Wind energy is the fastest growing alternate source of energy in the world since its purely economic potential is complemented by its great positive environmental impact. The wind turbine, whether it may be a Horizontal-Axis Wind Turbine (HAWT) or a Vertical-Axis Wind Turbine (VAWT), offers a practical way to convert the wind energy into electrical or mechanical energy. Although this book focuses on the aerodynamic design and performance of VAWTs based on the Darrieus concept, it also discusses the comparison between HAWTs and VAWTs, future trends in design and the inherent socio-economic and environmental friendly aspects of wind energy as an alternate source of energy.

Wind turbine design with emphasis on Darrieus concept Ion Paraschivoiu

Purpose




The purpose of this paper is to study the particle shape effects on Marangoni convection boundary layer flow of a nanofluid. The paper aims to discuss diverse issues befell for the said model.




Design/methodology/approach




The work undertaken is a blend of numerical and analytical studies. Analytical and numerical solutions of nonlinear coupled equations are developed by means of Mathematica package BVPh 2.0 based on the homotopy analysis method.




Findings




The velocity of nanofluid decreases by increasing particle volume friction and similarity parameters. With the increase in particle volume friction and similarity parameter, temperature profile is correspondingly enhanced and decline. The lowest velocity and highest temperature of nanofluid is cause by needle- and disc-shaped particle. Consequence for interface velocity and the surface temperature gradient are perceived by numeric set of results. It is found that the interface velocity is declined by increasing particle volume friction and volume concentration of ethylene glycol in the water. The minimum interface velocity is seen by needle-shaped particle and 30 percent concentrations of ethylene glycol. With increase in volume friction and size of particle, the behaviors of surface temperature gradient are found decreasing and increasing function, respectively. The maximum heat transfer rate at the surface is achieved when we chose sphere nanoparticles and 90 percent concentrations of ethylene glycol as compared to other shapes and concentrations.




Originality/value




This model is investigated for the first time, as the authors know.

Particle shape effects on Marangoni convection boundary layer flow of a nanofluid

The problem of steady, laminar, thermosolutal Marangoni convection flow of an electrically-conducting fluid along a vertical permeable surface in the presence of a magnetic field, heat generation or absorption and a first-order chemical reaction effects is studied numerically. The general governing partial differential equations are converted into a set of self-similar equations using unique similarity transformations. Numerical solution of the similarity equations is performed using an implicit, iterative, tri-diagonal finite-difference method. Comparisons with previously published work is performed and the results are found to be in excellent agreement. Approximate analytical results for the temperature and concentration profiles as well as the local Nusselt and sherwood numbers are obtained for the conditions of small and large Prandtl and Schmidt numbers are obtained and favorably compared with the numerical solutions. The effects of Hartmann number, heat generation or absorption coefficient, the suction or injection parameter, the thermo-solutal surface tension ratio and the chemical reaction coefficient on the velocity, temperature and concentration profiles as well as quantitites related to the wall velocity, boundary-layer mass flow rate and the Nusselt and Sherwood numbers are presented in graphical and tabular form and discussed. It is found that a first-order chemical reaction increases all of the wall velocity, Nusselt and Sherwood numbers while it decreases the mass flow rate in the boundary layer. Also, as the thermo-solutal surface tension ratio is increased, all of the wall velocity, boundary-layer mass flow rate and the Nusselt and Sherwood numbers are predicted to increase. However, the exact opposite behavior is predicted as the magnetic field strength is increased.

Similarity solutions for MHD thermosolutal Marangoni convection over a flat surface in the presence of heat generation or absorption effects

Exact analytical results for the thermosolutal MHD Marangoni boundary layers

Review and prospect of guidance and control for Mars atmospheric entry

Basics of Hypersonic Aerodynamics and Aerothermodynamics.- Fundamentals of Atmospheric Entry Dynamics.- Some Preliminary Considerations on Entry Vehicle Design.- Analysis of an Apollo-shaped Crew Return Vehicle.- Lifting-body Vehicles.- Winged Re-Entry Vehicles.- Analysis of Sample Return Capsules.- Launchers: Present and Future.- Appendices.

Aerodynamic and Aerothermodynamic Analysis of Space Mission Vehicles

The paper deals with the dissipative layers, called Marangoni boundary layers, that can be formed, along the interface of two immiscible fluids, in surface driven flows. Under the hypothesis that the flow fields of the two interfacing fluids are uncoupled, similar solutions are studied for the case in which an external pressure gradient is present. The similarity class is derived and the pertinent equations are solved numerically by mean of an algorithm based on a Quasi-Linearization Technique.

Non isobaric boundary layers related to Marangoni flows

Multi-objective optimization for re-entry spacecraft conceptual design using a free-form shape generator

Oscillatory Marangoni convection around the air bubble in a vertical surfactant stratification

The paper presents the experimental study of thermo- and solutocapillary Marangoni convection around a gas bubble in an inhomogeneous fluid with a vertical thermal or surfactant concentration gradient. The stationary bubble in the form of a short horizontal cylinder with a free lateral surface was placed into a vertically oriented thin liquid layer (Hele-Shaw cell). The evolution of thermal and concentration fields and fluid flows was studied applying the interferometric method. In contrast to a thermocapillary convection representing a stationary flow and stable temperature distribution, the periodic concentration disturbances around the bubble were observed in the solutocapillary case. The regularities of the discovered effect were revealed, and its interpretation was proposed.

Antonio Viviani

Papers

Aerodynamic and Aerothermodynamic Analysis of Space Mission Vehicles

Non isobaric boundary layers related to Marangoni flows

Multi-objective optimization for re-entry spacecraft conceptual design using a free-form shape generator

Oscillatory Marangoni convection around the air bubble in a vertical surfactant stratification

Thermal and Concentrational Maragoni Convection at Liquid/Air Bubble Interface