流体力学：开放获取

It is my pleasure to write a few words giving an editorial overview of this important and promising *Open Access* journal on the subject of Fluid Mechanics. I choose to base my comments and observations upon the content of its most recent issue (Volume 3, Issue 1, 2006).

Increasing of occupant comfort demands are leading to rising requirement for air conditioning, but deteriorating global energy and environment crisis are starving for energy saving and environmental protection. The need to come up with the new energy saving as well as environmental friendly air conditioning systems has been more urgent than ever before.

In hot and humid areas, the liquid desiccant air-conditioning systems based on evaporative cooling was proposed as an alternative to the traditional vapor compression systems due to its advantage in, removing the air latent load, friendly to environment, removing of pollutants from the process air and reduction of the electrical energy. In this project, recent researches and development activities in liquid desiccant dehumidification systems combined with evaporative cooling technologies are surveyed.

Following that, such a liquid dehumidifier is fabricated. In this system, CaCl2 salt solution is used for dehumidification of air. Strong solution is internally cooled to minimize heating up of the solution which causes reduction in its absorbing capacity. Evaporative cooling that follows is more effective because dehumidified air flows over cooling water spray. Weak solution is regenerated by an electric heater. Finally air gets cooled and dehumidified. Heating for regeneration can be done using any cheap heat source like waste heat, solar energy.

Direct evaporative cooling gives good effect in dry areas. Its effectiveness is not much in humid areas. To be suitable for such high humidity conditions in this system air is dried first, using cacl2 salt solution. Heat is generated during dehumidification. Cooling water is circulated to absorb this heat. Evaporative cooler also cools the salt solution after it got regenerated by heating.

The automobile industry has shown increased interest in the replacement of steel springs with fiberglass composites leaf spring due to high strength to weight ratio. The main aim of the project is to find the effects of replacement of the leaf spring and composite leaf spring made of E-Glass Epoxy is carried out. Comparing the load carrying capacity, stresses, stiffness, contact stiffness, and weight savings of the composite leaf spring with that of steel leaf spring is performed. The design constraints are stresses and deflections.

Finite element analysis with 3-D model of 9.525 mm thick leaf springs by introducing the contact pair in between the leafs a non-linear static analysis for the steel and composite material was done using ANSYS. The results are compared with the theoretical values and found in permissible limit.

The analysis is performed in three phases. They are by varying the load applied on the leaf springs, by varying the normal penalty stiffness (FKN) of contact pair, by varying the thickness of the composite leaf spring.

By varying the load and normal penalty stiffness the behavior of the steel and composite material multi-leaf spring is analyzed and the results are compared and holds good for composite material.

Since the composite leaf spring at 9.525 mm thickness is having the higher stiffness than required value for the comfort ride, so it is modified by reducing the thickness of the leaf spring from 9.525 mm to 8 mm and analysis is carried out and compared. From this analysis it is found that the composite leaf spring had 29.981% lesser stresses, 12.951% of higher stiffness than that of the steel leaf spring. The obtained results for varying thickness of composite leaf spring compared to the steel leaf spring are satisfactory. Due to the thickness variation the weight reduced of 69.48% was achieved. It is found that the obtained natural frequency of 8 mm thick composite leaf spring is away from the road irregularity usually have maximum frequency (12Hz) therefore resonance will not occurs and it provides improved ride comfort.

Overall engine performance of an engine can be obtained from the proper design of engine exhaust systems. With regard to stringent emission legislation in the automotive sector, there is a need design and develop suitable combustion chambers, inlet, and outlet manifold. Exhaust manifold is one of the important components which affect the engine performance. Flow through an exhaust manifold is time dependent with respect to crank angle position. In the present research work, numerical study on four-cylinder petrol engine with two exhaust manifold running at constant speed of 2800 rpm was studied. Flow through an exhaust manifold is dependent on the time since crank angle positions vary with respect to time. Unsteady state simulation can predict how an intake manifold work under real conditions. The boundary conditions are no longer constant but vary with time. The main objectives that to be studied in this work is: • To prepare the cad model in the CATIA software by using the actual parametric dimensions. • To prepare finite element model in the Computer aided analysis software by specifying the approximate element size for meshing. • To find and calculate the actual theoretical values for the input boundary conditions. • To study the flow patterns generated due to the flow of the exhaust gases from the manifold. • To study the velocity and pressure distribution in ports at maximum flow rate. • To study the static pressure drop, total pressure drop, and energy loss in the flow pattern generated in the exhaust manifold.

Over a century ago a Dutch physician, Willem Einthoven, developed a galvanometer that could record the voltages produced during the cardiac cycle using electrodes placed on the body surface. Einthoven assigned the letters P, Q, R, S and T to the various deflections, a terminology that is still in use today. His seminal discovery eventually led to the clinically useful field of electrocardiography, and Einthoven received the Nobel Prize in Medicine in 1924.

The reference length or scale length used in Reynolds number definition is of considerable importance. A quick review of Reynolds number definitions used in batch and continuous flow systems showed that this reference scale can be theoretical or conventional. Using curvature quantity coming from general relativity theory, we showed that Reynolds number could be seen as the ratio of two curvatures. This result could give interesting information for the design of high performances exchangers. Moreover, the use of curvature allowed establishing a relationship between momentum diffusivity and velocity gradient tensor. Applied to general relativity equation, we showed a strong link between gravity theory and hydrodynamics.

The suspension culture system is an increasingly popular method of culturing cells not only because of its up scaling ability, but also the non-enzymatic procurement of cells that is crucial for biomedical research, especially in the fields of pharmacology and regenerative medicine. Hypothetically, by controlling and reducing the shear stress applied to cells in a culture system, the higher viability and proliferation rates. In this study, we analyzed HEK 293 cells cultured with a commercially available spinner flask and our newly developed spinner flask which utilizes the theory of Couette flow for controlling shear stress. Fluid analysis and metabolic analysis of the cultured cells were measured at three different rotational speeds, 40, 50 and 60 rpm. It was apparent that 50 rpm was by far the best speed to proliferate the cells. A further viability test was also done in order to validate our hypothesis. Furthermore, by using the metabolic analysis results, it was observed that in the controlled stress system, the consumption of glucose doubled and lactate production was significantly higher compared to cells that were maintained in the conventional suspension method. Thus, Couette flow based suspension culture system will be a major contributor to the future biomedical and pharmacological field.

The unsteady MHD Non-Newtonain incompressible casson fluid flow due to a porous rotating disk with a uniform angular velocity in the presence of an axial uniform magnetic field and a uniform electric field is examined. The Hall current is not considered in this paper. The governing equations of the problem are then reduced to non-linear ordinary differential equations by introducing suitable similarity parameters. The similarity equations are derived in such a way that one can see the effects of the angular velocity explicitly unlike the usual similarity transformation of rotating disk problems. Numerical solutions to the reduced non-linear similarity equations are then obtained by adopting shooting method using the Nachtsheim-Swigert iteration technique.

Continuing the contribution about “wireless power transmission by scalar waves”, presented in Moscow 2012, the paper from PIERS Stockholm 2013 goes deeper, explaining the different types and properties of waves described by the wave equation. Starting with the wave description of Maxwell an extended version of the Laplace equation is derived, expanding the standard derivations of the near field, showing how to influence the zone, where the longitudinal wave parts occur. We come to the conclusion that the near field zone is enlarging, if the longitudinal parts of a wave or the antenna voltage are accelerated. This relationship is essential for the wireless transmission of energy. In addition this exciting new result could be tested experimentally. The simple experiment has been demonstrated more often. Only by changing the antenna design, it was shown how both, the speed of propagation and the near field are enlarging proportional to each other. In all practical applications, as discussed in different congress Proceedings, the extended near field is the key of success. This paper contents the calculation of the transition from near field to far field of an antenna, resp. from field vortex propagation, as a so called scalar wave, to an electromagnetic wave.