Konstantin I. Matveev

Spatio-temporal modeling of nanoparticle delivery to multicellular tumor spheroids

The inefficiency of nanoparticle penetration in tissues limits the therapeutic efficacy of such formulations for cancer applications. Recent work has indicated that modulation of tissue architecture with enzymes such as collagenase significantly increases macromolecule delivery. In this study we developed a mathematical model of nanoparticle penetration into multicellular spheroids that accounts for radially dependent changes in tumor architecture, as represented by the volume fraction of tissue accessible to nanoparticle diffusion. Parameters such as nanoparticle binding, internalization rate constants, and accessible volume fraction were determined experimentally. Unknown parameters of nanoparticle binding sites per cell in the spheroid and pore shape factor were determined by fitting to experimental data. The model was correlated with experimental studies of the penetration of 40 nm nanoparticles in SiHa multicellular spheroids with and without collagenase treatment and was able to accurately predict concentration profiles of nanoparticles within spheroids. The model was also used to investigate the effects of nanoparticle size. This model contributes toward the understanding of the role of tumor architecture on nanoparticle delivery efficiency. Biotechnol. Bioeng. 2008;101: 388–399.

Complex numerical modeling of dynamics and crashes of wing-in-ground vehicles

The Wing-In-Ground craft (WIG), a vehicle flying in the ground effect, is a promising transportation means of the near future. This paper describes mathematical modeling of WIG motion in all regimes, such as planing, take-off, transition to flight, and flight itself. The model, which includes nonlinear hydroaerodynamics, serves as a base for simulation of motion. The theory developed here enhances the process of designing WIG vehicles; its advantages and disadvantages are discussed. The results of numerical modeling are compared with experimental data obtained for planing and flight regimes of motion. The model is applied for studying emergency problems in WIG operation.

Modeling of hard-chine hulls in transitional and early planing regimes by hydrodynamic point sources

A linear potential-flow method based on hydrodynamic point sources is developed for modeling steady hydrodynamics of hard-chine hulls. Source singularities are distributed on the wetted hull surface and on the free water surface. The wetted hull area is not known in advance and is found iteratively. The outcome of the model is the pressure distribution on the hull and the water surface elevations. Validation studies with two- and three-dimensional hull forms demonstrate good agreement for the lift coefficient and center of pressure in transitional and early planing regimes. The near-field wake wash reasonably agree with empirical data for wave profiles behind a planing plate and for the trough position behind a submerged hydrofoil. The flexibility of the current method allows modeling of a variety of hull forms and systems with hydrodynamically interacting elements.

On the Coupling Between Standing-Wave Thermoacoustic Engine and Piezoelectric Transducer

Small thermoacoustic engines integrated with piezoelectric elements can be effective small-scale power sources to convert heat to electricity. A simplified mathematical model is developed to illustrate the effect of transducer parameters on the frequency and onset temperature difference in a standing-wave engine and to estimate efficiencies of energy conversion. Results of sample calculations show that efficiencies for the acoustic-electric energy conversion on the order of 10% are feasible.Copyright

Modeling of Finite-span Ram Wings Moving Above Water at Finite Froude Numbers

Power-augmented ram wings can be used for very fast transportation of heavy cargo over water and relatively flat solid surfaces. This article describes a coupled aerohydrodynamic model for a ram wing in steady forward motion. Effects of a finite wingspan and finite Froude numbers are accounted for by the extreme ground effect theory for airflow and a linearized potential flow theory for water. Representative results showing the influence of several variable parameters of the vehicle geometry and operational regimes are demonstrated for a selected ram-wing configuration. The developed method can be applied for modeling of airborne lifting surfaces operating in the strong ground effect on a variety of fast marine craft.

NUMERICAL MODELING OF A PLANAR UNCONFINED OBLIQUE JET MOVING ALONG THE GROUND SURFACE

Abstract Power-Augmented-Ram (PAR) and Vertical/Short Takeoff and Landing (V/STOL) vehicles use jet support at low speeds when the passive aerodynamic lift is not sufficient. Although V/STOL aircraft have been previously investigated, the PAR concept requires further understanding of the obliquely impinging jet. Previous modeling studies on jet impingement considered jets exiting from domain boundaries. However, many jet applications are not confined in the upward direction and require modeling of airflow entering the jet source. The unconfined jet, modeled as a ducted momentum source, is investigated in this work. The computational approach consists of a two-dimensional, steady, incompressible finite volume method utilizing the k-ε turbulence model. The numerical approach is validated for the planar turbulent free jet, jet normally impinging on the ground, and jet entering a channel under a ground-effect platform. New results are obtained for obliquely impinging jets moving along the ground. Flow structures are studied with focus on the upstream ground vortex, jet entrainment, downstream momentum flow, and effects of jet translating through a stagnant fluid. Beneficial aerodynamic configurations, which reduce ingestion and maximize downstream momentum flow, suggest small impingement angles and moderate ground distances.

Hydrodynamic modeling of semi-planing hulls with air cavities

Abstract High-speed heavy loaded monohull ships can benefit from application of drag-reducing air cavities under stepped hull bottoms. The subject of this paper is the steady hydrodynamic modeling of semi-planing air-cavity hulls. The current method is based on a linearized potential-flow theory for surface flows. The mathematical model description and parametric calculation results for a selected configuration with pressurized and open air cavities are presented.

Car-Top Test Module as a Low-Cost Alternative to Wind Tunnel Testing of UAV Propulsion Systems

In an effort to assess motor and propeller performance for small unmanned aerial vehicles (UAVs), a car-top test module has been developed. This device allows for characterization of propeller and motor combinations in mean flow without the investment that is inherent with wind tunnel testing. Additionally, propulsion systems can be tested for reliability in real-world environments without risk to an airframe. Measurements of the propeller efficiency, thrust coefficient, power coefficient, and temperature of the motor and the electronic speed controller as initial parameters of interest are reported. Thrust at different advance ratios is compared to data from wind tunnel testing in order to gauge the accuracy of this technique. The module performed well in its intended role, and it is recommended that similar devices be used for time-critical or low-cost applications.

Dynamics and Stability of Boats With Aerodynamic Support

Aerodynamic support is beneficial for achieving very high speeds of marine transportation. Wing-in-ground vehicles, power-augmented ram platforms, and ultrafast planing multihulls are examples of marine craft with air assistance. The main technical problems in the development and application of these concepts for marine transportation are to ensure motion stability and to provide adequate seaworthiness. In this article, the authors illustrate applications of several mathematical models for various air-supported marine vehicle concepts and discuss their specific stability issues. The aerodynamic submodels are based on nonlinear vortex-lattice methods and on the extreme ground effect theory, whereas unsteady hydrodynamics of planing surfaces are treated with added-mass strip theories. The static and dynamic stability in the vicinity of equilibrium states can be analyzed by linearized approaches. However, motions in transient regimes and unsteady environments require implementation of nonlinear and fully unsteady modeling methods.

Jet-induced pressure distribution under platform in ground effect

Power Augmented Ram (PAR) vehicles are supported by the dynamic air cushion formed by air jets injected below the vehicle platform. An experimental study has been undertaken to determine steady-state pressure distribution under a static PAR model. Main controlled parameters include the jet thickness, platform height, and deflection of the aft flap in a quasi-two-dimensional system. The potential-flow theory with empirical corrections for the jet expansion provides realistic pressure estimations for the high-pressure zone under the platform. Conducted tests confirm high lift efficiency of PAR systems and demonstrate variations in the centre of pressure with changing the aft flap position.