Information about the experiments of Vetter and Sturtevant
from

"Experiments on the shock-excited interfacial 
instability at an air/SF6 interface" 

Proceedings of the 20th International Symposium on
Shock Waves
p.593-598


Vetter and Sturtevant present the results of 7 different
experiments of a shock traveling from air into sf6 bouncing
off the end wall and reshocking the contact then exiting the 
domain.  The initial shock strength is varied by changing the
pressure of the SF6, and the length of the tube was adjusted
in some experiments to insure the interaction of the reflected
shock wave with the interface would be in the experimental field
of view (a window of diameter 15cm at 42cm down stream).


Experimental setup: 
      	_____ _______________________
	     {		             |     
	Air  {		SF6	     | end wall
	     {			     |     
	     {		P_1	     |  
        ____ {_______________________|  
	      <-------  L -----------> 	
     
     The length of the tube (L) varies from 62cm to 123cm
     and the pressure (P_1) of the SF6 ranges from 55kPa to 8kPa
     
     The cross-section of the domain is 27cm x 27cm


Experiments:

This is Table 1. from the paper.
 
         I	II	III	IV	V	VI	VII
------------------------------------------------------------
 Ms   :	1.18	1.24	1.43	1.45	1.50	1.50	1.98
      :
 P_1  :	55kPa	40kPa	31kPa	29kPa	23kPa	23kPa	8kPa
      :
 L    :	123cm	110cm	62cm	62cm	62cm	62cm	49cm
      :
 Mt   :	1.27	1.37	1.67	1.70	1.78	1.78	2.56	
      :
 u0   :	56m/s	72m/s	126m/s	126m/s	150m/s	150m/s	287m/s
      :
 rate1:	.94m/s	2.1m/s	3.0m/s	3.1m/s	4.0m/s	4.2m/s	7.5m/s
      :
 rate2:	19.2m/s	17.0m/s	31.5m/s	35.5m/s	32.6m/s	37.2m/s	74.4m/s
      :
 reshock  x     9.5ms   4.0ms      x     3.5ms      x    1.6ms		
      :
 final          16.5ms  6.0ms		 6.25ms		 2.5ms



The data for cases I, IV, VI were done with single spark-schlieren
cases II, III,V,VI were high-speed motion pictures. 

Ms    - Mach number of the incident shock in air
P_1   - Pressure of the SF6
L     - Length of the test section
Mt    - Mach number of the (transmitted) shock in SF6
u0    - the velocity (of the contact) behind the initially transmitted shock

rate1 - the growth rate of the mixing layer before reshock
rate2 - the growth rate of the mixing layer after reshock

The rows reshock and final come from Figure 1 and are only approximate
reshock - the time at which the reshock occurred
final - the final time of the experiment



Numerical simulations:
---------------------

The numerical simulation imagines a tube with air and sf6
at equilibrium (same temperature and pressure) with a contact
located at x=0. 

A shock traveling to the right is initiated in the air to the
left of the contact as the solution to a Riemann problem.
This allows the shock to develop into a numerical shock before 
interacting with the contact.

This initial pressure of the unshocked gas is taken to be P_1, 
and the density given (for the air) results in a temperature of 286K
(a room temp of about 56 F).  

	  
The conditions in the repository should simulate the initial shock
of Mach 1.5 (cases V,VI).

The init.dat file:
 0.27885		#rho_air - unshocked   
 23000.00               #p_air   - unshocked
 0.0                    #u_air   - unshocked
 0.00                   #cloc    - location of contact
 1.d2                   #amp     - inverse width of contact
 -0.05                  #sloc    - location of shock
 1.5d0                  #shockmach - machnumber of shock

These conditions result in a computed transmitted shock with a Mach number
of 1.78056 and and a contact velocity of ~155m/s.  The time between
shock and reshock is found to be approximately 0.0035s.