Abstract: The flight regime of modern transport aircraft, is at transonic speeds, in terms of Mach number M∞ = 0.75-0.85 and at very high Reynolds numbers. The transonic flow occurs when the two regimes of subsonic and supersonic flows occur in the same local flow field. It is characterized by the development of a supersonic pocket, delimited by the wall on the one hand and by the sonic line on the upper surface of the wing on the other hand. The appearance of a supersonic pocket on the under-surface of the wing is also possible; all depends on the incidence angle and the geometrical form of the wing. This work is devoted to the evaluation and the validation of the numerical results resulting from transonic calculation of flow around a NACA0012 aerofoil, then around a wing 3d having the same basic airfoil. All calculations are executed by using the turbulence models of two equations k-ε, k-ω and SST k-w.

Key words: Transonic flow, Numerical simulation, Aerofoil NACA0012, Mach wave, unmanned aircraft vehicle (UAV)

Abstract: Natural convection for a Herschel-Bulkely fluid, inside a differentially heated square cavity, is studied numerically using Fluent/Ansys 15.0 code. The cavity is heated from the vertical sides and insulated from the horizontal ones. We have studied the effect of Bingham-number (Bn) at a fixed Rayleigh-number (Ra), then the effect of Rayleigh-number at fixed Bn and finally the effect of the rheological index n at fixed Bn and Ra. Prandtl-number (Pr) is taken equal 1.0 for the whole study. Results showed that an increasing Bn leads to a flow-intensity decrease, and hence its perturbation. Therefore, temperature field becomes less perturbed and the Nusselt decreases. The opposite happens if Bn decreases. Increasing Ra, leads to similar results as those known for the Newtonian-case, but with a lower intensity because of Bn effect. The decrease of n has an opposite effect of that of increasing Bn, and inversely. A rapid tendency toward the conductive problem (Ra=0.0) is registered if Bn>0 particularly when n>1.0.

Key words: Natural convection, square cavity, Bingham fluid, Herschel-Bulkely fluid.

Abstract: A new design of a solar collector is proposed in this paper. The introduced novelty consists on using low cost flat reflectors with adjustable inclination. A detailed description of the solar collector as well as its functioning are also provided in the paper. Moreover, a mathematical model, that takes into account the variation of the heat transfer coefficients, is proposed and validated experimentally. Several experiments were also done in order to determine the influence of the new parameters that were induced by the use of reflectors. The parameters that were considered for this study are: the use or no-use of outer reflectors, the number of reflectors equipping the solar collector, and finally the reflectors inclination. The obtained results showed that the enhancement had a great effect on the performance of the solar collector. Indeed, the operating temperature range as well as the availability of the solar collector had increased. This allows the solar collector to work even during days with low solar radiation.

Keywords: New design; solar collector; flat outer reflectors; performance; experiment.

Abstract: The failure of the bone cement (PMMA) is the most prominent scenario, in a cemented total hip arthroplasty and an eventual implant loosening. Among the many factors influencing the long-term stability of cemented hip prostheses, the interface between the implant and bone cement is considered to be one of the most susceptible to failure. Implant surface roughness is an important parameter affecting the fracture behavior of the implant–cement interface. This study investigated the influence of implant surface roughness on the resistance of the implant–cement interface. Mechanical fixation at the implant–cement interface was evaluated in vitro using shear loading with stainless steel rods with different surface roughness preparations. Increasing surface roughness improved the mechanical properties at the implant–cement interface. Therefore, it increases the long-term stability of the hip prostheses assembly.

Keywords: Bone cement, Hip prostheses, Roughness, Mechanical properties, Shear strength.

Abstract: The work presented in this paper is the numerical study of a thermal converter. The main objective of the work is to study the effect of certain parameters on a flat solar collector. We are particularly interested in determining the influence of water flow on the operating characteristics of the solar collector and the effect of the orientation of a surface on the energy received. We have realized a mathematical model simulating the thermal behavior of collectors, to solve the mathematical model using an iterative method of Gauss-Seidel. According to the results obtained on this device, we note that: The inclination between 30 and 37 ° gives the best performances. The outlet temperature is higher for low flow. The overall efficiency increases with the flow of water.

Key words: the solar power, debit, solar converter, performance of the converter