We analyze a macroscopic model with a maximal density constraint which describes short range repulsion in biological systems. This system aims at modeling finite-size particles which cannot overlap and repel each other when they are too close. The parts of the fluid where the maximal density is reached behave like incompressible fluids while lower density regions are compressible. This paper in...

We say that a class of finite structures for a finite signature is r-compressible if each structure G in the class has a first-order description of size at most O(r(|G|)). We show that the class of finite simple groups is log-compressible, and the class of all finite groups is log-compressible. The result relies on the classification of finite simple groups, the bi-interpretability of the small...

In order to investigate turbulent phenomena in compressible flows the Variational Multiscale method is used. This method is usually applied to incompressible flows. In a first step, we derive the VMS method for the compressible Navier-Stokes equations. The resulting weak formulation of the flow equations is split into resolved and unresolved scales using multiresolution techniques based on bior...

Compressive sampling offers a new paradigm for acquiring signals that are compressible with respect to an orthonormal basis. The major algorithmic challenge in compressive sampling is to approximate a compressible signal from noisy samples. This paper describes a new iterative recovery algorithm called CoSaMP that delivers the same guarantees as the best optimization-based approaches. Moreover,...

The distributed-relaxation multigrid and defectcorrection methods are applied to the twodimensional compressible Navier-Stokes equations. The formulation is intended for high Reynolds number applications and several applications are made at a laminar Reynolds number of 10,000. A staggeredgrid arrangement of variables is used; the coupled pressure and internal energy equations are solved togethe...

We discuss hybrid atomistic-continuum methods for multiscale hydrodynamic applications. Both dense fluid and dilute gas formulations are considered. The choice of coupling method and its relation to the fluid physics is discussed. The differences in hybrid methods resulting from underlying compressible and incompressible continuum formulations as well as the importance of timescale decoupling a...

Title of thesis: VELOCITY TRANSFORMATION FOR COMPRESSIBLE WALL TURBULENCE WITH HEAT TRANSFER Andrew Trettel, Master of Science, 2015 Thesis directed by: Professor Johan Larsson Department of Mechanical Engineering A transformation is derived that removes the effects of variable properties from wallbounded turbulent flows. The transformation derives from the logarithmic velocity profile and the ...

Many stormy events in astrophysics occur due to the sudden magnetic energy release. This is possible if a magnetic configuration abruptly changes its topology, an event usually referred to as magnetic reconnection. It is known that pure Ohmic decay is inefficient, occurring during cosmological times (due to the huge characteristic scales L). It is recognized that the presence of current sheets ...

The present work introduces a modified scheme for the solution of compressible 2-D full Navier-Stokes equations, using Flux Vector Splitting method. As a result of this modification, numerical diffusion is reduced. The computer code which is developed based on this algorithm can be used easily and accurately to analyze complex flow fields with discontinuity in properties, in cases such as shock...

Over the last ten years, robustness of schemes has raised an increasing interest among the CFD community. The objective of this article is to solve the quasi-one-dimensional compressible flow inside a “Shubin nozzle” and to investigate Bean-Warming and flux vector splitting methods for numerical solution of compressible flows. Two different conditions have been considered: first, there is a sup...