Drag Reduction in 3D Modeling: DR3D-M

DR3D-M Logo

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Overview:

In the Reno Air Races, pilots, engineers, and aviation enthusiasts work on building the fastest experimental aircraft. An effective way to increase an aircraft’s top speed is by improving aerodynamics. This project focused on improving the aerodynamics on a Thunder Mustang, or a ¾ scale P-51 Mustang. There were two main points on the aircraft causing parasitic drag: the cockpit and the radiator scoop. DR3D-M focused on redesigning the radiator scoop.

Design and Origins:

When the idea for improving the aerodynamics on the radiator scoop was posed to the team, each team member took it upon themselves to come up with ideas. Originally, thirteen concepts were thought of. However, many of those were eliminated, a few were combined, and four different concepts were created for testing in the CFD simulations, or Computational Fluid Dynamics Simulations.

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Angled Intake on Plane Close Up

Angled Inlet Design:

Theory: took advantage of boundary layer and dissipated stagnation point

Rejected: CFD showed an increase in drag

 

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FormClosing Door on Plane Close Upat

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Variable Intake Design:

Theory: Spring powered doors. As plane moved faster, greater force of air would close doors causing less intake and diverting excess air

Rejected: created vacuum inside the scoop which would force the doors back open

 

NACA on Plane Close Up

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Side NACA Design:

Theory: closed off and rounded off radiator scoop, added NACA ducts to the sides for air intake

Questions: amount of air flow getting to radiator

 

Stater on Plane Close Up

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Stator Induction Design:

Theory: closed off and pointed front of radiator scoop, two inlet ducts on top and bottom

Questions: amount of air flow getting to radiator

 

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Chosen Design: DR3D-M NACA Concept:

DR3DM NACA Concept

The DR3D-M NACA Concept is a combination of two designs: the stator induction and the side NACA design. It closes off the radiator scoop and rounds it up to the bottom of the fuselage. Two larger NACA ducts are added on the bottom and angled inward to match the angle of the flow seen on the CFD simulations. The decision to use this was purely data driven.

CFD Simulations:

In order to validate the effectiveness of the design, two separate types of Computational Fluid Dynamics Simulations, or CFD, were ran. The CFD program chosen by this group is the Flow Simulator in Solidworks. Two separate models were put through CFDs: one model of the stock Thunder Mustang and the other model of the modified Thunder Mustang with the DR3D-M NACA Concept attached. After testing both models, the DR3D-M NACA Concept shows a reduction in drag from 5%-30% depending on the wind speed.

 

Here are the overall pressure readings on both models of the airplane: the unmodified aircraft is on the left.

Comparison Plane

A close up view of the radiator scoops with the pressure readings, red being highest. Note how the DR3D-M NACA Concept reduces the area where high pressure exists.

Comparison Pres Front

A side view of the two radiator scoops. Inside the black circle on the stock Thunder Mustang is a vortex which creates a stagnation point.

Comparison Pres Side

This is the change in density of air flowing through both scoops.

Comparison Dens

Here is the relative pressure or pressure difference.

Comparison Rel Pres

Wind Tunneling Testing:

Another means to validate the proof of concept was wind tunnel testing done at Palmer Engineering Lab at UNR.  Two models were used for the wind tunnel analysis.  The control model represents the airplane without modifications done and the second model (Model with Concept) represents the airplane with the product attached.


WindTunnelBaselineconcept model

 Control Model                                                                                                               Model With Concept

The models were greatly simplified by only including the fuselage and air intake scoop of the airplane.  This reduced the costs of 3D printing and simplified the analysis.  3D prints were obtained from the Innevation Center, Reno.  Drag as a function of wind speed was recorded on both models and compared.

 

wind tunnel results

The results from the wind tunnel analysis further validated the results from the CFDs.  A specific MATLAB program was created to correlate scaling effects with the Reynolds number.

 

Fabrication of Prototype:

The prototype of the DR3D-M NACA Concept was created in 3 steps: foam shaping, carbon fiber layup, and painting.

This video shows the fabrication process. Video created by Cody Vincent.

 

Foam Shaping:

First, the foam core had to be created. This meant taking pieces of foam and shaping them to two shapes: the prototype itself and the aircraft interface. For the aircraft interface, X-30 by Tap Plastics was used. It is a two-part liquid that, when mixed together, solidifies and fills the space to take the shape of its surroundings. After lining the scoop with plastic, the X-30 was mixed and cast. After removing this foam shell, it is then sanded down to the desired size and shape.

The DR3D-M NACA Concept had complex geometrical shapes like the NACA ducts, so special tooling was required. The foam core of the front nose of the prototype was created using a CNC machine, or Computer Numeric Coding. This was done by WeCutFoam, a company that specializes in custom foam part creation. They used 1.5 pound EPS or Expanded Polystyrene. Huge thanks to WeCutFoam for creating this piece for DR3D-M and to Mark Schlaich and Rex Lock & Safe for delivering the CNC piece.

Once the CNC piece was received, sanding and shaping this to the aircraft began. This also involved shaping the X-30 piece to the CNC piece and connecting them together. After they were connected, the NACA ducts were hollowed out. To create a smooth finish on the foam prototype, blue adhesive was used to fill in any small holes.

 

Carbon Fiber Layup and Painting:

Carbon Fiber comes as a cloth in a roll. It must be unrolled and cut to size.  To set the carbon fiber, epoxy was applied and spread onto the cut sheets. Once the epoxy was evenly distributed, the carbon fiber was laid. Two different release sheets were placed over the wet carbon fiber. The carbon fiber then cured for 12 hours. For mating the part to the aircraft, a large piece of carbon was laid directly onto the foam part while it was in place on the aircraft.

Once all carbon work was completed, the part then needed to be smoothed out. This was done with Bondo. It was applied, allowed to cure, then sanded smooth. Once the part had been completely smoothed, painting began. Painting consisted of 4 coats of primer and 6 coats of white paint.

 

Finished Prototype:

Here is the completed prototype.

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The DR3D-M on Blue Thunder II.

Part on BT2

Part on BT2 Side

Static Test:

In order to verify the security of the prototype to the aircraft, it is put through a static test also known as a full power check. The prototype is attached to the aircraft which is then secured to a pole to keep the aircraft from moving. Once the prototype and aircraft are secure, the engine is started and slowly brought to full power. This will test the prototype’s security to the aircraft without putting the pilot or aircraft at as much risk as actually flying.

 

The static test showed great results. The aircraft is equipped with pitot probes to measure wind speed as well as six accelerometers to detect vibrations. The DR3D-M NACA Concept withstood winds generated from the prop of up to 410 mph. The accelerometers detected no change in vibrations from the addition of the prototype. This meant that the prototype was properly secured to the aircraft.

As expected, the aircraft did overheat. When an aircraft is put through a full power check, less air is moving through the radiator scoop which increases the engine temperature. However, a cooling system issue unrelated to the static test was causing unforeseen issues with the engine.

 

Flight Testing:

Unfortunately, due to an issue with the aircraft (not related to the DR3D-M NACA Concept), the flight test would not take place before the conclusion of the project. Once the aircraft has been repaired, the group hopes to fly the prototype.

 

DR3D-M Team:

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The leader of this project, John Giese is a true aviation specialist. Born and raised in Reno, John graduated from Galena High School in 1999 and was U.S. Army Active from 1999-2005. He then received his Associate of Science degree from TMCC as well as his Private Pilot License. Having worked with American Air Racing team for 3 years, John created the original idea for the project. He took part in most of the project objectives such as the CFDs, 3D print, Solidworks design of the aircraft and part, foam construction and shaping, carbon fiber layup, and painting of prototype. John also was the team coordinator, main point of contact for the mentor, Dr. Logan Yliniemi, the sponsor and owner of the aircraft, John Parker, and the professor of the class, Mr. Steven King. With interests in aviation, the defense department, and automobiles, John plans to graduate with a B.S. in Mechanical Engineering in May 2016 and join the NAVAIR ESDP program. He also has great interests in long range shooting, photography, motorcycles, and drag racing.

775-287-4032     Renojpg@gmail.com

Cody

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Cody Vincent was born and raised in Kings Beach, CA. Coming from North Lake Tahoe High School, he was the Head of Public Relations for this project. He also took part in the Solidworks part design, CFDs, paperwork, foam shaping, carbon fiber layup, Bondo work, poster design, and supply acquisition. Cody shows interests in aviation, automobiles, alternative energy, recycling, and civil designs. He hopes to receive his Mechanical Engineering B.S. in December 2016. After, he looks to join the Peace Corps or Engineers without Borders or work on the development of alternative energy sources. Cody has outside interests in hiking, martial arts, fire spinning, running, and writing.

530-386-4611    cvincent@Nevada.unr.edu

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Rio Patraw was the computer “guru” for this project. She took the responsibility of handling the paperwork and documentation of this project, while also assisting with the Solidworks part design, Matlab correlation code, research, and records. Growing up in Reno, she was homeschooled and then attended TMCC. While also handling the paperwork, she also took part in the carbon fiber layup and the painting of the completed prototype. With interests in aerodynamics and robotics, she hopes to work on robotic toys after completing her Mechanical Engineering B.S. and mathematics minor in May of 2016. Rio also shows interest in chess, anime, video games, and cats.

775-313-6273     riopatraw@nevada.unr.edu

 

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Sergio Lemus was one of the team’s main hands-on man. From Redford, MI, Sergio took part in the Solidworks design of the prototype, the construction and shaping of foam, the carbon fiber layup, and the Bondo work, as well as taking the lead in the Prototype Fabrication and the Wind Tunnel Testing. He shows interest in working on automobiles, taking apart automobiles and appliances to study them for their functions and concepts, as well as fixing and modifying them. He has his Associate of Science degree in Automotive Technology, attended the College of Northern Nevada, Las Vegas, and participated in Operation Iraqi Freedom in June 2007- June 2008. After obtaining his B.S. in Mechanical Engineering in May 2016, Sergio hopes to be designing the next innovation of cars at a car manufacturer. He has interests in mechanical project, computer games, and exotic dancing.

775-229-5771     Lemuss4@outlook.com

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Originating from Walnut Creek, CA, and attending De La Salle High School, Steve Schlaich took the Lead on the CFD simulations for this project and was the main point of contact for WeCutFoam.com for the CNC’d part. He also took part in the 3D print, creation of the aircraft and prototype in Solidworks, wind tunnel testing, shaping and construction of foam prototype, carbon fiber layup, Bondo work, and painting of the finished part. Steve has a liking for exoskeletons, muscle and performance cars, robotics, weapons, and motorcycles. With plans of hoping to work on the research and development of exoskeletons, cars, or weapons in California, he will obtain his B.S. in Mechanical Engineering in May 2016 with the desire to return to UNR in August 2016 for a minor in Economics. Steve also has interests in basketball, driving and racing, Deadmau5 music, and horse racing.

925-726-5714    Sctr19@gmail.com

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LoganYliniemi

Dr. Logan Yliniemi took the role of team mentor for DR3D-M. Born in Oklahoma City and raised in Monmouth, OR, he is a first year assistant professor at the University of Nevada, Reno. He has earned his B.S. in Mechanical Engineering in 2010 from Arizona State University, M.S. in Mechanical Engineering from Oregon State University in 2012, and his Ph.D. in Robotics/Mechanical Engineering from Oregon State in 2015. Dr. Yliniemi has developed computational algorithms for multi-objective optimization that achieve performance at or above other state-of-the-art methods at one tenth of the computation cost. He has work published in AI Magazine, the International Conference on Autonomous Agents and Multitagent Systems (AAMAS), the Genetic and Evolutionary Computation Conference (GECCO), and the International Conference on Simulated Evolution and Learning (SEAL), with work funded by NASA, the U.S. Department of Energy, and the National Science Foundation. Dr. Yliniemi shows interests in Unmanned Autonomous Systems (UAS), Unmanned Aerial Vehicles (UAV), learning controllers, multi-objective problems, transfer learning, and probabilistic robotics, as well as soccer, golf, and hiking.

775-682-7479     logan@unr.edu

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Acknowledgements:

The following companies sponsor Blue Thunder II and will, therefore, be sponsoring this project:

Blue Thunder Logo51 AeroAmerican Air racingERCExotic EngineOdysseyR&E FastenersRC EngineeringRyan FAlconer EnginesStockton PropellersTempest

The following companies and teams contributed to the overall project success:

American Air racingNemesisBLind luckClas ThunderVoodooReality CzechPapa 51DassaultUNRInnevation CenterABEspruceRARAWeCutFoam logoRex

A very special thank you to:

John Parker

Rhonda Elwell

Mike Cummings

Dr. Logan Yliniemi

Dr. Angelina Padilla

Dr. Henry Fu

Steven King

Fred Rocher

Jon Sharp

Patricia Sharp

Steve Hill

Daren Kimura

Kevin Luttge

Bob Mills

Lewis Gabriel

Mark Schlaich

Michelle Rebaleati

University of Nevada Reno Media Lab

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