Engineering Commons^™

Regional Jet Aircraft Competitiveness: Challenges And Opportunities, Tamilla Curtis, Dawna L. Rhoades

Publications

The Purpose of the Study is to investigate the current trends in the aviation industry in regards to regional jets and to examine country-level factors that can potentially explain the number of Embraer and Bombardier regional jet deliveries. Possible factors include GDP, price of crude oil, prior aircraft deliveries and the land area of receiving RJ countries.

Persistent Vascular Collagen Accumulation Alters Hemodynamic Recovery From Chronic Hypoxia, Diana M. Tabima, Alejandro Roldan-Alzate, Zhijie Wang, Timothy A. Hacker, Robert C. Molthen, Naomi C. Chesler

Biomedical Engineering Faculty Research and Publications

Pulmonary arterial hypertension (PAH) is caused by narrowing and stiffening of the pulmonary arteries that increase pulmonary vascular impedance (PVZ). In particular, small arteries narrow and large arteries stiffen. Large pulmonary artery (PA) stiffness is the best current predictor of mortality from PAH. We have previously shown that collagen accumulation leads to extralobar PA stiffening at high strain (Ooi et al. 2010). We hypothesized that collagen accumulation would increase PVZ, including total pulmonary vascular resistance (Z₀), characteristic impedance (Z_C), pulse wave velocity (PWV) and index of global wave reflections (P_b/P …

Adding Ros Scavengers To Cold K+ Cardioplegia Reduces Superoxide Emission During 2 H Global Cold Cardiac Ischemia, Mohammed Aldakkak, David F. Stowe, James S. Heisner, Matthias L. Riess, Amadou K.S. Camara

Biomedical Engineering Faculty Research and Publications

We reported that the combination of reactive oxygen species (ROS) quenchers Mn(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), catalase, and glutathione (MCG) given before 2 hours cold ischemia better protected cardiac mitochondria against cold ischemia and warm reperfusion (IR)-induced damage than MnTBAP alone. Here, we hypothesize that high K⁺ cardioplegia (CP) plus MCG would provide added protection of mitochondrial bioenergetics and cardiac function against IR injury. Using fluorescence spectrophotometry, we monitored redox balance, ie reduced nicotinamide adenine dinucleotide and flavin adenine dinucleotide (NADH/FAD), superoxide (O₂ ^•−), and mitochondrial Ca²⁺ (m[Ca²⁺]) in the left ventricular free …

Study Of Mechanical And Thermal Behavior Of Polymeric Ablator Using Md, Abhishek Kumar, Veera Sundararaghavan

Ablation Workshop

The thermal protection materials used for spacecraft heat shields are subjected to various thermal and mechanical loads during an atmospheric entry which can threaten the structural integrity of the system. This paper describes the development of a molecular dynamics approach to understand the mechanical and thermal behavior of high temperature polymers. One such material PICA has successfully flown on the Stardust spacecraft and is the TPS material chosen for the Mars Science Laboratory (MSL) and SpaceX Dragon spacecraft. Although such polymers have good structural properties at moderate temperature,they became structurally weak at extreme region of temperature and loads. In order …

Aerothermal Characterization Of Silicon Carbide-Based Tps In High Enthalpy Airflow, Francesco Panerai, Olivier Chazot

Ablation Workshop

Inductively-coupled plasma generators provide an ideal environment to reproduce the aerothermal heating experienced by a spacecraft re-entering a planetary atmosphere. The flight boundary layer chemistry is duplicated around a TPS model, ensuring a similarity between the flight and ground stagnation-point heat flux.

Experiments conducted in an induction plasmatron on silicon carbide-based thermal protection materials will be described. Several specimens are tested under a wide range of pressure and temperature conditions and investigated by means of infrared radiometry and optical emission spectroscopy. The plasma to which the materials are exposed is characterized in details by calorimetric and Pitot pressure measurements, and …

Methodology For Ablation Investigations In The Vki Plasmatron Facility: Preliminary Results With A Carbon Fiber Preform, Bernd Helber, Olivier Chazot, Annick Hubin, Thierry Magin

Ablation Workshop

Following the current developments of a new class of low-density, carbon/resin composite ablators, new efforts were initiated at the VKI on ablation research to understand the complex material response under reentry conditions and to develop and validate new material response models. Promising experimental results were obtained by testing the low-density monolytic composite ablator (MonA) in the 1.2MW inductively heated VKI Plasmatron facility. The application of a high speed camera with short exposure times (2μs) enabled in-situ analysis of both (3D) surface recession and spallation and further made it possible to demonstrate the outgassing effects of pyrolizing ablators. A change in …

Thermo-Chemical And Mechanical Coupled Analysis Of Swelling, Charring And Ablative Materials For Re-Entry Applications, Gregory Pinaud

Ablation Workshop

One of the major challenges in the design of atmospheric reentry vehicles is the optimization of the thermal protection system (TPS). During a reentry, the vehicle encounter severs heating and mechanical stress. A robust sizing is therefore essential to insure vehicle integrity and the mission success. In order to maximize the payload mass of the vehicle, lightweight charring ablators are commonly chosen as TPS materials for this one shot mission.

To predict the behaviour of the TPS ablative materials under pyrolysis for reentry applications, Astrium ST initiated the development of a specific module of the finite element software SAMCEF: AMARYLLIS. …

Coupled Computation Of Fluid And Material Response For Non-Charring Ablative Materials In Hypersonic Flow, Jonathan E. Wiebenga, Iain D. Boyd

Ablation Workshop

Hypersonic vehicles are subjected to high heat loads throughout their flight trajectories, and as a result, some form of thermal protection system (TPS) is required to ensure the vehicle’s survival. Accurate prediction of the behavior of these materials in a hypersonic environment is crucial to the efficient design of a hypersonic flight vehicle. It can be very costly and difficult, however, to experimentally replicate the flow conditions found in many hypersonic regimes, and for this reason it is desirable to be able to simulate the behavior of TPS materials under these flight conditions. This study aims to improve the modeling …

Uncertainty Analysis Of Reaction Rates In A Finite Rate Gas-Surface Model, Thomas E. Schwartzentruber

Ablation Workshop

A finite–rate–catalytic wall boundary condition incorporated into hypersonic flow simulations is investigated. Benchmark simulations of hypersonic flow over a cylinder are presented using the finite–rate–catalytic model parameterized with a test air–silica chemical model comprising the gas–surface reaction mechanisms and their associated rates. It is demonstrated that backwards recombination rates should not be arbitrarily set but must be consistent with the gas–phase thermodynamics, otherwise a drift from the equilibrium state may occur. The heat flux predicted by the finite rate model lies between non–catalytic and super–catalytic limits depending on the surface temperature. It is found that even for a constant surface …

Cfd Ablation Predictions With Coupled Gsi Modeling For Charring And Non-Charring Materials, Daniele Bianchi, Alessandro Turchi, F. Nasuti, M. Onofri

Ablation Workshop

To this day, a major objective of TPS design is to reduce empiricism, and to increase fundamental modeling capability through increased understanding. One of the most challenging aspect is the proper coupling between the material response and the external flow field. With this regard, the goal of this research activity is the improvement of the numerical modeling capabilities through the development of advanced CFD tools integrated with Gas-Surface Interaction (GSI) modeling.

Numerical prediction of ablation is ambitious and cpu-time demanding due to the complex multiphase physical and chemical processes that occur. With improvements in computational algorithms and advances in computer …

Radiative Transfer Equation Solver Module For Coupled Simulation Of Hypersonic Flows, Ranjan S. Mehta, Paul J. Dionne, Samuel F. Owens

Ablation Workshop

Accurate numerical modeling of the aerothermal environment around an ablation-cooled hypersonic re-entry vehicle requires high-fidelity models for processes such as non-equilibrium surface themochemistry, non-equilibrium pyrolysis chemistry, multi-scale radiation, spallation and charring. It is expected that, these models when utilized in a coupled manner will be able to accurately capture the possible nonlinear interactions between various phenomena in a computationally efficient manner. Development of a coupled radiative solver is currently being carried out as part of a joint effort between CFDRC, University of Michigan and University of Kentucky to develop a fully coupled method of simulating atmospheric entry flows and response …

Modeling Of Heat Transfer Attenuation By Ablative Gases During The Stardust Re-Entry, Alexandre Martin, Iain D. Boyd

Ablation Workshop

The great majority of modern space vehicles designed for planetary exploration use ablative materials to protect the payload against the high heating environment experienced during re-entry. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain …

Ablation Modeling Of A Solid Rocket Nozzle, Mark E. Ewing, Galen H. Richards, Micheal P. Iverson, Daron A. Isaac

Ablation Workshop

No abstract provided.

Global Monthly Water Scarcity: Blue Water Footprints Versus Blue Water Availability, Arjen Y. Hoekstra, Mesfin Mekonnen, Ashok K. Chapagain, Ruth E. Mathews, Brian D. Richter

Daugherty Water for Food Global Institute: Faculty Publications

Freshwater scarcity is a growing concern, placing considerable importance on the accuracy of indicators used to characterize and map water scarcity worldwide. We improve upon past efforts by using estimates of blue water footprints (consumptive use of ground- and surface water flows) rather than water withdrawals, accounting for the flows needed to sustain critical ecological functions and by considering monthly rather than annual values. We analyzed 405 river basins for the period 1996–2005. In 201 basins with 2.67 billion inhabitants there was severe water scarcity during at least one month of the year. The ecological and economic consequences of increasing …

Sparsening Filter Design For Iterative Soft-Input Soft-Output Detectors, Raquel G. Machado, Andrew G. Klein, Richard K. Martin

Faculty Publications

A large body of research exists around the idea of channel shortening, where a prefilter is designed to reduce the effective channel impulse response to some smaller number of contiguous taps. This idea was originally conceived to reduce the complexity of Viterbi-based maximum-likelihood equalizers. Here, we consider a generalization of channel shortening which we term "channel sparsening". In this case, a prefilter is designed to reduce the effective channel to a small number of nonzero taps which do not need to be contiguous. When used in combination with belief-propagation-based maximum a posteriori (MAP) detectors, an analogous complexity reduction can be …

Agent Based Modeling And Simulation Framework For Supply Chain Risk Management, Tiffany J. Harper

Theses and Dissertations

This research develops a flexible agent-based modeling and simulation (ABMS) framework for supply chain risk management with significant enhancements to standard ABMS methods and supply chain risk modeling. Our framework starts with the use of software agents to gather and process input data for use in our simulation model. For our simulation model, we extend an existing mathematical framework for discrete event simulation (DES) to ABMS and then implement the concepts of variable resolution modeling from the DES domain to ABMS and provide further guidelines for aggregation and disaggregation of supply chain models. Existing supply chain risk management research focuses …

Definition Of Ablation Test-Case Series #3, Tom Van Eekelen, Jean R. Lachaud, Alexandre Martin, Ioana Cozmuta

Ablation Workshop

The test-case series #3 will be a further extension of the tests defined within the framework of the NASA ablation modelling workshops. In order to reduce the amount of work, all tests within test-case series #3, will use the TACOT material defined by Lachaud et al. The main goal of this new series, is to test the 3D modelling capabilities of the participating codes. The first 1D results were presented at the 4th Ablation workshop, and together with the results of the second test-case series, will be discussed and analyzed more thoroughly at the 5th Ablation Workshop, Feb. 28- March …

Ablation Test Case Series #2. Mopar: Results For The Inter-Code Calibration, Jonathan E. Wiebenga, Iain D. Boyd, Alexandre Martin

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Test Case Baseline Results, Tim Risch, Chris Kostyk

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Amaryllis Results, Tom Van Eekelen, Jean-Marc Bouilly

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Itrac Results, Mark E. Ewing

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Are The Test Problems Well Posed With Ch = Cm = 0?, Ben F. Blackwell

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Be13 Results, Jean-Marc Bouilly

Ablation Workshop

No abstract provided.

Prediction Of Tacot Decomposition Using The Chaleur Code, Ben F. Blackwell, Micah Howard

Ablation Workshop

This talk will briefly discuss the ablation thermochemistry data used for the TACOT code comparison test cases. Three areas of interest will be highlighted: codes and numerical methods for solving the thermochemical equilibrium problem, differences in ablation thermochemistry data (Bc and enthalpy) when using the CEA and JANAF databases, and the effect of the choice of pyrolysis gas species will be discussed.

A Perspective On The Design And Development Of The Spacex Dragon Spacecraft Heatshield, Daniel J. Rasky

Ablation Workshop

In December, 2010, Space Exploration Technologies (SpaceX) successfully orbited, re-entered and recovered their Dragon spacecraft, on an almost “picture perfect” first full mission. Earlier in 2009, SpaceX, announced the passing of a significant technical milestone with the successful arc jet testing of a their new high performance heat shield material, called PICA-X, which provided the primary (forebody) thermal protection for Dragon.

In 2008 and 2009, Dr. Rasky worked closely with SpaceX on the Dragon heatshield design and also developing the ability to manufacture PICA-X. The “X” stands for the SpaceX-developed variants that have several improved properties and greater ease of …

The Mysteries Of Real Materials, Bernard Laub

Ablation Workshop

The presentation will consist in showing arc jet data mysterious to the modelers. It will show a short movie (10-20 sec) of an arc jet test where a material exhibited a failure mode that nobody understands followed by thermocouple data from arc jet tests on another material of interest in which the T/Cs exhibit repeatable, consistent, fascinating yet frustrating response characteristics that have the modelers stumped. This all happens between RT and 200 F. Doesnt sound important? Unless we figure out what it is and can model it, we can’t size the TPS with any confidence.

Direct Observation Of Mechanical Ablation, Charles Powars, Craig Derbidge

Ablation Workshop

This presentation describes an experiment that solved a mysterious problem affecting the material that protects solid rocket motor cases from burning propellant gases: Why was the ablation of this material in the forward dome region of recovered flight test motors as much as 2x that observed in full-scale ground test firings?

Heat transfer to the forward dome elastomeric insulation is predominantly radiation from the burning propellant. The 15- kW CO2 laser at the Wright Patterson AFB Laser Hardened Material Evaluation Laboratory (LHMEL) was used to provide uniform incident radiation from 200 to 400 W/cm2. We suspected that the rocket acceleration …

Characterization Of Material Response During Arc-Jet Testing With Optical Methods–Status And Perspectives, Michael Winter

Ablation Workshop

The characterization of ablation and recession of heat shield materials during arc jet testing is an important step towards understanding the governing processes during these tests and therefore for a successful extrapolation of ground test data to flight. The behavior of ablative heat shield materials in a ground-based arc jet facility is usually monitored through measurement of temperature distributions (across the surface and in-depth), and through measurement of the final surface recession [1, 2]. These measurements are then used to calibrate/validate materials thermal response codes, which have mathematical models with reasonably good fidelity to the physics and chemistry of ablation, …

Sprite: A Tps Test Bed For Ground And Flight, P. Agrawal, A. Cassell, N. Mangini, K. Peterson, Dinesh K. Prabhu, K. Skokova, G. Swanson, D. M. Empey, S. Gorbunov, A. Howard, J. Arnold, E. Venkatapathy

Ablation Workshop

Engineers in the Entry Systems and Technology Division at NASA Ames Research Center developed a fully instrumented, small atmospheric entry probe called SPRITE (Small Probe Reentry Investigation for TPS Engineering). SPRITE, conceived as a flight test bed for thermal protection materials, was tested at full scale in an arc-jet facility so that the aerothermal environments the probe experiences over portions of its flight trajectory and in the arc-jet are similar. This ground-to-flight traceability enhances the ability of mission designers to evaluate margins needed in the design of thermal protection systems (TPS) of larger scale atmospheric entry vehicles.

Computation Of Surface Catalysis For Graphite Exposed To High Enthalpy Nitrogen Flow, Abhilasha Anna, Iain D. Boyd

Ablation Workshop

The high temperatures on a hypersonic vehicle surface caused by heat loads encountered during (re-)entry through a planetary atmosphere require a reliable Thermal Protection System (TPS) that makes a good understanding of the physical and chemical processes essential for its design. Surface catalysis is a crucial chemical process that directly impacts aerothermal heating of the vehicle TPS. The effects of surface catalysis for graphite exposed to high-enthalpy nitrogen flow are examined in this study.