nanoFluidX

2021

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nanoFluidX Overview
nanoFluidX is a software to simulate single- and multi-phase flows based on the Lagrangian Particle Method "Smoothed Particle Hydrodynamics" (SPH).
Theory and Advanced Features

What's New
Technical Capabilities
nanoFluidX Overview
Validation Cases
Bibliography

Index

2021

nanoFluidX

What's New
View new features for nanoFluidX 2021.
Technical Capabilities
Overview of nanoFluidX technical capabilities.
nanoFluidX Overview
nanoFluidX is a software to simulate single- and multi-phase flows based on the Lagrangian Particle Method "Smoothed Particle Hydrodynamics" (SPH).
- Basic Usage
  Sample configuration files and geometry input files are provided with the binary to test the proper system setting and see if the simulation starts correctly on the system.
- Pre-processing using SimLab
  nanoFluidX uses two files to setup a simulation. Apart from the configuration file, which defines all relevant simulation parameters and phase properties, a geometry file is required that defines the initial discretization of the problem with particles.
- Simulation Setup
  The general purpose of nanoFluidX is to simulate complex multi-phase or free surface flows using multiple GPUs.
- Theory and Advanced Features
  - Inlet Regions
    Inlet regions mimic the behavior of inlets with a superposed impose region and allow spawning particles anywhere within the computational domain.
  - Outlet Regions
    Outlet regions mimic the behavior of outlet and simple outlet using a combination of removal and extended regions.
  - Keychain Validator
    Keychain validator compares the keychains in the cfg file with valid nanoFluidX keychains, when activated.
  - Energy Equation
    Energy equation in nanoFluidX is implemented so that it accommodates for conduction and convection heat transfer with initial or Dirichlet boundary conditions.
  - Viscosity-temperature Dependence Models
    New viscosity-temperature coupling (viscTempCoupling) has been introduced into the nanoFluidX code as an option. Three models were implemented: polynomial, Sutherland, and power law.
  - Multiphase Surface Tension
    nanoFluidX implementation of the multiphase surface tension model heavily relies on the work of Adami et al. topics/nanofluidx/surface_tension_r.html#reference_jwp_11z_k2b__fn_lnr_2v5_s2b
  - Varying Body Force (Acceleration)
    The body force, defined through acceleration in units of [m/s²] can be varied over time using an input file.
  - Motion: POSITION_FILE
    The prescribed motion (transient wall boundary condition or 'position file' moving wall) is a capability of nanoFluidX which allows to prescribe any motion of a moving wall using an input .txt file.
  - Motion: CONROD
    CONROD motion is the only motion which defines a motion for two phases. This is done because conrods and pistons share a number of common parameters necessary to define their respective movement.
  - Motion: PASSIVE_RIGID_BODY
    It is possible to define a rigid body motion in nanoFluidX such that the body is freely interacting with the fluid (exchanging momentum and heat with the fluid).
  - Restart Option
  - Probes
  - Free Surface Formulation
    Standard SPH interpolation heavily depends on the basic premise that each particle has the so called “full support.” Full support implies that the owner particles can “see” particles all around itself within the smoothing length of the particle, which mathematically implies that the sum of the kernel (also known as Shepard coefficient) is equal to one.
  - Transport Velocity Formulation
    Some main principles and consequences of the transport velocity.
  - Aeration-Viscosity Models
    Improving torque estimates in nanoFluidX is of high importance. Currently, prediction of accurate absolute values of torque for general geometries has a series of quantitatively varying results.
  - Adhesion Model and Single Phase Surface Tension Models
    Both single phase surface tension and adhesion modeling is based on the work of Akinci et al.
  - Operation Modes
    The operationMode option allows you to change the solver for either minimal run time or maximum accuracy.
  - Riemann Particle Interaction Scheme
    The Riemann problem can be defined as a category of initial value problems that involve a conservation equation and a piecewise data set with a single discontinuity.
  - Sub-Phasing
    Sub-phasing capability, while essentially optional, represents structural change inside nanoFluidX more than a classic feature.
- nanoFluidX Companion
  nanoFluidX companion (also known as, nFX[c]) is a post-processing tool developed to accompany the nanoFluidX solver and allow for an easier execution of certain post-processing tasks.
- nanoFluidX Monitor - nFX[m]
  nFX[m] is a single file portable Python executable that is aimed for helping with monitoring a nanoFluidX simulation during runtime.
- nanoFluidX Prep – nFX[p]
  nanoFluidX prep, shortened as nFX[p], is an auxiliary executable for nanoFluidX intended to eliminate a number of potential user errors during the pre-processing phase.
- Use check_nFX.sh Script
  The check_nFX.sh script is able to collect case information for debugging. This can be done by adding the -c <path/to/case/directory> option.
- nanoFluidX Auxiliary Tools for ParaView
  Learn material library loading and how to install the nanoFluidX toolbar plugin.
- Tips, Tricks, and Advice for Best Practice
- WEIGHTED and RIEMANN Solver Options
  nanoFluidX options available in combination with the WEIGHTED and RIEMANN Solver.
Validation Cases
nanoFluidX validation cases.
Bibliography
References used throughout the nanoFluidX manual.

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nanoFluidX

2021

Home
nanoFluidX Overview
nanoFluidX is a software to simulate single- and multi-phase flows based on the Lagrangian Particle Method "Smoothed Particle Hydrodynamics" (SPH).
Theory and Advanced Features

What's New
Technical Capabilities
nanoFluidX Overview
Validation Cases
Bibliography

Index

Theory and Advanced Features

Inlet Regions
Inlet regions mimic the behavior of inlets with a superposed impose region and allow spawning particles anywhere within the computational domain.
Outlet Regions
Outlet regions mimic the behavior of outlet and simple outlet using a combination of removal and extended regions.
Keychain Validator
Keychain validator compares the keychains in the cfg file with valid nanoFluidX keychains, when activated.
Energy Equation
Energy equation in nanoFluidX is implemented so that it accommodates for conduction and convection heat transfer with initial or Dirichlet boundary conditions.
Viscosity-temperature Dependence Models
New viscosity-temperature coupling (viscTempCoupling) has been introduced into the nanoFluidX code as an option. Three models were implemented: polynomial, Sutherland, and power law.
Multiphase Surface Tension
nanoFluidX implementation of the multiphase surface tension model heavily relies on the work of Adami et al. ¹
Varying Body Force (Acceleration)
The body force, defined through acceleration in units of [m/s²] can be varied over time using an input file.
Motion: POSITION_FILE
The prescribed motion (transient wall boundary condition or 'position file' moving wall) is a capability of nanoFluidX which allows to prescribe any motion of a moving wall using an input .txt file.
Motion: CONROD
CONROD motion is the only motion which defines a motion for two phases. This is done because conrods and pistons share a number of common parameters necessary to define their respective movement.
Motion: PASSIVE_RIGID_BODY
It is possible to define a rigid body motion in nanoFluidX such that the body is freely interacting with the fluid (exchanging momentum and heat with the fluid).
Restart Option
Probes
Free Surface Formulation
Standard SPH interpolation heavily depends on the basic premise that each particle has the so called “full support.” Full support implies that the owner particles can “see” particles all around itself within the smoothing length of the particle, which mathematically implies that the sum of the kernel (also known as Shepard coefficient) is equal to one.
Transport Velocity Formulation
Some main principles and consequences of the transport velocity.
Aeration-Viscosity Models
Improving torque estimates in nanoFluidX is of high importance. Currently, prediction of accurate absolute values of torque for general geometries has a series of quantitatively varying results.
Adhesion Model and Single Phase Surface Tension Models
Both single phase surface tension and adhesion modeling is based on the work of Akinci et al.
Operation Modes
The operationMode option allows you to change the solver for either minimal run time or maximum accuracy.
Riemann Particle Interaction Scheme
The Riemann problem can be defined as a category of initial value problems that involve a conservation equation and a piecewise data set with a single discontinuity.
Sub-Phasing
Sub-phasing capability, while essentially optional, represents structural change inside nanoFluidX more than a classic feature.

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