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The flow around a circular-cone is 3D, unsteady and turbulent. As reported in many research works on this type of flow, boundary layer separations, vortex structures and the effect of surface roughness are strongly related. The effect of roughness is still not completely understood and proves challenging both for numerical and experimental approaches. The present work aims to gain more insights in understanding and numerically predicting this type of flows. Particularly, it attempts to improve the accuracy of numerical predictions of the effects of roughness on the asymmetric vortex flow around a circular-cone at subsonic flow conditions. This is performed using numerical simulations, which predict the flow field details across different transversal stations along the cone. Therefore, we have analyzed the effect of many turbulence models, notably, the transition SST, using ANSYS Fluent code. Flows characteristics are highlighted and validated against the well-known theory and some experimental measurements. The findings depict that a surface roughness height about 0.32 mm has efficaciously triggered the boundary layer to change from a laminar to a fully turbulent state in both sides of the body, in addition to a significant reduction in the global lateral force. Moreover, it seems that the roughness reduces the asymmetry of the vortex in the leeward side of the cone. Testing many roughness heights has allowed us to determine the way in which it is possible to reduce the side force effectively at high angles of attack without affecting the lift of the cone cylinder. [ABSTRACT FROM AUTHOR]

• Exhaust and intake valve are subdivided to several zones to isolate the effect of the surrounding. • Exhaust and intake valves are compared in of heat transfer coefficient and adiabatic wall temperature. • Heat transfer for each subdivision is evaluated during engine operating cycle at various engine speed. • Temperature maps through valves allow identifying region exposed to maximum temperature. The heat transfers within the intake valve differs than the exhaust valves, due to the difference in the boundary condition surrounding each valve. This paper concerns a comparison of the heat transfer coefficient (HTC) at various engine speed and the temperature distribution through exhaust valves and intake valves. The boundary condition are assessed using basic concept of heat transfer and correlation related to internal cbustin engine. To assess perfectly the real effect of the valves surrounding, an adequate subdivision of the valve is used where the heat transfer coefficient and the adiabatic wall temperature (AWT) for each subdivision are evaluated during one engine cycle. An average value of these two parameters is calculated and introduced as a boundary condition in a FEM model. This procedure is repeated for diverse engine speeds, and therefore, the trend of the real boundary condition in term of HTC and AWT are given versus engine speed. The comparison in term of HTCs shows different behaviour of valves surrounding mainly in the seat and stem zones. The obtained model is used to highlight the temperature map of an exhaust valve and intake valves for the different operating condition in addition to zones of fort thermal gradient and thus, areas of maximum thermal load can be specified, which help automobile manufactures to avoid valves failures. [ABSTRACT FROM AUTHOR]

• A predictive model for knocking in dual fuel engines is developed. • The model is validated experimentally on a dual fuel engine under a strong hydrogen enrichment. • The validated model is coupled with a CFD calculation code for knocking prediction. • Direct water injection strategy is implemented for knocking suppression. • Water injection effectiveness is proven after optimization of water quantity and injection time. In the face of increasing emission restrictions and the parsimony of conventional fuels, dual fuel engine is presented as a promising solution that is satisfactory for environmental and economic aspects. However, this type of engine is limited by certain problems such as knocking, which negatively influences overall operation. For this reason and for optimal engine operation, prediction of this undesirable auto-ignition is essential. The approach developed in this work for this purpose, is based on dividing the combustion chamber into two zones to follow the thermodynamic properties of the unburnt gases where knock may occur. This thermodynamic modeling is coupled with a model based on Arrhenius equation for the auto-ignition delay as a function of crank angle. In addition, in order to make the model more predictive with the minimum of parameters to be calibrated experimentally, an analysis of variables is used for different engine conditions. The selected parameters undergo a correction before being modeled according to response surfaces methodology. After validation of the model using experimental results, it is coupled with a CFD calculation model to develop a global approach aimed at preventing knocking during dual fuel mode. The model makes it possible to predict knock onset with good precision. Consequently, preventing this phenomenon is possible. Water injection technique is therefore used for this objective. Accurate prediction was useful for knock avoidance via water injection strategy. Our results confirmed the effectiveness of this technique, justified mainly by water injection characteristics. The precision of the instant of knocking predicted by the developed model implied an optimal instant for water injection. Overall, this global model can be considered as a valuable means for knock prediction and prevention in dual fuel mode. [ABSTRACT FROM AUTHOR]