+*solves a set of k and ε transport equations for each phase.
+*is appropriate choice when the turbulence transfer among the phases plays a dominant role.
+*Turbulence predictions are obtained from two long equations which both of that equations have two terms that must be approximated like these:
* Clq = 2,
* Cql = 2ηlq/(1+ηlq).
where: ηlq is the ratio of the characteristic particle relaxation time and the Lagrangian integral time scale of the phases q and l.
+*The turbulent viscosity defined as a equations.
Recomended for the thesis (1st priority), and use LAUNDER and SPALDING (1974), because so famous used by researchers like Lu and Howatrh (1996a, 1996b). Although we can use in simulation as 2nd priority,dispersed t. m. or mixture t. m. as the 3rd priority for these works.
Monday, June 4, 2007
dispersed-turbulence-model
This model is appropriate when the concentrations of the secondary phases are dilute. In this case, interparticle collisions are negligible and the dominant process in the random motion of the secondary phases is the influence of the primaryphase turbulence. Fluctuating quantities of the secondary phases can therefore be given in terms of the mean characteristics of the primary phase and the ratio of the particle relaxation time and eddy-particle interaction time.
Turbulence in the continuous phase is described by:
- a modified k-ε model,
- the influence of the dispersed phase on the continuous phase q, and
- the production of turbulent kinetic energy
- For the turbulence quantities of the dispersed phase user can use Mr. 'X' approach (for e.g. Muehlbauer, P 2004 use Simonin, Viollet (1990) approach).
Think that 1st phase=gas, air, and 2nd phase=particles, water,
Turbulence in the continuous phase is described by:
- a modified k-ε model,
- the influence of the dispersed phase on the continuous phase q, and
- the production of turbulent kinetic energy
- For the turbulence quantities of the dispersed phase user can use Mr. 'X' approach (for e.g. Muehlbauer, P 2004 use Simonin, Viollet (1990) approach).
Think that 1st phase=gas, air, and 2nd phase=particles, water,
mixture-turbulence-model
Mixture turbulence model (default in FLUENT), applicable for stratified (or nearly stratified) multiphase flows, and when the density ratio between phases is close to 1. In these cases,
using mixture properties and mixture velocities is sufficient to capture important features
of the turbulent flow. There are 5th equation for modeling turbulence in this mixture turbulence model, i.e.:
- ske-2 eqn
- mixture density
- mixture velocity
- the turbulent viscosity
- the production of turbulence kinetic energy
using mixture properties and mixture velocities is sufficient to capture important features
of the turbulent flow. There are 5th equation for modeling turbulence in this mixture turbulence model, i.e.:
- ske-2 eqn
- mixture density
- mixture velocity
- the turbulent viscosity
- the production of turbulence kinetic energy
Sunday, June 3, 2007
Sohn, et. al. 2004-using-CFD
CFD is a mathematical modeling procedure whereby the fluid parameters of velocity,
temperature, pressure, turbulence, and contaminant concentrations are calculated
by solving the governing partial differential equations for fluid flow, heat
transfer, and conservation of species. These differential equations describe a threedimensional
viscous fluid flow field. Due to the non-linearity of these equations,
they cannot be solved analytically. The CFD approach is to transform these differential
equations into a set of discrete algebraic equations and solve the algebraic
equations by an iterative procedure.
Researchers have used CFD since the early 1970s. Its use has increased dramatically
in the last decade as a result of advances in the computing power. In the
1980s, Cray supercomputers typically were used to process CFD simulations, with
solution times taking days (which followed a long wait to even gain access to use the
supercomputer). The same simulations may now be run on a personal laptop computer
in a matter of hours. CFD modeling has been continually validated since its
inception against many known fluid phenomena. It is considered a very useful tool
for engineers and scientists working on fluid flow problems across many disciplines.
temperature, pressure, turbulence, and contaminant concentrations are calculated
by solving the governing partial differential equations for fluid flow, heat
transfer, and conservation of species. These differential equations describe a threedimensional
viscous fluid flow field. Due to the non-linearity of these equations,
they cannot be solved analytically. The CFD approach is to transform these differential
equations into a set of discrete algebraic equations and solve the algebraic
equations by an iterative procedure.
Researchers have used CFD since the early 1970s. Its use has increased dramatically
in the last decade as a result of advances in the computing power. In the
1980s, Cray supercomputers typically were used to process CFD simulations, with
solution times taking days (which followed a long wait to even gain access to use the
supercomputer). The same simulations may now be run on a personal laptop computer
in a matter of hours. CFD modeling has been continually validated since its
inception against many known fluid phenomena. It is considered a very useful tool
for engineers and scientists working on fluid flow problems across many disciplines.
Saturday, June 2, 2007
Muehlbauer, et. al., 2001-future-needs-on-CFD
The document which written by Muehlbauer, P., (2001) describe the present capabilities of more than three CFD-type computer codes to simulate two-phase flows and the future needs on the two-phase CFD computer codes. Principal approaches to description of two-phase flows, their advantages, and disadvantages are discussed. Also for each of the codes two-phase flow and heat transfer are already described in some detail. From all of CFD-type computer codes that described, there are three CFD codes i.e., FLUENT, STAR-CD, and CFX which have more capabilities especially for “3D codes for open medium” to simulate two-phase flows and there is a short description of the two-phase flow capabilities of several other CFD-type computer codes i.e., TRIO-U, NEPTUNE, and PHOENICS.
CFD-Packages-in-the-market
[1]. CBNP Transport & Fate Team, http://www.lanl.gov/orgs/d/d4/pdf/air/model_review.pdf accesed May 2007. (Chemical & Biological Nonproliferation Program) had been classified become five-types of computer codes that already used in the world to modeling transport and fate phenomenons, i.e.,: CFD Models for Flow around Building, Building Interior Flow and Transport Models, Mesoscale Atmospheric Models, Plume Dispersion Models, and Subway System & Interior Flow Models.
[Examples of CFD Models for flow around buildings are: Dynaflow, FEM3C, GASFLOW, HIGRAD, and TEMPEST.
Examples of building Interior Flow and Transport Models are: COMIS, MIAQ4, CONVECT9, GASFLOW.
Examples of Mesoscale Atmospheric Models are: COAMPS, HOTMAC, NORAPS, RAMS.
Examples of Plume Dispersion Models are: ADPIC, HYPACT, LODI, RAPTAD, SALB.
Examples of Subway system & Interior flow models: GASFLOW, SES.]
[2]. Sohn, et. al. (2004) already reviewed many existing technologies that could protect the supply air systems of buildings from chemical/ biological (chem/bio) contaminants such as FEM3MP, HPOC, CONTAM, dan FLOVENT. FEM3MP and HPOC for external dispersion modeling, CONTAM and FLOVENT for internal dispersion modeling. The results provide a modeling approach that can be used to simulate the dispersion of contaminants inside buildings. Such a numerical simulation will help designers and managers evaluate possible ways to reduce occupant exposures to chem/bio contaminants.
[M]odeling Package Name: FLOVENT
[A]uthor: Flomerics Incorporated)
[N]umerical Simulation Description: CFD - Specific to the built environment(internal/external flows)
[M] Airpack
[A] FLUENT Incorporated
[N] CFD - Specific to the built environment (internal/external flows)
[M] STAR-CFD
[A] Adapco Group
[N] CFD - Multi-purpose code
[M] CFX
[A] ANSYS
[N] CFD - Multi-purpose code
CONTAM 2.1
National Institute of Science and Technology (NIST)
Nodal Analysis - Multizone indoor air quality and contaminant transport analysis.
IAQX (MIAQ4) (Nazaroff and Cass, 1989)
EPA
Add on to RISK for particulate, sources, spills
COMIS (Festel, 1999)
LBNL
Conjunction of Multizone Infiltration Specialists
Integration of CFD and COMIS (Sohn, et. al., 2006)
LBNL
Current research area for LBNL Airflow and Pollutant Transport Group
[3]. CFD is a mathematical modeling procedure whereby the fluid parameters of velocity, temperature, pressure, turbulence, and contaminant concentrations are calculated by solving the governing partial differential equations for fluid flow, heat transfer, and conservation of species. These differential equations describe a threedimensional viscous fluid flow field. Due to the non-linearity of these equations, they cannot be solved analytically. The CFD approach is to transform these differential equations into a set of discrete algebraic equations and solve the algebraic equations by an iterative procedure.
[4]. This thesis is about internal dispersion,... and have two fluid flow i.e.: particle and gas.
[5]. STAR-CFD, CFX dan FLUENT in two phase modeling.
[6] Sippola and Nazaroff (2002), describe four broad methods of predicting particle deposition rates that found in the literature: empirical equations, Eulerian models, sublayer models and Lagrangian simulations. These methods usually require information about the particle size and density, as well as the air speed and dimensions of the duct containing the flow. Deposition rates are most commonly reported in the form of the dimensionless deposition velocity, Vd+, versus the dimensionless relaxation time, τ+, a measure of particle inertia.
...[to be continued]...
[Examples of CFD Models for flow around buildings are: Dynaflow, FEM3C, GASFLOW, HIGRAD, and TEMPEST.
Examples of building Interior Flow and Transport Models are: COMIS, MIAQ4, CONVECT9, GASFLOW.
Examples of Mesoscale Atmospheric Models are: COAMPS, HOTMAC, NORAPS, RAMS.
Examples of Plume Dispersion Models are: ADPIC, HYPACT, LODI, RAPTAD, SALB.
Examples of Subway system & Interior flow models: GASFLOW, SES.]
[2]. Sohn, et. al. (2004) already reviewed many existing technologies that could protect the supply air systems of buildings from chemical/ biological (chem/bio) contaminants such as FEM3MP, HPOC, CONTAM, dan FLOVENT. FEM3MP and HPOC for external dispersion modeling, CONTAM and FLOVENT for internal dispersion modeling. The results provide a modeling approach that can be used to simulate the dispersion of contaminants inside buildings. Such a numerical simulation will help designers and managers evaluate possible ways to reduce occupant exposures to chem/bio contaminants.
[M]odeling Package Name: FLOVENT
[A]uthor: Flomerics Incorporated)
[N]umerical Simulation Description: CFD - Specific to the built environment(internal/external flows)
[M] Airpack
[A] FLUENT Incorporated
[N] CFD - Specific to the built environment (internal/external flows)
[M] STAR-CFD
[A] Adapco Group
[N] CFD - Multi-purpose code
[M] CFX
[A] ANSYS
[N] CFD - Multi-purpose code
CONTAM 2.1
National Institute of Science and Technology (NIST)
Nodal Analysis - Multizone indoor air quality and contaminant transport analysis.
IAQX (MIAQ4) (Nazaroff and Cass, 1989)
EPA
Add on to RISK for particulate, sources, spills
COMIS (Festel, 1999)
LBNL
Conjunction of Multizone Infiltration Specialists
Integration of CFD and COMIS (Sohn, et. al., 2006)
LBNL
Current research area for LBNL Airflow and Pollutant Transport Group
[3]. CFD is a mathematical modeling procedure whereby the fluid parameters of velocity, temperature, pressure, turbulence, and contaminant concentrations are calculated by solving the governing partial differential equations for fluid flow, heat transfer, and conservation of species. These differential equations describe a threedimensional viscous fluid flow field. Due to the non-linearity of these equations, they cannot be solved analytically. The CFD approach is to transform these differential equations into a set of discrete algebraic equations and solve the algebraic equations by an iterative procedure.
[4]. This thesis is about internal dispersion,... and have two fluid flow i.e.: particle and gas.
[5]. STAR-CFD, CFX dan FLUENT in two phase modeling.
[6] Sippola and Nazaroff (2002), describe four broad methods of predicting particle deposition rates that found in the literature: empirical equations, Eulerian models, sublayer models and Lagrangian simulations. These methods usually require information about the particle size and density, as well as the air speed and dimensions of the duct containing the flow. Deposition rates are most commonly reported in the form of the dimensionless deposition velocity, Vd+, versus the dimensionless relaxation time, τ+, a measure of particle inertia.
...[to be continued]...
Hinds1999-characteristic-of-particles
Real particles are not spherical in form, but have different shapes. That is why the aerodynamic particle diameter is introduced for simulations. The aerodynamic diameter used in the simulations, dp, is the diameter of the unit density ( ρp = 1 g/cm3) sphere that has the same settling velocity as the particle. Particles can appear as human hair, parts of human skin and parts of different building or other materials (Hinds, 1999).
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