ME 435 Spring 2011
Project Design and Management II
Old Dominion University Department of Mechanical Engineering
Standard Dynamics Model
William Lawrence
Andrew Snead
TJ Wignall
15 March 2011
Abstract
The Standard Dynamics Model (SDM) was developed in the late 1970’s to promulgate standardized testing in wind tunnels across the globe. The design was simplified in order to encourage use by researchers and maintain economic affordability. Since its conception, it has seen use in a variety of testing facilities around the world, including Canada, Germany, and the United States. The amount of test data accumulated from the use of the SDM makes it an asset to any institution interested in comparing data, or introducing dynamic test characteristics and procedures. Engineering professors at Old Dominion University have recognized the benefits of building and validating an SDM for use specifically in undergraduate and graduate coursework. In order to fulfill that requirement our group will model, construct, and validate a scaled version of the SDM for future use by the University for years to come.
Table of Contents
Introduction…………………………………………..5
SDM Modeling……………………………………… 5
Sting Modeling……………………………………….6
Data Acquisition…………………………………….7
Immediate Goals…………………………………….8
Summary……………………………………………….8
References……………………………………………..9
Appendix A
Appendix B
Appendix C
Gantt Chart
List of Figures
1. Standard Dynamics Model…..6
2. Internal Balance Assembly….6
3. Sting .………………………………..7
Introduction: The Standard Dynamics Model (SDM) is a calibration model first introduced by the National Research Council of Canada (NRC) / Institute for Aerospace Research (IAR) in 1978. The model is designed to represent a current advanced fighter aircraft configuration with special consideration given to simplifying the geometry to expedite the manufacturing process. These design considerations are intended to promote the widespread use of the model in testing facilities around the world. The SDM consists of an asymmetrical fuselage with flat, tapered lift surfaces. The body has an ogive-cylinder profile and mounts a tapered intake unit with a forward facing flat face and a biconvex, circular canopy (Beyers). The geometrical layout and relevant dimensions are given in Figure 1. The model is best suited for use in measuring the dynamic derivatives through all axes of flight at low and high angles of attack. Researchers at Old Dominion University will be able to test these dynamic characteristics and compare the data to published literature for a variety of different wind tunnel configurations and flow geometries. The model is mounted on a calibrated test balance assembly (Figure 2) designed to deflect when exposed to loading forces. This test balance will send the data to the computer software to be converted in usable data depending on the test being conducted. The design balance was obtained from the Aerospace Engineering department, and was not designed by our team. In order to facilitate undergraduate and graduate flight dynamic testing, our team will model and build an SDM for Old Dominion University.
SDM Modeling: As intended, the design process is simple. The first step is to scale the model to fit the wind tunnel intended for use. The low speed tunnel at Old Dominion measures 3’ by 4’; therefore, a model with a 1’ wingspan will provide sufficient clearance for the model to move through the desired testing envelope. Since the model is standardized with a constant aspect ratio, designing the model using 3-D modeling software is simply a process of scaling and drawing. A comprehensive force analysis conducted using hand calculations and the modeling software allowed us to measure the force loading on the model. Results were obtained using the force coefficients found in (Huang), and the model was found to have no more than 80% of the allowable loading at any given angle of attack. Detailed calculations regarding the maximum allowable force coefficients may be found in Appendix A. Currently, detailed engineering drawings have been submitted to the ODU machine shop for cutting and fitting. Job completion is a function of the shop’s workload and manpower availability with an expected completion time of 1-2 weeks. As of now, the shop is building the fuselage, wings, ventral fins, horizontal stabilizer, vertical tail, and bulkhead assembly. The engineering drawings can be found in Appendix B.
Figure 1: Standard Dynamics Model Figure 2: Internal Balance
Sting Modeling: The primary method of testing will be the utilization of an internal balance assembly provided by the Aerospace Engineering department of Old Dominion University. This balance contains internal strain gauges that measure the minute flexure of the model under a variety of test characteristics. The balance provides measurements for normal, side, vertical, axial, roll, and yaw forces. In order to mount the balance to the model, an internal bulkhead assembly will be machined inside of the forward fuselage. The front of the balance will fit into the bulkhead while the back of the balance will mount into the forward part of the sting utilizing a slotted keyway and two setscrews. The sting (Figure 3) measures approximately 14 inches and contains slots that allow the balance wiring to be routed clear of the pitch crescent and other moving parts. The sting attaches to the pitch crescent at its far end utilizing three counter-bored screws.
Figure 3: Sting Assembly
Data Acquisition: In order to validate the model, it is essential that it is tested through various wind envelopes at varying degrees of angle of attack. This testing will determine if the design parameters set for the SDM have been met and set a benchmark for our model that enables undergraduate and graduate students the ability to publish results found using the model. We will use LabView as the primary means of data collection, with a program written by our design team. In order to implement the balance data into the software, a special calibration matrix has been provided by the Aerospace department. Once collection of the test data is complete, it will be analyzed and furthering design or testing will be conducted as necessary.
Immediate Goals: At this point, our team has a series of immediate goals required to finish the project before the end of the semester. First, the balance calibration matrix has to be implemented into the LabView software and the test program has to be written and debugged. Secondly, the model and sting have to be returned, assembled, and tested. After the completion of these primary goals, our team will be able to move into the analysis phase and ultimately validate our model.
Summary: Recognizing the benefits of having a validated Standard Dynamics Model, Old Dominion University has moved forward with the process of designing and building one. Once validated thorough comparison with published literature, the model will be beneficial to undergraduate and graduate level work here at the University. The model is relatively inexpensive to build and simple in design in order to facilitate its use at testing facilities around the world. At present, we are complete with the design phase of the physical systems and are currently awaiting the finished product from manufacture. Concurrently, we are designing the test software and environment necessary to validate our model.
References
Beyers, M.E., Moulton B.E. Stability Derivatives Due to Oscillations in Roll for the Standard Dynamics Model. Ottawa: National Research Council Canada, 1983.
Huang, X.Z. Wing and Fin Buffet on the Standard Dynamics Model. Ottawa: IAR/NRC Canada, 1986.
Appendix A
SDM Scaling Calculations
Constants:
ρ=1.225kgm3 air density
U∞=30ms velocity
q=.5ρU∞2=551.25 (dynamic pressure)
AR=3.00 aspect ratio
Normal Forces (Z):
Zmax = 142.343 N
CZ=2.4
CZ=Zq*S
S=Zq*CZ=0.10759108 m^2
Pitch (M):
Mmax=4.519 N-m
CM=.1
CM=Mq*S*c
c=Mq*S*CM
b2S=AR
b=AR*S
c=bAR=AR*SAR
c2=AR*SAR2=SAR
S=c2*AR=Mq*S*CM2*AR=M*ARq*CM23=0.27216749 m2
Roll (L):
Lmax=.904 N-m
CL=.006
CL=LqSB
B=LqSCL
B2S=AR
B2=LqSCL2=sAR
s=LqCLAR23=.29201509 m2
Yaw (N):
Nmax=2.712 N-m
CN=.03
CN=NqSB
S=NqARCN23=.20773331 m^2
Side (Y):
Ymax=35.586 N
CY=.04
CY=YqS
S=YqCY=1.61387755 m2
Results
Normal forces, Zmax=142.343 N, resulted in the smallest allowable wing area, S=.1075910 m^2. When comparing the area we determined to the area for the experiment given a scaling factor of 87% was found. Using the equation, b=S*AR, we found the wing span of our model to be .5681316 m^2 (1.86 ft). We thought that this wing span would be too large for our wind tunnel, and used the published ratio of wing span to tunnel height of 0.333. Since our tunnel height is 3 ft, the wing span of our model is 1 ft. This is smaller than the maximum area allowed 1.86 ft.
Appendix B
A-1: Plane Assembly
A-2: Plane Exploded View
A-3: Plane Slice View
A-4: Bulkhead
A-5: Fuselage Main
A-6: Fuselage Slot Locations
A-7: Fuselage Slot Dimensions
A-8: Aft View
A-9: Fuselage Bolt Hole Locations
A-10: Fuselage Bolt Hole Dimensions
A-11: Bolt Hole Locations Aft View
A-12: Bolt Hole Aft View
A-13: Horizontal Tail Fin
A-14: Ventral Fin
A-15: Vertical Tail
A-16: Wings
A-17: Wings without Taper
Appendix C
Stress Analysis Report
Analyzed File: / Derived Part of Fuselage and Wing.iptAutodesk Inventor Version: / 2011 (Build 150239000, 239)
Creation Date: / 11/16/2010, 4:23 PM
Simulation Author: / Andrew Snead
Summary:
Project Info (Properties)
Summary
Author / Andrew SneadProject
Part Number / Derived Part of Fuselage and WingDesigner / Andrew Snead
Cost / $0.00
Date Created / 11/16/2010
Status
Design Status / Work In ProgressPhysical
Material / Aluminum-6061Density / 0.097905 lbm/in^3
Mass / 5.98835 lbm
Area / 283.78 in^2
Volume / 61.1649 in^3
Center of Gravity / x=-0.0000108358 in
y=0.0000240145 in
z=7.69515 in
Note: Physical values could be different from Physical values used by FEA reported below.
Simulation:1
General objective and settings:
Design Objective / Single PointSimulation Type / Static Analysis
Last Modification Date / 11/16/2010, 4:17 PM
Detect and Eliminate Rigid Body Modes / No
Advanced settings:
Min. Element Size (fraction of avg. size) / 0.2
Grading Factor / 1.5
Max. Turn Angle / 60 deg
Create Curved Mesh Elements / Yes
Material(s)
Name / Aluminum-6061General / Mass Density / 0.097905 lbm/in^3
Yield Strength / 39912.9 psi
Ultimate Tensile Strength / 44992.7 psi
Stress / Young's Modulus / 10000 ksi
Poisson's Ratio / 0.33 ul
Shear Modulus / 3759.4 ksi
Stress Thermal / Expansion Coefficient / 0.00004248 ul/f
Thermal Conductivity / 312.765 btu/( ft hr f )
Specific Heat / 0.972467 btu/( lbm f )
Part Name(s) / Derived Part of Fuselage and Wing
Operating conditions
Pressure:1
Load Type / PressureMagnitude / 0.313 psi
Selected Face(s)
Fixed Constraint:1
Constraint Type / Fixed ConstraintSelected Face(s)
Results
Reaction Force and Moment on Constraints
Constraint Name / Reaction Force / Reaction MomentMagnitude / Component (X,Y,Z) / Magnitude / Component (X,Y,Z)
Fixed Constraint:1 / 10.0624 lbf / 10.0624 lbf / 1.62768 lbforce ft / 0 lbf ft
0 lbf / -1.62768 lbf ft
0 lbf / 0 lbforce ft
Result Summary
Name / Minimum / MaximumVolume / 61.1655 in^3
Mass / 5.98841 lbm
Von Mises Stress / 0.0000011379 ksi / 0.668821 ksi
1st Principal Stress / -0.214754 ksi / 0.793848 ksi
3rd Principal Stress / -0.919521 ksi / 0.271143 ksi
Displacement / 0 in / 0.00116652 in
Safety Factor / 15 ul / 15 ul
Stress XX / -0.37397 ksi / 0.373299 ksi
Stress XY / -0.210691 ksi / 0.253725 ksi
Stress XZ / -0.215131 ksi / 0.0250921 ksi
Stress YY / -0.893983 ksi / 0.780786 ksi
Stress YZ / -0.2439 ksi / 0.239752 ksi
Stress ZZ / -0.318199 ksi / 0.348472 ksi
X Displacement / -0.00116592 in / 0.000155666 in
Y Displacement / -0.0000361945 in / 0.0000360543 in
Z Displacement / -0.0000217134 in / 0.0000218565 in
Equivalent Strain / 0.00000000010248 ul / 0.0000637947 ul
1st Principal Strain / -0.00000000933636 ul / 0.0000638729 ul
3rd Principal Strain / -0.0000741753 ul / 0.0000000168042 ul
Strain XX / -0.0000261191 ul / 0.0000267658 ul
Strain XY / -0.0000280413 ul / 0.0000337688 ul
Strain XZ / -0.0000286321 ul / 0.00000333955 ul
Strain YY / -0.0000707764 ul / 0.000061853 ul
Strain YZ / -0.0000324611 ul / 0.0000319091 ul
Strain ZZ / -0.0000100368 ul / 0.0000164519 ul
Gantt Chart
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