Isaiah M. Blankson

Solving the MHD equations by the space-time conservation element and solution element method

We apply the space-time conservation element and solution element (CESE) method to solve the ideal MHD equations with special emphasis on satisfying the divergence free constraint of magnetic field, i.e., @?.B=0. In the setting of the CESE method, four approaches are employed: (i) the original CESE method without any additional treatment, (ii) a simple corrector procedure to update the spatial derivatives of magnetic field B after each time marching step to enforce @?.B=0 at all mesh nodes, (iii) a constraint-transport method by using a special staggered mesh to calculate magnetic field B, and (iv) the projection method by solving a Poisson solver after each time marching step. To demonstrate the capabilities of these methods, two benchmark MHD flows are calculated: (i) a rotated one-dimensional MHD shock tube problem and (ii) a MHD vortex problem. The results show no differences between different approaches and all results compare favorably with previously reported data.

Perspectives on the Interaction of Plasmas With Liquid Water for Water Purification

Plasma production or plasma injection in liquid water affords one the opportunity to nonthermally inject advanced oxidation processes into water for the purpose of purification or chemical processing. Such technology could potentially revolutionize the treatment of drinking water, as well as current methods of chemical processing through the elimination of physical catalysts. Presented here is an overview of current water treatment technology, its limitations, and the future, which may feature plasma-based advanced oxidation techniques. As such, this field represents an emerging and active area of research. The role that plasma-driven water chemistry can play in addressing emerging threats to the water supply is discussed using case study examples. Limitations of conventional plasma injection approaches include limited throughput capacity, electrode erosion, and reduced process volume. At the University of Michigan, we are investigating two potential approaches designed to circumvent such issues. These include direct plasma injection using an underwater DBD plasma jet and the direct production of plasmas in isolated underwater bubbles via a pulsed electric field. These approaches are presented here, along with the results.

Passive millimetre-wave imaging architectures

This paper discusses various passive millimetre-wave imaging systems. It includes sources of radiation, atmospheric transmission and a brief summary of their various applications. This is followed by a review of methods for detecting millimetre-wave radiation. From a cost analysis it is shown that scanned systems are at present far more cost effective than focal plane array of receivers for high-performance systems. Then various types of imaging system available are considered with greater emphasis on recent developments and their methods of beam forming. It is concluded that at present, and for the foreseeable future, optical beam forming and beam steering are the most cost-effective solutions. Some general remarks are included as to how receivers are matched to their collection apertures, followed by a section on optical beam-forming components. The recent development of a lightweight, low-cost, high-performance reflective lens is included. It is then shown how this may be combined with mechanical scanning systems to form high-performance passive millimetre-wave imaging systems.

Review of imaging architecture

This paper reviews various passive mm-wave imaging systems. It includes sources of radiation, atmospheric transmission and a brief summary of their various applications. This is followed by a review of methods for detecting mm-wave radiation. From a cost analysis it is shown that scanned systems are at present far more cost effective than focal plane array of receivers for high performance systems. There is a review of the various types of imaging system available with greater emphasis being placed on recent developments and their methods of beam forming. It is concluded that at present, and for the foreseeable future, optical beam forming and beam steering are the most cost effective. Some general remarks are included as to how receivers are matched to their collection apertures, followed by a section on optical beam forming components. The recent development of a lightweight, low cost, high performance reflective lens is included. It is then shown how this may be combined with mechanical scanning systems to form high performance passive mm-wave imaging systems.

Design and development of a high-performance passive millimeter-wave imager for aeronautical applications

This paper describes a high performance opto-mechanically scanned mm-wave imager intended to monitor the ground movement of aircraft in adverse weather conditions. It employs two counter-rotating mirrors that are tilted about their axes of rotation. They simulate the linear scan of a single high speed, large aperture flapping mirror. When used with a linear receiver array they can produce a two-dimensional scan of the scene at TV rates. In the present application they were used with a single receiver and a large flapping mirror to produce a two-dimensional scan of the scene of ±10° vertically and 60deg; horizontally. One of the rotating mirrors had a concave surface and acted as the focusing element in the imager. The two mirrors were driven from a single servo motor using timing belts and toothed pulleys. The flapping mirror was slaved to the motion of the rotating discs using an electronic cam. The single channel 94GHz receiver consisted of an InP LNA followed by a down-converter and a detector. The video output passed to an A/D converter and was displayed on a conventional PC. This system has virtually 100% transmission and can be used at any waveband.

Exo-Skeletal Engine: Novel Engine Concept

The Exo-Skeletal Engine concept represents a new radical engine technology with the potential for a substantial revolution in engine design. It is an all composite drum rotor engine in which conventional heavy shafts and discs are eliminated and are replaced by rotating casings that support the blades in spanwise compression. Thus the rotating blades are in compression rather than in tension. The resulting open channel at the engine centerline has immense potential for jet noise reduction, and can also accommodate an inner combined-cycle thruster such as a ramjet. The Exo-Skeletal Engine is described in some detail with respect to geometry, components and potential benefits. Initial evaluation, results for drum rotors, bearings and weights are summarized. Component configuration, assembly plan and potential fabrication processes are also identified. A finite element model of the assembled engine and its major components are described. Preliminary results obtained thus far show at least 30 percent reduction of engine weight and about 10 db noise reduction, compared to a baseline conventional high bypass-ratio engine. Potential benefits in all aspects of engine technology are identified and tabulated. Quantitative assessments of potential benefits are in progress.Copyright

Problem of the radiovision system resolution improvement in millimeter-wave range

At the Faculty of Physics of Moscow State University experimental researches of the working radiovision systems on the base of phased antenna array and radio optical systems with the sensors rules are carried out. Since 1980 the system of Sun radio observation in 3-mm wavelength range created by the specialists of Bauman Moscow State Technical University is exploited. Investigations in the mathematical modeling of image formation systems in wide wavelength range with different receiving schemes and with distortion compensation task solution and super-resolution are conducted by mathematician and physicists.

Unsteady Fluid Structure Interaction in a Turbine Blade

An unsteady, three dimensional Navier-Stokes solution in rotating frame formulation for turbomachinery applications has been described. Casting the governing equations in a rotating frame enables the freezing of grid motion and results in substantial savings in computer time. Heat transfer to a gas turbine blade was computationally simulated by finite element methods and probabilistically evaluated in view of the several uncertainties in the performance parameters. The interconnection between the CFD code and finite element structural analysis code was necessary to couple the thermal profiles with the structural design. The stresses and their variations were evaluated at critical points on the turbine blade. Cumulative distribution functions and sensitivity factors were computed for stresses due to the aerodynamic, geometric, material and thermal random variables. These results can be used to quickly identify the most critical design variables in order to optimize the design and make it cost effective. The analysis leads to the selection of the appropriate materials to be used and to the identification of both the most critical measurements and parameters.© 2005 ASME

Characterization of electron density depletion in a cathode spot driven dusty plasma for reentry vehicle communications applications

Communications blackout, which is experienced by spacecraft re-entering the atmosphere at hypersonic velocities, is caused by the formation of a dense plasma envelope produced by shock heating. Communication signals at frequencies below the plasma cutoff frequency cannot propagate through this layer. Methods suggested for mitigating blackout have included aerodynamic shaping, magnetic windows, and the use of quenchants to reduce plasma densities. The Gemini 3 mission in 1965 successfully used water as a quenchant to cool the reentry plasma and increase communication signal strength.

Further designs of optomechanical scanners for use in passive millimeter-wave imaging

Mm-wave imaging has high potential for all weather performance but requires large apertures to acheive acceptable spatial resolution. These large apertures need to collect radiation from a range of angles in the field of view and form a two dimensional image. The ideal method for achieving such an image would be to have an aperture completely filled with receivers and to electronically beam-form. Unfortunately this technology is not sufficiently developed at present to make this a practical propostion. Receivers are far too expensive to form a completely filled aperture and the technology of beam-forming is still under development. The alternative and most cost effective solution at present is to have a comparatively small number of receivers and scan them across the scene using an opto-mechanical scanner. In scanned thermal imaging systems it is usual to employ high speed rotating polygons to perform the line scan and a flapping mirror for the framing motion. The pupil size is typically 10mm in thermal imaging and the polygons are 40mm in diamenter. If such an arrangement were used at mm-waves where the pupil size is of the order of 1m, the rotating polygon would be 4m in diameter. The paper describes new compact opto-mechanical systems based on rotating discs, prisms and using frequency and polarization selective surfaces.