Accession Number : AD0653860

Title :   SYNOPSIS OF A THEORY FOR SHOCK IMPEDANCE EFFECTS IN A ROUGH-WALLED TUNNEL.

Descriptive Note : Research paper,

Corporate Author : INSTITUTE FOR DEFENSE ANALYSES ARLINGTON VA RESEARCH AND ENGINEERING SUPPORT DIV

Personal Author(s) : Porzel,Francis B.

Report Date : MAY 1967

Pagination or Media Count : 45

Abstract : The paper postulates five related impedance mechanisms that control the propagation of blast wave through a rough-walled tunnel: entry diffraction, build-up, turbulent choke, wall roughness, and feedback. These combined impedance mechanisms from rough walls rapidly reduce tunnel overpressures down to structurally manageable levels (approx. = 1 bar) within the first few dozen lengths L/D, almost independently of surface pressure near the entry. A relatively slow decrease in tunnel pressures occurs beyond L/D = 50 or at low pressures (< 1 bar). Excellent correlation--within 20 percent--is found with measurements made in rough-walled shock tubes. A program in simple BASIC machine language (suitable for time-sharing teletype) summarizes the calculations, permits the user to input any surface pressure and wall roughness desired, and prints an annotated tabular history of shock pressure down the tunnel. Classic idealizations, such as one-dimensional analyses, or experiments close to the entrance of a smooth-walled tunnel are not considered usually relevant to these phenomena. (Author)

Descriptors :   (*SHOCK WAVES, DAMPING), (*UNDERGROUND STRUCTURES, EXPLOSION EFFECTS), BLAST, CONTROL, PROPAGATION, WALLS, SURFACE ROUGHNESS, THEORY, NUCLEAR EXPLOSIONS, PRESSURE, ATTENUATION

Subject Categories : Aerodynamics
      Structural Engineering and Building Technology
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE