Laser-Induced Thermal Treatment of Superficial Human Tumors: An Advanced Heating Strategy and Non-Arrhenius Law for Living Tissues

The most interesting, but insufficiently known results obtained by the author in modeling laser-induced hyperthermia of human tumors are discussed. It is important that the traditional equation for the local bio-heat transfer does not work in superficial layers of the body. It is shown also that the classical Arrhenius law is not applicable to living tissues because of the tissue regeneration due to oxygen supplied by the arterial blood. The latter is one of the main reasons of the suggested strategy of laser heating of tumors in the therapeutic window of semitransparency when the tumor asphyxiation is considered as one of important weapons against the cancer. The other advantages of this advanced strategy of a soft thermal treatment (in few of sessions), which is painless for patients, are discussed as well. Some features of modeling various heat transfer modes are also considered. The best choice between the simplest differential models for the radiative transfer calculations is dependent of the particular problem statement. The known finite-difference or finite element algorithms can be preferable in solving transient heat transfer problems. As a rule, it depends on the shape of the computational region. It is expected that this paper will help the colleagues to overcome some typical weaknesses of computational modeling of infrared photothermal treatment of superficial tumors.

A CFD Research on the Effect of Pre-Swirl Stator Blades Number on a Pumpjet Propulsor

In this paper, effect of different pre-swirl stator number on open water performance of a pumpjet propulsor was studied. The pumpjet propulsor consists of shaft system, pre-swirl stator, rotor and duct. The numerical simulations were based on HUST-Ship, a series of inhouse codes, solving the Reynolds Averaged Navier-Stokes (RANS) equation. The computational region was discretized by structured grids and SST k-ω turbulence equations was discretized by finite difference method. The performances of rotor, pre-swirl stator and duct were monitored separately in order to understand the effect in the thrust and the torque. It was found that with the increase of the number of pre-swirl stator blades, the thrust produced by rotor blades increased. However, the number of pre-swirl stator blades influences the thrust of stator, and may have negative effect on the total thrust. In the meantime, thrust of duct also has a little increase. With the increase of the number of pre-swirl stator blades, the propulsion efficiency increases first and then decreases.

Use of computational fluid dynamics tools to calculate the dispersion of gas and aerosol emissions in conditions of a complex terrain

ANSYS FLUENT tools were used as part of a standard turbulence k-ε model to simulate the air flow around a number of typical obstacles (a solid cube, a solid hemisphere, and a 2D hill) which form a potential terrain in the NPP emission dispersion area and roughly correspond to the geometry of the buildings and structures within this area. For reproducibility, a non-uniform spatial grid is plotted in the computational region which condenses near the obstacle surface and the outer boundaries. The dimensions and the positions of the obstacles were chosen such that to ensure their best possible coincidence with the conditions of the published experiments. The result of simulating the velocity and direction of the air flow as the whole shows a good agreement with the data from the wind tunnel experiments in the areas in front of and over the obstacle, as well as in its air shadow. Typical accelerated flow, vortex, and reverse flow areas are reproduced reliably. There are variances observed only in the local heavy turbulence regions in the obstacle’s air shadow near the ground surface. All this indicates that it is possible to model in full scale the dispersion of the NPP emissions taking into account the peculiarities of the plant site terrain and the major onsite structures to determine more accurately the personnel and public exposure dose.

AN EXPERIMENTAL STUDY ON WAVE RUNUP ON QUAY TOP AND ITS REPRODUCTION BY USING A BOUSSINESQ-TYPE WAVE MODEL

Ports and coastal industrial and commercial regions in Osaka bay were inundated with water due to storm wave overtopping during Typhoon Jebi passing through on September 4, 2018. Although the large storm surge was observed at the end of the bay, the sea level rarely rises over seawalls which prevent sea water from intruding onto residential areas, fortunately. Therefore, in this study, the characteristics of wave runup over the gap between berthing depth and quay top in high, normal and middle tide condition are investigated with vertical 2D model experiments. Moreover, numerical simulations are conducted by using a Boussinesq-type wave model, which can be also applied to wave overtopping and inundation in horizontal 2D computational region, to reproduce the results of model experiments.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/HCiUoj68xyY

Numerical Modeling of Electroelastic Fields in the Surface Piezoelectric Luminescent Optical Fiber Sensor to Diagnose Deformation of Composite Plates

We developed a three-dimensional numerical model of a piezoelectric luminescent optical fiber sensor fixed on a composite’s plate. The computational region of the sensor is the optical fiber with two concentric (with 6 sectors) shells of electroluminescent and piezoelectric materials, two control electrodes on interface surfaces, such as optical fiber-electroluminophore and piezoelectric-cover. The external sensor’s cover is made in the form of a semi-elliptic cylindrical polymer shell, which rectangular base is fixed on the surface of the fiberglass plate. In the piezoelectric shell sectors, the polarization directions of the PVDF transversal-isotropic polymer piezoelectric are different and non-planar for any three sectors. Deformation of the plate causes deformation of the sensor fixed on its surface, as well as the occurrence of informative piezoelectric fields in it, thus the occurrence of informative glows of electroluminescent elements. As a result, we find the requested information about the combined deformed state of the composite plate along the length of the sensor based on the digital processing of the integral intensities of the polychrome light signals at the output of the optical fiber. In simple cases of electric and mechanical loads, we present new numerical results of simulating the distribution of non-uniform electroelastic fields in the sensor multiphase volume, the sensor’s external cover and inside fragment of the composite plate. Loading of the sensor-covering-plate system is performed by controlling electric voltage on the sensor’s electrodes and the plate’s mechanical deformation by stretching along the transverse and longitudinal axes, as well as by twisting around these axes and bending in transverse and longitudinal planes. Numerical values of the control and informative transfer coefficients of the piezoelectric luminescent optical fiber sensor are determined, which makes it possible to perform a reliable and high-precision diagnostics of complex deformations of the composite plates and design sensors of this type.

Methods of simulating the front of the air shock wave for calculating the industrial structure

Introduction. The paper considers existing methods of simulating a wide front of an air shock wave for solving problems of shock wave interaction with an installation using gas-dynamic methods. When solving the problem of the air shock wave interaction with an installation in a dynamic setting, it was revealed that, when simulating a wide front of a distant explosion using point explosions, it is possible to obtain an underestimated time of the shock wave action. This results in a downward bias of loads to the installation. Thus, the loads obtained in this case do not correspond to the loads for which it is necessary to carry out the calculation of industrial installations protected from shock waves in accordance with domestic and international regulatory documents. To eliminate this drawback, another approach is proposed. It consists in setting the load on the computational region in the form of a pressure graph with specified parameters of overpressure and exposure time. Materials and methods. The interaction of the shock wave front with the installation is carried out using numerical simulation in a nonlinear dynamic setting using gas-dynamic methods in the LS-DYNA software package. Results. The following analyses were conducted in the scope of the study: an analysis of existing methods of forming the wide shock wave front of the distant explosion and an analysis of the parameters of the shock wave during the formation of the wide shock wave front of the distant explosion by setting the pressure graph with the specified parameters of the overpressure and the exposure time. Conclusions. The result of the analysis of methods for numerical simulation of the interaction of the air shock wave wide front with the installation showed that simulation of the explosion source in the form of volume elements and simulation of the shock wave using the CONWEP function of the LS-DYNA software package have disadvantages. These disadvantages do not allow obtaining the main parameters of the shock wave for the further use. A method for modeling the wide shock wave front is given by setting a pressure graph at the boundary of the computational region with the required overpressure parameters and exposure time.

Multidisciplinary Design Optimization of a Bladed Disc for Small-Size Gas-Turbine Engines

One of the most important units of small-size gas-turbine engines (GTE) is a turbine bladed disk, since it determines the total engine efficiency. Designing a turbine disks is a complex challenge due to the high loads and a large number of structural and technological constraints, as well as a variety of requirements to the bladed disks for small-size GTEs (higher efficiency, lower mass and adequate strength characteristics, etc.). Diverse requirements to the turbine bladed disks mean that modifying the structure in order to improve some characteristics will degrade other characteristics. A standard solution to this problem is to use the iterative approach, which reduces the design process to a consecutive iteration of setting and solving design problems concerning the bladed disk elements (blade and disk) separately for different aspects. The main drawback of this approach is its tremendous labor intensity and inferior quality of design, as this procedure does not consider the design object as a single entity. This paper proposes an approach to the turbine bladed disks design based on the use of a single multidisciplinary parametrized 3D model that contains several specialized submodels. These submodels define the essential computational regions, as well as the characteristics of the physical processes and phenomena in the object under study. The model also enables integration and interaction of the submodels in a single computational region. The single multidisciplinary model is modified and analyzed automatically, so the design problem is transformed into a multi-criteria optimization problem where the weight, gas dynamic and strength characteristics are used as criteria or constraints, and they are improved by varying the geometric parameters of the blade and disk. Each submodel simulates and analyzes the essential characteristics at the level comparable to the standard engineering calculations. Therefore, the designs obtained as a result of optimization do not need significant improvements, which facilitates and enhances the design process. The development of an integrated model is time consuming, but since the design and operation of bladed disks are similar, the created parametrized multidisciplinary 3D model can be used in the design of other similar disks after minor alternations taking into account the specifics of the new task.

Improvement of Combustion Process of Spark-Ignited Aviation Wankel Engine

This paper deals with the creation of modern high-performance aircraft power units based on the Wankel rotary piston engine. One of the main problems of Wankel engines is high specific fuel consumption. This paper solves the problem of improving the efficiency of this type of engine. The mathematical model of non-stationary processes of transfer of momentum, energy, mass, and the concentration of reacting substances in the estimated volume provides for the determination of local gas parameters in the entire computational region, which are presented as a sum of averaged and pulsation components. The k-ζ-f model is used as the turbulence model; the combustion is described by the coherent flame model (CFM) based on the concept of laminar flame propagation. As a result of the calculation, we obtained the values of temperature, pressure, and velocity of the working fluid in the working chamber cross-sections of a rotary–piston engine. Various options of the rotor recess shape are considered. Based on the data obtained, the rotor design was improved. The offered shape of the rotor recess has reduced emissions of both nitrogen oxides and carbon dioxide.

NUMERICAL MODELING AND SOFTWARE FOR DETERMINING THE STATIC AND LINKAGE PARAMETERS OF GROWING BODIES IN THE PROCESS OF NONSTATIONARY ADDITIVE HEAT AND MASS TRANSFER

Currently, methods of three-dimensional printing of products from polymer, metal and ceramic materials are widely used. Layer-by-layer synthesis technologies make it possible to obtain high-quality products with sufficiently high mechanical characteristics close to those realized using traditional technological processes. A related problem is solved, including calculating the temperature in the product and the operation area surrounding it in a flat setting based on two different approaches. For a layer-by-layer extensible body, the unsteady heat conduction problem is stated. At each step, the height of the computational region increases due to the filling of a new layer of powder. One time step of the calculation is determined by the interval between two consecutive passes of the laser. The temperature distribution found at each step is used as the initial conditions for the calculations at the next step. The temperature field obtained as a result of solving the problem that is implemented in the product in question with a step of 1000 (after applying and melting 1000 layers) is further compared with the solution of the quasi-stationary problem for the finite dimensions product. Using the example of the simple geometry taken, it is shown that a quasi-stationary solution can provide a satisfactory estimate of the macroscopic thermal state of the growing product.

Numerical simulation of swirling airflow dynamics in vortex spinning

In this paper, a computational fluid dynamics model has been established and a three-dimensional numerical simulation of the flow characteristics of airflow in a vortex spinning nozzle has been carried out. A realizable k-ɛ model is used to simulate the turbulence of airflow in the nozzle. Unstructured tetrahedral grids which have good adaptability to complex boundaries are used in this paper to mesh the computational region. The computational model of the airflow field is solved and the characteristics of airflow in a vortex spinning nozzle are obtained. The results show that the flow principle of the airflow is determined by the pressure distribution of the airflow. The airflow field in the nozzle can be divided into external and internal areas, according to the flow characteristics and functions of airflow. The trajectory of swirling airflow from the jet orifices has a regular rotational motion within the twisting chamber, but the trajectory of swirling airflow from nozzle inlet is complex and backflow occurs; finally, these two strands of airflow are fused together as a regular rotational motion.