Monthly Archives: September 2015

分科会「非平衡現象の流体力学」（第20回）

平成27年度第7回講演会（日本航空宇宙学会関西支部分科会）

日時：	平成27年11月13日（金）　13:30-14:30
場所：	京都大学桂キャンパスCクラスタ総合研究棟III（C3棟）　3階　b3n03室（航空宇宙工学専攻会議室）
講演：	Diffuse interface modeling of subcritical and supercritical flames
	Prof. Vincent Giovangigli (Centre de Mathematiques Appliquees, Ecole Polytechnique, France)
要旨：	During the ignition of rocket engines, or in Diesel engines, a transition may occur from subcritical to supercritical pressure conditions and such dynamics cannot be described by current fluid models. There is thus a need for models that transition smoothly from subcritical to supercritical pressure conditions. With this aim in mind we present a liquid/gas diffuse interface model of Van der Waals/Korteweg type valid at all pressures. In the subcritical regime, the model describes the continuous interface between a liquid and a gas mixture whereas in the supercritical domain the model thickens high density gradient zones. The interface model is further embedded into a nonideal multicomponent reactive fluid framework. The resulting equations are used to investigate the interface between cold dense and hot light oxygen as well as the structure of diffusion flames between cold dense oxygen and gaseous like hydrogen at all pressures, either subcritical or supercritical.

分科会「非平衡現象の流体力学」（第19回）

平成27年度第6回講演会（日本航空宇宙学会関西支部分科会）

日時：	平成27年11月9日（月）　13:30-14:30
場所：	京都大学桂キャンパスCクラスタ総合研究棟III（C3棟）　3階　b3n03室（航空宇宙工学専攻会議室）
講演：	Boundary layers for the discrete Boltzmann equation: mixtures, polyatomic molecules, chemical reactions and quantum extensions
	Prof. Niclas Bernhoff (Dept. of Mathematics, Karlstad University, Karlstad, Sweden)
要旨：	In the talk we will address two different questions. 1) An important aspect of constructing discrete velocity models (DVMs) for the Boltzmann equation is to obtain the right number of collision invariants. It is a well-known fact that DVMs can also have extra collision invariants, so called spurious collision invariants, in plus to the physical ones. A DVM with only physical collision invariants, and so without spurious ones, is called normal. The construction of such normal DVMs has been studied a lot in the literature for single species, but there are also several works where normal DVMs for binary mixtures are constructed. In this talk we will address ways of constructing DVMs for multi-component mixtures and for polyatomic molecules (here in the meaning that the molecules have one of a finite number of different internal energies, which can be changed, or not, during a collision). We present some general algorithms for constructing such models, but we also give some concrete examples of such constructions. The two different approaches above can be combined to obtain multi-component mixtures with a finite number of different internal energies, and then they can be applied for DVMs for chemical reactions. 2) We also consider some problems related to the nonlinear half-space problem of condensation and evaporation for the discrete Boltzmann equation (DBE; the general discrete velocity model) for mixtures, polyatomic molecules, and chemical reactions, and for the discrete quantum Boltzmann equation. We assume that the flow tends to a stationary point (Maxwellian for the DBE) at infinity and that the outgoing flow is known at the wall (complete absorption at the wall). The number of conditions on the assigned data at the wall needed for existence of a unique solution is found. The number of parameters to be specified in the boundary conditions depends on if we have subsonic or supersonic condensation or evaporation. We obtain similar results for more general boundary conditions at the wall.All our results are valid for any finite number of velocities.