Atch 3 - hdbk03-2 VKF Test Article Design.pdf

AEDC-HDBK-03-2

Test Article Design Information Handbook AEDC/VKF Wind Tunnels A/B/C

Aerospace Testing Alliance Test & Facilities Support Department and

Flight Systems T & E Department

October 2003

ARNOLD ENGINEERING DEVELOPMENT CENTER

ARNOLD AIR FORCE BASE, TENNESSEE

AIR FORCE MATERIEL COMMAND

UNITED STATES AIR FORCE

Cleared for public release; distribution unlimited.

DESTRUCTION NOTICE

For unclassified, limited documents, destroy by any method that will prevent disclosure or reconstruction of the document.

APPROVAL STATEMENT

This report has been reviewed and approved.

Carmen Evans, 1Lt, USAF Flight Systems Test Division Test Operations Directorate

Approved for publication:

FOR THE COMMANDER

Gary Mattasits Chief, Flight Systems Test Division Test Operations Directorate

NOTICES

When U. S. Government drawings, specifications, or other data are used for any purpose other than a definitely related Government procurement operation, the Government thereby incurs no responsibil-ity nor any obligation whatsoever, and the fact that the Government may have formulated, furnished, or in any way supplied the said drawings, specifications, or other data, is not to be regarded by impli-cation or otherwise, or in any manner licensing the holder or any other person or corporation, or con-veying any rights or permission to manufacture, use, or sell any patented invention that may in any way be related thereto.

Qualified users may obtain copies of this report from the Defense Technical Information Center.

References to named commercial products in this report are not to be considered in any sense as an endorsement of the product by the United States Air Force or the Government.

REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188

1. REPORT DATE (DD-MM-YYYY)

July 2003

2. REPORT TYPE

Handbook

4. TITLE AND SUBTITLE

Test Article Design Information Handbook AEDC/VKF Wind Tunnels A/B/C

5a. CONTRACT NUMBER N/A

6. AUTHOR(S)

Jacobs Sverdrup AEDC Group Test & Facilities Support Department and Flight Systems T & E Department

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

AEDC/DOF

Arnold AFB, TN

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

AEDC/DOF

Arnold AFB, TN

8. PERFORMING ORGANIZATION

REPORT NUMBER

AEDC-HNBK-03-02

10. SPONSOR/MONITOR'S ACRONYM(S)

N/A

13. SUPPLEMENTARY NOTES

None

12. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release, distribution unlimited.

14. ABSTRACT

The purpose of this handbook is to aid a Customer/Designer in preparing for tests in the VKF Tunnels A/B/C.

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OF

PAGES

19a. NAME OF RESPONSIBLE PERSON Lt. Carmen Evans a. REPORT

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c. THIS PAGE

U

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(931) 454-6225

CONTENTS

Section Page

I. INTRODUCTION

1.1 General Comments

1.2 Design Philosophy

II. GENERAL DESIGN INFORMATION

2.1 Normal Procedures

2.2 Subcontractor Selection Guidelines

2.3 Design Review and Model Inspection

2.4 Shipping Information

2.5 General Model Requirements

2.5.1 Allowable Stresses

2.5.2 Model Joints

2.5.3 Sting Interfaces

2.5.4 Pressure Piping

2.5.5 Electrical Equipment and Components

III. MODEL SIZING CRITERIA

3.1 Tunnel A Model Sizing

3.2 Tunnel B and C Model Sizing

IV. FORCE MODEL DESIGN AND FABRICATION REQUIREMENTS

4.1 Force Models for Tunnels A/B/C

4.1.1 Balances

4.1.2 Model Weight

4.1.3 Materials and Heat Considerations

4.1.4 Balance Temperature Control

4.1.5 Model-to-Balance Attachments

4.1.6 Model Alignment

4.1.7 Model-Sting Deflection

4.1.8 Auxiliary Measurements

4.1.9 Check Loads

V. PRESSURE MODEL DESIGN AND FABRICATION REQUIREMENTS

5.1 Pressure Models for Tunnels A/B/C

5.1.1 Pressure Transducers

Section Page

5.1.2 Material

5.1.3 Heat Considerations

5.1.4 Pressure Tubing

5.1.5 Pressure Lag Time

VI. HEAT-TRANSFER MODEL DESIGN AND

FABRICATION REQUIREMENTS

6.1 Tunnels A/B/C

6.1.1 Thin-Skin Model Design Requirements

6.1.2 Heat-Transfer Gage Model Design Requirements

6.1.3 Thermal Mapping Requirements

VII. DYNAMIC STABILITY MODEL DESIGN AND FABRICATION

7.1 Dynamic Balances

7.2 One-Degree-of-Freedom Forced- and Free-Oscillation Models

7.3 Three-Degree-of-Freedom Model Design

7.4 Magnus and Roll Damping Models

7.5 Free-Flight Models

APPENDIX

A. TUNNEL DESCRIPTIONS AND FLOW CONDITIONS

TUNNEL A

TUNNELS B AND C

CAPTIVE TRAJECTORY SYSTEM

SECTION I

INTRODUCTION

1.1 GENERAL COMMENTS

The purpose of this handbook, along with the Test Facilities Handbook and Test Planning Information Handbook, is to aid a Customer/Designer in preparing for tests in Tunnels A/B/C of the von K rm n Gas Dynamics Facility (VKF), Arnold Engineering Development Center (AEDC). In-cluded are (1) basic information necessary for the design of an efficient, cost effective model and

(2) criteria for ensuring model compatibility with AEDC-VKF systems.

The information provided, however, is not exhaustive. AEDC-VKF must be consulted when model design work is begun. The data presented do not account for all restrictions because criteria are frequently changing. The Customer risks having a model rejected if AEDC-VKF is not consult-ed concerning model sizing, balance selection, stress analysis, etc. Ideally, AEDC-VKF should be involved to a limited extent in the whole design process.

The requirements, in the form of this handbook, are issued to the Customers of the VKF facilities to establish ground rules for acceptable model designs. Fulfillment of these requirements provides a satisfactory resolution of some hazards identified in the System Safety and Hazard Analysis for each project as per MIL-STD-882 and AEDC Procedures. Items that do not meet the requirements herein must be brought to the attention of the VKF staff as soon as possible for consideration of changes or countermeasures that will permit safe, satisfactory testing. Deviations from these requirements may be permitted in special cases after AEDC-VKF personnel have reviewed the design and make an assessment of the consequences of failure. Any deviations from the requirements will be documented in the system safety hazard analysis and risk assessment.

1.2 DESIGN PHILOSOPHY

Wind tunnel testing involves the art of simulation. “Real world” conditions must be duplicated or simulated as much as possible for meaningful data to be produced. Aerodynamicists can com-pensate with a high degree of accuracy for tunnel flow conditions that are not exactly those of flight;

however, experimentalists realize that final, meaningful data can be no better than the test model with which the data were obtained. Wind tunnel models, therefore, must simulate full-scale vehicles, including all aerodynamically significant protuberances, as closely as practical. Previous experience has shown that when flight data and the corresponding wind tunnel data were in disagreement, the problem could frequently be traced to inadequate modeling. Correct scaling of components, location of control surfaces (including hinge lines), and basic geometry cannot be overemphasized. Unless the model is built either by or for AEDC-VKF, it is the Customer’s a′ a′ responsibility to confirm accurate modeling. Unless specific agreements are made in test planning conferences, only basic measurements, such as overall length, wing span, diameter, etc., are checked at AEDC-VKF.

Wind tunnel test hours are costly. The designer must design efficiency into the model to obtain an optimum amount of data during an operating shift. The cost per tunnel operating shift hour will continue regardless of whether or not data are produced.

Testing actual flight articles in wind tunnels is not necessarily safe, since the structural stress is different during flight and ground tests. In flight, airloads are opposed by distributed weight and inertia forces. In the tunnel, weight and air loads are transmitted to only a few support points, and the model or flight article is exposed for longer periods to extreme conditions. Tunnel mountings introduce vibrations that in turn require fatigue strength of all components and positive locking of all connectors and fasteners. Flight articles must, therefore, be reanalyzed for tunnel testing. The wind tunnel challenges the designer because of the unique environment for test hardware.

SECTION II

GENERAL DESIGN INFORMATION

This section includes information pertinent to model design and procurement procedures.

Included are guidelines for Customer responsibility; model subcontractor selection, design review, and inspection; model requirements; and shipping.

2.1 NORMAL PROCEDURES

According to AEDC policy the Customer will design and fabricate the test article whenever possible. AEDC-VKF limits its involvement to (1) outlining general design, fabrication, and test criteria according to this handbook and providing normal interaction between the Project Engineer and the Customer, (2) reviewing Customer drawings and stress reports, and (3) providing a general (undetailed) check of model dimensions and tunnel compatibility upon arrival of the model at AEDC.

Under certain circumstances the Air Force, Sverdrup (the AEDC operating contractor), and the Customer may agree that the model should be built at AEDC or procured outside AEDC by Sverdrup. Outside procurement of test models by Sverdrup is possible when the Customer requests that a model be furnished and Sverdrup is unable to design and/or fabricate the model with existing resources to meet a scheduled test date.

In general, test models are generated through one of six channels, viz.,

1. Customer furnished (normal method)

2. Customer designed, Sverdrup fabricated

3. Customer designed, subcontractor fabricated (Sverdrup procured)

4. Sverdrup designed and fabricated

5. Sverdrup designed, subcontractor fabricated (Sverdrup procured)

6. Subcontractor designed and fabricated (Sverdrup procured)

Procurement of outside services by Sverdrup is involved in three of the six cases above. Bids for these services are solicited by ACS, with design criteria, specifications, and shop drawings supplied by the von rm n Facility from Customer-furnished information. The subcontractor for these out-side services is selected in accordance with guidelines given in Section 2.2.

2.2 SUBCONTRACTOR SELECTION GUIDELINES

A combination of factors determines the selection of a subcontractor to design and/or fabricate test models. Of primary importance is the capability to design, fabricate, and inspect the model to meet given criteria and specifications and the ability to supply the model to meet a scheduled test date.

To assure Sverdrup that a bidder is capable of meeting the requirements specified in the invitation for bid, proof that the bidder has already manufactured items of similar complexity may be requested. Further, Sverdrup may request from the Air Force a capabilities report, which outlines the plant capabilities of the bidder, or Sverdrup representatives may elect to visit the subcontractor’s plant. Finally, if the job is unusually difficult or complex, Sverdrup may choose to call a pre-award conference of all bidders, to assure that a common understanding prevails between the bidders and Sverdrup.

In addition to capability, price of the finished contract item plays an important role in selection of the successful bidder. Obviously, with all other factors equal, the contract will be awarded to the lowest bidder. The bidder is encouraged to submit alternates or substitutions with his bid (for evaluation before release of contract) if such substitutions reduce the bid price of the contract item without compromising quality or design.

Ka′ a′

Other factors that may be considered in selecting a subcontractor include plant location (location affects overall cost of required liaison), favorable (or unfavorable) history of financial dealings with Sverdrup or the Air Force, integrity and completeness of the proposal, delivery date, and laws governing procurement, e.g., Buy American Act.

2.3 DESIGN AND REVIEW AND MODEL INSPECTION

Regardless of the model procurement procedure, model drawings should be reviewed by both the Customer and AEDC-VKF before model manufacture if possible. The Customer should be particularly attentive to design features that affect stated test objectives. AEDC-VKF will be concerned with model compatibility to test objectives plus compatibility with tunnel hardware and systems. When the model is designed outside AEDC, a stress report including design and fabrica-tion details must accompany the model drawings (see Section 2.5.1).

If the model is fabricated or procured by Sverdrup, Sverdrup will provide a detailed inspection of all components. However, models furnished or procured by the Customer must be inspected by the Customer. Unless specific agreements are made in the test planning conferences, AEDC-VKF will make only a general inspection and compatibility check of the model upon its arrival at AEDC.

2.4 SHIPPING INFORMATION

The Customer shall provide sufficient packing protection for models and test equipment consistent with their value and sensitivity for shipment to and from and/or storage at VKF. To ensure proper handling during shipment, all boxes to be handled by cranes or forklifts must have skids of 3 in. height and must have weight and center-of-gravity (c.g.) location indicated on the out-side of the box. For tests with many model components, boxes need to be provided with special ar-bors and identification for each component. Packing lists shall accompany each box identifying at least all subassemblies by drawing numbers. It is recommended that a Customer representative remain after the test until model and test equipment are packed and ready for shipment.

The shipment of models and other test equipment should be coordinated with the Project Engineer. The following instructions concerning shipping should be followed:

a. Bills of Lading: All bills of lading and packing lists pertaining to either inbound or out-bound shipments should be forwarded via first-class mail to:

1. Traffic Manager

ACS

Arnold Air Force Base, TN 37389

b. Communications: Personnel may be contacted during scheduled duty hours, 0730 through 1600 hours, Central Standard Time, Monday through Friday:

1. Traffic Manager Area Code 931, 454-7805

2. Supply Branch, Storage and Distribution Section Area Code 931, 454-5411

3. Western Union-- Arnold Air Force Base, TN

4. TELEX − 554435 AEDC

5. Telefax Area Code 931, 454-3523

6. AUTOVON 340-xxxx Arnold Air Force Base, TN

c. Consignment: All material shipped to the AEDC will be consigned and must be marked as follows:

1. Shipments moving on Government Bills of Lading:

Transportation Officer Arnold Engineering Development Center Arnold Air Force Base, TN 37389

Mark for: ACS Project No.

Facility Attention: Project Engineer

2. Shipments moving on Commerical Bills of Lading will be on a PREPAID basis:

Materials Division

ACS

Arnold Air Force Base, TN 37389 Mark For: Project No.

Facility Attention: Project Engineer

3. Conversion: If the original Commercial Bill of Lading is annotated “Convert to Govern-ment Bill of Lading at Destination,” it must contain the “Appropriation Chargeable” number, or this number must be furnished in writing by the most expeditious method.

4. Identification: Each container must be marked with the applicable project number, facility name (VKF) for which the container is intended, and the name of the Project Engineer.

d. Accountability:

1. Government-Owned Property: Shipping documents must be annotated as follows:

(a) Accountability transferred to AEDC, EY 1441.

(b) Accountability retained under (Enter appropriate station, account number, and applicable contract number.)

(c) Accountability will not be transferred to Account EY 1441 without prior approval of AEDC Property Administrator.

(d) Indicate on Shipping Document if property is Government or Contractor owned and send three copies of Shipping Document with shipment.

2. Proprietary Property (other than government-owned): All packing lists or shipping papers must be annotated as follows:

(a) Title to the material shown hereon is vested in (Enter name and address of the owner.)

e. Security: Classified information and material are safeguarded in accordance with the requirements of the U. S. Government. Proprietary information and material are protected.

Local security escort is available within a 20-mile radius of the AEDC.

1. Inbound Shipments: Receipt, handling, and security protection will be provided as set forth in the “DOD Industrial Security Manual for Safeguarding Classified Information.”

2. Outbound Shipments: Classified property will be handled as prescribed by DOD Industrial Security Manual. Unclassified proprietary property will be accorded only such special handling as officially requested by the proprietor.

f. Receiving and Handling: The AEDC's facilities for handling and storage of high-energy fuels, rocket motors, igniters, propellants, and explosives meet Air Force requirements.

These facilities include:

1. Bulk Liquids: Activity can receive shipment of bulk petroleum products, liquid nitro-gen, and cryogenic and storable liquid rocket propellants in tank cars or tank trucks.

2. Heavy Lifts: Mobile lift capacity is 80 tons. Maximum lift of 200 tons can be effected with stationary overhead cranes at the Center.

3. Ramps: Side and end door ramps are available.

g. Handling Equipment at AEDC:

1. Forklift: 4000-lb capacity, explosion proof, diesel engine-driven

2. Trucks: 1-1/2 to 2-ton capacity, conventional covered-stake type, equipment to trans-port dangerous articles

3. Forklifts: 6 to 15,000-lb capability, gasoline engine-driven

4. Rigging: Tractor-trailers, cranes, and related equipment are available.

5. Temperature Control: Surface transportation equipment includes a van truck, inside dimensions, 14 ft by 6 ft, 9 in. by 6 ft with a one-half ton monorail hoist, equipped with a conditioning unit capable of maintaining temperatures of +60° to −5°F.

h. Storage Facilities: Permanent facilities for storing “Dangerous Articles” include:

1. Igloos: Two—standard-type construction, reinforced-concrete, earth covered, temperature range from 48 to 95°F with 5°F accuracy, size 34 ft long by 26 ft wide by 12 ft high, entrance of 11 ft high by 8 ft wide. One igloo is equipped with a 3-ton monorail hoist and one with a 7-1/2-ton hoist.

2. Ammunition Building: Metal construction, temperature controlled, +5 to 90°F in winter; 50 ft long by 25 ft wide by 9 ft high, with entrance dimensions of 8 ft high by 7 ft wide

3. Drum Storage: Three-shed type with concrete slab floors, total storage area of 6500 ft2

4. Cylinder Storage: Five-shed type with concrete slab floor, total storage area 1900 ft2 for 1-ton capacity cylinder only

5. Fuel Sheds: One shed for the storage of a mobile tank unit with capacity up to 5000 gal. One heated shed for storage of RR tank cars for liquid fuels/oxidizers.

6. Igniter Storage: Three earth-covered, metal, construction, transportainers, non-temperature-controlled; each unit has inside dimensions of 74 in. high by 74 in. wide by 89 in. deep, and entrance (door) size of 71 in. high by 62 in. wide. One concrete block building 11 by 18 by 8 ft with humidity controls.

i. Personnel: Operating crews are trained in the techniques of receiving, handling, storing, and transporting dangerous articles.

j. Outbound Shipments: Routing instructions received in writing from the owner of the material will be honored.

1. Government Bills of Lading: The “Appropriation Chargeable” number must be furnished before preparation of the bill of lading.

2. Commercial Bills of Lading: Shipments will be forwarded on a COLLECT basis via the routing authorized by the owner of the material.

3. SRO’s: Standing Route Orders: Those authorized by Military Traffic Management Terminal Services (MTMTS) will be adhered to.

4. L-HRI’s: Letter-Head Routing Instructions received from industry will be followed.

5. Security Shipments: Paragraph 2.4e will apply.

6. Packaging of Shipments: Each item will be packaged as directed by the “Test Repre-sentative” on duty at Arnold Center. In the absence of the “Test Representative” or written instructions from the owner, Commercial and/or Military packaging specifications will prevail.

k. Carrier Claims: In the event of intransit damage to inbound material the following action will be taken:

1. For shipments moving on a Commercial Bill of Lading:

(a) Notify the delivering carrier.

(b) Notify the “Test Representative” on duty at Arnold Center.

(c) Obtain Carrier’s Inspection report.

(d) Photos will be taken when deemed necessary.

(e) Forward supporting papers to the owner of the material for the purpose of initiating claim with carrier(s) involved.

l. Completed Project: Test material remaining after project completion will be shipped to user “Freight Collect” unless Sverdrup is notified otherwise within 30 days after project completion.

2.5 GENERAL MODEL REQUIREMENTS

In this section the guidelines given for model design and construction are applicable to all models to be tested in AEDC-VKF.

2.5.1 Allowable Stresses

All models and support hardware components must be designed and evaluated not only for steady-state loads but also for inadvertent transient flow breakdown or choked-flow (blockage) loads. Safety factor requirements are provided herein. Computations should include the worst-case combinations of aerodynamic, thermal, gravity, and acceleration loads due to model injec-tion. Allowable component stresses must be based on material properties of the component at predicted elevated temperatures.

Safety factor requirements for both steady state (run) and inadvertent transient (blockage or flow breakdown) load conditions are provided in Table 2.5-1. The model designer should work closely with AEDC-VKF personnel to ensure that he/she understands how the magnitudes and lo-cations of the transient loads are calculated. Notice in Table 2.5-1 that safety factors are not fixed, but rather they depend upon (1) the component being analyzed in the model/balance/support instal-lation, (2) the load type (steady-state or transient), and (3) the risk category assigned by VKF to a given installation.

Table 2.5-1: Safety Factor Requirements*

a. Balances

b. First Clutch-Face Connection Aft of the Balance

c. Test Articles/Support Hardware Not Identified in Tables 2.5-1a or -1b

This table is applicable to balance/sting/clutch-face connections with thread sizes ≤ 1.75 in. The connection includes both the connecting nut and the thread reliefs at either end of the nut. Specifications in Table 2.5-1c apply to connections with thread sizes > 1.75 in.

* Dunkin, O. L. “Instructions for Performing Test Project Safety Analyses for Test Units A, B, C, ACL, and APTU.” OI-SB-C32SB-000001, November 2, 1989

Load Type Blockage Category Min. Recommended

Safety Factor @ Max.

Expected Temperature

Run Loads All Categories 1.8 (Ultimate Strength)

Blockage Loads Will Not Block 1.0 (Yield Strength)

Marginal 1.0 (Yield Strength) Will Block 1.8 (Ultimate Strength)

Load Type Blockage Category Min. Recommended

Safety Factor @ Max.

Expected Temperature

Run Loads All Categories 2.0 (Yield Strength)

Blockage Loads Will Not Block 1.0 (Yield Strength)

Marginal 1.0 (Yield Strength) Will Block 2.0 (Yield Strength)

Load Type Blockage Category Min. Recommended

Safety Factor @ Max.

Expected Temperature

Run Loads All Categories 1.6 (Yield Strength) or

4.0 (Ultimate Strength), Whichever is More Conservative

Blockage Loads Will Not Block 1.0 (Yield Strength) Marginal 2.0 (Yield Strength)

Will Block 1.6 (Yield Strength) or

4.0 (Ultimate Strength), Whichever is More Conservative

In cases where safety factor requirements cannot be met, VKF should be contacted to discuss the possibility of relaxing the requirements by use of additional instrumentation, close monitoring of critical areas, provision of additional safety devices, and/or special proof loadings. Deviations from required safety factors may be permitted in special cases after VKF personnel have reviewed the design and made an assessment of the consequences of failure. Any deviations from required safety factors will be documented in the system safety hazard analysis and risk assessment.

Acceleration loads and allowable steady-state load ratings for the injection mechanism are ad-dressed in Appendix A for each tunnel.

Provisions should be made for differential thermal expansion attributable to variances in temperature or different thermal expansion coefficients between mating parts of models to be tested in Tunnels A, B, or C.

Complete drawing packages must be provided, and stress reports must address all Customer-furnished model and support hardward components. Two copies are required at least six weeks in advance of the test entry. The stress report should be complete and sufficiently comprehensive to preclude further explanation.

The stress analysis must show that allowable stresses or loads specified by VKF are not ex-ceeded for the worst load case considering dynamic factors, thermal stress, and stress concentrations.

Each detailed analysis section should contain a sketch showing forces and moments acting on each part or assembly being analyzed and should provide an explanation of assumptions and approximations, and it should include section properties, heat condition of the material, and perti-nent drawing numbers. Equations and their sources should be provided before substitiution of numerical values.

All parts with lifting surfaces (vertical stabilizers, pylons, struts, etc.) that are normally at zero angle of attack must be checked for air loads resulting from a ± 1 degree flow misalignment.

If the model is to be used for sideslip (yaw) testing, it must be checked for those test conditions.

Static tests may be permitted instead of an analysis for components that are difficult to accu-rately analyze if the customer supplies the loading rigs, devices, weights, etc., and obtains a waiver from the VKF safety coordinator. Requirements for load testing in lieu of an analysis are as follows:

– Where the primary aerodynamic loads can be directly and continuously monitored, the static load tests shall be carried to twice the predicted operating load without permanent set, and measured deflections for the complete loading cycle must be included in the stress report.

– Where the primary aerodynamic loads cannot be directly and continuously monitored (non-metric canards, ailerons, elevators, rudders, flaps, etc.), the static load tests shall be carried to three times the predicted operating load without permanent set, and measured deflections for the complete loading cycle must be included in the stress report.

In cases where safety factor requirements cannot be met such as for actual flight components (or dynamically similar components) and aeroelastic models, VKF shall be contacted to discuss the possibility of reducing the requirements by use of additional instrumentation, close monitoring of critical areas, provision of added safety devices, and/or special proof loadings. As with static tests, the provisions of this paragraph can only be implemented by waiver approval.

Models and support equipment utilizing gas or any type of pressurized system must be leak checked and hydrostatically proofed to 1.5 times the maximum VKF upstream supply pressure be-fore shipment to AEDC. Certification must be supplied for all systems in excess of 100 psig rated pressure. Special tooling and closures for making pressure checks should be shipped with the model to AEDC to facilitate leak checking prior to testing. Written verification of hydrostatic test is to be furnished with the stress report.

2.5.2 Model Joints

Several purposes of model joints are to (1) permit interchangeability of parts, (2) gain access to the model interior, (3) reduce weight of individual components, and (4) reduce the size of fabri-cation materials. Location of joints should not interfere with desired instrumentation locations, model components, or internal equipment. Joints should be constructed such that repeated assem-blies will always bring components into alignment within quoted tolerances. Also, they should never have forward-facing steps. Rearward-facing steps should be no greater than 0.001 in.

Piloted Joints

For accurate and repeatable location, all joints should have a pilot to duplicate assembled positions. There are several methods of providing pilots, but two types are commonly used in AEDC-VKF: dowel pins and short concentric sockets. If roll alignment is important, dowel pins are advisable; otherwise, the concentric socket may be used. The two types are often used in combination.

Bolted Joints

Bolted joints provide high strength on large model sections where access is available. They are particularly attractive for the aft sections of most models and the base plates of heat and pressure models. These joints lend themselves to accurate roll alignment with the addition of dowel pins, and they are the preferred joint for normal applications.

Screw Joints

Screw joints are used primarily on symmetrical models where roll orientation between sections is not critical. Their use is popular on models having replaceable sections, such as noses and forebodies, that must be quickly changed during a test. However, they do not lend themselves to instrumented pressure model sections or heavily instrumented heat-transfer model sections since several revolutions would be required to make up the joint. In addition, the type of material, clearances, and the possibility of galling must be considered.

The forward section of the joint should carry the internal thread since the higher thermal expansion of the forward section permits the parts to be disengaged before temperature stabilization.

Socket Joints

Socket joints are useful on models requiring close roll alignment. They feature set screw-type closure and are often used with dowel pin pilots. Use of these joints is common on both concentric and noncentric model sections. Operational model changes are somewhat slower and more difficult to make with these joints compared to the screw-type joints since the set-screw holes must be filled and smoothed to the model contour. The set-screw-type closure should only be used when it is not feasible to use the bolted or screw-type joint.

Modified Socket Joint

Although similar to the standard socket joint, the modified joint features a shorter, close-fit socket length and a relief over the remainder of the joint. This procedure results in reduced costs during construction, but prevents the joint from being used in high-load situations.

Screws

In general, screw sizes should be standard. Extra small, cut-off, or nonstandard heads should not be used unless absolutely necessary. Whenever possible all screws should be the same size even though some may be stronger than required.

2.5.3 Sting Interfaces

A variety of mounting hardware is available in the AEDC-VKF for attaching models to the pitch sectors in Tunnels A/B/C. These hardware components normally are made with clutch faces to provide interlocking connections. Many of these parts are water-cooled for use in Tunnels B and C. The preferred tehcnique for mating the model to the AEDC-VKF hardware is for the model to have a sting with a clutch face to match the tunnel components. Design details are available from the AEDC-VKF, and clutch-face gages and thread gages may be obtained on loan from the AEDC- VKF for a period of two weeks. The clutch-face standard is presented in Fig. 2.5-1 and Table 2.5-2.

Thread Relief (Typ.)

If it is not feasible to provide a sting with a clutch face, socket adapters are available to hold simple round stings. Design details for machining a sting to fit an adapter will be supplied by AEDC-VKF. Figure 2.5-2 shows a typical socket sting. It should be noted, however, that some models, e.g., models with high rolling moments, will not be mounted in a socket adapter. Regardless of the type sting attachment provided, the inside diameter of the sting is of prime consideration in determining the number of pressure tubes and/or cooling lines allowable for a particular model.

Again, early consultation with AEDC-VKF personnel is suggested.

Figure 2.5-1. Standard Clutch-Face Nomenclature

Figure 2.5-2. Typical Socket-Type Sting

- A -

G

M R. (Typ.)

Chamfered 45 deg x Threaded Dp.

Threaded X (L.H. or R.H. as Required per Detail Drawing) Threaded Finish 63 micro inches

LC per Detail Drawing)

All Dimensions in Inches

H I

Threaded Relative Diameter

Y Tooth Clutch Fact with 60-deg Tooth Form Oriented as required per Detail Drawing (Ref. Alignment Gage VKF Drawing No. 3307138, Part No. Z)

Flats of Teeth

J

K Diam.

L Diam.D

(Typ.)

C (Typ.)

A (Ref.)

Bottom of Relief

To Theo.

F Crest Theo. Root of Tooth

Bottom of Relief

Φ (Ref.)α (Ref.)

β θ

C of Teeth (Ref.)L

E (Ref.)

Theo. Crest of Tooth

Actual Flats of Teeth

A 0.001

Flats of Teeth

B

LC Teeth

A 0.001

60º ± 2' True Cutter

Angle

6.75

0.250

0.500

0.40

- A -

II A 0.001

A 0.002

0.030

0.062 x 45 Chamfer

1.50 Diameter

Through

Diameter

All Dimensions in Inches

2.30

0.060 Radius

2.4996 2.4991 o

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S ta nd ar d Th d.

N o.

X

D im en si on s

An gl es

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2.5.4 Pressure Piping

General All piping shall be designed, fabricated, inspected, tested, and installed in com-pliance with the latest edition of the ANSI Standard Code for Pressure Piping.

Powered Models For powered models, the internal supply tubing is considered pressure piping.

Pressure Vessels Pressure vessels fabricated from standard pipe, standard pipe fittings, and standard flanges are also considered pressure piping. They are defined as those covered by the following ANSI (formerly USA) dimensional standards:

Standards – Pipe: B.36.10 and B.36.19

– Fittings: B.16.9

– Flanges: B.16.5

Welding Welders, welding operations, and welding procedures are to be qualified in compliance with Section IX, ASME Boiler and Pressure Vessel Code, except as modified by the applicable section of the Piping Code.

Pipe Threading Allowances shall be made as required or recommended by the Piping Code for pipe threading, corrosion, and thinning of wall due to pipe bending.

Threaded Joints Threaded joints, flange joints, and seal welding of threaded joints shall be in compliance with the requirements and recommendations of the Piping Code.

Tube Fittings Tube fittings shall be in compliance with the latest issue of applicable Military Standards.

Service Line Because of safety, installation, checkout, maintenance, and operation it is Identification required that all service lines be properly identified for working pressures, flow direction (in or out), and fluid or gas carried.

Loose Line Identify all loose lines including spares, shipped separately from the model, and the Identification model interfaces where customer's lines and/or lines furnished by others need to be connected. Metal tags supported by wire which is compatible with the pip-ing and/or hose material are preferred.

Internal Line Identify the internal lines for large models.

Identification

2.5.5 Electrical Equipment and Components

General All electrical devices and wires used in the test section must be capable of with-standing the test section environment.

Material Criteria Use only qualified hardware or equipment and material conforming to the National Electrical Code.

Use the standard copper plastic-insulated wire with good abrasive resistance. All wiring is to be identified in accordance with schematic and wiring diagrams by:

– Color code

– Bands

– Tags, etc.

Protect electric circuits with proper fuses.

Pressure transducers, strain gages, vibration pickups, and other low-voltage devices should have each set of wires shielded, where the shield carries an above-ground potential.

Determine the required size, type, and length of wiring at the planning-conference or soon thereafter.

Select thermocouple type and range needed during the test planning.

The customer is to provide:

– Control panels and/or control boxes required to operate model components, when requested.

– Control panel leads of sufficient length to make proper connections in the respective control rooms.

– Mating electrical connectors for any customer-furnished equipment requir-ing connectors at interfaces located at control boxes in and/or at the model.

– Electrical schematics, wiring diagrams, and hookup sheets for model and control panels with the model design drawings in compliance with documentation requirements.

Customer- Furnished Material, Equip-ment, and Documentation

SECTION III

MODEL SIZING CRITERIA

3.1 TUNNEL A MODEL SIZING

NOTICE: AEDC-VKF must make the final decision regarding model size. Failure on the part of the Customer/designer to consult AEDC-VKF may result in rejection of the model.

In order to obtain the largest aerodynamic forces and Reynolds number, it is desirable to design a model for the maximum size possible. However, there are certain aerodynamic limitations on model size that require attention.

One of these limits is that of the reflected bow shock impinging on the model. Permissible model length for Tunnel A can be estimated with the experimental shock-wave coordinates, reflection angles, and effective test section heights presented in Table 3.1-1.

Another factor that limits the maximum model size is the blockage or choking that results when a model is too blunt or large in frontal area. The one-dimensional normal shock theory does not adequately define the ratio of the model area to test section area over a range of Mach numbers even when it is adjusted by some rule-of-thumb percentage. Model sizes are therefore selected using experimental blockage data. These data are presented in Fig. 3.1-1. Additional information on mod-el blockage is presented in AEDC-TN-59-165* and AEDC-TMR-87-V50†.

The curves in Fig. 3.1-1 relate the ratio of the model frontal area to the aerodynamic test area, model nose angle, and Mach number. The aerodynamic test area at two tunnel stations is presented in Fig. 3.1-2. In some cases, the model and support system combination will have a pronounced effect on the maximum size model that can be tested.

* Schueler, C. J. “An Investigation of Model Blockage for Wind Tunnels at Mach Numbers 1.5 to 19.5.”

AEDC-TN-59-165 (AD232492), February 1960.

† Carver, D. B., Strike, W. T., and Anderson, A. “Blockage Analysis Handbook for AEDC Tunnels A, B, C, & APTU.” AEDC-TMR-87-V50, January 1988.

Table 3.1-1. Shock Wave Coordinates

Figure 3.1-1. Model Blockage Data Figure 3.1-2. Effective Cross-Sectional Area of Test Section, Tunnel A y, in.

(yr/d) Reflection Boundary d/2 x θ θr c θc, deg θr, deg = 48

Mach Number

1.5 2.5 3 4 5 6 y/d = 1.90 3.80 5.60 7.50 9.40

2.30 4.45 6.50 8.60

10.70

3.75 5.95 8.00

10.05

1.20 2.40 3.65 4.90 6.10

1.60 3.20 4.65 5.95 7.20

2.65 4.10 5.37 6.70 7.95

0.95 1.90 2.80 3.80 4.70

1.35 2.60 3.65 4.65 5.60

2.20 3.35 4.45 5.40 6.35

0.80 1.70 2.50 3.30 4.15

1.20 2.30 3.10 4.00 4.90

2.00 3.00 3.90 4.70 5.60

0.65 1.30 2.00 2.60 3.30

1.00 1.90 2.55 3.25 3.95

1.70 2.75 3.20 3.90 4.65

0.60 1.15 1.70 2.30 2.90

1.00 1.70 2.30 2.85 3.40

1.65 2.30 2.95 3.60 4.20

0.55 1.00 1.50 2.13 2.63

0.95 1.55 2.15 2.65 3.10

1.60 2.20 2.80 3.40 3.90 x/d

32.50 25.50 21.50 16.00 13.00 11.00

19.35 19.30 19.20 18.80 18.20 17.40

Hemi

Tunnel A

40 x 40 yr, in. = 19.35

0.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

0.4

0.3

0.2

0.1

45-90 40

4.0 4.5 5.0 6.0

MAM = Model Frontal Area AT = Aerodynamic Test Section Area θc = Model Nose Half Angle

35 30

3.5

3.0

2.5

2.0

1.5

25 20 15 θc, deg

A M

/A T

(90 deg-2θc)/57.3

1.00

1.08

1.16

A /A

T

1.24

1.48

1 2 3

Mach Number

4 5 6

1.32

1.40

Tunnel Station (0)

Nominal Test Section Area 1,600 in.2 Aerodynamic Test Section Area

A =

AT =

Tunnel Station (-30)

The ability to establish supersonic flow around a model does not necessarily guarantee interference-free results. Although the tunnel may have started, the model size may be too large to permit proper formation of the wake. This problem, for the most part, is associated with tests of short, blunt bodies where the shock interference moves upstream toward the rear of the model as the critical model area is approached.

Model weight may also be a limiting factor in model sizing. For example, force models should weigh no more than 25 percent of the balance capacity (see Section 4.1.2).

Model size is sometimes dictated by the available window area for taking optical data. The double-pass, optical flow visualization system of Tunnel A has a 35-in. field of view. The system may be used through the test section windows illustrated in Fig. A-2 of Appendix A.

3.2 TUNNEL B AND C MODEL SIZING

The optimum size of models depends upon many factors, such as fineness ratio, nose blunt-ness, and desired angle of attack. Because of the high Mach number, no problem is encountered with reflected shock waves. Models up to 60 in. long can be tested up to an angle of attack of 15 deg. From tunnel blockage considerations, blunt models up to 14 in. in diameter have been tested, whereas delta-wing models with a frontal area of 170 in.2 at angle of attack have been tested. The span of a winged configuration should be less than 28 in. to permit injection into the test section.

The nose of the model should not extend beyond the limit shown in Fig. A-5 of Appendix A.

Thermal growth attributable to temperature changes must be taken into account in model design. This is especially true of models that require moving parts or dimensionally stable surfaces.

Likewise, model distortion can be considerable under uneven heating. Thin-skinned and/or unusually long models are more critical than thick-skinned and shorter models. During the planning of any particular test, consultation with the wind tunnel staff is required for appropriate solutions.

Each pair of windows in each tunnel is equipped with a single-pass optical flow visualization system that can be used for shadowgraph or schlieren recordings. The systems are equipped with direct and television viewing, and flow-field recordings can be made on 70-mm roll film with a 1-µsec exposure time, 16-mm film up to 10,000 frames per second, or on video tape. Figure 3.2-1 is an example of a shadowgraph recording.

Figure 3.2-1. Shadowgraph Photograph of Hypersonic Interceptor Configuration (Refer to Fig. A-5 for Dimensions)

In tests where flow visualization is important, model size may be dictated by photo-coverage area. Figure A-5 of Appendix A gives the pertinent dimensions for Tunnels B and C.

Model weight may also be a limiting factor in model sizing. For example, force models should weigh no more than 25 percent of the balance capacity (see Section 4.1.2).

SECTION IV

FORCE MODEL DESIGN AND FABRICATION REQUIREMENTS

4.1 FORCE MODELS FOR TUNNELS A/B/C

The design criteria for models to be tested in continuous tunnels depend directly on the required test conditions. Conventional design and fabrication techniques may be used only for models tested in Tunnel A because heating is not a problem. On the other hand, the high temperatures experienced in Tunnel C (To ~ 2,000°R) dictate model materials and design techniques that allow for thermal expansion. In Tunnel B the M∞ = 6 conditions are more in line with Tunnel A model requirements, where the M∞ = 8 conditions (To ~ 1,300°R) are approaching the Tunnel C requirements. It is recommended that the model designer contact AEDC-VKF personnel as early as possible in the design phase for guidelines concerning specific requirements.

The following table is presented to provide typical stagnation point heat-transfer coefficients, ho, for the various test conditions in Tunnels A/B/C. The adiabatic wall temperature values, Taw, are based on 90 percent of To and indicate the maximum temperature expected at any point on the model.

The values of ho are combined with model nose radius (rn) so that the values of ho for any nose ra-dius can be obtained. For example: A model with a 0.5-in. nose radius is to be tested in Tunnel B at M∞ = 6 and po = 200 psia.

where ho = Stagnation heat-transfer rate/(Taw-Tw), Btu/ft2-sec-°R

M∞ = Freestream Mach number

Po = Reservoir pressure, psia

Tw = Model wall temperature, °R

Taw = Adiabatic wall recovery temperature

Tunnel M∞ po, psia To, °R Taw, °R

A 1.5 15 640 576 0.00715

3.0 37 730 657 0.00729

5.5 25 640 576 0.00213

5.5 200 750 675 0.00621

B 6 50 790 711 0.00272

120 820 738 0.00420

200 850 765 0.00544

8 100 1,175 1,058 0.00215

450 1,286 1,157 0.00455

900 1,346 1,211 0.00644

C 10 300 1,700 1,530 0.00235

1,000 1,835 1,652 0.00427

1,900 1,900 1,710 0.00586 ho rN Btu/ft 0.5 ft 2 °R–sec– ho rN 0.00544 rN 0.5 in. 0.0417 ft==;= ho 0.00544 rN

----------------- 0.00544

0.0417 -------------------- 0.0267 Btu ft 2 °R–sec–

4.1.1 Balances

Force and moment measurements are made with strain-gage balances mounted inside the model. These six-component balances measure forces and moments in the pitch and yaw planes, rolling moment, and axial force. A typical balance and water jacket are shown in Fig. 4.1-1.

Customers must contact AEDC-VKF concerning balance requirements. AEDC-VKF personnel will select the balance most suitable for the expected load range.

When the Customer supplies a balance for testing, all necessary calibration equipment must also be supplied in most cases (such as adapters to mate the balance to AEDC-VKF calibration equipment) because AEDC-VKF is likely to recalibrate or check-calibrate the balance.

Figure 4.1-1. Typical AEDC-VKF Force Balance and Water Jacket

4.1.2 Model Weight

Definite advantages in data quality can be realized by minimizing model weight:

1. Lightweight models reduce tare corrections (i.e., balance loading produced by model weight). Data quality diminishes when the desired measurement is obtained by taking the difference between the measurement of two large quantities. This is the case when model weight approaches the aerodynamic load. Therefore, minimizing model weight reduces the magnitude of the tare, and thus the uncertainty in the aerodynamic load approaches the uncertainty in the basic measurement.

2. Heavy models, relative to balance and sting capacities, can also affect data quality by producing undesirable dynamic effects. This situation usually results in model-balance-sting combinations with very low natural frequencies, whereas high frequencies are desirable for data recording and reduction. Heavy models can also overload the balance/ sting during injection or retraction cycles. A total of 2 g’s should be assumed.

The only known advantage of a heavy model is that a normal force larger than the balance capacity can be measured if the normal force opposes the corresponding component of the model weight, e.g., a lifting body at positive angle of attack and zero roll. This advantage can become a disadvantage if the model-balance-sting assembly must be inverted during testing such that the weight and normal-force components are additive. In this case the aerodynamic normal-force limit is less than the balance capacity. Similar loading restrictions on other balance components are possible depending on model center-of-gravity (cg) location and balance orientation, as indicated in the following example. In general, model weight should be limited to 25 percent (or less) of the balance normal-force capacity.

Example: (Refer to Fig. 4.1-2)

W = 60 lb = 2.5 in. = 0.5 in. = 2.0 in.

Balance Capacities: FN = ±200 MY = ± 800 in.-lb

FY = ± 50 MZ = ± 200 in.-lb

FA = 25 MX = ± 100 in.-lb

For this model/balance combination:

1. The model weight alone overloads the balance in side force, FY, when the model and balance combination is rolled to either ± 90 deg (W > 50 lb).

2. The model weight alone overloads the balance axial force, FA, when the model and balance combination is pitched to an angle greater than 25 deg.

3. The model weight alone overloads the balance rolling moment, MX, when the model and balance combination is rolled to either ± 90 deg

These are typical checks that must be made during the test planning to be sure the model and balance are compatible. These examples also show the importance of the balance location in the model. All possible load combinations on each balance component must be carefully examined.

x y z

W • z 120 in.-lb=( ).

Figure 4.1-2. Model Weight Tare and…