Computational Fluid Dynamics (CFD), blending disciplines like fluid mechanics and computer science, plays a pivotal role in various engineering and scientific endeavors. Despite its importance, the prohibitive costs and restricted access to commercial CFD tools pose significant barriers. This study addresses the need for accessible CFD solutions by conducting a comprehensive review of open-source CFD tools, highlighting their role in promoting open science. Through methodical analysis, the present study explores the capabilities, performance, and applicability of these tools in various contexts. The findings reveal that open-source CFD tools not only offer a cost-effective alternative to proprietary software but also foster collaboration and transparency in the scientific community. This study concludes that these tools are not only viable but essential for the advancement of CFD applications, encouraging wider adoption and development. This review serves as a bridge in the literature, enhancing understanding and accessibility of open-source tools in CFD, and supporting the paradigm shift towards open science.

The design and development of Stratospheric Airships for High-Altitude Long-Endurance missions (HALESAs) has generated interest worldwide. Conventional airships usually have a single-lobed axisymmetrical envelope shape. In contrast, several non-axisymmetric envelope configurations have been proposed for the HALESAs, such as flattened single lobed and multi lobed. This paper describes a methodology for carrying out a comparative analysis of a conventional HALESA and the multi-lobed HALESA designed for the same design mission. A sizing methodology which enables the estimation of its design parameters to meet some user-specified requirements has been developed for airships with envelopes of both these shapes. A Multidisciplinary Design Optimisation (MDO) approach has been followed in this methodology, which includes considerations from the disciplines of aerodynamics, energy, environment and structures. The study indicates that the envelope volume, solar array area and total mass of the single-lobed conventional airship are better than those of the tri-lobed HALESA. While the multi-lobed HALESA has the advantage of a flatter upper surface resulting in higher efficiency of the solar panels, the conventional airship has lower drag, which results in superior mission performance.

In recent years, there has been an increasing interest in the research and development of hybrid airships for various applications. Airship design involves multiple design parameters from various disciplines that interact mutually. Existing design methodologies, however, are often limited to fixed shapes and geometry. This paper provides a comprehensive parametric design approach for the sizing of multi-lobed hybrid air vehicles for low- and high-altitude applications. The proposed design techniques are robust so that the designer has the freedom to change the number of lobes, the relative location of lobes, the envelope profile, and the optimiser for the design optimisation process. The outcomes of the proposed methodology are envelope volume, wetted surface area, length and span of the envelope, sizing and layout of the solar array, and sizing and layout of the fins. The modeling techniques highlighted in this paper are very efficient for the design and optimisation of multi-lobed airships in the conceptual design phase with a large design exploration space. The robustness of the shape generation algorithms is tested on some of the standard envelope profiles of airships. The effect of the shape and geometry of the multi-lobed envelope on added mass is demonstrated through the added mass estimation using Boundary Element Method.

The excessive depletion of fossil fuels and increasing environmental concerns have led to the need to explore alternative sources of power for aircraft. This has spurred various stakeholders in the aerospace industry to explore hybrid electric propulsion technology and fully electric vehicles. Airships are aerial platforms based on lighter-than-air systems technology. They have several unique features compared to other vehicles, chiefly their being more environmentally friendly due to low fuel consumption. Among airships, lifting-body dynastats are the most suitable configuration for implementing different levels of hybridization in propulsion systems owing to their large surface-to-volume ratio. The present study deals with the relevance of a hybrid propulsion (conventional engine + electric motor) system and its comparison to conventional ones. An objective function based on envelope volume is formulated to achieve an optimal configuration of a tri-lobed dynastat to carry 10 tons of payload over a 500 km range for specified operating conditions powered by conventional fuel and batteries. The design space is explored assuming a predicted future battery technology level with specific energies ranging from 250 to 750 Wh/kg. Three case studies based on the source of power are investigated: fuel alone, fuel + batteries, and fuel + batteries + solar array. It is seen that the airship can be fully electric with zero carbon emissions but at the expense of a longer length (+18%) and higher envelope volume (+63%) compared to the baseline model.

In recent years, hybrid airships have been identified as promising alternatives for high altitude, long endurance missions. In this study, a design methodology to study the feasibility of a winged hybrid airship powered by solar energy is presented. The proposed methodology involves five disciplines of the airship, viz., geometry, aerodynamics, environment, energy and structures that have been coupled in order to develop an optimum design which incorporates the maximum advantages of the modules. A total of fourteen design variables have been finalized, which are required to carry out the sizing of the envelope, wing, and solar panel layout. The Particle Swarm Optimization (PSO) algorithm is implemented to carry out optimization of a user-defined fitness function for given user-defined operating conditions. The optimization study is subjected to general constraints of weight balance and energy balance. Optimal solutions have been obtained for two different configurations. These are—conventional airship and winged hybrid airship. The solutions have been obtained for four different days of the year, in order to analyse any potential benefits and pitfalls of the two configurations for the varying conditions over the course of one year. The results obtained are generally found to be in excellent agreement with the imposed constraints. The winged hybrid airship configuration was found to have offered no significant benefits in comparison to the conventional configuration. The analysis of the key parameters and data values readily supports this conclusion.