Martin Sandve Alnæs

Simula Research Laboratory · Scientfic Computing - Biomedical Flows and Structures

Several cardiovascular diseases are caused from localised abnormal blood flow such as in the case of stenosis or aneurysms. Prevailing theories propose that the development is caused by abnormal wall‐shear stress in focused areas. Computational fluid mechanics have arisen as a promising tool for a more precise and quantitative analysis, in particul...

Several cardiovascular diseases are caused from localised abnormal blood flow such as in the case of stenosis or aneurysms. Prevailing theories propose that the development is caused by abnormal wall-shear stress in focused areas. Computational fluid mechanics have arisen as a promising tool for a more precise and quantitative analysis, in particul...

Therapeutic parent artery flow reversal is a treatment option for giant, partially thrombosed basilar tip aneurysms. The effectiveness of this treatment has been variable and not yet studied by applying computational fluid dynamics. Computed tomography images and blood flow velocities acquired with transcranial Doppler ultrasonography were obtained...

Syringomyelia, fluid-filled cavities within the spinal cord, occurs frequently in association with a Chiari I malformation and produces some of its most severe neurological symptoms. The exact mechanism causing syringomyelia remains unknown. Since syringomyelia occurs frequently in association with obstructed cerebrospinal fluid (CSF) flow, it has...

p>The FEniCS Project is a collaborative project for the development of innovative concepts and tools for automated scientific computing, with a particular focus on the solution of differential equations by finite element methods. The FEniCS Projects software consists of a collection of interoperable software components, including DOLFIN, FFC, FIAT,...

We present the Unified Form Language (UFL), which is a domain-specific language for representing weak formulations of partial differential equations with a view to numerical approximation. Features of UFL include support for variational forms and functionals, automatic differentiation of forms and expressions, arbitrary function space hierarchies f...

At the heart of any finite element simulation is the assembly of matrices and vectors from discrete variational forms. We propose a general interface between problem-specific and general-purpose components of finite element programs. This interface is called Unified Form-assembly Code (UFC). A wide range of finite element problems is covered, inclu...

A central component of FEniCS is the UFC interface (Unified Form-assembly Code). UFC is an interface between problem-specific and general-purpose components of finite element programs. In particular, the UFC interface defines the structure and signature of the code that is generated by the form compilers FFC and SFC for DOLFIN. The UFC interface ap...

This chapter concerns the finite element library SyFi and its form compiler SFC. SyFi is a framework 8315 for defining finite elements symbolically, using the C++ library GiNaC [Bauer et al., 2002] and its 8316 Python interface Swiginac [Skavhaug and Certik, 2009].

Instant is a small Python module for just-in-time (JIT) compilation (or inlining) of C/C++ code.Instant accepts plain C/C++ code and is therefore conveniently combined with the code generating tools in DOLFIN, FFC and SFC.

Efficient and easy implementation of variational forms for finite element discretization can be accomplished with metaprogramming. Using a high-level language like Python and symbolic mathematics makes an abstract problem definition possible, but the use of a low-level compiled language is vital for run-time efficiency. By generating low-level C++...

Wall shear stress (WSS) and pressure are important factors in the development of cerebral aneurysms. We aimed to develop a computational fluid dynamics simulator for flow in the complete circle of Willis to study the impact of variations in vessel radii and bifurcation angles on WSS and pressure on vessel walls. Blood flow was modeled with Navier-S...

The present paper addresses the use of high level languages, symbolic mathematical tools and code generation in an implementation of the finite element method, using a nonlinear hyperelasticity equation as example. Advantages of the software development method that will be demonstrated include closeness to the mathematics, enabling high human effic...