Upstream Tank Research Articles

Experimental Study on Self-Excited Vibration Characteristics of a Flexible Weir due to Fluid Discharge.

This paper deals with the characteristics of unstable self-excited vibrations of a rectangular, flexible weir installed in a tank, over which water in the upstream tank discharges into the down-stream one. Experiments were carried out for measuring the vibrational strains of the weir, and the oscillation of the water surface in the up-stream tank with changing inlet velocity of water and discharge height. We examined the vibration characteristics of the weir with changing tank ratio (defined as the down stream tank length/the upstream tank length), and found that the occurrence of unstable vibration depends strongly on the tank ratio. The phase relations of the weir vibration to the upstream tank water oscillation were experimentally investigated.

Investigation of ablation-dominated AC nozzle arcs

The behaviour of ablation-dominated AC arcs in supersonic nozzle has been analysed. For a given gas and nozzle material, the dynamic behaviour of arcs burning in affinely related nozzles is fully determined by three non-dimensional coefficients: the nozzle coefficient N; the ablation coefficient Ab; and the non-dimensional frequency Ω. For circuit-breaker operations, the values of these three non-dimensional parameters are such that flow reversal (i.e. from the nozzle to the upstream tank), caused by inner nozzle wall ablation, cannot be avoided. When this happens, the arc and flow conditions at current-zero are dependent on N (i.e. peak current for a fixed stagnation pressure). The temperature of the gas in the external flow can be much higher than that in the upstream tank. The peak current therefore has a direct influence on the thermal and dielectric recovery processes inside the nozzle. Arc modelling cannot in general be divided into a quasi-steady-state (hence DC) phase and a current-zero period.

Self-Induced Manometer Oscillation of Free Surface Caused by the Circulating Flow.

A self-induced manometer oscillation in a flow channel connecting two large tanks is observed, which is caused by the circulating flow in the upstream tank. Water flows into the thin rectangular tank horizontally and flows out vertically through the outlet duct located at the bottom center. The duct is connected to the large overflow tank directly. At a certain water level and flow rate, the free surface of the test section oscillates upward and downward periodically, causing the oscillation of the outlet flow rate. The period of the oscillation is found to be that of the manometer oscillation without flow. Consequently, the oscillation occurs in the multi-free-surface system, i.e., the test section surface and the overflow tank surface. The oscillation growth model based on the flow pattern transformation is proposed.

Some Effects of Injection of Foreign Gases in a Decelerating Laminar Boundary Layer in Supersonic Flow

The purpose of this research program was to investigate the effects of a diffusion field on a laminar boundary layer in a supersonic flow. Specifically, helium, nitrogen, and argon were uniformly injected into the laminar boundary layer of a highspeed flow in a tube with the objective of determining the effects of such injection on the pressure, temperature, and recovery factor distribution along and downstream of the injection region. A continuously operating axially-symmetric wind tunnel has been designed, constructed, and operated. This tunnel consists of an air supply system, a flowmeter, an upstream stagnation tank, a supersonic nozzle (throat diameter 0.262% and exit diameter 1.400), a test section of variable length (zero to 81 diameters, test section diameter of 1.400), a downstream stagnation tank, an exhaust system, a foreign gas supply system, and all necessary instrumentation. The overall performance of this apparatus in terms of the design specifications was excellent. The tunnel was instrumented with 109 thermocouples. All temperatures except ambient temperatures were automatically measured and recorded by means of a self-balancing recording potentiometer. There was 29 pressure taps distributed along the tunnel, 23 along the test section itself. Pressures were measured by means of an interconnected micromanometer and a vacuum referenced manometer system with overlapping ranges. For all of the results reported herein, the overall test section was 41 diameters in length; composed of a porous test section approximately 7.2 diameters in length (leading edge approximately 1.8 diameters from the nozzle exit plane) and four nylon test sections of 8 diameters each. The experimental results of 38 runs (13 with zero injection, 12 with helium injection, 8 with nitrogen injection, and 5 with argon injection) are reported herein. With zero injection, pressure distributions were reproduced to within 2 percent, and temperature distributions were reproduced to within 1.5 percent. With injection, pressure distributions were reproduced to within 2 percent, and temperature distributions were reproduced to within 0.6 percent. For uniform injection of helium, nitrogen, or argon gas, it was found that there was about a 1 percent change in the recovery factor and adiabatic wall temperature for the range of variables investigated. The effect of foreign gas injection on the pressure distribution was to increase an already adverse pressure gradient.

Design Studies for Chute Des-Passes Surge-Tank System

Downstream surge chamber for hydroelectric plant is provided in form of large draft-tube manifold running parallel to powerhouse; design of upstream tank required provision for plant to operate as isolated power source subject to large, instantaneous load increases; description of design studies, aided by electronic analog computer, that led to adoption of restricted orifice type upstream surge tank with unusually large diam of 130 ft.