Thin Metallic Ribbons Research Articles

Transient boiling heat transfer to water

Experimental transient boiling heat transfer in water for exponential heat inputs to thin metallic ribbons of 0.015 × 10 6 e t t 0 Btu/ft 2h are compared with steady state predictions. The nominal values of controlled variables included velocity: ⩽ 1, 14 ft/s; pressure; 14.7, 500, 1000, 2000 psia; subcooling: ⩽ 10,42,112°F; exponential period : 5,15,50 ms.

On Turbulence-Induced Vibrations of a Thin Ribbon With Velocity-Dependent Damping

Results of an experimental study of the turbulence-induced random vibrations of a thin metal ribbon show that an interaction between the vibrating surface and the turbulence exists which results in an increase in the turbulent energy within the boundary layer. In addition, the system damping is shown to vary with the free-stream velocity and to be proportional to the amplitude response of the ribbon. The experimental data and an accompanying theoretical analysis give support to the belief that the damping is primarily a velocity-squared type which is characteristic of a flat plate vibrating normally in a fluid.

Experimental Study of the Velocity-Dependent Damping of a Turbulence-Induced Vibrating System

This paper presents the results of a recent experimental study of the damping characteristics of boundary-layer-induced vibrations of a thin metal ribbon. One side of the metal ribbon was subjected to a turbulent boundary layer in a subsonic wind tunnel. The displacement of the ribbon was measured by a capacitance probe. (The spectral content of the probe's output was analyzed using a wave analyzer.) Each frequency component was then scrutinized to determine its damping characteristics; that is, the −3 dB-down points about each center band/or modal frequency were observed to increase significantly with velocity. This increased damping is attributed primarily to the surface shear stress caused by the fluid on the ribbon. These results can significantly affect the radiated sound from turbulence-induced vibrating surfaces.

Experimental Investigation of Boundary-Layer-Induced Vibrations

Results of a recent experimental study of boundary-layer-induced vibrations of a thin metal ribbon are presented. These results were obtained by subjecting one side of a stainless-steel ribbon to a turbulent boundary layer in a subsonic wind tunnel. The displacements of the ribbon were measured with a capacitance probe. The coincidence effect that was encountered by R. H. Lyon in a similar study is observed in the present investigation. This coincidence effect occurs in the fifth mode of vibration when the free-stream velocity is approximately 1.2 times the wave velocity of the ribbon. This value of the velocity ratio differs from that observed by Lyon, which was approximately 0.85 for the fifth mode. It is believed that the coincidence effect occurs when the convection velocity equals the wave velocity. Following this line of reasoning, the present velocity ratio value of 1.2 is supported since the convection velocity has been found experimentally to be approximately 0.8 times the free-stream velocity.

The structure of surface films. Part XVII.—γ hydroxy-stearic acid and its lactone

This paper describes observations, mostly made in 1924 and not hitherto published in detail,* on the surface pressure of γ hydroxy-stearic acid (I) and its lactone (II) spread as monomolecular films on aqueous solutions. CH3 3 CH3 3 (CH 2 ) 13 (CH 2 ) 13 CHOH CH CH 2 CH 2 CH 2 O COOH CH 2 – CO I II Most of the measurements were made with the modification of Langmuir’s apparatus described in Parts I and II of this series of papers,† in which jets of air prevent the film passing the ends of the float. A few confirmatory observations have been made since, with the apparatus of Adam and Jessop, in which thin metallic ribbons block these gaps. The acid and lactone were kindly given me by Dr. P. W. Clutterbuck, of Manchester University.