A truly Newtonian softening length for disc simulations

Abstract : The softened point mass model is commonly used in simulations of gaseous discs including self-gravity while the value of associated length \lambda remains, to some degree, controversial. This ``parameter'' is however fully constrained when, in a discretized disc, all fluid cells are demanded to obey Newton's law. We examine the topology of solutions in this context, focusing on cylindrical cells more or less vertically elongated. We find that not only the nominal length depends critically on the cell's shape (curvature, radial extension, height), but it is either a real or an imaginary number. Setting \lambda as a fraction of the local disc thickness -- as usually done -- is indeed not the optimal choice. We then propose a novel prescription valid irrespective of the disc properties and grid spacings. The benefit, which amounts to 2-3 more digits typically, is illustrated in a few concrete cases. A detailed mathematical analysis is in progress.
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Article dans une revue
Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2015, 447 (2), pp.1866-1872. <10.1093/mnras/stu2511>
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https://hal.archives-ouvertes.fr/hal-01090827
Contributeur : Marie-Paule Pomies <>
Soumis le : jeudi 4 décembre 2014 - 11:29:39
Dernière modification le : mercredi 27 juillet 2016 - 14:48:48

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J.-M. Huré, Audrey Trova. A truly Newtonian softening length for disc simulations. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2015, 447 (2), pp.1866-1872. <10.1093/mnras/stu2511>. <hal-01090827>

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