Effect Of Peened Surface Characteristics On Flow Resistance

Author:  Hiromitsu Kiyoto
Source:  Conf Proc: ICSP-10 Tokyo, Japan 2008
Doc ID:  2008123
Year of Publication:  2008
Abstract:  
ABSTRACT This paper experimentally considers the influence of the dimple on the flow resistance of peened surfaces. In this study, in order to clarify the influence of peened surface characteristics on flow resistance, test cylinders were shot peened under the following conditions. Centrifugal and direct pressure peening machines were used. The centrifugal machine was used for shot velocities varying from 30 m/s to 50 m/s and shot diameters of 2.00-2.38mm. A direct pressure machine was used with projection pressure of 2.5atm and shot diameters of 1.00-1.19mm. The work material is aluminum alloy, whose diameters were 30, 35, 40mm. Air velocity in the wind tunnel over the peened surfaces was varied from 10-20 m/s. Results of this experiment include:(1) When the test cylinder has a large surface roughness, and air velocity exceeds a fixed value, the point that flow changes from laminar to turbulent flow shifts to turbulent, and the drag coefficient decreases. (2) The drag coefficient decreases with increasing surface roughness on the peened test cylinder. (3) When the test cylinder diameter is relatively large, the influence of the surface of a wall of the wind tunnel increases and then the air velocity increases locally. (4) The drag coefficient decreases with profile surface roughness produced by shot peening, this is why the peened surface affects air velocity V or the Reynolds number characteristic length L. KEYWORDS Shot peening, drag coefficient, flow resistance, Reynolds numbers, critical Reynolds number, laminar flow, turbulent flow