Fluid Structure Interaction System Requirements Specification

System Purpose

The purpose of this software is to allow simulation of interfacial interactions between fluid and solid domains. Both acoustic and full Navier-Stokes models of the fluid domain are supported; small and finite strain models from the tensor mechanics module may be used for the solid domain.

System Scope

The MOOSE Fluid Structure Interaction module provides interface kernels for simulating the interactions between neighboring fluid and solid subdomains. It can be used as a standalone application or can be included in downstream applications interested in modeling fluid structure interactions.

System Context

The Fluid Structure Interaction module is command-line driven. Like MOOSE, this is typical for a high-performance software that is designed to run across several nodes of a cluster system. As such, all usage of the software is through any standard terminal program generally available on all supported operating systems. Similarly, for the purpose of interacting through the software, there is only a single user, "the user", which interacts with the software through the command-line. The Fluid Structure Interaction module does not maintain any back-end database or interact with any system daemons. It is an executable, which may be launched from the command line and writes out various result files as it runs.

Figure 1: Usage of the Fluid Structure Interaction module and other MOOSE-based applications.

System Functions

Since the Fluid Structure Interaction module is a command-line driven application, all functionality provided in the software is operated through the use of standard UNIX command line flags and the extendable MOOSE input file. The Fluid Structure Interaction module is completely extendable so individual design pages should be consulted for specific behaviors of each user-defined object.

User Characteristics

Like MOOSE, there are three kinds of users working on the Fluid Structure Interaction module:

• Fluid Structure Interaction module Developers: These are the core developers of the Fluid Structure Interaction module. They are responsible for following and enforcing the software development standards of the module, as well as designing, implementing, and maintaining the software.

• Developers: A scientist or engineer that uses the Fluid Structure Interaction module alongside MOOSE to build their own application. This user will typically have a background in modeling or simulation techniques (and perhaps numerical analysis) but may only have a limited skillset when it comes to code development using the C++ language. This is the primary focus group of the module. In many cases, these developers will be encouraged to contribute module-appropriate code back to the Fluid Structure Interaction module, or to MOOSE itself.

• Analysts: These are users that will run the code and perform analysis on the simulations they perform. These users may interact with developers of the system requesting new features and reporting bugs found and will typically make heavy use of the input file format.

Assumptions and Dependencies

The Fluid Structure Interaction module is developed using MOOSE and can itself be based on various MOOSE modules, as such the SRS for the Fluid Structure Interaction module is dependent upon the files listed at the beginning of this document. Any further assumptions or dependencies are outlined in the remainder of this section.

The Fluid Structure Interaction module is designed with the fewest possible constraints on hardware and software. For more context on this point, the Fluid Structure Interaction module SRS defers to the framework Assumptions and Dependencies and Navier-Stokes and solid mechanics module assumptions and dependencies. Any physics-based assumptions in this module's objects are highlighted in their respective documentation pages.

Definitions

• Verification: (1) The process of: evaluating a system or component to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase. (2) Formal proof of program correctness (e.g., requirements, design, implementation reviews, system tests) (24765:2010(E), 2010).

Acronyms

Functional Requirements

• fsi: 2D-Finite-Strain-Steady
• 6.1.1The system shall be able to model fluid channel compression and solid expansion with a finite strain material model, which requires being able to evaluate stateful material properties on interfaces.

• fsi: 2D-Small-Strain-Transient
• 6.2.1We shall be able to combine navier-stokes and tensor-mechanics simulation capabilities to do some basic fluid-structure interaction simulations and produce equivalent results when the Navier-Stokes equations are implemented using
  1. scalar field variables for velocity components and hand-coded Jacobians,
  2. and a vector field variable for velocity and a Jacobian computed using automatic differentation. Additionally,
  3. the automatic differentation Jacobian shall be (nearly) perfect when the fluid domain equations are run on the displaced mesh, and
  4. perfect when the fluid domain equations are run on the undisplaced mesh, and

• fsi: Fsi Acoustics
• 6.3.1The system shall reproduce fluid pressures that match accurately with theoretical pressures.
• 6.3.2The system shall reproduce fluid pressures and structural stresses that match accurately with the ones provided.
• 6.3.3The system shall reproduce fluid pressures and structural stress that match accurately with values provided.
• 6.3.4The system shall reproduce wave heights that are consistent with the ones provided.

Usability Requirements

Performance Requirements

System Interfaces

System Operations

System Modes and States

MOOSE applications normally run in normal execution mode when an input file is supplied. However, there are a few other modes that can be triggered with various command line flags as indicated here:

Physical Characteristics

The Fluid Structure Interaction module is software only with no associated physical media. See System Requirements for a description of the minimum required hardware necessary for running the Fluid Structure Interaction module.

Environmental Conditions

Not Applicable

System Security

MOOSE-based applications such as the Fluid Structure Interaction module have no requirements or special needs related to system security. The software is designed to run completely in user-space with no elevated privileges required nor recommended.

Information Management

The core framework and all modules in their entirety will be made publicly available on an appropriate repository hosting site. Day-to-day backups and security services will be provided by the hosting service. More information about MOOSE backups of the public repository on INL-hosted services can be found on the following page: GitHub Backups

Polices and Regulations

MOOSE-based applications must comply with all export control restrictions.

System Life Cycle Sustainment

MOOSE-based development follows various agile methods. The system is continuously built and deployed in a piecemeal fashion since objects within the system are more or less independent. Every new object requires a test, which in turn requires an associated requirement and design description. The Fluid Structure Interaction module development team follows the NQA-1 standards.

Packaging, Handling, Shipping and Transportation

No special requirements are needed for packaging or shipping any media containing MOOSE and Fluid Structure Interaction module source code. However, some MOOSE-based applications that use the Fluid Structure Interaction module may be export-controlled, in which case all export control restrictions must be adhered to when packaging and shipping media.