developing layers and from the well-known asymptotic theory. Using a recent theoretical specification for the variation of spread rate parameter σ with free stream Mach number, it was found that the predictions of the developing layer analysis were in general agreement with measurements. It was demonstrated that the asymptotic theory, in conjunction with the virtual origin technique, can also be utilized to predict developing layer growth. An experimental specification of σ yielded uncertainties ranging from 15 to 50 percent, although the results tended to confirm the general validity of some recent theoretical postulations for the spread rate parameter.
The flow-induced vibrations of metal bellows with internal cryogenic flow are examined experimentally, and analytical techniques are given to predict vibration suppression characteristics. Heat transfer is shown to create local vaporization inside the convolutes which kills the primary source of bellows vibration, vortex shedding. The reduction in vibration amplitude is shown to be a function of the state properties of the liquid inside the bellows and the heat transfer rate into the liquid. External damping from frost, ice, or condensed liquid, which can appear on the bellows exterior, is discussed, and a method for estimating the reduction in vibration severity with external condensation is presented.
Boundary-layer and trailing-edge flow activities were recorded using hydrogen bubble flow visualization techniques on an oscillating lifting surface in a two-dimensional water tunnel. Simultaneous with flow documentation, unsteady lift was measured over a range of reduced frequencies of 0.5-10. Unsteady loads using classical, inviscid theories were predicted for the experimental conditions investigated. Reduced frequency bands exhibiting poor agreement between experiment and theory were identified and a correlation to observed flow phenomena was accomplished. The results support the utilization of a separate viscous model near the trailing edge coupled with an inviscid flowfield model to predict unsteady loads. The results further show that for certain reduced frequency bands, classical inviscid solutions may be applicable and adequate.
Nomenclature=time V = freestream velocity X = distance along chord from leading edge a = instantaneous angle of attack a.= oscillatory angle-of-attack amplitude a 0 = mean angle of attack 6 = boundary-layer thickness 5* = boundary-layer displacement thickness A W = width of lifting surface v -fluid kinematic viscosity co = circular frequency p = fluid density 6 = phase shift in Theodorsen's function
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