Computerized heat-transfer and stress analysis of wind tunnel metal throat liners

Wind tunnels are devices used to test models of flight vehicles. The main component of the wind tunnel is the converging-diverging nozzle or liner. This study presents a computerized approach to analyze the structural integrity of the liner.

Many wind tunnels at Arnold Engineering Development Center (AEDC), Arnold Air Force Station, Tennessee, are of the continuous-flow, axisymmetric design. Some are used for heat-transfer studies requiring high temperature of the flowing medium, usually air. In order to maintain liner configurations to produce accurate test conditions, the liners must be externally cooled, usually with water. In doing this, thermal gradients are set up in the liner and an analysis must be made to ensure adequate design.

One of the most difficult problems in analyzing the liner is determining the airside, forced-convection, heat transfer coefficient. The main reason it is so difficult is due to the boundary layer that develops along the grammed, and experimentally checked a method for calculating the turbulent boundary-layer properties in the supersonic section of a liner. Using the results from

Numbers in brackets refer to similarly numbered references in the Bibliography.

Sivells' program and an iterative radial heat balance, one can write a subroutine, called HEAT, to determine the following:

1. The thermal gradient through the thickness of the liner.

2. The temperature profile along the length of the liner.

3. The total stresses at any point in the liner. Included in the subroutine is a method for determining the same three conditions for the subsonic section of the liner. This gives a complete analysis of the entire liner.

Thus, the design analysis of a wind tunnel liner, both aerodynamically and structurally, can be performed using one program. The program will also solve any number of cases at one time.

An example problem is presented showing all steps required to operate the program.