Water Channel Tests Research Articles

RECOVERY SYSTEM FOR URANIUM FROM SEAWATER USING BRAID TYPE ABSORBENT

The density of uranium in the seawater is only 3.3 mg/m3, but its total amount 4.5 billion tons is 45, 000 times of annual demand of nuclear fuel in the world. The target of this study is the cost-down of the collection of theuranium from the sea to three times of the market price and cheaper than the recycle fuel by nuclear reprocessing. In this study, the high performance adsorbent deformed to the race is proposed with its mooring system, and thefeasibility of the cost down is shown in the Kuroshio influenced basin offshore the west coast of the Okinawa Island, based on the field test on the adsorption ratio of uranium and the quantity and kind of the adhered creature and the water channel test on the drag force on the adsorbent due to waves and currents.

An Experimental Analysis of Vortex Trapping Techniques

An experimental verification is presented for the theoretical vortex trapping concept. A suction orifice located along one wall of a water channel test section was used to simulate a point sink to trap spanwise vortices downstream of a backward-facing step and between two parallel fences. Results from the backward-facing step geometry indicated an increase in the sink strength required to hold a vortex as the sink is positioned closer to the step, closely following previous theoretical predictions made using conformal mapping. The experimental data also showed reasonable agreement with the theoretical position for optimum vortex trapping. Flow visualization has shown a three-dimensional cross-stream effect due to bending of the forced-vortex core by suction. Results from the dual-fence geometry, on the other hand, verified the ability to use a lower level of suction for vortex trapping when compared with the backward-facing step.

Measuring Flutter Derivatives for Bridge Sectional Models in Water Channel

Experimental results of flutter derivatives for sectional models of long-span bridges are presented. The tests were carried out in the Water Channel Laboratory of the Center for Applied Stochastics Research of Florida Atlantic University, which has an 8-m-long test section and a maximum flow speed of 0.5 m/s. The experiments were conducted in the forced-oscillation mode. Specifically, each model is forced to execute a sinusoidal motion, either torsional or vertical, one at a time. In each test, both lift force and torsional moment are measured to obtain the noncoupled flutter derivatives as well as the coupled ones. The advantages of using water as the fluid medium, instead of air, are described. The flutter derivatives obtained in the water-channel tests are then compared with some published data obtained in the wind-tunnel tests using the free-vibration mode. The comparison shows that the water-channel data and the respective wind-tunnel data share the same trends. Finally, the measured flutter derivatives are converted to the corresponding impulse response functions required for the stochastic stability analysis in the time domain.

33 回流水槽を用いた天文台ドームの形態に関する検討

Studies of seeing conditions inside telescope domes indicate a need to provice substantial air ventilation to prevent image degradation due to thermal variation of the air within the dome that means fluid-dynamic designing is necessary for choosing dome style. Althoughthe traditional enclosure is a cylinder topped by a hemispherical dome, alternative style such as flat-loof or tapezoidal topped cylinder could be considered from view point of fluid dynamic feature. Significant flushing flow without thermal ground boundary layer coming into the dome is the subjects to investigate. Water channel tests were made using 3 Types of 1:500 scale enclosure models with flow visualization methods. Dye injection method was mainly used and some quantitative measurements were done. Among the models, the cylindrer with near-flat roofs appear to be superior. And the sidewalls on either side of the telescope were found to be beneficial for flushing the flow.

Experimental Studies on Fluctuating Lift Force on a Single Circular Cylinder at High Reynolds Numbers

Vortex shedding vibration is one of the most important problems to consider in the design of circular cylindrical structures such as the thermowell, the thimble tube for the ICIS and the support columns in nuclear reactors. The objectives of this study are to investigate the vibration response of these structures due to cross flaw aver the range of the high Reynolds numbers, and to propose suggestions to guide future designs of these structures. Experimental studies on the fluctuating lift force which acts on a single circular cylinder for the Reynolds numbers from 3x104 to 3x106 were conducted in a MEI waterchannel test apparatus. The tests were carried out by using two types of models with different stiffness characteristics. One was a stationary model which was used to measure the fluctuating lift force and the Strouhal number. The other was an elastic model which wasused to investigate the vibration response. The results obtained using these two models were a lift coefficient of CL rms and a Strouhal number of st. These results were the same values which have previously been reported by many other investigators. The “locked-in” vibration observed with the elastic model for the critical Reynolds number range was the same phenomena found in the subcritical Reynolds number range.

Model studies of the wind-induced oscillations of a hexagonal-section boom having tapered end-portions

Further wind-tunnel and water-channel model studies have been carried out on the wind-excited vibration of a hexagonal-section boom used to support traffic signal lanterns. Previous tests on two-dimensional hexagons, carried out because vortex-shedding data were not available for such shapes, had predicted a wind-speed for the onset of vibration 21% above that found during actual full-scale measurements. Wind-tunnel tests on a full, but rigid, model of the actual boom-structure confirmed that the earlier results for two-dimensional hexagons were correct for the relevant section of the boom. However, measurements behind the tapered outer parts of the model boom yielded a shedding frequency 21% higher than that for the parallel centre part and effectively constant across the span of the tapered section. Confirmation that the boom vibration was due to vortex-shedding from these tapered hexagonal end-portions was obtained from water-channel tests on the model boom mounted as a linear-mode, flexible model.

Aerodynamics of High-Performance Wing Sails

Some of the primary requirements for the design of wing sails are discussed. In particular, the requirements for maximizing thrust when sailing to windward and tacking downwind are presented. The results of water channel tests on six sail section shapes are also presented. These test results include the data for the double-slotted flapped wing sail designed by David Hubbard for A. F. Di Mauro's IYRU "C" class catamaran Patient Lady II.

Faired Towline Hydrodynamics

A theoretical analysis for determining the hydrodynamic forces on a faired towline is developed. The analysis requires that the hydrodynamic forces acting on an element of the towline be defined as a function of the towlines local inclination angle to the flow, and of the Reynold's number. These hydrodynamic forces are known as loading functions. The analysis is based on consideration of the boundary layer formed on the airfoil shaped cross section used for the towlines. The Reynold's number effect on the loading functions is derived using momentum theory, and requires that the pressure distribution around the airfoil section be defined. Potential flow theory is used, and gives excellent results when compared with pressure distribution measurements made on models. The theoretical loading functions are compared with model data obtained from water channel, tow tank and wind-tunnel tests. The analytical results show excellent correlation with the data. The analysis has been termed Boundary-Layer Loading Functions (BLLF).