Investigating the Strut Braced Wing For Reducing Aviation's Environmental Impact

Environmental Background▰ Earth's surface temp. will increase between 1.8 and

5.8 ºC by 2100

▰ Aircraft release emissions at higher altitudes

▰ Aircraft emissions will triple by 2050

▰ Between 2016 and 2050 aviation will generate 43 gigatonnes of CO2 emissions

Design Background▰ Efficiency currently

improved with ○ Composites○ Better engines○ Small design

improvements▰ Cantilever design has been

pushed to limit

Boeing 787 Dreamliner

Introduction● The SBW design

● Consists of a strut supporting the wing

● Allows designers to create a more efficient shape

● The TBW is a more complex design to analyze

SBW and TBW Diagram

Introduction● Past Aircraft

● Has been used on past aircraft including○ Cessna 172○ Piper Cub○ Hurel-Dubois HD.31

▰ Never Implementation on a large jet aircraft

Cessna 172

Hurel-Dubois HD.31

Introduction● Current Research▰ Current research conducted by:

○ Boeing○ Nasa○ Virginia Tech○ Georgia Tech

▰ Noteworthy projects:○ Sugar Program○ Onera Program (Albatros)

Boeing Sugar SBW Test Model

Introduction

The Strut Braced Wing● utilize struts to strengthen the wing ● Allows for a higher aspect ratio● Reduces drag through:

○ Wingtip vortices (Vortex Drag)○ Thickness to chord ratio (Transonic Wave

Drag)● Vortex Drag is roughly 40% of total

drag

Wing Tip Vortex

Purpose▰ Examine drag, lift, and weight to compare the

efficiency of a traditional cantilever aircraft to a strut braced wing aircraft

▰ Discuss the broader context of this efficiency in terms of environmental impact

Research QuestionTo what extent is it viable to implement a strut brace wing design into future commercial airliners for the purpose of reducing aviation's environmental impact?

▰ Aims to fill the research gap of a direct comparison

Hypothesis

Alternative: The strut braced wing will improve the aircrafts efficiency

Null: The strut braced wing will have no effect on the aircrafts efficiency

MethodsScientific Literature Review▰ Built a larger picture of the characteristics of

SBW ▰ Focused on weight and lift▰ Used online databases

○ Research Gate○ EBSCOhost○ Google Scholar

MethodsSimulation▰ Goal is to examine drag individually▰ Used Fusion 360 program to design model

aircraft for testing▰ Used Flow Design to complete wind tunnel

analysis

Methods● Creating the Models

▰ Autodesk Fusion 360 was the cad program used

▰ Cantilever aircraft was a Boeing 737-800

▰ Three variables were tested ▰ The best of each variable were

combined into one model

Optimized SBW in Fusion 360

Cantilever Control in Fusion 360

Methods● Simulation▰ Autodesk Flow Design was

used▰ Drag coefficient and force were

measured five times▰ measurements made after the

simulation stabilized▰ All variables were held

constant

Control Cantilever Aircraft in Flow Design Wind Tunnel Simulation

Results● Sweep Angle

● Model 1 with a 20 degree sweep had the lowest average drag coefficient and drag force

model Sweep AngleAverage Coefficient Average Force

control cantilever 25° 0.17 15693.6control strut 25° 0.23 22515.8strut 1* 20° 0.21 20435.6strut 2 15° 0.21 20568.4strut 3 10° 0.23 22002.8strut 4 5° 0.246 23710.6strut 5 0° 0.24 22942

Results● Length

● Model 5 with a 130% length increase was chosen despite not having the lowest drag because realistically it would offer more lift than model 1

modelLength increase

Average Coefficient Average Force

control cantilever 0% 0.17 15693.6control strut 0% 0.23 22515.8strut 1 5% 0.21 20209.6strut 2 10% 0.22 22195.6strut 3 15% 0.24 24513.4strut 4 20% 0.24 24104.6strut 5* 30% 0.22 23141.6

Results● Vertical Thickness

● Model 5 with 75% of the controls thickness had the lowest average drag coefficient and drag force

model ThicknessAverage Coefficient Average Force

control cantilever 100% 0.17 15693.6control strut 100% 0.23 22515.8strut 1 95% 0.23 22486.4strut 2 90% 0.21 19214.4strut 3 85% 0.202 18518.2strut 4 80% 0.19 16839strut 5* 75% 0.19 16635.6

Results

● 4x10 -̂10 p value is less than .05 so optimized strut has statistically less drag than control strut

● 1.4x10 -̂13 p value is less than .05 so optimized strut has more drag than the control cantilever statistically

Model ModificationMean (drag coefficient)

Standard Deviation (drag coefficient)

Mean (drag force)

Standard Deviation (drag force)

Control cantilever None 0.17 0 15693.6 29.3

control strut Strut added 0.23 0 22515.8 58.3

optimized strut

Thickness:75%Length:130%Sweep: 20° 0.2 0 18265.2 18.91

Results● Weight and Lift

Advanced Cantilever Wing

Optimized Strut Braced Wing

Aspect ratio 9.9 13Zero fuel weight (lbs) 354,356 331,847Fuel weight (lbs) 186,332 157,977Takeoff gross weight (lbs) 540,689 489,826

● Overall decrease in weight for Strut Braced Wing aircraft

● Boeing Sugar aircraft has higher L/D ratio

Boeing 737-800 Boeing Sugar aircraftAspect Ratio 9.45 19.55Empty Weight(lbs) 90710 75600

Lift/Drag Ratio 17 24

Naghshineh-Pour, A. H. (1998, November 30). Structural Optimization and Design of a Strut-Braced Wing Aircraft. Retrieved from https://mafiadoc.com/structural-optimization-and-design-of-a-strut-braced-wing-aircraft_59b6a12a1723dddbc635a0be.html

Boeing 737-800/900. (n.d.). Retrieved from https://www.airliners.net/aircraft-data/boeing-737-800900/96Brady, C. (n.d.). Detailed Technical Data. Retrieved from http://www.b737.org.uk/techspecsdetailed.htmOuhib, A. (2014). Boeing 737-700 Drag. Retrieved from https://www.scribd.com/doc/220607389/Boeing-737-700-DragWells, D. (n.d.). Cruise Speed Sensitivity Study for Transonic Truss Braced Wing. Retrieved from https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170001025.pdf

Virginia Tech

Boeing/Nasa

Discussion● The Breguet Range Equation

● A lower drag increases range● A greater lift increases range● Lower Weight increases range● High range indicates high efficiency and less of an environmental

impact

Discussion● efficiency

▰ The SBW’s lower weight =increased efficiency▰ The SBW’s higher drag = decreased efficiency▰ The SBW’s high lift = increased efficiency▰ A higher L/D for the SBW indicates that high lift

outweighs the slight drag increase

Discussion● environmental

▰ Higher L/D ratio and lower weight indicate better efficiency and lower emissions

▰ A 30% fuel reduction is possible▰ Airlines can sustain the cost of improved

technology ▰ Replacing half of airliners would reduce CO2

emissions by 2050 roughly 6.4 gigatons

Conclusion▰ Reject null hypothesis, and accept the alternative ▰ Airlines/environment would benefit from reduced

fuel consumption of SBW▰ Further investigation of the SBW concept would be

worthwhile given the potential benefits

AcknowledgementsI would like to thank the following individuals for their assistance to this research

○ Dr. Paulo Iscold ○ Dr. Robert Breidenthal○ Dr. Arnold Deffo○ Dr. Malhotra

ReferencesAirfoil Tools. (n.d.). Retrieved from http://airfoiltools.com/search/index

Benson, T. (2014, June 12). Lift to Drag Ratio. Retrieved from https://wright.nasa.gov/airplane/ldrat.html

Boeing 737-800/900. (n.d.). Retrieved from https://www.airliners.net/aircraft-data/boeing-737-800900/96

Brady, C. (n.d.). Detailed Technical Data. Retrieved from http://www.b737.org.uk/techspecsdetailed.htm

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