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The goal of this study was to characterize the effect of propeller variables as relevant to the design of a flight vehicle with numerous distributed propulsors. The impact of propeller radius, quantity, airfoil section characteristics, and blade count is examined. The test case is a small general aviation aircraft evaluated at a condition corresponding to cruise, such that thrust is constrained and propeller slipstream effects are negligible. From the perspective of power required, a minimal number of large-radius propellers are preferable. Increasing the number of propellers or blade count reduces the individual loading on each blade, which can lead to a significant drop in efficiency if the airfoil characteristics of the blade’s section are not well matched to the operating conditions. Reducing propeller radius is associated with a reduction in estimated range and endurance for a battery-powered aircraft.
Lance W. Traub. Propeller Characterization for Distributed Propulsion. Journal of Aerospace Engineering 2021, 34, 04021020 .
AMA StyleLance W. Traub. Propeller Characterization for Distributed Propulsion. Journal of Aerospace Engineering. 2021; 34 (3):04021020.
Chicago/Turabian StyleLance W. Traub. 2021. "Propeller Characterization for Distributed Propulsion." Journal of Aerospace Engineering 34, no. 3: 04021020.
Programs in mechanical and aeronautical engineering commonly include courses in compressible fluid flow. As such, learning can be greatly enhanced if theory is taught in conjunction with hands on experimentation. While supersonic wind tunnels are not uncommon at many universities, such facilities are generally of the blow down configuration. Consequently, run time is very short and ear protection is required during operation, potentially hindering instruction. Furthermore, blow down configurations are typically expensive and large. This article presents the design and manufacture of a continuous, indraft, miniature supersonic wind tunnel. The tunnel was designed for a nominal test section Mach number of 2; validation indicated a Mach number of 1.96 was achieved. Vacuum was provided by a regenerative blower. The facility is portable and quiet; measurements indicated that the sound level around the tunnel when operational was less than 81 dB (compared to 119dB generated by the department’s blow down supersonic wind tunnel).
Monty Bruckman Ii; Lance W Traub. Design of a continuous portable indraft supersonic wind tunnel. International Journal of Mechanical Engineering Education 2020, 1 .
AMA StyleMonty Bruckman Ii, Lance W Traub. Design of a continuous portable indraft supersonic wind tunnel. International Journal of Mechanical Engineering Education. 2020; ():1.
Chicago/Turabian StyleMonty Bruckman Ii; Lance W Traub. 2020. "Design of a continuous portable indraft supersonic wind tunnel." International Journal of Mechanical Engineering Education , no. : 1.
A low-speed wind tunnel investigation is presented documenting drag reduction to a golf driver club. Geometrical modifications (or elements) were attached to the golf driver. The size, spacing, and location of the elements were varied. Wind tunnel velocities spanned a range from the amateur to professional golfer. Measurements included both force balance and surface pressure accompanied by flow visualization to aid in flow diagnostics. The results indicated that a 40% reduction in drag can be achieved, primarily due to reduced pressure over the forward face of the crown and increased pressure over the crown’s aft extents. This reduction in drag was estimated to yield a 0.54 m/s (1.2 mph) club head speed gain, causing a 3.65 m (4 yds) increase in carry distance.
Lance W. Traub; Anthony Munson; Justin McBurney. Experimental study of drag reduction on a golf driver club using discrete surface elements. Sports Engineering 2019, 22, 12 .
AMA StyleLance W. Traub, Anthony Munson, Justin McBurney. Experimental study of drag reduction on a golf driver club using discrete surface elements. Sports Engineering. 2019; 22 (2):12.
Chicago/Turabian StyleLance W. Traub; Anthony Munson; Justin McBurney. 2019. "Experimental study of drag reduction on a golf driver club using discrete surface elements." Sports Engineering 22, no. 2: 12.
A low-speed wind tunnel investigation is presented characterizing the impact of Gurney flaps on an elliptical airfoil. The chordwise attachment location and height of the flaps were varied, as was the Reynolds number. The results showed strong nonlinearities in the lift curve which were present for all tested geometries. Flap effectiveness was seen to diminish as the flap was moved closer to the trailing edge stemming from flap submersion in separated flow. For the tested cases, the measured lift coefficients showed a weak Re dependency. The upper airfoil surface was shown to carry approximately 80% of the total lift load. The top surface caused a pitching moment reversal associated with nonlinearity in the lift curve.
Lance W. Traub. Effect of Gurney Flaps on an Elliptical Airfoil. Journal of Fluids Engineering 2017, 139, 101102 .
AMA StyleLance W. Traub. Effect of Gurney Flaps on an Elliptical Airfoil. Journal of Fluids Engineering. 2017; 139 (10):101102.
Chicago/Turabian StyleLance W. Traub. 2017. "Effect of Gurney Flaps on an Elliptical Airfoil." Journal of Fluids Engineering 139, no. 10: 101102.
One of the most commonly implemented devices for stall control on wings and airfoils is a leading-edge slat. While functioning of slats at high Reynolds number is well documented, this is not the case at the low Reynolds numbers common for small unmanned aerial vehicles. Consequently, a low-speed wind tunnel investigation was undertaken to elucidate the performance of a slat at Re = 250,000. Force balance measurements accompanied by surface flow visualization images are presented. The slat extension and rotation was varied and documented. The results indicate that for small slat extensions, slat rotation is deleterious to performance, but is required for larger slat extensions for effective lift augmentation. Deployment of the slat was accompanied by a significant drag penalty due to premature localized flow separation.
Lance W. Traub; Mashaan P. Kaula. Effect of Leading-Edge Slats at Low Reynolds Numbers. Aerospace 2016, 3, 39 .
AMA StyleLance W. Traub, Mashaan P. Kaula. Effect of Leading-Edge Slats at Low Reynolds Numbers. Aerospace. 2016; 3 (4):39.
Chicago/Turabian StyleLance W. Traub; Mashaan P. Kaula. 2016. "Effect of Leading-Edge Slats at Low Reynolds Numbers." Aerospace 3, no. 4: 39.
The effect of wing sweep on the aerodynamic characteristics of Gurney flaps is examined. Wind tunnel models incorporating un-tapered 2.1 aspect ratio wings with sweeps of 0, 45 and 60 deg were designed and manufactured. Flap heights of 1% and 3% of the chord were evaluated. Testing was undertaken at Reynold's numbers of 100,000 and 150,000. The overarching result was that sweep attenuates the lift modulating ability of the flap, resulting from the effects of spanwise flow and reduced base suction behind the flap. Aerodynamic parameters were found to show a strong dependence on the cosine of the leading edge sweep angle as well as the square root of the flap height.
Lance W. Traub; Samarth M. Chandrashekar. Experimental study on the effects of wing sweep on Gurney flap performance. Aerospace Science and Technology 2016, 55, 57 -63.
AMA StyleLance W. Traub, Samarth M. Chandrashekar. Experimental study on the effects of wing sweep on Gurney flap performance. Aerospace Science and Technology. 2016; 55 ():57-63.
Chicago/Turabian StyleLance W. Traub; Samarth M. Chandrashekar. 2016. "Experimental study on the effects of wing sweep on Gurney flap performance." Aerospace Science and Technology 55, no. : 57-63.
Standard battery testing procedure consists of discharging the battery at constant current. However, for battery powered aircraft application, consideration of the cruise portion of the flight envelope suggests that power should be kept constant, implying that battery characterization should occur over a constant power discharge. Consequently, to take advantage of existing battery discharge curves it would be useful to have a methodology that can extract a constant power discharge curve from a constant current discharge curve. The development of such a methodology for lithium batteries is described in this article.
Lance W. Traub. Calculation of Constant Power Lithium Battery Discharge Curves. Batteries 2016, 2, 17 .
AMA StyleLance W. Traub. Calculation of Constant Power Lithium Battery Discharge Curves. Batteries. 2016; 2 (2):17.
Chicago/Turabian StyleLance W. Traub. 2016. "Calculation of Constant Power Lithium Battery Discharge Curves." Batteries 2, no. 2: 17.
A simplified method to analyse propellers based on vortex theory is presented. Small-angle approximations are implemented to eliminate the need for iteration in the determination of the induced angle-of-attack. A stall model is developed and combined with analytic relations describing the blade aerofoil characteristics, eliminating the need for look-up tables of aerofoil behaviour. The method is also extended to serve as an optimal propeller design tool. Comparisons of the approach with experiment are presented for validation as an analysis tool. Use of the theory as a design tool is also demonstrated through contrast with an existing blade design methodology.
L.W. Traub. Simplified propeller analysis and design including effects of stall. The Aeronautical Journal 2016, 120, 796 -818.
AMA StyleL.W. Traub. Simplified propeller analysis and design including effects of stall. The Aeronautical Journal. 2016; 120 (1227):796-818.
Chicago/Turabian StyleL.W. Traub. 2016. "Simplified propeller analysis and design including effects of stall." The Aeronautical Journal 120, no. 1227: 796-818.
A semi-empirical method is presented to estimate the angular excursion and the lift loss associated with static hysteresis on an airfoil. Wind tunnel data of various airfoils is used to define and validate the methodology. The resulting equation provides a relationship between the size of the hysteresis loop and characteristics of the airfoil. Comparisons of the equation with experiment show encouraging agreement both in terms of the magnitude of the lift loss and the extent of the loop.
Lance W. Traub. Semi-Empirical Prediction of Airfoil Hysteresis. Aerospace 2016, 3, 9 .
AMA StyleLance W. Traub. Semi-Empirical Prediction of Airfoil Hysteresis. Aerospace. 2016; 3 (2):9.
Chicago/Turabian StyleLance W. Traub. 2016. "Semi-Empirical Prediction of Airfoil Hysteresis." Aerospace 3, no. 2: 9.
A low speed wind tunnel investigation was conducted to examine the effect of a pusher propeller on a 65 deg sweep delta wing. Two different propeller diameters were evaluated. The data showed that the pusher geometry can cause a delay in vortex breakdown yielding an increase in lift at high angles of attack. Surface pressure measurement showed that the propeller increased suction levels on both the leeward and windward surfaces, limiting lift enhancement. Lift augmentation was observed to favor low advance ratios.
L.W. Traub. Effect of a pusher propeller on a delta wing. Aerospace Science and Technology 2016, 48, 115 -121.
AMA StyleL.W. Traub. Effect of a pusher propeller on a delta wing. Aerospace Science and Technology. 2016; 48 ():115-121.
Chicago/Turabian StyleL.W. Traub. 2016. "Effect of a pusher propeller on a delta wing." Aerospace Science and Technology 48, no. : 115-121.
Estimation of the lift of an aerofoil is one of the fundamental measurements of fluid mechanics. Lift is commonly measured using a load cell or a force balance. Non-intrusive methods to measure lift are usually pressure based. Aerofoils may be pressure tapped where small surface orifices are connected via tubing to a pressure measurement system, either a multi-tube manometre or an electronic system. Both measurement options add cost and complication, especially in an educational setting. Pressure tapping small aerofoils can also be difficult, especially if the models are rapid prototyped (RP). Low model surface resolution (from RP manufacture) and confined geometry complicate model assembly and finishing. Boundary-layer transition caused by poorly implemented tappings (too large a diametre or poorly aligned, i.e. straight aft) can also alter results. Wall pressure tappings may also be used and have the benefit of being non-intrusive. To implement, the test section roof and floor is tapped with a streamwise row of ports that facilitate measurement of the wall pressure signature. Integration of the pressure differential then relates to the lift produced. This measurement methodology still requires a multi-channel pressure acquisition system and modification of the wind tunnel. In Refs 4,5 methods are presented that facilitate calculation of the instantaneous forces acting on a body through flow field measurements determined using particle image velocimetry. However, the required flow field measurements encompass those surrounding the body, and are not a simple point measurement. In Ref. 6 a method is presented to estimate the lift of an aerofoil using two Pitot-static tubes that are used to measure the velocity above and below the aerofoil’s quarter chord. Wall corrections are required to yield an accurate lift estimate.
L. W. Traub. Estimating aerofoil lift from flow angle. The Aeronautical Journal 2015, 119, 1167 -1173.
AMA StyleL. W. Traub. Estimating aerofoil lift from flow angle. The Aeronautical Journal. 2015; 119 (1219):1167-1173.
Chicago/Turabian StyleL. W. Traub. 2015. "Estimating aerofoil lift from flow angle." The Aeronautical Journal 119, no. 1219: 1167-1173.
In this article, the effect of on-surface flow visualisation (SVF) techniques on measured loads over an airfoil are explored. Titanium dioxide based mixture effects on the lift and drag coefficient are experimentally quantified at low Reynolds numbers by recording the time history as the patterns evolve and freeze. With statistical comparison based on Student’s t-distribution method, it was determined that the effect on the drag coefficient was minimal but the lift coefficient was slightly attenuated. Additionally, it was observed that at high angles-of-attack the temporal history of the flow as the wind tunnel ramps up may alter the steady-state flow field in the presence of a SFV mixture.
L. W. Traub; R. Waghela; E. M. Botero. Effects of surface flow visualisation on aerodynamic loads at low Reynolds number. The Aeronautical Journal 2015, 119, 663 -672.
AMA StyleL. W. Traub, R. Waghela, E. M. Botero. Effects of surface flow visualisation on aerodynamic loads at low Reynolds number. The Aeronautical Journal. 2015; 119 (1215):663-672.
Chicago/Turabian StyleL. W. Traub; R. Waghela; E. M. Botero. 2015. "Effects of surface flow visualisation on aerodynamic loads at low Reynolds number." The Aeronautical Journal 119, no. 1215: 663-672.
A low speed wind-tunnel investigation is presented documenting the impact of taper ratio at low Reynolds number. An AR=5.56 wing using a S8036 section was tested at Re=100,000 and 150,000. Taper ratio was varied from 1 down to 0.2 in 0.2 increments. An analytic prediction method as well as extended numerical lifting line theory incorporating nonlinear section data was implemented to compare with experiment. The experimental results indicated a weak dependence of peak lift to drag ratio on taper ratio for both Reynolds numbers. Surface flow visualization showed the presence of a large laminar transitional bubble on the upper wing surface. The relative extent of the bubble was observed to increase towards the tip region for tapered planforms. Agreement between theory and experiment in terms of lift and drag estimation was good. Planform optimization using the extended numerical lifting line theory indicated that at the test conditions and using the selected airfoil section, a planform that differs from straight taper or elliptic may be most efficient.
Lance W. Traub; Emilio Botero; Rajmohan Waghela; Ryan Callahan; Aaron Watson. Effect of Taper Ratio at Low Reynolds Number. Journal of Aircraft 2015, 52, 734 -747.
AMA StyleLance W. Traub, Emilio Botero, Rajmohan Waghela, Ryan Callahan, Aaron Watson. Effect of Taper Ratio at Low Reynolds Number. Journal of Aircraft. 2015; 52 (3):734-747.
Chicago/Turabian StyleLance W. Traub; Emilio Botero; Rajmohan Waghela; Ryan Callahan; Aaron Watson. 2015. "Effect of Taper Ratio at Low Reynolds Number." Journal of Aircraft 52, no. 3: 734-747.
An investigation is presented to elucidate the performance of a staggered, spanwise cambered biplane. The spanwise camber yielded wings forming a ‘∧’ or ‘∨’ when viewed streamwise. The configuration is examined in terms of its aerodynamic and stability characteristics. The feasibility of negating the requirement for a conventional empennage is explored. Geometric variation encompassed front and back wing anhedral/dihedral angles yielding 49 combinations. Evaluation of the geometry was accomplished using both wind tunnel testing and numerical simulation. The results indicated that front wing dihedral in conjunction with aft wing anhedral was most beneficial, such that the benefit of wake spacing was maximised. Aerodynamic benefit was indicated compared to a conventional empennage geometry. The greatest disparity in behaviour of the fore and aft wing anhedral/dihedral distribution was in the high lift regime, where the nature of the stall varied. Simulations to establish the viability of the geometry in terms of controllability were also conducted and indicated that the configuration is viable.
L.W. Traub; R. Waghela; K.A. Bordignon. Characterisation of a highly staggered spanwise cambered biplane. The Aeronautical Journal 2015, 119, 203 -228.
AMA StyleL.W. Traub, R. Waghela, K.A. Bordignon. Characterisation of a highly staggered spanwise cambered biplane. The Aeronautical Journal. 2015; 119 (1212):203-228.
Chicago/Turabian StyleL.W. Traub; R. Waghela; K.A. Bordignon. 2015. "Characterisation of a highly staggered spanwise cambered biplane." The Aeronautical Journal 119, no. 1212: 203-228.
An experimental investigation is presented to validate endurance estimates for a battery powered flight vehicle. In this study a radio controlled model aircraft was ‘flown’ inside a wind tunnel. Various Lithium Ion batteries were used to power the model. Battery electrical characteristics were recorded during each run to assess battery discharge behaviour. Theoretical estimates based upon battery characteristics yielded endurance estimates within 3% of that measured experimentally. The discharge characteristics of the batteries were found to be the largest source of uncertainty for endurance estimates.
L. W. Traub. Validation of endurance estimates for battery powered UAVs. The Aeronautical Journal 2013, 117, 1155 -1166.
AMA StyleL. W. Traub. Validation of endurance estimates for battery powered UAVs. The Aeronautical Journal. 2013; 117 (1197):1155-1166.
Chicago/Turabian StyleL. W. Traub. 2013. "Validation of endurance estimates for battery powered UAVs." The Aeronautical Journal 117, no. 1197: 1155-1166.