Sunday, May 27, 2012

Analyze, Print & Export NACA Airfoils

A limited edition version of VisualFoil 5.0 is now available for the price of $69.
This version allows the analysis of NACA 4, 5 and 6-digit airfoils using the built-in library. In addition, the airfoils can be modified within the program and exported to ASCII (text) or .dxf file formats.
VisualFoil 5.0 uses a linear strength vortex panel method coupled with boundary layer analysis solver  to compute lift, drag and moment coefficients for subsonic (Prandtl-Glauert correction) and incompressible flows past airfoils. The stall model allows the estimation of the angle of maximum lift. Graphs of Cl vs angle of attack, Cl vs Cd and other curves are available within the software and can be exported to external reports.

More information about VisualFoil can be found at:
VisualFoil 5.0 is excellent for:
  • accurate airfoil analysis and computing lift, drag and moment coefficients
  • NACA 4, 5 & 6-Digit Airfoil library 
  • student projects (aircraft, wind energy, hydrofoils)
  • an inexpensive airfoil reference tool
  • classroom demonstrations
  • printing airfoils templates on a Windows supported printer
  • exporting accurate representations of airfoils to .dxf files  
The NACA-Version of VisualFoil requires a PC or Laptop running Windows XP, Vista or Version 7. The purchase price is $69 US.

Please use the following link to purchase the software.

Do not hesitate to contact me at (352) 249-3658 if you have any questions.

Thanks for reading.

Monday, May 21, 2012

Setting Sails

It is important to realize that sails are wings and they often act like wings (this applies to almost any sail and not just rigid wing sails now popular in the America's Cup race). Therefore, when it is required to optimize the sail settings for a specific boat, we can rely on our knowledge of wing aerodynamics and our bag of accumulated tricks (experience & tools) to do an efficient job.

The primary goal of sail optimization is to increase the lift (for a good drive force component) and reduce the drag (stability must be maintained during the process).  Sail optimization is a repetitive job.  This is because, like wings, the drive force of the sail in up-wind sailing depends on the apparent wind vector (direction and magnitude), the planform (area & aspect ratio), the camber (flat or curved cross sections), the gap between the fore and main sails, the mast and other parameters (such as height above the deck, hull shape, etc.).

Stallion 3D Simulation of flat thin sails. The graphs shows pressure.

A good design does not simply mean infinite aspect ratio to reduce tip vortices (tip vortices increase drag as seen in above picture).  The heeling moment will be too big (unless, of course, you have this installed on your boat).  Large camber or deeper sails can increase the drive force, however, stability and drag from supporting underwater devices (keel and rudder) can erode this advantage. To obtain the optimal (or best we can do at the moment) specifications for a particular sail, we must test our design iterations against a number of possible sailing conditions. 

Stallion 3D Simulation of cambered thin sails. 

Deadlines are the natural enemy of testing and optimization.  Experimental setup and testing in a wind tunnel can be time consuming and costly (and might even require a minor in wood carving).  Wind tunnel and tow-tank test can be made more efficient and cost-effective only if the most promising designs are tested prior to making the final decision.

Stallion 3D Simulation of cambered thin sails with a larger angle between jib and main sail.

Computational methods can be used to test conceptual and preliminary design ideas.  However, a good understanding of the assumptions used in a particular method is required to get useful information to test in the wind tunnels and water tanks.  What is the difference between 2D sections, vortex lattice, panel methods, Euler/Navier-Stokes methods? They are all useful.   Knowing the answer and how to apply the various concepts in a concerted manner can speed up your upwind sail to the best design.

No sail optimization study is complete without the consideration of the underwater systems (keel, rudders and other appendages). Like sails, keels and rudders are wings and also behave as wings.  The goal to provide stability and lateral resistance can result in drag (induced and profile).  Also, an efficient keel for up-wind sailing can be terrible otherwise.  In short, sail and keel/rudder analysis are coupled and equal partners in sailboat optimization.

Stallion 3D simulation of a keel and bulb.

In the area of aerodynamics conceptual design, a lot of nautical mileage can be quickly covered with a tool that has a built-in set of realistic physical assumptions, automatic grid generation and cost effective and readily available computing platform.  Stallion 3D can be deployed on an ordinary Windows PC, run in multiple directories to take advantage of multi-core processing and efficiently and accurately analyze the most difficult models.

Stallion 3D simulation of sails and hull (3D model from
Graph shows surface speed in m/s.

More information can be found at  The cost of a 3-months lease of Stallion 3D is $895.

Thanks for reading. 

Do not hesitate to email or call me at (352) 240-3658 if you have any questions.

Tuesday, May 15, 2012

Faster Target Drones

Transonic jets are not easy targets and valuable training and experience can be gained by using faster drone aircraft as targets during training. 

Transonic & supersonic jets make very expensive drones. One solution is to use outdated airplanes as targets.  However, retrofitting these airplanes with new equipment can be equally expensive especially in light of their inevitable fate.

A cost reducing solution is to modify existing target UAVs so they can efficiently fly at higher Mach numbers with relatively inexpensive propulsion systems.  This requires drag reducing techniques at the regime of flight in the neighborhood of the drag divergence Mach number aka Mdd.

Stallion 3D Simulation of UAV at M=0.95

Drones designed for subsonic flight look and behave differently than those designed for supersonic flight.  A proven method for increasing the Mdd is to sweep back the main wings.  However, if an existing UAV is redesigned with a swept wing, the stability and flight characteristics of the aircraft will change and the cost of the modifications can increase.  

Stallion 3D was used for a quick design study with  four  different Mach numbers near Mdd and two similar UAVs to test the concept of airfoil modification as apposed to sweep to improve the aircraft performance at high transonic Mach numbers.  

Grid generation for the aircraft was automatic and the total set of calculations (8 separate cases) was completed in under 12 hours on a 4-core laptop computer running Windows 7.

Existing UAV System with Modified Airfoil at Mach number of 0.7, 0.8, 0.9 & 0.95.

Existing UAV System with Modified Wing Sweep at Mach numbers of 0.7, 0.8, 0.9 & 0.95.

Drag Divergence for Modified UAVs

The studies show that as far as Mdd is concerned,  a cost effective airfoil modification option can be used to increase the efficiency of a drone aircraft near Mdd and it can be effective as swept wings.  In addition, this aircraft can also be more efficient at lower speeds.

This is an example of valuable information than can be quickly obtained due to the unique algorithm contained in Stallion 3D.  The software can be used to compute lift, drag, moments and stability derivatives for your unique aircraft shape at subsonic, transonic and supersonic speeds.  Grid generation is automatic and the setup of a complete aircraft configuration can take less than one minute.

How would you use Stallion 3D to quickly solve your  aircraft modification problems?

For more information, please visit or call us at (352) 240-3658.

 Please visit for more information about Stallion 3D.  

Thanks for reading. 

Wednesday, May 9, 2012

Stallion 3D Comes to The Aerodynamics ClassPack

Every student in your class (or member of your small business group) can have a copy of the Aerodynamics ClassPack on their notebook computer for the entire year!

ClassPack is a yearly class/group license of our software suite consisting of  Stallion 3D, MultiSurface Aerodynamics, MultiElement Airfoils and VisualFoil Plus. Each module in ClassPack has proven accuracy and utility in both the professional and academic worlds.

The advantages of ClassPack include:
  • engaging content for lectures and labs
  • independent student activities
  • complete software packages (no need to purchase extra pre & post processing tools)
  • engineers and students do not need to have advanced aerodynamics or computer programming skills
  • accurate solvers for realistic project and lab experiments
  • interactive visualizations for engaging aerodynamics presentations and lectures
  • standard graphs (as you will find in text books or reports) & analysis for reports and capstone year end projects
  • design interface for international design competitions
  • ideally suited for fulfillment of design credits
  • already used in industry for aerodynamics conceptual analysis & design
Under the ClassPack license, all engineers, faculty, staff & students involved with a specific small business group or academic class will be able to access the software suite under a single class password.
The software can be installed in the classroom,  engineer or faculty offices, group members and students' PCs or notebooks and in labs associated with the class.

Stallion 3D race car simulation. Graph show surface velocity in m/s.

The Aerodynamics ClassPack Suite is ideally suited for:
  • aerodynamics conceptual analysis and design
  • introductory courses in aerodynamics and fluid dynamics
  • intermediate courses covering flow fields, airfoil analysis, 3D wing analysis & design, compressible flows & boundary layers and high lift devices
  • advanced courses covering 2-D panel methods, 3-D vortex lattice methods and finite volume CFD methods
  • senior projects & design-build-test competitions
  • consulting projects
  • aircraft, marine and automobile design and analysis
  • transonic and supersonic aircraft design and analysis

Stallion 3D Simulation of NASA CRM, 800K+ cells, 5% error in Cl/Cd (Cl=0.58).

The following modules are available in our class pack:
The introductory price for one year of the Aerodynamics ClassPack is $2,995.  Please click here to purchase.

For more information, please visit or call us at (352) 240-3658.
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