CFD News/Conferences/Competitions update

CFDToy VidBar



ASME / FEDSM 2012 is now open: Submit abstracts

More details can be found at

Thursday, July 1, 2010


I know I have posted similar posts before: but the website presented below has a comprehensive list of learning modules, progressing from a simple to more complex solution using FLUENT.

Great for teaching undergraduates - course ware or even for understanding new CFD fronts !!

Enjoy !!

Wednesday, April 28, 2010

CFD : Wind Turbine Simulations

There has been quite some interest lately in modeling and simulating wind turbine flow using CFD operations. Thought, may be my simulation work in this concern may be of interest. I have attached my sample work on computing local wind turbine blade characteristics as well as the wake characteristics generated by these rotating blades.

Boundary condition and set up

Front View of the blades (Meshed)

I used the comfortable ;) sliding mesh techniques to run transient simulations of the rotating turbine blades. Turbulence activated using RNG k-e model. Ofcourse, I am carrying out some LES runs now to check out more interesting eddy characteristics. But, fundamental framework on this transient process remains the same.

All work reported here were of incompressible nature. Air was used as the fluid medium. Geometry of the turbine was generated using some earlier available models from literature. Ofcourse, more complicated profiles can be built based on specifications.

Contours plots of vorticity magnitude around the rotating blades - various increasing time instants (a-j)

Movie of vorticity shedding near the rotating blades - used FieldView for post-processing (could have been better ;)

Plots of Velocity vector to show local flow characteristics

Wake Flow Studies

I carried out several tests with increasing the incoming fluid flow velocity, changing the rotational speeds etc and interesting flow modification appeared throughout the domain.

This is just a preliminary post. I will keep adding some more information with respect to these simulations. More so, if you have any comments on the modeling and/or application, kindly let me know.

Wednesday, February 17, 2010

Eulerian Multi-fluid modeling: Developer and User Perspective

Understanding and implementing a multi-fluid model in any software code is a tedious and strenous process. The complication, not only arises owing to coding the procedure, rather to make sure that the system is stable after being washed with multiple "stablizing" approaches such as treatment of implicit drag terms to indicate a few. Often, CFD vendors have a single route for multiphase solution and it takes different forms based on the approach required: such as VOF, Eulerian or mixture type approaches. So, basically a given multiphase code assumes different formulations for fluxes, source / sink terms and induces the need for coupling (only in eulerian multifluid approach) based on the user specification.
Although, most of the users are not quite interested in the "background coding" involved in the blackbox tool, sometimes it becomes essential that they understand the physical significance of the methodology employed.

For example, let me indicate an off the shelf trick to make your eulerian multi-fluid runs much stable. Increasing the drag terms, involved between the phases, results in higher coupling and hence stable runs. Lowering the interaction terms makes the system (or the involved fluids) decoupled and may pose problems for mass convergence. Well, while writing papers people indicate, "enhancement in convergence was obtained by improving the interaction terms between the fluids" - which essentially a developer would read, the left hand side diagonal terms were made dominant :) !!! Such is the essence of CFD - both the user with a physical representation of the phenomena and the developer in a mathematical state of mind can mingle together talking about the same stuff!!

For those who are interested in the formulation part: I am presenting some nice lectures/notes on multi-fluid formulation.

Ofcourse, if you have any comments on the algorithms or suggest different approaches, please feel free to comment - i would be very interested in getting to know new techniques !

Take a look at this website for a decent understanding of the multi-fluid approach〈=en

For detailed understanding of the Multi-fluid approach, one can always lean to the Fluent presentation

Modeling of Gas-fluidized systems require very detailed investigation of the drag formulations (although, people tend to think of it more in a physical manner- the truth is ..such systems are extremely unstable owing to the multiple interaction terms and hence a good implicit approach is required to enhance convergence!) (Formulations in MFIX explained)

A nice presentation of gas-liquid reactor simulation with multiple bubble size distribution with discussion on moments, breakup and coalescence rates ..definitely something worth investigating..

CFD modeling of particulate flows (from the Stanford institute) (turbulent combustion part)

Eulerian models for polydisperse evaporating sprays:

I tend to use the keywords such as polydisperse models, dilute sprays, etc so that if one is searching for these keywords over the web, the blog presented here may be useful in finding some relevant papers.

A very nice use of Eulerian multi-fluid modeling for biological transport:

Tuesday, February 16, 2010

CFD Forums

In order to obtain complete control over the "commercial" blackbox codes, it is imperative that users discuss the finer details of the code implementation (user functions) so as to maximize the benefits ..the code has to offer. As most of the readers know, CFD-online has the primary source for many of us. Given that, several other forums such as

Fluent University Forums:


can provide elaborate discussions on certain stuff that may be missing in CFD-online.

I, in fact, strongly recommend Fluent users to become a part of the Fluent University Forum community. Besides getting answers from fellow CFD users, sometimes the developers themselves post results to queries which just makes it perfect ;) - straight from the source. Search for other topics (anything in Fluent) and errors/bugs that you think exists within the code can be discussed here. In fact, this portal serves as a nice forum to let Fluent guys know your exact problems.

Website providing tips for CFD modeling (especially multiphase flows such those using VOF etc) are also very helpful

I came across this site where manuals for different softwares and discussions pertaining to their usage are available.

Tuesday, February 9, 2010

VOF Modeling / Applications : Sprays / Droplet Breakup-Deformation-Coalescence .....

One the important problems where more academic fellows look to employ multiphase-VOF approach concerns the breakup of droplets (bunch of stuff can be investigated here : effect of shear, liquid/gas density ratios, velocity of impact etc). They keep publishing stuff back and forth so that they can honor their "commitment to publications!" either during tenure period or post-tenure (this time, the grad students are made to kill the problem !)

Anyways, being beaten down time to time or not, droplet simulations is something I have personally grown fond of ..especially the use of VOF in creating almost real droplets is simply artistic nonetheless !From studies on droplets, emerge, more sophisticated studies such as spray breakup, spray impingement problems etc that are of vast interest in real-world applications.

Having said that, it still becomes essential to find lot of literature in this special field so as to improve one's understanding of the phenomena and the applied numerical methods.

In this edition of the blog, I am going to share some of the droplet dynamics (breakup coalescence) studies that I have bookmarked and read over the years. Hopefully, someone may find it useful to read further into these nicely written work.

I came across this nice presentation sometime ago,

detailing aspects of droplet breakup from an industrial point of view. The presentation infact shows how droplet entering into a matrix of obstacles gets torn apart ! Mechanisms such as "stick and pull", spreading, etc are nicely indicated. Effect of viscosity ratios on the breakup rates are also available.

Dr. Renardy's work in VOF flows is well known. Their group site has a complete list of VOF papers including their PROST model.

All kind of publications dealing with droplet oscillations, shear flow (droplet dynamics), deformation due to strain in both 2D/3D approximation are available for download.

Also, you can find the PROST model here,%20Prost-%20a%20parabolic%20reconstruction%20of%20surface%20tension%20for%20the%20volume-of-fluid%20method.pdf

How could I not include the famous openFoam based VOF studies: (fundamental presentation by Dr. Jasak)

Droplet sedimentation simulation using Finite Element - Level Set Methods - interesting one !

Simulation of the dynamics of insoluble surfactant from Univ of Minnesota !

The above publication has extensive details of the numerical approach. The modeling includes surface tension force term represented by a linear/non-linear function of surfactant concentration using the continuum surface force (CSF) model. Nice read for developers and new onlookers.

How about DNS of droplets in a closed channel:

The presentation below is litte off from the VOF topic: NEvertheless, you can see the application of VOF in inkJET print heads !!

A study on droplet deformation through a micro-fluidic orifice can be downloaded here.

Some VOF papers using different approaches (other than conventional VOF type)

1. Buoyancy driven droplets simulated using hybrid vof - LEVEL SET approach

2. Simulations of droplet flows using Lattice Boltzmann approach (just to make sure I do not shun LB approach ;)

3. A good article on jet breakup using particle method,%20.pdf

Shared Presentation of the Day:
(Nice work VOF methods in Spray modeling !)

Wednesday, February 3, 2010

Multiphase Applications - Spray Breakup Simulations using VOF

From time to time, I come across some nice articles on VOF applications - also call them "cool multiphase applications" since most VOF runs typically try representing an "actual physical process". Note that the requirements for VOF are similar to DNS in the sense that as the mesh refinement is increased, better and better approximation of the physical phenomena is reached. Isnt it? Think about applications of VOF?

-Spray breakup modeling - when you actually animate the VOF runs - seems like there is a real spray started ..!!

- Droplet splash - now this has been beaten down several times and authors have proven that with nice refinement, one can present results which really puts the user in a stiff situation..which one is the experiment and which one represents simulation !! (Well, after properly rendering the volume fraction iso-surfaces etc )

-Boiling ...a very nice application - still researchers use this as standard benchmarking

-Sloshing, Spilling etc...VOF has been found to be an excellent tool to get these process nicely re-constructed in the virtual environment ..

I could keep adding to the links here ...VOF applications although, at times, forces the computers burn their guts out ...often end with some nice results which, at the end, prove heart warming.

I have been following several VOF applications - being a developer myself - and use of VOF in Spray breakup (primary breakup part) has been quite thrilling. I am posting some videos of Spray breakup using VOF (using openFoam). I contacted several authors long time ago to see if they have any images / videos that they could provide - just to get a glimpse of their research.

Some nice work I have been following

1. Dr. Hermann's work :

Check out the images in (liquid jet atomization in cross flows).

LES of Atomization using VOF techniques

2. I came across this paper "Numerical investigation on the disintegration of round turbulent liquid jets using LES/VOF techniques", Srinivasan et al., Atomization & Sprays, 2008.

Based on their work, using openFoam, I found some movies that I post here for guests view :)

Case - liquid jet velocity = 20 m/s in staganant gas

Case - Liquid Jet Velocity = 5 m/s in Stagnant gas

I will post some more videos of other breakup modeling work by researchers. Browsing along, one may be easily able to find vof simulations of droplet splashing, boiling etc which is why I left it out of the current discussion.

Kindly let me know your thoughts and comments. If you have something to share, kindly post your comments.

Tuesday, January 26, 2010

Presentations on Multiphase Flow

Its always nice to keep a directory loaded with presentations that contain valuable information such as modeling basics, some applications, discussions that we come across quite frequently. Sometimes, when I run out of ideas as to what kind of modeling should I consider or concerns regarding the physical approximations, an quick glimpse of some presentation slides provide me with the much needed break.

I am trying to load the blog with some presentations that I came across recently

An workshop conducted in Michigan State on MP flows with discussions and applications is available here state.ppt

CFD usage in particle separation etc (from Alstom site)

the above site clearly shows the industrial CFD procedures - what the industrial CFDers really want to look at etc..its more of a perspective based presentation ..not too much tech :)

A nice presentation by Dr. Pannala (MFIX guy)

Another work by Dr. Syamlal - (The guy from Syamlal - Obrien model in Gas-Solid flows)

A general publication on mixing layers and particle dispersion :

An presentation on Solid phase systems (transport of solid particles)

CFD code validation study from Canada:
(has some nice modeling part inside !!)

CFD Presentation on multi-poly-dispersed flows :

 CFD in Bio-Respiratory work: 

Multiphase CFD applications in Fluidized beds (a nice one ..I will probably use this later ?) 

Friday, January 22, 2010

CFD multiphase simulations : Cavitation Modeling Papers

Many multiphase CFD studies such as those of bubbly flows find extensive industrial applications which in turn induces higher interest among researchers to push for achieving higher level of details. It wouldnt be wrong if we call 'cavitation' as one of the most sought physical phenomena involving multiphase flow that has attracted so many academicians and industrial research fellows all around the world.

Cavitation, for its part, find applications right from your house pump to complicated industrial mixing devices, such as spray applicators, injectors in automotive units, in ultrasonics industry (sono-luminescence) to just quote a few.

The interest has been so over whelming...that conferences among the world have started dedicating separate sessions on cavitation - experiments, numerical simulations, modeling...

Having worked with this unique multiphase flow application myself, I have often wondered how everytime I dig into the fundamental nature of this process, it unveils a completely different nature that keeps me wandering around the far, having done some serious numerical computations (using incompressible, compressible, analytical modeling ..just not experiments yet...well wait..i did produce cavitation using airfoils in a simple lab experiment..nope that doesnt count? ), I thought this special topic requires some nice postings so that people can find it useful to reference and compare their own work with peers.

Several colleagues have come over to my desk inquiring .."hey, do you have any information / notes concerning bubble dynamics? " and i go, wow..there is an entire book available on this topic ..for FREE !

The cavitation and bubble dynamics book by Dr. Brennan should be your first reference to cite and read !

The book is available as html , pdf etc...Nice images of cavitating process - vortex type, chain, cloud cavitation are alllll available !!

1. Find multiphase modeling of super cavitating flows here: Publication text by Kunz et al.

2. On Propellar sheet cavitation:

3. By the way, I find a complete list of papers to follow, read, quote / reference and use for my own work from the listing of CAV2001 symposium !!

Its free for download based on category (within cavitation ofcourse !) : bubbly flows, erosion, turbomachinery, vortex type...

4. Cavitation in Pumps:

5. Cavitation Simulation : Shock Emission

6. Dispersion in Cavitating Flows

7. Dr. Kunz's work on Pump Cavitation

8. Here is an article on Vortex Cavitation !

If you notice the commercial CFD vendors, here is my take on their release versions:

Everytime, a new release is made by the software...from version v.x to v.y etc, notice that, on most occasions, there is some type of enhancement to cavitation prediction claimed by the software developers! Now, that should shed a lot of light on how much the industrial expectation out of these vendors to predict most accurate results !!! Experimentally, work on cavitation has been quite extensive as well. However, I fail to report their stand owing to my strong belief in numerical modeling ;)

Some other cavitation models other than the conventional (familiar ones) can be accessed here

a recent article on tracking cavitation as a scalar: doi:10.1016/j.apm.2008.02.005 

Homogeneous equilibrium modeling approaches:


2. (Dr. Schmidt's work)

3. Found one in the cav2001 symposium :

4. Found another one but not able to link it from ICLASS 2006 based on HEM

Title: "Computational investigation of cavitating injectors flows using Homogeneous Equilibrium Model supplemented with a pressure correction equation" using openFOAM
Paper 06-087, ICLASS 06, Kyoto, Japan, 2006.

While looking for cavitation and corrosion, I found this book link: useful i guess

Happy Cavitating !!!!

Tuesday, January 19, 2010

CFD Publications : Download, Share and Reference

On several occasions, I come across listing of publications/ conference papers available for free download for educational purpose and would try to mark the website for future reference. But, however, in time, I lose track of such nice websites and the link to those papers I wanted to download and read then. This has been a constant challenge to me and I hope, by creating this blog, I can put several listings on lectures / journals etc together and make them freely accessible to others.

Papers from NETL - the Energy Lab workshop on multiphase flow science (Fundamentals of Multiphase Flow) is available for download

The NETL workshop has some exciting papers on transport phenomena such as fluidisation CFD, discussions regarding MFIX, multi-scale CFD simulations count a few.

Publications from the Institue for corrosion and multiphase technology can be found at

The Ohio site has listings of patents - particularly in the area of slug flow, sediment transport etc. Interested people can take a look at these drafts at

Dr. Pai's site has some nice listings on modeling of droplet dispersion, DNS, LES, Sprays etc.. (only few papers are available for download)

Several part of his work such as spray modeling (DNS, LES etc) are very famous and definitely be in my reference list while publishing in these areas.

Also, the website provides a comprehensive list of CFD conference proceedings from 1997 to 2008 !!! Publications of varying interest in the CFD area such as Electromagnetic processes, Mixing and turbulence, power generation, flash melting, numerical methods, fluidised beds, stirred tanks, casting, combustion / particle flows are available by categories. One can choose the papers to download by organizing by authorship as well.

For example, Papers on Mixing and Turbulence from 1997 CFD conference proceedings can be downloaded from

Download the proceedings of openSource CFD International Conference 2008 from here

Download complete listings of Univ Iowa based researcher Dr. Becker's papers on phase change modeling !!

Also, provides the list directly.

Dr. Kirby's work (univ of Delaware) can be obtained from

The website  can be used to download publications from the 42nd conference on simulation and modeling organized by the Scandinavian Simulation Society. The complete list organized by session is available for download.

More archival publication listings (complete from 1998 - present) of the society of petroleum engineers can be accessed through

The publication has nice discussions ranging from energy to technical issues in modeling / simulation (Principles of Modeling and Simulation: A Multidisciplinary Approach, Theory of Modeling and Simulation, Second Edition).

I will be adding some more listings for easy access to fellow CFDers and Fluid dynamics researchers :)

Monday, January 18, 2010

CFD Simulations: Matlab Usage / Coding / Applications ...

Over time, there has been increasing discussions on whether or not other commercial softwares be used to program CFD and post process calculations...for example: use of Matlab (Matlab: A Practical Introduction to Programming and Problem Solving). In this blog, I will try to post links and articles - which uses matlab for CFD (/ general numerical) calculations.

Website maintained in the mech and material science dept., oregon

has some nice listing of matlab codes for 1D, 2D finite volume based calculations !! A nice start for beginners and others who look to use Matlab for their scientific needs.

Discussions in the good groups on whether or not Matlab could be used in the CFD world was interesting:

How about some nice shallow water modeling (CFD) using matlab: The file is available for download from the matlab central server

I found a paper on

1. CFD graphical interface using Matlab:

2. 2D Airfoil optimization using CFD (matlab based) :

3. Thesis work: CFD program to model pressure distribution of melt flow using Matlab

4. Discussions on SIMPLE algorithm in Matlab

In the pre-processing segment, the use of matlab has been extensive as well:

1. DistMesh: a simple mesh generator using matlab can be found here ( . Nice application for unstructured triangular and tetrahedral meshes.

2. Gridgen: a matlab based orthogonal grid generator to construct orthogonal curvilinear grids is available here.

The gridgen site has tutorials and details for download and installation.

3. The cornell based QMG package does finite element mesh generation in two and three dimensions

For some fundamental functions usage and programming for coding the entire CFD structure or in parts (pre / post processing) these books may be helpful.

1. MATLAB Programming for Engineers
2. An Introduction to Programming and Numerical Methods in MATLAB
3. Engineering Analysis: Interactive Methods and Programs with FORTRAN, QuickBASIC, MATLAB, and Mathematica

Multiphase Modeling: Eulerian-Eulerian simulations / applications

Simulation of multi-fluid flows (Multiphase Phenomena and Cfd Modeling and Simulation in Materials Processes) are often complex and requires complex mathematical treatment at the interfaces defining the fluid boundaries. Modeling the interfacial effects have been the core research for multi-fluid researchers. Often, a typical multi-scale phenomena that needs to be simulated is broken down into different zones identified by the acting scales and then "modeled" based on the acting physics. The work is still on-going but has definitely met with a lot of success and is often the default setting in major industrial practices [Comparison of different model approaches for the simulation of multiphase processes [An article from: Atmospheric Environment]).

I have come across the smash-project some time ago and thought this post on multifluid modeling will get a good facelift starting with a decent description of this modeling project.

As stated in their website: "Smash is a common project between INRIA and the University of Provence. The main topic of our project focuses on problems related to mathematical and numerical modeling of heterogeneous flows such as multiphase media, granular materials or reactive flows with mass transfer" presents a good description of the team goal. The website contains in-depth details of the applied methods (with assumptions yes..., mathematical treatment and aspects of parallel / grid computing)

Theses work following this project are listed here

and publication description:

With reference to multi-fluid flow modeling and numerical analysis, the work of the Center for Risk studies and safety is a must read.

Their website gives a complete picture of the their code MUSIC and associated publications and presentations made at major conferences and journals.

The link: lists all their publications and reports...i had bookmarked their information several years back and continue to look at their recent development in numerical analysis.

The papers (on multifluid analysis) from the 6th int. conf on CFD (Norway) can be downloaded from

I noted some papers which can be used for referencing and for extracting some finer numeric details while performing multifluid calculations include

1. Simulation of flow behavior in bubble column:

2. CFD modeling in gas fluidized beds

(Take a look at another papers on CFD work on fluidized bed:

3. 2D/3D investigations of dispersion and mass transfer coefficients in a Eulerian multifluid model

4. Evaluation of num methods for solving population balance eqn

There are several other nice papers available in the area of Environment/Combustion, fundamental methods and validation, some aspects of industrial CFD, oil and gas systems..

Nice application : Cyclone separators (gas-liquid) type

I normally tend to download the entire directory and keep it in my repository for future references ..even if i dont need them now. These papers are worth looking at and most of the time saves us lot of times when modeling similar to these are required to be computed.

For all those looking at ( or working with ) multifluid methods, the following paper can definitely be considered as a bible ;)

Also, Kunz's paper:

Other publications of interest

1. (CFD in Trickle bed reactor)

2. (Nice presentations on multifluid - granular flow etc!)

3. (openFoam based polydispersed flow modeling)

4. (free surface flows in metallurgical vessels)

5. (CFD : subcooled flow under high steam flux)

I would post some more research articles that is focused on 1. Numerics 2. Applications.

Some nice books for reference on MP flows validation and application:
1. Improvements in multiphase flow measurement.(Measurement Matters)(Column): An article from: Pipeline & Gas Journal
2. Fundamentals of Multiphase Flow
3. Computational Methods for Multiphase Flow
4. Multiphase Flow Dynamics 3

If you have any queries or publications that you think should be posted in this regard, kindly let me know. Sharing the knowledge is the only way to excellence !!

Friday, January 15, 2010

CFD Simulations (Animations ?)

I came across nice animations of free surface flows from the CFD team of Dr. Veldman (

The familiar droplet bouncing problem treated by the CFD group is shown below.

The work on 3D dambreaking problem is shown below.

The website for downloading some impressive videos on Free surface flows can be found at

Sample simulations of Free surface modeling is also available in the Univ Iowa website

A sample video downloaded from their site is posted here.

Flow over a Weir

An fire simulation is also available in the groups' site

Materials on : An introduction to CFD is available in their main page

Other handouts can be downloaded from

An virtual album of fluid flow can be viewed at :

These videos are copyrighted and have been posted here for educational purposes only. You can contact the respective institutions for further information.

Thursday, January 14, 2010

Fluent UDF Programming : Guides / References to User Defined Function Implementation

An guide to programming in Fluent can be found from the Stanford site

with details of data structure (Data Structures Using C), variable macro description and usage, journal files, batch execution, automatic adaptation, optimization (including procedure). A good reference that comes handy.

The complete Fluent 6.3 manual for UDFs can be downloaded from

With this file, it should be straightforward to create and work on your own physical/numerical modeling.

I came across this CFD FAQ in

describing typical user conversations on errors, not able to interpret/compile UDFs similar to CFD-online discussions. Some details are nicely explained and makes sure that we know what we are doing !

Found this thesis:
with some nice UDF implementation for properties and coupling with FIDAP.

udf Usage for modeling evaporation (Assessment of convection, conduction, and evaporation in nucleate boiling (NASA technical note)), mass transfer etc :

udf usage for particle trapping:

udf usage for momentum source :

udf for predicting particle deposition frequency:

udf for predefined pictch heave motion :

udf for calculation of second law of thermodynamics (really nice one!)

UDF for varying CFD boundary conditions + stratified energy storage:

UDF : setting target mass flow rate in pressure outlet, and some matlab data processing routines.

UDF listings for source terms implementation:

UDF's for calculating temperature dependent properties of single species and mixture

Nice UDF implementation for Chemical Vapor deposition modeling !

Wednesday, January 13, 2010

CFD Softwares: Other than Standard Commercial ones...

Among the list of several CFD vendors / Application programs that we normally come across the internet, few programs caught my attention with respect to its user-friendly nature and ease with which it can be incorporated into a fundamental CFD curriculum.

1. EasyCFD (

Quicknote: An simple CFD software tool for the numerical simulation of two-dimensional fluid flows in a boundary fitted structured grid. (predictions like Two-Dimensional Separated Flows, Study Of Abrupt Transitions in Two-Dimensional Flows: A Singular Perturbation Approach etc can be done)

The code is mainly oriented for didactic or educational purposes, it may become a valuable tool for a first analysis in practical situations. Contact and Download available in the home page.

Some features listed in the website include

· Laminar or turbulent flow
. Conduction in solids and conjugate heat transfer ( Theory of Periodic Conjugate Heat Transfer)
· Isothermal or non-isothermal flow (Incompressible Flow and the Finite Element Method, Volume 1, Advection-Diffusion and Isothermal Laminar Flow)
. Multicomponent fluid flow (Multicomponent Flow Modeling (Modeling and Simulation in Science, Engineering and Technology))
· Steady-state or transient flow
. Transport of passive scalars (eg. smoke, Transport of passive scalars in turbulent channel flow (SuDoc NAS 1.15:89463) )
· Numerical grid generation(Geometry and Topology for Mesh Generation (Cambridge Monographs on Applied and Computational Mathematics))
. Geometry import from DXF or point data files

Pre-processing (meshing, import of files..) and post-processing (contour plots, vectorial rep,
statistical data extraction features) are nicely done.

2. FluidFlow (

original software program for the design and optimization of pipe networks, transporting compressible, incompressible, gas-liquid two phase, settling slurries or non-Newtonian fluids.

The code looks pretty effective for product is used succesfully in many diverse industries to model new and existing systems, size pipes, select boosters, controllers and other fluid equipment (Fluid Dynamics Of Industrial Equipment: Flow Distribution Design Methods).

This is a definite piece of software - designers - should be looking at!! New release information and contact info are available in the website .

3. ChannelFlow

A C++ based software system for numerical analysis of the incompressible Navier-Stokes flow in channel geometries. Core idea is based on Spectral CFD algorithm for integrating NS eqns (Spectral/hp Element Methods for CFD (Numerical Mathematics and Scientific Computation)) . It is based on Flexible Object oriented programming concept. Classes act as building blocks for presenting particular channel flow models, and associated data analysis.

Nice description of the code set up is avaiable in the home page.

4. Enzo (an open-source cosmological simulation code that uses an adaptive mesh)

an adaptive mesh refinement (AMR), grid-based hybrid code (hydro + N-Body) which is designed to do simulations of cosmological structure formation (For those astro-physicists / computational /mechanical engineers !)Cosmological Inflation and Large-Scale Structure

The code - Enzo - has been parallelized using the MPI message-passing library and can run on any shared or distributed memory parallel supercomputer or PC cluster. Simulations using as many as 1024 processors have been successfully carried out on the San Diego Supercomputing Center's Blue Horizon, an IBM SP.

5. FLASH (free for non-commercial use, adaptive mesh, compressible solver for astrophysical flows)

Code support/mailing lists and research pages are available in the website.

Take a look at the movie based on convection simulation below (available in their website).


Other nice problems on flame propagation, burning in shear flow etc are well noted.

6. CFD Studio (Educational program to study CFD Problems)

is an application to solve 2D CFD problems. It contains a basic mesh generator, a numeric method that solves the conservation equations and it has also a data visualization. The software uses the finite volumes method in generic coordinates. A snapshot of the website is shown here.

Suite contains:
. CFD Studio solver
. CSFL-Lib - CFD C++ classes
. CFD Mesh - 2D mesh creator from complex geometries
. CFD Grid Editor - Edit 2D simple mesh using easy click approach.
. CFD SciView - visualization of meshes, scalar, vector fields obtained by the runs.

Several emerging codes, similar to those discussed here, have already started making some good impressions among the researchers in both academia and industry with some good comparisons in the results produced (Data for Validation of Cfd Codes (Fed; Vol. 146)). Its now a matter of when would these "opensource" applications would take over the commercial ones !

I am looking for similar opensource codes for adding to my repository...kindly advice me on something that you come across..happy openSourcing !!

Tuesday, January 12, 2010

CFD Simulations : Boiling Channel Flows Num Simulations / Experiments

Boiling channel/tube flows is one of the foremost process where use of multiphase modeling comes in handy. Several researchers have devoted their time and money in developing/adjusting the existing MP models specifically suited for their specific needs such as - to simulate MP flows in boiling chambers, nuclear reactors, tubes and containers to name a few (Boiling Heat Transfer And Two-Phase Flow (Series in Chemical and Mechanical Engineering), Boiling Heat Transfer and Two-Phase Flow). As a result, there are numerous publications in this area and to add, most of them are unique in their own way, in a sense that, each article provides a different insight into the modeling criteria and the assumptions used to treat the process.

Modeling in convective-in-tube systems:

MP Boiling applications find extensive use in microscale heat transfer flows and eventually help in designing systems to relieve vapor clot, removing bubbly flow altogether or enhancing it, modulating the curvature of the flow for better heat transfer characteristics etc..(Heat Transfer in Boiling Metals by Natural Convection, Boiling Heat Transfer: Modern Developments and Advances)

The article
presents a good review of the fundamentals of microscale flow heat transfer.

Also, note, a experimental study for one's numerical validation: Experimental work on saturated flow boiling in micro channels

I found the work by Dr. Mudawar on flow boiling heat transfer in microchannels : development of two-phase flow model quite interesting..Take a look here

PhD work by Dr. Geisler in the area of buoyancy driven 2phase flow and boiling heat transfer in channels,

gives a nice review of the modeling and experiments.

Also, find a good review of flow instabilities arising in boiling 2phase flow in natural circulation systems

Find Several Journal papers of Dr. Kandlikar's group doing heat transfer studies (multiphase experiments)

Find multiple journal articles available for download from the Multiphase lab from Israel inst of tech.

I am quite thrilled by the use of mp models for boiling purposes. For ex. treatment of wall heat flux using RPI boiling model, to convert Q to Twall is a nice procedure. These are modeling innovations one must definitely appreciate.

For a quick review on boiling heat transfer models / applications: I, on most occasions, look to the WLV handbook. It has been quite useful in providing you with quick information that one would otherwise have to obtain using advanced text books.
(Chapter on boiling heat transfer on external surfaces)

Another favorite handbook of mine is

- has nice descriptions of boiling heat transfer with quick graphs, plots, brief theories, heat transfer correlations and schematics for easy understanding..

Other applications of boiling heat transfer:
(boiling heat transfer in silicon microchannel arrays)

CFD modeling of subcooled flow boiling in nuclear sector (CFX software) - the article contains description of the forces, numerical treatment of the heat transfer problem etc..
(contains forced convective boiling in channels)

Subcooled boiling near wall

Modeling liquid velocity near wall during boiling flow

If you have any specific paper/work that you would like me to add here, kindly let me know.

CFD multiphase simulations : Eulerian-Lagrangian type

Modeling of multi-fluid flows is a complex task. Especially, identifying if the presented multiphase system can
be modeled with dilute particle or otherwise, can sometimes be a daunting task. Lagrangian type flows are normally encountered in spray simulations, in fluidized bed or even in snow transport applications as pointed out by a CFD-Online user.(Information on the treatment can be found in Intermediate Dynamics for Engineers: A Unified Treatment of Newton-Euler and Lagrangian Mechanics and/or Theory & Problems of Lagrangian Dynamics With a Treatment of Euler's Equations of Motion, Hamilton's Equations, & Hamilton's Principles, )

The formulation of Eulerian multi-fluid approach is much complex in comparison to the Euler-Lagrangian type work.This is primarily due to the fact that more interaction at the continuum level is expected out of the former,and in the latter, complexities may occur based on the coupling that one seeks: one-way to four-way coupling.

For those who are working on model-picking and in the stage of deciding to go with Euler-euler or Euler-
Lagrangian type: This observation may be of help.

The issues in Eulerian-Lagrangian simulation of complex transport of multiphase flow is elaborated in the following presentation.

In particular, the presenation above discusses the use of Lagrangian advection, and adjoint characteristics of the variables. Detailed conceptualtopics are well dealt. Nice to have this reference while writing a journal!

Several aspects of dealing with the multiple scales in Multiphase flows while modeling using Euler-Lag type situation is presented here.

A nice research article on Euler-Lagrangian modeling to simulate particulate flows can be found from
the archives of stanford research division:

Details of atomization simulations  using Eul-Lag methods can be obtained from Atomization simulations using an Eulerian-VOF-Lagrangian method (SuDoc NAS 1.26:201983) or A coupled Eulerian/Lagrangian method for the solution of three-dimensional vortical flows (SuDoc NAS 1.26:196785)

Presentation on modeling multi-phase flows with underlying assumptions is also available.

The multiflow : a fully coupled multiphase flow solver provides some introduction to multiphase applications

similar to a STAR intro:

Fluent stuff:

For someone trying to use Euler-Lagrangian type particulate affair: this publication may be a good reference.

Influence of Eulerian multiphase model parameters on the runs for a spouted bed grain dryer ? is nicely available from this journal article

For those industrial guys looking at CFD as an option, the article here may suggest why?

This book Multiphase reacting flows: modelling and simulation (CISM International Centre for Mechanical Sciences) provides a good understanding of the reacting multiphase flows with elaborate simulation examples.

Applications of Eulerian-Lagrangian modeling is quite prominent in the industrial settings where a compromise has to be made between the computational time vs computer resources in order to make quick decisions.

Monday, January 11, 2010

Fluid Mechanics / Dynamics : Lecture Notes, Applets..

I came across this 350+ page lecture notes "Fluid Mechanics for Civil Engineers" by Bruce Hunt of Univ of Canterbury and straightaway, having read a few chapters, included it in my important online book list.

The chapters listed in the book include
1. Fundamental eqns of fluid motion (such as Fundamentals of Fluid Mechanics)
2. Fluid Statics
3. Control Volume Methods (There you go..nice fundamental description)
4. Differential eqn methods
5. Irrotational Flow
6. Laminar / Turb flow
7. Boundary layer aspects
8. Drag / Lift theories and discussions
9. Dimensional analysis and model similitude (now im gathering my undergrad
10. Steady pipe / open channel flows
11. unsteady pipe and open channel flows

I kinda liked the overall description provided in the notes..its pretty easy to understand and numerics are well organized.

Another nice lecture notes I found in the web:

This is the Univ Iowa's Dr. Stern's course on mechanics of fluids and transport processes. Contains some nice
chapters and discussions.

Applets / Calculators

This is an yet another fluid applet that I recently came across. An Rotating U-tube Applet !!
Check it out here

Another Water-Mercury Manometer applet developed by UT Austin guys

Some more sweet applets !!

Looking at the impulse-momentum principle using Applets (from UT austin again)

Hydrofoil flow Applet:

I just listed a few applets that I was viewing...Find more applets and cool fluid stuff from Prof. Kinnas lab here.

With some knowledge in JAVA, the fundamental fluid mechanics (An Introduction to Fluid Dynamics) can be churned into nice movie type models....I guess, these java applets induce more curiosity among the undergrad/grad students to learn more about fluid systems ..conventional chalk boards definitely need to be replaced ?

Let me know if this information (the lecture notes / online applets) were helpful.

Books to read: Fluid Flow Handbook, Introduction to Mathematical Fluid Dynamics (Dover Books on Physics)

Sunday, January 10, 2010

VOF Simulations : Waves, Bubbles, Spillways....

Use of Volume-of-Fluid methods in wide environment has helped researchers gather tonnes of test cases / simulation studies that one could now use to enhance the interface capturing or try comparing the influence of other parameters such as turbulence in estimating the over all flow field.

This is particularly useful feature which encourages VOFers to try things that they werent sure before..since their random tests cannot be validated quite effectively. Being more towards the multiphase front, tests with VOF has intrigued me for a while and still does...Whenever, I come across tests / cases on multiphase modeling, Eulerian, VOF with advanced turbulence modeling, I tend to mark them for more in-depth analysis.

I am posting some of the VOF studies that once again found in my research directory. Hope it helps in providing someone with case study or for further analysis.

Anyone, having  developed a VOF method or trying its capability, has always come across the typical DAM breaking problem...tiring one ..appears in the to-do list all the time. The ERCOFTAC community has a typical 3D dam  case for readers

Find droplet deformation studies using PROST VOF code here:

Some sample cases / validation studies: Hydraulic jump free surface modeling

FLOW3D work on droplet based Microfluidics problem using VOF methods is available here

Interestingly, recently I came across a similar question in CFD-online

Similar discussions on mixing of gas / liquid flows invoking the question: should we use VOF or other Eulerian strategies...
My view is : its a case-by-case situation. Based on what one would like to capture and the refinement of the grids that one would like to achieve, VOF or other Eulerian methods can be appropriately put to test.

A presentation of combined VOF/ Level Set methods (which are becoming sort of popular these days ...)

These methods try combining the effective mass conservation of VOF type schemes with production of sharp interfaces using the distance function based LEVEL set methods. I really havent tried exploring this option (implementing this idea) yet.

And, how about simulating WaterFalls for a change...hello Niagara !

LES/VOF studies of liquid jet breakup:

Also, take a look at the study of liquid-metal flows

A more numerical study on "total volume conservation during free surface flows" can be found here

Collection of bubbles simulated using VOF ! Wow, now thats resource-intensive study !!

Comparisons of various CFD models in simulating flow field near tailrace zones : A nice report presented by US army corps.

btw, the report compares VOF methods in STAR, FLOW3D and they explain what other softwares were considered for this project and details on choosing STAR and FLOW3D !!!

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