Aerodynamic Optimization of the Nose Shape of a Train Using the Adjoint Method

Abstract

The adjoint method is used in this paper for the aerodynamic optimization of the nose shape of a train. This method has been extensively applied in aircraft or ground vehicle aerodynamic optimization, but is still in progress in train aerodynamics. Here we consider this innovative optimization method and present its application to reduce the aerodynamic drag when the train is subjected to front wind. The objective of this paper is to demonstrate the effectiveness of the method, highlighting the requirements, limitations and capabilities of it. Furthermore, a significant reduction of the aerodynamic drag in a short number of solver calls is aimed as well. The independence of the computational cost with respect to the number of design variables that define the optimal candidate is stressed as the most interesting characteristic of the adjoint method. This behavior permits a more complete modification of the shape of the train nose because the number of design variables is not a constraint anymore. The information obtained from the sensitivity field permits determining the regions of the geometry where a small modification of the nose shape might introduce a larger improvement of the train performance. A good agreement between this information and the successive geometry modifications is observed here.

The Migration Industry and the H‐2 Visa in the United States: Employers, Labour Intermediaries, and the State

“…As discussed earlier, the three basic private components in the H-2 visa are generally the US-based agent who works with employers to file the paperwork to the US government, the recruiters who go and find workers, and the visa agents who help workers apply for the visa from US Consulates abroad. Yet, while for some firms all three activities might be done in-house, in many cases there are many instances of sub-contracting and sub-sub-contracting involved in these various steps (Muñoz Paniagua, 2016). Because it exists across borders, it also becomes difficult for the US to enforce rules or prosecute fraud that takes place in other countries (Pittman, 2016;Farbenblum and Nolan, 2017).…”

“…Within migration research, labour brokers have formed part of the "black box" of migration McKeown, 2012) as both their roles and the frequency of their involvement is often poorly understood. Furthermore, while much of the research on brokerage both generally (Kaur, 2012;Lindquist, 2012;Groutsis et al, 2015) and in the context of the US (CDM, 2013;Muñoz Paniagua, 2016) has focused on the services brokers provide to employers and migrants, the role that they play relative to state institutions has largely been overlooked (Surak, 2017). Here, through examining the prevalence of brokers and the services they offer, it is possible to interrogate whether brokers function as an optional facilitator of movement or whether they have become an integral and unavoidable part of the migration process.…”

“…While the role of brokers is comparatively well documented in the context of Asian "guest worker" programmes (see for example Lê, 2010;Kaur, 2012;Lindquist, 2012) it has been less explored within the US (cf. CDM, 2013;Muñoz Paniagua, 2016) as "temporary worker programmes obscure the role of brokers behind the brilliant glare of laws and regulation" (McKeown, 2012: 45). Yet this fact that guest worker programmes are both state-sanctioned programmes with established regulatory frameworks and heavily reliant on brokers and other private migration actors (Griffith, 2014) is precisely what makes them a ripe field for examining the intersection of state and private prerogatives.…”

“…Within the H-2 visa, brokers have been identified as playing three distinct roles: helping employers obtain permission to hire workers; recruiting workers from abroad; and aiding migrants in receiving visas. These roles may be inhabited by entirely distinct actors operating independently, or through any of a wide variety of collaborative or contractual relationships (Muñoz Paniagua, 2016). Yet it is incredibly difficult to find comprehensive data on the extent of labour broker involvement, due to the largely unregulated way that brokers operate and the complexity of migration networks.…”

Optimal Design of Orifice Flow Meter Using Computational Fluid Dynamics (CFD)

“…Tonomura et al [17] conducted a shape optimization of microchannel using the adjoint method. The shape of train's nose was optimized by using adjoint method to reduce the drag on train [18]. It is shown above that little researches take in consideration using adjoint method in internal flow.…”