Comparison of force measurement techniques in a short duration hypersonic facility

Force measurement experiments have been conducted within the University of Oxford’s High Density Tunnel with a (Formula presented.) half-angle cone. The purpose of the study was to provide a direct comparison between two independent force techniques in the same facility at the same free-stream conditions to provide a quantitative and qualitative discussion of the advantages and disadvantages of both techniques. The first force measurement technique used a conventional 4-axis sting-mounted force balance which was calibrated both statically and through the stress wave deconvolution method, whilst the second technique used the less established static free-flight methodology. Experiments were conducted at a Mach 5 test condition which provided sufficient dynamic pressure to generate aerodynamic forces suitable for the measurement range of the force balance. Results for lift, drag and pitching moment coefficients were obtained over a range of angles of attack and compared with predictions from a hypersonic panel method code. Agreement between the independent force techniques and numerical data sets was good over the range of angles of attack. Maximum uncertainties were shown to be 38.46 ± 0.56 N and 22.52 ± 0.44 N for free-flight in lift and drag, respectively, and 38.74 ± 1.59 N and 22.13 ± 1.27 N for the dynamically calibrated force balance which demonstrates the superiority of free-flight

Simulation of a low enthalpy ablator into a hypersonic boundary-layer

Understanding the behaviour of ablative materials is required for improved margins for TPS for spacecrafts. Low enthalpy ablators are used in place of more typical ablative materials when the high enthalpies required for their ablation can not be reached in ground testing. These materials simulate the highly coupled nature of the heat and mass transfer that occurs at the surface of an ablative heat shield during re-entry, through their ability to sublimate. As a result, the study of low enthalpy ablators can provide insight into the behaviour of ablative materials during hypersonic fight by isolating a handful of phenomena that occur and interact with one another at their surface. Predicting the material response prior to any experimental test is needed. The code CLEARR (Code for Low Enthalpy Ablator Recession Rate) is presented in this work and provides a low cost method of predicting low enthalpy ablator response. The code utilises empirical correlations to determine the energy and mass balances at the material's surface and time evolution of internal temperature distribution, discretised using a crank-Nicholson algorithm. Its functionality is showcased by modelling a cylindrical sample composed entirely of the low enthalpy ablator naphthalene subject to a wide range of hypersonic flow conditions. The evaluated rate of ablation of the material and ultimately the total mass injected into the boundary-layer over a range of test times including the nominal test time in a hypersonic facility are shown in addition to the effect of the varying flow properties on the material response

Experimental non-equilibrium radiation measurements for low-Earth orbit return

This paper reports on absolute radiation measurements performed in synthetic air (20.78% O2, 79.22% N2) shock-heated flows. Experiments were carried out in the Oxford T6 Stalker Tunnel in Aluminium Shock Tube mode. Data is presented for velocities ranging from 5.5-7.2 km/s at a nominal 1 bar post-shock pressure, in both UV/Vis and Vis/NIR spectral ranges. Simulations of the equilibrium radiance using NASA CEA and NEQAIR codes underpredict that obtained from the experimental data. An analysis using the newly developed LASTA code removes shock deceleration from consideration as a cause for this discrepancy. Non-equilibrium data is analysed in the form of spectral and absolute non-equilibrium metrics, and the effects of shock speed and post-shock pressure on the non-equilibrium radiance isolated. Finite-rate one-dimensional two-temperature simulations using POSHAX3 with Park 1993 rates are performed, which significantly underpredict the experimentally acquired data

Enhancing the test time performance of Ludwieg tunnels

Ground testing at hypersonic conditions requires either expensive heating or reduced test time. This paper discusses further developments to a mode of operation for Ludwieg Tunnels - Plenum Augmented Ludwieg Mode (PALM) - in the Oxford High Density Tunnel (HDT). PALM offers increased test time performance relative to standard Ludwieg Mode at the expense of total pressure and unit Reynolds number capability. A description of the theory of operation and the implementation of PALM in the HDT is given. Experimental results, quasi-1D numerical simulations and a performance map are presented. PALM has been demonstrated to offer a factor of 10 increase in the test time with a reduction in maximum Unit Reynolds number of approximately 50% relative to standard Ludwieg Mode. Theoretical performance maps predict that PALM can offer a factor of 10 improvement in test time for all Mach 7 unit Reynolds numbers run to date in HDT without any facility upgrades. Hence, operation in PALM significantly improves the capability of the HDT to investigate unsteady and long duration flow phenomena relative to standard Ludwieg Mode operation

Queensland Spanner Crab Fishery: Commercial quota setting for June 2016 – May 2018

The Queensland (QLD) fishery for spanner crabs primarily lands live crab for export overseas, with gross landings valued around A$5 million per year. Quota setting rules are used to assess and adjust total allowable harvest (quota) around an agreed target harvest of 1631 t and capped at a maximum of 2000 t. The quota varies based on catch rate indicators from the commercial fishery and a fishery independent survey. Quota management applies only to ‘Managed Area A’ which includes waters between Rockhampton and the New South Wales (NSW) border. This report has been prepared to inform Fisheries Queensland (Department of Agriculture and Fisheries) and stakeholders of catch trends and the estimated quota of spanner crabs in Managed Area A for the forthcoming annual quota periods (1 June 2016–31 May 2018). The quota calculations followed the methodology developed by the crab fishery Scientific Advisory Group (SAG) between November 2007 and March 2008. The QLD total reported spanner crab harvest was 1170 t for the 2015 calendar year. In 2015, a total of 55 vessels were active in the QLD fishery, down from 262 vessels at the fishery’s peak activity in 1994. Recent spanner crab harvests from NSW waters average about 125 t per year, but fell to 80 t in 2014–2015. The spanner crab Managed Area A commercial standardised catch rate averaged 0.818 kg per net-lift in 2015, 22.5% below the target level of 1.043. Compared to 2014, mean catch rates in 2015 were marginally improved south of Fraser Island. The NSW–QLD survey catch rate in 2015 was 20.541 crabs per ground-line, 33% above the target level of 13.972. This represented an increase in survey catch rates of about four crabs per groundline, compared to the 2014 survey. The QLD spanner crab total allowable harvest (quota) was set at 1923 t in the 2012-13 and 2013-14 fishing years, 1777 t in 2014-15 and 1631 t in 2015-16. The results from the current analysis rules indicate that the quota for the next two fishing years be retained at the base quota of 1631 t

Queensland Spanner Crab Fishery : Commercial quota setting for June 2015 – May 2016

The Australian fishery for spanner crabs is the largest in the world, with the larger Queensland (QLD) sector’s landings primarily exported live overseas and GVP valued ~A$5 million per year. Spanner crabs are unique in that they may live up to 15 years, significantly more than blue swimmer crabs (Portunus armatus) and mud crabs (Scylla serrata), the two other important crab species caught in Queensland. Spanner crabs are caught using a flat net called a dilly, on which the crabs becoming entangled via the swimming legs. Quota setting rules are used to assess and adjust total allowable harvest (quota) around an agreed target harvest of 1631 t and capped at a maximum of 2000 t. The quota varies based on catch rate indicators from the commercial fishery and a fishery-independent survey from the previous two years, compared to target reference points. Quota management applies only to ‘Managed Area A’ which includes waters between Rockhampton and the New South Wales (NSW) border. This report has been prepared to inform Fisheries Queensland (Department of Agriculture and Fisheries) and stakeholders of catch trends and the estimated quota of spanner crabs in Managed Area A for the forthcoming quota period (1 June 2015–31 May 2016). The quota calculations followed the methodology developed by the crab fishery Scientific Advisory Group (SAG) between November 2007 and March 2008. The total reported spanner crab harvest was 917 t for the 2014 calendar year, almost all of which was taken from Managed Area A. In 2014, a total of 59 vessels were active in the QLD fishery, the lowest number since the peak in 1994 of 262 vessels. Recent spanner crab harvests from NSW waters have been about 125 t per year. The spanner crab Managed Area A commercial standardised catch rate averaged 0.739 kg per net-lift in 2014, 24% below the target level of 1.043. Mean catch rates declined in the commercial fishery in 2014, although the magnitude of the decreases was highest in the area north of Fraser Island. The NSW–QLD survey catch rate in 2014 was 16.849 crabs per ground-line, 22% above the target level of 13.972. This represented a decrease in survey catch rates of 0.366 crabs per ground-line, compared to the 2013 survey. The Queensland spanner crab total allowable harvest (quota) was set at 1923 t in 2012 and 2013. In 2014, the quota was calculated at the base level of 1631 t. However, given that the 2012 fisheryindependent survey was not undertaken for financial reasons, stakeholders proposed that the total allowable commercial catch (TACC) be decreased to 1777 t; a level that was halfway between the 2012/13 quota of 1923 t and the recommended base quota of 1631 t. The results from the current analysis indicate that the quota for the 2015-2016 financial year be decreased from 1777 t to the base quota of 1631 t

Queensland Spanner Crab Fishery: Commercial quota setting for June 2016 – May 2018

The Queensland (QLD) fishery for spanner crabs primarily lands live crab for export overseas, with gross landings valued around A$5 million per year. Quota setting rules are used to assess and adjust total allowable harvest (quota) around an agreed target harvest of 1631 t and capped at a maximum of 2000 t. The quota varies based on catch rate indicators from the commercial fishery and a fishery independent survey. Quota management applies only to ‘Managed Area A’ which includes waters between Rockhampton and the New South Wales (NSW) border. This report has been prepared to inform Fisheries Queensland (Department of Agriculture and Fisheries) and stakeholders of catch trends and the estimated quota of spanner crabs in Managed Area A for the forthcoming annual quota periods (1 June 2016–31 May 2018). The quota calculations followed the methodology developed by the crab fishery Scientific Advisory Group (SAG) between November 2007 and March 2008. The QLD total reported spanner crab harvest was 1170 t for the 2015 calendar year. In 2015, a total of 55 vessels were active in the QLD fishery, down from 262 vessels at the fishery’s peak activity in 1994. Recent spanner crab harvests from NSW waters average about 125 t per year, but fell to 80 t in 2014–2015. The spanner crab Managed Area A commercial standardised catch rate averaged 0.818 kg per net-lift in 2015, 22.5% below the target level of 1.043. Compared to 2014, mean catch rates in 2015 were marginally improved south of Fraser Island. The NSW–QLD survey catch rate in 2015 was 20.541 crabs per ground-line, 33% above the target level of 13.972. This represented an increase in survey catch rates of about four crabs per groundline, compared to the 2014 survey. The QLD spanner crab total allowable harvest (quota) was set at 1923 t in the 2012-13 and 2013-14 fishing years, 1777 t in 2014-15 and 1631 t in 2015-16. The results from the current analysis rules indicate that the quota for the next two fishing years be retained at the base quota of 1631 t

LASTA 2.0: validation of a reverse time integration method

Shock tube experiments provide critical insight into the thermochemical processes that occur in the shock layer of hypersonic flight vehicles and are used to validate many chemical-kinetic and radiative models for vehicle design. Shock tube flows exhibit a number of non-ideal behaviours that must be accounted for when interpreting experimental data. Previous work has shown that variations in shock speed and boundary layer growth along the length of the shock tube have a strong effect on the test slug properties. The LAgrangian Shock Tube Analysis code (LASTA) is an a posteriori tool that successfully addressed this problem, allowing reconstruction of the test slug from an experimentally obtained shock trajectory. LASTA 2.0 is presented here, which further constrains the test slug properties using an additional experimental pressure boundary condition whose effects are included via a backwards time integration scheme. The tool is validated against ideal gas cases following accelerating and decelerating shock trajectories, each with a tube-end Mach number of 6.5 and a fill pressure of 66.66 Pa. Agreement between the method and results from a viscous, axisymmetric Navier-Stokes solution is found to be within 1% in pressure and temperature in the majority of cases. Improved agreement with experimental data is evident when compared to the previous version of LASTA, particularly where there is strong shock speed non-uniformity