Modeling of Air Flow Over a Generic Aircraft Carrier With and Without Island Structure

The study of external aerodynamics of an aircraft carrier is of utmost importance in ensuring the safety of aircraft and pilots during take-off and recovery. The velocity deficit in the forward direction and the downwash together combine to give a sinking effect to the aircraft, along its glideslope path and is known as the ‘burble’ in naval aviation parlance. This phenomenon is primarily responsible for the potential increase in pilot workload on approach to the aircraft carrier. There is little literature in the open domain regarding ways and means to alleviate the burble effect. Unlike in the case of the automobile industry, which has the generic ‘Ahmed body’ and for the frigates/destroyers, for which there is the Simplified Frigate Ship (SFS), on which experiments and validation through CFD could be carried out, by researchers from all over the world, there is no generic Aircraft Carrier model for carrying out experiments and validation of CFD codes. The aim of this study is to define the Generic Aircraft Carrier Model (GAC), as developed at IIT Delhi, and to carry out numerical studies on the GAC and a variant of GAC without the island, BGAC (Baseline GAC), to assess the contribution of the island to the burble behind an Aircraft Carrier. This study gives a quantitative estimation of the effect and contribution of individual components of an Aircraft Carrier (like flight deck, island, etc.) to the burble behind the carrier, and would give a Naval Ship Designer an understanding of the effect of the geometrical configuration of the flight deck and the island on generation of the burble behind the carrier, which could aid the designer in potentially reducing the pilot workload.

Experimental Study and Finite Element Modeling of Workpiece Temperature in Finish Cylinder Boring

Thermal expansion of the workpiece during cylinder boring process is one of the sources causing the bore cylindricity error. To study thermal expansion induced bore distortion, detailed workpiece temperature distribution in cylinder boring is required. Four finite element models, namely, the advection model, surface heat model, heat carrier model, and ring heat model, were developed to predict the workpiece temperature in cylinder boring. Cylinder boring experiments were conducted utilizing the tool–foil and embedded thermocouple experimental approaches to measure the workpiece temperature, predict the temperature distribution using the inverse heat transfer method, and evaluate the capability of the four models in terms of accuracy and efficiency. Results showed an accurate global temperature prediction for all models and a good correlation with the embedded thermocouple experimental measurements. Good correlation was also obtained between the tool–foil thermocouple measurement of machined surface temperature and model predictions. Advantages and disadvantages as well as applicable scenarios of each model were discussed. For studying detailed cylinder boring workpiece temperature, it is suggested to use the ring heat model to estimate the moving heat flux and the heat carrier model for local workpiece temperature calculation.