Accession Number:

ADA234552

Title:

Optical Studies of the Flow Start-Up Processes in Four Convergent-Divergent Nozzles

Descriptive Note:

Final rept. Jun 1989-Sep 1990

Corporate Author:

ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s):

Report Date:

1991-03-01

Pagination or Media Count:

122.0

Abstract:

In the context of design studies for the U.S. Large BlastThermal Simulator, BRL has sponsored optical studies of the flow start-up in convergent- divergent nozzles which have the flow-initiating diaphragm located in the nozzle throat. The experiments were performed in the 200-mm shock tube at the Ernst- Mach-Institute in Freiburg Breisgau, West-Germany. The scope of the studies included divergent nozzles with half-cone angles of 6, 16, 45 and 90 deg tested at seven diaphragm pressure ratios ranging from four to 188 and resulting in shock strengths ranging from 1.4 to 4.4. Results were summarized in graphs of significant parameters, e.g., shock formation time, flow start-up period, flow expansion angle and shock strength versus the driver pressure ratio and further compared with numerical results obtained with the BRL-Q1D hydrocode. The numerical-experimental comparison shows qualitative agreement. The flow phenomena are generally reproduced by the computations as long as they are not strongly dependent on viscous effects. The study shows that a pressure loss of 10 is connected to the presence of a large area discontinuity at the exit plane of the nozzle throat when no divergent nozzle is attached. Results suggest that a 45deg divergent nozzle may present an acceptable compromise for minimizing these pressure losses by reducing the associated area discontinuities.

Subject Categories:

  • Test Facilities, Equipment and Methods
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE