Research Projects

Title: Effect of Porosity on Shock Interaction with a Rigid, Porous Barrier

Sponsor: Rutgers University

Student: Hadassah Naiman

This work investigates the pressure amplification experienced behind a rigid, porous barrier that is exposed to a planar shock. Numerical simulations are performed in two dimensions using the full Navier-Stokes equations for a Mach 1.3 incoming shock wave. An array of cylinders is positioned at some distance from a solid wall and the shock wave is allowed to propagate past the barrier and reflect off the wall. Pressure at the wall is recorded and the flowfield is examined using numerical schlieren images. This work is intended to provide insight into the interaction of a shock wave with a cloth barrier shielding a solid boundary, and therefore the Reynolds number is small (Re=500 to 2000). Additionally, the effect of porosity of the barrier is examined. While the pressure plots display no distinct trend based on Reynolds number, the porosity has a marked effect on the flowfield structure and endwall pressure, with the pressure increasing as porosity decreases until a maximum value is reached.

Title: Analysis of Purdue Quiet Tunnel Expansion Test Section

Sponsor: Air Force Office of Scientific Research

Student: Hadassah Naiman

A proposed modification of the test section in the Boeing/AFOSR Mach 6 Quiet Tunnel at Purdue University is evaluated using CFD. The new design incorporates a section of increased diameter with the intention of enabling the tunnel to start in the presence of larger blunt models. Cone models with fixed base diameter (and hence fixed blockage ratio) are selected for this study. Cone half-angles from 15 deg to 75 deg are examined to ascertain the effect of the strength of the test model shock wave on the tunnel startup. The unsteady, laminar, compressible, laminar Navier Stokes equations are solved. The resulting flowfields are examined to see what effect the shocks and shear layers would have on the quiet test section flow. This study indicates that cone angles less than or equal to 20 deg allow the tunnel to start.

Title: Automated Optimal Design of Quiet Flow Hypersonic Wind Tunnels

Sponsor: US Air Force Office of Scientific Research

Student: Hadassah Naiman

One of the major challenges in hypersonic flow research is the accurate prediction of transition. The location and extent of laminar-turbulent transition is a critical parameter in hypersonic vehicle design due to its significant effect on predictions of aerodynamic heating, skin friction drag and other boundary layer properties. Most of the experimental data obtained from ground test facilities are contaminated by the high levels of noise that radiate from the turbulent boundary layers normally present on the nozzle walls. These high noise levels can cause transition to occur an order of magnitude earlier than in flight where rms pitot pressure fluctuations are typically less than 0.1%. Quiet flow wind tunnels have been developed to simulate hypersonic flow in flight by maintaining laminar boundary layers on the nozzle walls. The Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) at Purdue University was constructed during 1995-2001 to study transition at Mach 6. It was designed to achieve quiet flow at a stagnation pressures of 150 psi and Reynolds number of 13 million. The objectives of our research program, initiated in March 2006, are to apply modern CFD and design optimization tools to 1) extend the capabilities of the BAM6QT, and 2) develop a reliable, rational methodology for prediction, understanding and design of quiet flow wind tunnels.

Title: Electromagnetic Local Flow Control using Microwave Pulse

Sponsor: US Air Force Office of Scientific Research

Faculty: Doyle Knight

Electromagnetic} Local Flow Control (ELFC) in high speed flows has emerged as a potential alternative to conventional flow control techniques. A wide variety of technologies are investigated for ELFC including DC discharge, Dielectric Barrier Discharge (DBD), laser, microwave and combined laser/microwave. Pulsed microwave-generated plasmoids in particular have been shown experimentally to achieve significant drag reduction in supersonic flow past blunt bodies. Moreover, the power expended for the pulsed microwave is substantially less than the power savings associated with the drag reduction, thereby achieving high energy efficiency. A complete gas dynamic model of microwave energy deposition in air with full thermochemistry has been developed by our team of researchers at Rutgers University (USA), the Institute of High Temperatures (Moscow, Russia) and St. Petersburg State University (St. Petersburg, Russia). The software is denoted the Gas Dynamic Kinetic (GDK) code. The model includes 23 species and 234 reactions. The kinetic model has been validated through comparison with experimental data at the Institute for High Temperatures. The GDK code has been applied to the simulation of the interaction of a microwave plasmoid with a hemisphere cylinder at Mach 2.1. The freestream static pressure and static temperature are 26 Torr and 154 K, respectively. The cylinder diameter D is 2 cm. The microwave frequency $f$ is 9 GHz with a maximum electric field of 2.3 kV/cm and pulse duration of 1.2 mcs. The focal point for the microwave pulse is 2.5 cm upstream of the center of the hemisphere. The flow conditions and microwave parameters correspond to experiments performed at St. Petersburg State University. The figure displays the computed and experimental surface pressure on the centerline of the hemisphere surface vs time. Excellent agreement is observed.

Title: Interaction of Microwave Filament with Blunt Body in Supersonic Flow

Sponsor: US Air Force Office of Scientific Research

Student: Farnaz Farzan

Pulsed microwave energy has been demonstrated experimentally to reduce drag of aerodynamic bodies in supersonic flow. The principal mechanism is the interaction of the thin hot plasma filaments with the blunt body shock which lead to the effective streamlining of the body through creation of a separation region ahead of the body. The interaction of finite filaments with the shock layer formed ahead of a blunt cylinder is examined using the unsteady Euler equations. The basic phenomena explaining the flow structure are 1) modification of the shape of the bow shock (lensing effect), 2) generation of toroidal vortex region, 3) formation of stagnation point and consequent aerodynamic streamlining of the body, 4) convection of the vortex region past the cylinder

Title: Interaction of Microwave Filament with Blunt Body in Supersonic Flow

Sponsor: US Air Force Office of Scientific Research

Student: Kellie Norton

Recent experiments have demonstrated the capability of pulsed microwave energy deposition for drag reduction in supersonic flows. The principal mechanism of this phenomenon is the interaction of the hot filaments generated by the microwave energy pulse with the shock system formed by the aerodynamic body. In this paper, the filament is modeled as a thin fluid region of high temperature. The interaction of the filaments with a cylindrical body at in Mach 1.89 flow is examined using the compressible Navier Stokes equations. This study is an advancement of the inviscid simulations of pulsed energy deposition in supersonic flow performed by Farzan (2008). For the present research, a code is developed which includes viscous and heat transfer effects.

Title: Prediction of Protein Retention in Hydrophobic Interaction Chromatography

Sponsor: National Institutes of Health

Research Associate: Dr. Aurora Costache

Hydrophobic Interaction Chromatography (HIC) is an experimental technique for separation or purification of proteins. Since this technique is labor intensive and requires significant effort to determine the conditions for optimal separation, a computational model for predicting the behavior of proteins in HIC systems is a valuable tool. Previously, Ladiwala et al (2006) developed a Quantitative Structure-Retention Relationship (QSRR) model for protein retention time in HIC systems based on a Support Vector Machine (SVM) algorithm and using three different categories of descriptors for the proteins including a novel set of protein hydrophobicity descriptors. The present study reconsiders the experimental data of Ladiwala et al using a different approach to predict the protein retention time based on a hybrid Decision Tree and Artificial Neural Network model and traditional 2D and 3D protein descriptors. The objectives of this paper are 1) investigate the performance and sensitivity of our statistical methods, and 2) compare with the predictions of Ladiwala et al. Three different modeling scenarios are considered. The first scenario examines the accuracy of the hybrid model wherein only one half of the experimental dataset is used to train the model. This is a more restrictive approach than Ladiwala et al who used experimental data for all but two of the twenty seven proteins to train their model. Modest but reasonable accuracy is achieved in comparison of the predictions for the remaining half of the experimental dataset. The second scenario examines the accuracy of the hybrid model for one resin wherein the experimental dataset excludes those proteins which were not included in the model of Ladiwala et al. Significant improvement in the model accuracy was observed. The third scenario examined the accuracy of the hybrid model using the same training set as Ladiwala et al. Reasonable accuracy was achieved; however, the predictions of Ladiwala et al were significantly more accurate, thereby indicating that their inclusion of additional protein hydrophobicity descriptors is important.

Title: Experimental and Theoretical Investigation of Water Uptake in Polymers

Sponsor: National Institutes of Health

Research Associate: Loreto Valenzuela

Biodegradable polymers are important materials for clinical applications in medicine. For example, polylactic acid is widely used as a dissolvable suture or stent, and also for dialysis media and drug delivery devices. The physical process of biodegradation begins with the absorption of water into the polymer. This study focuses on water uptake for a library of tyrosine-derived polymers (polyarylates). Experiments are performed for measuring water uptake at discrete time points up to twenty eight days using a radioactive labeling technique. Bioinformatics methods are used to predict water uptake for the entire library of polyarylates based upon experimental measurements for a subset of the library.

Title: Prediction of Drug Binding to Polymeric Nanospheres

Sponsor: National Institutes of Health

Research Associate: Dr. Aurora Costache

Research Associate Professor: Dr. Larisa Sheihet

Delivery of drugs for clinical treatment is a challenging problem. A programmed release of drug at specified levels is optimal for various types of clinical treatments including cancer therapy. Encapsulation of drugs in biodegradable plymeric nanospheres is a recent technology that offers significant advantages over conventional therapies. An important issue is the binding efficiency of a specific drug to different types of polymers. Experiments performed at the New Jersey Center for Biomaterials have identified promising polymer-drug combinations. Prediction of drug binding to polymers is performed using the Autodock software.