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Author: Graham de Vahl Davis Publisher: ISBN: Category : Aerodynamic noise Languages : en Pages : 0
Book Description
Sound and vibrations affect convective heat transfer. An oscillating flow field can induce Reynolds stresses in a boundary layer. These Reynolds stresses may affect the time-mean motion, or even be its sole cause. Solutions for convection by streaming alone have already been found, within the framework of boundary-layer analysis for a circular cylinder under transverse oscillations. Solutions are obtained here to the coupled momentum and energy boundary layer equations for the interaction of a transverse sound field with natural convection on a horizontal cylinder in terms of aximuthal series of functions of the (transformed) radial coordinate. The solutions treat the cases where the direction of oscillations, transverse to the cylinder, is either horizontal or vertical. It has been found that horizontal oscillations increase the heat transfer coefficient at the bottom of a heated cylinder, while vertical oscillations cause a decrease.
Author: Graham de Vahl Davis Publisher: ISBN: Category : Aerodynamic noise Languages : en Pages : 0
Book Description
Sound and vibrations affect convective heat transfer. An oscillating flow field can induce Reynolds stresses in a boundary layer. These Reynolds stresses may affect the time-mean motion, or even be its sole cause. Solutions for convection by streaming alone have already been found, within the framework of boundary-layer analysis for a circular cylinder under transverse oscillations. Solutions are obtained here to the coupled momentum and energy boundary layer equations for the interaction of a transverse sound field with natural convection on a horizontal cylinder in terms of aximuthal series of functions of the (transformed) radial coordinate. The solutions treat the cases where the direction of oscillations, transverse to the cylinder, is either horizontal or vertical. It has been found that horizontal oscillations increase the heat transfer coefficient at the bottom of a heated cylinder, while vertical oscillations cause a decrease.
Author: G. de Vahl Davis Publisher: ISBN: Category : Languages : en Pages : 69
Book Description
Sound and vibrations affect convective heat transfer. An oscillating flow field can induce Reynolds stresses in a boundary layer. These Reynolds stresses may affect the time-mean motion, or even be its sole cause. Solutions for convection by streaming alone have already been found, within the framework of boundary-layer analysis for a circular cylinder under transverse oscillations. Solutions are obtained here to the coupled momentum and energy boundary layer equations for the interaction of a transverse sound field with natural convection on a horizontal cylinder in terms of aximuthal series of functions of the (transformed) radial coordinate. The solutions treat the cases where the direction of oscillations, transverse to the cylinder, is either horizontal or vertical. It has been found that horizontal oscillations increase the heat transfer coefficient at the bottom of a heated cylinder, while vertical oscillations cause a decrease. (Author).
Author: E. E. Soehngen Publisher: ISBN: Category : Heat Languages : en Pages : 84
Book Description
Experiments have been conducted on the interaction of strong sound fields with freq convection boundary layers on horizontal heated cylinders of 0.750-inch diameter. The interaction effects were observed through the measurements of total heat transfer from the cylinders to air under the influence of different types of sound environments. Three different types of sound fields were employed for the experiments: (1) standing plane waves generated by loud-speakers in an anechoic chamber; (2) Traveling plane wave fields generated by a mechanical siren in an anechoic duct; (3) Constant pressure or diffuse sound fields generated by a mechanical siren in a reverberant chamber. In all cases the generated sound was monochromatic ...
Author: Timothy William Martin Publisher: ISBN: Category : Heat Languages : en Pages : 118
Book Description
An experimental study has been made of the local natural convective heat transfer coefficient around the circumference of a heated horizontal cylinder oscillating vertically in water. The heat transfer surface consisted of a 1 3/8-inch diameter cylinder with a small test section imbedded in its surface. This enabled data to be taken so that the local and overall values of the heat; transfer coefficient could be determined. The cylinder was oscillated sinusoidally in a tank of distilled water at a frequency of 0 to 25-cps with an amplitude of 0 to 0.100-inch. The temperature difference between the water bath and the test cylinder was held at approximately twenty degrees. Observations of the flow patterns around the cylinder were made using a shadowgraph technique and a dye stream visualization, The local heat transfer coefficient versus position data were taken at six different conditions of frequency and amplitude. These conditions were: (1) stationary, (2) n = 500 rpm, a = 0.100-inch, (3) n = 750 rpm, a = 0.0667-inch, (4) n = 1000 rpm, a = 0.100-inch, (5) n = 1500 rpm, a = 0.0667-inch, and (6) n = 1500 rpm, a = 0.100-inch. The overall cylinder results were similar to the results found by V.H. Swanson and by Martinelli and Boelter in similar work. The maximum increase in the overall cylinder heat transfer rate was of the order of 200 percent. The data for the local heat transfer coefficient showed that the maximum increase in the heat transfer coefficient occurred at the top of the cylinder and was on the order of 290 percent. At the same condition of oscillation the coefficient at the side increased 230 percent while the coefficient at the bottom increased 72 percent. In comparing the shapes of the distributions of local Nusselts number with the shapes Fand, Roos, Cheng, and Kaye found by imposing a sound field on a air-cylinder system, a difference was noted which can be attributed to the difference in the direction of oscillation between the two investigations. In the present investigation the cylinder was oscillated vertically while Fand, Roos, Cheng, and Kaye used a horizontal oscillation of the fluid particles. The resulting differences in the acoustic streaming pattern account for the differences noted in the shapes of the local heat transfer coefficient versus position curves. The shapes did show that the effect of mechanical oscillation and the effect of a sound field on the convective heat transfer rate were similar. A dye stream visualization of the flow pattern indicated Fand, Roos, Cheng, and Kaye were correct when they concluded that the shape of the distribution of Nusselt number was caused by the interaction of a natural convection flow pattern and acoustic streaming. This study sheds some light on the mechanism causing the increase in the natural convection heat transfer coefficient when oscillation is introduced, and it shows the need for more experimental investigation into the distribution of the local heat transfer coefficient around cylinders.
Author: Graham de Vahl Davis Publisher: ISBN: Category : Languages : en Pages : 74
Book Description
In a previous paper by Richardson an analysis was made of the extension measurements available in heat transfer from a horizontal heated cylinder in a transverse sound field or in mechanical vibration transverse to its axis. The results were particularly good when the influence of buoyancy was small. This paper extends the analysis to include the buoyancy effect and gives some illustrated solutions. (Author).
Author: Thomas Woodrow Jackson Publisher: ISBN: Category : Air flow Languages : en Pages : 136
Book Description
Results are presented for a series of experiments conducted for the purpose of studying the local and overall effects of a resonant acoustic vibration on the heat transfer coefficient for air flowing through a constant temperature isothermal tube at Graetz Numbers from 33 to 5400. The local heat transfer coefficient is shown to vary periodically between the nodes and loops of the resonant sound wave. Local heat transfer coeffients up to 3.6 times the no-sound values have been obtained. Extensive tables of data are included for possible use in analytical investigations. Sound pressure levels to 162 decibels are reported.
Author: Graham de Vahl Davis
Author: Graham de Vahl Davis
Author: G. de Vahl Davis
Author: E. E. Soehngen
Author: United States. Wright Air Development Division
Author: Timothy William Martin
Author: Graham de Vahl Davis
Author: Thomas Woodrow Jackson
Author: 
Author: 
Author: United States. National Aeronautics and Space Administration