Wind turbine wake aerodynamics

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.

Recent progress in the development and properties of novel metal matrix nanocomposites reinforced with carbon nanotubes and graphene nanosheets

http://www.msc.univ-paris-diderot.fr/~phyexp/uploads/EolienneFlexible/EolienneStateArt.pdf

State of the art in wind turbine aerodynamics and aeroelasticity

https://cyberleninka.org/article/n/544115.pdf

Hydrodynamic lubrication of textured surfaces: A review of modeling techniques and key findings

Nomenclature Ac = accumulation parameter Cd drag coefficient Ci = lift coefficient Cm = moment coefficient Cp = pressure coefficient c = specific heat at constant pressure, J/(kg-K); airfoil chord, m D = propeller diameter, m; flexural stiffness, N-m D drag force, N d = droplet diameter, m E = total collection efficiency / = freezing fraction g = acceleration caused from gravity, m/s Hi = ice thickness, m Hp = plate thickness, m h = airfoil projected height, m hc = convective heat transfer coefficient, W/(m-K) hfg = heat of vaporization, J/kg hsi = heat of fusion, J/kg / = airfoil drag constant K = thermal conductivity, W/(m-K); inertia parameter K0 = modified inertia parameter k = roughness diameter, m LWC = liquid water content, kg/m M = local Mach number MVD = median volume droplet diameter, m m = mass, kg ra = mass flow rate, kg/s m' = mass flow rate per unit width, kg/(m-s) m" = mass flux, kg/(m-s) n = normal direction P = pressure, Pa p spatial pressure distribution, N/m <2 = heat rate, W q = normal pressure distribution, N/m

Aircraft Anti-Icing and De-Icing Techniques and Modeling

A numerical procedure to predict the effects of gaseous cavitation in moderately to heavily loaded bearings is developed. The method is an outgrowth of the Elrod algorithm which is simple to use and which automatically implements cavitation boundary conditions at film rupture and reformation. The current procedure makes use of type differencing in the shear induced flow formulation to automatically switch from central to upwind differences, and vice versa, at cavitation boundaries. Comparison is made with the results obtained using Elrod's algorithm for various test cases involving both slider and journal bearings. Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

Development and evaluation of a cavitation algorithm

In this paper, an implicit numerical scheme, based on an approximate factorization technique, is applied to a cavitation algorithm. The algorithm is a modified version of the Elrod cavitation algorithm, which automatically predicts film rupture and reformation in bearings. At each time step, Newton iterations are performed to achieve time accurate solutions for unsteady problems. This numerical scheme is applied in both orthogonal and nonorthogonal grid arrangements. An aligned finite grooved bearing and a flared, misaligned line grooved bearing are analyzed using this new approach. The predictions are compared with the results obtained with procedures currently being used. The new scheme is robust, quickly convergent, and provides time accurate solutions with a minimum expenditure of CPU time.

An Efficient, Robust, and Time Accurate Numerical Scheme Applied to a Cavitation Algorithm

Effect of cavitation on the performance of a grooved misaligned journal bearing

The effect of journal misalignment on the predicted performance of a finite grooved journal bearing is analyzed in this paper. The numerical procedure used incorporates a cavitation algorithm, which automatically predicts film rupture and reformation in the bearings. The misalignment considered varies in magnitude and direction with reference to the boundaries of the bearing. In addition to the misalignment, the effect of lubricant starvation at the groove is also considered and compared with flooded inlet conditions. The effects of various degrees of starvation, or higher lubricant supply pressure, bearing length to diameter ratio and groove size are also investigated

Analysis of a Finite Grooved Misaligned Journal Bearing Considering Cavitation and Starvation Effects

A time domain approach is used to determine the dynamic aeroelastic stability of a cascade of blades. The structural model for each blade is a typical section with two degrees of freedom. The aerodynamic model is the unsteady, two-dimensional, full-potential flow through the cascade of airfoils. The unsteady equations of motion for the structure and the fluid are integrated simultaneously in time starting with the steady flowfield and a small initial disturbance applied to the airfoils. The motion of each blade is analyzed to determine the aeroelastic stability of the cascade. The effect of interblade phase angle is included in the analysis by allowing each blade to have an independent motion and considering a number of blade passages. Calculations are made using an airfoil section and structural parameters that are representative of a propfan. The results are compared with those from a separate frequency domain analysis. Good agreement between the results is observed. With the time domain approach, it is possible to consider nonlinear structural models and nonlinear force-displacement relations. The method allows a realistic simulation of the motion of the fluid and the cascade blades for a better physical understanding and it also has the potential for saving computational time when compared to the frequency domain approach for the flutter analysis of cascades.

Theo G. Keith

Papers

Development and evaluation of a cavitation algorithm

An Efficient, Robust, and Time Accurate Numerical Scheme Applied to a Cavitation Algorithm

Effect of cavitation on the performance of a grooved misaligned journal bearing

Analysis of a Finite Grooved Misaligned Journal Bearing Considering Cavitation and Starvation Effects

Time domain flutter analysis of cascades using a full-potential solver