流体力学：开放获取

Thermal comfort in vehicle cabin can affect drivers and passenger’s health, performance and comfort. Due to spatial and temporal variation of state variables and boundary conditions in the vehicle cabin , the heating, ventilating and air-conditioning (HVAC) does not have to be designed to provide a uniform environment, especially because of individual differences regarding to physiological and psychological response, clothing insulation, activity, air temperature and air movement preference, etc. The main objective of this research is to study the air flow regimes and thermal comfort in vehicle cabin using computational fluid dynamics (CFD) software. For this purpose, the CFD software from ANSYS Inc., called FLUENT 17.2, is employed. In which the solar load model is embedded s2s (surface to surface) as a solar radiation model. The CFD modeling techniques solved the continuity, momentum and energy conservation equations in addition to standard k – ε model equations for turbulence closure (The use K-epsilon turbulence mode was recommended as it had been widely tested and investigated in the seventies of last century). Meshing is processed around 4.0 million unstructured tetra-elements approximately. The performance of the air conditioning system is characterized by airflow regimes (air temperature, air velocity, relative humidity, PMV and PPD contours), the present work is focus on the effect of air terminal shape of Hvac system, two configurations are used case (1) and case (2). Case (1) is the existing design of air terminals of the Hvac system of the selected car (Skoda Superb), the air terminals are in rectangular shape. While case (2) are in circle shape

In this paper, we provide some interesting spot calculations from the Theory of Elastic Stability. Certain key constants of Cusack’s Astrotheology are derived from basic structural mechanics’ formula. No attempts for proofs are made. The reader is referred to Timoshenko and Gere’s classic book on stability. Proton Mass was determined to be within the margin of error.

The paper presents the study of the influence of surface tension and cohesive angle changes on the behavior of bubbles (drops), fixed on the solid surface, in decreased gravity and microgravity conditions. A new mathematical model of the behavior of the gas bubbles (drops), fixed on the solid surface under the surface tension and cohesive angle changes in decreased and microgravity and has been developed. The developed model permitted to numerically calculate the gas bubbles (drops) profiles behavior and their common surface energy change under surface tension and cohesive angle changes in decreased gravity and microgravity conditions. The developed model permitted also to estimate conditions of bubbles (drops) tear from and fixation on the solid surface under surface tension and cohesive angle change in these conditions. These calculations and estimations have been proved on the conducted parabolic aircraft's tests. The tests showed that the developed model can correctly simulate the gas bubbles and drops profiles behavior, precisely calculate their common surface energy change and estimate conditions of their tear from and fixation on the solid surface in reduced and microgravity conditions.

The law of conservation of energy is an empirical based physical law, which states that energy can neither be created nor be destroyed; it can only be converted into another. As example the EME system transforms from electrical to mechanical and again to electrical energy. For a closed system like the EME, this means that the total energy is unchanged with time. The law of conservation of energy can be breached due to the uncertainty principle of Heisenberg; it has to do with "position and momentum”.

Pyramid Mekaniska Konsult (PMK) has defined the problems referable to the “Golden Role of Mechanics” which rule stipulates “What is gained in power is lost in working distance” by using two independent axels in the closed “inertial” system. The EME system separates the two variables in the pulley system.

Materials are the heart and soul of photovoltaic devices. Based on the nature of materials, photovoltaics (solar cells) have been classified into various types. Based on its classifications many oxide and metallic materials are mainly used for photovoltaic applications. Device structure and nature of materials are very critical for the overall efficiency and performance of photovoltaics. However here in this particular review we will be only converging on the nature of various materials used to develop solar cells and their performances by using the materials of C, Cd, In doped Selenides and Telluride. Likewise the use of nanomaterials for biosensors based in thin film, particularly carbon based materials and its doping with selenides and telluride have attracted considerable attention due to provide a high surface-volume ratio, faster electron transfer and label-free responses. This review discussed these materials and its efficiencies.

In this paper are developed modifications of the Godunov scheme, based on Kolgan's scheme of the second order of accuracy in the spatial variables for smooth solutions. It is constructed schemes of the first and the variable order of approximation, which exceed the Godunov scheme in accuracy. Referencing to the system of differential equations for propagation of flat sound waves in a gas at rest, the Kolgan scheme and the first-order schemes obtained are investigated onto the ability to ensure the non decrease of entropy, that is, to product of physically justified numerical solutions. The test problems of nonlinear gas dynamics on the decay of a discontinuity in a pipe and the transformation of a non uniformity in a plane-parallel flow are solved. Cylindrical explosion task is considered as the main one. The stability of a contact discontinuity behind a blast wave is investigated numerically in the Cartesian and polar coordinate systems. Analysis of obtained and published solutions does not confirm the instability of the contact discontinuity which initially has the circular shape. Change of the shape of initially perturbed break is largely caused by the instability of Taylor, not Richtmyer-Meshkov. Calculations are partially fulfilled using supercomputer “Lomonosov” of Moscow state university.

The tombs of the kings in Valley of the Kings, Luxor, are considered to be one of the tourism industry’s bases in Egypt due to their uniqueness all over the world. Hence, they should be preserved from the different factors that might cause harm for their wall paintings. One of these factors is the excessive relative humidity as it increases the bacteria and fungus activity inside the tomb in addition to its effect on the mechanical and physical properties of materials. This chapter describes the Research work to design ventilation systems to some of these important tombs. The chapter aims to investigate, design, and implement controlled climate to the tombs of the valley of kings with complete monitoring of air properties, temperature, relative humidity and carbon oxides and air quality parameters mechanical distributions inside selected tombs of the valley of the kings that are open for visitors. A complete climate control and monitoring of air will be effected with the aid of a mechanical ventilation system extracting air at designated locations in the wooden raised floor of the tombs. The location, size and extracted air are to be predicted and optimized the use of Computational Fluid Dynamics software (CFD). The CFD modelling techniques would solve the continuity, momentum, energy, and species transport equations in addition to k-epsilon model equations for turbulence closure. The SIMPLEC algorithm is used for the pressure-velocity coupling and a second order upwind scheme was use for discretization of the governing equations. Mesh sizes used in the present work exceeded 700,000 mesh volumes to adequately represent the flow characteristics at various locations. Throughout the first phase of this investigation, the outside air conditions, number of visitors, and airside system design effect on the tombs’ airflow characteristics will be studied in order to reach the optimum ventilation design as well as the favourable working conditions for a particular tomb. Mechanical engineering design of air flow system including under raised floor flexible duct routings, sizes, grills locations etc. with be provided in professional design drawing to be used as bases for execution and installation at the second phase. A complete set of measuring and monitoring equipment will be installed for each tomb to intelligently direct the visitors to the tomb where relative humidity and CO2 levels are permissible. A permissible number of the simultaneous of visitors for each tomb should be made in order to limit the relative humidity inside any given tomb.