Computer Program for Calculation of Complex Chemical Equilibrium Compositions and Applications

A detailed description of the equations and computer program for computations involving chemical equilibria in complex systems is given. A free-energy minimization technique is used. The program permits calculations such as (1) chemical equilibrium for assigned thermodynamic states (T,P), (H,P), (S,P), (T,V), (U,V), or (S,V), (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. The program considers condensed species as well as gaseous species.

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Computer Program for Calculation of Complex Chemical Equilibrium Compositions, Rocket Performance, Incident and Reflected Shocks, and Chapman-Jouguet Detonations

Berridge, Dennis C. PhD, Purdue University, December 2015. Generating LowPressure Shock Waves for Calibrating High-Frequency Pressure Sensors. Major Professor: Steven P. Schneider. Measurements of hypersonic boundary-layer instabilities have recently been performed in a wide range of wind tunnels with fast-response pressure transducers. In order to achieve accurate amplitude measurements, the calibration and frequency response of the sensors must be understood. Hypersonic instabilities are high-frequency, low-amplitude waves, so relevant calibrations must use similar inputs. This is particularly important for the PCB-132 sensors which have been widely used to measure hypersonic boundary-layer instabilities despite the lack of low-amplitude calibrations or frequency response information. This work demonstrates the creation of extremely low-amplitude shock waves in a shock tube, which can be used to calibrate sensors for instability measurements. The shocks are created using weak diaphragms and low driven pressures on the order of 1 millitorr. A method for automatically measuring the shock arrival time and amplitude was developed. The method uses a rising-edge detector, a minimum peakwidth criterion, and a simple low-pass filter to detect small shock waves in traces with low signal-to-noise ratio. Shock amplitudes as low as 0.001 psi are demonstrated. The flow is shown to agree with theoretical expectations within the existing uncertainties. Calibrations of PCB-132 sensors were performed between 0.001 and 1 psi. The sensors were found to have a linear calibration over the entire range within the sensor uncertainty. Step responses were measured for PCB-132 and Kulite sensors. The PCB-132 step responses are complicated and vary between sensors, but they are repeatable. They

Generating low-pressure shock waves for calibrating high-frequency pressure sensors

Condensation of water vapor in rarefaction waves. III - Experimentalresults

The head-on collision between a normal shock wave, propagating into a quiescent gas, and a rubber-supported plate was investigated theoretically and experimentally. In the theoretical part, a physical model was developed for describing the collision process. Three different modes in which the rubber could be loaded, due to its collision with the incident shock wave, were studied. They are: uni-axial stress loading, bi-axial stress loading and uni-axial strain loading. In the first two modes the rubber can expand while carrying the shock-wave induced compressive load, and therefore can be treated as an incompressible medium. This is not the case in a uni-axial strain loading where the rubber cannot expand while carrying the shock-wave-induced load. The model developed was based on both the conservation equations and on an appropriate strain stress relation which describes the rubber behaviour under loading. The model was solved numerically for each of the above-mentioned loading modes. Experiments were conducted in a shock tube; the rubber response to its collision with normal shock wave was studied for the case of bi-axial stress loading. Pressures, in the gas, and stresses, in the rubber, were recorded by using piezoelectric pressure transducers; the shock-wave reflection, in the gas, and the rubber displacement and compression processes were recorded on successive shadowgraphs. Good agreement was found between the experimental and numerical results for the case of bi-axial stress loading. This agreement validates the model developed for the collision process and the reliability of the numerical scheme used for its solution.

Head-On Collision of Normal Shock Waves with a Rubber-Supported Wall

: Contents: Performance of Simple Constant-Area Shock tubes; Observed flows in a constant-area shock tube; Production of strong shock waves; Application of the shock tube; Shock-tube materials; Design and Construction; and shock-tube.

J. G. Hall

Papers

Handbook of Supersonic Aerodynamics. Section 18. Shock Tubes